title: Push-pull effects and emission from ternary complexes of platinum(II), substituted terpyridines, and the strong-field cyanide ion.
abstract: As part of an effort to develop new lumaphors involving late transition metal ions, this report describes the synthesis and characterization of the first platinum(II) derivatives containing 2,2':6',2''-terpyridine (trpy) and cyanide as co-ligands. According to existing models, including cyanide in the coordination sphere should raise the energies and minimize the influence of short-lived d-d excited states that otherwise compromise the excited-state lifetime. Both [Pt(trpy)(CN)]+ and the 4'-cyano-2,2':6',2''-terpyridine analogue [Pt(CN-T)(CN)]+ are emissive in dichloromethane solution, but the signals are weak. Part of the problem is that the d-pi* charge-transfer excited states also rise in energy, so that the emission actually originates from a (3)pi-pi* state with a relatively low radiative rate constant. However, another member of the series, the 4'-dimethylamino-2,2':6',2''-terpyridine (dma-T) derivative [Pt(dma-T)(CN)]+, proves to be a very promising platform with an emission quantum yield of phi= 0.26 and an excited-state lifetime of tau = 22 micros in room-temperature, deoxygenated dichloromethane solution. In the dma-T complex the electron-rich dimethylamino substituent provides the basis for an emissive, but largely ligand-based, charge-transfer excited state. The orbital parentage is such that the photoluminescence persists in donating solvents like dimethylformamide, which ordinarily quenches d-pi* excited states in complexes of this type.
authors.affiliation: Department of Chemistry, 560 Oval Drive, Purdue University, West Lafayette, IN 47907-2084, USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Wilson
authors.forename: L Peter
authors.initials: LP
authors.lastname: Ledwaba
authors.forename: John S
authors.initials: JS
authors.lastname: Field
authors.forename: David R
authors.initials: DR
authors.lastname: McMillin
mesh_terms: D003486:Cyanides / Q000737:chemistry*; D004563:Electrochemistry; D008163:Luminescent Measurements; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods; D015394:Molecular Structure; D009944:Organoplatinum Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D012680:Sensitivity and Specificity
chemical_list: D003486:Cyanides; D009944:Organoplatinum Compounds; D011725:Pyridines