Supramolecular isomerism

Supramolecular isomerism Supramolecular isomerism has been defined by Zaworotko64 as the existence of more than one type of network superstructure for the same molecular building blocks, and hence he adds that it is therefore related to structural isomerism at the molecular level. In cases where the molecular building blocks are capable of forming more than one type of supramolecular synthon then supramolecular isomerism is identical to polymorphism. Zaworotko defines another kind of supramolecular isomerism, however, in which the same building blocks exhibit different network architectures or superstructures. We will see examples of this phenomenon in chapter 9, particularly regarding interpenetrated networks. 

Moulton, B., Zaworotko, M. J., From molecules to crystal engineering Supramolecular isomerism and polymorphism in network solids. Chem. Rev. 2001,101, 1629-1658. 

Supramolecular isomerism the existence of more than one type of network superstructure for the same molecular building blocks (Section 8.5.2). 

Supramolecular isomerism also lies at the heart of gaining a better understanding of supramolecular synthons and, by inference, how they develop and occur in other solid phases and even solution. The Cambridge Structural Database remains a very powerful tool in this context but it must be remembered that even such a large database will not necessarily be reflective of the full range of compounds that will be isolated and characterized in future years. 

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. 

In one sense, the alkylsulfonates are more versatile since they can exhibit architectural (i.e. supramolecular) isomerism so as to generate either bilayer or clay-like architectures. In order to generate a clay-like architecture, organic... 

Scheme 12. Illustration showing the effect of the orientation of the ancillary functional group on supramolecular isomerism.

B. Moulton, M.J. Zaworotko, From Molecules to Crystal Engineering Supramolecular Isomerism and Polymorphism in Network Solids , Chem. Rev., 101, 1629 (2001)... 

Biradha, K. and Zaworotko, M. (1998). Supramolecular isomerism and polymorphism in dianion salts of pyromellitic acid. Cryst. Eng., 1, 67-78. [81]... 

Catenanes and Other Interlocked Molecules, p. 206 DNA Nanotechnology, p. 475 Nomenclature in Crystal Engineering, p. 967 Plutonic and Archimedean Solids, p. 1100 Self-Assembling Catenanes. p. 1240 Strict Self-Assembly and Self-Assembly with Covalent Modifications, p. 1372 Supramolecular Isomerism, p. 1420 The Template Effect, p. 1493... 

Mesoporolls Silica and Silica-Organic Hybrids, p. 852 Organic Zeolites, p. 996 Supramolecular Isomerism, p. 1420 Zeolites Structures and Inclusion Properties, p. 1623... 

The existence of more than one type of network super-stracture for the same molecular building block represents supramolecular isomerism. Therefore, it is related to stractural isomerism at the molecular level. Supramolecular isomerism is the existence of different architectures (i.e., architectural isomerism) or superstructures. Polymorphism is a type of supramolecular isomerism but not vice versa. Supramolecular isomerism can be classified as structural (the same components result in different network superstructures), conformational (different conformations of a flexible molecule generate different, but often related, network architectures), catenane (the different maimer and degrees in which networks interpenetrate or interweave), and optical (chirai networks that... 

Isostructurality of Inclusion Compounds, p. 767 Neutron Diffraction, p. 959 71-71 Interactions Theory and Scope, p. 1076 Polymorphism, p. 1129 Supramolecular Isomerism, p. 1420 Tectons Definition and Scope, p. 1484... 

The existence of several energetically similar forms for the same compound is another typical feature of soft supramolecular materials. This property is a result of the weak linkage between building units and the variety of ways the units can assemble into a structure. A small change in external conditions can lead to another thermodynamically stable form, or. a little change in preparative conditions can lead to another kinetically stable product. The problem may show as polymorphism for forms having the same (polymorphs) overall composition, or pseudopolymorphism, where the components are present in different proportions, or as so-called supramolecular isomerism for forms having the same composition of the host framework. Water exemplifies such a structural... 

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