Spin Frustration in an Organic Radical Ion Salt Based on a Kagome-Coupled Chain Structure

Electro-oxidation
of the quinoidal bisdithiazole BT in dichloroethane
in the presence of [Bu4N]­[GaBr4] affords the
1:1 radical ion salt [BT]­[GaBr4], crystals of which belong
to the trigonal space group P3. The packing pattern
of the radical cations provides a rare example of an organic kagome
basket structure, with S = 1/2 radical ion chains
located at the triangular corners of a trihexagonal lattice. Magnetic
measurements over a wide temperature range from 30 mK to 300 K suggest
strongly frustrated AFM interactions on the scale of J/kb ∼ 30 K, but reveal no anomalies
that would be associated with magnetic order. These observations are
discussed in terms of the symmetry allowed magnetic interactions within
and between the frustrated layers.