Solid state structural and theoretical investigations of

Journal of Molecular Structure 1112 (2016) 124e135

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Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc

Solid state structural and theoretical investigations of a biologically active chalcone € kce b, Semiha Bahceli c, *, Michael Bolte d, Asghar Abbas a, Halil Go Muhammad Moazzam Naseer a, * a

Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan Giresun University, Vocational High School of Health Services, Güre Campus, 28200 Giresun, Turkey Physics Department, Faculty of Arts and Science, Süleyman Demirel University, 32260 Isparta, Turkey d Institut fur Anorganische Chemie, J. W. Goethe-Universitat Frankfurt, Max-von-Laue-Str. 7, 60438 Frankfurt/Main, Germany b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 17 November 2015 Received in revised form 5 February 2016 Accepted 5 February 2016 Available online 10 February 2016

The computational methods are presently emerging as an efficient and reliable tool for predicting structural properties of biologically important compounds. In the present manuscript, the solid state structural and theoretical investigations of a biologically active chalcone i-e (E)-3-(4-(hexyloxy)phenyl)1-phenylprop-2-en-1-one (6c) have been reported. The solid state structure of 6c was measured by X-ray crystallographic technique whereas the optimized molecular geometry, vibrational frequencies, the simulated UVevis spectra (in gas and in methanol solvent), 1H and 13C NMR chemical shift (in gas and in chloroform solvent) values, HOMO-LUMO analysis, the molecular electrostatic potential (MEP) surface and thermodynamic parameters were calculated by using DFT/B3LYP method with 6-311þþG(d,p) basis set in ground state. The results of the theoretical investigations were found to be in good agreement with experimental data. © 2016 Elsevier B.V. All rights reserved.

Keywords: Alkoxychalcone FT-IR Raman NMR and UVevis spectroscopies DFT calculations

1. Introduction Chalcones (benzylideneacetophenones) are the biologically important molecules which represent one of the largest classes of plant metabolites and are important precursors in the biosynthesis of flavonoids and related compounds that play major role in the plant defense mechanism [1e8]. Due to their immense importance, a number of chalcone derivatives have been synthesized in recent years with diverse applications in medicinal chemistry. These are usually accessed by the ClaiseneSchmidt condensation reaction of acetophenones and benzaldehydes. The opportunity of installing different substituents on the two aryl rings and their ability to undergo Michael reaction are the two important features that make this class of compounds extremely attractive drug scaffold. They are known to have anti-fungal, anti-bacterial, anti-cancer, antiglycation, anti-inflammatory, analgesic, anti-oxidant, anti-plasmodial, immunosuppressive, anti-leishmanial and anti-pyretic properties [9e16]. In addition to their applications in medicinal

* Corresponding authors. E-mail addresses: [email protected] (S. Bahceli), [email protected] (M.M. Naseer). http://dx.doi.org/10.1016/j.molstruc.2016.02.023 0022-2860/© 2016 Elsevier B.V. All rights reserved.

chemistry, they have recently been explored as molecules with nonlinear optical and luminescent properties [17e20]. Recently, the computational methods have become an efficient and reliable tool for predicting structural properties and solving chemical reactivity related problems [21e26]. Keeping the importance of various computational methods in view, and our recent interest in the solid state structural [27e31] and spectral properties [32e35] of biologically active molecules, we started a program [36,37] on theoretical calculations of solid state and spectral properties of biologically important molecules in comparison to experimental data. Herein, as continuation of this program, we report the solid state structure, measured through X-ray diffraction technique and the quatum chemical computations, calculated at B3LYP/6-311þþG(d,p) level of the theory of (E)-3-(4-(hexyloxy) phenyl)-1-phenylprop-2-en-1-one (6c), which we previously [15] reported as antiglycating agent. The results of the theoretical calculations including molecular geometry, vibrational frequencies (IR and Raman spectra), 1H and 13C NMR chemical shift values, electronic absorption spectrum, HOMO-LUMO analysis, and molecular electrostatic potential (MEP) of 6c are described in comparison to experimental results.

A. Abbas et al. / Journal of Molecular Structure 1112 (2016) 124e135

2. Experimental 2.1. General The FT-IR (Fourier Transform InfraRed) and the Raman spectra of compound 6c were recorded at Bruker Tensor-37 spectrophotometer and Horiba Jobin-Yvon LabRAM HR High Resolution Raman Spectrometer (Laser Power 14.7 mW at 632.8 nm laser wavelength, Grating 1800), respectively. The UVevis (ultravioletevisible) spectrum of 6c was measured at Shimadzu UV-1800 UVevis Spectrophotometer. The 1H and 13C NMR spectra were obtained from Bruker 300 MHz NMR spectrophotometer using CDCl3 solvent containing TMS as internal reference. 2.2. Crystallographic studies Single crystal of 6c was mounted in random orientation on a glass fiber on a Stoe IPDS-II two circle diffractometer [38] equipped with graphite monochromated Mo Ka radiation (l ¼ 0.71073 Å). The structure was solved by direct methods using SHELXS97 and refined with full-matrix least-squares on F2 with SHELXL-97 [39]. All non-hydrogen atoms were refined anisotropically. The crystal data and refinement details of 6c are summarized in Table 1. Further information can be seen in Table S1eS4, supplementary material. 2.3. Computational details All calculations in this study were carried out with the GaussView 05 molecular visualization program and Gaussian 09 package program [40,41]. The optimized molecular structure, vibrational frequencies, HOMO-LUMO analyses, molecular electrostatic potential (MEP) surface and thermodynamic parameters and atomic charges of 6c have been calculated using DFT/B3LYP method with 6-311þþG(d,p) basis set. In DFT method, since the high frequency region for the vibrational modes usually includes the stretching vibrational modes related to functional groups of a molecule and the lower frequency region can cover the overlapped bands of the compounds, the characteristic properties of high and low frequency

