Para-acylcalix[6]arenes: Their synthesis, per-O-functionalisation, solid-state structures and interfacial assembly properties

Article abstract of DOI:10.1007/s10847-010-9769-5

The para-acylcalix[6]arenes bearing butanoyl, hexanoyl and octanoyl chains have been synthesized by Friedel-Crafts acylation of the parent calixarene. Persubstitution at the phenolic face was achieved to yield the methoxy-diethoxy, ethoxycarbonylmethoxy, methoxycarboxylic acid and butoxysulphonate derivatives. In the case of the derivatives, 5,11,17,23,29,35-hexa-octanoyl-37,38,39,40,41,42-hexa-methoxy-diethoxy-calix[6]arene, 5,11,17,23,29,35-hexa-butanoyl-37,38,39,40,41,42-hexaethoxycarbonyl methoxy-calix[6]arene and 5,11,17,23,29,35-hexa-octanoyl-37,38,39,40,41,42-hexaethoxycarbonyl methoxy-calix[6]arene the solid state structures were determined and show inclusion of two ester groups in the cavity. While for the para-acylcalix[6]arenes no stable monolayers can be formed at the air-water interface, stable monolayers are formed with the methoxy-diethoxy, ethoxycarbonylmethoxy, methoxycarboxylato compounds which show apparent molecular areas in the range 150-200 A² depending on the length of the acyl chains.

Full text of DOI:10.1007/s10847-010-9769-5

J Incl Phenom Macrocycl Chem (2010) 68:207–217
DOI 10.1007/s10847-010-9769-5
ORIGINAL ARTICLE
Para-acylcalix[6]arenes: their synthesis, per-O-functionalisation,
solid-state structures and interfacial assembly properties
•
Said Jebors Barbara Lesniewska
•
´
Oleksandr Shkurenko Kinga Suwinska
Anthony W. Coleman
•
•
´
Received: 27 November 2009 / Accepted: 7 March 2010 / Published online: 25 April 2010
Ó Springer Science+Business Media B.V. 2010
Abstract The para-acylcalix[6]arenes bearing butanoyl,
hexanoyl and octanoyl chains have been synthesized by
Friedel–Crafts acylation of the parent calixarene. Persub-
stitution at the phenolic face was achieved to yield the
methoxy-diethoxy, ethoxycarbonylmethoxy, methoxycarb-
oxylic acid and butoxysulphonate derivatives. In the case of
the derivatives, 5,11,17,23,29,35-hexa-octanoyl-37,38,39,
40,41,42-hexa-methoxy-diethoxy-calix[6]arene, 5,11,17,23,
29,35-hexa-butanoyl-37,38,39,40,41,42-hexaethoxycarbonyl
methoxy-calix[6]arene and 5,11,17,23,29,35-hexa-octanoyl-
37,38,39,40,41,42-hexaethoxycarbonyl methoxy-calix[6]arene
the solid state structures were determined and show inclu-
sion of two ester groups in the cavity. While for the para-
acylcalix[6]arenes no stable monolayers can be formed at
the air–water interface, stable monolayers are formed with
the methoxy-diethoxy, ethoxycarbonylmethoxy, methoxy-
carboxylato compounds which show apparent molecular
Introduction
The calix[n]arenes are amongst the most highly studied
classes of macrocyclic host molecules, this arises both from
the facile selective synthesis and also from their ease of
modification as they present two very different chemistries,
at one face phenolic groups and at the other activated para-
aromatic group [1]. Their complexation chemistry has been
extensively studies [2], and more recently their biological
activity has become of interest [3].
Of the calixarene derivatives we have been, for some
time, studying the para-acylcalix[n]arenes [4], synthesised
via Friedel–Crafts acylation at the para-aromatic position
[5]. In the case of the para-acylcalix[4]arenes it has been
demonstrated that they are capable of forming stable
monolayers at the air–water interface, of forming Solid
Lipid Nanoparticles [6], and that they possess extremely
varied properties in the solid state. Particularly, in the
solid-state they have been demonstrated to be non-porous
materials, in the sense that there are no channels or voids
in the packing [7] and yet that they are capable of
undergoing guest exchange via single crystal to single
crystal transformations [8], and also gas uptake [9]. The
lack of porosity allows them to protect photosensitive
materials [10] and allow stabilization of organic free
radicals [11]. We have recently synthesized para-acylca-
lix[8]arenes [12], and have succeeded in fully and cleanly
substituted them at the phenolic functions, interestingly
these molecules do not form monolayers at the air–water
interface and also do not form Solid Lipid Nanoparticles
[13]. In recent work, the synthesis of the para-acylca-
lix[9]arenes has been achieved [14], and here the situation
is analogous to that for the para-acylcalix[4]arenes with
formation of monolayers, and also stable Solid Lipid
Nanoparticles [6].
2
˚
areas in the range 150–200 A depending on the length of the
acyl chains.
Keywords Calixarene Á Amphiphilic Á Structure Á
Langmuir Á Synthesis
Electronic supplementary material The online version of this
article (doi:10.1007/s10847-010-9769-5) contains supplementary
material, which is available to authorized users.
S. Jebors Á A. W. Coleman (&)
´
Institut de Biologie et Chimie des Proteines, UMR 5086, CNRS,
Universite Lyon 1, 7 passage du Vercors, 69367 Lyon, France
´
e-mail: aw.coleman@ibcp.fr
´
´
B. Lesniewska Á O. Shkurenko Á K. Suwinska
Institute of Physical Chemistry, Polish Academy of Sciences,
Kasprzaka, 44/52, 01224 Warszawa, Poland
e-mail: kinga@ichf.edu.pl
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There, thus, remains the synthesis of the para-acylca-
A saponification reaction was realised on the relevant
product with 150 mL of a solution of KOH (10%) in eth-
anol/water (70/30) during 24 h. The ethanol was removed
under reduced pressure. Compounds 2a–c were precipitated
by acidification with HCl 1 M (500 mL) and filtered. The
resultant compounds were solubilised in chloroform
(400 mL), washed with water (4 9 400 mL) and dried over
anhydrous MgSO4. The chloroform was removed under
reduced pressure to give a volume of 60 mL and com-
pounds 2a–c were precipitated with methanol (500 mL).
lix[6]arenes and the study of their properties, for which it
has taken several years to achieve clean and efficient para-
acylation.
