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research chronicle |
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Contributions To Self-Assembly
Processes And Molecular Nanotechnology
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Stoddart
is ranked by the Thomson Scientific Institute as the Third
Most-Cited Researcher in Chemistry with a total of 13,595
citations from 298 papers at a frequency of 45.6 citations per
paper for the period from January 1997 to June 30, 2007. He has
an h-Index (Nature 2005, 436, 900) of 87.
(Publication #) To access the PDF
version of an article, click on the corresponding number.
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2007.
In collaboration with Jim Heath at Caltech, Stoddart describes a
160,000-bit molecular electronic memory circuit based on
bistable [2]rotaxane and fabricated at a density of
100,000,000,000 bits per square centimeter – that is roughly
analogous to the dimensions of a DRAM circuit projected to be
available in 2020. The entire 160,000-bit cross-bar, described
in a letter in Nature (#775)
is approximately the size of a white blood cell. |
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2007.
With a judicious choice of ions and solvents, it is possible
to amplify a molecular Solomon link by kinetically controlled
crystallization from a dynamic combinatorial library of
molecular knots that includes the molecular Borromean rings. By
incorporating mixed-metal ion templates into the usual protocol
employed in the synthesis of the molecular Borromean rings,
the Stoddart group has obtained a molecular Solomon link as the only
crystalline product. Its crystal structure graces the inside
front cover of Issue 1 for 2007 of Angewandte Chemie. See #773 |
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2006. In
collaboration with the Balzani group in Bologna, the Stoddart group has
described an autonomous nanomotor powered by solar energy in the
Proceedings of the National Academy of Sciences (#739).
It is autonomous because it can work continuously without
external interference: it is powered by an inexhaustible energy
source (sunlight) and operates without consuming or generating
chemical fuels or waste. The system operates according to
a four-stroke cycle which is reminiscent of an internal
combustion engine in a motor car. A full cycle is carried
out in less than one thousandth of a second which means that the
motor can operate at a frequency of 1000 Hertz – a speed that is
equivalent, using the car engine analogy to 60,000 RPM.
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2006.
The Stoddart group reports on the kinetics and thermodynamics associated with
electrochemically driven molecular mechanical switching of a bistable
rotaxane perched in its lower-conducting ground-state on the brink
between being ON and OFF, and after writing, in its fully conducting
metastable state. The nuances of this indecisive molecular switch
lend credence to the postulated mechanism of action of such switches.
Science is so beautiful! The implications of these findings are
displayed on the front cover of Issue 1 for 2006 of Chemistry – A
European Journal. See
#737. |
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2006.
The Stoddart group describes structure control at the organic-solid interface in a
review (#738)
in the Journal of Materials Chemistry. The research is
highlighted on the front cover of the first issue in 2006. |
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2005.
The Stoddart group describes a rational design of molecular switches and sensors
from a tool-kit of chemical building blocks in a review (#735)
in Topics in Current Chemistry. |
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2005.
The Stoddart group explores dynamics and stereochemistry in mechanically
interlocked compounds in a lengthy review (#731)
in the Collection of Czechoslovak Chemical Communications. |
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2005. In
collaboration with Bjfrnholm, Goddard and Heath, the Stoddart group provides
structural evidence for the mechanical switching of amphiphilic bistable
rotaxanes in Langmuir monolayers at air water interfaces. The
experimental results, which are described in a communication (#732)
in Angewandte Chemie, are supported by monolayer dynamics
simulation: see a full paper (#725)
published in the Journal of the American Chemical Society. |
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2005. The
design of an electronic paper display, working in conjunction with Bill
Goddard, is announced by the Stoddart group in a communication (#726)
in the Journal of the American Chemical Society. |
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2005. In
reflective mood, the Stoddart group traces, in an article published in
Pure and Applied Chemistry (#722),
the hurly-burly life of a scientific nomad through thick and thin from
the Athens of the North to the City of Angels with brief and not so
brief interludes on the edge of the Canadian Shield, in the Socialist
Republic of South Yorkshire, on the plains of Cheshire beside the
Wirrall, and in the Midlands in the heartland of Albion. |
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2005.
