Crinkled tape

Figures 5.2 and 6.2), the complex involving hydrogen-bonded barbiturate that should serve as sensor (Figure 6.9) and 234 have been presented earlier. The Whitesides rosette 3a [ 1 ], tapes 3b [2] and 109, crinkled tape 3c [ 1 ] (Figure 1.1) formed by melamine 1 and cyanuric acid 2 also shown earlier as well as... 

Two different of supramolecular synthons have been detected in the two polymorphs of the carbamazepine-saccharin cocrystal system [45]. In the Form-I structure, the carbamazepine molecules formed a homo-synthon, with the saccharine molecules also forming a hydrogen-bonded homodimer. The interaction of these two synthons resulted in formation of a one-dimensional array of molecules in a crinkled tape motif. In the Form-II structure, a heterosynthon is formed by the interaction of a carbamazepine and a saccharin molecule. This latter synthon packs in one-dimensional chains that extended along the crystallographic c-axis. 

Hexagonal layer structure of the 1 1 complex of melamine and cyanuric acid. Three kinds of assembly in lower dimensions are possible (a) linear tape, (b) crinkled tape, and (c) rosette. 

The complex between melamine and cyanuric acid (1 1) was reported in the literature in the late 1970s, but it was only in the early 1990s that the contributions from Whitesides and the concept of self-assembly popularized these systems [45]. Whitesides and co-workers reported the formation of tapes (Fig. 11.11), crinkled tapes and cyclic hexamers (rosettes) formed between barbituric acid and N,N -bis(p-substituted phenyl)melamine [46], In this they effectively blocked one face of melamine and, by manipulating substituents at the para position, different structures were obtained. Whiteside s putative suggestion that melamine/cyanuric acid formed an extended array (Fig. 11.12) was confirmed recently by Rao et al. with the crystal structure [47]. Hamilton and coworkers reported the crystal structure of a 5-substituted isophthalic acid derivative, which forms a cyclic aggregate held together with six pairs of hydrogen bonds, which in a way resembles the trimesic acid (Fig. 11.13) [48]. 

Figure 12.1. Aromatic carboxylic acids linked via synthon I (a) 1 forms centro-symmetric dimers, (b) 2 forms linear tapes, (c) 3 forms crinkled tapes and...

Zerkowski, J. A., Seto, C. T. and Whitesides, G. M. (1992). Solid-state structures of rosette and crinkled tape motifs derived from the cyanuric acid-melamine lattice. J. Am. Chem. Soc. 114, 5473. 

Fig. 22a, b Schematic representations of a linear tapes b crinkled tapes observed in structures based on N,AT-disubstituted melamines and 5,5-diethylbarbituric acid [169]... 

Figure 2 The structure of the hydrogen-bonded CA M lattice. Three classes of aggregates that we have observed in solution and the solid state are highlighted the rosette, crinkled tape, and linear tape motifs. The molecular strucmres of melamine and cyanuric acid and their abbreviated representation as dark and light disks are shown...

Figure 4 Incorporation of large groups (black disks) on the periphery of CA and M results in steric interaction between these groups in the tape (left) and crinkled tape (center) motifs, the arrows indicate these regions. In the rosette motif (right) these unfavorable steric interactions are minimized...

J.A. Zerkowski, C.T. Seto, G.M. Whitesides, Solid State Structure of Rosette and Crinkled Tape Motifs Derived from the Cyanuric Acid and Melamine Lattice , J. Am. Chem. Soc., 114,5473 (1992)... 

An example of formation of ordered supramolecular strands by co-crystallization of complementary molecular components, each of which presents two identical recognition sites (Figure 11.32), was reported by Lehn and co-workers [232], using the molecular components shown in 80. A similar approach has been adopted by Whitesides and co-workers for the engineering of co-crystals containing crinkled tapes or cyclic arrangements [233]. 

Among extended polymeric structures, two-dimensional hydrogen-bonded frameworks are enormously popular, and the resulting assemblies resemble practically crinkled tapes (153,154) and infinite sheets (155-158). Smith and co-workers have structurally characterized a... 

As previously noted, discrete assemblies based on 1-dimensional H-bonded motifs, also termed a-networks, may be obtained by covalently tethering the H-bonding recognition arrays or by their fusion to yield Janus molecules (Fig. 2). The information manifested in the relative orientation (120°) and juxtaposition of H-bonding donor/acceptor sites (DAD/ADA), in the specific case of 5 and 6, may generate three types of association a linear ribbon or tape, a H-bonded macrocycle and an intermediate wavy ribbon or crinkled tape [46]. These structures have been characterized in the solid state by X-ray crystallographic analysis. Homochiral crinkled tapes are formed in the course... 

The complementary molecular functionality of substituted melamines and barbituric acids leads to efficient hydrogen bonding between such compounds. This pattern is shown in Figure 6 and has been used by Whitesides, Lehn and others to design various supramolecular structures such as a linear tape, a crinkled tape and a cyclic rosette [68,69]. These structures are also illustrated in... 

Figure 6 (opposite) Melamine-barbituric acid recognition pattern and a schematic depiction of the linear tape, crinkled tape and rosette structures derived from this pattern (see Zerkowski et al. [68].)... 

Bielejewska. A.G. Maijo. C.E. Prins. L.J. Timmerman, P. De Jong, F. Reinhoudt, D.N. Thermodynainic stabilities of linear and crinkled tapes and cyclic rosettes in nielamine-cyanurate assemblies, a model description. J. Am. Chem. Soc. 2001. 123. 7518-7533. 

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