Magnetic behavior and raman spectroscopy of the composite system of cucl2 2h2o c12h9no

The introduction of magnetic property in the nanocomposite state of the sample containing the ligand, 2-BOP may be quite interesting for applica-tions in different bio-medicalﬁelds[10,20

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Original Article

Magnetic behavior and Raman spectroscopy of the composite system

S Dattaa, A.S Mahapatraa, P Settb, M Ghoshc, P.K Mallicka, P.K Chakrabartia,*

a SSRL, Department of Physics, Burdwan University, Burdwan 713104, India

b Physics Department, Gobardanga Hindu College, N 24 Parganas 743273, India

c Spectroscopy Department, Indian Association for the Cultivation of Science, Kolkata 700033, India

a r t i c l e i n f o

Article history:

Received 16 June 2017

Received in revised form

23 October 2017

Accepted 23 October 2017

Available online 28 October 2017

Keywords:

Nanocomposite sample

Chemical synthesis

Raman and infrared spectroscopy

Magnetic properties

a b s t r a c t

The metaleligand nanocomposite system of CuCl2-2-benzoyl pyridine (C12H9NO) was prepared by a chemical route and its crystallographic phase has been conﬁrmed by analyzing the X-ray diffractograms The strain was developed in the composite due to the lattice mismatch of the two constituting com-ponents The composite exhibits a paramagnetic behavior in the temperature range of 14e300 K with an effective magnetic moment of about 1.923mB This is attributed to the incomplete quenching of the orbital angular momentum Room temperature Raman spectra of the composite and the individual components, CuCl2$2H2O and 2-BOP have been analyzed along with their respective FTIR spectra These comparative studies have yielded some interesting information related to the structure of the composite The observed structural, morphological and spectroscopic properties are found compatible with those obtained from the magnetic studies

© 2017 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

Preparation and investigation of physical properties of

com-posite systems derived from organic molecules and transition

metal ion based compounds is now-a-days an interestingﬁeld of

research[1e5] The importances of the metal ion coordinated with

the suitable bridging ligands are quite attractive for applications in

differentﬁelds of physics, chemistry and biology For the synthesis

of such compounds, different choices of organic molecules are

considered of which aza aromatic and carbonyl complexes are of

much interests due to their certain elusive photophysical [6],

photochemical [7], and biological [8] properties, which have

attracted the attention of many researchers for thorough

in-vestigations The distinguishing features of the photophysical and

photochemical properties of aza complexes with respect to their

hydrocarbon analogs arise due to the presence of some low lying

np* states in the immediate neighborhood of the lowest singlet and

tripletpp* states Pyridine derivatives are very useful compounds

in different areas of both theoretical and experimental research For

example, the 2-benzoylpyridine (2-BOP) and its derivatives have

been found to be important as complexation agent for the spec-troscopic determination of a great variety of metals[9] Also, syn-theses of such compounds with benzoylpyridines are significant issues in coordination chemistry for the study of geometric isom-erism and the reactivity of the isomers In thefield of genomic and medicinal research, copper (II)-benzoylpyridine complexes are used for their DNA cleavage efficiency[10e14]

Some works on different composites of 2-BOP with salts of different 3d transition metal ions are reported[15e21] In these investigations, no detailed studies on their magnetic properties and spectroscopic behaviors have been carried out Moreover, the preparation of these systems in the nano regime and the investi-gation on their thermophysical properties would be interesting to study the inﬂuence of the nanoparticles when compared with the respective entities of their bulk counterparts In this paper we present the preparation and investigations of the copper (II) chlo-ride composite with the 2-BOP ligand in detail Metaleligand nanocomposite system of CuCl2-2-benzoyl pyridine (C12H9NO) was prepared by a chemical route and its phase formation was conﬁrmed by X-ray diffraction and Field Emission Scanning Elec-tron Microscopy (FESEM) analyses Due to the mismatch of the crystal structure of the individual components, strain was found to develop in the nanocomposite Structural morphology of the syn-thesized nanocomposite has also been studied The strain and the

* Corresponding author Fax: þ91 3422530452.

E-mail address: pabitra_c@hotmail.com (P.K Chakrabarti).

