Difluoroboron Chelation to Quinacridonequinone: A Synthetic Method for Air-Sensitive 6,13-Dihydroxyquinacridone via Boron Complexes.

This study aims to perform the chelation of difluoroboron (BF2 ) to quinacridonequinone (QQ). The resulting dark green solid was determined to be QA-BF2 , which is a BF2 complex of 6,13-dihydroxyquinacridone (QA-OH), and not QQ-BF2 , which is a BF2 complex of QQ. This result indicated that QQ-BF2 was first generated as an O,O-bidentate chelate, which immediately underwent a two-electron reduction to produce QA-BF2 . This compound was converted to air-sensitive QA-OH by undergoing hydrolysis in argon. Since QA-OH has a strong electron-donating property, it easily produced QQ via air oxidation in the solution. QA-OH also acts as a reducing reagent for quinones. The crystal packing of QA-OH is a herringbone type with short π⋅⋅⋅π contacts, and a good hole mobility has been suggested by theoretical calculations. Herein, a new synthetic method from QQ to QA-OH using BF2 chelation and hydrolysis was proposed. QA-BF2 and QA-OH are useful organic functional pigments and reducing reagents.