Novel Zinc(II) 2,6-dimethoxybenzamidine Schiff Base Complexes: Design, Synthesis, X-ray Crystal Structure, Fluorescence Properties and Density Functional Theory Calculations.

This study presents the rational design, synthesis, and comprehensive characterization of three novel zinc(II) Schiff base complexes derived from 2,6-dimethoxybenzamidine ligands. Single-crystal X-ray diffraction analysis reveals these complexes adopt distorted square pyramidal geometries (τ = 0.00-0.42), with their supramolecular architectures stabilized by intricate hydrogen bonding (C-H···Cl) and π···π stacking interactions. Spectroscopic investigations demonstrate ligand-centered fluorescence emissions in the blue-green-yellow region (491-531 nm), with observed red shifts correlating to reduced HOMO-LUMO energy gaps (3.29-3.46 eV) as confirmed by DFT calculations. Notably, complex 3 exhibits superior thermal stability with decomposition onset at 316.5 °C. Beyond fundamental structural insights, this work systematically explores how geometric distortion and intermolecular interactions modulate photophysical properties, providing valuable design principles for developing luminescent materials with potential applications in optoelectronics and sensing. The combined experimental and theoretical approach offers a robust framework for future studies on structure-property relationships in coordination complexes.