Recognition of anions and monocarboxylic acids by a fluorescent guanidine-based receptor

Article abstract of DOI:10.1080/10610270902980614

A guanidine-based fluorescent receptor has been synthesised to study its binding behaviour towards anions (F^-, Cl^-, Br^-, I^- and AcO^-). The two donor N-H bonds of the receptor do not point in the same direction; rather, one N-H bond is intramolecularly hydrogen-bonded with the carbonyl oxygen atom. The nature of the donor-acceptor (DA) arrangement induces moderate binding properties. The binding behaviour towards monocarboxylic acids (benzoic acid and phenylacetic acid) is also compared. The binding behaviour of receptor 1 towards the F^- anion is higher among the anions studied, whereas in the case of monocarboxylic acid, the binding constant with phenylacetic acid is higher than benzoic acid.

Full text of DOI:10.1080/10610270902980614

Supramolecular Chemistry
Vol. 22, No. 3, March 2010, 143–148
Recognition of anions and monocarboxylic acids by a fluorescent guanidine-based receptor
b
a
Shyamaprosad Goswami *, Subrata Jana , Rinku Chakrabarty and Hoong-Kun Fun
a†
a
a
b
Department of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah 711 103, West Bengal, India; X-Ray
Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
(Received 19 September 2008; final version received 25 March 2009)
2
2
2
A guanidine-based fluorescent receptor has been synthesised to study its binding behaviour towards anions (F , Cl , Br ,
2
2
and AcO ). The two donor NZH bonds of the receptor do not point in the same direction; rather, one NZH bond is
I
intramolecularly hydrogen-bonded with the carbonyl oxygen atom. The nature of the donor–acceptor (DA) arrangement
induces moderate binding properties. The binding behaviour towards monocarboxylic acids (benzoic acid and phenylacetic
2
acid) is also compared. The binding behaviour of receptor 1 towards the F anion is higher among the anions studied,
whereas in the case of monocarboxylic acid, the binding constant with phenylacetic acid is higher than benzoic acid.
Keywords: molecular recognition; hydrogen bonding; fluorescence sensor; guanidine
The guanidinium group is a versatile moiety in bioactive
molecules (1). Many synthetic receptors containing a
guanidinium moiety have been designed and studied for
their recognition pattern for a wide range of anions (2).
These types of receptors interact strongly with the
oxoanions such as carboxylates and phosphates in enzymes
the actual form adopted in the solid state as confirmed by the
single-crystal X-ray structure determination (see Support-
ing Information), although molecular structures in the solid
1
and solution states may also differ. But here the H NMR
spectrum of the complex also proves the similar
arrangement of the DA array, in the solid state (Figure 1).
The anions bind with receptor 1 via a single donor NZH
site, whereas the monocarboxylic acid interacts via two-
point binding modes. The overall binding interaction of
receptor 1 is weak towards guests. In the case of
monocarboxylic acid, either the ring ‘N’ or exo ‘N’ acts
as the hydrogen bond acceptor towards a hydroxyl group,
whereas the NZH of either the N(ring)ZH or N(exo)ZH
acts as the hydrogen bond donor towards the carbonyl
oxygen (Scheme 2).
(
3). In the case of synthetic receptors, they are mainly used
to recognise different anions. Although the guanidinium
moiety is used extensively for recognition purposes, there is
not much discussion on its dynamic nature in donor–
acceptor (DA) arrays. It is thus a challenging task to use the
guanidine moiety for the recognition of anions. It is also
interesting to study its binding with a monocarboxylic acid
using a receptor containing a single guanidine amide
moiety as a part of a dihydroperimidine at the peri positions
of a naphthalene ring.
The receptor 1 was synthesised by a simple one-pot,
two-step procedure (Scheme 3). The yellow-coloured
product was isolated and used for the binding studies. The
To study the recognition behaviour, we have
synthesised a fluorescent guanidine-based receptor 1 in
which two nitrogen atoms make up the six-membered ring
of the naphthalene moiety and the other nitrogen atom is
attached to a benzoyl group. This type of benz-fused
dihydroperimidine amide has a very interesting DA array.
Herein, the binding behaviour of this receptor 1 towards
different anions (4) and benzoic acid has been discussed.
