BORON-DIPYRROMETHENE DYES FOR INCORPORATION IN SYNTHETIC MULTI-PIGMENT LIGHT-HARVESTING ARRAYS

The synthesis of light-harvesting arrays requires modular pigment buil ding blocks. Boron-dipyrromethene dyes are well-suited for the photoch emical sensitization of free base or metalloporphyrins. Direct access to boron-dipyrromethene dyes bearing reactive substituents is provided by a simple synthetic route involving two one-flask reactions. Reacti on of pyrrole or 2-methylpyrrole with an aldehyde under gentle acid ca talysis affords the corresponding dipyrromethane. Subsequent oxidation (DDQ or p-chloranil) and complexation affords the dye. Boron-dipyrrom ethene dyes bearing iodo- or ethynyl-phenyl substituents at the meso-p osition have been prepared as modular components for building block ap plications. These dyes are stable, accessible, and have suitable spect roscopic features for use as porphyrin accessory pigments in light-har vesting arrays.