A new class of small gold nanoclusters with molecular characteristics has been constructed using 1,1′-bis(diphenylphosphino)ferrocene (dppf) as the stabilizing ligand. The identities of the small gold nanoclusters have been fully characterized by NMR, electrospray ionization mass spectrometry, elemental analysis, and single-crystal X-ray diffraction analysis. Octa- and undecagold clusters are found to display different UV-vis absorption behavior. The ligation of the bidentate ligands and halides or pseudohalides has resulted in the symmetry breaking of these nanoclusters with C symmetry. The small gold nanoclusters with different coordinating halides or pseudohalides show distinct reactivities and stabilities in ligand/anion exchange experiments. The current research has provided insights into the origin of chirality in the diphosphine-stabilized small gold nanoclusters.

Yao Liao-Yuan    任咏华    

Journal of the American Chemical Society

2016

This chapter highlights the importance of structure-property relationships in transition metal complexes for the construction of molecular-and supramolecular-based photofunctional materials and summarizes the recent advancements of this class of complexes with potential applications in the areas of energy, catalysis, materials, biology, and diagnostics.

Wong Hok-Lai    Yeung Margaret Ching-Lam    任咏华    

Structure and Bonding

2016

Au-Yeung Ho-Leung    Leung Sammual Yu-Lut    Anthony yiu yan Tam    任咏华    

Journal of the American Chemical Society

2015

A series of dithienylethene-containing triarylboranes has been designed, synthesized, and characterized. The electrochemistry, photophysics, and photochromic behavior have also been studied. The photophysical and photochromic properties could be facilely tuned in this system by varying the thiophene spacers (thiophene, thienothiophene, and bithiophene) between the dithienylethene and the dimesitylboron (BMes) or the position of the BMes substitution in the thiophene spacers. The absorption of closed form has been found to be more sensitive towards the structural modification upon incorporation of the BMes unit. Moreover, multi-addressable photochromic reactivity is obtained upon addition of Lewis base (F), which is due to the formation of boron-Lewis base adduct. The dependence of the photophysical and photochromic properties on the thiophene spacers and the position of the BMes substitution has been further supported by computational studies.

Poon Chun-Ting    Wai han Lam    Wong Hok-Lai    任咏华    

Chemistry - A European Journal

2015

A series of multiaddressable platinum(II) molecular rectangles with different rigidities and cavity sizes has been synthesized by endcapping the U-shaped diplatinum(II) terpyridine moiety with various bisalkynyl ligands. The studies of the host-guest association with various square planar platinum(II), palladium(II), and gold(III) complexes and the related low-dimensional gold(I) complexes, most of which are potential anticancer therapeutics, have been performed. Excellent guest confinement and selectivity of the rectangular architecture have been shown. Introduction of pH-responsive functionalities to the ligand backbone generates multifunctional molecular rectangles that exhibit reversible guest release and capture on the addition of acids and bases, indicating their potential in controlled therapeutics delivery on pH modulation. The reversible host-guest interactions are found to be strongly perturbed by metal-metal and π-π interactions and to a certain extent, electrostatic interactions, giving rise to various spectroscopic changes depending on the nature of the guest molecules. Their binding mode and thermodynamic parameters have been determined by 2D NMR and van't Hoff analysis and supported by computational study.

Chan Alan Kwun-Wa    Wai han Lam    Tanaka Yuya    Wong Keith Man-Chung    任咏华    

Proceedings of the National Academy of Sciences of the United States of America

2015

A series of luminescent polynuclear alkynylgold(I) complexes with different lengths of alkyl chains attached at the N-heterocyclic carbene moieties has been synthesised and demonstrated to display intriguing self-assembly behaviours through a cooperative growth mechanism. Variation of the alkyl chain length was found to cause drastic morphological differences in the aggregates and to strongly affect the thermodynamic parameters as revealed by the nucleation-elongation model. Turnover a new leaf: A series of luminescent non-amphiphilic polynuclear alkynylgold(I) complexes has been synthesised and demonstrated to undergo self-assembly in a THF-water mixture through a cooperative growth mechanism. Simple modifications of the alkyl chain length were found to cause drastic morphological differences in the aggregates and to strongly affect the thermodynamic parameters of the self-assembly process (see figure).

