Alkyl and aryl substituted corroles. 3. Reactions of cofacial cobalt biscorroles and porphyrin-corroles with pyridine and carbon monoxide

摘要

The synthesis and characterization of three new cofacial biscorroles and three new linked Co(II) porphyrins and Co(III) corroles with the same face to face orientation are described. The biscorroles are represented as (BCS)Co-2, (BCO)Co-2, (BCX)Co-2 while the porphyrin-corrole dyads are represented as (PCA)Co-2, (PCB)Co-2, (PCO)Co-2 where BC represents the Co(III) cofacial biscorroles and PC represents the porphyrin-corrole complexes which are linked to each other by a dibenzothiophene (S), dibenzofuran (0), or 9,9-dimethylxanthene (X) bridge in the case of the corroles and an anthracene (A), biphenylene (B), or dibenzofuran (0) bridge in the case of the mixed macrocycle derivatives. The electrochemical and spectroscopic data on these new bismacrocycles are compared to those of previously reported biscorroles of the type (BCA)Co-2 and (BCB)Co-2. The CO and/or pyridine binding properties of each biscorrole and porphyrin-corrole in CH2Cl2 are also presented. Only one CO ligand is bound axially to each corrole unit of the bismacrocycle but five- and six-coordinate pyridine complexes can be generated for the same compounds, with the exact stoichiometry depending upon the concentration of pyridine in solution. In all cases, the six-coordinate bispyridine corrole complex can be unambiguously identified by a strong diagnostic marker band located at 598-601 nm. The formation constants for pyridine binding to the biscorroles range from log K-1 = 3.14 to 5.08 while log K-2 ranges from 1.10 to 2.61 depending upon the specific spacer. Carbon monoxide binding constants range from log K = 3.6 to 4.0 in the case of the biscorroles and from log K = 3.4 to 4.1 in the case of the porphyrin-corrole dyads. These values also depend on the specific spacer in the complex and, like the pyridine binding constants, decrease in the order BCO > BCA > BCB for the biscorroles and PCO > PCA > PCB for the porphyrin-corrole complexes. [References: 40]