Structurally Engineered Cu(II)–4-Chloro-2-nitrobenzoate–Picoline Complexes Immobilized in PVA/Cellulose Composite Films for Sustainable Catalytic and Antimicrobial Applications

Herein, sustainable facile immobilization of two new Cu(II) complexes into poly(vinyl alcohol)–cellulose (PVA–CE) matrices for their potential dip-catalytic and antibacterial applications is reported. In particular, structurally isomeric complexes [Cu(4C2N-Bz)2(β-pic)2(H2O)2] (1) and [Cu(4C2N-Bz)2(γ-pic)2(H2O)2] (2), where 4C2N-Bz = 4-chloro-2-nitrobenzoate and β-/γ-pic = 3-/4-methylpyridine, were isolated at room temperature and structurally evaluated by single-crystal X-ray diffraction (SCXRD). Distinct coordination geometries and the role of various noncovalent interactions that influence the overall electronic and reactivity characteristics were validated by packing analysis, Hirshfeld surface (HS) mapping, and DFT calculations. Immobilization of complexes 1 and 2 into PVA–CE matrices via solution casting yielded hybrid blends PC1 and PC2. Comprehensive characterization (UV–Vis, FT-IR, PXRD, SEM, and AFM) unveiled uniform dispersion and strong interfacial interactions, indicating that the complexes were successfully integrated as fillers within the matrix. Besides, both PC1 and PC2 exhibited an enhanced tensile strength and negligible Cu leaching, suggesting excellent mechanical stability and recyclability. For application aspects, catalytic evaluations revealed significant oxidase-mimetic activity with Kcat values of 1913.4 and 1947.6 h–1 in a 30 min period for the hybrid blends PC1 and PC2, comparable to impregnated complexes 1 and 2 alone. Antibacterial assays demonstrated potent inhibition efficiency of both polymeric blends. These findings established a direct correlation between the structural features of the Cu(II) centers and the functional performance of hybrid materials, highlighting their potential as robust, reusable systems for sustainable dip-catalytic and antimicrobial applications.