Synthesis and theoretical studies on new mono and bis-triazole derivatives

Abstract

In this work, a series of novel mono- and bis-1,2,3-triazole derivatives incorporating quinoline scaffolds were synthesized via efficient one-pot azide-alkyne cycloaddition strategies and comprehensively investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods theoretically. Detailed conformational analyses identified the most stable geometries governing metal-ligand interactions with Zn2+, Cd2+, and Hg2+ ions. For all cases the dihedral angle through oxygen of hydroxy quinoline and nitrogen of triazole ring has been computed to be 180 degrees. NBO and Mulliken charge analysis demonstrates substantial metal charge reduction upon coordination, particularly for Hg2+, indicating strong ligand-to-metal charge transfer and increased covalency. TD-DFT calculations show pronounced bathochromic shifts and band broadening upon metal binding, with the largest spectral modulation observed for bis-triazole-Hg2+ complexes. The secondary bands shift, from similar to 240-270 nm (Zn and metal-free) to similar to 300-320 nm (Cd) and up to similar to 330-370 nm for Hg, indicating a pronounced red shift with the largest displacement reaching similar to 100-120 nm in the higher-wavelength region. PCMbased TD-DFT calculations revealed that the absorption spectra of the studied systems are strongly influenced by solvent polarity, with THF and DMSO environments inducing notable bathochromic shifts, enhanced absorption intensities, and increased excited-state stabilization relative to the gas phase, particularly for charge-transferrelated electronic transitions. Frontier molecular orbital and molecular electrostatic potential analyses further elucidate the role of ligand multiplicity in electronic delocalization and metal affinity. Collectively, these results establish bis-triazole frameworks as highly effective platforms for tunable metal coordination and optoelectronic applications.