Nitrogen-bridged Ni(II) porphyrinoid trimers with a central quinodiimine unit

Buchwald-Hartwig amination of 5,15-dibromo and 5,10-dibromo Ni(II)porphyrins with 5-amino Ni(II)porphyrin gave linear and bent trimers 4Ni and 5Ni with a central quinodiimine-type Ni(II)porphyrinoid. The structures of 4Ni and 5Ni have been confirmed by X-ray diffraction analysis in both cases. The formation of unusual products 4Ni and 5Ni has been ascribed to facile oxidation of 5,15- and 5,10-amino Ni(II) porphyrin unit. Reduction of 4Ni and 5Ni under proper conditions gave NH-bridged Ni(II)porphyrin trimers 4Ni-2H and 5Ni-2H in high yields. Trimers 4Ni and 5Ni exhibit the lowest energy band as compared with 4Ni-2H and 5Ni-2H. Especially the bent trimer 5Ni exhibits a broad absorption tail beyond 1400 nm.