Exploration of trimethylsilicon(IV) complexes of chalcone-based thiosemicarbazone and semicarbazone derivatives: synthesis, spectral studies, NLO, NBO analysis

The current study examines the structure, nonlinear optical (NLO) response and NBO analysis of semicarbazones, thiosemicarbazones, and their organosilicon(IV) complexes. A new series of triorganosilicon(IV) complexes [Me₃Si(L^1–10)] have been synthesis and characterized by elemental analysis, conductance measurements, FTIR, UV–Visible, NMR (¹H,¹³C,²⁹Si) spectra. According to elemental analysis of the metal complexes, the metal–ligand stoichiometry was 1:1. The nitrogen of the azomethine (>C = N−) and the oxygen/sulfur atoms in the complexes are in agreement with coordination to the metal in the IR spectra. Spectral analyses indicate that all complexes have distorted trigonal bypramidal geometry. Using DFT calculations, parameters such as global reactivity parameters (GRP), frontier molecular orbital (FMO) analysis, natural bond orbital (NBO) analysis, and first hyperpolarization were theoretically tested using DFT calculations at the B3lyp/LanL2DZ level. Using FMO analysis, we were able to reveal the charge transfer potential of the newly synthesized molecules. All compounds produced by the GRPs showed an increase in hardness and a decrease in softness, indicating reduced reactivity and higher stability. Various types of intramolecular hydrogen bonding, bond species, hyperconjugation interactions, and intramolecular charge transfers (ICTs) were examined using the NBO methodology. The molecules have a six-fold higher potential linear polarizability than urea. Moreover, the rate displayed by the molecule was almost ten times greater than the first-order hyperpolarizability. The results suggest that the most typical description is of naturally polarized, strongly dipole-moment crystals. The examined compounds stand out as attractive NLO candidates with potential for usage in upcoming technological advancements when compared to urea molecules.