Kam-Hung Low

Strongly Luminescent Gold(III) Complexes with Long‐Lived Excited States: High Emission Quantum Yields, Energy Up‐Conversion, and Nonlinear Optical Properties

Strongly Luminescent Gold(III) Complexes with Long-Lived Excited States: High Emission Quantum Yields, Energy Up-Conversion, and Nonlinear Optical Properties Photochemistry : A series of emissive gold(III) complexes with fluorene-containing cyclometalating ligands exhibits strong phosphorescence and long-lived excited states with emission quantum yields and lifetimes up to 58 % and 305 ms, respectively. These complexes can sensitize energy up-conversion of 9,10-diphenylanthracene (DPA; see picture) and display rich two-photon absorption properties (TPA; TTA = triplet–triplet annihilation). Angewandte Chemie

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.

A Binuclear Gold(I) Complex with Mixed Bridging Diphosphine and Bis(N-Heterocyclic Carbene) Ligands Shows Favorable Thiol Reactivity and Inhibits Tumor Growth and Angiogenesis In Vivo†

In the design of anticancer gold(I) complexes with high in vivo efficacy, tuning the thiol reactivity to achieve stability towards blood thiols yet maintaining the thiol reactivity to target cellular thioredoxin reductase (TrxR) is of pivotal importance. Herein we describe a dinuclear gold(I) complex (1-PF6) utilizing a bridging bis(N-heterocyclic carbene) ligand to attain thiol stability and a diphosphine ligand to keep appropriate thiol reactivity. Complex 1-PF6 displays a favorable stability that allows it to inhibit TrxR activity without being attacked by blood thiols. In vivo studies reveal that 1-PF6 significantly inhibits tumor growth in mice bearing HeLa xenograft and mice bearing highly aggressive mouse B16-F10 melanoma. It inhibits angiogenesis in tumor models and inhibits sphere formation of cancer stem cells in vitro. Toxicology studies indicate that 1-PF6 does not show systemic anaphylaxis on guinea pigs and localized irritation on rabbits.

Dirhodium Carboxylates Catalyzed Enantioselective Coupling Reactions of α-Diazophosphonates, Anilines, and Electron-Deficient Aldehydes

Chiral dirhodium carboxylate complexes ([Rh(2)(S-PTAD)(4)] or [Rh(2)(S-PTTL)(4)]) efficiently catalyze asymmetric three-component coupling reactions of α-diazophosphonates, anilines, and electron-deficient aldehydes to give α-amino-β-hydroxyphosphonates. The high level of enantiocontrol provides evidence for the intermediacy of metal-bound ammonium ylide in the product-forming step.

Bulk heterojunction photovoltaic cells based on tetra-methyl substituted copper(II) phthalocyanine:P3HT:PCBM composite.

Insoluble CuMePc nanocrystals were incorporated into P3HT:PCBM bulk heterojunction photovoltaic cells to increase the carrier mobility and photon harvesting. The P1C1-based (weight ratio of P3HT: CuMePc = 1:1) OPV cell exhibited the best photovoltaic performance with a J(SC) of 16.3 mA cm(-2), V(OC) of 0.58 V, FF of 0.56 and PCE of 5.3%.

Highly conducting two-dimensional copper(I) 4-hydroxythiophenolate network

An unprecedented 2-D Cu-S network is constructed by self-assembly coordination between Cu(I) and 4-hydroxythiophenol and its structure was determined by using powder X-ray diffraction data. The self-assembled coordination network displays ionic behavior with a bulk electrical conductivity value of 120 S cm(-1).

Homoleptic Copper(I) Arylthiolates as a New Class of p‐Type Charge Carriers: Structures and Charge Mobility Studies

Polymeric homoleptic copper(I) arylthiolates [Cu(p-SC(6)H(4)-X)](infinity) (X=CH(3) (1), H (2), CH(3)O (3), tBu (4), CF(3) (5), NO(2) (6), and COOH (7)) have been prepared as insoluble crystalline solids in good yields (75-95 %). Structure determinations by powder X-ray diffraction analysis have revealed that 1-3 and 6 form polymers of infinite chain length, with the copper atoms bridged by arylthiolate ligands. Weak intra-chain pi***pi stacking interactions are present in 1-3, as evidenced by the distances (3.210 A in 1, 3.016 A in 2, 3.401 A in 3) between the mean planes of neighboring phenyl rings. In the structure of 6, the intra-chain pi***pi interactions (d=3.711 A) are insignificant and the chain polymers are associated through weak, non-covalent C-H...O hydrogen-bonding interactions (d=2.586 A). Samples of 1-7 in their polycrystalline forms proved to be thermally stable at 200-300 degrees C; their respective decomposition temperatures are around 100 degrees C higher than that of the aliphatic analogue [Cu(SCH(3))](infinity). Data from in situ variable-temperature X-ray diffractometry measurements indicated that the structures of both 1 and 7 are thermally more robust than that of [Cu(SCH(3))](infinity). TEM analysis revealed that the solid samples of 1-5 and [Cu(SCH(3))](infinity) contained homogeneously dispersed crystalline nanorods with widths of 20-250 nm, whereas smaller plate-like nanocrystals were found for 6 and 7. SAED data showed that the chain polymers of 1-3 and [Cu(SCH(3))](infinity) similarly extend along the long axes of their nanorods. The nanorods of 1-5 and [Cu(SCH(3))](infinity) have been found to exhibit p-type field-effect transistor behavior, with charge mobility (micro) values of 10(-2)-10(-5) cm(2) V(-1) s(-1). Polycrystalline solid samples of 6 and 7 each showed a low charge mobility (<10(-6) cm(2) V(-1) s(-1)). The charge mobility values of field-effect transistors made from crystalline nanorods of 1-3 and [Cu(SCH(3))](infinity) could be correlated with their unique chain-like copper-sulfur networks, with the para-substituent of the arylthiolate ligand influencing the charge-transport properties.