125

regions require different scaling factors [42,43]. Therefore, the calculated vibrational wavenumbers were scaled as 0.958 for frequencies higher than 1700 cm1 and as 0.983 for frequencies less than 1700 cm1 for the B3LYP/6-311þþG(d,p) level [44]. The assignments of fundamental vibrational modes of 6c were performed on the basis of potential energy distribution (PED) analysis by using VEDA 4 program [45,46]. The UVevis. calculations or the electronic absorption maximum wavelengths (lmax) of 6c in both gas phase and methanol solvent were performed using the time dependent DFT (TD-DFT) method with integral equation formalism polarizable continuum model (IEFPCM) at the B3LYP/6-311þþG(d,p) level [47,48]. The HOMOs and LUMOs energy values and their 3D plots were calculated and simulated at the B3LYP/6-311þþG(d,p) level. For the NMR analysis, the optimized molecular geometry of 6c was first obtained at the B3LYP/6-311þþG(d,p) level in the framework of IEFPCM and then, the 1H and 13C NMR chemical shifts were calculated using the gauge-invariant atomic orbital (GIAO) method after the molecular geometry was optimized at the B3LYP/ 6-311þþG(d,p) level in gas phase and in chloroform solvent (ε ¼ 4.71) [49,50]. The computed 1H and 13C NMR chemical shifts were compared with the experimental analogs recorded with respect to TMS as the reference for chemical shielding. In Gaussian package program, the quantum chemical computations have been performed for gas phase of isolated molecule, while the experimental data was recorded in both solid and solution state of molecule.

3. Results and discussion 3.1. Molecular geometry The optimized molecular structure of 6c is given in Fig. 1, whereas the optimized molecular geometry parameters using DFT/ B3LYP method with 6-311þþG(d,p) basis set are presented in Table 2 in comparison to experimental values. As shown in Fig. 1, two aromatic rings are connected through a,b-unsaturated carbonyl which is the main chalcone moiety [37]. Therefore, by considering Table 1 and Fig. 1, C1eC2 single bond and

Table 1 Crystal data and structure refinement parameters of 6c. Crystal data

6c

CCDC Chemical formula Mr Crystal system, space group Temperature (K) a, b, c (Å) b ( ) V (Å3) Z Radiation type m (mm1) Crystal size (mm) Data collection Diffractometer Absorption correction No. of measured, independent and observed [I > 2s(I)] reflections Rint (sin q/l)max (Å1) Refinement R[F2 > 2s(F2)], wR(F2), S No. of reflections No. of parameters H-atom treatment D〉max, D〉min (e Å3)

1409316 C21H24O2 308.40 Triclinic, P1 173 5.8269 (4), 15.4577 (13), 19.3483 (15) 91.588 (6), 90.411 (6), 94.827 (6) 1735.8 (2) 4 Mo Ka 0.07 0.35 0.31 0.27 STOE IPDS II two-circle-diffractometer e 16299, 6455, 4020 0.050 0.608 0.043, 0.107, 0.86 6455 416 H-atom parameters constrained 0.19, 0.17

126


Fig. 1. The optimized molecular structure of 6c.

Table 2 The experimental and calculate molecular geometric parameters of 6c. Bond lengths (Å)

X-Ray

B3LYP

Bond angles ( )

X-Ray

B3LYP

Bond angles ( )

X-Ray

B3LYP

C1eC2 C1eC11 C1eO17 C2eC3 C2eH24 C3eC20 C3eH25 C4eC5 C4eO10 C4eH26 C4eH27 C5eC6 C5eH28 C5eH29 C6eC7 C6eH30 C6eH31 C7eC8 C7eH32 C7eH35 C8eC9 C8eH33 C8eH34 C9eH45 C9eH46 C9eH47 O10eC19 C11eC12 C11eC16 C12eC13 C12eH40 C13eC14 C13eH39 C14eC15 C14eH38 C15eC16 C15eH37 C16eH36 C18eC19 C18eC22 C18eH42 C19eC21 C20eC22 C20eC23 C21eC23 C21eH43 C22eH41 C23eH44

1.471(2) 1.498(2) 1.228(17) 1.336(2) 0.950 1.456(2) 0.950 1.506(2) 1.436(17) 0.990 0.990 1.522(2) 0.990 0.990 1.518(2) 0.990 0.990 1.522(2) 0.990 0.990 1.524(2) 0.990 0.990 0.980 0.980 0.980 1.364(18) 1.386(2) 1.391(2) 1.379(2) 0.950 1.375(2) 0e950 1.376(2) 0.950 1.381(2) 0.950 0.950 1.390(2) 1.385(2) 0.950 1.397(2) 1.395(2) 1.403(2) 1.376(2) 0.950 0.950 0.950

1.480 1.505 1.226 1.348 1.082 1.455 1.088 1.520 1.433 1.097 1.097 1.533 1.095 1.095 1.533 1.098 1.098 1.533 1.098 1.098 1.531 1.097 1.097 1.094 1.093 1.095 1.357 1.403 1.402 1.389 1.083 1.396 1.084 1.393 1.084 1.394 1.084 1.083 1.398 1.393 1.081 1.406 1.402 1.411 1.380 1.083 1.085 1.084

C2eC1eC11 C2eC1eO17 C11eC1eO17 C1eC2eC3 C1eC2eH24 C3eC2eH24 C2eC3eC20 C2eC3eH25 C20eC3eH25 C5eC4eO10 C5eC4eH26 C5eC4eH27 O10eC4eH26 O10eC4eH27 H26eC4eH27 C4eC5eC6 C4eC5eH28 C4eC5eH29 C6eC5eH28 C6eC5eH29 H28eC5eH29 C5eC6eC7 C5eC6eH30 C5eC6eH31 C7eC6eH30 C7eC6eH31 H30eC6eH31 C6eC7eC8 C6eC7eH32 C6eC7eH35 C8eC7eH32 C8eC7eH35 H32eC7eH35 C7eC8eC9 C7eC8eH33 C7eC8eH34 C9eC8eH33 C9eC8eH34 H33eC8eH34 C8eC9eH45 C8eC9eH46

