Compounds of general formula I are disclosed ##STR1## wherein R.sup.1 denotes an unsubstituted or substituted carbocyclic or heterocyclic aryl radical, R.sup.2 and R.sup.3 are different from each other and either denote a hydrogen atom or a 4,6-bis-trichloromethyl-s-triazin-2-yl group, and n and m independently of each other, denote one of the numbers 0 and 1. The compounds are effective free-radical-forming photoinitiators and photolytically-activatable acid donors for photosensitive compositions.