vibrational spectra of bis(l-ornithinium) chloride nitrate sulfate

JOURNAL OF RAMAN SPECTROSCOPYJ. Raman Spectrosc. 2005; 36: 12–17Published online 12 November 2004 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jrs.1257

Vibrational spectra of bis(L-ornithinium) chloridenitrate sulfate

S. Ramaswamy,1† R. K. Rajaram2 and V. Ramakrishnan1∗

1 Laser Laboratory, Department of Microprocessor and Computer, School of Physics, Madurai Kamaraj University, Madurai 625 021, India2 Department of Physics, School of Physics, Madurai Kamaraj University, Madurai 625 021, India

Received 8 May 2004; Accepted 1 August 2004

The Raman and infrared absorption spectra of 2(C5H14N2O22+)·Cl−·NO3

−·SO42− crystal containing three

anions were recorded at room temperature and were interpreted in the light of crystal structure data.The presence of a carbonyl group was identified. The carboxylic group was found to exist as COOH.The formation of O — H· · ·O, N — H· · ·O and N — H· · ·Cl asymmetric hydrogen bonds contributesconsiderably to the crystal cohesion and is responsible for the changes in the position and intensity ofseveral bands. The vibrational spectra show that the anions were found to coordinate through hydrogenbonding interactions to other ligands in the crystal. The lattice wavenumbers of the halide radical (chlorineanion) were also assigned in terms of hydrogen bond vibrations. Copyright 2004 John Wiley & Sons,Ltd.

KEYWORDS: bis(L-ornithinium) chloride nitrate sulfate; vibrational spectra; FT-IR; FT-Raman; carbonyl group; hydrogenbonding

INTRODUCTION

Amino acids, the building blocks of protein, are essentialto the formation of muscle tissue and mass. L-Ornithine(˛,υ-diaminovaleric acid or 2,5-diaminopentanoic acid) is anon-protein, basic amino acid. L-Arginine and L-ornithinehave the physiological role of stimulating the pituitary glandto release natural growth hormone, a supplement of whichmay speed up wound healing.1,2 In burn, trauma and surgi-cal patients, muscle wasting is reduced, new muscle growthis increased and wound healing is promoted by ornithine ˛-ketoglutarate therapy.3,4 The inhibition of human ornithinedecarboxylase activity by enantiomers of difluoromethylor-nithine has already been studied.5 The use of L-ornithine,L-arginine and L-lysine as growth hormone secretagogues iswell documented in the medical literature.6 – 9

Raman and infrared vibrational spectra throw light onthe structural features, molecular conformation, behavior ofnormal modes, effects of various types of intermolecularforces and nature of hydrogen bonding in biologicallyimportant substances such as proteins. There have been

ŁCorrespondence to: V. Ramakrishnan, Laser Laboratory,Department of Microprocessor and Computer, School of Physics,Madurai Kamaraj University, Madurai 625 021, India.E-mail: ramaswamy s [email protected]/grant sponsor: UGC, Government of India.†Permanent address: Department of Physics, NMSSVN College,Madurai 625 019, India.

several spectroscopic studies of the inorganic acid complexesof various amino acids and their derivatives. The vibrationalspectral analysis of some amino acids combined withinorganic acids, viz. hydrochloric,10 – 13 nitric14 – 20 and sulfuricacids,21,22 has been carried out.

In this paper, we have investigated in detail the completevibrational spectra of bis (L-ornithinium) chloride nitratesulfate to elucidate the dynamics of various groups and theinfluence of hydrogen bonding on molecular vibrations.

EXPERIMENTAL

Equimolar amounts of L-ornithine hydrochloride, nitric acidand sulfuric acid were mixed, and single crystals of bis (L-ornithinium) chloride nitrate sulfate were obtained by slowevaporation method under natural conditions. The colorlesscrystals obtained were collected after about a month.

A Bruker IFS 66V Fourier transform (FT) IR spectrometerwas used to record the spectrum. An FRA 106 Raman modulewas used as an accessory for the FT-Raman measurements.The instrument has a resolution of ¾2–3 cm�1. Multi-taskingOPUS software on a PC/AT 486 computer was used forprocesses such as signal averaging, signal enhancement,baseline corrections.

An air-cooled diode pumped Nd: YAG laser operated at1064 nm and with the laser power output maintained at 200mW was used for Raman spectral measurements. The spec-tra were recorded over the range of 3500–50 cm�1. Since the

Copyright 2004 John Wiley & Sons, Ltd.