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.2017.10.005

Journal of Science: Advanced Materials and Devices 3 (2018) 113e121

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average particle size have been determined Magnetic properties of

the composite have been investigated in a critical manner in the

temperature range of 14e300 K Besides these, detailed

investiga-tion on the Raman and infrared spectra of the system and their

comparative analyses with those of the free ligand[22]has been

carried out to get a critical insight into the system The introduction

of magnetic property in the nanocomposite state of the sample

containing the ligand, 2-BOP may be quite interesting for

applica-tions in different bio-medicalﬁelds[10,20]

2 Materials and methods

Nanocomposite samples of CuCl2$2H2O-2-BOP are synthesized

by the chemical method using CuCl2$2H2O and 2-BOP as precursor

materials To prepare the sample we have consulted different

methods adopted earlier[15,16,20,21]and a modiﬁed method has

been considered and applied to synthesize the samples 2-BOP,

with purity grade 98%, was purchased from Aldrich chemical

company, USA and was used after checking its purity by HPLC

CuCl2$2H2O, with purity grade 99%, was purchased from Merck

India Spectroscopic grade methanol was purchased from S.L.R,

India and used as such First of all, 20 ml of methanol was taken in a

beaker and the required amount of CuCl2$2H2O (0.40 gm,

2.37 m mol) was added to prepare the solution of CuCl2$2H2O in it

In another beaker, the required amount of 2-BOP (1.610 gm,

8.82 m mol) was taken and 20 ml methanol was added drop wise to

prepare the 2-BOP solution To get homogeneity, both the solutions

were stirred for about 15 min at room temperature (RT) After the

completion of stirring, the solution of the organic ligand (2-BOP)

was added drop wise to the salt solution at RT and the rigorous

stirring condition of the salt solution was maintained during the

addition of the ligand solution The color of this solution was light

green Then the homogeneous mixture of the two solutions was

covered with a parafﬁn ﬁlm and several tiny pours were created on

theﬁlm for slow evaporation The beaker containing the ﬁnal

so-lution was kept inside a larger beaker containing silica gel and this

beaker was also covered by the porous parafﬁn ﬁlm Finally, this

homogeneous mixture of the two solutions was left for slow

evaporation After two weeks, small powder like tiny crystals of the

compound were collected after washing in methanol, dried under

vacuum at 40C and used for investigation

3 Experimental

X-ray diffraction patterns of the individual component

(CuCl2$2H2O and 2-BOP) and the nanocomposite were recorded by

Brukers Advanced D8 diffractometer with Cu Kf radiation (l

¼ 0.15425 nm) in the range of 2qfrom 10to 80 FESEM

obser-vations were carried out by using a FEI Inspect-F50 scanning

electron microscope TEM micrograph was obtained using a JEOL

JEM 1400 Plus (120 KV) electron microscope Raman spectra of the

samples were recorded with J.Y HORIBA, T 64000 system RAMAN

Spectrophotometer interfaced with a computer in the photon

counting mode andﬁtted with an Arþion laser using 514.5 and

488.0 nm as exciting wavelengths FTIR spectra of the compound

were recorded by PerkineElmer Model 783 spectrophotometer

Static magnetic susceptibility of the sample was measured in the

temperature range 14e300 K using a sensitive Faraday

magne-tometer fabricated in our Laboratory[23,24] The low temperature

environment in the magnetic measuring set up was generated by a

closed cycle helium cryo-cooler of APD cryogenics All the

measuring instruments were interfaced with a computer and the

measurements were carried out at different low temperatures with

special reference to the temperature calibration of the sample

chamber To measure the magnetic susceptibility, a small plastic

packet containing the sample was suspended by a thin quartzﬁber

in a region of constant vertical magneticﬁeld gradient [i.e., Hz(dHz/ dx) is constant] Diamagnetic correction for the suspension system including the empty plastic packet was duly considered in the calculation of the susceptibility

3.1 X-Ray Diffraction analysis

An X-ray diffraction (XRD) pattern of the nanocomposite sample

is shown inFig 1(c) To conﬁrm the formation and also to distin-guish the crystallographic phase of the synthesized nanocomposite sample of 2BOP-CuCl2$2H2O from those of the individual compo-nents, we have also recorded the X-ray diffraction patterns of 2BOP and CuCl2$2H2O, and the corresponding patterns are shown in

