This article was downloaded by: [Emory University]On: 04 June 2014, At: 15:42Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

Molecular Physics: An International Journal at theInterface Between Chemistry and PhysicsPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/tmph20

Experimental and ab initio computational studies on 4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylanilineNamık Özdemir a , Bilge Eren b , Muharrem Dinçer a & Yunus Bekdemir b

a Department of Physics, Faculty of Arts and Sciences , Ondokuz Mayıs University , 55139Kurupelit, Samsun, Turkeyb Department of Chemistry, Faculty of Arts and Sciences , Ondokuz Mayıs University , 55139Kurupelit, Samsun, TurkeyPublished online: 13 Jan 2010.

To cite this article: Namık Özdemir , Bilge Eren , Muharrem Dinçer & Yunus Bekdemir (2010) Experimental and ab initiocomputational studies on 4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline, Molecular Physics: An International Journal atthe Interface Between Chemistry and Physics, 108:1, 13-24

To link to this article: http://dx.doi.org/10.1080/00268970903476688

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use ofthe Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Molecular PhysicsVol. 108, No. 1, 10 January 2010, 13–24

Experimental and ab initio computational studies on

4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline

Nam|k Ozdemira*, Bilge Erenb, Muharrem Dincera and Yunus Bekdemirb

aDepartment of Physics, Faculty of Arts and Sciences, Ondokuz May{s University, 55139 Kurupelit, Samsun, Turkey;bDepartment of Chemistry, Faculty of Arts and Sciences, Ondokuz May{s University, 55139 Kurupelit, Samsun, Turkey

(Received 26 October 2009; final version received 10 November 2009)

The title molecule, 4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline (C15H15N3), was prepared and charac-terised by 1H-NMR, 13C-NMR, IR and single-crystal X-ray diffraction. The molecular geometry, vibrationalfrequencies and gauge including atomic orbital (GIAO) 1H- and 13C-NMR chemical shift values of the titlecompound in the ground state have been calculated using the Hartree–Fock (HF) and density functional theory(DFT) methods with 6–31G(d) basis sets, and compared with the experimental data. The calculated results showthat the optimised geometries can well reproduce the crystal structural parameters and the theoretical vibrationalfrequencies, and 1H- and 13C-NMR chemical shift values show good agreement with experimental data.To determine conformational flexibility, the molecular energy profile of the title compound was obtained bysemi-empirical (AM1) calculations with respect to the selected torsion angle, which was varied from �180� toþ180� in steps of 5�. The energetic behaviour of the title compound in solvent media was examined using theB3LYP method with the 6–31G(d) basis set by applying the Onsager and the Polarizable Continuum Model(PCM). In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis andthermodynamic properties of the title compound were investigated using theoretical calculations.

Keywords: 4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline; crystal structure; IR and NMR spectroscopy;ab initio calculations; electronic structure

1. Introduction

Benzimidazoles are regarded as a promising class of

bioactive heterocyclic compounds that exhibit a range

of biological activities. Because of its synthetic utility

and broad range of pharmacological activities, the

benzimidazole nucleus is an important heterocyclic

ring. Specifically, this nucleus is a constituent of

vitamin-B12 [1]. This ring system is present in numer-

ous antioxidant [2–4], antiparasitic [5,6], antihelmintics

[7], antiproliferative [8], anti-HIV [9], anticonvulsant

[10], antiinflammatory [11–14], antihypertensive

[15,16], antineoplastic [17,18], antitrichinellosis [19],

antimicrobial [20,21], antihistaminic [22], antifungal

[23,24], and anticancer [25] activities. Owing to the

immense importance and varied bioactivities exhibited

by benzimidazoles, efforts have been made from time

to time to generate libraries of these compounds and

screen them for potential biological activity.It is also well known that imidazole-containing

molecules can easily coordinate to metal ions as well as

act as hydrogen-bond acceptors or donors in supra-

molecular assembly reactions [26,27], and thus their

chemistry has been investigated extensively in

coordination chemistry [28,29]. The inclusion of the

benzimidazole functional group can lead to different

coordination modes and may play a crucial role in the

construction of supramolecular compounds driven by

hydrogen-bonding interactions [30–32]. In addition,

benzimidazole-based organic ligands and their metal

complexes continue to attract interest as components

in homogeneous catalysis [33]. These different applica-

tions have attracted many experimentalists and theorist

to investigate the spectroscopic and structural proper-

ties of benzimidazole [34–36] and some of its deriva-

tives [37].Due to the importance of the benzimidazole

nucleus, we believed it worthwhile to design and

synthesise new benzimidazole derivatives. In this

study, we present the results of a detailed investigation

of the synthesis and structural characterisation of the

title compound using single crystal X-ray diffraction,

IR-NMR spectroscopy and quantum chemical meth-

ods. The geometrical parameters, fundamental fre-

quencies and GIAO 1H- and 13C-NMR chemical shift

values of the title compound in the ground state were

calculated using the Hartree–Fock (HF) and DFT

*Corresponding author. Email: namiko@omu.edu.tr

ISSN 0026–8976 print/ISSN 1362–3028 online

� 2010 Taylor & Francis

DOI: 10.1080/00268970903476688

http://www.informaworld.com

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

(B3LYP) methods with the 6–31G(d) basis set. Thesecalculations are valuable for providing insight intomolecular parameters and the vibrational and NMRspectra. The aim of this work is to explore themolecular dynamics and the structural parametersthat govern the chemical behaviour, and to comparepredictions made from theory with experimentalobservations.

2. Experimental and theoretical methods

2.1. Experimental

2.1.1. General

The melting point was determined using a capillarytube and a digital melting point apparatus(Gallenkamp Electrothermal) and is uncorrected.Reactions under microwave irradiation were per-formed in a modified domestic microwave oven(Bosch HMT 812C). Reactions were monitored bythin-layer chromatography (TLC) on silica-gel 60 F254

plates (Merck) and an UV lamp. The IR spectrum ofthe title compound was recorded in the range 4000–400 cm�1 with a Bruker Vertex 80v FT-IR spectrom-eter using KBr pellets. The 1H-NMR and 13C-NMRspectra were recorded on a Bruker Vertex 80V FT–IRspectrometer (400MHz) using TMS as an internalstandard and DMSO-d6 as solvent. All the chemicalsand solvents used were of analytical grade.

2.1.2. Synthesis

The title compound was obtained by condensation ofo-phenylenediamine with the NaHSO3 adduct of4-N,N-dimethylaminobenzaldehyde according to themethod described by Ridley and co-workers [38]but under neat microwave conditions (Figure 1).4-N,N-Dimethylaminobenzaldehyde (3.01 g, 20mmol)was dissolved in 10ml ethanol and NaHSO3 (2.08 g,20mmol) in 10ml water was added in portions.

