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Solid-state NMR spectroscopy of 13C is used to structurally characterize and quantify carbonyl groups in Rh6(CO)16 and Rh+(CO)2 complexes entrapped in NaY zeolite. MAS NMR line shape simulations show that the dicarbonyl groups present in Rh6(CO)16 and Rh+(CO)2 have the same shielding parameters (σiso ∼ 178 ppm, CSA ∼ 400 ppm, and η ∼ 0.2) but exhibit greatly different spin−lattice relaxation rates. Bridged groups exist only in clusters and are bonded to three Rh atoms. Their shielding parameters [σiso ∼ 251 ppm, CSA ∼ 180 ppm, and negligible anisotropy (η)] differ from bulk Rh6(CO)16 and from those found earlier for CO bridged between two Rh atoms. The Rh6:Rh+ ratio can be measured directly from the MAS spectra or from the relaxation data. The residual broadening of 150−200 Hz in the MAS spectra is due to distribution of isotropic resonances in the sample. All CO species are immobile at room temperature on the NMR time scale (of the order of a millisecond), whereas slow exchange between dicarbonyls on hex...

An approach for the control and understanding of supported molecular catalysts is demonstrated with the design and synthesis of open and closed variants of a grafted Lewis acid active site, consisting of Al(III)-calix[4]arene complexes on the surface of silica. The calixarene acts as a molecular template that enforces open and closed resting-state coordination geometries surrounding the metal active sites, due to its lower-rim substituents as well as site isolation by virtue of its steric bulk. These sites are characterized and used to elucidate mechanistic details and connectivity requirements for reactions involving hydride and oxo transfer. The consequence of controlling open versus closed configurations of the grafted Lewis acid site is demonstrated by the complete lack of observed activity of the closed site for Meerwein-Ponndorf-Verley (MPV) reduction; whereas, the open variant of this catalyst has an MPV reduction activity that is virtually identical to previously reported soluble molecular Al(III)-calix[4]arene catalysts. In contrast, for olefin epoxidation using tert -butyl-hydroperoxide as oxidant, the open and closed catalysts exhibit similar activity. This observation suggests that for olefin epoxidation catalysis using Lewis acids as catalyst and organic hydroperoxide as oxidant, covalent binding of the hydroperoxide is not required, and instead dative coordination to the Lewis acid center is sufficient for catalytic oxo transfer. This latter result is supported by density functional theory calculations of the transition state for olefin epoxidation catalysis, using molecular analogs of the open and closed catalysts.

Cab-O-Sil HS5, used as the support in silica supported ruthenium (Ru/SiO{sub 2}) catalysts, was characterized via single and multiple quantum (MQ) {sup 1}H NMR spectroscopy. The samples were studied both in the presence and in the absence of ruthenium. Single quantum spin counting of protons on silica support with and without ruthenium metal indicated that the total number of hydroxyl groups decreased significantly with increasing reduction temperature over the range of 350-530{degree}C. Two different components shown in static {sup 1}H NMR were found to reveal homogeneous and inhomogenous broadening via spectral hole burning experiments. {sup 1}H MQ-NMR spin, counting, based on the number of MQ coherences observed, showed the existence of small clusters of proton spins on the silica surface. The maximum measured cluster size was 6-7, or less, spins. Segments of silica resembling the 100 face of cristobalite on the surface are postulated to be possible sites for the clusters. The clusters in pure silica became smaller as the reduction temperature increased over 500{degree}C. No such change was detected in the presence of ruthenium. 33 refs., 11 figs., 2 tabs.

Beyond hydrogen storage: The first example of reversible magnesium deposition/stripping onto/from an inorganic salt was seen for a magnesium borohydride electrolyte. High coulombic efficiency of up to 94 % was achieved in dimethoxyethane solvent. This Mg(BH(4))(2) electrolyte was utilized in a rechargeable magnesium battery.

