Wide- and narrow-rim functionalised calix[4]arenes: synthesis and characterisation

Article abstract of DOI:10.1016/j.tet.2006.06.096

Functionalisation of calix[4]arene at both the wide and narrow rims leads to the formation of compounds containing bipyridyl, via an amide linkage, at the wide rim and having either a butyl chain, a benzyl group or an alkyl ester functionality at the narrow rim. All compounds were characterised using ¹H and ¹³C NMR spectroscopies. Initial binding studies with Ru(bipy)₂Cl₂ are reported.

Full text of DOI:10.1016/j.tet.2006.06.096

Tetrahedron 62 (2006) 9066–9071
Wide- and narrow-rim functionalised calix[4]arenes: synthesis
and characterisation
a
Bernadette S. Creaven,a Tammy L. Gernon,a,b John McGinley,b, Ann-Marie Moore
*
and Hans Toftlundc
aDepartment of Science and Advanced Smart Materials Research Centre, Institute of Technology, Tallaght, Dublin 24, Ireland
bDepartment of Chemistry, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
cDepartment of Chemistry, University of Southern Denmark, DK-5230 Odense M, Denmark
Received 27 February 2006; revised 13 June 2006; accepted 29 June 2006
Available online 26 July 2006
Abstract—Functionalisation of calix[4]arene at both the wide and narrow rims leads to the formation of compounds containing bipyridyl,
via an amide linkage, at the wide rim and having either a butyl chain, a benzyl group or an alkyl ester functionality at the narrow rim. All
compounds were characterised using 1H and 13C NMR spectroscopies. Initial binding studies with Ru(bipy)2Cl2 are reported.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
employed as platforms that permit functional groups to be
orientated to provide well-organised cavities. The great in-
terest in compounds of this type is primarily motivated by
the ionophoric property of the narrow rim, which leads to ap-
plications in the area of cation binding and transport, as well
as highly selective receptors and novel sensors for poly-
anionic species.1 This polyfunctional property stems from
the fact that the narrow rim is relatively easy to chemically
modify via well-established acid–base and nucleophilic
reactions. The chemistry of the wide rim has not been fully
exploited, and this can be explained by the relatively more
difficult chemistry involved in its functionalisation; wide-
rim modified derivatives are, for the most part, di-1,3- and
tetrasubstituted species.
Calix[4]arenes are macrocyclic molecules with unique
three-dimensional structures. They belong to a larger family
of calix[n]arene molecules that is relatively old, and is gen-
erated from the chemical condensation of formaldehyde and
phenol.1 When all four oxygen atoms point in the same direc-
tion, the macrocycle exhibits a bowl-shaped structure called
the cone conformation. Functionalisation of the calix[4]-
arene is referred to as either narrow rim (previously called
lower rim), if it occurs at the phenolic oxygen, or wide rim
(previously called upper rim), if it occurs at the para position
after the removal of p-tert-butyl groups (see Fig. 1).
Hydrophobic
Furthermore, the functionalisation of calix[4]arenes at both
the wide and narrow rims has not been widely discussed in
the literature,1 though such molecules are desirable in the de-
velopment of calixarene-based supramolecular structures.
As part of a broad study of the interactions of various func-
tional groups at both the wide and narrow rims, we have pre-
pared and characterised some dipyridyl calix[4]arenes and
their copper(I/II) complexes.2 This paper describes the func-
tionalisation of the narrow rim with either n-butyl, benzyl or
ester groups and the subsequent wide-rim derivatisation via
amide groups containing a bipyridyl group.
upper rim
Hydrophobic
RO
OR
OR
OR
lower rim
Figure 1. Structural formula of calix[4]arene.
Their controlled synthetic functionalisation and their versa-
tile complexation properties1 allow the use of these com-
pounds in supramolecular chemistry as molecular scaffolds
for the construction of various receptors. They are frequently
2. Results and discussion
Keywords: Calix[4]arene; Functionalisation; Synthesis; Amide linkage;
NMR.
Both NMR and IR spectroscopies were used to characterise
all the products synthesised. The NMR signals for the
* Corresponding author. Tel.: +353 1 708 4615; fax: +353 1 708 3815;
e-mail: john.mcginley@nuim.ie
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.06.096

B. S. Creaven et al. / Tetrahedron 62 (2006) 9066–9071
9067
Table 1. Selected 1H NMR data for compounds 1–13
by the presence of two sharp doublets at approximately 4.3
and 3.3 ppm in each case.
