Understanding Pt•••Pt and Pt•••Au metallophilic interactions in single salt and double salt complexes using photophysical tools
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Seven [Pt(tpy)X]Y (X=Cl, Y=Cl•2H2O, X=Cl, Y=Cl•DMSO, X=Cl, Y=PF6, X=Cl, Y=SbF6, X=Cl, Y=SbF6•CH3CN, X=Br, Y= Br•2H2O, and X=Br, Y=PF6) complexes were prepared and characterized. Structural analysis shows consistent patterns in Pt^...Pt interactions that vary slightly depending on the coordinating halogen, X, counteranion, Y, and lattice solvent. Diffuse reflectance was used to identify solid-state ^1MMLCT absorption bands, and the relationship between Pt-Pt distance and ^1MMLCT absorption energy will be discussed. Metallophilic Pt^...Au interactions in [Pt(tpy)X][AuX'2] (X=X'=CN, X=Cl, X'=C6F5, X=Br, X'=C6F5, X=I, X'=C6F5) double salts were investigated. Structural characterization showed Pt^...Au metallophilic interactions were only observed in X=X'=CN, while Pt^...Pt interactions were observed in X=I, X'=C6F5. The closest contacts in X=Cl, X'=C6F5 and X=Br, X'=C6F5 were between the Lewis acidic Pt center of the cation and a Lewis basic ortho carbon of the pentafluorophenyl group on the anion. Photophysical characterization showed MMLCT features in the solid-state but only monomeric MLCT features localized on the [Pt]+ and [Au]- units in solution. The chromophore [Pt(tpy)(CCPh)]^+ was studied in [Pt][Au(C6F5)2] and [Pt][Pt(C^N)(CN)2] (C^N = ppy, F2ppy, or bzq) double salts. Structural characterization showed formation of a channel of [Pt(tpy)(CCPh)]+ moieties supported by metallophilic interactions in [Pt][Au(C6F5)2] and [Pt][Pt(F2ppy)(CN)2]. Solution electronic absorption spectra showed MLCT features centered on the cation and anion units for all four complexes. An additional ^1MMLCT band near 520 nm is present in the solid-state arising from Pt^...Pt interactions formed between cation units. Three [Pt(tpy)Cl][Pt(C^N)(CN)2] (C^N = ppy, F2ppy, and bzq) double salts were prepared and characterized. A new solution MMLCT feature was identified for all three double salts using UV-vis and fluorescence spectroscopy. Support of solution cation and anion association using solution conductivity and dynamic light scattering measurements will be discussed.