The mixture was stirred vigorously for 1 h in an icebath. The precipitate, the NaHSO3 adduct of4-N,N-dimethylaminobenzaldehyde, was filtered as awhite solid and dried under vacuo (3.8 g, yield: 75%).2mmol (0.22 g) o-phenylenediamine and 2mmol(0.50 g) NaHSO3 adduct of 4-N,N-dimethylaminoben-zaldehyde were mixed. After adding a few drops ofDMF, the mixture was irradiated in a modifieddomestic microwave oven for 16min until the reactionwas complete according to the TLC data. The mixturewas cooled and poured onto ice-cold water undervigorous stirring. The precipitate was collected byfiltration and washed with water and dried (0.39 g,yield: 77%; m.p. 565–567K). The single crystals, whichwere suitable for X-ray analysis, were obtained byrecrystallisation from methanol/water.

2.1.3. Crystallography

A suitable colorless needle-shaped crystal sample ofsize 0.80� 0.32� 0.05 was chosen for the crystal-lographic study and then carefully mounted on thegoniometer of a STOE diffractometer with an IPDS(II)image plate detector. All diffraction measurementswere performed at room temperature (296K) usinggraphite monochromated Mo-Ka radiation(�¼ 0.71073 A) in !-scanning mode. The structurewas solved by direct methods using SHELXS-97 [39]implemented in the WinGX [40] program suit.Refinement was carried out using the full-matrixleast-squares method on the positional and anisotropictemperature parameters of the non-hydrogen atoms,or, equivalently, corresponding to 164 crystallographicparameters, using SHELXL-97 [41]. All H atoms werepositioned geometrically and treated using a ridingmodel, fixing the bond lengths at 0.86, 0.93 and 0.96 Afor the NH2, CH and CH3 atoms, respectively. Thedisplacement parameters of the H atoms were fixed atUiso(H)¼ 1.2Ueq (1.5Ueq for methyl) of their parentatoms. Data collection, X-AREA [42]; cell refinement,X-AREA; data reduction, X-RED32 [42]. Details ofthe data collection conditions and the parameters ofthe refinement process are given in Table 1. Thegeneral-purpose crystallographic tool PLATON [43]was used for the structure analysis and presentation ofthe results.

2.2. Theoretical

The molecular structure of the title compound in theground state (in vacuo) was optimised using Hartree–Fock (HF) andDFT(B3LYP) [44,45] with the 6–31G(d)[46] basis set. For modeling, the initial guess of thetitle compound was first obtained from theFigure 1. Formation of the title compound.

14 N. Ozdemir et al.

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

X-ray coordinates. Then, vibrational frequencies for theoptimised molecular structures of the title compound

were calculated using these methods and then scaled by0.8929 and 0.9613 [47], respectively. The geometry ofthe title compound, together with that of tetramethyl-silane (TMS), is fully optimised. 1H- and 13C-NMRchemical shifts were calculated within the GIAOapproach [48,49] applying the same methods and basisset as used for geometry optimisation. The 1H- and13C-NMR chemical shifts were converted to the TMSscale by subtracting the calculated absolute chemicalshielding of TMS (�¼�0��, where � is the chemicalshift, � is the absolute shielding and �0 is the absoluteshielding of TMS), with values of 32.52 and 199.79 ppmfor HF/6–31G(d) and 32.10 and 189.40 ppm forB3LYP/6–31G(d), respectively. All calculations wereperformed using the GaussView Molecular

Visualization program [50] and Gaussian 03 programpackage [51] on a personal computer without specifyingany symmetry for the title molecule. The effect ofsolvent on the theoretical NMR parameters wasincluded using the default model IEF-PCM(Integral-Equation-Formalism Polarizable ContinuumModel) [52] provided by Gaussian 03.Dimethylsulfoxide (DMSO), with a dielectric constant(") of 46.7, was used as solvent. A preliminary search oflow-energy structures was carried out with the AM1computations. Conformational energies were calcu-lated as a one-dimensional scan by varying the’(N1–C1–C8–C9) dihedral angle from �180� toþ180� in steps of 5�, and the molecular energy profilewas obtained. In order to investigate the total energyand dipole moment behaviour of the title compoundin solvent media, we also carried out optimisationcalculations in three solvents ["¼ 4.90, chloroform(CHCl3); "¼ 32.63, methanol (CH4O), "¼ 78.39,water (H2O)] at the B3LYP/6–31G(d) level using theOnsager [53] and Polarizable ContinuumModel (PCM)[54–57] methods.

3. Results and discussion

3.1. Crystallographic results

The title compound, an Ortep-3 [58] view of which isshown in Figure 2, crystallises in the orthorhombicspace group Pbca with eight molecules in the unit cell.The asymmetric unit in the crystal structure containsonly one molecule. The title molecule is composed of abenzimidazole ring and an N,N-dimethylaminophenylgroup. The benzimidazole and benzene rings of themolecule are not coplanar but rather have a dihedralangle of 31.49(8)�. Furthermore, the dihedral anglebetween the five- and six-membered rings of thebenzimidazole ring system is 0.69(13)�, and the max-imum deviation from planarity is 0.0093(17) A foratom C3, while the crossed torsion angles at thejunction, i.e. N1–C2–C7–C6 and N2–C7–C2–C3, are�179.79(19) and 179.85(19)�, respectively.

Table 1. Crystal data and structure refinement parametersfor the title compound.

Color/shape Colorless/needlesChemical formula C15H15N3Formula weight 237.30Temperature (K) 296

Wavelength (A) 0.71073 Mo-KaCrystal system OrthorhombicSpace group Pbca (No. 61)Unit cellparameters a, b, c (A)

8.9146(5), 9.6915(4),28.9757(14)

Volume (A3) 2503.4(2)Z 8Calculated density (mgm�3) 1.259� (mm�1) 0.077Absorption correction Integration (X-RED32)Tmin, Tmax 0.7953, 0.9522F000 1008Crystal size (mm) 0.80� 0.32� 0.05Diffractometer/measurementmethod

STOE IPDS II/rotation(! scan)

Index ranges �10� h� 10, �11� k� 11,�34� l�35

Theta range for datacollection (deg)

1.41� �� 25.64

Measured reflections 15,418Independent/observedreflections

2354/1530

Rint 0.0766Refinement method Full-matrix least-squares

on F2

Data/restraints/parameters 2354/0/164Goodness-of-fit on F2 1.011R indices [I4 2�(I )] R1¼ 0.0511, wR2¼ 0.1003R indices (all data) R1¼ 0.0930, wR2¼ 0.1136Weighting scheme w¼ /[�2(F2

0)þ (0.0528P)2],P ¼(F2

0 þ 2F2c )/3

D�max, D�min (e A�3) 0.14, �0.12Extinction coefficient 0.00216(7)CCDC 733748

Figure 2. A view of the title compound showing theatom-numbering scheme. Displacement ellipsoids are drawnat the 40% probability level and H atoms are shown as smallspheres of arbitrary radii.

