Doublet Ground State in a Vanadium(II) Complex: Redox and Coordinative Noninnocence of Tripodal Ligand Architecture.

We report on the geometric and electronic structures of a series of V tren-bridged iminopyridine complexes [tren = tris(2-aminoethyl)amine] that enable the observation of an unexpected doublet ground state for a nominally 3d species. Tren undergoes condensation reactions with picolinaldehyde or methyl-6-formylnictonate to form the respective tripodal ligand sets of (py)tren and (5-COMepy)tren. The (py)tren ligand is coordinated to V and V metal centers to form complex salts (OTf) and (OTf), respectively (OTf = CFSO).

Electronic Structures of Cr(III) and V(II) Polypyridyl Systems: Undertones in an Isoelectronic Analogy.

A recently reported description of the photophysical properties of V polypyridyl systems has highlighted several distinctions between isoelectronic, d, Cr, and V tris-homoleptic polypyridyl complexes of 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen). Here, we combine theory and experimental data to elucidate the differences in electronic structures. We provide the first crystallographic structures of the V complexes [V(bpy)](BPh) () and [V(phen)](OTf) () and observe pronounced trigonal distortion relative to analogous Cr complexes.

Long-Lived Mixed MLCT/MC States in Antiferromagnetically Coupled d Vanadium(II) Bipyridine and Phenanthroline Complexes.

Exploration of [V(bpy)] and [V(phen)] (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline) using electronic spectroscopy reveals an ultrafast excited-state decay process and implicates a pair of low-lying doublets with mixed metal-to-ligand charge-transfer (MLCT) and metal-centered (MC) character. Transient absorption (TA) studies of the vanadium(II) species probing in the visible and near-IR, in combination with spectroelectrochemical techniques and computational chemistry, lead to the conclusion that after excitation into the intense and broad visible MLCT ← GS (ground-state) absorption band (ε = 900-8000 M cm), the MLCT state rapidly (τ < 200 fs) relaxes to the upper of two doublet states with mixed MLCT/MC character. Electronic interconversion (τ ∼ 2.