Fig 1(a) and (b), respectively The X-ray diffraction pattern of 2-BOP was taken as the standard pattern for the preparation of the nanocomposite sample of CuCl2$2H2O-2-BOP To substantiate this fact we have also consulted the available JCPDSﬁle (No 13-0717) in this family of compounds Results show that almost all peaks (except very few) are matched well with the observed peaks shown

inFig 1(a) All the peaks in the XRD pattern ofFig 1(b) are matched very well with those of the desired phase of CuCl2$2H2O and the peaks are assigned by using the JCPDSﬁle (No 33-0451) Interest-ingly, all the peaks of CuCl2$2H2O and 2-BOP are also developed in this pattern According to the JCPDS ﬁle No of 13e0717 for CuCl2$2H2O it is seen that the strongest peak of CuCl2$2H2O is found at̴ 16.22 This peak is also developed in the XRD pattern of the composite sample marked as symbol♯ (Fig 1) Actually this peak is the superposition of two peaks corresponding to CuCl2$2H2O and 2-BOP The peak for the nanocomposite is slightly shifted which is quite likely due to the mismatch of the crystal structures of CuCl2$2H2O and 2-BOP Normally, strain is developed due to this mismatch which leads to the shift of the peak compared

to its position in the pristine state Similarly, other peaks of CuCl2$2H2O (at̴ 44.74 and̴ 68.62) are also developed in the composite sample (indicated by♯inFig 1) The crystalline structure

of CuCl2$2H2O, thus, is retained in the composite sample There is a superposition of the peak of CuCl2$2H2O around 44with a peak of 2-BOP as shown inFig 1indicated by the symbol♯ The peak of CuCl2$2H2O at around 68is not visible in the XRD pattern of the composite because of the dominantly high intensity of the other peaks in the pattern This peak is present in the composite sample pattern which is shown in the inset ofFig 1 This fact conﬁrmed the

Fig 1 X-ray diffraction patterns of (a) 2-benzoylpyridine (2-BOP), (b) copper chloride (CuCl 2 $2H 2 O) and (c) copper chloride-2-benzoylpyridine nanocomposite sample (Cue2BOP).

S Datta et al / Journal of Science: Advanced Materials and Devices 3 (2018) 113e121 114

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presence of each individual phase in the composite sample It

should be mentioned here that in the XRD pattern of the composite

sample (Fig 1(c)) some peaks of the CuCl2$2H2O and the ligand

(2-BOP) are shifted with reference to those of their individual pattern

These slight shifts are attributed to the fact that the lattice strain

has developed in the composite state causing the positions of these

peaks to change No additional peak is found in the nanocomposite

state and this conﬁrms the formation of the desired composite

phase The average crystallite size of each component of the

com-posite was also calculated from the broadening of the most intense

peaks in the pattern ofFig 1(c) using the DebyeeScherrer equation,

〈D〉 ¼ 0:89l=ðb1 =2cosqÞ Here 〈D〉 is the average crystallite

diam-eter,lis the wavelength of the incident X-ray radiation andqis the

corresponding Braggs angle,b1/2is the full width at half maximum

(FWHM) of the most intense peak The average size of crystallites of

the composite is ~68 nm We have estimated the average crystallite

size of CuCl2$2H2O and 2-BOP in the composite using the

broad-ening of the most intense peaks of the respective individual

com-ponents The crystallite sizes of CuCl2$2H2O and 2-BOP in the

composite are 77 nm and 58 nm, respectively The crystallite size of

the CuCl2$2H2O and 2-BOP components in the pure individual form

are 90 nm and 20 nm, respectively The formation of the

nano-crystalline composite has been conﬁrmed by the estimated size

obtained from the XRD pattern The uncertainty in the

determi-nation of crystallite size was estimated from the error in theﬁtting

procedure and it lies within the range±1 nm The estimated values

of the crystallite size differ largely from the respective values of the

individual components This difference is attributed to the fact that

in the composite phase, there may exist a strain due to the presence

of two different phases of CuCl2$2H2O and 2-BOP Owing to this fact

the estimation of the crystallite size by DebyeeScherrer equation

may not be justiﬁed since the broadening of each peak in the XRD

pattern is not only due to the size of the nanocrystallite but also due

to the lattice strain, apart from the inherent instrumental

broad-ening For this, we have considered the HalleWilliamson (HeW)

