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Journal of Computational Science 10 (2015) 237–246

Contents lists available at ScienceDirect

Journal of Computational Science

journa l h om epage: www.elsev ier .com/ locate / jocs

ynthesis, spectroscopic characterization, electronic and opticaltudies of (2Z)-5,6-dimethyl-2-[(4-nitrophenyl)methylidene]-2,3-ihydro-1-benzofuran-3-one

iwakera, C.S.Chidan Kumarb,c, Ashish Kumara, Siddegowda Chandrajud,∗,hing Kheng Quahb, Hoong-Kun Funb,e,∗∗

School of Basic Sciences, Indian Institute of Technology Mandi, Mandi, HP 175005, IndiaX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia (USM), 11800 Penang, MalaysiaDepartment of Chemistry, Alva’s Institute of Enginering & Technology, Mijar, Moodbidri 574225, Karnataka, IndiaDepartment of Sugar Technology & Chemistry, University of Mysore, Sir M.V. PG Center, Tubinakere, Mandya 571 402, Karnataka, IndiaDepartment of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia

r t i c l e i n f o

rticle history:eceived 13 October 2014eceived in revised form5 November 2014ccepted 18 November 2014vailable online 16 December 2014

a b s t r a c t

The title compound, (2Z)-5,6-dimethyl-2-[(4-nitrophenyl) methylidene]-2,3-dihydro-1-benzo furan-3-one, has been synthesized and characterized using experimental (XRD) and theoretical methods (FTIR,NMR, electronic and optical studies). The compound crystallizes in monoclinic space group P21/c witha = 7.527 (7) Å, b = 15.9397(15) Å, c = 13.5106 (10) Å, ˇ = 117.649 (4)◦ and Z = 4. The initial coordinate geom-etry obtained by XRD is further used to obtain the optimized ground state geometry of the title compound

eywords:rystal structureolecular geometryptical propertiesand structure

using DFT/B3LYP/6-311++G (2d,2p) level of theory. Geometrical parameters, vibration frequencies, Gaugeinvariant atomic orbital (GIAO) 1H and 13C NMR chemical shifts of the title compound have been calculatedtheoretically using the optimized ground state geometry. Apart from this, density of states of differentatoms, band gap studies and optical properties have also been studied successfully using theoreticalmodels.

© 2014 Elsevier B.V. All rights reserved.

. Introduction

Combining crystallography with molecular modelling hasained popularity in the recent years for characterization ofolecules and to explore their physical and chemical properties.FT, HF and MP2 along with other modelling methods are widelysed in the theoretical modelling of molecules to understand thehysical and chemical properties. We have explored the title com-ound by both experimental and theoretical methods to throw

ight on some of its properties which can be used for developmentf advanced applications. The title compound is an aurone type.laisen–Schmidt reaction is one of the most important reactions

or the synthesis of donor–acceptor conjugated dienes, known ashalcones [1]. Chalcones are precursors of open chain flavonoidsnd isoflavonoids, which are abundant in edible plants. It is

∗ Corresponding author. Tel.: +91 8232 291112; fax: +91 8232 291111.∗∗ Corresponding author.

E-mail addresses: chandraju1@yahoo.com (S. Chandraju), hfun.c@ksu.edu.sa,kfun@usm.my (H.-K. Fun).

ttp://dx.doi.org/10.1016/j.jocs.2014.11.005877-7503/© 2014 Elsevier B.V. All rights reserved.

generally synthesized by the reaction of acetophenone and benzal-dehyde in acidic [2] and basic medium [3,4]. Chalcones are the classof active compounds that have displayed a broad spectrum of phar-macological activities such as anti-oxidant [5], anti-inflammatory,antibacterial, anticancer, anti-allergic, antimalarial, antiviral andantifungal agents. In recent years, chalcones have been used inthe field of material science as non-linear optical (NLO) mate-rial because chalcone derivatives are notable materials for theirsecond harmonic generation (SHG). Researchers have reporteddifferent synthetic methods, such as, refluxing in an organic sol-vent [6], the solvent-free solid-phase reaction [7], ultra sonication[8], photosensitization [9] and microwave radiation [10]. Minorchanges in their skeletal structure have offered a high degree ofdiversity that has proven useful for the development of new antiox-idants having improved potency and lesser toxicity. In addition,the nucleus has been found to be used as antioxidant in a widerange of formulations targeting for the anti-aging activity. Aurones,

(Z)-2-benzylidenebenzofuran-3-(2H)-ones, constitute a less stud-ied subclass of flavonoids, which occur rarely in nature: to datea few aurones have been reported that were obtained from natu-ral sources, mainly flowering plants, and a few ferns, mosses and

2 utational Science 10 (2015) 237–246

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Table 1Crystal data and parameters for structure refinement of the title compound (I).

