引用本文

. [J]. 光谱学与光谱分析, 2018,38(6): 1963-1969.
Halil Oturak, Neslihan Kaya K#cod#x00131;nayt#cod#x000fc;rk, #cod#x000c7;ag#cod#x002d9;r#cod#x00131; #cod#x000c7;#cod#x00131;rak. Experimental and Theoretical Spectral (FT-IR, Raman, NMR, UV-Vis and NLO) Analysis of a Potential Anti-Tumor Drug: 1-Methyl-6-Nitro-1H-Benzimidazole[J]. Spectroscopy and Spectral Analysis, 2018,38(6): 1963-1969.
Doi:10.3964/j.issn.1000-0593(2018)06-1963-07 复制到剪切板

Permissions

《光谱学与光谱分析》期刊社所有

收稿日期: 2016-02-07 接受日期: 2016-08-09

摘要

关键词:

中图分类号:O657.3 文献标志码:A

Experimental and Theoretical Spectral (FT-IR, Raman, NMR, UV-Vis and NLO) Analysis of a Potential Anti-Tumor Drug: 1-Methyl-6-Nitro-1H-Benzimidazole

Halil Oturak^1,^*, Neslihan Kaya Kınaytürk², Çag˙rı Çırak³

1. Department of Physics, Süleyman Demirel University, Isparta 32100, Turkey;

2. Experimental and Observational Research and Application Centre, Süleyman Demirel University, Isparta 32100, Turkey;

3. Department of Physics, Erzincan University, Erzincan 24100, Turkey

*Corresponding author e-mail: haliloturak@sdu.edu.tr

Abstract

In the present work, the experimental and the theoretical spectroscopic properties of 1-Methyl-6-Nitro-1H- Benzimidazole were investigated. The FT-IR (400~4 000 cm^-1) and FT-Raman spectra (100~4 000 cm^-1) of 1-Methyl-6-Nitro-1H- Benzimidazole in the solid phase were recorded. Also, experimental NMR and UV spectra of titled molecule were measured. To interpret the experimental data, geometric parameters, vibrational frequencies, NMR, UV spectra and NLO analysis of the optimized molecule were calculated using ab initio Hartree-Fock (HF) method and density functional theory (B3LYP) method with the 6-31++G(d,p) and 6-311++G(d,p) basis sets. Vibrational bands were assigned based on the potential energy distribution using the VEDA 4 program. The theoretical results showed good agreement with the experimental values.

Keyword: FT-IR; FT-Raman; NMR; 1-Methyl-6-Nitro-1H-Benzimidazole; B3LYP

文章图片

Introduction

The title compound, C₈H₇N₃O₂ is benzimidazole derivative compound and a potential antitumor drug and an antioxidant agent. Benzimidazole derivatives are heterocyclic compounds that attracted great attention during the last few years because of their its biological and pharmacological effects^{[1, 2]} such as anticancer, antimicrobial, antihelmintic, antifungal, antiparasitic, antitumor, antiviral, antidiabetic, etc^{[1, 2, 3]}. Spectroscopic studies of certain benzimidazole derivatives are already report^{[1, 2, 4, 5, 6]}. As our best knowledge, There is no a detailed analysis of vibrational frequencies, IR and Raman spectra of 1-Methyl 6-Nitro 1H Benzimidazole (1M6N1HBz) has not been reported. As a result of, experimental and theoretical investigation of the vibrational frequencies, ¹H and ¹³C NMR chemical shifts, geometric structure, HOMO-LUMO energies, excitation energies of this molecule were studied by using Gaussian 09 program package, for the first time. The detailed assignments of the vibrational spectra of title molecule have been performed on the basis of the calculated potential energy distribution (PED). The calculated harmonic frequency values are bigger than the observed ones, due to neglecting anharmonicity in calculations. Scaling procedure has been performed to provide an agreement between the harmonic and the observed vibrational frequencies. Also, harmonic frequencies are calculated for gaseous phase of isolated 1M6N1HBz, while experimental spectra are obtained from solid phase of title molecule. These experimental and theoretical data are important for offer an insight into the vibrational, UV-Vis, NMR spectrum and molecular geometry parameters.

