T-shaped CH···π and antiparallel π···π interactions of metronidazole benzoate and phenyl supporting paddle-wheel manganese(II) and zinc(II) carboxylate complexes: Structural, spectroscopic, and theoretical studies

Abstract

The interaction and mixing of MnCl2·4H2O with 4-methylbenzoic acid (pMeBz) (1) or ZnSO4·7H2O with phenoxylacetic acid (HPOA) (2) in alkaline alcoholic solution at room temperature, in the presence of metronidazole benzoate afforded novel paddle-wheel complexes. The complexes have been characterized by single crystal Xray diffraction (SCXRD) and spectroscopic techniques (FT-IR, NIR-Vis-UV). Both complexes exhibit weak hydrogen bonds and π···π interactions, which impact the isolated molecule arrangement for optimal packing. The crystal packing of these complexes is dependent on π···π interactions. In the manganese complex, parallel and T-shaped benzene···imidazole stacking dominates, while the zinc complex utilizes antiparallel π···π interactions involving the metronidazole benzoate. A π-hole interaction, π(CC)···π*(CO), with a π(CC)···π*(CC) transfer primarily drives the benzoate dimers formation. An additional antiparallel imidazole···imidazole dimer contributes to this crystal assembly. These findings highlight these metal complexes' interplay of electronic structure, electrostatics, and noncovalent interactions. The insights gained from this study can pave the way for designing functional materials with targeted properties by tailoring ligands to exploit specific interactions.