Heteronuclear correlation HETCOR

The development and application of multidimensional solid state homo- and heteronuclear correlation (HETCOR) NMR techniques have lead to an increasingly important role in structure solution of zeolitic materials and have had many practical applications in the detailed structural characterization of completely siliceous zeolites[6,7] and AlPOs.[8-ll] However, HETCOR NMR is not readily applicable to aluminosilicates... 

Information about the surface and interface structures in hexadecylamine-capped CdSe NC of 2 nm size has been obtained by a variety of 1H, 13C, 113Cd, and 77Se NMR techniques [342]. The 77Se CP-MAS-NMR spectrum showed five partially resolved peaks from surface or near-surface Se environments. It was possible to obtain 2D heteronuclear correlation (HETCOR) spectra between 1H and the other three nuclei despite the inherent sensitivity limitations (the 77Se- 3I-I HETCOR experiment required 504 h ). The latter experiment indicated that the methylene protons of the hexadecylamine chain interact with the surface Se atoms via a tilt of the chain toward the surface. The surface Se atoms were not seen to interact with thiophenol present, and it was suggested that thiophenol binds to a selenium vacancy at the surface. 

In the presence of excess ammonia, the surface complex coexists with its ammonia adduct ](=SiO)2Ta(=NH)(NH2)(NH3)]. NMR studies on the fuUy N-labeled samples have led to unambiguous discrimination between imido, amido and amino resonances of the surface complex and its NH3 adduct, and [=Si- NH2] through the combination of soHd-state magic-angle spinning(MAS), heteronuclear correlation (HETCOR), 2D proton double-quantum (DQ), singlequantum (SQ) correlation, and 2D proton triple quantum (TQ) single quantum... 

Recently, the two-dimensional 13C H heteronuclear correlation (HETCOR) NMR method, using the frequency-switched Lee-Goldberg (FSLG) H decoupling sequence55 at high MAS rates, has been developed, in order to provide intermolecular and spatial distance information. The HETCOR spectrum often has multiple proton cross peaks for each carbon, and these cross peaks can be extremely helpful for assigning the spectrum. Thus, this method can be used to characterize the structure of polymers in solids.55 71... 

Frequency-switched Lee-Goldburg (FSLG) 13C-1H heteronuclear correlation (HETCOR) experiments... 

A useful approach to solve these problems is solid-state two-dimensional (2D) C H heteronuclear correlation (HETCOR) spectroscopy. 

H and 13C NMR techniques have widely been used to determine the configuration of new dioxepins and dithiepins and to elucidate the constitution and conformation of new naturally occurring substances. For example, the configuration of oximes 14 was determined by H and 13C correlated spectra, correlation spectroscopy (COSY), nuclear Overhauser enhancement spectroscopy (NOESY), heteronuclear correlation (HETCOR) spectroscopy, and hetero-nuclear multiple bond correlation (E1MBC) spectroscopy <1998CCA557>. 

Heteronuclear correlation (HETCOR) is an experiment establishing a correlation between the chemical shift of proton and that for another nucleus (i.e. C, P, Nor Si). The experiment relies on the heteronuclear dipolar interactions and uses a CP to transfer magnetization from protons to a rare spin.4,6 We have used 2D HETCOR experiment to characterize support/counter-cation/cluster interaction in the supported mesoporous catalysts.21... 

Heteronuclear correlation (HETCOR) spectroscopy is a standard two-dimensional NMR technique. The resolution of 31P 1H CPMAS spectra is generally not sufficient to unequivocally detect the HP042 ions and the apatitic OH- ions in bone or dentin samples.15 In this regard, the breakthrough came from the first application of 31P 1H HETCOR to HAp and bone samples,24 where the correlation peak at 0.2 and 3 ppm of the 1H and 31P dimensions, respectively, has been established as the spectral marker of apatitic OH- ions. To enhance the spectral resolution in the XH dimension, 1H homonuclear decoupling was employed during the fi... 

In the early stage of development of NMR spectroscopy, the applicability of multi-dimensional approach was tested for condensed matter. Today, because of the excellent progress on this field, the "library" of different ND techniques used in SS NMR is pretty rich. On the basic level, these methods can be assigned to two groups homo- (HOMCOR) and heteronuclear correlations (HETCORs). Both correlations employ indirect (through-bond) or direct (through-space) coupling to correlate different spins. 

Heteronuclear-correlation (HETCOR) MQMAS NMR is a very useful method for studying the connectivity between spin-1/2 and quadrupolar nuclei under high-resolution conditions. It was first demonstrated for a spin-3/2 nucleus by Wang et al. with a spectrum of NajPjOg correlating the Na and P (1=1/2) isotropic resonances [69]. Several schemes have been proposed to obtain similar spectra for spin-5/2 nuclei [92-94]. However, we have recently demonstrated that these schemes result in distorted spectra and that an extension of the original scheme proposed by Wang et al. should be used instead[95]. 

For heteronuclear correlations, HETCOR historically was the standard experiment used to detect proton-carbon scalar couplings. 127-129 disad-... 

So far, homonuclear dipolar interactions were used to correlate spins. Alternatively, a 2D — C heteronuclear correlation (HETCOR) experi-... 

In a 2D heteronuclear correlation (HETCOR) experiment, the h and t2 periods correspond to the evolution of SQC of two different nuclei, e. g., and A number of different HETCOR experiments have been proposed which differ with respect to, e. g., the means by which coherence transfer is achieved, the type of coherence which evolves during h, as well as the application of homonuclear decoupling sequences. 

Carbon peak assignments were not available in the earlier reports, and hence, a comprehensive study utilizing H, correlation spectroscopy (COSY), heteronuclear correlation (HETCOR), and heteronuclear multibond correlation (HMBC) nuclear magnetic resonance was undertaken. NMR CDCI3 (5 ppm vs. TMS (multiplicity H s coupling constant assignment)) 7.36 (d IH J5.4 Hz, H-2),... 

Two-dimensional covariance NMR spectroscopy, which was originally established to extract homonuclear correlations (HOMCOR), has been extended to include heteronuclear correlations (HETCOR) by Takeda et al. In a 2D chemical shift correlation experiment, and N... 

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