Receptor 1 may exist in three different tautomeric forms in
the solution phase (Scheme 1) (5). Among these three,
forms I and II may recognise a carboxylic acid moiety (6),
whereas form III may recognise anions or oxoanions.
In fact, both anions as well as benzoic acid bind with the
most stable conformation of receptor 1 (form I), which is
1
structure of receptor 1 was confirmed by the spectral data
(7) as well as by the single-crystal X-ray structure
2
determination.
To study the binding behaviour of receptor 1 for
1
anions, we performed H NMR studies with an equivalent
amount of tetrabutylammonium fluoride in which one
NZH (d 10.08 ppm) peak remains unchanged, whereas
a
the other NZHb (d 9.09 ppm) peak disappeared. This
implies that the NZH proton did not interact with the
a
fluoride ion and that proton H was deprotonated by the
b
fluoride base (Figure 1) (8). From this observation, it is
clear that the receptor 1 binds the fluoride ions using only
*Corresponding author. Email: spgoswamical@yahoo.com
†
Present address: Department of Chemistry, University of Victoria, Victoria, BC, Canada.
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2010 Taylor & Francis
DOI: 10.1080/10610270902980614
http://www.informaworld.com

1
44
S. Goswami et al.
Scheme 1. (a) Receptor 1, (b) ORTEP diagram of receptor 1 and (c) tautomeric forms of receptor 1.
1
Figure 1. Partial H NMR spectra (300 MHz, CDCl
fluoride.
3
) of (a) receptor 1 (3 mM) and (b) an equivalent amount of tetrabutylammonium

Supramolecular Chemistry
145
Scheme 2. Mode of binding of receptor 1 to (a) a fluoride ion and (b) the carboxylic acid moiety of a monocarboxylic acid.
one donor site through form I or II. A similar observation
1
was found in the case of H NMR studies with an
benzoic acid and phenylacetic acid with receptor 1 were
calculated by plotting 1/DI versus 1/[G ] (Table 1) (10).
equivalent amount of benzoic acid. In this case, the NZHa
peak also remained unchanged, whereas the chemical shift
Fluorescence titrations were also performed in CHCl .
3
2
4
The emission spectra of receptor 1 (1.017 £ 10 M)
of NZH was very small (Dd ¼ 0.02 ppm) with respect to
appear as double humps (l
almost equal intensity. These two humps gradually merged
during titration upon addition of the increasing amount of
¼ 400 and 417 nm) with
b
max
our recently reported pyridine amide-based receptors (9).
The binding behaviour with anions and benzoic acid,
determined by both UV–vis and fluorescence titration
methods (Table 1), is comparable.
2
guest substrates (F and AcO ) in CHCl (see Supporting
2
3
Information). The receptor 1 also behaves as a possible
sensor towards different monocarboxylic acids (10). The
enhancement of emission intensity of receptor 1 in the case
The binding behaviour of receptor 1 was studied
by UV–vis and fluorescence titrations. In both cases,
the binding patterns were almost similar. The UV–vis
2
2
of F and AcO is much higher than other anions as well
as monocarboxylic acids. In these cases, the receptor 1
titrations were carried out with receptor
2
1
4
2
2
(
1.017 £ 10 M) in CHCl solution. The solutions of
strongly binds to the F and AcO ions through the NZH
proton. In all the cases, the fluorescence intensity
gradually increases upon continuous addition of the
guest solution but through a slight initial decrease in
intensity. Although the nature of the emission spectra with
other anions and monocarboxylic acids is similar, their
enhancement of emission intensity is very weak. The
nature of emission spectra is partially governed by the
basicity of anions. Among all the anions, the enhancement
3
2
3
guest substrates were also prepared in ca. 1 £ 10
M
order in CHCl . Upon addition of the guest solutions,
3
the absorbance (lmax ¼ 282 nm) decreased gradually
(
Figure 2, inset). The binding constants for all the anions,
2
of emission intensity is the weakest in the case of I . The
nature of the emission spectra with monocarboxylic acids
was almost similar to the anions, where regular
enhancement of the intensity was observed. The emission
intensity of receptor 1 was enhanced more in the case of
phenylacetic acid than benzoic acid. Thus, in all the cases,
4
Scheme 3. Reagents and conditions: (i) (a) NH SCN, dry
acetone, reflux, 20 min; (b) 1,8-naphthalene diamine, dry
acetone, reflux, 3 h, 54%.