Vibrational spectra of bis(L-ornithinium) chloride nitrate sulfate 13

grown crystals were small in size, the sample was finely pow-dered and pressed into a small depression on a metal disc andmounted on the sample stage of the sample compartment.

For infrared measurements, a globar source was used andthe spectra were recorded over the range 4000–400 cm�1. Thesample for this measurement was finely ground and mixedwith KBr. This mixture was then pressed under vacuumat very high pressure to obtain a transparent disc, whichwas then placed in the sample compartment. In the FT-IRmode, the detector was a pyroelectric device incorporatingdeuterium triglycine sulfate (DTGS) in a temperature-resistant alkali metal halide window. For reliability of thedata obtained, Raman spectral measurements were alsomade with the facilities developed in our laboratory.23

RESULTS AND DISCUSSION

Crystal structure analysisThe crystal structure of the title compound was accuratelydetermined by single-crystal x-ray diffractometry by ourgroup.24 The crystal structure consists of L-ornithiniumcation and chloride, nitrate, sulfate anions connectedby a system of hydrogen bonds. The title compound2�C5H14N2O2

2C�ÐCl�ÐNO3�ÐSO4

2� crystallizes in a mono-clinic system with the space group C2�C3

2�, having twoformula units per unit cell. The asymmetric part of theunit cell contains one ornithinium cation and half each ofa chloride anion, a nitrate anion and a sulfate anion. Allthree anions sit on twofold axes. In the crystal structure,the ornithinium cation is linked to the sulfate anion viaa strong O—HÐ Ð ÐO hydrogen bond and the structure isfurther stabilized by N—HÐ Ð ÐCl and N—HÐ Ð ÐO hydrogenbonds.24

Vibrational analysisFactor group analysis of the title compound gives 165genuine normal modes (excluding acoustic modes) ofvibrations distributed as D 81A C 84B. Here the vibrationalspecies A and B are both IR and Raman active.25 Thestructural formula of bis(L-ornithinium) chloride nitratesulfate is shown in Fig. 1. The observed infrared spectrum ofthe title compound in the spectral range between 4000 and400 cm�1 is presented in Fig. 2 and the corresponding Ramanspectrum in the spectral range between 3500 and 50 cm�1

is depicted in Fig. 3. In Table 1, the observed vibrationalbands in the infrared and Raman spectra and the tentativeassignments are given. The title compound has a large degreeof hydrogen bonding and this is expected to modify thespectra of the pure amino acids. The knowledge of theinfrared and Raman spectral data of some similar complexmolecules14 – 22,26 – 30 is of great importance in assigning thevibrational bands of the title crystal.

Vibrations of the ornithinium cationThe ornithinium cation consists of a number of functionalgroups. The characteristic wavenumbers of these groups are

O1O2

O2*

O3#

O4#

O4O3

S

C5

N2

N3

C4O1b

O1aC1

C1C3

C2

N1

= Hydrogen

Figure 1. Structural formula of bis(L-ornithinium) chloridenitrate sulfate.

Tra

nsm

ittan

ce /

%

100

80

60

40

20

4000 3000 2000 1500 1000 500

Wavenumber / cm-1

Figure 2. Infrared spectrum of bis(L-ornithinium) chloridenitrate sulfate.

Inte

nsity

3250 2750 2250 1750 1250 750 250

Wavenumber / cm-1

Figure 3. Raman spectrum of bis(L-ornithinium) chloride nitratesulfate.

expected to undergo changes in their intensity and positionaccording to their environment and extensive intermolecularhydrogen bonding among the different parts of the molecule.

In the FT-IR spectrum recorded in the range 4000–400cm�1, the higher wavenumber region of the spectrum con-sists of bands due to NH3

C, (C)O–H, >C O, CH2 andC—H group stretching vibrations. The lower wavenumber

Copyright 2004 John Wiley & Sons, Ltd. J. Raman Spectrosc. 2005; 36: 12–17

14 S. Ramaswamy, R. K. Rajaram and V. Ramakrishnan

Table 1. Experimental wavenumbers (�) and relativeintensitiesa in the vibrational spectra of bis(L-ornithinium)chloride nitrate sulfate

Infrared (�/cm�1) Raman (�/cm�1) Assignment

3042(s,br) NH3C str.

