Preparation, Structure and Spectra

Preparation, Structure and Spectra of Some Tetravalent Praseodymium Compounds... 

Asprey, L.B., J.S. Colman and M.J. Reisfeld, 1967, Preparation, Structure and Spectra of some Tetravalent Praseodymium Compounds, in Gould, R.F., ed., Advances in Chemistry Series No. 71 (American Chemical Society, Washington), pp. 122-126. 

The two forms are not strict polymorphs because I is a hydrate (one H2O per five lamivudines), but have different crystal structures and spectra. The O-H stretching mode from the hydrate water in I can clearly be seen at 3545 cm . The strong bands just below 3000 cm are from the hydrocarbon muUing agent used to prepare the material for spectroscopic measurement. 

Some triazepinones in which one of the nitrogen atoms belongs to a fused azole moiety have been reported. For instance, compound 63 was prepared (74JHC751) and its X-ray structure determined (75CSC317). Similarly, and NMR spectra and X-ray structural determination of 64 revealed that this compound exists as a 3//-tautomer with the 1,2,4-triazepine ring in a distorted boat conformation (88T7185). 

Complexes. The structure of an n a charge-transfer complex between quinoxaline and two iodine atoms has been obtained by X-ray analysis and its thermal stability compared with those of related complexes. The hydrogen bond complex between quinoxaline and phenol has been studied by infrared spectroscopy and compared with many similar complexes. Adducts of quinoxaline with uranium salts and with a variety of copper(II) alkano-ates have been prepared, characterized, and studied with respect to IR spectra or magnetic properties, respectively. 

Abstract Inorganic polysulfide anions and the related radical anions S play an important role in the redox reactions of elemental sulfur and therefore also in the geobio chemical sulfur cycle. This chapter describes the preparation of the solid polysulfides with up to eight sulfur atoms and univalent cations, as well as their solid state structures, vibrational spectra and their behavior in aqueous and non-aqueous solutions. In addition, the highly colored and reactive radical anions S with n = 2, 3, and 6 are discussed, some of which exist in equilibrium with the corresponding diamagnetic dianions. 

A cationic molybdenum sulfide cluster [Mo3S4(H20)9] " with incomplete cubane-type structure and a cationic nickel-molybdenum mixed sulfide cluster [Mo3NiS4Cl(H20)9p " with complete cubane-type structure were introduced into zeolites NaY, HUSY and KL by ion exchange. Stoichiometry of the ion exchange was well established by elemental analyses. The UV-visible spectra and EXAFS analysis data exhibited that the structure of the molybdenum cluster remained virtually intact after ion exchange. MoNi/NaY catalyst prepared using the molybdenum-nickel sulfide cluster was found to be active and selective for benzothiophene hydrodesulfurization. 

Whilst sample preparation may not be the most interesting aspect of NMR spectroscopy, it is nonetheless extremely important as it will have a huge bearing on the quality of the data obtained and therefore on your ability to make logical deductions about your compounds. This is particularly true when acquiring the most straightforward 1-D proton spectra. The most typical manifestation of sub-standard sample preparation is poor line shape. It is worth remembering that in terms of 1-D proton NMR, the devil can be very much in the detail . Detail , in this context, means fine structure and fine structure is always the first casualty of poor sample preparation. 

The main application of double resonance is the resolution of hyperfine and particularly superhyperfine interactions that are not extractable from regular EPR spectra because they are lost in the inhomogeneous line. The biological relevance is in otherwise unavailable detailed information on the electronic structure and the coordination of active sites and their interaction with reactants, such as enzyme substrates. To be well prepared, check off the items in the following list. 

In addition to observing Knight shifts in nanoparticles of the usual WZ form of GaN (h-GaN), this study also observed them in the rarer ZB c-GaN form. Various proportions of c-GaN could be identified in nano-GaN prepared by nitridation of GaAs, which has a cubic (ZB) structure and therefore provides topochemical conditions favoring c-GaN. Figure 13 (right side) shows the 69Ga spectra of three... 

FIGURE 4.7 (Left) Chemical structures of PPLED materials. (Right) The device structure and the electroluminescence spectra of the PPLEDs prepared with PYK (4) host polymer and the above dopants (5wt%). (From Kawamura, Y., Yanagida, S., and Forrest, S.R., J. Appl. Phys., 92, 87, 2002. With permission.)... 

The preparation methods of aluminum-deficient zeolites are reviewed. These methods are divided in three categories (a) thermal or hydrothermal dealumination (b) chemical dea-lumination and (c) combination of thermal and chemical dealumination. The preparation of aluminum-deficient Y and mordenite zeolites is discussed. The structure and physico-chemical characteristics of aluminum-deficient zeolites are reviewed. Results obtained with some of the more modern methods of investigation are presented. The structure, stability, sorption properties, infrared spectra, acid strength distribution and catalytic properties of these zeolites are discussed. 

Preparative details and extensive i.r., n.m.r., and mass spectra have been described for the phosphoranes (87).48 These phosphoranes have a TBP structure, and for (87a)—(87c) their n.m.r. spectra are temperature-independent, and indicate that the fluorines bonded to phosphorus are equivalent. The authors have suggested an explanation based on rapid intramolecular isomerization, and discussed the possibility that a facile TR pathway exists for this process.46 Octahedral adduct formation between (87) and fluoride ion or trimethylphosphine has also been described,46 as shown in (88). 

Details have been published of the synthesis and spectra of a wide range of mono-alkoxyphosphoranes (97), prepared by the silane-exchange method as shown.83 The 19F n.m.r. compilation on these phosphoranes is very impressive, and their structures... 

CZE has been employed for the analysis of another set of dyes in foodstuffs. The chemical structures, numbers and names of the dyes included in the investigation are listed in Fig. 3.142. A fused-silica capillary column of 57 cm length (50 cm effective length 75 jum i.d.) was employed for the separations. The capillary was conditioned by 1.0 M NaOH for 20 min followed by 10 min wash with water and 10 min wash with the running buffer. The buffer was prepared by adding NaOH to 10 mM phosphoric acid to reach pH 11.0. The capillary was thermostated at 25°C and the separation voltage was 20 kV. A hydrodynamic injection mode was applied (0.5 psi, 4 s, 21 nl) and spectra of... 

Experimental difficulties include sample preparation, intensity and stability of X-ray beam, and resolution. Insufficient resolution in even the best spectra presently attainable obscures some details of the fine structure. The spectra reported here are obtained with resolution of 1 or 2 ev. the present limit to resolution in the energy range explored here is about 0.5 ev. 

Charge-transfer interactions have been observed between NbFj and MX4 (M = Si, Ge. or Sn. X = alkyl M = C, Si, or Sn, X = Cl) and several organic solvents, and for NbClj and TaClj with aromatic hydrocarbons and fluorocarbons. Tn these latter cases the enthalpies of interaction were estimated as 6.3 kJ mol The new complexes [MF L] (M = Nb or Ta, L = DMSO, EtCN, or CH CICN), [TaF, 2-Mepy)]. and [tap5(4-Mepy)2] have been prepared. Their vibrational spectra have been recorded and. together with those of [MF5(MeCN)] and [MFjLJ (M = Nb or Ta and L - DMSO or py), discussed in terms of MFjL and [MF L4][MFg] structures." ... 

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