An unexpected network in guanidinium rhodizonate

Abstract

The highly symmetrical rhodizonate ion, C6O6 2-, would appear to be an ideal candidate to form double hydrogen bonds to six guanidinium cations as part of an infinite (3,6)-connected, 2D network of formula [C(NH2)3]2[C 6O6], in which each guanidium cation would link to three rhodizonate anions. As anticipated, the crystal structure reveals that the rhodizonate and the guanidinium ions serve as 6-connecting and 3-connecting nodes respectively; however, instead of a 2D network, a 3D network is formed. The 3D net is one that can be expanded or contracted by concerted rotation around connections lying in one particular direction. The relationship between the anticipated 2D net and the actual 3D ..