Previously, the synthesis of amphiphilic calix[6]arenes
has been carried out either by introducing polar functions at
the para-position for example quaternary amines [15],
boronic acids or alcohols [16] along with coupling long
alkyl chains at the phenolic face or by simple per-O-
substitution at the phenolic face with, for example ethyl-
eneglycol chains [17] or amide functions [18]. Selective
di- and tri-substitution have been reported, and a selective
di-demethylation using TiCl4 was published some time ago
[19]. Starting from the selective 1,3,5-O-methylation of
para-tert-butylcalix[6]arene, a wide range of features can be
introduced at the free hydroxyls positions [20, 21].
In the current paper we describe the synthesis of some
para-acylcalix[6]arenes, and successful and unsuccessful
work on the per-O-substitution of these molecules. The
formation of stable monolayers at the air–water interface by
the per-O-substituted derivatives is observed. The crystal
structures of three compounds have been determined.
5,11,17,23,29,35-Hexa-butanoylcalix[6]arene
2a: 1H NMR (DMSO) d 7.69 ppm (s, 12H, HmAr),
3.88 ppm (br s, 12H, Ar–CH2–Ar), 2.92 ppm (s, 12H,
CH2CO), 1.45 ppm (s, 12H, –CH2–CH2–CO), 1.22 ppm (s,
–CH2–CH3, 36H), 0.84 ppm (s, CH3–CH2, 18H). 13C NMR
(CDCl3) d 199.1 (C=O), 152.7 (Cipso), 132.3 (Cpara), 129.8
(Cortho), 128.4 (Cmeta), 40.2 (CH2CO), 31.3 (CH2), 17.8
(CH2), 14.0 (CH3). 1079.5 [?Na?], m.p. [250 °C,
Rf = 0.21 (CHCl3), yield = 73%.
5,11,17,23,29,35-Hexa-hexanoylcalix[6]arene
2b: 1H NMR (DMSO) d 7.66 ppm (s, 12H, HmAr),
3.91 ppm (br s, 12H, Ar–CH2–Ar), 2.75 ppm (s, 12H,
CH2CO), 1.46 ppm (s, 12H, –CH2–CH2–CO), 1.19 ppm (s,
–(CH2)2–, 24H), 0.88 ppm (t, CH3–CH2, 18H). 13C NMR
(CDCl3) d 198.7 (C=O), 152.3 (Cipso), 132.7 (Cpara), 129.8
(Cortho), 128.4 (Cmeta), 38.8 (CH2CO), 32.0–23.2 (4 9 CH2),
14.1 (CH3). 1247.7 [?Na?], m.p. [250 °C, Rf = 0.25
(CHCl3), yield = 77%.
Experimental
General experimental details
1
NMR spectra were recorded on a Bruker 500 MHz for H
and 125 MHz for 13C (TMS as internal standard, chemical
shifts in ppm). Mass spectra (MALDI-TOF) were recorded
on a Voyager DE-PRO instrument (Applied Biosystems).
Langmuir isotherms were recorded on a NIMA 6010 film
balance on pure water ([18 MX) at 20 °C, all isotherms
were repeated at least three times, variability was less than
3% in all cases. 1 was synthesized as per the literature and
all physical data concord with literature values [22].
5,11,17,23,29,35-Hexa-octanylcalix[6]arene
2c: 1H NMR (DMSO) d 7.65 ppm (s, 12H, HmAr),
3.91 ppm (br s, 12H, Ar–CH2–Ar), 2.71 ppm (br s, 12H,
CH2CO, 1.49 ppm (s, 12H, –CH2–CH2–CO), 1.22 ppm (s,
–(CH2)4–, 48H), 0.81 ppm (s, CH3–CH2, 18H). 13C NMR
(CDCl3) d 198.9 (C=O), 152.6 (Cipso), 132.6 (Cpara), 129.8
(Cortho), 128.3 (Cmeta), 38.8 (CH2CO), 32.2–23.0 (6 9 CH2),
14.5 (CH3). MS (MALDI-TOF): 1415.9 [?Na?], m.p.
[250 °C, Rf = 0.28 (CHCl3), yield = 83%.
Typical procedure for para-acylation of calix[6]arene
Under anhydrous nitrogen, aluminium trichloride (12 equiv.)
and the relevant acid chloride (9 equiv.) were added to
nitrobenzene (75 mL) and the mixture was stirred for
10 min. The solution became dark brown, to this was added 1
(5 g, 1 equiv.). The resultant solution was stirred at room
temperature for 24 h. Pouring onto ice stopped the reaction.
The organic phase was extracted with chloroform (400 mL),
washed with 1 M HCl (2 9 400 mL), 1 M NaCl
(2 9 400 mL), water (4 9 400 mL) and dried over anhy-
drous MgSO4. The chloroform was removed under reduced
pressure, and the nitrobenzene distilled off under vacuum
(10-2 T) to give a clear brown paste.
5,11,17,23,29,35-Hexa-butanoyl-37,38,39,40,41,42-
hexa-ethoxycarbonylmethoxycalix[6]arene
2a (1 g, 1 equiv.), ethyl bromoacetate (0.8 mL, 10 equiv.),
potassium carbonate (1 g, 10 equiv.), were combined and
refluxed in acetone during 48 h. The acetone was removed
under reduced pressure and the resultant compound was
solubilised in chloroform (30 mL) washed with 1 M HCl
(2 9 30 mL), 1 M NaCl (2 9 30 mL), water (2 9 30 mL)
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J Incl Phenom Macrocycl Chem (2010) 68:207–217
209
and dried under anhydrous MgSO4. The chloroform was
removed under reduced pressure to give a volume of 5 mL
and the product was precipitated in methanol.
