Combined Experimental and Computational Investigation of 2-(2-Hydroxyphenylimino) Phenolic Derivatives: Synthesis, Molecular Structure and NLO Studies

A series of substituted 2-(2-hydroxyphenylimino) phenolic (salen) derivatives (1-4) have been synthesized and their structures of obtained compound were characterized by analytical, FT-IR, UV-Vis and C{H}-NMR experimentally. The geometry structure optimization, frequencies (IR), NMR, electronic character, frontier molecular orbital (HOMO-LUMO) and first static hyperpolarizability (βtot) studies of reported compounds were calculated using DFT with B3LYP/6-311G(d,p) level of theory. The calculated HOMO and LUMO energies showed that charge transfer occurs within the molecule and from the MEP, the molecular stability and bond strength have been explained. In addition to that influence of energy gap (∆Egap) between the HOMO-LUMO orbitals on the first static hyperpolarizability (βtot), we calculated the ∆Egap for all the salen compounds. These results reveals that the smaller HOMO-LUMO ∆Egap is, larger the βtot is.