The Stoddart group reviews the concepts of multivalency and cooperativity in
supramolecular chemistry in Accounts of Chemical Research
(#721). |
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2005. In
collaboration with Jeff Zink, the Stoddart group reports on a reversible molecular
valve using beads of mesoporous silica coated with a switchable
[2]rotaxane. This nanovalve system, which can be recycled many
times, was described in an article published in the Proceedings of
the National Academy of Sciences (#720). |
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2005.
The Stoddart group has shown that borohydride reduction of the parent Borromean
linked complex containing six zinc (II) ions and 12 imine bonds results
in its demetallation producing a neutral Borromean link compound and
also its free macrocycle. This intellectually satisfying proof of
the chemical topology of the Borromean link compound is summarized in
Chemical Communications (#719). |
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2005. By
employing atom labels on one of the ligand precursors, the lability of
at least some of the 30 dative and 12 imine bonds stabilizing and
constituting the three rings of a metallo-Borromean (Borromeate) linked
compound is demonstrated by the Stoddart group in acidic methanolic solution.
The demonstration of dynamic nanoscale Borromean links is recorded in
Chemical Communications (#718). |
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2005.
The Stoddart group announces the making of donor-acceptor pretzelenes in
Angewandte Chemie (#714).
See also
#727 and
#733. |
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2005.
The Stoddart group describes the powering of the 1993 supramolecular machine with
a photoactive molecular triad in the first issue of the new journal
Small (#705).
See also
#724. |
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2004.
The Stoddart group (and Heath) publish a perspective in Science (#703)
entitled “Whence Molecular Electronics?’ It transpires that the
metastable to ground state relaxation times of the bistable molecular
switches in solution (#702)
are much shorter than they are in the polymer matrix (#699)
and in the ‘half-device’ by an order of magnitude. By the same
token, the relaxation times in the ‘full devices’ are longer than they
are in the polymer matrices and in the ‘half-device’ by an order of
magnitude. In terms of the activation barriers to get from the
metastable back to the ground state, a value of around 16 kcal/mol in
the polymer matrices and ‘half-device’ and finally up to around 22
kcal/mol in the ‘full-device’ have been noted. The metastable
state of a switch in a ‘full-device’ decays back to the ground state
during a period of 10-60 minutes. |
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2004.
The Stoddart group describes in Applied Physics Letters (#697)
the use of a donor-acceptor doubly bistable, palindromic [3]rotaxane,
tethered through its two rings to gold-coated cantilevers in a series of
experiments that demonstrate the transduction of chemical into
mechanical energy. For a detailed description of these linear
artificial molecular muscles, see the full paper in the Journal of
the American Chemical Society (#723). |
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2004.
The Stoddart group demonstrates that the relative mechanical movements between the
components of bistable switchable catenanes and rotaxanes can be
stimulated (i) chemically in condensed phases, e.g., Langmuir films and
Langmuir-Blodgett monolayers (#686,
#697,
#711, and
#725) and (ii) electrochemically in a highly viscous polymer
matrix (#699),
as well as (iii) electrochemically in a ‘half-device’ as a
self-assembled monolayer on gold (#671
and
#709) and (iv) electronically in a ‘full device’ within
solid-state molecular switch tunnel junctions (#582,
#618, and
#631). |
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2004. In
collaboration with Jeremy Sanders, the Stoddart group describes the
template-directed synthesis of some neutral bistable rotaxanes in a
communication in the Journal of the American Chemical Society (#689).
