| Polymeric metal complexes (PMCs) with beta-diketonate ligand functionalities have been prepared using living polymerization methodologies. In these materials, the central metal complex serves not only to introduce such properties as luminescence and chemical reactivity, but also provides a template for synthesis. The PMC structure allows for systematic tuning of the functional components, affording architectural and compositional control of the resulting material.; Poly(lactic acid) (PLA) and poly(epsilon-caprolactone) (PCL) were prepared by the ring-opening polymerization using a hydroxyl-functionalited beta-diketone (dbmOH) as the initiator, providing biocompatible, biodegradable macroligands for chelation to various metals. Much of this work has focused on the development of luminescent europium (Eu) based systems, which may have application in the field of photonics. Additionally, many transition metal beta-diketonates are of interest in the area of biomedicine, and their incorporation into biocompatible polyesters may address their use in drug design and delivery.; An alternative strategy for the preparation of these complexes was developed due to difficulties preparing well-defined dbmPLA and dbmPCL samples above ∼10,000 Da. Coordination of the dbmOH initiator to Fe(III) produced a metalloinitiator, from which polymerization proceeded smoothly to higher molecular weights, and with significantly faster rates than polymerization from uncomplexed dbmOH. The Fe complex acts not only as the initiator, but also as the polymerization catalyst for the generation of dbmPLA, dbmPCL, and block copolymer macroligands dbmPCL-b-PLA. Acid treatment dissociates the polymers from the Fe center, affording dbm-functionalized macroligands for subsequent chelation to other metals.; Star-shaped homopolymers were prepared by coordination of these PLA and PCL-functionalized dibenzoylmethanes to europium. Incorporation of bipyridine (bpy) macroligands enabled the formation of polymeric Eu(dbm)3(bpy) adducts, producing luminescent block copolymers with Eu at the block junction. A Eu(dbmPLA)3(bpyPCL2) sample exhibited microphase assembly into a discrete nanoscale morphology due to differences in polymer composition. The morphology of this material changed upon heating, perhaps due to the dissociation of bpyPCL2 from the Eu center to yield a mixture of Eu(dbmPLA) 3 and bpyPCL2 homopolymers. |
