Preparation and properties of 4-amino-TEMPO-substituted benzoquinone derivatives and related charge-transfer complexes

The reaction of DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) with 4-amino-TEMPO (4-amino-2,2,6,6-tetramethylpiperidin-1-yloxyl) led to the 5-(4-amino-TEMPO)-substituted benzoquinone derivative 2 as the main product with the replacement of one cyano group, whereas bis(4-amino-TEMPO)-substituted benzoquinone derivatives 4 or 5 were obtained as the main products in the reaction of chloranil(dagger) or bromanil(dagger) with 4-amino-TEMPO under the same reaction conditions, The benzoquinone acceptor 2 formed charge-transfer complexes with the donors such as TTF (tetrathiafulvalene) or the 4-hydroxy-TEMPO-substituted TTF derivative, showing weak anti-ferromagnetic interactions in the complexes.