Structural diversity in a series of alkyl-substituted cesium aryloxides.

A family of cesium aryloxides [Cs(OAr)](n) were synthesized and structurally characterized from the reaction of 1:1 or 1:excess stoichiometry of Cs(0) and the appropriate alkyl-substituted phenol: 2-alkylphenol [alkyl = methyl (H-oMP), isopropyl (H-oPP), and tert-butyl (H-oBP)] and 2,6-dialkylphenol [alkyl = methyl (H-DMP), isopropyl (H-DIP), tert-butyl (H-DBP), and phenyl (H-DPhP)]. The products were structurally identified as [Cs(oMP)(H-oMP)(2)](n) (1), [Cs(5)(oPP)(5)](n) (2), [Cs(4)(oBP)(4)(H-oBP)(6)](n) (3x, shown), [Cs(3)(DMP)(3)](n) (4), [Cs(2)(DIP)(2)](n) (5), [Cs(DIP)(H-DIP)](n) (5x), and [Cs(DPhP)](n) (7). Compounds 1-7 were found to adopt complex polymeric structures employing π interactions from the neighboring pendant phenoxide ligands. The solution behavior of these compounds was studied using solution (133)Cs NMR spectroscopy, and for each compound, a single (133)Cs NMR resonance was observed, with chemical shift values found to be strongly solvent-dependent. This implies that monomeric cesium salt species involving solvent interactions exist in solution.

Structural Characterization of Methanol Substituted Lanthanum Halides.

The first study into the alcohol solvation of lanthanum halide [LaX(3)] derivatives as a means to lower the processing temperature for the production of the LaBr(3) scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(micro-Br)(H(2)O)(7)](Br)(2)}(2) (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H(2)O)(7)(MeOH)(2)](Br)(3) (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH(2), crystals of [Ca(MeOH)(6)](Br)(2) (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr(2.75)*5.25(MeOH)](+0.25) [LaBr(3.25)*4.75(MeOH)](-0.25)} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr(3) in MeOH forming the 8-coordinated [LaBr(3)(MeOH)(5)] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX(3) derivatives were isolated as [(MeOH)(4)(Cl)(2)La(micro-Cl)](2) (6) and [La(MeOH)(9)](I)(3)*MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR ((139)La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4 - 6 were slightly higher in comparison to their hydrated counterparts.

Homo- and heterometallic complexes of tetra-(di-substituted hydroxybenzyl)-N,N'-ethylenediamine derivatives.

The coordination behavior of a series of group 4 metal alkoxides [M(OR)(4)] modified by a set of novel substituted hydroxybenzyl ethylene diamine (H(4)-ED-L(4)) ligands {[tetra(3,5-di-t-butyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DBP(4) (1), [tetra(3,5-di-t-amyl-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DAP(4) (1a), and [tetra(3,5-dichloro-2-hydroxybenzyl)-N,N'-ethylenediamine] termed H(4)-ED-DCP(4) (2)} was elucidated. The reaction of 1 or 1a with the M(OR)(4) precursor led to the isolation of the structural similar species M(ED-L(4)) where L = DBP, M = Ti (3), Zr (4), Hf (5); L = DAP, M = Zr (4a), Hf (5a). In contrast, the reaction of 2 with the M(OR)(4) precursors yielded Ti(ED-DCP(4)) (6), (py)(2)Zr(ED-DCP(4)) (7), and (HOBu(t))Hf(ED-DCP(4)) (8) where py = pyridine and HOBu(t) = HOC(CH(3))(3). For 3-6, the cations of the monomeric species were completely encapsulated by all available heteroatoms (four O and two N) of the ED-L(4) ligands, yielding an octahedral geometry for each metal center. For 7 and 8, an identical binding by the ED-DCP(4) ligand was observed with the additional coordination of Lewis basic adducts, forming 8- and 7-coordinated metal centers, respectively. Switching to +2 cations led to the isolation of [(THF)Ca](2)(ED-DBP(4)) (9a) where THF = tetrahydrofuran, {[(py)Ca](4)(ED-(mu-DBP-eta(6))(4))(2)}(n) (9b), and [(py)Zn](ED-DBP(4))[Zn(py)(2)] (10) *5py and [(py)Sn](2)(ED-DBP(4)) (11). The structures of these species were significantly different in arrangement compared to the Group 4 derivatives. Further attempts to produce a mixed +4/+2 cationic species yielded [(py)(ONep)(2)Ti(ED-DBP(4))Zn(py)] (12). Reacting the single-source precursor Co[mu-OC(6)H(4)(CHMe(2))(2)-2)(2)Li(py)(2)](2) with 1, led to the isolation of (py)Li[ED-DBP(3)(H-DBP)]Co (13), with one of the phenol protons remaining unreacted. The synthesis and characterization of these compounds are presented in detail.

Investigation of chemometric instrumental transfer methods for high-resolution NMR.

The implementation of direct standardization (DS), piecewise direct standardization (PDS), and double-window piecewise direct standardization (DWPDS) instrumental transfer techniques for high-resolution (1)H NMR spectral data was explored. The ability to transfer a multivariate calibration model developed for a "master or target" NMR instrument configuration to seven different ("secondary") NMR instrument configurations was measured. Partial least-squares (PLS) calibration of glucose, glycine, and citrate metabolite relative concentrations in model mixtures following mapping of the secondary instrumental configurations using DS, PDS, or DWPDS instrumental transfer allowed the performance of the different transfer methods to be assessed. Results from these studies suggest that DS and PDS transfer techniques produce similar improvements in the error of prediction compared to each other and provide a significant improvement over standard spectral preprocessing techniques including reference deconvolution and spectral binning. The DS instrumental transfer method produced the largest percent improvement in the predictions of concentrations for these model mixtures but, in general, required that additional transfer calibration standards be used. Limitations of the different instrumental transfer methods with respect to sample subset selection are also discussed.