2
2
except for F and AcO , the host–guest interactions
occurred through hydrogen bonding in a neutral

1
46
S. Goswami et al.
21 a
Table 1. Association constants [K (M )] and free energy changes [DG(kcal/mol)] at 258C for receptor 1 and guests in a 1:1 mode of
a
interaction as determined by the UV–vis and fluorescence titration methods in CHCl
Method
3
.
b
UV
c
Fluorescence
Guest
K
a
DG
K
a
DG
2
3
2
2
2
3
2
3
3
2
2
3
2
2
2
F
Cl
1.24 £ 10
6.79 £ 10
4.73 £ 10
3.93 £ 10
1.11 £ 10
1.61 £ 10
1.03 £ 10
24.22
23.86
23.65
23.54
24.15
23.01
24.11
1.73 £ 10
9.17 £ 10
8.41 £ 10
1.08 £ 10
4.05 £ 10
6.20 £ 10
9.54 £ 10
24.41
24.04
23.99
24.14
23.56
23.81
24.06
2
2
Br
2
I
AcO
2
Benzoic acid
Phenylacetic acid
a
All the errors are ^ 20%.
For receptor 1: lmax ¼ 282 nm.
b
c
For receptor 1: lmax(ex) ¼ 282 nm, lmax(em) ¼ 416 nm, emission slit width ¼ 15.0 nm, excitation slit width ¼ 10.0 nm, scan rate ¼ 400 nm/min.
2
2
environment. But in the case of F and AcO , the host–
guest interactions occurred in a partial ionic environment.
This also inferred a higher association constant (Table 1)
2
with F , determined by both UVand fluorescence titration
1
methods as well as the H NMR spectra of a 1:1 complex of
receptor 1 with tetrabutylammonium fluoride (Figure 1).
These results also reflect the nature of the binding constant
values (Table 1), which were determined by plotting
I /I 2 I versus 1/[G] from the fluorescence titrations
0
0
(
Figure 3) (11).
Recently, Chetia and Iyer (12) reported benzimidazole-
based receptors for the sensing of anions, where the two
NZH bonds are directed inwards and bind with the spherical
2
anions. In this case, selectivity towards F was observed,
2
whereas in the present perimidine-based system both F and
2
AcO show higher interactions. The binding constant
values for the receptor 1 containing a single donor site
as well as reported two donor sites are comparable (8, 12).
Figure 3. (a) Binding constant calculation curves of receptor 1
with anions and monocarboxylic acids (inset: fluorescence
Figure 2. Binding constant curves calculated by the UV–vis
method of receptor 1 with various anions (inset: UV–vis titration
2
titration spectra with AcO ) and (b) Stern–Volmer plots
determined by fluorescence titration methods.
2
spectra with F ) and monocarboxylic acids in CHCl .
3

Supramolecular Chemistry
147
The association constants of the guests with receptor 1 show
the overall binding behaviour. Among the anions,
7.43 (t, 1H, J ¼ 7.0 Hz), 7.20 (d, 2H, J ¼ 4.1 Hz), 6.51 (d,
1
2
H, J ¼ 5.0 Hz). H NMR (CDCl
3
, 300 MHz) [Complex
2
the association constant for F is higher with respect to
with TBAF (1 eq.)]: d (ppm): 10.08 (bs, 1H), 8.09 (d, 2H,
J ¼ 7.5 Hz), 7.85 (d, 1H, J ¼ 8.4 Hz), 7.64 (t, 1H,
J ¼ 7.4 Hz), 7.55–7.48 (m, 2H), 7.40 (t, 1H, J ¼ 7.4 Hz),
7.20 (d, 2H, J ¼ 4.1 Hz), 6.54 (dd, 2H, J ¼ 5.7 Hz), 3.35 (t,
8H, J ¼ 8.4 Hz), 1.65 (m, 8H), 1.46 (m, 8H), 0.99 (t, 12H,
3
, 125 MHz): d (ppm): 177.04,
the other anions due to the influence of equilibrium between
the receptor and its deprotonated form during interaction
with these anions; however, all the other anions bind with the
receptor via a single-point hydrogen bonding interaction.
