Development of Stable <i>π</i>-Conjugated Hydrocarbons with Narrow HOMO-LUMO Gaps

Carbon and hydrogen are fundamental components of organic molecules. Various functional π-systems have been created via the structural modification of conventional π-conjugated hydrocarbons. Novel π-conjugated hydrocarbon skeletons with attractive electronic structures are a source of novel functional materials. Notably, π-conjugated hydrocarbons with a narrow HOMO-LUMO gap are attractive research targets. Hydrocarbons with antiaromaticity or diradical character often exhibit narrow HOMO-LUMO gaps. However, these molecules are inherently reactive, thus requiring kinetic stabilization by sterically hindered peripheral substituents. This article describes the synthesis and properties of as-indaceno[3,2,1,8,7,6-ghijklm]terrylene, indeno[1,2,3,4-pqra]perylene, and its π-extended derivatives. These π-conjugated hydrocarbons are sufficiently stable under ambient conditions despite their narrow HOMO-LUMO gaps.