Design and synthesis of heteroditopic aza-thioether macrocycles for metal extraction

Article abstract of DOI:10.1039/b609180f

A series of pendant arm aza-thioether macrocycles containing hydrogen-bonding amide functionalities have been synthesised and the single crystal X-ray structures of [12]aneS₃N-CONHCOPh, [12]aneS ₃N-CSNHCOPh, [12]aneS₂ON-CO

Full text of DOI:10.1039/b609180f

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Design and synthesis of heteroditopic aza-thioether macrocycles for
metal extraction
Mark W. Glenny,a Marie Lacombe,a Jason B. Love,a Alexander J. Blake,a
Leonard F. Lindoy,b Robert C. Luckay,b Karsten Gloe,c Bianca Antonioli,c
a
a
¨
Claire Wilson and Martin Schroder*
Received (in Montpellier, France) 28th June 2006, Accepted 14th August 2006
First published as an Advance Article on the web 26th September 2006
DOI: 10.1039/b609180f
A series of pendant arm aza-thioether macrocycles containing hydrogen-bonding amide
functionalities have been synthesised and the single crystal X-ray structures of
[12]aneS3N–CONHCOPh, [12]aneS3N–CSNHCOPh, [12]aneS2ON–CONHCOPh,
[12]aneS2ON–CH2CONHCONH–tBu, [15]aneS2ON2–(CH2CONHCONH–tBu)2 and
[15]aneS3N2–(CH2CONHPh)2 are presented. The structural results confirm that the majority of
the macrocyclic C–S linkages adopt gauche conformations with all sulfur atoms being exo-
orientated with respect to the macrocyclic ring, while the oxygen atoms, when present, are endo-
orientated. The pendant arms, formed by reaction of the parent macrocycle with acyl isocyanates,
are twisted from co-planarity and typically form a distorted U-shape with angles between planes
formed around the carbonyl units varying from 50.811 to 68.051. The dominant motif in these
structures involves dimeric units linked through hydrogen-bonds: however, such a network is
disrupted in [12]aneS3N–CSNHCOPh by the substitution of a carbonyl unit for a thiocarbonyl
unit. When more than one amide unit is present in the pendant arm, intramolecular hydrogen-
bond networks are observed resulting in coplanar pendant arms and highly directional hydrogen-
bonding. Inclusion of a methylene linker between the macrocycle and carbonyl function in the
pendant arm inhibits intermolecular hydrogen-bond formation resulting in interaction of the
amide proton with the macrocyclic nitrogen centres. A single crystal X-ray structure of
[Ag([12]aneS3N–CH2CONH–tBu)(NO3)] confirms binding of Ag(I) to the macrocyclic moiety with
additional hydrogen-bonding [N–HÁ Á ÁO 2.901(3) A] between the macrocyclic pendant arm amide
unit and the nitrate anion demonstrating that in the solid-state these ligands can act as
heteroditopic receptors for metal salts. Overall, the solid-state structure of this complex is a one-
dimensional polymer in which the Ag(I) cation is in a distorted square-pyramidal geometry with
the apical sulfur donor emanating from an adjacent macrocyclic molecule. The efficacy of these
ligands in competitive membrane transport and liquid–liquid metal ion extraction of Co(II), Ni(II),
Cu(II), Zn(II), Cd(II), Ag(I) and Pb(II) has been assessed using selected ligands. In preliminary
experiments, clear extraction and transport selectivÀity for Ag(I) was observed in all systems
investigated, while only modest extraction of TcO4 was identified.
