Block structures stoichiometry

Structural supramolecular isomerism is exemplified by the range of structures that has thus far been observed in coordination polymers for some of the simplest building blocks and stoichiometries. We shall illustrate this by looking at two of these situations. 

When X Me < 3 two possibilities exist coordination-type structure (3, 2, 1) or blocks (2.67), when the stoichiometry of the compounds does not correspond to the formation of any coordination- type compound. 

What happens to the methoxy formed by this process is strongly temperature dependent. At low temperature (up to - 340K) it is stable on the surface and forms the beautiful structures shown in fig.2. Since the active oxygen is used in such reactions then the methoxy must (i) not block the active site at its formation or (ii) diffuses away from the active site. Our evidence indicates the latter to be the case since methoxy is present at sites away from the oxygen islands. Above approximately 340 K the methoxy is unstable and decomposes to yield formaldehyde and hydrogen in the gas phase. Above approximately 400 K, the stoichiometry of the reaction changes to... 

The excess of Na ions (above the NaAlnOi7 stoichiometry) requires some means of charge balance and the mechanism is found to be different in the P and P" structures. In P", some AP ions in the spinel blocks are replaced by Li /Mg " the consequent reduction in positive charge compensates that of the excess Na" ions in the conduction planes. In P,... 

Fig. 12 Generalized block diagram of PGAA design structure and structures of the 16-polymer library of PGAAs. These polymers allow the direct comparison of changes in amine stoichiometry, as well as hydroxyl number and stereochemistry, on biological properties. Figure adapted with permission from [186], (C) 2006 John Wiley Sons, Inc...

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