Steven C. F. Kui

Semiconducting and electroluminescent nanowires self-assembled from organoplatinum(II) complexes

Organometallic nanowires with luminescent and current‐modulating properties were self‐assembled from cyclometalated/terpyridyl platinum(II) complexes with auxiliary arylisocyanide/arylacetylide ligands and incorporated into a compact organic light‐emitting field‐effect transistor (see picture) by solution‐processable protocols. The nanowires exhibit both electron and hole mobilities of 0.1 cm2 V−1 s−1.

Robust Phosphorescent Platinum(II) Complexes Containing Tetradentate O^N^C^N Ligands: Excimeric Excited State and Application in Organic White‐Light‐Emitting Diodes

The bright white lights: A series of highly robust platinum(II) complexes supported by tetradentate O N C N ligands with high emission quantum yields (0.72-0.93) and high T(d) (>400 °C) have been synthesized. Among the complexes, that shown in the figure has strong excimer emission attributed to the monomer triplet excited state with a localized structure. The application of this low band-gap material on single-dopant organic or polymer white-light-emitting diodes (WOLED) is highlighted.

Structurally robust phosphorescent [Pt(O^N^C^N)] emitters for high performance organic light-emitting devices with power efficiency up to 126 lm W−1 and external quantum efficiency over 20%

A series of robust, bulky and strongly emissive platinum(II) complexes supported by tetradentate O^N^C^N ligands with tert-butyl groups (1–4), a bridging tertiary amine (5) or a biphenyl group with a spiro linkage (6) at the periphery of the [O^N^C^N] ligand scaffold have been prepared. Their photophysical properties were examined by absorption and emission spectroscopy, density functional theory calculations, and ultra-fast time-resolved emission measurements. These complexes display emission quantum yields of up to 95%, with emission maxima λmax in the range of 522 to 570 nm, and have a good thermal stability of up to Td > 423 °C. Notably, the kq values of 4–6 are in the range of 8.5 × 106 to 2.0 × 107 mol−1 dm3 s−1, smaller than those (∼108 to 109 mol−1 dm3 s−1) of other reported Pt(II) complexes. The bulky groups at the periphery of the [O^N^C^N] ligand disfavour intermolecular interactions and hence excimer formation in solutions. These complexes are good light-emitting materials (dopants) for OLEDs, since the triplet–triplet annihilation (TTA) and concentration quenching effect arising from intermolecular interactions can be minimized even at a high dopant concentration. The efficiency of the devices fabricated with 4–6 increased with dopant concentration up to a high level of 10% with no extra emitting component or significant shift in the CIE observed. The maximum power efficiency (PE) values achieved for the 5 (yellow-emitting) and 6 (green-emitting) based devices were 118 and 126 lm W−1, respectively. These PE values are the highest among the reported Pt(II)-OLEDs and comparable to those of the best reported Ir(III)-OLEDs without the out-coupling technique. Complex 7 is structurally analogous to, but less bulky than 3–6 and is prone to giving excimer emission in the solid state. A high PE of up to 55.5 lm W−1 and external quantum efficiency of up to 25.1% have been realized in the white OLEDs fabricated with 7 as a single emitting material. These values are comparable with those of the best reported WOLEDs based on a single emitting material.

High‐Efficiency Polymer Light‐Emitting Devices with Robust Phosphorescent Platinum(II) Emitters Containing Tetradentate Dianionic O∧N∧C∧N Ligands

[Pt(O(∧) N(∧) C(∧) N)]-type complexes are used as single emitters in solution-processed PLEDs with maximum EQEs of 15.55% for green and 12.73% for white devices, which are the highest values ever achieved for PLEDs based on Pt(ii) complexes.

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.

Anticancer gold(I)–phosphine complexes as potent autophagy-inducing agents

A panel of anticancer gold(I)-phosphine complexes exhibit significant autophagy-inducing properties in cancer cells.

