Cyclophane size drives the photochemical behaviour of benzophenone.

A new series of all-heterahomocalixarene-type structures was prepared. The new hetera[2(n)]metacyclophanes obtained contain a benzophenone moiety as photoactive component. Although both forms possess identical building blocks and differ only in ring size, they are markedly different in photochemical reactivity. The cyclophane size is the driving force for the photochemical behaviour of the benzophenone.