8-Aminoquinoline-Based Promising Zn Complexes with Dicyanamide and Tricyanomethane Anions: Supramolecular <i>R</i>₄⁴(8)/<i>R</i>₂²(16) Synthons, DFT Rationalization, and Biological Insights

Considering the new crystal engineering integrity utilizing the DFT and the issues surrounding antimicrobial resistance in complexes, there is a pressing need to tackle antifungal photodynamic therapy about global health challenges. Within the sphere of this study, we meticulously introduce the synthesis, characterization, and single-crystal structure of two 8-aminoquinoline-based Zn complexes [Zn{(8-AMQ) (X)}₂], X = dca (<b>1</b>) and TCM (<b>2</b>). The X-ray study reveals that the complexes crystallize in the monoclinic and triclinic space groups <i>P</i>2₁/<i>c</i> and <i>P</i>-1. The crystal packing in both complexes feature N-H···N hydrogen bonds as well as weak C-H···N interactions. The Hirshfeld surface provides quantitative insight into various supramolecular interactions, including π···π stacking, at large Cg···Cg distances. FMO supports the complexes' conductive behavior, excellent stability, and reactivity parameters. DOS investigation suggests good conductivity and reactivity properties. NBO analyzed that <b>2</b> exhibits a greater reactive and high potential charge transfer mechanism. The QTAIM/NCI-RDG plot ensured N···Zn/H···N interactions and explored new supramolecular <i>R</i> ₄ ⁴ (8)/<i>R</i> ₂ ²(16) crystal engineering synthons. The Trypan blue exclusion method was used to evaluate cytotoxicity against the DLA cell line, demonstrating <b>1</b>'s effectiveness against the cell, the lowest % of cell death, and a promising anticancer agent. The Zn complex antifungal photodynamic therapy finding showed significant activity against <i>C. albicans</i>.