Synthesis and complexation study of calix[4]arene diamine derivative incorporated in a polymeric backbone with chiral monomers

Article abstract of DOI:10.1007/s10847-010-9820-6

The novel chiral polymeric compounds containing more than one calix[4]arene have been synthesized by reacting a new calix[4]arene diamine derivative with two chiral monomers. These newly prepared compounds were studied by extraction of toxic heavy metal (

Full text of DOI:10.1007/s10847-010-9820-6

J Incl Phenom Macrocycl Chem (2011) 69:107–117
DOI 10.1007/s10847-010-9820-6
ORIGINAL ARTICLE
Synthesis and complexation study of calix[4]arene diamine
derivative incorporated in a polymeric backbone with chiral
monomers
•
A. R Hajipour S. Habibi A. E. Ruoho
•
Received: 5 September 2009 / Accepted: 8 June 2010 / Published online: 22 July 2010
Ó Springer Science+Business Media B.V. 2010
Abstract The novel chiral polymeric compounds con-
taining more than one calix[4]arene have been synthesized
by reacting a new calix[4]arene diamine derivative with
two chiral monomers. These newly prepared compounds
years a growing interest in their use in conjunction with
polymeric matrices, either covalently bounded or blended
to them. A considerable amount of fundamental studies and
practical applications regarding their use as sensors,
selective electrodes, non-linear optics materials and devi-
ces for selective sorption of ions and neutral molecules,
have been reported recently [9–13]. In particular, the
chemically bounded calixarenes have been prepared by two
general synthetic methods. One is based on the immobili-
zation of the calixarene unity on an existing polymeric
matrix [14–20] and the other relied on copolymerization
reactions of a properly functionalized calixarene monomer,
either through linear step-growth polymerization [21–26]
or radical addition [27–30] reactions.
were studied by extraction of toxic heavy metal (Cu2?
,
Co2?, Cd2?, Hg2?), silver and alkali metal (Na?, K?)
cations from aqueous phase. It was observed that the
resulting calixarene-based polymers have a good com-
plexing ability towards silver, alkali metal and toxic heavy
metal cations.
Keywords Polymeric ionophores ꢀ Toxic heavy metals ꢀ
Complexation studies ꢀ Chiral polymeric calixarenes
The host–guest chemistry of the calixarenes is of great
interest, since the calixarenes exhibit complexing abilities
towards alkali, alkaline-earth and some transition metal
cations by means of functional group modification of the
phenolic groups [31–33]. In particular, the easy accessi-
bility of p-tert-butyl calix[4]arene has made this member of
the series increasingly popular with ligating side-arms or
podands for the reception of guest species, notably alkali,
alkaline-earth and some transition metal cations [34–36].
Chiral calixarenes have attracted increasing research
interest in the fields of organic, biological and medicinal
chemistry. Many of the chiral calix[4]arene derivatives
have shown remarkable recognition properties toward
achiral cations and anions, however, more interestingly,
some of them have exhibited significant chiral discrimi-
nation abilities for chiral guests such as organic ammonium
salts, amino alcohols and amino acids [37–39]. Also, by
immobilizing metal ions such as nickel or cobalt ions on a
chiral polymer as a chiral ionophore, an affinity support
that specially binds to proteins can be created. Such affinity
columns are used for purification of proteins [40–42].
Introduction
Calixarenes are a well-known class of synthetic receptor
molecules that possess intramolecular bow-shaped cavities
capable of accommodate neutral and ionic molecular
guests as well as metal ions through the establishment of
selective and specific interactions of diverse origin. Their
synthesis, properties and applications have been exten-
sively reviewed [1–8]. The interesting properties shown by
these cyclic oligomeric compounds have attracted in recent
A. R Hajipour ꢀ A. E. Ruoho
Department of Pharmacology, University of Wisconsin,
Medical School, 1300 University Avenue,
Madison 53706-1532, WI, USA
A. R Hajipour (&) ꢀ S. Habibi
Pharmaceutical Research Laboratory, Department of Chemistry,
Isfahan University of Technology, Isfahan 84156,
Islamic Republic of Iran
e-mail: Haji@cc.iut.ac.ir
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J Incl Phenom Macrocycl Chem (2011) 69:107–117
On the other hand, during the last decade, resolution of
IR spectra were recorded on a FT/IR-680 plus spectro-
photometer using KBr pellets. Inherent viscosities were
measured by a standard procedure using a Cannon Fenske
routine viscometer at 25 °C using DMF as solvent. 1H
NMR spectra were recorded on 500 and 300 MHz instru-
ment, using DMSO-d6 as a solvent and tetra methyl silane
as a chemical shift reference (tube diameter 5 mm).
