Synthesis, crystal structure and excellent photoluminescence properties of copper (II) and cobalt (II) complexes with Bis (1[(4-butylphenyl)imino]methyl naphthalen-2-ol) Schiff base

Encouraged by the photoluminescence properties of metal complexes derived from Schiff bases, an attempt has been made to synthesize and study the photoluminescent properties of Copper (I[r]

Trang 1

Original Article

Synthesis, crystal structure and excellent photoluminescence

properties of copper (II) and cobalt (II) complexes with Bis

(1[(4-butylphenyl)imino]methyl naphthalen-2-ol) Schiff base

V.B Nagavenia,b, K.M Mahadevana, G.R Vijayakumarc,*, H Nagabhushanad, S Naveene,

a Department of Chemistry, Kuvempu University, P G Centre, Kadur, 577548, India

b Department of Chemistry, Government Science College, Chitradurga, 577501, India

c Department of Chemistry, University College of Science, Tumkur University, Tumakuru, 572 103, India

d Prof C.N.R Rao Centre for Advanced Materials Research, Tumkur University, Tumakuru, 572 103, India

e Department of Basic Sciences, School of Engineering & Technology, Jain University, Bangalore 562 112, India

f Department of Studies in Physics, Manasagangotri, University of Mysore, Mysuru, 570006, India

a r t i c l e i n f o

Article history:

Received 30 September 2017

Received in revised form

31 December 2017

Accepted 16 January 2018

Available online 31 January 2018

Keywords:

1[(4-butylphenyl)imino]methylnaphthalen-2-ol

Schiff base

Cu (II) and Co (II)complex

Photoluminescence

Single crystal XRD

OLED

a b s t r a c t Copper (II) and Cobalt (II) metal complexes (4a- and 4b-complexes) using Schiff base ligand 1-[(4-butylphenyl)imino]methyl naphthalen-2-ol (3) have been synthesized The single crystals of Copper (II) and Cobalt (II) complex phosphors were grown and characterized by Fourier-Transform Infrared (FT-IR), single crystal X-ray diffraction (XRD), SEM (Scanning Electron Microscope) and EDS (Energy Dispersive X-ray spectroscopy) Photoluminescence study of the phosphors revealed the presence of excitation peaks at 333 nm and 360 nm for 4a-complex (lemi¼ 495 nm) and excitation peaks at 300 nm and 360 nm for 4b-complex (lemi¼ 496 nm) The calculated CCT values of the complexes pointed out that these materials can be used to obtain cold white light from the light emitting devices Diffuse

reﬂectance spectra (DRS) showed the measured band gap energies of 1.78 eV and 1.44 eV for Cu (II) and

Co (II) complexes, respectively It is concluded that the 4a- and 4b-complexes become white and blue green light emitting diodes respectively and will be useful in the development of strong electrolumi-nescent materials

© 2018 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

1 Introduction

New metal-organic ligand materials with efﬁcient light emitting

properties have attracted many researchers in recent years[1e3]

due to their prospective applications as organic light-emitting

di-odes (OLEDs)[4e6], light emitting electro-chemical cells (LEECs)

[7], lumophores for cell imaging [8,9], conductors and

semi-conductors [10e13] Some organic transition metal complexes,

which exhibit strong luminescence at low driving voltages, are of

much interest for designing a ﬂat panel display system [14,15]

Additionally, transition metal complexes of Schiff bases have

received signiﬁcant importance in material chemistry owing to

their wide range of applications[16e18] Metal complexes of Zn (II),

Pt (II), Co (III), Cu (II) and Ag (I) with Schiff bases were described as luminescence organic materials that are used in organic optoelec-tronics [17,18e21] In particular, cobalt complex [Co(PLAGeþ2H)(NH3)3]NO3 was reported as a higher photo-luminescence material [22] and the methanolic solution of {[Cu(2,5-pdc)(H2O)4]$H2O} complex exhibitsﬂuorescence at room temperature [23] Further, the novel Cu (I) complex of [Cu(ABPQ)(DPEphos)]BF4 was shown to be a good photo-luminescence material[24e27] Recently, copper (II) complex with (1R, 2R)-cyclohexanediamine derived Schiff base has been pre-pared and used as a dye for light emitting devices due to its excellent luminescence properties[28]

Encouraged by the photoluminescence properties of metal complexes derived from Schiff bases, an attempt has been made to synthesize and study the photoluminescent properties of Copper (II) and Cobalt (II) complex phosphors (4a- and 4b-complexes) of

* Corresponding author.