2975(vs) (C) O–H str.2943(vs) CH2 asym. str.2914(w)

}

2880(w) CH2 sym. str.1750–2800 Overtones and

combination bands1733(vs) 1723(s) C O str.1621(vs,br) 1622(sh) NH3

C def.1601(s)

}

1509(vs) 1517(w,br) CH2 in-plane def.1471(w)

}

1448(sh) 1453(m) CH def.1431(m)

}

1400(sh) NO3� asym. str.

1384(m) 1388(sh) CH2 wag1371(w)

}

1336(m,br) 1331(s) NO3� asym. str.; OH

in-plane def.1303(sh) 1302(w) CH2 twist1250(m,br) 1258(m)

}

1181(sh) 1191(m) C–O(H) str.1136(sh) 1145(w) NH3

C rock1112(vvs) 1107(m) SO4

2� asym str.; NH3C

rock1062(vvs) SO4

2� asym str.; NO3�

sym. str.; C–N str.;C–C–N asym.str.

1039(sh) 1034(vw) C–N str.977(w) 976(s) SO4

2� sym str.; OHout-of-plane def.

955(vw) 922(sh) C–C skeletal str.897(vw) C–C–N sym.str.

858(vw) 844(m) C–C skeletal str.830(m) 832(sh) NO3

� sym. def.800(vw) 806(vw) ?773(m) 781(m) C–C skeletal str.739(s) 724(m) NO3

� asym. def.; CH2

713(sh)

}rock.

636(sh) 638(w)618(vvs)

615(m)

SO4

2� asym def.;590(sh) O–C O in-plane def.538(m) C–C O in-plane def.495(m) 500(w) NH3

C torsion474(w)

}

455(sh) 444(m) SO42� sym def.

374(vw) C–C–N def.

Table 1. (Continued).

Infrared (�/cm�1) Raman (�/cm�1) Assignment

357(vw) Skeletal vibration323(m) C–C torsion178(s) � (NH)Ð Ð ÐCl129(s) υ (NH)Ð Ð ÐCl93(s) � (NH)Ð Ð ÐCl

a Asym, asymmetric; br, broad; def, deformation; m, medium;s, strong; sh, shoulder; str, stretch; sym, symmetric; v, very; w,weak; �, stretching; υ, in-plane bending; � , out-of-plane bending.

region contains bands due to deformation vibrations of thevarious functional groups. A number of vibrational bandsappearing below 250 cm�1 in the Raman spectrum are due tothe vibrations of the N—HÐ Ð ÐCl-type hydrogen bonds andlattice vibrations.

Vibrations of the >C O groupThe stretching vibration of the C O bond in a non-ionized carboxylic (COOH) group usually appears in thewavenumber region 1755–1700 cm�1.31 The present crystalhas the characteristic >C O group which gives rise to avery strong band at 1733 cm�1 in the IR and a strong band at1723 cm�1 in the Raman spectrum, indicating that the >C Ois likely to be involved in weak hydrogen bonding.

Vibrations of the OH groupA three-centered hydrogen bond, formed by one of thehydrogen atoms in the ˛-amino group, is bonded simultane-ously with the oxygen atoms of both carboxylic and nitrategroups. Further, the carboxylic group forms a two-centeredstrong hydrogen bond with the sulfate group. For thesereasons, the O–H stretching wavenumber of the carboxylicgroup is lowered and observed as a very strong band at2975 cm�1 in the Raman spectrum.29 The strong Raman bandat 1331 cm�1 is due to the O–H in-plane deformation mode,which is well within the expected range (1380–1280 cm�1).As these bending vibrations overlap with the asymmet-ric stretching vibrations of the nitrate anion, a broad bandappears in the IR spectrum. However, the O–H out-of-planedeformation is observed as a weak band at 977 cm�1 inthe IR spectrum and a strong Raman line at 976 cm�1. Asthe bending wavenumbers are not much different from theexpected range, the linear distortion in this case is verymuch greater than the angular distortion. The band due tothe C–O(H) stretching vibration is generally strong and itoccurs in the region 1190–1075 cm�1. The C–O(H) stretchingmode is observed as a medium-intensity band at 1191 cm�1

in the Raman spectrum and as a shoulder peak at 1181 cm�1

in the IR spectrum.