1 Experimental Details

The compound 1-Methil-6-Nitro-1H-Benzimidazole in solid form was purchased from Sigma-Aldrich (St. Louis, MO, USA) and used with no further purification. The FT-IR spectrum was recorded using KBr pellets on a Perkin Elmer Spectrum BX FTIR spectrophotometer in the region 4 000~400 cm^-1. The FT-Raman spectrum was obtained on a DXR-Raman Microscope in the region 3 500~12 cm^-1. The ¹H and ¹³C NMR were taken in DMSO solutions on a Bruker Ultrashield 400 Plus NMR spectrometer. Proton and carbon signals were referenced to TMS. UV-Visible analyses were carried out with a Perkin Elmer Lambda 20 spectrophotometer. All spectra were measured at room temperature.

2 Computational Details

Gaussian 09^[7] software was used for the quantum chemical calculations. The calculations were performed by using DFT/B3LYP and HF method, with the 6-311G(d, p) basis set. The vibrational frequencies are calculated with these methods and then scaled by 0.968 2 and 0.905 1, respectively^[8]. The geometry optimizations were performed by frequency calculations using the same basis set. Furthermore, the DFT/B3LYP/6-311G(d, p) basis set was used for the ¹H and ¹³C NMR shielding constants calculations by using the GIAO method. UV-Vis spectra and electronic properties were obtained by time-dependent DFT (TD-DFT). Gauss View program was used for visualizing of theoretical data^[9]. Poten-

tial energy distribution (PED) analysis was performed by using VEDA 4 program^[10].

3 Result and Discussion

3.1 Molecular geometry

The optimized molecular structure of 1-methyl-6-nitro-1H-benzimidazole calculated using DFT theory at B3LYP/6-311G(d, p) level is shown in Figure 1. Experimental crystal geometry for the title compound has been reported by Lokaj et all.^[11] the geometrical parameters such as bond length, bond angle and dihedral angles are compared with the X-Ray data of title compound shown in Table 1. The optimized and experimental mlecular structure shows good agreement.

	Figure Option View Download New Window
	Fig.1 Optimized molecular structure of 1M6N1HBz

Table 1 Geometrical parameters bond leght, bond angle and dihedral angle of title compound in ground state and comparison with experimental data

3.2 Vibrational frequencies

3.2.1 C— H vibrations

Bands characteristic of aromatic compounds can be located in five region of IR spectrum. These regions are 3 100~3 000 cm^-1 as CH stretching, 2 000~1 700 cm^-1 as combinations and overtones, 1 650~1 430 cm^-1 as C＝C stretching, 1 275~1 000 cm^-1 as in-plane CH deformation and 900~690 cm^-1 as out of plane CH deformation^{[12, 13]}. The title molecule stretching vibrational band are observed at 3 126, 3 122, 3 121, 3 099 cm^-1. The vibrational frequencies are assigned 1 220 and 1 110 cm^-1 for in plane CH deformation.

The observed symmetric and asymmetric stretching bands for CH₃ group at the interval 2 927~2 814 were calculated at the interval 3 034~2 940 cm^-1. Show good agreement with recorded as well as literature data^{[14, 15, 16]}.

Asymmetric deformation of the HCH angles of a CH₃ group cause to very strong IR absorption in the 1 470~1 440 cm^-1 region. The symmetric CH₃ deformation gives a strong sharp IR band between 1 380~1 360 c ${m^{- 1}}^{[12 ⁃ 13]}$ . In our title molecule, the H— C— H asymmetric deformation band are observed 1 477~1 448 cm^-1, the symmetric deformation band are observed 1 442~1 448 cm^-1. On the other hand, stretching, deformation, torsion and combination of these ones vibrational mode of aliphatic or aromatic C— H vibrational bands are displayed in Table 2. Also, theoretical and experimental FT-IR and Raman spectrum is given in Figure 2 and Figure 3, respectively.