Molecular Physics 15

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

The imine N2¼C1 and amine N1–C1 bonddistances in the benzimidazole group (1.324(3) and1.359(2) A, respectively) are not equal, with the ‘imine’length shorter than the ‘amine’ length, asexpected. These distances are comparable to thosefound for 2-[(1H-imidazol-1-yl)-methyl]-1H-benzimi-dazole (1.315(3) and 1.352(3) A, respectively [32]),4-ethylamino-2-methyl-1H-benzimidazole (1.3218(16)/1.3216(16) and 1.3589(16)/1.3597(15) A, respectively[59]), 2-[2-tri(2-furyl)phosphoniophenyl]benzimidazole(1.317(11)/1.327(10) and 1.367(11)/1.347(10) A, respec-tively [60]) and 2-(1H-benzo[d]imidazol-2-yl)-4,6-di-tert-butylphenol hemihydrate (1.328(2)/1.329(2) and1.363(2)/1.358(2) A, respectively [61]).

The crystal structure does not exhibit any intramo-lecular hydrogen bonds. However, similar to what isobserved in benzimidazole itself [62], the molecules ofthe title compound are linked by N–H � � � N hydro-gen bonds between the protonated and unprotonated Natoms of the imidazole rings of adjoining molecules intoa C(4) chain [63] running parallel to the b axis (Figure 3),details of which are given in Table 2. The packing isfurther stabilised by van der Waals forces. There areno other significant intermolecular interactions inthe crystal structure of the title compound.

Benzimidazole crystallises in a non-centrosymmetricspace group and is of interest as a potential nonlinearoptical material [62]. However, in spite of the similarhydrogen bonding, the title compound crystallises in acentrosymmetric space group.

3.2. Vibrational spectra

The FT-IR spectrum of the title compound is shown inFigure 4. It is well known that the calculated HF andDFT ‘raw’ or ‘non-scale’ harmonic frequencies cansignificantly overestimate experimental values due tolack of electron correlation, insufficient basis sets andanharmonicity. Much effort has been devoted toaccurately reproducing experimental frequencies intheoretical calculations. The Hartree–Fock calculatedresults are usually more overestimated than the corre-sponding DFT values [64]. To make a comparison, wecalculated the theoretical vibrational spectra of the titlecompound using both the HF and B3LYP methodswith the 6–31G(d) basis set. Frequency calculations atthe same levels of theory revealed no imaginaryfrequencies, indicating that an optimal geometry atthese levels of approximation was found for the titlecompound. We compared our calculation for the titlecompound with the experimental results. Theoreticaland experimental results of the title compound areshown in Table 3. The vibrational band assignments

Figure 3. Part of the crystal structure of the title compound,showing a C(4) chain along [010]. For the sake of clarity,H atoms bonded to C atoms not involved in the motif shownhave been omitted.

Figure 4. FT-IR spectrum of the title compound.

Table 2. Hydrogen-bonding geometry for the titlecompound.

D–H � � �A D–H(A)

H � � �A(A)

D � � �A(A)

D–H � � �A(deg)

N1–H1 � � �N2i 0.86 2.04 2.872(2) 163

Note: Symmetry code: ixþ 1/2, yþ 1/2, z.

16 N. Ozdemir et al.

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

were made using the GaussView MolecularVisualization program [50].

The solid phase of the compound includes variouscrystal interactions. Benzimidazole derivatives areknown to be strongly associated through intermolecular

hydrogen bonding. The spectrum of the title compoundshows strong bands in the 3051–2666 cm�1 region whichindicate N–H� � � N type hydrogen bonds. These bandsare characteristic for 1H-benzimidazole derivatives inthe 3200–2400 cm�1 region [65]. In addition, the absence

Table 3. Comparison of the observed and calculated vibrational spectra of the title compound.

Calculated (cm�1)

HF/6–31G(d) B3LYP/6–31G(d)

ExperimentalIR with KBr Scaled I (kmmol–1) Scaled I (kmmol–1)

Assignment (cm�1) freq. freq.

�N–H 3507 61.08 3524 29.05�sC–H (r) 3055 15.09 3110 13.03�asC–H (r) 3052 19.44 3106 18.03�asC–H (r) 3051 3036 4.01 3095 4.92�sC–H (R) 3029 25.67 3091 25.27�asC–H (R) 3019 42.06 3081 36.71�asC–H (R) 3007 17.49 3068 14.72�asC–H (r) 2997 22.91 3051 24.31�asC–H3 2966 81.08 3033 49.61�asC–H3 2950 4.74 3021 2.34�asC–H3 2914 65.93 2953 49.01�asC–H3 2910 24.14 2950 29.70�sC–H3 2842 83.78 2893 113.39�sC–H3 2834 66.56 2884 79.44�C¼N 1610 1636 125.19 1616 119.39�C¼C (r) 1590 1620 214.69 1610 176.85�C¼C (R) 1570 1596 6.84 1576 9.13�C¼C (r) 1559 1576 26.41 1553 6.28�C¼C (r) 1541 1554 10.27 1532 19.09C–H (r)þC–H3 1500 1508 410.49 1501 170.10C–H3 1502 40.53 1485 9.55C–H3 1475 1471 7.96 1460 14.92!C–H3 1463 55.02 1454 63.10C–H (R)þ!C–H3 1435 1437 67.45 1427 114.44!C–H3 1421 1424 90.47 1413 32.12N–Hþ C–H 1399 1398 53.92 1384 33.35�C–N(CH3)2 1342 1337 307.20 1344 293.98N–Hþ C–H 1318 1325 23.49 1301 2.60�C–NHþ C–H 1276 1306 10.60 1286 12.27�C–Nþ C–H (R) 1274 22.56 1263 78.63�N–CH3þ C–H 1228 1263 22.24 1235 34.26N–Hþ �C¼C (R) 1217 1225 61.49 1211 7.98C–H (r) 1195 1187 68.38 1189 78.26!C–H3þ �C–N(CH3)2 1169 1163 55.98 1163 25.81�C–H3 1119 1120 82.63 1108 42.69!C–H3 1061 1050 25.74 1050 26.89�deformation (R) 880 870 4.41 875 3.16!C–H (r) 854 837 55.55 805 36.70� 818 793 14.47 800 7.63!C–H (R) 746 760 64.49 726 53.20�deformation (R) 614 605 1.06 605 1.91� 555 602 3.40 536 8.70! C–H (r) 538 537 25.44 516 17.79

Notes: Vibrational modes: �, stretching; s, symmetric; as, asymmetric; , scissoring; , rocking; !,wagging; �, twisting; �, ring breathing; �, in-plane bending. Abbreviations: R, benzimidazole ring; r,benzene ring.

