The motion of electrons in bulk metals like iron delivers both electrical conductivity and ferromagnetism. Though molecular materials have many electrons, they are not expected to exhibit either type of behavior because they keep their electrons under tight control. Nevertheless there are some such materials that conduct electricity and some which display magnetism. The former are to be found as conducting polymer wires and their discovery earned Alan MacDiarmid, Alan Heeger, and Hideki Shirakawa the Nobel Prize for Chemistry in 2000.

So-called "organic" or "molecule-based" magnets are also known, but a molecular material that simultaneously showed both conductivity and ferromagnetism would appear to be almost contrary to the laws of physics. Yet even as the above scientists were receiving the Nobel prize, a remarkable paper appeared in Nature that announced just such a material.

Eugenio Coronado and colleagues at the Institute for Molecular Science, University of Valencia, had synthesized single crystals of a compound composed of layers of BEDT-TTF interleaved with layers of manganese chromium oxalate. BEDT-TTF is bis(ethylenedithio)tetrathiofulvalene, and the molecule consists of two fused rings. When positively charged, BEDT-TTF has semiconductor and conducting properties, and their charge balances the negative charge of manganese chromium oxalate. In this the manganese is in oxidation state II and the chromium in state III, and these provide a two-dimensional array with ferromagnetic behavior.

Others had tried to combine BEDT-TTF and the oxalate without success, but then the Valencia chemists gave it their attention. They generated crystals by allowing a solution composed of BEDT-TTF, chromium tris-oxalate and manganese ions, dissolved in a mixture of organic solvents, to crystallize slowly while under the oxidizing influence of a current of 0.1 microamps. After a week, shiny brown plate-like crystals had formed, and their structure was analyzed by X-ray crystallography revealing alternate layers of BEDT-TTF and metal oxalate. The former were 1.3 nanometers thick, and provided the conduction, while the latter were 0.36 nm thick and delivered the ferromagnetism. What was particularly noteworthy was that the two layers behaved independently of each other, and that the conductivity has a strong two-dimensional character being 10,000 times larger along the layers than across them. The magnetic layers either "communicate" with one another by electron tunnelling or via the electrons of the BEDT-TTF conducting layer, but however they do it the result is a unique material with remarkable magnetoresistance properties.

Coronado and coworkers have a paper on dual function molecular crystals soon to appear in the Journal of the American Chemical Society. They have also made other materials with unusual properties, some of which show both optical activity and magnetism (see E. Coronado, et al., Inorg. Chem., 41[18]: 4615-7, 2002), while some are hybrid magnets with two different magnetic networks (see E. Coronado, et al., Chem. Eur. J., 6: 2000), and yet others are molecular conductors whose conductivity responds to the effects of light (see M. Clemente-Leon, et al., Inorg. Chem., 39[23]: 5394, 2000). While such phenomena have been observed in non-molecular systems, the fact that they can be manipulated at a molecular level has significant implications for those working in the field of nanotechnology.

Coronado thinks there may be an even more impressive future for multifunctional molecular materials: "Our work has opened the way for the design of molecular compounds exhibiting coexistence of superconductivity and ferromagnetism," he says, although he admits that it will be quite a challenge. Even so, he may not be dreaming of the impossible. Indeed, the results reported in paper #4 would have been considered little short of fantasy only a few years ago.