E-mail address: vijaykumargr18@gmail.com (G.R Vijayakumar).

Peer review under responsibility of Vietnam National University, Hanoi.

Contents lists available atScienceDirect Journal of Science: Advanced Materials and Devices

j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d

https://doi.org/10.1016/j.jsamd.2018.01.001

Journal of Science: Advanced Materials and Devices 3 (2018) 51e58

Trang 2

Schiff base ligand 1-[(4-butylphenyl)imino]methyl

naphthalen-2-ol (3) As suggested by their structures, the prepared complexes

include high electron mobility and are soluble in organic solvents

The present work has been carried out based on our earlier

in-vestigations on OLED materials, which yielded prominent results

[29,30]

2 Experimental

2.1 Materials and methods

Chemicals and reagents used for the synthesis and analysis were

procured from a commercial supplier, Sigma Aldrich, India

Analytical grade solvents were purchased from SD Fine Pvt Ltd.,

Mumbai, India and used as such without puriﬁcation Melting

points of the synthesized compounds were carried out by an open

capillary method using electrical heating apparatus The wave

number range from 650 cm1to 4000 cm1was used for recording

Fourier-Transform Infrared (FT-IR) spectra of the samples using

Agilent FT-IR Spectrometer Proton Nuclear Magnetic Resonance

(NMR) spectrum of the ligand was recorded using JEOL 500 MHz

NMR instrument X-ray diffraction data were collected at RT using

Bruker Proteum2 CCD diffract meter Diffuse Reﬂectance Spectra

(DRS) of the samples were recorded using l35 Perkin-Elmner

UVeVisible Spectrophotometer Photoluminescence (PL) spectra

of the prepared samples were recorded on Jobin Yvon

Spectro-ﬂourimeter Fluorolog-3 which used 450W Xenon lamp as an

excitation source Surface morphology of the compounds was

studied using Hitachi (Table top, Model TM 3000) Scanning

Elec-tron Microscope (SEM)

2.2 Synthesis of ligand 1-[(4-butylphenyl)imino]methyl

naphthalen-2-ol (3)

The solution of 4-butylaniline (1) (6.0 mmol) in dry ethanol

(15 mL) was stirred on a magnetic stirrer at room temperature An

ethanolic solution (15 mL) of

2-hydroxynapthalene-1-carbaldehyde (2) (6.0 mmol) was added slowly to the stirring

so-lution of 1 followed by the addition of catalytic amount of acetic

acid The resulting reaction mixture was continued to be stirred for

4 h at the same temperature, during which the color of the solution

changes to yellow The TLC (mobile phase pet-ether:ethyl acetate

70:30 v/v) revealed the product formation, after which the solvent

was removed under vacuum and triturated with petroleum ether

(15 mLx2) to afford the ligand (3) as yellow solid The yellow solid

was subjected to recrystallization using hot ethanol Yield: 90%,

mp: 68e70 C IR (KBr), (n, cm1): 3054(¼CeH), 2928(CeH),

2854(CeH), 1619(C]N), 1214(CeO).1H NMR(400 MHz, DMSO-d6):

d(ppm) 0.92 (t, J¼ 6.00 Hz, 3H), 1.29e1.31 (m, 2H), 1.55e1.57 (m,

2H), 2.63 (t, J¼ 6.00 Hz, 2H), 6.99 (d, J ¼ 7.20 Hz, 1H), 7.31e7.35 (m,

3H), 7.52e7.56 (m, 3H), 7.78 (d, J ¼ 5.20 Hz, 1H), 7.91 (d, J ¼ 7.20 Hz,

1H), 8.48 (d, J¼ 6.40 Hz, 1H), 9.64 (s, 1H)

2.3 Synthesis of Cu (II) complex (4a-complex)

A mixture of ligand 3 (5 mmol) in hot ethanol, CuCl2$2H2O

(2.5 mmol) and triethylamine (5 mmol) was reﬂuxed for 8e10 h

The Cu (II) complex (4a-complex) was precipitated out as brown

solid after cooling the reaction mixture to room temperature The

solid wasﬁltered, washed with ethanol and dried in vacuum The

product 4a-complex was further puriﬁed by recrystallization using

a mixture of chloroform and hexane (1:1 v/v) which afford brown

crystals of the complex Yield: 80%; mp: 180e184C; IR (KBr), (n,

cm1): 3021(CeH), 2926(¼CeH), 2854(CeH), 1614(C]N),

1215(CeO), 526(MO)

