A new family of oxidovanadium complexes [(L-1(R))(VO)(L-R)] (R = H R' = H 1 R = H R' = -CMe3 2 R = H R' = Me 3 R = -CMe3 R' = H 4 and R = -CMe3 R' = -CMe3 5) incorporating tridentate L-1 H-R ligands (L-1 H-R = 2,4-di-R-6-{(2-(pyridin-2-yl)hydrazono)n-iethyl}phenol) and substituted catechols ((LH2)-H-R') was substantiated. The V-O-phenolato (cis to V=O) V-O-CAT (cis to V=O) and V-O-CAT (trans to V=0) lengths span the ranges 1.894(2)-1.910(2) 1.868(2)1.887(2) and 2.120(2)-2.180(2) A. The metrical oxidation states (MOS) of the catechols in 1-5 are fractional and vary from -1.43 to -1.60. The V-51 isotropic chemical shifts of solids and solutions of 1-5 are deshielded (V-51 CP MAS: -19.8 to +248.6 IDMSO-d(6): +173.9 to +414.55 ppm). The closed shell singlet (CSS) solutions of 1-5 are unstable due to open shell singlet (OSS) perturbations. The ground electronic states of 1-5 are defined by the resonance contribution of the catecholates (L-CAT(R')2-) and L-SQ(R')-center dot coordinated to the [VO](3+) and [VO](2+) ions. 1-5 are reversibly reducible by one electron at -(0.58 0.87) V referenced vs ferrocenium/ferrocene to VO2+ complexes [(L-1(R-))(VO2+)(L-CAT(R')2-)] [1-5]-. 1-5 display anothe quasi-reversible or irreversible reduction wave at -(0.80-1.32) V due to the formation of hydrazone anion radical (L-1(R2-center dot)) complexes [(L-1(R2-center dot))(VO2+)(L-CAT(R')2-)](2-) [1-5](2-) with S = 1 authenticated by the unrestricted density functional theory (DFT) calculations on 1(2-) and 3(2-) ions. Frozen glasses electron paramagnetic resonance (EPR) spectra of [1-5] ions [e.g. for 2 g(parallel to) = 1.948 g(perpendicular to) = 1.979 A(parallel to) = 164 A(perpendicular to) = 60] affirmed that [1-5](-) ions are the [VO](2+) complexes of L-CAT(R,)2-. SPectro-electrochemical measurements and time-dependent DFT (TD DFT) calculations on 1 3 1(-) 3(-) and 1(2-) disclosed that the near infrared (NIR) absorption bands of 1-5 at 800 nrn are due to the CSS-OSS metal to ligand charge transfer which are red-shifted in the solid state and disappear in [1-5](-) and [1-5](2-) ions.