Mono Versus Dinuclear Vanadium(V) Complexes: Solvent Dependent Structural Versatility and Electro Syntheses of Mixed-Valence Oxovanadium(IV/V) Entities in Solution

Abstract

Two mononuclear oxidovanadium(V) complexes type of [V V O(L 1 )(OMe)(MeOH)] ( 1 ), [V V O(L 2 )(OMe)(MeOH)] ( 2 ) and two [V 2 O 3 ] 4+ core of μ-oxidodioxidodivanadium(V) complexes (L 1 )(O)V V –O–V V (O)(L 1 ) ( 3 ) and (L 2 )(O)V V –O–V V (O)(L 2 ) ( 4 ) and two complexes [V V O(L 1 )(8-Hq)] ( 5 ) and [V V O(L 2 )(8-Hq)] ( 6 ) incorporating 8-hydroxyquinoline (8-hq) as co-ligand have been reported where L 1 [( E )- N ′-(2-hydroxybenzylidene)cinnamohydrazide] and L 2 [(2 E , N ′ E )- N ′-(2-hydroxybenzylidene)-3-(naphthalen-1-yl)acrylohydrazide] are the dianionic forms of the conjugated keto-imine functionalized substituted hydrazone ligands. The μ-oxidodioxidodivanadium complexes are generated upon switching the solvent from methanol to acetonitrile. The X-ray analysis showed octahedral geometry for the mononuclear complexes 1 , 2 and 5 but oxido-bridged dinuclear complexes 3 and 4 formed penta-coordinated square-pyramidal geometry about metal atoms. Two mixed-valence species of type II, 3a and 4a, of general formulae (L)(O)V IV –O–V V (O)(L), are being generated upon constant potential electrolysis (CPE) of 3 and 4 respectively. Frozen solution EPR spectra have 13 hyperfine lines, revealing the unpaired electron is majorly localized on one of the two vanadium centres. All these complexes have been well characterized by physio-chemical techniques and the density functional theory (DFT) calculations were applied to obtain further insight into the electronic structure of this type of molecule. The oxidomethoxido complexes 1 and 2 were taken to investigate the catechol oxidase mimicking activity following the oxidation of 3,5-di- tert -butyl catechol (3,5-DTBC) to 3,5-di- tert -butyl benzoquinone (3,5-DTBQ).

Syntheses, Structures, and Electrochemical Properties of Metallacyclic Oxidovanadium(V) Complexes with Asymmetric Multidentate Linking Ligands

“…Molecules 2024, 29, x FOR PEER REVIEW 2 of 13 on the reactivity of the ligand itself and the composition of the obtained Mn(III) complex, it is likely that this ligand readily forms complexes with redox-active metal ions in the +3 charge. Therefore, we focused on synthesizing VO 3+ complexes, which are expected to find applications in catalysis development utilizing the high oxidation ability of V(V) [14][15][16]. Moreover, they are anticipated to serve as model complexes for metalloenzymes, contributing to our understanding of the role of vanadium ions in bioinorganic chemistry, including those present in the active sites of haloperoxidase [17][18][19] or the vanadium-containing anion amavadin, found in certain mushrooms [20].…”