Polymeric Platinum(II) Bipyridine Dithiolate Complexes: Exploring the Influence of Macromolecular Outer Spheres on Solvatochromism with UV-Vis Spectroscopy

Solvatochromic properties were investigated for a series of Pt(bpyR(2))(tdt) complexes where bpyR(2) represents a polymeric 4,4'-disubstituted bipyridine (bpy) ligand of the form bpyPEG(2) (ester or ether linkage), bpyPCL(2), bpyPMMA(2), or bpy(PCL)(PMMA) (tdt, toluene-3,4-dithiolate; PEG, poly(ethylene glycol); PCL, poly(epsilon-caprolactone); and PMMA, poly(methyl methacrylate). Previously reported trends for small molecule analogues [i.e., Pt(dbbpy)(tdt), where dbbpy = 4,4'-di-t-butyl-2,2'-bipyridine] were not closely followed with many of these polymeric samples due to the influence of the outer sphere, and thus, local electronic environment of the metal center, by the substituted polymer chains. Absorption spectra for precursor polymeric Pt(bpy)Cl-2 complexes shifted as expected based on the electronic nature of substituents on the bipyridine, however the solvated polymer outer spheres may also be playing a role.