Compound (I)

CCDC 934224Molecular formula C17H13NO4

Molecular weight 295.28Temperature (K) 297Crystal system MonoclinicSpace group P21/ca (Å) 7.5257 (7)b (Å) 15.9397 (15)c (Å) 13.5106 (10)˛ (◦) 90ˇ (◦) 117.649 (4)� (◦) 90V (Å3) 1435.6 (2)Z 4Dcalc (g cm−3) 1.366Crystal dimensions (mm) 1.00 × 0.36 × 0.22 (mm−1) 0.10Radiation � (Å) 0.71073Reflections measured 37134Ranges/indices (h, k, l) −11, 11; −24, 24; −19, 20� limit (◦) 2.6–32.3Unique reflections 5201Observed reflections(I > 2� (I)) 3460Parameters 201Goodness of fit on F2 1.06R1, wR2 (I ≥ 2� (I)) 0.054, 0.189

Table 2Hydrogen-bond geometry (Å, ◦).

D H· · ·A D H HA DA D HA

C5 H5A· · ·O4i 0.93 2.55 3.394 (2) 151C12 H12A· · ·O2ii 0.93 2.38 3.163 (2) 142

38 Diwaker et al. / Journal of Comp

arine brown algae [10]. They are also responsible for the brightellow colour of some ornamental flowers such as snapdragon, cos-os and dahlia which are biosynthesized from chalcones by the key

nzyme aureusidin synthase [11]. The naturally occurring auronesre aureusidin [12], sulfuretin [13] and maritimetin [14] possess-ng various hydroxylation patterns. A few natural aurones bearing

ethoxy substituent(s) on either or both rings have been reported15–21]. Many synthetic routes have been proposed to synthesizeurones from 2-hydroxychalcone [22–27].

Encouraged with the above findings, an optically active auroneerivative: (2Z)-5,6-dimethyl-2-[(4-nitrophenyl)methylidene]-,3-dihydro-1-benzofuran-3-one is synthesized successfully,pectroscopic characterization, its electronic and optical propertiesre discussed in detail.

. Experimental and theoretical methods

.1. Synthesis of the title compound

The reagents and solvents for the synthesis were obtainedrom the Sigma–Aldrich Chemical Co., and used as such with-ut further purification. Melting point was determined by Stuartcientific (UK) apparatus. The synthesis of the title compoundas carried out according to the procedure reported earlier [3,4].

-Nitrobenzaldehyde (0.1 mol) was reacted with 1-(2-hydroxy-,5-dimethylphenyl)ethanone (0.1 mol) in presence of catalyticmount of sodium hydroxide in methanol (10 mL). The reactionixture was stirred at room temperature for about 5 h. The progress

f the reaction was monitored by TLC. After completion of the reac-ion, the reaction mixture was poured into ice-cold water. The solidbtained was filtered and washed successively with distilled water.he dried product was recrystallized with ethanol to get.

.2. Crystallography study

A yellowish, block-shaped single crystal of the title compound,ith dimensions of 1.00 mm × 0.36 mm × 0.22 mm was selected

nd mounted on a Bruker APEX-II CCD diffractometer with ane-focus sealed tube graphite-monochromated Mo K ̨ radiation� = 0.71073 Å) at 297 K in the range of 2.6 ≤ � ≤ 32.3 ◦. The dataere processed with SAINT and corrected for absorption using

ADABS [28]. A total of 37,134 reflections were collected, ofhich 5201 were independent and 3460 reflections with I > 2�(I).

he structure was solved by direct method using the programHELXTL [29] and was refined by full-matrix least squares tech-ique on F2 using anisotropic displacement parameters for allon-hydrogen atoms. All the hydrogen atoms were positionedeometrically [C H = 0.93–96 Å] and refined using riding modelith isotropic displacement parameters set to 1.2 or 1.5 (methyl

roup) times the equivalent isotropic U values of the parentarbon atoms. A rotating group model was used for methyl groups.he final full-matrix least squares refinement gave R = 0.054nd wR = 0.185 (w = 1/[�2(F0

