Elaboration, structure and fluorescence spectroscopy of iodophenyl-BODIPY crystals

We present the synthesis of 2,6-diethyl-4,4-difluoro-8-(-4-iodophenyl)-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene labeled as iodophenyl-BODIPY (IP-BDPY) and the growth of microcrystals or spherulitic crystal plates in typical free solutions. Their crystal structures, the absorption and fluorescence spectroscopies were investigated. Relations between crystal structure and absorption, dichroism and fluorescence properties were established. The first results obtained for the preparation of IP-BDPY nanocrystals grown in sol–gel thin films were also introduced. Their absorption and fluorescence spectra were compared with the spectra of the corresponding bulk crystal and diaplectic amorphous solid obtained by a drastic crushing. Unexpected results were obtained: amorphization of molecular nanocrystals just after their growth by capillary forces generated during the drying of sol–gel thin films.

Fluorescence images (left) and fluorescence lifetime images (FLIM, right) of IP-BDPY crystals (a) and (b) and of hybrid thin films (c) and (d), respectively. The crystal exhibits a red fluorescence (a) associated to a short lifetime of 1 ns (b). It is surrounded by a hallo of dispersed molecules with a green fluorescence and a longer lifetime of 3 ns. The hybrid sample shows particles with a yellow-orange emission associated to a short lifetime (around 1 ns) surrounded by a green background exhibiting a longer fluorescence lifetime (3 ns).Figure optionsDownload as PowerPoint slideHighlights
► Synthesis of BODIPY.
► Crystal structure determination, absorption and fluorescence characterizations.
► Nanocrystallisation of BODIPY crystals in sol–gel thin film.
► Amorphiszation of nanocrystals during the drying of the sol–gel thin films.
► Formation of diaplectic amorphous particles in sol–gel thin films.