Their switching behavior is discussed in the subsequent full paper
published in Chemistry – A European Journal. See
#701. |
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2004. The
total synthesis of molecular Borromean rings employing dynamic covalent
chemistry (DCC) is reported in an article in
Science (#683). It represents the highest level of
sophistication so far achieved in synthesis by templation methods in the
Stoddart laboratories. Guided by intuition and an appropriate
amount of molecular modeling, the Stoddart group combines the equilibrium-based
methods of imine formation with the templation power of zinc (II) to
effect a one-step total synthesis of a molecular Borromean link in over
90% yield for 18 precursors. The strategy uses a set of six endo-
and six exo-oriented ligands designed to form an oriented trigonal
bipyramidal unit around the zinc ions, six of which are incorporated
into the Borromean link topology. In a recent review, Daryle
Busch, the “father’ of templation in chemistry has commented – “The
achievement was remarkable in a number of ways. It involved what is
probably the most complicated template in the chemical literature, based
on six zinc(II) ions and both convergent (or endo-directed) and
divergent (or exo-directed) molecular turns. In contrast to the overall
complexity of the templating system, the reactants were relatively
simple. The divergent component was a dipyridyl while the convergent
component was an a,a'-diiminopyridyl unit formed by a thermodynamic, or
equilibrium, templating process. Top of the outstanding characteristics
of the template is the fact that it involves both kinetic and
thermodynamic template components, a combination that should become
common. Both of these distinctive template types were used in their
fully modern contexts. The combination is extremely powerful; the
components of the kinetic template hold the subjugated components in
place while the thermodynamic components find their final disposition at
equilibrium. In the classic equilibrium template the reactants form
their normal distribution of products and the anchoring/selecting factor
(often a metal ion) selects the product that binds best, combines with
it and shifts the equilibrium accordingly. Only the authors know
the extent to which alternative components were selected and rejected in
failure, but their final choices contain still another special feature.
The choice of zinc as the template anchor provided a second opportunity
for flexibility in the reacting system because zinc, being a spherical
ion, is adaptable when it comes to coordination numbers and coordination
geometries. So, this template system allowed the chemistry to determine
critical features both in the Schiff base reaction steps and in the
basic stereochemistry of the metal ion anchor. Further, the yield in
this scientific triumph was 90%. The success over the enormous challenge
of synthesizing the molecular embodiment of the Borromean link suggests
that the science of using the molecular template has reached a level of
maturity from which scientists may be expected to produce new molecular
entanglements and interlocked structures of profound significance,
despite the equally profound challenges they represent.”The
all-in-one synthetic strategy (#729)
for the making of nanoscale Borromean links combines (#707)
all the virtues of reversibility, proof reading, and error checking that
we associate with DCC (#623),
together with the geometrical guidance and precision we entrust to
coordination chemistry. It is the template-directed protocol (#629
and
#717), working in chemical synthesis with such a vengeance,
that tells us that much more is possible. The making of the Borromean
links by supramolecular assistance to covalent synthesis (#454)
heralds the beginning of a new era in topological chemistry. |
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2004.
The Stoddart group, in collaboration with Vincenzo Balzani, describes the design,
construction and operation of a molecular elevator, operated by changing
pH, in an article in Science (#676).
This mechanically interlocked molecule represents one of the most
complex artificial molecular machines described in the literature to
date. See also
#726. |
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2004.
The Stoddart group, in collaboration with Jeff Zink, reports an operational
supramolecular nanovalve in a communication published in the
Journal of the American Chemical Society (#675).
It is operated by redox chemistry and is based on the attachment of the
supramolecular machine described back in 1993 to beads of mesoporous
silica. |
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2004. The
metastable co-conformation (MSCC) of a bistable [2]rotaxane monolayer
self-assembled onto a gold electrode is identified electrochemically by the
Stoddart group. In an article published in
ChemPhysChem (#671),
an activation barrier of just under 18 kcal/mol is obtained for the
spontaneous decay of the MSCC back to the ground-state co-conformation (GSCC)
as a result of performing many experiments at different scan rates and
temperatures. This research on a ‘half-device’ represents a
compelling vindication of the proposed electromechanical switching
mechanism between the MSCC and the GSCC in the self-assembled monolayer
SAM of a surface-bond bistable [2]rotaxane. |
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2003. A
semiconducting single-walled carbon nanotube (SWNT) based molecular
switch tunnel junction (MSTJ) is shown by the Stoddart group, in an article
published in ChemPhysChem (#668),
to sustain a remnant molecular signature arising from within a bistable
[2]catenane containing diazapyrenium units that are believed to complex
to the sides of SWNTs. |
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2003. The
concepts of displaying lactosides in a multivalent fashion by tethering
them to cyclodextrins that are threaded onto polymer chains is announced
by the Stoddart group in Organic Letters (#665).
