Solvothermal synthesis and characterization of two inorganic-organic hybrid materials based on barium.

Two metal-organic frameworks containing barium were synthesized hydrothermally and investigated for their catalytic properties. Ba(2)F(2)[O(3)SC(2)H(4)SO(3)] has barium fluoride layers linked by organic 1,2-ethanedisulfonate molecules. Ba[O(3)SC(2)H(4)SO(3)] has discrete barium centers arranged in layers and connected covalently by ethanedisulfonate bridges. Thermogravimetric analysis showed that Ba(2)F(2)[O(3)SC(2)H(4)SO(3)] is stable to ca. 325 °C and Ba[O(3)SC(2)H(4)SO(3)] to ca. 375 °C. These materials expand the metal-organic frameworks available for group II metals bound to organodisulfonate linkers and are potentially useful for a range of heterogeneous acid catalysis reactions.

Geometric control of ground state multiplicity in a copper(I) bis(verdazyl) complex.

A copper(I) complex of a 3-(6'-isopropylpyridyl)-substituted verdazyl was synthesized and characterized by X-ray crystallography and magnetic susceptibility. The complex crystallizes in the monoclinic space group C2/c with cell dimensions a = 22.544 A, b = 11.576 A, c = 17.157 A, ß = 123.907°, V = 3716.2 A(3). The coordination geometry at copper is distorted tetrahedral, with the two ligand planes separated by 75°. Magnetic susceptibility measurements indicate that the ground state of the diradical is a triplet at this geometry. Fitting to a simple Heisenberg Hamiltonian (H = -JS(1)·S(2)) gave J = 47(1) cm(-1). The triplet ground state results from exchange mediated by the copper ion; in particular, the direction of the distortion from tetrahedral geometry appears to be essential to maintain the high-spin ground state.

Enantiomerically pure trans-beta-lactams from alpha-amino acids via compact fluorescent light (CFL) continuous-flow photolysis.

Photolysis of alpha-diazo-N-methoxy-N-methyl (Weinreb) beta-ketoamides derived from enantiomerically pure (EP) alpha-amino acids affords the corresponding EP beta-lactams via an intramolecular Wolff rearrangement. The photochemistry is promoted with either standard UV irradiation or through the use of a 100 W compact fluorescent light; the latter affords a safe and environmentally friendly alternative to standard photolysis conditions. A continuous-flow photochemical reactor made from inexpensive laboratory equipment reduced reaction times and was amenable to scale-up. The diastereoselectivity (cis or trans) of the product beta-lactams has been shown to vary from modest to nearly complete. An extremely facile, atom-economical method for the epimerization of the product mixture to the trans isomer, which is generally highly crystalline, has been developed. Evidence for C3 epimerization of Weinreb amide structures via a nonbasic, purely thermal route is presented. Subsequent transformations of both the Weinreb amide at C3 (beta-lactam numbering) and the amino acid side chain at C4 are well-tolerated, allowing for a versatile approach to diverse beta-lactam structures. The technology is showcased in the synthesis of a common intermediate used toward several carbapenem-derived structures starting from unfunctionalized aspartic acid.

Hydrothermal synthesis of two cationic bismuthate clusters: an alkylenedisulfonate bridged hexamer, [Bi6O4(OH)4(H2O)2][(CH2)2(SO3)2]3 and a rare nonamer templated by triflate, [Bi9O8(OH)6][CF3SO3]5.

This paper reports the synthesis, characterization, and application of two cationic bismuthate clusters by anion templating. The compounds were synthesized under mild hydrothermal treatment and characterized by powder and single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The first material consists of a cationic hexanuclear bismuthate cluster octahedral in geometry and linked by 1,2-ethanedisulfonate molecules. This structure is thermally stable to about 235 degrees C. In the second compound, discrete cationic nonanuclear bismuthate clusters interact electrostatically with trifluoromethanesulfonate anions to pack into a nearly layered assembly. The material undergoes a transformation to Bi(2)O(3) upon loss of the triflate groups at about 385 degrees C. Both materials demonstrate the use of sulfonate groups for the anion-directed assembly of these rare cationic inorganic structures. The application of the 3D octahedral bismuth cluster material toward acidic heterogeneous catalysis is also reported.

Reversible anion exchange and catalytic properties of two cationic metal-organic frameworks based on Cu(I) and Ag(I).

We report the synthesis and characterization of two Ag(I)/Cu(I)-based cationic metal-organic frameworks and their application in both heterogeneous catalysis and anion exchange. The Cu(I)-based material was designed from our previously reported Ag(I) cationic topology. Both structures consist of cationic layers with pi-pi stacked chains of alternating metal and 4,4'-bipyridine. Alpha,omega-alkanedisulfonate serves as an anionic template, electrostatically bonding to the cationic layers. Due to weak interaction between the sulfonate template and cationic extended framework, both materials display reversible anion exchange for a variety of inorganic species. Indeed, the Ag(I)-based material exhibits highly efficient uptake of permanganate and perrhenate anion trapping, a model for pertechnetate trapping. The materials also display heterogeneous Lewis acidity, likely due to the coordinatively unsaturated metal sites which only bind to two bipy nitrogens and a weak interaction with one sulfonate oxygen. A comparative study on the influence of structure versus size selectivity and reusability for both exchange and catalysis is discussed.

