Water-Soluble Pyrrolo[3,2-b]pyrroles: Synthesis, Luminescence and Two-Photon Cellular Imaging Properties

Water-soluble, quadrupolar (A-pi-D-pi-A) pyrrolo[3,2-b]pyrrole dyes have been prepared, and their photophysical properties, including solid-state fluorescence, are characterized. Analysis of packing patterns of the para analogue in single crystal shows negligible pi-pi interactions between molecular planes in stacked layers, resulting in no fluorescence quenching in the aggregate state. One of the dyes is used for fluorescence imaging of cells by confocal and two-photon microscopy, showing potential applicability of such dyes as bioimaging agents.