ordinative ability of hosts such as crown ethers and calixarenes
Introduction
are combined with anion receptors such as uranyls,5 amides,2,6
boryls7 and zinc porphyrins.8 However, these systems have
tended to be useful for the tandem complexation of main
group halides and hydrogen phosphates. We were interested in
targeting transition metal ions, specifically the precious metals,
with the aim of using heteroditopic molecules to bind and
recover metal cations together with their associated
anion(s).3,9–11 Tasker and co-workers have used zwitterionic
ionophores derived from salen incorporating both phenoxy
and protonated amine centres to bind CuSO4 and NiSO4
salts.3 We were interested in developing ionophores based
around thioether macrocycles which are well known to co-
ordinate strongly to a range of heavy and precious transition
metal ions.12 We report herein the synthesis of a series of
functionalised aza-thioether and aza-oxa-thioether macro-
cycles incorporating peripheral hydrogen-bonding amide
A powerful strategy to achieve discrimination in binding and
transport of metal ions is via the use of mixed donor ligands in
which the complexing properties of the ionophore can be fine-
tuned.1 The design and synthesis of heteroditopic ionophores
incorporating both cationic and anionic binding sites repre-
sents a powerful methodology for the binding, extraction and
transport of metal salts.2,3 Cooperative ion-pair binding,
where complexation of a metal cation acts as a switch for
selective anion binding or vice versa is also of interest.4 Most
commonly in these types of systems the well-established co-
a School of Chemistry, University of Nottingham, University Park,
UK NG7 2RD. E-mail: m.schroder@nottingham.ac.uk
b Centre for Heavy Metals Research, School of Chemistry, F11, The
University of Sydney, NSW 2006, Australia
c Department of Chemistry, TU Dresden, 01062 Dresden, Germany
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groups. The parent aza-thioether macrocycles can be readily
synthesised in relatively large scales and incorporate a second-
ary nitrogen atom as a design feature for subsequent facile
derivatisation.10,13 The new derivatives reported herein con-
tain amide anion receptors, which were designed to fulfil
several design criteria, including ease of synthesis, possible
enhanced lipophilicity, and the potential for extensive hydro-
gen-bonding interactions.
Results and discussion
Synthesis and structural studies
Several routes were explored towards the synthesis of sub-
stituted macrocycles for use in the present study (Fig. 1). In
this context the most useful were found to be the reaction of
the aza-thioether macrocycles with isocyanates, isothiocya-
nates, chloroacylureas and benzyl halides. An advantage of
using these reagents is that they are either commercially
available or may be readily prepared in high yield. In a typical
Fig. 2 Synthesis of macrocycles with pendant amide arms. (i. 1,2-
dichloroethane, reflux.)
reaction, a mixture of benzoylisocyanate and [12]aneNS3 was
heated in 1,2-dichloroethane to yield the amide derivative,
[12]aneS3N–C(O)NHC(O)Ph (1) in high yield (Fig. 2). The 1H-
NMR spectrum of 1 shows the amide hydrogen resonating
downfield (9.04 ppm) of the aromatic proton signals. The
amide bond to the macrocyclic ring of 1 might be expected
to display restricted rotation since the N–Carm bond has
significant double bond character; however, there is no clear
1
evidence for this in either the H- or 13C-NMR spectra which
contain sharp resonances, although some spectral overlap
occurs in this region. In contrast, the NMR spectrum of
[12]aneS3N–C(S)NHC(O)Ph (2), prepared in a similar manner
to 1 but from benzoylisothiocyanate, shows multiple reso-
nances attributable to severely hindered rotation about the
macrocyclic N–Carm bond. Characterisation of both 1 (Fig. 3)
and 2 (Fig. 4) by X-ray diffraction was undertaken in order to
examine the effect of the amide and thioamide pendant arms
on the structures of these compounds in the solid-state. In
both structures the respective carbonyl or thiocarbonyl groups
in the pendant arms are non–co-planar with angles between
planes defined by N(1), C(9), O(1), N(2) and C(11), C(10),
O(2), N(2) of 50.811 for the first and 53.111 for the second
independent molecule of 1; the angle between N(1), C(9), S(4),
N(2) and C(11), C(10), O(1), N(2) is 56.501 in 2, while the
phenyl rings are also twisted from co-planarity with the
Fig. 3 X-Ray crystal structure of 1 showing intermolecular hydro-
gen-bonding between pendant arms. Displacement ellipsoids are
drawn at 50% probability, all non-imide hydrogen atoms have been
omitted for clarity.
