| Abstract
| - A novel heterobimetallic alkynyl-bridged complex, [Re(bpy)(CO)3(C⋮CC6H4C⋮C)Fe(C5Me5)(dppe)], 1, and itsoxidized species, [Re(bpy)(CO)3(C⋮CC6H4C⋮C)Fe(C5Me5)(dppe)][PF6], 2, have been synthesized and theirX-ray crystal structures determined. A related vinylidene complex, [Re(bpy)(CO)3(C⋮CC6H4(H)CC)Fe(C5Me5)(dppe)][PF6], 3, has also been synthesized and characterized. The cyclic voltammogram of 1 shows aquasireversible reduction couple at −1.49 V (vs SCE), a fully reversible oxidation at −0.19 V, and a quasireversibleoxidation at +0.88 V. In accord with the electrochemical results, density-functional theory calculations on the hydrogen-substituted model complex Re(bpy)(CO)3(C⋮CC6H4C⋮C)Fe(C5H5)(dHpe) (Cp = C5H5, dHpe = H2P(CH2)2PH2) (1-H) show that the LUMO is mainly bipyridine ligand π* in character while the HOMO is largely iron(II)d orbital in character. The electronic absorption spectrum of 1 shows low-energy absorption at 390 nm with a420 nm shoulder in CH2Cl2, while that of 2 exhibits less intense low-energy bands at 432 and 474 nm and additionallow-energy bands in the NIR at ca. 830, 1389, and 1773 nm. Unlike the related luminescent rhenium(I)−alkynylcomplex [Re(bpy)(CO)3(C⋮CC6H4C⋮CH)], 4, complex 1 is found to be nonemissive, and such a phenomenonis attributed to an intramolecular quenching of the emissive dπ(Re) → π*(bpy) 3MLCT state by the low-lying MLCTand LF excited states of the iron moiety. Interestingly, switching on of the luminescence property derived from thedπ(Re) → π*(bpy) 3MLCT state can be demonstrated in the oxidized species 2 and the related vinylidene analogue3 due to the absence of the quenching pathway.
- Luminescent [Re(CO)3(bpy)] and electroactive [(C5Me5)(dppe)Fe] moieties are linked by a 1,4-diethynylbenzene bridge to form a new heterobimetallic alkynyl complex [Re(bpy)(CO)3(C⋮CC6H4C⋮C)Fe(dppe)(C5Me5)], and its luminescent property can be switched “on” upon oxidation of the iron(II) metal center to iron(III).
|
