Synthesis and cellular studies of porphyrin-cobaltacarborane conjugates

The total syntheses of five new porphyrin-cobaltacarborane conjugates (1-5) have been achieved in 88-98% yields in a single-step reaction between a nucleophilic meso-pyridyl-containing porphyrin and zwitterionic cobaltacarborane [3,3'-Co(8-C4H8O2-1,2-C2B9H10)(1',2'-C2B9H11)]. These unique zwitterionic compounds have one to four cobaltabisdicarbollide anions conjugated to the porphyrin macrocycle via (CH2CH2O)(2) chains. The X-ray structure of one of these conjugates (1) is presented and discussed. The cellular uptake, cytotoxicity, and subcellular localization of cobaltacarboraneporphyrins 1-5 were investigated in human HEp2 cells. The number and distribution of cobaltacarborane residues linked to the porphyrin macrocycle has a significant effect on the cellular uptake of the conjugates.