hydrogen-bonded water molecules are located at the intersections 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.
Experimental Sect ion
1: A mixture of NH,C1 (0.60 mL, O S M ) , V,O, (0.0929 g), H,C,O, (0.2276 g) (V:H,C,O, molar ratio =1:2), and H,O (10mL) was sealed in a Teflon-lined stainless autoclave (volume 23 mL), heated at 180Β°C for three days, and cooled to 90Β°C at 5Β°C h-'. The product (yellow green crystals of 1; yield: 0.1740g, 88% based on V), was filtered off and washed with deionized water. This compound is stable in air and insoluble in water. Monophasic crystalline material was confirmed by X-ray powder diffraction. Thermogravimetric analysis in air showed one-step weight loss of 54.41 % over the temperature range 150-400Β°C, which agrees well with the theoretical values of 54.1 % assuming that the final decomposition product is V20,. IR(KBr): i. = 3483 (s, OH), 3145 (br, w, H,O), 1621 (s, pendant C=O), 1518 and 1456 (s. C = O and C=C), 1086(m), 1145(m), 861 and 843cm-' (m. V-(OH)-V) 2 : A mixture of NH,CI (0.60mL. 0 . 5 ~) .
V,O, (O.O904g), H,C,O, (0.1143 g) (V:H,C,O, molar ratio = 1). and H,O (10 mL) was sealed in a Teflon-lined stainlessautoclave(23 mL). heatedat 200"Cforthreedays,cooled to 150"Cat 5"Ch-', and quenched to room temperature. The product (0.1877 g), which is a mixture of dark purple crystals of 2 and an about equal amount of 1, was filtered off and washed with deionized water This compound is stable in air and insoluble in water. The compound retains its structure at 200Β°C in air with partial loss of water rnolecules. and decomposes at 250 "C, as indicated from powder X-ray diffraction and thermogravimetric analysis. IR(KBr): G = 3463 (m, OH), 2900 (br, w), 1500 (s, C=C and C=O). 870~x1-I (m, V-(OH)-V).