Bodipy/dipyridylamino-based "turn-on" fluorescent chemosensor for trivalent chromium cations: characterization and photophysical properties

{{3,5-Bis[4,4-difluoro, 8-(2,6-diethyl,1,3,5,7-tetramethyl-4-bora-3a, 4a-diaza-s-indacene)]}}phenyl-N,N-di( pyridin-2-yl) benzamide (Bodipy-DPy) was designed as an efficient fluorescent chemosensor for Cr(III). The structure of Bodipy-DPy was confirmed by UV-vis spectroscopy, fluorometry, melting point analysis, H-1-NMR, C-13-NMR, elemental analysis and ESI-TOF-MS. Its photophysical properties was investigated by absorption, emission and excitation techniques. Based on chelation assisted fluorescence enhancement, a fluorometric method was developed for trace level detection, selectivity and concentration studies of chromium(III) in EtOH-H2O. The fluorescent ligand behaved as a chemosensor for Cr(III) cations and showed a strong red fluorescence upon coordination with Cr(III), whereas almost no fluorescence was observed for the other metal cations studied. The Bodipy-DPy has absorption and emission maxima at 528 nm and 535 nm, respectively. The equilibrium binding constant of Bodipy-DPy with Cr(III) was calculated as 1.17 x 10(6) from the Stern-Volmer equation.