Photo/thermo Switches and Binding of Bispiro-polymer Systems

摘要

Spiropyrans/spirooxazines are a class of photochromic compounds whose molecular structure is alterable upon exposure to UV/visible light or changes in temperature. Two typical forms are a colorless spiro (Sp) and a colored merocyanine (MC) forms. The planer MC structure, furthermore, tends to associate into stacking structures so called J-aggregates and H-aggregates by ionic and pi-pi interaction. We are particularly interested in remarkable changes in polarity and structure (especially, planarity) between Sp and MC forms. We have designed and synthesized two unique spiro-dimers: bispiropyran (BIPSD) and bispirooxazine (SPOD) (Figure 1). To effectively utilize photochromic properties, polymers were attached to the top of spiro-dimer molecules. These photo-switchable polymers are potential as drug delivery vehicles, site recognition tools of specific biomolecules, and sensors of organic/inorganic compounds. The polar site of the MC form of bispiro-polymer would strongly attract ionic species which can be released through visible light irradiation upon transformation into the non-polar Sp form. Moreover, the aggregates of the bispiro-polymers are attractive since MC-to-Sp conversion destroys the planarity of the molecules, which disallows maintenance of the self-assembling structure. In this presentation, we will focus on photochromism studies and binding/releasing ability for guest species using BIPSD/SPOD and the polymers.