New cross π-conjugated aromatic polyketones: Synthesis and chemical properties

• Syntheses of cross π-conjugated aromatic polyketones.
• The polymers show PL with a phosphorescence character.
• Conjugation system is expanded through the ketone unit.
• Polymer of 2,2′-bipyridyl ketone has a low-energy LUMO.
• Self-assembly of the polymer.

Two new cross π-conjugated polyketones, (ArCOArC6H2(OC12H25)2)n (Ar = p-phenylene (Polymer-1) and pyridine-2,5-diyl (Polymer-2)) have been synthesized via Suzuki-type organometallic polycondensation. Polymer-1 and Polymer-2 had number average molecular weights (Mn) of 32,000 and 8000, respectively, in GPC analysis and were thermally stable up to 300 °C under N2. Polymer-1 and Polymer-2 showed photoluminescence (PL) peaks at λEM = 466 and 515 nm in chloroform with quantum yields of Φ = 0.46 and 0.04, respectively. The PL peak position of Polymer-1 agrees with the electroluminescence (EL) peak observed with an ITO/PEDOT-PSS/Polymer-1/Ba:Al PLED configuration (λEL = 460 nm). PLs of Polymer-1 and Polymer-2 showed phosphorescence characteristics with long decay lifetimes of 0.58 and 1.08 s and quantum yields of 20% and 19% at 77 K in frozen glass matrices, respectively. Cyclic voltammograms of Polymer-1 and Polymer-2 films on a Pt plate showed electrochemical reduction (n-doping) peaks at −2.17 and −1.91 V vs. Ag+/Ag, respectively.

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