The binding constant with monocarboxylic acids is also
comparable due to the two-point interactions with the exo
imide ‘N’ and the ring NZH of the receptor.
1
3
J ¼ 7.2 Hz). C NMR (CDCl
1
1
53.47, 135.93, 135.24, 132.34, 129.41, 129.08, 128.57,
28.51, 127.85, 120.33, 110.95. Mass (ESI): m/z (%): 288.0
þ
þ
[M þ H , 100], 289 [M þ 2H , 29], 130 (14), 105.1 (32).
Anal. calcd for C H N O; C, 75.25; H, 4.56; N, 14.62.
1
8 13 3
From this study, it can be concluded that the simple
dihydroperimidine-based fluorescent receptor 1 can
recognise both anions and monocarboxylic acids by
single-point and two-point hydrogen bonding interactions,
respectively, and the values of their binding constants are
close to one another. Receptor 1 may be considered as a
new fluorescent chemosensor for a wide range of guest
substrates. The nature of the receptor towards the anions is
Found: C, 75.20; H, 4.62; N, 14.65.
Single crystals of receptor 1 were grown by slow evaporation
at room temperature from chloroform solution. Crystal data
2
.
(
CCDC No. 672282): C18
H
13
N
3
O, M ¼ 287.31, Monoclinic,
Space group ¼ C2/c (No. 15); a ¼ 23.0876(11); b ¼
8.7890(4); c ¼ 13.8108(9) A˚ , b ¼ 106.315(5)8; V ¼
3
23
˚
2689.6(3) A , Z ¼ 8, D
¼ 1.419 g cm , R ¼ 0.0577,
c
1
wR
2
¼ 0.1807.
2
also very important for studying the selectivity for F and
2
AcO . Another structural feature is that the two donor
References
(
1) (a) Luecke, H.; Quiocho, F.A. Nature 1990, 347, 402–406.
b) Pflugrath, J.W.; Quiocho, F.A. Nature 1985, 314, 257–
sites of the guest substrate are not involved in the
recognition of anions due to strong intramolecular
hydrogen bonding as confirmed by the spectral changes
(
260. (c) Hannon, C.L.; Anslyn, E.V. Bioorg. Chem. Front.
1993, 3, 193–256.
1
in the H NMR and also by the single-crystal X-ray
structure of receptor 1.
(
2) (a) Cotton, F.A.; Hazen, E.E., Jr.; Legg, M.J. Proc. Natl
Acad. Sci. USA 1979, 76, 2551–2555. (b) Christianson,
D.W.; Lipscomb, W.N. Acc. Chem. Res. 1989, 22, 62–69.
(
1
6
c) Berger, M.; Schmidtchen, F.P. Angew. Chem., Int. Ed.
998, 37, 2694–2696. (d) Schmuck, C. Chem. Eur. J. 2000,
, 709–718. (e) Best, M.D.; Tobey, S.L.; Anslyn, E.V.
Acknowledgements
We wish to express our appreciation to CSIR [Project No.
Coord. Chem. Rev. 2003, 240, 3–15. (f) Wright, A.T.;
Anslyn, E.V. Org. Lett. 2004, 6, 1341–1344. (g) Schug,
K.A.; Lindner, W. Chem. Rev. 2005, 105, 67–114.
0
1
1(1913)/04/EMR-II] and DST [Project No. SR/S1/OC-
3/2005], Govt of India, for financial support. S. J. and R. C.
thank CSIR, Govt of India, for a research fellowship. We also
thank the Malaysian Government and Universiti Sains Malaysia
for the Scientific Advancement Grant Allocation (SAGA) Grant
No. 304/PFIZIK/653003/A118.
(
h) Jadhav, V.D.; Schmidtchen, F.P. Org. Lett. 2005, 7,
3
3
8
311–3314. (i) Schmuck, C. Coord. Chem. Rev. 2006, 250,
053–3067. (j) Suhs, T.; Konig, B. Chem. Eur. J. 2006, 12,
150–8157. (k) Tominey, A.F.; Docherty, P.H.; Rosair,
G.M.; Quenardelle, R.; Kraft, A. Org. Lett. 2006, 8, 1279–
1
282. (l) Oton, F.; Tarraga, A.; Molina, P. Org. Lett. 2006, 8,
107–2110. (m) Shepherd, J.; Langley, G.J.; Herniman,
J.M.; Kilburn, J.D. Eur. J. Org. Chem. 2007, 1345–1356.
