Catalytic alcoholysis of epoxides using metal-free cucurbituril-based solids.

Metal-free cucurbit[7]uril (CB7) solid-state assemblies promote acid-catalysed alcoholysis of aliphatic and aromatic epoxides under mild conditions to give ß-alkoxy alcohols, which are important intermediates for the synthesis of a vast range of compounds such as bioactive pharmaceuticals. The catalytic process is heterogeneous and the catalyst can be reused in consecutive runs without any reactivation treatment. The acid species responsible for the catalytic activity of CB7 may be entrapped hydronium ions.

Crystal structure and temperature-dependent luminescence of a heterotetranuclear sodium-europium(III) ß-diketonate complex.

A heterotetranuclear Na2Eu2 complex with uncommon photoluminescence properties is reported. The complex exhibits good emission efficiency at ambient temperature, coupled with strong temperature dependence of the emission intensity and lifetime in the 273-333 K range, all of which are key features for non-contact luminescence-based thermometers capable of sensing and imaging temperatures in the physiological range.

Preparation of crystal-like periodic mesoporous phenylene-silica derivatized with ferrocene and its use as a catalyst for the oxidation of styrene.

The surface silanol groups in crystal-like mesoporous phenylene-silica have been derivatized with trimethylsilyl, benzyldimethylsilyl and dimethylsilyl(ferrocene) groups by performing a post-synthetic grafting reaction with the corresponding chlorosilane precursors. The success of the grafting procedure was demonstrated by transmission FT-IR spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and (13)C and (29)Si magic-angle spinning (MAS) NMR spectroscopy. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N2 adsorption data for the modified materials indicated preservation of the mesostructure as well as the molecular-scale periodicity in the pore walls. Ferrocene and the ferrocenyl-modified periodic mesoporous organosilica (PMO) were employed in the catalytic oxidation of styrene at 55 °C using either hydrogen peroxide or tert-butylhydroperoxide as an oxidant. The main reaction product was always benzaldehyde (BzCHO), and other products included styrene oxide, benzoic acid and 2-hydroxyacetophenone. Using a styrene:H2O2 molar ratio of 1:5, the highest BzCHO yields at 24 h were 65% (85% selectivity) for ferrocene (semibatch conditions involving stepwise addition of H2O2, 1 mol% Fe) and 34% (83% selectivity) for the modified PMO (batch conditions, 0.06 mol% Fe). The modified PMO could be recovered and reused, albeit with a drop in catalytic activity due to partial metal leaching during the first catalytic run.

Intercalation of a molybdenum η3-allyl dicarbonyl complex in a layered double hydroxide and catalytic performance in olefin epoxidation.

A Zn-Al layered double hydroxide (LDH) intercalated by [Mo(η(3)-C3H5)Cl(CO)2(bpdc)](2-) anions (bpdc = 2,2'-bipyridine-5,5'-dicarboxylate) has been prepared by coprecipitation from aqueous solution and characterised by various techniques. The one-pot method gives rise to a highly organised intercalate with an interlayer spacing of 18.3 Šand up to six (00l) basal reflections in the powder X-ray diffraction pattern. Spectroscopic studies (FT-IR, FT-Raman, (13)C CP MAS NMR and UV-Vis) confirm the presence of structurally intact [Mo(η(3)-C3H5)Cl(CO)2(bpdc)](2-) anions. The interlayer spacing of 18.3 Šindicates that the material contains a monolayer of guest anions positioned in such a way that the bpdc ligands are arranged with their longest dimension roughly perpendicular to the hydroxide layers of the host. Thermal properties were studied by thermogravimetric analysis and differential scanning calorimetry. The intracrystalline reactivity of intercalated dicarbonyl complexes was probed by using the hybrid nanocomposite as a precatalyst in the liquid phase epoxidation of cis-cyclooctene with tert-butylhydroperoxide as oxidant. Under the reaction conditions used, oxidative decarbonylation of the guest molecules takes place (with release of CO and CO2 as confirmed by on-line gas chromatography experiments) to give intercalated molybdenum oxide/bipyridine species that selectively catalyse the epoxidation reaction. The intracrystalline oxidative decarbonylation reaction is topotactic in nature.

Molybdenum(VI) catalysts obtained from η3-allyl dicarbonyl precursors: synthesis, characterization and catalytic performance in cyclooctene epoxidation.