These self-assembled multivalent pseudopolyrotaxanes show considerably
enhanced binding for galectin-1. |
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2003.
The Stoddart group discovers that a collection of donor-acceptor [2]catenanes
containing elements of axial, planar and helical chiralties, exhibit a
keen selectivity for just one of up to eight diastereoisomers. The
research is described in a full paper in
Chemistry – A European Journal. See also
#656 and
#704. |
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2002.
The Stoddart group reports solubilization of single-walled carbon nanotubes (SWNTs)
in an aqueous solution of the starch-iodine complex. These
starched carbon nanotubes are a result of a ‘disproportionation
reaction’ in which amylose in a helical conformation wraps itself around
the SWNTs. The communication, reported in
Angewandte Chemie (#634)
and already cited 100 times, acts as an incentive to other scientists to
use carbohydrates, proteins and nucleic acids to bind SWNTs in aqueous
media, thus integrating an important nanoscopic material with the world
of biology. See also
#687. |
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2002.
The Stoddart group describes two-dimensional molecular electronic circuits based
on amphiphilic bistable [2]rotaxanes in an article (#631)
published in ChemPhysChem and already cited over 130 times.
This piece of research has been extended as far as the realization of a
64 K-bit memory with a density of 1011 bits per square centimeter which
corresponds to 2028 on the semiconductor roadmap. |
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2002. An
Angewandte Chemie review (#623)
on ‘Dynamic Covalent Chemistry’ is published and is cited over 150
times. This review gives substance to the rapidly growing
importance of thermodynamic control in the chemical synthesis of
unnatural products. |
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2002. As
part of a long-standing interest in making the molecular counterpart of
the Borromean links, the Stoddart group reports a ring-in-ring complex in
Angewandte Chemie (#622). |
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2001. In
collaboration with Jeff Zink, the Stoddart group describes in
Angewandte Chemie (#610)
working supramolecular machines trapped in glass and mounted on a film
surface. This work is important in as far as it shows,
qualitatively at least that mechanical motion, observed in a
[2]pseudorotaxane in solution (#305),
is actually carried over into condensed phases and also remains true to
form at interfaces. From the point of view of harnessing the
potential of artificial molecular machines in devices, this is an
important observation. |
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2001.
The Stoddart group reports in Angewandte Chemie (#599)
the preparation and properties of single-walled carbon nanotubes wrapped
with conducting polymers. This communication is cited almost 200
times. See also
#624,
#635, and
#651. |
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2001. The
extremely efficient (near quantitative) template-directed synthesis of a
[2]rotaxane by clipping under thermodynamic control of a crown
ether-like macrocycle incorporating two imine bonds around a
dialkylammonium ion center is described (#604;
see also
#661). This observation is used subsequently to make
multiply mechanically interlocked molecules under thermodynamic control
(#713
and
#716). |
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2000.
The Stoddart group reports the template-directed synthesis of the first of several
generations of amphiphilic bistable [2]rotaxanes incorporating
tetrathiafulvalene and dioxynaphthalene recognition sites for the
cyclobis(paraquat-p-phenylene) ring (#590;
see also
#598,
#603,
#627,
#659,
#662). Many of these amphiphilic bistable [2]rotaxanes
are subsequently incorporated into crossbar memory devices and also
become the focus of in-depth quantitative studies (kinetic and
thermodynamic) in condensed phases as well as in solutions.
Vide infra. |
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2000.
The Stoddart group describes the first-steps towards synthesizing mechanically
interlocked molecules beyond catenanes and rotaxanes (#583).
In, as yet, unpublished work, interlocked molecules, for which Stoddart
has coined the name suitanes, have been synthesized by a
combination of templation and dynamic covalent chemistry that relies on
the formation of multiple imine bonds, cf.
#580 where the formation of dynamic hemicarcerands and
hemicarceplexes involving multiple imine bond formation is described. |
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2000. In
collaboration with Jim Heath, the Stoddart group reports a bistable
[2]catenane-based solid-state electronically reconfigurable switch in
Science (#582).
