Stable Polyradicals with High Spin Ground States

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Some polyradical polymers have been proposed as potential organic ferromagnetic materials. Through the preparation of chlorinated, polymeric, non-disjoint, and alternant hydrocarbons (AH’s) we envisage the realization of materials joining a very high spin to a high stability for which relevant magnetic properties are expected. We have selected the perchlorinated homologues of Thiele’s, Schlenk’s and Leo’s hydrocarbons (3–5) as model compounds to test the viability of our presumptions. These compounds have been isolated as stable solids at ambient conditions and exist in several stereoisomeric forms due to restricted correlated rotation of their aryl groups. Biradical 4 has been obtained as a mixture of the meso form (Cs symmetry) and the enantiomeric d1 pair (C2 symmetry) and triradical 5 as an equilibrated mixture of two diastereoisomeric d1 pairs with C 2 and D 3 symmetries. The corresponding diastereoisomers of both compounds have been separated and their interconversion rates measured. The diastereoisomers of biradical 4 and triradical 5 have been unambiguously identified by EPR and UV-Vis spectroscopies. The magnetic properties of compounds 3–5 were studied by EPR, magnetic susceptibility and magnetization measurements. Singlet, Triplet, and Quartet ground states have been found respectively for 3, both diastereoisomers of 4 and both diastereoisomers of 5. For these three representative cases, the results presented here validate the current theories for the prediction of ground state multiplicities in AH’s, regardless of the lack of planarity and changes in symmetry.