1.64 ppm (s, 12H, –CH2–CH2–CO), 1.26 ppm (s, –(CH2)4–,
48H), 1.19 ppm (s, 18H, O–CH2–CH3), 0.91 ppm (s, CH3–
CH2, 18H). 13C NMR (CDCl3) d 199.2 (C=O), 168.2 (COO),
159.2 (Cipso), 133.3 (Cpara), 129.9 (Cortho), 129.3 (Cmeta),
69.8 (Ar–O–CH2), 61.1 (O–CH2–CH3), 38.3 (CH2CO),
31.5–22.6 (4 9 CH2), 14.1 (2 9 CH3). MS (MALDI-TOF):
1765.3 [?Na?], 1781.2 [?K?], m.p. = 167 °C, Rf = 0.71
(CHCl3), yield = 62%.
1
Compound 5a: H NMR (CDCl3) d 7.72 ppm (s, 12H,
HmAr), 4.81–3.72 ppm (br s, 12H, Ar–O–CH2–, 12H, O–
CH2–CH3, 12H, Ar–CH2–Ar), 2.79 ppm (s, 12H, CH2CO),
1.66 ppm (s, 12H, –CH2–CH2–CO), 1.31 ppm (s, –(CH2)4–,
48H), 1.19 ppm (s, 18H, O–CH2–CH3), 0.95 ppm (s, CH3–
CH2, 24H). 13C NMR (CDCl3) d 199.1 (C=O), 168.2 (COO),
158.8 (Cipso), 133.4 (Cpara), 133.2 (Cortho), 129.7 (Cmeta),
69.8 (Ar–O–CH2), 61.1 (O–CH2–CH3), 40.2 (CH2CO), 31.1
(CH2), 17.8 (CH2), 13.8 (2 9 CH3). MS (MALDI-TOF):
1595.8 [?Na?], 1611.8 [?K?], m.p. = 160 °C, Rf = 0.68
(CHCl3), yield = 63%.
5,11,17,23,29,35-Hexa-hexanoyl-37,38,39,40,41,42-
hexa-2-carboxymethoxy calix[6]arene
5b (1 g, 1 equiv.) was added to 50 mL of a solution of
KOH (10%) in ethanol/water (70/30) during 24 h. The
ethanol was removed under reduced pressure. Compound
was precipitated with a solution of HCl 2 M (60 mL) and
filtered. The resultant compound was solubilised in chlo-
roform (30 mL), washed with water (4 9 30 mL) and
dried over anhydrous MgSO4. The chloroform was
removed under reduced pressure to give a volume of 5 mL
and the product was precipitated in hexane.
5,11,17,23,29,35-Hexa-butanoyl-37,38,39,40,41,42-
hexa-2-carboxymethoxycalix[6]arene
5a (1 g, 1 equiv.) was added in 50 mL of a solution of
KOH (10%) in ethanol/water (70/30) during 24 h. The
ethanol was removed under reduced pressure. Compound
was precipitated with a solution of HCl 2 M (60 mL) and
filtered. The resultant compound was solubilised in chlo-
roform (30 mL), washed with water (4 9 30 mL) and
dried over anhydrous MgSO4. The chloroform was
removed under reduced pressure to give a volume of 5 mL
and the product was precipitated in hexane.
1
Compound 6b: H NMR (CDCl3) d 7.70 ppm (s, 12H,
HmAr),4.38 ppm (s, 12H, Ar–O–CH2–), 3.48 ppm (s, 12H,
Ar–CH2–Ar), 2.73 ppm (s, 12H, CH2CO), 1.51 ppm (s,
12H, –CH2–CH2–CO), 1.20 ppm (br s, –(CH2)4–, 48H),
0.79 ppm (s, CH3–CH2, 18H). 13C NMR (CDCl3) d 199.6
(C=O), 169.3 (COO), 159.5 (Cipso), 133.3 (Cpara), 129.8
(Cortho), 129.6 (Cmeta), 69.9 (Ar–O–CH2), 38.4 (CH2CO),
31.5–22.6 (4 9 CH2), 13.9 (CH3). MS (MALDI-TOF):
1595.6 [?Na?], 1609.6 [6a ? K?], m.p. = 220 °C,
Rf = 0.23 (CHCl3/MeOH/75/25), yield = 87%.
1
Compound 6a: H NMR (CDCl3) d 7.70 ppm (s, 12H,
HmAr),4.38 ppm (s, 12H, Ar–O–CH2–), 3.48 ppm (s, 12H,
Ar–CH2–Ar), 2.73 ppm (s, 12H, CH2CO), 1.51 ppm (s,
12H, –CH2–CH2–CO), 1.20 ppm (s, –(CH2)4–, 48H),
0.79 ppm (s, CH3–CH2, 18H). 13C NMR (CDCl3) d 199.4
(C=O), 169.5 (COO), 158.5 (Cipso), 133.6 (Cpara), 133.2
(Cortho), 129.4 (Cmeta), 70.2 (Ar–O–CH2), 39.9 (CH2CO),
31.4 (CH2), 17.7 (CH2), 14.0 (CH3). MS (MALDI-TOF):
1427.5 [?Na?], 1443.5 [?K?], m.p. = 175 °C, Rf = 0.2
(CHCl3/MeOH/75/25), yield = 88%.
5,11,17,23,29,35-Hexa-octanoyl-37,38,39,40,41,42-
hexa-ethoxycarbonylmethoxycalix[6]arene
2c (1 g, 1 equiv.), ethyl bromoacetate (0.8 mL, 10 equiv.)
and potassium carbonate (1 g, 10 equiv.), were combined
and refluxed in acetone during 48 h. The acetone was
removed under reduced pressure and the resultant com-
pound was solubilised in chloroform (30 mL) washed with
HCl 1 M (2 9 30 mL), NaCl 1 M (2 9 30 mL), water
(2 9 30 mL) and dried under anhydrous MgSO4. The
chloroform was removed under reduced pressure to give a
volume of 5 mL and the product was precipitated in
methanol.
