Switch in turn-on' signaling preferences from Fe(III) to Hg(II) as a function of solvent and structural variation in rhodamine based probes

Abstract

Two rhodamine based probes having same N,N-dimethyl-aminoethylamino- receptor but differ in their signaling subunit, i. e. rhodamine B (1) and rhodamine 6G (2) were synthesized and their metal ion induced photophysical signaling pattern were investigated. Both 1 and 2 exhibited Fe(III) specific fluorescence and absorption spectral enhancement in EtOH due to complexation mediated spiro-ring opening of the probes. However, such spectral amplifications were observed in 1 in preferential presence of Hg(II) when investigated in EtOH-H2O (PBS, pH 7.1, v/v, varied proportions) binary mixture medium. On contrary, the Fe(III) specificity in signaling with 2 did not vary under similar solvent conditions. One way, the complexation induced absorption and fluorescence spectral behaviour of 1 inferred to an alteration in metal ion selective signaling preferences from Fe(III) to Hg(II) as a function of solvent medium. In another way, the Fe(III) specificity in 2 reoriented to Hg(II)-specific signalling responses in I as a function of structural variation in signalling subunit when investigated in EtOH-H2O (PBS, pH 7.1, v/v, varied proportions) solvent conditions. (C) 2016 Elsevier Ltd. All rights reserved.