Synthesis of Well-Defined Oligo(2,5-dialkoxy-1,4-phenylene vinylene)s by Combined Olefin Metathesis and Wittig-type Coupling: Effect of Conjugation Repeat Units and End Groups Toward Optical Properties

Defect‐free, highly trans oligo(2,5‐dialkoxy‐1,4‐phenylene vinylene)s [alkoxy = O(CH2)2OSiiPr3] with both repeat units (ex. 9, 15, and 31 repeat units) and end groups (aldehyde, C6F5, terthiophene, ferrocene) well‐defined are prepared by a stepwise combined olefin metathesis using Mo(CHCMe2Ph)(N‐2,6‐Me2C6H3)[OCCH3(CF3)2]2 with subsequent Wittig‐type coupling. End‐functionalized oligomers with uniform distributions are also prepared by acyclic diene metathesis (ADMET) condensation using a ruthenium‐carbene catalyst, followed by the above combined olefin metathesis and Wittig coupling. The effects of the repeat units and the end functional groups on the optical properties are explored; the photoluminescence quantum yields in the end‐functionalized oligomers (e.g., 9 mers) are affected by the end groups. Defect‐free, highly trans oligo(2,5‐dialkoxy‐1,4‐phenylene vinylene)s with well‐defined repeat units and end groups are prepared by a stepwise combined olefin metathesis with subsequent Wittig‐type coupling. End‐functionalized oligomers with uniform distributions are prepared by acyclic diene metathesis (ADMET) condensation followed by the above coupling. The photoluminescence quantum yields in the end‐functionalized oligomers are affected by the end groups.