New fluorescent indolium and quinolinium dyes for applications in aqueous halide sensing

Bromide and teraphenylborate salts of six new highly fluorescent dyes, prod uced by the reaction of two heterocyclic nitrogen bases with 8-bromo-octano ic acid, 11-bromo-undecanoic acid and 15-bromo-pentadecanoic acid have been prepared. Unlike the bases themselves, the quaternary salts are water solu ble and have fluorescence characteristics independent of pH in the pH range 7-11. Both the fluorescence intensity and fluorescence lifetime of these d yes are reduced in the presence of aqueous halide ions, allowing halide con centrations to be determined accurately at concentrations of importance to both medicine and industry. All the dyes have been characterised in terms o f steady state fluorescence spectra and steady-state Stern-Volmer analysis. The Stern-Volmer constants, (K-SV), for the dyes are compared to those obt ained for some commercially available dyes. The prospects for using these d yes in halide sensor devices are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.