2.4 Synthesis of Co (II) complex (4b-complex)

A mixture of ligand 3 (5 mmol) in hot ethanol, CoCl2$6H2O (2.5 mmol) and triethylamine (5 mmol) was reﬂuxed for 8e10 h The Co (II)complex (4b-complex) was precipitated out as dark vi-olet colored solid after cooling the reaction mixture to room tem-perature The product 4b-complex was worked up and recrystallized as described in the earlier procedure (4a-complex) Yield: 80%; mp: 235e240 C; IR (KBr), (n, cm1): 3022(CeH), 2926(¼CeH), 2851(CeH), 1613(C]N), 1253(CeO), 526(MO)

3 Results and discussion 3.1 Formation of 4a- and 4b-complexes The reaction between amino group of 4-butylaniline (1) and aldehyde group of 2-hydroxynapthalene-1-carbaldehyde (2) afforded the Schiff's base ligand 1-[(4-butylphenyl)imino]methyl-naphthalen-2-ol (3) [29] Reaction conditions and the use of catalyst were the key parameters in obtaining product with satisfactory yield In the preparation of 3, acetic acid was used as a catalyst The product 3 was puriﬁed by recrystallization, charac-terized by FT-IR and NMR spectral analysis and utilized for further step to get Cu (II) and Co (II) complexes Metal salts CuCl2$2H2O and CoCl2$6H2O were reacted with 3 in the presence of triethyl-amine as a mild base to afford the 4a-complex and 4b-complex, respectively The reaction scheme followed for the synthesis of Cu (II) complex (4a-complex) and Co (II) complex (4b-complex) is shown inFig 1 During theﬁnal reaction one equivalent of metal reacted with two equivalents of ligand which produced a four coordinated complex (4a-complex and 4b-complex) The solvent mixture chloroform:hexane (1:1) was found to be suitable for the recrystallization of both 4a-complex and 4b-complex Structures

of the complexes were established from single crystal X-ray diffraction studies (Fig 2) The single crystal X-ray diffraction conﬁrms the trans orientation for 4a-complex and cis orientation for 4b-complex with respect to two N and two O donor atoms of the ligand Even though the ligand is same for the two complexes, the opposite orientation of the donor atoms in 4a-complex and 4b-complex may be due to unequal size and different interaction of metals with the ligand The square planar geometry with reference

to metal and donor atoms in the 4a-complex has been conﬁrmed from the bond angles of O1eCu1eN1 (~90), O1eCu1eO1 (180 and N1eCu1eN1(180) But the planarity was almost lost in the 4b-complex, which resulted in distorted square pyramidal geom-etry having cobalt at the apical position and four donor atoms of the ligand occupy the basal equatorial positions with slight changes in the regular bond angles The L-M-L bond angles (º) of 4b-complex were found to be O2eCo1eO1 (88.27), O2eCo1eN1

(155.98), O1eCo1eN1 (91.54), O2eCo1eN2 (92.28), O1eCo1eN2

(151.66) and N1eCo1eN2(99.05)

3.2 Single crystal X-ray diffraction studies Bruker Proteum 2 CCD diffractometer equipment operated at

45 kV, 10 mA and radiation of wavelength 1.54178 Å was used for the collection of X-ray data of the samples The complete crystal data and data refinement for the structures of 4a-complex and 4b-complex are given inTable 1 SAINT PLUS[31]soft ware was employed for processing of the data set of the samples Full-matrix least squares method on F2 using SHELXS and SHELXL programs [32] were used to solve the structures of the com-plexes The non-hydrogen atoms were identified in the first difference Fourier map and hydrogen atoms were positioned geometrically and refined using a riding model PLATON[33]and V.B Nagaveni et al / Journal of Science: Advanced Materials and Devices 3 (2018) 51e58

52

Trang 3

MERCURY [34] software programs were used for geometrical

calculation and generation of molecular/packing diagrams

respectively

3.3 UV-Visible spectrum

Diffuse reﬂectance (DR) study can be useful to know the

conductance properties of the materials and hence the study was

carried out for the synthesized materials DR spectra were

measured in the range 200e1000 nm (Fig 3) The major peaks

were identiﬁed in the range 300e400 nm, which may be

accounted for the transition of electrons from the valence band to

the conduction band The transitions involving surface traps or

impurities resulted in the weak absorption in UV-Visible region of

the spectra Band gaps of the complexes were determined from

the respective DR spectra by using KubelkaeMunk theory The

intercept of the tangents to the plots of [F(R∞)hn]1/2 versus

photon energy hn was shown in Fig 3(b) The KubelkaeMunk

function F(R∞) and photon energy (hn) were calculated using

the following equations:[35]

