Californian chemists have made a compound of interlocked rings in the shape of Solomon’s Knot: an ancient symbol of wisdom considered sacred in many cultures. Older than Judaism, with which it is generally associated, the knot motif has been found in stone age carvings.
In a marriage of nanoscience, mathematics and art, UCLA graduate student Cari Pentecost produced a 2-nanometre sized molecular analogue of Solomon’s Knot, which is comprised of two rings that interlace each other four times. Pentecost made the discovery while investigating another topology that goes by the name of Borromean Rings.
The synthesis of Borromean Rings relies on the presence of a transition metal ion template in the reaction pot, and zinc and copper ions are commonly used. When Pentecost tried equal parts of zinc and copper ions, there emerged from the process not mixed-metal Borromeates, as were expected, but high quality crystals in the form of Solomon’s Knots.
Pentecost refers to the process in Darwinian terms: ‘Chemical evolution is made possible by dynamic covalent chemistry, where you could say a process of natural selection occurs to amplify, out of a library of many possible products, exclusively the one that is the most stable under those reaction conditions.’
As for practical applications of molecular Solomon’s Knots, Fraser Stoddard, Pentecost’s PhD supervisor and director of the California Nanosystems Institute, is something of a long-term thinker. Referring to a catenane molecule he first synthesised in 1989, Stoddart said: ’Events in our laboratory have traced a pathway to a near-relative being the memory component of what could one day become a part of a molecular computer.’
On the connection between science and art, Pentecost quotes Albert Einstein: ‘After a certain high level of technical skill is achieved, science and art tend to coalesce in aesthetics, plasticity and form. The greatest scientists are always artists as well.’
Further information: “A molecular Solomon link”, Pentecost et al., Angewandte Chemie International Edition 46, 218, 2006 (subscription required).
Figure: Adapting the recipe for Borromean Rings (BR), using zinc and copper ions in equal parts, yields single crystals in the form of Solomon’s Knots.
Article first published in Nanomaterials News.