Wen-Ting Liu

Single‐Crystal‐to‐Single‐Crystal Transformation from 1 D Staggered‐Sculls Chains to 3 D NbO‐Type Metal‐Organic Framework through [2+2] Photodimerization

A new approach to synthesize 3D structures through a [2+2] photodimerization process has been carried out by transforming two isostructures of 1D staggered-sculls chains [M(1,2-chdc)(bpe)(2)(H(2)O)(2)]⋅H(2)O (M = Zn, Mn) into 3D NbO-type metal-organic frameworks through UV irradiation in single-crystal-to-single-crystal mode. (see figure; bpe = trans-1,2-(bis(4-pyridyl)ethene, chdc =cyclohexanedicarboxylate).

Solvochromic and photodimerization behaviour of 1D coordination polymer via single-crystal-to-single-crystal transformation.

The coordination polymer [Zn(2)(1,2-bda)(2)(bpe)]·MeOH, which exhibits solvochromic effects upon reversible linear alcohol removal and adsorption, can be turned into [Zn(2)(1,2-bda)(2)(tpcb)(0.5)] in two-step SCSC transformations.

Spontaneous resolution of four-coordinate Zn(II) complexes in the formation of three-dimensional metal–organic frameworks

The three-dimensional chiral helical framework of the four-coordinate zinc complexes, [Zn(bdt)]n (1a and 1b) (H2bdt = 1,4-benzeneditetrazol-5-yl), has been prepared via hydrothermal reaction. At the chiral centers, the tetrahedral zinc centers link with bdt ligands to form a chiral unc-type network, which exhibits an intense blue emission and spontaneous chiral resolution. The enantiomers of 1a and 1b have been confirmed by solid-state circular dichroism spectra.

Spontaneous resolution of chiral metal mandelates by stereochemical control

Spontaneous resolution of mandelic acid occurred upon coordination via stereochemical control on the metal centres. The ‘ideal’ octahedral coordination geometry with bis-chelation in cis-conformation is critical for chiral discrimination. The successful induction of homochiral packing of the mandelates by five different metals suggests general applicability of stereochemical control on the resolution of the chiral organic compounds.

Nanoporous metal–organic framework comprising of 1D cobalt oxalate chains and flexible ligands exhibiting both dynamic gas adsorption and antiferromagnetic chain behaviours

A novel three-dimensional (3D) nanoporous metal–organic framework with moganite topology, [Co2(ox)2(dchtpy)]n·9nH2O (1·9H2O), has been obtained from the hydrothermal reaction of CoCl2, oxalic acid, NaOH and 1a,4a-dihydroxy-1e,2e,4e,5e-tetra(4-pyridyl)cyclohexane (dchtpy). X-ray analysis reveals that the bulky dchtpy ligands link four adjacent metal oxalate chains and form a 3D hybrid network with both moganite topology and 3D channels in various sizes. The largest pores (channel A) are the ones viewed along the a-axis, which are composed of two [Co(ox)]n chains and two bulky ligands in the dimensions of 10.76 × 10.67 A excluding the van der Waals radii. Along the {101} direction there was found the second large channels (channel B) in the size of 10.51 × 4.66 A. Notably the hydroxyl groups of dchtpy extend towards the channels on the middle of the walls, dividing the pores with two small channels in approximately 4.50 × 4.66 A. Besides, small pores in dimensions of 7.07 × 8.24 A and 6.98 × 6.06 A can also be found along the a- and c-axes, respectively. The potential solvent accessible void of the framework, calculated by PLATON, is 46.1% of the total volume and is occupied with disordered aqua molecules. Variable-temperature powder X-ray diffraction experiments confirmed that the crystallinity and network integrity of 1 can be retained up to 375 °C upon the removal of guest aqua molecules, in which thermal stability is among the most stable metal organic coordination frameworks. The framework shows guest-induced dynamic flexibility and elasticity and has a gating effect on the sorption of small gas molecules. The hydroxyl groups from the ligands functionalize the walls of the channels and have strong hydrogen bonds with adsorbents, leading to high sorption capacity at ambient temperature. Magnetic studies revealed significant antiferromagnetic interaction between the Co(II) ions in 1·9H2O with J = −12.4(1) cm−1 and g = 2.450(4).

