Pressure-Induced Enhancement of Magnetic-Ordering Temperature in an Organic Radical to 70 K: A Magnetostructural Correlation

The structure of the canted antiferromagnet beta-p-NCC6F4CNSSN (1) was determined from synchrotron powder-diffraction studies in the pressure range 021.6 kbar. Radical 1 crystallizes in the orthorhombic space group Fdd2, but undergoes an asymmetric contraction of the unit-cell size with increasing pressure. At the molecular level, this contraction of the unit cell is simultaneously accommodated by: 1) an increase in twist angle between aryl and heterocyclic rings; and 2) a shortening of the intermolecular S...N contacts, which propagate the magnetic-exchange pathway. DFT calculations based on the structures in this pressure range revealed an increase in the magnetic-exchange interaction (J) with increasing pressure, and an excellent correlation was observed between J and the magnetic-ordering temperature, which increased from 36 K at ambient pressure up to 70 K at 16 kbar.