Switchable and selective detection of Zn ²⁺ or Cd ²⁺ in living cells based on 3′-O-substituted arrangement of benzoxazole-derived fluorescent probes

Two benzoxazole-derived ESIPT fluorescent sensors and show highly selective detection of Zn(2+) and Cd(2+), respectively, in aqueous solution and living cells. The selectivity switching from Zn(2+) to Cd(2+) is attributed to the different binding mode which is dependent on the 3'-O-substituted arrangement.