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Density functional theory and ab initio Hartree–Fock calculations the Structure of Phenyl salicylate
Mohammad Emami 1, Abbas Teimouri*2 , Ali Reza Najafi3
1. Department of Chemistry, Shahid Beheshti University, Tehran, Iran; E-mail:
2. Payame Noor University, Isfahan, Iran, Tel. 0311-7380003; fax: 0311-7381006;
E-mail: [email protected]
3. Department of Chemistry, Yasouj University, Yasouj, Iran
Introduction
Salicylates are the class of compounds that are widely valued for their pain killing, antipyretic and anti-inflammatory properties [1]. Recently, salicylic acid has been used primarily as an intermediate in the production of agrochemicals, dyes and colorants products [2]. Pharmacological effects and biotransformation pathways of salicylic acid and its derivatives are well known [3–6], and the effects of the structural features on the physico-chemical properties and on the bioactivity of these compounds were investigated in numerous theoretical and experimental studies [7–11]. Salicylic acid and its derivatives have recently become attractive to theoreticians as well as experimentalists since their structures are of some biological significance particularly in medicinal and enzyme chemistry [12].
Result and discussion
The optimized structure parameters of the methyl salicylate calculated by ab initio HF and DFT-B3LYP levels with the 6-31G* basis set are listed in Tables. The aim of this study is to give optimal molecular geometry and vibrational modes of this compound.
The optimized configurations are shown in Fig 1.
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Figure 1. The structure of Phenyl salicylate, Optimization have been performed by B3LYP/6-311G*
method.
The observed experimental FT-IR spectra and theoretically pridected IR spectra are shown in Figs. The vibrational frequency and approximate description of each normal modes obtained using HF and DFT/B3LYP methods with 6-31G* basis set are given for methyl salicylate in Tables.
In our study, vibrational frequencies calculated at B3LYP/6-31G* level were scaled by 0.9613 and those calculated at HF/6-31G* level were scaled by 0.8929. Gauss-view program was used to assign the calculated harmonic frequencies. On the basis of the comparison between calculated and experimental results, assignments of fundamental modes were examined. The assignment of the experimental frequencies are based on the observed band frequencies in the infrared spectra of this species confirmed by establishing one to one correlation between observed and theoretically calculated frequencies.
The experimental and theoretical values for 1H, 13C NMR, and calculated structural parameters of the methyl salicylate are given in Tables. We have calculated the theoretical
1H, 13C NMR chemical shifts, and structural parameters of the methyl salicylate. The theoretical 1H and 13C NMR chemical shifts of methyl salicylate have been compared with the experimental data. According to these results, the calculated chemical shifts and coupling constants are in compliance with the experimental findings. In order to compare the experimental chemical shifts, the correlation graphics based on the calculations have been presented in Figs.
Absorption maximum (Zmax) this compound were calculated by the CIS, TD, ZINDO methods.
Conclusions
The DFT B3LYP/31G(d), B3LYP/6-311G(d) and B3PW91/6-31G(d) calculations were performed for methyl salicylate. The calculated results show that the predicted
3
p,m m m p,m
geometry can well reproduce the structural parameters. Predicted vibrational frequencies have been assigned and compared with experimental IR spectra and they are supported each other. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT methods. 13C, 1H NMR of the methyl salicylate have been calculated by means of B3LYP density functional method with 6-31G* basis set. Comparison between the experimental and the theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting NMR properties. On the basis of vibrational analyses, the thermodynamic properties of the methyl salicylate at different temperatures have been calculated, revealing the correlations between C° , S° , H° ,G° and temperatures.
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