Diketones 1.2- , LUMO

The biggest challenge today for the EL devices containing RE + /3-diketonates is the increase of efficiency and stability of the devices. Double layer devices, such as ito/tpd/[Eu /3-dike ton ate]/Al, have demonstrated the ability of the RE + /3-diketonates to act also as electron transporters, despite the large electron energy barrier between the Al electrode Fermi level and the RE + /3-diketonate LUMO level. 

Just as the one electron reduction of a neutral molecule produces an anion radical, the one electron reduction of an organic anion can yield a dianion radical, assuming that the LUMO of the anion is not too high in energy. Two anions familiar in organic chemistry are the dibenzoylmethide (an enolate of a 6-diketone) [112] and fluorenide anions [113] (Scheme 68). 

In 2003, further enlargement of the orifice of diketone 54 was achieved by Komatsu and co-workers [74]. Cyclic voltammetry of diketone 54 exhibited at least four reversible reduction waves in a similar way to that of Ceo itself, in spite of such a severely torn out 7i-system. Furthermore, the first reduction potential was even less negative than C o by 0.2 V, indicating that 54 is a stronger re-acceptor than C(so. The coefficients of the LUMO of 54 are relatively localized on the conju-... 

---