Structural control of dithiazolyl radicals:: Case studies on 3′- and 4′-cyano-benzo-1,3,2-dithiazolyl, NCC6H3S2N

Dithiazolyl radicals with pi-stacking motifs have attracted particular interest because of their ability to exhibit spin-switching between diamagnetic distorted pi-stacks and paramagnetic regular pi-stacked structures through a solid state phase transition. Previous studies indicate that inclusion of electronegative heteroatoms into the backbone favours lamellar structures. This methodology has been extended to the synthesis and characterisation of the title compound, 4'-cyanobenzo-1,3,2-dithiazolyl (4-NCBDTA). Its electronic structure is probed through DFT calculations, cyclic voltammetry and EPR spectroscopy and its crystal structure determined by X-ray powder diffraction at room temperature. Variable temperature SQUID magnetometry reveals that 4-NCBDTA undergoes two phase transitions, each exhibiting bistability; a high temperature phase transition occurs at room temperature (T-C down arrow = 291 K, T-C up arrow = 304 K, Delta T = 13 K); whilst the low temperature phase transition occurs below liquid nitrogen temperatures (T-C down arrow = 37 K, T-C up arrow = 28 K; Delta T = 9 K). (c) 2007 Elsevier B.V. All rights reserved.