Herein, we present a lithium-doped fullerane (Li(x)-C(60)-H(y)) that is capable of reversibly storing hydrogen through chemisorption at elevated temperatures and pressures. This system is unique in that hydrogen is closely associated with lithium and carbon upon rehydrogenation of the material and that the weight percent of H(2) stored in the material is intimately linked to the stoichiometric ratio of Li:C(60) in the material. Characterization of the material (IR, Raman, UV-vis, XRD, LDI-TOF-MS, and NMR) indicates that a lithium-doped fullerane is formed upon rehydrogenation in which the active hydrogen storage material is similar to a hydrogenated fullerene. Under optimized conditions, a lithium-doped fullerane with a Li:C(60) mole ratio of 6:1 can reversibly desorb up to 5 wt % H(2) with an onset temperature of ~270 °C, which is significantly less than the desorption temperature of hydrogenated fullerenes (C(60)H(x)) and pure lithium hydride (decomposition temperature 500-600 and 670 °C respectively). However, our Li(x)-C(60)-H(y) system does not suffer from the same drawbacks as typical hydrogenated fullerenes (high desorption T and release of hydrocarbons) because the fullerene cage remains mostly intact and is only slightly modified during multiple hydrogen desorption/absorption cycles. We also observed a reversible phase transition of C(60) in the material from face-centered cubic to body-centered cubic at high levels of hydrogenation.

New material UCB-1 is synthesized via the delamination of zeolite precursor MCM-22 (P) at pH 9 using an aqueous solution of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride at 353 K. Characterization by powder X-ray diffraction, transmission electron microscopy, and nitrogen physisorption at 77 K indicates the same degree of delamination in UCB-1 as previously reported for delaminated zeolite precursors, which require a pH of greater than 13.5 and sonication in order to achieve exfoliation. UCB-1 consists of a high degree of structural integrity via ^(29)Si MAS NMR and Fourier transform infrared spectroscopies, and no detectable formation of amorphous silica phase via transmission electron microscopy. Porosimetry measurements demonstrate a lack of hysteresis in the N_2 adsorption/desorption isotherms and macroporosity in UCB-1. The new method is generalizable to a variety of Si:Al ratios and leads to delaminated zeolite precursor materials lacking amorphization.

The conventional method of data analysis and interpretation of time‐resolved multiple quantum (MQ) nuclear magnetic resonance (NMR) spectra of solids is closely examined. Intensity profiles of experimental 1H MQ NMR spectra of polycrystalline adamantane and hexamethylbenzene serve to test the Gaussian statistical model approach. Consequences of this model are explored with a least‐squares fitting procedure, transformation of data to yield linear plots, and a scaling analysis. Non‐Gaussian behavior of the MQ NMR spectral intensity profiles, as a function of order of coherences, is demonstrated with all these methods of analysis. A heuristic argument, based on the multiplicative properties of dipolar coupling constants in the equation of motion of the density operator, leads to the prediction of exponentially decaying MQ NMR spectral intensity profiles. Scaling analysis and semilog plots of experimental time‐resolved MQ NMR spectra of adamantane and hexamethylbenzene support this deduction. Dynamical scale ...

The concepts involved in production and detection of n-quantum coherence in nuclear magnetic resonance (NMR) are considered. The use of coherent averaging to reduce internal Hamiltonians to zero, and to something other than their non-averaged values is reviewed. The experimental procedure necessary to produce and detect multiple quantum coherence in strongly dipolar coupled spin 1 2 solids is described. This procedure, using a single quantum propagator described in the initial sections, is then used to probe the densities (as distinguished from the chemical identities supplied by a 1-quantum fingerprint) of protons on silica gel surfaces of fumed, Cab-O-Sil HS5 silica gels which have: (a) not been relaxed by hydration, but have been reduced under flowing hydrogen; (b) been relaxed by hydration and subsequently reduced; (c) had deposited particles of metallic Ru, Pt, and Ag. As reflected in the highest order of multiple quantum coherence observed under a fixed time for development, the relaxed and reduced sample, and the sample with Ru deposited on it exhibit lower densities of protons than do the other samples. The implications to assuming that silica gel is an “inert” support for reactions involving reactions of hydrocarbons on supported metal catalysts are discussed.

[Pd(allyl)]BF4 (I), [Pd(allyl)(2,4-hexadiene)]BF4 (II), and [Pd(MeCN)4](BF4)2 (III) catalyze the dehydrogenation of NH3BH3 most efficiently with a release of 2.0 equiv.

