Synthesis, structure, and catalytic- and bio-activity of some metal complexes and a coordination polymer featuring imidazo[1,5-a]pyridine and chromen[4,3-b]pyrrole-4-one

Abstract

A series of M^II (M = Ni, Cu, Pd and Pt) complexes and a copper(II) coordination polymer (CP) were synthesized using ligands containing imidazo[1,5-a]pyridine and chromen[4,3-b]pyrrole-4-one moieties. These complexes and the CP were explicitly characterized using several spectroscopic techniques and the molecular structures were confirmed by single crystal X-ray diffraction measurement. Computational calculations were also carried out that support the experimental findings. The N(II) complexes were employed as catalysts in α-alkylation of acetophenone via a hydrogen auto-transfer strategy, while palladium counterparts were used to catalyze Heck coupling under mild reaction conditions. The presence of m/z peaks due to ligand-bound aryl–Pd(II) and σ–alkyl–Pd(II) intermediates in HRMS indicated the involvement of a molecular Pd(0)/Pd(II) catalytic cycle. Copper and platinum complexes and the copper CP were examined for their interaction with biomolecules such as CT-DNA and BSA. The binding interaction of the imidazo[1,5-a]pyridine–Pt(II) complex with DNA and BSA was also visualized using molecular docking. This study explored the effect of the ligand frameworks on the geometry and reactivity of their bivalent Ni, Cu, Pd and Pt complexes. In both catalytic assessments, Ni(II)/Pd(II) complexes containing the imidazo[1,5-a]pyridine ligand were found to be more effective than the corresponding complexes having a coumarin–pyrrole moiety.