Molecular Physics 17

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

of any band �(N–H) in the 3200–3600 cm�1 region ofthe IR spectrum of the compound indicates thato-phenylenediamine has reacted with the NaHSO3

adduct of 4-N,N-dimethylaminobenzaldehyde andformed the benzimidazole ring system. The free�(N–H) stretching frequency is not observed in the3400–3500 cm�1 region. The characteristic �(C–H)stretching vibrations of the heteroaromatic structureare expected to appear in the 3000–3100 cm�1 frequencyrange. The band observed at 3051 cm�1 is attributed toaromatic �(C–H) stretching vibrations of the titlecompound, and was calculated using HF and B3LYPat 3036 and 3095 cm�1, respectively. Another charac-teristic region of the benzimidazole derivative spectrumis 1500–1650 cm�1, which is attributed to �(C¼N) and�(C¼C) stretching vibrations. The title compoundshows a strong band at 1610 cm�1 which is assigned to�(C¼N) stretching. This band was computed as 1636and 1616 cm�1 for HF and B3LYP, respectively. Thebands observed at 1590, 1570, 1559 and 1541 cm�1,which can be attributed to C¼C stretching vibrations,were calculated at 1620, 1596, 1576 and 1554 cm�1 forHF and at 1610, 1576, 1553 and 1532 cm�1 for B3LYP.All these data agree with the results of the study ofSundaraganesan and co-workers [66].

To make a comparison with experimental observa-tions, we studied the correlation between the calculatedand the experimental data, and obtained a correlationcoefficient of 0.99863 for HF/6–31G(d) and 0.99952for B3LYP/6–31G(d). According to these results, theexperimental vibrational frequencies are in betteragreement with the results of the B3LYP methodthan those for the HF method.

3.3. NMR spectra

GIAO 1H and 13C chemical shift calculations werecarried out using the HF and B3LYP methods withthe 6–31G(d) basis set for the optimised geometry.The results of these calculations are shown in Table 4.Since experimental 1H chemical shift values were notavailable for individual hydrogen atoms of methylgroups, we have presented the average of the computedvalues for these hydrogen atoms.

1H-NMR results for the compound showed a1,2-disubstituted benzene system at the ring of thebenzimidazole nucleus and a 1,4-disubstituted benzenesystem due to the 4-N,N-dimethylaminophenyl group atthe 4-position. The six protons of the N,N-dimethyla-mino group were detected at 2.98 ppm as a singlet, andhave been calculated using HF and B3LYP at 2.55–2.54and 2.93–2.94 ppm, respectively. The NH hydrogen ofthe benzimidazole ring appears at 12.6 ppm as a broad

band, while this signal is observed computationally at8.24 and 8.74 ppm for HF and B3LYP, respectively.Because of the fast tautomeric proton exchange betweenthe N1 and N2 atoms of the benzimidazole ring, H3/H6hydrogens and H4/H5 hydrogens are equivalent, assupported by the literature [67]. H3 and H6 protonsappear together as a broad singlet at 7.48 ppm, while H4and H5 appear together as a neat doublet of doublets at7.12 ppm. The two doublets observed at 7.97 and6.82 ppm are assigned to H9/H13 and H10/H12protons, respectively, according to the influence of theN,N-dimethylamino group at the 4-position of the1,4-disubstituted benzene ring.

The experimental 13C spectra data also support thestructure of the compound. The signal at 152.71 ppm isassigned to the C1 carbon next to two nitrogen atomsof the benzimidazole ring, which indicates the forma-tion of the benzimidazole ring system. This signal hasbeen calculated at 151.18 ppm for HF and at143.90 ppm for B3LYP. The signals at 117.80, 121.77and 145.81 ppm are assigned to the C3/C6, C4/C5 andC2/C7 carbons, respectively. The carbons of theN(CH3)2 group are detected at 40.10 ppm, whereas

Table 4. Theoretical and experimental 1H and 13C isotropicchemical shifts (with respect to TMS, all values in ppm) forthe title compound.

Experimental (ppm)Calculated (ppm)

Atom (DMSO-d6) HF/6–31G(d) B3LYP/6–31G(d)

C1 152.71 151.18 143.90C2 145.81 129.42 127.29C3 117.80 107.56 103.54C4 121.77 119.58 115.87C5 121.77 117.49 114.74C6 117.80 116.40 111.79C7 145.81 137.12 136.35C8 123.10 111.16 110.33C9 127.98 131.33 122.41C10 112.29 106.53 105.63C11 151.70 151.18 140.78C12 112.29 105.55 105.24C13 127.98 128.67 119.31C14 40.10 35.36 39.08C15 40.10 35.32 39.12H1 12.60 (bs) 8.24 8.74H3 7.48 (bs) 7.59 7.38H4 7.12 (dd) 7.40 7.19H5 7.12 (dd) 7.32 7.22H6 7.48 (bs) 7.74 7.46H9 7.97 (d) 8.63 8.27H10 6.82 (d) 6.71 6.58H12 6.82 (d) 6.65 6.54H13 7.97 (d) 8.10 7.63H14 2.98 (s) 2.55a 2.93a

H15 2.98 (s) 2.54a 2.94a

Note: aAverage.

18 N. Ozdemir et al.

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

these are computed as 35.36–35.32 ppm for HF and

39.08–39.12 ppm for B3LYP.We studied the relation between calculation and

experiment by comparing the calculated and experi-

mental data, and obtained linear function formulae

of y¼ 0.96437x� 0.52335 (R2¼ 0.99504) for HF/6–

31G(d) and y¼ 0.92447xþ 0.40818 (R2¼ 0.9978) for

B3LYP/6–31G(d). According to these results, it can be

seen that the results of the B3LYP method provide a

better fit to the experimental values than those for HF

when evaluating 1H and 13C chemical shifts.

3.4. Theoretical structures

Selected geometric parameters obtained experimentally

and those calculated theoretically using HF and

B3LYP with the 6–31G(d) basis set are listed in

Table 5. It is well known that DFT-optimised bond

lengths are usually longer and more accurate than HF,

due to the inclusion of electron correlation. However,

according to our calculations, the HF method corre-lates well for the bond length compared with the other

method (Table 5). Although the largest difference

between experimental and calculated bond lengths is

about 0.035 A for HF and 0.028 A for B3LYP, the root

mean square error (RMSE) is found to be about

0.011 A for HF and 0.016 A for B3LYP, indicating that

the bond lengths obtained by the HF method show the

strongest correlation with the experimental values.

The same trend was also observed for bond angles.