120.29(13) 120.98(14) 118.73(14) 120.09(14) 120.0 120.0 128.66(14) 115.7 115.7 106.77(11) 110.4 110.4 110.4 110.4 108.6 113.67(12) 108.8 108.8 108.8 108.8 107.7 111.94(12) 109.2 109.2 109.2 109.2 107.9 114.25(13) 108.7 108.7 108.7 108.7 107.6 112.69(14) 109.1 109.1 109.1 109.1 107.8 109.5 109.5

118.885 121.556 119.553 120.364 118.669 120.950 128.243 115.916 115.841 107.992 110.794 110.790 109.530 109.469 108.254 112.305 108.743 108.714 110.071 110.043 106.797 113.135 109.546 109.506 109.128 109.119 106.169 113.527 109.251 109.248 109.236 109.238 106.072 113.220 109.193 109.195 109.442 109.463 106.078 111.197 111.401

C8eC9eH47 H45eC9eH46 H45eC9eH47 H46eC9eH47 C4eO10eC19 C1eC11eC12 C1eC11eC16 C12eC11eC16 C11eC12eC13 C11eC12eH40 C13eC12eH40 C12eC13eC14 C12eC13eH39 C14eC13eH39 C13eC14eC15 C13eC14eH38 C15eC14eH38 C14eC15eC16 C14eC15eH37 C16eC15eH37 C11eC16eC15 C11eC16eH36 C15eC16eH36 C19eC18eC22 C19eC18eH42 C22eC18eH42 O10eC19eC18 O10eC19eC21 C18eC19eC21 C3eC20eC22 C3eC20eC23 C22eC20eC23 C19eC21eC23 C19eC21eH43 C23eC21eH43 C18eC22eC20 C18eC22eH41 C20eC22eH41 C20eC23eC21 C20eC23eH44 C21eC23eH44

109.5 109.5 109.5 109.5 119.01(11) 117.91(14) 123.97(14) 118.12(15) 121.13(16) 119.4 119.4 120.25(16) 119.9 119.9 119.37(17) 120.3 120.3 120.67(17) 119.7 119.7 120.45 119.8 119.8 119.15(14) 120.4 120.4 124.79(13) 115.40(12) 119.80(3) 119.72(13) 122.93(14) 117.32(13) 120.19(13) 119.9 119.9 122.25(13) 118.9 118.9 121.27(27) 119.4 119.4

111.189 107.657 107.554 107.656 119.268 117.655 123.612 118.726 120.717 118.150 121.133 120.072 119.911 120.017 119.796 120.140 120.064 120.109 120.102 119.788 120.575 120.641 118.772 119.423 121.129 119.448 124.825 115.754 119.421 118.967 123.738 117.296 120.394 118.369 121.237 122.132 118.898 118.970 121.334 119.944 118.722

C1]O17 double bond lengths (exp./cal.) were found as 1.478/ 1.480 Å and 1.288/1.226 Å, respectively. Furthermore, the C2]C3 double bond length (exp./cal.) was found as 1.336/1.348 Å. As for the C19eO10 and O10eC4 bond lengths which were taken place in the chain were measured as 1.364 Å and 1.436 Å, respectively and these values are in a good agreement with the calculated values at

the B3LYP/6-311þþG(d,p) level, as seen in Table 2. For the other bond lengths, we can state that there is a good agreement between the observed and calculated values. However, the largest difference between the calculated and experimental values is 0.108 Å for the CeH bond lengths of methyl group at the end of chain. This may be due to their involvement in intermolecular interactions (Fig. S1).


127

Table 3 The calculated and experimental vibrational wavenumbers, assignments and the calculated IR intensities and Raman scattering activities of 6c. Assignments (TED%)

Exp. (cm1) IR

The calculated with B3LYP/6-311þþG(d,p) level Raman

Lattice mode Lattice mode Lattice mode Lattice mode Lattice mode Lattice mode Lattice mode Lattice mode tCpCpCpC(16) þ gCCpCpCp(13) þ tCpCCC(13) þ tCCCCp(11) tCpOCC(26) þ taliphaticCCCC(26) daliphaticCCC(22) þ dCOCp(11) taliphaticCCCC(66) e

tCCOCp(29) þ taliphaticCCCC(27) þ tCpCCC(14) tCCCCp(22) þ gCCpCpCp(14) dCpCpC(13) þ tCCCCp(11) tCpCpCpC(51) tCH3(79) daliphaticCCC(17) daliphaticCCC(34) þ dOCC(15) þ dCCpCp(11) dCCpCp(26) þ dOCC(15) gOCCC(22) daliphaticCCC(26) þ nCpC(11) tCCCC(70) daliphaticCCC(28) þ dOCpCp(16) tCCCC(61) tCCCC(10) tCCCC(25) daliphaticCCC(34) þ dCOCp(16) þ dOCpCp(13) gOCpCpCp(21) þ tCpCpCpC(14) þ dCpCC(13) dCpCC(39) dOCC(12) þ dCOC(12) þ dphenyl(11) dphenyl(86) dphenyl(57) dOCC(18) þ dphenyl(13) gOCCC(26) þ tCCCC(21) tHCCC(45) þ tCCCC(19) tHCCC(12) þ gOCCC(12) þ tCCCC(12) rCH2(87) rCH2(60) nCpC(14) þ dphenyl(10) gOCCC(15) þ tHCCC(15) þ gCCCC(12) tHCCC(32) þ rCH2(22) tHCCC(48) þ rCH2(21) tHCCC(63) þ gOCCC(15) nCC(30) in ring þ nOCp(12) tHCCC(95) taliphaticHCCC(63) þ gOCCC(10) rCH3(25) þ nCH2-CH2(21) þ nCH2-CH3(17)þ daliphaticCCC(38) þ nCC(13) in ring rCH2(38) tHCCC(47) tHCCC(65) tHCCC(63) tHCCC(62) tHCCC(77) þ tCCCC(11) nCH2-CH2(43) þ nCH2-CH3(28) þ nO-CH2(10)

