Synthesis, Characterization, Biological Evaluation, and Theoretical Insights of a Novel Zinc(II) Carboxylate Complex

Abstract

A novel zinc(II) carboxylate complex [Zn(L)₂], where L represents the 9H-fluorene-9-carboxylate ligand, was synthesized and characterized through FTIR, ¹H and ¹³C NMR spectroscopy, elemental analysis, and atomic absorption spectroscopy. The spectral data confirmed bidentate coordination via carboxylate oxygen atoms, and the complex exhibited high thermal stability with a melting point above 280 °C. Biological evaluation revealed moderate antioxidant activity in total reducing power (32.1 µg AAE/mg), total antioxidant capacity (22.2 µg AAE/mg), and DPPH radical scavenging assays (15.7% at 50 µg/mL). Cytotoxic activity was observed against Artemia salina with 35% lethality at 50 µg/mL, while hemolytic activity reached 64.25% at 100 µg/mL, indicating potential membrane-disruptive effects. Computational electrostatic potential (ESP) analysis showed negative charge localization over carboxylate groups and a positively charged zinc center, highlighting potential reactive sites. The complex also demonstrated promise for non-biological applications as a Lewis acid catalyst and thermal stabilizer. This study integrates synthetic, biological, and theoretical approaches to explore the multifunctional potential of zinc(II) coordination complexes.