However, this time, both the largest difference and the

root mean square error for the bond angles obtainedby the HF method are smaller than those determined

by B3LYP.When the X-ray structure of the title compound is

compared with its optimised counterparts (see

Figure 5), slight conformational discrepancies are

observed The dihedral angle between the benzimida-

zole and benzene rings of the title molecule is

calculated at 17.122� for HF and at 6.125� for

B3LYP, whereas the dihedral angle between the five-

and six-membered rings of the benzimidazole ringsystem is calculated at 0.371 and 0.169� for HF and

B3LYP, respectively.A logical method for globally comparing the

structures obtained with the theoretical calculations is

by superimposing the molecular skeleton with that

obtained from X-ray diffraction, giving a RMSE of

0.191 A for HF/6–31G(d) and 0.277 A for B3LYP/6–

31G(d) calculations (Figure 5). Consequently, the HF

method correlates well for the geometrical parameters

when compared with B3LYP.

Table 5. Optimised and experimental geometries of the titlecompound in the ground state.

Calculated (6–31G(d))

Parameter Experimental HF B3LYP

Bond lengths (A)N1–C1 1.359(2) 1.36837 1.38651N1–C2 1.372(3) 1.37830 1.38288N2–C1 1.324(3) 1.28926 1.31982N2–C7 1.393(3) 1.38056 1.38286N3–C11 1.386(3) 1.38391 1.38502N3–C14 1.456(3) 1.44767 1.45336N3–C15 1.431(3) 1.44670 1.45254C1–C8 1.463(3) 1.46976 1.46115C2–C3 1.385(3) 1.38704 1.39486C2–C7 1.397(3) 1.39396 1.41763C3–C4 1.374(3) 1.38085 1.39407C4–C5 1.396(3) 1.40029 1.40893C5–C6 1.376(3) 1.37970 1.39180C6–C7 1.384(3) 1.39126 1.40112C8–C9 1.386(3) 1.39186 1.40541C8–C13 1.381(3) 1.38798 1.40293C9–C10 1.379(3) 1.37673 1.38524C10–C11 1.391(3) 1.40450 1.41670C11–C12 1.397(3) 1.40113 1.41442C12–C13 1.374(3) 1.38093 1.38894RMSEa 0.01081 0.01611Max. differencea 0.03474 0.02751

Bond angles (deg)N1–C1–N2 112.41(18) 112.70873 112.01391N1–C2–C3 132.21(19) 132.90925 133.00120N1–C2–C7 105.58(17) 104.49949 104.36658N1–C1–C8 122.88(18) 122.45300 123.11646N2–C1–C8 124.71(17) 124.83820 124.86957N2–C7–C2 109.47(18) 110.05638 110.44099N2–C7–C6 130.58(19) 130.04864 129.98640N3–C11–C10 122.0(2) 121.41528 121.44944N3–C11–C12 121.3(2) 121.54854 121.46361C1–N1–C2 107.48(17) 107.03188 107.55357C1–N2–C7 105.06(16) 105.69319 105.62329C11–N3–C14 119.2(2) 118.93813 119.66558C11–N3–C15 120.2(2) 118.93950 119.67819C14–N3–C15 115.0(2) 117.12638 118.71042C1–C8–C9 120.44(19) 119.68569 119.34282C1–C8–C13 122.54(18) 122.87982 123.31383C2–C3–C4 116.8(2) 116.82255 116.77350C2–C7–C6 120.0(2) 119.89488 119.57261C3–C2–C7 122.2(2) 122.59044 122.63215C3–C4–C5 121.8(2) 121.34268 121.44011C4–C5–C6 120.9(2) 121.27140 121.41895C5–C6–C7 118.3(2) 118.07690 118.16248C8–C9–C10 121.5(2) 121.52239 121.59013C8–C13–C12 122.0(2) 121.74867 121.73297C9–C8–C13 117.0(2) 117.43067 117.34232C9–C10–C11 121.5(2) 121.24831 121.21796C10–C11–C12 116.6(2) 117.03412 117.08641C11–C12–C13 121.3(2) 121.00290 121.01820RMSEa 0.64336 0.88081Max. differencea 2.12638 3.71042

(continued )

Molecular Physics 19

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

3.5. Conformational analysis

In order to define the preferential position of thebenzimidazole ring system with respect to the N,N-dimethylaminophenyl group, a preliminary search oflow-energy structures was performed using AM1computation as a function of the selected torsionangle, ’(N1–C1–C8–C9). The respective value of theselected torsion angle is 149.1(2)� in the X-ray struc-ture, whereas the corresponding value in optimisedgeometries is 163.53988� for HF/6–31G(d) and174.18169� for B3LYP/6–31G(d).

The molecular energy profile with respect torotations about the selected torsion angle is presentedin Figure 6. According to the results, the low-energydomains for ’(N1–C1–C8–C9) are located at �150,�30, 30 and 150� with energies of 100.910, 100.910,100.797 and 100.795 kcalmol�1. The energy differencebetween the most favourable and most unfavourableconformers, which arises from the rotational potentialbarrier calculated with respect to the selected torsionangle, is calculated to be 1.490 kcalmol�1.

3.6. Total energies and dipole moments

In order to evaluate the total energy and dipolemoment behaviour of the title compound in solventmedia, we carried out calculations in three solvents(chloroform, methanol and water). Total energies and

dipole moments were calculated in solvent media at theB3LYP/6–31G(d) level using the Onsager and PCMmethods and the results are given in Table 6. As can beseen from the table, the obtained total energies of thetitle compound using the Onsager and PCM methodsdecrease with increasing polarity of the solvent, so thatthe stability of the title compound increases. Theenergy difference between the gas phase and solventmedia was found to be significant for both methods.The PCM method supplied a more stable structurethan Onsager’s method with increasing polarity of thesolvent. The trend in the total energies is not observed

in the dipole moments. The dipole moments calculatedby the Onsager method are larger than those for the

Table 5. Continued.

Calculated (6–31G(d))

Parameter Experimental HF B3LYP

Torsion angles (deg)N1–C2–C7–C6 �179.79(19) �179.36259 �179.77854N1–C1–C8–C9 149.1(2) 163.53988 174.18169N1–C1–C8–C13 �31.6(3) �17.18954 �6.19758N2–C7–C2–C3 179.85(19) �179.75985 �179.84871N2–C1–C8–C9 �30.8(3) �16.35838 �5.72219N2–C1–C8–C13 148.6(2) 162.91219 173.89854

Note: aRMSE and maximum differences between the bondlengths and angles computed using theoretical methods andthose obtained from X-ray diffraction.

Figure 6. Molecular energy profile of the optimised coun-terpart of the title compound versus selected degrees oftorsional freedom.

Figure 5. Atom-by-atom superimposition of the structurescalculated (red) (A¼HF/6–31G(d), B¼B3LYP/6–31G(d))on the X-ray structure (black) of the title compound.Hydrogen atoms have been omitted for clarity.

Table 6. Total energies and dipole moments of the titlecompound in different solvents.

