Time-resolved infrared studies on two isomeric ruthenium(II)/rhenium(I) complexes containing a nonsymmetric quaterpyridine bridging ligand
- Los Alamos National Lab., NM (United States). Chemical Science and Technology Div.
- Univ. of Bristol (United Kingdom). School of Chemistry
- Univ. di Ferrara (Italy). Dipt. di Chimica
In this paper, time-resolved infrared (TRIR) spectroscopy is used to study the lowest energy metal-to-ligand charge transfer (MLCT) excited state of the isomeric complexes [(bpy){sub 2}Ru{sup II}-ABRe{sup I}(CO){sub 3}Cl]{sup 2+} (RuABRe) and [(CO){sub 3}CIRe{sup I}ABRu{sup II}(bpy){sub 2}]{sup 2+} (ReABRu; AB is 2,2{prime}:3{prime},2{double_prime}:6{double_prime},2{prime}{double_prime}-quaterpyridine; bpy is 2,2{prime}-bipyridine). The AB bridge is asymmetric and contains two electronically inequivalent metal-binding sites due to different bipyridyl substitution patterns, and the B site is more sterically hindered. An earlier study demonstrated that at room temperature the visible luminescence is Ru-based for the RuABRe isomer and Re-based for the ReABRu isomer, suggesting that the lowest energy state and the direction of energy transfer in these isomers are actually reversed. However, this result was based on luminescence lifetimes and could be influenced by the establishment of an equilibrium between an intrinsically longer lived Ru-based excited state and a shorter lived Re-based excited state, leaving open the possibility that the Ru-based MLCT is lower in energy in both cases. Time-resolved vibrational spectroscopy is useful to resolve this ambiguity since the v(CO) bands for the carbonyl ligands on Re are an excellent probe of the excited-state electronic distribution in these complexes. Infrared difference spectra have been measured following photoexcitation and the data analyzed to address the orbital origin of the excited state, the transient oxidation states of the metals, and specifically, the possibility of the presence of equilibrated states having different electronic configurations.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 642393
- Journal Information:
- Inorganic Chemistry, Vol. 37, Issue 10; Other Information: PBD: 18 May 1998
- Country of Publication:
- United States
- Language:
- English
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