Characterization of amorphous carbon films by 13C CP MAS NMR spectroscopy

¹³C CP MAS NMR spectroscopy was used to characterize α-C:H materials generated from methane and hydrogen mixtures using a microwave plasma. Dipolar dephasing experiments indicate a range of T_dd making quantification of quaternary “diamond”-like carbons difficult. Unconstrained lineshape analysis is not suitable for the deconvolution of the NMR spectra, but linewidth constrained analyses gave reasonable results. © 1993 John Wiley & Sons, Inc.     

NMR study of solid C60(γ-cyclodextrin)2

A solid complex of C₆₀ with γ-cyclodextrin (γ-CyD) was examined with NMR spectroscopic methods in order to understand the dynamics of C₆₀, and the interaction between C₆₀ and γ-CyD. A ¹³C solid-state cross-polarization magic angle spinning (CP/MAS) NMR spectra shows C₆₀ resonance at 142.6 ppm. This provides the evidence of interaction between ¹³C spins in C₆₀ and ¹H spins in the γ-CyD host. Ambient temperature experiments on the ¹³C CP/MAS NMR, with varying contact time, shows that the water associated with γ-CyDs plays an important role in the nuclear relaxation processes. The dynamics of C₆₀ in γ-CyD was investigated using temperature and field-dependent ¹³C spin-lattice relaxation time measurements. The influence of water on the dynamics of C₆₀ was less significant below 250 K.     

New synthesis of alkyldihydrosilanes and their applications in modification of silica gel

Summary A comparison of newly synthesized, reversed-phase bonded stationary phases is presented. The materials studied include monomeric n-octyl, n-octadecyl, aryl and n-octyldihydrogeno bonded-phases. Differences in reactivity of the silane functional groups are demonstrated and the high coverage obtained with the hydrogeno-bonded phases is shown. The structures of the bonded phases have been determined by²⁹Si and¹³C CP/MAS NMR spectroscopy.     

硫酸交联壳聚糖湿膜的13C CP MAS NMR研究

首次采用¹³C CP MAS NMR技术对接近膜分离状态时的湿膜进行研究.结果表明:温膜的分子构象和分子运动能较全面地反映出膜的分离特性,弱的交联以及过快或过慢的分子运动均不利于膜的分离.     

Strukturen und intramolekulare Bewegungen spezieller polycyclischer Germanium(II)-amide

Structures and Intramolecular Motions of Special Polycyclic Germanium(II) Amides Compounds of the general formula MeSi(NtBu)₃Ge₂X (X = Cl ( 1 ), N(SiMe₃)₂ ( 2 ), P(C₆H₅)₂ ( 3 )) have been synthesized and characterized by X-ray structure analyses and multinuclear NMR-spectroscopy. The temperature dependent NMR investigations of 2 in solution show bond fluctuations concerning the metal-nitrogen bonds and ElMe₃ (El = C, Si) rotations. Some of these intramolecular motions also occur in the solid state as detected by means of temperature dependent ¹³C CP/MAS NMR spectroscopy. The special nature of these NMR spectroscopically detected movements in solution are compared with the results of the X-ray structure analyses. A model of the dynamical behaviour of 2 in solution suggests a quasi circular movement of the two germanium atoms within the molecular cage. After the phase transition from solution to the solid state at ambient temperature this special metal fluctuation is stopped. In the solid state the rotations of the SiMe₃ groups in 2 are only hindered at low temperatures.     

Width effects of theZ resonance and CP-violating asymmetry ine + e − annihilation

CP-violating rate asymmetry can be generated in a process only if its amplitude possesses an absorptive part. It is pointed out that such an absorptive part can be provided ine ⁺ e ⁻ annihilation by the presence of aZ(Z′) resonance of non-zero width. The CP asymmetry in the process , wherel _i are charged leptons, is discussed in several models. In a specific two-Z model, large and observable CP asymmetry ine ⁺ e ⁻ →τ ⁺ e ⁻ (τ ⁻ e ⁺) is shown to be possible at LEP/SLC energies.     

Formation and multinuclear magnetic resonance investigation of silylammonium tetracarbonylcobaltate contact ion pairs

Silylcobalt tetracarbonyls were reacted with various amines (B) in non-polar solvents to form silylammonium tetracarbonylcobaltate contact ion pairs formulated as [BSiR ₃ ⁺ , ⁻Co(CO)₄]. The compounds were characterized by IR and multinuclear magnetic resonance spectroscopy both in solution and in solid state. Their properties are analogous to the known ion pairs [BH⁺, ⁻Co(CO)₄] and to amine adducts of halosilanes as well.     

Solid state N and C NMR study of dioxomolybdenum (VI) complexes of Schiff bases derived from trans-1,2-cyclohexanediamine

The ¹³C, ¹⁵N CP MAS NMR and FT-IR spectra of dioxomolybdenum (VI) complexes of trans-N,N′-bis-(R-salicylidene)-1,2-cyclohexanediamine (R=H, R=3,5-diCl, R=3,5-diBr, R=4,6-diOCH₃), trans-N,N′-bis-(2-OH-naphthylidene)-1,2-cyclohexanediamine and trans-N-(salicylidene)-N′-(2-OH-naphthylidene)-1,2-cyclohexanediamine have been measured. Comparative analysis of the NMR and IR spectra of the complexes with those of the corresponding ligands has shown that the complexation of the di-Schiff bases leads to changes in the conformation of the ligands and the charge redistribution. The asymmetric structure and non-planar structure of the complexes have been suggested.     

Molecular structure of the unusual complex of 1-piperidineacetic acid with 2,4,6-trinitrophenol studied by X-ray, FTIR and H, C and C CP MAS NMR

Crystals containing three kinds of molecules 1-piperidiniumacetate (II), 1-piperidiniumacetic acid (III) and 2,4,6-trinitrophenolate (picrate, TNP⁻), belong to the monoclinic system, space group P2₁/c and Z=4, a=12.831(3), b=26.093(5), c=7.157(1) Å, β=101.18(3)°, R=0.0758. The zwitterion molecule (II) is a double acceptor of protons from two molecules of 1-piperidiniumacetic acid (III) (N–HO, 2.735(5) Å and O–HO, 2.472(5) Å), and a donor of proton to the picrate molecule (N–HO, 2.747(5) Å). These three molecules, which have three donor centers and several acceptor groups, form hydrogen-bonded chains parallel to the z axis. The oxygen atoms inactive in these hydrogen bonds, are engaged in the C–HO short contacts, which can be treated as weak hydrogen bonds, and join the chains into a three-dimensional network. The presence of protonated 1-piperidineacetic acid (III) and its zwitterion (II) in the crystal has been confirmed by ¹³C CP MAS NMR and solid state FTIR spectra.     

Variable temperature CP/MAS13C NMR study of cyclodextrin complexes of benzaldehyde

Fully hydrated as well as dried benzaldehyde complexes of - and -cyclodextrins were studied by using CP/MAS¹³C NMR techniques. Variable temperature studies have shown that below 200 K the guest is rigidly held in the complex, whereas at 328 K, only the aromatic ring performs rapid two-fold flips about the C₁–C₄ axis. In the -Cd complex the benzaldehyde performs more general reorientation. Removal of water causes marked changes in both guest and host spectra, generally consistent with a loss of short-range order and increase in guest motional rate.NRCC No. 27826.