Method " Energy (a.u.) DE (kcalmol�1) � (Debye)

B3LYP 1 �744.89947573 5.2271

Onsager 4.90 �744.90182882 �1.477 7.453532.63 �744.90308823 �2.267 8.670678.39 �744.90325725 �2.373 8.8400

PCM 4.90 �744.91319266 �8.608 6.659532.63 �744.91992746 �12.834 7.325578.39 �744.92108903 �13.563 7.3822

Note: DE¼ESolvation�EGas; "¼ dielectric constant.

20 N. Ozdemir et al.

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

PCM method in the different solvents, and the dipolemoments obtained for the two solvation methodsincrease with increasing solvent polarity.

3.7. Molecular electrostatic potential

The molecular electrostatic potential, V(r), at a givenpoint r(x, y, z) in the vicinity of a molecule, is defined interms of the interaction energy between the electricalcharge generated from the molecule electrons andnuclei and a positive test charge (a proton) located at r.For the system studied, the V(r) values were calculatedas described previously using the equation [68]

VðrÞ ¼X

ZA=jRA � r j �

Z�ðr0Þ=j r0 � r j d3r0

where ZA is the charge of nucleus A located at RA, �(r0)

is the electronic density function of the molecule, and r0

is the dummy integration variable.The molecular electrostatic potential (MEP) is

related to the electronic density and is a very usefuldescriptor for determining sites for electrophilic attackand nucleophilic reactions as well as hydrogen-bondinginteractions [69–71]. The electrostatic potential V(r) isalso well suited for analysing processes based on the‘recognition’ of one molecule by another, as in drug–receptor and enzyme–substrate interactions, because itis through their potentials that the two species first‘see’ each other [72,73]. Being a real physical property,V(r) can be determined experimentally by diffractionor by computational methods [74].

To predict reactive sites for electrophilic andnucleophilic attack for the title molecule, MEP wascalculated at the B3LYP/6–31G(d) optimised geome-try. The negative (red) regions of MEP were related toelectrophilic reactivity and the positive (blue) regionsto nucleophilic reactivity shown in Figure 7. As can be

seen from the figure, there is one possible site on the

title compound for electrophilic attack. The negative

region is localised on the unprotonated nitrogen atom

of the imidazole ring, N2, with a maximum value of

�0.056 a.u. However, a maximum positive region is

localised on atom N1, probably due to the hydrogen,

with a maximum value of 0.058 a.u. These results

provide information concerning the region where the

compound can interact intermolecularly and bond

metallically. Therefore, Figure 7 confirms the existence

of an intermolecular N–H� � � N interaction between the

protonated and unprotonated N atoms of the imida-

zole ring.

3.8. Frontier molecular orbitals analysis

The frontier molecular orbitals play an important role

in the electric and optical properties, as well as in

UV–Vis spectra and chemical reactions [75]. Figure 8

shows the distributions and energy levels of the

HOMO–1, HOMO, LUMO and LUMOþ1 orbitals

computed at the B3LYP/6–31G(d) level for the title

compound. As can be seen from the figure, both

the highest occupied molecular orbital (HOMO) and

the lowest-lying unoccupied molecular orbital

(LUMO) are mainly delocalised among all the atoms.

However, the HOMO–1 and LUMOþ1 orbitals are

partially localised on different parts of the title

molecule. The HOMO–1 orbitals are delocalised on

the benzimidazole ring, while the LUMOþ1 orbitals

are delocalised on the benzene ring. Both the highest

occupied molecular orbitals (HOMOs) and the lowest

unoccupied molecular orbitals (LUMOs) are mostly

�-antibonding-type orbitals. The value of the energy

separation between the HOMO and LUMO is 4.232 eV

and this large energy gap indicates that the title

structure is quite stable.

Figure 7. Molecular electrostatic potential map (in a.u.) ofthe title compound with an isodensity value of 0.0004 a.u.calculated at the B3LYP/6–31G(d) level.

Figure 8. Molecular orbital surfaces and energy levels givenin parentheses for the HOMO–1, HOMO, LUMO andLUMOþ1 of the title compound computed at the B3LYP/6–31G(d) level. The positive phase is red, and the negativephase is green.

Molecular Physics 21

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

3.9. Thermodynamic properties

Based on the vibrational analysis at the B3LYP/6–31G(d) level and statistical thermodynamics, thestandard statistical thermodynamic functions i, stan-dard heat capacities (C0

p,m), standard entropies (S0m), and

standard enthalpy changes (DH0m (0!T )) were

obtained and are listed in Table 7. The scale factor forthe frequencies is 0.9613, which is a typical value for theB3LYP/6–31G(d) level of calculations. As can be seenfrom Table 7, the standard heat capacities, entropiesand enthalpy changes increase at any temperature from100.00 to 1000.00K, since increasing the temperaturecauses an increase in the intensity of the molecularvibration. For the title compound, the correlationequations between these thermodynamic propertiesand temperature T, which can be used for furtherstudies of the title compound, are as follows:

C 0p,m ¼ �1:73802þ 0:24915T

� 1:02256� 10�4T 2 ðR2 ¼ 0:99915Þ,

S 0m ¼ 59:72407þ 0:2484T

� 4:9971� 10�5T 2 ðR2 ¼ 0:99999Þ,

DH 0m ¼ �2:61322þ 0:02592T

þ 6:88611� 10�5T 2 ðR2 ¼ 0:99934Þ:

4. Conclusions

In this study, we have synthesised a novel benzimida-zole compound, C15H15N3, and characterised it usingspectroscopic (FT-IR and NMR) and structural(XRD) techniques. The X-ray structure is found tobe very slightly different from its optimised counter-parts, and the crystal structure is stabilised by a

N–H� � � N-type hydrogen bond between the proto-nated and unprotonated N atoms of adjacent imida-zole rings as well as by van der Waals forces. Theresults of the HF method show a better fit toexperimental values than B3LYP in evaluating geo-metrical parameters. It is noted here that the experi-mental results are for the solid phase and thetheoretical calculations are for the gaseous phase. Inthe solid state, the existence of the crystal field togetherwith the intermolecular interactions holds the mole-cules together, which results in differences betweenthe calculated and experimental values for the bondparameters. Despite the differences observed in thegeometric parameters, the general agreement is goodand the theoretical calculations support the solid-statestructures. However, it can be seen from the theoreticalresults that the B3LYP method is more appropriatethan the HF method for the calculation of vibrationalfrequencies and chemical shifts. The calculated MEPmap agrees well with the solid-state interactions. Thetotal energy of the title compound decreases withincreasing polarity of the solvent and the stability ofthe title compound increases in going from the gasphase to the solution phase.

