Synergistic experimental and computational insights into the photophysical tuning of cyanopyridines via conjugation extension

There is an immense demand for novel fluorescent cyanopyridines with superior photophysical characteristics appropriate for optoelectronic applications. Herein, we synthesized the Toluene substituted Cyanopyridine derivative TC (1–4) by hetero cyclization of chalcone using malononitrile and sodium methoxide. These compound structures were analyzed using Infrared spectroscopy (IR) analysis, ¹H NMR, ¹³C NMR, and mass spectral methods. Their optical properties were experimentally explored with the help of UV–visible spectroscopy and Fluorescence spectroscopy. Cyanopyridines' structures, electronic absorption, and emission spectra have all been investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT). Effects of elongation of conjugation chain, solvents, and substituents have all been studied in relation to photophysical properties. Due to a dimethyl amino group, the high conjugated chalcone TC4's absorption maxima exhibited a notable redshift. In acetonitrile, all showed good emission; however, TC2 exhibited prominent dual emission bands due to its extended conjugation and structural flexibility. The minimal difference in absorption maxima of fluorophores in various solvents indicates that their local environments are the same in the ground state. On the other hand, emission maxima showed a notable solvent polarity dependence. A positive solvatochromic effect is observed as the solvent's polarity changes from non-polar to polar.