Novel bis-calix[4]arene based molecular probe for ferric iron through colorimetric, ratiometric, and fluorescence enhancement response

Article abstract of DOI:10.1016/j.tetlet.2014.12.078

A new bis-calix[4]arene platform (4) formed by upper rim-upper rim linking of two calixarene units has been obtained by 1:1 condensation of diformyl calixarene with carbohydrazide. The synthesized bis-calixarene has been found to selectively sense Fe

Full text of DOI:10.1016/j.tetlet.2014.12.078

Accepted Manuscript
Novel bis-calix[4]arene based molecular probe for ferric iron through colori-
metric, ratiometric and fluorescence enhancement response
H.M. Chawla, Tanu Gupta
PII:
S0040-4039(14)02144-3
DOI:
http://dx.doi.org/10.1016/j.tetlet.2014.12.078
TETL 45602
Reference:
To appear in:
Tetrahedron Letters
Received Date:
Revised Date:
Accepted Date:
27 October 2014
12 December 2014
14 December 2014
Please cite this article as: Chawla, H.M., Gupta, T., Novel bis-calix[4]arene based molecular probe for ferric iron
through colorimetric, ratiometric and fluorescence enhancement response, Tetrahedron Letters (2014), doi: http://
dx.doi.org/10.1016/j.tetlet.2014.12.078
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Graphical Abstract
Novel bis-calix[4]arene based molecular
probe for ferric iron through colorimetric,
ratiometric and fluorescence enhancement
response
Leave this area blank for abstract info.
H.M. Chawla* and Tanu Gupta

1
Tetrahedron Letters
journal homepage: www.elsevier.com
Novel bis-calix[4]arene based molecular probe for ferric iron through colorimetric,
ratiometric and fluorescence enhancement response
H.M. Chawla∗ and Tanu Gupta
Department of Chemistry, Indian Institute of Technology Delhi, Hauz Khas, New Delhi – 110016, India
ARTICLE INFO
ABSTRACT
Article history:
Received
A new bis-calix[4]arene platform (4) formed by upper rim- upper rim linking of two calixarene
units has been obtained by 1: 1 condensation of diformyl calixarene with carbohydrazide. The
3
+
Received in revised form
Accepted
synthesized bis-calixarene has been found to selectively sense Fe , without interference from
ferrous or any other metal ion through enhancement in the fluorescence intensity as well as
ratiometric absorption changes accompanied by a color change. The importance of bridged
macro cyclic framework has been further highlighted by comparison with an acyclic reference
compound.
Available online
Keywords:
Keyword_1 bis- calix[4]arenes
Keyword_2 ferric iron
2
009 Elsevier Ltd. All rights reserved.
Keyword_3 fluorescence enhancement
Keyword_4 ratio metric
Keyword_5 ionic recognition
Transition metal ions play a very important role in many
recognition. The same group has reported another biscalixarene
1
-2
13
+
+
derivative for selective sensing of K and Ag ions. Hudrlik and
fundamental biological processes . Several attempts have been
made by various research groups to develop chemosensors for
specific metal ion detection by making use of diverse recognition
1
4
coworkers have also reported their recent attempts to join two
calixarene scaffolds by means of a three-carbon bridge.
3
systems such as fluorescein fluoroinophores , triazole
derivatives , crown ethers etc. Amongst transition metal ions,
4
5
Bifunctional reagents can react with calix[4]arene to result in
intermoleculary bridged systems. Although enough efforts have
been devoted to the synthesis and characterization of
6
-7
iron plays an indispensable role at cellular level, as it enhances
physiological activities and greatly influences gene expression in
prokaryotes. An imbalance of iron concentration is known to
cause severe deleterious effects. For example, an excess
accumulation of iron can cause clinical deterioration and often
death in patients with severe forms of thalassemia. In such cases,
excess iron can be removed from the patient’s body only by
means of iron binding drugs called iron chelators. It is therefore
important to devise novel methods for sensitive resolution of
ferric ion.