Hong Eugene Yau-Hin    Wong Hok-Lai    任咏华    

Chemistry - A European Journal

2015

A series of dithienylethene-containing phosphole derivatives has been designed, synthesized and characterized. One of the compounds has been characterized by X-ray crystallography. Upon photoexcitation, the compounds exhibit drastic color changes, ascribed to the reversible photochromic behavior. Their photochromic, photophysical and electrochemical properties have been studied. They show photochromic reactivities with high photocyclization quantum yields. Their photophysical and photochromic properties are found to be facilely tuned in this system by substitution at the phosphole backbone, as well as variation on the extent of π-conjugation of the phosphole backbone. Some selected compounds have been demonstrated to exhibit photochromic properties in polymethylmethacrylate (PMMA) films.

Chan Jacky Chi-Hung    Wong Hok-Lai    Wing tak Wong    任咏华    

Chemistry - A European Journal

2015

A urea-containing, (Ph2P(R)PPh2)-bridged, dinuclear, gold(I) thiolate complex, [Au2{Ph2PN(C6H4OMe-4)PPh2}(SC6H4NHCONHC6H5)2] (1) was designed and synthesized and its photophysical and anion recognition properties studied. The results show that 1 has a high selectivity toward F^-. Upon addition of F^-, the yellow solution was decolorized, and drastic changes of emission and ¹H and ³¹P{¹H} NMR signals were observed. Interestingly, these changes are attributed to fluoride-assisted P-N bond hydrolysis, instead of the expected hydrogen-bonding interactions with the urea receptor. Similar changes were observed for two other basic anions, AcO^- and H2PO4^-, but to a much lesser extent; and these anions were found to bind to the urea receptor at the same time. On the other hand, Cl^- was found to only bind to the urea moiety through hydrogen-bonding interactions. Further studies with the control complex [Au2{Ph2PN(C6H4OMe-4)PPh2}Cl2] (2) indicate that F^- assists the hydrolysis process via cleavage of the P-N bond. DFT calculations were performed to study the reaction mechanism for the fluoride-assisted P-N bond hydrolysis of 2; these provide a better insight into the role of fluoride in the hydrolysis.

He Xiaoming    Wai han Lam    Cheng Eddie Chung-Chin    任咏华    

Chemistry - A European Journal

2015

A series of tetrakis(isocyano)rhodium(I) complexes with different chain lengths of alkyl substituents has been found to exhibit a strong tendency toward solution state aggregation upon altering the concentration, temperature and solvent composition. Temperature- and solvent-dependent UV-vis absorption studies have been performed, and the data have been analyzed using the aggregation model to elucidate the growth mechanism. The aggregation is found to involve extensive Rh(I)···Rh(I) interactions that are synergistically assisted by hydrophobic-hydrophobic interactions to give a rainbow array of solution aggregate colors. It is noted that the presence of three long alkyl substituents is crucial for the observed cooperativity in the aggregation. Molecular assemblies in the form of nanoplates and nanovesicles have been observed in the hexane-dichloromethane solvent mixtures, arising from the different formation mechanisms based on the alkyl chain length of the complexes. Benzo-15-crown-5 moieties have been incorporated for selective potassium ion binding to induce dimer formation and drastic color changes, rendering the system as potential colorimetric and luminescent cation sensors and as building blocks for ion-controlled supramolecular assembly.

Chan Alan Kwun-Wa    Wong Keith Man-Chung    任咏华    

Journal of the American Chemical Society

2015

Other than traditional cation detection strategies, which are solely based on the ion-receptor complementarity, the extension of the concept of supramolecular chemistry and the mechanisms of irreversible analyte-specific reactions have also been integrated into the design of luminescent probes for the detection of cation in view of the exploration of highly sensitive and selective sensors. In this highlight, a versatile range of organic and organometallic architectures with cation-sensing capabilities based on the above mechanisms will be discussed.

Yeung Margaret Ching-Lam    任咏华    

Chemical Society Reviews

2015