Bis(5,7-dimethyl-8-hydroxyquinolinato)platinum(II) Complex for Efficient Organic Heterojunction Solar Cells

Organic photovoltaic (OPV) cells using metal(II) (Pt, Pd, Cu, and Ni) chelates of 8-hydroxyquinoline (Hq) or 5,7-dimethyl-8-hydroxy-quinoline (HMe(2)q) as an electron donor were fabricated by vacuum deposition. The bis(5,7-dimethyl-8-hydroxyquinolinato)platinum(II) [Pt(Me(2) q)(2)]-based OPVs showed the best performance with an open voltage (V(OC)) of 0.42 V, a short circuit current density (J(SC) ) of 14.8 mA cm(-2) , and a maximum power conversion efficiency (η(P) ) of 2.4%. The X-ray single-crystal structures together with the grazing incidence X-ray diffraction (GIXRD) data of thin film samples reveal that the peripheral methyl substituent(s) and platinum(II) ion are essential for the high degree of film crystallinity resulting in improved performance of the as-fabricated field-effect transistors (FETs) and OPV cells.

From Cluster to Polymer: Ligand Cone Angle Controlled Syntheses and Structures of Copper(I) Alkynyl Complexes.

Copper(I) alkynyl complexes have attracted tremendous attention in structural studies, as luminescent materials, and in catalysis, and homoleptic complexes have been reported to form polymers or large clusters. Herein, six unprecedented structures of Cu(I) alkynyl complexes and a procedure to measure the cone angles of alkynyl ligands based on the crystal structures of these complexes are reported. An increase of the alkynyl cone angle in the complexes leads to a modulation of the structures from polymeric [((PhC≡CC≡C)Cu)2 (NH3 )]∞ , to a large cluster [(TripC≡CC≡C)Cu]20 (MeCN)4 , to a relatively small cluster [(TripC≡C)Cu]8 (Trip=2,4,6-iPr3 -C6 H2 ). The complexes exhibit yellow-to-red phosphorescence at ambient temperature in the solid state and the luminescence behavior of the Cu20 cluster is sensitive to acetonitrile.

Phosphorescent Cyclometalated Iridium(III) Complexes That Contain Substituted 2-Acetylbenzo[b]thiophen-3-olate Ligand for Red Organic Light-Emitting Devices

We report the synthesis of a new class of thermally stable and strongly luminescent cyclometalated iridium(III) complexes 1-6, which contain the 2-acetylbenzo[b]thiophene-3-olate (bt) ligand, and their application in organic light-emitting diodes (OLEDs). These heteroleptic iridium(III) complexes with bt as the ancillary ligand have a decomposition temperature that is 10-20 % higher and lower emission self-quenching constants than those of their corresponding complexes with acetylacetonate (acac). The luminescent color of these iridium(III) complexes could be fine-tuned from orange (e.g., 2-phenyl-6-(trifluoromethyl)benzo[d]thiazole (cf3 bta) for 4) to pure red (e.g., lpt (Hlpt=4-methyl-2-(thiophen-2-yl)quinolone) for 6) by varying the cyclometalating ligands (C-deprotonated C^N). In particular, highly efficient OLEDs based on 6 as dopant (emitter) and 1,3-bis(carbazol-9-yl)benzene (mCP) as host that exhibit stable red emission over a wide range of brightness with CIE chromaticity coordinates of (0.67, 0.33) well matched to the National Television System Committee (NTSC) standard have been fabricated along with an external quantum efficiency (EQE) and current efficiency of 9 % and 10 cd A(-1) , respectively. A further 50 % increase in EQE (>13 %) by replacing mCP with bis[4-(6H-indolo[2,3-b]quinoxalin-6-yl)phenyl]diphenylsilane (BIQS) as host for 6 in the red OLED is demonstrated. The performance of OLEDs fabricated with 6 (i.e., [(lpt)2Ir(bt)]) was comparable to that of the analogous iridium(III) complex that bore acac (i.e., [(lpt)2 Ir(acac)]; 6a in this work) [Adv. Mater.- 2011, 23, 2981] fabricated under similar conditions. By using ntt (Hnnt=3-hydroxynaphtho[2,3-b]thiophen-2-yl)(thiophen-2-yl)methanone) ligand, a substituted derivative of bt, the [(cf3bta)2Ir(ntt)] was prepared and found to display deep red emission at around 700 nm with a quantum yield of 12 % in mCP thin film.