Vibrations of the NH3+ group

The NH3C group, which forms a part of the crystal, has

C3v symmetry in the free state with a pyramidal struc-ture. Its normal modes of vibrations are �1�A1�, �2�A1�,�3�E� and �4�E�. All these four modes of vibrations areboth infrared and Raman active.27 As the NH3

C group isattached to the rest of the molecule through hydrogen bond-ing, the symmetry of the amino group may be lowered,thereby causing the shift in the vibrational wavenum-bers.

The asymmetric and symmetric stretching modes of theNH3

C group are expected in the region 3150–3000 cm�1,where as the asymmetric and symmetric deformationmodes of this group appear in the regions 1660–1610 and1550–1480 cm�1, respectively.28,29 The strong and broad bandat 3042 cm�1 in the IR spectrum is assigned to the stretchingvibrations of the NH3

C group. The deformation vibration ofthis group is observed as a very strong and broad peak at1621 cm�1 in the IR spectrum whereas the strong peak at1601 cm�1 in the Raman spectrum along with a shoulder at1622 cm�1 is assigned to the same vibration.

The weak band at 1145 cm�1 and a medium-intensityband at 1107 cm�1 in the Raman spectrum are tentativelyassigned to the rocking mode of the NH3

C group. The bandat 1112 cm�1 in the IR spectrum is very strong for this modeas it is overlapped with the asymmetric stretching modeof the sulfate anion present in the crystal. For most of theamino acids and the other compounds with amino groups,this mode lies only in this region.32 The medium-intensityband at 495 cm�1 in the IR spectrum and a weak doublet at500 and 474 cm�1 in the Raman spectrum are attributed tothe torsional mode of the NH3

C group.

Vibrations of the CH2 groupThe CH2 asymmetric and symmetric stretching modes areexpected to occur at 2935 (strong) and 2865 cm�1 (weak),respectively.30 The two peaks in the Raman spectrum, one at2943 cm�1 (very strong) and the other at 2914 cm�1 (weak),indicate the CH2 asymmetric stretching mode of vibration.The CH2 symmetric stretching vibration appears as a weakband at 2880 cm�1 in the Raman spectrum.

In a chain of CH2 groups, the CH2 deformation oscilla-tions are weakly coupled and the in-phase and out-of-phasevibrations have nearly the same wavenumber.30 The verystrong infrared peak at 1509 cm�1 along with a weak peak at1471 cm�1 reveal the CH2 in-plane deformation mode.

The in-phase CH2 rock vibrations cause a prominent bandwith a splitting at 724 (medium) and 713 cm�1 (shoulder) inthe Raman spectrum. The intensity of this split band is mainlydue to the presence of a large number of CH2 groups in thecrystalline state of the title crystal.30 However, this split isnot clearly seen in the IR spectrum. The CH2 twist and wagvibrations have also been identified and assigned.

Vibrations of the CH (chain) groupThe hydrocarbon CH stretch occurs near 2900 cm�1 andis usually lost among other aliphatic absorptions. Thestronger CH2 stretching vibrations overlap with the CHstretching vibrations14,30,33 observed around 2943 cm�1. TheCH deformation mode occurs as medium-intensity bandsat 1453 and 1431 cm�1 in the Raman spectrum and itscounterpart in IR spectrum is observed as a shoulder peak at1448 cm�1, as expected.14,15,30

Vibrations of CN and CCN groupsSeveral vibrations arise due to the asymmetric motion of thebranched carbon atom against its neighbors. In the crystalinvestigated, the Raman bands at 1034 and 1062 cm�1 andthe infrared band at 1039 cm�1 can be assigned to the C–Nstretching vibrations. The asymmetric C–C–N vibrations aredue to the motion along the C—N bond, whereas motionat right-angles to the C—N bond gives rise to asymmetricC–C–C vibrations.

The C–C–N asymmetric stretching vibration is observedas a strong peak at 1062 cm�1 in the Raman spectrum. Theoverlapping of stretching modes of nitrate and sulfate anionswith the C–C–N asymmetric stretching mode is responsiblefor the appearance of this peak as a very strong band. In theRaman spectrum, the very weak band at 897 cm�1 has beenassigned to the C–C–N symmetric stretching vibration. TheC–C–N bending mode at 374 cm�1 and C–C torsion modeat 323 cm�1 in the Raman spectrum have also been observedand assigned as reported.14

Vibrations of the OC O and CC O groupsUsually ˛-branched aliphatic monocarboxylic acids exhibitthree strong bands at ¾655, ¾635 and ¾620 cm�1. Owing tothe in-plane vibration of the O—C O group, these bandsare not usually well resolved in the region 665–610 cm�1. Inaddition, a strong band is found at 555–520 cm�1, which isattributed to the in-plane vibration of the C—C O group.34

The in-plane deformation modes of O—C O and C—C Ogroups are identified and assigned.

