The self-assembly of triazine-containing alkynylplatinum(ii) terpyridine complexes has revealed the formation of sophisticated helical ribbons. Fine control of the morphological transition from plates to helical structures has been demonstrated through an interplay of the bent molecular structure and Pt⋯Pt, π-π stacking and hydrophobic-hydrophobic interactions.

Fu Heidi Li-Ki    Leung Sammual Yu-Lut    任咏华    

Chemical Communications

2017

A series of platinum(II) terpyridine complexes with tetraphenylethylene-modified alkynyl ligands has been designed and synthesized. The introduction of the tetraphenylethylene motif has led to aggregation-induced emission (AIE) properties, which upon self-assembly led to the formation of metal-metal-to-ligand charge transfer (MMLCT) behavior stabilized by Pt···Pt and/or π-π interactions. Tuning the steric bulk or hydrophilicity through molecular engineering of the platinum(II) complexes has been found to alter their spectroscopic properties and result in interesting superstructures (including nanorods, nanospheres, nanowires, and nanoleaves) in the self-assembly process. The eye-catching color and emission changes upon varying the solvent compositions may have potential applications in chemosensing materials for the detection of microenvironment changes. Furthermore, the importance of the directional Pt···Pt and/or π-π interactions on the construction of distinctive superstructures has also been examined by UV-vis absorption and emission spectroscopy and transmission electron microscopy. This work represents the interplay of both inter- and intramolecular interactions as well as the energies of the two different chromophoric/luminophoric systems that may open up a new route for the development of platinum(II)-AIE hybrids as functional materials.

Cheng Heung-Kiu    Yeung Margaret Ching-Lam    任咏华    

ACS Applied Materials and Interfaces

2017

A water-soluble anionic alkynylplatinum(II) 2,6-bis(benzimidazol-2′-yl)pyridine (bzimpy) complex has been strategically designed and synthesized to show supramolecular self-assembly with cationic arginine-rich peptides through unique noncovalent Pt(II)⋯Pt(II) and π-π stacking interactions. Upon introduction of trypsin, the arginine-rich peptides can be hydrolyzed into small fragments and deaggregation of the platinum(II) complex molecules is observed. The aggregation-deaggregation process has been probed by UV-vis absorption, emission, and resonance light scattering (RLS) studies. This platinum(II) complex has been employed for developing a new, continuous and label-free luminescence assay for trypsin as well as for inhibitor screening, and has been successfully applied to detect trypsin in diluted serum solutions.

Law Angela Sin Yee    Yeung Margaret Ching-Lam    任咏华    

ACS Applied Materials and Interfaces

2017

A new family of cationic dinuclear cyclometalated Pt(II) complexes containing an organometallic assembling ligand has been reported. The general formulas for these compounds is as follow: [R-(NCN)Pt - L-L - Pt(NCN)-R][X], where L-L = [Cp∗Ir-p-(η-CHS)], R = H, X = OTf (5); R= CF-, X = OTf (6a), SbF (6b); L-L = [Cp∗Ir-p-(η-CHSe)] R= CF-, X = OTf (7a), SbF (7b). In these coordination assemblies two cyclometalated R-(NCN)Pt moieties are held by either η-dithio-p-benzoquinone complex [Cp∗Ir-p-(η-CHS)] (3) or η-diseleno-p-benzoquinone complex [Cp∗Ir-p-(η-CHSe)] (4). The molecular structures of the known complex [4-CF-(NCN)PtCl] as well as two compounds of the above family [(NCN)Pt-Cp∗Ir-p-(η-CHS) - Pt(NCN)][CFSO] (5) and [CF-(NCN)Pt - Cp∗Ir-p-(η-CHS) - Pt(NCN)-CF][CFSO] (6a) were ascertained by single crystal X-ray diffraction study and confirmed the formation of the target molecules. The solid-state packing of 5 and 6a confirms the presence π-π and short Pt···Pt interactions among individual units providing 1D supramolecular chains. To our knowledge, these are the only known examples where two cyclometalated Pt(NCN) units are assembled by a bridging ligand (vide infra). All compounds show phosphorescence in the bluish-green region (486-521 nm) in the solution at room temperature and exhibit higher luminescence quantum yields relative to the analogous compounds containing a Pt(terpy) chromophore in thin film.

Sesolis Hugo    Chan Carmen Ka Man    Geoffrey Gontard    Fu Heidi Li-Ki    任咏华     Amouri   

Organometallics

2017

The end-to-end aggregation of gold nanorods (GNRs) has been demonstrated to be directed by a thioacetate-containing alkynylplatinum(II) terpyridine complex. The in situ deprotected complex is preferentially attached at the ends of the gold nanorods (GNRs) and induce the aggregation of GNRs in an end-to-end manner by Pt···Pt and interactions, which have been characterized by electron microscopy, energy dispersed X-ray (EDX) analysis, and UV-vis absorption spectroscopy. The assembly of the nanorods into chain-like nanostructures can be controlled by the concentration of the Pt(II) complexes.