2) + (0.0954P)2 + 0.15897P] where = (F0

2 + 2Fc2)/3, S = 1.06, (�/�) max = 0.001, ��max = 0.32 eÅ−3

nd ��min = −0.20 eÅ−3. A summary of crystal data and parame-ers for structure refinement details are given in Table 1. Hydrogenonding geometries are listed in Table 2. The ORTEP diagramf the compound (I) with atom labelling scheme drawn at 50%robability ellipsoids is depicted in Fig. 1.

.3. Computational details

Ground state geometry using B3LYP/DFT/6-311++G (2d,2p) levelf theory has been used for calculation of geometrical parame-ers, vibrational frequencies and NMR (GIAO) chemical shifts asmployed in Gaussian 09 package (G09 Rev:D.01) [30] and Gauss

C15 H15A· · ·O1 0.93 2.35 2.9889 (16) 125

Symmetry codes: (i) x, y, z + 1; (ii) x, − y − 1/2, z − 3/2.

view (version 5) molecular visualization software [31]. The molec-ular geometry of the title compound has been fully optimizedby using tight convergence criteria along with redundant inter-nal coordinates and Berny’s optimization algorithm. Using GIAO(Gauge-Invariant Atomic orbital) approach [32,33] and DFT/6-311++G (2d,2p) level of theory, we herewith report the NMR (1Hand 13C) chemical shifts of the compound. The theoretical vibra-tional spectrum of the compound is investigated by means of VEDA4 program. For calculations of electronic bands, density of statesand optical properties of the compound, CASTEP package [34] asimplemented in MATERIAL STUDIO program has been used. Thegeometry of the compound is again optimized in CASTEP packageand this optimized geometry is further used in the calculationsof the electronic bands, density of states and optical propertiesof the title compound. Geometry of the compound for optical,electronic and DOS calculations have been optimized using BFGSalgorithm. The BFGS scheme uses a starting hessian which is recur-sively updated during the optimization process Scheme 1.

3. Results and discussion

3.1. Molecular geometry

The structures of (I) as predicted from X-ray analysis andDFT/6-311G + (2d,2p)/BLYP level of theory are shown in Fig. 1(aand b), respectively. X-ray analysis reveals that (I) crystallizes inmonoclinic system with space group P21/c with a = 7.527 (7) Å,

b = 15.9397 (15) Å, c = 13.5106 (10) Å, ̌ = 117.649 (4)◦, Z = 4 andV = 1435.6 (2) Å3. To the best of our knowledge, the experimentaland theoretical molecular parameters for the title compound havebeen calculated for the first time. In the compound (I), C17H13NO4,

Diwaker et al. / Journal of Computational Science 10 (2015) 237–246 239

F t ellipc

ta(iarfSociaClr

4mhmaOl

ig. 1. (A) Molecular view of compound (I), showing 50% probability displacemenompound using DFT/B3LYP/6-311++G (2d,2p) level of theory.

he molecule as a whole is planar which is evident from the dihedralngle of 2.20 (6)◦ between the 3-benzofuranone unit and the phenylC10 C15) ring. The C7 C8 C9 C10 torsion angle of 178.41(13)◦

nvolving the C9 = C8 double bond confirms the (Z)-configurationssigned to naturally occurring and synthetic aurones from a cor-elation of dipole-moment measurements. The crystal structureeatures for an intramolecular C H· · ·O hydrogen bond producing(6) ring motif [35], which is assumed to contribute to the planarityf the molecule. The molecules are connected into anti-parallelhains extending along c axis direction in head-to-tail fashion viantermolecular C H· · ·O hydrogen bonds (Fig. 2 and Table 2). Twodjacent chains are further connected to each other via another

H· · ·O intermolecular hydrogen bonds (Fig. 2 and Table 2). Bondengths and bond angles in (I) are in normal range and are compa-able with closely related structures reported earlier [36,37].

