Porphyrin building blocks bearing two or four divergent ethynes

Abstract

Tetrapyrrole building blocks are invaluable constituents in the construction of molecular architectures for use in biomimicry, functional materials, and biomedicine. The reaction of dipyrromethane and the triisopropylsilyl-protected 3,5-diethynylbenzaldehyde afforded the corresponding trans-[Formula: see text]-porphyrin (free base) bearing four ethynes. Subsequent meso-bromination, Suzuki coupling, and protecting group removal afforded a porphyrin building block bearing four ethynes and one benzylamine. The reaction of dipyrromethane and 3,5-bis(propargyloxy)benzaldehyde afforded the corresponding trans-[Formula: see text]-porphyrin (free base) bearing four ethynes. The reaction of 5-(3,5-bis(propargyloxy)phenyl)dipyrromethane and the Eschenmoser (1,9-dimethylaminomethyl) derivative of a 5-([Formula: see text]-substituted aryl)dipyrromethane was used to create two trans-AB-porphyrins (zinc chelates). The [Formula: see text]-substituent of the aryl group was cyano or an acetal moiety. Hydrolysis of the acetal and a click reaction with m-PEG24-azide gave the bis(PEGylated)porphyrin-carboxaldehyde. The porphyrins present readily derivatizable functional groups in a compact architecture.