Département de chimie moléculaire

The radical complex {\{}($μ$4-TCNQF4)[Re(CO)3(bpy)]4{\}}(PF6)3, as prepd. and isolated from the reaction between TCNQF4 and [Re(CO)3(bpy)(MeOH)](PF6), was studied electrochem. and by IR vibrational spectroscopy, UV-Vis-NIR absorption spectroscopy, and by EPR at 9.5, 190 and 285 GHz. The isotropic g factor of 2.0058, the detectable g anisotropy, and the 185,187Re EPR hyperfine coupling of 0.95 mT for four equiv. metal nuclei support predominant, but not exclusive, spin localization at the bridging ligand. Nitrile and metal carbonyl stretching frequencies as well as the typically structured near IR absorption band lend further support to (TCNQF4-)(ReI)4 as the most appropriate oxidn. state formulation. In comparison to the non-radical complex {\{}($μ$4-TCNQ)[Re(CO)3(bpy)]4{\}}(PF6)4 an X-ray structure anal. of {\{}($μ$4-TCNQF4)[Re(CO)3(bpy)]4{\}}(PF6)3 shows a marginally more twisted (ReNCCCNRe)(C6X4)(ReNCCCNRe) configuration and a different up/down arrangement of the [Re(CO)3(bpy)]+ groups. This first isolation, electrochem., structural and spectroscopic characterization of a discrete tetranuclear radical complex of a TCNQ-type ligand suggests a link between the stability of such materials and the rather small structural changes on ligand-based electron transfer. [on SciFinder(R)]