The article, which presents the experimental evidence of an
electromechanical mechanism of switching by the bistable [2]catenanes
molecules between open (OFF) and closed (ON) states that are,
respectively, of lower (ground-state) and higher (metastable-state)
conductivities, is cited almost 400 times. See also #601,
#604,
#606, and
#618. The proposed mechanism is subsequently supported
by first-principles modeling of the switching in the device by the
Goddard Group at Caltech. See Phys. Rev. Lett.
2005, 94, 156-801. |
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2000.
The Stoddart group reports an extremely stable interwoven supramolecular bundle (#570)
formed between a tris-crown ether and a tris-ammonium trication.
On further elaboration (#674,
#678, and
#685), the concepts of multivalency and cooperativity in
binding are exposed and discussed subsequently in a review (#721)
on ‘Multivalency and Cooperativity in Supramolecular Chemistry’
published in Accounts of Chemical Research. |
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2000.
The post-assembly covalent modification
of triphenylphosphonium-stoppered [2]rotaxanes using the Wittig reaction
allows surrogate stoppers to be exchanged in [2]rotaxanes
(#560;
see also
#566 and
#640).
This rare example of the subsequent chemical modification of rotaxanes
makes possible the highly controlled synthesis of higher order rotaxanes,
molecular shuttles, dendritic rotaxanes, and polyrotaxanes. |
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2000.
The Stoddart group reports a strategy in
Langmuir
for molecular information storage materials by introducing [2]catenanes
into Langmuir monolayers and Langmuir-Blodgett films
(#555).
This piece of research anticipated the need to self-assemble molecular
switches on solid substrates (electrodes) and becomes increasingly
important in the subsequent fabrication of crossbar devices. See
also
#581. |
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1999.
Both hydrogen-bond based and donor-acceptor rotaxanes are formed under
thermodynamic control using imine formation and exchange in relation to
functional groups present in their dumbbell components (#552
and
#553). |
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1999. By employing amphiphilic
molecules (rotaxanes and dumbbells) containing bipyridinium units,
electronically configurable molecular-based logic gates were constructed
in collaboration with Jim Heath. This Science article has been
cited almost 500 times. See also
#575. |
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1999. The template-directed
synthesis of the first rotacatenane is reported (#539). |
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1998.
The Stoddart group reports the self-assembly of supramolecular daisy chains in
Angewandte Chemie
(#484
and
#499; see also
#613).
This first publication, relating to this particular recognition motif,
is cited more than 70 times. |
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1998.
A chemically and electrochemically switchable [2]catenane incorporating
tetrathiafulvalene and dioxynaphthalene units is reported in
Angewandte Chemie
(#472;
see also
#563).
This approximately one nanometer cube switch is subsequently employed in
solid-state devices as a molecular switch. |
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1997.
The template-directed synthesis of the first donor-acceptor molecular
trefoil knot is reported by the Stoddart group (#463). |
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1997. A review on synthetic
supramolecular chemistry appears in Accounts of Chemical Research (#454)
and is subsequently cited over 270 times. |
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1997.
The Stoddart group announces the template-directed synthesis of an acid-base
switchable [2]rotaxane
(#453)
which is employed subsequently to construct a nanoscale elevator (#676;
see also
#726).
This research describes the first quantitatively switchable rotaxane
based on orthogonal recognition motifs – namely, hydrogen bonding and
donor-acceptor interactions. |
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1996. As a result of a
collaboration with Helmut Ringsdorf, the Stoddart group describes the first
Langmuir monolayers and Langmuir Blodgett multilayers incorporating
mechanically threaded molecules (#417). |
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1996.
The Stoddart group describes his first synthesis of carbohydrate containing
dendrimers
(#403; see also
#429, #435, #441,
#488,
#496,
#504,
#578,
#595,
#632,
#638,
#639,
#664,
#665, and
#690). This research represents yet another set of
remarkable feats in chemical synthesis by the Stoddart group. It
has been exploited subsequently in the context of carbohydrate
recognition in biological systems and has led to some fundamental
questions being asked about the nature of cooperativity and multivalency.
See also
#685 and
#721. |
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1996.
The first cyclo-oligomerizations of disaccharides which crystallize to
form carbohydrate nanotubes are announced (#381;
see also #442,
#444,
#449,
#488, and
#497).
