Synthesis and Characterization of a Metal-to-Polyoxometalate Charge Transfer Molecular Chromophore

[P4W35O124{Re(CO)3}2]16– (1), a Wells–Dawson [α2-P2W17O61]10– polyoxometalate (POM)-supported [Re(CO)3]+ complex containing covalent WVI–O–ReI bonds has been synthesized and characterized by several methods, including X-ray crystallography. This complex shows a high visible absorptivity (ε470 nm = 4000 M–1 cm–1 in water) due to the formation of a ReI-to-POM charge transfer (MPCT) band. The complex was investigated by computational modeling and transient absorption measurements in the visible and mid-IR regions. Optical excitation of the MPCT transition results in instantaneous (<50 fs) electron transfer from the ReI center to the POM ligand.