Encapsulation of Cu(II) and Zn(II) Acylpyrazolonate Complexes in Ethyl Cellulose Matrix: A Study of Intermolecular Matrix‐Complex Interactions

A series of homoleptic Cu(II) acylpyrazolonate complexes, [Cu(Q PhtBu ) 2 (CH 3 OH)] ( 1 ), [Cu(Q PhNO2 ) 2 ] ( 2 ), [Cu(Q PhF ) 2 ] ( 3 ), [Cu(Q PhCF3 ) 2 ] ( 4 ), and [Cu(Q CF2CF3 ) 2 ] ( 5 ), were synthesized and characterized by elemental analysis, molar conductivity, FT‐IR spectroscopy, PXRD, and single‐crystal X‐ray diffraction for 1 , 3 , and 5 . Complex 1 , selected because of its good solubility in dichloromethane, was incorporated into ethyl cellulose (EC) films by solvent casting to afford EC@Cu1 n materials. These films were directly compared with analogous EC@Zn6 n films containing the previously reported complex [Zn(Q PhtBu ) 2 (CH 3 OH) 2 ] ( 6 ). PXRD, FT‐IR, thermal, and mechanical analyses indicated molecular dispersion of both additives within EC and different matrix–complex interaction patterns. Antioxidant activity, evaluated by DPPH assay, revealed that Cu(II)‐based films display lower activity than their Zn(II) counterparts, likely due to the tighter encapsulation of the Cu complex with EC chains creating steric hindrance and limiting access of the bulky DPPH radical to the metal center. In both systems, optimal performance is observed at low additive concentrations, whereas higher loadings lead to decreased efficiency, probably due to matrix segregation effects. These findings highlight the critical role of metal complexes–polymer interactions in the design of functional hybrid materials.