the invention provides compounds and compositions of formulas i - vii , and methods of using the compounds . the compounds can be used to prepare dye conjugates that are uniformly and substantially more fluorescent on proteins , nucleic acids or other biopolymers , than conjugates labeled with structurally similar known carbocyanine dyes . in addition to having more intense fluorescence emission than structurally similar dyes at virtually identical wavelengths , and decreased artifacts in their absorption spectra upon conjugation to biopolymers , the compounds can have greater photostability and / or higher absorbance at the wavelength of peak absorbance than such structurally similar dyes .