title: Heteroditopic ligand accommodating a fused phenanthroline and a schiff base cavity as molecular spacer in the study of electron and energy transfer.
abstract: The synthesis and characterisation of the heteroditopic ligand N,N'-bis(3,5-di-tert-butylsalicylidene)-5,6-(1,10-phenanthroline)diamine (DPSalH(2)) bearing a phenanthroline and a bis(salicylidene)diimine cavity are reported. This versatile ligand combines two of the most widely used ligands in coordination chemistry. Sequential metallation of the phenanthroline end with Ru(II) and the salophenic cavity with Cu(II) is described. Electrochemical behaviour of the supramolecular complexes [Ru(bpy)(2)(DPSalH(2))](2+) and [Ru(bpy)(2)(DPSalCu)](2+) are analysed in connection with UV/Vis and EPR spectroscopy. The data for the one-electron-reduced species and the singly oxidised species of the binuclear Ru(II)-Cu(II) complex confirmed the formation of metalloradical complexes. Density functional calculations on the free ligand and the copper-only complex indicate in both cases that the HOMOs and LUMOs are developed on the Schiff base cavity with minor contributions on the bipyridine end. These findings support a bichromophoric character for our ruthenium complexes in the ground state, a necessary condition in the design of supramolecular systems for the study of electron transfer. Photophysical studies indicate fast quenching of the triplet excited state in both complexes, which suggests strong intercomponent excited-state interactions. Evidence is presented that this quenching is due to intramolecular electron transfer, at least in the case of [Ru(bpy)(2)(DPSalH(2))](2+), for which a charge-separated state with a remarkable lifetime of about 30 mus was observed.
authors.affiliation: Laboratoire de Chimie Inorganique, UMR 8613, Université de Paris-Sud, Orsay, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Pellegrin
authors.forename: Annamaria
authors.initials: A
authors.lastname: Quaranta
authors.forename: Pierre
authors.initials: P
authors.lastname: Dorlet
authors.forename: Marie France
authors.initials: MF
authors.lastname: Charlot
authors.forename: Winfried
authors.initials: W
authors.lastname: Leibl
authors.forename: Ally
authors.initials: A
authors.lastname: Aukauloo
mesh_terms: D003300:Copper / Q000737:chemistry; D003959:Diamines / Q000138:chemical synthesis / Q000737:chemistry; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D004735:Energy Transfer; D007097:Imines / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods / Q000592:standards; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis; D010618:Phenanthrolines / Q000138:chemical synthesis / Q000737:chemistry*; D012015:Reference Standards; D012428:Ruthenium / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: D003959:Diamines; D007097:Imines; D008024:Ligands; C506870:N,N'-bis(3,5-di-tert-butylsalicylidene)-5,6-(1,10-phenanthroline)diamine; D009942:Organometallic Compounds; D010618:Phenanthrolines; D012545:Schiff Bases; C506872:bis(salicylidene)diimine; D003300:Copper; D012428:Ruthenium