	Figure Option View Download New Window
	Fig.2 (a) Theoretical and (b) experimental FT-IR spectra of 1M6N1HBz

	Figure Option View Download New Window
	Fig.3 (a) Theoretical and (b) experimental Raman spectra of 1M6N1HBz

Table 2 Fundamental band as signments of 1-Methyl-6-Nitro-1H-Benzimidazole

Mode		DFT/B3LYP/ 6-311G(d, p)				HF/ 6-311G(d, p)			Experimental				Assignment
Mode		unscaled		scaled		unscaled		scaled	IR		Raman		Assignment
1		3 229		3 126		3 401		3 078			3 156		ν CH(99)
2		3 225		3 122		3 398		3 076	3 103				ν CH(100)
3		3 224		3 121		3 385		3 064			3 087		ν CH(100)
4		3 201		3 099		3 364		3 045	3 047				ν CH(99)
5		3 134		3 034		3 280		2 969	2 927				ν CH(100)
6		3 096		2 998		3 249		2 941	2 853				ν CH(100)
7		3 037		2 940		3 185		2 883	2 814				ν CH(100)
8		1 660		1 607		1 841		1 666	1 620		1 919		ν CC(55)+ν NC(10)
9		1 637		1 585		1 805		1 634	1 591				ν ON(66)+ν CC(18)+δ CCC(12)+δ CCN(10)
10		1 592		1 541		1 758		1 591	1 561		1 495		ν ON(58)+ν CC(11)
11		1 526		1 477		1 684		1 524	1 513				ν NC(30)+ν CC(10)+δ HCN(19)+δ HCH(13)
12		1 524		1 476		1 649		1 493	1 458				δ HCH(54)+τ HCNC(21)
13		1 496		1 448		1 631		1 476					ν CC(38)
14		1 489		1 442		1 616		1 463					δ HCC(31)+ν CC(26)+δ HCH(11)
15		1 486		1 439		1 608		1 455					δ HCH(73)+τ HCNC(26)
16		1 456		1 410		1 605		1 453	1 406				δ HCH(71)
17		1 399		1 355		1 582		1 432	1 373				ν CC(45)+δ CCN(16)
18		1 392		1 348		1 534		1 388	1 341		1 339		ν NC(59)
19		1 371		1 327		1 462		1 323	1 302				ν ON(76)+δ ONO(12)
20		1 339		1 296		1 426		1 291					ν NC(33)+τ HCNC(12)
21		1 310		1 268		1 399		1 266	1 278		1 276		ν NC(31)+δ HCC(27)+δ HCN(17)
22		1 260		1 220		1 347		1 219	1 239		1 236		δ HCC(64)+δ HCN(14)
23		1 227		1 188		1 324		1 198	1 212				ν NC(19)+δ HCN(35)
24		1 147		1 111		1 248		1 130	1 130		1 128		τ HCNC(72)+δ HCH(26)
25		1 146		1 110		1 247		1 129			1 114		δ HCC(24)+δ NCN(10)
26		1 135		1 099		1 217		1 102	1 064		1 077		δ HCC(43)+δ CCC(23)
27		1 071		1 037		1 166		1 055	1 048				τ HCNC(21)+δ NCN(14)+δ HCC(11)
28		1 057		1 023		1 144		1 035					τ HCNC(16)+ν NC(10)+δ CNC(10)+δ HCC(10)
29		989		958		1 097		993	950				τ HCCN(86)
30		948		918		1 042		943	892				δ CCC(20)+δ NCN(13)+δ CNC(12)+ν NC(11)
31		906		877		1 028		930					τ HCCN(82)
32		883		855		1 019		922	825				τ HCCN(79)
33		857		830		947		857			840		δ ONO(39)+ν CCC(16)+ν ON(10)
34		855		828		945		855	794		826		τ HCCN(69)+γ CNCC(18)
35		814		788		873		790			800		ν CC(17)+δ CNC(18)+ν NC(11)
36		777		752		852		771	761		765		τ CNCN(41)+τ CCCN(14)+τ CNCC(16)
37		757		733		839		759	738				ν NC(36)+δ ONO(14)+δ CNC(14)
38		742		718		816		739	691				γ OCON(73)+τ HCCN(15)
39		651		630		700		634	621		635		ν NC(26)+δ NCN(13)+δ CNC(13)+δ CCN(12)+δ ONO(13)
40		629		609		681		616	586				τ CNCN(49)
41		588		569		637		577					τ CCCN(37)+τ CNCN(13)+γ CNCC(21)
42		577		559		619		560					δ CCN(10)+δ CCC(11)+δ CNC(15)+δ NCC(11)
43		544		527		585		529	534		524		δ ONC(38)+δ CCC(16)+δ CCN(11)
44		477		462		513		464	475		487		δ CCN(26)+δ CNC(28)+δ ONC(26)
45		432		418		472		427	421				τ CCCN(42)+γ CNCC(33)
46		353		342		383		347					ν NC(34)+δ CCN(12)+δ CCC(16)+ν CC(10)
47		305		295		332		300			282		τ CCCN(20)+γ CNCC(13)+γ NCCC(37)
48	281		272		302		273					τ CCCN(46)+τ CNCN(14)+γ CNCC(29)
49	277		268		300		272					δ CNC(32)+δ NCC(31)+δ ONC(14)
50	171		166		185		167					δ CCN(26)+δ CNC(22)+δ NCC(35)
51	147		142		151		137					τ HNCN(11)+γ CCCN(59)
52	118		114		129		117			125		τ HCNC(21)+τ CCCN(13)+τ CNCN(25)+γ NCCC(19)
53	100		97		107		97					τ HCNC(38)+τ CCCN(10)
54	53		51		47		43					τ CNCN(92)

