TCA self-assembled fluorescence probe for Cu (II) ion based on the unique configuration of extra nuclear electrons of metal ions: A TDDFT study

Abstract A molecule fluorescence probe of a new ON-OFF type, used for detecting transition metal ions, reported recently, is self-assembled by thiacalix[4]arene(TCA) molecules, micelles and a fluorescence group. It only presents high selectivity for Cu 2+ ions, in a solution with the coexistence of Zn 2+ , Ni 2+ , Hg 2+ , Cu 2+ Cd 2+ ions. Since the mechanism of the ON-OFF signal response of such self-assembled micelle probes has always been a controversial issue of uncertainty, the mechanisms of the signal response and the high selectivity for Cu 2+ ions were studied here by DFT/TDDFT method. The spatial arrangement, geometric and electronic structures of the functional units of the probe were calculated, and the response mechanism was investigated by the molecular transition orbital pairs method to explore the origination of the ON-OFF fluorescence signal response. The results told that the signal response process was based on forster resonance energy transfer (FRET) mechanism. The high selectivity for Cu 2+ ions was due to the unique electron configuration of the copper complex, by the comparing of the calculation results of the TCA complexes M 1-4 (TCA)(M = Cu, Hg, Ni). The results provided new sights different from most of the conclusions by the related research works reported.