ABSTRACT
A novel oxonitridosilicate phosphor host Sr(3)Si(2)O(4)N(2) was synthesized in N(2)/H(2) (6%) atmosphere by solid state reaction at high temperature using SrCO(3), SiO(2), and Si(3)N(4) as starting materials. The crystal structure was determined by a Rietveld analysis on powder X-ray and neutron diffraction data. Sr(3)Si(2)O(4)N(2) crystallizes in cubic symmetry with space group Pa Ì 3, Z = 24, and cell parameter a = 15.6593(1) Å. The structure of Sr(3)Si(2)O(4)N(2) is constructed by isolated and highly corrugated 12 rings which are composed of 12 vertex-sharing [SiO(2)N(2)] tetrahedra with bridging N and terminal O to form three-dimensional tunnels to accommodate the Sr(2+) ions. The calculated band structure shows that Sr(3)Si(2)O(4)N(2) is an indirect semiconductor with a band gap ≈ 2.84 eV, which is close to the experimental value ≈ 2.71 eV from linear extrapolation of the diffuse reflection spectrum. Sr(3-x)Si(2)O(4)N(2):xEu(2+) shows a typical emission band peaking at ~600 nm under 460 nm excitation, which perfectly matches the emission of blue InGaN light-emitting diodes. For Ce(3+)/Li(+)-codoped Sr(3)Si(2)O(4)N(2), one excitation band is in the UV range (280-350 nm) and the other in the UV blue range (380-420 nm), which matches emission of near-UV light-emitting diodes. Emission of Sr(3-2x)Si(2)O(4)N(2):xCe(3+),xLi(+) shows a asymmetric broad band peaking at ~520 nm. The long-wavelength excitation and emission of Eu(2+) and Ce(3+)/Li(+)-doped Sr(3)Si(2)O(4)N(2) make them attractive for applications in phosphor-converted white light-emitting diodes.
ABSTRACT
The promotion for hydrogen release from ammonia-borane (AB) was observed in the presence of ZIF-8. Even at concentrations of ZIF-8 as low as 0.25 mol %, a reduction of the onset temperature for dehydrogenation accompanies an increase in both the rate and amount of hydrogen released from AB.
ABSTRACT
Oxime targeted reactions of the complexes trans-[(kappa(3)-dapdOH)Ru(CO)(PPh(3))(2)]PF(6) (1) (dapdOH = diacetylpyridinedioxime) and trans-[(kappa(3)-dapmOH)RuCl(PPh(3))(2)]PF(6) (2) (dapmOH = diacetylpyridinemonooxime) with SOCl(2), NaBH(4), or HCHO led into conversion of oxime to oximato, imino, or hydroxymethylimino groups. The reaction products have been characterized by analytical and spectral studies. Molecular structures of the representative homo/heteroleptic oxime/oximato complexes trans-[(kappa(3)-dapdOH)Ru(CO)(PPh(3))(2)]PF(6) (1), trans-[(kappa(3)-dapdO)Ru(CO)(PPh(3))(2)] (11) and oximato/imino complex trans-[(kappa(3)-dapd-NH)Ru(CO)(PPh(3))(2)]PF(6) (13) have been authenticated by single-crystal X-ray diffraction analyses. Structural studies revealed the presence of various oxime/oximato/imino based O-H...O, C-H...O, and N-H...F interactions in the complexes 1, 11, and 13.
ABSTRACT
Three novel 3D metal-organic frameworks of [Ni(2)(hfpdpt)(bpy)(2)(H(2)O)(2)](H(2)O)(8) (1), [Ni(3)(Hhfpdpt)(2)(bpy)(4)](H(2)O)(2) (2), and [Mn(2)(hfpdpt)(H(2)O)(2)] (3) have been synthesized by the hydrothermal reaction of Ni(II) or Mn(II) nitrate, 4,4'-(hexafluoroisopropylidene)diphthalic acid (H(4)hfpdpt), and 4,4'-bipyridyl (bpy). Complex 1 self-assembles into a 3D framework with unconventional 4-connected network topology, while 2 and 3 exhibit two kinds of unusual (4,8)-connected topological networks. Notably, in 1 and 2, the bpy coligand participates in the construction of their 3D frameworks, and the pH value also plays an important role to tune their space arrangements, while in 3, the bpy coligand is not involved in the final crystalline lattice. Furthermore, a detailed investigation on their magnetic and adsorptive properties is carried out.
