Dimethylalloxazine as an Electron Donor and Acceptor

Abstract

I WISH to report that 1,3-dimethylalloxazine (I) can form molecular complexes acting not only as an electron acceptor but also as a donor. It was possible to crystallize complexes from ethylene dichloride with the following compounds: pyrene, tetracyanoethylene (TCNE), and 2,3-dichloro-5,6-dicyano-p-benzoquinone. The results of the elemental analysis indicate that these complexes contain dimethylalloxazine and the other component in a ratio of 2 : 1 regardless of whether the latter is a donor or acceptor. As the infra-red spectra of the complexes are very close to the superimposed spectra of the components, there is no appreciable change in the intramolecular bonds by complex formation. Therefore, the ground states of the complexes are essentially non-bonding. The complexes are more deeply coloured than the components. For example, the pyrene and TCNE complexes are deep yellow. On the other hand, dimethylalloxazine is pale yellow and the other two components are colourless. As shown in Fig. 1, the appearance of a new absorption is clearly seen in these complexes. It can be concluded that these complexes are of the charge transfer type; dimethylalloxazine in the pyrene complex is acting as an electron acceptor and in the TCNE complex as a donor.