227 262 321

403 422 445 458 498 519 574 636 662 690 722 729 751 778

382 404 409 421 450 459 521 533 578 619 640 668 684 726 733 754 773 783 787

805

850 866 891

828 836 843 869

894 928 940 951 985

988

tCH2(67)

dphenyl(79) dphenyl(72) taliphaticHCCC(74) nCC(27) in aliphatic þ dphenyl(14) nO-CH2(53) þ nCH2-CH3(15) nCH2-CH2(59) dHCC(23) nCH2-CH2(45) þ nCH2-CH3(19) nCH2-CH2(62) [dHCC(24) þ nCC(22)] in ring dHCC(57) daliphaticCCC(27) þ nCH2-CH2,3(24) þ rCH3(15) dHCC(63) rCH3(73)

1005 1018 1022 1030 1037 1060 1092 1120 1130 1170

1059 1072 1122 1131 1161 1172

Freq. (Unscaled)

Freq. (Scaled)

SRaman

IIR

13.58 22.92 24.13 28.54 50.64 53.50 56.11 88.11 103.91 115.28 116.89 142.54 152.61

13.35 22.53 23.72 28.05 49.78 52.59 55.15 86.61 102.14 113.32 114.91 140.11 150.01

0.017 0.156 0.231 1.001 0.069 0.262 0.344 1.544 0.718 0.756 0.313 0.706 0.139

3.122 2.150 0.690 0.620 0.803 1.238 0.155 1.325 2.063 0.851 0.972 0.348 2.143

154.18 171.63 198.82 212.33 239.32 254.46 268.67 314.30 371.62 404.60 411.71 417.60 425.42 435.10 458.82 508.84 524.92 529.00 584.56 631.95 652.72 677.82 690.83 702.78 732.18 735.86 758.64 780.21 796.51 812.79 823.62 844.29 845.23 856.73 884.48 897.85 904.98 909.92 945.29 947.02 972.78 991.14 1002.33 1009.68 1014.28 1016.26 1022.02 1024.29 1033.82 1042.71 1046.42 1053.50 1063.82 1075.12 1106.73 1137.32 1142.64 1182.31 1187.39

151.56 168.71 195.44 208.72 235.25 250.14 264.10 308.95 365.30 397.72 404.71 410.50 418.19 427.70 451.02 500.19 516.00 520.01 574.63 621.21 641.62 666.30 679.08 690.84 719.73 723.35 745.74 766.95 782.97 798.98 809.62 829.93 830.86 842.16 869.45 882.59 889.60 894.46 929.22 930.92 956.24 974.29 985.29 992.51 997.03 998.99 1004.65 1006.87 1016.25 1024.98 1028.63 1035.59 1045.74 1056.84 1087.91 1117.99 1123.22 1162.21 1167.21

0.783 0.495 0.786 0.378 0.007 0.092 1.578 11.409 1.624 0.823 0.422 3.202 0.207 0.501 2.490 1.617 12.417 9.296 79.930 1.164 7.064 14.634 1.500 45.353 16.357 3.979 0.432 3.301 39.714 1.095 0.114 45.082 21.581 0.577 2.944 1.271 0.980 0.887 0.270 0.589 0.515 0.694 12.747 0.067 0.009 1.032 6.050 25.810 209.703 126.032 0.643 46.629 31.375 2.636 2.036 16.488 12.366 10.742 1.451

0.159 3.802 3.591 2.197 0.011 3.368 0.611 3.527 1.677 3.108 0.450 3.831 0.135 2.073 4.846 0.371 5.388 22.310 29.997 4.744 22.752 7.591 0.568 1.191 0.999 0.068 0.175 1.907 11.052 0.460 0.398 0.692 41.932 0.944 9.692 11.185 22.524 0.154 2.224 0.496 0.139 0.260 1.575 1.329 0.050 90.374 7.341 2.255 280.572 7.659 4.155 22.142 8.789 9.475 6.226 34.002 20.124 21.451 1.160

(continued on next page)

128


Table 3 (continued ) Assignments (TED%)

Exp. (cm1) IR

dHCC(58) dHCC(62) þ nCC(14) nCpC(26) þ dHCC(17) tCH2(65)

Freq. (Unscaled)

Freq. (Scaled)

IIR

SRaman

1176

1192.93 1201.60 1224.30 1229.36 1235.21 1261.91 1280.97 1285.24 1317.16 1321.69 1323.55 1326.97 1334.28 1335.89 1338.33 1345.63 1357.92 1371.52 1382.80 1402.22 1413.42 1426.88 1455.03 1475.07 1487.91 1489.86 1496.56 1499.16 1504.44 1512.78 1520.10 1520.80 1541.94 1596.23 1612.46 1625.86 1637.92 1652.47 1712.58 2993.42 2997.26 2999.90 3009.71 3013.72 3019.75 3026.12 3029.95 3032.22 3046.99 3074.28 3080.46 3085.56 3144.99 3162.87 3168.99 3173.14 3176.83 3183.44 3189.85 3195.45 3201.16 3204.46 3209.63

1172.65 1181.17 1203.49 1208.46 1214.22 1240.46 1259.19 1263.39 1294.77 1299.22 1301.05 1304.41 1311.60 1313.18 1315.58 1322.75 1334.83 1348.20 1359.30 1378.38 1389.39 1402.62 1430.29 1450.00 1462.62 1464.53 1471.12 1473.68 1478.87 1487.06 1494.26 1494.95 1515.73 1569.09 1585.05 1598.22 1610.07 1624.38 1640.65 2867.70 2871.37 2873.90 2883.30 2887.14 2892.92 2899.02 2902.69 2904.87 2919.02 2945.16 2951.08 2955.97 3012.90 3030.03 3035.89 3039.87 3043.40 3049.74 3055.88 3061.24 3066.71 3069.88 3074.83

382.664 7.667 290.594 0.469 17.359 4.437 495.201 0.081 177.240 0.147 0.538 4.798 0.213 70.226 0.667 7.049 19.812 52.874 2.748 0.130 3.593 34.728 83.361 9.703 0.324 0.257 2.533 8.194 3.273 22.913 11.196 65.812 195.607 261.361 126.204 517.504 174.220 1.416 160.328 10.734 7.477 13.629 65.909 0.336 45.346 1.282 45.238 15.997 30.945 50.457 84.453 43.858 0.715 0.367 7.218 10.974 3.946 26.591 4.986 2.411 13.280 14.790 13.530

