Comparative theoretical study of the UV/Vis absorption spectra of styrylpyridine compounds using TD-DFT calculations

Abstract

This study examined absorption properties of 2-styrylpyridine, trans-2-(m-cyanostyryl)pyridine, trans-2-[3-methyl-(m-cyanostyryl)]pyridine, and trans-4-(m-cyanostyryl)pyridine compounds based on theoretical UV/Vis spectra, with comparisons between time-dependent density functional theory (TD-DFT) using B3LYP, PBE0, and LC-ωPBE functionals. Basis sets 6-31G(d), 6-31G(d,p), 6-31+G(d,p), and 6-311+G(d,p) were tested to compare molecular orbital energy values, gap energies, and maxima absorption wavelengths. UV/Vis spectra were calculated from fully optimized geometry in B3LYP/6-311+G(d,p) in gas phase and using the IEFPCM model. B3LYP/6-311+G(d,p) provided the most stable form, a planar structure with parameters close to 2-styrylpyridine X-ray data. Isomeric structures were evaluated by full geometry optimization using the same theory level. Similar energetic values were found: ~4.5 kJ mol(-1) for 2-styrylpyridine and ~1 kJ mol(-1) for derivative compound isomers. The 2-styrylpyridine isomeric structure differed at the pyridine group N-atom position; structures considered for the other compounds had the cyano group attached to the phenyl ring m-position equivalent. The energy difference was almost negligible between m-cyano-substituted molecules, but high energy barriers existed for cyano-substituted phenyl ring torsion. TD-DFT appeared to be robust and accurate approach. The B3LYP functional with the 6-31G(d) basis set produced the most reliable λmax values, with mean errors of 0.5 and 12 nm respect to experimental values, in gas and solution, respectively. The present data describes effects on the λmax changes in the UV/Vis absorption spectra of the electron acceptor cyano substituent on the phenyl ring, the electron donor methyl substituent, and the N-atom position on the electron acceptor pyridine ring, causing slight changes respect to the 2-styrylpyridine title compound.

Theoretical and Experimental Spectroscopic Analysis of Cyano-Substituted Styrylpyridine Compounds

“…[33] and the experimental value of 304 nm [30] for 4-styrylpyridine. Castro et al [34] also reported that the calculated values for the maximum absorption for the 2-styrylpyridine and cyano- and methyl-substituted derivatives by DFT methods were close to experimentally determined values.…”

“…Some have been characterized by X-ray diffraction [22,24–29], IR [19,22,25–30], 1 H-NMR [19,24–30], UV-Vis [19,28], mass spectroscopy [19,27] and complementary theoretical studies [23,31]. Theoretical calculations on 2,6-distyrylpyridine [23,31], 4-styrylpyridine [32,33] and 2-styrylpyridine and derivatives [34] have been carried out using ab initio and Density Functional Theory (DFT) approximations.…”

“…TD-DFT was used for calculating the absorption spectra of both isomers [33], where the main absorption band was predicted at 314.5 nm, due to the double bond in the trans isomer, which originated from the S 0 to S 1 transition. On the other hand, trans -4-( m -cyanostyryl)pyridine was recently studied using DFT methods [34], in order to predict the maximum absorption using the TD-DFT approach. The absorption maximum was calculated to be 307.2 nm, similar to the values obtained by Daku et al .…”

Theoretical investigation of the substituent effects on the electronic and optical properties of 6-substituted coumarin derivatives

“…It is found that time-dependent density functional theory (TD-DFT) at the B3LYP/6-311+G (d, p) level correctly reproduced the absorption wavelength and intensity of many organic molecules [33][34][35][36]. And as you can see in our previous work, in the case of 6-fluoro coumarin, the calculated absorption and emission spectrum at this level were found to be in good agreement with the experimental values [37].…”

A Comparative Picture of Structural and Electrochemical Properties of Fluorinated Liquid Crystals - a Theoretical Study

“…The methods based on time dependent density functional theory (TDDFT) applied to small and middle sized systems [7,8] provide rather good accuracy at low computational cost. These methods still remain of rather limited application for establishing realistic molecular models, and biological systems.…”