Excited state properties of norbornadiene adducts of nickel(II), palladium(II) and platinum(II) bis-1,2-diphenyl-1,2-dithiolene complexes

The norbornadiene adducts of nickel(II) and palladium(II) bis-1,2-diphenyl-1,2-dithiolene complexes, M(S2C2Ph2)2×C7H8, are rather light sensitive. In solution they release the olefin with high quantum yields (φ∼0.2). It is suggested that the reactive excited state is of the LF type. The liberation of the olefin is a consequence of the steric strain of the tetradentate ligand in the LF state which is distorted toward a tetrahedral coordination. On the contrary, the corresponding platinum complex Pt(S2C2Ph2)2×C7H8 is only slightly light sensitive (φ∼0.02), but shows a room temperature luminescence (λmax=520 nm; φ=4.5×10−3) which originates from a IL/MLCT excited state.