Specific rotations were measured by a JASCO P-1030
Polarimeter. Thermal gravimetric analysis (TGA) was
obtained by a Mettler TGA-50 under air atmosphere at a
rate of 10 °C/min. Melting points were measured in open
capillaries with a gallenkamp instrument.
racemic compounds attracted a great attention in analytical
chemistry, especially in pharmaceutical analysis, because
each enantiomer of the chiral drugs exhibits great differ-
ences in pharmacological, pharmacodynamic, and toxico-
logical manners [43, 44]. High performance liquid
chromatography (HPLC) using a chiral stationary phase is
one of the most popular methods for the direct separation
of chiral compounds [45, 46]. Hitherto, several optically
active polymers have been used for enantiomeric HPLC
separation as the chiral stationary phase [47, 48]. Although
aromatic polyesters (PEs) and polyamides (PAs) with
excellent pattern of physical and chemical properties are
special candidates for chromatographic purposes, high
melting or glass-transition temperatures and restricted
solubility in organic solvents, due to their rigid structure,
have limited their processability. In this regard, they exert a
useful strategy, such as the use of monomer containing
pendent groups, aimed for the improvement of solubility
and processability of these polymers, without significant
decrease of thermal and mechanical properties [49].
Synthesis of calix[4]arene derivatives
Synthesis of 5,11,17,23-tetra-tert-butyl-25,27-bis[(4-
nitrobenzyloxy)-6,28-dihydroxy] calix [4]-arene (1)
A mixture of p-t-butyl calix[4]arene (10.0 g, 15.0 mmol),
anhydrous K2CO3 (2.4 g, 17.6 mmol) and p-nitrobenzyl
bromide (6.7 g, 30.7 mmol) in CH3CN (80 mL) was
refluxed for 20 h. The solvent was removed under reduced
pressure, the mixture was treated with CH3Cl (200 mL)
and filtered. The filtrate was concentrated under reduced
pressure (50 mL). Then CH3OH (100 mL) was added and
the pale yellow crystals appeared gradually. After a few
hours the crystals were filtered under vacuum and washed
with cold methanol to give 12.0 g (91.6%) of the pure
compound 1. m.p: 148–149 °C. FTIR (KBr, cm-1): 3434
(s, br), 3113 (m), 3047 (m), 2959 (s), 2906 (s), 2866 (s),
1606 (m), 1524 (s), 1483 (s), 1461 (s), 1393 (m), 1366 (s),
1348 (s), 1347 (s), 1297 (m), 1193 (s), 1123 (m), 1109 (m),
1031 (m), 946 (m), 919 (w), 824 (s), 852 (s), 819 (m), 796
(m), 780 (m), 736 (s), 699 (w), 650 (w), 629 (w), 578 (w),
Recently, the first use of a chiral resorcinarene has been
reported as a chiral stationary phase in enantioselective
capillary gas chromatography [50], but until now chiral
polymeric calix[4]arenes have not been synthesized and used
yet and most complexation studies have been conducted with
monomeric calixarenes. In this regard, given the high ther-
mal, chemical, mechanical stability and good solubility of
the polymers containing hexafluoroisopropylidene diph-
thalimide moieties [51] along with complexing ability of
calix[4]arene based polymers, we synthesized novel chiral
polymeric ionophores with complexing ability toward toxic
heavy metals in a solid–liquid sorption system. We intro-
duced chirality to the polymer backbone using aminoacids
because of their biologically importance and biodegradab-
ality for enantiometric recognition of amino acid derivatives
[52]. These novel chiral polymers are good candidates in
chromatographic purpose for separation of chiral biological
compounds like amines, amino acids and their derivatives
along with organic cations such as ammonium salts.
552 (m), 530 (m) cm-1 1H NMR (500 MHz, CDCl3,
.
25 °C): d 0.96 (s, 18H), 1.29 (s, 18H), 3.34 (d, 4H,
J = 13.0 Hz), 4.23 (d, 4H, J = 13.0 Hz), 5.17 (s, 4H),
6.83 (s, 4H), 7.08 (s, 4H), 7.26 (s, 2H), 7.91 (d, 4H,
J = 8.5 Hz), 8.17 (d, 4H, J = 8.6 Hz). Elemental analysis:
Calculated for C58H66N2O8: C (75.79%), H (7.24%), N
(3.05%); Found: C (75.81%), H (7.23%), N (3.06%).