497.704 56.474 42.980 1.548 268.437 2.305 200.729 0.363 76.832 23.205 80.557 24.901 3.940 38.669 4.782 89.883 138.119 235.282 5.413 1.259 0.606 37.633 231.088 73.437 27.141 5.288 28.816 8.790 4.246 4.724 96.028 7.183 51.839 1376.279 1565.541 5405.069 270.144 25.185 57.095 10.649 318.928 11.954 122.901 160.747 176.466 1.613 72.119 72.492 20.605 5.914 39.442 122.796 25.090 49.678 65.185 149.581 39.944 158.242 156.539 62.079 87.851 182.732 142.092

1210

1208 1219

1251

1253

dHCC(17) þ nCpC(12) wCH2(73) nOCp(41) þ [dHCC(47) þ nCC(15)] in ring tCH2(74) nCpC(18) þ nCC(12) in ring þ dCpCpC(11) tCH2(68) dalihpaticHCC(28) wCH2(51) tCH2(85) [dHCC(36) þ nCC(17)] in ring tCH2(61) nCC(42) in ring þ dalihpaticHCC(12) dalihpaticHCC(30) þ nC ¼ C(13) dalihpaticHCC(28) þ [dHCC(14) þ nCC(12)] in ring þ nCpC(14) wCH2(74) wCH2(74) dCH3(77) wCH2(74) dHCC(21) þ nCC(15) dHCC(26) þ nCC(16) dsCH2(66) dsCH2(74) dsCH2(76) dsCH3(98) dsCH2(68) dsCH2(74) dHCC(61) dsCH2(62) dHCC(46) þ dCCC(11) þ nCC(10) nCC(35) nCC(27) þ nO ¼ C(12) nCC(25) þ nC2 ¼ C3(24) þ nO ¼ C(10) nCC(49) nCC(30) þ nC2 ¼ C3(13) nO ¼ C(59) nsCH2(96) nsCH2(94) nsCH2(94) nsCH2(95) nasCH2(83) nsCH3(98) nasCH2(83) þ nasCH3(14) nsCH2(95) nasCH2(96) nasCH2(53) þ nasCH3(22) nasCH2(71) þ nasCH3(15) nasCH3(54) þ nasCH2(41) nasCH3(96) n ¼ CH(99) nCH(81) nCH(98) nCH(90) nCH(84) nCH(63) þ n ¼ CH(22) nCH(47) þ n ¼ CH(23) nCH(87) nCH(91) nCH(90) nCH(99)

The calculated with B3LYP/6-311þþG(d,p) level Raman

1290 1301 1309

1312

1320

1327

1341

1345 1353 1379

1379 1392 1421 1449 1462

1398 1425 1450

1474

1475

1496 1510 1570 1590 1597 1620 1650

1572 1586 1592 1605 1657 2855 2872

2895 2906 2924 2936

3024 3040

3069

n, stretching; d, in-plane bending; ds, scissoring; r, rocking; t, twisting; w, wagging t, torsion; g, out-of-plane bending; p, phenyl; IIR, IR intensity (km/mol); SRaman, Raman scattering activity (Å4/amu); TED, total energy distribution.

Since the packing in the solid state is mainly driven by CH$$$O and CH$$$p interactions [27e31] (see Fig. S1) having interatomic distances >2.6 Å (relatively week interactions), which may be the reason of good agreement between the performed gas-phase calculations and the experimental results in solid state. In fact, the

calculations performed in Gaussian package program are valid for the isolated molecules and in gas-phase cases. Furthermore, the computed CH bond lengths and angles are usually longer than the experimental ones and this situation can be explained by considering the large deviation from experimental bond lengths which


129

Fig. 2. The experimental (top) and simulated (bottom) IR spectra of 6c.

may be available for the low scattering factors of hydrogen atoms in the X-ray diffraction experiment. On the other hand, as presented in Table 2, the C1eC2eC3 and C4eO10eC19 bond angles (exp./cal.) were found as 120.09 / 120.364 and 119.01 /1119.268 , respectively. The presence of a good agreement between the observed and calculated values for

the other bond angles can be clearly expressed. In order to find out the harmony between the calculated and experimental values, the linear correlation coefficients (R2) were found as 0.99265 and 0.97537 for bond length and bond angles, respectively (Table 2).

Fig. 3. The experimental (top) and simulated (bottom) Raman spectra of 6c.

130


Table 4 The calculated and experimental 1H and

13

C NMR isotropic chemical shifts (with recpect to TMS, all values in ppm) of 6c.

Nucleus

dexp. (in CHCl3-d)

dcal. (in gas)

dcal. (in chloroform)

Nucleus

dexp. (in CHCl3-d)

dcal. (in gas)

dcal. (in chloroform)

C1 C2 C3 C4 C5 C6 C7 C8 C9 C11 C12 C13 C14 C15 C16 C18 C19 C20 C21 C22 C23

190.6 119.6 144.8 68.2 29.1 25.6 31.5 22.6 14.0 138.5 128.4 128.5 132.5 128.5 128.4 114.9 161.3 127.3 114.9 130.2 130.2

189.693 116.821 150.415 70.893 34.387 30.489 37.035 27.872 15.209 144.581 134.980 133.777 136.496 131.765 131.903 112.625 169.647 133.138 122.291 140.991 131.168

191.417 117.058 151.183 71.054 34.290 30.103 36.854 27.661 14.961 144.128 133.902 134.044 137.850 132.728 132.966 113.734 170.503 132.166 122.312 141.907 131.708

H24 H25 H26 H27 H28 H29 H30 H31 H32 H33 H34 H35 H36 H37 H38 H39 H40 H41 H42 H43 H44 H45 H46 H47

7.43 7.71 4.02 4.02 1.82 1.82 1.34e1.52 1.34e1.52 1.34e1.52 1.34e1.52 1.34e1.52 1.34e1.52 8.03 7.48e7.58 7.48e7.58 7.48e7.58 8.03 7.61 6.95 6.95 7.61 0.93 0.93 0.93

