To understand the preference for face-to-face stacking of rhodizonates carrying a charge near -3, we first look at the highest occupied Molecular Orbital (MO) levels of the isolated anion. The π-MO ordering in the neutral (D6h) C6O6 molecule has been extensively studied theoretically (see e.g., ). Figure shows a schematic subset, the highest occupied MOs, which suffices to highlight the major electronic differences between the rhodizonates we study. Whereas (C6O6) -and (C6O6) 2-are both closed shell anions, the singly occupied e1g molecular orbital (SOMO) of the (C6O6) 3-radical anion permits us to rationalize some of the unusual electronic -and through them structural -properties of K3C6O6.