2, 7-Dihydro-3, 4-5, 6-dibenzoheteropins (1-heterodibenzo [a, c][3, 5]-cycloheptadienes) have been prepared where the hetero function is represented by sulfide, selenide, sulfone, methylsulfonium and methylselenonium groups. As predicted from molecular models, these materials, with the exception of the sulfonium compound, show ultraviolet absorption maxima at shorter wave lengths than the corresponding carbocyclic and other seven- ...