Triplet States in Organic Chemistry

The investigation of organic multispin systems—with the triplet state as the initial member—has contributed considerably to the understanding of chemical bonding and to the examination of quantum mechanical model concepts. Structural information is accessible from the form and strength of the interaction between unpaired electrons in triplet ground states; in photochemistry triplet excited states play an important role both from a mechanistic and a preparative point of view. Besides triplet states, spin states of higher multiplicity (that is, molecules with more than two unpaired electrons) are attracting increasing interest. One way to superparamagnetic organic molecules has been shown by the synthesis of a branched nonacarbene with 18 unpaired electrons (S = 9 state).