Syntheses, Characterization, and Luminescence of Pt^II−M^I (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 M2(dppm)2(MeCN)22+ (dppm = bis(diphenylphosphino)methane) gave heterotrinuclear complexes [PtCu2(edt)(μ-SH)(dppm)3](ClO4) (11) and [PtCu2(diimine)2(edt)(dppm)2](ClO4)2 (diimine = 2,2‘-bpyridine (bpy), 12; 4,4‘-dibutyl-2,2‘-bipyridine (dbbpy), 13; phenanthroline (phen), 14; 5-bromophenanthroline (brphen), 15) when M = CuI. 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 = AgI and AuI, respectively. The complexes were characterized by elemental analyses, electrospray mass spectroscopy, 1H and 31P NMR, IR, and UV−vis spectrometry, and X-ray crystallography for 14, 17, and 18. The PtIICuI2 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)−π*(diimine)] transitions for 12−16. The PtII2AgI2 heterotetranuclear complexes 17 and 18 are nonemissive in the solid states and in solutions at 298 K but show photoluminescence at 77 K. The PtIIAuI2 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/dithiolate character to a diimine π* orbital.