научная статья по теме EXPERIMENTAL AND DFT STUDIES ON THE VIBRATIONAL AND ELECTRONIC SPECTRA OF 2-(4,5-PHENYL-1H-IMIDAZOLE-2-YL)-PHENOL Физика

Текст научной статьи на тему «EXPERIMENTAL AND DFT STUDIES ON THE VIBRATIONAL AND ELECTRONIC SPECTRA OF 2-(4,5-PHENYL-1H-IMIDAZOLE-2-YL)-PHENOL»

ОПТИКА И СПЕКТРОСКОПИЯ, 2015, том 118, № 2, с. 215-226

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АТОМОВ И МОЛЕКУЛ

УДК 543.42

EXPERIMENTAL AND DFT STUDIES ON THE VIBRATIONAL AND ELECTRONIC SPECTRA OF 2-(4,5-PHENYL-1H-IMIDAZOLE-2-YL)-PHENOL

© 2015 г. Yunfeng Ye*, Guodong Tang***, Tingting Tang**, Lance F. Culnane***, Jianyin Zhao**, and Yu Zhang**

*Huaiyin Advanced Vocational & Technical School of Health, Huai'an 223300, Jiangsu Province, P. R. China **Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huai'an 223300, Jiangsu Province, P. R. China ***UCB 215 Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO, 80309 E-mail: hysytanggd@hotmail.com Received May 14, 2014

The compound 2-(4,5-phenyl-1H-imidazole-2-yl-phenol (PIP) was synthesized, followed by structure determination by X-ray diffraction, the results of which agree well with the calculated optimized, lowest energy geometrical structure. Vibrational information was obtained by FT-IR and Raman spectroscopy which also agree well with calculations (of harmonic vibration frequencies). The calculations were carried out with density functional theory B3LYP methods using 6-311++G** and LANL2DZ basis sets. Absorption UV-Vis experiments of PIP in CH3CH2OH solution reveal three maximum peaks at 245, 292 and 317 nm, which are in agreement with calculated electronic transitions using TD-B3LYP/6-311++G** in CH3CH2OH solution, and agree to the gas-phase calculations.

DOI: 10.7868/S0030403415020221

I. INDTRODUCTION

The imidazole derivative ligands have played a particularly important role in the advancement of various supramolecular networks because imidazoles are a class of heterocyclic compounds that contain nitrogen and are currently under intensive focus due to their wide range of applications [1, 2]. A series of imidazole derivatives have been synthesized and characterized by UV-Vis, IR, 1HNMR and elemental analysis [3-5]. Investigations of their applications have been reported in several disciplines of science, such as chemistry, physics, and material, as well as biological science [6-9]. The im-idazole derivatives have attracted significant interdisciplinary attention because of their unique properties as chelating agents and common usage as ligands in metal-organic coordination polymers [10-14]. Imid-azole derivatives play a key role in the performance of biological systems, such as antimalarial, antifungal, antitumoral, anti-allergic, anti-inflammatory and antiviral drugs [7, 15-18]. They have also been used in DNA-binding, photophysical and electrochemical applications, and in non-linear optical (NLO), and fluorescent materials [19-22]. The compound 2-(4,5-phenyl-lH-imidazole-2-yl)-phenol (PIP) is one of the derivatives of imidazoles. The title compound has

multiple binding sites (N, O) and has interesting optical properties. In order to present an in-depth study of PIP, we report a synthesis route, and in addition, the purpose for this work is (i) to determine the structure with X-ray diffraction and compare it to DFT calculations, (ii) to thoroughly study the vibration spectra of this molecule and to identify the various normal modes with the aid of HF and DFT studies, (iii) to compare the different DFT methods for the calculated vibration spectra, and (iv) to calculate the absorption bands in CH3CH2OH solution with an optimized geometry by using the time-dependent density functional theory (TDDFT) at B3LYP/6-311++G**, B3LYP/LANL2DZ, HF/6-311++G** and HF/LANL2DZ level associated with the polarized continuum model (PCM)

2. EXPERIMENTAL AND COMPUTATIONAL SECTION

2.1. Experimental

The ligand was synthesized according to scheme shown in Fig. 1. Benzil (5 mmol, 1.05 g), salicylalde-hyde (5 mmol, 0.610 g) and ammonium acetate (80 mmol, 6.16 g) were refluxed in glacial acetic acid (20 mL) for 4 hrs. The mixture was poured into

100 mL ice deionized water after cooling, and then the pH was adjusted to about 7 with aqueous ammonia. Gray-red solid was generated and recrystallized with

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

Empirical formula C21H16N2O

Formula weight 312.36

Temperature 293(2)

Radiation Mo Ka(\ = 0.71073 Â)

Space group P-1

« (Â) 10.554(2)

b (Â) 12.481(3)

c (Â) 13.840(3)

a(°) 68.88(3)

ß(°) 86.64(3)

Y(°) 85.68(3)

F (Â3) 1694.7(6)

