Synthesis and properties of conjugated thiophenes fused onto a dehydro[15]annulene scaffold

A short series of dehydrobenzothieno- and dehydropyridothieno[15]annulene ([15]DBTA and [15]DPTA) hybrids were assembled from thiophene, acetylene, and benzene/pyridine components. The molecules were constructed in a convergent manner and their properties examined optically, electrochemically, and thermally. In addition to lowered energy of electronic transitions of the 15-membered macrocycles, their emissive properties are discussed. The observed trends correspond with previously reported [14]annulenes, and are further rationalized using DFT (B3LYP/6-311G∗∗) calculations.