Group 10 complexes of benzothiazolehydrazone- and imidazo[1,5-a]pyridine-based ligands: structural artistry, biophysical study, and catalytic activity

Abstract

A series of bivalent complexes of group 10 metals using benzothiazolehydrazone- and imidazo[1,5-a]pyridine-based ligands with NNP-, NNN-, and NNO-donor sites were synthesized and characterized, and their molecular structures were determined by X-ray crystallography. Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations were performed to optimize the molecular geometries, evaluate the energies of the frontier molecular orbitals (FMOs), and analyze possible electronic transitions. The chemodiverse ligands featuring various donor sites revealed how they were responsible for the geometry of the complexes as well as altering the catalytic activity and bioactivity of the respective complexes. The bivalent nickel complexes were applied as catalysts in imine/diimine formation reactions via acceptorless dehydrogenative coupling (ADC) of alcohols and amines/diamines. Using 1.0 mol% catalyst and toluene as solvent at 110 °C, Ni(II) catalysts produced imines/diimines in excellent yields with remarkable tolerance for various functional groups in 12 hours. Under similar catalyst loading, Pd(II) complexes were employed as catalysts in the Heck coupling reaction, which adeptly facilitated the formation of C–C bonds with a yield of 98% in alcoholic solvent under significantly milder reaction conditions than those of traditional protocols relying on DMF or DMSO at higher temperatures. Among all Ni(II) and Pd(II) complexes, 1a and 2f were found to be superior catalysts in their respective conversion. The platinum(II) complexes were examined for their interactions with biomolecules such as CT-DNA and BSA, wherein 3c exhibited the highest binding affinity. The binding mode of 3c was also estimated and visualized through molecular docking with CT-DNA and BSA.