7.644 8.160 3.675 3.629 1.926 1.913 1.285 1.292 1.324 1.336 1.320 1.305 8.138 7.512 7.577 7.623 8.610 7.551 6.650 7.100 8.030 0.899 1.194 0.898

7.804 8.199 3.795 3.748 1.913 1.898 1.333 1.340 1.331 1.344 1.328 1.313 8.328 7.695 7.771 7.751 8.549 7.696 6.859 7.182 8.163 0.891 1.175 0.889

3.2. Vibrational analysis The 6c includes 47 atoms and 135 normal vibrational modes. All vibrations of 6c are active in both IR and Raman. The experimental and calculated vibrational frequencies, the calculated IR intensities and Raman scattering activities and vibrational frequency assignments of 6c are provided in Table 3. The assignments of vibrational frequencies with greater than 10% weight percentage of internal coordinate contributions were presented. Furthermore, the experimental and simulated IR and Raman spectra of 6c are shown in Figs. 2 and 3, respectively. 3.2.1. CH, CH2 and CH3 vibrations It is well known that the CH stretching vibrations of aromatic compounds appears in the range of 3100e3000 cm1 [51e55]. The CH stretching bands of aromatic rings in Raman spectrum of 6c are observed at 3024, 3040 and 3069 cm1. However, the hot band appeared at the interval 2800-3100 cm1 in IR spectrum of 6c covers these mentioned CH vibrations as seen in Fig. 2 (top). The calculated wavenumbers corresponded to experimental bands in Raman spectra have been computed as 3030.03, 3039.87 and 3069.88 cm1 with PED contributions of 81%, 90% and 90% respectively.

The CH in-plane and out-of-plane bending vibrations of 6c are observed as strong or medium peaks in the regions 1000e1600 cm1 and 650e1000 cm1, respectively [51e55]. The experimental and calculated wavenumbers corresponded to CH inplane and out-of-plane bending modes in aromatic rings are listed in Table 3. In ketoethylenic group (eCOeCH]CH-) of 6c, the ]CeH stretching modes are not observed in both IR and Raman spectra since the computed values for these group are found as 3012.90, 3049.74 and 3055.88 cm1 with 99%, 22% and 23% contributions of PED, respectively. The CH in-plane bending modes (exp./cal.) in this group are found at 1341 (IR)-1345 (R) cm1/1348.20 cm1/28%, 1334.83 cm1/30%, 1320 (IR)-1327 (R) cm1/1322.75 cm1/12% and 1301 (R) cm1/1301.05 cm1/28%, while the CH out-of-plane bending modes are found at 1006.87 cm1/74% and 866 (IR)-869 (R) cm1/869.45 cm1/63% (exp./cal./PED) [37]. The methyl (CH3) and methylene (CH2) groups give rise to CH stretching bands in the region 2800e3000 cm1 [51e55]. The asymmetric stretching bands for methyl and methylene groups are appeared at 2936, 2924, 2906 and 2895 cm1 in Raman spectrum, while the symmetric stretching bands are observed at 2855 and 2872 cm1. The computed values for asymmetric and symmetric stretching modes for these groups were found at the interval

Table 5 The experimental and calculated UVeVis. spectroscopic parameters of 6c. Exp. lmax. (nm) (in methanol)

Transition

The calculated with B3LYP/6-311þþG(d,p) level (Vacuum/methanol)

lmax. (nm)

Excitation energy (eV)

f (oscillator strength)

e 347

e

378.14/372.47

3.2788/3.3287

0.0002/0.9549

p/p*

e

e

349.95/360.03 290.43/295.81

3.5429/3.4437 4.2690/3.1913

0.8615/0.0038 0.0162/0.0169

e

e

278.51/282.50

4.4518/4.3888

0.1174/0.1756

e 246

e

261.76/263.82

4.7366/4.6996

0.1163/0.1130

e

n/s* e

250.20/252.50 245.14/245.15

4.9554/4.9103 5.0577/5.0576

0.1253/0.1204 0.0083/0.0824

e

e

232.28/225.70

5.3377/5.4934

0.0002/0.0155

e 213

e

221.68/211.54

5.5929/5.8609

0.0000/0.0347

s/s*

213.67/208.13

5.8027/5.9569

0.0276/0.0840


131

[51e55]. The strong band at 1650 cm1 (IR) and weak band at 1653 cm1 (R) can be assigned to the C]O stretching mode whose computed value was found to be 1640.65 cm1 with PED contribution of 59%. These values are in good agreement with the experimental and calculated vibrational results of previous studies on chalcone derivatives [37,63e65]. The CeO stretching mode between C19 atom in phenyl ring and O10 atom in hexyloxy group is observed as a strong peak at 1251 cm1(IR) and as a weak peak at 1253 cm1 (R) and its computed value was found as 1260.24 cm1 with PED contribution of 41%. Similarly, the OeCH2 stretching vibration in hexyloxy group gives rise to absorption band with a medium intensity at 1022 cm1 (R) and this band was calculated as 1024.98 cm1 with 53% contribution of PED [37].

Fig. 4. The experimental (top) and simulated (bottom) UV spectra of 6c.

