Even though their modest 10-20 carats will not impress your girlfriend, cyclohexamantane
molecules are, despite their nanometer-scale dimensions, a part of the diamond family. They belong to the class of molecules known as diamondoids, unusual hydro
carbons whose cage-like
carbon atom arrangements correspond to sections of the
crystal structure of diamond. Researchers from oil company
ChevronTexaco recently found these
diamonds/order_t/'>nanodiamonds in crude oil.
The simplest diamondoid is called adamantane (Greek for diamond) and consists of ten carbon
atoms, whose arrangement corresponds exactly to a single "cell" of the diamond structure. Jeremy E. P. Dahl and his co-workers have been able to identify over 20 different higher diamondoids, which consist of up to eleven adamantane units. Dahl and researchers from ChevronTexaco, several American and European Universities,
Pfizer and BP, have now characterized and verified the structure of a special representative of the diamondoids, cyclohexamantane. The cyclohexamantane framework consists of 26 carbon atoms, as though six adamantane units were fused into a disk-shaped molecule. A total of 30
hydrogen atoms occupy the corners of the carbon cage.
Jewelers may not be able to muster up much enthusiasm for diamondoids, but scientists are fascinated by nanodiamonds, which not only share a common structure with their macroscopic cousins, but also possess their extraordinary strength and
stability. At the same time, the different structures of the molecules provide an enormous structural diversity. In principle, the corner atoms could also be equipped with very different
functional groups, which would result in great chemical versatility.
Diamondoids are thus ideal
building blocks for
nanotechnology, and pharmacological applications are also possible.
"It has thus far not been possible to produce cyclohexamantane by synthetic routes," reports Dahl. "Petroleum is the only known source." "How cyclohexamantane is formed remains unclear, however, the reaction pathway which leads to their
Formation, could also have led to larger diamondoids, even to microcrystalline diamonds. We are currently testing this hypothesis."