Dibenzodehydro[16]annulenes containing silicon-silicon and germanium-germanium a bonds were newly prepared, and their structures were established by spectroscopic methods and X-ray diffraction analysis. On the photolysis, these sila- and germa-cycles evolve the corresponding divalent species, silylene and germylene, respectively, and in addition, the germanes led to the ring contraction to give a fourteen-membered germacycle.