Charge-Transfer Complexes of PXX (PXX = 6, 12-Dioxaanthanthrene). The Formal Charge and Molecular Geometry

Three kinds of charge-transfer (CT) complexes of PXX (PXX = 6, 12-dioxaanthanthrene) have been newly prepared and structurally characterized. In the 1 : 2 CT complex with TNP (TNP = 2,4,6-trinitrophenol), PXX is practically neutral. In the semiconducting partially oxidized salt with I3, the PXX molecules form a trimer and each PXX is formally oxidized by e/3. In the 3 : 2 salt with [Ni(mnt)2]- (mnt = maleonitriledithiolate), the PXX molecules again form a trimer unit and each PXX is formally oxidized by 2e/3. Together with the structural data obtained from the PXX single component crystal, the molecular geometry change by the formal charge on PXX has been examined. A noticeable change has been found in the aromatic ring framework, which is consistent with the distribution of the HOMO coefficients obtained from the extended Hückel calculation.