A rare example of a molecular species prepared by solvothermal synthesis is the macrocyclic cobalt phosphonate/carboxylate 1, whose structure is shown schematically. At low temperatures this compound displays spontaneous magnetization due to canted antiferromagnetic ordering, which is very unusual for a discrete molecular material.

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a 0.4 I L 3800 3800 3700 3600 3500 3400 +/cm-'-Figure 5. Comparison of the OH regions of the IR spectra ofactivated cloverite (a) and Y zeolite (b. Linde LZY62, Si/Al = 2.4). The spectra were normalized to 10 mg solid, and based on the structures of the solids the ratio between the area of OH bands in cloverite and Y zeolite should be at least approximately 1 :3; however, the observed value is only 1 :40. I = Absorbance.In conclusion, this study reveals that the postulated terminal OH groups in the framework of cloverite are not detectable by IR spectroscopy. Free OH groups, in particular those due to POH groups that vibrate at 3676 cm-', are observed before and after activation of cloverite at 573 K under ozone. Their number increases upon activation but remains quite low, about 3.5 % of the expected number, indicating that they correspond to defect sites. This study does not cast doubt on the results of the X-ray structure analysis, but rather on whether the terminal oxygen atoms in the structure really belong to hydroxyl groups.Many microporous main group oxides have been prepared by hydrothermal synthesis"] but it has long been a goal to produce lacunary materials with modulated catalytic activity by constructing frameworks with d-block metals in close proximity to the voids. Haushalter et al. have shown how this can be achieved for vanadium and molybdenum phosphates.['] The usefulness of superheated fluids for preparing extended frameworks based on metal-ligand interactions has recently been demonstrated both by ourselvesL3] and and we now wish to report the extension of this technique to the preparation of a cobalt squarate with a microporous structure. The cobalt -squaric acid system has been extensively investigated under ambient condit i o n~'~] and gives compounds based on the framework found in 1 in most cases; analogous structures are also formed by the corresponding compounds of manganese, iron, nickel, and zinc. We report herein on compound 2, which has a structure unlike those previously observed.

The hydrothermal reaction of manganese dichloride with the potassium salt of benzene-1,3,5-tricarboxylic acid at 220 "C gives [Mn3{C6H3(C02)3-1,3,5)2] which exhibits two pathways for antiferromagnetic coupling.

A strategy for preparing open-framework coordination solids by hydrothermal synthesis has been developed and tested by the synthesis of a new porous cobalt carboxylate which can A number of groups are developing methods for synthesising open framework materials incorporating transition metals. These strategies include methods which aim to modify premade materials [1Ϫ8] as well as ones designed to construct the framework with the transition metal already incorporated. [9Ϫ19] Amongst the first class are syntheses in which the transition metal is substituted into a preformed zeolite, [1Ϫ3] or a metal complex is encapsulated within zeolite channels (ship-in-a-bottle catalysts) [4Ϫ7] and chemical modification of mesoporous (e.g. MCM-41) materials. [8] The second class includes the synthesis of molybdenum and vanadium phosphates, [9,10] zeolite-like cobalt (alumino) phosphate networks [11] and metal-organic coordination frameworks. [12Ϫ20] It is hoped that these materials will have the stability of zeolites with enhanced catalytic activity.Our recent synthesis [20] of [Co 3 (OH) 2 (C 4 O 4 )·3H 2 O] has shown that microporous transition-metal-containing species can be produced based on metal hydroxide structural members joined together by anionic ligands. These materials can be viewed as being made up from assemblies of tubes with rectangular or diamond-shaped cross sections in which the ligands are the walls of the tube and the metal hydroxide chains form the corners. From the isolation of this material we postulated that the formation of open framework materials could be encouraged by a number a factors and we have now illustrated the usefulness of this theory by the preparation of the title compounds.The factors which are important in the rational synthesis of open framework coordination solids relate to both the types of structural members (i.e. ligands) which can be used and also the way in which the voids can be stabilised during synthesis. The ligand should be capable of forming part of the metal hydroxide backbone and it should have a central [a] 2739 be dehydrated by heating to give a material with coordinatively unsaturated metal ions. Figure 1. Schematic view of the construction of open-framework materials; black areas represent metal-oxo strips, shaded areas represent ligand ''spacer'' regions portion which will act as part of the channel wall (Figure 1). Therefore we should be able to control the dimensions of the channel by choosing ligands with different distances between the donor groups. The channel structure can be stabilised by filling the lacunae with water molecules held in place by hydrogen bonds, particularly to bridging hydroxide ligands but also to coordinated water. The formation of species containing bridging hydroxide ligands is therefore encouraged by the use of high pH conditions for these reactions.The structure [21] (Figure 2) of the title compound is built around a Co 5 (µ 3 -OH) 2 ''bow-tie'' cluster in which two metal triangles have a common vertex. Each triangle has a µ 3 -OH a...