Table 2 Fundamental band as signments of 1-Methyl-6-Nitro-1H-Benzimidazole

3.2.2 N— O vibrations

The asymmetric stretching vibrations of the N— O bands bring about to a strong IR band between 1 590~1 530 cm^-1. The symmetric stretching vibration of NO₂ group exhibits a strong IR band at 1 380 cm^-1. Aromatic nitro compounds show this band at lower frequencies^[17]. The N— O stretching band is observed at 1 302 cm^-1 in the experimental infrared spectrum. The same mode calculated at 1 327 cm^-1 of title molecule. This calculated wavenumber is good agreement with the experimental frequencies.

3.2.3 C— N vibrations

Rani et al identified the C— N stretching bands in the region 1 328~1 266 c ${m^{- 1}}^{[18]}$ . The C— N stretch bond observed 1 341 and 1 212 cm^-1. The theoretical predicted scaled values at 1 348~1 188 cm^-1.

3.2.4 C— C vibrations

The C— C ring stretch in the precursor gives rise to several peaks in the region 1 600 to 1 400 cm^{-1 [19]}. In the present study the frequency bands at 1 620, 1 373 cm^-1 in IR spectrum are assigned to C— C stretching vibration mode. The theoretical computed wave number also present consisted agreement with experimental result. The ring breathing mode is calculated at 918 and 1 099 cm^-1 and is observed in FTIR spectra 1 064 and 892 cm^-1.

On the other hand, while the peaks 958, 877, 855, 830 cm^-1 can be attributed to the HCCN torsion vibration modes, the peaks 1 111, 1 037, 1 023, 118, 100 can be done the HCNC torsion vibration modes of 1M6N1HBz. The CNCN torsion vibration modes are observed in FTIR spectrum at 761 and 586 cm^-1. These bands theoretical computed B3LYP method at 752, 609, 142 and 51 cm^-1.

In addition to, stretching, deformation, torsion, bending and combination of these ones vibration modes of 1M6N1HBz are submitted in Table 2.