Compound
Ar-H
–CH2–
t-Bu
1
2
3
4
5
6
7
8
7.04
4.23, 3.49
4.31, 3.28
4.25, 3.29
4.43, 3.30
4.30, 3.49
4.23, 3.40
4.54, 3.50
4.25, 3.20
4.25, 3.18
4.50, 3.24
4.40, 3.49
4.36, 3.41
4.55, 3.39
1.21
The diprotected-calix[4]arene, with either the benzyl group
(2), the n-butyl group (3) or the ester group (4), was then
treated with concentrated nitric acid in acetic acid to give
the dinitro-diprotected-calix[4]arenes 5, 6 and 7. In all cases,
the nitro group replaces the tert-butyl group opposite the free
OH group. The 1H NMR spectra of compounds 5–7 showed
several characteristic signals. The signal for the OH group
shifts downfield from d 8.00 (3) and 7.15 (4) to d 8.66 (5),
9.44 (6) and 8.94 (7); the OH signal for compound 2 is hid-
den under the signal for one of the benzyl protons at d 7.35. A
large downfield shift is also observed for the aromatic proton
on the phenyl ring to which the nitro group becomes attached
(see Table 1). The signal for one of the tert-butyl groups is
also lost, confirming the replacement of the tert-butyl group
by the nitro group. Finally, the cone conformation of each
calix[4]arene is also retained. Reinhoudt et al. describe simi-
lar shifts for the OH signals in their paper on the nitration of
calix[4]arenes.3 One interesting point regarding the yields of
the nitration reactions is that the nitration of the diester calix[4]-
arene (4) proceeds only in very low yield (17% in our case
and 24% in the literature3). The conclusion that can be drawn
is that the ester group, and in particular the carbonyl group, is
playing some unexpected role in the reaction, thereby caus-
ing the yield to decrease. Reinhoudt et al.3 suggest that the
presence of electron donating groups on the narrow rim
should enhance the nitration reaction but offer no explana-
tion as to the low yield for this particular compound.
7.03, 6.84
7.03, 6.83
7.02, 6.85
8.03, 6.96
8.03, 6.89
8.02, 7.07
6.90, 6.45
6.84, 6.42
6.97, 6.32
7.40, 7.00
7.40, 6.96
7.39, 7.01
1.26, 1.00
1.27, 0.98
1.25, 1.00
1.06
1.01
1.11
1.15
1.04
1.16
1.10
9
10
11
12
13
1.06
1.12
methylene bridges, aromatic protons and tert-butyl groups
for all of the calix[4]arene derivatives are summarised in
Table 1; complete data for all compounds are given in
Section 4. Scheme 1 shows the synthetic approach chosen
for the n-butyl, benzyl and ester derivatives.
(i)
HO
OR
2, 3, 4
OR
OH
HO
OH
1
OH
OH
(ii)
NO2
NH2
O2N
H2N
The dinitro compounds then underwent reduction with
Sn(II)Cl2 in ethanol to give the diamino-diprotected-calix-
[4]arenes 8, 9 and 10, in a similar manner to that reported
in the literature.4 These compounds are easily identified by
the large upfield shift of the aromatic protons from, for ex-
ample, d 8.03 and 6.89 in compound 5 (the dinitro-di-benzyl
compound) to d 6.84 and 6.42 in compound 8 (the diamino-
di-benzyl compound). This type of shift has been observed
previously in various wide-rim amino-calix[4]arenes.4
Again, the presence of two doublets in the 4.5–3.0 ppm
region indicates cone conformation retention. The diamino-
calix[4]arenes (8–10) were not particularly air or moisture-
stable but all decomposed to a sticky material when exposed
to air, as a solid, for several hours. The 1H NMR spectrum of
the sticky material indicated that breakdown of the calix[4]-
arene was occurring. For this reason, all samples were only
made prior to proceeding with the next reaction in Scheme 1.
(iii)
HO
OR
OH
HO
OR
5, 6, 7
OR
OR
8, 9, 10
OH
(iv)
N
N
N
N
O
O
NH
HN
11, 12, 13
HO
OR
OH
OR
Scheme 1. Reagents and conditions: (i) K2CO3, appropriate halo-com-
pound, MeCN, reflux 18 h; (ii) HNO3, acetic acid, DCM, reflux 3 h; (iii)
SnCl2, EtOH, reflux 12 h; (iv) 4-methyl-40-carboxylic acid-2,20-bipyridine,
DMT-MM, MeOH, reflux 4 h. R¼n-C4H9, benzyl or CH2CO2Et.