2867.70e2855.97 cm1. The observed bands at 1462 (IR), 1474 (IR)1475 (R) and 1496 (R) cm1 can be assigned to the scissoring modes of methyl and methylene group. Although the symmetric bending vibration is not observed in IR and Raman spectra, its computed value was found to be 1389.39 cm1 with PED contribution of 77%. The wagging modes of methylene group are observed at 1392 (IR)1398 (R), 1379 (IR) and (R) and 1353 (R) cm1, their calculated values were found as 1402.62 (74%), 1378.38 (74%), 1359.30 (74%), 1304.41 (51%) and 1240.46 (79%) cm1. The bands at 1309 (IR)-1312 (R) cm1/1311.60 cm1/85%, 1299.22 cm1/68%, 1263.39 cm1/72%, 1210 (IR)-1208 (R) cm1/1208.46 cm1/65% and 997.03 cm1/67% can be attributed to the twisting modes of methylene, while rocking modes in our study were found as 805 (IR) cm1/809.62 cm1/ 21%, 787 (IR) cm1/798.98 cm1/22%, 894 (R) cm1/894.46 cm1/ 38%, 751 (IR)-754 (R) cm1/745.74 cm1/60% and 729 (IR)-733 (R) cm1/723.35 cm1/87% (exp./cal./PED). Similarly, the peaks of rocking modes of methyl group are observed at 891 (IR), 1130 (IR)1131 (R) and 1170 (IR)-1172 (R) cm1 and the computed values fot these bands were found as 882.59, 1123.22 and 1167.21 with PED contributions of 25%, 15% and 73%, respectively. The torsion mode of methyl group is observed 227 cm1 in Raman spectrum and it was computed as 235.25 cm1 with 79% contribution of PED. By considering the present results, it can be said that the calculated and experimental wavenumbers of alkyl chains of 6c are not only in good agreement with each other but also with literature [37,56e61].

3.2.2. C]O and CeO vibrations The carbonyl (C]O) carbon-oxygen double bond is formed by overlap of p-orbitals of carbon and oxygen atoms and is highly polar due to the highly electrophilic due to the electronegatively of oxygen [62]. The C]O stretching gives rise to absorption bands in the region of 1850e1600 cm1 in IR and Raman spectra of 6c

3.2.3. CC vibrations The aromatic ring CC stretching vibration modes which are called as skeletal vibration usually arise in the region 14001625 cm1 [66]. The observed bands at the interval 1510-1620 cm1 in the experimental IR and Raman spectra can be assigned to the CC stretching modes of phenyl rings in 6c. These CC stretching vibration bands were computed at the interval 1515.75e1624.38 cm1. The C2]C3 stretching modes in ketoethylenic group were found as 1592 (IR)e1597 (R) cm1/1598.22 cm1/24% and 1620 (IR) cm1/ 1624.38 cm1/13% combining with CC stretching modes of aromatic rings (exp./cal./PED). The in-plane bending, torsional and out-ofplane bending vibrational modes of phenyl rings are presented in Table 2. The CeC stretching modes of hexyloxy group (eO(CH2)5CH3) of 6c are observed in the region of 1150e850 cm1 as shown in Table 3. The observed peaks at 1130 (IR)e1131 (R), 1060 (IR)e1059 (R), 1030 (IR), 1022 (R) and 891 (IR) cm1 can be credited to the CeC stretching vibrations in hexyloxy group [37,67]. The computed values for these aliphatic CeC stretching vibrations were found as 1123.22, 1056.84, 1045.74, 1028.63, 1024.98, 992.51 and 882.59 cm1 with PED contributions of 24%, 62%, 64%, 59%, 15%, 71% and 38% respectively. 3.3. NMR analysis The isotropic chemical shift analysis in NMR (nuclear magnetic resonance) spectroscopy helps us in order to determine the relative ionic species and to calculate reliable magnetic properties required for the accurate predictions of molecular geometries [68e71]. The experimental and the calculated 1H and 13C NMR chemical shift values (in gaseous phase and in the chloroform solution) of 6c at the B3LYP/6-311þþG(d,p) level are presented in Table 4. As shown in Table 4, the rings carbon atoms of 6c which are the C11, C12, C13, C14, C15, C16 and C18, C19, C20, C21, C22, C23 have the chemical shift values (exp./cal. in chloroform solvent) at the intervals 114.9/113.7e161.3/170.500 ppm. The C1 atom which is connected to the electronegative O17 oxygen atom of the carbonyl group of 6c has the highest chemical shift value (exp./cal.) as 190.6/ 191.417 ppm. Likewise, the methylene group carbon atoms (C4, C5, C6, C7 and C8) have the chemical shift values (exp./cal.) at the interval 22.6/27.661e68.2/71.055 ppm while the methyl group C9 atom has the chemical shift value (exp./cal.) of 14.0/14.961 ppm (Table 4). As for the chemical shift values of the hydrogen atoms of 6c, the methyl group hydrogens H45, H46 and H47 have the lowest values (exp./cal.) as 0.93/0.899, 1.194 and 0.898 ppm, respectively. For other hydrogen atoms, proton chemical shift values (exp./cal.) take place at the interval 1.34/1.313e8.03/8.328 ppm. It can clearly be stated that the observed values are in a good agreement with the calculated ones for both carbons and protons of 6c (Table 4).

132


Fig. 5. The HOMO-1, HOMO, LUMO and LUMOþ1 plots of 6c.

3.4. UVevis. absorption and FMOs analysis The maximum absorption wavelengths (lmax), excitation energies and oscillator strengths calculated by using TD-DFT/B3LYP method with the same 6-311Gþþ(d,p) basis set in ground state of 6c in both gas and methanol solvent are presented in Table 5. Furthermore, the experimental and simulated Uv.evis spectra of 6c are provided in Fig. 4. Three absorption bands at 213, 246 and 347 nm were observed for 6c (Fig. 4, top). As shown in Table 5, the calculated maximum absorption wavelengths (lmax) in methanol solvent at the B3LYP/6-

311Gþþ(d,p) level as, 208.13, 245.15 and 360.03 nm are in a good agreement with the experimental values. Therefore, the observed three absorption bands, i-e, 213 nm, 246 nm and 347 nm can be attributed to the s/s*, n/s* and p/p*transitions for 6c, respectively [72]. As for HOMO-LUMO analysis, it is well-recognized that the highest occupied molecular orbital (HOMO) is the one with the filled outermost orbital and is directly linked to the ionization potential, behaving as electron donor, while the lowest unoccupied molecular orbital (LUMO) is the first empty innermost orbital and is directly associated with the electron affinity and behaves as an


133

Fig. 6. Molecular elecrostatic potantial (MEP) surface of 6c.

electron acceptor. The HOMO and LUMO are known as frontier molecule orbitals (FMOs). The energy gap between HOMO and LUMO is a sign of molecular chemical stability and is usually used to determine the molecular electrical transport properties. Therefore,

it can be a critical parameter. Additionally, the molecular properties such as the chemical reactivity, kinetic stability, polarizability, chemical hardness and softness, aromaticity and electronegativity can be estimated by using this energy gap [73,74].