The oxidative decarbonylation of the η(3)-allyl dicarbonyl complexes [Mo(η(3)-C(3)H(5))Cl(CO)(2)(L)] (L = 2,2'-bipyridine (bipy) (1), 4,4'-di-tert-butyl-2,2'-bipyridine (di-tBu-bipy) (2)) by reaction with aqueous tert-butylhydroperoxide (TBHP) or H(2)O(2) gave the following compounds in good to excellent yields: the oxo-bridged dimers [MoO(2)Cl(L)](2)O (L = bipy (3), di-tBu-bipy (6)) using TBHP(10 equiv.)/CH(3)CN/r.t.; the molybdenum oxide/bipyridine hybrid material {[MoO(3)(bipy)][MoO(3)(H(2)O)]}(n) (4) and the octanuclear complex [Mo(8)O(24)(di-tBu-bipy)(4)] (7) using TBHP(50 equiv.)/H(2)O/70 °C; the oxodiperoxo complexes MoO(O(2))(2)(L) (L = bipy (5), di-tBu-bipy (8)) using H(2)O(2)(10 equiv.)/CH(3)CN/r.t. The structure of 7·x(solvent) (where solvent = CH(2)Cl(2) and/or diethyl ether) was determined by single crystal X-ray diffraction. Despite possessing the same windmill-type complex as that described previously for 7·10CH(2)Cl(2), the crystal structure of 7·x(solvent) is unique due to differences in the crystal packing. Compounds 1-8 were examined as catalysts or catalyst precursors for the epoxidation of cyclooctene using aqueous TBHP or H(2)O(2) as oxidant at 55 or 70 °C. Reactions were performed without co-solvent or with the addition of water, ethanol or acetonitrile. Cyclooctene oxide was always the only reaction product. Solids recovered after 24 h reaction at 70 °C were identified by FT-IR spectroscopy as the hybrid 4 from (1,3-5)/TBHP, complex 5 from (1,3-5)/H(2)O(2), and complex 8 from (2,6-8)/H(2)O(2). With TBHP as oxidant, the highest epoxide yields (for 24 h reaction at 70 °C) were obtained using excess H(2)O as solvent (28-38% for 1,3-5; 87-98% for 2,6-8), while with H(2)O(2) as oxidant, the highest epoxide yields were obtained using CH(3)CN as solvent (54-81% for 3-8).

[(E)-1-(Naph-thalen-2-yl)ethyl-idene](naph-thalen-1-ylmethyl)amine.

The title compound, C(23)H(19)N, was obtained unexpectedly from the reaction of [Eu(nta)(3)(PzPy)] {Hnta = 1-(2-naphtho-yl)-3,3,3-trifluoro-acetone and PzPy = 2-[3(5)-pyrazol-yl]pyridine} with 1-naphthyl-methyl-amine. The 1- and 2-naphthyl groups are essentially planar [r.m.s. deviations of 0.007 and 0.011 Å, respectively] and subtend angles of 38.69 (11) and 16.50 (11)°, respectively, with the central CH(3)-C=N-CH(2) unit, which is also almost planar [r.m.s. deviation = 0.002 Å]. In the crystal, the mol-ecules are disposed in zigzag-type fashion, forming layers perpendicular to [100]. Weak supra-molecular C-H⋯π inter-actions contribute to the packing forces.

Propyl-ammonium 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate.

The title salt, C(3)H(10)N(+)·C(14)H(8)F(3)O(2) (-), constitutes the first organic crystal containing a residue of 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dione. The terminal -CF(3) group is disordered over two locations [occupancy ratio = 0.830 (7):0.170 (7)]. Bond delocalization involving the two carbonyl groups and the α-carbon was observed. The crystal packing is mediated by several supra-molecular inter-actions, namely charged-assisted N-H⋯O hydrogen bonds, C-H⋯F and C-F⋯F short contacts and C-H⋯π inter-actions.

Thermal transformation of a layered multifunctional network into a metal-organic framework based on a polymeric organic linker.

The preparation of layered [La(H(3)nmp)] as microcrystalline powders from optimized microwave-assisted synthesis or dynamic hydrothermal synthesis (i.e., with constant rotation of the autoclaves) from the reaction of nitrilotris(methylenephosphonic acid) (H(6)nmp) with LaCl(3)·7H(2)O is reported. Thermogravimetry in conjunction with thermodiffractometry showed that the material undergoes a microcrystal-to-microcrystal phase transformation above 300 °C, being transformed into either a three-dimensional or a two-dimensional network (two models are proposed based on dislocation of molecular units) formulated as [La(L)] (where L(3-) = [-(PO(3)CH(2))(2)(NH)(CH(2)PO(2))O(1/2)-](n)(3n-)). The two crystal structures were solved from ab initio methods based on powder X-ray diffraction data in conjunction with structural information derived from (13)C and (31)P solid-state NMR, electron microscopy (SEM and EDS mapping), FT-IR spectroscopy, thermodiffractometry, and photoluminescence studies. It is shown that upon heating the coordinated H(3)nmp(3-) anionic organic ligand undergoes a polymerization (condensation) reaction to form in situ a novel and unprecedented one-dimensional polymeric organic ligand. The lanthanum oxide layers act, thus, simultaneously as insulating and templating two-dimensional scaffolds. A rationalization of the various steps involved in these transformations is provided for the two models. Photoluminescent materials, isotypical with both the as-prepared ([(La(0.95)Eu(0.05))(H(3)nmp)] and [(La(0.95)Tb(0.05))(H(3)nmp)]) and the calcined ([(La(0.95)Eu(0.05))(L)]) compounds and containing stoichiometric amounts of optically active lanthanide centers, have been prepared and their photoluminescent properties studied in detail. The lifetimes of Eu(3+) vary between 2.04 ± 0.01 and 2.31 ± 0.01 ms (considering both ambient and low-temperature studies). [La(H(3)nmp)] is shown to be an effective heterogeneous catalyst in the ring opening of styrene oxide with methanol or ethanol, producing 2-methoxy-2-phenylethanol or 2-ethoxy-2-phenylethanol, respectively, in quantitative yields in the temperature range 40-70 °C. The material exhibits excellent regioselectivity to the ß-alkoxy alcohol products even in the presence of water. Catalyst recycling and leaching tests performed for [La(H(3)nmp)] confirm the heterogeneous nature of the catalytic reaction. Catalytic activity may be attributed to structural defect sites. This assumption is somewhat supported by the much higher catalytic activity of [La(L)] in comparison to [La(H(3)nmp)].