FðR∞Þ ¼ð1 R∞Þ2

hn¼1240

where R∞ ¼ sample reﬂection coefﬁcient; l ¼ absorption wavelength

The measured band gap energy for 4a-complex and 4b-complex were found to be 1.78 eV & 1.44 eV respectively It was clearly indicated from the band gap energy values that the allowed direct transitions were responsible for the inter band transitions Reaction conditions used for the preparation of materials were directly responsible for the Eg values These conditions may inhibit or favor the formation of defect, control the degree of structural order-disorder and consequently the number of intermediary energy levels within the band gap

3.4 Photoluminescence

PL Spectra of the 4a- and 4b-complexes recorded at room temperature are given in Fig 4 The photoluminescence study revealed that the excitation peaks at 333 nm and 360 nm for 4a-complex atlemi¼ 495 nm, and the peaks at 300 nm and 360 nm for 4b-complex at lemi ¼ 496 nm were appeared The Commission International De I-Eclairage (CIE) 1931 chromaticity co-ordinates [36,37] under different excitations were calculated for the

H O O H

Ethanol

Reflux, 8 h

AcOH

N

O H

MCl2.6H2O Ethanol, Et3N

RT, Stirr, 4-5 h

3

+

N O

C

N O

M

N O

C

N O M

Fig 1 Reaction scheme for the synthesis of bis(1[(4-butylphenyl)imino]methyl naphthalen-2-ol) Cu (II) (4a-complex) and bis(1[(4-butylphenyl)imino]methyl naphthalen-2-ol)Co (II) (4b-complex).

V.B Nagaveni et al / Journal of Science: Advanced Materials and Devices 3 (2018) 51e58 53

Trang 4

Fig 2 ORTEP of 4a- and 4b-complexes with thermal ellipsoids drawn at 50% probability V.B Nagaveni et al / Journal of Science: Advanced Materials and Devices 3 (2018) 51e58 54

Trang 5

Table 1

Crystal data and structure reﬁnement details for 4a- and 4b-complexes.

Cell dimensions a ¼ 6.9703 (5) Å, b ¼ 8.5861 (7) Å, c ¼ 14.9618 (12) Å

a¼ 88.264 (2) ,b¼ 87.177 (2) ,g¼ 66.336 (2)

a ¼ 10.4699 (6) Å, b ¼ 26.1070 (15) Å, c ¼ 13.0709 (8) Å

a¼ 90.00 ,b¼ 107.623 (2) ,g¼ 90.00

10 k 10

17 l 17

12 h 12

30 k 29

13 l 15

0 5 10 15 20 25 30 35 40 45

Wavelength (nm)

4a-complex

(a)

0 100 200 300

Energy (eV) 1.78 eV

4a-complex

0 5 10 15 20 25 30 35

40

(a)

Wavelength (nm)

4b-complex

0 50 100 150 200 250 300

350

(b)

Energy (eV) 1.44 eV

4b-complex

Fig 3 (a) Diffuse reﬂectance spectra of Cu (II) complex (4a-complex) and Co (II) complex (4b-complex) (b) Plots of [F(R ∞ )hn] 1/2 against photon energy (hn) for these two samples,

Trang 6

complexes The estimated CIE values were found to be X¼ 0.33474;

Y¼ 0.34496 for 4a-complex and X ¼ 0.22326; Y ¼ 0.34695 for

4b-complex The location of the color coordinates were represented in

the CIE chromaticity diagram by solid circle sign (star) indicates the

color appearance of the sample powder From thisﬁgure, one can

conclude that the 4a-complex and 4b-complex located in the white

and blue green region so that these complexes become promising

white and blue green light emitting diodes, respectively

The correlated color temperature (CCT) is a speciﬁcation of the

color appearance of the light emitted by a light source, relating its

color to the color of light with respect to a reference light source

when heated up to a speciﬁc temperature, in Kelvin (K) The CCT

rating for a lamp or a source is a general‘‘warmth’’ or ‘‘coolness’’

measure of its appearance However, opposite to the temperature scale, lamps with a CCT rating below 3200 K are usually considered