Calcium borohydride can reversibly store up to 9.6 wt% hydrogen; however, the material displays poor cyclability, generally associated with the formation of stable intermediate species. In an effort to understand the role of such intermediates on the hydrogen storage properties of Ca(BH_4)_2, calcium dodecahydro-closo-dodecaborate was isolated and characterized by diffraction and spectroscopic techniques. The crystal structure of CaB_(12)H_(12) was determined from powder XRD data and confirmed by DFT and neutron vibrational spectroscopy studies. Attempts to dehydrogenate/hydrogenate mixtures of CaB_(12)H_(12) and CaH_2 were made under conditions known to favor partial reversibility in calcium borohydride. However, up to 670 K no notable formation of Ca(BH_4)_2 (during hydrogenation) or CaB_6 (during dehydrogenation) occurred. It was demonstrated that the stability of CaB_(12)H_(12) can be significantly altered using CaH_2 as a destabilizing agent to favor the hydrogen release.

Calcium borohydride can reversibly store up to 9.6 wt% hydrogen; however, the material displays poor cyclability, generally associated with the formation of stable intermediate species. In an effort to understand the role of such intermediates on the hydrogen storage properties of Ca(BH_4)_2, calcium dodecahydro-closo-dodecaborate was isolated and characterized by diffraction and spectroscopic techniques. The crystal structure of CaB_(12)H_(12) was determined from powder XRD data and confirmed by DFT and neutron vibrational spectroscopy studies. Attempts to dehydrogenate/hydrogenate mixtures of CaB_(12)H_(12) and CaH_2 were made under conditions known to favor partial reversibility in calcium borohydride. However, up to 670 K no notable formation of Ca(BH_4)_2 (during hydrogenation) or CaB_6 (during dehydrogenation) occurred. It was demonstrated that the stability of CaB_(12)H_(12) can be significantly altered using CaH_2 as a destabilizing agent to favor the hydrogen release.

We report that a ternary magnesium nickel boride (MgNi_(2.5)B_2) mixed with LiH and MgH_2 can be hydrogenated reversibly forming LiBH_4 and Mg_2NiH_4 at temperatures below 300 °C. The ternary boride was prepared by sintering a mechanically milled mixture of MgB_2 and Ni precursors at 975 °C under inert atmosphere. Hydrogenation of the ternary, milled with LiH and MgH_2, was performed under 100 to 160 bar H_2 at temperatures up to 350 °C. Analysis using X-ray diffraction, Fourier transform infrared, and ^(11)B magic angle spinning NMR confirmed that the ternary boride was hydrogenated forming borohydride anions. The reaction was reversible with hydrogenation kinetics that improved over three cycles. This work suggests that there may be other ternary or higher order boride phases useful for reversible hydrogen storage.

Hydrogen and ^(23)Na NMR were performed to 400 °C on NaMgH3 powder produced by reactive ball-milling of NaH and MgH2. The H resonance shows narrowing already at 100 °C as a narrow line superimposed on the broad, rigid-lattice signal. With increasing temperature, the fraction of spins in the narrow component grows smoothly, approaching 100% near 275 °C. This heterogeneous narrowing suggests a wide distribution of H motion rates. After annealing at 400 °C, the narrow component intensity at temperatures below 200 °C was substantially reduced and both H and ^(23)Na relaxation rates 1/T_1 were decreased. Thus, it appears that the high rates of H motion, particularly on first heating, are due to regions with poorly organized crystal structure. If this disorder could be maintained, this might be an avenue toward improved reaction kinetics of this or other hydrides. In the annealed sample, the activation energy for H diffusion is approximately 95 kJ/mol.

A structure analysis of the borosilicate zeolite MCM-70, whose synthesis had been patented in 2003, was reported in 2005. Unfortunately, that structure analysis was somewhat ambiguous. Anisotropic line broadening made it difficult to model the peak shape, some peaks in the electron density map could not be interpreted satisfactorily, the framework geometry was distorted, and MAS NMR results were partially contradictory. In an attempt to resolve some of these points, an optimization of the synthesis was undertaken, and the structure was reinvestigated. The structure was solved from synchrotron powder diffraction data collected on an as-synthesized sample (Pmn2_1, a = 13.3167(1) A, b = 4.6604(1) A, c = 8.7000(1) A) using a powder charge-flipping algorithm. The framework topology, with a 1-dimensional, 10-ring channel system, is identical to the one previously reported. However, the B in this new sample was found to be ordered in the framework, fully occupying one of the four tetrahedral sites. Two extra-framework K^+ ion positions, each coordinated to five framework O atoms and one water molecule, were also found. The solid state ^(29)Si, ^(11)B and ^1H NMR results are fully consistent with this ordered structure.

