TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 4223–4226
A stopperless tetrathiafulvalene based [2]pseudorotaxane
molecular shuttle
a
b,
a
b
Martin R. Bryce, Graeme Cooke, * Wayne Devonport, Florence M. A. Duclairoir and
c
Vincent M. Rotello
a
Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK
b
Department of Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, UK
c
Department of Chemistry, University of Massachusetts at Amherst, Amherst, MA 01002, USA
Received 19 February 2001; accepted 11 April 2001
Abstract—The first stopperless TTF containing molecular shuttle is described. © 2001 Elsevier Science Ltd. All rights reserved.
An important recent development in supramolecular
chemistry has been the construction of molecular
machines. Molecular shuttles based upon [2]rotaxanes
are an important representative class. These mechani-
cally linked molecules display switching properties
resulting from the relative positioning of a macrocyclic
p-deficient macrocyclic wheels based upon cyclobis-
(paraquat-p-phenylene) 3. More recently, the reversible
multi-stage redox properties and good electron donor
1
4
properties of tetrathiafulvalene (TTF) have been used
to create donor–acceptor based [2]rotaxanes, in which
this electron rich unit forms multiple stations along the
5
‘
wheel’ component over recognition ‘stations’ situated
axle for the cyclic acceptor 3. Remarkably, analogous
along a dumbbell shaped ‘axle.’ To prevent the wheel
from becoming detached from the axle, the latter mus2t
be terminated by bulky stoppers (Fig. 1a).
[2]pseudorotaxane molecular shuttles, which involve the
shuttling of macrocyclic wheels between multiple TTF
units situated along the axle, have not been described
(Fig. 1c). Here, we exploit for the first time the effective
binding properties between the TTF unit and acceptor
[
2]Pseudorotaxane based shuttle-like systems have also
been described; however, the shuttling process in
supramolecules of this type has been restricted to
threading/dethreading of the axle and wheel compo-
nents under chemical, photochemical and electrochemi-
3,
to
fabricate
the
first
TTF
containing
6
[2]pseudorotaxane based molecular shuttle.
1
,3
cal control (Fig. 1b). The majority of [2]rotaxane
based molecular shuttles have traditionally been fabri-
cated from p-rich polyhydroquinol containing axles and
In order to produce a TTF containing axle suitable for
a [2]pseudorotaxane molecular shuttle, we opted for a
†
structure based upon 2. In this system, the axle is
(b)
(c)
(a)
Figure 1. Rotaxane and pseudorotaxane molecular shuttles.
*
Corresponding author. Fax: 0131 451 3180; e-mail: g.cooke@hw.ac.uk
†
Selected data for 2: mp 154–156°C. Analysis found: C, 48.90; H, 2.60%; required for C28H18O S : C, 48.70; H, 2.60%; m/z (DCI) 691
5
8
+
(
M ); l [(CD ) CO] 8.04 (4H, d, J=9.0 Hz), 7.17 (4H, d, J=9.0 Hz), 6.80 (2H, s), 6.59 (4H, s), 5.13 (4H, s).
H 3 2
0
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