5c: 1H NMR (CDCl3) d 7.71 ppm (s, 12H, HmAr),
4.26 ppm (s, 12H, Ar–O–CH2–), 4.13 ppm (s, 12H, O–CH2–
CH3), 4.01 ppm (s, 12H, Ar–CH2–Ar), 2.79 ppm (s, 12H,
CH2CO), 1.61 ppm (s, 12H, –CH2–CH2–CO), 1.27 ppm (s,
–(CH2)4–, 48H), 1.17 ppm (s, 18H, O–CH2–CH3), 0.88 ppm
(s, CH3–CH2, 18H). 13C NMR (CDCl3) d 199.1 (C=O),
168.1 (COO), 159.3 (Cipso), 133.6 (Cpara), 133.2 (Cortho),
129.8 (Cmeta), 69.7 (Ar–O–CH2), 61.3 (O–CH2–CH3), 38.7
5,11,17,23,29,35-Hexa-hexanoyl-37,38,39,40,41,42-hexa-
ethoxycarbonylmethoxycalix[6]arene
2b (1 g, 1 equiv.), ethyl bromoacetate (0.8 mL, 10 equiv) and
potassium carbonate (1 g, 10 equiv.), were combined and
refluxed in acetone during 48 h. The acetone was removed
under reduced pressure and the resultant compound was
solubilised in chloroform (30 mL) washed with HCl 1 M
(2 9 30 mL), NaCl 1 M (2 9 30 mL), water (2 9 30 mL)
and dried under anhydrous MgSO4. The chloroform was
removed under reduced pressure to give a volume of 5 mL
and the product was precipitated in methanol.
1
Compound 5b: H NMR (CDCl3) d 7.72 ppm (s, 12H,
HmAr),4.86–3.62 ppm (br s, 12H, Ar–O–CH2–, 12H, O–
CH2–CH3, 12H, Ar–CH2–Ar), 2.81 ppm (s, 12H, CH2CO),
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5,11,17,23,29,35-Hexa-octanoyl-37,38,39,40,41,42-
hexa-sulphonatobutoxycalix[6]arene
(CH2CO), 31.6–22.7 (6 9 CH2), 14.3 (CH3), 14.1 (CH3).
MS (MALDI-TOF): 1933.2 [?Na?], 1949.1 [?K?], mp =
120 °C, Rf = 0.74 (CHCl3), Yield = 66%.
Under nitrogen atmosphere 2c (1 g, 1 equiv.) was dissolved
in 50 mL of freshly distilled THF and was added an excess of
NaH (0.35 g, 12 equiv.). The mixture was stirred and
refluxed and after 20 min, 1,4-butanesultone (0.88 mL, 12
equiv) was added. The introduction of NaH and 1,4-bu-
tanesultone was repeated 1 time for 2 days allowing total
substitution of the hydroxyl groups. MeOH was added to the
solution for neutralise the excess of NaH. The precipitate was
filtered and washed with THF and MeOH, dissolved in water,
passed on an exchange resin, and lyophilised.
5,11,17,23,29,35-Hexa-octanoyl-37,38,39,40,41,42-
hexa-2-carboxymethoxy calix[6]arene
5c (1 g, 1 equiv.) was added in 50 mL of a solution of
KOH (10%) in ethanol/water (70/30) during 24 h. The
ethanol was removed under reduced pressure. Compound
was precipitated with HCl 2 M (60 mL) and filtered. The
resultant compound was solubilised in chloroform
(30 mL), washed with water (4 9 30 mL) and dried over
anhydrous MgSO4. The chloroform was removed under
reduced pressure to give a volume of 5 mL and the product
was precipitated in hexane.
1
Compound 4c: H NMR (CDCl3) d 7.66 ppm (broad s,
12H, HmAr), 4.09 ppm (br s, 12H, Ar–O–CH2), 3.67 ppm
(br s, 12H, Ar–CH2–Ar), 2,94 (br s, 12H, S–CH2), 2.79 ppm
(br s, 12H, –CH2–CO), 1.69–1.52 ppm (br s, 36H, CH2–
CH2–CO, CH2–CH2–CH2–S), 1.24 ppm (s, –(CH2)4–,
48H), 0.86 ppm (s, CH3–CH2, 18H). 13C NMR (CDCl3) d
199.8 (C=O), 157.6 (Cipso), 133.1 (Cpara), 132.9 (Cortho),
129.9(Cmeta), 73.7 (ArOCH2), 51.4 (S–CH2), 39.8
(CH2CO), 31.7–21.9 (7 9 CH2), 14.2 (CH3). (MALDI-
TOF): 2208.9 [-H?] m.p. = 160 °C, yield = 51%.
1
Compound 6c: H NMR (CDCl3) d 7.78 ppm (s, 12H,
HmAr),4.37 ppm (s, 12H, Ar–O–CH2–), 3.46 ppm (s, 12H,
Ar–CH2–Ar), 2.90 ppm (s, 12H, CH2CO), 1.61 ppm (s,
12H, –CH2–CH2–CO), 1.19 ppm (s, –(CH2)4–, 48H),
0.79 ppm (s, CH3–CH2, 18H). 13C NMR (CDCl3) d 199.3
(C=O), 169.6 (COO), 159.5 (Cipso), 133.7 (Cpara), 133.2
(Cortho), 129.9 (Cmeta), 69.9 (Ar–O–CH2), 38.8 (CH2CO),
31.6–22.7 (6 9 CH2), 14.2 (CH3). MS (MALDI-TOF):
1764.0 [?Na?], 1781.0 [?K?], m.p. = 245 °C, Rf = 0.25
(CHCl3/MeOH/75/25), yield = 90%.