The crystal structure of solvent-free Li2B12H12 has been determined by powder X-ray diffraction and confirmed by a combination of neutron vibrational spectroscopy and first-principles calculations. This compound is a possible intermediate in the dehydrogenation of LiBH4, and its structural characterization is crucial for understanding the decomposition and regeneration of LiBH4. Our results reveal that the structure of Li2B12H12 differs from other known alkali-metal (K, Rb, and Cs) derivatives.

Multiple quantum spin counting is shown to yield an upper limit ofn = 6 for strongly bound, rigid intermediates CmHn in the reaction of ethylene over Ru/SiO2. The results eliminate the possibility of major components of such intermediates being polymer-like coke precursers. A precurser to 2-butene is one possible intermediate.

The synthesis of organic-functionalized pure-silica-zeolites (PSZs) with MFI- and MEL-type structures for low-k applications prepared through a direct-synthesis method by adding a fluorinated silane to the synthesis solution is reported. The added fluorine functionality increases the hydrophobicity of the zeolites, which are characterized by scanning electron microscopy, X-ray diffraction, 29Si and 19F solid-state NMR spectroscopy, nitrogen adsorption, and thermogravimetric analysis. The functionalized zeolite powders have low water content and calcined spin-on films prepared from the functionalized nanoparticle suspensions exhibit higher water contact angles and lower k values (2.1 and 1.8 for the functionalized MFI- and MEL-type zeolites, respectively) than PSZ films. The use of a direct-synthesis method to decrease the moisture adsorption in the films eliminates the extra post-spin-on silylation steps that are traditionally used to render the zeolite films hydrophobic.

Two novel zeolites SSZ-33 and SSZ-35 were investigated with respect to their acidic properties using different probe molecules to characterize the accessibility and acid strength of Lewis and Bronsted acid sites. Ammonia, pyridine, pivalonitrile, and acetonitrile-d3 were used as probe molecules, and the results were correlated with 27Al and 1H magic angle spinning (MAS) NMR. Both SSZ-33 and SSZ-35 zeolites were found to possess bridging Si−OH−Al groups of virtually uniform and high acid strength. For both SSZ-33 and SSZ-35, there is the typical presence of highly disturbed OH groups (IR band around 3500 cm-1), which amounts to almost half of the overall Bronsted acidity. It was found that almost all bridging Si−OH−Al groups in SSZ-33 are located in the 12-MR rings. Both acetonitrile-d3 and pyridine sorptions suggest the presence of two types of Lewis sites in SSZ-35, differing in acid strength and electron-acceptor properties, whereas in the SSZ-33 zeolite only one type is present. The relative strength o...

An eight bit digital phase shifter is described which is suitable for multiple pulse NMR of solids in terms of settling time (≂2 μs) and phase resolution (1.406°). The unit incorporates an 8‐bit Merrimac digital phase shifter model PSDW‐84‐1, and an amplification‐damping‐pulse shaping circuit to solve the problem of variable attenuation as a function of phase setting. Results of multiple quantum spin counting and homonuclear dipolar decoupling experiments on ensembles of strongly dipolar coupled spin 1/2 systems are used to demonstrate the capability of the unit.

The high polarization of optically pumped 129Xe was transferred to surface carbon and silicon species under magic angle spinning (MAS) conditions to afford enhanced solid-state NMR of surfaces. High-resolution 29Si MAS spectra of fumed silica and 13C spectra of chemisorbed methanol on silica were obtained using a steady flow of hyperpolarized xenon adsorbed onto the surface at 135 K. Cross polarization to 29Si from SPINOE enhanced hydroxyl protons and to 13C from enhanced methyl protons is observed with good efficiency. A direct SPINOE transfer from 129Xe to 13C without cross polarization is observed to give the highest enhancement under these conditions.

In this paper we report, for the first time, the synthesis and characterization of new zincosilicate Zn-SSZ-42. New method of synthesizing pure-silica SSZ-42 via the OH– route without using F– anions is presented. Furthermore, the synthesis and characterization of the novel layered zincosilicate and pure-silica designated as SSZ-71 are discussed.

