Advances in chemistry research volume 8

It is necessary to underline, that for lack of alkali in a MG oxalate ethanol solution Figure 1а, the curve 1 in a spectrum is not found out any signs of increase in time of an intensive

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C ONTENTS

Yu A Mikheev, L N Guseva, Yu A Ershov andG E Zaikov 

Polycarbonate and Syndiotactic Poly(Methyl-Methacrylate) 29  

Maurizio Penco, Stefania Della Sciucca, Gloria Spagnoli and Luca Di Landro 

of Molecular Insectitsid DDT (Nobel Award 1948, P Muller) 47  

V A Babkin, V U Dmitriev and G E Zaikov 

V A Babkin, K V Sergeeva, E S Titova and G E Zaikov 

Alexei A Gridnev, Dmitry B Gorbunov and Gregory A Nikiforov 

in Poly(Methyl Methacrylate) (PMMA) as a Way

N Guarrotxena 

in the Selective Alkylarens Oxidations with Dioxygen:

L I Matienko, L A Mosolova and G E Zaikov

Jon Meegan, Mogon Patel, Anthony C Swain, Jenny L Cunningham, Paul R Morrell and Julian J Murphy

Solmaz Karabulut

Marina Ciancia and Alberto S Cerezo

P REFACE

This book presents original research results on the leading edge of chemistry research Each article has been carefully selected in an attempt to present substantial research results across a broad spectrum Topics discussed include thermal behaviour and enthalpy relaxation

in aromatic polycarbonate; cobalozimes with functionalized ligands; parameters of the combustion of differential propellant in mixture of oxidants and the modeling of transition metal complex catalysts

Chapter 1 - In the range of waves lengths 200-800 nm are studied absorption electronic spectra of individual molecules of triphenilmethane, xanthene and thiazene dyes In triphenilmethane a number are studied the malachite green, crystal violet, diamond green and methyl violet In xanthene number are studied rodamine B and rodamine G; in thiazene a number - methylene blue Molecular solutions of dyes prepared by heptane extraction from commercial powders, and also by thermal processing of triacetate cellulose and the cellophane films, painted by these dyes It is established, that individual molecules of dyes do not absorb light in visible range of a spectrum, i.e have no chromogene groups From here follows, that usually observable chromaticity of dyes is caused by supramolecular structures - dimers and larger dyes molecules associates at mutual orientation favorable for molecular interaction From here follows, that existing quantum-chemical theories of chromaticity of the studied dyes classes are incorrect and demand revision

Chapter 2 - The structural relaxation of polymers depends on the kinetic character of the glass-transition phenomenon: amorphous polymers below their Tg are not at equilibrium and their structures continuously relax in attempt to reach the equilibrium state Several phenomenological and molecular approaches have been proposed to describe the structural relaxation but a universal model is still lacking The enthalpy relaxation of glasses is usually described with models developed on the basis of Tool-Narayanaswamy-Moynihan (TNM) theory [1,2]: it is assumed that the instantaneous relaxation time(s) (τ) for enthalpy relaxation depends on both the temperature (T) and the structure of the glass, identified by its fictive temperature (Tf) This approach is able to describe the enthalpy relaxation in low-molecular-weight glass-forming system fairly well [3,4], but discrepancies have been observed in several polymeric systems [5,6] One of these discrepancies concerns the overestimation of enthalpy lost on aging the samples for long periods of time Hodge [7], Gomez Ribellez [8] and Cowie [9] ascribed this features in polymers to the effect of topological constraints, such

as chain entanglements, which are completely ignored in the TNM-based models

James C Taylor viii

In this work, the enthalpy relaxation of aromatic polycarbonates and of syndiotactic poly(methyl methacrylate)s (PMMA) are investigated performing DSC experiments with the intention of characterize the effect of the composition and of the molar mass in aromatic polycarbonates and the relaxation dynamic as a function of the molecular mass and to highlight the effect of PMMA entanglement mass (Me) in syndiotactic poly(methyl methacrylate)s (PMMA)

Chapter 3 - Quantum-chemical calculation of molecular of insectitsid DDT was done by method AB INITIO in base 6-311G** Optimized by all parameters geometric and electronic structures of these compound was received The universal factor of acidity was calculated (pKa=26.5) Molecular of insectitsid DDT pertain to class of very weak Н-acids (рКа>14) Chapter 4 - Calculation of the mixture of oxidants of differential propellant (molecular oxygen – ozone) was made by classical quantum-chemical semitheoretical method CNDO/2

in parametrization of Santri-Poppl-Segal Optimized geometric and electronic structure of the combination of these oxidants was received Parameters of the combustion of this mixture were evaluated Parameters of the combustion of mixture of oxidants (O2+O3) practically do not differ from parameter of the combustion of the molecular oxygen

Chapter 5 - Cobaloximes, alkylcobaloximes and borofluoride adducts on the basis of asymmetric functionalized ligandes have been synthesized These cobaloxime systems form geometric isomers The presence of chiral center in axial ligand gives rise to the appearance

of diastereotopics effect

Chapter 6 - Three industrial samples of Poly(methyl methacrylate) (PMMA), prepared under different conditions, have been extensively analyzed by means of 1H-NMR

spectroscopy Starting from the mm, rr and mrandrm triad contents, as given by the spectra,

the type of tacticity statistics distribution has been deduced Sample X appears to be completely Bernoullian, while samples Y and Z deviate somewhat from this behaviour

exhibiting a tiny trend towards Markovian statistics The fraction of mmrm and rrrm pentads

and that of pure heterotactic and atactic triad moieties has been calculated by assuming either

a Markovian statistics for samples Y and Z or a Bernoullian statistics for all the samples On the other hand, the fraction of the same pentads has been determined by deconvoluting the overall triad signals of the spectra into the corresponding pentad signals An appreciably good agreement with the values obtained assuming Bernoullian statistics for all the samples appears evident As a result, the evolution of every pentad content from sample X to Sample

Z could be stated Thus the samples prove to be appropriate models to study the relationship between any physical property and the stereomicrostructure of PMMA as was done previously for Poly(vinyl chloride) (PVC) and Polypropylene (PP)

Chapter 7 - The different methods of improvement of catalytic activity of transition metal complexes in the oxidations of alkylarens with molecular oxygen are stated briefly The offered at first by authors and developed in their works the method of control of catalyst activity of transition metal complexes with additives of electron-donor mono- or multidentate exo ligands L2 in the oxidations of alkylarens (ethylbenzene, cumene) with molecular oxygen into corresponding hydroperoxides is presented The modeling of catalytic nickel and iron complexes with use of ammonium quaternary salts and macro-cycle polyethers as exo ligands-modifiers is described in detail The role of the Hydrogen–Bonding interactions in mechanisms of homogeneous catalysis is discussed The modeling of catalyst activity of complexes Fe(II,III)(acac)n with R4NBr (or 18-crown-6) (18C6) in the ethylbenzene oxidation

in the presence of small amounts additives of water (~10-3 mol/l) is analyzed The role of

Preface ix

micro steps of the chain initiation (O2 activation), and propagation in the presence of catalyst (Cat + RO2•→) in the mechanism of nickel- and iron-catalyzed oxidation of ethylbenzene is evaluated

Chapter 8 - New carbofunctional oligoisiloxanes containing trifluorinepropil and methacrylic groups at silicon atoms have been synthesized and studied On the basis of the data of IR and NMR spectral analysis the process of hydrosilylatrion, composition and structure of synthesized compounds have been investigated By using of diferential-thermal and thermogravimetric analisis method the thermal stability of sintesized oligomers have been studied By the diferential-scanning calomerty method the phase transition temperatures of synthesized oligomers were determined It was established that synthesized oligomers are amorphic one-phase systems

The preliminary ivestigation showd that the sybthesized carbofunctional oligomers in combination with polyepoxides and non-volatile bioactive organo-ellement arsenic complex compounds new composite materials of multifunctional application for individual and enviro-nmental protection of various materials may be created

Chapter 9 - In this article we will review the design, formulation and development of materials exhibiting simplified structure / property relationships, reversible cure mechanisms, increased resistance to physical property changes over time and stress sensitive behaviours These properties are discussed within the context of the external literature The article also provides a brief overview of the processes employed by AWE to qualify materials and further understand their storage, ageing and compatibility properties

Chapter 10 - MoCl5-e−-Al-CH2Cl2 catalyst system can efficiently polymerize ene-2-yl acetate in moderate yields and in relatively high molecular weights The analyses of the product by FTIR, 1H NMR and 13C NMR spectra give the verification of metathetical polymers The polymer shows narrow molecular weight distribution and good solubility in common organic solvents

noborn-5-Chapter 11 - In the last seventeen years it has been shown that red seaweeds classified as

