Ferromagnetic spin-coupling 4,4″-through metaterphenyl: models for high-spin polymers

Abstract

Model diradical dications have been synthesised which have the 4,4″-through metaterphenyl spin-coupling pathway found in arylamine high-spin polymers. In the model triplet diradical dication derived by a two-electron oxidation of N,N,N″,N″-tetrakis(4-tert-butyl-2-methoxyphenyl)-3,3″-dimethoxy[1,1′;3′,1″]terphenyl-4,4″-diamine the separation between the triplet and singlet states was found to be 0.083 kcal mol⁻¹. This value is close to that predicted on the basis that the energy difference should be proportional to the product of the spin densities in the ‘common’ ring (the ring in which the two spin densities overlap). This is an important principle in the design of new high-spin polymers.