Compounds 11, 12 and 13 were synthesised by reaction
of the appropriate diamino-calix[4]arene with 4-methyl-
40-carboxylic acid-2,20-bipyridine5 using 4-(4,6-dimeth-
oxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride6
(DMT-MM) as condensing agent. The successful condensa-
tion of carboxylic acids and amines by DMT-MM in THF to
give the corresponding amides in good yields was reported
by Kunishima et al.6 The selective formation of carbox-
amides (–CONH–) in alcohol or water by a convenient
one-step procedure, in which the condensing agent (DMT-
MM) is simply added to a mixture of acids and amines,
was also achieved successfully by the same group.7 The
choice of DMT-MM as the base for this reaction was based
on the fact that the workup in these cases was a simple
The parent calix[4]arene 1 was reacted with potassium car-
bonate and the appropriate halo-compound (benzyl chloride,
1-bromo-butane or ethyl bromoacetate) in acetonitrile at
reflux temperature to give the narrow-rim 1,3-disubstituted
compounds 2, 3 and 4 in good yields. Compounds 2–4
show the expected NMR pattern, with two signals being ob-
served for both the aromatic protons of the calix[4]arene and
the tert-butyl groups, indicative of 1,3-disubstitution on the
narrow rim of the calix[4]arene. Furthermore, the cone con-
formation of the derivatised calix[4]arenes is also confirmed

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B. S. Creaven et al. / Tetrahedron 62 (2006) 9066–9071
filtration. DMT-MM also has the added advantage that the
reaction conditions are very mild, that is, a 3-h stir in meth-
anol. In all cases, the presence of the amide carbonyl group
in the IR spectra was clearly seen at approximately
we decided to carry out an initial study of the reaction
between cis-bis(2,20-bipyridine)dichloro-ruthenium(II) (Ru-
(bipy)2Cl2) and the calix[4]arene derivatives 11, 12 and
13. This consisted of carrying out the reaction, in each
case, in ethanol at reflux temperature for 3 h followed by
the addition of tetrabutylammonium hexafluorophosphate
in order to precipitate a solid material. In all cases, orange/
brown coloured solids were obtained. TLC analysis on these
complexes, using CHCl3/MeOH (9/1) as the solvent system,
showed no sign of the starting calix[4]arene compounds.
Preliminary characterisation of the ruthenium(II) complexes
1
1670 cmꢀ1 for the bipyridyl compounds (11–13). The H
NMR spectra again showed that the cone conformation
was retained in all cases. The 9.0–6.5 ppm region of each
spectrum contained many signals but in all cases there
were no overlapping signals and all the signals were sharp
and well-defined, making assignment straightforward. The
use of an 1H–1H COSY spectrum further simplified the pro-
cess, together with a COSY spectrum previously published
by Hesek et al.8 The presence of a sharp singlet at d 2.49,
due to the methyl group on the bipyridyl group, was a useful
reference signal to indicate that attachment had taken place.
1
was carried out using only H NMR spectroscopy. A more
in-depth characterisation will be reported for all the com-
plexes at a later date. The 1H NMR spectra of the three ruthe-
nium complexes were obtained and all showed a more
complicated spectrum, particularly in the aromatic region,
than that obtained for the starting calix[4]arene derivative.
Figure 2 shows the 1H NMR spectra of 13 prior to and after
complexation with the ruthenium compound.
These bipyridyl calixarenes are potential building blocks for
supramolecular structures as they should be able to bind
transition metal centres at the wide rim. To test this theory,
Figure 2. 1H NMR spectra in CDCl3 of (a) 13 and (b) [13$(Ru)2]4+ complex.

B. S. Creaven et al. / Tetrahedron 62 (2006) 9066–9071
9069
The resonance signals for the tert-butyl, ester/butyl/benzyl
groups and the bipyridyl methyl group were clearly seen.
Only one set of doublets was seen for the methylene bridges
in all cases; the second set was covered by the DMSO signal.
Because of the additional signals for the [Ru(bipy)3]2+ moi-
ety, only one aromatic signal at 7.10 ppm was distinguished
for the calixarene in the case of the butyl derivative (12); the
second signal was under the signals for the [Ru(bipy)3]2+
moiety itself. The 3-H and 30-H signals for the bipyridyl
group attached to the calix[4]arene were easily distinguished
in the proton spectrum, as they were singlet peaks; the rest of
the spectra relating to the [Ru(bipy)3]2+ was complicated.
Therefore, the attachment of this ruthenium moiety to the
functionalised calix[4]arenes 11, 12 and 13 produced the
desired [Ru(bipy)3]2+ moiety on the upper rim of the modi-
fied calix[4]arenes. The di-ruthenium complexes were all
isolated as their hexafluorophosphate salts in good yields
(78, 64 and 90% using compounds 11, 12 and 13,
respectively). From these preliminary reactions it can be
seen that the di-ruthenium calix[4]arenes were easily iso-
lated in acceptable yields.
throughout. Starting materials were commercially obtained
and used without further purification. The syntheses of
compounds 4-tert-butyl-calix[4]arene, 1,9 5,11,17,23-tetra-
tert-butyl-25,27-dibenzyloxy-calix[4]arene, 2,10 5,11,17,23-
tetra-tert-butyl-25,27-dibutoxycalix[4]-arene, 3,2 5,11,17,23-
tetra-tert-butyl-25,27-diethoxycarbonylmethoxycalix[4]arene,
4
11 and 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-mor-
pholinium chloride6 (DMT-MM) have been described in the
literature previously.
