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, P1̅) 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 Streptococcus mutans (MIC = 1000 μg/mL) with no activity against Gram-negative Escherichia coli. Systematic control experiments
confirmed that antibacterial activity originates from the intact coordination
complex rather than individual components. In silico 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 S. mutans 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.