Excitation- and Emission-Wavelength-Based Multiplex Spectroscopy Using Red-Absorbing Near-Infrared-Emitting Lanthanide Complexes.

Multiplex imaging in the red and near-infrared (NIR) should be an enabling tool for the real-time investigation of biological systems. Currently available emitters have short luminescent lifetimes, broad absorption and emission bands, and small Stokes shifts, which limits multiplexing in this region to two colors. NIR-emitting luminescent lanthanide (Ln) complexes carrying hydroporphyrin (chlorin) sensitizing antennae are excitable in the red through the narrow, intense and tunable chlorin absorptions. Both emission- and excitation-based multiplexing are possible, the former by exciting the same antenna appended to different Lns, the latter by attaching different chlorins with nonoverlapping absorptions to the same Ln. The combination of excitation and emission spectroscopies allows for the straightforward differentiation of up to four different complexes.