Crystallographic data
Crystals were obtained by slow evaporation of 5,11,17,23,
29,35-hexa-octanoyl-37,38,39,40,41,42-hexa-methoxy-die-
thoxy-calix[6]arene, 5,11,17,23,29,35-hexa-butanoyl-37,
38,39,40,41,42-hexaethoxycarbonyl-methoxy-calix[6]arene
5,11,17,23,29,35-Hexa-octanoyl-37,38,39,40,41,42-
hexa-methoxy-diethoxycalix[6]arene
and
5,11,17,23,29,35-hexa-octanoyl-37,38,39,40,41,42-
2c (1 g, 1 equiv.), 1-bromo-2-(2-methoxyethoxy)ethane
(0.97 mL, 10 equiv.), potassium carbonate (1 g, 10 equiv.),
were combined and refluxed in acetone. The introduction of
potassium carbonate and 1-bromo-2-(2-methoxyethoxy)eth-
ane was repeated 1 time. The acetone was removed under
reduced pressure and the resultant compound was solubilised
in chloroform (30 mL) washed with water (4 9 30 mL) and
dried under anhydrous MgSO4. The chloroform was
removed under reduced pressure to give a volume of 5 mL
and the product was precipitated in methanol.
hexaethoxycarbonylmethoxy-calix[6]arene directly from
the reaction medium.
Intensity data were collected at 100(2) K on a Nonius
KappaCCD diffractometer using MoKa radiation
(k = 0.71073 A). Data were corrected for Lorentz and
˚
polarisation effects but not for absorption. The structure
was solved by direct methods and Fourier techniques
(SHELXS-86) and refined, on |F|2 (SHELX-97). H-atoms
were included in geometric positions and refined as ‘riding’
atoms with isotropic thermal parameters based upon the
corresponding bonding carbon atom [Uiso = 1.5Ueq for
CH3 and Uiso = 1.2Ueq for the rest].
1
Compound 3c: H NMR (CDCl3) d 7.62 ppm (s, 12H,
HmAr), 4.11 ppm(s, 12H, Ar–O–CH2), 3.83 ppm (br s,
12H, Ar–CH2–Ar), 3.60 ppm (s, 12H, –CH2–CH2–O–),
3.51 ppm (s, 24H, O–CH2–CH2–O), 3.29 ppm (s, 18H, O–
CH3), 2.77 ppm (s, 12H, –CH2–CH2–CO), 1.59 ppm (s,
12H, CH2–CH2–CO), 1.21 ppm (s, –(CH2)4–, 48H),
0.86 ppm (s, CH3–CH2, 18H). 14.5. 13C NMR (CDCl3) d
199.1 (C=O), 159.1 (Cipso), 134.2 (Cpara), 133.4 (Cortho),
129.3 (Cmeta), 72.8 (ArOCH2), 71.5 (ArOCH2CH2), 71.1–
705 (OCH2CH2O), 58.2 (OCH3), 38.3 (CH2CO), 31.8–22.3
(6 9 CH2), 14.5 (CH3). MS (MALDI-TOF): 2045.1
[?K?], m.p. = 115 °C, Rf = 0.65 (CHCl3/MeOH 95/05),
yield = 62%.
Crystal data for 3c:
colourless prism, 0.45 9 0.24 9 0.20 mm, triclinic, P1;
C120H180O24, Mr = 2006.64,
ꢀ
˚
a = 13.1862(3), b = 13.3901(4), c = 18.6719(7) A, a =
84.965(2), b = 77.480(2), c = 63.165(1)°, V = 2871.6(2)
3
A , Z = 1, qcalc = 1.160 Mg/m3, hmax = 26.7°, l(MoKa) =
˚
0.079 mm-1, 42104 reflections collected, 12109 independent
reflections, 7403 [I [ 2r (I)]. R = 0.057, wR = 0.136
(R = 0.100, wR = 0.1518 for all data), GOF = 0.97.
Crystal data 5a: C90H108O24, Mr = 1573.76, colorless,
ꢀ
0.18 9 0.18 9 0.15 mm, triclinic, P1; a = 15.6156(6),
123

J Incl Phenom Macrocycl Chem (2010) 68:207–217
211
˚
b = 16.1077(6), c = 18.6192(5) A, = 73.445(2), b =
13008 [I [ 2r (I)]. R = 0.079, wR = 0.207 (R = 0.118,
wR = 0.248 for all data), GOF = 1.02.
3
˚
80.540(2), c = 70.099(1)°, V = 4209.3(3) A , Z = 2,
qcalc = 1.283 Mg/m3, hmax = 20.81°, l(MoKa) = 0.093
mm-1, 17546 reflections collected, 8996 independent
reflections, 6045 [I [ 2r (I)]. R = 0.087, wR = 0.213
(R = 0.129, wR = 0.235 for all data), GOF = 1.03.
Crystal data for 5c: C122H170O29, Mr = 2100.58, col-
Crystallographic data (excluding structure factors) have
been deposited in the Cambridge Crystallographic Data
Centre as supplementary publication numbers CCDC
752129, 752130, 752131.
ꢀ
ourless prism, 0.60 9 0.50 9 0.20 mm, triclinic, P1; a =
˚
! 13.6346(10), b = 17.8962(13), c = 26.0386(18) A, a =
Results and discussion
70.839(3), b = 78.043(3), c = 77.150(4)°, V = 5788.9(7)
3
A , Z = 2, qcalc = 1.205 Mg/m3, hmax = 24.7°, l(MoKa) =
The synthetic route to the para-acylcalix[6]arenes along with
the routes to clean per-O-substitution are given in Scheme 1.
˚
0.085 mm-1 136610 reflections collected, 19043 unique,
O
R
O
R
O
R
O
R
O
R
O
R
R-COCl, AlCL3
OH
OH
Nitrobenzene
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
2 a,b,c
1
1,4-butane-sultone, NaH
THF
Br(CH2)2O(CH2)2OCH3, K2CO3
Acetone
BrCH2COOEt, K2CO3
Acetone
R
O
R
O
R
O
6
6
O
O
6
O
O
COOEt
O
SO3H
5 a,b,c
4
3
KOH/EtOH
R
O
6
O
COOH
6 a,b,c
Scheme 1 Synthetic route to the para(acylcalix[6]arene derivatives, 3 and 3 are the octanoyl derivatives, 3c and 4c
123

212
J Incl Phenom Macrocycl Chem (2010) 68:207–217
The para-acyl compounds 2a–c, a = butanoyl,
Treatment of 2a-c with ethylbromoacetate, 10 equiva-
lents and K2CO3, 10 equivalents under reflux in acetone for
48 h yields 5a-c in yields of 62, 83 and 63%, respectively.