4.2. General synthesis of 2, 3 and 4
To a stirring suspension of 4-tert-butylcalix[4]arene (1,
3.1 mmol) and potassium carbonate (7.7 mmol) in aceto-
nitrile (60 ml), under nitrogen, was added the appropriate
halo-compound (6.8 mmol) in acetonitrile (10 ml), and the
mixture was heated to reflux for 18 h. After being cooled
to room temperature, the suspension was filtered to remove
inorganic salts and the filtrate was concentrated on a rotary
evaporator to yield the appropriate compound.
4.2.1. 5,11,17,23-Tetra-tert-butyl-25,27-dibenzyloxy-
calix[4]arene, 2.10 White solid, yield¼72%; mp 216–
218 ꢁC (lit. 216–220 ꢁC); nmax (KBr) 3395 (OH) cmꢀ1; dH
(300 MHz, CDCl3): 7.64 (4H, t, J 6.5 Hz, Ph-H), 7.42 (4H,
d, J 6.5 Hz, Ph-H), 7.35 (2H, m, Ph-H), 7.03 (4H, s,
Ar-H), 6.83 (4H, s, Ar-H), 5.05 (4H, s, OCH2Ph), 4.25
(4H, d, J 13.0 Hz, Ar-CHaHb-Ar), 3.29 (4H, d, J 13.0 Hz,
Ar-CHaHb-Ar), 1.27 (18H, s, t-Bu), 0.98 (18H, s, t-Bu).
3. Conclusions
The syntheses of calix[4]arenes, which are derivatised at
both the wide (bipyridyl) and narrow rims (benzyl, butyl
and ester groups), were carried out and the compounds
were characterised by NMR and IR spectroscopies. Follow-
ing 1,3-difunctionalisation of the narrow rim, the wide rim
was nitrated, followed by reduction to the amine before
condensation with the bipyridyl acid to form an amide
group took place. All yields were moderate to good, except
in the case of the dinitro-diester calix[4]arene (6) where
the yield was very low. These bipyridyl calixarenes are
potential building blocks for supramolecular structures.
We have carried out some initial complexation reactions
with Ru(bipy)2Cl2 and we are currently investigating
further transition metal reactions based on these initial
findings.
4.2.2. 5,11,17,23-Tetra-tert-butyl-25,27-dibutoxycalix[4]-
arene, 3.2 White solid, yield¼45%; mp 262–265 ꢁC (lit.
264–266 ꢁC); nmax (KBr) 3395 (OH) cmꢀ1; dH (300 MHz,
CDCl3): 8.00 (2H, s, OH), 7.03 (4H, s, Ar-H), 6.84 (4H, s,
Ar-H), 4.31 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 3.97 (4H, t,
J 6.5 Hz, OCH2CH2), 3.28 (4H, d, J 12.8 Hz, Ar-CHaHb-
Ar), 2.02 (4H, m, CH2), 1.70 (4H, m, CH2), 1.26 (18H, s,
t-Bu), 1.08 (6H, t, J 7.4 Hz, CH2CH3), 1.00 (18H, s, t-Bu).
4.2.3. 5,11,17,23-Tetra-tert-butyl-25,27-diethoxycarbo-
nylmethoxycalix[4]arene, 4.11 White solid, yield¼64%;
mp 184–186 ꢁC (lit. 182–184 ꢁC); nmax (KBr) 3442 (OH),
1747 (ester C]O) cmꢀ1; dH (300 MHz, CDCl3): 7.15 (2H,
s, OH), 7.02 (4H, s, Ar-H), 6.85 (4H, s, Ar-H), 4.73 (4H, s,
OCH2CO), 4.43 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 4.29
(4H, q, J 6.5 Hz, COCH2CH3), 3.30 (4H, d, J 12.8 Hz, Ar-
CHaHb-Ar), 1.33 (6H, t, J 7.3 Hz, CH3), 1.25 (18H, s,
t-Bu), 1.00 (18H, s, t-Bu).