method for the estimation of the average particle size and the

lattice strain of the sample[25,26] The required equation in the

HeW plot isbcosq¼ Κl/Dþ 2εsinq, where D is the average particle

size, b is the full width at half maximum (FWHM) after the

instrumental broadening correction, K is a constant (¼ 0.89),lis

the wavelength,q is the Bragg angle, and ε is the lattice strain

introduced inside the sample.bcosqis plotted as a function of 2sinq,

which normally gives a straight line Theﬁtting is quite satisfactory

which indicates the existence of lattice strain in the composite

sample The strain is obtained from the slope of the line and the

average particle size is also determined from the ordinate intercept

(see Fig 2) The calculated particle size is 105 nm and the strain in the nanocomposite CuCl2$2H2O-2-BOP is 27.5 104, which arises mainly due to the mismatch of crystal structures of the two com-ponents in the composite This strain also has some inﬂuence on the Raman spectra of the nanocomposite, which will be discussed

in the section of Raman and infrared spectra

3.2 FESEM analysis The morphology of the composite sample has been observed in FESEM micrographs shown in Fig 3where two selected micro-graphs recorded during the SEM observations are displayed (see 3a and 3b) The particles inFig 3(a) and (b) are mostly spherical but bigger size particles of different shapes are also seen in the mi-crographs Most of the particles have an average diameter of

105 nm which is in agreement with the crystallite size obtained from the HeW plot To check the presence of the elements and also,

to estimate the chemical composition of the compound, EDAX data

of the nanocomposite sample has been recorded The correspond-ing results are shown inFig 3(c) The EDAX measurement shows that the weight percentage of Cu and 2-BOP in CuCl2$2H2O-2-BOP are 27.95% and 72.05%, respectively and this is quite close with our chosen stoichiometry of the precursors used for the preparation of the sample

3.3 TEM analysis The observed TEM micrograph is shown inFig 4(a) The nano-structure of the particles is clearly evidenced in the micrograph Nanoparticles are more-or-less spherical in shape The measured size of nanoparticles varies from 20 to 120 nm As shown by the particle size distribution inFig 4(b), the size of most of the particles lie in the range between 40 and 70 nm The particle size distribu-tion inFig 4(b) is wellﬁtted by the log normal function which is usual for nanoparticles system The weighted average size obtained from the distribution graph is ~75 nm

3.4 Molecular geometry The detailed structural view of the composite was achieved by

ab initio DFT calculations Using the Gaussian 03 program package, the theoretical calculations were performed by density functional level of theory (DFT) using unrestricted B3LYP [i.e Becke three hybrid exchange and LeeeYangeParr correlation functional pro-gram (LYP)] The calculations of the system containing C, H, N, O and Cl centers were described by the standard Pople split valance polarization basis set 6e31þG(d,p), while for Cu2 þ ion the LanL2DZ was used By allowing relaxation of all the parameters a realistic optimized structure was obtained which corresponds to the true energy minimum This optimized structure is shown in

Fig 5and some selected values of the parameters of this structure are shown inTable 1 The structural parameters calculated theo-retically, were compared with those obtained from the similar type

of studies of the ligand Bond lengths and bond angles of the phenyl and pyridyl rings are in good agreement with those found

in the structure of the ligand 2-BOP[22] The structural features of the inner sphere of the metal ion point towards a distorted octa-hedral symmetry of the composite with the two chlorine atoms lying on the axial line The angle between the two ring planes of the ligand in the composite is about 43which can be compared with 60in the free ligand[22] The two rings are found slightly distorted and increased in size in the nanocomposite However, as

in the case of the carbonyl group, its planarity is maintained Another interesting thing is that the length of the CCxbonds (be-tween carbonyl carbon and its nearest pyridyl/phenyl ring carbon)

b q q(HalleWilliamson plot) of the nanocomposite sample.