Fig. 1 Summary of ionophores prepared with numbering scheme.
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sulfur arrangement has been attributed to the preference of
C–S linkages to adopt gauche conformations, balanced with
the destablising effect of the mutual repulsion of S-lone
pairs.16 In 3 the torsion angles around the O-donor, C–O–C–C
(1691 and 1781), take up the favoured antiperiplanar confor-
mation with the O-centre pointing into the ring. The S-lone
pairs are directed out of the ring in the prevalent exo-orienta-
tion, as is the N-donor, with C–S–C–C torsion angles of À102,
80, À128 and 671. This results in a heart-shaped structure for
the macrocycle. Despite the preference for gauche torsion
angles at C–S linkages in thioether macrocycles, it can be
clearly seen from the angles in 3 that significant flexibility
exists: at least one of the torsion angles is more properly
described as being eclipsed with a neighbouring hydrogen
atom. Examination of torsion angles in other crystallographi-
cally characterised thioether macrocycles17 reveals that this
phenomenon is reasonably common, and a computational
study of four thioether macrocycles in the gas phase has
predicted the presence of eclipsed conformations in high
energy structures.18 The situation in 3 is complicated by the
presence of other heteroatoms, which are known to disrupt
gauche placements through opposing influences in various
segments of the macrocyclic ring. This is particularly evident
when compared to the macrocyclic C–S and C–N torsion
angles in 1 and 2 which are all gauche (a spread of 63.7 to
82.81 occurs for both independent molecules of 1 in the unit
cell and from 66.6 to 87.71 for 2). For 3, hydrogen-bonded
dimers are formed involving an amide hydrogen on one
molecule and the carbonyl attached to the macrocycle on
another, while the second carbonyl unit plays no role in
hydrogen bonding. This is similar to the arrangement
found in 1.
Fig. 4 X-Ray crystal structure of 2. Displacement ellipsoids are
drawn at 50% probability, all non-imide hydrogen atoms have been
omitted for clarity.
adjacent carbonyl function. Unlike cyclic amides where the
carbonyl functions are forced to occupy a ‘W’ type conforma-
tion, in these acyclic amides a range of conformations is
possible. The three planar, cis-cis, cis-trans, trans-trans, con-
formations and the factors leading to their relative stability
have been discussed elsewhere.14,15
The hydrogen-bonding network in 1 comprises dimeric units
with N–HÁ Á ÁO distances of 2.746(4) and 2.893(4) A involving
the carbonyl group closest to the macrocyclic ring [C(9)–O(1)]
and the amide hydrogen on the opposing molecule. The
second carbonyl unit [C(10)–O(2)] is not involved in hydro-
gen-bonding interactions. The hydrogen-bonding network in 2
is interesting since all H-bonds involve the more basic thioa-
mide group and not the amide oxygen donor, with intermo-
lecular N–HÁ Á ÁS contacts of 3.331(2) A.
The X-ray structure of [12]aneS2ON–CONHCOPh (3, Fig.
5), formed by the reaction of [12]aneNOS2 and benzoylisocya-
nate, shows an angle of 68.051 for the equivalent angle
between the planes of adjacent carbonyl functions as discussed
above for 1 and 2. The common conformation found for most
structurally characterised thioether macrocycles involves an
exo-arrangement of the S-donors although an endo-arrange-
ment can sometimes be favoured.16 The tendency for an exo-
Reaction of the aza function of the respective macrocycles
with isocyanates to form amide-containing pendant arms has
been generally successful, as demonstrated by the range of
isocyanates and macrcocycles that we have employed (Fig. 1).