1
5
biscalixarenes, most of the past work has concentrated majorly
on the lower rim- lower rim type of double calixarenes. We
report herein a new bis-calix[4]arene derivative 4, which is
doubly bridged at the upper rims of two calixarene macrocycles
by means of carbohydrazide linkers. To the best of our
knowledge, 4 is the first example of an upper rim- upper rim
double calixarene bridged through a carbohydrazide framework.
Our synthetic strategy was based upon the utilization of the
diformylated calix[4]arene as the pivotal compound that could
allow bridging at the upper rim when reacted with
carbohydrazide. Spectroscopic evaluation of 4 reveals that it
shows a high affinity towards ferric ions. It is significant to note
Calixarenes represent one of the most extensively studied
molecular receptors for recognition of various ions and neutral
8
-9
molecules . While most studies in calixarene chemistry have
focused on mono calixarene derivatives, there has been increased
1
6
recent
interest in the development of multi calixarene
that only a few chemosensors are available in the literature for
17-18
for
1
0
3+
Fe and most of them suffer from cross-sensitivity
compounds . In this connection, bis-calixarenes have attracted
special attention from several research groups as higher order
supramolecular systems which may possess special recognition
2
+
2+
3+
competitive metal ions like Cu , Hg and Cr . Moreover, due
to well known quenching effect of iron on the excited state of
fluorophores by electron transfer processes, the design of turn-on
fluorescent sensors for its detection tends to be much more
1
1
abilities. For example, while Rao and coworkers have reported
double calixarene for metal ion sensing, Lhoták and
a
coworkers have reported a bis-calixarene derivative for anion
———
1
2
19
3+
challenging . A chemosensor that not only detects Fe even in
∗
Corresponding author. Tel.: +91-11-265-91517; fax: +91-11-265-81102; e-mail: hmchawla@chemistry.iitd.ernet.in,
hmchawla@chemistry.iitd.ac.in (H.M. Chawla).

2
Tetrahedron
2
the presence of high concentrations of Cu and Cr , but also
+
3+
3+
complex species formed between 4 and Fe . The change in
exhibits enhancement in emission intensity would be much more
attractive. In this context, chemosensor 4 proves to be highly
absorbance spectrum was accompanied by a color change of
solution from colorless to light yellow. However, addition of
other competitive metal ions to the DMSO solution of 4 did not
alter its absorption spectrum (Supplementary data, fig. S3).
Figure 1 shows the changes in the absorption spectrum as well as
3
+
advantageous not only for exclusive selectivity towards Fe from
amongst 14 test metal ions but also for a significant enhancement
3
in fluorescence emission in response to Fe ions.
+
3
+
color of a solution of 4 upon gradual addition of Fe from 0 to
7.5 equiv.
The reaction of 3 with carbohydrazide in ethanol furnished
compound 4 in 72% yield (Scheme 1). Carbohydrazide was
2
0
synthesized as described previously in the literature . The
2
structure of bis-calixarene 4 was established by H NMR,
1
1
13
C
NMR spectrum
I
NMR and HRMS analysis. The
(
H
Supplementary data, fig. S1) of 4 exhibited deuterium
exchangeable singlets at 10.30 ppm and 7.94 ppm corresponding
to carbohydrazone NH and calixarene phenolic protons
respectively, while calixarene aryl ring protons were obtained at
7
.48 and 7.11 ppm. The existence of the synthesized compound
1
3
in its cone conformation was further confirmed by C NMR
Supplementary data, fig. S2) which showed a signal for syn
Ar CH at 30.02 ppm The formation of double calixarene was
(
2
2
further confirmed by HRMS analysis which showed peak at m/z
1
+
659.73 [M+Na] corresponding to 4.
