Two-photon-induced cycloreversion reaction of coumarin photodimers

Photochemical reactions induced by two-photon-absorption processes offer several advantages over common one-photon initiated photoreactions, e.g., three-dimensional spatial control. We present the photocleavage reaction of coumarin photodimers via a two-photon process using pulsed frequency-doubled Nd:YAG-laser light. The two-photon-induced cycloreversion reaction leads selectively to the cleavage of the coumarin photodimers resulting in the formation of monomeric coumarin molecules. The two-photon cross section of the coumarin photodimer was determined to be of 1.6 x 10(-52) cm(4) s photon(-1). The presented reaction is of interest, e.g., for the photo-triggered release of chemicals in areas which cannot be directly optically addressed due to cover layers which have a high absorption at the single-photon-absorption wavelength. (C) 2003 Elsevier Science B.V. All rights reserved.