Spectacular luminescent behaviour of tandem terpyridyl platinum(II) acetylide complexes attributed to solvent effect on ordering of excited states, “ion-pair” formation and molecular conformations

A series of oligomeric tandem terpyridyl platinum(II) complexes, namely [(tBu3tpy)Pt(CCtpy)PtCl](OTf)2 (3), [(tBu3tpy)Pt(CCtpy)PtCCtBu](OTf)2 (4), [(tBu3tpy)Pt(CCtpy)PtCCtpy](OTf)2 (5), and [(tBu3tpy)Pt(CCtpy)Pt(CCtpy)PtCl](OTf)3 (6), were prepared and their spectroscopic properties and self-aggregating behaviour were examined. In particular, complex 4 exhibits unusually higher emission quantum yield in CH2Cl2 (ϕ = 0.43) than that in CH3CN (ϕ < 0.1), which is attributed to the formation of a “contact ion pair” in chlorinated solvents, such as CHCl3, CH2Cl2 and C6H5Cl. DFT calculations revealed that both intersystem crossing (ISC) and radiative decay of this complex are less effective in CH3CN than in CH2Cl2, thus accounting for the low emission quantum yield in CH3CN.

High-efficiency orange and yellow organic light-emitting devices using platinum(II) complexes containing extended π-conjugated cyclometalated ligands as dopant materials

Two luminescent platinum(II) complexes 1 and 2 containing extended π-conjugated cyclometalated ligands have been used as dopant materials for the construction of two high-efficiency organic light-emitting devices I and II. Device I (containing dopant 1) emits orange emission and exhibits a maximum external quantum efficiency of 12.4%, a maximum luminous efficiency of 32.3cd∕A, and a maximum power efficiency of 11.2lm∕W. Device II (containing dopant 2) emits yellow light and exhibits a maximum external quantum efficiency of 16.1%, a maximum luminous efficiency of 51.8cd∕A, and a maximum power efficiency of 23.2lm∕W.

Self-Assembly of a Cyclic Metalladecapyridine from the Reaction of 2,6-Bis(bis(2-pyridyl)methoxymethane)pyridine with Silver(I)

Reaction of Ag( p-MeC 6H 4SO 3) with 2,6-bis(bis(2-pyridyl)methoxymethane)pyridine (PY5) in CH 2Cl 2 gave [Ag (I) 2(PY5) 2](p-MeC 6H 4SO 3) 2 (1). Treatment of 2,6-bis(bis(2-pyridyl)hydroxymethane)pyridine (PY5-OH) with AgNO 3 in MeOH gave [Ag (I) 2(PY5-OH) 2](NO3) 2 (2); in the presence of PPh 3, this reaction afforded [Ag (I)(PY5-OH)(PPh 3)]NO 3 (3). The structures of 1- 3 have been determined by X-ray crystal analysis, revealing four-coordinate Ag (I) ions in these complexes. Both 1 and 2 feature a quadruply branched 28-membered C 16N 10M 2 metallamacrocycle fused to 10 pyridyl groups. On the basis of (1)H NMR measurements, the dinuclear 1 and 2 dissociate into a mononuclear complex upon dissolving in MeCN but in MeOH an equilibrium between the mono- and dinuclear species can be detected.

Phosphorescent Platinum(II) Complexes for White Organic Light-Emitting Diode Applications

The applications of phosphorescent platinum(II) complexes in white organic light-emitting diode (WOLED) are discussed. White electroluminescence formed by complementary colors mixing has been achieved by employing phosphorescent platinum(II) complexes as dopants. The approach is to mix triplet monomer emissions of the platinum(II) dopant complexes at orange-red region with a blue-emitting component or, alternatively, to mix the emissions from both monomer and aggregate states of the same platinum(II) complex in the blue-green (λ max~480nm) and orange-red (λ max~600nm) regions. Platinum(II) material-based WOLEDs could be fabricated from both thermal deposition and solution process, since polymeric WOLED materials could be prepared by incorporating platinum(II) complexes in polymer backbone. The WOLEDs fabricated from platinum(II) complexes exhibit good Commission Internationale de l’Eclairage, color-rendering index, and device efficiency, which may find potential applications for solid-state lighting.