DESIGN OF MULTIPLEX DYES

Fluorescent dyes which are almost identical in their absorption and emission spectral characteristics but differ in fluorescence lifetime (''Multiplex Dyes'') have been developed for analytical applications. First investigations to design such dyes were carried out with rhodamines. In order to influence the excited state lifetime without changing the spectral characteristics we studied rhodamines modified with non-conjugated substituents that promote non-radiative transitions. We used two different methods to control the fluorescence lifetime in rhodamine dyes with rigidized amino groups: (A) Substitution with benzyl derivatives of different electron acceptor strength at the amino position. (B) Substitution of the carboxyphenyl group by phenyl groups with reduced steric requirements and varying acceptor properties.