When di-aza macrocycles, e.g. [12]aneN2S2, undergo reaction
with two equivalents of an isocyanate, the NMR spectra of the
resulting products tend to be complicated by the restricted
rotation about each N–Carm bond. The solubility of the
resulting di-substituted products is often very low, especially
for nitrophenylisocyanate derivatives and to a lesser extent for
the related mono-aza macrocycles.
A particular goal was to incorporate further functionality
into the pendant arms, one target being the incorporation of
amino groups which are synthetically versatile. Thus, inclusion
of a nitro functionality into the pendant-macrocycles (6, 7, 10
and 26) allowed the possibility of reduction to an amino group
for subsequent derivatisation. Trial reduction reactions on a
model compound, formed from diethylamine and 4-nitrophe-
nylisocyanate, showed that excellent conversion to the corre-
sponding amine was achieved using Pd/C–hydrazine hydrate19
and lower yields with SnCl2–EtOH.20 Unfortunately, all at-
tempts using these and other reagents with the present macro-
cyclic derivatives almost exclusively resulted in cleavage of the
pendant arm, which was rapid in acidic media. Initial metal
complexation experiments also indicated that the N–Carm
bond is prone to cleavage in the presence of many metal
salts.
Fig. 5 X-Ray crystal structure of 3 showing intermolecular hydro-
gen-bonding between pendant arms. Displacement ellipsoids are
drawn at 50% probability, all non-imide hydrogen atoms have been
omitted for clarity.
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Fig. 6 Synthesis of pendant arm macrocycles via chloroacylamides.
(i. K2CO3, MeCN, reflux.)
Fig. 8 X-Ray crystal structure of 15 showing the high degree of
intramolecular hydrogen-bonding. Displacement ellipsoids are drawn
at 50% probability, all non-amide hydrogen atoms have been omitted
for clarity.
In order to avoid such decomposition, the pendant arms
were modified by introducing a methylene linker between the
macrocycle and the amide moieties. A versatile reaction
involving chloroacylureas and chloroacylamides was used to
introduce these pendant arms onto the macrocycle (Fig. 6).
For example, reaction of 12]aneNOS2, 1-tert-butyl-3-(chloro-
acetyl)urea and K2CO3 in MeCN afforded the pendant macro-
cycle, [12]aneS2ON–CH2CONHCONH–tBu (12), in 60%
yield after aqueous workup. The presence of the pendant
[angle between planes defined by C(9), C(10), O(2), N(2) and
N(3), C(11), O(3), N(2) is 8.821] with N(2)–H(2A)Á Á ÁN(1) and
N(3)–H(2A)Á Á ÁO(2) distances of 2.6927(18) and 2.7168(18) A,
respectively.21
1
arm was confirmed by H-NMR spectroscopy, which showed
Compounds 13–24 incorporating amide and urea moieties
in the pendant arm(s) were prepared in an analogous manner
to that of 12. The di-aza macrocycles undergo substitution at
one or both nitrogen atoms depending on the stoichiometry of
the reactants employed. For example, [15]aneS2ON2–
(CH2CONHCONH–tBu)2 (15)10 was isolated in 67% yield after
workup. The pendant arms appear equivalent in the NMR
spectra, although in concentrated solutions the signals attrib-
uted to the tert-butyl groups in the 1H-NMR spectrum are split
(d 1.34 and 1.35 ppm), with the amide protons observed at 8.19
and 9.19 ppm. In the 13C-NMR spectra of both 12 and 15 the
methylene units directly bound to the ether oxygen donor are
observed downfield of the other signals at 74.34 and 73.00 ppm,
respectively. The latter compound also exhibits two infrared
bands at 1552 and 1715 cmÀ1 attributable to the n(CO) modes
of the carbonyls in the pendant arms.
a shift in macrocyclic ring resonances compared to the metal-
free ionophore and the presence of two additional broad
signals at d 8.21 and 9.32 assigned to the amide protons of
the pendant arm. These latter signals were shown to shift
considerably in the presence of a diamagnetic metal ion such
as Ag(I).
