Topological Bifurcation Analysis: Electronic Structure of CH5+

tions of the channels. The p4 squarate has C,, crystallographic symmetry, whereas the pJp, squarate and vanadium dimer have D,, symmetry. The window of the square channels has dimensions p a l 2 x c = 7.04 x 7.11 A, which is comparable to the pore size of SAPO-40 zeolite (6.7 x 6.9 The water cluster in the ab plane is further hydrogen-bonded into a layer, resulting in additional eight-membered rings condensed with themselves and the four-membered rings. It is interesting to note that the 0 . .O separation of 2.88 A in the water tetramer compares well with the results of vibration-rotation tunneling spectroscopy['41 and of ab initio calculations.[* 51 In summary, the two polymeric structures are composed of similar macrocyclic units constructed from cationic octahedral vanadium dimers and squarate anions, a new building principle for supramolecular architectures and microporous structures. The pore sizes are determined by the coordination modes of the bridging squarates: 2 provides large square channels where cyclic water tetramers are located, whereas 1 has a layer structure with rectangular windows within the layer. These first examples show that there is a great potential for the preparation of topologically unique zeolitic materials in the metal squarate system by hydrothermal methods.