Syntheses, electrochemistry and photophysical properties of a series ofmeso-pyridylpentafluorophenylporphyrins

Abstract

This work presents the synthesis and characterization of a series of substituted pyridylpentafluroporphyrins, including the separation of the cis- and trans-isomers, the latter being characterized by X-ray crystallography. The spectroscopic and electrochemical properties of the series are dependent on the number of electron withdrawing pentafluorophenyl substituent, but they do not depend on the symmetry of the molecule. Ongoing from the monosubstituted to the more substituted pentafluorophenyl porphyrin H2(MPyTFPP) derivative, the Soret bands are slightly red-shifted and their quantum fluorescence yields range from 0.035 to 0.046, consistent with the value of 0.045 for the fully substituted 5,10,15,20-tetrapentafluorophenylporphyrin (dichloromethane solutions). The redox potentials of the reductive processes of monoanion and dianion formation are also sensitive to the number of pentafluoro substituents, shifting 180 mV to more positive values for the P0/P-1process ongoing from the monopentafluoro to the tris-pentafluorophenyl substituted derivative.

Electrochemical and Spectroelectrochemical Properties of Free‐Base Pyridyl‐ and N‐Alkyl‐4‐Pyridylporphyrins in Nonaqueous Media

“…[40][41][42][43][44][45][46] In each case, there are two one-electron reductions, with the E 1/2 values being dependentu pon the number of meso-pyridyl groups and the specific electron-donating or electron-withdrawing substituents on the phenylg roups at the other meso positions of the macrocycle. The pyridyl groups are highly electron withdrawing and the E 1/2 values progressively shift in ap ositive direction with increasei nt he number of meso-pyridyl substituents, from one in the case of 1,w hich is reduced at E 1/2 = À1.13 and À1.52 Vi np yridine, to four in the case of 4,w hichi sr educed at À0.93 and À1.22 V, under the same solution conditions.…”

“…The electrochemical behavior for the currently investigated compounds is similar to that for related pyridylporphyrins, which has been reported in the literature for derivatives having one, two, three, or four meso pyridyl substituents. [40][41][42][43][44][45][46] In each case, there are two one-electron reductions, with the E 1/2 values being dependentu pon the number of meso-pyridyl groups and the specific electron-donating or electron-withdrawing substituents on the phenylg roups at the other meso positions of the macrocycle.…”

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

“…The potentials for reduction and oxidation of free‐base and zinc pyridylporphyrins have been reported in CH 2 Cl 2 and other non‐aqueous solvents for derivatives having 1, 2, 3 or 4 meso ‐pyridyl substituents . In aprotic solvents, the electroreduction behavior is generally similar to that of the tetraphenyl‐ or substituted tetraphenylporphyrin complexes in that two well‐defined one‐electron reductions are generally obtained, the main difference between the two series of compounds being an approximate 50–100 mV positive shift in potential with each added meso ‐pyridyl group on the compound, the exact value of E 1/2 depending upon the solvent and the other meso ‐substituents on the porphyrin macrocycle …”

“…[9] The potentials for reduction and oxidation of free-base and zinc pyridylporphyrins have been reported in CH 2 Cl 2 and other non-aqueous solvents for derivatives having 1, 2, 3 or 4 mesopyridyl substituents. [8,[23][24][25][26][27][28][29] In aprotic solvents, the electroreduction behavior is generally similar to that of the tetraphenyl-or substituted tetraphenylporphyrin complexes in that two welldefined one-electron reductions are generally obtained, the main difference between the two series of compounds being an approximate 50-100 mV positive shift in potential with each added meso-pyridyl group on the compound, the exact value of E 1/2 depending upon the solvent and the other mesosubstituents on the porphyrin macrocycle. [8] The prevailing redox behavior, as well as the chemical and physical properties of pyridyl porphyrins, can be substantially changed by coordination of metal ions or metal complexes to nitrogens of the meso-pyridyl groups of the porphyrins and it can also be changed by protonation of the pyridyl nitrogen atoms in the nonaqueous solvent.…”

Synthesis, structure, electrochemical, DNA interaction and antimicrobial studies of fluorinated trans-dicationic pyridinium porphyrins

“…compared to those of simple tetraphenylporphyrins, MTPPs [M = 2H, Cu(II) and Zn(II)] (Table 2). 33 Due to the presence of electron withdrawing / positively charged substituents at the porphyrin periphery, the possible oxidation process was not observed in the studied compounds 35,36. The trans-pyridyl porphyrins, 1−3 undergo two reversible one electron reduction reaction, forming the anion and dianion similar to that of MTPP counter parts.…”