Pentaleno[1,2-c:4,5-c′]dithiophene Derivatives: First Synthesis, Properties, and a Molecular Structure

New π-extended pentalene derivatives bearing two thiophene rings are synthesized from 3-bromo-4-ethynylthiopenes as stable orange crystals by using a nickel complex. The observed electronic properties and molecular structure clearly indicate low contribution of the pentalene π system as predicted by the TD-DFT calculations.