(n) Lin, C.; Simov, V.; Drueckhammer, D.G. J. Org. Chem.
2007, 72, 1742–1746.
2
Notes
1.
Spectral data of receptor 1 [N-(1H,3H-perimidin-2-ylidene)-
benzamide ]: To an ammonium thiocyanate (152 mg,
2
(
mmol) solution in dry acetone (20 ml), benzoyl chloride
0.25 ml, 2.1 mmol) was added dropwise at room tempera-
(3) (a) Schiessl, P.; Schmidtchen, F.P. J. Org. Chem. 1994, 59,
509–511. (b) Metzger, A.; Anslyn, E.V. Angew. Chem., Int.
Ed. 1998, 37, 649–652. (c) Bell, T.W.; Khasanov, A.B.;
Drew, M.G. B.; Filikov, A.; James, T.L. Angew. Chem., Int.
Ed. 1999, 38, 2543–2547. (d) Linton, B.; Goodman, M.S.;
Jubian, V.; Hamilton, A.D. Chem. Eur. J. 2000, 6, 2449–
2452. (e) Jensen, K.B.; Braxmeier, T.M.; Demarcus, M.;
Frey, J.G.; Kilburn, J.D. Chem. Eur. J. 2002, 8, 1300–1309.
(f) Wiskur, S.L.; Lavigne, J.J.; Metzger, A.; Tobey, S.L.;
Lynch, V.; Anslyn, E.V. Chem. Eur. J. 2004, 10, 3792–
3804. (g) George, N.; Pick, H.; Vogel, H.; Johnsson, N.;
Johnsson, K. J. Am. Chem. Soc. 2004, 126, 8896–8897. (h)
Schmuck, C.; Schwegmann, M. Org. Lett. 2005, 7, 3517–
3517. (i) Schmuck, C.; Geiger, L. J. Am. Chem. Soc. 2005,
127, 10486–10487.
ture. This mixture was refluxed for 20 min and cooled down
to room temperature. Now, 1,8-naphthalene diamine
(
316 mg, 2 mmol) in dry acetone (10 ml) was added dropwise
and the whole mixture was again refluxed for another 3 h.
The solvent was distilled off and the residue dried under
vacuum. This mixture was washed with water and extracted
with CHCl
anhydrous Na
pressure to obtain a deep brown crude solid. The crude was
purified by column chromatography using silica gel (100–
2
6
3
(25 ml £ 4). The CHCl
3
solution was dried over
4
SO and evaporated out under reduced
2
00 mesh) and 15% EtOAc in petroleum ether (boiling range
0–808C) as the eluent to afford a yellow solid compound
(
(
1
receptor 1, 310 mg, 54%). Mp. 226–2278C. FT-IR
CH Cl ): 3197, 2923, 2852, 1670, 1622, 1458, 1360,
(4) (a) Mangani, S.; Ferraroni, M. In Supramolecular Chemistry
of Anions; Bianchi, A., Bowman-James, K., Garcia-Espana,
E., Eds.; Wiley: New York, 1997; Chapter 3. (b) Beer, P.D.;
Gale, P.A.; Smith, D.K. Supramolecular Chemistry. In
2
2
2
268 cm . H NMR (CDCl
1 1
3
, 300 MHz): d (ppm): 10.08 (bs,
1
H), 9.09 (bs, 1H), 8.09 (d, 2H, J ¼ 7.8 Hz), 7.85 (d, 1H,
J ¼ 7.2 Hz), 7.64 (t, 1H, J ¼ 7.4 Hz), 7.55–7.49 (m, 2H),

1
48
S. Goswami et al.
Oxford Chemistry Primers; Evans, J., Ed.; Oxford
(7) Shestakov, A.S.; Gusakova, N.V.; Shikhaliev, Kh.S.;
Zagoruiko, A.V. Russ. J. Gen. Chem. 2006, 76, 1647–1652.
