Synthesis, characterization and application of enrofloxacin complexes as thermal stabilizers for rigid poly(vinyl chloride)

Abstract

Synthesis and characterization of both binary Co(II)- (1), Ni(II)- (2) complexes with enrofloxacin drug (HL₁) and ternary Co(II)- (3), Ni(II)- (4) complexes in presence of DL-alanine (H₂L₂) are reported using physico-chemical techniques. The antimicrobial activity of these complexes has been screened against two Gram-positive and two Gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with reference drug. All the binary and ternary complexes showed remarkable potential antimicrobial activity higher than the recommended standard agents. Ni(II)- complexes exhibited higher potency as compared to the parent drug against bacterial and fungal strain. In addition, it was of interest to investigate the reported complexes as thermal stabilizers and co-stabilizers for rigid PVC in air at 180 °C. Their high stabilizing efficiency is detected by their high induction period values (T_s) compared with some of the common reference stabilizers used industrially, such as dibasic lead carbonate (DBLC) and calcium-zinc soap. Blending these complexes with some of the reference stabilizers in different ratios had a synergistic effect on both induction period as it gave better thermal stability and lower extent of discoloration. The stabilizing efficiency is attributed at least partially to the ability of the metal complex stabilizer to be incorporated in the polymeric chains, thus disrupting the chain degradation and replace the labile chlorine atoms on PVC chains by a relatively more s moiety of the inorganic stabilizer. Their amenability to use as a biomedical additives for PVC, has afforded them great potential for various medical applications.