“carrageenophytes” also biosynthesize agaran structures, while certain “agarophytes” produce small amounts carrageenan structures No neat separation of these carrageenan/agaran systems was obtained, leading to the idea of “hybrid” molecules, called DL-hybrid galactans Several points concerning these polysaccharide systems have been addressed:

1 Description of the systems of galactans, in which carrageenan and agaran structures were found (DL-galactan systems), as well as the methodology necessary for their detection

2 Isolation of “pure” carrageenans or agarans from these systems using degrading conditions and the consequent new hypothesis of the formation of molecular complexes

non-3 Evidences favoring each hypothesis, namely, the existence of hybrid molecules versus molecular complexes formation

Versions of these chapters were also published inPolymers Research Journal, Volume 3,

Numbers 1-4, edited by Frank Columbus, published by Nova Science Publishers, Inc They were submitted for appropriate modifications in an effort to encourage wider dissemination of research

In: Advances in Chemistry Research Volume 8 ISBN 978-1-61209-089-4

Chapter 1

Yu A Mikheev1, L N Guseva1, Yu A Ershov2 and G E Zaikov*

1N.M Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygin str., 119334 Moscow, Russia

2N.E Bauman Moscow State Technical University, 2-rd Baumanskaya str 5, 105005

Moscow, Russia

In the range of waves lengths 200-800 nm are studied absorption electronic spectra

of individual molecules of triphenilmethane, xanthene and thiazene dyes In triphenilmethane a number are studied the malachite green, crystal violet, diamond green and methyl violet In xanthene number are studied rodamine B and rodamine G; in thiazene a number - methylene blue Molecular solutions of dyes prepared by heptane extraction from commercial powders, and also by thermal processing of triacetate cellulose and the cellophane films, painted by these dyes It is established, that individual molecules of dyes do not absorb light in visible range of a spectrum, i.e have no chromogene groups From here follows, that usually observable chromaticity of dyes is caused by supramolecular structures - dimers and larger dyes molecules associates at mutual orientation favorable for molecular interaction From here follows, that existing quantum-chemical theories of chromaticity of the studied dyes classes are incorrect and demand revision

Keywords: nature of dyes, electronic spectra, supramolecular structures,

quantum-chemical calculations, chromaticity

* E-mail: Chembio@sky.chph.ras.ru

Yu A Mikheev, L N Guseva, Yu A Ershov et al

However, in works [10, 11] at copper phtalocyanine research (a pigment of dark blue color) the important fact has been established, that chromogene of this dye are individual molecules, but supramolecular dimers and larger molecular associates are not In these works applied extraction molecules of dye from powders by means of polymeric films (polyethylene, cellulose triacetate) and heptane This method allows separating single molecules from pigment particles It is established, that commercial copper phtalocyanine powders contain a cmall amount of an amorphous phase, heptane soluble As a result did received solutions of individual molecules possess a characteristic spectrum with the developed system of electronic-oscillatory bands These bands are in ultra-violet area, i.e individual molecules do not absorb visible light and do not form the painted solutions From here follows, that color of the given dye arises only as a result of compound of molecules in supramolecular dimers and larger associates

In the given work individual molecules of cation triphenilmethane, xanthene and thiazene classes dyes are releaseed by extraction and thermal processing It has appeared, that, as well

as in a case copper phtalocyanine, chromogenes of this dyes type are not individual molecules, and their supramolecular dimers and larger associates are chromogene From the received results the urgency of working out of quantum chemistry methods follows with reference to supramolecular structures of dyes

In this work used commercial powders of triphenilmethane (TPMD), xanthene (XD) and thiazene (TD) dyes (Shostkinsky chemical reactants plant) Are studied TPMD - malachite green (MG), crystal violet (CV), methyl violet (MV) and diamond green (DG) (in the form of 1% spirit solution) Are studied also XD – rodamins B and G, and representative of– methylene blue (MB)

Molecules of the listed dyes contain developed positively charged π-systems and

oxalate-or chloxalate-orine anions

Extraction of MG, CV and MV molecules from powders carried out by spectroscopic pure heptane on a water bath Extraction of DG and rodamine B molecules carried out from their spirit solutions at 25º C To notice, that chromogene molecular associates of the studied dyes not soluted in heptane

Association Nature of Dyes Chromaticity 3

For preparation of a rodamine B heptane molecular solution ~1mg dye sample dissolved

in ethanol (2 ml), added heptane (4 ml) Then the received mix diluted with water Water action consists, first, in heptane miscibility decrease with spirit, secondly, in heptane extraction strengthening of dye molecules from an aqueous-alcoholic layer

Heptane processing of rodamins and MG powders does not lead to formation of molecular solutions Thus rodamine and the MG molecules was not possible extract as well from their specially prepared spirit solutions Extraction subjected also solutions of immonium hydroxides TPMD which prepared, mixing powders or their spirit solutions with water solutions of alkali KOH (2-5%)

Used also release ion of molecular fractions of dyes by absorption from alcoholic solutions of dyes by triacetate cellulose (TAC) films Solutions of dyes for extraction prepared, mixing their spirit solutions (~10 mg in 10 ml of ethanol) with the distilled water (~10 ml)

aqueous-Influence of heating on electronic spectra of TAC and the cellophane films, containing

XD and MG is studied

XD entered into TAC films (20 microns) from solutions in the mixed solvent (9 parts of chloroform on one part of ethanol), evaporating solvent in Petri dishes XD and MG entered also into cellophane films (a thickness 40 microns) by absorption from aqueous-alcoholic solutions For this purpose mixed solutions of dye of 3 mg in 1 ml of ethanol about 20 ml of the distilled water As a result dyes concentration in films exceeded concentration in water approximately in 100 times

Solutions and films spectra registered on “Specord UV-VIS” and “Shimadzu 1240” spectrophotometers

UVmini-DISCUSSION OF RESULTS

Spectral Properties of Individual and Aggregated Cationic

Triphenilmethane Dyes (TPMD)

The Chromogene Nature of the Malachite Green

TPMD molecules studied comprise grouping with developed π-system and a fragment with the chinoid structure bearing a positive charge on atom of nitrogen (immonium cation) Consider [1-4] what exactly such molecular structure serves as the reason of occurrence of coloring, i.e is chromogene

The immonium cation structural formula of TPMD looks like:

ts (Ar) makes

ge

N Guseva, Yu

СН3 and R ' =and R ' =NH (

es dissolved in

ε617 = 4.4×104

u A Ershov et

= N (CH3) 2 (C(CH3) (MV)

and oxalate-anorganic imm

nylene radical

lution (1 molem)): 16 200 (61ethanol solutio

s, Рħ - a cyclo

e/l) is resulted7); 23 500 (42

on correspondfor the main nting on conce)

Association Nature of Dyes Chromaticity 5

(b) Figure 1 Changes of optical spectra ethanol (a) and heptane (b) solutions of commercial MG oxalate in the presence of KOH (a) and ethanol (b) Explanatory in the text

On Figure 1а curves 2-4 represent transformation of a spectrum 1 in a MG carbinol leycoform spectrum at addition of alkali KOH in a solution Curves 2 and 3 characterize change of a spectrum 1 in time (through 40 and 80 mines accordingly) at very low concentration KOH - 8·10-5 mole/l, and 4 - at 3·10-3 mole/l

It is necessary to underline, that for lack of alkali in a MG oxalate ethanol solution (Figure 1а, the curve 1) in a spectrum is not found out any signs of increase in time of an intensive carbinol leycoform band at frequency ν =38000 cm-1 It testifies to stability MG oxalate in ethanol solution

In alkaline environment MG oxalate is hydrolyzed finally with carbinol formation It is necessary to notice, that MG and CV carbinols for the first time are received in work [14] by processing of these dyes chlorides by weak water solutions of alkalis Thus MG and CV carbinols were released in the form of deposits, slightly solved in water Pure carbinols received by recrystallization from heptane or ether, are steady and, contrary to representations

of authors of work [13], do not dissociate in ethanol solutions on Ar-cations and ions [14, 15]

hydroxyl-Observed on Figure 1а character of spectral transformation of MG solution under the influence of alkali finds out the step nature of this process So, already at very low concentration of alkali there is an intensity decrease chromogene bands νmax = 16200 cm-1 of dye to simultaneous increase of a wide band νmax = 38 000 cm-1 Thus on curves 1-3 (Figure 1а) is available an isobiestic point at ν = 35 500 cm-1 From here follows, that at an intermediate stage of hydrolysis intermediate products with identical spectroscopic properties are formed which, however, are not carbinol For reception of carbinol it is required to increase concentration of alkali So, at increase in concentration KOH to 3×10-3 mole/l the isobiestic point disappears, and the UV-band arising thus (Figure 1а, a curve 4) an end-product - carbinol keeps the form of a band of predecessors, but has higher intensity

