Evaluation of the structure and characteristics of circumtrindene derivatives: a DFT study

Abstract

The structures and properties of circumtrindene derivatives were studied at M062X/6-31+G(d,p) level of theory. The UV spectra of compounds were simulated by TD DFT methods. The calculated values of λmax (344 nm to 403 nm) were attributed to HOMO to LUMO electronic transitions of compounds. The frontier molecular orbitals have been studied based on NBO calculations and the results were used to estimate the HOMO—LUMO energy gap, ionization potential, electron affinity, electronegativity, electrophilicity index, global hardness, softness, and chemical potential of the compounds. Among the studied derivatives, the structure containing pyridine and furan rings possessed the highest ionization energy (9.007 eV), electron affinity (2.667 eV), electronegativity (5.837 eV), and was the most polar molecule. In addition, compound 7 had the smallest chemical potential (–5.837 eV), polarizability (328.560 a.u.) and the lowest energy levels of HOMO (–8.3672 eV) and LUMO (–3.3062 eV) orbitals. While the derivative having pyrrole rings had the highest softness (0.172 e/V), chemical potential (–4.272 eV), and the greatest λmax (403 nm) in the UV spectrum. In addition, this compound had the lowest hardness (2.912 eV), ionization energy (7.184 eV) and electronegativity (4.272 eV). Also, the aromaticity of individual rings was evaluated by calculating NICS and HOMHED indices. The NICS results showed that the peripheral 6-membered rings represented the best aromatic properties.