Polymer-templated nanospider TiO(2) thin films for efficient photoelectrochemical water splitting.

We have discovered a facile and inexpensive approach to fabricate "nanospider" TiO(2) thin films with not only an amazing morphology but highly efficient water splitting to produce hydrogen. Our method employs benzene-swollen poly(ethylene glycol) as a sacrificial organic polymer to template the semiconductor thin film. The synthesized TiO(2) thin films are highly crystalline with optimized particle and channel size to enhance the liquid-semiconductor junction interaction. This enhanced contact area leads to more than twice the water splitting performance than conventional P25 thin films. In addition, the nanospider thin films also outperform P25 films in the photodegradation of toxic organics.

Ruthenium nitrosyls derived from tetradentate ligands containing carboxamido-N and phenolato-o donors: syntheses, structures, photolability, and time dependent density functional theory studies.

In order to examine the role(s) of designed ligands on the NO photolability of {Ru-NO}(6) nitrosyls, a set of three nitrosyls with ligands containing two carboxamide groups along with a varying number of phenolates have been synthesized. The nitrosyls namely, (NEt(4))(2)[(hybeb)Ru(NO)(OEt)] (1), (PPh(4))[(hypyb)Ru(NO)(OEt)] (2), and [(bpb)Ru(NO)(OEt)] (3) have been characterized by X-ray crystallography. Complexes 1-3 are diamagnetic, exhibit nu(NO) in the range 1780-1840 cm(-1) and rapidly release NO in solution upon exposure to low power UV light (7 mW/cm(2)). Density Functional Theory (DFT) and Time Dependent DFT (TDDFT) calculations on 1-3 indicate considerable contribution of ligand orbitals in the MOs involved in transitions leading to NO photolability. The results of the theoretical studies match well with the experimental absorption spectra as well as the parameters for NO photorelease and provide insight into the transition(s) associated with loss of NO.

A metal-organic framework via the reaction of benzoate with a cationic inorganic material.

Our research group previously reported a two-dimensional cationic inorganic material (BING-5, Pb(3)F(5)NO(3)) where nitrate resides in the interlamellar space and can be anion exchanged. Investigation of the possible exchange of nitrate for benzoate led to the discovery of a layered metal-organic framework, lead benzoate hydrate [Pb(C(6)H(5)CO(2))(2)(OH(2))]. The compound crystallizes as colourless plates in the monoclinic space group P2(1)/c. The two dimensional lead-oxygen layers contain bridging benzoate oxygen atoms, with bridging water molecules further supporting the layers. The benzoate molecules are positioned perpendicular to the layers and form a hydrophobic bilayer region. The material shows basic character when immersed in various solvents suggesting potential as a base catalyst.

Two related gadolinium aquo carbonate 2-D and 3-D structures and their thermal, spectroscopic, and paramagnetic properties.

We report two new extended inorganic materials based on gadolinium. The first, [Gd(CO(3))(2)H(2)O][NH(4)], consists of negatively charged 2-D sheets of gadolinium carbonate with one coordinated water molecule and an ammonium cation between the layers. The coordinated water and one carbonate extend into the interlayer space, connecting the layers via an extensive hydrogen bonding network which includes the ammonium ions. The second, a closely related yet more condensed framework structure, [Gd(2)(CO(3))(3)NH(3)H(2)O], is formed at a higher hydrothermal temperature and was characterized by single crystal X-ray diffraction data collected at a synchrotron. This second structure contains layers that are isostructural to the first, bridged together by carbonate, and coordinated by water and ammonia. The properties of these materials were studied by thermogravimetric analysis-mass spectrometry, photoluminescence, electron paramagnetic resonance, and Raman and infrared spectroscopy. The 2-D [Gd(CO(3))(2)H(2)O][NH(4)] is stable to about 175 degrees C, though water and ammonium loss continues through the entire thermogravimetric analysis trace. The 3-D material remains intact until about 325 degrees C. Both structures exhibit broad luminescence bands in the near-ultraviolet region centered at 354 nm. Electron paramagnetic resonance and magnetic susceptibility show spin-spin coupling between adjacent gadolinium atoms in both structures and confirm that they are paramagnetic. These materials show interesting photoluminescent and paramagnetic properties that could possibly be exploited for chemical sensing or magnetic materials applications.

Antimony oxide hydroxide ethanedisulfonate: a cationic layered metal oxide for Lewis acid applications.

We have discovered a rare example of a cationically charged inorganic material. The layered structure is an example outside the extensively studied isostructural set of anionic clays/layered double hydroxides and our previously reported lead fluoride nitrate. For the present compound, the antimony oxide hydroxide layers are positively charged and are templated by anionic alkylenedisulfonate. The organic molecules are only bonded electrostatically to the layers with sulfonate oxygen to antimony distances beyond the covalent range. The material catalyzes a ketal formation reaction as a Lewis acid without the need for drying the solvent before the reaction or a nonaqueous medium such as toluene. The catalyst is heterogeneous and is completely recovered after the catalysis for reapplication.