Novel palladium(II) complexes with Schiff bases derived from 4,5-methyl enedioxy-2-nitrobenzaldehyde and 5-Bromo-2-hydroxybenzaldehyde as potential antimicrobial agents: Synthesis, characterization and studies in vitro-

Two novel palladium(II) complexes, [Pd(L1)(HL1)]Cl (1) and [Pd(HL2)2] (2), were synthesized an equimolar 2:1 ligand-to-metal reaction between the ligands 4,5-Methylenedioxy-2-nitro-benzaldehyde-thiosemicarbazone (HL1) and 5-Bromo-2-hydroxy-benzaldehyde-beta-alanine (H2L2) with bis(acetonitrile)dichloropalladium(II) [Pd (CH3CN)2Cl2]. The complexes were characterized using spectroscopic techniques, including IR and 1H/13C NMR. Additionally, for complex 2, the structure was determined by single-crystal X-ray diffraction, revealing a complex with a distorted square planar geometry. The results revealed that the ligands (HL1 and H2L2) coordinated in a bidentate fashion via the azomethine group, thione group, and phenolate oxygen, resulting in the formation of one cationic (1) and one neutral complex (2). Antimicrobial activity was assessed using Streptococcus mutans (ATCC 700,610) and Candida albicans (ATCC MYA-2876) strains. The minimum inhibitory concentration (MIC), minimum bactericidal/fungicidal concentration (MBC/MFC), microbial death kinetics, and biofilm inhibition capacity were evaluated. Complexation with palladium(II) significantly enhanced the antimicrobial efficacy of the Schiff bases against S. mutans and C. albicans. The complexes with HL1 and H2L2 eradicated the microorganisms within 24 h, with complex 1 exhibiting bactericidal and fungicidal activity as early as 4 h against C. albicans and 8 h against S. mutans. Furthermore, both complexes inhibited S. mutans biofilm formation by >75 % at a concentration of 15.63 mu g/mL.