All the compounds show a single peak in the MALDI-TOF
Mass Spectrum corresponding to the fully O-substituted
b = hexanoyl and C = octanoyl, were prepared in good
final yields, 73, 77 and 83%, respectively, by reacting the
parent compound 1 with 9 equivalents of the corresponding
acid chloride in nitrobenzene in the presence of 12 equiv-
alents of aluminium trichloride at room temperature for
24 h. When esterification at the phenolic face also occur-
red, de-esterification was achieved in 100% yield by
treatment of the ester with ethanolic-potassium hydroxide
for 24 h.
1
derivatives. In the H NMR spectra the methyl groups are
present at 1.19 and 0.95 ppm. Again there is a single peak
for the C=O function at 199 ppm.
Alcoholysis of 5a-c was achieved using KOH in etha-
nol/water(70/30) during 24 h to yield 6a-c, the peak at
1
1.19 ppm has totally disappeared in the H NMR spectra
The MALDI mass spectra show only a single peak,
Fig. 1, corresponding to the fully acylated products. This is
similar to the previously reported para-acylcalix[8]arene
analogues, and confirms the utility of MALDI for the
analysis of substitution reactions on the larger calix[n]
arenes [23].
and here the terminal methyl groups of the cay chains are
observed at 0.79 ppm. Again the MALDI-TOF Mass
Spectra show single peaks corresponding to the per-car-
boxylic acid.
Compound 4c containing an O-butyl-sulphonato func-
tion requires much more forcing conditions in the synthe-
sis, 2c is treated with sodium hydride (12 equivalents) in
tetrahydrofuran under reflux for 20 min and then 1,4-bu-
tanesultone (12 equivalents) is added and the mixture
refluxed for 48 h. After this period NaH (12 equivalents)
and 1,4-butanesultone (12 equivalents) are again added to
the reaction mixture which was heated under reflux during
a further 48 h. After workup and freeze drying 4c was
obtained in 51% yield. The MALDI-TOF Mass Spectrum,
is given in Fig. 2.
1
The H NMR spectra show the Ar–CH2–Ar methylenic
protons as a broad peak in the region 3.9 ppm consistent
with a conformationally flexible structure in solution. In the
13C NMR the corresponding carbon atoms give rise to
signals at 31 ppm and the C=O carbon atoms give a single
peak at 199 ppm.
Treatment of 2a with 10 equivalents of 1-bromo-2-(2-
methoxyethoxy)ethane and 10 equivalents of K2CO3 in
acetone under reflux yields the polar ethylene glycol
derivative 3c, denominated Long PEG in 62% yield. In the
MALDI-TOF Mass Spectrum a single peak at 1247.7 mass
units is observed confirming complete substitution at the
phenolic face. In the 1H NMR spectrum the terminal
methyl group appears as a sharp triplet at 3.29 ppm, here
the Ar–CH2–Ar bridging methyelene protons are present as
a broad peak at 3.88 ppm. In the 13C NMR the carbonyl
groups are present as a singlet at 199 ppm.
However, in a large number of cases substitution at the
phenolic face does not occur, is incomplete with intractable
mixtures of varying degree of substitution or is incomplete
with clean disubstitution. In the case of the bromomethyl,
bromoethyl or bromoproyl pthalamides no reaction occurs,
this is also the case with all the activated compounds with
three carbon atoms: for example ethylbromopropriate. For
Fig. 1 MALDI-TOF Mass Spectrum for 2b, the peak at 1247.7
correspond to M ? Na?
Fig. 2 MALDI-TOF Mass Spectrum of 4c the peak at 2208.9
corresponds to M - H?
123

J Incl Phenom Macrocycl Chem (2010) 68:207–217
213
Fig. 3 MALDI-TOF Mass
Spectrum for the reaction
between para-octanoyl-
calix[6]arene and
bromoacetonitrile using K2CO3
as base
bromoacetonitrile or bromobutorynitrile only mixtures are
obtained, Fig. 3. However for ethylbromobutyrate or 1,4-
butanesultone using a weak base clean 1,4 disubstitution
occurs.
Thus a somewhat chemically constrained route is avail-
able for clean substitution of the para-acylcalix[6]arenes,
and this should open up the possibility by further substitu-
tion of introducing more complete moieties at the phenolic
face of these compounds.
Solid state structures
The solid-state structures of 3c, 5a, and 5c have been
determined. All molecules are in the alternate cone con-
formation with two symmetry related sets of three aromatic
rings pointing up and down, this corresponds to the con-
formation uo, u, d, do, d, u as defined by Gutsche and co-
workers [24] (see Fig. 7a). In the case of 3c the confor-
mation is stabilized by a number of C–HÁÁÁO hydrogen
˚
bonds (2.48–2.72 A), where the oxygen atoms belong to
Fig. 4 Molecular structure of 3c 5,11,17,23,29,35-hexa-octanoyl-
37,38,39,40,41,42-hexa-methoxy-diethoxy -calix[6]arene. Intramo-
lecular C–HÁÁÁO hydrogen bonds are shown. The hydrogen atoms
which do not participate in the hydrogen bonds are omitted
methoxydiethoxy (methyldiethylene glycol) groups
(Fig. 4). In hexaethoxycarbonyl methoxy-calix[6]arenes 5a
and 5c two of the ester groups are deeply included on the
molecular cavity and two opposing aromatic groups lie
parallel to each other. However, while the two aromatic
rings are parallel they are not in close contact with a
˚
3.24 A CÁÁÁO distance and [C=OÁÁÁO=C\contacts of 3.63
˚
and 3.55 A in the structure of 5a. The corresponding dis-
˚
centroid to centroid distance of 10.77 and 10.50 A in 5a,
˚
˚
10.77 and 10.83 A in 5c. In contrast the two ester functions
interact strongly (through the center of calixarene macro-
tances in 5c equals to 3.15 and 3.03 A for C–HÁÁÁO=C\
˚
hydrogen bonds and 3.29 and 3.37 A for carbonyl–car-
bonyl contacts (Figs. 5, 6).
