Chi-Fai Leung

Synthesis and antitumor activity of a series of osmium(VI) nitrido complexes bearing quinolinolato ligands

A series of osmium(VI) nitrido complexes supported by quinolinolato ligands have been prepared and they exhibit promising in vitro anti-cancer activities. These results establish that Os(VI)≡N is a potentially versatile and promising platform for the design of a variety of high-valent anti-cancer drugs.

A recyclable polymer-supported ruthenium catalyst for the oxidative degradation of bisphenol A in water using hydrogen peroxide

A polypyridyl ruthenium(II) complex, cis-[RuII(2,9-Me2phen)2(H2O)2]2+, has been adsorbed onto the cation-exchange resins Dowex-50W and Chelex-100. The potential use of the supported ruthenium(II) complex as catalyst for the oxidative degradation of organic pollutants in water has been investigated using bisphenol A, an emerging endocrine disruptor, as substrate; and the environmentally friendly H2O2 as oxidant. These solid-supported catalysts are found to be efficient for the degradation of bisphenol A in aqueous solution by H2O2 under ambient conditions. The intermediates and products formed during the oxidative degradation of bisphenol A by these catalytic systems have been identified and a mechanism is proposed. The supported catalysts are easily recovered by simple filtration and display no loss of activity when recycled.

Photocatalytic Conversion of CO2 to CO by a Copper(II) Quaterpyridine Complex

The invention of efficient systems for the photocatalytic reduction of CO2 comprising earth-abundant metal catalysts is a promising approach for the production of solar fuels. One bottleneck is to design highly selective and robust molecular complexes that are able to transform the CO2 gas. The CuII quaterpyridine complex [Cu(qpy)]2+ (1) is found to be a highly efficient and selective catalyst for visible-light driven CO2 reduction in CH3 CN using [Ru(bpy)3 ]2+ (bpy: bipyridine) as photosensitizer and BIH/TEOA (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole/triethanolamine) as sacrificial reductant. The photocatalytic reaction is greatly enhanced by the presence of H2 O (1-4 % v/v), and a turnover number of >12 400 for CO production can be achieved with 97 % selectivity, which is among the highest of molecular 3d CO2 reduction catalysts. Results from Hg poisoning and dynamic light scattering experiments suggest that this photocatalyst is homogenous. To the best of our knowledge, 1 is the first example of molecular Cu-based catalyst for the photoreduction of CO2 .

Luminescence behaviour of Pb2+-based cage-containing and channel-containing porous coordination polymers

Luminescent porous coordination polymers, cage-containing chains [Pb5(L1)6(N3)2(OH)2]n (1) and 1-D double helical chains [Pb(L2)(N3)]n (2) with 1-D channels were prepared by solvothermal reactions. These polymers can take up metal ions and induce different luminescence responses depending on the metal ions.

Addition of [CH(CN)2]− and [TCNE]˙− to RuVIN bearing 8-quinolinolato ligands

Reaction of Ru(VI)≡N complexes bearing 8-quinolinolato ligands with NCCH(2)CN/piperidine and NaTCNE afford novel ruthenium(ii) dicyanoimine and diimine/imino-oxazolone complexes, respectively.

Efficient photocatalytic water reduction by a cobalt(II) tripodal iminopyridine complex

The visible light-driven catalytic water reduction by a cobalt(II) tripodal iminopyridine complex [Co(tachpy3)](ClO4)2 (1) (tachpy3 = cis,cis-1,3,5-tris(pyridine-2-carboxaldimino)-cyclohexane) has been investigated in aqueous acetonitrile. The catalysis is found to be homogeneous and an impressive H2 TON of 16 440 has been achieved, which is far better than that by a structurally related complex [Co(trenpy3)](ClO4)2 (2) (trenpy3 = tris-[4-(2-pyridyl)-3-azabut-3-enyl]amine) bearing identical donor groups. A comparison between the two complexes reveals that the catalytic properties are sensitive to the change in ligand rigidity and thus the coordination geometry, as reflected by their respective reaction potentials and H2 TONs. The catalysis of 1 proceeds via a penta-coordinate species formed by the protonation of the corresponding CoI state. The results in spectroscopic and electrochemical studies are supplemented by DFT computation.

Synthesis, structures and photophysical properties of luminescent cyanoruthenate(II) complexes with hydroxylated bipyridine and phenanthroline ligands

Treatment of (PPh4)2[RuII(PPh3)2(CN)4] (1) with bpyOH and phenOH in DMF afforded two mononuclear compounds fac-(PPh4)[RuII(bpyOH)(PPh3)(CN)3] (2) and fac-(PPh4)[RuII(phenOH)(PPh3)(CN)3] (3), respectively (bpyOH = 6-hydroxy-2,2′-bipyridine; phenOH = 2-hydroxy-1,10-phenanthroline). These complexes have been characterized by various spectroscopic techniques. The structures of 1 and 2 have also been determined by X-ray crystallography. Their photophysical and electrochemical properties have been investigated. Compound 3 displays intense emission with much higher quantum efficiency (Φem = 19.4%) in solution, compared with other related ruthenate(II) diimine complexes. In addition, their solvatochromism, pH effects, and ion perturbation have also been investigated. The different photoluminescent behaviors between these complexes and the previously reported complex [RuII(phen)(PPh3)(CN)3]− suggest that the introduction of the hydroxyl group into the diimine ligand would significantly affect their emission properties. Through spectrophotometric titrations, the ground state pKa and excited state pKa* values, as well as the dynamic pH response ranges of these complexes have been determined. Their photophysical response towards various metal ions have also been studied.

First-principles calculations and re-analysis of optical spectra and electron paramagnetic resonance parameters for Yb3+ in YAl3(BO3)4 crystal

Abstract In this paper, the energy levels of Yb 3+ ions in yttrium aluminum borate (YAB) crystal were calculated from a first-principles approach with an optimized defect structure obtained from the WIEN2k package and a traditional fitting method using a more reliable computer package. The calculated results were then compared with those obtained from a re-calculation using the values of parameters given by some previous researchers. Three types of likely mistakes in the previous researchers paper, namely over fitting, incorrect use of irreducible representation, and errors in the calculations for the EPR parameters were clearly identified and effectively rectified in this paper. The electron paramagnetic resonance (EPR) parameters, which included g factors like g // and g ⊥ and hyperfine structure constants A // and A ⊥ , were also calculated through the perturbation method and compared with some observed values available in literature. There was reasonable agreement found with the experimental values which lay between the values obtained from the first-principles calculation ( g // =4.000 and g ⊥ =1.391; A // =1032 and A ⊥ =360 in 10 −4 cm −1 for 171 Yb 3+ ) and those from the fitting approach ( g // =3.612 and g ⊥ =1.702; A // =867 and A ⊥ =470 in 10 −4 cm −1 for 171 Yb 3+ ).

CCDC 1498291: Experimental Crystal Structure Determination

Related Article: Lin-Li Hu, Chang Shen, Wing-Kin Chu, Jing Xiang, Fei Yu, Ge Xiang, Yan Nie, Chun-Leung Kwok, Chi-Fai Leung, Chi-Chiu Ko|2017|Polyhedron|127|203|doi:10.1016/j.poly.2017.01.046