A STABLE FREE-RADICAL AS DONOR - A LAYER-STRUCTURE ORGANIC PRESSURE SENSOR

A novel charge transfer salt was prepared by the addition of TCNQ to t he stable free radical, 1,3-diphenyl-1,2,4-benzotriazin-4-yl (R.), res ulting in (TCNQ)(5)(R.)(2). Analysis by x-ray revealed the crystal str ucture to be triclinic, <P(1)over bar>, with a = 7.696(4) Angstrom, b= 16.428(3) Angstrom, c = 16.706(2) Angstrom alpha = 91.96(1)degrees, be ta = 103.16(2)degrees, and gamma = 97.36(3)degrees, V = 2035(1) Angstr om(3), Z = 2, D-X = 1.297 gcm(-3). Both variable temperature ESR and m agnetic susceptibility measurements indicated the material behaved as a Curie paramagnet down to 20 K, where a transition to an antiferromag netically ordered state occurred. The pressed pellet room temperature conductivity was 10(-4) Slcm. Single crystal conductivity measurements of the current parallel to the TCNQ layer indicated a strong pressure dependence of the conductivity; where 'sigma' increased true orders o f magnitude at 2 kbar.