Yong-Cong Ou

Two novel Dy8 and Dy11 clusters with cubane [Dy4(μ3-OH)4]8+ units exhibiting slow magnetic relaxation behaviour

Two unique octa- and hendeca-nuclear dysprosium(III) clusters incorporating [Dy(4)(μ(3)-OH)(4)](8+) cubane units have been synthesized with the 1,10-phenanthroline-2,9-dicarbaldehyde dioxime (H(2)phendox) ligand and DyCl(3)·6H(2)O or Dy(OAc)(3)·4H(2)O. They are [Dy(8)(OH)(8)(phendox)(6)(H(2)O)(8)]Cl(2)(OH)(2)·18H(2)O·18MeOH (1) and [Dy(11)(OH)(11)(phendox)(6)(phenda)(3)(OAc)(3)](OH)·40H(2)O·7MeOH (2). Adjacent Dy(8) in 1 or Dy(11) in 2 motifs are packed by off-set π-π interactions of the aromatic rings on phendox(2-) to generate a 3D supramolecular architecture in the honeycomb topology and with 1D or 3D channels along the c-axis. Adsorption research shows that complex 1 has selective adsorption ability for H(2)O over small gas molecules (H(2), N(2), CO(2)). Complex 2 is stable upon the removal of guest molecules and the desolvated compound absorbed a considerable amount of CO(2). Furthermore, the oximes underwent hydrolysis to carboxylic acid and the resulting 1,10-phenanthroline-2,9-dicarboxylate link the dysprosium atoms to form a hendecanuclear cluster of 2. Magnetic studies reveal that both clusters exhibit slow magnetic relaxation behavior, expanding upon the recent reports of the pure 4f type single-molecule magnets (SMMs).

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.

Hydrothermal in situ ligand reaction: copper(II)-mediated stepwise oxidation of 2,3,5- and 2,4,6-trimethylpyridine to pyridinecarboxylates

Hydrothermal reactions of 2,3,5-trimethylpyridine (2,3,5-tmpy) yielded two pyridinecarboxylates, 3,5-dimethyl-2-pyridinecarboxylate (2-dmpya) and 3-methyl-2,5-pyridine dicarboxylate (2,5-mpyda) in the presence of copper nitrate. The in situ generated pyridinecarboxylates were derived from copper-mediated stepwise oxidation of 2- or/and 5-methyl groups on the pyridine by nitrate in acidic aqueous solution. The selectivity might be due to the different electronic distribution resulting from the asymmetric substitution on the aromatic ring and steric hindrance between two neighboring methyl groups. When 2,4,6-trimethylpyridine (2,4,6-tmpy) was used in the reactions, the three evenly-distributed methyl groups were oxidized simultaneously to form 2,4,6-pyridine tricarboxylate (2,4,6-pyta). Interestingly in nearly neutral solution a new ligand 3-hydroxy-2,4,6-pyridine tricarboxylate (2,4,6-Opyta) was yielded and trapped in the compound [Cu4(2,4,6-Opyta)2(H2O)6]·2H2O (4). The in situ copper-mediated oxidation of 2,4,6-tmpy to 2,4,6-Opyta4−via 2,4,6-pyta3− can be further supported by the formation of 4 from a hydrothermal reaction of 2,4,6-pyridine tricarboxylic acid with copper nitrate at 185 °C for 4 days. The new Opyta ligand was isolated as an ammonium (NH4)(2,4,6-OpytaH3)·H2O and characterized by NMR, MS and X-ray crystallography. The magnetic property of 4 was investigated.

Unique (H2O)(14) water cages with cyclic (H2O)(4) tetramer unit trapped in 3D porous lanthanide-cyclohexanetetracarboxylate frameworks

Two kinds of water clusters, the unique dodecahedral (H2O)14 cage and the truncated cubic (H2O)12 cluster formed from both coordinated and lattice water molecules, are captured in three lanthanide complexes [Ln4(chtc)3(H2O)10]·9H2O (Ln = Tb 1, Yb 2, Dy 3, H4chtc = cyclohexane-1,2,4,5-tetracarboxylic acid). Compound 1 exhibits the characteristic photoluminescence of the Tb3+ ion in the visible region, while 2 exhibits NIR luminescence properties.

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‥