In order to examine the effect of introducing the methylene
linker into its pendant arm, a crystal structure determination
of 12 was undertaken (Fig. 7). The arrangement of the
macrocyclic ring is generally the same as that found in 3, with
the N and S-donors exodentate and the O-donor endodentate:
however, the torsion angles around the sulfur donors in 12 are
all gauche (57.15–67.531). The main differences occur in the
pendant arm since in 12 an extra amide function is present.
The pendant arm is well set-up for intramolecular hydrogen-
bonding and the structure shows a nearly planar pendant arm
The crystal structure of [12]aneS2ON2–(CH2CONH-
CONH–tBu)2 15 was obtained in order to examine the con-
sequences of adding two urea moieties onto the macrocycle
(Fig. 8).10 The sulfur and nitrogen donors in 15 are exodentate
while the oxygen donor takes up its normal endodentate
arrangement with anti conformations about the C–O bonds
[À176.2(3)1 and 177.9(3)1]. There are three gauche C–S–C–C
torsion angles [74.5(2)1,82.4(3)1 and 82.8(3)1] and one anti
conformation [177.4(2)1], consistent with the preference for
these conformations in thioether macrocycles.16 As for the
urea pendant arm in 12, the carbonyl units in the pendant
arms of 15 are also coplanar [angle between planes defined by:
C(11)–C(12)–O(2)–N(3) and N(4), C(13), O(3), N(3) is 5.041;
C(18), C(19), O(4), N(5) and N(6), C(20), O(5), N(5) is 1.681]
Fig. 7 X-Ray crystal structure of 12 showing the intramolecular
hydrogen-bonding in the pendant arm. Displacement ellipsoids are
drawn at 50% probability, all non-imide hydrogen atoms have been
omitted for clarity.
with
a complex network of both intramolecular and
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Fig. 9 View showing the intermolecular hydrogen-bonding between
pendant arms in 15. Displacement ellipsoids are drawn at 50%
probability, all non-amide hydrogen atoms have been omitted for
clarity.
Fig. 11 View of structure of [Ag(18)(NO3)] showing the intermole-
cular hydrogen-bonding between macrocycle pendant arm and nitrate
anion. Displacement ellipsoids are drawn at 50% probability, all non-
imide hydrogen atoms have been omitted for clarity.
intermolecular hydrogen-bonding being present. The resultant
structure is made up of hydrogen-bonded dimers bridged
through one pendant arm [N(3)–H(3)Á Á ÁO(3)], which is also
involved in an intramolecular interaction [N(4)–H(4N)Á Á ÁO(2)]
(Fig. 8). The other pendant arm is only involved in intra-
molecular hydrogen-bonding involving the amide nearest to
the macrocycle and the macrocyclic nitrogen atoms; the out-
ermost amide [N(6)–H(6)] interacts with the carbonyl oxygen
[O(4)] of the innermost amide unit (Fig. 9). This leaves the
outermost carbonyl oxygen atom [O(5)] free and taking no
part in any strong hydrogen-bonding interactions.
reflection of the odd number of atoms in the ring; however, it
is significant that no highly unfavoured conformations are
present.
We were also able to selectively substitute only one of the
macrocyclic nitrogen atoms in the di-aza macrocycles. Thus,
slow addition of one equivalent of N-phenyl-2-chloroaceta-
mide in MeCN to a mixture of K2CO3 and [15]aneN2S3 in
MeCN at 501C results in formation of [15]aneS3N2–
CH2CONHPh (24) in 43% isolated yield. The resonance
attributed to the amide hydrogen appears at d 9.71 ppm in
In contrast, the crystal structure of [15]aneS3N2–
(CH2CONHPh)2 (23) (Fig. 10), which contains two amide
functionalities rather than two urea functions, shows the
pendant arms extending on either side of the plane of the
macrocycle which leaves no potential for hydrogen-bonding
between the arms. Both amide units are involved in hydrogen-
bonds with the macrocyclic nitrogen centres, while, as in 15,
the carbonyl oxygen atoms are not involved in hydrogen-
bonding interactions with a nearest contact of over 5 A. The
C–C–S–C torsion angles in the macrocyclic ring yield a
mixture of gauche and anti arrangements which may be a
1
the H-NMR spectrum, considerably shifted downfield from
that found in the analogous disubstituted species (d 9.29 ppm).
