Photochromic properties of [2.2]paracyclophane-bridged imidazole dimer with increased photosensitivity by introducing pyrenyl moiety. 2011

Hiroaki Yamashita, and Jiro Abe
Department of Chemistry, School of Science and Engineering, Aoyama Gakuin University, Chuo-ku, Sagamihara, Kanagawa, Japan.

The photochromic [2.2]paracyclophane-bridged imidazole dimers show instantaneous coloration upon exposure to UV light and rapid fading in the dark. A new [2.2]paracyclophane-bridged imidazole dimer, pseudogem-PPI-DPI[2.2]PC, with high photosensitivity to UVA radiation was developed. To enhance the photosensitivity, we introduced pyrenyl moieties to the [2.2]paracyclophane-bridged imidazole dimer. The localized π-π* transition of pyrenyl moieties appears in the UVA radiation region by introducing a pyrenyl moietiy on the 4-position of the imidazole rings. The expansion of the π-electron system also affects the absorption spectrum of the colored species. The broad absorption band of the colored species covers the whole range of visible light region and its absorbance is approximately equal throughout the visible light region. Thus, pseudogem-PPI-DPI[2.2]PC shows the photochromic reaction coloring black upon light irradiation and successive fast thermal bleaching following the monoexponential kinetics with a time constant of 12 ms at room temperature.

UI MeSH Term Description Entries
D007093 Imidazoles Compounds containing 1,3-diazole, a five membered aromatic ring containing two nitrogen atoms separated by one of the carbons. Chemically reduced ones include IMIDAZOLINES and IMIDAZOLIDINES. Distinguish from 1,2-diazole (PYRAZOLES).
D011083 Polycyclic Compounds Compounds which contain two or more rings in their structure. Compounds, Polycyclic
D011721 Pyrenes A group of condensed ring hydrocarbons.
D014466 Ultraviolet Rays That portion of the electromagnetic spectrum immediately below the visible range and extending into the x-ray frequencies. The longer wavelengths (near-UV or biotic or vital rays) are necessary for the endogenous synthesis of vitamin D and are also called antirachitic rays; the shorter, ionizing wavelengths (far-UV or abiotic or extravital rays) are viricidal, bactericidal, mutagenic, and carcinogenic and are used as disinfectants. Actinic Rays,Black Light, Ultraviolet,UV Light,UV Radiation,Ultra-Violet Rays,Ultraviolet Light,Ultraviolet Radiation,Actinic Ray,Light, UV,Light, Ultraviolet,Radiation, UV,Radiation, Ultraviolet,Ray, Actinic,Ray, Ultra-Violet,Ray, Ultraviolet,Ultra Violet Rays,Ultra-Violet Ray,Ultraviolet Black Light,Ultraviolet Black Lights,Ultraviolet Radiations,Ultraviolet Ray
D055668 Photochemical Processes Chemical reactions effected by light. Processes, Photochemical
D019281 Dimerization The process by which two molecules of the same chemical composition form a condensation product or polymer. Dimerizations

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