A selective colorimetric anion sensor based on an amide group containing macrocycle

Article abstract of DOI:10.1039/b207335h

A new colorimetric anion sensor 4 allows for selective 'naked-eye' differentiation of F-, AcO- and H₂PO₄- with similar basicity.

Full text of DOI:10.1039/b207335h

A selective colorimetric anion sensor based on an amide group
containing macrocycle†
Piotr Pia˜teka and Janusz Jurczak*ab
a Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
E-mail: jjurczak@chem.uw.edu.pl
b Institute of Organic Chemistry, Polish Academy of Science, Kasprzaka 44/52, 01-224 Warsaw, Poland.
E-mail: jurczak@icho.edu.pl
Received (in Cambridge, UK) 26th July 2002, Accepted 13th August 2002
First published as an Advance Article on the web 25th September 2002
A new colorimetric anion sensor 4 allows for selective
As shown in Table 1, except for the fluoride anion, an
increase of all association constants were observed. The most
dramatic enhancement was observed for H2PO42: Ka = 142
(DMSO-d6) and Ka = 4271 (CD3CN). In contrast to dihy-
drogenphosphate, the increase of association constants for more
basic acetate ion was negligible. The selectivity for H2PO42 ion
can be attributed to the additional hydrogen bonding inter-
actions between the OH group of dihydrogenphosphate and
ethereal oxygen atoms of receptor 4. Such interactions seem to
be enhanced in acetonitrile and suppressed by DMSO.
‘naked-eye’ differentiation of F2, AcO2 and H2PO4 with
2
similar basicity.
The design and synthesis of systems that are capable of sensing
various biologically and/or chemically important negatively
charged species is an area of current interest.1 One of the most
attractive approaches in this field involves the construction of
colorimetric anion sensors.2 Such sensors allow ‘naked-eye’
detection of anions without the use of any spectroscopic
instrumentation. Such systems are generally composed of two
parts. One is the anion binding part (receptor) which is based on
various combinations of pyrrole, urea, thiourea, sulfonamide,
amine or phenol moieties. The other is a chromophore which
converts binding induced changes into an optical signal. These
two parts are either directly linked2 or intramoleculary asso-
ciated.3 However, few such systems exist at present, and a need
for selective ‘naked-eye’ anion sensors remains.
Although a variety of artificial anion receptors coordinate
anions by amide groups,4 there are no colorimetric anion
sensors based on such groups. In this communication, we report
a new amide-based macrocyclic anion sensor 4. This compound
possesses two aromatic rings connected by an amide group. One
of them is electron-rich, whereas the second has two electron
withdrawing NO2-groups. Such a system should act as an H-
bond donor and an optically sensitive indicator of anion
binding. The two aliphatic amide groups could serve as
important additional anion binding sites.
The synthesis of receptor 4 is outlined in Scheme 1. The
catalytic reduction of the nitro group of 2-nitroresorcinol and
subsequent acylation of the amino function by 3,5-dini-
trobenzoyl chloride gave compound 1. Then the phenolic
groups were alkylated by methyl bromoacetate in the presence
of sodium carbonate and a catalytic amount of potassium iodide.
Reaction of the resulting a,w-dimethyl ester 2 with a,w-
diaminoether 3, under non-high-dilution conditions,5 afforded
macrocyclic compound 4 in 46% yield.
The association of receptor 4 with various anionic guests, in
polar solvents such as DMSO-d6 and CD3CN, was studied by
the 1H NMR titration method.6 The resulting binding isoterms
were analyzed by a nonlinear regression method7 which gave
the association constants listed in Table 1. All titration curves
gave a satisfactory fit to a 1+1 binding model, except for
fluoride anion for which a 1+2 ligand+anion complex stoichio-
metry was found. The selectivity trends in binding affinities of
anions for receptor 4 in DMSO-d6 were determined to be: F2 ì
AcO2 > H2PO4 > HSO42 > Cl2 ~ Br2. The observed
2
binding order can be easily rationalized based on the guest
basicity. A change of the solvent from DMSO-d6 to CD3CN
causes crucial changes of association constants as well as the
selectivity trends of the binding ability of receptor 4 for
anions.
