Tuesday, May 19, 2009

Bioinorganic and Biomedical Chemistry of Gold

To please your inner aurophile, check out the special issue of Coordination Chemistry Reviews dedicated to Bioinorganic and Biomedical Chemistry of Gold. The (relatively) low toxicity and strong antiproliferative activity make gold complexes the promising anticancer drugs.

Thursday, May 14, 2009

Aurophile, argentophile...

One can expect that these terms have something to do with alchemistry. Wrong. Apparently, aurophilic bond is just a weak Au—Au bond, and argentophilic bond is a Ag—Ag bond. On the other hand, Merriam-Webster’s Medical Dictionary defines argentophilic (argyrophilic) as
having an affinity for silver — used of certain cells, structures, or tissues that selectively reduce silver salts to metallic silver.
“Cuprophilic” has been used in both senses, viz. Cu—Cu bond (as, for example, here) and “having an affinity for copper” (as in here). Similarly, “metallophilic” has been used to describe both “generic” metal—metal bond and for “metallophilic cells”. I find the use of this terminology in its former (more restrictive) sense both confusing and unnecessary. For example, this paper describes “Hg(II)···Pd(II) metallophilic interactions”. It could as well be named simply “Hg(II)—Pd(II) interactions”.

Saturday, May 09, 2009

Colour-changing mechanophores

The recent Nature publication shows that one can literally see a mechanically-induced ring-opening reaction.
Previously, we have shown with dissolved polymer strands incorporating mechanically sensitive chemical groups — so-called mechanophores — that the directional nature of mechanical forces can selectively break and re-form covalent bonds. We now demonstrate that such force-induced covalent-bond activation can also be realized with mechanophore-linked elastomeric and glassy polymers, by using a mechanophore that changes colour as it undergoes a reversible electrocyclic ring-opening reaction under tensile stress and thus allows us to directly and locally visualize the mechanochemical reaction. We find that pronounced changes in colour and fluorescence emerge with the accumulation of plastic deformation, indicating that in these polymeric materials the transduction of mechanical force into the ring-opening reaction is an activated process.
I guess we have to introduce a new ChEBI role: mechanophore.

Tuesday, May 05, 2009

Iron stars

According to Freeman Dyson, in rather unimaginable 101500 years from now, and in case proton decay does not happen, most of nuclei will either fuse or decay into iron. This will leave the universe inhabited by “cold spheres of pure iron”. I think it is cool, even if I won’t live that long to see it. However, I came across a report of recent (2006) observation of ‘iron star’ with NASA's Spitzer Space Telescope. I don’t think these objects are the same as Dyson’s iron stars though, just the next best thing.

Monday, May 04, 2009

Copper butterfly

In a recent paper, I came across this rather poetic description:
Each of the Cu(I) centers is trigonally coordinated by three S atoms, and each of the six dithiophosphate ligands is connected to a Cu4 butterfly, where the hinge positions are occupied by two copper atoms situated at the vertex of the central tetrahedron and the wingtips are two capping Cu atoms.
However, to understand what they are talking about, one really should see one of these beautiful structures in 3D. I used this CIF file and Mercury program to create the image below.

Copper butterfly