This is probably a result of inductive effects from hydrogen-
bonding interactions between the macrocyclic nitrogen atom
and the amide oxygen. In all other species containing the
phenylacetamide arm, except that derived from [12]aneNOS2
(21), this signal appears in the region d 9.3–9.4 ppm. The effect
of the electron donating ability of the tert-butyl group over
that of the phenyl group is also noticeable in the position of
the amide hydrogen resonance for 18–23. All phenylacetamide
derivatives have this resonance at d 9.29 or above, while in the
tert-butylacetamide derivatives this signal appears at much
higher field (d 7.22 for 18; d 7.06 for 19).
Complexation studies
A preliminary investigation into the solid-state structures of
these ligands with selected metal salts has proved encouraging.
The single-crystal X-ray structure of [Ag(18)(NO3)] (Fig. 11)
demonstrates that relatively strong hydrogen-bonding inter-
actions occur between the amide hydrogen atom and a nitrate
oxygen atom [N(2)H(2A)Á Á ÁO(1A) 2.02 A, N(2)Á Á ÁO(1A)
2.901(3) A, +N(2)–H(2A)Á Á ÁO(1A) 1781]. The Ag(I) ion is
bound to four sulfur atoms, three from one macrocycle and
one from an adjacent macrocycle, and one N-donor. Overall,
the co-ordination geometry is distorted square-pyramidal with
the apical position occupied by the sulfur donor from the
Fig. 10 X-Ray crystal structure of 23 showing the intramolecular
hydrogen-bonding. Displacement ellipsoids are drawn at 50% prob-
ability, all non-amide hydrogen atoms have been omitted for clarity.
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adjacent macrocycle [S(3A)], with the resulting structure being
a one-dimensional zig-zag polymer. Each macrocyclic cationic
moiety is bridged to the next by the Ag–S(3A) bond [2.5349(8)
A] which is also the shortest of the four Ag–S bond distances,
the remaining bond lengths being 2.6082(8), 2.7299(8) and
2.7153(9) A for Ag–S(1), Ag–S(2) and Ag–S(3), respectively,
while the Ag–N(1) bond length is 2.490(2) A.