Table 6 The calculated thermodynamic parameters and Mulliken atomic charges in gas phase of 6c. Parameters Termal energy (kcal/mol) Total Electronic Translational Rotational Vibrational Heat capacity, Cv (cal/mol K) Total Electronic Translational Rotational Vibrational Entropy, S (cal/mol K) Total Electronic Translational Rotational Vibrational Dipol moment, (Debye)

mx my mz mTotal Rotational Constant (GHz)

Zero-point vibrational energy (kcal/mol)

Value 263.702 0.000 0.889 0.889 261.924 84.718 0.000 2.981 2.981 78.757 168.861 0.000 43.073 35.839 89.949 3.8636 2.0460 0.0874 4.3728 1.40318 0.04906 0.04753 249.43454

Zero-point correction (Hartree/Particle)

0.397499

Thermal correction to Energy (Hartree/Particle)

0.420235

Thermal correction to Enthalpy (Hartree/Particle)

0.421179

Thermal correction to Gibbs Free Energy (Hartree/Particle)

0.340948

Sum of electronic and zero-point Energies (Hartree/Particle)

964.995514

Sum of electronic and thermal Energies (Hartree/Particle)

964.972778

Sum of electronic and thermal Enthalpies (Hartree/Particle)

964.971834

Sum of electronic and thermal Free Energies (Hartree/Particle)

965.052065

E(RB þ HF-LYP)

965.39301313

Atoms

Mulliken charges (a.u.)

C1 C2 C3 C4 C5 C6 C7 C8 C9 O10 C11 C12 C13 C14 C15 C16 O17 C18 C19 C20 C21 C22 C23 H24 H25 H26 H27 H28 H29 H30 H31 H32 H33 H34 H35 H36 H37 H38 H39 H40 H41 H42 H43 H44 H45 H46 H47

0.569972 0.038586 0.199568 0.444650 0.293548 0.205962 0.284775 0.200153 0.649309 0.055231 1.301634 0.362690 0.254425 0.336984 0.201275 1.260885 0.240775 0.145721 0.255988 1.205605 0.454582 0.227319 0.836553 0.083606 0.200718 0.181289 0.185040 0.160041 0.158794 0.116489 0.116181 0.121720 0.128163 0.128109 0.121376 0.099043 0.181332 0.155561 0.172695 0.199996 0.179167 0.139349 0.190185 0.107488 0.136214 0.143538 0.136336

134


3D plots and energy gap values of HOMO-1, HOMO, LUMO LUMOþ1 of 6c are shown in Fig. 5. The calculated energy gaps between the HOMO-LUMO and HOMO-1-LUMOþ1 of 6c were found as 3.810 eV and 5.922 eV at the B3LYP/6-311Gþþ(d,p) level, respectively. 3.5. Molecular electrostatic potential (MEP) To locate possible non-covalent interactions sites in any given molecule, the molecular electrostatic potential (MEP) may be a useful tool. More specifically, the prediction of relative reactivity sites for electrophilic and nucleophilic reactions, hydrogen bond donor and acceptor sites, studies of zeolite, molecular cluster and solid state packing, investigation of biological recognition and prediction of a variety of macroscopic properties can be done by MEP [73,74]. The 3D plots of the MEPs for 6c is presented in Fig. 6 which was calculated by using the optimized molecular structure at the B3LYP/ 6-311Gþþ(d,p) level. The electrostatic potentials at the surface of 6c are shown by different colors. The red color parts signify the regions of negative electrostatic potential whereas the blue sites represent the regions of positive electrostatic potential and the parts with green color show the regions of zero potential. The negative electrostatic potential means that protons are attracted by the concentrated electron density in the molecules, while positive electrostatic potential represents the repulsion of the proton by the atomic nuclei in regions of low electron density where the nuclear charge is incompletely shielded. The potential rises in the order red < orange < yellow < green < blue. Moreover, the negative regions (red color) of MEP are associated with electrophilic reactivity and the positive ones (blue color) represent the nucleophilic reactive site. As shown in Fig. 6, the negative regions of MEP surface for 6c are localized on the O17 atom in ketoethylenic group and O10 atom in the side chain indicating possible site for electrophilic reactivity due to the presence of lone pair while the positive regions of MEP surface are localized on the protons of the side chain. 3.6. Thermodynamic parameters and Mulliken atomic charges For any molecule, the total energy is the sum of electronic, vibrational, rotational and transition energies i-e. E ¼ Ee þ Ev þ Er þ Et. In this framework, Table 6 displays the calculated thermodynamic parameters of 6c such as the magnitudes of total static dipole moment m, the heat capacity, entropy, thermal energy etc. and Mulliken atomic charges in gas phase at the B3LYP/6-311G(d,p) level (298.15 K temperature and 1 atm pressure). As shown in Table 6, the total calculated thermal energy is 263.702 kcal/mol (Table 6). The major part of this thermal energy is contributed by vibrational energy of 261.924 kcal/mol. The zeropoint vibrational energy (ZPVE) was computed as 249.43454 kcal/ mol. The minimum total energy of 6c was found as 965.39301313 a.u. with B3LYP/6-311þþG(d,p) level. 4. Conclusions In conclusion, we have analyzed a biologically active chalcone ie. (E)-3-(4-(hexyloxy)phenyl)-1-phenylprop-2-en-1-one (6c) in both solution and the solid state. To support the experimental results, the quantum chemical computations (molecular geometry parameters, vibrational frequencies, the simulated UVevis spectra (in gas and in methanol solvent), 1H and 13C NMR chemical shift (in gas and in chloroform solvent) values, HOMO-LUMO analysis, the molecular electrostatic potential (MEP) surface and

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