Vibrations of the skeletonIn the L-ornithinium cation, we have two C—C—C oscilla-tors coupled together, which are excited simultaneously sothat the C—C—C—C group can be considered as a whole.30

The C—C skeleton has characteristic wavenumbers in therange 1132–885 cm�1. This skeleton leads to three differentC–C stretching modes. In bis(L-ornithinium) chloride nitratesulfate crystal, three C–C stretching modes were identifiedas weak bands at 955, 858 and a medium-intensity band at773 cm�1 in the IR spectrum. This indicates the three dif-ferent orientations of the C—C bonds in the crystal. Thedeformation mode of the skeletal vibration is also observedat 357 cm�1 in the Raman spectrum.


16 S. Ramaswamy, R. K. Rajaram and V. Ramakrishnan

Other vibrationsThe IR spectra of the compound obtained in KBr, Nujol andFluorolube generally show a strong broad absorption bandaround 3440 cm�1.35 In the title crystal also, a strong andbroad band at 3428 cm�1 is observed in the IR spectrum.

Hydrogen bonding: spectroscopic featuresX-ray analysis has shown that a complex network ofhydrogen bonds holds the bis(L-ornithinium) chloride nitratesulfate crystal together, all hydrogen atoms bonded tonitrogen and oxygen being involved in such bonds. TheN—HÐ Ð ÐCl hydrogen bond is weak whereas N—HÐ Ð ÐOhydrogen bonds are normal in strength.

The O—HÐ Ð ÐO bond involving the carboxylic groupand the oxygen of the sulfate anion is very strong withan O—O distance of 2.569 A. Based on the stretching ofthe O–H vibration and the length of the hydrogen bond,the band corresponding to the O—HÐ Ð ÐO bonds can beexpected at 2900 cm�1.18 This is reflected in the infrared andRaman spectra of the compound, where the O–H stretchingwavenumbers (appearing at 2975 cm�1) were lowered byabout 500 cm�1 and also became very strong. However,the bending wavenumbers are not much different from theexpected range of 1380–1280 cm�1, indicating that the lineardistortion is much greater than the angular distortion.15

The normal hydrogen bonds observed between thenitrogen atoms of the amino and oxygen atoms of the nitrateand sulfate anions influenced the various vibrational modesof the NH3

C group and this is responsible for the loweringof the stretching wavenumbers and the shift of deformationmodes to higher wavenumbers than the expected range.

The Cl atom plays an important role in the intermolecularinteraction. This structural property makes this materialan interesting system to observe the vibrational motion ofhydrogen bonds. The vibrational spectra of systems withhydrogen bonds are important sources of information onthe dynamics and nature of the interaction.12 Hammeret al.36 studied the single-crystal IR spectroscopy of verystrong hydrogen bonds in pectolite and serandite. Foglizzoand Novak37 reported the low-wavenumber infrared andRaman spectra of hydrogen-bonded pyridinium halides.The stretching and bending vibrations of the N—HÐ Ð ÐClhydrogen bond have also been identified and assigned in thelow-wavenumber region.

Vibrations of the nitrate ionIn the bis(L-ornithinium) chloride nitrate sulfate crystal, allthree anions sit on the twofold axes. When the nitrate ion isfree, it has D3h symmetry and its normal modes of vibrationsare A0

1 ��1�, A002 ��2� and E0 (�3 and �4); The �1 mode is Raman

active, the �2 mode is infrared active and the �3 and �4 modesare both infrared and Raman active. In its free ion state,�1 (symmetric stretch) occurs at 1049 cm�1, �2 (symmetricbend) at 830 cm�1 and �3 and �4 (asymmetric stretch andasymmetric bend) at 1355 and 690 cm�1, respectively.38

When the nitrate ion is attached to the ornithiniumcation, there is a reduction in symmetry from D3h to C2

and some of the forbidden modes may be excited. For anymolecule, the totally symmetric stretching vibration leadsto a very strong band in the Raman spectrum. The verystrong band at 1062 cm�1 in the Raman spectrum, with nocounterpart in the infrared spectrum, corresponds to this�1 (symmetric stretch) mode of vibration. In the infraredspectrum, a medium-intensity band observed at 830 cm�1

with a shoulder peak at 832 cm�1 in the Raman spectrum isassigned to the �2 (symmetric bending) mode of vibration.The bands to the �1 and �2 modes of NO3