5. Supplementary material

CCDC733748 contains supplementary crystallographicdata (excluding structure factors) for the structurereported in this article. These data can be obtained freeof charge via http://www.ccdc.cam.ac.uk/data_request/cif, by e-mailing data_request@ccdc.cam.ac.uk or bycontacting The Cambridge Crystallographic DataCentre, 12 Union Road, Cambridge CB2 1EZ, UK;fax: þ44-1223-336033.

Acknowledgement

This study was supported financially by the Research Centreof Ondokuz May|s University (project No: F-461).

References

[1] M.J. O’Niel, M. Smith, and P.E. Heckelman, The Merck

Index, 13th ed. (Merck & Co. Inc., New Jersey, 2001),

p. 10074.[2] G. Ayhan-K|lc|gil, C. Kus� , E.D. Ozdamar, B. Can-Eke,

and M. _Is� can, Arch. Pharm. 340, 607 (2007).

[3] C. Kus� , G. Ayhan-K|lc|gil, B. Can-Eke, and M. _Is� can,Arch. Pharm. Res. 27, 156 (2004).

[4] Z. Ates� -Alagoz, C. Kus� , and T. Coban, J. Enzyme Inhib.

Med. Chem. 20, 325 (2005).

Table 7. Thermodynamic properties of the title compoundat different temperatures at the B3LYP/6–31G(d) level.

C0p,m S0

m DH0m

T (K) ðcalmol�1 K�1Þ ðcalmol�1 K�1Þ ðkcalmol�1Þ

100.00 24.002 84.162 1.719200.00 42.457 107.701 5.221298.15 62.303 129.124 10.552300.00 62.678 129.522 10.671400.00 82.008 150.826 18.123500.00 98.481 171.398 27.373600.00 111.889 190.944 38.113700.00 122.764 209.343 50.063800.00 131.686 226.603 62.999900.00 139.102 242.789 76.7481000.00 145.329 257.986 91.177

22 N. Ozdemir et al.

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

[5] G. Navarrete-Vazquez, R. Cedillo, A. Hernandez-

Campos, L. Yepez, F. Hernandez-Luis, J. Valdez,

R. Morales, R. Cortes, M. Hernandez, and

R. Castillo, Bioorg. Med. Chem. 11, 187 (2001).[6] S.K. Katiyar, V.R. Gordon, G.L. McLaughlin, and

T.D. Edlind, Antimicrob. Agents Chemother. 38, 2086

(1994).[7] E. Ravina, R. Sanchez-Alonso, J. Fueyo, M.P. Baltar,

J. Bos, R. Iglesias, and M.L. Sanmartin, Arzneim.-

Forsch./Drug Res. 43, 684 (1993).

[8] L. Garuti, M. Roberti, M. Malagoli, T. Rossi, and

M. Castelli, Bioorg. Med. Chem. Lett. 10, 2193

(2000).[9] A. Rao, E Chimirri, A.M. De Clercq, P. Monforte,

C. Monforte, M. Pannecouque, and M. Zappala, Il

Farmaco 57, 819 (2002).[10] A. Chimirri, A. De Sarro, G. De Sarro, R. Gitto, and

M. Zappala, Il Farmaco 56, 821 (2001).[11] P.A. Thakurdesai, S.G. Wadodkar, and C.T. Chopade,

Pharmacologyonline 1, 314 (2007).[12] H.T. Le, I.B. Lemaire, A.K. Gilbert, F. Jolicoeur,

N. Leduc, and S. Lemaire, J. Pharmacol. Exp. Ther. 30,

146 (2004).[13] T.E. Lackner and S.P. Clissold, Drugs 38, 204 (1989).[14] S. Ersan, S. Nacak, N. Noyanalpan, and E. Yes� ilada,

Arzneim.-Forsch./Drug Res. 47, 834 (1997).[15] G. Serafin, J. Borkowska, I. Glowczyk, S. Kowalska,

and S. Rump, Pol. J. Pharmacol. Pharm. 41, 89 (1989).[16] K. Kubo, Y. Inada, Y. Kohara, Y. Sugiura, M. Ojima,

K. Itoh, Y. Furukawa, Y.K. Nishikawa, and T. Naka,

J. Med. Chem. 36, 1772 (1993).[17] A. Abdel-monem Abdel-hafez, Arch. Pharm. Res. 30,

678 (2007).[18] S. Ram, D.S. Wise, L.L. Wotring, J.W. McCall, and

L.B. Townsend, J. Med. Chem. 35, 539 (1992).[19] A.Ts. Mavrova, P. Denkova, Y.A. Tsenov,

K.K. Anichina, and D.I. Vutchev, Bioorg. Med.

Chem. 15, 6291 (2007).

[20] G. Ayhan-K|lc|gil and N. Altanlar, Il Farmaco 58, 1345

(2003).

[21] S. Ozden, D. Atabey, S. Y|ld|z, and H. Goker, Bioorg.

Med. Chem. 13, 1587 (2005).

[22] N. Terzioglu, R.M. van Rijn, R.A. Bakker,

I.J.P. de Esch, and R. Leurs, Bioorg. Med. Chem.

Lett. 14, 5251 (2004).[23] H. Kucukbay, R. Durmaz, E. Orhan, and S. Gunal, Il

Farmaco 58, 431 (2003).[24] N.M. Agh-Atabay, B. Dulger, and F. Gucin, Eur. J.

Med. Chem. 38, 875 (2003).[25] M. Andrzejewska, L. Yepez-Mulia, R. Cedillo-Rivera,

A. Tapia, L. Vilpo, J. Vilpo, and Z. Kazimierczuk, Eur.

J. Med. Chem. 37, 973 (2002).[26] S.E. Castilo-Blum and N. Barba-Behrens, Coord.

Chem. Rev. 196, 3 (2003).[27] K.K. Monthilal, C. Karunakaran, A. Rajendran, and

R. Murugesan, J. Inorg. Biochem. 98, 322 (2004).[28] J.B. Wright, Chem. Rev. 48, 397 (1951).[29] P.N. Preston, Chem. Rev. 74, 279 (1974).

[30] C.-L. Chen, A.M. Goforth, M.D. Smith, C.-Y. Su, and

H.C. zur Loye, Inorg. Chem. 44, 8762 (2005).[31] X.-L. Zheng, Y. Liu, M. Pan, X.-Q. Lu, J.-Y. Zhang,

C.-Y. Zhao, Y.-X. Tong, and C.-Y. Su, Angew. Chem.

Int. Ed. Engl. 46, 7399 (2007).

[32] D.-Q. Qi, G.-G. Hou, J.-P. Ma, R.-Q. Huang, and

Y.-B. Dong, Acta Crystallogr. C65, o85 (2009).

[33] W.A. Herrmann, Angew. Chem. Int. Ed. Engl. 41, 1290

(2002).

[34] S. Mohan and N. Sundaraganesan, Spectrochim. Acta

A 47, 1111 (1991).

