Abstract
Ladder-type quinoidal molecules of carbon-bridged phenylenevinylenes were designed and synthesized. The novel biradical nature was confirmed by ESR and SQUID measurements and further elucidated by theoretical calculations. Compared to the corresponding aromatic precursors, the band gaps of the compounds remarkably decreased, which are in agreement with the biradical feature. Significantly high stability was observed in solid and solution states, which can be ascribed to the anti-oxidation ability due to deep HOMO levels confirmed by DPV measurements. Unexpectedly, near-infrared (NIR) emission was observed at room temperature for both compounds. Both compounds afford stable dianion species by electrochemical and chemical reduction, accompanied with emission switching behavior.