‘‘warm’’ sources, while those with a CCT above 4000 K are considered‘‘cool’’ in appearance

Correlated Color Temperature (CCT) can be estimated by Planckian locus, which is only a small portion of the (x, y) chro-maticity diagram and there exist many operating points outside the Planckian locus CCT values were determined as described in the earlier reports[25]and were found to be ~5400 K (atlexi¼ 333 nm) and ~5755 K (atlexi¼ 300 nm) for 4a- and 4b-complexes respec-tively Since the CCT values for both complexes were above 4000 K, these could be used as a cold light emitting source in commercial lightening applications

0.2 0.4 0.6 0.8 1.0 1.2 1.4

Wavelength (nm)

4a-complex

333 nm

360 nm

(a)

0.0 0.5 1.0 1.5 2.0 2.5 3.0

3.5

360 nm

300 nm

Wavelength (nm)

4b-complex

(a)

0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6

Wavelength (nm)

4a-complex

457 nm

550 nm

(b)

1.5 1.6 1.7 1.8

1.9

496 nm

Wavelength (nm)

411 nm 4b-complex

(b)

(c)

0.0 0.3 0.6 0.9

CIE X

λexi = 300 nm

4b-complex

(c)

0.0 0.3 0.6 0.9

CIE X

4a-complex

Fig 4 Photoluminescence spectra of the complexes: (a) excitation spectra, (b) emission spectra, and (c) CIE graphs for 4a-complex (X ¼ 0.33474; Y ¼ 0.34496) and 4b-complex (X ¼ 0.22326; Y ¼ 0.34695).

Trang 7

3.5 SEM and EDS studies

The surface morphology of 4a- and 4b-complexes was studied

by using scanning electron microscope images and composition of

the complex was revealed by energy dispersive X-ray spectroscopy

(EDS) analysis of the respective complexes The SEM and EDS

im-ages of 4a- and 4b-complexes are shown inFig 5 Broken pieces

with smooth surface morphology for 4a-complex and soft surface

stone like morphology for 4b-complex were observed in the

respective SEM images Further these metal complexes were

sub-jected to EDS analysis to conﬁrm the composition of the complexes

and experimental values as shown in Table 2 The EDS spectra

(Fig 5) conﬁrm the elemental composition of copper, carbon and

oxygen in 4a-complex and cobalt, carbon and oxygen in

4b-complex

4 Conclusion

In summary, the two transition metal complexes of Cu (II) and

Co (II) containing Schiff base ligand 1-[(4-butylphenyl)imino]

methyl naphthalen-2-ol (3) were synthesized using mild reaction

conditions, and their physical properties were studied The single

crystals of the complexes were grown and structures were

identi-ﬁed by the single crystal XRD analysis The structures 4a-complex

and 4b-complex were further characterized by FT-IR, SEM and EDS studies

PL spectrum of 4a-complex showed the excitation peaks at

333 nm and 360 nm for the emission wavelength of 495 nm Similarly, 4b-complex yielded the excitation peaks at 300 nm and

360 nm for the emission wavelength of 496 nm The band gap energies were determined from the DRS study to be 1.78 eV (4a-complex) and 1.44 eV (4b-(4a-complex) The SEM images of the ma-terials revealed smooth broken piece surfaces for 4a-complex and the soft surface stone morphology for 4b-complex Both the com-plexes were highly soluble in THF, DMF and DMSO and found to be suitable for fabricating electroluminescent devices Due to their excellent photophysical properties, these complexes would be useful as the promising white and blue green light emitting diodes

in fabricating strong electroluminescent materials for ﬂat panel display applications as an emissive layer

Fig 5 (a) SEM and (b) EDS images of the 4a- and 4b-complexes.

Table 2 Elemental compositions of the 4a- and 4b-complexes obtained from EDS analysis.

