Synthesis of Tetrasilatetrathia[8]circulenes by a Fourfold Intramolecular Dehydrogenative Silylation of C−H Bonds

The first two examples of a tetrasilatetrathia[8]circulene were synthesized in two steps from a tetraiodotetrathienylene by using a fourfold intramolecular dehydrogenative silylation of C-H bonds as the key step. A single-crystal X-ray diffraction analysis revealed that tetrasilatetrathia[8]circulene contains a perfectly planar [8]radialene skeleton. The excited-state dynamics of tetrasilatetrathia[8]circulene were evaluated by steady-state and time-resolved spectroscopic measurements, revealing an efficient intersystem crossing in the excited state.