Prof. Lahti Publishes in the Journal of the ACS Detailed Studies of a Pure Organic Radical Showing Magnetic Ordering

In a full article in Journal of the American Chemical Society, the Lahti group reported detailed studies of a pure organic radical that shows magnetic ordering. Although magnetic properties are commonly considered to occur only in metals and alloys, the report highlights a new member of the small but growing number of metal-free magnetic materials. Postdoctoral associate Dr. Hidenori Murata made stable radical F4BImNN with assistance by graduate student Zeynep Delen. F4BImNN has a stable nitronyl nitroxide radical attached to a fluorinated benzimidazole ring. Hydrogen bonding between the benzimidazole rings causes F4BImNN molecules to assemble into chain- like stacks where the radical spins are likewise assembled into chains. Magnetic measurements at the UMass-Amherst Nanomagnetic Characterization Facility showed ferromagnetic interactions between spins in the chains, such that the spins align in the same direction.

Full details of the magnetic behavior of this pure organic solid were obtained by international collaboration of the UMass Amherst scientists with physicists Profs. Nei Fernandes Oliveira Jr., Armando
Paduan-Filho, and Valdir Bindilatti of University of Sao Paulo (USP) in Brazil, and with physical chemists Prof. Yuji Miyazaki and associate Akira Inaba of Osaka University (OU) in Japan. Long-standing ties between the Lahti group and the scientists in Brazil and Japan were crucial to gaining detailed understanding of F4BImNN. Each group provided unique skills and facilities that contributed to
the publication in the prestigious American Chemical Society journal. The Brazilian team used their uniquely designed low temperature, high magnetic field apparatus at the USP Instituto de Física to prove that radical electron spins in F4BImNN all become ordered at 0.7 K. The Japanese team carried out heat capacity measurements down to similarly low temperature at the OU Research Center for Molecular Thermodynamics and found the same behavior calorimetrically. The corresponding findings by two completely different methods showed that F4BImNN acts as a one-dimensional ferromagnet, that orders throughout the bulk of the solid to become an antiferromagnet below 0.7 K. This behavior was explained by the crystallographic close contacts between F4BImNN molecule, while the crystallography is determined by hydrogen bond driven molecular assembly of F4BImNN into the bulk solid.

Lahti is an internationally recognized expert in the area of molecular magnetism, with numerous publications and international presentations in this area and a frequently-cited book, "Magnetic Properties of Organic Materials". The UMass-Amherst work was supported by the National Science Foundation.

The link for the article is here: http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2008/130/i01/abs/ja074211g.html

Lahti Group Page

(January 2008)