Search

A novel mononuclear bis(formazanate)zinc complex (1) based on a redox-active 1-(benzothiazol-2-yl)-5-(2-benzoyl-4-chlorophenyl)-3-phenyl formazan ligand has been synthesized and characterized. Complex 1 was prepared by reacting one equivalent of Zn(OCOCH3)·2H2O with two equivalents of the corresponding formazan derivative. X-ray crystallography was employed to ascertain the solid-state structure of compound 1, and the analysis revealed a distorted octahedral geometry for the complex where the symmetrical ligands exhibit a preference for coordinating with the zinc center in the 'open' form, generating five-membered chelate rings. Moreover, cyclic voltammetry analysis reveals that complex 1 exhibits the capacity for electrochemical reduction as well as oxidation, resulting in the formation of radical anionic (L2Zn−) and dianionic (L2Zn2−) states as well as the oxidation state of 1. Additionally, the developed solution-processable complex 1 was employed as the fundamental building material for resistive switching memory applications. The [FTO/ZnIIL2(1)]/Ag RRAM device demonstrates exceptional resistive memory switching properties, with a substantial ION/IOFF ratio (103), low operational VSET and VRESET (0.9 V and −0.75 V) voltages, excellent endurance stability (100 cycles), and decent retention time (more than 2000 seconds). The findings presented in this study underscore the importance of redox-active formazanate metal complexes for creating promising memory storage devices. [ABSTRACT FROM AUTHOR]

The sustainable chemical energy of H2O2 as a fuel and an oxidant in an advantageous single-compartment fuel cell design can be converted into electric energy, which requires molecular engineering to design suitable cathodes for lowering the high overpotential associated with H2O2 reduction. The present work covers the synthesis and structural characterization of a novel cathode material, [Fe III2 (hnmh-PLY)3] complex, 1, designed from a PLY-derived Schiff base ligand (E)-9-(2-((2-hydroxynaphthalen-1-yl)methylene)hydrazineyl)-1H-phenalen-1-one, hnmh-PLYH2. Complex 1, when coated on the surface of a glassy carbon electrode (GC-1) significantly catalyzed the reduction of H2O2 in an acidic medium. Therefore, a complex 1 modified glassy carbon electrode was employed in a one-compartment H2O2 fuel cell operated in 0.1 M HCl with Ni foam as the corresponding anode to produce a high open circuit potential (OCP) of 0.65 V and a peak power density (PPD) of 2.84 mW cm−2. CV studies of complex 1 revealed the crucial participation of two Fe(III) centers for initiating H2O2 reduction, and the role of coordinated redox-active PLY units is also highlighted. In the solid state, the π-conjugated network of coordinating (hnmh-PLY) ligands in complex 1 has manifested interesting face-to-face π–π stacking interactions, which have helped the reduction of the complex and facilitated the overall catalytic performance. [ABSTRACT FROM AUTHOR]

In this paper, we report the synthesis and characterization of a mononuclear zinc complex (1) containing a redox-active bis(4-antipyrinyl) derivative of the 3-cyanoformazanate ligand. Complex 1 was readily obtained by refluxing zinc acetate with 3-cyano-1,5-(4-antipyrinyl)formazan (LH) in a methanolic solution. Single-crystal X-ray diffraction analysis of complex 1 shows that the formazanate ligands bind to the zinc center in a five-member chelate "open" form via the 1- and 4-positions of the 1,2,4,5-tetraazapentadienyl formazanate backbone leading to the formation of the mononuclear bis(formazanate) zinc complex exhibiting a distorted octahedral geometry. We also report the study of resistive-switching random access memory application of this solution-processable bis(formazanate) Zn(II) complex to facilitate the practical implementation of transition metal complex-based molecular memory devices. The complex demonstrated high conductance switching with a large ON–OFF ratio, good stability, and a long retention time. A trap-controlled space charge limited current mechanism is proposed for the observed resistive switching behavior of the device, wherein the role played by the [ZnIIL2] complex that comprises the extended redox-active conjugated ligand backbone is revealed by corroborating electrochemical studies, spectrochemical experiments, and DFT calculations. In addition to providing significant insights into the molecular design of transition metal complexes for memory applications, this study also presents the utilization of ZnIIL2 towards the realization of non-volatile resistive random access memory (RRAM) devices with inorganic/organic hybrid active layers that are highly cost-effective and sustainable. These devices exhibited multilevel switching and low current operation, both of which are desirable for advanced memory applications. [ABSTRACT FROM AUTHOR]

Closed-shell phenalenyl (PLY) systems are increasingly becoming more attractive as building blocks for developing promising catalysts and electroactive cathode materials, as they have tremendous potential to accept electrons and participate in redox reactions. Herein, we report a PLY-based dinuclear [Fe III2 (hmbh-PLY)3] complex, 1, and its utility as a cathode material in a H2O2 fuel cell. Complex 1 was synthesized from a new Schiff base ligand, (E)-9-(2-(2-hydroxy-3-methoxybenzylidene)hydrazineyl)-1H-phenalen-1-one, hmbh-PLYH2, designed using a PLY precursor, Hz-PLY. The newly derived ligand and complex 1 were characterized by various analytical techniques, including single-crystal X-ray diffraction (SCXRD). The cyclic voltammetry (CV) study revealed that complex 1 undergoes five electron reductions under an applied electric potential. When the electroactive complex 1 was employed as a cathode in a membrane-less one-compartment H2O2 fuel cell, with Ni foam as the corresponding anode, the designed fuel cell exhibited an exceptionally high peak power density (PPD) of 2.41 mW cm−2, in comparison with those of all the previously reported Fe-based molecular complexes. DFT studies were performed to gain reasonable insights into the two-electron catalytic reduction (pathway I) of H2O2 by the Fe-center of complex 1 and to explore the geometries, energetics of the electrocatalyst, reactive intermediates and transition states. [ABSTRACT FROM AUTHOR]

We report the isolation of five new discrete diorganotin di-/mono-carboxylate structures achieved by employing an intramolecular coordination approach. Two diorganotin dicarboxylates, complexes 1 and 2, were obtained from reactions of R2SnCl2 (R = 2-phenylazophenyl) with pyridine-2,6-dicarboxylic acid and pyrazole-3,5-dicarboxylic acid, respectively, in the presence of a base. However, the reactions of R2SnCl2 with 3,4,5-trimethoxybenzoic acid in different stoichiometric ratios in the presence of a base produced two diorganotin monocarboxylates, complexes 3 and 4. An equimolar reaction of R2SnO with 2-(1,8-naphthalimido)ethanoic acid afforded a dinuclear diorganotin carboxylate [R2Sn(μ-OH){C14H8NO4}]2 (5). All the complexes (1–5) are structurally characterized using single-crystal X-ray diffraction analysis. The molecular structures of complexes (1–5) revealed the retention of both N → Sn intramolecular coordinations. Each tin (Sn) center in complexes (1–5) is present in a high coordination number of seven with distorted pentagonal bipyramidal geometry. Time-dependent density functional theory (TDDFT) calculations revealed that ligand-to-ligand transitions dominate electronic transitions in these complexes. The Hirshfeld surfaces and 2D fingerprint plots were analyzed for all the complexes to understand the intermolecular interactions involved in crystal packing. [ABSTRACT FROM AUTHOR]