A pyridine and pyrrole coupled rhodamine derivative for Co(II) ion detection and its imaging application in plant tissues

A rhodamine derivative (3) incorporating 2-[(1H-pyrrol-2-ylmethyl)-(2-pyridinylmethyl) amino]- tripodal receptor in its architecture exhibited both fluorogenic and chromogenic signalling responses preferentially in presence of Co(II) ion. The observed absorption and fluorescence spectral enhancements along with a colour change in 3 on addition of Co(II) ion is associated with its complexation mediated structural transformation from spirolactam conformation to ring-opened amide derivative. The associated photophysical spectral modulations with Co(II) specificity, higher association constant corresponding to effective complexation, faster metal-probe kinetics, reversibility in 'on-off signalling and a wider operation pH range endorses potential utility of 3 as chemosensing probe in practical applications such as detection of Co(II) ion uptake and accumulation in root and shoot tissues of Hybanthus enneaspermus plant species. (C) 2016 Elsevier B.V. All rights reserved.