Impedance Spectroscopy as a Powerful Tool for Researching Molybdenum-Based Materials with Schiff Base Hydrazones

Abstract

Molybdenum coordination complexes are widely applied due to their biological and pharmacological potential, as well as their performance in different catalytic processes. Parent dioxidomolybdenum Schiff base complexes were prepared via the reaction of [MoO2(acac)2] with a hydrazone Schiff-base tetradentate ligand. A new hydrazone-Schiff base (H2L1 and 2) and its corresponding mononuclear and polynuclear dioxidomolybdenum(VI) complex were synthesized and characterized by spectroscopic methods and elemental analyses, and their thermal behavior was investigated by thermogravimetry. The crystal and molecular structures of H2L2 ligands and the complexes [MoO2(L1)(H2O)], [MoO2(L2)(H2O)], [MoO2(L1)(MeOH)]∙MeOH, [MoO2(L1)(EtOH)]∙EtOH, [MoO2(L1)(2-PrOH)]∙2-PrOH, and [MoO2(L1)]n were determined by single-crystal X-ray diffraction. Using the in situ impedance spectroscopy method (IS), the structural transformations of chosen complexes were followed, and their electrical properties were examined in a wide range of temperatures and frequencies.

Molybdenum Complexes Derived from 2-Hydroxy-5-nitrobenzaldehyde and Benzhydrazide as Potential Oxidation Catalysts and Semiconductors

“…Observed trends are in line with the recent study of Sarjanovic et al [28] on a similar class of compounds. In the case of transformed methanol-and water-coordinated complexes, as in our case complex [MoO 2 (L)(MeOH)] ( 1) and [MoO 2 (L)(H 2 O)] (2), it is expected to result in the same polymerized [MoO 2 (L)] n species after heating, which is additionally indicated by the range of value for activation energy, around 60-65 kJ/mol.…”

“…The second one, at the highest temperatures and lowest frequencies, begins with the formation of a frequency-independent region (DC-part) that corresponds to the DC conductivity that arises from the translational motions of charge. Similar features in conductivity spectra can be observed via IS in a wide range of semiconductive materials, crystalline and/or amorphous [27,28,[33][34][35][36]. Owing to the lack of a discernible plateau in the graph, directly ascertaining the DC conductivity value from the plot is impractical.…”

“…where σ DC is DC conductivity, σ 0 * is the pre-exponential factor, T represents the temperature in K, and k B is the Boltzmann constant. The investigated complexes exhibit a minimal temperature dependency, thereby necessitating the calculation of activation energy in the higher temperature domain (above 100 2) are following analogue materials documented in reference [28].…”

“…Furthermore, vanadium coordination compounds derived from simple acyl-hzdrazones, containing 5-nitrobenzaldehyde, showed prominent potential as semiconducting materials [27]. Conversely, molybdenum-based complexes derived from closely related hydrazones as applied in this investigation, distinguished by the selection of hydrazide, specifically 2-hydroxybenzhydrazide (H 2 L 1* = Schiff base obtained by the reaction of 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxybenzhydrazide) and 4-hydroxybenzhydrazide (H 2 L 2* = Schiff base obtained by the reaction of 2-hydroxy-5nitrobenzaldehyde and 4-hydroxybenzhydrazide), exhibited enhanced electrical conductivity with rising temperature [28], which enables their classification as semiconductors. DC conductivity was determined: [MoO 2 (L 1* )(MeOH)] to be 1.82 In response to the recent literature contributions, the objective of this study was to synthesize molybdenum complexes coordinated by aroyl hydrazone-type ligands (Figure 1) and to conduct a comprehensive examination of their catalytic and electrical properties, providing materials with dual functionalities.…”

Evaluation of vanadium coordination compounds derived from simple acetic acid hydrazide as non-conventional semiconductors

“…37 Notably, references in the literature regarding vanadium complexes emphasize the insufficient exploration of their electrical and dielectric properties. For instance, vanadium complexes with tetradentate Schiff bases 38 and vanadium indanone derivatives 39 exhibit semiconductor characteristics which can be further employed in the manufacturing of electronic gadgets such as light-emitting diodes, rechargeable batteries, sensors, and electronic devices. Moreover, the electrical and magnetic properties of vanadium( iv ) complex compounds prepared through reactions with aroyl-hydrazone ligands have been explored.…”