[35] T.D. Klots, P. Devlin, and W.B. Collier, Spectrochim.

Acta A 53, 2445 (1997).

[36] M.A. Morsy, M.A. Al-Khaldi, and A. Suwaiyan,

J. Phys. Chem. A 106, 9196 (2002).

[37] S� . Yurdakul and C. Y|lmaz, Vibr. Spectrosc. 21, 127

(1999).

[38] H.F. Ridley, R.G.W. Spickett, and G.M. Timmis,

J. Heterocyclic Chem. 2, 453 (1965).

[39] G.M. Sheldrick, SHELXS-97; Program for the solution

of crystal structures. University of Gottingen,

Gottingen, 1997.[40] L.J. Farrugia, J. Appl. Crystallogr. 30, 837 (1999).

[41] G.M. Sheldrick, SHELXL-97; Program for crystal

structures refinement. University of Gottingen,

Gottingen, 1997.[42] Stoe & Cie, X-AREA Version 1.18 and X-RED32

Version 1.04 (Stoe & Cie, Darmstadt, 2002).[43] A.L. Spek, J. Appl. Crystallogr. 36, 7 (2003).

[44] C. Lee, W. Yang, and R.G. Parr, Phys. Rev. B 37, 785

(1988).

[45] A.D. Becke, J. Chem. Phys. 98, 5648 (1993).[46] R. Ditchfield, W.J. Hehre, and J.A. Pople, J. Chem.

Phys. 54, 724 (1971).[47] J.B. Foresman and A. Frisch, Exploring Chemistry with

Electronic Structure Methods, 2nd ed. (Gaussian Inc.,

Pittsburgh, PA, 1996).

[48] R. Ditchfield, J. Chem. Phys. 56, 5688 (1972).[49] K. Wolinski, J.F. Hinton, and P. Pulay, J. Am. Chem.

Soc. 112, 8251 (1990).[50] R. Dennington II, T. Keith and J. Millam, GaussView,

Version 4.1.2 (Semichem, Inc., Shawnee Mission, KS,

2007).

[51] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria,

M.A. Robb, J.R. Cheeseman, J.A. Montgomery Jr,

T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam,

S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci,

M. Cossi, G. Scalmani, N. Rega, G.A. Petersson,

H. Nakatsuji, M. Hada, M. Ehara, K. Toyota,

R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima,

Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li,

J.E. Knox, H.P. Hratchian, J.B. Cross, V. Bakken,

C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann,

O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli,

J.W. Ochterski, P.Y. Ayala, K. Morokuma,

G.A. Voth, P. Salvador, J.J. Dannenberg,

V.G. Zakrzewski, S. Dapprich, A.D. Daniels,

M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck,

Molecular Physics 23

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4

K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui,

A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov,

G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,

R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham,

C.Y. Peng, A. Nanayakkara, M. Challacombe,

P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong,

C. Gonzalez and J.A. Pople, Gaussian 03, Revision

E.01 (Gaussian, Inc., Wallingford, CT, 2004).[52] E. Cances, B. Mennucci, and J. Tomasi, J. Chem. Phys.

107, 3032 (1997).[53] L. Onsager, J. Am. Chem. Soc. 58, 1486 (1936).[54] S. Miertus, E. Scrocco, and J. Tomasi, Chem. Phys. 55,

117 (1981).[55] V. Barone and M. Cossi, J. Phys. Chem. A 102, 1995

(1998).[56] M. Cossi, N. Rega, G. Scalmani, and V. Barone,

J. Comput. Chem. 24, 669 (2003).[57] J. Tomasi, B. Mennucci, and R. Cammi, Chem. Rev.

105, 2999 (2005).[58] L.J. Farrugia, J. Appl. Crystallogr. 30, 565 (1997).

[59] C.P. Walczak, M.M. Yonkey, P.J. Squattrito,

D.K. Mohanty, and K. Kirschbaum, Acta Crystallogr.

C64, o248 (2008).[60] D.W. Allen, S.J. Coles, M.E. Light, and

M.B. Hursthouse, Inorg. Chim. Acta 357, 1558 (2004).[61] L. Benisvy, E. Bill, A.J. Blake, D. Collison, E.S. Davies,

C.D. Garner, G. McArdle, E.J.L. McInnes,

J. McMaster, S.H.K. Ross, and C. Wilson, Dalton

Trans. 1, 258 (2006).

[62] N. Vijayan, G. Bhagavannarayana, T. Kanagasekaran,

R. Ramesh Babu, R. Gopalakrishnan, and

P. Ramasamy, Cryst. Res. Technol. 41, 784 (2006).

[63] J. Bernstein, R.E. Davis, L. Shimoni, and N.-L. Chang,Angew. Chem. Int. Ed. Engl. 34, 1555 (1995).

[64] W. Zhou, J. Lu, Z. Zhang, Y. Zhang, Y. Cao, L. Lu,and X. Yang, Vibr. Spectrosc. 34, 199 (2004).

[65] P.N. Preston, D.M. Smith and G. Tennant, inBenzimidazoles and Congeneric Tricyclic Compounds:

The Chemistry of Heterocyclic Compounds, edited byA. Weissberger and E.C. Taylor (Wiley–Interscience,Chichester, 1981), Part 1, pp. 63–64.

[66] N. Sundaraganesan, S. Ilakiamani, P. Subramani, andB.D. Joshua, Spectrochim. Acta A 67, 628 (2007).

[67] V. Sridharan, S. Saravanan, S. Muthusubramanian, and

S. Sivasubramanian, Magn. Reson. Chem. 43, 551(2005).

[68] P. Politzer and J.S. Murray, Theor. Chem. Acc. 108, 134(2002).

[69] E. Scrocco and J. Tomasi, Adv. Quant. Chem. 11, 115(1979).

[70] F.J. Luque, J.M. Lopez, and M. Orozco, Theor. Chem.

Acc. 103, 343 (2000).[71] N. Okulik and A.H. Jubert, Internet Electron. J. Mol.

Des. 4, 17 (2005).

[72] P. Politzer, P.R. Laurence, K. Jayasuriya, in:J. McKinney (Ed.), Structure Activity Correlation inMechanism Studies and Predictive Toxicology, Special

issue of Environ. Health Perspect. 61, 191 (1985).[73] E. Scrocco and J. Tomasi, Topics in Current Chemistry

(Springer, Berlin, 1973), Vol. 7, p. 95.[74] P. Politzer and D.G. Truhlar, Chemical Applications of

Atomic and Molecular Electrostatic Potentials (Plenum,New York, 1981).

[75] I. Fleming, Frontier Orbitals and Organic Chemical

Reactions (Wiley, London, 1976).

24 N. Ozdemir et al.

Dow

nloa

ded

by [

Em

ory

Uni

vers

ity]

at 1

5:42

04

June

201

4