Abstract
Switching of the physical and chemical properties of materials by photochromic compounds has been the subject of considerable research. Increasing switching rates, particularly the thermal bleaching rate, is required for certain applications, such as optical data processing and light modulators. We recently developed the photochromic bridged imidazole dimers that show instantaneous coloration upon exposure to UV light and rapid fading in the dark. We designed and synthesized several bridged imidazole dimers, having a naphthalene or a [2.2]paracyclophane moiety that bridge two triphenylimidazole or diphenylimidazole units, and succeeded in accelerating the thermal bleaching rate. These photochromic compounds show photoinduced homolytic bond cleavage of the C–N bond between the imidazole rings and successive fast C–N bond formation. Rapid thermal bleaching kinetics enables a solution color change only where it is irradiated with UV light because the thermal bleaching rate is much faster than the diffusion rate of the colored species at room temperature. Photochromic materials showing such intense photocoloration and rapid thermal bleaching performance are promising materials for prospective fast light modulator applications.
Published Version
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