Hsiu-Yi Chao

Triplet luminescent dinuclear-gold(I) complex-based light-emitting diodes with low turn-on voltage

The electroluminescence (EL) from a dinuclear-gold(I)-chlorate compound containing bridging phosphine ligands [Au2(dppm)Cl2] as emitting layer is reported. Devices with a structure Al/Au2(dppm)Cl2/indium–tin–oxide demonstrated a uniform emission under the driving voltage below 1 V. The EL emission was from triplet excited state and the emission color of the device was found to depend on the deposition rate of Au2(dppm)Cl2, which can be explained as the different aggregation forms of the stacking compound in the deposition process.

The 3[ndσ*(n+1)pσ] Emissions of Linear Silver(I) and Gold(I) Chains with Bridging Phosphine Ligands

The complexes [Au(3)(dcmp)(2)][X](3) {dcmp=bis(dicyclohexylphosphinomethyl)cyclohexylphosphine; X=Cl(-) (1), ClO(4) (-) (2), OTf(-) (3), PF(6) (-) (4), SCN(-)(5)}, [Ag(3)(dcmp)(2)][ClO(4)](3) (6), and [Ag(3)(dcmp)(2)Cl(2)][ClO(4)] (7) were prepared and their structures were determined by X-ray crystallography. Complexes 2-4 display a high-energy emission band with lambda(max) at 442-452 nm, whereas 1 and 5 display a low-energy emission with lambda(max) at 558-634 nm in both solid state and in dichloromethane at 298 K. The former is assigned to the (3)[5dsigma*6psigma] excited state of [Au(3)(dcmp)(2)](3+), whereas the latter is attributed to an exciplex formed between the (3)[5dsigma*6psigma] excited state of [Au(3)(dcmp)(2)](3+) and the counterions. In solid state, complex [Ag(3)(dcmp)(2)][ClO(4)](3) (6) displays an intense emission band at 375 nm with a Stokes shift of approximately 7200 cm(-1) from the (1)[4dsigma*-->5psigma] absorption band at 295 nm. The 375 nm emission band is assigned to the emission directly from the (3)[4dsigma(*)5psigma] excited state of 6. Density functional theory (DFT) calculations revealed that the absorption and emission energies are inversely proportional to the number of metal ions (n) in polynuclear Au(I) and Ag(I) linear chain complexes without close metalanion contacts. The emission energies are extrapolated to be 715 and 446 nm for the infinite linear Au(I) and Ag(I) chains, respectively, at metalmetal distances of about 2.93-3.02 A. A QM/MM calculation on the model [Au(3)(dcmp)(2)Cl(2)](+) system, with Au...Cl contacts of 2.90-3.10 A, gave optimized Au...Au distances of 2.99-3.11 A in its lowest triplet excited state and the emission energies were calculated to be at approximately 600-690 nm, which are assigned to a three-coordinate Au(I) site with its spectroscopic properties affected by Au(I)...Au(I) interactions.

Structures and photoluminescence of dinuclear platinum(II) and palladium(II) complexes with bridging thiolates and 2,2′-bipyridine or 2,2′∶6′,2″-terpyridine ligands

A series of mononuclear and dinuclear platinum(II) thiolates with 2,2′-bipyridine (bpy) and 2,2′∶6′,2″-terpyridine (terpy) ligands having emissive LLCT (ligand-to-ligand charge-transfer) excited states were prepared and characterized by X-ray diffraction analyses. The [M2(dtbpy)2(NS)2][ClO4]2 (Mxa0=xa0Pt or Pd; dtbpyxa0=xa04,4′-di-tert-butyl-2,2′-bipyridine, NS–xa0=xa0pyridine-2-thiolate) complexes are isostructural to each other with intramolecular Pt·xa0·xa0·Pt and Pd·xa0·xa0·Pd distances being 2.917(2) and 2.891(4) A, respectively. Assignment of LLCT absorption bands for the platinum(II) complexes was based on the shift in absorption energy with the substituents on the diimine and thiolate ligands. In the solid state or in solution at room temperature the platinum(II) complexes show photoluminescence with λmax ranging from 603 to 710 nm. The PtII·xa0·xa0·PtII and/or ligand–ligand interactions are not primarily responsible for the emissions of the dinuclear platinum(II) thiolates which have intramolecular metal–metal separations greater than 2.9 A.

A BLUE ELECTROLUMINESCENT MOLECULAR DEVICE FROM A TETRANUCLUEAR ZINC(II) COMPOUND ZN4O(AID)6 (AID = 7-AZAINDOLATE)

A tetranuclear zinc(II) compound with 7-azaindolate (AID) as a bridging ligand exhibits an intense blue emission at 425 nm with a quantum yield of 0.21 in acetonitrile solution at room temperature; a blue-light emitting diode based on the Zn(II) complex as the active emitting layer attains an EL efficiency of 0.25% and brightness of 88 cd m–2 at 7.1 V driving voltage with current density of 10 mA cm–2.

Structure and spectroscopic properties of luminescent cyclometalated platinum(II) complexes with chiral phosphine substituted carbohydrate ligands

A series of new chiral cyclometalated platinum(II) complexes containing carbohydrate phosphine ligands have been prepared. The reaction of [Pt(ppy)Cl]2 (Hppyxa0=xa02-phenylpyridine) with the chiral phosphines n-Hmbpa (methyl 4,6-O-benzylidene-n-deoxy-n-(diphenylphosphino)-α-D-altropyranoside, nxa0=xa02 or 3) afforded cis-[Pt(ppy)(n-Hmbpa)Cl] (nxa0=xa02 2a or 3 2b) in high yields. Treatment of 2a or 2b with an excess of NaOCH3 gave the alkoxoplatinum(II) complexes trans-[Pt(ppy)(n-mbpa)] (nxa0=xa02 3a or 3 3b). The crystal structure of 3b shows that the phosphorus atom is located trans to the nitrogen atom of the ppy ligand and the pyranose ring is in a boat conformation. Moderately intense UV-vis absorption bands assigned to metal-to-ligand charge-transfer (MLCT) transitions are shifted from ca. 376–382 to ca. 414–416 nm when the chloride ligand is substituted by the pendant alkoxide group. In solid state and 77 K MeOH–EtOH (4∶1) glass solution, complexes 2 and 3 show a vibronic structured emission in the range 450–650 nm. Complex 2 is non-emissive in fluid solution at room temperature whereas 3 shows a long-lived 3MLCT emission in both CH3CN and CH2Cl2 at room temperature.