Experimental section
Reduction of compound 1 (2)
Materials and instrumentation
To a mixture of 1 (4.50 g, 49 mmol), Raney-Ni (5.50 g),
ethyl acetate (80 mL) and MeOH (40 mL) was added
gradually N2H4.H2O (11.5 mL). The reaction mixture was
stirred at room temperature for 1 h, and was then refluxed
for 2 h with continuous stirring. Then the solvent
was evaporated under vacuum and Toluene (300 mL) was
added and heated to its boiling point. The hot mixture was
filtered and after concentrating the solvent, the white
crystals appeared. The crystals were filtered and washed
All the chemicals were purchased from Merck. All aqueous
solutions were prepared with deionized water. NMP was
purified with distillation over calcium hydride under
reduced pressure and stored over the molecular sieve.
Dichloromethane was dried over CaCl2. Reactions were
monitored by TLC on silica gel. p-tert-butyl calix[4]arene
were prepared as described [53].
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J Incl Phenom Macrocycl Chem (2011) 69:107–117
109
with cold methanol to give 3.00 g (71.4%) of compound 2.
m.p: 278 °C. FTIR (KBr, cm-1): 3551 (m), 3469 (m), 3415
(m), 3176 (m, br), 3048 (m), 3026 (m), 2954 (s), 2906 (s),
2869 (s), 1637 (m), 1617 (m), 1481 (s), 1456 (m), 1384
(m), 1361 (m), 1304 (m), 1284 (m), 1257 (w), 1250 (m),
1199 (s), 1157 (m), 1124 (m), 1102 (m), 946 (w), 889 (w),
870 (m), 815 (m), 781 (s), 729 (m), 709 (m), 695 (m), 673
(m), 619 (m), 591 (m), 552 (w), cm-1. 1H NMR (300 MHz,
DMSO-d6, 25 °C): d 0.91 (s, 18H), 1.16 (s, 18H), 1.8 (brs,
4H), 3.20 (d, 4H, J = 13.0 Hz), 4.18 (d, 4H, J = 13.0 Hz),
4.61 (s, 4H), 7.01–7.26 (m, 18H). Elemental analysis:
Calculated for C58H70N2O4: C (81.08%), H (8.21%), N
(3.26%); Found: C (80.80%), H (8.40%), N (3.00%).
(s), 1344 (m), 1295 (m), 1249 (s), 1182 (s), 1159 (m), 1106
(m), 1029 (m), 978 (m), 948 (m), 917 (m), 870 (m), 747
(m), 726 (m), 700 (w), 623 (m), 550 (w). 1H NMR
(500 MHz, DMSO-d6) d (ppm): 3.08 (dd, 2H), 3.48 (dd,
2H), 5.13 (m, 2H), 7.17 (m, 10H), 7.80 (m, 2H), 7.98
(s, 2H), 8.01 (dd, 2H), 13.33 (s, 2H). Elemental analysis:
Calculated for C37H24N2O8F6: C (60.17%), H (3.27%), N
(3.79%); found C (59.70%), H (3.60%), N (3.30%).
Diacid chloride 6a
25
White powder, yield: 93%, mp: 154–155 °C.½aꢁD
=
-26.82° [0.050 g in 10 mL acetone]. FTIR (KBr, cm-1):
2948 (m), 2874 (m), 1798 (s), 1784 (s), 1725 (s), 1626 (m),
1540 (w), 1489 (m), 1438 (m), 1381 (s), 1299 (m), 1256
(s), 1211 (s), 1191 (s), 1143 (m), 1105 (m), 1022 (m), 983
(m), 965 (m), 945 (m), 890 (m), 850 (m), 750 (m), 722 (m),
691 (m), 647 (m), 609 (w), 572 (m), 545 (w), 528 (w).
Elemental analysis: Calculated for C25H14N2O6F6Cl2: C
(48.18%), H (2.26%), N (4.49%); found C (47.80%), H
(2.50%), N (3.90%).
Synthesis of chiral monomers
Into a 25-mL, round-bottomed flask 0.50 g (1.12 mmol) of
hexafiuoroisopropylidene diphthalic anhydride (3),
2.24 mmol of amino acids 4a or 4b, 10.0 mL of acetic acid
and a stirring bar were placed. The mixture was stirred at
room temperature overnight then was refluxed for 6 h. The
solvent was removed under reduced pressure and 20 mL of
cold diluted HCl (5%) was added to the residue. A white
precipitate was formed, filtered off, washed with water and
dried under vacuum at 100 °C to give compounds 5a, 5b.
Recrystallization from methanol/water gave pure crystals.
Then, into a 25 mL round-bottomed flask were placed
1.0 g (2.3 mmol) of compounds 5a, 5b and 5 mL (an
excess amount) of thionyl chloride. The mixture was
refluxed for 3 h. Unreacted thionyl chloride was removed
under reduced pressure and the residue was washed with n-
hexane, to leave diacid chlorides 6a and 6b.