Element Weight % Atomic % Element Weight % Atomic %

Trang 8

The authors are thankful to the DST-Purse, UGC-CPEPA and

Institution of Excellence, Vijnana Bhavana, University of Mysore,

Manasagangotri, Mysore, for providing the single-crystal X-ray

diffraction data Authors acknowledges to DST, New Delhi SERB, for

theﬁnancial support, Reference No: SB/EMEQ-351/2013 and

DST-FIST No.SR/FST/ETT-378/2014

Supplementary information (SI)

Crystallographic data for the structural analysis were deposited

with the CCDC numbers 1559055 (4a-complex) and 1559054

(4b-complex) Copy of this information will be obtained free of charge

from‘The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK

(faxþ44 1223 336033; e-mail:deposit@ccdc.cam.ac.uk orhttp://

www.ccdc.cam.ac.uk)

References

partial-conjugated hyperbranched poly(p-phenylene vinylene) (HPPV), Synthetic

complexes (soft salts) and their application in organic light emitting diodes,

S.J Kim, S.O Kang, Generation of blue light-emitting zinc complexes by

band-gap control of the oxazolylphenolate ligand system: syntheses,

characteriza-tions, and organic light emitting device applications of 4-coordinated

Y Liu, Charge carrier transporting, photoluminescent, and electroluminescent

properties of zinc (II)-2-(2-hydroxyphenyl)benzothiazolate complex, Chem.

Electro-chemiluminescent Systems as Devices and Sensors Electrochemistry of

iridium (III) complexes for phosphorescence staining in the cytoplasm of

J.A Weinstein, J.A.W Gareth, Time resolved and two-photon emission

imag-ing microscopy of live cells with inert platinum complexes, Proc Natl Acad.

metal ions on the orientation of phthalocyanine based coatings, Spectrochim.

C Boissiere, L Nicole, Chimie douce': a land of opportunities for the designed

construction of functional inorganic and hybrid organic-inorganic

stability of interfaces in organic light emitting diodes with high Tg materials

Synthesis and characterization of dialkylgallium (dialkylindium) complexes of

N-salicylidene 2-aminopyridine and N-salicylidene-2-methoxyaniline: crystal

structure of dimethyl[N-salicylidene-2-aminopyridine]gallium, J Organomet.

(b) J Qiao, L.D Wang, L Duan, Y Li, D.Q Zhang, Y Qiu, Synthesis, crystal structure, and luminescent properties of a binuclear gallium complex with

photo-luminescent Zn (II) Schiff base complexes and it's derivative containing

(b) P.F Wang, Z.R Hong, Z.Y Xie, S.W Tong, O.Y Wong, C.S Lee, N.B Wong, L.S Hung, S.T Lee, A bis-salicylaldiminato Schiff base and its zinc complex as

conjugated molecular materials for optoelectronics, J Mater Chem 10 (2000)

Schiff base platinum (II) complexes as new class of phosphorescent materials for high-efﬁciency and white-light electroluminescent devices, Chem

of symmetrical hexadentate N-donor Schiff bases towards zinc (II) pseudo-halides: syntheses, crystal structures and luminescence, Polyhedron 25 (2006)

naphthalene diimides fused with sulfur heterocycles and end-capped with electron-withdrawing groups for air-stable solution-processed n-channel

Photoluminescence study of cobalt (III) and copper (II) complexes with the

tetraaqua-(pyridine-2,5-dicarboxylato)-copper (II) complex: crystal structure, TD-DFT approach, electronic spectra, and photoluminescence study, J Coord Chem.

theo-retical studies of novel Cu (I) complex, Inorg Chem Commun 12 (2009)

R.B Basavaraj, G.R Vijayakumar, Dual colour emitting Eu doped strontium ortho silicate phosphors synthesized by bio-template assisted ultrasound for solid state lightning and display applications, Ultrason Sonochem 34 (2017)

lumines-cence studies of nickel (II) and copper (II) complexes with (1R,2R)-cyclo-hexanediamine derived unsymmetric Schiff base, Dalton Trans 40 (2011)

G.R Vijayakumar, H Nagabhushana, M.N Kumara, N.K Lokanath, Synthesis, crystal structure and photoluminescence study of green light emitting bis (1 [(4-butylphenyl) imino] methyl naphthalen-2-ol) Ni (II) complex, J Sci Adv.

Naik, Synthesis, photoluminescence and forensic applications of blue light emitting azomethine-Zinc (II) complexes of

[31] Bruker, APEX2 SAINT-plus and Bruker, AXS Inc., Madison, Wisconsin, USA; Sheldrick G M, 1990 Phase annealing in SHELX-90: direct methods for larger structures, Acta Cryst A46, (2004) 467e473.

L.M Rodriguez, R Taylor, J van de Streek, P.A Wood, Mercury CSD 2.0-new features for the visualization and investigation of crystal structures, J Appl.

optical characterization of un-supported nanostructures, Rev Mex Fis 53

Định dạng
Số trang	8
Dung lượng	1,44 MB