Selective Syntheses and Derivatisation of A2B-Type meso-Triarylcorroles

Corroles are porphyrin analogues, lacking one meso carbon. Until recently they were rather rare chemicals, but in the last few years a number of publications have appeared describing the synthesis of corroles and core-modified corroles. This has made these interesting compounds much more available than before, allowing the study of their coordination chemistry, applications of metallocorroles in catalysis and their photophysical behaviour. In this work a two-step synthesis of sterically encumbered triarylcorroles by an acid catalysed condensation of dipyrromethanes and aromatic aldehydes followed by oxidation with p-chloranil (or DDQ) is described. An attempt has been made to optimise the yields by varying the reaction conditions in the syntheses of several model compounds and then extend the use of the optimised conditions for the preparation of more target compounds. Careful monitoring of temperature, solvent, acidic catalyst and reaction time ultimately gave a reliable yield of 15-20% of the corroles, which is a significant improvement as compared to the procedures published earlier. A2B substituted corroles have been used as sensor elements for small molecules in membranes or self-assembled monolayers. The corroles are much more sensitive than the calixpyrroles we investigated earlier. Alternatively, conjugates with indoles can be prepared in order to give rise to novel probes for indole-binding proteins.