ISMSC 2007 - Università degli Studi di Pavia

PL 5
Anion-Templated Assembly of Interpenetrated and Interlocked Structures
Paul D. Beer
Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks
Road, Oxford, OX1 3QR, UK
Although mechanically bonded molecules have enormous potential for use in applications
based on nanometre-scale switching and motion [1], their unique topological cavities intrinsic to
these interlocked structures also make them of great interest in the molecular sensing arena. In
the majority of cases cationic and neutral species have been employed as efficient templates in
mechanical bond construction, whereas the manipulation of anions to direct supramolecular
assembly remains largely under-developed [2].
With the ultimate objective of constructing novel anion sensory receptor systems with
unprecedented selective anion recognition behaviour we have recently undertaken the
challenge of exploiting anions to template the formation of interpenetrated and interlocked
supramolecular assemblies [3]. The lecture will discuss our latest results in the rational designoriented
development of a general anion templation methodology for the formation of a range of
pseudorotaxanes [4], rotaxanes [5] and catenanes [6].
The application of this anion templation protocol is exploited further in the fabrication of redoxactive
rotaxane self-assembled monolayers (SAMs) on to gold electrode surfaces which are
shown to electrochemically recognise chloride anions selectively. Importantly, the unique
interlocked binding domain that results from macrocycle and thread interpenetration,
simultaneously amplifies the rotaxane SAMs electrochemical voltammetric response to chloride
and switches off a response to basic oxoanions such as phosphate.
[1] J-P. Sauvage, C. Dietrich-Buchecker (Eds.): Molecular Catenanes, Rotaxanes and Knots,
1999, Wiley-VCH, Weinheim
[2] R. Vilar, Angew. Chem. Int. Ed., 2003, 42, 1460
[3] P. D. Beer, M. R. Sambrook, D. Curiel, Chem. Commun., 2006, 2105
[4] M. R. Sambrook, P. D. Beer, J. A. Wisner, R. L. Paul, A. R. Cowley, F. Szemes, M. G. B.
Drew, J. Am. Chem. Soc., 2005, 127, 2292
[5] J. A. Wisner, P. D. Beer, M. G. B. Drew, M. R. Sambrook, J. Am. Chem. Soc, 2002, 124,
12469. M. R. Sambrook, P. D. Beer, M. D. Lankshear, R. F. Ludlow, J. A. Wisner, Org.
Biomol. Chem., 2006, 4, 1529
[6] M. R. Sambrook, P. D. Beer, J. A. Wisner, R. L. Paul, A. R. Cowley, J. Am. Chem. Soc.,
2004, 126, 15364. K-Y. Ng, A. R. Cowley, P. D. Beer, Chem. Commun., 2006, 3676
Transition Metal-Complexed Catenanes, Rotaxanes and Molecular
Machines
Jean-Pierre Sauvage
PL 6
Laboratoire de Chimie Organo-Minérale, Université Louis Pasteur/CNRS, U.M.R. 7177, Institut
de Chimie, 4, rue Blaise Pascal, F-67070 Strasbourg-Cedex, France
Catenanes represent attractive synthetic challenges in molecular chemistry. The creation of
such complex molecules as well as related compounds of the rotaxane family demonstrates
that synthetic chemistry is now powerful enough to tackle problems whose complexity is
sometimes reminiscent of biology, although the elaboration of molecular ensembles displaying
properties as complex as biological assemblies is still a long-term challenge.
The field of artificial molecular machines and motors has experienced a spectacular
development in the course of the last fifteen years, in relation to biological motors or information
storage and processing at the molecular level. A recent example consists of a fast-moving
rotaxane whose ring undergoes a pirouetting motion on the millisecond time scale by oxidizing
or reducing the central copper atom (Cu II /Cu I ).
Recently, our group has also proposed a transition metal-based strategy for making twodimensional
interlocking and threaded arrays. Large cyclic assemblies containing several
copper(I) centres could be prepared which open the gate to controlled dynamic two-dimensional
systems and membrane-like structures consisting of multiple catenanes and rotaxanes.
In the course of the last three years, we have been much interested in endocyclic but non
sterically hindering chelates. These compounds are based on carefully designed 3,3'biisoquinoline
derivatives. Some of them have even been incorporated into macrocyclic
compounds. A particularly efficient and fast moving molecular "shuttle" based on such a chelate
has been made and investigated as well as three-component molecular entanglements
constructed by assembling three such ligands around an octahedral metal centre. These
biisoquinoline-based compounds are particularly promising in relation to fast-responding
controlled dynamic systems and novel topologies.