It is necessary to notice, that at the first stage of MG oxalate-ions hydrolysis are replaced with hydroxide-ions with formation immonium-basis I.e immonium cations remain At very low alkali concentration disappearance of dye band (Figure 1, curves 1-3) is accompanied by

Yu A Mikheev, L N Guseva, Yu A Ershov et al

6

simultaneous growth of an ultra-violet band (38 000 cm-1) which position in accuracy corresponds to the carbinol UV-band At such low KOH concentration reaction stops at presence isobiestic point on a spectrum Thus dye transforms in immonium hydroxide, carbinol precursor The solution becomes colorless, that is rather essential It testifies that in itself individual MG cations are not chromogenes

The MG oxalate hydrolysis end-product - leycocarbinol is formed at increase in alkali concentration with isobiestics infringement in a spectrum

Leycocarbinol has two alkilaniline groups absorbing UV-light at 38 000 cm-1 (263 nm) [13, 16] Therefore its UV-band is more intensive in comparison with MG immonium cations, having one alkilaniline group Received for carbinol value of extinction coefficient ε263 = 2.8×104 l/ (mole.cm), calculated on a spectrum 4 (Figure 1а), practically coincides with resulted in [15] The same size turns out from parity D617/D263 = ε617 / ε 263, that corresponds

to practically full transform of arils MG Ar-fragments in carbinol On a low-frequency slope

of a band of 38 000 cm-1 the excess in the range of 33 000 cm-1 (~ 300 nm) where according

to [13, 15] there is a weak additional carbinol absorption band is observed

Simultaneously with carbinol UV- bands in a spectrum 4 (Figure 1а) is observed a weak band at 28 000 cm-1 It belongs not MG cations, but to by-product Х which is formed at MG synthesis This collateral Х, too, as well as MG, is in an initial preparation of dye in oxalate form That a band ~ 28 000 cm-1 in its spectrum appear at big enough maintenance of alkali (Figure 1а testifies to it, a curve 4) in that interval of frequencies, where a spectral curve of dye (Figure 1а, the curve 1) has a minimum Oxalate product Х the group eliminates not only under the influence of alkali does not possess high firmness, and oxalate, but also at heating

in heptaneе

On Figure 1б represented the spectrum (a curve 1) of compounds, heptane extracted (volume of 10 ml) from initial MG sample (~ 100 mg) at ~ 100 ºС The received extract has been filtered through the paper filter and diluted in 2.5 times In this spectrum the UV-band

νmax = 30 300 cm-1 (~ 330 nm) of compounds Х have big enough intensity and is batohrome displaced to 28 000 cm-1 at replacement heptane by ethanol (Figure 1б, a curve 3) The maximum of the same band in heptane, saturated with ethanol, is located at 30 000 cm-1, and

in the ethanol saturated heptane at 28 250 cm-1 (350 nm) (Figure 1б, a curve 2) (Heptane and ethanol limited mix up with each other, forming two layers)

It is necessary to notice, that the compounds of type Х having the UV-bands with similar properties are found out in all investigated dyes It testifies that admixture compounds molecules in them have identical chromophore groups It is essential, that in spectra of solutions (Figure 1б, curves 1 - 3), received heptane extraction, are absent signs of bands of absorption of initial dye which practically we will not dissolve in heptane There are no also band signs MG carbinol forms (38 000 cm-1, see Figure 1а, a curve 4)

On Figure 1б the spectrum 3 characterizes ethanol solution received after heptane evaporation from heptane extract and the subsequent dissolution of the dry rest in ethanol It

is visible, that after transition in ethanol, the UV-band extracted compounds Х tests batohrome displacement concerning a heptane solution band However, the characteristic band of carbinol MG forms at 33 000 cm-1 here is absent This band appears only in the presence of alkali For example, the spectrum 2 (Figure 1б) is transformed to a spectrum 4 (Figure 1б) at addition in a solution of 20 mg KOH Alkali entering, apparently, is not reflected in the form and intensity of the UV-band at 28 250 cm-1, belonging to compound Х, however, thus there is characteristic for carbinol UV-band at 33 000 cm-1

Association Nature of Dyes Chromaticity 7

It is necessary to notice, that the spectrum 4 (Figure 1б) UV-light absorption is a little deformed in area ν>33 000 cm-1 by spectrum imposing turbidness from light-scattering KOH colloid particles Light scattering deformed the widened band at 40 000 cm-1 represents the sum of bands from formed carbinol and, probably, high-frequency band of compound Х

It is necessary to pay attention also that in a spectrum heptane extract 1 (Figure 1б) the UV-band with νmax = 41 200 cm-1 (243 nm) is clear expressed The considerable contribution

to this band absorption not having bands in visible area of a spectrum bring passed in heptane individual MG molecules, including immonium cations, but That fact testifies to presence of individual MG molecules in heptane extract, that band of 33 000 cm-1 arises under the influence of alkali (Figure 1б, a spectrum 4) at absence in the extract chromogene associates

of MG molecules Individual MG molecules can be a unique source of carbinol in this case only

Considering absence of visible bands of absorption of light at individual MG molecules,

it is necessary to assume, that formation dye chromogene associates from nonchromogene (colorless) molecules take place probably in this case by self-assemblage of these associates Such conclusion proves to be true that at evaporation colorless heptane solutions with a spectrum 1 (Figure 1б) on glass surfaces of vessels blue-green layers of dye are formed

Formation chromogene MG crystals from colorless MG molecules can be observed also

by means of a band chromatographic paper absorbing heptane solution and painted during movement on it and evaporation of solvent

As MG chromogenes can act not only MG oxalate crystal particles, but also dimers, formed of nonchromogene individual MG molecules at the expense of enough strong intermolecular interactions

The proof of that a band with λmax = 617 nm belong dimers molecules of MG oxalate, is change of intensity of this band, observed at mixture of two parts spirit solution MG with one part of ice acetic acid Value ε617 MG spirit solutions = 4.4×104 l / (mole.cm) In the mixed solution ε617 = 5.5·104 l / (mole.cm) Despite such increase, absorption coefficient oxalate MG

in a mix of spirit with acetic acid approximately in 2 times it is less, than at chloride MG in

98 % acetic acid (ε617=1.04·105 l/mole·cm) [4] The observable divergence of characteristics caused by distinction of the nature of solvents, is rather great Such influence should be expected at enough cmall size molecular associates, such as dimers

Heptane Extracts Spectra of Products of Malachite Green Hydrolysis

Independent evidence is received in experiences with heptane extracts of products of water-alkaline hydrolysis initial MG oxalate that individual MG cations do not possess chromogene property It is obvious, that thus chromogenes particles are formed only as a result of association of the molecules bearing on compensated electric charges of ionic pairs

As it was already marked, MG oxalate alkaline hydrolysis finds out, at least, two macroscopical kinetic stages clear observed on UV-spectra From the kinetic point of view hydrolysis reaction proceeds through three consecutive stages [12]

The first stages of MG oxalate alkaline hydrolysis - fast reaction of an exchange of oxalate ions on HO- anions going from cmall energy of activation:

(Ox–N+H(CH3)2–Ph'–С(Ph)=Pħ=N+–OCO–)2 + 2 HO– → (I)

Yu A Mikheev, L N Guseva, Yu A Ershov et al

8

2 Ox–N+H(CH3)2–Ph'–C(Ph)=Pħ=N+(CH3)2–OH + –OCOCOO–, (II) After this the stage of neutralization of ammonium ions proceeds

HO– + II → H2O + Ox– + N(CH3)2Ph'–C(Ph)=Pħ=N+(CH3)2–OH, (III)

In it the saltless form of hydroxide immonium is formed

The final, third stage of process is carried out, most likely, by reaction hydroxydeа immonium with HO- anion, attacking the central atom of carbon:

HO - + III → N (CH3) 2Ph '-C (OH) (Ph)-Ph '-N (CH3) 2 (carbinol) +-OH

Molecules II and III bear on one dimetilaniline group, whereas a carbinol molecule - two such groups According to it, intensity of a band of UV-absorption at a carbinol molecule should be twice more in the event that quinoid groups of compounds II and III do not bring the considerable contribution to the given UV-band Such situation it is possible to explain ν

= 38 000 cm-1 band strengthening in the conditions of the step hydrolysis, observed on spectra Figure 1а at transition from curves 1-3 (with isobiestic point) to a curve 4 (That quinoid groups in II and III have rather weak absorption in the range of frequencies 32 000 - 42 000

cm-1, proves to be true properties of compound X which will be considered later.)

