Oxidovanadium Complexes of 2,2′‐Bipyridine, 1,10 Phenanthroline, and p ‐Nitro‐ o ‐aminophenol – Radical versus Nonradical States

2,2′‐Bipyridine (bpy), 1,10‐phenanthronline (phen) and p ‐nitro‐ o ‐aminophenol ( NO2 LH 2 ) oxidovanadium complexes of the types [(L ONO 2– )(VO)(bpy)] ( 1 ), [(L ONO 2– )(VO)(phen)] ( 2 ) and [(L ONO 2– )(VO)( NO2 L ISQ · – )][NHEt 3 ] ( 3 –  NHEt 3 + ; NO2 L ISQ · – = p ‐nitro‐ o ‐iminobenzosemiquinonate radical) were isolated with ( E )‐2‐(3‐hydroxy‐3‐phenyltriaz‐1‐en‐1‐yl)benzoic acid (L ONO H 2 ) as a coligand. The single‐crystal X‐ray bond parameters and electron paramagnetic resonance (EPR) spectra authenticated that 1 and 2 are the oxidovanadium(IV) complexes of bpy and phen, whereas 3 – is the NO2 L ISQ · – complex of oxidovanadium(IV) and undergoes reversible one‐electron oxidation and reduction at lower potentials. Density functional theory (DFT) calculations established that the closed‐shell‐singlet (CSS) solution of 3 – is unstable owing to open‐shell‐singlet (OSS) perturbation. The CSS → OSS charge‐transfer transition that appears at λ = 632 nm is absent for 1 and 2 . Complex 3 is a hybrid of the [(L ONO 2– )(VO 2+ )( NO2 L IQ )] ( NO2 L IQ = p ‐nitro‐ o ‐iminobenzoquinone) and [(L ONO 2– )(VO 3+ )( NO2 L ISQ · – )] states, whereas 3 2– is an oxidovanadium(IV) complex of the type [(L ONO 2– )(VO 2+ )( NO2 L AP 2– )] 2– ( NO2 L AP 2– = p ‐nitro‐ o ‐amidophenolato).