Diacid chloride 6b
25
White powder, yield: 89%, mp: 141–143 °C.½aꢁD
=
-78.31° [0.050 g in 10 mL acetone]. FTIR (KBr): 2925
(m), 2875 (m), 1798 (s), 1783 (s), 1723 (s), 1624 (m), 1490
(m), 1445 (m), 1427 (m), 1382 (s), 1298 (m), 1254 (s),
1210 (s), 1144 (m), 1105 (m), 1023 (m), 980 (m), 891 (w),
787 (m), 748 (m), 692 (m), 568 (w). Elemental analysis:
Calculated for C37H22N2O6F6Cl2: C (57.31%), H (2.86%),
N (3.61%); found C (56.80%), H (3.20%), N (3.10%).
Diacid 5a
Synthesis of polymeric calixarenes
25
White crystals, yield: 94%, m.p: 176–178 °C.½aꢁD
=
Method 1: polymerization under microwave irradiation
-27.40° [0.050 g in 10 mL acetone]. FTIR (KBr, cm-1):
3245 (m, br), 2949 (m), 1783 (s), 1719 (s), 1626 (m), 1438
(m), 1387 (s), 1300 (m), 1256 (s), 1210 (s), 1143 (m), 1095
(m), 1024 (m), 982 (m), 965 (m), 919 (m), 890 (m), 876
(m), 850 (m), 748 (m), 724 (m), 627 (m), 570 (m), 546 (w),
Into a porcelain dish were placed 0.233 mmol of diacid
chloride 6a or 6b and 0.200 g (0.233 mmol) of diamine 2.
After the reagents were completely ground for 5 min,
0.3 mL of NMP as a solvent was added and the mixture
was ground for 5 min. The reaction mixture was irradiated
in the microwave oven for 7 min at 100% power. The
resulting polymer film was isolated by addition of 20 mL
of methanol/water (10/1) and trituration; it was then filtered
and dried at 80 °C for 10 h in vacuo.
1
528 (w). H NMR (500 MHz, DMSO-d6) d (ppm): 1.1 (d,
6H), 4.81 (q, 2H), 7.71 (s, 2H), 7.84 (d, 2H), 8.05 (dd, 2H),
13.20 (s, 2H). Elemental analysis: calculated for
C25H16N2O8F6: C (51.21%), H (2.75%), N (4.78%); found
C (50.90%), H (2.90%), N (4.50%).
Diacid 5b
PA 7a
25
White crystals, yield: 95%, m.p: 194–195 °C. ½aꢁD
=
FTIR (KBr): 3162 (m, br), 3064 (m), 2955 (s), 2868 (m),
1781 (s), 1721 (s), 1695 (s), 1603 (m), 1482 (s), 1462 (m),
1385 (s), 1362 (m), 1286 (m), 1257 (m), 1242 (m), 1200
(s), 1158 (m), 1123 (m), 1103 (m), 1027 (m), 982 (m), 946
-80.96° [0.050 g in 10 mL acetone]. FTIR (KBr): 3240
(m, br), 3063 (m), 2927 (m), 1780(s), 1719 (s), 1673 (m),
1620 (m), 1601 (m), 1497 (m), 1455 (s), 1427 (m), 1384
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(m), 916 (m), 889 (m), 872 (m), 816 (m), 782 (m), 738 (m),
728 (m), 710 (m), 675 (m), 619 (m), 592 (w), 570 (w), 553
(m), 1101 (m), 1072 (m), 1023 (m), 981 (m), 917 (m), 873
(m), 847 (m), 817 (m), 782 (m), 743 (m), 724 (m), 711 (w),
1
676 (m), 620 (m), 592 (m), 570 (m), 554 (w), 513 (w). H
1
(w). H NMR (500 MHz, DMSO-d6, 25 °C): d (ppm) 1.1
(s, 18H), 1.34 (s, 18H), 1.51 (d, 6H), 3.38 (d, 4H), 4.21
(d, 4H), 4.82 (q, 2H), 5.24 (s, 2H), 7.02–7.34 (m, 18H), 7.6
(s, br, 2H), 7.71 (s, 2H), 7.82 (d, 2H), 8.03 (m, 2H).
NMR (300 MHz, DMSO-d6, 25 °C): d (ppm) 1.16 (s, 18H),
1.38 (s, 18H), 1.42 (d, 6H), 1.82 (s, br, 4H), 3.43 (m, 4H),
4.00 (m, 4H), 5.09 (m, 2H), 5.60 (s, 4H), 6.72–7.31
(m, 16H), 7.74 (m, 2H), 7.86 (m, 2H), 8.09 (m, 2H).
