Polymeric metal complexes: Synthetic approaches to metal-containing materials with responsive properties

Synthetic approaches to polymeric metal complexes are described. The development of efficient methods for preparing simple bipyridine derivatives and corresponding metal complexes has greatly facilitated their use as initiators and coupling agents in polymer synthesis. Ligand reagents were utilized as initiators in controlled polymerization reactions to form polystyrenes, poly(methyl methacrylate)s, poly (ϵ-caprolactone)s, polylactides, as well as block copolymers with these chains, with bipyridine chelates at the end or centers of the macromolecule. Poly(ethylene glycol) macroligands were formed by a chain coupling method. Detailed studies of reaction kinetics were performed to determine the scope and limitations of each reaction type, using different catalysts and reaction conditions. Macroligands thus prepared were coordinated to a labile metal ion, Fe(II), to synthesize inorganic-organic star-shaped macromolecules that respond to various stimuli (i.e. changes in temperature and pH). An inert metal, Ru(II), was used as a template for generating architectural diversity; heteroarm star polymeric complexes with three, four, or six chains emanating from the central core were prepared. Bpy-functionalized polymers were also coordinated to Pt(II) centers to produce Pt(bpyPolymer)Cl₂ complexes. These dichlorides were then further exploited at the metal center to produce dithiolate complexes, Pt(bpy)(dithiolate), which exhibit dramatic solvatochromism that is influenced by the presence of polymer chains in the platinum outer sphere.