FERROMAGNETIC INTERACTION IN ORGANIC RADICAL-ION SALTS

The N-methylated and/or N-ethylated 1- and BF4- salts of 2-(3-pyridyl) - (2(m)) and (4-pyridyl)-4,4,5,5-tetramethyl-nitronylnitroxides (2(p)) , and -(4-pyridyl)-4,4,5,5-tetra-methylimidazolin-1-oxyl (3(p)), and a lso the radical cation/radical anion salts obtained by the exchange re action of 1- and BF4- in the above radical cation salts with radical a nions of TCNQ, TCNQF4 and HCBD were synthesized, and their paramagneti c susceptibilities (chi(para)'s) were measured in the temperature rang e of 2 (or 5) - 300 K. As shown from the chi(para).T vs. T plots, amon g the radical cation and radical cation/radical anion salts 2(m)-Me+.( TCNQ2)-, 2(m)-Me+.TCNQF4-.,3(p)-Me+.TCNQF4-. and 3(p)-Me+.HCBD-. exhib ited ferromagnetic interaction. The X(para).T value almost equal to S= 1/2 at r.t. and the production of the thermally-accessible triplet sug gest that the ferromagnetic interaction comes from that between the ra dical cations as a result of dimer formation of the radical anions. Ne vertheless, the radical anion also plays a crucial role as a partner i n the tight contact and/or the ferromagnetic interaction between the r adical cations.