Nonlinear optical behavior of non‐centrosymmetric biferrocenyl Schiff‐base derivatives and their DNA binding potential supported by DFT and electrochemical investigations

Abstract

AbstractTwo new non‐centrosymmetric biferrocenyl Schiff bases, that is, N‐(ferrocenylmethylene)‐4‐(4‐(ferrocenylmethyleneamino)phenoxy)benzenamine (FeL1) and 4,4′‐([1,1′‐biferrocenyl]‐4,4′‐diylbis(methylene)bis(N‐benzylideneaniline) (FeL2), have been synthesized and studied by density functional theory (DFT) to understand their nonlinear optical (NLO) behavior. The synthesized compounds were characterized by FTIR, NMR, and UV–visible spectroscopic techniques. DFT studies were performed to obtain the polarizability and first‐order hyperpolarizability parameters useful in determining the NLO response. Results indicate that the substituted biferrocenyl Schiff bases show a substantial increase in first‐order hyperpolarizability (44 times greater than the reference urea) compared with unsubstituted ferrocene. The enhanced NLO behavior follows the trend FeL2 > FeL1 > urea. Bader's atoms in molecules (AIM) theory has been employed to obtain topological parameters and critical points to evaluate the nature and strength of different types of intramolecular interactions. Charge delocalization in the complexes was investigated through natural bond order (NBO) analysis. It was observed that intramolecular charge transfer (ICT) is responsible for the optical nonlinearity of the biferrocenyl Schiff bases, with hydrogen bonding playing a prominent role in the bonding networks leading to increased hyperpolarizability. Furthermore, molecular electrostatic potential (MEP) surfaces of the molecular systems have also been analyzed. From an application viewpoint, the interaction of the biferrocenyl derivatives with fish‐sperm DNA was studied through spectrophotometric and electrochemical measurements. Results indicate major groove binding with DNA, which is also predicted by molecular docking studies.