UV-bands in the range of 33 000 cm-1 belonging immoniumе hydroxide (II, III) and carbinol, too differ on the intensity The spectra presented on Figure 2а proof to it So, the heptane extract spectrum in which forms immonium hydroxides II and III prevail, is presented on Figure 2а, a curve 1 The given solution has been prepared by heptane extraction (~ 10 ml) of the compounds formed at once after mixture spirit of a MG oxalate solution (~

50 mg in 20 ml of ethanol) with a water solution of alkali (to a consistence of 4 % KOH) and then diluted in 100 times At this spectrum there is implicitly expressed band at 33 000 cm-1 The subsequent extraction the compounds collecting in the same alkaline solution, has allowed to establish, that the band of 33000 cm-1 becomes more intensive during solution ageing

Similarly Rise in Temperature Operates Also at Extraction

On Figure 2а 2 and 3 spectra are presented of heptane extract received by heating (20 min) sample 54 mg MG oxalate to 10 ml of water alkali (5 %) at stirring about 10 ml heptane and filtering (dilution in 40 times and 320 times accordingly) In both spectra the clear maximum is observed at 33 200 cm-1, characteristic for a low-frequency band MG carbinol Mixture heptane extract with ethanol leads to formation of two layers, one of which represents the spirit heptane saturated The spectrum of such layer is presented on Figure 2а, a curve 4 In this spectrum the carbinol band at 33 000 cm-1 is washed away, losing a maximum and taking the form of a shoulder, practically repeating the form of the spectrum resulted in [13] We will notice also, that present at spectra 1-3 (Figure 2а) heptane solutions in the form

of an excess at 30 000 cm-1 the weak band of compound X, batochrome shift is in a spectrum spirit a solution heptane saturated, receiving clear expressed maximum at 28 000 cm-1 (350 nm)

Association Nature of Dyes Chromaticity 9

There is one more important feature: freshly prepared heptane extracts colored by alkali

MG oxalate form dye layers on glass ampoules and spectroscopic a ditch During ageing of water-alkaline solutions of compound II and III gradually turn in carbinole, and received of them heptane extracts give ever less a dye deposit In itself carbinole does not form the painted deposits

Formation of the painted deposits from molecules II and III proceeds with the big ease on the glass ampoules surface as adsorption of individual molecules gives them favourable mutual orientation Thus it is possible to use and chromatographic papers bands, immersing them in heptane solution containing compounds II and III Formed on a paper band during movement and evaporation heptane dye is easily washed off by spirit

The spectrum of eluate from a chromatographic papers band is presented on Figure 2б, a curve 1 It has not only a band of dye of 16 100 cm-1 (621 nm), but also rather intensive carbinol band at 37 900 cm-1 (264 nm) which too has been absorbed by chromatographic paper Formation of dye particles at adsorption goes in a competition to carbinol formation, and easily proceeds also on a powder not polar polyethylene oxide, not soluble neither in heptaneе, nor in spirit

(a) Figure 2 Continued on next page

Yu A Mikheev, L N Guseva, Yu A Ershov et al

10

(b) Figure 2 Optical spectra гептановых extracts of products of alkaline hydrolysis оксалата МЗ (a) and spirit eluates (b) of the compounds formed at adsorption of colourless products of MG hydrolysis on a filtering paper and polyethylene oxide particles Explanatory in the text

On Figure 2б spectra of 2-4 heptane extract from the concentrated water-alkaline solution

MG oxalate, after its mixture with ethanol (in the ratio 1:1) and entering into a mix of 2 mg polyethylene oxide powder are resulted Long-wave absorption bands of the spectra 2-4, observed right after mixing and through 4 and 26 ч accordingly, practically do not differ by the spectral position from bands MG oxalate in spectra spirit solutions and MG cations in 98

% acetic acid [4]

Spectra of Solutions and Extracts of the Crystal Violet

Spirit solution of CV sample spectrum, presented on Figure 3а (the curve 1), has a visible light absorption band at 17 380 cm-1 (575 nm), ε575 = 9.5×104 l / (mole.cm) We will notice, that in extinction coefficient calculations considered presence crystallization waters in CV powder: 18 molecules of water on 2 CV molecules [1, p.191] In CV water solution (Figure 3а, the curve 2) a band maximum of dye is at 17 000 cm-1 (588 nm), ε588 = 8.8×104 l / (mole.cm), that will be co-coordinated with data [1, 17] On spectra 1, 2 (Figure 3а) is present also a band not marked in the literature at 29 000 cm-1, belonging to admixture compound

XCV which molecules have chromophore group of type X

Spectral CV bands are stable enough in time both in spirit, and in water solutions, however, their intensity decreases at hit in solutions even rather low quantities of alkali Entering KOH to concentration of 10-3 mole/l in spirit solution with a spectrum 1 (Figure 3а) causes its decoloration during 1 – 2 sec Simultaneously there is a band at 38 000 cm-1 with low intensive shoulder at 33 000 cm-1 (Figure 3а, a curve 3) The given transformation

Association Nature of Dyes Chromaticity 11

reflects formation carbinol CV forms and actually repeats a situation with formation MG carbinol (Figure 1, a curve 4)

Observed in spirit a solution at 28 000 cm-1 a band (Figure 3а, the curve 1), belonging to compound XCV, does not change in the presence of alkali Dilution spirit heptaneом (spirit have evaporated to 0.3 ml and then have added heptane to 3 ml) has caused гипсохромное displacement of the given band to 29 000 cm-1 (Figure 3а, a curve 4)

Initial samples CV contain an impurity not only XCV, but also the rests not reacted leycobase (triphenilmethane derivative), used for CV synthesis Both compounds heptane extracted at heating on a water bath, however residual triphenilmethane it is dissolved at 25

ºС in heptaneе better, than XCV The spectrum of freshly prepared heptane extract of both compounds is presented on Figure 3б, a curve 1 Curves 2, 3 (Figure 3б) represent spectra of heptane solution received after loss from it (through 20) a colorless XCV deposit (spectra wrote down after filtering and разбавления initial heptane extract accordingly in 140 (1), 100 (2) and 280 times (3).)

Observed during ageing heptane extract spectral transformation testifies, that in a deposit passes mainly compound XCV (its band in heptaneе has νmax = 30 100 cm-1 (333) nm) whereas

in a solution remains triphenilmethane with an intensive band at νmax = 37 800 cm-1 (264.5 nm) and a weak band at 32 600 cm-1 (306 nm)

Repeated keeping in heptaneе parts of the deposit which has dropped out at 25 ºС, has given the solution of compound XCV close to saturation, with a spectrum 4 (Figure 3б) and

νmax = 30 100 cm-1 Dissolution of other part of a deposit in spirit has given a spectrum 5 (Figure 3б) with a band displaced to 27 200 cm-1 (367 nm) In both cases practically there are

no triphenilmethane absorption bands (with νmax = 37 800 and 32 600 cm-1) which has appeared will be better dissolved in heptaneе at 25 ºС, than XCV It is necessary to notice, that the UV-absorption spectrum of heptane solution triphenilmethane is very similar to a spectrum of absorption of spirit solution CV carbinol [13] However, as is known, carbinol is badly dissolved in heptaneе at 25 ºС [14, 15]

(a) Figure 3 Continued on next page

Yu A Mikheev, L N Guseva, Yu A Ershov et al

12

(b) Figure 3 Optical spectra of crystal violet solutions in various mediums (a) both extract

triphenilmethane residual and by-product XCF of synthesis of dye (b) Explanatory in the text

Good solubility in heptane compounds with νmax = 37 800 and 32 600 cm-1 allows to identify it with triphenilmethane Additional acknowledgment of that the given impurity is not carbinol, serves that processing spirit a solution (a spectrum 5, Figure 3б) chloride hydrogen does not lead to occurrence of spectral bands of dye - a reaction product carbinols with HCl Meanwhile, at processing of the same solution weak сернокислым a dichromate solution калия it gets color, characteristic for CV, that corresponds to the mechanicm of synthesis of the given dye [3, 4, 6,]

