Synthesis and photophysical properties of new SNARF derivatives as dual emission pH sensors

We report the synthesis and properties of two new seminaphthorhodafluor (SNARF) derivatives, SNARF-F and SNARF-Cl. Both these derivatives exhibit typical red shifts of absorption and fluorescence, and higher cell permeability as compared to traditional SNARF, while the pH-dependent dual-emission characteristics are well retained. In particular, the lower pK(a) (7.38) of SNARF-F makes it more suitable than traditional SNARF derivatives for intracellular applications. (C) 2011 Elsevier Ltd. All rights reserved.