Luminescence of azobenzene derivatives induced by cyclopalladation

In a series of organometallic azobenzene Pd(II) complexes, which are of interest as mesogenic materials, cyclopalladation blocks the azo group in the trans configuration. Whereas the uncomplexed azobenzene reference compound is not luminescent, the complexes are weakly luminescent (Φ ∼ 10−4, τ = 1–3 ns) owing to the emissive properties of nπ∗ excited states localized on the trans-blocked azobenzene ligand. These findings suggest that cyclopalladated azo-containing compounds may afford luminescent liquid crystalline materials.