(8) Caltagirone, C.; Gale, P.A.; Hiscock, J.R.; Hursthouse,
M.B.; Light, M.E.; Tizzard, G.J. Supramol. Chem. 2009, 21,
University Press: New York, 1999; Chapter 3. (c) Dudziuk,
H. Introduction to Supramolecular Chemistry; Kluwer
Academic Publishers: Dordrecht, The Netherlands, 2002;
Chapter 7.8. (d) Steed, J.W.; Atwood, J.L. Supramolecular
Chemistry; Wiley: New York, 2000; Chapter 4. (e) Sessler,
J.L.; Gale, P.A.; Cho, W.S. Anion Receptor Chemistry;
Royal Society of Chemistry: Cambridge, UK, 2006. (f)
Kang, S.O.; Begum, R.A.; Bowman-James, K. Angew.
Chem., Int. Ed. 2006, 45, 7882–7894. (g) Gale, P.A. Acc.
Chem. Res. 2006, 39, 465–475. (h) Vickers, M.S.; Beer, P.D.
Chem. Soc. Rev. 2007, 36, 211–225.
1
25–130. (DOI: 10.1080/10610270802348243).
9) (a) Goswami, S.; Jana, S.; Fun, H.-K. CrystEngComm.
008, 10, 507–517. (b) Goswami, S.; Jana, S.; Dey, S.;
Razak, I.A.; Fun, H.-K. Supramol. Chem. 2006, 18, 571–
74. (c) Goswami, S.; Dey, S.; Maity, A.C.; Jana, S.
(
2
5
Tetrahedron Lett. 2005, 46, 1315–1318. (d) Goswami, S.;
Dey, S.; Fun, H.-K.; Anjum, S.; Rahman, A.-U. Tetrahedron
Lett. 2005, 46, 7187–7191.
(
5) (a) Pozharskii, A.F.; Konstantinchenko, A.A.; Kashparov,
(
(
10) (a) Connors, K.A. Binding Constants- The Measurement of
Molecular Complex Stability; Wiley: New York, 1987.
I.S. Chem. Heterocycl. Compd 1978, 14, 93–100. (b)
Lopatin, B.V.; Drusvyat-skaya, S.K.; Bekhli, A.F. Chem.
Heterocycl. Compd 1978, 14, 694–698.
(
b) Benesi, H.; Hildebrand, J.H. J. Am. Chem. Soc. 1949, 71,
703–2707.
11) (a) Chou, P.-T.; We, G.-R.; Wei, C.-Y.; Cheng, C.-C.;
2
(
6) (a) Goswami, S.; Jana, S.; Hazra, A.; Fun, H.-K.;
Chantrapromma, S. Supramol. Chem. 2008, 20, 495–500.
Chang, C.-P.; Hung, F.-T. J. Phys. Chem. B 2000, 104,
818–7829. (b) Liao, J.-H.; Chen, C.-T.; Chou, H.-C.;
(
b) Goswami, S.; Jana, S.; Hazra, A.; Fun, H.-K.; Anjum,
7
S.; Rahman, A.-U. CrystEngComm. 2006, 8, 712–718. (c)
Ghosh, K.; Masanta, G. Supramol. Chem. 2005, 17, 331–
Cheng, C.-C.; Chou, P.-T.; Fang, J.-M.; Slanina, Z.; Chow,
T.J. Org. Lett. 2002, 4, 3107–3110.
334. (d) Goswami, S.; Ghosh, K.; Ghosh, S. J. Ind. Chem.
(
12) (a) Chen, H.-M.; Li, J.-W.; Lin, H.; Cai, Z.-S.;
Lin, H.-K. Supramol. Chem. 2009, 21 (DOI: 10.1080/
10610270802072785). (b) Chetia, B.; Iyer, P.K. Tetrahe-
dron Lett. 2008, 49, 94–97.
Soc. 2003, 80, 1187–1192. (e) Goswami, S.; Ghosh, K.;
Mukherjee, R. J. Ind. Chem. Soc. 1999, 76, 661–664. (f)
Goswami, S.; Ghosh, K.; Dasgupta, S. Tetrahedron 1996,
52, 12223–12232.

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