In this report we discuss the synthesis and physicochemical characterizations of three zeolites with unsolved crystal structures: SSZ-57, SSZ-74, and IM-5. The diffraction data of SSZ-57 are similar to, but distinct from, the data for ZSM-5, ZSM-11, or ZSM-5/11 intergrowths. The powder diffraction data of SSZ-74 can be indexed in a unit cell with dimensions similar to those found in ZSM-5 and ZSM-11. The organic structure directing agents (SDA) used to prepare SSZ-74 and IM-5 are similar to SDA molecules that often yield multidimensional 10-ring zeolites. The micropore volumes, adsorption uptake rates of 2,2-dimethylbutane, and the constraint index tests of these three unknown materials are also consistent with those expected for multidimensional 10-ring zeolites.

Measurements of nuclear magnetic resonance (NMR) relaxation times allow the rates of H and D atomic hopping in metal-hydrides to be determined. A first example compares the rates of H hopping in Mg65Sc35Pd2.4H220, a promising new battery electrode and storage alloy, to LaNi5Hx and to the end-members of the alloy system, ScH2 and MgH2. The motion of MgScH is more rapid than in the metallic ScH2 and the ionic MgH2, but slower than in LaNi5Hx. Magic-angle spinning (MAS) NMR of metal-deuterides is a newer method that can resolve inequivalent D atoms and measure the rate of diffusive exchange between the sites. Examples include the tetrahedral and octahedral sites in YD2+x and D in ZrNiDx.

ZrNiDx samples with compositions between x=0.87 and x=3.0 were investigated by 2H magic-angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR), powder x-ray diffraction (XRD), neutron vibrational spectroscopy (NVS), and neutron powder diffraction (NPD). The rigid-lattice MAS-NMR spectrum for a ZrNiD0.88 sample in the triclinic beta phase shows a single phase with two well-resolved resonances at +11.5 and −1.7 ppm, indicating that two inequivalent D sites are occupied, as was observed previously in ZrNiD1.0. For ZrNiD0.88, the ratio of spectral intensities of the two lines is 1:0.76, indicating that the D site corresponding to the +11.5 ppm line has the lower site energy and is fully occupied. Similarly, the neutron vibrational spectra for ZrNiD0.88 clearly confirm that at least two sites are occupied. For ZrNiD1.0, XRD indicates that ~5% of the metal atoms are in the gamma phase, corresponding to an upper composition for the beta phase of x=0.90±0.04, consistent with the MAS-NMR and neutron vibrational spectra indicating that x=0.88 is single phase. The MAS-NMR and NVS of ZrNiD1.87 indicate a mixed-phase sample (beta+gamma) and clearly show that the two inequivalent sites observed at x=0.88 cannot be attributed to the sites normally occupied in the gamma phase. For ZrNiD2.75, NPD results indicate a gamma-phase boundary of x=2.86±0.03 at 300 K, increasing to 2.93±0.02 at 180 K and below, in general agreement with the phase boundary estimated from the NVS and MAS-NMR spectra of ZrNiD1.87. Rigid-lattice 2H MAS-NMR spectra of ZrNiD2.75 and ZrNiD2.99 show a ratio of spectral intensities of 1.8±0.1:1 and 2.1±0.1:1 (Zr3Ni:Zr3Ni2), respectively, indicating complete occupancy of the lower-energy Zr3Ni2 site, consistent with the NPD results. For each composition, the correlation time for deuterium hopping was determined at the temperature where resolved peaks in the MAS-NMR spectrum coalesce due to motion between inequivalent D sites. The measured correlation times are consistent with previously determined motional parameters for ZrNiHx.

Several solid state NMR techniques including magic-angle-spinning (MAS) and multiple-quantum (MQ) MAS experiments have been used to characterize various AlH3 samples. MAS-NMR spectra for the 1H and 27Al nuclei have been obtained on a variety of AlH3 samples that include the β- and γ- phases as well as the most stable α-phase. While the dominant components in these NMR spectra correspond to the aluminum hydride phases, other species were found that include Al metal, molecular hydrogen (H2), as well as peaks that can be assigned to Al-O species in different configurations. The occurrence and concentration of these extraneous components are dependent upon the initial AlH3 phase composition and preparation procedures. Both the β-AlH3 and γ-AlH3 phases were found to generate substantial amounts of Al metal when the materials were stored at room temperature while the α-phase materials do not exhibit these changes.