The title compound possesses C1 symmetry, dipole moment of.1128 Debye and ground state energy of −1012.08289 a.u. In inter-olecular hydrogen bondings, (I) consists of two types of C H· · ·O

ydrogen bonds. In the first case, atom C5 acts as donor to the sym-

etry related O4 at (x, y, z + 1) [3394 (2) Å], while in the other case,

tom C12 acts as a hydrogen bond donor to the symmetry related2 at (x, −y − 1/2, z − 3/2) [3163 (2) Å]. D H, H· · ·A, DA, D H· · ·A

engths and angles of such kind of interactions are listed in Table 2.

Scheme 1. Synthetic pathway for the

soids and atom labeling scheme. (B) Ground state optimized geometry of the title

We also reported the molecular structure of the title compoundusing DFT/B3LYP/6-311G++ (2d,2p) level of theory. The optimizedparameters of the title compound (bond length, bond angles) alongwith their experimental counterparts are listed in Table 3.

Theoretical values are correlated with their experimental coun-terparts and a good correlation value has been found as per givenin Fig. 3. It was found that correlation R2 values for bond lengthand bond angle is 0.97 and 0.99, respectively, which indicate a goodagreement between the experimental and theoretical results. It alsoshows the wise choice of basis set for geometry optimization as theoptimized ground state geometry with good correlation values willbe further used for calculation of different properties of (I).

3.2. Vibrational spectra

In the present work, the FTIR spectrum of (I) has been computedtheoretically using DFT/6-311+ +G (2d,2p)/B3LYP level of theorywhere it consists of C1 point group and possesses 102 normalmodes of vibration. The computed IR spectra using DFT/B3LYP/6-

311G++ (2d,2p) level of theory is shown in Fig. 4.

The different modes of vibrations are also analysed in terms ofPED analysis using VEDA 4 program [38] and have been reportedin Table 4. PED analysis methodology is an important tool to

synthesis of the title compound.

240 Diwaker et al. / Journal of Computational Science 10 (2015) 237–246

F ydroga

aaisc

TR

ig. 2. Crystal packing of the title compound (I), showing intermolecular C H· · ·O hre omitted for clarity.

nalyze mode of vibration for molecule having large number oftoms. In PED analysis, each normal mode of vibrations is expressed

n terms of an internal normal mode contribution. During our analy-is, we observed that (I) consists of 102 normal modes of vibrationsomprising of stretching, bending and twisting modes.

able 3andomly selected geometrical parameters (in angles, degrees).

Numberingscheme for DFTcalculatedstructure

Numberingscheme for X-raystructure

Experimental(X-ray)

DFT/6-311G++(2d,2p)/B3LYP

Bond length (Å)C1–C2 C12–C13 1.37 1.38C2–C3 C13–C14 1.37 1.38C3–C4 C14–C15 1.38 1.38C4–C5 C10–C15 1.39 1.40C5–C6 C16–C11 1.38 1.38C6–C1 C11–C12 1.38 1.38C2–N20 C13–N1 1.46 1.47N20–O22 N1–O4 1.22 1.22N20–O21 N1–O3 1.21 1.22C5–C7 C10–C9 1.45 1.45C7–C8 C9–C8 1.33 1.34C8–C12 C8–C7 1.49 1.49C12–O17 C7–O2 1.21 1.21C11–C12 C6–C7 1.45 1.46C10–C11 C6–C1 1.37 1.38C10–O9 C1–O1 1.39 1.39C11–C16 C6–C5 1.39 1.39C16–C15 C9–C5 1.38 1.38C15–C14 C4–C3 1.41 1.41C14–C15 C2–C3 1.39 1.39C15–C18 C3–C16 1.50 1.50C14–C19 C4–C17 1.50 1.50

Angles (◦)C2–N20–O22 C13–N1–O4 118.03 118.71O21–N20–C2 O3–N1–C13 118.52 118.70O17–C12–C11 O2–C7–C6 130.30 130.45C8–C12–O17 C8–C7–O2 125.76 125.96C8–O9–C10 C8–O1–C1 106.42 107.17C7–C8–O9 C9–C8–O1 124.85 125.19O9–C10–C13 O1–C1–C2 124.23 125.07C1–C7–C8 C10–C9–C8 130.49 130.43C14–C15–C18 C3–C4–C17 121.26 120.40C16–C15–C19 C4–C3–C16 120.15 120.05

en bonding interactions as dashed lines. H atoms not involved in hydrogen bonding

3.3. Aromatic C H vibrations

In all kind of aromatic compounds, the C H stretchingvibrations give rise to bands in the region from 3100 to3000 cm−1 [39,40]. We observed that three bands in (I) whichare assigned to stretching C H vibrations out of which two arepresent in ring 1 (C10 C11 C14 C15 C16 C17) at 3194 and3184 cm−1, respectively, while the third one is present in ring 2(C1 C2 C3 C4 C5 C6) at 3177 cm−1. Out of plane C H bendingmodes of vibrations are also observed in (I) at 1031 and 860 cm −1,respectively.

