Efficient second-order nonlinear optical chromophores based on dithienothiophene and thienothiophene bridges

Two series of push–pull systems bearing dithienothiophene or thienothiophene as (part of) π-conjugated spacer have been synthesized. These compounds combine high second-order molecular nonlinearities with good thermal stabilities, showing one of the thienothiophene (TT) derivative the highest μβ0 value found for a 4H-pyranylidene-containing merocyanine.