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 ( 1 ) and 4,9-dibromo-2,7-bis(2-decyltetradecyl)benzo[ lmn ][3,8]-phenanthroline-1,3,6,8-tetraone ( 2 ) with ratios ranging from 1:1 to 1:10. The model reaction using 2-(tributylstannyl)thiophene ( 3 ) and 4,9-dibromo-2,7-bis(2-hexyl)benzo[ lmn ][3,8]-phenanthroline-1,3,6,8-tetraone ( 4 ) at a 1:1 molar ratio in the presence of catalytic Pd 2 (dba) 3 /P( o -tolyl) 3 indicated that the rate constant of the second substitution reaction ( k 2 ) is 15 times higher than that of the first one ( k 1 ). 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.