ABSTRACT
A fluorescent sensor L based on a pyrazolopyrimidine core simultaneously detects Cu2+ and Ni2+ ions by photoluminescence quenching, even in the presence of other metal cations. Sensor L possesses high association constants of 5.24â¯×â¯103â¯M-1 and 2.85â¯×â¯104â¯M-1 and low detection limits of 0.043⯵M and 0.038⯵M for Cu2+ and Ni2+, respectively. The binding stoichiometry ratios of L to Cu2+ or Ni2+ is 1:1 as determined by Benesi-Hildebrand and Job's plots, and by crystal structures. DFT calculations on L-Cu2+ indicated reduced electron donation from the coordinated pyrazolopyridine to the fused pyrimidine and pendant phenyl group which, together with a smaller HOMO-LUMO orbital gap could favour non-radiative decay and explain the observed fluorescence quenching. Sensor L possessed low cytotoxicity and good imaging characteristics for Cu2+ and Ni2+ in living cells, suggesting potential applications for detecting Cu2+ and Ni2+in vivo.