cycle!) with two C–HÁÁÁO=C\hydrogen bonds of 3.25 and
123

214
J Incl Phenom Macrocycl Chem (2010) 68:207–217
Fig. 5 The two independent
molecules of 5a;
5,11,17,23,29,35-hexa-
butanoyl-37,38,39,40,41,42-
hexaethoxycarbonyl methoxy-
calix[6]arene
It is necessary to note that if calix[6]arene macrocycle
conformations in all described structures are the same (uo,
u, d, do, d, u) [24], in the case of a crystallographically
independent molecule of 5a the ethoxycarbonylmethoxy
groups are tilted in the opposite direction to that seen in all
the other structures (Fig. 7 blue).
Intramolecular C–HÁÁÁO interactions stabilize the
calix[6]arene conformation while intermolecular interac-
˚
tions one strong and seven weaker (2.53 A and other of
˚
about 2.70–2.72 A, are responsible for layer formation as a
2D network in the ab plane, where layers have hydrophobic
surfaces covered with alkyl chains which are combined
into a 3D structure by hydrophobic chain interdigitation.
The interpenetrating of neighbouring layers is shown in
Fig. 8.
The packing of 5a is shown in Fig. 9, and consists of
two sets of columns arranged perpendicular to each other
along the a and b axes, respectively. The intra column
˚
molecular spacings are 15.62 and 16.7 A. Coherence in the
˚
columns is via short aromatic–aromatic contacts, 4.3 A
(Fig. 10).
As in the structure of 3c, the molecules in 5c aggregate
into a layer structure. A molecule of EtO2CCH2OCH2-
CO2Et is present in the crystal structure of the host and
plays different roles. Firstly, it forms quite strong C–HÁÁÁO
˚
hydrogen bonds about 2.41–2.66 A with one of crystallo-
Fig. 6 The two independent molecules of 5c; 5,11,17,23,29,35-hexa-
octanoyl-37,38,39,40,41,42-hexaethoxycarbonyl methoxy-calix[6]arene
graphically independent molecules. Secondly, it loosens
Fig. 7 Overlaid molecular
structures of 3c—green, 5a—
magenta and blue, and 5c—red
and orange. (Color figure
online)
123

J Incl Phenom Macrocycl Chem (2010) 68:207–217
215
Interfacial assembly
The use of Langmuir compression isotherms provides
information on the molecular areas, mechanical properties,
phase changes and stabilities of monolayers of insoluble
amphiphilic molecules at the air–water interface. In the
experiment a known quantity of the amphiphilic molecule
is spread as a solution in an immiscible solvent onto a
water surface of a known area. The surface pressure is
measured using a Wilhemy plate balance. The available
area for the amphiphilic molecules is reduced by com-
pressing with a movable Teflon barrier and the apparent
molecular is measured as a function of the observed surface
pressure.
The formation of monolayers was studied for the hexa-
ester compounds 5a, 5b and 5c and the hexa-acids 6a, 6b
and 6c and for comparison the para-octanoyl compounds
3c, 5c and 6c. Compound 4c does not yield a stable
monolayer.
Fig. 8 Packing diagram for 3c, 5,11,17,23,29,35-hexa-octanoyl-
37,38,39,40,41,42-hexa-methoxy-diethoxy-calix[6]arene, view along
a axis. Only intermolecular C–HÁÁÁO hydrogen bonds are shown
The surface pressure, p, versus apparent molecular area
isotherms for 5a, 5b and 5c are given in Fig. 11 and the
plot of the compression modulus, Cs against p in Fig. S1
(see Supplementary Data) [25], Fig. 12 and Fig. S2 (see
Supplementary Data), present the same information for the
per-acid derivatives 6a, 6b and 6c, for comparison in
Fig. 13 and Fig. S3 (see Supplementary Data), are given
the isotherms and Cs versus p data for 3a, 5a and 6a. The
isotherm data are summarized in Table 1. The values for
A
limit, calculated by taking a tangent from the steepest part
of the isotherm to a value of zero for p, are in the region
2
150 A which is in agreement with previously reported
˚
values [16–18], however the apparent Alimit observed for
2
6a at 100 A is much lower than expected and may imply
˚
molecular folding due to intramolecular hydrogen bonding.
For the series 6a–6c there is an increase in the observed
2
molecular area of about 30 A for the addition of two
˚
carbon atoms in the acyl chain length, the derived molec-
˚
ular radii are 5.44, 6.72 and 7.35 A the difference of
˚
approximately 1 A is not in agreement with the increase of
˚
about 2 A expected for the increase in the chain length
Fig. 9 Packing diagram for 5a, 5,11,17,23,29,35-hexa-butanoyl-
37,38,39,40,41,42-hexaethoxycarbonyl methoxy-calix[6]arene
implying some tilt in the molecular orientation. There is no
real difference in the collapse pressure pc at around 37 mN/
m for all the compounds this behaviour is the inverse of
that observed for the para-acylcalix[4]arenes where the
observed molecular area remains constant while the col-
lapse pressure increases as a function of chain length. The
use of Cs against p plots allows the identification of a phase
change for 6b at around 17 mN/m (see Supplementary
Data).
the layers of the host molecules, so hydrogen atoms of long
alkyl chains and ester groups can take part in strong and
weak C–HÁÁÁO hydrogen bonds not only in the ac plane
˚
(layer formation, 2.37–2.77 A), but also in b axis direction
˚
(2.30–2.71 A), as a result, a 3D network of hydrogen bonds
is formed. The molecule of EtO2CCH2OCH2CO2Et is
undoubtedly formed by a hydrolysis of bromoethylacetate
to hydroxyethylacetate followed by a Williamson coupling
to a second molecule of bromoethylacetate, its presence is
explained by the fact that the crystals grew directly from
the reaction medium.