This research represents a remarkable feat in chemical synthesis by the
Stoddart group. It awaits development and exploitation. |
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1996.
Numerous articles describing the prototypes of molecular machines,
switches and devices in solution are published (#379
and
#380; see also
#426, #464,
#500,
#509,
#519,
#522,
#533,
#569,
#587,
#588,
#614, #625, #643, and
#653).
In this remarkable series of publications, many of them carrying the
name of Vincenzo Balzani as a co-author, the Stoddart group introduces the concept
of molecular machinery in the context of the relative movements, both
circumrotational and linear, undergone by the component parts of
bistable catenanes and rotaxanes when stimulated either (i) chemically
(e.g., pH change), (ii) electrochemically, or (iii) photochemically.
In so doing, he gives the concept of translational isomerism, introduced
by Schill, real practical expression and finds it necessary to introduce
the term co-conformation (and co-conformer) to describe the relative
movements of the components in interlocked molecules. This
substantial body of research identifies Stoddart as one of the very
first chemists to see the potential applications for mechanically
interlocked molecules. Essentially, he recognizes their importance
in addressing memory and logic in molecular electronics, as well as the
central role they can play in the fabrication of nanoelectromechanical
systems (NEMS). |
|
1996. The Stoddart group writes an
authoritive review which receives over 260 citations, on self-assembly
in natural and unnatural systems for Angewandte Chemie (#383). |
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1995. The Stoddart group publishes a
review of interlocked and intertwined structures in Chemical Reviews (#365)
which is cited over 720 times during the following decade.
Presently, it is the Stoddart’ group's most highly cited publication. |
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1995.
The Stoddart group describes the forerunners to a new family of interlocked
molecules templated by the hydrogen bonding of dialkylammonium ions
within crown ether macrocycles containing at least 24 ring atoms (#355
and #356; see also
#392, #523, and
#592).
This discovery – which is made coincidentally at around the same time by
Daryle Busch in Kansas – leads to a blossoming of research on catenanes
and rotaxanes (also polyrotaxanes) in many laboratories around the
world, employing this easy-to-use recognition motif. |
|
1995. The Stoddart group reports the
first branched [n]rotaxanes (#343)
and bis[2]catenanes (#347), respectively the building blocks for
dendrimers and mechanically linked polymer chains (#356; see also #368). |
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1994.
The synthesis of the [5]catenane, olympiadane, which can be achieved in
two successive template-directed steps via a [3]catenane intermediate,
is reported with full characterization, including a solid-state
structure, in Angewandte Chemie
by the Stoddart group (#323;
see also
#314,
#460, and
#485).
This synthesis is epoch-making as well as symbolic. The very fact
that these compounds can be made in good quantities demonstrates the
remarkable power of supramolecular assistance to covalent synthesis in
the making of mechanical bonds. Between them, these four articles
are cited more than 220 times. |
|
1994. The first chemically and
electrochemically switchable [2]rotaxane is described in Nature by
the Stoddart group and Kaifer (see
#322). This article, which is cited nearly 400 times,
marks the beginning of research into bistable rotaxanes (and catenanes)
as molecular switches and motors, using a range of different structural
types including the metal-based rotaxanes and catenanes (catenates)
reported earlier by Sauvage. |
|
1994. The template-directed
synthesis of the first optically-active donor-acceptor catenane is
described by the Stoddart group (#319). |
|
1993.
The Stoddart group, in collaboration with Balzani, describes the first
photochemically driven supramolecular machine in
Angewandte Chemie
(#305;
see also
#473).
This particular supramolecular machine becomes a favorite one to probe
the movements of components of molecular machinery in condensed phases.
This communication is cited over 140 times. |
|
1993.
The control of translational isomerism in non-degenerate donor-acceptor
[2]catenanes is discussed by the Stoddart group for the first time in a full paper
published in the New Journal of
Chemistry
(#306; see also
#304,
#311,
#329, and
#340). |
|
1993.