� ions are readilyassignable, as the positions and characteristics of vibrationsremain unchanged. The asymmetric stretching vibration isboth infrared and Raman active, which appears as a medium-intensity broad band at 1336 cm�1 in the infrared and asa strong peak at 1331 cm�1 in the Raman spectrum. Thesplitting of intense �3 modes is very common in the group ofamino acid nitrates. The second branch of �3 doublets can beassigned to a shoulder at 1400 cm�1 in the IR spectrum andthe localization of this band may arise from the interaction ofthe nitrate anion with KBr due to the KBr disc techniqueof measurement. The strong infrared band at 739 cm�1

and the corresponding Raman bands at 724 and 713 cm�1

could originate from the �4 mode of vibration. The splittingof �4 modes was observed only in the Raman spectrumand it could not be clearly seen in the infrared spectrum.Shifts were observed in the bands of the �3 vibrations byabout 20 cm�1 towards lower wavenumbers (IR and Raman)and of the band of the �4 vibrations by ¾35 cm�1 in thehigher wavenumber region (Raman). The facts that there isa splitting of degenerate modes (�3 and �4) and that only oneof the forbidden modes (�2) in the Raman spectrum is excitedindicate that the interaction of the NO3

� ion is strong in theenvironment and its behavior is not much influenced by thehydrogen bonding network.

Vibrations of the sulfate ionIn the free state, the sulfate ion has tetrahedral (Td) symmetrywith its vibrational modes distributed as D A1 C E C 2F2.The A1 and E species are Raman active only whereas theF2 species are both infrared and Raman active. A1 is aone-dimensional species; E is doubly degenerate and the F2

species have threefold degeneracy. These modes are expectedto occur at 981, 451, 1104 and 613 cm�1, respectively.26,39,40

As the symmetric stretching mode �1 of the sulfate groupis expected to be very strong in the Raman spectrum, thevery strong band at 976 cm�1 is easily assigned to this mode.In the infrared spectrum, this mode is observed as a veryweak band at 977 cm�1, which is forbidden under free ionsymmetry. The activation of this inactive IR mode is due tothe site symmetry effect (from Td to C2). The shoulder peakat 455 cm�1 in the infrared spectrum and the correspondingmedium-intensity band at 444 cm�1 in the Raman spectrumare assigned to �2 modes.



The triply degenerate asymmetric stretching vibration(�3) is expected in the region around 1050–1100 cm�1 for thesulfate group.26 The very strong line at 1062 cm�1 and themedium-intensity band at 1107 cm�1 in the Raman spectrum,and a very strong line at 1112 cm�1 in the IR spectrum areassigned to this mode of vibration. The components of thetriply degenerate asymmetric deformation vibrations (�4)are observed at 618 cm�1 with shoulder peaks on either side(636 and 590 cm�1) in the infrared spectrum and at 638 and615 cm�1 in the Raman spectrum.

CONCLUSION

Vibrational bands in the infrared and Raman spectra havebeen assigned for the bis(L-ornithinium) chloride nitratesulfate crystal. The stretching wavenumbers of the hydroxylgroup deviate very much from their positions owing tothe strong hydrogen bond existing between the carboxylgroup and sulfate anion. In the case of the NH3

C group, thesame effect is also observed owing to the hydrogen-bondingnetwork existing in the crystal. The lattice wavenumbers ofthe halide radical (chloride anion) have also been assignedin terms of hydrogen bond vibrations. The hydrogen bondvibrational wavenumbers have been identified at 178, 129and 93 cm�1 for chloride anion.

AcknowledgementsThe authors are grateful to DST, Government of India, New Delhi, forestablishing the laser laboratory and also to the UGC, Governmentof India, New Delhi, for having recognized our group’s (V.R.)activities as a thrust area of research in the DRS-Phase II andCOSIST programmes in the School of Physics and also havingprovided assistance to our laboratory. One of the authors (S.R.)thanks the management of NMSSVN College, Madurai, India, fortheir encouragement. One of the authors (V.R.) is thankful to DST,Government of India, New Delhi, for financial assistance in the formof a research project to support this work.

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vibrational spectra of bis(l-ornithinium) chloride nitrate sulfate

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