Self-assembly and magnetic alignment in cetyltrimethylammonium bromide/sodium perfluorooctanoate surfactant mixtures investigated using 2H nuclear magnetic resonance spectroscopy.

Deuterium nuclear magnetic resonance (2H NMR) spectroscopy has been used to investigate the phase behavior for mixtures of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and the anionic surfactant sodium perfluorooctanoate (FC7) for total surfactant concentrations ranging from 1 to 25 wt %. The deuterated methyl of the quaternary methyl-ammonia group in CTAB-y-d3 gives rise to a superposition of spectral components in the 2H NMR spectra allowing for the identification and quantification of the different phases present. The CTAB/FC7 mixture exhibits a coexisting two-phase region composed of an isotropic (Iso) micelle/vesicle phase along with a lamellar (Lalpha) phase for all of the composition ranges investigated. The variation of the phase composition as a function of sample temperature, total wt % surfactant, and surfactant molar ratio are presented. In addition, the 2H NMR reveals that the Lalpha phase spontaneously aligns in the magnetic field, with the extent and distribution of magnetic alignment being determined. The 2H NMR results are discussed in light of previously reported surfactant-templated material synthesis involving the CTAB/FC7 mixture.

Stepwise modification of titanium alkoxy chloride compounds by pyridine carbinol.

The stepwise modifications of stoichiometric mixtures of titanium chloride (TiCl 4) and titanium iso-propoxide (Ti(OPr (i)) 4) by 2-pyridine methanol (H-OPy) led to the isolation of a systematically varied, novel family of compounds. The 3:1 reaction mixture of Ti(OPr (i)) 4:TiCl 4 yielded [Cl(OPr (i)) 2Ti(mu-OPr (i))] 2 ( 1). Modification of 1 with 1 and 2 equiv of H-OPy produced [Cl(OPr (i)) 2Ti(mu c-OPy)] 2 ( 2, where mu c = chelating bridge) and "(OPy) 2TiCl(OPr (i))" ( 3, not crystallographically characterized), respectively. Altering the Ti(OPr (i)) 4 to TiCl 4 stoichiometry to 1:1 led to isolation and identification of another dimeric species [Cl 2(OPr (i))Ti(mu-OPr (i))] 2 ( 4). Upon modification with 1 equiv of H-OPy, [Cl 2(OPr (i))Ti(mu c-OPy)] 2 ( 5) was isolated from toluene and (OPy)TiCl 2(OPr (i))(py) ( 6) from py. An additional equivalent of H-OPy led to the monomeric species (OPy) 2TiCl 2 ( 7). Because of the low solubility and similarity in constructs of these compounds, additional analytical data, such as the beryllium dome or BeD-XRD powder analyses, were used to verify the bulk samples, which were found to be in agreement with the single crystal structures.

17O NMR investigation of phosphite hydrolysis mechanisms.

The use of solution 17O NMR spectroscopy in verifying the mechanism of trialkyl phosphite hydrolysis is presented. Trimethyl phosphite was reacted with 17O-labeled H2O at different temperatures and two reactant concentrations, with the reaction being monitored by 17O NMR. Kinetic details elucidated from the NMR spectra are also discussed.

Double quantum 1H MAS NMR studies of hydrogen-bonded protons and water dynamics in materials.

Two-dimensional double quantum (DQ) 1H MAS NMR was used to investigate different proton environments in a series of alkali (Na, K, Rb, Cs) [Nb6O19]8- Lindqvist salts, with the water and hydrogen-bound intercluster protons being clearly resolved. Through the analysis of the DQ 1H NMR spinning sideband pattern, it is possible to extract both the mean and distribution of the motionally averaged intramolecular homonuclear 1H-1H dipolar coupling for the different water environments and the intercluster protons. Motional order parameters for the water environments were then calculated from the averaged dipolar couplings. The influence of additional intermolecular dipolar couplings due to multispin interactions were simulated and discussed.

Distinguishing individual lipid headgroup mobility and phase transitions in raft-forming lipid mixtures with 31P MAS NMR.

A model membrane system composed of egg sphingomyelin (SM), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and cholesterol was studied with static and magic angle spinning (31)P NMR spectroscopy. This model membrane system is of significant biological relevance since it is known to form lipid rafts. (31)P NMR under magic angle spinning conditions resolves the SM and DOPC headgroup resonances allowing for extraction of the (31)P NMR parameters for the individual lipid components. The isotropic chemical shift, chemical shift anisotropy, and asymmetry parameter can be extracted from the spinning side band manifold of the individual components that form liquid-ordered and liquid-disordered domains. The magnitude of the (31)P chemical shift anisotropy and the line width is used to determine headgroup mobility and monitor the gel-to-gel and gel-to-liquid crystalline phase transitions of SM as a function of temperature in these mixtures. Spin-spin relaxation measurements are in agreement with the line width results, reflecting mobility differences and some heterogeneities. It will be shown that the presence of DOPC and/or cholesterol greatly impacts the headgroup mobility of SM both above and below the liquid crystalline phase transition temperature, whereas DOPC displays only minor variations in these lipid mixtures.