Synthesis and ion‐sensing phenomena of two new helical conjugated oligomers containing 1,10‐phenanthroline and oligo‐alkylthiophene

Two new 1,10‐phenanthroline (Phen) containing conjugated oligomers, oligo‐3,8‐bis(4‐octylthiophene‐2‐yl)‐1,10‐phenanthroline) (PDTPh) and oligo‐3,8‐bis‐(4‐octyl‐5‐(4‐ctylthiophene‐2‐yl)thiophene‐2‐yl)‐1,10‐phenanthroline) (PTTPh), as well as their corresponding monomers (OTPhOT and OTOTPhOTOT) were prepared and their metal ion‐sensing properties were investigated. The oligomers showed high thermal stability, good proccessibility, and gave varied color when reacted with different metal ions. Oligomers also showed distinct responses toward metal ions when compared with their corresponding monomers, suggesting that the ionochromic responses were determined by not only the coordinating ability of Phen unit but also the conformation of oligomer chains. Moreover, the differences in the ion‐sensing behaviors between OTPhOT and OTOTPhOTOT also suggested that the coordination ability of Phen depends on its substituents. The oligo‐alkylthiophene moieties in PDTPh and PTTPh acted as spacers to reorganize the conformation of the oligomer chains, as well as the electron donating groups to adjust the coordination ability of the Phen. These findings provide a clue for designing Phen‐containing ion‐sensors for specified ion‐sensing applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1586–1597, 2008