Structures, Dynamic Behavior, and Spectroscopic Properties of 1,8-Anthrylene–Ethenylene Cyclic Dimers and Their Substituent Effects

Abstract

Cyclic compounds consisting of two 1,8-anthrylene units and two ethenylene linkers were studied as π-conjugated compounds. Three derivatives having substituents (H, Me, and Ph) at the linker moieties were synthesized by Suzuki–Miyaura coupling of the corresponding diethenylanthracene boronic esters with 1,8-diiodo-10-mesitylanthracene. The X-ray analysis and DFT calculations revealed that all the compounds had nonplanar cyclic frameworks where the two ethenylene linkers were syn to the anthracene units. Exchanges between the two syn forms were observed from the line shape changes in the ¹H NMR signals of the mesityl group. Their barriers increased in the order of H, Ph, and Me compounds from 34 to 70 kJ mol⁻¹. The effects of substituents on the molecular structure, dynamic behavior, and electronic properties are discussed.