7-Nitro- and 7-aminosubstituted spiropyrans of 1-benzothieno[3,2-b]pyrrole

Amino and nitro derivatives of spiropyrans based on 1-benzothieno[3,2-b]pyrrole were synthesized employing an efficient method for the reduction of nitro group in thienopyrroles and spiropyrans. Novel bi-functional compounds, containing salicylideneaniline and dithienylethene fragments, along with spiropyran were prepared from the aminospiropyran derivative.     

Reversible Diffraction Efficiency of Photochromic Polymer Gratings Related to Photoinduced Dimensional Changes

In this Full Paper, the possibility of reversibly changing the diffraction efficiency of gratings, fabricated by soft molding lithography on polymer films, containing photochromic molecules, is demonstrated. In particular, alternating UV and visible laser irradiation of the gratings causes the doped photochromic molecules to undergo transformations, which induce reversible dimensional changes to the samples. As a result, reversible changes are monitored in the intensity of the beams of a diode laser, transmitted and diffracted from the gratings. These changes affect the diffraction efficiency, which is increased upon irradiation with UV and decreased after irradiation with visible laser light. Such gratings are promising candidates for the fabrication of modern optical components such as optical switching devices.     

Mesostructured self-assembled silica films with reversible thermo-photochromic properties

A spiropyran molecule has been introduced via one-pot synthesis into mesostructured silica films, which have been obtained through a micelle templating self-assembling process. The mesostructure has been characterized by transmission electron microscopy and small-angle X-ray scattering performed with synchrotron light. The final material exhibited a p6mm 2d-hexagonal organization and the mesostructure has not been affected by the introduction of spiropyrans in the precursor solution. A comparative characterization of the optical properties of the spiropyrans dissolved in different solvents and after incorporation in the mesostructured films has been done by UV–Vis absorption spectroscopy, fluorescence spectroscopy and ellipsometric spectroscopy. The spiropyran-doped films appeared transparent before external stimuli had applied, a colour change to yellow (thermally induced) or to red (light induced) has been observed. Both the colour changes have been observed to be reversible under room temperature or visible light exposure; the colour transitions have been attributed to different equilibria among the various forms of merocyanine of spiropyrans.