(538c) Conjugated Copolymers Based on Purines: Linking Monomer Design and Macromolecular Properties

Purines seem to be compelling building blocks for conjugated polymers: They are susceptible to a wide range of site-specific chemical transformations that affect energy levels and emission wavelengths, and they possess the ability to self-assembly through non-bonded interactions. Motivated by these ideas, we describe the preparation of “poly(purine)” copolymers in which purine-derived monomers are introduced directly into a polymer backbone via Stille cross-coupling polymerization with benzodithophene (BDT), as well as purine-based donor-acceptor small molecules. Variations in the nature of the BDT comonomer and substitution pattern of purinyl comonomer lead to changes in thermal and charge-transfer characteristics. Specifically, UV-Vis and fluorescence spectroscopies show that poly(purine)s exhibit intramolecular charge-transfer characteristics and display distinct changes in emission wavelengths based on purinyl comonomer design. These efforts are extended toward fully conjugated poly(purine)s through the development of small molecule donor/acceptor chromophores in which purines behave either as electron-donating or electron-accepting unit, which tunes the charge transfer behavior, excited state lifetime, and quantum yield of the building block. These demonstrations of main chain poly(purine)s and pi-conjugated, purine-based chromophores highlight the potential of purines as useful motifs in conjugated polymers for optoelectronic applications.