MOLECULAR MODELING OF CARBORANES USING DISTANCE RESTRAINTS - THE MOLECULAR-DYNAMICS SIMULATION OF APPENDED THIOETHER MACROCYCLES

A molecular mechanics model for o-carborane cages has been developed, using distance restraints to hold the polyhedron in position. The comb ination of o-carborane cage interatomic distance restraints (a modifie d central force field) and CHARMm parameters gives a good representati on of the carborane cage geometry. Molecular dynamic simulations of ma crocyclic thioethers ligated to the carbons of the carborane have been carried out. The rigid cage section seems to provide an accessible in terconversion route between conformers of the macrocycle, effectively an entatic state. The new carborane ecane-1',11'-diyl)-1,2-dicarba-clo so-dodecaborane, the four-step synthesis and crystal structure of whic h are presented, provided a contrasting macrocyclic appendage with thi oethers indirectly linked to the o-carborane cage through ethane bridg es. Molecular dynamics simulation of this molecule was also carried ou t.