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Dr Stuart Batten

Stuart Batten Senior Lecturer
BSc(Hons), PhD, MRACI, C.Chem, GCHE
Address: School of Chemistry, Monash University 3800, Australia.
Telephone: (03) 9905 4606
Fax: (03) 9905 4597
Email: stuart.batten@sci.monash.edu.au
Web: http://www.chem.monash.edu.au/staff/sbatten/index.html
   
 

Interpenetration

Table of known examples

Attempts to synthesise polymeric networks with porous structures often result in the formation of interpenetrating networks. These networks have no chemical bonds connecting them and yet cannot be separated without breaking of bonds. They can be considered to be polymeric analogues of rotaxanes and catenanes. The links above are to a comprehensive table of all known examples.

Information of a more general nature is given below.

Definition

Entanglement of polymeric networks such that, although there is no direct connection between the networks, they cannot be separated (in a topological sense) without requiring the breaking of network connections.

This is highlighted by the two examples below which are not interpenetrating. The individual networks could theoretically be separated without breaking bonds.


The chains, although entangled like threads in cloth, can be separated without breaking them.
The sheets are interdigitating not interpenetrating.
The networks must also interpenetrate each other in a mutual fashion - i.e. each network must be penetrated by another. Again, the example below, which shows 1D linear chains within channels created by the stacking of 2D nets, is not interpenetrating because the 1D chains are not penetrated by the 2D sheets.

This system is not interpenetrating.

Nomenclature

To properly describe a structure with interpenetrating networks, one must describe not only the topology of the individual networks, but also the topology of interpenetration, i.e. the way the networks interpenetrate each other. We have developed a descriptive nomenclature to assist with this.

The first consideration is the dimensionality of the individual nets - 1D, 2D or 3D. If the nets are 1D or 2D, then there are two possibilities. For 1D nets, the mean directions of propogation of the nets can be either parallel or inclined. Similarly, for 2D nets the mean planes of the nets can also be either parallel or inclined.

The next consideration is whether the overall dimension of the entanglement is the same as the constituent nets or higher. For example, parallel interpenetration of 1D nets can lead to overall 1D, 2D or 3D entanglements. In contrast, however, inclined interpenetration of 2D nets can only lead to a 3D entanglement.

These considerations are drawn together in the following notation:

mD → nD parallel/inclined interpenetration

For networks which involve interpenetration between networks of different dimensions (see below), then mD is replaced by mD/pD. For interpenetrating nets which have the same dimensionality but different topology (also see below), mD is replaced by mD/mD. For 2D inclined interpenetration, only a 3D entanglement is possible, so the → 3D is redundant and omitted. Similarly, for 3D interpenetration, everything from the arrow onwards in the nomenclature is redundant and omitted.

Types of Interpenetration

The links below illustrate the different types of interpenetration possible.

Further considerations

The above nomenclature is a useful but often not sufficient description of the topology of interpenetration. For example, the four schematic diagrams below all show 2D → 2D parallel interpenetration of (4,4) nets, however the interpenetration topologies are all different.
Four different topologies of interpenetration.

Similarly, 3D nets can interpenetrate with different topologies. For example, below are two different ways in which two alpha-Po networks can interpenetrate. In the left example, the "normal" mode of interpenetration, each cubic cavity catenates with eight such cavities of the other net. In the example on the right, an "abnormal" mode, a cavity of one net catenates with ten cavities of the other net. Diamond is another 3D topology which commonly shows a normal mode of interpenetration, with a minority of structures which show abnormal modes.

Normal mode of interpenetration.
Abnormal mode of interpenetration.

Selected References

  • "Interpenetration", S.R. Batten, Encyclopedia of Supramolecular Chemistry, Eds. J.L. Atwood and J.W. Steed, Marcel Dekker, New York, USA, 2004, 735-741.
  • "Topology of Interpenetration", S.R. Batten, CrystEngComm, 2001, 3, 67-73.
  • "Catenane and Rotaxane Motifs in Interpenetrating and Self-Penetrating Coordination Polymers", Stuart R. Batten and Richard Robson, in Molecular Catenanes, Rotaxanes and Knots, A Journey Through the World of Molecular Topology, Eds. J.-P. Sauvage and C. Dietrich-Buchecker, Wiley-VCH, Weinheim, 1999, 77-105.
  • "Interpenetrating Nets: Ordered, Periodic Entanglement", S.R. Batten and R. Robson, Angew. Chem. Int. Ed., 1998, 37, 1460-1494; Angew. Chem., 1998, 110, 1558-1595.
  • "Interpenetrating metal-organic and inorganic 3D networks: a computer-aided systematic investigation. Part II. Analysis of the Inorganic Crystal Structure Database (ICSD)", I.A. Baburin, V.A. Blatov, L. Carlucci, G. Ciani and D.M. Proserpio, J. Solid State Chem., 2005, 178, 2471-2493.
  • "Interpenetrating metal-organic and inorganic 3D networks: a computer-aided systematic investigation. Part I. Analysis of the Cambridge structural database", V.A. Blatov, L. Carlucci, G. Ciani and D.M. Proserpio, CrystEngComm, 2004, 6, 377-395.
  • "Borromean links and other non-conventional links in 'polycatenated' coordination polymers: re-examination of some puzzling networks", L. Carlucci, G. Ciani and D.M. Proserpio, CrystEngComm, 2003, 5, 269-279.
  • "Polycatenation, polythreading and polyknotting in coordination network chemistry", L. Carlucci, G. Ciani and D.M. Proserpio, Coord. Chem. Rev., 2003, 246, 247-289.