Steric Influence on the Excited-State Lifetimes of Ruthenium Complexes with Bipyridyl−Alkanylene−Pyridyl Ligands
Citations Over TimeTop 10% of 2008 papers
Abstract
The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane ( 1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane ( 2). A homoleptic ([Ru( 2) 2] (2+)) and a heteroleptic complex ([Ru(ttpy)( 2)] (2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru( 1) 2] (2+). The excited-state lifetime of the homoleptic Ru (II) complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru (II) complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru (II) ion less octahedral in [Ru( 2) 2] (2+) than in [Ru( 1) 2] (2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ( (3)MLCT) and metal-centered ( (3)MC) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru (II) complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (3)MLCT states to short-lived (3)MC states.
Related Papers
- → Light-Driven Expulsion of the Sterically Hindering Ligand L in Tris-diimine Ruthenium(II) Complexes of the Ru(phen)2(L)2+ Family: A Pronounced Ring Effect(2005)54 cited
- → Synthesis of Heteroleptic Phosphorus(I) Cations by P+ Transfer(2018)11 cited
- → New Acridine-Based Tridentate Ligand for Ruthenium(II): Coordination with a Twist(2018)10 cited
- → Formation of a homoleptic unbridged metal–metal bonded isocyanide dimer of ruthenium(I) by metal–carbon bond cleavage in [Ru(1–2,5-η-C8H13)(CN-xylyl)4]PF6: the X-ray structure determination of [Ru2(CN-xylyl)10][BPh4]2(1985)8 cited
- → Novel Ruthenium Complexes with Sterically Demanding Cyclopentadienyl Ligands : Syntheses, Reactivity and Catalytic Applications(2010)