Multi-branched triphenylamine–rhodamine derivatives: Synthesis and fluorescent sensing for Cu2+ and Hg2+ ions

Three multi-branched rhodamine based fluorescent probes TPARH1-3 have been designed and synthesized by incorporating the rhodamine fluorophore with triphenylamine. The probe TPARH1 displayed high sensitivity to Cu2+ in aqueous CH3CN. The probes TPARH2 and TPARH3 showed high sensitivity towards Hg2+ in aqueous EtOH medium as reflected by their signalling responses. The cooperative effects of multi-branched structures towards metal ions were carried out by UV–vis absorption titrations and time scanning fluorescence spectroscopic. In addition, the binding mode was proposed based on the jobʹs plot. The absorption of probes 1–3 at 558 nm went through a maximum at a molar fraction of 0.5, indicating a 1:1 stoichiometry of the Hg2+ to 1, 2 and 3 in the complex, respectively.