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) x C7H8, are rather light sensitive. In solution they release the olefin with high quantum yields (phi similar to 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) x C7H8 is only slightly light sensitive (phi similar to 0.02), but shows a room temperature luminescence (lambda (max) = 520 nm; phi = 4.5 x 10(-3)) which originates from a IL/MLCT excited state. (C) 2001 Elsevier Science B.V. All rights reserved.