854049-38-0Relevant academic research and scientific papers
Luminescence studies of copper(I)-containing [2]pseudorotaxanes
Briggs, Breeze N.,Durola, Fabien,McMillin, David R.,Sauvage, Jean-Pierre
experimental part, p. 98 - 103 (2011/04/23)
This report describes photoluminescence studies of copper-containing [2]pseudorotaxanes that mimic elements of functioning molecular machines. Excitation with visible light induces a formal oxidation of the metal center and simulates an actuation process. In all four [2]pseudorotaxanes studied, the ring ligand is the same, but the thread ligand is variable, namely 2,9-di(anisol-4-yl)-1,10-phenanthroline (dap), 6,6′-di(anisol-4-yl)-2, 2′-bipyridine (o-dabipy), 5,5′-di(anisol-4-yl)-2,2′-bipyridine (m-dabipy), or 8,8′-di(anisol-4-yl)-3,3′-bi-isoquinoline (dabiiq). The absorbance bandshapes suggest that aryl substituents extending from the core ligands engage in stacking interactions and induce a partially flattened structure in the ground state. More severe flattening occurs in the excited state and precludes the observation of emission if inter-ligand steric forces do not limit the distortion. Thus, the [2]pseudorotaxanes containing dap or o-dabipy as the thread ligand exhibit uncorrected emission maxima at around 720 nm in room-temperature dichloromethane, while the less constrained analogues, containing dabiiq or m-dabipy, are not emissive in fluid solution and barely exhibit a signal in rigid media. In dichloromethane, the luminescence quantum yields of the dap-and o-dabipy-containing systems are 6 × 10-4 and 4 × 10-4, and the excited-state lifetimes are 98 ns and 90 ns, respectively.
Role of substitution on the photophysical properties of 5,5′-diaryl-2,2′-bipyridine (bpy*) in [Ir(ppy) 2(bpy*)]PF6 complexes: A combined experimental and theoretical study
Ladouceur, Sebastien,Fortin, Daniel,Zysman-Colman, Eli
scheme or table, p. 5625 - 5641 (2010/08/04)
The synthesis of a family of 4′-functionalized 5,5′-diaryl-2, 2′-bipyridines (bpy*; 6a-6g) is reported. These ligands were reacted with the dimer [(ppy)2IrCl]2 (ppyH = 2-phenylpyridine) and afforded, after subsequent counterion exchange, a new series of luminescent cationic heteroleptic iridium(III) complexes, [(ppy)2Ir(bpy*)] PF6 (8a-8g). These complexes were characterized by electrochemical and spectroscopic methods. The crystal structures of two of these complexes (8a and 8g) are reported. All of the complexes except for 8c and 8f exhibit intense and long-lived emission in both 2-MeTHF and ACN at 77 K and room temperature. The origin of this emission has been assigned by computational modeling to be an admixture of ligand-to-ligand charge-transfer [3LLCT; π(ppy) → π*(bpy*)] and metal-to-ligand charge-transfer [ 3MLCT; dπ(Ir) → π*(bpy*)] excited states that are primarily composed of the former. The luminescent properties for 8a-8c are dependent upon the functionalization at the 4′ position of the aryl substituents affixed to the diimine ligand, while those for 8d-8g are essentially independent because of an electronic decoupling of the aryls and bpy due to the substitution of o,o-dimethyl groups on the aryls, causing a near 90° angle between the aryl and bipyridyl moieties. A combined density functional theory (DFT)/time-dependent DFT study was conducted in order to understand the origin of the transitions in the absorption and emission spectra and to predict accurately emission energies for these complexes.