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is small in comparison to the corresponding entities of the free

ligand In addition to this it is also noticed that the C]O bond

length is larger in the composite (1.283 Å) than that of the free

ligand (1.213 Å) The increase in the carbonyl (C]O) and the

decrease in the Ccarbonyl CC/N (ligand)bond lengths are compatible

with the observed interesting spectral features, which will be

discussed below in the Raman/infrared spectra of the composite

3.5 Magnetic properties

To investigate the magnetic behavior of the nanocomposite

sample of CuCl$2HO-2-BOP and also to estimate the valency of

the Cu-cation in the compound, the magnetic susceptibility was measured in the temperature range of 14e300 K To know the modulation of the magnetic cation behavior in the presence of the organic ligand in the composite, the magnetic susceptibility of 2-BOP was also measured The measured value of the molar suscep-tibility of 2-BOP conﬁrms its diamagnetic nature But the magnetic susceptibility of the composite is found to be much higher than that

of 2-BOP The measured value of the susceptibility at RT with an appliedﬁeld 1000 Gauss is 1.82 106emu/g This observation clearly proves that the magnetic contribution of the compound arises mainly due to the copper chloride part whose magnetic moment arises from the incomplete shell of the Cu-ions The

Fig 3 SEM image of the nanocomposite sample Cu-2-BOP in (a) 3mm, (b) 10mm scale and (c) Energy dispersive X-ray (EDX) spectra of Cu-2-BOP.

Fig 4 TEM image: (a) micrograph and (b) histogram of particle size distribution.

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average value of the magnetic moment of the compound has been

estimated from the average molar susceptibility using the formula

Peff¼ 2.828 (cMT)0.5, (wherecMbeing the average molar

suscep-tibility) and the magnetic moment thus found at RT is as large as

1.923mB We have calculated the theoretical value of the magnetic

moment of the Cuþ2ion from the equation ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

4SðS þ 1Þ

p

and the corresponding calculated value is 1.732mB[27] In this calculation

we did not consider the contribution of the orbital angular

mo-mentum which is normally quenched by the crystalﬁeld acting on

the 3d-ion in the crystalline environment of diamagnetic

neigh-bors Thus the measured value of the magnetic moment of the

sample, obtained from the measured value of the susceptibility at

RT, is higher than the corresponding theoretical value The higher

value of the magnetic moment of the sample suggests that the

crystalﬁeld effect of the Cu-ions is less in the composite compared

to that of CuCl2$2H2O, where the orbital momentum contribution is

almost nil due to the quenching effect In the present

nano-composite, the magnetic ion in the salt is coordinated to the organic

molecule, 2-BOP and the higher magnetic moment indicates

incomplete quenching of the orbital moments Due to this

incom-plete quenching, the magnetic moment gets some contribution

from the orbital part This fact of incomplete quenching is also

correlated with the formation of the nanocrystallite of CuCl2$2H2O

in the nanocomposite phase which is not the case in the bulk phase

Here the ground state (2D) of the Cu2þion would split into one

triplet and one doublet states, where the distribution of different

levels in the triplet will depend on the strength of the crystalﬁeld

The ground state of the ion has two fold spin degeneracy andﬁve

fold orbital degeneracy In fact, this will further split the

degen-erated levels and consequently the population will be redistributed

The ions will be populated among these levels according to

Maxwell-Boltzmann law and the susceptibility can be calculated

from the Van-Vleck expression, which will give the proper value of

the magnetic moment The present value suggests that most of the

Cu2þ ions are populated in the higher states among the crystal

ﬁeld levels Due to this fact the free ion magnetic moment is

modiﬁed, where different crystal ﬁeld levels contribute to the

magnetic moment according to their population The thermal

variation of magnetization recorded under zeroﬁeld conditions of

the compound is shown inFig 6, which shows that the magneti-zation increases slowly with the lowering temperature To know the magnetic state and its transition, if any, in the measured tem-perature range (14e300 K) of the compound, we have tried to

ﬁt the observed susceptibility vs temperature curve by the CurieeWeiss law,c¼ C/(T q), where C is the Curie constant andq

is the Curie temperature It is evident from Fig 6 that the susceptibility increases with lowering the temperature and the CurieeWeiss law successfully fits the observed variation of the susceptibility measured in the range of 14e300 K This in turn also indicates that the sample is paramagnetic in the entire investigated range of temperature The values of C and qestimated from the CurieeWeiss fitting are 0.00078 emu K/mole and 1.2156 K, respectively This negative value ofqis mainly due to the crystal field effect which is also found in different cases of our earlier studies[23,24]rather than any antiferromagnetic effect The ther-mal variations of the inverse susceptibility (1/c ¼ H/M) of the nanocomposite sample is also displayed in the inset ofFig 6 The linear fitting suggests that the sample exhibits paramagnetic behavior in the entire measured range of temperature (14e300 K) 3.6 Raman and infrared spectra

