Theoretical and Experimental Spectroscopic Analysis of Cyano-Substituted Styrylpyridine Compounds

Maria Castro,Guillermo Soriano-Moro,Maria Percino,Jorge Lopez-Cruz,Margarita Ceron,Francisco Melendez,Victor Chapela

doi:10.3390/ijms14024005

Abstract

A combined theoretical and experimental study on the structure, infrared, UV-Vis and 1H NMR data of trans-2-(m-cyanostyryl)pyridine, trans-2-[3-methyl-(m-cyanostyryl)] pyridine and trans-4-(m-cyanostyryl)pyridine is presented. The synthesis was carried out with an efficient Knoevenagel condensation using green chemistry conditions. Theoretical geometry optimizations and their IR spectra were carried out using the Density Functional Theory (DFT) in both gas and solution phases. For theoretical UV-Vis and 1H NMR spectra, the Time-Dependent DFT (TD-DFT) and the Gauge-Including Atomic Orbital (GIAO) methods were used, respectively. The theoretical characterization matched the experimental measurements, showing a good correlation. The effect of cyano- and methyl-substituents, as well as of the N-atom position in the pyridine ring on the UV-Vis, IR and NMR spectra, was evaluated. The UV-Vis results showed no significant effect due to electron-withdrawing cyano- and electron-donating methyl-substituents. The N-atom position, however, caused a slight change in the maximum absorption wavelengths. The IR normal modes were assigned for the cyano- and methyl-groups. 1H NMR spectra showed the typical doublet signals due to protons in the trans position of a double bond. The theoretical characterization was visibly useful to assign accurately the signals in IR and 1H NMR spectra, as well as to identify the most probable conformation that could be present in the formation of the styrylpyridine-like compounds.

Highlights

Low molecular weight and oligomeric organic compounds with optical or electrical properties have been widely used as dyes in organic electronic devices, including organic light emitting diodes (OLEDs), solar cell organic semiconductor lasers, etc. [1,2,3,4,5,6]
The optimization calculations in gas and solution phases were performed by the Density Functional Theory (DFT) method taking into account the electron correlation contribution, which is especially important in conjugated systems
This study showed that the methyl group attached to the pyridine ring in molecule IIIb had no effect on either the highest-occupied MO (HOMO) or the lowest-unoccupied MO (LUMO) distributions

Summary

Introduction

Low molecular weight and oligomeric organic compounds with optical or electrical properties have been widely used as dyes in organic electronic devices, including organic light emitting diodes (OLEDs), solar cell organic semiconductor lasers, etc. [1,2,3,4,5,6]. Low molecular weight and oligomeric organic compounds with optical or electrical properties have been widely used as dyes in organic electronic devices, including organic light emitting diodes (OLEDs), solar cell organic semiconductor lasers, etc. It is well know that cyano-substituted compounds show good optical and electrical properties due to their high electron affinities [9]. Pyridine is an important electron-acceptor group, due to its high electron affinity. Epstein et al described poly(p-pyridine)- and poly(p-pyridyl vinylene)-based polymers as emissive layers in light-emitting devices [12]. Bartholomew et al [13] studied model compounds, such as phenylated PPV, with the electron withdrawing cyano group attached to the olefin, and they can be used as a model cyano substitute (CN-PPV)

Methods

Results

Conclusion