ABSTRACT
Two novel zinc and cadmium 4,4'-(hexafluoroisopropylidene)diphthalate metal-organic frameworks have been synthesized and characterized using single crystal X-ray diffraction analysis, and exhibit a unique fluorite topology and high thermal stabilities.
ABSTRACT
Reactions of laser-ablated lanthanum atoms with CO molecules in solid argon have been studied. The neutral lanthanum monocarbonyl (LaCO), produced upon sample deposition at 7 K, exhibits a C-O stretching frequency of 1772.7 cm(-1); to the best of our knowledge this is the lowest yet observed for a terminal CO in a neutral metal-carbonyl molecule (MCO, M = metal atom), implying anomalously enhanced metal-to-CO back-bonding. The infrared (IR) absorption band at 1145.9 cm(-1) is assigned to the C-O stretching mode of the side-on-bonding CO in the La2[eta2(mu2-C,O)] molecule. This CO-activated molecule undergoes an UV/Vis-photoinduced rearrangement to the CO-dissociated molecule, c-La2(mu-C)(mu-O). Density functional theory (DFT) calculations have been performed on these molecules, the results of which lend strong support to the experimental assignments of the IR spectra. LaCO is predicted to have a quartet ground state, corresponding to a linear geometry. Its formation involves La 6s-->4f promotion, which increases the strength of La-CO bonding by decreasing the sigma repulsion and, remarkably, by increasing the La 5d and 4f-->CO 2pi back-bonding. The observations schematically depict the whole process, starting with the interaction of CO with metal and ending with CO dissociation by the lanthanum dimer.
ABSTRACT
The reaction of cadmium(II) perchlorate with urocanic acid under different conditions created three novel coordination compounds: [Cd2(L2)2-(L3)2(H2O)8] (1), {[Cd(L)(L2)](H2O)(1/2)}n (2), and {[Cd(L3)2](H2O)(3/2)(EtOH)}n (3), in which L, L2, and L3 are three urocanate tautomers. Complex 1 consists of two separate mononuclear units with different urocanate tautomers, which self-assemble into a 3D hydrogen-bonding network constructed by alternating 2D layers, whereas complexes 2 and 3 self-assemble into 3D alpha-polonium and four-fold interpenetrated diamondoid networks, respectively. The tautomerism of the urocanate ligands and the enormous structural diversity of their complexes are present in this system, which illustrates that the reaction temperature, pressure, and the metal ions themselves act cooperatively to tune the tautomerism of the ligands and the frameworks of their metal coordination compounds. The fluorescence-emission and nitrogen-adsorption properties of these complexes are also investigated.
ABSTRACT
A novel 3D metal-organic framework with predesigned cubic building blocks and 1D open channels exhibiting significant N2 adsorption has been synthesized and characterized by single crystal X-ray diffraction analysis.
ABSTRACT
Five new eclipsed two-dimensional (2D) coordination polymers, [[Cd(2)(TPT)(2)L(2)](GM(1))(3/2)(H(2)O)](infinity) (1) (TPT = terephthalate, L = 3-(2-pyridyl)pyrazole, GM(1) = terephthalic acid), [[Cd(TPT)L](GM(2))(H(2)O)(2)]( infinity) (2) (GM(2) = L = 3-(2-pyridyl)pyrazole), [[Cd(TPT)L](GM(3))(1/2)(H(2)O)](infinity) (3) (GM(3) = mesitylene), [[Cd(4)(TPT)(4)L(4)](GM(4))(7/2)](infinity) (4) (GM(4) = tetramethylbenzene), and [[Cd(TPT)L](GM(5))(1/2)](infinity) (5) (GM(5) = naphthalene), have been synthesized and characterized by X-ray diffraction. All the five complexes take the similar eclipsed 2D open-channel framework with different guest molecules included in the cavities of their channels. TGA analysis indicates that the eclipsed open-channel frameworks are thermally stable up to 300 degrees C. The porous property of the 2D framework of 5 was also investigated by the XRPD technique, which indicated that the guest molecules included in the open-channel frameworks are removable and the framework is maintained after the removal of the guest molecules. Moreover, complexes 1-5 also display strong blue emission in the solid state.
