Pd Complexes of N-Methylcorroles.

Alkylation of one of the inner core nitrogen atoms is one possible approach to obtain dianionic corrole ligands, suitable for the coordination of divalent metal ions. The inner core N-methylation can be obtained by reaction of the corrole with CH3I, but the reaction conditions should be optimized to limit the formation of the di-methylated derivative. Two regioisomers, the N-21 and the N-22 methyl derivatives are obtained from the reaction, with the first product achieved in a higher amount. The structural characterization of the reaction products evidenced the distortion induced by the introduction of the methyl groups; the N-methylcorroles are chiral compounds and the enantiomers have been separated and their absolute configuration assigned by ECD computations. The Pd insertion has been achieved in the case of monosubstituted corroles and the X-ray characterization of the complexes showed the distortion of the macrocycles. The Pd complexes do not show luminescence emission but are able to produce singlet oxygen upon irradiation. The Pd(II) complexes have been inserted in Human Serum Albumin (HSA) and dispersed in water: the protein protects the corroles from photobleaching and a switch from the type II to the type I mechanism in reactive oxygen species (ROS) production is observed.