Hydrogen bonds graph sets

The 1 1 cocrystal of 2-amino-5-nitrothiazole with 4-aminobenzoic acid comprises two constituent molecules associated by a hydrogen-bonded graph set dimer through the carboxylic group across the N/N site of the thiazole [0-H...N, 2.614(3)A N-H...O, 2.991(3)A] [144], 2-Bromo-5-nitrothiazole [145], tetrakis (mefa-acetato)bis[2-(2-thionyl)-amino-5-nitrothiazole]-dirhodium-II-dihydrate [146], and /V-(4-melhoxyben/yl (-/WS-nilro-1,3-thia/ol-2-yl) urea [147] have been studied by X-ray analysis. 

Fig. 12.7 C60H36(D3d)(CK) hydride Schlegel diagram black circles refer to the 36 Carbon-Hydrogen bonds graph has two benzenoid rings it contains C3V C6QH18(a) hydrogen atoms sub-set (see Fig. 12.4)...

According to Graph Theory, a molecule may be represented by its skeletal molecular graph which, from a mathematical point of view, is the union of a set of points, symbolising the atoms other than hydrogens, and a set of lines, symbolising bonds. Its properties can be then expressed in terms of graph-theoretical invariants, Njj, which have been defined as "the number of distinct ways in which skeleton i... 

O/tT)o-substituted primary nitroanilines usually form two-centre intermolecular hydrogen bonds rather then three-centre, with graph set Rj (6) (8.21). 

Some examples of graph-set descriptors of hydrogen-bonded structural motifs. 

Patterns of hydrogen bonding found in three polymorphic forms of 5,5-diethylbarbituric acid. The graph-set descriptors are (a)... 

Fig. 2.17 Examples of the use of graph set descriptors to define motifs and first and second level graph sets for schematic representations of the hydrogen-bond patterns in the crystal structure of benzamide. (From Bernstein and Davis 1999, with permission.)...

Fig. 2.19 First level graph sets for the three polymorphs of anthranrhc acid 2-V. The two molecules in the asymmetric unit of Form 1 are shown in their true crystallographic relationship to each other (see text). In (d) and (e) the third ammoniacal hydrogen, which does not participate in a hydrogen bond, is hidden hy the nitrogen to which it is attached, (a) Form II (b) Form ni (c) Form I, C(6) of A type molecnles (d) Form I, C(6) of B type molecules (e) Form I, intramolecular motifs S(6) for molecules A and B and the dimer D relationship connecting them. (Adapted from Bernstein et al. 1995, with permission.)...

To distinguish between Form n and Form III we mrn to the binary graph sets. In principle it is possible to combine the three hydrogen bonds pairwise in three different ways. One of the combinations, 0 (4) for Form n is shown in Fig. 2.20(a), which reflects the fact that both hydrogen bonds in the chain are to the same carbonyl oxygen acceptor. For Form III (Fig. 2.20(b)) the chain C (6) contains both oxygens of the carboxyl group hence there are two acceptors and two additional atoms in each chain link . Also, note that an equal number of atoms in the chain formed by ca in both Forms II and III, but the former has one acceptor and the latter has two acceptors. The... 

Bernstein, J. and Davis, R. E. (1999) Graph set analysis of hydrogen bond motifs. In Implications of molecular and materials structure for new technologies, NATO Science Series E Applied Science (ed. J. A. K. Howard and F. H. Allen and G. P. Shields), Kluwer Academic Publishers, Dordrecht, Vol. 360 275-290 [57f, 58f, 81]. 

Etter, M. C., MacDonald, J. C. and Bernstein, J. (1990a). Graph-set analysis of hydrogen-bond patterns in organic crystals. Acta Crystallgr. B, 46, 256-62. [55, 56, 77]... 

Grell, J., Bernstein, J. and Tinhofer, G. (2002). Investigation of hydrogen bond patterns The graph set approach. Part I. General ideas and their application to crystal structures with exactly one molecule in the asymmetric unit. Crystallogr. Rev., 8, 1-56. [58]... 

---