Let's notice, that in heptane extracts of CV powders, as well as in a case with extracts of powders MG, are present nonchromogene molecules CV which band of absorption masks absorption initial triphenilmethane and compounds XCV A presence nonchromogene molecule CV in heptane extracts is fixed on gradual release from heptane violet deposits on walls spectroscopic a ditch Similar process as it was marked, proceeds and in initially colorless heptane solutions nonchromogene molecules MG oxalate The painted layers especially quickly cover the ampoules glasses containing such extracts, in the conditions of heating on a water bath when molecules CV and MG have an opportunity to evaporate together with heptane and then are adsorbed on glasses Presence nonchromogene molecules

CV in heptane is easily defined the same as and in a case with MG, by means of a band chromatographic paper shipped in a colorless extract, on occurrence of violet coloring during moving of a solution and heptane evaporation

Properties of Alkaline Solutions of the Crystal Violet

The spectral picture of interaction CV with alkali qualitatively reproduces a situation with

MG So, an end-product of CV alkaline hydrolysis is corresponding carbinol, and formed at intermediate stages of hydrolysis individual molecules CV hydroxide immonium (type II and

Association Nature of Dyes Chromaticity 13

III) it is possible extract by heptane As it has appeared, heptane extracts in itself are colorless, however, being in them hydroxide immoniumя can, as well as in a case with MG, competely with carbinol formation to turn in supramolecularе dimers and larger units of violet color Unlike immonium hydroxide, colorless CV carbinol, as well as MG carbinol, does not give the painted products without special acid processing

Formation of layers of dye, as well as in a case with MG, easily proceeds at adsorption of molecules CV immonium hydroxide on glass ampoules, especially at their evaporation simultaneously with heptane Are evident as well experiences with a chromatographic paper band absorbing heptane extract immonium hydroxide

Let's notice, that considerable similarity of CV and MG hydroxides immonium spectra with spectra corresponding carbinols and their ability to form painted dimers, have served as the reason of occurrence of idea about carbinols dissociation on cation dyes and anions HO- at carbinol adsorption on firm surfaces [1, 13] It was supposed [1], that such dissociation especially easily proceeds at presence on ionized centers of firm surfaces Meanwhile, results

of the present work proof, first, that cation dyes are not chromogene, secondly, that process of formation of layers of dyes does not depend on presence ionized centers on adsorbents surfaces Really, the surface chromatographic papers contains only the HO- groups which polarity not bigger polarity of HO- groups of ethanol, and in ethanol CV and MG carbinols do not form chromogene structures in itself, without influence of acids At the same time immonium hydroxides easily form layers of paints even on a surface of particles not polar polyethyleneoxyde, and especially quickly if particle preliminary to moisten with ethanol for the purpose of plasticification and increase in molecular-segmental mobility

It is necessary to notice, that all described above property are characteristic as well for heptane extracts and for studied by us samples of diamond green (a spirit medical preparation) and methyl violet, spectra of which spirit solutions qualitatively coincide with

MG and CV spirit solutions spectra

Spectra and Properties of Compounds with Quinoid Structure of Molecules

As it was marked, all commercial dyes studied in the present work contain heptane extracted impurity, whose molecules possess chromophore groups responsible for occurrence

in heptane solutions of similar UV-absorption bands in the range of 30000 - 31 000 cm-1 (333

- 320 nm) These bands are equally displaced at replacement heptane on ethanol to 28 000

cm-1 (357 nm) Batohrome displacement of UV-bands at carrying over of the molecules possessing conjugated π-electronic system, from the hydrocarbonic environment in hydroxyl one, as is known, stimulates to increase in polarity of molecules at electronic excitation and accordingly about increase in energy of interaction with environment in comparison with not exitated molecules [1]

Cmall amount admixture of molecules with similar spectra in all studied samples of dyes

it is possible to explain, proposing the mechanicm applied in manufacture of dyes This processing include oxidizing of triphenilmethane in case of MG, DG, CV and oxidizing of initial compound - dimetilaniline in case of MV [3, 6, 18]

Oxidation triphenilmethane (general formula PhH1 (Ph2) CH-Ph'-N (CH3)2, here Ph1 and

Ph2 - phenyl groups having in para-position substitutants of corresponding dyes) - initiated

Yu A Mikheev, L N Guseva, Yu A Ershov et al

Here r• - a radical of the initiator

In parallel with carbinol formation chains of oxidation of CH3- (CH3CH2-) groups proceed:

ROO• (R1OO•) + R2• → ROOH (R1OOH) + Ph1(Ph 2) С=Pħ = NCH3 (X)

In technological synthesis of MV dye use oxidation dimetilaniline PhN(CH3)2 in which in system formaldehyde is formed Then consecutive condensation reactions of formaldehyde with molecules initial dimetilaniline and formed monometilaniline proceed For monometilaniline formation in system enter phenol PhOH [18] which serves as the donor of hydrogen for the nitric radical formed during oxidation, differing low reaction ability

Association Nature of Dyes Chromaticity 15

The subsequent endurance of the hydrochlorinated film on air within days leads to practically full restoration of a 28 600 cm-1 band (Figure 4, a spectrum 4) The lung spontaneous dehydrochlorination of muriatic salt X+HCl- testifies about weak quinoid compounds nucleophylity It is possible to explain presence at X the developed aromatic system interaction of π-electrons

Reversible hydrochlorination was observed as well with a spirit solution of compound

XCV: its UV-band with νmax = 27 800 cm-1 strongly reduced the intensity under the influence

of HCl, but again increased it at neutralization of acid by alkali

Figure 4 Spectra of triacetate cellulose (TAC) film in the thickness 40 microns in an initial condition (1); after absorption of compound XMG (2); after 30 min of endurance in steams of hydrochloric acid (3) and after endurance on air within days (4) Explanatory in the text

Yu A Mikheev, L N Guseva, Yu A Ershov et al

16

Experiments with reversible hydrochlorination of compounds XMG and XCV are important That proof to absence chromogene properties both at initial quinoid compounds, and at quinoid cations, i.e quinoid cations and electroneutral quinoid structures do not give to individual molecules of properties of dyes Thus the fact of loss by compounds XMG and XCVthe UV-bands at transition in cation form has a direct relation with the property known for aniline compounds

In this case occurrence of positive charges on atoms of nitrogen essentially complicates participation their electrons in aromatic π-systems photoexcitation [16]

Thus, single triphenilmethane dyes molecules, representing aromatic immonium cations with neutral aniline (or cation aniline groups), do not absorb visible light, as well as electroneutral phtalocyanine molecules And the same as and in a case phtalocyanine, chromogene particles of these dyes are formed as a result of self-assemblage enough strong supramolecular dimers and larger units under intermolecular forces

Spectral Properties of Individual and Aggregated Cation Xanthene Dyes

As VIP-representatives xanthene dyes (XnD) used rodamine B and rodamine G, forming

in water and spirit solutions of scarlet or raspberry-red color The structure of their molecules

is

Here symbols Y and X correspond:

Y = (C2H5) 2N, X = H for rodamine B; Y = (C2H5) HN, X = H for rodamine G

Let's notice, that the rodamine B ethyl ether (X = C2H5), named rodamine 3B, forms solutions with similar coloring It demonstrates that presence carboxyl (acid) group in xanthene molecules has no basic value for chromaticity display

Apparently, the structures of XnD molecules have certain similarity to molecules TFMD, such as the diamond green, malachite green and crystal violet At the same time, they more flat owing to rigid fixing of two 6-cycles through atom of oxygen while in molecules TFMD 6-cycles are cut rather each other under a cmall corner (30º) on type a propeller [4]

In works [17, 19-21], carried out about 50 years ago, it is established, that XnD films, as well as TFMD, undergo transformations at heating in hydrazine steams with formation of the colorless compounds possessing only UV-spectra with similar bands These transformations have been interpreted as consequence of similar chemical reactions At the same time, possessing flat molecules rodamine B, G, 3B, unlike TFMD, form colorless films with the same UV-bands as well for lack of steams hydrazine For this purpose enough simple heating

in atmosphere of helium or sublimation in vacuum with the subsequent condensation on

C

N(C2H5)2

COXO

+

Cl

-Association Nature of Dyes Chromaticity 17

quartz plates At sublimation temperature 70ºС the spectrum of condensed layer rodamineа B

is close to a spectrum of a film of the initial dye received by sedimentation from spirit solution In this case a visible light absorption band is considerably above accompanying absorption UV-bands However in process of sublimation temperature rise the sublimate spectrum changes, and at 145-160ºС received films possess three sharply expressed UV-bands with maxima at 235, 277 and 315-317 nm, many times surpassing the visible band responsible for coloring Precisely same bands are characteristic and for the films discolored

at 120ºС in helium atmosphere (750 mm Hg)

