Synthesis, spectral and electrochemical studies of vanadyl β-substituted porphyrins and their use as a catalyst for olefin epoxidation and oxidative bromination in aqueous medium

2-Nitro-meso-tetraphenylporphyrinatooxido vanadium (IV), [V[Formula: see text]OTPPNO 2 ] (1a), and 2,3-dibromo-12-nitro-meso-tetraphenylporphyrinatooxidovanadium (IV), [V[Formula: see text]OTPPBr 2 NO 2 ] (2a), were designed and synthesized in good yields. These catalysts characterized by various spectroscopic techniques, viz. UV-Visible, FT-IR, and EPR, MALDI-TOF mass spectrometry. A DFT study was used to optimize the structures of these complexes. Porphyrins 1a and 2a show good thermal stability up to 277°C and 303°C, respectively. Typical eight-line EPR spectra of these paramagnetic vanadium species at 100 K correspond to the I value of the vanadium metal (I [Formula: see text] 7/2). The HOMO-LUMO gap of 1aand 2awas reduced relative to the parent [V[Formula: see text]OTPP], a finding supported by cyclic voltammetry. Structural optimization through DFT calculations revealed significant electronic and geometric differences between the two compounds. The asymmetrically [Formula: see text]-trisubstituted porphyrin 2a, with two bromo and one nitro group, exhibited slight nonplanarity compared to the [Formula: see text]-monosubstituted porphyrin 1a, attributed to the electronic effects of the bromo substituents. Compounds 1a and 2awere investigated as catalysts for the selective epoxidation of various alkenes using H 2 O 2 as an oxidant in the presence of NaHCO 3 as promoter in CH 3 CN at 60°C with good TOF values (6159-8746 h[Formula: see text]. Both catalysts mimic vanadium bromoperoxidase activity in the oxidative bromination of thymol and other phenol derivatives using the HClO 4 -KBr-H 2 O 2 system in water at room temperature, with good TOF values (22899–35357 h[Formula: see text], highlighting their potential as efficient catalysts. Both catalysts are recoverable at the end of the various catalytic cycles, further underscoring their sustainability, offering a promising foundation for future developments in functionalized porphyrin-based catalysis.