Coordination polymers of the conformation-flexible 1,2,4,5- cyclohexanetetracarboxylate: synthesis, structures and transforming mechanism studies†

Four new cobalt coordination polymers based on cyclohexane-1e,2a,4a,5e-tetracarboxylic acid (2e+2a, H4LI), [Co4(μ4-LI)2(4,4′-bpy)3(H2O)6]·2H2O (1), [Co4(μ5-LI)2(4,4′-bpy)3(H2O)4]·3H2O (2), [Co2(μ4-LIV)(2,2′-bpy)2(H2O)2] (3) and [Co2(μ4-LIV)(1,10-phen)2(H2O)2]·4H2O (4), were synthesized in hydrothermal reactions with some auxiliary ligands to study the conformations and coordination chemistry of H4L. The structural analysis revealed a new conformation, cyclohexane-1e,2e,4e,5e-tetracarboxylic acid (4e, H4LIV), for the flexible ligand H4L trapped in compounds 3 and 4, which were synthesized in the presence of different chelating ligands whereas in the compounds of 1 and 2, the ligands adapt the same conformation (2e+2a, H4LI) as found in the solid state when the linear bridging 4,4′-bpy was added as auxiliary ligand. The conformational transformation originated from the removal of α-protons of H4L, which has been confirmed via the production of [CuI(4,4′-bpy)(H2O)]2(ip)·2H2O (5) (H2ip = isophthalic acid) from the reaction of Cu2+ ions, H4LI ligand and 4,4′-bpy under hydrothermal conditions. The magnetic properties of 2 and 3 were investigated‥

A Platinum(II)-based photosensitive tripod as an effective photodynamic anticancer agent via DNA damage

Herein, two photosensitive platinum(II)-based tripods were designed and synthesized. Notably, complex 1 ({[Pt(dien)]3 L}(NO3 )6 , L=tri(4-pyridylphenyl)amine and dien=diethylenetriamine), which mainly accumulated in the cell nucleus, exhibited very low cytotoxicity in the absence of light irradiation, but displayed a remarkable increase in cytotoxicity upon visible light irradiation. Mechanistic investigations revealed that the tripod interacted with DNA in the nucleus, induced ROS generation upon light irradiation, and consequently elicited rapid DNA damage response; thereby triggering cancer cell apoptosis.

Solution structures of multiple G-quadruplex complexes induced by a platinum(II)-based tripod reveal dynamic binding

DNA G-quadruplexes are not only attractive drug targets for cancer therapeutics, but also have important applications in supramolecular assembly. Here, we report a platinum(II)-based tripod (Pt-tripod) specifically binds the biological relevant hybrid-1 human telomeric G-quadruplex (Tel26), and strongly inhibits telomerase activity. Further investigations illustrate Pt-tripod induces the formation of monomeric and multimeric Pt-tripod‒Tel26 complex structures in solution. We solve the 1:1 and the unique dimeric 4:2 Pt-tripod–Tel26 complex structures by NMR. The structures indicate preferential binding of Pt-tripod to the 5ʹ-end of Tel26 at a low Pt-tripod/Tel26 ratio of 0–1.0. After adding more Pt-tripod, the Pt-tripod binds the 3ʹ-end of Tel26, unexpectedly inducing a unique dimeric 4:2 structure interlocked by an A:A non-canonical pair at the 3ʹ-end. Our structures provide a structural basis for understanding the dynamic binding of small molecules with G-quadruplex and DNA damage mechanisms, and insights into the recognition and assembly of higher-order G-quadruplexes.DNA G-quadruplexes occur in oncologically relevant regions, thus are interesting targets for cancer research and treatment. Here, the authors solved the 1:1 and 4:2 (ligand/DNA) NMR structures of human telomeric DNA in complex with platinum(II)-tripod ligand and show that the binding is dynamic.