Z 4

DJ(g cm-3) 1.224

^/mm-1 0.076

Crystal size (mm) 0.16 x 0.14 x 0.12

0 range for data collection 1.58-25.5°

Index ranges -12 < h < 12

-14 < k < 12

-14 < 1 < 16

Total reflections 11946

Goodness -of- fit on F2 0.946

R indices [I > 2o(I)] 0.0543

R indices (all data) 0.1192

Largest difference peak and hole 0.18/-0.16

ethanol. Yield 90%, m. p.: 213.0-213.8°C), Elemental Analysis Calculate (%): C, 80.75; H, 5.16; N, 8.97. Found: C, 80.04; H, 4.86; N, 8.66. IR (KBr, cm-1): 3417.09 (s), 3208.27 (vs), 3058.89 (vs), 1602.23 (vs), 1474.96 (vs), 1383.88 (m), 1294.47 (m). 1H NMR (DMSO, 6, ppm): 13.05(s, 1H), 12.95 (s, 1H), 8.03 (d, J = 9.1,2.4 Hz 1H), 7.53 (t, J = 7.2 Hz 2H), 7.49 (t, J = 7.2 Hz 4H), 7.42 (d, 1H), 7.35 (t, 2H), 7.27 (t, 2H), 6.98 (d, J = 9.1 Hz 1H), 6.94 (d, J = 9.1 Hz 1H), 13C NMR (DMSO, 6, ppm): 157.15, 146.32, 134.31, 130.58, 129.01, 127.56, 125.41, 119.36, 117.31, 113.32, 40.18. The absorption UV-Vis spectrum in CH3CH2OH solution shows three maximum bands at 245, 292 and 317 nm.

X-ray diffraction measurements of the crystal were performed on a Bruker Smart Apex CCD diffractom-eter at 293 K. The intensity data were collected using graphite monochromated Mo-Ka radiation (X = = 0.71073 A). The data collection 26 range was 3.1651.00° No significant decay was observed during the data collection. The raw data were processed to give structure factors using the SATNT-plus program [23].

Empirical absorption corrections were applied to the data sets using the SADABS program [24]. The structure was solved by direction method and refined by full matrix least-squares against F2 for all data using SHELXTL software [25]. All non-hydrogen atoms in the compound were anisotropically refined. All hydrogen atoms were included in the calculated positions and refined using a riding model with isotropic thermal parameters 1.2 times larger than those of the parent atoms. The crystal data, further details of the experimental conditions and the structure refinement parameters for the compound are given in Table 1 and the atomic numbering scheme is shown in Fig. 2.

The FT-IR spectrum of the title compound was recorded as KBr discs using an AVATAR 360 spectro-photometer in the range of 400-4000 cm-1 at room temperature. The Raman spectrum was recorded on a Bruker RFS 100/S FT-Raman spectrometer in the 50-3500 cm-1 regions with a diode-pumped air-cooled Nd-YAG laser source giving 532 nm as an exciting line at 10 mW powers. The electronic spectra were recorded on a UV-Vis 916 spectrophotometer in the region of 200-400 mn using CH3CH2OH as the solvent.

Fig. 2. Optimized geometry of the title compound.

2.2. Methods of Calculation

The geometry optimization proceeded in two steps; firstly, the initial geometry was constructed by MM+ molecular modeling with the HyperChem 6.0 package [26], Secondly, the equilibrium geometry was optimized ab initio by restricted Hartree-Fock (HF) and density functional theory (DFT) B3LYP (Becke's three parameters hybrid method with the Lee, Yang and Parr non-local functions [27, 28]) levels of theory with 6-311++G** and LANL2DZ (Los Alamos ECP plus double-zeta) [29, 30] basis sets. The structure was found to be a minimum since there is no imaginary frequency in the frequency calculation. Time-dependent density functional theory (TDDFT) [31] excited-state calculations were determined at the HF/6-311++G**, HF/LANL2DZ, B3LYP/6-311++G** and B3LYP/LANL2DZ level of theory both in gas phase and in CH3CH2OH solution. A polarizable continuum model (PCM) [32] including the solvent effect was chosen for excitation energy calculations. All calculations were performed using the Gaussian 03W program package [33]. All geometries converged perfectly. The vibrational frequencies and intensities were computed in a similar fashion.

3. RESULTS AND DISCUSSION 3.1. Molecular Geometry

The optimized geometry with atomic numbering scheme for the title compound is shown in Fig. 2.

Crystal data are summarized in Table 1. The selected experimental bond lengths and angles are given in Table 2. In the compound, the experimental bond length of C6-O10 (1.359(3) A) is typical for a C-O single bond, and slightly longer than that reported (1.352(3) A) [34]. The theoretical bond length of C-O was obtained by B3LYP/6-311++G**, (1.378 A), and HF/6-311++G**, (1.358 A), which agree well with the experimental value, (1.359 A). While the theoretical bond length of C-O was obtained by B3LYP/LANL2DZ, (1.415 A), and HF/LANL2DZ (1.392 A). The error of these theoretical values is 1.40%, 0.00%, 4.12% and 2.43%, respectively. The DFT (B3LYP/6-311++G**, B3LYP/LANL2DZ) and HF (HF/6-311++G**, HF/LANL2DZ) methods were used for geometrical optimization of the DPIP molecule. The theoretical results show all atoms nearly co-planar, and all optimized bond lengths and angles agree well with the experimental values.

The optimized parameters of the title compound with DFT (B3LYP/6-311++G**, B3LYP/LANL2DZ) and HF (HF/6-311++G**, HF/LANL2DZ) methods are listed in Table 2. The overall magnitude of the bond lengths listed in decreasing order for each calculation method is: B3LYP/LANL2DZ > HF/LANL2DZ > > B3LYP/6-311++G** > HF/6-311++G**, which vary due to different exchange finctions. The HF/6-311++G** method pairing is found to predict bond length values most accurately. The B3LYP/LANL2DZ,

Table 2. Optimized bond distances (A) and bond angles (°) for the title compound with DFT and HF methods

Exp. B3LYP/6-311++G** B3LYP/LANL2DZ HF/6-311++G** HF/LANL2DZ

R(6,10) 1.359(3) 1.378 1.415 1.358 1.392

R(9,

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