3.3 NMR Analysis

The isotropic chemical shifts are currently used for structure of organic molecules^[16]. Calculation of chemical shifts in ¹³C and ¹H NMR spectra in often a complicated problem and it is first of all true for the methods of the electron density functional theory (DFT). Beside the necessity to select efficient functional and basis sets used for the calculation of chemical shifts in ¹³C and ¹H NMR spectra by DFT methods^[20]. In recent years, gauge- including atomic orbital GIAO computational method is efficient in predicting chemical shifts of various organic compounds. In this study, the optimized structure of 1M6N1HBz is used to calculate the NMR spectra at the DFT/B3LYP methods with 6-311G(d, p) level using the GIAO method. The experimental and calculated values for ¹³C and ¹H NMR are shown in Table 3. As shown in Table 3, the range ¹³C NMR chemical shift of the typical organic molecule usually is > 100 ppm^{[16, 18]}. In this study, as to be expected ¹³C NMR chemical shifts in the ring for the title molecule are > 100 ppm. Nitrogen atom shows more electronegative property. Therefore, the chemical shift values of C7, C1, C2 and C4 has been observed 146.68, 147.69, 133.89 and 142.54 ppm, respectively. On the other hand, three carbon peak in the ring are observed 107.6, 116.99 and 117.52 ppm. Those was calculated 112.87, 123.47, 126 ppm. Besides, another carbon peak is calculated at 33.85 ppm is observed at 31.26 ppm (N— CH₃). In the ¹H NMR spectra just one type of protons appears at 3.92, 3.92, 3.96 ppm as a singlet (CH₃) whereas the chemical shift value of 3.85, 3.85, 4.05 ppm have been determined by using B3LYP/6-311G(d, p) method. Signals for aromatic protons were observed at 7.78~8.58 ppm. Between the experimental and theoretical chemical shifts in ¹³C and ¹H NMR spectra is very good agreement.

Table 3 Experimentalandtheoreticalchemicalshifts (¹³C, ¹H) of 1-Methyl-6-Nitro-1H- Benzoimidazolby B3LYP/6-311G(d, p) method [δ (ppm)]

3.4 UV-Vis Analysis

The electronic excited states of title molecule were calculated at the B3LYP/6-311G(d, p) level by using the TD-DFT method on the optimized ground- state geometry of the titled molecule. The theoretical excitation energies, oscillator strength (f) and wavelength (λ ) and spectral assignments are carried out and compared with measured experimental wavelength given in Table 4. As stated in Frank-Condon principle, the maximum absorption peaks (λ _max) correspond to an UV-Vis spectrum to vertical excitation^[16]. Theoretical and experimental UV-Vis spectrum of titled molecule is given in Figure 4.

Table 4 The experimental and calculated UV-Vis excitation enegy (Δ E) and oscillator strength (f) for 1M6N1HBz molecule calculated by TD-DFT/B3LYP/6-311G(d, p)

	Figure Option View Download New Window
	Fig.4 (a) Theoretical and (b) experimental UV spectra of 1M6N1HBz

The calculation predicts three electronic transitions at 291, 326, 339 nm in DMSO show good agreement with the experimental data (λ _exp=316 nm). This absorption assigned to the transition from molecular orbital (MO) 46→ 47, which the highest occupied molecular orbital (HOMO) is the orbital 46 and lowest unoccupied molecular orbital (LUMO) is orbital 47. This transition is assigned to π → π ^* type. According to Figure 5, the HOMO of 1M6N1HBz present a charge density localized on the ring and N atom of the ring. HOMO-LUMO plots for DFT/B3LYP/6-311G(d, p) method is given in Figure 5.

	Figure Option View Download New Window
	Fig.5 Atomic orbital composition of the frontier molecular orbitals and related energies in gas phase

4 NLO Analysis

In this study, molecular polarizability, the electronic dipole moment and anisotropy of polarizability molecular first hyperpolarizability of title compound were computed using DFT/B3LYP/6-311G(d, p) method. The total electronic dipole moment μ , the mean polarizability < α > , and the total first order hyperpolarizability (β _total) were calculated using their x, y, z components and listed in Table 5. The calculation of polarizability (α ) and first hyperpolarizability (β ) is based on the finite field approach. The calculated value of mean polarizabilty < α > and total firs order hyperpolarizability (β _total) of title molecule are 0.993× 10^-30 esu and 6.972× 10^-30 esu, respectively. Urea was used as a prototypical molecule to calculate the NLO properties of the molecular systems. In this study, calculated β value is 35 times that of urea (0.194 7× 10^-30 esu) and therefore title molecule purposes.

