Stability of bicalicene isomers - a topological study

Abstract

Bicalicene is the conjugated hydrocarbon obtained by joining two calicene fragments. This can be done in two different ways, thus resulting in two bicalicene isomers (tentatively referred to as cis and trans). The trans isomer is a stable compound whereas cis-bicalicene appears to be less stable and has never been prepared. The stability order of the bicalicene isomers cannot be rationalized by means of standard topological theory of conjugated π-electron systems, and requires a special graph-theory-based analysis.