Electrical Properties of Cu-Based Coordination Complexes: Insights from In Situ Impedance Spectroscopy.

This study examines the influence of ligand design on the structural, optical, and electrical properties of copper-based coordination complexes. Ligands HL and HL were synthesized via the reaction of 5-nitrosalicylaldehyde with 2-hydroxy- or 4-hydroxybenzhydrazide. HL was obtained from the reaction of carbohydrazide and salicylaldehyde, while HL was prepared by condensing 4-methoxysalicylaldehyde with thiocarbohydrazide. The research focuses on two key design elements: (1) the effect of hydroxyl group positioning on the aroyl ring in hydrazide ligands (HL vs. HL) and (2) the impact of carbonyl versus thiocarbonyl groups and aldehyde substituents in hydrazone ligands (HL vs. HL). The resulting complexes, [Cu(L)], [Cu(L)(MeOH)], [Cu(L)(HO)], and [Cu(L)(HO)], were synthesized and characterized using attenuated total reflectance infrared (IR-ATR) spectroscopy, thermogravimetric analysis (TG), and UV-Vis diffuse reflectance spectroscopy. Their electrical properties were investigated using solid-state impedance spectroscopy (IS). The crystal and molecular structure of the complex [Cu(L)(MeOH)]∙MeOH was determined by single-crystal X-ray diffraction (SCXRD). This study underscores the pivotal role of ligand modifications in modulating the functional properties of coordination complexes, offering valuable insights for the advancement of materials chemistry.