Abstract of Publication No. 296
Frederik W. M.
Vanhelmont, Hans U. Güdel, Marcel Förtsch and Hans-Beat Bürgi
We have synthesized the new cyclometalated complex [Re(CO)4(thpy)]
(thpy– = 2-(2-thienyl)pyridinate) and determined the crystal and
molecular structure by X-ray diffraction. By application of high-resolution
optical spectroscopy to single crystals and glasses at cryogenic temperatures,
the first excited state is identified as a nominally ligand-centered
3p-p* state with some 1MLCT
character mixed in by spin-orbit coupling. The coefficient a describing the charge-transfer
character in the wave function of the first excited state has a value of 0.019.
This admixture leads to a reduced luminescence lifetime (258
ms at 10 K) and the occurrence of sidebands in the
absorption and luminescence spectra which are due to metal-ligand vibrations.
The parameters characterizing the first excited state are compared with the
corresponding parameters of related cyclometalated and noncyclometalated
complexes of Rh(III), Ir(III), and Re(I). An extended Hückel calculation was
performed to identify the relevant one-electron excitations.