Fig.1 Variation in absorption spectrum of 4 (30µM) upon titration
3
with Fe (0-7.5 equiv) in DMSO. Inset shows color change upon
+
3
Fe addition
+
(
i)
O H
O H
O H
O H
O H
H O
O
O
1
2
Such a change in absorbance values at two different
O
O
O
O
wavelengths offered an interesting opportunity for the ratiometric
determination of the analyte. When absorbance intensity ratios at
O
O
O
O
3
+
O
( i i)
370 and 308 nm were plotted as the function of Fe equivalents
added, a typical ratiometric calibration graph was obtained as
shown in figure 2. The absorbance ratio (A370/A308) exhibits
O H
O H
O
C H O
C H O
3
+
N
N
nearly 6- fold enhancement upon addition of Fe (7.5 equiv).
(
ii i)
N H
H N
O H
O H
O
O
O
O
3
N H
N
H N
N
O
O
O
O
O H
O H
O
O
4
O
O
O
O
S
Fig.2 Ratiometric plot of A370/A308 as a function of
equivalents of Fe added.
cheme 1. Synthesis of 4 and 7. Reagents and conditions: (i) Ethyl
bromoacetate, CO CH CN, reflux, 24h, yield: 70%; (ii)
hexamethylenetetramine, trifluoroacetic acid, reflux, 48h, yield:
1%; (iii) carbohydrazide, ethanol, reflux, 2h, yield: 72%; (iv)
3+
K
2
3
,
3
6
A Job's Plot was constructed to estimate the binding
3
stoichiometry of 4 with Fe , which exhibited a 1: 1 metal ligand
+
ethanol, reflux, 2h, yield: 70%.
3
complexation. The association constant for 4/Fe was calculated
+
4
-1
as 6.0×10 M (Supplementary data, fig. S4).
The selectivity and sensitivity of receptor 4 towards different
2
metal ions (Mn , Co , Cu , Fe , Fe , Ni , Hg , Ag , Cd ,
+
2+
2+
2+
3+
2+
2+
+
2+
from absorption titration data by using Benesi- Hildebrand
2
2
+
3+
+
+
+
2
Zn , Cr , Na , Cs , Li
)
was determined by UV-vis,
fluorescence and H NMR spectroscopy. The stock solutions
1mM) of perchlorate salts of all metal ions were prepared in
equation.
An acyclic reference compound 7 was synthesized by adopting
adopting a process reported in the literature. 7 was subjected to
1
(
3
+
HPLC grade DMSO. Absorbance and fluorescence spectra were
recorded by gradual addition of increasing amounts of ions to the
receptor solution (30µM).The absorption spectrum of a DMSO
solution of 4 exhibited characteristic absorption bands at 308 nm
similar recognition experiments with Fe . It was determined that
showed an absorption maximum at 295 nm along with a
shoulder band at 315 nm. The absorption spectrum of 7 did not
7
show any obvious changes even on addition of excess (10 equiv)
4
-1
-1
3
of Fe ions, thereby confirming the importance of bridged
+
and 321 nm (molar extinction coefficient: 2.22Χ10 M cm and
4
-1
-1
3
+
2
.20Χ10 M cm respectively). The addition of just 0.1 equiv of
macrocyclic framework of 4 for Fe sensing. Figure S5,
Supplementary data), shows the absorption spectrum of 7 upon
addition of excess of Fe .
3+
Fe to a DMSO solution of 4 (30µM) resulted in the appearance
of a new absorption band around 370 nm, which exhibited
(
3
+
3
significant absorption enhancement upon further addition of Fe .