PA 7b
PE 7b0
FTIR (KBr): 3171 (m, br), 2956 (m), 2868 (m), 2284 (m),
1782 (m), 1723 (s), 1696 (s), 1604 (m), 1482 (s), 1462 (m),
1383 (s), 1362 (m), 1302 (m), 1256 (m), 1202 (s), 1143
(m), 1110 (m), 981 (m), 947 (m), 914 (m), 871 (m), 847
(m), 817 (m), 782 (m), 744 (m), 724 (m), 709 (m), 675 (m),
FTIR (KBr): 3567 (m), 3526 (m), 3168 (m), 2961 (m),
2870 (m), 1768 (s), 1731 (s), 1727 (s), 1626 (m), 1602 (m),
1483 (s), 1462 (m), 1383 (s), 1301 (m), 1256 (m), 1206 (s),
1142 (m), 1100 (m), 1070 (m), 1022 (m), 981 (m), 918 (m),
873 (m), 847 (m), 817 (m), 782 (m), 743 (m), 724 (m), 675
(m), 621 (w), 592 (m), 570 (m), 553 (w), 526 (w). 1H NMR
(300 MHz, DMSO-d6, 25 °C): d (ppm) 0.94 (s, 18H), 1.20
(s, 18H), 1.87 (s, br, 4H), 3.00-3.12 (m, 4H), 3.25–3.45
(m, 4H), 4.10–4.30 (m, 4H), 5.18 (s, 4H), 5.97–6.09
(m, 2H), 6.60–7.40 (m, 26H), 7.98–8.18 (m, 6H).
1
619 (m), 592 (m), 570 (m), 554 (m), 524 (w), 512 (w). H
NMR (300 MHz, DMSO-d6, 25 °C): d (ppm) 0.91
(s, 18H), 1.20 (s, 18H), 3.01–3.11 (m, 4H), 3.27–3.40 (m,
4H), 3.96–4.00 (m, 4H), 4.81–4.86 (m, 4H), 5.11–5.18 (m,
2H), 6.89 (s, 10H), 7.04–7.28 (m, 18H), 8.03–8.23 (m, 8H).
Method 2: solution polycondensation
Complexation studies
In a suspension of compound 2 (0.2 g, 0.233 mmol) in dry
CH2Cl2 (5 mL) in the presence of TEA (0.2 mL,
1.44 mmol) was added drop wise a solution of diacid
chloride 6a or 6b (0.233 mmol) in dry CH2Cl2 (5 mL) at
room temperature. The solution was stirred at room tem-
perature for 30 min and then was refluxed for 1 h. During
this time the polymer precipitate was appeared. The solvent
was evaporated and methanol/water (10/1) (20 mL) was
added. The polymer powder was filtered and washed with
methanol/water (10/1) (10 mL) and vacuum dried.
Picrate extraction experiments were performed following
the Cram procedure [54, 55]: 0.01 g of polymer was mixed
with 10 mL of an aqueous solution containing 2.5 9 10-5
M of picric acid (2,4,6-trinitrophenol) and 10-3 M of an
alkali and transition metal salt MNO3, M(NO3)2 and was
shaken at room temperature for 20 min in a stoppered glass
flask. The sorbent was removed by filtration before mea-
surements. The concentration of the picrate remaining in
aqueous phase after the sorption was determined spectro-
photometrically using a Perkin-Elmer Lambda 6 spectro-
photometer equipped with integrating sphere. The salts
used for the extraction, NaNO3, KNO3, CsNO3, AgNO3,
Cu(NO3)2, Cd(NO3)2, Co(NO3)2 and Hg(NO3)2 were
reagent grade. The alkali picrates were made by preparing
an aqueous solution containing 2.5 9 10-5 M of picric
PE 7a0
FTIR (KBr): 3568 (m), 3521 (m), 3161 (m), 2961 (m), 2869
(m), 1766 (s), 1730 (s), 1724 (s), 1603 (m), 1603 (m), 1483
(s), 1382 (s), 1363 (m), 1301 (m), 1256 (m), 1203 (s), 1143
NO2
NH2
NO2
NH2
OH
OH
OH
OH
OH
OH
OH
OH
p-Nitrobenzyl bromide
O
O
O
O
OH
O
Diphenyl Ether
Raney/Ni
+
CH3CN, K2CO3
NH2NH2.H2O
EtOAc/MeOH
H
H
t-Bu
t-Bu
t-Bu
t-Bu
4
-
4
4
-
-
2
1
Scheme 1 Synthesis of p-tert-butyl-calix[4]arene diamine derivative (2)
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J Incl Phenom Macrocycl Chem (2011) 69:107–117
111
O
CF3
F3C
O
H2N
COOH
O
+
H
R
O
CH3
4a, R=
O
CH
4b, R=
2
3
O
O
CH3COOH
O
O
O
CF3
F3C
O
CF3
F3C
O
O
O
R
SOCl2
N
N
Cl
