Abstract
The mechanically mobile rotaxanes and pseudorotaxanes have been synthesized to architect the elegant molecular machines. These supramolecules can be applied for the photonic and electronic materials via change of the co-conformation between their component molecules. In this research, we report the temperature dependence of the supramolecular structure of the [2]pseudorotaxane having a crown ether and ferrocenyl group on the axis molecule by X-ray single crystallography, and demonstration of the thermo-optic switching via the reversible co-conformation change of the pseudorotaxane in the single crystal state. The supramolecular structure was stabilized by π-π interaction between the axis and macrocyclic molecules at 30 °C. Heating of the crystal led to solid-to-solid phase transition with rotation of the axis molecule at 128 °C. At the high temperature phase, the optical anisotropic parameters of the crystal such as retardation and birefringence were smaller than that of the crystal at 30 °C, because of the disproportionation of the direction of the aromatic rings of the pseudorotaxane in the single crystal at 128 °C.