Scheme 1 The synthesis of receptor 4. Reagents and conditions: (i) H2, Pd/
C, THF, rt, 10 h ; (ii) 3,4-dinitrobenzoyl chloride, Et3N, THF, rt, 2 h, 78%;
(iii) methyl bromoacetate, Na2CO3, KI, MeCN, 80 °C, 48 h, 58%; iv) Na,
MeOH, rt, 72 h, 46%.
† Electronic supplementary information (ESI) available: experimental
details for 1, 2 and 4; sample binding curves. See http://www.rsc.org/
suppdata/cc/b2/b207335h/
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The complexation-induced chemical shifts, which are ob-
tained during titration experiments, can be used to infer a quite
detailed picture of anion binding. The aromatic amide NH
signal becomes broad and disappeared when ca. 0.5 equivalent
of F–, H2PO42 or AcO2 was added. In the case of chloride and
hydrogensulfate anions, this signal is easy to follow during the
titration experiment, and large downfield shifts ( > 0.8 ppm)
were observed. These findings indicated that the aromatic
amide proton strongly interacts with anionic guests. Upon
addition of the anions, upfield movements of all aromatic proton
signals were observed. This observation was tentatively as-
cribed to charge transfer interactions between the amide-bound
anion and the electron-deficient 3,5-dinitrobenzene moiety.
Downfield shifts of the aliphatic amide NH signal, typical for
hydrogen bonding interaction, were detected upon exposure to
certain anions. The degree of these shifts varied considerably
from 1.7 ppm for fluoride to 0.2 ppm for hydrogensulfate ion
(CD3CN).
turn turquoise (l = 408, 700 nm), yellow (l = 378 nm) and
purple (l = 537, 393 nm), respectively. These visual changes
are completely consistent with the association constants
recorded for 4 in acetonitrile solutions, namely F2 ì H2PO4
2
ì AcO2 > Cl2 ~ HSO42 ì Br2.
In conclusion, we have developed an amide-based macro-
cyclic sensor for anions that not only allows for the colorimetric
detection of F2, AcO2 and H2PO4 ions in both DMSO and
2
acetonitrile solutions, but also shows selective coloration in
acetonitrile for those anions with similar basicity.
Financial support from the State Committee for Scientific
Research (Project T09 A 087 21) is gratefully acknowledged.
Notes and references
1 F. P. Schmidtchen and M. Berger, Chem. Rev., 1997, 97, 1609; M. M. G.
Antonisse and D. N. Reinhoudt, Chem. Commun., 1998, 443; P. A. Gale,
Coord. Chem. Rev., 2000, 199, 181; P. A. Gale, Coord. Chem. Rev., 2001,
213, 79; P. D. Beer and P. A. Gale, Angew. Chem., Int. Ed., 2001, 40,
486.
A DMSO solution of receptor 4 (231024 M) shows dramatic
color changes upon addition of F–, AcO– and H2PO4– ions (Fig.
1). Specifically, it was found that initially colorless solutions
turn dark blue (l = 593, 708 nm), yellow (l = 375 nm) and
yellow (l = 384 nm) when exposed to fluoride, dihydrogen
phosphate and acetate ions, respectively. On the other hand, no
color changes were observed upon addition of chloride,
bromide or hydrogensulfate anions.
The observed color changes also took place in CH3CN
solutions. Receptor 4 forms a colorless solution, either alone or
in the presence of Cl2, Br2 or HSO42. Upon addition of
fluoride, acetate and dihydrogen phosphate ions, the solutions
2 C. B. Black, B. Andrioletti, A. C. Try, C. Ruiperez and J. L. Sessler, J.
Am. Chem. Soc., 1999, 121, 10438; H. Miyaji, W. Sato, J. L. Sessler and
V. M. Lynch, Tetrahedron Lett., 2000, 41, 1369; P. Anzenbacher Jr., A.
C. Try, H. Miyaji, K. Jursikova, V. M. Lynch, M. Marquez and J. L.
Sessler, J. Am. Chem. Soc., 2000, 122, 10268; H. Miyaji, W. Sato and J.
L. Sessler, Angew. Chem., Int. Ed., 2000, 39, 1777; H. Miyaji and J. L.
Sessler, Angew. Chem., Int. Ed., 2001, 40, 154; C. Lee, D. H. Lee and J.-I.
