Neutron diffraction elucidates the structures of two-dimensional (2D) water layers (278 K) or 2D ice layers confined in an organic slit-shaped nanospace. The two-dimensional ice phases reported here consist of individual eight-membered rings or folded-chain segments (263 K) and condensed twelve-membered irregular rings (20 K). This is quite different from bulk or other 2D ice structures; the latter usually form hexagonal honeycomb lattices. Both low-temperature structures typically feature water molecules which are surrounded by two or three other water molecules. Neutron diffraction and thermochemical studies indicate a liquid-solid-phase transition around 277 K for two-dimensional D2O layers. A further solid-solid-phase transition occurs between 263 and 20 K.

The mode of co-ordination of the multidentate ligand 2,2Ј-dimethyl-4,4Ј-bipyrimidine (L) was found to depend on the metal ion, the crystallization conditions, the metal-to-ligand ratio, and the anion. With nickel a chelating co-ordination through the endo-dentate nitrogen donor set is observed in the molecular complex [NiCl 2 (L)(H 2 O)]ؒCH 3 NO 2 , derived from hot CH 3 NO 2 . With Cu(NO 3 ) 2 and CuI-CH 3 CN one-and two-dimensional (1-D and 2-D) co-ordination polymers of formula ∞

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Abstract:The electronic effect of substituting CH with N in poly(pyrazoly1)-borato ligands and their transition-metal complexes is shown to be a decrease in energy of the filled metal and ligand orbitals. This conclusion is based on the cyclovoltammograms and photoelectron spectra of bis(hydrotris(azoly1)borato)-iron(") and -cobalt(It) complexes (azolyl = pyrazolyl and 1,2,4-triazolyl) spectra of bis(hydrotris(l,2,4-triazolyl)-borato)iron(rI) show that there is a finetuning of the HOMO-LUMO gap by a shift in transition temperature for the spin and on MO calculations. "Fe Mossbauer

The replacement of the pyrazole rings (pz) in the popular poly(pyrazolyl)borate ligands, 1 [H n B(pz) 4-n ] -, by e.g. 1,2,4triazole or tetrazole leads to novel poly(triazolyl)-and -(tetrazolyl)borates which can bridge between metal centers, thereby creating coordination polymers with interesting solid-state structures and properties, whereas the versatile poly(pyrazolyl)borate ligands form exclusively molecular chelate complexes. 2 We report here the synthesis, structure, and optical properties of [hydrotris(1,2,4-triazolyl)borato]silver(I) (1), which was obtained from the potassium salt of the ligand and AgNO 3 in water, followed by recrystallization from aqueous ammonia (eq 1). 3 Compound 1 presents itself as a two-dimensional coordination polymer according to the single-crystal X-ray analysis. 5 The metal-ligand coordination in 1 is detailed in Figure 1; Figure 2 illustrates the packing and the crystal morphology. In an unprecedented coordination mode 2 the hydrotris(triazolyl)borate ligand bis-chelates one silver center with two endodentate nitrogens and also bridges to two other silver atoms through two of the three exodentate nitrogen donors. Hence, in one triazolyl ring both nitrogens become utilized as donor atoms.The coordination sphere of silver is a strongly distorted tetrahedron. To the best of our knowledge, no [tris(pyrazolyl)borato]silver complex has been structurally characterized. 1,7 Compound 1 crystallizes in the acentric orthorhombic space group Pna2 1 which belongs to the crystal class mm2, where optical activity can occur as specific physical effects. 9 The tetrahedrally-coordinated silver and boron atoms have four