New poly(p-phenylene vinylene) derivatives with two oxadiazole rings per repeat unit: Synthesis, photophysical properties, electroluminescence, and metal ion recognition

Two new poly(p-phenylene vinylene) derivatives OX1-PPV and OX2-PPV bearing two 1,3,4-oxadiazole rings per repeat unit and a fully conjugated backbone with solubilizing dodecyloxy side groups were synthesized and investigated. The amorphous conjugated polymers had glass-transition temperature values of 60-75 °C and emitted intense blue or greenish-blue light in solution with photoluminescence (PL) emission maxima at 379-492 nm and PL quantum yields of 0.41-0.52. In the solid state they emitted yellowish-green light with PL emission maxima at 533-555 nm. Cyclic voltammetry showed that both conjugated polymers had reversible reduction and irreversible oxidation, making them n-type materials. The electron affinity of OX2-PPV was estimated as 2.85 eV whereas that of OX1-PPV was 2.75 eV. Yellow electroluminescence (EL) was achieved from single-layer light-emitting diodes of OX2-PPV with an EL emission maximum at 555 nm and a brightness of 70 cd/m 2 . Polymer OX2-PPV, which was functionalized with 2,6-bis(1,3,4-oxadiazole-2-yl)pyridine, demonstrated sensitivity to various metal ions as a fluorescence-mode chemosensor.