Small Heterocyclic D‐π‐D‐π‐A Push‐Pull Molecules with Complex Electron Donors

Abstract A large series of small push‐pull chromophores based on electron‐withdrawing N , N '‐dibutylthiobarbituric acid has been designed and successfully synthesized. The electron donating part involves common mesomeric donors such as methoxy, N , N ‐dimethylamino, N , N ‐diphenylamino, and piperidin‐1‐yl groups. Five‐membered heteroaromatics, namely thiophene, N ‐methylpyrrole, and furan have been employed as electron rich π‐linkers and auxiliary donors. Structural analogues bearing aromatic 1,4‐phenylene linker were also synthesized for comparison. Fundamental thermal and optoelectronic properties were studied by differential scanning calorimetry, cyclic voltammetry, and absorption spectroscopy. Thorough structure‐property relationships were elucidated, focusing mostly on type of the used π‐linker and donor. All experimental conclusions are corroborated by theoretical calculations. The study has shown that a complex donor moiety may be built by properly combining mesomeric and auxiliary donors. Whereas strong mesomeric donor (amino) suppresses the donating effect of auxiliary donors/π‐linkers, a combination of weak donor (methoxy) appended at a five‐membered heterocycle pronounces the donating ability of the latter.