Hinged bis-porphyrin scaffolds I. The synthesis of a new porphyrin diene and its role in constructing hinged porphyrin dyads and cavity systems

Norbornene building BLOCKs formed by the reaction of porphyrin 1,3-dienes with norbornadiene or dimethyl tricyclo[4.2.1.02,5]nona-2,7-diene-3,4-dicarboxylate were coupled with an ester-activated cyclobutene epoxide BLOCK to afford the first examples of hinged porphyrin-spacer-acceptor dyads. Similar dual coupling with a bis-(cyclobutene epoxide) formed doubly hinged POR-spacer-POR scaffolds separated by up to 16σ-bonds. The ability of the doubly hinged ZnPOR-16σ-ZnPOR scaffold to adopt cavity-shaped conformations was indicated by semiempirical AM1 calculations of these conformationally flexible bis-porphyrin scaffolds.