3.4. C N vibration modes

C N modes of vibrations for (I) are assigned on the basis of PEDcalculations. The calculated band using DFT/B3LYP and 6311G++(2d,2p) level of theory at 1613 cm−1 is assigned to stretching C Nvibrations. It is not a pure mode and is mixed with stretching C Cvibrations of ring 2. The bands observed at 1613, 1555, 1564, 1315,1254 and 1248 cm−1 are also assigned to the C N vibrations on thebasis of PED analysis. These bands are not pure bands and are mixedwith C H3 vibrations of ring 2.

3.5. N O vibration modes

It has been observed that N O modes of vibrations give rise tobands in the range from 1200 to 1300 cm−1 [41–44]. The calculatedband observed at 1248 and 1315 cm−1 are assigned to N O modesof vibrations. The bands observed at 1248 cm−1 are not pure bandsand are mixed with C H vibrations of ring 2, while the one observed

−1

at 1315 cm is mixed with O-H modes of vibrations.

3.6. C O vibration modes

Using DFT/B3LYP/6-311++G (2d,2p) level of theory, the C Omodes of vibrations are predicted at 1555, 1564, 1613, 1636 and1666 cm−1, respectively. These are stretching modes and are mixed

Diwaker et al. / Journal of Computational Science 10 (2015) 237–246 241

Table 4Assignement of selected important modes of vibrations for the title compound.

S.No Assignment (modes of Vibration) Calculated(cm−1)DFT/B3LYP/6-311G++(2d,2p)

1 C H,ring1 31942 C H,ring2 31773 �C H, Aromatic ring 2 10314 sym,C C + sym, C N, ring2 15645 ıC H,ring2 + sym, C N, ring2 12486 ıC H,ring2 + sym, C H3, ring3 12547 �N O + �C-H, ring2 12488 �N O+ �O-H 13159 C O + C C, ring2 1613

V ing; �,bending;ring1 (C11–C10–C13–C4–C15–C16), ring2(C1–C2–C3–C4–C5–C6),r

w1o9aui

sym, sym,

ibrationla modes-: , strecthing; �, scissoring; �,rocking; �,twisting3(O9–C10–C11–C12–C8)).

ith stretching C C vibrations of ring 2. The band observed at613 cm −1 for C O modes of vibrations is intense in comparison tother modes of vibrations and its PED contribution is approximately8%. These values are consistent with the values reported in liter-ture for C O vibrations. The important modes of vibration for (I)

sing DFT/B3LYP/6-311G++ (2d,2p) level of theory are summarized

n Table 4.

Fig. 3. Correlation plots for bond length and bond angles of title compound.

Fig. 4. Computed FTIR spectra of the title compound using DFT/B3LYP/6-311++G(2d,2p) level of theory.

4. NMR (1H and 13C) Chemical shifts

4.1. 1H NMR chemical shifts

For structural and functional characterization of molecules,NMR spectroscopy is considered as a valuable and important tool.NMR chemical shifts are investigated by means of DFT/B3LYP/6-311G++ (2d,2p) level of theory with GIAO, IGAIM and CGST [45,46]approach. The calculated NMR chemical shifts using all of thesethree approaches are summarized in Tables 5 and 6 , respectively.(I) consists of 14 protons, out of which 6 protons are attached tomethyl groups, 6 are aromatic protons while the other two arealiphatic CH and OH. These aliphatic protons give a singlet peakat 6.95 ppm with GIAO and IGAIM approach (7.11 ppm with CGST

approach) for aliphatic CH whereas for aliphatic OH, it shows a sin-glet peak at 6.42 ppm using GIAO and IGAIM approaches (5.87 ppmusing CGST approach). The aromatic protons are numbered as H23,

Table 51H NMR chemical shift (ppm) relative to the TMS for the title compound usingB3LYP/6-311++G (2d,2p) level of theory.

