Trans-substituted porphyrin building blocks bearing iodo and ethynyl groups for applications in bioorganic and materials chemistry

The modular synthesis of linear or cyclic multiporphyrin arrays relies on the availability of trans-substituted porphyrin building blocks with high solubility in organic solvents. Eleven porphyrin building blocks were synthesized bearing iodo, ethynyl and 2-(trimethylsilyl)ethynyl groups at the 4-, 3- or 3,5-positions of two meso-aryl units and mesityl groups at the other two meso-positions. The synthesis involves condensation of 5-mesityldipyrromethane with one or two aryl aldehydes. Combinations of functional groups include di-iodo, tetra-iodo, bis[(2-(trimethylsilyl)ethynyl], iodo and 2-(trimethylsilyl)ethynyl and ethynyl and 2-(trimethylsilyl)ethynyl. In addition, a porphyrin bearing one 4-iodophenyl group and one 3,5-bis(boron-dipyrrin)phenyl group was synthesized for applications in molecular photonic devices. The iodo and ethynyl groups are ideally-suited for Pd-mediated coupling reactions, allowing the porphyrin building blocks to be joined in the systematic construction of soluble multiporphyrin arrays