4. Experimental
4.1. General
1H and 13C NMR (d ppm, J Hz) spectra were recorded on
a JOEL JNM-LA300 FTNMR spectrometer using saturated
CDCl3 solutions with Me4Si reference, unless indicated
otherwise, with resolutions of 0.18 Hz and 0.01 ppm. Infra-
red spectra (cmꢀ1) were recorded as KBr discs or liquid
films between KBr plates using a Nicolet Impact 410
FT-IR. All UV–vis spectra were recorded on a Shimadzu
UV-160A spectrometer. Melting point analysis was carried
out using a Stewart Scientific SMP 1 melting point apparatus
and is uncorrected. Mass spectra were obtained using
a Bruker-Esquire-LC_00050 electrospray ionisation mass
spectrometer at positive polarity with cap-exit voltage of
167 V. Spectra were recorded in the scan range of 50–2200
m/z with a potential between 30 and 70 V. Microanalysis
was carried out at the Microanalytical Laboratory of either
University College, Dublin or the National University of
Ireland Cork. Standard Schlenk techniques were used
4.3. General synthesis of 5, 6 and 7
Diprotected calix[4]arene 2, 3 or 4 (9 mmol) was dissolved
in a mixture of acetic acid (40 ml) and dichloromethane
(40 ml). Concentrated nitric acid (8 ml, 90 mmol) was
added dropwise over 10 min at 0 ꢁC. The reaction was
kept at 0 ꢁC for a further 15 min before being warmed to
room temperature for 3 h. The mixture was quenched by
the addition of ice-water (100 ml) and the organic layer
was separated. The aqueous layer was then extracted with
dichloromethane (3ꢂ30 ml). The organic layers were com-
bined, dried with MgSO4 and then filtered. Removal of the
solvent followed by recrystallisation from methanol yielded
5, 6 or 7, respectively.

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B. S. Creaven et al. / Tetrahedron 62 (2006) 9066–9071
4.3.1. 5,17-Di-tert-butyl-11,23-dinitro-25,27-dibenzyl-
oxycalix[4]arene, 5. Yellow solid, yield¼57%. Found: C,
74.24; H, 6.35; N, 3.58. Calcd for C50H50N2O8: C, 74.42;
H, 6.25; N, 3.47; mp 220 ꢁC dec; nmax (KBr) 3340 (OH),
1520 (NO2), 1320 (NO2) cmꢀ1; dH (300 MHz, CDCl3):
8.86 (2H, s, OH), 8.03 (4H, s, Ar-H), 7.61 (4H, m, Ph-H),
7.46 (4H, m, Ph-H), 7.39 (2H, m, Ph-H), 6.89 (4H, s,
Ar-H), 5.07 (4H, s, OCH2Ph), 4.23 (4H, d, J 13.0 Hz, Ar-
CHaHb-Ar), 3.40 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 1.01
(18H, s, t-Bu).
4.4.3. 5,17-Di-tert-butyl-11,23-diamino-25,27-diethoxy-
carbonylmethoxycalix[4]arene, 10. Pink solid, yield¼
88%; mp 200 ꢁC dec; nmax (KBr) 3345 (OH), 1618 (NH2),
1752 (ester C]O) cmꢀ1; dH (300 MHz, CDCl3): 7.04 (2H,
s, OH), 6.97 (4H, s, Ar-H), 6.32 (4H, s, Ar-H), 4.83 (4H, s,
OCH2CO), 4.50 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 4.30
(4H, q, J 6.8 Hz, COCH2CH3), 3.24 (4H, d, J 12.8 Hz, Ar-
CHaHb-Ar), 1.23 (6H, t, J 7.4 Hz, CH3), 1.16 (18H, s, t-Bu).
4.5. General synthesis of 11, 12 and 13
4.3.2. 5,17-Di-tert-butyl-11,23-dinitro-25,27-dibutoxy-
calix[4]arene, 6. Yellow solid, yield¼70%. Found: C,
71.59; H, 7.37; N, 3.79. Calcd for C44H54N2O8: C, 71.52;
H, 7.37; N, 3.79; mp 280 ꢁC dec; nmax (KBr) 3285 (OH),
1510 (NO2), 1330 (NO2) cmꢀ1; dH (300 MHz, CDCl3):
9.44 (2H, s, OH), 8.03 (4H, s, Ar-H), 6.96 (4H, s, Ar-H),
4.30 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 4.00 (4H, t, J
6.5 Hz, OCH2CH2), 3.49 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar),
2.05 (4H, m, CH2), 1.68 (4H, m, CH2), 1.13 (6H, t, J
7.4 Hz, CH2CH3), 1.06 (18H, s, t-Bu).
To a methanol solution (20 ml) of diamino-calix[4]arene 8, 9
or 10 (0.15 mmol) and 4-methyl-40-carboxylic acid-2,20-bi-
pyridine (0.31 mmol) was added DMT-MM (0.33 mmol).
The mixture was stirred under nitrogen for 3 h. Over the
course of the reaction, a solid, which is the product, precipi-
tated. On cooling, the solid was filtered and dried.