For 5a, 5b and 5c both observed molecular areas and
collapse pressures increase with increasing chain length,
the Cs against p plots allows confirmation that for 5a and
5b there exists a phase change at 22 mN/m for each
123

216
J Incl Phenom Macrocycl Chem (2010) 68:207–217
Fig. 10 Packing diagram
for 5c, 5,11,17,23,29,35-
hexa-octanoyl-37,38,39,40,
41,42-hexaethoxycarbonyl
methoxy-calix[6]arene, view
along a axis
70
60
50
40
30
20
10
0
50
40
30
20
10
0
5c
5b
5a
6c
6b
6a
-10
20 40 60 80 100 120 140 160 180 200 220 240
Area (Å2/molecule)
-10
50
100
150
200
250
300
350
Area (Å2/molecule)
Fig. 11 Compression isotherms for the per-ester derivatives, 5a, 5b
and 5c
Fig. 13 Compression isotherms for the acid derivatives 6a, 6b and 6c
40
Table 1 Monolayer data, pc is the collapse pressure, Acoll collapse
area, Alim the limiting area defined from extrapolation of the isotherm,
A1 is the molecular area at 1 mN/m and A0 is the molecular area at
the point of non-zero pressure for compounds 3c, 5a, 5b, 5c, 6a, 6b
and 6c
5c
6c
3c
30
20
10
0
2
Acoll (A )
2
Alim (A )
2
A1 (A )
2
A0 (A )
˚
˚
˚
˚
pc (mN/m)
3c
5a
5b
5c
6a
6b
6c
35.7
49.9
30.4
34.18
33.3
37.8
37.3
149
53
191
148
151
161
93
195
155
153
163
95
209
172
160
189
105
183
195
121
139.98
82
-10
117
152
142
170
155
182
0
50
100
150
200
250
300
350
Area (Å2/molecule)
Fig. 12 Compression isotherms for the para-octanoyl derivatives 3c,
5c and 6c
arranged in a more perpendicular conformation with
respect to the water surface.
derivative. The very small increase in the molecular areas
as compared to those observed in the per-acid series 6a–c
suggest that the molecules 5a–c of the per-ester series are
For the series 3a, 5a and 6a the chain length, at 4 carbon
atoms is kept constant and the effect of changing the polar
function studied, the least polar headgroup the ester
123

J Incl Phenom Macrocycl Chem (2010) 68:207–217
217
10. Pojarova, M.A., Gennady, S., Udachin, K.A., Daroszewska, M.,
Perret, F., Coleman, A.W., Ripmeester, J.A.: Solid lipid nano-
particles of p-hexanoyl calix[4]arene as a controlling agent in the
photochemistry of a sunscreen blocker. Chem. Mater. 18, 5817–
5819 (2006)
function in 5a yields the lowest collapse pressure, while
those of 3a, with a di-ethylene glycol chain and 6a with a
carboxylic acid function are essentially the same.
11. Bagryanskaya, E.G., Polovyanenko, D.N., Fedin, M.V., Kulik, L.,
Schnegg, A., Savitsky, A., Mobius, K., Coleman, A.W., Ana-
nchenko, G.S., Ripmeester, J.A.: Multifrequency EPR study of
the mobility of nitroxides in solid-state calixarene nanocapsules.
Phys. Chem. Chem. Phys. 11, 6700–6707 (2009)
12. Jebors, S.A., Gennady, S., Coleman, A.W., Ripmeester, J.A.:
Synthesis and self-assembly properties of para-acyl-calix[8]are-
nes. Tetrahedron Lett. 48, 5503–5506 (2007)
13. Jebors, S., Fache, F., Balme, S., Devoge, F., Monachino, M.,
Cecillon, S., Coleman, A.W.: Designer amphiphiles based on
para-acyl-calix[8]arenes. Org. Biomol. Chem. 6, 319–329 (2008)
14. Ghera, B.B., Qiongzhi, X., Leydier, A., Coleman, A.W.: Para-
acyl calix[9]arenes: synthesis and interfacial assembly. J. Incl.
Phenom. Macrocycl. Chem. 64, 367–371 (2009)
15. Li, J.J., Janout, V., Regen, S.L.: Gluing Langmuir-Blodgett
monolayers onto hydrocarbon surfaces. J. Am. Chem. Soc. 128,
682–683 (2006)
Conclusion
A reasonable synthetic route to the para-acylcalix[6]arenes
has been established, the per-O-derivatisation with certain
activated halo-alkyl substituents has been demonstrated.
The synthesis of the carboxylato derivatives opens up the
possibility to use peptide coupling to generate a wider
range of compounds. The compounds form stable mono-
layers at the air–water interface and may be useful for
prodrug transport. Work is currently underway to investi-
gate the interactions of the para-acylcalix[6]arene deriva-
tives with phospholipids and other membrane constituents
including membrane proteins.
16. Hendel, R.A.J., Janout, V., Lee, W., Regen, S.L.: Extraordinary
cohesiveness of a boronic acid-based calix[6]arene monolayer at
the air–water interface. Langmuir 12, 5745–5746 (1996)
17. Conner, M.K., Ivo, K., Regen, S.L.: Octopus molecules at the air–
water interface. Mechanical control over tentacle orientation.
Langmuir 7, 982–987 (1991)
Acknowledgements This research was partially supported by the
Polish Ministry of Science and Higher Education (Grant 401/ERA-
NET/2009), and the DGA and CNRS.
18. Lo Nostro, P.C., Casnati, A., Bossoletti, L., Dei, L., Baglioni, P.:
Complexation properties of calixarenes in Langmuir films at the
water–air interface. Colloids Surf. B 116, 203–209 (1996)
19. Bott, S.G., Coleman, A.W., Atwood, J.L.: Preparation and
structure of the first complex of an early transition metal and a
calixarene, calix[6]arene[TiCl2(l-O)TiCl3]2. Chem. Commun.
610–611 (1986)
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