Molecule Within a Molecule

May 12, 2006

All children are fascinated by Russian dolls: when the largest outer wooden figure is opened, a second, smaller, nearly identical doll appears. This one can also be opened and so on…. This toy could well have inspired T. Shinmyozu, H. Takemura, M. Yasutake, and K. Sato in Japan to synthesize their cyclophane within a cyclophane.

Cyclophanes are nonplanar polycyclic aromatic compounds, benzene rings in which two opposite carbon atoms are linked by a handle-like bridge. The simplest example would be a benzene ring “basket” with an alkane “handle”. Of course, this cannot be used to make tubes, so the Japanese scientists synthesized larger rings made of several building blocks whose opening is large enough to enclose larger molecules.

They thus allowed pyromellitic dianhydride (benzene-1,2,4,5-tetracarboxylic acid dianhydride) to react with 1,4-bis(aminomethyl)-2,5-dimethoxybenzene. The acid anhydrides combine with the amino groups to form acid imides, which results in rigid rings made of six building blocks with alternating acid imide and dimethoxybenzene units.

X-ray structure analyses show that these rings are not perfectly round but are shaped more like a triangle. At its widest point, the diameter of the ring is 1.2 to 1.3 nm. That is large enough to take up two molecules of the solvent p-xylene. In doing this, two of the cyclophane rings stack on top of each other to form longer smooth tubes. If the solvent for the crystallization was switched to toluene instead of p-xylene, the rings could enclose three solvent molecules. However, in this case the tubes were no longer smooth but had a zig-zag structure instead.

The researchers were interested in trying to incorporate larger molecules, such as a smaller cyclophane made of three benzene rings each bound to the others by a C2H4 bridge. This little cyclophane also has a triangular structure and is able to lodge in the larger cyclophane like a “doll within a doll”. These structures also organized themselves into longer, smooth tubes.

Citation: Teruo Shinmyozu, Cyclophanes Within Cyclophanes: The Synthesis of a Pyromellitic Diimide-Based Macrocycle as a Structural Unit in a Molecular Tube and Its Inclusion Phenomena, Angewandte Chemie International Edition 2006, 45, No. 22, 3643–3647, doi: 10.1002/anie.200504499

Source: Angewandte Chemie

Explore further: 'NanoSuit': Researchers use nano-coating to allow for electron microscopy of living insects

add to favorites email to friend print save as pdf

Related Stories

Obama recommends extended wilderness zone in Alaska

10 hours ago

US President Barack Obama said Sunday he would recommend a large swath of Alaska be designated as wilderness, the highest level of federal protection, in a move likely to anger oil proponents.

NASA craft set to beam home close-ups of Pluto

10 hours ago

Nine years after leaving Earth, the New Horizons spacecraft is at last drawing close to Pluto and on Sunday was expected to start shooting photographs of the dwarf planet.

Navy wants to increase use of sonar-emitting buoys

12 hours ago

The U.S. Navy is seeking permits to expand sonar and other training exercises off the Pacific Coast, a proposal raising concerns from animal advocates who say that more sonar-emitting buoys would harm whales and other creatures ...

Uganda seizes massive ivory and pangolin haul

12 hours ago

Ugandan wildlife officers have seized a huge haul of elephant ivory and pangolin scales, representing the deaths of hundreds of endangered animals, police said Sunday.

Recommended for you

Holes in valence bands of nanodiamonds discovered

13 hours ago

Nanodiamonds are tiny crystals only a few nanometers in size. While they possess the crystalline structure of diamonds, their properties diverge considerably from those of their big brothers, because their ...

Engineering self-assembling amyloid fibers

Jan 26, 2015

Nature has many examples of self-assembly, and bioengineers are interested in copying or manipulating these systems to create useful new materials or devices. Amyloid proteins, for example, can self-assemble ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.