An Iminosemiquinone-Coordinated Oxidovanadium(V) Complex: A Combined Experimental and Computational Study

Abstract

Ligand HSar contained two terminal amidophenolate units that were connected by a disulfane bridge. The ligand reacted with VOSO·5HO in the presence of EtN under air and provided a mononuclear octahedral oxidovanadium complex (1). X-ray crystal structure analysis of complex 1 revealed that the oxidation state of the V ion was V and the VO unit was coordinated to an iminosemiquinone radical anion. An isotopic signal at g = 1.998 in the X-band electron paramagnetic resonance (EPR) spectrum and the solution magnetic moment μ = 1.98 μ at 298 K also supported the composition. The formation of complex 1 preceded through the initial generation of a diamagnetic VO-iminoisemiquinone species, as established by time-dependent UV-vis-near-IR (NIR), X-band EPR, and density functional theory studies. The UV-vis-NIR spectrum of complex 1 consisted of four ligand-to-metal charge-transfer transitions in the visible region, while an intervalence ligand-to-ligand charge transfer appeared at 1162 nm. The cyclic voltammogram of the complex showed four oxidation waves and one reduction wave. Spectroelectrochemical studies at fixed potentials revealed that the oxidation and reduction processes were ligand-based.

Geometry-Driven Iminosemiquinone Radical to Cu(II) Electron Transfer and Stabilization of an Elusive Five-Coordinate Cu(I) Complex: Synthesis, Characterization, and Reactivity with KO2

“…This featured a quinoid-type distortion . The C1–N1 = 1.302(3) Å and C2–O1 = 1.227(3) Å bond distances were unambiguously double bond, and therefore, consolidated the [L IBQ(Ph) ] 0 form of the coordination ligands in complex 2 . The oxidation state of the central Cu1 atom was thus being assigned as +I, and the neutrality of the complex was maintained by the coordinated-chloride anion [Cu1–Cl1 = 2.2352(10) Å].…”

“…Three long bonds followed by an alternate short–long–short bonds sequence were observed. This featured a quinoid-type distortion . The C1–N1 = 1.302(3) Å and C2–O1 = 1.227(3) Å bond distances were unambiguously double bond, and therefore, consolidated the [L IBQ(Ph) ] 0 form of the coordination ligands in complex 2 .…”

Assigning Ligand Redox Levels in Complexes of 2-Aminophenolates: Structural Signatures

“…Seven-coordinate molybdenum­(VI) complex 14 [average MOS: −1.52(9)] reveals a substantial delocalization. , a For six-coordinate vanadium­(V) complex 80 , the average C–O/N distances and Δ a values imply a delocalized electronic state. The MOS values [−1.17(10), −1.26(7), and −1.33(6)] also point toward π bonding between the metal ion and redox-active 2-aminophenolates.…”

Cobalt Complex with Redox-Active Imino Bipyridyl Ligand for Electrocatalytic Reduction of Carbon Dioxide to Formate

“…[2e] The 1 0 species showedafree radical signal at g = 2.00, consistent with an organic radical; [23] therefore, the electronic structure of 1 0 should be a (L 1 C À )Co I ligand radicals pecies insteado fatrue L 1 Co 0 species. The formal Co 0 species reactedw ith CO 2 to yield an ew Co intermediate species 1 CO 2 under anhydrous conditions.…”