Table 5 Dipol moment, polarizability and hyperpolarizability data for 1M6N1HBz calculated at B3LYP/6-311G(d, p) level of theory

5 Conclusion

The FT-IR and FT-Raman spectrums have been measured and detailed vibrational assignment was presented for 1M6N1HBz. The optimized geometries, harmonic vibrational wavenumbers, NMR shields, FT-IR and FT-Raman spectrums of title compound were obtained and analyzed by DFT/B3LYP/6-311(d, p) method. The theoretical NMR shields were also in good agreement with experimental data. UV analysis of title compound have been studied using TD-DFT/B3LYP/6-311G(d, p) basis set. All calculated data were compared with experiment and found to be in good agreement.

The authors have declared that no competing interests exist.

参考文献

文献列表

[1]	Mary Y S, Jojo P J, Panicker C Y, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014, 499. [本文引用:3]
[2]	Sundaraganesan N, Ilakiamani S, Subramani P, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007, 628. [本文引用:3]
[3]	Shah K, Sumit C, Sushant S K, et al. Medicinal Chemistry Research, 2013, 5077. [本文引用:1]
[4]	Sekerci M, Atalay Y, Yakuphanoğlu F, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007, 503. [本文引用:1]
[5]	Xavier T S, Rashid N, Joe I H. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011, 319. [本文引用:1]
[6]	Asiri A M, Karabacak M, Kurt M, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011, 444. [本文引用:1]
[7]	Frisch M J, Truks G W, Schlegel H, et al. Gaussian 09 Revision D. 01, Gaussian Inc. Wallingford CT. , 2009. [本文引用:1]
[8]	Merrick J P, Moran D, Radon L. Journal of Phys. Chem. , 2007, 11683. [本文引用:1]
[9]	Dennington R, Keith T, Millam J. Gaussview Version 5, Semichem Inc. Shawnee Mission, KS, 2009. [本文引用:1]
[10]	Jamroz M H. Vibrational Energy Distribution Analysis, VEDA 4, 2006. [本文引用:1]
[11]	Lokaj J, Kettmann V, Solcan T, et al. Acta Crystallographica Section E, 2008, 3: 671. [本文引用:1]
[12]	Karakaya M, Kürekçi M, Eskiyurt B, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015, 137. [本文引用:1]
[13]	Shurvell H H. Spectra-Structure Correlations in the Mid- and Far-Infrared-Hand book of Vibrational Spectroscopy, John Wiley & Sons, Inc. Publication, 2006. [本文引用:1]
[14]	Karabacak M, Asiri A M, Al-Youbi A O, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014. 144. [本文引用:1]
[15]	Balachand ran V, Janaki A, Nataraj A. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014, 321. [本文引用:1]
[16]	Shoba D, Periand i S, Boomadevi S, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014, 438. [本文引用:4]
[17]	Schrader B. Infrared and Raman Spectroscopy: Methods and Applications, 2008. [本文引用:1]
[18]	Rani A U, Sundaraganesan N, Kurt M, et al. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2010, 1523. [本文引用:1]
[19]	Griffiths P R, de Haseth J A. Fourier Transform Infrared Spectrometry, A John Wiley & Sons, Inc. Publication, 2007. [本文引用:1]
[20]	Fedorov S V, Rusakov Y Y, Krivdin L B. Russian Journal of Organic Chemistry, 2014, 1: 160. [本文引用:1]

2014

0.0

... Benzimidazole derivatives are heterocyclic compounds that attracted great attention during the last few years because of their its biological and pharmacological effects^[1,2] such as anticancer, antimicrobial, antihelmintic, antifungal, antiparasitic, antitumor, antiviral, antidiabetic, etc^[1,2,3] ...