Macrocyclic aromatic ether-imide-sulfones: Versatile supramolecular receptors with extreme thermochemical and oxidative stability

Article abstract of DOI:10.1021/ja027851m

Macrocyclic receptors having extreme thermo-oxidative stability, and which bind a wide range of electron-donor substrates via π-stacking donor-acceptor interactions, are accessible by cycloimidization of an amine-functionalized aryl ether-sulfone with pyr

Full text of DOI:10.1021/ja027851m

Published on Web 10/22/2002
Macrocyclic Aromatic Ether-Imide-Sulfones: Versatile Supramolecular
Receptors with Extreme Thermochemical and Oxidative Stability
Howard M. Colquhoun,*,† David J. Williams,*,‡ and Zhixue Zhu†
Department of Chemistry, UniVersity of Reading, Whiteknights, Reading RG6 6AD, UK, and Department of
Chemistry, Imperial College, South Kensington, London SW7 2AY, UK
Received July 25, 2002
Over the past two decades there has been an explosion of interest
in the design and synthesis of molecular receptors,1 including those
which exploit donor-acceptor interactions between aromatic
π-systems2 to direct, for example, the synthesis of catenanes and
rotaxanes.3 This latter chemistry has enabled the fabrication of
nanoscale devices including light- and redox-driven switches4 and
most recently molecular logic-gates.5 However, the components of
such systems have generally involved rather labile substructures
such as N-benzylbipyridinium units6 or N-alkynyl-methylene-imide
linkages,7 and it seems probable that much more chemically robust
systems will be needed for molecular computing to be developed
into a fully practicable technology. Recognizing that all-aromatic
polyimides and polysulfones are among the most stable of all
organic materials,8 we have investigated the synthesis of macro-
Figure 1. X-ray structure of the 1:1 complex (6) formed between
cyclic analogues of such polymers and here report that macrocycles
of this type are both readily obtained and show considerable
versatility as supramolecular receptors.
macrocycle 5 and perylene.
Chart 1
Direct [1 + 1] cyclocondensation of diamine 1 with pyromellitic
dianhydride (2) or 1,4,5,8-naphthalenetetracarboxylic dianhydride
(3) in refluxing dimethylacetamide, under pseudohigh dilution
conditions, gave the macrocyclic aromatic imide-sulfones 4 and 5
in 23 and 20% yields, respectively (Chart 1). These macrocycles
have extremely high but still clearly observable melting points
(sharp DSC endotherms at 493 and 547 °C, respectively) and show
no eVidence for thermo-oxidatiVe decomposition in air at temper-
atures up to 400 °C (see Supporting Information).
Addition of the π-electron donor molecules pyrene, perylene,
2,6-dimethoxynaphthalene, tetrathiafulvalene, and pyren-1-ol to
solutions of the almost colorless 4 and 5 produced intense colors
assigned to intermolecular charge-transfer absorptions, and 1H NMR
spectra for equimolar ratios of receptor to substrate showed large
ring-current-induced complexation shifts (up to 1.5 ppm; see
Supporting Information Figures 1 and 2). Binding constants for
macrocycle 5 with different substrates were determined by UV-
visible spectroscopy in chloroform-hexafluoro-2-propanol (6:1 v/v)
using the dilution technique and gave values ranging from 40 M-1
for 2,6-dimethoxynaphthalene, to 800 M-1 for pyrene, 1400 M-1
for perylene, and 2300 M-1 for 1-hydroxypyrene. A Job plot
confirmed the stoichiometry of complex formation in solution
between 5 and pyrene to be 1:1. Dark green crystals of a 1:1
complex (6) between 5 and perylene were isolated from solution
in dimethylformamide by vapor diffusion with diethyl ether, and
single-crystal X-ray analysis showed the perylene molecule to be
inserted almost symmetrically into the macrocyclic cavity (Figure
1). Distances between the center of the perylene molecule and the
centers of the biphenyl linkage and diimide ring system are 3.57
and 3.51 Å, respectively, and the vectors linking these centers are
essentially collinear (179°). Notably, the transannular separation
between the centers of the biphenyldisulfonyl and diimide units in
complex 6 is only 7.08 Å, a Very significant (∼14%) contraction
from the value of 8.19 Å observed for the “pure” macrocycle which
contains only dichloromethane of solvation. Complexation evidently
induces the receptor to flex substantially to optimize the fit with
its substrate (Supporting Information, Figure 3).
Transition metal derivatives of 8-hydroxyquinoline have long
been known to act as π-donor molecules in conventional “charge-
transfer” complexes.9 In the present work, we have shown that
addition of bis(8-quinolinolato)palladium(II) to a solution of
macrocycle 5 in chloroform leads to rapid crystallization of a
complex (7) having 2:1 (host:guest) stoichiometry. Remarkably,
this complex can also be obtained in essentially quantitative yield
* To whom correspondence should be addressed. E-mail: h.m.colquhoun@
reading.ac.uk.
† University of Reading.
‡ Imperial College.
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10.1021/ja027851m CCC: $22.00 © 2002 American Chemical Society

C O M M U N I C A T I O N S
although here again the imide unit approaches the substrate rather
more closely than does the biphenylene fragment (centroid-centroid
separations are 3.66 and 3.91 Å, respectively). It is significant that,
in the corresponding perylene complex 6, much closer contact (3.57
Å) between the biphenylene-disulfone unit and the substrate results
in a considerable flattening of the torsion angle about the biaryl
linkage (19° in 6, 30° in 7, and 42° in 8).
Receptors 4 and 5 and their complexes represent only prototype
structures for an entire new family of self-assembling molecular
architectures with very high thermochemical stability. In view of
their ready accessibility (see Supporting Information), robust
chemical nature, and evident versatility in complexation, receptors
of this type clearly have the potential to become “workhorse”
molecules in the future development of supramolecular chemistry.
Acknowledgment. This work was supported by a grant from
the University of Reading and by an Overseas Research Studentship
(to Z.Z.) from Universities UK.
Figure 2. X-ray structure of the 1:2 complex (7) formed between bis(8-
quinolinolato)palladium(II) and macrocycle 5.
Supporting Information Available: Synthetic procedures, spec-
troscopic analyses, and thermo-oxidative stabilities for macrocycles 4
and 5; proton NMR data for complexation of 4 with pyrene and of 5
with pyren-1-ol; synthesis of the metallo-[3]pseudorotaxane 7 (PDF);
full crystallographic data for 4, 5, 6, 7, and 8 (CIF). This material is
available free of charge via the Internet at http://pubs.acs.org.
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