Conjugated organic polymer-based materials from the activated polymerization of 2-ethynylpyridine using naphthoyl chlorides

• Synthesis of new ionic conjugated polymers with naphthoyl substituents in high yield.
• The conjugated polymer structure was confirmed by instrumental analysis data.
• The photoluminescence peak at 589 and 590 nm corresponds to photon energy of 2.1 eV.
• This material showed well-defined and stable redox process.

New ionic conjugated polymers with naphthoyl functional groups, poly[2-ethynyl-N-(1-naphthoyl)-pyridinium chloride)] (PE1NPC) and poly[2-ethynyl-N-(2-naphthoyl)-pyridinium chloride)] (PE2NPC) were prepared via the uncatalyzed polymerization of 2-ethynylpyridine using 1- and 2-naphthoyl chlorides. The polymerization proceeded well under mild reaction conditions to provide a high yield of the polymer. The polymer structure was characterized by such instrumental methods as NMR (1H- and 13C-), IR, and UV–visible spectroscopies and was shown to have a conjugated polymer backbone system having N-(naphthoyl)pyridinium chloride as substituents. The electrical conductivities of iodine-doped PE1NPC and PE2NPC were 7.2 × 10−3 S/cm and 3.5 × 10−3 S/cm, respectively. UV–Vis. absorption maximum values were 394, 478, 523 nm for PE1NPC and 394, 478, 527 nm for PE2NPC, respectively. Also, photoluminescence maximum peaks of PE1NPC and PE2NPC were located at 589 and 590 nm which corresponds to the photon energy of 2.1 eV. The cyclovoltamograms of two compounds exhibited the electrochemically stable window at a −1.25 to 1.75 V region. It was found out that HOMO, LUMO levels and the band gap were measured at 4.98 eV, 2.84 eV, 2.14 eV for PE1NPC, and 4.92 eV, 2.74 eV, 2.18 eV for PE2NPC, respectively.

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