Hong-Ke Liu

Two solvent and temperature dependent copper(II) compounds formed by a flexible ligand: syntheses, structures and SC-SC transformation.

A nonporous neutral framework [CuCl(2)(m-bttmb)(2)](n) (1) was changed into a porous ionic {[Cu(m-bttmb)(2)(H(2)O)Cl]Cl(CH(3)CN)(0.5)(H(2)O)(2.75)}(n) (2) by simply increasing the amount of CH(3)CN in the mixed solvent (CH(3)CN and H(2)O) or temperature in the reactions of CuCl(2)·2H(2)O with 1,3-bis(triazol-1-ylmethyl)-2,4,6-trimethylbenzene (m-bttmb). 1 undergoes transformation into 2 when treated with CH(3)CN. Both 1 and 2 have 2D 4-connected (4,4) network architectures but in different packing arrangements. These compounds have been characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectra and thermogravimetric analysis. This work may provide a way to control the formation of neutral or ionic frameworks, as well as porosities by adjusting the polarity and components of the solvents.

A new strategy to construct metal–organic frameworks with ultrahigh chemical stability

A novel two-dimensional metal–organic framework has been constructed from Fe3+ and meso-tetra(4-imidazoyl)porphyrin, which can remain in saturated (~27.5 M) NaOH solution for a week. To the best of our knowledge, this is the first report of a MOF that is stable in saturated NaOH solution. The utilization of an imidazolyl-based porphyrin ligand and a high-valence metal is a new and promising strategy for constructing porphyrinic MOFs with ultra-high stability.

Shape-controlled synthesis of α-Fe2O3 nanocrystals for efficient adsorptive removal of Congo red

A facile solvothermal reaction was developed to synthesize α-Fe2O3 nanocrystals at relatively low temperature in the presence of small organic compound 2,4,6-tris(pyrazol-1-yl)-1,3,5-triazine (Tptz) as template. α-Fe2O3 nanocrystals with three different morphologies were obtained by simply changing the volume ratio of the reaction solvents, N,N-dimethylformamide (DMF) and H2O. The purities and morphologies of these samples were characterized by powder X-ray diffraction (PXRD), infrared spectrum (IR), high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). It is remarkable that both the template Tptz ligand and the volume ratios of the mixture solvents are playing very significant roles for the formation and the morphological control of the products in this work. Furthermore, Congo red adsorption experiment showed that the adsorption capacities increased in an order of the samples with morphologies of nanopolyhedra, nanorods and rice-shaped. And the determined maximum adsorption capacity is up to 161 mg g−1 for the rice-shaped α-Fe2O3, which has the biggest BET surface area of 110.2 m2 g−1. These α-Fe2O3 nanocrystals reported here may have the potential to use as low-cost and efficient adsorbent materials to remove organic pollutants from water.

Synthesis and characterization of oxidovanadium complexes as enzyme inhibitors targeting dipeptidyl peptidase IV

Two oxidovanadium(IV) complexes carrying Schiff base ligands obtained from the condensation of 4,5-dichlorobenzene-1,2-diamine and salicylaldehyde derivatives were synthesised and characterised, including their X-ray crystallographic structures. They were evaluated as dipeptidyl peptidase IV (DPP-IV) inhibitors for the treatment of type 2 diabetes. These compounds were moderate inhibitors of DPP-IV, with IC50 values of ca. 40μM. In vivo tests showed that complexes 1 and 2 could lower significantly the level of glucose in the blood of alloxan-diabetic mice at doses of 22.5mgV·kg-1 and 29.6mgV·kg-1, respectively. Moreover, molecular modeling studies suggested that the oxidovanadium complexes 1 and 2 could fit well into the active-site cleft of the kinase domain of DPP-IV. To the best of our knowledge, this is the first report of vanadium complexes capable of inhibiting DPP-IV.

Bioactive ruthenium(II)-arene complexes containing modified 18β-glycyrrhetinic acid ligands

Metal-arene complexes containing bioactive natural-product derived ligands can have new and unusual properties. We report the synthesis, characterization and antiproliferative activity of two new Ru(II) arene complexes with imidazole (dichlorido complex 1) or bipyridyl (chlorido complex 2) ligands conjugated to 18β-glycyrrhetinic acid, an active triterpenoid metabolite of Glycyrrhiza glabra. In general, the conjugated ligands and complexes showed only moderate activity against HeLa (cervical), MCF-7 (breast) and A2780 (ovarian) cancer cells, although the activity of complex 2 in the former two cell lines approached that of the drug cisplatin. Complex 2 (in contrast to complex 1) also exhibited significant activity towards both Gram-positive S. aureus and Gram-negative E. coil bacteria. Complex 2 can induce condensation of DNA and enhances the generation of intracellular reactive oxygen species (ROS). The conjugation of natural products to ligands in organometallic half-sandwich complexes provides a strategy to enhance their biological activities.

Imaging of a clickable anticancer iridium catalyst

Iridium-based anticancer reagents are receiving increasing attention for their high cytotoxicity. Herein, by activating CH bonds in the well-known antioxidant α-phenyl-N-tert-butylnitrone (PBN), we synthesized and characterized a series of new iridium complexes. Complex 1-AMP exhibited the best antiproliferation activity towards human ovarian cancer A2780 cells. The azide group in complex 1-AMP underwent the Cu(I)-catalysed azide-alkyne cycloaddition (CuAAC) reaction and the resulting fluorescent imaging in cells suggested it mainly accumulated in mitochondria. In comparison, to eliminate cytotoxicity of Cu(I) catalyst, we conducted a reaction between complex 1-AMP and a commercialized dye via strain-promoted alkyne-azide cycloaddition (SPAAC) reaction in live cells, confirming its targeting mainly in the mitochondria. Iridium-based anticancer complexes containing a nitrone ligand and azide group may offer a useful tool to probe the mechanism of metallodrugs.

Rigid dinuclear ruthenium-arene complexes showing strong DNA interactions

Six novel dinuclear Ru(II)-arene complexes [Ru2(η6-p-cymene)2(1,3-bib)2Cl2]×2·Solvent (X = Cl- (1), I- (2), NO3- (3), BF4- (4), PF6- (5), CF3SO3- (6); 1,3-bib = 1,3-di(1H-imidazol-1-yl) benzene) were synthesized and fully characterized by FT-IR, 1H NMR, ESI-MS, Elemental Analysis (EA) and Powder X-ray Diffraction (PXRD). Single crystal X-ray diffractions studies showed that 3 and 4 have rigid bowl-like structures, where one counter-anion (NO3- for 3 and BF4- for 4) was trapped inside the cavity to balance the charge, respectively. Even complexes 1-6 showed only moderate or little anti-proliferative activity toward cancer cells, strong interactions with DNA molecules through intercalation, however, were confirmed by UV-Vis, CD and fluorescence spectroscopy. Apoptosis and cell cycle arrest studies for complex 2 with cancer A549 cells indicated concentration-dependent late apoptosis and the G1/G0 phase arrest. Interactions with the tripeptide glutathione (γ-L-Glu-L-Cys-Gly, GSH) might explain the relatively low antiproliferative potency of these complexes. This class of rigid dinuclear cations hold potential as DNA-targeting anticancer agents if their uptake and delivery could be under controlled.