More than three dozen different metal ions have been incorporated into the macrocyclic core of water-soluble tetra-N-methylpyridylporphyrins, and many of these complexes have been studied with respect to their physicochemical [1][2][3][4][5][6][7][8][9] and electrochemical [10][11][12][13][14][15][16][17][18][19][20][21][22] properties in both aqueous and nonaqueous media. These compounds are easily reducible in both water and nonaqueous solvents, and an umber of the complexes have been used in nuclear medicine, [21,[23][24][25][26] examples being given by tetra-N-methylpyridylporphyrins having the formula [M(TMPyP)] n + (X À ) n where TMPyP represents the porphyrin macrocycle with four meso-substituted N-methylpyridyl groups, n = 4o r5 ,X À = an anion and M = In II ,Mn III ,Fe III ,o rG d III .The electrochemistry of [M(TMPyP)] n + (X À ) n in nonaqueous media has been characterizeda lmoste xclusively with respect to the reductionst hat can occur at the conjugated p-ring system of the macrocycle, the electroactive N-methylpyridyl substituents, and, in some cases, at the central metal ions. Early electrochemical studies of these compounds were carried out in DMF,D MSO,a nd acetonitrile, [1,3,27] all of which possess [a] Y.

Complexes of 5,10,15-triferrocenylcorrole were synthesized from the crude free-base corrole product obtained by the reaction of ferrocenyl aldehyde and pyrrole. Direct formation of the complex in this manner leads to an increase of the reaction yield by protecting the corrole ring toward oxidative decomposition. The procedure was successful and gave the expected product in the case of the copper and triphenylphosphinecobalt complexes, but an unexpected result was obtained in the case of the nickel derivative, where metal insertion led to a ring opening of the macrocycle at the 5 position, giving as a final product a linear tetrapyrrole nickel complex bearing two ferrocenyl groups. The purified 5,10,15-triferrocenylcorrole complexes have been fully characterized by a combination of spectroscopic methods, electrochemistry, spectroelectrochemistry, and density functional theory calculations. Copper derivatives of 10-monoferrocenyl- and 5,15-diferrocenylcorrole were prepared to investigate how the number and position of the ferrocenyl groups influenced the spectroscopic and electrochemical properties of the resulting complexes. A complete assignment of resonances in the (1)H and (13)C NMR spectra was performed for the cobalt and nickel complexes, and detailed electrochemical characterization was carried out to provide additional insight into the degree of communication between the meso-ferrocenyl groups on the conjugated macrocycle and the central metal ion of the ferrocenylcorrole derivatives.

The electrochemistry and spectroelectrochemistry of four tetrapositively charged and two tetranegatively charged porphyrins were characterized in two nonaqueous solvents (dimethyl sulfoxide and N,N-dimethylformamide) containing 0.1 M tetra-n-butylammonium perchlorate. The tetrapositively charged compounds are represented by the tetrapyridylporphyrins [TRPyPM](X), where R is a methyl or [2-[2-(2-methoxy)ethoxy]ethoxy]ethyl group, M = MnI, MnCl, Cu, or Pd, and X = I or Cl. The tetranegatively charged porphyrins are represented by the tetrasulfonato derivatives [TPPSMn(OAc)](NH) and [TArPSMn(OAc)](NH), where Ar = 4-O-[2-[2-(2-methoxy)ethoxy]ethoxy]ethylphenyl. Up to seven electrons can be added to the tetrapyridyl porphyrins in three to five reversible reductions, while up to four electrons can be added to the tetrasulfonato derivatives in four reversible processes. Three types of electrochemical behaviors are observed for reduction of the pyridinium groups on the tetrapyridyl porphyrins. One is for the manganese(II) complexes where the four equivalent pyridinium groups are reduced in a single overlapping four-electron-transfer step. Another is for the free-base porphyrin, where four well-separated one-electron reductions occur, while the third is for copper(II) and palladium(II) derivatives, where reduction of the four pyridinium groups proceeds in two well-separated two-electron-transfer steps. The electrochemical and spectroelectrochemical properties were also characterized for a 1:1 mixture of the tetrapositively and tetranegatively charged manganese porphyrins to investigate possible interactions between these two species. An interaction between the two porphyrins was indeed observed in both solvents after electroreduction of the four pyridinium groups, which led to a substantial change in the mechanism for reduction of the pyridinium groups from an initial single overlapping four-electron-reduction process to two well-separated two-electron-transfer processes.

International audienceA detailed study of reduction potentials, electroreduction mechanisms, and acid-base chemistry was carried out on two series of free-base porphyrins in nonaqueous media. The first series is represented by four -pyrrole-substituted tetraphenylporphyrin (TPP) derivatives, two of which are planar and two of which are nonplanar in their nonprotonated form. The second comprises porphyrins with 0-4 meso-phenyl groups on the macrocycle. Equilibrium constants for the conversion of each neutral porphyrin to its diprotic [H4P](2+) form were determined and the electrochemistry was then elucidated as a function of: 1)type of nonaqueous solvent, 2)anion of supporting electrolyte, 3)porphyrin ring substituents, and 4)concentration of acid added to solution. Spectroelectrochemistry was used to characterize absorption spectra of each electroreduced species and, when combined with results of the above studies, significantly improves our ability to tune redox reactivity of these types of compounds

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