Atom 6-311++G(2d,2p)/GIAO

6-311++G(2d,2p)/CGCST

6-311++G(2d,2p)/IGAIM

H33 (CH3) 2.33 2.50 2.33H31 (CH3) 2.40 2.54 2.40H32 (CH3) 2.40 2.54 2.40H30 (CH3) 2.40 2.57 2.40H35 (CH3) 2.50 2.69 2.50H34 (CH3) 2.50 2.69 2.50H27 (CH) 6.95 7.11 6.95H28 (ArCH) 7.23 7.42 7.23H26 (ArCH) 7.50 7.56 7.50H25 (ArCH) 7.67 7.72 7.67H29 (ArCH) 7.91 8.98 7.91H24 (ArCH) 7.97 7.79 7.97H23 (ArCH) 10.63 10.35 10.63

242 Diwaker et al. / Journal of Computatio

Table 613C NMR chemical shift (ppm) relative to the TMS for the title compound usingB3LYP/6-311++G (2d, 2p) level of theory.

Atom6-311++ G(2d,2p)/GIAO6-311++ G(2d,2p)/CGST6-311++ G(2d,2p)/IGAIM

C1 (ArC) 137.52 137.10 137.52C2 (ArC) 137.81 140.15 137.81C3 (ArC) 122.28 121.90 122.28C4 (ArC) 141.18 140.15 141.18C5 (ArC) 120.51 119.05 120.51C6 (ArC) 137.71 137.25 137.71C7 (CH) 127.14 126.31 127.14C8 (ArC) 155.36 155.92 155.36C10(ArC) 170.43 170.31 170.43C11(ArC) 127.05 125.79 127.05C12(ArC) 186.14 185.15 186.14C14(CH3) 115.48 114.66 115.48C15(ArC) 153.32 152.90 153.32C16(ArC) 137.49 136.68 137.49C13(ArC) 129.16 128.77 129.16

H7atmHr2bC

4

rGor

C18(CH3) 20.06 19.49 20.06C19(CH3) 22.42 21.67 22.42

24, H25, H26, H28, and H29 with singlet peaks at 10.63, 7.97,.67, 7.50, 7.23 and 7.91 ppm, respectively, using GIAO and IGAIMpproaches (10.35, 7.79, 7.72, 7.56, 7.42, and 8.98 ppm, respec-ively, using CGST approach). The aliphatic protons attached to

ethyl groups are numbered as H30, H31, H32, H33, H34 and35 with singlet peaks at 2.40, 2.40, 2.40, 2.33, 2.50 and 2.50 ppm,

espectively, using GIAO and IGAIM approaches (2.57, 2.54, 2.54,.50, 2.69 and 2.69 ppm, respectively, using CGST approach). It haseen observed that (I) possess higher NMR chemical shifts withGST approach in comparison to GIAO and IGAIM approaches [47].

.2. 13C NMR chemical shifts

13C NMR chemical shifts [48] of the title compound also been

eported using DFT/B3LYP/6-311G++ (2d,2p) level of theory withIAO, CGST and IGAIM approaches. (I) consists of a total 19 numberf carbon atoms out of which 16 are aromatic carbons atoms whileemaining three are aliphatic carbon atoms. The aromatic carbon

Fig. 5. Calculated Band structure (A

nal Science 10 (2015) 237–246

atoms show singlet peaks in the range from 122.28 to 186.14 ppmusing GIAO and IGIAM approaches and in the range from 121.90 to185.15 ppm using CGST approach. The aliphatic carbon atoms showsinglet peaks in the range from 20.06 to 127.14 ppm using GIAO andIGAIM approaches and in the range from 19.49 to 126.31 ppm usingCGST approach. The detailed 1H and 13C NMR chemical shifts forindividual atoms are summarized in Table 5 and 6, respectively.

4.3. Band structure, DOS and optical properties

The physical properties of many materials depend on the elec-tronic band structure of the material and the basis of the bandstructure can be related to the density of states [49]. The band struc-ture is calculated using two types of functional, namely LDA (CA-PZ)and GGA (PBE) i.e. (GW0 based upon Perdew–Burke–Ernzerhof(PBE) GGA single particle Hamiltonian) [50], using ultra-soft pseudopotentials in reciprocal space. Fig. 5 represents the calculated bandstructure (I).

