A pyrazolopyrimidine based fluorescent probe for the detection of Cu2+ and Ni2+ and its application in living cells

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 5.24 x 10(3) M-1 and 2.85 x 10(4) M-1 and low detection limits of 0.043 mu M and 0.038 mu M for Cu2+ and Ni2+, respectively. The binding stoichiometry ratios of L to Cu2+ or Ni2+ is 1:1 as determined by BenesiHildebrand and Job's plots, and by crystal structures. OFT 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. (C) 2018 Elsevier B.V. All rights reserved.