Synthesis, characterization, X-ray structure, and DFT calculations of Zn complex encompassing HLN2O ligand: Relevance in cytotoxicity and antifungal photodynamic therapy.

Abstract

This article presents the synthesis, characterization, and X-ray crystallographic features of one new Zn complex derived from a Salen-type tridentate ligand (HL^N2O). A single-crystal diffraction study determined the complex crystal structure, which confirms that it crystallizes in the orthorhombic space group P2₁2₁2₁. The single-crystal structure is constructed using the unique mononuclear component [ZnL^N2°] and supramolecular CH∙∙∙π type interaction, resulting in a 1D structure. The IR, HRMS, and NMR study also support the complex structure. The Zn metal centre has a distorted square pyramidal geometry with τ value of 0.49. The Hirshfeld surfaces and 2D fingerprint confirm predominant H…H (77.9 %) interactions, with minor H…O, H…C, and H…N (5.0 %, 4.9 %, and 0.2 %). DFT calculations employed the B3LYP-D3/Lanl2DZ class of theory. FMO/MEP explains the complex reactivity perspective, while IP (4.71 eV) and low EA (1.11 eV) suit biological applications. The bonding gateway was analysed using NBO/QTAIM-NCI and ELF-LOL plots. Cytotoxicity was assessed using the Trypan blue exclusion method and tested against the DLA cell line, showing effectiveness against the DLA cell and suggesting complex potential as an anticancer agent. Antifungal photodynamic therapy (APDT) explored that ligand and Zn complex have significant activity against C. albicans. Finally, molecular docking simulations substantiate the experimental findings.