Leung Frankie Chi-Ming    Leung Sammual Yu-Lut    Chung Clive Yik-Sham    任咏华    

Journal of the American Chemical Society

2016

By employing chiral precursors, a new class of chiral gold(I)-sulfido clusters with unique structures has been constructed. Interestingly, pure enantiomers of the precursors are found to self-Assemble into chiral hexa-and decanuclear clusters sequentially, while a racemic mixture of them has resulted in heterochiral self-sorting of an achiral meso decanuclear cluster. Chirality has determined not only the symmetry and structures but also the photophysical behaviors of these clusters. The racemic mixture of decanuclear clusters undergoes rearrangement and heterochiral self-sorting to give a meso decanuclear cluster. The thermodynamic-driven heterochiral self-sorting of gold(I) clusters provides a means to develop controlled self-Assembly that may be of relevance to the understanding of chirality in nature.

Yao Liao-Yuan    Lee Terence Kwok-Ming    任咏华    

Journal of the American Chemical Society

2016

A series of dithienylethene-containing boron(III) ketoiminates, as well as their corresponding β-ketoimine ligands, have been synthesized and characterized. The photophysical, electrochemical, and photochromic properties of the compounds have been studied. Photocyclization has been found to be suppressed upon introduction of a phenyl substituent on the nitrogen atom of the β-ketoiminate core, whereas photochromism could be observed by replacement of the phenyl substituent with a bulky mesityl group. It is believed that the steric effect of the mesityl unit restricts molecular rotation, resulting in such a prominent difference in the photochromic properties.

Wong Cheok-Lam    Poon Chun-Ting    任咏华    

Chemistry - A European Journal

2016

The straightforward synthesis of a new Cu(i) metal-rich small metallacycle is presented. This compound is luminescent in the solid state with an emission quantum yield of 72% at room temperature and displays a pronounced reversible red-shift of its emission spectra upon cooling. Quantum chemical calculations reveal that these properties are governed by important geometrical relaxations that imply the formation of cuprophilic interactions at the excited states.

El Sayed Moussa Mehdi    Evariste Sloane    Wong Hok-Lai    Le Bras    Roiland    Le Pollès Laurent    Boris Le Guennic    Costuas Karine    任咏华     Lescop Christophe   

Chemical Communications

2016

A novel class of chiral luminescent square-planar platinum complexes with a π-bonded chiral thioquinonoid ligand is described. Remarkably the presence of this chiral organometallic ligand controls the aggregation of this square planar luminophor and imposes a homo- or hetero-chiral arrangement at the supramolecular level, displaying non-covalent Pt-Pt and π-π interactions. Interestingly these complexes are highly luminescent in the crystalline state and their photophysical properties can be traced to their aggregation in the solid state. A TD-DFT calculation is obtained to rationalize this unique behavior.

Sesolis Hugo    Dubarle-Offner Julien    Chan Carmen Ka Man    Puig Emmanuel    Geoffrey Gontard    Winter Pierre    Cooksy Andrew L.    任咏华     Amouri   

Chemistry - A European Journal

2016

A new series of cyclometalated platinum(II) complexes of N^C^N ligands, where N^C^N = 1,3-bis(1-n-alkylpyrazol-3-yl)benzene (bpzb), namely, [Pt(bpzb)Cl] (1 and 2) and [Pt(bpzb)(C≡C-R)] (3-10) (R = CH, CH-OCH-p, CH-NO-p, CH-NH-p, 4-cholesteryl phenyl carbamate, and cholesteryl methylcarbamate) were synthesized and characterized. Their electrochemical and photophysical properties were investigated. Two of the platinum(II) complexes were also structurally characterized by X-ray crystallography, and short intermolecular C-H···Pt contacts were observed. Vibronic-structured emission bands originating from triplet IL (IL) excited states of the bpzb ligands with mixing of some MLCT [dπ(Pt)→π∗(bpzb)] character were observed in solution state. Interestingly, complex 5 shows a low-energy emission that is derived from the involvement of the p-nitrophenylethynyl ligand. Complex 9 with hydrophobic cholesteryl 4-ethynylphenyl carbamate ligand was found to form stable metallogels in several organic solvents, which are responsive to mechanical sonication and thermal stimuli and show circular dichroism activity.

Ai Ye-Ye    Li Yongguang    Ma Huiqing    Chengyong Su    任咏华    

Inorganic Chemistry

2016