The calculated energy gap for (I) is 1.760 eV with LDA (CA-PZ)functional and 1.818 eV with GGA (PBE) functional. The better bandsplitting is observed using GGA(PBE) functional. Apart from carbonand hydrogen atoms, our title compound possesses nitrogen andoxygen atoms, which contribute a lot to the density of states. Hence,we have reported the DOS and PDOS studies using ultra-soft pseudopotentials with both LDA (CA-PZ) and GGA (PBE) functional. Thetotal and partial density of states is represented in Fig. 6(a–e). Inthe energy range from −25 eV to 10 eV, the bands are originatedwhich had contributions from all the s, p, d and f states of all atomsconstituting the title compound. In the present work, we discussedthe two important atom constituents of (I) in the context of partialdensity of states. The partial density of states for the oxygen aswell as nitrogen atom is calculated using both LDA (CA-PZ) andGGA (PBE) functional and are reported in Fig. 6(b–e).

If we look at the Fig. 6b where PDOS for nitrogen is calculated

using LDA (CA-PZ) functional we found that in the energy rangefrom −30 eV to 25 eV contributions from s states is dominant incomparison to the p states and is almost negligible from d andf states. In the range from −25 eV to 20 eV the trend is reversed

) LDA (CA-PZ) (B) GGA (PBE).

Diwaker et al. / Journal of Computational Science 10 (2015) 237–246 243

tle com

wpihatttawbnt

Fig. 6. Total and partial DOS (6A–6E) of the ti

here we have dominant contribution to the valence band from states in comparison to the s, d and f states whose contribution

s zero. In the energy range −15 eV to −5 eV we observed that weave higher contribution form the p states in comparison to s statesnd almost zero contribution from both d and f states. As we moveowards the valence band we did not find any contribution fromhe any of the states in the energy range from −5 eV to 0 eV. Theop of the conduction band had its main contribution from p statesnd as we move towards the lower end of the conduction bande have equal contribution from both s and p states while negligi-

le contribution form d and f states. The same trend is observed foritrogen atom treated with GGA (PBE) functional. For Oxygen atomreated with LDA (CA-PZ) functional we found that in the energy

pound using LDA and GGA (PBE) functional.

range from −30 eV to 5 eV the s states are dominant over p statesin its contribution and from d and f states is almost negligible. Fur-ther moving towards the Fermi level the upper part of the valenceband in the range from −5 eV to 0 eV p states have more contribu-tion than s states and the same trend is followed in the conductionband upper part from 0 eV to 10 eV with almost negligible contri-bution form the d and f states. The same trend is observed whenoxygen atom is treated with the GGA (PBE) functional.

4.4. Optical properties

To get advancement in photonic devices, it is very importantto understand and analyze the optical properties of a particular

244 Diwaker et al. / Journal of Computational Science 10 (2015) 237–246

(7A–7

ttTuttouctbc

Fig. 7. Optical properties

ype of material. Calculation of dielectric function of a molecule ishe main aspect of calculation of optical properties of a compound.he title compound has been subjected to CASTEP package usingltra-soft pseudo potentials for the calculation of optical proper-ies. For calculation of optical properties, it is important to evaluatehe complex dielectric function and then express other propertiesut in terms of this function. Different properties which can be eval-ated from the complex dielectric function are namely absorption

oefficient, refractive index, loss function, conductivity and reflec-ivity. Absorption coefficient indicates the fraction of energy losty a wave when it passes through the material under study. Opti-al conductivity is used to characterize the material whereas loss

F) of the title compound.

function is basically the energy lost by an electron when passingthrough a material. The different formulas representing all thesefunctions can be read as:

� = �1 + i�2 = N2 (1)

� = �1 + i�2 = −iω

4�(� − 1) (2)

1 − N 2 (n − 1)2 + K2

R = |

1 + N| =

(n + 1)2 + K2(3)

Eq. (1) represents the dielectric function, Eq. (2) represents theoptical conductivity and Eq. (3) represents the reflectivity. The

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dpfwratEoti

�

Ief1Htc

�

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Lcsq1bIspsfair1ftfrT

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sbdtattsoDftcL

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Diwaker et al. / Journal of Comp

ifferent optical properties of the title compound using CASTEPackage with ultra-soft pseudopotentials and both LDA, GGA (PBE)unctionals are shown in Fig. 7(a–f). From the optical properties,e observe that both the LDA (CA-PZ) and GGA (PBE) functional

eveal same kind of optical properties with negligible differences observed from the Fig. 7(a–f). For calculation of dielectric func-ion which depends on frequency, we should find out the energyigen values and electron wave functions which are natural outputf calculation of band structure. The imaginary part of the dielec-ric function for complete characterization of dielectric propertiess calculated using the expression as given below [51].

