State-centric nature

The centric scan, one-dimensional, DHK SPRITE measurement was used to study the ingress of lithium. This measurement technique was selected due to the low absolute sensitivity of 7Li (27% of [36]), the small amounts that are present and the short signal lifetimes (bulk Tx of 10 ms and T2 of 120 ps). In addition to the robust, quantitative nature of this technique, lithium is a quadrupolar nucleus and interpretation of the image intensity is more complex than spin % nuclei. Once again Eq. (3.4.2) is quantitatively correct for even quadrupolar nuclei due to the fact the longitudinal steady state does not influence the image intensity. 

Although the absence of nuclei-centric structure makes direct chemical interpretation difficult, the EMD does have some other advantages. For instance, it is related to energy via the virial theorem stated previously and carries the valence information around p = 0. The entire nature of EMD topography is fixed by that at p = 0, as described by the hierarchy principle. 

Unfortunately, nature is unreliable when it comes to providing chiral space groups for achiral molecules, and the great majority of achiral substances crystallize in centric or otherwise symmetric packing arrangements [6]. The question thus became not whether the chiral crystalline state would serve as a useful medium for asymmetric synthesis—this had already been demonstrated—but how a chiral space group could be guaranteed for the achiral compound whose photochemistry one wished to study. 

The first example is that of cinchomeronic acid, which has been known for almost a century [48]. The cinchomeronic acid 3,4-dicarboxypyridine is one of the six isomers of the acid pyridinedicarboxyl all isomers are widely utilized in the construction of coordination networks [49-51]. The presence of two of cinchomeronic forms is reported in the PDF-2 [52], while the crystal structure has been determined only for one form [53]. We have investigated the structural relationship between these two crystal forms by a combined use of single-crystal X-ray diffraction, IR and Raman spectroscopy, and solid state NMR spectroscopy [54]. Form 1 crystallizes in an acentric orthorhombic group, while form 11 crystallizes in a centric monoclinic group (Fig. 4), due to a static disorder for the nitrogen position (Fig. 5). The zwitterionic nature of the acid in both forms has been confirmed by MAS,... 

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