Radical-substituted allenes as high-spin species and subunits of organic ferromagnets

Allenes, substituted with radicalic groups (CH2., NH2.+, HN-O-.) at the ter minal carbon atoms, have been investigated theoretically by ab initio metho ds. It is shown that the 1,3-dimethyleneallene and the 1,3-diaminoallene di cation are molecules with triplet ground states due to the formation of car bene-like triplet state structures. In contrast, the closed-shell singlet s tate and the triplet state are degenerate for the 1,3-dinitroxideallene due to orthogonally arranged and hence decoupled a-electron systems. (C) 1999 Elservier Science B.V. All rights reserved.