Preparation of soluble tetrabenzoporphyrins with substituents at the peripheral positions

The preparation of 1,4,8,11,15,18,22,25-octamethyltetrabenzo[b,g,l,q] porphinatonickel (II) having substituents at the peripheral positions was performed by the cyclotetramerization of a 5-substituted 1,3,4,7-tetramethylisoindole, which was prepared by the condensation of 5-substituted hexane-2,5-dione with 2,5-dimethylpyrrole. It was found that the products consist of mixtures of macrocycles with different numbers of peripheral substituents. This resulted from the ring-opening reaction of 2,5-dimethylpyrrole to form unsubstituted 2,5-hexanedione during the isoindole synthesis, The acidolytic side reaction of the dimethylpyrrole was suppressed by employing hexadecane-7,10-dione so that purified tetrabenzoporphinatonickels with hexyl residues at the 'beta'-position were obtained. The macrocycles thus prepared displayed excellent solubility in organic solvents. (C) 1998 Elsevier Science S.A. All rights reserved.