In order to get structural information of the composite sample,

to verify the valence state of the metal ion and also to get insight into the effect of coordination on the ligand, we have thoroughly examined the vibrational spectra (both Raman and infrared) of the sample For comparison, the Raman spectra of the sample and the pure ligand (2-BOP) are both recorded under identical conditions for exciting wavelengthslexc¼ 515.5 and 488.0 nm and they are shown inFigs 7 and 8, respectively The measured infrared spec-trum was analyzed and the obtained results are shown inTable 2 Some interesting changes are noted in the Raman spectra of the sample when compared with those of the pure ligand It is worth mentioning that the composite exhibits an overall reduction of intensity of the Raman bands with respect to the free ligand Moreover that the composite exhibits not only an overall reduction

of intensity of the Raman bands, but some changes in the relative intensities of the bands have also been observed compared with the free ligand The C]O stretching frequency has revealed a downshift from 1665 cm1in the free ligand to about 1650 cm1in the sample indicating the coordination of the metal with both oxygen and nitrogen atoms of the ligands[21] Some new bands are found to appear in the lower frequency region (below 500 cm 1) of the Raman spectra of the composite (Figs 7 and 8), which signify the coordination of the divalent metal (Cu2þ) ions with the nitrogen and oxygen atoms and also with the two chlorine atoms The two weak Raman bands at 242 and 265 cm1have been assigned to the

CueCl stretching vibrations[26] Two new Raman bands, appearing

in the sample at 317 and 393 cm1are assigned to the two CueO stretching vibrations in accordance with the previous works

[28,29] Another weak but prominent IR bands is observed at

498 cm1 This band along with another equally weak infrared band

at 517 cm1(having a weak Raman counterpart at 520 cm1) have been assigned to two CueN stretching vibrations[29] Interestingly these two bands are absent in the infrared spectra of the free ligand Four Raman bands, observed around 989, 1001, 1026 and

1053 cm1, are respectively correlated with the angle bending, a

(CCC/CNC/CCN), a (CCC), d (CH) and ring stretching, n (CC/CN) modes of the two rings This group shows an overall reduction in intensity relative to the n(C]O) mode in the compound when compared with the free ligand Besides this, the intensity of the second band is reduced so signiﬁcantly that the relative intensities

of the second and the third bands are found to be reversed in the sample with respect to those of the free ligand Moreover, theﬁrst

Fig 5 Optimized structural view, obtained from ab initio DFT calculation, of CuCl 2

-2-benzoyl pyridine (Cu-2-BOP) nanocomposite.

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one exhibits a red shift along with a signiﬁcant reduction in in-tensity and the last one a blue shift in the composite Similar ob-servations were evidenced in the case of the two bands at 1165 and

1177 cm1 Of these, theﬁrst one in the sample exhibits an increase

in the relative intensity Another weak Raman band around

Table 1

Equilibrium geometry of CuCl 2 -2-BOP.

(A) Bond lengths and bond angles in the geometry formed by copper ion with O, N and Cl atoms

Bond lengths in Å

Bond angles in degrees

(B) Selected bond lengths and bond angles of the ligand

Bond lengths in Å

(C) Bond lengths and bond angles of the carbonyl group

Bond lengths in Å

Fig 7 Raman spectra of (a) 2-BOP, (b) Cue2BOP nanocomposite (forlexc ¼ 514.5 nm).

1

Fig 6 Thermal variation of the molar susceptibility of the nanocomposite sample

Cue2BOP The thermal variations of the inverse susceptibility (1/c¼ H/M) of the

nanocomposite sample is shown in the inset.

