Novel one‐dimensional polymeric Cu(II) complexes via Cu(II)‐assisted hydrolysis of the 2,4‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐6‐methoxy‐1,3,5‐triazine pincer ligand: Synthesis, structure, and antimicrobial activities

Abstract

Two unexpected one‐dimensional coordination polymers, [Cu(PT)(H2O)Cl]n 1 and [Cu2(BPT)(ClO4)3(H2O)4]n·2nH2O 2, of symmetrical triazine‐based ligands were synthesized by Cu(II)‐mediated hydrolysis of the 2,4‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐6‐methoxy‐1,3,5‐triazine (MBPT) pincer ligand. The reaction of Cu(ClO4)2·6H2O with MBPT proceeded via hydrolysis of the methoxy group to produce the dicompartmental 4,6‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐1,3,5‐triazin‐2(1H)‐one ligand (HBPT) that then undergoes in situ complexation with Cu(II) to afford 2. In case of CuCl2, the reaction proceeds further with C–N cleavage of one pyrazolyl unit leading to the formation of 6‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐1,3,5‐triazine‐2,4(1H,3H)‐dione ligand (HPT) that also undergoes in situ complexation with Cu(II) affording 1. The role of Cu(II) is to increase the Lewis acid reactivity of the water molecule where similar hydrolytic reactions for MBPT were observed in acidic medium in presence of an aqueous HCl (1:1 v/v) solution. The molecular and supramolecular structures of complexes 1 and 2 were investigated using X‐ray diffraction of single crystal, Hirshfeld analysis, and density functional theory calculations. The Cl…H (11.7%) and O…H (24.7%) contacts are the most important in 1, whereas the molecular packing of 2 is controlled mainly by the O…H (58.7%) hydrogen bonds. Complex 2 showed better activity against Escherichia coli, Bacillus subtilis, and Candida albicans compared with the standard antibiotics amoxicillin, tetracycline, and ampicillin. In general, complexes 1 and 2 showed good antimicrobial activity than these antibiotics and have the advantage to be used as both antibacterial and antifungal agents.