Triphenylamine based reactive coloro/fluorimetric chemosensors: Structural isomerism and solvent dependent sensitivity and selectivity

Triphenyl amine based chemosensors, (24((2-(9H-carbazol-9-yl)phenyl)imino)methyl)-5-(diphenylamino)phenol (ortho-CPDP) and 2-(((4-(9H-carbazol-9-yl)phenyeimino)methyl)-5-(diphenylamino)phenol (para-CPDP), showed solvent and isomerism dependent selective coloro/fluorometric sensing of multiple metal ions (Fe3+, Al3+ and Zn2+) with distinguishable responses. In CH3CN, ortho and para-CPDP selectively produced yellow color upon addition of Al3+ and Fe3+ that was slowly disappeared. The yellow color of ortho and para-CPDP in DMF was decolourised selectively by adding Al3+ and Fe3+. Both ortho and para-CPDP in CH3CN showed nearly similar rate of decolourization for Fe3+ and Al3+. However, the rate of decolourization of ortho and para-CPDP in DMF was different for Fe3+ (10 mu M, 8 min) and Al3+ (5 x 10(-4) M, 40 min) ions. The limit of detection of para-CPDP for Fe3+ is 10 mu M and Al3+ 500 mu M. The mechanistic studies revealed the imine hydrolysis of ortho and para-CPDP in presence of Lewis acidic Fe3+ and Al3+. The reactivity based sensing lead to high selectivity for Al3+ and Fe3+ ions. Further, para-CPDP exhibited selective fluorescence turn-on for Zn2+ in DMF (lambda(max) = 513 nm) and detection limit of 6.0 mu M. Thus, reactive chemosensors, ortho and para-CPDP, exhibited selective and distinguishable colorimetric sensing of Fe3+ and Al3+ ions and isomerism and solvent dependent fluorescence sensing of Zn2+. (C) 2017 Elsevier B.V. All rights reserved.