Tren-spaced rhodamine and pyrene fluorophores: Excimer modulation with metal ion complexation

A new chromogenic and fluorogenic probe (1) exhibits a significant selectivity towards Cu(II) and Hg(II) ions to give the modulation of pyrene (Py) excimer emission. Also, its sensing behaviours towards Cu(II) and Hg(II) ions were investigated experimentally and computationally. Hg(II) complexation induces the ring opening of the rhodamine spirolactam unit of 1 and shows enhanced dynamic excimer emission. Cu(II), on the other hand, is found to be encapsulated in the Py amide group to provide a static excimer emission. Hg(II) in the Hg(II)1 complex can be readily replaced by Cu(II), and then the static excimer emission of two Pys in 1 is reformed.