Abstract
Two series of oxovanadium N-confused porphyrins (NCPs) were synthesized and characterized using HRMS, UV-Vis, IR, and EPR spectroscopy. The free-base NCPs [CTPPH]H-2 (1a) and [MeCTPPH]H (1b) reacted with VO(acac)2 in DMF to form oxovanadium complexes [VO(HCTPP)] (2a) and [VO(MeCTPP)] (2b). Oxidation of [VO(HCTPP)] (2a) with meta-chloroperbenzoic acid (mCPBA) or iodosobenzene (PhIO) yielded [VO(HCTPPO)] (3a) and [VO(CTPPOMe)] (4a), respectively, illustrating a substituent exchange on the inner carbon. In contrast, [VO(MeCTPP)] (2b) produced a single oxidized product, [VO(MeCTPPO)] (3b), regardless of the oxidant. X-ray crystallography revealed that 2a adopted a 2H tautomeric form, while 4a exhibited a 3H tautomeric form. EPR spectroscopy confirmed the V(IV) oxidation state in all complexes. Formation of 2a and 2b induced redshifts in the Soret band, while oxygen insertion in 3a and 3b caused further bathochromic shifts and Soret band splitting. The catalytic activity of these oxovanadium NCPs was evaluated for cyclohexene and thioanisole oxidation using H2O2 in CH3CN. Cyclohexene oxidation at 60 degrees C for 8 hours yielded 2-cyclohexen-1-one and cyclohexane-1,2-diol, while thioanisole oxidation at room temperature for 24 hours produced sulfone. An oxidoperoxidovanadium(V) intermediate was identified via ESI-MS. Notably, 3b and 4a exhibited turnover frequencies (TOFs) of 5.25-6.84 h(-1 ) for cyclohexene oxidation, while all complexes showed TOFs of 3.09-4.17 h(-1 )for sulfur oxidation. This study highlights the structural and catalytic versatility of oxovanadium NCPs.