Syntheses, characterization, and luminescence of PtII-MI (M = Cu, Ag, Au) heterometallic complexes by incorporating Pt(diimine)(dithiolate) with [M2(dppm)2]2+ (dppm = bis(diphenylphosphino)methane)

Reaction of Pt(diimine)(edt) (edt = 1,2-ethanedithiolate) with M-2(dppm)(2)(MeCN)(2)(2+) (dppm = bis(diphenylphosphino)methane) gave heterotrinuclear complexes [PtCu2(edt)(mu-SH)(dppm)(3)](CIO4) (11) and [PtCu2(diimine)(2)(edt)(dppm)(2)]-(CIO4)(2) (diimine = 2,2'-bpyridine (bpy), 12; 4,4'-dibutyl-2,2'-bipyridine (dbbpy), 13; phenanthroline (phen), 14; 5-bromophenanthroline (brphen), 15) when M = Cu'. The reaction, however, afforded tetra- and trinuclear complexes [Pt2Ag2(edt)(2)(dppm)(2)](SbF6)(2)(17) and [PtAu2(edt)(dppm)(2)](SbF6)(2) (21) when M = Ag-\ and Au-\, respectively. The complexes were characterized by elemental analyses, electrospray mass spectroscopy, H-1 and P-31 NMR, IR, and UV-vis spectrometry, and X-ray crystallography for 14, 17, and 18. The (PtCU\2)-C-\\ heterotrinuclear complexes 11-15 exhibit photoluminescence in the solid states at 298 K and in the frozen acetonitrile glasses at 77 K. It is likely that the emission originates from a ligand-to-metal charge transfer (dithiolate-to-Pt) 3[p(S) --> d(Pt)] transition for 11 and from an admixture of (3)[d(Cu)/p(S)-pi*(diimine)] transitions for 12-16. The P-2(\\) Ag-2(\) heterotetranuclear complexes 17 and 18 are nonemissive in the solid states and in solutions at 298 K but show photoluminescence at 77 K. The (PtAu2\)-Au-\\ heterotrinuclear complexes 19-21, however, are luminescent at room temperature in the solid state and in solution. Compounds 19 and 20 afford negative solvatochromism associated with a charge transfer from an orbital of a mixed metal/clithiolate character to a diimine pi* orbital.