Structure and magnetism of a phenazinium cyclopentadienide salt

Electron spin resonance (esr) study of the salt of the stable organic cation radical, N,N′-dimethylphenazinium (M2P+) with the symmetric diamagnetic anion, penta(methoxycarbonyl)cyclopentadienide (PMC−), reveals weak antiferromagnetic interactions in this material. Analysis of the crystal structure shows dimerized stacks of the cation radical with electrostatic stabilization offered by the surrounding anion lattice. The antiferromagnetic coupling of the spins can be explained as arising from the direct exchange interaction between the radicals in the stack. The anions do not appear to have any specific influence on the magnetic property of this material.