The important property of XnD films discolored in such a way is that they is reversible restore the initial color at storage on air, and not at the expense of reaction with oxygen, and under the influence of a moisture Besides, dye color is restored at dissolution of colorless films in water On the basis of the author results [17, 19-21] has excluded possibility of thermal disproportion of molecules XnD and has stated idea about course of their certain isomerisation At the same time the concrete nature of such reaction, and also structure of a colorless product, remained not opened

The question on the nature received in [17, 19-21] colorless rodamine films receives the necessary answer taking into account results of works [10-12] and considered above a result

on properties TFMD According to stated above, individual TFMD molecules absorb only UV-light At the same time, for chromaticity of the given dyes are responsible supramolecularе dimers and larger units consisting of mutually ordered molecules Besides, quinoid cation (immonium fragment of TFMD molecule), offered in the literature as TFMD chromogene Actually is not that as does not absorb light of a visible range Similar quinoid cation till now it is considered chromogene as well in a case xanthene dyes

Considering the new facts concerning the chromaticity nature, it is natural to believe, that XnD chromogene and, in particular, rodamine B and G, individual molecules, and them supramolecularе and larger units are too not In that case received in works [17, 19-21] rodamine colorless films should be considered as a film with amorphed structure consisting mainly from disorder placed individual molecules

Really, the fact chromogenity absence at individual molecules rodamine have established

by means of two techniques In one of them for registration of spectra of a rodamineа B molecules superseded water in heptane layer from a dye solution in spirit-heptane mixes In other molecules received by heating of the dye entered into TAC and cellophane films

Heptane Extracts Properties

Used in a case with heptane extraction TFMD molecules from powders has not led to positive result in application to xanthene powders Assuming, that xanthene individual molecules (or particles of an amorphous phase) can strongly enough occludates in a crystal lattice of dye, we used a technique with dissolution of powders in ethanol and the subsequent XnD molecules extraction from solutions

Optical spectra of rodamine B molecules heptane extracts are presented on Figure 5, curves 1, 2 For preparing of these solutions 1 mg of a dye powder dissolved in ethanol (2 ml) and diluted with pure heptane (4 ml) The received solution diluted with the distilled water (2 ml) Water action consisted, first, in heptane miscibility decrease with spirit, secondly, in extraction strengthening of rodamine molecules exfoliating heptaneом We will underline,

0, 270 and 30rty of all hepta

of visible light

re 5 the optica

um is resulted

n condensed isresult It has Uass intensity oible band the

of condensatull qualitative ated films (Fimate UV-banmilar displacemolutions in a s

re identical ch

discolored rodamogene forms in

n (8) Additiona

N Guseva, Yu

ot dissolved iceived colourl1) and 10 timeare in spectru

7 nm) gradualane solutions,

t and, accordin

al spectrum of

d at 145°C Bsomerisation pUV-absorptio

of a visible ban

e author [17, tion by molecconformity oigure 5, a cunds are batohroment is an eversolid [17] It aromogene gro

es (Figure 5, a

um UV-area

lly decrease wincluding an ngly, color

f 4 rodamineа

By the author product of rod

n bands λmax

nd observed in19] connectscules of the

f heptane soluurve 4) Someome displacedryday occurrenallows considoups

in heptane (1, 2TAC film: initia

B films, receiopinion [17, damine B mole

= 235, 277 an

n a spectrum w

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nd 317 nm with λmax =

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on of both cases

light-ayer (4) and ined in

Association Nature of Dyes Chromaticity 19

As it was marked, the author [17, 19-21] has found out the fact of regeneration of dye from colorless rodamine sublimate films on restoration characteristic for dyes of a visible band λmax ~ 550нм at a premise of films in steams of water or dissolution in liquid water On Figure 5 the spectrum 5 received at dissolution of a colorless rodamineа B film with a spectrum 4 in water [17] is resulted Apparently, in water there is a sharp growth of a visible band and decrease in UV-bands

Similar inversion of the specified bands takes place and in a heptane solutions case, and it can be carried out in two various ways We will underline, that in itself heptane solutions, being in glass ampoules, remain colorless long time (~ 4 months) At the same time it is enough to place a filtering paper band as its surface becomes covered by a layer of dye of raspberry-red color in such solution The formed layer of dye, insoluble in heptaneе, is easily dissolved in spirit

Dyeing can be recycled and another by For example, to colorless heptane to a solution (3 ml) with a spectrum presented on Figure 5, a curve 2, have added 4.5 ml of ethanol and 0.5

ml of water As a result of it the mix at first became мутно pink, but through ~ 20 mines мутность has disappeared and was formed water-spirit layer which spectrum is resulted on Figure 5, a curve 3 Apparently, this layer has an intensive visible band with λmax = 548 nm, and characteristic for heptane the UV-band solution in it have considerably lowered the intensity

The result with heptane extraction colorless rodamineа B fraction and regeneration of dye from heptane solutions has great value for understanding of the mechanicm of formation of rodamine colorless forms Really, extraction of the colorless rodamineа B form in experiences with heptane it was carried out at a room temperature, and experiment conditions excluded possibility dye molecules isomerisation The idea such isomerisation has arisen at the author [17, 19-21] owing to similarity of the UV-spectrum colorless sublimates with alkilamine group spectra of aniline compounds To what concern, in particular, rodamine leycobases (lactones) Meanwhile, lactone formation reaction (including intermediate compound formation previous lactone) proceeds only at very high alkali concentration [18] that is excluded in experiences with heptane extraction

Besides, as is known, lactones are intermediate compounds at xanthene dyes synthesis, and they transform in rodamine only with the assistance of protonic acids [18] In our experiences with adsorption on a filtering paper bands shipped in heptane solutions, rodamine

B dye was recycled for lack of acids Thus the dye which molecules bear on themselves carboxyl groups does not turn spontaneously to the colorless form at a room temperature On the basis of the told it is necessary to conclude, that being in heptane solution chromophore centers (with absorption UV-bands) belong to individual rodamine B molecules Adsorption

of these molecules bearing on flat chromophore groups, as well as adsorption of molecules TFMD, leads to fast regeneration chromogene rodamine particles thanks to that at adsorption

is provided oriental conformity for chromophore groups dispose (which in an individual kind are colorless) against each other At the same time, in liquid heptane the probability of realization such oriental conformity, apparently, is low Adsorption processes stimulate dye regeneration as well at mixture heptane solutions with an aqueous-alcoholic composition At initial stages of such mixture it is formed thin emulsion with the developed surface between aqueous-alcoholic medium and heptane microdrops

It is necessary to notice, that attempt repeated rodamine B molecules extraction from samples that have already been subjected such extraction, has shown practical absence of

Yu A Mikheev, L N Guseva, Yu A Ershov et al

Received in [17] UV-spectra of solid colorless sublimate films of rodamine B, 3B and G practically coincide with heptane extract rodamine B spectra On this basis it is possible to conclude, that sublimate films really represented amorphous state of dyes A little intensive visible bands thus present at their spectra at 550 nm belonged to microunits into which molecules have been packed as crystals, and units were formed in cmall amounts at condensation of colorless rodamine molecules of a steam phase

Thus, received for XnD results confirm the conclusion drawn earlier [12] about quinoid immonium fragment nonchromogenity which is present and in molecules TFMD Thus presence at individual molecules XnD and TFMD only UV-absorption bands as at leycobase molecules and leycocarbinoles, it is caused by that those and others bear on themselves aniline structures with alkilsubstituted amino groups

Spectroscopy of TAC films Containing Rodamines

Polymeric films used for thermal experiences which as a matter of fact represent updating

= 557 nm The last is combined with appreciable growth of two UV-bands belonging to individual molecules (the most short-wave UV-band with λmax = 230 - 235 nm in this case mask own UV-absorption of TAC film)

Containing rodamine B TAC film discolored as a result of heating does not change the spectrum (Figure 5, a curve 7) within a week Meanwhile, at film immersing in water its spectrum is quickly transformed with practically full restoration of a visible band of dye and leveling of UV-bands (Figure 5, a curve 8)

It is characteristic, that value λmax = 548 at the film shipped in water corresponds to this indicator of an aqueous-alcoholic solution of dye, whereas at a dry film λmax = 557 nm It can

be considered as the evidence of that chromogene rodamineа B particles in the placed in water film are in water nanodrops, formed as a result of water absorption

It is rather interesting, that water desorption from a wet film during its drying on air at

Тroom again leads to its full discoloration and spectrum restoration heated a dry film (Figure 5,

a curve 7) Repeated immersing of the dried up film in water causes again occurrence of a spectrum Figure 5, a curve 8, characteristic for chromogene particles As it has appeared,

