Dill, Ryan D.; Portillo, Romeo I.; Shepard, Samuel G.; Shores, Matthew P.; Rappe, Anthony K.; Damrauer, Niels H. published the artcile< Long-Lived Mixed 2MLCT/MC States in Antiferromagnetically Coupled d3 Vanadium(II) Bipyridine and Phenanthroline Complexes>, Product Details of C10H8N2, the main research area is antiferromagnetically Vanadium bipyridine phenanthroline complex; DFT Long Lived Mixed MLCT MC States; time resolved spectroscopy support spectroelectrochem computational; electronic spectroscopy Antiferromagnetic Vanadium Bipyridine Phenanthroline Complexes.
Exploration of [V(bpy)3]2+ and [V(phen)3]2+ (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 spectroelectrochem. techniques and computational chem., lead to the conclusion that after excitation into the intense and broad visible 4MLCT ← 4GS (ground-state) absorption band (ε400-700 nm = 900-8000 M-1 cm-1), the 4MLCT state rapidly (τisc < 200 fs) relaxes to the upper of two doublet states with mixed MLCT/MC character. Electronic interconversion (τ ~2.5-3 ps) to the long-lived excited state follows, which we attribute to formation of the lower mixed state. Following these initial dynamics, GS recovery ensues with τ = 430 ps and 1.6 ns for [V(bpy)3]2+ and [V(phen)3]2+, resp. This stands in stark contrast with isoelectronic [Cr(bpy)3]3+, which rapidly forms a long-lived doublet metal-centered (2MC) state following photoexcitation and lacks strong visible GS absorption character. 2MLCT character in the long-lived states of the vanadium(II) species produces geometric distortion and energetic stabilization, both of which accelerate nonradiative decay to the GS compared to [Cr(bpy)3]3+, where the GS and 2MC are well nested. These conclusions are significant because (i) long-lived states with MLCT character are rare in first-row transition-metal complexes and (ii) the presence of a 2MLCT state at lower energy than the 4MLCT state has not been previously considered. The spin assignment of charge-transfer states in open-shell transition-metal complexes is not trivial; when metal-ligand interaction is strong, low-spin states must be carefully considered when assessing reactivity and decay from electronic excited states. Metal-to-ligand charge-transfer (MLCT) states of vanadium(II) polypyridyl complexes are characterized by antiferromagnetic coupling, leading to exceptions to Hund′s rule of maximum multiplicity. Time-resolved spectroscopy, with support from spectroelectrochem. and computational studies, suggests mixing of the low-spin 2MLCT with doublet metal-centered states. This should be considered for the development of related complexes for photoredox catalysis. Inorganic Chemistry published new progress about Antiferromagnetic materials. 366-18-7 belongs to class pyridine-derivatives, and the molecular formula is C10H8N2, Product Details of C10H8N2.