New Zinc(II) Coordination Compound with 1,10-Phenanthroline and Maleate: Comprehensive Structural Analysis, Periodic-DFT Calculations, and Evaluation of Biological Potential

The escalating crisis of bacterial resistance necessitates the development of novel antimicrobial agents. Herein, we report the synthesis and comprehensive characterization of a new zinc-(II) coordination compound, [Zn-(phen)-(maleate)-(H₂O)]·H₂O (phen = 1,10-phenanthroline). Single-crystal X-ray diffraction revealed a distorted square pyramidal geometry around the Zn-(II) center, forming a supramolecular framework (triclinic, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>P</mml:mi> <mml:mi>1̅</mml:mi></mml:math> ) stabilized by hydrogen bonding (H···O/O···H: 30.6%) and π-π stacking interactions (C···C: 9.0%), as quantified by Hirshfeld surface analysis. Periodic density functional theory (DFT) calculations confirmed a direct energy gap of 3.45 eV and thermodynamic stability under ambient conditions. Vibrational spectroscopy (infrared and Raman) combined with DFT calculations provided suitable mode assignments. The compound exhibited selective antibacterial activity against Gram-positive <i>Streptococcus mutans</i> (MIC = 1000 μg/mL) with no activity against Gram-negative <i>Escherichia coli</i>. Systematic control experiments confirmed that antibacterial activity originates from the intact coordination complex rather than individual components. <i>In silico</i> pharmacokinetics predictions indicated favorable gastrointestinal absorption, full compliance with drug-likeness rules (Lipinski, Ghose, Veber, Egan, Muegge), and no cytochrome P450 inhibition. Molecular docking studies revealed specific binding to a <i>S. mutans</i> enzyme (ΔG = -7.4 kJ/mol), suggesting enzyme inhibition as the primary mechanism. This work establishes a multidisciplinary framework for rational Zn-coordination compounds design while highlighting critical needs for toxicological validation and structural optimization to enhance potency and broaden antimicrobial spectrum.