Association Nature of Dyes Chromaticity 21

realization of several similar cycles does not lead to washing away chromogene particles from

a film

The picture of spectral transformations representing specific effect of memory and observed at Тroom, it will completely be connected with that the colorless rodamine B form are its individual molecules Really, in TAC films there are no both alkaline, and the acid compounds necessary for transfer of dye in leycoform and back with participation of corresponding intermediate compounds

It is necessary to notice, that the found out alternation at Тroom. processes of discoloration and coloring of films proofs that the colorless molecules formed as a result of painted units rodamineа B dissociation, remain in a polymeric matrix nearby with each other, without diffusing on a long distance Only full restoration of particles of dye in which quality should act supramolecularе dimers will be observed in this case

It is possible to make a certain notion about structure rodamine B dimers Most likely, in them molecules are focused flat quinoid fragments to each other whereas phenyl rings bearing carboxyl groups, are parted Tightening of two molecules in dimers is not connected with formation of chemical bonds between them, and caused by the synchronized dispersive interactions arising between π-systems of both molecules and, probably, occurrence of synchronous electric currents in these systems providing a mutual electromagnetic attraction

of molecules

On the basis of told it is possible to assume, that formed in initial films at solvent evaporation chromogene dimers are stabilized in a dry polymeric matrix in an environment of segments of the polymeric chains receiving certain mechanical pressure This pressure relax somewhat at film heating, changing a spatial configuration of the polymeric chain segments forming the nearest environment dimers, and simultaneously displacing dye molecules from each other As a result of such displacement it is broken rather weak noncovalent interaction

of molecules in dimers, and molecules appear as independent (in optical sense) the centers with absorption bands in UV-area spectrum

Immersing of the colorless films comprising deformed supramolecularе dimers, in water leads to their humidifying and, in certain degree, to plasticization with formation of water nanodrops around dimers Dye molecules inside water nanodrops become mobile and have an opportunity to realize power interaction among themselves, that leads to regeneration chromogene dimers

In the conditions of the subsequent drying of films rigidity of a polymeric matrix and chain segments of the nearest environment dimers is restored come back to that balance of mechanical pressure which has been received at heating of films Character of mutual displacement of dye molecules, components chromogene dimers simultaneously comes back Thus, considering nochromogenety individual molecules rodamineа B and chromogenety its physical dimmers, it is possible to describe specific effect of structural memory observed

on spectra that cannot be made proceeding from representation about chromogenityи individual molecules of dye

The similar effect of structural memory is reproduced in certain degree and on films TAC painted rodamine G by a technique described above

So, by heating (160ºС, more than 30 mines) can achieve practically full discoloration of such films that is presented on Figure 6 in the form of transition from a spectrum 1 to a spectrum 2 at considerable decrease in a visible band with λmax = 526 nm (νmax = 19 000 cm-

1) At the same time, a little big duration of heating for this purpose is required Besides,

the given sitciation of paincules rodamine

N Guseva, Yu

of restoration optical densitlowered optic

of coloring o

tuation realizanted dimers ro

e G can dispe

of their subseqNHC2H5 and molecules saene

G forms in filmsccordingly and planatory in the

u A Ershov et

of optical den

ty of thermallcal density of a

of films durin

ation of two podamine G in erse in the envquent meeting COOH at mo

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5 mines and 3 text

at plasticizatiolecules rodam

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- after saturation

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First, in the the part of polymer on

on of films mine G can

ot allowing

hane: 1, 4 -

n by water

Association Nature of Dyes Chromaticity 23

Spectroscopy of the Painted Cellophane Films

The results considered above force to reconsider known treatment of the spectral transformations observed at change of concentration of painted XnD solutions

At dyes of this type the properties specifying in occurrence associates in concentrated solutions [1, 22, 23] are brightly shown

So, for example, at concentration increase rodamine visible light absorption band of their water solutions are deformed Till now it is considered, that characteristic for very low concentration of dyes the basic maximum of a visible band belongs to individual molecules (monomers) The concentration increase leads to occurrence of the second maximum on short-wave recession of the basic visible band This maximum attributes dimers [1, 23] Rise

in temperature causes decrease in a new maximum so the form of a absorption spectrum of the concentrated solutions approaches with the spectrum form of weak solutions This spectral effect explains disintegration dimers

Now, on the basis of the new information that single molecules are not responsible for rodamine chromaticity, and them dimers, it is necessary to draw a conclusion, that occurrence

of new, more short-wave visible band is caused by dimers aggregation, existing already at the lowest dyes concentration

For the purpose of the additional proof of the given statement have made experiments with use of cellophane films differing from TAC films by presence of micropores, containing

in it not only XnD dimers, but also larger chromogene units

On Figure 6 is the spectrum of 4 of the cellophane films, absorbing rodamine G during 10 min from the mixed solution of 3.5 mg dye in 1 ml of spirit and about 20 ml of the distilled water

In a visible range of the given spectrum the dye band with λmax = 535 nm (ν=18 700 cm-1) which in the literature attribute to rodamine G monomers, and the short-wave band with λmax

= 505 nm (ν = 19 800 cm-1) is lased on it, attributed dimers

Heating of a film with a spectrum 4 (Figure 6) at 160 ºС during 5 min causes practically full disappearance of a band at 505 nm, accompanied by considerable growth of a band with

λmax = 535 nm (Figure 6, a spectrum 5) Simultaneously with it the UV-band with λmax = 350

nm (28 500 cm-1) considerably grows During the further heating intensity of band at 350 and

short-On the second phase of heating of films both dyes dimers dissociate with formation of the individual molecules which are not possessing absorption of visible light That leads to decrease in intensity of visible band like a situation with TAC films (Figure 5, curves 6,7;

Yu A Mikheev, L N Guseva, Yu A Ershov et al

24

Figure 6, curves 1,2) Thus visible band and long-wave UV-band (at 350 and 357 nm) of both rodamins decrease synchronously, that testifies to an accessory of these UV-band dimers the given dyes

Thus, for an explanation of the nature of chromaticity xanthene dyes, as well as in case of CuPc [10, 11] and TFMD [12], it is necessary to consider not only properties of individual molecules of these compounds, but also properties corresponding supramoleculare units Spectroscopy of Individual Molecules and Chromogenes

of Methylene Blue Dye

Flat molecular chromophore of methylene blue dye (MB), as well as TFMD and XnD chromophores, includes quinoid structure with immonium cation:

The positive cation charge is compensated by a negative chloride anion charge

In elementary MG crystal cell 4 molecules of MG and 16 molecules of water contain [1, 24] Forces of coupling in a crystal lattice do not allow to molecules of MG extract from a dye powder in all temperature interval of a liquid heptane (T <100ºC) Attempts to extract

MG individual molecules from spirit solutions too have not led to success In this connection for release of individual molecules and registration of their optical spectrum have spent thermal experiences with application of films of the cellophane, similar described above for rodamine

In work [19] the layer of MG on a quartz plate heats up at 135ºС within several hours per atmosphere of steams of water (pressure of 15-20 mm Hg) As a result of distillation with water steam and sublimate condensation on a pure quartz surface the transparent layer of a distillation product is formed The absorption spectrum of this product consists only of two band laying in UV-area, namely, with λmax=334 and 265 nm (Figure 7а, a curve 1) and practically completely coinciding with UV-band of the leyko-basis synthesized by reduction

of MG by gaseous hydrogen sulphide [24-26]

If the colorless layer with an initial spectrum 1 on Figure 7а long time is in atmosphere of humid air in the beginning it gets blue color (Figure 7а, a curve 2) Then, under the influence

of characteristic humidity for air, there is a continuous change of coloring of a layer As a result it becomes violet with a spectrum presented on Figure 7а, a curve 3 Solution of colorless sublimate in water instantly turns to a dye solution

The author [19] has not offered a concrete explanation to the found out fact, having limited to ascertaining, that colorless compound is a product of interaction of molecules of

MG with water and possesses properties of the leyko-basis

S N

N

Association Nature of Dyes Chromaticity 25

From considered for TFMD and XnD a material the colorless product received by distillation with water steam follows, that, represents such condensate in which orientation of molecules of MG from each other corresponding hromogene structures

Really, as it is established for individual molecules TFMD and XnD, in itself quinoid groups of molecules are not chromogenes Besides, its do not bring the essential contribution

to absorption of UV-light in the field of 250-400 nm For this reason quinoid groups of molecules of MG cannot essentially deform the UV-band at 334 and 265 nm observed at colorless MG sublimates and belonging dimetilaniline groups In other words, individual MG molecules should have the same two UV-absorption band, as a molecule of the reducted leyko-form

