Abstract: The present invention provides a method for cleavage of labile functional groups from molecules by the action of electromagnetic radiation, wherein the molecules are contacted with a chemical compound whose triplet state is energetically higher than the triplet state of the labile functional group, and are subsequently exposed to electromagnetic radiation.

Abstract: The present invention provides a method for cleavage of labile functional groups from molecules by the action of electromagnetic radiation, wherein the molecules are contacted with a chemical compound whose triplet state is energetically higher than the triplet state of the labile functional group, and are subsequently exposed to electromagnetic radiation. Further, the invention provides a method for preparing DNA chips by spatially addressed, light-controlled nucleotide synthesis on solid substrates, said method comprising the following steps: a) reacting the unprotected terminal 3? or 5? hydroxy croup of a nucleoside and/or of a nucleotide arranged on the solid substrate under usual conditions with a photolabile protective group and optionally purifying the reaction product. b) applying a solution, suspension or dispersion of a chemical compound, whose triplet state is energetically higher than the triplet state of the photolabile protective group.