Issue 7, 2001

Inducing asymmetry in free-base, MnIII, NiII and CuII (ethylsulfanyl)porphyrazines: synthetic aspects and spectro-electrochemical implications

Abstract

Treatment of 2,3,7,8,12,13,17,18-octakis(ethylsulfanyl)-5,10,15,20-porphyrazine (H2OESPz) with CrCl2 in a 1,2,4-trichlorobenzene–n-BuOH mixture resulted in one ethylsulfanyl branch at the pyrrolic β positions of the macrocycle being replaced by an hydrogen atom with >40% yield. The structure of the asymmetric pyrrolic subunit and of the nearest pyrrolic subunits have been determined by NMR spectroscopy. The reaction path leading to the asymmetric porphyrazine implies the formation of a two-electron reduced diprotonated porphyrazine, [H2OESPz(−4)(2H+)], that, as a consequence of charge and structural intramolecular rearrangements at high temperature, undergoes nucleophilic substitution of an ethyl sulfide group by H. UV-Vis and near-IR results suggest that the asymmetric substitution modifies the (sulfanyl)porphyrazine π and nSulfur levels. On the contrary, ESR spectroscopy shows that the electronic properties of the coordinated Cu2+ ion are affected only marginally. The half-waves of the ligand first reductive processes sensibly shift towards cathodic potentials in the asymmetric metal porphyrazines, but not in the asymmetric free-base porphyrazine, probably due to conflicting electronic and structural effects induced by removal of an ethylsulfanyl tail.

Graphical abstract: Inducing asymmetry in free-base, MnIII, NiII and CuII (ethylsulfanyl)porphyrazines: synthetic aspects and spectro-electrochemical implications

Article information

Article type
Paper
Submitted
02 Jan 2001
Accepted
20 Feb 2001
First published
16 Mar 2001

J. Chem. Soc., Dalton Trans., 2001, 1143-1150

Inducing asymmetry in free-base, MnIII, NiII and CuII (ethylsulfanyl)porphyrazines: synthetic aspects and spectro-electrochemical implications

S. Belviso, G. Ricciardi, F. Lelj, L. M. Scolaro, A. Bencini and C. Carbonera, J. Chem. Soc., Dalton Trans., 2001, 1143 DOI: 10.1039/B100145K

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