A Modified Procedure for Sonogashira Couplings: Synthesis and Characterization of a Bisporphyrin, 1,1-Bis[zinc(II) 5′-ethynyl-10′,15′,20′-trimesitylporphyrinyl] niethylenecyclohexane

The preparation of a bisporphyrin, 1,1-bis[zinc(II) 5′-ethynyl-10′15′20′-trimesitylporphyrinyl]- methylenecyclohexane (1), is described. The new molecule was prepared by two routes employing modified palladium-mediated coupling methodology. Our modification consists of in situ liberation of alkyne from the corresponding TMS-protected compound. This variation decreases yields of undesired products presumably by keeping the unprotected alkyne concentration low during the reaction. In addition, our method obviates TMS-alkyne deprotection and subsequent purification steps. The electronic absorption spectrum of 1 is compared to two model compounds.