Spectroscopy HETCOR

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) 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... 

Very recently, an interesting modification of HETCOR correlation was published by Chan and co-workers.69 In this experiment, a DQ filter is incorporated into the pulse sequence of HETCOR spectroscopy so that a DQ excitation profile can be obtained by measuring a series of 2D spectra (Figure 14). This method offers a simple experimental approach to extract the van Vleck second moment of a multiple-spin system under high-resolution condition. Hydroxyapatite (Ca10(PO4)6(OH)2) and brushite (CaHP04 2H20) were used as reference samples. 

D heteronuclear correlation (HETCOR) spectroscopy is a cornerstone technique for many assignment strategies and is the method of choice for distance measurements through time-oscillatory magnetization build-up curves, REDOR (rotational echo double resonance) dephasing curves or rotor-encoded SSB analysis. 

The aluminated brain tissue has a considerably different Al MAS NMR spectrum. In addition to the transferrin-type resonance, additional peaks are seen. From these data it was concluded that brain tissue is susceptible to a broad range of coordination by aluminum. Furthermore, the moderate Al Cq values (all less than 10 MHz) suggest future NMR studies may be performed at 9.4 T and a spin rate of 20 kHz. The P NMR spectrum of octacalcium phosphate was assigned by P double quantum and HETCOR spectroscopy. 

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