Linear and Nonlinear Optical Properties of Selected Rotaxanes and Catenanes

Linear and nonlinear optical properties of catenanes and rotaxanes in thin films and in solution are reviewed and discussed. The compounds represent a new class of molecules, with mobile subparts. It offers a new kind of applications, particularly for optical switching. The rotational mobility of the subparts of these molecules was studied by the electro-optic Kerr effect. Both catenanes and rotaxanes can be processed into partly ordered thin films by vacuum sublimation. The degree of order may be controlled by an adequate chemical modification of the molecules, as it was observed in a series of substituted rotaxanes. Methods for controlling the motion of the components using light and electric fields are presented. The linear optical properties were studied by UV-Vis spectrometry and m-lines technique. The nonlinear optical properties were studied in solution and/or in thin films by the optical second and third harmonic generation techniques and by the quadratic electro-optic Kerr effect. The knowledge on the rotaxanes and the catenanes linear and nonlinear optical properties obtained by theses studies is important for the future construction of synthetic molecular machines and optical switching elements