N
Cl
OH
H
N
HO
R
R
H
H
R
O
H
O
O
O
CH3
6a, R=
6b, R=
CH3
5a, R=
5b, R=
CH
2
CH
2
Scheme 2 Synthesis of chiral monomers 6a, 6b
O
O
CF3
F3C
N
O
N
NH2
NH2
O
H
R
H
H
O
N
N
H
R
O
OH
OH
O
O
OH
OH
O
O
CH3
7a, R=
Method 1
NMP/Microwave
7b, R= CH2
t-Bu
-
4
-
-
t Bu
4
+
O
CF3
F3C
NH2
O
O
O
R
Method 2
CH2Cl2/TEA
N
NH2
Cl
N
Cl
O
O
R
H
H
CF3
O
F3C
O
N
O
O
CH3
6a, R=
6b, R=
H
R
O
O
CH
2
N
O
O
O
H
R
O
CH
3
7a', R=
7b', R=CH2
-
t-Bu
4
Scheme 3 Synthesis of chiral polymeric calixarenes 7a–7b0
acid and 10-3 M of an alkali nitrates. Transition metal
Results and discussion
picrates were prepared by stepwise addition of a 1.0 9
10-3 M of metal nitrate solution to a 2.5 9 10-5
M
In this work, the extraction properties of a diamine deriv-
ative of p-tert-butyl calix[4]arene and its polymers has
been investigated and compared. Also we introduced
amino acid moiety to induce chirality to the polymers.
p-tert-butylcalix[4]arene was treated with p-nitrobenzyl
bromide in dry acetonitrile in the presence of potassium
carbonate to obtain the cone conformer of 1 in 91.6% yield
(Scheme 1). The IR spectrum of 1 displays the nitro group
absorptions at 1524 and 1348 cm-1 and the 1H NMR
aqueous picric acid solution and shaken at room tempera-
ture for 1 h.
The percent sorption of ion (S%) has been calculated as
ꢀ
where Ci and Ce are the initial and final concentrations of
ꢁ
Ci ꢂ Ce
Sð%Þ ¼
ꢃ 100
ð1Þ
Ci
metal picrate before and after sorption, respectively.
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surprisingly we observed the evidences of polyamide for-
mation (7a, 7b) in the first method and polyester formation
(7a0, 7b0) in the second method (Scheme 3). The NH2
groups in calix diamine derivative are more reactive
towards carbonyl groups in the acid chloride, but the OH
groups are acidic and buried in the calix cavity, so in the
microwave irradiation method, where no catalyst is used,
NH2 groups react with acid chlorides and the amide link-
ages are formed. In the second polycondensation method
where triethyl amine is used as a catalyst and an acid
scavenger, the acidic protons of phenolic groups in the
calix derivative are removed and phenolate ions which are
more reactive towards acid chloride, reacted and the ester
linkages are formed. The introduction of the monomeric
calix derivative 2 as a bulky group in the polymer back-
bone, reduce the molecular weight of the resulted poly-
mers. It is worth knowing that using triethyl amine as a
catalyst and an acid scavenger with aliphatic acid chlorides
with alpha hydrogen can cause ketene formation which
causes racemization at the chiral center and reduces the
optical rotation. The FTIR spectra of polymers 7a and 7b
showed an amide band at 1695–1696 cm-1 and a broad
band at 3162–3171 cm-1 for the hydroxyl group (OH), but
for polymers 7a0 and 7b0 it was shown an ester band at
1730-1731 cm-1 and two absorption bands in the region of
3521–3568 cm-1 for NH2 groups and a broad band at
around 3160 cm-1 for OH (Fig. 1). Also the 1H NMR
spectra of these polymers verify this evidence (Fig. 2).
Examination of the 1H NMR spectra of the polymers
suggests the existence of the cone conformation of the
macrocyclic molecules in the polymer chain.
