title: Light-Induced Regiospecific Bromination of meso-Tetra(3,5-di-tert-butylphenyl)Porphyrin on 2,12 β-Pyrrolic Positions.
abstract: The antipodal introduction of two bromine atoms on the 2,12 β-pyrrolic position of 5,10,15,20-tetra(3,5-di-tert-butylphenyl)porphyrin was successfully achieved by a light-induced reaction of the substrate with excess NBS. Complexation with Ni(II) of the major regioisomer led to good quality crystals, suitable for X-ray structure determination with unprecedented probability levels. The regiospecific character of the synthetic procedure and the exactness of the bromine atom position assignment were thus confirmed, suggesting an unexpected electrophilic aromatic substitution pathway rather than a free-radical halogenation process. A QTAIM topological analysis on the DFT-optimized wave function of the monosubstituted free-base porphyrin intermediate carrying a bromine atom in C2 β-pyrrolic position confirmed the largest negative charge for the C12 carbon atom in antipodal position, in agreement with the proposed electrophilic aromatic substitution mechanism.
authors.affiliation: †Department of Chemistry, University of Milan, Via C. Golgi 19, 20133 Milano, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Di Carlo
authors.affiliation: ‡Institute of Molecular Sciences and Technologies of CNR (ISTM-CNR), Via Golgi 19, 20133 Milano, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Orbelli Biroli
authors.affiliation: †Department of Chemistry, University of Milan, Via C. Golgi 19, 20133 Milano, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Tessore
authors.affiliation: †Department of Chemistry, University of Milan, Via C. Golgi 19, 20133 Milano, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Rizzato
authors.affiliation: †Department of Chemistry, University of Milan, Via C. Golgi 19, 20133 Milano, Italy.|‡Institute of Molecular Sciences and Technologies of CNR (ISTM-CNR), Via Golgi 19, 20133 Milano, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Forni
authors.affiliation: †Department of Chemistry, University of Milan, Via C. Golgi 19, 20133 Milano, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Magnano
authors.affiliation: †Department of Chemistry, University of Milan, Via C. Golgi 19, 20133 Milano, Italy.
authors.forename: Maddalena
authors.initials: M
authors.lastname: Pizzotti