Solvent effect, dipole moment, and DFT studies of multi donor–acceptor type pyridine derivative

Abstract

A donor–acceptor substituted derivative 2,6-diamino-4-(3,4,5-trimethoxy-phenyl)-pyridine-3,5-dicarbonitrile (DTPP) has been synthesized and its photophysical properties have been studied. Effect of solvent on the photophysical features of DTPP has been undertaken by steady state absorption and emission techniques. Strong solvatochromic emission has been observed due to intramolecular charge transfer characteristics, upon changing the solvent polarity, revealing the highly polar character of the excited state. Dipole moment changes between the excited and ground state have been estimated by using the theory of solvatochromism from Lippert–Mataga and Reichardt’s correlations. The geometrical parameters for ground and excited states, conformational flexibility, and NLO behavior of the molecule have been theoretically investigated. The electronic distributions of DTPP in HOMO and LUMO were also investigated using density functional theory (DFT) methods at B3LYP/6-31 G** level. The correlation of experimental results with theoretical predictions obtained via DFT substantiates the presence of polarity dependent of the emission spectra.

Keywords

• multi donor–acceptor organic compounds
• effect of solvent
• fluorescence