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1095 cm1in the free ligand 2-BOP becomes much enhanced in the compound and shows an upshift of about 20 cm1 (to around

1115 cm1) Although this mode isbCH(I) (angle bending mode of ring I), there is also a good contribution of the stretching vibrations

to this mode[22] This indicates that the ring (I) bond which is the main contributor to the potential energy distribution of this vi-bration is signiﬁcantly contracted Three ring stretching n

(CC) modes are observed in the free ligand in the region between

1560 and 1600 cm1 Interestingly, the relative intensity of the third vibration (around 1596 cm1) with respect to then(C]O) mode is found to increase largely in the composite Three low frequency Raman bands are observed at 129, 137 and 178 cm1, of which the last one is very weak These modes are assigned to the metal centered angle bending modes as already reported[30e32] Drastic change of intensities of some of the Raman bands of both the rings, for example, enhancement of the CH-bending mode of the pyridyl ring (I) at 1113 cm1and phenyl ring modes at 1026, 1165 and

Table 2

Raman and infrared spectra (cm1) of 2-benzoylpyridine (2-BOP) and copper chloride-2-benzoylpyridine nanocomposite sample (Cu-2-BOP).

600 (vwsh) 165 þ 437

688 (s) 692 (vs) Ring torsion (II)

876 (vvw) 875 (vw) 416 þ 460

(bracketed wave numbers) e taken from Ref 22 C corresponds to the carbon atom belonging to the carbonyl group IR intensities are accordingly abbreviated.

Fig 8 Raman spectra of (a) 2-BOP, (b) Cue2BOP nanocomposite (forlexc ¼ 488.0 nm).

The spectrum in the region between 100 and 600 cm1is shown in the inset.

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1598 cm1 and reduction in intensity of the CCC angle bending

mode of the pyridyl ring (I) at 994 cm1, indicate that coordination

of the metal ion [Cu2þ] modiﬁes the charge distribution of the two

rings in conformity with the change of the intensity pattern It also

generates both upward and downward frequency shifts both in the

infrared and Raman spectra of the composite with respect to the

free ligand of an amount in the range of 0e20 cm1 All these things

indicate the coordination with the nitrogen and oxygen atoms and

the back donation from the metal ion to the anti bonding orbital of

C]O The latter not only increases the C]O bond lengths and

decreases the carbonyl stretching wavenumber but also modiﬁes

the charge distribution of the CCx(i.e CxCrings) bonds resulting in

the upshifts of the CxCrings stretching wavenumbers in the

com-posite (seeTable 2) The shifts and intensity changes of the Raman

bands in the composite compared to those of their individual

components are also in agreement with the developed strain

ob-tained from the HeW plot Thus from the spectral characteristics

and the presence of the metal e oxygen/nitrogen/chlorine

stretching vibrations, two each, a distorted octahedral structure is

expected in conformity with the previous observations made by

Plytzanopoulous et al.[21]and also compatible with the structure

shown inTable 1

4 Conclusion

Composite samples of CuCl2$2H2O-2-BOP with desired

crystal-lographic phase have been successfully prepared by the chemical

method The nanocrystallite size of the individual components is

found not calculated by the DebyeeScherrer method due to the

strain developed in the nanocomposite The strain developed due

to the mismatch of the crystal structure of the two constituting

components and the crystallite size of the nanocomposite was

estimated from the HeW plot The nanocrystallite size cannot be

calculated by the DebyeeScherrer method However, it is quite

reliable and comparable with that obtained from FESEM and TEM

micrographs This observation also suggests that most of the

par-ticles displayed in the micrographs are single crystallites, but not

clusters of nanocrystallites Interestingly, the magnetic property of

2-BOP has been enhanced thanks to the combination with the

relatively strong magnetic part of CuCl2$2H2O through the

forma-tion of the composite system The composite system exhibits a

paramagnetic behavior in the range of 14e300 K This

para-magnetic behavior would be useful for applications, where

sub-stantial magnetic moment is needed In addition, the magnetic

property may be fruitful for different biomedical ﬁelds, where

positive and relatively high value of magnetic moment of 2-BOP is

required The observed value of magnetic moment is high

compared to that of the free ion magnetic moment, where orbital

contribution is not fully quenched in the crystalﬁeld of the organic

environment The departure is attributed to the redistribution of

Cu2þ ion in different crystal ﬁeld levels, where the magnetic

moment mainly gets its contribution from the high spin state

ac-cording as the population determined by Boltzmann distribution

All theseﬁndings are in good agreement with the observed features

of Raman and infrared spectra where the presence of the ion in the

valence state (Cu2þ) has been predicted in the distorted octahedral

ﬁeld The structural information of the composite has been

extracted from the detail analyses of the Raman and infrared

spectra which may be fruitful for further study on such systems

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