+
The new spectral band at 370 nm, could be attributed to the
The selectivity of 4 was also investigated by measuring the

3
+
3+
n+3
fluorescence emission spectra against different metal ions in
DMSO. When excited at 320 nm, the fluorescence spectrum of 4
of 2 equiv of Fe alone. Green bar denotes intensity of Fe / M
coexisting systems
3
+
exhibited a maximum at 445 nm. Addition of 2 equiv of Fe to a
DMSO solution of 4 (30µM) resulted in an appreciable
enhancement (~97%) in the fluorescence intensity at 445 nm
3
A plausible binding mode of 4 and Fe was examined by
+
1
recording the H NMR spectra of DMSO-d
6
solution of 4
5mM), before and after the addition of Fe . As depicted in
3
+
(
figure 5, it was determined that the peak corresponding to
(
the fluorescence intensity of 4, indicating that 4 is a reliable,
fig.3), while other tested metal ions virtually had no effect on
3
sensitive and highly selective turn-on fluorescent sensor for Fe .
+
carbohydrazide NH underwent a downfield shift from 10.30 to
10.48 ppm. This shift in the peak of NH protons in the presence
The increase in the emission intensity could be attributed to the
3
+
of iron could be attributed to the coordination of carbohydrazide
carbonyl oxygen functionality with ferric ion during
complexation.
formation of 4-Fe complex.
λ
ex 320 nm
(d)
(
(
c)
b)
Fig.3 Changes in the emission spectrum of 4 (30µM) upon addition
of Fe (0- 2 equiv.) in DMSO.
3+
Supplementary data, fig. S6 depicts the relative increase in
the fluorescence intensity (at λ. 445 nm) of 4 upon addition of
various metal ions. It is quite evident that binding of 4 and Fe is
3
+
2
+
remarkably selective, while other competing ions (including Fe
ions) caused insignificant changes in the emission spectrum of 4.
n+
3+
n+
3+ 23
The selectivity coefficients (k
M
,
for all the tested metal ions (inset, figure S5) showed that the
Fe = ∆F
M
/∆FFe ) measured
(a)
interaction of other ions with 4 (especially ferrous ions) was
3
too miniscule to affect the detection of Fe by 4.
+
2
The limit of detection (LOD) for Fe binding by 4, as
4
3+
-
determined from the fluorescence titration data was 3×l0 M.
7
3
This LOD is lower than the maximum level of Fe (5.4µM)
+
1
Fig. 5 Partial H NMR (300 MHz) spectra of (a) 4 in DMSO ; (b) 4 +
2
ions permitted in drinking water by the US Environmental
5
3+
0.1 equiv. Fe ; (c) 4 + 0.5 equiv. Fe ; (d) 4 + 1 equiv. Fe .
3+
3+
Protection Agency, implying that probe 4 holds a great potential
3
for use in the development of sensor materials for Fe .
+
In conclusion, we have realized teh synthesis of a new type of
upper rim linked bis-calixarene platform possessing
carbohydrazide moiety as the bridging unit. It is noteworthy that,
while turn-ON fluorescence sensors for iron are quite sparse, 4
shows a selective enhancement of fluorescence intensity in
Further, competitive experiments were conducted to know the
effects of coexisting biologically relevant ions on the detection
3
of Fe (fig 4) by 4 (30µM). Addition of an equimolar amount (2
+
3
+
3+
-7
equiv) of other interfering metal ions to a solution of 4.Fe
resulted in negligible effect on the fluorescence intensity of the
response to Fe ions with a quite low detection limit of 3×10
M. Furthermore, 4 shows a ratiometric absorption response
3
+
complex, indicating that 4 is a reliable, highly selective and
sensitive "turn-on" fluorescence sensor for Fe in DMSO.
towards Fe along with a specific color change which
additionally augments the prospects of 4 to be used as an iron
selective chemosensor.
3
+
Acknowledgement. Tanu Gupta thanks CSIR, India for a
research fellowship. Financial assistance from DST(for purchase
of HRMS by Chemistry Department), DBT, MoEF, MoRD and
MoFPI is gratefully acknowledged
References
1
.
Linder, M. C.; Hazegh- Azam, M. Am. J. Clin. Nutr. 1996, 63, 797S-
11S.
Uauy, R.; Olivares, M.; Gonzalez, M. Am. J. Clin. Nutr. 1998, 67,
52S- 959S.