The nature of the self-assembled core-shell interface in gold@silica nanoparticles synthesized via a 3-aminopropyltrimethoxysilane (APTMS) route is investigated using materials synthesis as a sensitive tool for elucidating interfacial composition and organization. Our approach involves condensation of the gold@silica nanoparticles within a silica framework for synthesis of a composite gold-silica material containing approximately 30 wt % gold. This material contains one of the highest gold loadings reported, but maintains gold core isolation as ascertained via a single surface plasmon resonance absorption band frequency corresponding to that of gold nanoparticles in dilute aqueous solution. The immobilized gold cores are subsequently etched using cyanide anion for the synthesis of templated porosity, which corresponds to the space that was occupied by the gold. Characterization of immobilized amines is performed using probe molecule binding experiments, which demonstrate a lack of accessible amines after gold removal. Solid-state 13C CPMAS NMR spectroscopy on these materials demonstrates that the amount of amine immobilization must be less than 10% of the expected yield, assuming that all of the APTMS becomes bound to the gold nanoparticle template. These results require a core-shell interface in the gold@silica nanoparticles that is predominantly occupied by inorganic silicate species, such as Si-O-Si and Si-OH, rather than primary amines. Such a result is likely a consequence of the weak interaction between primary amines and gold in aqueous solution. Our method for investigating the core-shell interface of gold@silica nanoparticles is generalizable for other interfacial structures and enables the synthesis of bulk imprinted silica using colloidal templates.

The local structures of framework boron atoms in borosilicate zeolites B-β, B-SSZ-33 and B-SSZ-42 have been studied in the course of hydration/dehydration by employing solid-state NMR methods. In particular, characterization of trigonal boron sites has been studied in great detail. ^(11)B MAS NMR spectra showed that boron trigonally coordinated to the framework (B(OSi)_3, denoted as B[3]) can be readily transformed to a defective trigonal boron site (B(OSi)_2(OH), denoted as B[3]-I) as a result of hydration. The presence of B[3]-I sites was proven by utilizing a number of different NMR methods including ^(11)B MAS NMR at two different fields (11.7 and 19.6 T), ^(11)B MQMAS, ^(11)B CPMAS, and ^(11)B 2D HETCOR experiments. The B[3]-I species can be converted into B[3] upon dehydroxylation, but its presence can also be sustained even after very high-temperature treatment (at least up to 500 °C). The formation of deboronated species, B(OH)_3, in distorted form was detected even under a mild hydration treatment. HETCOR NMR revealed that hydroxyl protons with chemical shifts at 2.4 and 3.3 ppm in ^1H NMR are correlated with B[3] and B[3]-I sites, respectively. The presence of a new hydroxyl proton at 3.8 ppm in ^1H NMR that showed selective correlation with B[3]-I in HETCOR NMR was also identified.

Hydrogen absorption and desorption isotherms have been measured on ballmilled mixtures of LiH+Si powders to evaluate the thermodynamic parameters of these reversible reactions. The phase compositions at the various stages of reaction have been examined by Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR) of the 7Li, 1H, and 29Si nuclei and powder x-ray diffraction (XRD). The initial mixtures of LiH and Si were found to convert into known Li-Si silicide intermetallics (i.e., Li12Si7, Li7Si3, and Li13Si4) as well as providing evidence for a previously unknown ternary Li-Si-H phase as hydrogen was first desorbed and then absorbed. While the absorption reactions are reversible over portions of the Li-Si-H composition range, incomplete recovery of the original LiH + Si phases was also observed under some test conditions.

Our studies reveal that the structural defects such as framework boron sites and SiOH groups are the driving force for Pt dispersion in zeolites and that boron species remain in the zeolite framework after both Pt impregnation and dehydration. The framework boron sites in zeolites are necessary to provide acid sites of weak strength for certain catalytic reactions.

A set of zeolite synthesis experiments is described where lattice substitution is varied in the context of the structure of particular structure-directing organocations (at times referred to as templates). In this particular series, the organocations are constructed as members of a fused bicyclo organonitrogen class of compounds, described as having ring construction [l.m.n], where n = 0. We show that these compounds can best be achieved from starting cyclic ketones that are converted to imines via a Beckman rearrangement reaction. A particular approach to the Beckmann reaction works best in our hands. In some instances isomeric organocations are made and separated. Often their use in zeolite synthesis led to different products. There is a high correlation for the space-filling details of the guest organocations and the type of crystalline host lattice developed in the synthesis. In one instance involving isomers of a decahydroquinoline derivative, a new zeolite, SSZ-48, is discovered and contains only one of the isomers. Characterization of the isomers and their use in the zeolites is followed by (13)C MAS NMR analyses. Some details of the new zeolite are given and it is shown that a reasonable symmetry operation predicting a 14-ring zeolite could be generated under similar conditions to SSZ-48 (a 12-ring zeolite).

