Synthesis and properties of a delocalized singlet biradical compound with anthraquinoid structure

Abstract

Phenalenyl based closed shell compounds with small HOMO-LUMO energy gap have been studied in our laboratory. Recently, we revealed the singlet biradical character of these compounds and their unique properties resulting from the biradical character. Compounds with benzoquinoid and naphthoquinoid structure along with two phenalenyl rings have been studied to clarify the relationship between biradical character and properties. This time, we succeeded in the synthesis of compound 1 having anthraquinoid structure along with two phenalenyl rings. Electronic absorption spectrum of 1 gave a lower energy band than compounds with benzoquinoid and naphthoquinoid structure. Considering the shape of HOMO and LUMO of 1, this result supports the large biradical character of 1.