Nano-Sized Golden Crown

Chinese researchers recently created a "golden crown" with a diameter of only a few nanometers. The large ring-shaped structure containing 36 gold atoms is held together exclusively by gold to gold bonds and is thus the largest ring system made of gold atoms produced to date.

Small rings made of positively charged gold atoms have been known for some time, but only recently could the Chinese team make a ring containing 16 gold atoms. Now the researchers, led by Shu-Yan Yu, Yi-Zhi Li, and Vivian Wing-Wah Yam, have introduced a new representative of this class of compounds, the biggest gold ring to date held together exclusively by gold to gold bonds.

Since the discovery of crown ethers in 1967, large molecular rings have fascinated chemists and have played an important role in the search for new functional materials and nanotechnology. The synthesis of ring systems held together exclusively by metal to metal bonds has remained a challenge.

The researchers started their synthesis with a ring system containing six gold atoms. Three of the gold atoms are linked into a triangle. Each of these gold atoms is attached to another gold atom that sticks out from the corner of the triangle. Three organic ligands are then bound to this flat double triangle to form a molecule that resembles a three-blade propeller.

Six such "propellers"” can be linked into a larger ring by means of a self-assembly process. Within this ring system, the gold atoms are arranged into a shape that resembles a crown: six double triangles are each bound to each other by two corners. The free double-corners point outward in a pattern that alternates above and below the plane of the ring.

-- Justin Jernigan