8
2
.
9
3
.
(a) Li, T.; Yang, Z.; Li, Y.; Liu, Z.; Qi, G.; Wang, B. Dyes and
Pigments 2011, 88, 103-108; (b) Chawla, H. M.; Shukla, R.; Pandey,
S. Tetrahedron Lett. 2013, 54, 2063-2066.
3
+
Fig.4 Competitive selectivity of 4 for Fe in preference to other
metal ions. Red bar represents the intensity of 4 (30 µM) in presence

4
Tetrahedron
0
4
.
(a) Pathak, R. K.; Hinge, V. K.; Mondal, P.; Rao, C. P. Dalton
Trans. 2012, 41, 10652-10660; (b) Park, S. Y.; Yoon, J. H.; Hong, C.
S.; Souane, R.; Kim, J. S.; Matthews, S. E.; Vicens, J. J. Org. Chem.
21. Analytical data for 4: Yield: 72%; Mp: 194-196 C ; UV (λmax,
-1
DMSO): 308 nm, 321 nm; IR (KBr pellet, cm ): 3384, 2956, 1610,
1541, 1196; Anal. Calcd: C 68.93, H 6.65, O 17.58; Found: C 68.95,
2
008, 73, 8212- 8218.
H 6.66, O 17.55; HRMS (ESI-MS) m/z:calcd 1659.76, found 1659.73;
1
H NMR (300 MHz, DMSO, δ in ppm): 10.30 (s, 4H, NH, D
O exchangeable),
.48 (s, 8H), 7.11 (s, 8H), 4.82 (s, 8H), 4.42 (d, 8H), 4.32 (q, 8H), 3.60
2
O
5
.
.
Surowiec, M.; Custelcean, R.; Surowiec, K.; Bartsch, R. A.
exchangeable), 8.24 (s, 4H), 7.94 (s, 4H, OH, D
2
Tetrahedron 2009, 66, 7777-7783.
7
6
(a) Palacios, M. A.; Wang, Z.; Montes, V. A.; Zyryanov, G. V.;
Anzenbacher, P.; Jr. J. Am. Chem. Soc. , 2008, 130 , 10307–10314; (b)
Tolosa, J.; Zucchero, A. J.; Bunz, U. H. F. J. Am. Chem. Soc. 2008,
1
3
(
d, 8H), 1.32 (t, 12H),1.28 (s, 36H); C NMR (75 MHz, DMSO, δ in
ppm) 12.96, 30.02, 32.93, 59.92, 70.94, 116.99, 117.58, 125.04,
1
1
26.75, 127.75, 129.02, 131.42, 146.21, 149.50, 151.13, 152.65,
68.01.
1
30 , 6498 – 6506.
7
8
.
.
Youdim, M. B. H. Neurotoxic. Res. 2008, 14 (1), 45 –56.
2
2
2
2. Benesi, H. A.; Hildebrand, J. H. J. Am. Chem. Soc. 1949, 71, 2703–
707.
(a) Sahin, O.; Yilmaz, M. Tetrahedron Lett. 2012, 53, 2319- 2234; (b)
Pathak, R. K.; Dessingou, J.; Rao, C. P. Anal. Chem. 2012, 84, 8294-
2
3. Pandey, S.; Azam, A.; Pandey, S.; Chawla, H. M. Org. Biomol. Chem.
009, 7, 269-279.
8
300; (c) Nimse, S. B.; Kim, T. Chem. Soc. Rev. 2013, 42, 366-386.
2
9
.
(a) Lee, J. W.; Park, S. Y.; Cho, B. K.; Kim, J. S. Tetrahedron Lett.