A series of calcined borosilicate molecular sieves are treated hydrothermally with aqueous acetic acid and subsequently characterized in detail. The acid treatments are shown to expel boron from the molecular sieves, and the defects created by the boron removal are subsequently healed with silicon dissolved from other parts of the crystal. By use of this procedure, highly crystalline, hydrophobic all-silica CIT-1 and SSZ-33 (CON topology) molecular sieves are synthesized for the first time. ^(29)Si Bloch decay (BD) and cross-polarization magic-angle spinning (CPMAS) NMR spectra indicate that the materials have few internal defects and allow for structural characterization of CON materials by 29Si MAS NMR. Seven unique tetrahedral silicon species are identified in the spectra in agreement with the published crystal structure. The effects of treatment conditions such as acid type, solution pH, and temperature are studied in detail. Conditions near the isoelectric point of silica (pH = 0−2) are found to be efficient for the production of a variety of hydrophobic materials with few structural defects including molecular sieves of the *BEA, CON, and MWW topologies. Detailed control studies using SSZ-33 show that the nearly defect-free materials contain triangular mesopores that are clearly distinguishable in field-emission electron microscopy images. The silica that previously inhabited the mesopores is a likely source for the species required to heal the defects created by boron expulsion. In addition to healing the vacancies previously inhabited by boron with dissolved silicon, an additional aluminum or gallium source can be added to the acetic acid solution and the ions are incorporated into the framework. Many of the defects that are not filled with the Al^(3+) or Ga^(3+) species are filled with silicon during the treatment to produce a more hydrophobic metallosilicate than the one containing internal silanol defects.

Polyetheral additives were found to be efficient promoters to enhance the rate of H2-release from ammonia borane (AB) at various temperatures. In particular, tetraethylene glycol dimethyl ether (T4EGDE, 29 wt% relative to AB + T4EGDE) exhibited significantly improved activities for AB dehydrogenation, with the material-based hydrogen storage capacity of 10.3 wt% at 125 °C within 40 min. In situ FT-IR spectroscopy indicated the formation of B-(cyclodiborazanyl)amino-borohydride (BCDB), borazine, and μ-aminodiborane as gaseous byproducts. In addition, (11)B nuclear magnetic resonance (NMR) spectroscopy further revealed that diammoniate of diborane (DADB) was initially formed to give polyaminoborane as liquid and/or solid spent-fuel, consistent with previous reports. Density Functional Theory (DFT) calculations suggested that hydrogen bonding interactions between AB and a polyetheral promoter initially played an important role in increasing the reactivity of B-H bonds of AB by transferring electron density from oxygen atoms of the promoter into B-H bonds of AB. These partially activated, hydridic B-H bonds were proposed to help promote the formation of diammoniate of diborane (DADB), which is considered as a reactive intermediate, eventually enhancing the rate of H2-release from AB. In addition, our in situ solid state (11)B magic angle spinning (MAS) NMR measurements further confirmed that the rate of DADB formation from AB with a small quantity of T4EGDE was found to be much faster than that of pristine AB even at 50 °C. This metal-free method for H2-release from AB with an added, small quantity of polyethers would be helpful to develop feasible hydrogen storage systems for long-term fuel cell applications.

Particle size and particle–framework interactions have profound effects on the kinetics, reaction pathways, and even thermodynamics of complex hydrides incorporated in frameworks possessing nanoscale features. Tuning these properties may hold the key to the utilization of complex hydrides in practical applications for hydrogen storage. Using carefully synthesized, highly-ordered, nanoporous carbons (NPCs), we have previously shown quantitative differences in the kinetics and reaction pathways of LiBH_4 when incorporated into the frameworks. In this paper, we probe the anion mobility of LiBH_4 confined in NPC frameworks by a combination of solid state NMR and quasielastic neutron scattering (QENS) and present some new insights into the nanoconfinement effect. NMR and QENS spectra of LiBH_4 confined in a 4 nm pore NPC suggest that the BH_4− anions nearer the LiBH_4–carbon pore interface exhibit much more rapid translational and reorientational motions compared to those in the LiBH_4 interior. Moreover, an overly broadened BH_4− torsional vibration band reveals a disorder-induced array of BH_4− rotational potentials. XRD results are consistent with a lack of LiBH_4 long-range order in the pores. Consistent with differential scanning calorimetry measurements, neither NMR nor QENS detects a clear solid–solid phase transition as observed in the bulk, indicating that borohydride–framework interactions and/or nanosize effects have large roles in confined LiBH_4.