4.5.1. 5,17-Di-tert-butyl-11,23-bis(2,20-bipyridine-
4-methyl-40-carboxyamido)-25,27-dibenzyloxy-calix[4]-
arene, 11. Red/pink solid, yield¼32%. Found: C, 77.85; H,
6.05; N, 7.24. Calcd for C74H70N6O6: C, 78.01; H, 6.19; N,
7.38; mp 179–180 ꢁC; nmax (KBr) 3368 (OH), 1669 (amide
C]O) cmꢀ1; dH (300 MHz, CDCl3): 8.85 (2H, d, J
6.8 Hz, 6-H), 8.73 (2H, s, 3-H), 8.58 (2H, d, J 7.8 Hz, 60-
H), 8.31 (2H, s, 30-H), 8.06 (2H, s, OH), 7.89 (2H, t, J
7.6 Hz, 5-H), 7.61 (4H, m, Ph-H), 7.40 (4H, s, Ar-H), 7.38
(6H, m, Ph-H), 7.20 (2H, d, J 7.8 Hz, 50-H), 6.90 (4H, s,
Ar-H), 5.06 (4H, s, OCH2Ph), 4.32 (4H, d, J 13.3 Hz, Ar-
CHaHb-Ar), 3.34 (4H, d, J 13.3 Hz, Ar-CHaHb-Ar), 2.46
(6H, s, CH3), 1.03 (18H, s, t-Bu); ESMS: m/z 1140.35
(11+H+); C74H71N6O6 requires 1140.39; 1162.35 (11+Na+);
C74H70NaN6O6 requires 1162.37.
4.3.3. 5,17-Di-tert-butyl-11,23-dinitro-25,27-diethoxycar-
bonylmethoxycalix[4]arene, 7.3 Yellow solid, yield¼17%;
mp 190–192 ꢁC; nmax (KBr) 3360 (OH), 1752 (ester C]O),
1516 (NO2), 1332 (NO2) cmꢀ1; dH (300 MHz, CDCl3): 8.94
(2H, s, OH), 8.02 (4H, s, Ar-H), 7.07 (4H, s, Ar-H), 4.84 (4H,
s, OCH2CO), 4.54 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 4.29
(4H, q, J 6.8 Hz, COCH2CH3), 3.50 (4H, d, J 12.8 Hz, Ar-
CHaHb-Ar), 1.37 (6H, t, J 7.4 Hz, CH3), 1.11 (18H, s, t-Bu).
4.4. General synthesis of 8, 9 and 10
To a stirred solution of the appropriate dinitro-calix[4]arene
8, 9 or 10 (1.4 mmol) in 25 ml ethanol was added SnCl2
(14 mmol). The reaction mixture was heated under nitrogen
for 24 h and then quenched by pouring into ice-water
(100 ml). The pH was adjusted to 9–10 using 5 M KOH.
The aqueous phase was then extracted with dichloromethane
(3ꢂ30 ml) and the combined organic phases were dried over
MgSO4. After filtration, the evaporation of the solvent under
reduced pressure yielded the diamino-calix[4]arene, which
was used immediately without further purification. No ele-
mental analyses were obtained for either 8, 9 or 10, as the
samples decomposed while being sent for microanalysis.
4.5.2. 5,17-Di-tert-butyl-11,23-bis(2,20-bipyridine-4-
methyl-40-carboxyamido)-25,27-dibutoxy-calix[4]arene,
12. Cream solid, yield¼53%. Found: C, 76.09; H, 6.82; N,
7.96. Calcd for C68H74N6O6: C, 76.23; H, 6.96; N, 7.84;
mp 185–187 ꢁC; nmax (KBr) 3430 (OH), 1672 (amide
C]O) cmꢀ1; dH (300 MHz, CDCl3): 8.85 (2H, d, J 6.8 Hz,
6-H), 8.71 (2H, s, 3-H), 8.56 (2H, d, J 5.8 Hz, 60-H), 8.25 (2H,
s, 30-H), 8.10 (2H, s, OH), 7.86 (2H, t, J 7.6 Hz, 5-H), 7.40
(4H, s, Ar-H), 7.20 (2H, d, J 6.2 Hz, 50-H), 6.96 (4H, s, Ar-
H), 4.36 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 4.01 (4H, t, J
6.5 Hz, OCH2CH2), 3.41 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar),
2.42 (6H, s, CH3), 2.06 (4H, m, CH2), 1.68 (4H, m, CH2),
1.09 (6H, t, J 7.4 Hz, CH2CH3), 1.06 (18H, s, t-Bu); ESMS:
m/z 1071.35 (12+H+); C68H75N6O6 requires 1071.36;
1093.34 (12+Na+); C68H74NaN6O6 requires 1093.34.
