Hydrogen-bonding-based tapes

Among the classes of molecules able to form hydrogen-bonding-based tapes, the diketopiperazine (DKP) family now appears to be the most attractive [30]. The molecular packing in this system of crystals is less complex than systems based on CA M or cyclic ureas, because there is only one possible tape. The locations of the 3,6-substituents seems to protect the secondary amide groups from interactions... 

Solid-State Structures of Hydrogen-Bond Tapes Based on Cyclic Secondary Diamides [J. C. MacDonald, G. M. Whitesides, Chem. Rev. 1994, 94, 2383]. 

Zerkowski, J. A., MacDonald, J. C., Seto, C. T., Wierda, D. A. and Whitesides, G. M. (1994). Design of organic structures in the solid state molecular tapes based on the network of hydrogen bonds present in the cyanuric acid melamine complex. J. Am. Chem. Soc. 116, 2382. 

Fig. 11 Hydrogen-bonded tapes formed by l,l -bicyclohexylidene-4,4 -dione dioxime, based on Rl(6) motifs [94]...

We will present examples of tapes, ribbons, and sheets based on hydrogen bonding and other intermolecular interaction patterns. The use of both strong hydrogen bonding groups such as carboxylic acids and amides, as well as, weak interactions such as C-H---0 hydrogen bonds and iodo---nitro polarization interactions will be covered. 

The crystal structures of several 5-alkoxyisophthalic acids form tapes and ribbons when cocrystallized with pyrazine, pyrimidine and ethanol [45]. The carboxylic acid units of 13 engage in hydrogen bonding to other acids as well as to the bases and alcohol (Fig. 11 a,b). In Fig. 11c the pyrimidine acts as a spacer between 14, extending the tape formation. However, when acid 14 is recrystallized in its pure form, the formation of the carboxylic acid dimer motif occurs... 

Macdonald JC, Whitesides GM. 1994. Sohd state structures of hydrogen bonded tapes based on cyclic secondary diamides. Chem Rev 94 2383 2420. 

The improvement in results with more accurate electrostatic models can also be seen by studying the blind test results in more detail. For example, the observed crystal structure of molecule VIII contains molecular tapes based on / (8) hydrogen bond dimers... 

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