Ferromagnetic Nature of Silicon-Substituted Meta-Xylylene Polyradicals

Abstract

Electronic and magnetic properties of silicon-substituted meta- xylylene polyradicals containing meta-phenylene groups as couplers and silicon atoms in >Si−H groups as radical sites are quantum chemically investigated. The polyradicals are found to be stable with alternately periodic structure. They have high-spin ground states and show ferromagnetic interaction among all pairs of radical sites. The silicon sites are somewhat creased. A periodic calculation on the dimeric unit predicts the long-chain polyradical to be a one-dimensional ferromagnet. Band energy calculation gives a large gap between virtual and valence bands. The large energy gap owes its origin to the radical sites being out of plane of the phenylene rings, a twist between successive monomer units, and the difference between the pz orbital energy in carbon and silicon. The polyradical chains are electron insulators unlike substituted polysilene chains, though they are predicted to be good ferromagnets.