4.4.1. 5,17-Di-tert-butyl-11,23-diamino-25,27-dibenzyl-
oxycalix[4]arene, 8. Dark pink solid, yield¼55%; mp
200 ꢁC dec; nmax (KBr) 3360 (OH), 1615 (NH2) cmꢀ1; dH
(300 MHz, CDCl3): 7.60 (4H, m, Ph-H), 7.38 (4H, d,
J 6.8 Hz, Ph-H), 7.37 (2H, m, Ph-H), 6.87 (2H, s, OH),
6.84 (4H, s, Ar-H), 6.42 (4H, s, Ar-H), 4.98 (4H, s,
OCH2Ph), 4.25 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 3.18
(4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 1.04 (18H, s, t-Bu).
4.5.3. 5,17-Di-tert-butyl-11,23-bis(2,20-bipyridine-4-
methyl-40-carboxyamido)-25,27-diethoxycarbonyl-meth-
oxycalix[4]arene, 13. Pale pink solid, yield¼51%. Found:
C, 72.44; H, 6.35; N, 7.65. Calcd for C68H70N6O10: C,
72.19; H, 6.24; N, 7.43; mp 218–221 ꢁC; nmax (KBr) 3416
(OH), 1742 (ester C]O), 1670 (amide C]O) cmꢀ1; dH
(300 MHz, CDCl3): 8.81 (2H, d, J 7.2 Hz, 6-H), 8.52 (2H,
d, J 7.2 Hz, 60-H), 8.26 (2H, s, 3-H), 7.82 (2H, d, J 7.2 Hz,
5-H), 7.58 (2H, s, 30-H), 7.57 (2H, s, OH), 7.39 (4H, s, Ar-
H), 7.18 (2H, d, J 7.2 Hz, 50-H), 7.01 (4H, s, Ar-H), 4.81
(4H, s, OCH2CO), 4.55 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar),
4.34 (4H, q, J 6.9 Hz, COCH2CH3), 3.39 (4H, d, J
12.8 Hz, Ar-CHaHb-Ar), 2.44 (6H, s, CH3), 1.35 (6H, t, J
4.4.2. 5,17-Di-tert-butyl-11,23-diamino-25,27-dibutoxy-
calix[4]arene, 9. Dark pink solid, yield¼81%; mp 140–
142 ꢁC; nmax (KBr) 3365 (OH), 1619 (NH2) cmꢀ1; dH
(300 MHz, CDCl3): 7.68 (2H, s, OH), 6.90 (4H, s, Ar-H),
6.45 (4H, s, Ar-H), 4.25 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar),
3.89 (4H, t, J 6.5 Hz, OCH2CH2), 3.20 (4H, d, J 12.8 Hz,
Ar-CHaHb-Ar), 2.08 (4H, m, CH2), 1.64 (4H, m, CH2),
1.15 (18H, s, t-Bu), 1.09 (6H, t, J 7.4 Hz, CH2CH3).

B. S. Creaven et al. / Tetrahedron 62 (2006) 9066–9071
9071
7.4 Hz, CH2CH3), 1.12 (18H, s, t-Bu); ESMS: m/z 1132.35
(13+H+); C68H75N6O6 requires 1132.33; 1154.29 (13+Na+);
C68H74NaN6O6 requires 1154.31.
Postgraduate R&D Skills programme (Technological Sector
Research, Strand I) for financial assistance. We also thank
Maurice Burke for running the mass spectra.
4.6. General synthesis of complexation reactions of
11, 12 and 13
References and notes
A solution of the appropriate calix[4]arene derivative
(0.078 mmol) and [Ru(bipy)2(Cl)2] (0.156 mmol) in ethanol
(20 ml) was heated to reflux for 3 h under nitrogen. After the
reaction cooled to room temperature, 10 ml of a saturated
tetrabutylammonium hexafluorophosphate (TBAPF6) solu-
tion was added, resulting in precipitation of the product as
an orange/brown powder. The product was filtered, air dried
for 24 h and collected.
€
1. (a) Asfari, Z.; Bohmer, V.; Harrowfield, J.; Vicens, J.
Calixarene 2001; Kluwer Academic: Dordrecht, 2001; (b)
Mandolini, L.; Ungaro, R. Calixarene in Action; Imperial
College: London, 2000; (c) Gutsche, C. D. Calixarenes
Revisited: Monographs in Supramolecular Chemistry; Royal
€
Society of Chemistry: London, 1998; (d) Vicens, J.; Bohmer,
V. Calixarenes, a Versatile Class of Macrocyclic Compounds;
Kluwer Academic: Dordrecht, 1991; (e) Gutsche, C. D.
Calixarenes: Monographs in Supramolecular Chemistry;
Royal Society of Chemistry: London, 1989.
