Cyclotriveratrylene structure

The network structures to be discussed will all involved hydrogen bonding as the supramolecular synthon. It should be noted however that other interactions such as coordinate bonds and host-guest interactions may also organise host molecules into network structures. Coordination polymers constructed from molecular hosts may involve functionalised calixarenes [8-11], cyclotriveratrylene [12], or cucurbituril [13]. Calixarenes have also been used to build up network structures via host-guest interactions [14,15]. It is also notable that volatile species may be trapped within the solid state lattice of calix[4] arene with a structure entirely composed of van der Waals interactions [16]. 

Typically, the cumulative electron-withdrawing effect of metallating more than half of the arenes of the macrocycle is required in order to observe anion inclusion. Thus, we have focused on tetrametallated derivatives of calix[4]arene and di- or trimetalated derivatives of the related orr/io-cyclophane, cyclotriveratrylene (CTV). The X-ray crystal structure of the BF salt of the water soluble bear trap 51 demonstrates the suitability of the narrow calix[4]arene cavity for small tetra-... 

Cyclotriveratrylene/1180-60-5] (34) is a cyclocondensation product of veratrole with formaldehyde. It possesses a stable trigonal crown conformation and forms crystalline inclusion compounds with benzene, chlorobenzene, toluene, thiophene, decalin, chloroform, acetone, carbon disulfide, acetic acid, and butyric acid (101). Their structures consist of columns of cyclotriveratrylene molecules that are not amenable to close packing and provide channels into which the guests are accommodated. A number of modified host structures, derived from prototype (34) have been prepared. The hexaphenol analogue cyclotricatechylene also yields well-defined channel inclusions (101). They involve mosdy polar guests and the structures are held by hydrogen bonding. 

Ahmad, R., Hardie, M. J., Synthesis and structural studies of cyclotriveratrylene derivatives. Supramol. Chem. 2006, 18, 29-38. 

A number of other receptors structurally relating to 36 were described that possess overall similar binding properties although some characteristic differences were noted. Compound 37, for example, containing a cyclotriveratrylene-derived cap instead of a TREN moiety, also binds imidazolidin-2-one or ammonium halides, but since this compound lacks the tertiary amino group it does not allow binding properties to be controlled by protonation [84],... 

That Robinson s and Ewins compounds did in fact have the trimer structures 1 and 2, respectively, was only established 50 years later by the works of Lindsey [3], Erdtman et al. [4], and Goldup et al. [5], The name cyclotriveratrylene (CTV) was given by Lindsey to 1, which was shown by NMR to adopt the locked crown conformation shown on the stereoformula and later evidenced by X-ray crystallography (Fig. 1) [6, 7], More recently [8], the inversion barrier of the crown in 1 was found to be ca. 26.5 kcal mol 1 from the racemization rate of the isotopically chiral C3-cyclotriveratrylene-d9 (3) relatively uniform values (AG 26.5 to 27.2 kcal/mol) were found [9] for a variety of chiral cyclotriveratrylenes, including the parent compound 4, C3-cyclotribenzylene-d3. Thus, in these compounds, the half-life of a crown conformer in solution is around one month at 20 °C, a few minutes at 100 °C and less than 0.1 second at 200 °C. 

Since the end of the seventies, interest in cyclotriveratrylene has moved towards the use of its cone shaped structure for applications in various fields, including investigations of the electronic transitions of the benzene chromophore via UV and CD spectroscopy, studies in the area of host-guest chemistry, synthesis of new types of liquid crystals, and searches for new three-dimensional organic charge-transfer materials. These works have been made possible because efficient synthetic... 

The name cryptophane [23], which designates molecules made of two cyclotriveratrylene units assembled by three bridges in the way shown in Fig. 3, recalls the [l.l.ljorthocyclophane structure of CTV and underlines the presence of an enforced cavity in these compounds allowing the inclusion of suitable guest species (Sect. 3). 

In order to increase the extension of the concave surface of cyclotriveratrylene, and to obtain potentially useful host structures, Cram and coworkers have synthesised cavitands 60-65 [33]. In these compounds the additional walls (e.g., the o-xylylene units in 60) are conformationally very mobile in solution. On crystallization from CH2Cl2-cyclohexane, 60 afforded a complex with one CH2C12 molecule inside the host cavity. The stereoview in Fig. 9 shows that two of the o-xylylene walls are turned upward from the cavity bottom and the third outward. 

D3)-Bis(cyclotriveratrylene) derivatives [35] as new macrocage hosts (13) (Structure 7) possess roughly spherical and considerably rigid lipophilic cavities. They have strong complexing ability toward neutral guests, namely poly-halomethanes, in water [36] and even in lipophilic media [37-39]. Stability... 

Cyclotriveratrylene is a trimeric, bowl-shaped molecular skeleton, known to form solid-state inclusion compounds. A variety of cyclotriveratrylene derivatives, e.g. 96 and 97, resulted from r-complexation of the aromatic nuclei with one, two, or three Ru( / -arene) (arene = CeHe, p-MeC6H4Pr ) and Ir( -C5Me5) organometallic moieties [195-197], Some of their structures were established by X-ray diffraction. 

The macropolycyclic speleand (30 a) combines the [18]-N303 macrocyclic binding subunit with the cyclotriveratrylene shaping component [23]. Its tight intramolecular cavity allows inclusion of the CH3-NH3 ion yielding the speleate [CH3--NH3 c (30 a)] whose structure should be of the type shown schematically by (30 b). 

Cryptophane A host that combines the structural features of a cryptand and a cyclophane. Typically two cone-shaped cyclotriveratrylenes are linked with three bridges to create an enforced cavity. 

FIGURE 28 (a) Saucerlike structure of cyclotriveratrylene and (b) related octopus molecule. 

Similarly, cyclotriveratrylene forms an inclusion complex only with Cao, but not with Cvo- Again, the driving force is the creation of K-n charge transfer interactions. The X-ray structure is simplified in Figure 10 and shows that Ceo adopts a nesting position above the concave surface of cyclotriveratrylene, with close contacts between the two entities at the van der Waals limits (3.34 - 3.51 A). These short contacts compare well with the contacts in cubic close packed Ceo-... 

Cyclotriveratrylene-based dendritic structures reveal a similar trend the association constant increases with the generation number of the surrounding dendritic substituents. 

The rigid bowl-shaped cyclotriveratrylene (CTV in Fignre 26.29) with its molecnlar cavity is capable of complexing guest molecules. Unsubstituted CTV forms supramolecular structures... 

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