Fig. 1 FTIR spectra of a polymer 7a and b polymer 7a0
spectrum of this compound has a typical AB system for the
methylene bridge protons (ArCH2Ar) of the calixarene
moiety at d 3.34 and 4.23 (J = 13.0 Hz), the aromatic meta
protons at d 7.91 (J = 8.5 Hz), and ortho protons at d 8.17
(J = 8.6 Hz) which indicated that the substitution of
p-nitrobenzyl bromide had occurred. A reduction of the
nitro groups of 1 by Raney-Ni/N2H4.H2O gave the amino
derivative 2 in 71.4% yield (Scheme 1). Completion of the
reaction was followed by IR spectroscopy, which showed
the disappearance of the band because of the nitro groups at
1524 and 1348 cm-1 and appearance of the new bands at
3551 and 3469 cm-1 for the amine groups.
Polymeric calixarenes are potentially capable of forming
stable complexes with many metal ions. In recent years a
large amount of work has been reported in the literature
related to the functionalization of the calixarenes. How-
ever, investigations of chiral polymeric macro structures
containing more than one compound are quite limited. In
the present work, because of the high chemical, mechanical
and thermal character of the imide groups along with
biodegradability of amino acids and their biological prop-
erties, we envisioned the introduction of imide moieties in
distal calix[4]arenes derivative 2 as an entry to a new class
of chiral receptors for metal cations. Hence, condensation
reactions of dianhydride 3 with two moles of chiral amino
acids L-alanine (4a) and L-phenylalanine (4b) in acetic acid
afforded the corresponding chiral imide-diacids (5a, 5b).
The diacids were converted into the corresponding diacid
chlorides (6a, 6b) by reaction with thionyl chloride
(Scheme 2). The subsequent polymerization reactions of 2
with 6a and 6b were carried out using two methods:
polymerization under microwave irradiation in NMP as a
solvent and solution polycondensation in the presence of
triethyl amine (TEA) as a catalyst and dichloromethane as
a solvent. All polymers were characterized by a combina-
Some physical properties of these chiral polymers are
listed in Table 1. The inherent viscosities of the resulting
polymers under optimized condition were in the range of
0.22–0.26 dL g-1 and the yields were 84–87%.
All polymers were optically active and soluble in polar
aprotic solvents such as DMF, DMSO, DMAc, NMP but
insoluble in solvents such as water, CH3OH, CH2Cl2,
CHCl3 and nonpolar organic solvents. The elemental
analysis of all polymers has been shown in Table 2.
Thermal properties
The thermal properties of polymers 7b and 7b0 was eval-
uated by means of TGA/DTG in a nitrogen atmosphere at a
heating rate of 10 °C/min. Both polymers exhibited good
resistance to thermal decomposition up to 200 °C and
began to decompose gradually above those temperatures.
The temperature of 5 and 10% weight loss together with
char yield at 600 °C have been calculated by means of
thermograms, and used as criterion for evaluation of ther-
mal stability of the polymers. The thermoanalysis data of
these polymers are summarized in Table 3. It is interesting
1
tion of FTIR, H NMR and elemental analysis. Since the
compound 2 has two functionalities (NH2 and OH groups),
123

J Incl Phenom Macrocycl Chem (2011) 69:107–117
113
to note that T10% weight loss for the polymer 7b0 is 400 °C
that shows the high thermal stability of this polymer.
liquid extraction was performed with alkali and transition
metal picrates such as Na?, K?, Cs?, Cu2?, Co2?, Cd2?
,
Hg2? and Ag? from aqueous solutions. The ionophoric
calixarenes were subjected to comparative study. The
sorption percentages (S%) were calculated according to the
Eq. 1 and given in Tables 4 and 5. These data were obtained
by using the solid ligands to extract metal ions from aque-
ous picrate solutions. The equilibrium concentration of
metal ions was then determined spectrophotometrically.
With all ligands substituted with more than one
calix[4]arenes 6.75–46.61% extraction was accomplished
for toxic heavy metals and 17.47–53.04% for alkali metal
Evaluation of extraction capabilities
Polymeric calixarenes have been employed widely in the
formation of metal complexes and in the study of inclusion
phenomena due to their relatively easy preparation,
remarkable stability and high versatility [56, 57]. The
molecular recognition properties of p-tert-butyl calix[4]
diamine (2) and its polymeric derivatives (7a–7b0) were
studied by solid–liquid extraction experiments. The solid–
Fig. 2 1H NMR spectra of
a polymer 7a and b polymer 7a0
123

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J Incl Phenom Macrocycl Chem (2011) 69:107–117
Table 1 Some physical properties of polymers 7a–7b00
Table 4 Sorption percentages (S%) of toxic heavy metal ions by
monomer 2 and polymers 7a–7b0
Monomer
Polymer
Polymer
Liganda
Metal ions
Cu2?
25
b
Yield
(%)
g(inh(dL/
½aꢁD
Colorc
g)a
Cd2?