For the purpose of independent check of the given conclusion thermal experiences have carried out with the MG entered into cellophane films by absorption from a water solution of dye Solution prepared, dissolving 4 mg of a MG powder in 1 ml of ethanol and mixing about

15 ml of the distilled water In it placed on 10 min cellophane film in the thickness 40 microns The spectrum of the film painted in such a way contains two band of absorption of visible light imposed against each other with λmax = 668 and 613 nm (Figure 7б, a curve 1)

At the initial stage of absorption of MG the short-wave band at 613 nm has no obviously expressed maximum, but grows in a course of process and at last stages can exceed a long-wave band at 668 nm as last ceases to grow The picture observed thus qualitatively repeats transformation of visible band of absorption of water solutions at increase in them concentration of MG [24] Unlike absorption band in visible area of a spectrum, a ratio of maxima of UV-band of dye with λmax = 294 and 248 nm considerably do not change at increase in the maintenance of dye in films and water solutions

The effects observed at heating of films, containing MG, qualitatively same, as in a case with the films containing rodamineы

So, heating of a film with a spectrum 1 (Figure 7б) at 133ºС between steel surfaces of elements of the press form during short time (1 min) leads to practical disappearance of short-wave peak (at 613 nm) and to considerable growth of optical density from 1.8 to 3.0 long-wave band λmax = 668 nm For this short time of the UV-band of dye with λmax = 294 and 248

nm practically do not change the position and intensity During the further heating a visible band λmax = 668 nm (attributed as in a case with TFM and XnD, to monomers [1, 24]) strongly decrease It leads to considerable discoloration of a film (Figure 7б, a curve 3, 130 mines of heating) For same time of heating in a film spectrum UV-band of dye with λmax =

294 and 248 nm disappear and there are UV-band at 334 and 265 nm belonging dimetilaniline groupings

Yu A Mikheev, L N Guseva, Yu A Ershov et al

26

Figure 7 Changes of spectra: (a) - a layer of the colorless compound (1) formed as a result of

sublimation of MG dye in water steams (temperature 135ºС, steam pressure 15 mm Hg), at storage on air during 2 h (2) and 200 h (3); (b) - a cellophane film with the absorbed MG (1) at heating (133ºС) during 1 min (2) and 130 min (3), after 50 min of keeping heated films in a ditch with water (4), the water which have remained in a ditch after removal of a film (5) A spectrum of an initial film - (6) Observable changes of a spectrum of a film with MG dye allow, as well as in a case with rodamins, to conclude, that heating leads at first dissociation of large chromogene MG units with formation supramolecular dimers Then occurs диссоциация dimers or their transition in dimers with nonchromogene orientation of MG molecules from each other

After immersing warmed films in water coloring regeneration is observed, and a part of dye desorbed in water

Association Nature of Dyes Chromaticity 27

On Figure 7б the curve 4 corresponds to total light absorption of a film with water in spectroscopic a ditch, and a curve 5 - to a spectrum of the water which have remained in a ditch after withdrawal of a film Dye regeneration does not lead to restoration of initial intensity of visible light absorption band (the curve 4 below a curve 1), That can be connected with evaporation of a part of MG molecules from a film during heating Besides, as a result of heating there can be a change of structure of units to formation of the particles which lost or have lowered chromogene property

It is necessary to note presence of an intensive band with λmax = 265 nm and much less intensive band at 330 nm in a spectrum 3 (Figure 7б), characterizing warmed a film Both these band correspond to UV-band of a colorless product of distillation with the water steam, received in [19] In our case the product with these two UV-bands has been received without participation of water steam Hence, the corresponding leyko-form cannot be explained chemical reaction of molecules of MG with water

Regeneration MG chromogene forms at immersing warmed films in water too corresponds to the effect which has been found out in [19] As a whole, character of spectral transformations of a MG film qualitatively corresponds to the transformations observed by us for films, containing rodamineы B and G On this basis it is possible to conclude, that distillation with water steam in experiences [19] really led to formation of firm layers in which molecules of MG had no the mutual orientation necessary for display chromogene properties

It is necessary to notice, that on Figure 7б the weak visible light absorption band - a curve

5 is observed The band form differs from an initial curve 1 (with two maxima) and a curve 2 (with a long-wave maximum at 668 nm) This residual absorption band is caused chromogene units of MG molecules rather steady against heating Destruction of these residual units by the further heating did not observe, since experience stopped earlier that moment when the heated up cellophane film starts to turn yellow owing to thermal destruction

It is possible to make following, the general for the studied dyes, a conclusion Chromaticity of triphenilmethane, xanthene and thiazene dyes does not grow out of optical electronic transitions between occupied and vacant orbitals of individual molecules Electrons photoexcitation at the given dyes are carried out in supramolecular units possessing mutual orientation necessary for it of molecules and suficient stability The received results changes supposition about the monomer nature of chromaticity of the given organic dyes and put forward a problem which decision is beyond quantum chemistry of individual molecules

[1] Terenin AN Photonics of dyes and organic compounds molecules L Nauka, 1967 [2] Nonbehzoid aromatic compounds Ed D Ginsburg Inostrannya literature М.:1963 [3] Nenicesku KD Organic chemistry Inostrannya literature М.:1963

[4] Gordon P., Gregory P Dye’s organic chemistry М Mir, 1987

Yu A Mikheev, L N Guseva, Yu A Ershov et al

[9] Symon J., Andre J Molecular semiconductors М Mir, 1988

[10] Miheev YA., Guseva LN, Ershov YA.// J Physical Chemistry (russian) 2007 V.81

[13] Perekalin VV ea, J Common Chemistry 1952 V.22 №5 P.821

[14] Villiger L., Kopetschni E.//Chem Berichte 1912 B.45 №13 P 2910

[15] Harris L., Kaminsky J., Simard R.G.//J Amer Chem Soc 1935 V.57 №7 P.1151 [16] Stern E., Timmons K Electronic absorption spectroscopy in organic chemistry М Mir,

1974

[17] Vartanian AT.// J Physical Chemistry (russian) 1956 V.30 №5 P 1028

[18] Kogan IM Dye’s chemistry (synthetic) М ONTI, 1938

[19] Vartanian AT//Izvestya USSR AS, physical (russian) 1956 V.20 №4 P 448

[20] Vartanian AT// J Physical Chemistry (russian) V.35 №10 P 2241

[21] 21 Vartanian AT// J Physical Chemistry (russian) 1962 V.36 №9 P.1890

[22] Levshin V.L // Izvestya USSR AS, physical (russian).1956 V 20 №4 P.397

[23] Levshin V.L., Baranova EG.// Izvestya USSR AS, physical (russian) 1956 V 20 №4

P 421

[24] Vartanian AT // J Physical Chemistry (russian) 1955 V.29 №8 P.1445

[25] Vartanian AT.// J Physical Chemistry (russian) 1955 V.29 №7 P.1304

[26] Vartanian AT // Izvestya USSR AS, physical (russian) 1954 V 18 №4 P 731

In: Advances in Chemistry Research Volume 8 ISBN 978-1-61209-089-4

Chapter 2

Maurizio Penco*,1, Stefania Della Sciucca1, Gloria Spagnoli1

and Luca Di Landro2

1Dipartimento di Chimica e Fisica per l’Ingegneria e i Materiali,

University of Brescia Italy

2Dipartimento di Aeronautica, Politecnico di Milano, Italy

The structural relaxation of polymers depends on the kinetic character of the transition phenomenon: amorphous polymers below their Tg are not at equilibrium and their structures continuously relax in attempt to reach the equilibrium state Several phenomenological and molecular approaches have been proposed to describe the structural relaxation but a universal model is still lacking The enthalpy relaxation of glasses is usually described with models developed on the basis of Tool-Narayanaswamy-Moynihan (TNM) theory [1,2]: it is assumed that the instantaneous relaxation time(s) (τ) for enthalpy relaxation depends on both the temperature (T) and the structure of the glass, identified by its fictive temperature (Tf) This approach is able to describe the enthalpy relaxation in low-molecular-weight glass-forming system fairly well [3,4], but discrepancies have been observed in several polymeric systems [5,6] One of these discrepancies concerns the overestimation of enthalpy lost on aging the samples for long periods of time Hodge [7], Gomez Ribellez [8] and Cowie [9] ascribed this features in polymers to the effect of topological constraints, such

glass-as chain entanglements, which are completely ignored in the TNM-bglass-ased models