ij2 = 4�2e2

Vm2ω2× �

nn′�〈kn�|pi|kn′�〉〈kn′�|pj|kn�〉

× fkn (1 − fkn′) ı (Ekn′ − Ekn − �ω) (4)

n the expression (4), m, e and p represent mass, charge of anlectron and momentum operator. From the absorption graph, weound that strong absorption occurs in the frequency range from0,000 to 15,000 cm−1 and there is no absorption beyond this range.owever, before 10,000 cm−1, small peaks which show less absorp-

ion were observed. The real part of the dielectric function can bealculated using Kramers–Kronig inversion which is given as (5),

1(ω) = 1 + 2�

p

∫ ∞

0

ω′�2(ω′)ω′ − ω2

dω′ (5)

here P represents the principal value of the integral.The real and imaginary parts of the dielectric function using both

DA (CA-PZ) and GGA(PBE) functional are shown in Fig. 7(d). Thealculation of optical properties include drude term which causesharp increase at lower energies. Fig. 7(d) shows that threshold fre-uency for imaginary part of the dieletcric function occurs about5,000 cm−1 which gives threshold for direct optical transitionsetween the highest valence band and lowest conduction band.t is known as fundamental absorption edge. The main peak of thepectrum is sisuated about 25,000 cm−1. The main peak for the realart of the dielectric function is also around 20,000 cm−1. The curvehows a zigzag increase and decrease when we move towards highrequency regions. The calculated refractive index both imaginarynd real parts of the title compound are reported in Fig. 7(e) and its around 1.8. The real and imaginary parts of the conductivity areeported in Fig. 7(b) and the main peak of the spectrum is around8,000 cm−1. Its behaviour is similar to the imaginary dielelectricunction at all frequencies. Peaks in the optical conductivity spec-rum are due to interband transitions. Fig. 7(f) represents the lossunction and its main peak known as plasmon frequency which cor-esponds to collective oscillations of electrons in the valence shell.he main peak of the spectrum is around 12,000 cm−1.

. Conclusions

In conclusion, a novel aurone derivative compound has beenynthesized. The structure of the compound has been determinedy using both X-ray analysis and DFT theoretical methods. The coor-inates obtained using X-ray analysis is further used to optimizehe ground state geometry of the title compound using DFT methodlong with 6-311G++ (2d,2p) basis and a good agreement betweenhe experimental and theoretical values has been obtained. Further,hese optimized parameters are used to explore various spectro-copic properties of the title compound. Also the electronic andptical properties of the title compound are also reported usingFT methods. LDA (CA-PZ) and GGA (PBE) approximations are used

or exchange correlation potentials to calculate the band structure,otal and partial density of states along with optical properties. Cal-ulated band gap of around 1.8 eV using GGA(PBE) and 1.7 usingDA (CA-PZ) functional reveals the semiconducting nature of the

[

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nal Science 10 (2015) 237–246 245

title compound making it suitable for a potential candidate in semi-conductor industry and for making optoelectronic devices. Thereal and imaginary part of the dielectric function throw light ontransitions from occupied to unoccupied bands. We hope that ourtheoretical calculations of the title compound to investigate variousproperties will be helpful in designing new applications to benefitthe society.

Supplementary material

Crystallographic data for compound (I) has been deposited atthe Cambridge Crystallographic Data Centre with the CCDC No:934,224. Copies of the data can be obtained free of charge on appli-cation to the CCDC, 12 Union Road, Cambridge CB2 IEZ, UK. Fax:+44 1223 336033 or e mail: deposit@ccdc.cam.ac.uk.

Acknowledgements

Diwaker would like to thank IIT mandi for HTRA scholarshipas well as computational facilities. CSCK thanks to Universiti SainsMalaysia (USM) for a postdoctoral research fellowship. CKQ thanksMalaysian Government and USM for Fundamental Research GrantScheme (FRGS) (203/PFIZIK/6711411). The authors extend theirappreciation to The Deanship of Scientific Research at King SaudUniversity for the research group project No. RGP VPP-207.

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