Synthesis and characterization of a novel series of meso (nitrophenyl) and meso (carboxyphenyl) substituted porphyrins

Abstract

As porfirinas aniônicas 5,10,15-tris(4-carboxifenil), 20-mono(2-nitrofenil) porfirina (1), 5,10(ou 15)-bis(4-carboxifenil), 15(or 10),20-bis(2-nitrofenil)porfirina (2) and 5-mono(4-carboxifenil), 10,15,20-tris(2-nitrofenil)porfirina (3), foram sintetizadas diretamente através da reação de pirrol com os benzaldeídos substituídos em meio de ácido propiônico/nitrobenzeno. A relação molar dos benzaldeídos foi controlada para otimizar a síntese e purificação das porfirinas desejadas. Esta nova série de porfirinas foi caracterizada por cromatografia em camada delgada, espectrometria de massas (FAB MS), RMN 1 H, UV/Vis, IV e eletroquímica. As porfirinas 5,10,15,20-tetrakis(4-carboxifenil)porfirina (4) e 5,10,15,20-tetrakis(2-nitrofenil)porfirina (5) também foram estudadas para comparação, tornando a série completa. A redução eletroquímica das porfirinas base livre e correspondentes ferro(III) porfirinas foi investigada em eletrodos de carbono e mercúrio. Os potenciais de redução mostraram a dependência esperada do número de grupos nitro, fortemente retirador de elétrons, presentes no anel porfirínico, fornecendo evidências adicionais para a caracterização dos compostos sintetizados.The anionic 5,10,15-tris(4-carboxyphenyl), 20-mono(2-nitrophenyl) porphyrin (1), 5,10(or 15)-bis(4-carboxyphenyl), 15(or 10),20-bis(2-nitrophenyl)porphyrin (2) and 5-mono(4-carboxyphenyl), 10,15,20-tris(2-nitrophenyl)porphyrin (3) were sinthesized directly by reaction of pyrrole with substituted benzaldehydes in nitrobenzene/propionic acid media. The benzaldehydes molar ratio was controlled to optimize the synthesis and purification of the desired porphyrins. This new series of porphyrins was characterised by TLC, mass spectrometry (FAB MS), 1 H NMR, UV/Vis, IR and electrochemistry. 5,10,15,10,15,porphyrin (5) were also characterised for comparative purposes, completing the series The electrochemical reduction was investigated for the free base and corresponding iron(III) porphyrins on glassy carbon and mercury electrodes. The reduction potentials showed the expected dependence on the number of electron-withdrawing nitro groups present on the porphyrin ring providing additional evidences for the characterisation of the synthesised compounds.

β-Nitro Derivatives of Iron Corrolates

“…A single multi-electron reduction of meso- C 6 H 4 NO 2 groups has previously been reported for copper triarylcorroles 39 as well as for tetraphenylporphyrins having the same electroactive substituents at the four meso -positions of the macrocycle. 34, 35 …”

Synthesis, Characterization and Dielectric Properties of New 5-(4-Hydroxyphenyl)-10,15,20-tri-4-[2-(3-pentadecylphenoxy)ethoxy]phenyl porphyrin and Their Ni, Co and Cu Complexes

“…13 C NMR data to 4a showed signals that confirm the presence of alkyl (13.85-35.83 ppm), ethers (66.22 ppm) and aromatic groups (111.37-158.45 ppm). Similar signals were observed for metalloporphyrins 4b-d ( Figure S1).…”

“…were obtained via mixed aldehyde condensations, using a mixture of two different aldehydes as starting materials. [11][12][13] Asymmetric porphyrins are molecules that exhibit some advantages over the symmetric porphyrins (A4) like: reduced aggregation, groups that allows the use of a wide range of solvents, and presence of dipole moment, which may facilitate the electron injection into the TiO 2 conduction band.…”

Synthesis, spectroscopy and photosensitizing properties of hydroxynitrophenylporphyrins

“…8 In order to decrease the number of porphyrins obtained in the synthesis and to avoid extremely tedious chromatographic purification, the system was optimised with small-scale reactions using different rations of the two aldehydes. In this way, in the synthesis of A 3 B porphyrin, the initial ratio of pyrrole: 2-hydroxy-5-nitrobenzaldehyde: 4-carboxybenzaldehyde used was 4: 2,7: 1.…”