International Journal of Catalysis and Chemical Engineering
DFT Exploration of Molecular Structures, Frontier Molecular Or-bitals, NBO, and Optical Properties for Certain 2,3-Disubstituted Pyrazines in Gas and Aqueous Phases
Abstract
Vahideh Hadigheh Rezvan and Hanieh Abdoli
Non-linear optical (NLO) materials have interesting properties in designing optical crystals. So, in this project, a DFT study of the effect of different functional groups was performed on the NLO behavior of the pyrazine molecule. This study delves into the impact of various functional groups on the nonlinear optical (NLO) behavior of pyrazine through density functional theory (DFT) calculations. Substituting electron-accepting and withdrawing groups at the ortho position in the pyrazine ring gained significant insights into the molecular structures, frontier molecular orbitals, and optical properties. The findings highlighted the enhanced NLO behavior resulting from functional group substitutions, with particular emphasis on the compound exhibiting superior NLO characteristics in the aqueous phase. This underscores the importance of solvent effects in determining optical properties in NLO materials design. Calculations were done in the gas and aqueous phases using 6-311++G(d,p) basis sets in the B3LYP level of theory.
Frontier molecular orbitals (FMOs), HOMO-LUMO gap (�??Eg), electron affinity (EA), ionization potential (IP), chemical hardness (η), softness (s), electronegativity (χ), chemical potential (Pi), and global electrophilicity index (ω) were calculated to assess and the relation between these parameters and the NLO properties. Investigation of calculated polarizability and hyperpolarizability parameters (αave and βtotal) showed that the bare pyrazine molecule did not show NLO behavior. Substitution of pyrazine molecule with different functional groups in the ortho position causes more nonlinear optical behavior than urea molecule as a reference. Further investigations revealed that 3-nitropyrazin-2- amine (E) exhibited more NLO behavior than the other molecules. Also, the compounds showed more NLO behavior in the aqueous phase rather than in the gas phase.