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-Formula: see text-tetraphenylporphyrinatooxido vanadium (IV), V IV OTPPNO 2 (1a), and 2,3-dibromo-12-nitro-Formula: see text-tetraphenylporphyrinatooxidovanadium (IV), V IV OTPPBr 2 NO 2 (2a), were designed and synthesized in good yields. Various spectroscopic techniques, Formula: see text Formula: see text Formula: see text Formula: see text. UV-Visible, FT-IR, EPR spectroscopy, MALDI-TOF mass spectrometry, and cyclic voltammetry. A DFT study was used to optimize the structures of these complexes. Porphyrins 1a and 2a show good thermal stability up to 277 Formula: see textC and 303 Formula: see textC, respectively. Typical eight-line EPR spectra of these paramagnetic vanadium species at 100 K correspond to the I value of the vanadium metal (I = 7/2). The HOMO-LUMO gap of 1a and 2a was reduced relative to the parent V IV 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 2a were 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 Formula: see textC with good TOF values (6159-8746 hFormula: see text). Both catalysts mimic vanadium Formula: see text 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 hFormula: 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.