The practice of slippage is popularized by the Stoddart group as an alternative
method to clipping or threading-followed-by-stoppering for the
self-assembly of rotaxanes under thermodynamic control (#301
and
#302; see also
#478,
#495,
#506,
and #589). The procedure allows many rotaxanes to be accessed that
would otherwise be difficult to synthesize: it finds wide applicability
in many other research laboratories. |
|
1993. The first
template-directed synthesis of catenated cyclodextrins is announced in
Angewandte Chemie (#293;
see also #341). Since the first reported (and failed) attempt in
the literature to make a [2]catenane away back in 1958 involved a
cyclodextrin as one of the two interlocked rings, this research is of
considerable historical significance. |
|
1992.
In a series of three back-to-back communications (#278,
#279, and
#280)
published in
Synlett,
the design and synthesis of the first non-degenerate molecular shuttles
are described by the Stoddart group. They are the forerunners to the first
molecular switch based on a bistable [2]rotaxane published two years
later. |
|
1992. The Stoddart group publishes the
first (#264)
of a long series of full papers on “Molecular Meccano” in the Journal of
the American Chemical Society and also discusses, in Chemistry in
Australia, the prospect of ‘Whither and Thither Molecular Machines’ for
the first time in the context of mechanically interlocked molecules.
This series of scholarly papers does much to establish the nature of the
mechanical bond in chemistry. The first full paper in the series
is cited over 500 times. |
|
1991.
The Stoddart group coins the term [2]pseudorotaxane
(#247
and
#253) to describe the self-assembly of the ring and rod
components that precede either catenation or the formation of a rotaxane
(see also
#260 and
#261). |
|
1991.
The use of molecular recognition, self-assembly, and template-directed
synthesis in the making of mechanically interlocked molecular compounds
is outlined by the Stoddart Group in a review (#250)
and two communications (#251
and
#252)
published in
Synlett.
The review is cited over 240 times. |
|
1991. The first degenerate
donor-acceptor [2]rotaxane – dubbed a molecular shuttle by the Stoddart –group is
described in a communication (#249)
in the Journal of the American Chemical Society. This publication
marks the beginning of the development of artificial linear molecular
motors based on the [2]rotaxane constitution. It captures the
imaginations of many other researchers, stimulating an enormous amount
of activity along conceptually similar lines in countless other research
laboratories around the world. It is illustrated and discussed at
length in the Fourth Edition of Jerry March’s Advanced Organic Chemistry
published in 1992. The advent of the molecular shuttle opens up
the possibility of constructing controllable molecular switches that can
be employed as memory and logic in electronic devices. There is
every reason to believe that these molecular switches will have a
profound impact on the new communications-based technologies of the next
few decades. The communication is cited over 210 times. |
|
1991.
The Stoddart group announces the synthesis and characterization of the
per-3,6-anhydrocyclodextrins (#240;
see also
#262)
as receptors for cationic substrates in organic solvents. |
|
1989. In a seminal
contribution published in Angewandte Chemie (#218),
the Stoddart group announces the template-directed synthesis, under kinetic
control, of a degenerate donor-acceptor [2]catenane in an impressive 70%
yield. The work describes the prototype for the subsequent design
and development of bistable molecular switches. Also, as the first
all-organic catenane to be made in gram quantities, it opens up the
search for more examples, e.g., the Hunter-Vögtle-Leigh amide-based
catenanes (and rotaxanes) where hydrogen bonding is the molecular
recognition motif that is exploited. This class of mechanically
interlocked molecular compounds is now being studied in a highly
creative manner by David Leigh in Edinburgh. The communication is
cited over 180 times. |
|
1988.
The Stoddart group reports, in two back-to-back
Angewandte Chemie
communications (#201
and
#202),
the synthesis of cyclobis(paraquat-p-phenylene),
a tetracationic cyclophane which subsequently gains notoriety as ‘the
little blue box’ because of its voracious appetite to complex with
π-electron rich guests (see also
#248,
#259, and
#413).
This one compound is to dominate research in the Stoddart group right up
to the present day and undoubtedly beyond into the future! The two
communications are cited over 250 times. |
|
1987.