Co2?
Hg2?
6a
6b
a
7a
86.1
83.7
87.2
84.3
0.24
0.23
0.26
0.22
-5.74
-4.72
-31.60
-1.10
OW
OW
PY
Y
7a
7b
7a0
7b0
2
36.64
9.91
17.36
8.26
14.53
11.81
44.02
6.75
40.55
19.07
46.61
45.76
28.11
7a0
7b
7b0
14.22
4.31
33.06
28.10
18.80
43.96
18.37
Measured at a concentration of 0.5 g/dL in DMF at 25 °C
Measured at a concentration of 0.5 g/dL in DMF at 25 °C
Y Yellow, PY Pale Yellow, OW Off-White
b
c
Concentration: 1.0 9 10-2 M of metal nitrate salts in aqueous solu-
tion containing 2.0 9 10-5 M of picric acid
a
10 mg of ligand in 10 mL of aqueous metal picrate solution
(aqueous phase) was shaken at 25 °C for 20 min
Table 2 Elemental analysis of polymers 7a–7b0
Polymer Formula
C (%) H (%) N (%)
Table 5 Sorption percentages (S%) of toxic heavy metal ions by
monomer 2 and polymers 7a–7b0
7a
(C83H81N4O10F6)n (1409)n Calcd 70.77 5.80 3.98
Found 70.90 5.70
4.10
3.59
3.50
3.98
3.70
3.59
4.10
Liganda
Metal ions
Ag?
7b
7a0
7b0
Calcd 73.11 5.75
Found 73.00 6.00
Calcd 70.77 5.80
Found 70.60 6.10
Calcd 73.11 5.75
Found 73.30 5.90
Na?
K?
Cs?
7a
7b
7a0
7b0
2
47.58
49.19
30.64
44.09
42.74
18.55
47.54
51.30
53.04
59.42
17.47
22.60
34.93
30.14
55.14
0.0
0.0
0.0
0.0
0.0
Concentration: 1.0 9 10-2 M of metal nitrate salts in aqueous solu-
tion containing 2.0 9 10-5 M of picric acid
Table 3 Some thermogravimetric analysis results of polymers 7b
and 7b0
a
10 mg of ligand in 10 mL of aqueous metal picrate solution
(aqueous phase) was shaken at 25 °C for 20 min
Polymer
T5% ( °C)a
T10% ( °C)b
Char yield (%)c
7b
7b0
a
200
271
281
400
21.4
29.2
Temperature at which 5% weight loss was recorded by TG at
heating rate of 10 °C/min in N2
b
Temperature at which 10% weight loss was recorded by TG at
heating rate of 10 °C/min in N2
c
Percentage weight of material left undecomposed after TG analysis
at maximum temperature 600 °C in N2
ions. Most of the polymeric ligands had good sorption
capacity for toxic heavy metals. Also all of them extracted
silver and alkali metal ions but Cs?. Monomer 2 had the
highest sorption ability for Na?, K? and Cu2?. But the
polymers extracted Ag?, Na? and Hg2? better than
the other metal ions. The extraction value of the polymers
for toxic heavy metals is higher than the value of the
monomeric ligand. These results indicate that the existence
of more than one calix[4]arene in the polymeric com-
pounds and imide groups in the polymer backbone play
important roles in the extraction process. Also all of the
polymers and calix[4]arene diamine derivative (2) had no
extraction ability towards Cs? ion. This result showed that
Fig. 3 Sorption percentage of the polymers 7a–7b0 and calix diamine
derivative 2
the binding ability of the compound (2) and the polymers is
related to the macrocycle ring and metal ion size. The
extraction percentages of the compound 2 and the poly-
meric ligands 7a–7b0 were illustrated in Fig. 3. As an
123

J Incl Phenom Macrocycl Chem (2011) 69:107–117
115
introducing calix[4]arene into the chiral polymer chain and
giving the complexing properties to these polymers. The
different polymerization methods influenced the chemical
and physical properties of the corresponding polymeric
ligands. We synthesized a new class of chiral polymers as
good polymeric ionophores for sorption of alkali and toxic
heavy metal ions. These polymers can be a choice for
chiral recognition in the fields of organic, biological and
medicinal chemistry.
Acknowledgments We gratefully acknowledge the funding support
received for this project from Isfahan University of Technology
(IUT), IR Iran (ARH) and grant GM 33138(AER) from the national
Institute of health, USA. Further financial support from center of
Excellency Sensor and Green in chemistry research (IUT) is grate-
fully acknowledged.
Fig. 4 UV curves of the aqueous cobalt picrate solutions after
sorption by 7a–7b0 and 2
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