Nonstoichiometric Stille Coupling Polycondensation for Synthesizing Naphthalene-Diimide-Based π-Conjugated Polymers.

A nonstoichiometric Stille coupling polycondensation was first succeeded between 2,5-bis(trimethylstannyl)thiophene () and 4,9-dibromo-2,7-bis(2-decyltetradecyl)benzo[][3,8]-phenanthroline-1,3,6,8-tetraone () with ratios ranging from 1:1 to 1:10. The model reaction using 2-(tributylstannyl)thiophene () and 4,9-dibromo-2,7-bis(2-hexyl)benzo[][3,8]-phenanthroline-1,3,6,8-tetraone () at a 1:1 molar ratio in the presence of catalytic Pd(dba)/P(-tolyl) indicated that the rate constant of the second substitution reaction () is 15 times higher than that of the first one (). It was found that the selective intramolecular catalyst transfer was promoted by the naphthalene-diimide (NDI) skeleton. The results also provided a new one-pot symmetrical end-functionalization method to synthesize an NDI-based n-type polymer with NDI groups at both α,ω-chain ends.