The Stoddart group announces the structure-directed synthesis of molecular belts
and collars in Angewandte
Chemie
using tandem Diels-Alder reactions (#169;
see also
#196,
#214,
#215,
#216,
#289, and #291),
leading to the development of the concept of ‘Molecular Lego’ (#203;
see also
#271,
#284, #287, and
#298). |
|
1987.
A series of six back-to-back communications is published in
Chemical Communications,
describing the complexation of paraquat (and diquat) by
bisparaphenylene[34]crown-10. This work is important since it
demonstrates for the first time that organic dications can be threaded
through crown ethers: the stage is now set from here on to develop the
chemistry of the mechanical bond in all-organic systems based on the
self-assembly of donor macrocycles and threaded acceptor dications (#160,
#161,
#162,
#163,
#164, and
#165).
The fourth of the six communications, which points the way forward to
the first synthesis of the first (degenerate) donor-acceptor
[2]catenane, is reported (#218)
in
Angewandte
Chemie
two years later and is cited over 125 times. |
|
1986. A seminal review on
second-sphere coordination, which has been highly cited, is published in
Angewandte Chemie (#151;
for subsequent reviews, see #200 and #406). At this stage,
the Stoddart group essentially leaves the field after five years for other
researchers to develop further. The review is cited over 200
times. |
|
1985.
The isolation of an adduct between the anti-cancer drug cisplatin and
[18]crown-6 is described (#129)
and the concept of second-sphere coordination is extended to the use of
cyclodextrins as second sphere ligands for transition metal ammines
including the anti-cancer drug carboplatin (#139,
#140, and
#141; see also
#221).
The work becomes the subject of a patent with Johnson-Matthey who
supports the research at Sheffield. |
|
1983.
Donor-acceptor interactions are extended beyond second-sphere
coordination to their complex formation between dibenzo crown ethers and
the diquat dication in a seminal paper published in
Chemical Communications
(#111;
see also
#131 and
#136).
This communication draws attention to the importance of [C–H···O]
interactions, in addition to the donor-acceptor interactions, in
stabilizing 1:1 complexes of this type. |
|
1981.
The Stoddart group describes the use of donor-acceptor interactions between a
cationic platinum complex carrying a bipyridyl ligand and
dibenzo[30]crown-10 in a seminal communication published in
Angewandte Chemie
(#94,
see also #130,
#184, and
#212).
The X-ray crystal structure solved by David Williams at Imperial College
graces the front cover of the journal and heralds the beginning of the
establishment of self-assembly processes for making donor-acceptor
complexes. |
|
1981.
The Stoddart group reports on the investigation of the second-sphere coordination
of neutral and cationic transition metal ammines by crown ethers
(#90,
#91,
#92, and
#93; see also
#109 and
#152).
This research represents the first really successful attempt to
illustrate a phenomenon about which Werner had speculated over half a
century ago. |
|
1979. The Stoddart group writes a
much-cited review "From Carbohydrate to Enzyme Analogues" for Chemical
Society Reviews (#73).
This article, which coincides with Stoddart's leaving Sheffield for the
first time to join the Imperial Chemical Industries (ICI) Corporate
Laboratory, marks the end of an era where the research goals had
included supramolecular catalysis. It is cited over 180 times. |
|
1979.
The Stoddart group describes the complexation of primary alkylammonium salts by
asymmetric [18]crown-6 derivatives incorporating the 4,6-O-benzylidene
unit in some methyl D-glycopyranosides for the first time
(#67,
#68, and
#69).
This research line is subsequently pursued vigorously by researchers in
Eastern Europe and Japan. |
|
1977.
The complexation of secondary dialkylammonium salts by
1,7-diaza[12]crown-4 is reported
(#58).
Some 18 years later many of the same salts are found to thread through
[24]crown-8 derivatives. See
#354. |
|
1975.
The chiral recognition by configurationally chiral cryptands synthesized
from carbohydrate precursors is described
(#40
and
#41). |
|
1974.
The Stoddart group describes the first synthesis of macrobicyclic polyethers with
carbon bridgeheads
(#30;
see also
#52). |
|
1969.
Stoddart describes the synthesis and characterization of medium and
large heterocyclic rings from cyclic carbohydrate precursors (#11 and
#17). |
