Cup-shaped molecules

A trinuclear system, whose structure was published,555 was formed in high yield by the cyclometalation of a l,3-bis(alkylbenzimidazol-2-yl)benzene ligand, followed by the trimerization of the unit, which possesses a vacant coordination site on the palladium atom and a pendant noncoordinated benzimidazole moiety. The resulting product forms a cup-shaped trimer or tricorn, presented in Figure 46, that includes a molecule of acetonitrile in the crystal structure.556... 

X-Ray crystallographic analysis of 24-AcOH established the r ,yv, /,t -configii ration <1993TL5555>. The phenyl rings are positioned in the way that the molecules are cup-shaped in the crystals. Each molecule of 24 has a molecule of AcOH which is hydrogen-bonded to one of the carbonyl oxygen atoms. 

Lipocalins are a family of proteins, which serve to transport small molecules around the body. A sub-set of the lipocalin family is found in the nasal mucosa and its members are known as odour-binding proteins (OBPs). These proteins are known to bind odorants but their role in olfaction is not understood at present. Each OBP is really a complex of two cup-shaped proteins with a hinge formed by the amino acid backbone of one passing through that of the other. Once they have bound a substrate, the cups come together at the rims and so form a spherical hydrophilic unit and an X-ray crystal structure of such an OBP odorant complex has been published (Bianchet et al., 1996). The role of the OBP could be to... 

The X-ray crystal structure of 27(cone) confirmed that the calixindole adopts a cone conformation with a hydrogen-bonded array of axial groups at the lower rim of the calixindole. Interestingly an ethanol molecule (not shown) is bound within the cup-shaped cavity of the molecule (Figure 30). 

Calixarene An oligomeric molecule originally obtained from the condensation of a / -alkyl phenols and formaldehyde. The term now applies to a variety of derivatives of cyclo oligo[(l,3-phenylene) methylene] In the name calix[n]arene, the [n] refers to the number of phenol and aldehyde units per molecule. The name is derived from the cup shaped cone conformation of calix[4]arene. See also resorcinarene. 

Matsuo Y, Muramatsu A, Hamasaki R, Mizoshita N, Kato T, Nakamura E (2004) Stacking of molecules possessing a fullerene apex and a cup-shaped cavity connected by silicon-connection. J Am Chem Soc 126 432 33. doi 10.1021/ja038816y... 

Fig. 16.16 (a) Examples of macrocyclic compounds used to modify CPEs. (b) Example highlighting the chemical structure of a simple calixarene from which it is easy to see the cup shape of the molecule likely to act as a host for guest species. The symbol R is not a single element but represents a group of atoms. The structure of the R group can be varied to give the basic calixarene structure a more selective action rather than simply working on the basis of size... 

Molecular sizes and shapes play key roles in determining chemical and physical properties. The immense variety of chemical and physical properties displayed by substances in the natural world mirrors an equally immense variety of different types of molecules. However, variety need not come from a large number of different elements. The molecules that make up a cup of coffee are made up almost entirely of atoms of just five elements hydrogen, carbon, oxygen, nitrogen, and sulfur. Carbon, in particular, is capable of combining in many different ways, generating molecules with elaborate stractures. 

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