Structural and photoluminescence studies of a europium(III) tetrakis(beta-diketonate) complex with tetrabutylammonium, imidazolium, pyridinium and silica-supported imidazolium counterions.

Tetrakis(naphthoyltrifluoroacetonato)lanthanate(III) complexes (Ln = Eu, Gd) containing the cations tetrabutylammonium, [NBu(4)](+); 1-butyl-3-methylimidazolium, [C(4)mim](+); and 1-butyl-3-methylpyridinium, [C(4)mpyr](+), have been prepared and structurally characterized by single-crystal X-ray diffraction. The {EuO(8)} coordination sphere in [NBu(4)][Eu(NTA)(4)] is best described as a distorted dodecahedron, where the metal ion is located at the 4-fold inversion axis with only one crystallographically independent NTA residue. In [C(4)mim][Eu(NTA)(4)] and [C(4)mpyr][Gd(NTA)(4)], the central Ln(3+) ions are coordinated by eight oxygen atoms from four distinct beta-diketonate ligands, in an overall distorted square-antiprismatic geometry. Besides electrostatic interactions, the crystal packing in all three structures is stabilized by offset pi-pi interactions involving the naphthyl rings of neighboring complexes (and, for [C(4)mim][Eu(NTA)(4)] and [C(4)mpyr][Gd(NTA)(4)], neighboring naphthyl/imidazolium and naphthyl/pyridinium rings) and C-H...pi contacts. The photoluminescence properties of the three Eu(III) complexes were studied at room temperature and -259 degrees C by measuring emission and excitation spectra, (5)D(0) emission decay curves, and absolute emission quantum yields. Under ligand excitation (lambda(ex) = 290-395 nm), the quantum yields (room temperature) were in the range 0.72-0.77 for the 1-butyl-3-methylimidazolium salt. An immobilized analogue of this complex was prepared by supporting [Eu(NTA)(4)](-) on an ordered mesoporous silica derivatized with 1-propyl-3-methylimidazolium groups. The disappearance of the intra-4f(6) lines in the excitation spectrum of the supported material indicated an increase in the ligand's sensitization process of the Eu(3+) ions, relative to direct intra-4f(6) excitation. The emission quantum yield measured for the supported material (0.32-0.40, for excitations between 265 and 360 nm) is the highest so far reported for lanthanide-containing ordered mesoporous silicas.

Catalytic properties of the dioxomolybdenum siloxide MoO2(OSiPh3)2 and its 2,2'-bipyridine adduct MoO2(OSiPh3)2(bpy).

The tetrahedral triphenylsiloxy complex MoO(2)(OSiPh(3))(2) (1) and its Lewis base adduct with 2,2'-bipyridine, MoO(2)(OSiPh(3))(2)(bpy) (2), were prepared and characterised by IR/Raman spectroscopy, and thermogravimetric analysis. Both compounds catalyse the epoxidation of cis-cyclooctene at 55 degrees C using tert-butylhydroperoxide (t-BuOOH) is decane as the oxidant, giving 1,2-epoxycyclooctane as the only product. The best results were obtained in the absence of a co-solvent (other than the decane) or in the presence of 1,2-dichloroethane, while much lower activities were obtained when hexane or acetonitrile were added. With no co-solvent, catalyst 1 (initial activity 272 mol x molMo(-1) x h(-1)for a catalyst:substrate: oxidant molar ratio of 1:100:150) is much more active than 2(initial activity 12 mol x molMo(-1) x h(-1)). The initial reaction rates showed first order dependence with respect to the initial concentration of olefin. With respect to the initial amount of oxidant, the rate order dependence for 1 (1.9) was higher than that for 2 (1.6).The dependence of the initial reaction rate on reaction temperature and initial amount of catalyst was also studied for both catalysts. The lower apparent activation energy of 1 (11 kcal x mol(-1)) as compared with 2 (20 kcal x mol(-1)) is in accordance with the higher activity of the former.