Synthesis of Stannole-Containing π-Conjugated Polymers by Post-Element Transformation of Organotitanium Polymer

The synthesis of stannole-2,5-diyl-containing π-conjugated polymers by the post-element transformation of a regioregular organotitanium polymer is described. For example, a 1,1-diphenylstannole-containing polymer is obtained in 83% yield by the reaction of a regioregular organotitanium polymer, which is prepared from 1,4-bis(2-ethylhexyloxy)-2,5-diethynylbenzene and a low-valent titanium complex with diphenyltin dichloride at -50 °C to ambient temperature. The number-average molecular weight and molecular weight distribution (M_n and M_w /M_n ) of the stannole-containing polymer are estimated as 4800 and 1.8, respectively. The obtained polymer is found to have the extended π-conjugated backbone and relatively low-lying lowest unoccupied molecular orbital (LUMO) energy level (-3.12 eV), which is supported by its UV-vis absorption spectrum and cyclic voltammetric (CV) analysis. In addition, the stannole-containing polymer is found to be applicable to a chemosensor for fluoride anion where the color and photoluminescence intensity of the polymer solution exhibits a distinct change in the presence of a fluoride anion.