007, 48, 2541- 2546; (b) Chawla, H. M.; Sahu, S. N.; Shrivastava, R.;
4. Ono, A.; Togashi, H. Angew. Chem. Int. Ed. 2004, 43, 4300- 4302.
2
Kumar, S. Tetrahedron Lett. 2012, 53, 2244- 2247; (c) Chawla, H. M.;
Pant, N.; Kumar, S.; Kumar, N.; Black David St, C. Calixarene-based
materials for chemical sensors In Chemical Sensors Fundamentals of
Sensing Materials; Korotcenkov, G., Ed.; Momentum Press: New
York, 2010; Vol. 3, p 300.
25. Yi, C.; Tian, W.; Song, B.; Zheng, Y.; Qi, Z.; Qi, Q.; Sun, Y. J.
Lumin. 2013, 141, 15-22.
1
0. (a) Gac, S. L.; Zeng, X.; Reinaud, O.; Jabin, I. J. Org. Chem. 2005, 70,
204-1210; (b) Tsai, C. –C.; Chang, K. –C.; Ho, I. –T.; Chu, J. –H.;
Cheng, Y. –T.; Shen, L. –C.; Chung, W. –S. Chem. Commun. 2013, 49,
037-3039.
1. Ali, A.; Joseph, R.; Mahieu, B.; Rao, C. P. Polyhedron 2010, 29, 1035-
040.
1
3
1
1
1
1
2. Stastny, V.; Lhoták, P.; Michlová, V.; Stibor, I.; Sykora, J.
Tetrahedron, 2002, 58, 7207-7211.
3. Budka, J.; Lhoták, P.; Stibor, I.; Michlová, V.; Sykora, J.; Cisarová, I.
Tetrahedron Lett. 2002, 43, 2857-2861.
1
1
4. Hudrlik, P. F.; Hailu, S. T.; Hudrlik, A. M.; Butcher, R. J. J. Mol.
Struct. 2013, 1054-1055, 271-281.
5. (a) Kim, S. K.; Sim, W.; Vicens, J.; Kim, J. S. Tetrahedron Lett. 2003,
4
4, 805-809; (b) Morales- Sanfrutos, J.; Ortega- Muñoz, M.; Lopez-
Jaramillo, J.; Hernandez- Mateo, F.; Santoyo- Gonzalez, F. J. Org.
Chem. 2008, 73, 7768-7771; (c) Luo, J.; Shen, L. –C.; Chung, W. –S.
J. Org. Chem. 2010, 75, 464-467.
1
1
6. (a) Pandya, A.; Sutariya, P. G.; Lodha, A.; Menon, S. K. Nanoscale
2
013, 5, 2364-2371; (b) Yang, L.; Yang, W.; Xu, D.; Zhang, Z.; Liu,
A. Dyes and Pigments 2013, 97, 168-174.
7. (a) Liu, J.-M.; Zheng, Q.-Y.; Yang, J.-L.; Chen, C.-F.; Huang, Z.-T.
Tetrahedron Lett. 2002, 43, 9209-9212; (b) Ali, A.; Joseph, R.;
Mahieu, B.; Rao, C. P. Polyhedron 2010, 29, 1035-1040; (c) Wang,
M.; Wang, J.; Xue, W.; Wu, A. Dyes and Pigments 2013, 97, 475-480.
1
1
8. (a) Narayanaswamy, N.; Govindaraju, T. Sens. Actuators, B 2012,
1
61, 304-310; (b) Liu, R.-L.; Lu, H.-Y.; Li, M.; Hu, S.-Z.; Chen, C.-F.
RSC Adv. 2012, 2, 4415-4420.
9. a) Shellaiah, M.; Wu, Y.-H.; Singh, A.; Raju, M. V. R.; Lin, H.-C. J.
Mater. Chem. A 2013, 1, 1310-1318; (b) Bhalla, V.; Sharma, N.;
Kumar, N; Kumar, M. Sens. Actuators, B 2013, 178, 228-232.
2
0. Li, Z.; Zhu, W.; Yu, J.; Ma, X.; Lu, Z.; Xiao, S. Synth. Commun.
2
006, 36, 2613-2619.