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 H2L1 and H2L2 were synthesized via the reaction of 5-nitrosalicylaldehyde with 2-hydroxy- or 4-hydroxybenzhydrazide. H4L3 was obtained from the reaction of carbohydrazide and salicylaldehyde, while H4L4 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 (H2L1 vs. H2L2) and (2) the impact of carbonyl versus thiocarbonyl groups and aldehyde substituents in hydrazone ligands (H4L3 vs. H4L4). The resulting complexes, [Cu2(L1)2], [Cu2(L2)2(MeOH)3], [Cu2(L3)(H2O)2], and [Cu2(L4)(H2O)2], 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 [Cu2(L2)2(MeOH)3]∙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.

New bis[MoO2] and [MoO(O2)] compounds: An artificial enzyme with peroxidase activity against o-phenylenediamine and dopamine

In this study, two binuclear dioxido- and oxidoperoxido molybdenum (VI) complexes, [{Mo^VIO₂}₂(L)(H₂O)₂] 1 and [{Mo^VIO(O₂)}₂(L)(H₂O)₂] 2, were synthesized. Complex 1 was obtained through a 1:2 reaction of ligand I with MoO₂(acac)₂, while complex 2 was synthesized in situ by reacting MoO₃ with H₂O₂ in a 1:2 ratio. The structures and characteristics of the complexes were examined employing several techniques such as elemental (CHN) analysis, spectroscopy (FT-IR, UV-Vis, ¹H, and ¹³CNMR), and thermal study (TGA). SC-XRD analysis of complex 1a revealed that the molybdenum central atom adopts an octahedral geometry and is bonded to phenolic oxygen, enolate oxygen, and azomethine nitrogen atoms. Powder X-ray diffraction was used to determine the purity of the bulk material, and the results were compared to single crystal data. Computational calculations were performed using density functional theory (DFT) at the B3LYP/6-31G(d, p) level of theory for the ligand and the LANL2DZ level of theory for the complexes, yielding geometry optimized structures that were then employed in frequency and NMR-calculations. These theoretical findings were compared to the experimental results and showed a good correlation. Furthermore, the complexes exhibited peroxidase-like activity in the presence of hydrogen peroxide as evidenced by the oxidation of o-phenylenediamine and dopamine.

Coordinating and supramolecular prospects of unsymmetrically substituted carbohydrazides

Unsymmetrically substituted carbohydrazides serve as multifunctional ligands, practicing their chelating and supramolecular roles with cis-dioxomolybdenum(vi) cationic core and the Lindqvist anion.