Effect of substitution on some photophysical properties of pyridine: A comparison with benzene analogues

The effects of substitutions on pyridine for different photophysical properties, namely HOMO, LUMO energies, band gap, ionization potential, electron affinity, and excited state energies (S₁ and T₁) are studied systematically. A comparison with substituted benzene shows that the substitution of pyridine has significantly different influence on these molecular properties for a given electron-donating/withdrawing substituent. The molecular properties vary significantly with the position of the substitution with respect to the nitrogen atom of pyridine. For the substituents like −OH or −OMe, the electron donation ability through +R effect counters electron withdrawing ability through −I effect, depending on their attachment with respect to the nitrogen atom of pyridine. The study highlights the significance of substituent in modifying the electronic properties of organic materials. These insights are crucial for advancing the design of organic electronic materials, where pyridine plays an important role in electron transport.