One-pot synthesis of 5,10,15-triphenylcorrole has been achieved by reaction of benzaldehyde with an excess of pyrrole; the triphenylphosphinocobalt complex of 5,10,15-triphenylcorrole has been structurally characterized using X-ray crystallography
The Rothemund condensation reaction of pyrrole and aldehydes is an extensively used route to meso-tetraarylporphyrins, but simple modifications of the reaction conditions allow the formation of different macrocycles other than the expected porphyrin. In the presence of an excess of pyrrole, this modified Rothemund approach leads to the synthesis of meso-triary-substituted corroles. This methodology allows the preparation of a wide range of substituted corroles starting from commercially available products. Higher yields have been obtained in the case of benzaldehydes bearing electron-withdrawing substituents, while the reaction fails in the presence of 2,6-disubstituted benzaldehydes. Although if not isolated, some experimental evidences indicate that the linear 5,10,15-triphenylbilane 4 is the precursor of the final corrole ring. Reaction of 5,10,15-triphenylcorrole 2 with an excess of NBS leads to the complete bromination of the macrocycle. Spectroscopic characterization seems to indicate the formation of the porphodimethene-like structure 5, where the macrocyclic aromatic conjugation is interrupted at the 10 position. Metalation of this compound with cobalt acetate and PPh3 affords the corresponding complex. The X-ray crystal structure of triphenylphosphine [2,3,7,8,12,13,17,18-octabromo-5,10,15-tris(4-nitrophenyl)corrolato]- cobalt(III) 8 confirms the ability of corrole ring to retain an almost planar conformation when fully substituted at the peripheral position.
The luminescence properties at room temperature and 77 K of octamethylcorrole are reported for the first time, together with the photophysical behaviour of corrole-corrole and porphyrin-corrole dyads covalently linked through the 10-position with a phenyl bridge. The photophysical properties of corrole free base are very similar to those of the porphyrin analogues, whereas the dimeric systems show luminescence bands different from those of the parent monomers, indicating an unexpectedly high degree of interaction between the chromophores. The porphyrin-corrole dyad undergoes photocatalysed ring opening of the corrole moiety to give the corresponding porphyrin-biliverdin species.
The first example of deposition of Langmuir-Blodgett (LB) films of a manganese complex of corrole is described. Characterization of the morphological and molecular structure of these LB films has been carried out by means of different microscopic and spectroscopic methods. Depositions onto different substrates afford very uniform films of determined thickness; all the experiments carried out suggest that manganese corrolates in LB films are normally oriented to the substrate, with a face-to-face packing of the macrocycles, due to π-π interactions. The interactions of these LB films with different volatile organic compounds (VOCs) have been investigated using the quartz microbalance (QMB) technique.
A dimeric structure that is held together by hydrogen bonds and is stable in solution is adopted by the hydrochloride salt of the expanded corrole shown. The synthesis, X-ray structure, and NMR and electronic absorption spectra of the new species all confirm the structural assignment in solution and in the solid state.
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