Past examples of magnetic organic materials were either unstable in air or were mostly made of metal, making them unsuitable for linking together into a plastic, says chemist Robin Hicks of the University of Victoria, British Columbia, lead author of the study reporting the find in this week's Nature. "There's been relatively few success stories in actually making a molecule that's magnetic at room temperature," he says.
The new molecules themselves could not be formed into plastics because they clump into loose powders that do not dissolve. But Hicks says that finding three related molecules suggests there are many others waiting to be found. "We have the ability in principle to change in relatively subtle ways the structure of the organic," he says, such as to make it more soluble.
The discovery was partly accidental. The researchers were mixing organic nitrogen-rich compounds with nickel atoms and water. Normally during such reactions, multiple organic molecules will attach to each metal ion, so a relatively small amount of nickel should have been needed. But Hicks says his postdoc, Rajsapan Jain, noticed that the chemicals were not completely used up in the reaction, so they kept adding nickel to see what would happen. They ended up with a mudlike powder in their test tubes.
The group seems to have discovered an entirely new route to magnetic molecules, says experimental physicist Christopher Landee of Clark University, who was not part of the study.
Although Hicks's team could not determine the exact structure of the molecules or how they formed, they found that, in this case, each organic molecule ended up with two nickels. Hicks says the magnetism probably stems from one lone (unpaired) electron on the nickel ion, which would therefore be positively charged, and another on the organic molecule, giving it a negative charge.
To be magnetic a molecule has to have isolated electrons, which act like tiny bar magnets. Normally electrons pair up and cancel out each other's magnetism, but Hicks says the organic molecules used in the experiment were selected because they can tolerate extra electrons.
"It's the first big step forward in 10 years, and that's what's encouraging about it," says Landee. "There will be a lot of chemists going back into the lab."