Spin-dependent delocalization-promoted nanoscopic electron correlation

INOR 454

Robert D. Schmidt, rdschmid@gmail.com1, David A. Shultz, shultz@ncsu.edu1, Martin L. Kirk, mkirk@unm.edu2, and Hyoyoung Lee, hyoyoung@etri.re.kr3. (1) Department of Chemistry, North Carolina State University, 2620 Yarborough Drive, Box 8204, Raleigh, NC 27695-8204, (2) Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, NM 87131-0001, (3) IT-NT, IT Convergence Components Laboratory, The Center for Smart Molecular Memory, 161 Gajeong-Dong, Yuseong-gu, Daejon, 305-330, South Korea

            Spin-dependent delocalization (SDD) describes those systems where intramolecular electron transfer impacts the spin-state energies in multinuclear spin systems.  In mixed-valent dyads (e.g. M+n-L-M+(n+1)), delocalization and a strong single-site ferromagnetic exchange conspire to stabilize high-spin ground states, termed “double exchange”.  Systems demonstrating this interaction are comprised of two metal centers, delocalized through some diamagnetic ligand.  We present a novel system based on the semiquinonate (SQ)/catecholate (Cat) dyad, where the bridge is a diamagnetic metal, and the spin carriers are purely organic.  The addition of pendant nitronylnitroxide (NN) radical substituents to the SQ/Cat ligands imparts spin-dependence on the itinerant electron, stabilizing a high-spin ground state.  The delocalization through the SQ-Co-Cat plane results in exchange coupling of the NN radicals, over a distance of 2.2 nanometers.  The exchange parameter (J) for NN-NN coupling drops only 25% relative to the single-site exchange, whereas the well-known exponential distance dependence of J predicts a 94% attenuation!

 

Coordination Chemistry: Applications
2:30 PM-4:50 PM, Tuesday, March 24, 2009 Salt Palace Convention Center -- Combo Rooms 253 A-B, Oral

Division of Inorganic Chemistry

The 237th ACS National Meeting, Salt Lake City, UT, March 22-26, 2009