The DCDHF dyes are under development as a promising new class of single-molecule fluorophores. The utility of these fluorophores is derived from a range of attributes including their synthetic accessibility, structural versatility and photostability, all permitting a range of practical labelling applications. Their polarity- and viscosity-dependent emission, required for their application as local environment nanoprobes, is of particular interest. A wide range of DCDHF chromophores with different p-systems have been prepared for control of absorption and emission characteristics. Structure-function analysis has been performed in conjunction with theoretical evaluations of these chromophores.