Synthesis and Characterization of Azadipyrromethene-alt-p-Phenylene Ethynylene Conjugated Polymers and Their Chelates

Abstract

Several n-type conjugated polymers incorporating azadipyromethene (aza-DIPY) dyes in the main chain were synthesized by Sonogashira coupling of bisiodo(tetraphenylazadipyrromethene)s with 1,4-bis((2-ethylhexyl)oxy)-2,5-diethynylbenzene. Using branched alkoxy groups on the diethynylbenzene comonomer resulted in polymers with higher molecular weight and higher solubility in organic solvents than our previous report with dodecylalkoxy groups. The physical properties of these polymers were further tuned by coordination of the aza-DIPY moiety with BF2, Cu(I)PEt3, or Ag(I)PEt3 via a postpolymerization reaction. Coordination with the electron-deficient BF2 resulted in improved solubility in organic solvents, higher electron affinity (∼4.5 eV), lower LUMO energy levels (<−5.6 eV), and lower optical bandgaps (<1.34 eV) than the unchelated precursor. Coordination with the electron-rich Cu(I) and Ag(I) metals resulted in higher optical bandgaps (1.5 eV) and higher HOMO (−5.3 eV) and LUMO (−4.0 eV) energy levels. X-r...