Conformational dependence of energy transfer rate between photochromic molecule and fluorescent dye

The dependence of the energy transfer rate from the fluorescent dye, bis(phenylethynyl)anthracene, to the diarylethene derivative on the dihedral angle around the adamantyl spacer, which is used in the single-molecule photoswitching experiment based on the photochromism [T. Fukaminato, T. Sasaki, T. Kawai, N. Tamai, M. Irie, J. Am. Chem. Soc. 126 (2004) 14843], is examined using the ab initio calculations. For the interpretation of the single-molecule photoswitching experiment, most desirable condition is that the on/off of the florescence is directly due to the photochromic reaction, but not others. One of the undesirable factors is the dependence of the energy transfer rate on the dihedral angle around spacer. The computational results show that the energy transfer rate depends little on the dihedral angle.