An acetate bridged centrosymmetric trinuclear Zn( <scp>ii</scp> ) cluster: structural insights, biomolecular interactions, sensing and cytotoxic activity

A multifunctional trinuclear zinc cluster with the formula [Zn₃L₂(μ^1,2-OAc)₂(μ^1,1,2-OAc)₂] (C1) was synthesized from a tridentate Schiff base ligand (L1) and thoroughly characterized by various spectral (FTIR, ¹H & ¹³CNMR, UV-vis, and sc-XRD studies) and analytical techniques. The sc-XRD studies of C1 revealed a monoclinic crystal system with a space group of <i>P</i>21/<i>c</i>, wherein three zinc (Zn₃) centers are bridged <i>via</i> four acetate ions. The DFT and TDDFT studies were also performed to validate the chemical and electronic structures of the Zn(II) cluster. The HOMO electron density is mainly restricted on the bridging acetate ions and the ligand moiety while the LUMO electron density is distributed throughout the metal complex. We exploited the sensing activity of the Zn(II) cluster using spectral techniques which validated a selective and efficient sensing of Al³⁺ ions in aqueous medium. Moreover, the catecholase activity of C1 was evaluated and interestingly, our results indicated a ligand-centered radical pathway with a remarkable catalytic activity. We further carried out <i>in vitro</i> biomolecular interactions with ct-DNA using multispectral methods to authenticate the chemotherapeutic potential of C1. Furthermore, the cytotoxicity of C1 was evaluated against HCT116 (colon cancer), MDA-MB-231 (triple-negative breast cancer) and SH-SY5Y (neuroblastoma) cancer cells and toxicity studies were carried out against the normal VERO (kidney) cell line which revealed selective cytotoxicity of C1 against the MDA-MB-231 cancer cells with a remarkably low IC₅₀ value.