The decomposition pathway is crucial for the applicability of LiBH_4 as a hydrogen storage material. We discuss and compare the different decomposition pathways of LiBH_4 according to the thermodynamic parameters and show the experimental ways to realize them. Two pathways, i.e. the direct decomposition into boron and the decomposition via Li_2B_(12)H_(12), were realized under appropriate conditions, respectively. By applying a H_2 pressure of 50 bar at 873 K or 10 bar at 700 K, LiBH_4 is forced to decompose into Li_2B_(12)H_(12). In a lower pressure range of 0.1 to 10 bar at 873 K and 800 K, the concurrence of both decomposition pathways is observed. Raman spectroscopy and ^(11)B MAS NMR measurements confirm the formation of an intermediate Li_2B_(12)H_(12) phase (mostly Li_2B_(12)H_(12) adducts, such as dimers or trimers) and amorphous boron.

The 1H and 13C nuclear magnetic resonance (NMR) of thin diamond films deposited from naturally abundant (1.1 at.%) as well as 50% and 100% 13C-enriched CH4 heavily diluted in H2is described and discussed. Less than 0.6 at.% of hydrogen is found in the films which contain crystallites up to ∼15 μm across. The 1H NMR consists of a broad 50–65 kHz wide Gaussian line attributed to H atoms bonded to carbon and covering the crystallite surfaces. A narrow Lorentzian line was only occasionally observed and found not to be intrinsic to the diamonds. The 13C NMR demonstrates that >99.5% of the C atoms reside in a quaternary diamond-like configuration. The 13C spin-lattice relaxation times T1 are four orders of magnitude shorter than in natural diamond and believed to be due to 13C spin diffusion to paramagnetic centers, presumably carbon dangling bonds. Analysis of T1 indicates that within the 13C spin diffusion length of ∼0.05 μm these centers are uniformly distributed in the diamond crystallites, possibly concentrated on the internal surfaces of a relatively dense system of nanovoids.

Environmental catalysts that can efficiently degrade hazardous chemicals are of growing importance. Among these, TiO2 photocatalysts show high potential for effective degradation of harmful species, particularly chlorine containing compounds, which are chemically persistent.1-3 TiO2 photocatalysts can display efficiencies (degradation rate/unit energy) that are 1-2 orders of magnitude higher than thermal catalysts, particularly for the low chlorocarbon concentrations often encountered.4 Gassurface experiments5-10 show that reactions occur both in the gas phase and/or on the surface of TiO2 catalysts and can involve the following radical initiators: O2, OH, and Cl. Although a number of studies have been carried out by means of GC,7-9 MS,6,8 and FT-IR,5-8,10 a detailed understanding of the reaction mechanisms remains elusive. In the present work, we report a new approach to the study of photocatalysis, namely in situ solid-state nuclear magnetic resonance (SSNMR) spectroscopy.11-13 SSNMR methods are advantageous because they allow a quantitative examination of the reactions on the catalyst surface as well as in the gas phase. We have characterized the reaction of trichloroethylene (TCE) over two types of TiO2 photocatalysts and have identified new intermediates in the complex surface chemistry. Figure 1 shows proton-decoupled 13C magic angle spinning (MAS) NMR spectra obtained from photooxidation of TCE in the presence of O2 and Degussa P-25 TiO2 powder.14 The NMR spectra show the degradation of TCE, the formation of dichloroacetyl chloride (Cl2CHCOCl, DCAC), CO, phosgene (CCl2O), and pentachloroethane (C2HCl5), and their conversion to the final product CO2. The narrow line widths of the peaks indicate that these species are very mobile and most likely exchange rapidly between the surface and the gas phase. Assignment of these intermediates are confirmed by comparing 13C NMR shifts for liquid samples reported in the literature15 or prepared in our lab and from proton coupled spectra during the photoreactions. Most of the intermediates identified above are in good agreement