4.6.1. 11DRu(bipy)2(PF6)2. Orange/brown solid, yield¼
78%, dH (300 MHz, DMSO-d6): 10.40 (2H, s, OH), 9.14
(2H, s, H-3), 8.96–8.88 (4H, m, bipy H-3), 8.20–8.17 (4H,
m, bipy H-4), 7.91 (2H, s, H-30), 7.84–7.77 (6H, m, bipy
H-5), 7.62 (4H, m, Ph-H), 7.59–7.49 (6H, m, bipy H-6),
7.44 (6H, m, Ph-H), 7.09 (2H, s, Ar-H), 5.06 (4H, s,
OCH2Ph), 4.38 (4H, d, J 12.8 Hz, Ar-CHaHb-Ar), 2.48
(6H, s, CH3), 1.03 (18H, s, t-Bu).
2. Creaven, B. S.; Gernon, T. L.; McCormac, T.; McGinley, J.;
Moore, A.-M.; Toftlund, H. Inorg. Chim. Acta 2005, 358,
2661–2670.
3. Verboom, W.; Durie, A.; Egberink, R. J. M.; Asfari, Z.;
Reinhoudt, D. N. J. Org. Chem. 1992, 57, 1313–1318.
€
4. (a) Danila, C.; Bolte, M.; Bohmer, V. Org. Biomol. Chem.
4.6.2. 12DRu(bipy)2(PF6)2. Orange/brown solid, yield¼
90%, dH (300 MHz, DMSO-d6): 10.58 (2H, s, OH), 9.20
(2H, s, H-3), 8.99–8.84 (4H, m, bipy H-3), 8.22–8.17 (4H,
m, bipy H-4), 7.88 (2H, s, H-30), 7.82–7.75 (6H, m, bipy
H-5), 7.63–7.47 (6H, m, bipy H-6), 7.11 (2H, s, Ar-H),
4.29 (4H, d, J 12.3 Hz, Ar-CHaHb-Ar), 3.99 (4H, m,
OCH2), 2.57 (6H, s, CH3), 2.02 (4H, m, CH2), 1.80 (4H,
m, CH2), 1.16 (18H, s, t-Bu), 1.09 (6H, t, J 7.3 Hz, CH2CH3).
2005, 3, 172–184; (b) Webber, P. R. A.; Beer, P. D.
Dalton Trans. 2003, 2249–2252; (c) Pelizzi, N.; Casnati,
A.; Friggeri, A.; Ungaro, R. J. Chem. Soc., Perkin Trans. 2
1998, 1307–1311.
5. McCafferty, D. G.; Bishop, B. M.; Wall, C. G.; Hughes, S. G.;
Macklenberg, S. L.; Meyer, T. J.; Erickson, B. W. Tetrahedron
1995, 51, 1093–1106.
6. Kunishima, M.; Kawachi, C.; Morita, J.; Terao, K.; Iwasaka, F.;
Tani, S. Tetrahedron 1999, 55, 13159–13170.
4.6.3. 13DRu(bipy)2(PF6)2. Orange/brown solid, yield¼
64%, dH (300 MHz, DMSO-d6): 10.30 (2H, s, OH), 9.10
(2H, s, H-3), 8.86–8.81 (4H, m, bipy H-3), 8.20–8.16 (4H,
m, bipy H-4), 7.92 (2H, s, H-30), 7.87–7.72 (6H, m, bipy
H-5), 7.60–7.47 (6H, m, bipy H-6), 7.42 (2H, s, Ar-H),
7.10 (2H, s, Ar-H), 4.86 (4H, s, OCH2CO), 4.47 (4H, d, J
7. Kunishima, M.; Kawachi, C.; Hioki, K.; Terao, K.; Tani, S.
Tetrahedron 2001, 57, 1551–1558.
8. Hesek, D.; Inoue, Y.; Everitt, S. R. L.; Kunieda, M.; Ishida,
H.; Drew, M. G. B. Tetrahedron: Asymmetry 1998, 9, 4089–
4097.
9. Gutsche, C. D.; Johnston, D. E., Jr.; Stewart, D. R. J. Org.
Chem. 1999, 64, 3747–3750.
12.8 Hz, Ar-CHaHb-Ar), 4.30 (4H, q,
J
6.9 Hz,
COCH2CH3), 2.52 (6H, s, CH3), 1.34 (6H, t, J 6.9 Hz,
CH2CH3), 1.13 (18H, s, t-Bu).
10. (a) Dijkstra, P. J.; Brunink, J. A. J.; Bugge, K.-E.;
Reinhoudt, D. N.; Harlema, S.; Ungaro, R.; Ugozzoli, F.;
Ghidini, E. J. Am. Chem. Soc. 1989, 111, 7567–7575; (b)
Gutsche, C. D.; Reddy, P. A. J. Org. Chem. 1991, 56,
4783–4791.
Acknowledgements
We are grateful to Enterprise Ireland for International
Collaboration grants for T.L.G. and A.-M.M. and
11. Collins, E. M.; McKervey, M. A.; Harris, S. J. J. Chem. Soc.,
Perkin Trans. 1 1989, 372–374.