Protonation and Electrochemical Properties of Pyridyl‐ and Sulfonatophenyl‐Substituted Porphyrins in Nonaqueous Media

Abstract

International audienceThe protonation and electrochemical properties of positively charged and negatively charged porphyrins are reported in up to five different nonaqueous solvents. The positively charged porphyrins are represented by mono- and di-pyridyl derivatives having the formula Pyx(PhMe)4-xPM, where P=the dianion of the porphyrin macrocycle, PhMe is a meso-tolyl group, Py a meso-pyridyl group, x=1 or 2, and M=H2, NiII, CuII, ZnII, or CoII. The negatively charged porphyrins are comprised of meso-tetrasulfonato derivatives having the formula [(R)4(TPPS)H2]4−(X+)4, where [(TPPS)H2]4− represents the porphyrin with four SO3− groups on the meso-phenyl substituents of the macrocycle, R=H or PEG (PEG=C7H15O4) and X+=H+ or Na+. Each pyridylporphyrin was shown to undergo an initial protonation of the meso-pyridyl group(s) upon addition of acid to the porphyrin solutions and, in the case of the free-base derivatives, this was followed in a second step by a simultaneous protonation of the two core nitrogen atoms on the macrocycle. Two central nitrogen atoms of the sulfonatophenyl porphyrins are also protonated in a single-step process, and the constants for each protonation reaction of Pyx(PhMe)4-xPM and [(R)4(TPPS)H2]4−(X+)4 were determined through spectral titration with trifluoroacetic acid in DMF, DMSO, CH2Cl2, or PhCN, after which the data were related to solvent properties, the measured redox potentials, and the mechanisms for electroreduction under the same solution conditions

Supramolecular porphyrin as an improved photocatalyst for chloroform decomposition

“…15,16,[73][74][75] Moreover, the PP-Supra-H 2 TPyP 419 nm peak redshis in z2 nm, which is a signature for the protonation of the photomodied RuCl(dppb)(5,5 ′ -Me-bipy). 16,76 In fact, a closer inspection of RuCl(dppb)(5,5 ′ -Me-bipy) intraligand bands shows that the peak at ∼327 nm is enhanced (Fig. 3a).…”