Hong, Tetrahedron Lett., 2001, 42, 8665; K. H. Lee, H.-Y. Lee, D. H. Lee
and J. -I Hong, Tetrahedron Lett., 2001, 42, 5447; D. H. Lee, K. H. Lee
and J.-I. Hong, Org. Lett., 2001, 3, 5; D. H. Lee, H. Y. Lee, K. H. Lee and
J. -I Hong, Chem. Commun., 2001, 1188; R. Kato, S. Nihizawa, T.
Hayashita and N. Teramae, Tetrahedron Lett., 2001, 42, 5053; F.
Sancenon, A. B. Descalzo, R. Martinez-Manaez, M. A. Miranda and J.
Soto, Angew. Chem., Int. Ed., 2001, 40, 2640; F. Sancenon, R. Martinez-
Manaez and J. Soto, Angew. Chem., Int. Ed., 2002, 41, 1416.
Table 1 Association constants (dm3 mol21) from 1H NMR titrations for
complexes of receptor 4 with anionic guests in DMSO-d6 or CD3CNa
3 P. A. Gale, L. J. Twyman, C. I. Handlin and J. L. Sessler, Chem.
Commun., 1999, 1851; K. Niikura, A. P. Bisson and E. V. Anslyn, J.
Chem. Soc., Perkin Trans. 2, 1999, 1111; J. J. Lavigene and E. V. Anslyn,
Angew. Chem., Int. Ed., 1999, 38, 3666.
b
H+G
Ka (DMSO-d6) Ka (CD3CN) pKa
F2
1+2
1+1
1+1
1+1
1+1
7.8 3 106
337
142
32
7.5 3 106
503
4271
138
3.18
4.76
2.15
23.1
26.1
AcO2
H2PO4
4 S. Valiyaveettil, J. F. J. Engbersen, W. Verboom and D. N. Reinhoudt,
Angew. Chem., Int. Ed., 1993, 32, 900; A. P. Bisson, V. M. Lynch, M.-K.
C. Monahan and E. V. Anslyn, Angew. Chem., Int. Ed., 1997, 36, 2340;
A. P. Davis, J. J. Perry and R. P. Williams, J. Am. Chem. Soc., 1997, 119,
1793; K. Kavallieratos, C. M. Bertao and R. H. Crabtree, J. Org. Chem.,
1999, 64, 1675; G. M. Hubner, J. Glaser, C. Seel and F. Vögtle, Angew.
Chem., Int. Ed., 1999, 38, 383; A. Danby, L. Seib, N. W. Alcock and K.
Bowman-James, Chem. Commun., 2000, 973; F. Werner and H.-J.
Schneider, Helv. Chim. Acta, 2000, 83, 465; M. A. Hossain, J. M.
Llinares, D. Powell and K. Bowman-James, Inorg. Chem., 2001, 40,
2936; P. A. Gale, S. Camiolo, C. P. Chapman, M. E. Light and M. B.
Hursthouse, Tetrahedron Lett., 2001, 42, 5095; S. Kubik, R. Goddard, R.
Kirchner, D. Nolting and J. Seidel, Angew. Chem., Int. Ed., 2001, 40,
2648; A. Szumna and J. Jurczak, Eur. J. Org. Chem., 2001, 21, 4031.
5 D. T. Gryko, D. Gryko and J. Jurczak, Synlett, 1999, 1310; P. Pia˜tek, M.
M. Gruza and J. Jurczak, Tetrahedron: Asymmetry, 2001, 12, 1763.
6 T. R. Kelly and M. H. Kim, J. Am. Chem. Soc., 1994, 116, 7072.
7 Binding constants Ka were calculated using HypNMR curve-fitting
software: C. Frassineti, S. Ghelli, P. Gans, A. Sabatini, M. S. Moruzzi and
A. Vacca, Anal. Biochem., 1995, 231, 374.
–
2
HSO4
Cl2
5
164
a Anions were added as their tetrabutylammonium salts, all errors are ±10%.
b In water at 25 C, I = 0; D. D. Perrin, Pure Appl. Chem., 1969, 20,133.
Fig. 1 Color changes (if any) induced by the addition of anions. From left
to right (acetonitrile solutions): 4; 4 + F2; 4 + Cl2; 4 + Br2; 4 + AcO2; 4
+ H2PO42; 4 + HSO4
.
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