Table 1 Data for 1H-NMR titration of (13) with AgNO3 and n-
Bu4NNO3 carried out in d3-MeCN. Total volume 0.4 mL: 0.25 mL L
(0.071 mmol mLÀ1) and portions of 0.071 mmol mLÀ1 AgNO3 (0.2 eq,
0.4 eq, 0.6 eq and 1 eq) followed by solvent to make up to 0.4 mL
volume. After 1 eq was reached, n-Bu4NNO3 was added in portions of
1 equiv. (entries 6–8)
Entry Equiv. Ag+ Equiv. n-Bu4NNO3 d NHcentral d NHterminal
1
2
3
4
5
6
7
8
0.0
0.2
0.4
0.6
1.0
1.0
1.0
1.0
0
0
0
0
0
1
2
3
9.01
8.75
8.65
8.73
8.85
9.39
9.55
9.65
8.23
8.15
8.09
8.09
8.12
8.15
8.15
8.16
Polymeric structures are known for the Ag(I) complexes of
thioether macrocycles, and these often involve exocyclic bind-
ing of the Ag(I) ion.22,23 The co-ordination chemistry of the
Ag(I) complexes of [9]aneS3, [15]aneS5 and [18]aneS6 has been
investigated previously and the structures of [Ag([9]aneS3)2]+
and [Ag([18]aneS6)]+ reported.24 It has been demonstrated
that the structure of the [Ag([15]aneS5)]+ cation is significantly
altered iÀn the presence of different anions.25 In the structure of
the PF6 complex, a [4 + 1] co-ordination geometry, similar
to that observed in the structure of [Ag(18)(NO3)], was
observed, with four donors from one macrocycle and a further
donor from an adjacent macrocycle forming the co-ordination
sphere. In [Ag([15]aneS5)]PF6, however, the intermolecular
Ag–S bond distance is the longest. Comparison of the Ag–S
distances in structurally characterised Ag–thioether macro-
cycle complexes shows that the Ag–S distance is highly vari-
able and depends on a range of factors such as the co-
ordination geometry adopted, the nature of crystal packing
forces, the size of macrocycle and the nature of the anion. In
the structure of [Ag(18)(NO3)], the Ag–S distances lie at the
upper end of the observed bond distance range. The macro-
cyclic geometry in the latter complex maintains the square
shape found in other structures containing [12]aneNS3; how-
ever, the donor atoms sacrifice their preferred corner positions
and becomes part of a ‘side’, each of which is made up of runs
of gauche–anti-gauche torsion angles. The positions of both
n(NH) and n(CO) stretching vibrations in the infra-red spec-
trum of the complex are both shifted to higher frequency
compared to the free ligand. We interpret this as being a result
of significant changes in the hydrogen-bonding network due
both to new ligand-nitrate interactions as well as disruption of
the hydrogen-bonding pattern found in the free ligand. The
1H-NMR spectrum of [Ag(18)(NO3)] in d3-MeCN shows that
the signal attributed to the amide hydrogen is shifted upfield (d
6.53) from that of the free ligand (d 7.18 for 18 in d3-MeCN).
This shift is in the opposite direction from that usually
associated with hydrogen-bonding interactions;26 however,
strong solvation of the cationic moiety very likely perturbs
the hydrogen-bonding present in the solid-state structure. This
is not entirely unexpected since the nitrate anion is not known
as an especially strong hydrogen-bond acceptor27 and the
ligand contains only one hydrogen-bond donor. The signals
attributed to the macrocyclic methylene units collapse into a
broad singlet in the 1H-NMR spectrum of the complex,
suggesting a high degree of flexibility or fluxionality in the
macrocyclic co-ordination.
on complexation to Ag(I) (Fig. 12). On further addition of
AgNO3, this resonance shows the expected downfield shift to
d
H 8.85 reflecting H-bonding of the acylurea arm to the nitrate
anion as confirmed by the crystal structure of [Ag(13)(NO3)].9
Further addition of nBu4NNO3 leads to further downfield
shifts for the N(15)–H resonance (to dH 9.39, 9.55 and 9.65
n
on addition of 1, 2 and 3 equivalents of Bu4NNO3, respec-
tively) consistent with anion binding in solution (Table 1).
n
Significantly, addition of Bu4NNO3 to 13 does not shift the
N(15)–H resonance; therefore, anion binding to 13 can only
occur once cation binding within the macrocyclic cavity and
concomitant cleavage of the internal H-bonding takes place,
thus affording an element of cooperativity to this system.
Thus, once the internal hydrogen-bond is broken by com-
plexation of the ionophore by Ag(I), the central urea proton is
freed to interact with anions in solution as confirmed by the
À
downfield shift of this proton resonance on addition of NO3
.
Membrane transport
Competitive mixed metal transport experiments (water–
chloroform–water) employed an organic phase containing
the ionophore (chosen from 14–16, 20) at 1 Â 10À3 mol
dmÀ3. The aqueous source phase contained equimolar con-
centrations (each 1 Â 10À2 mol dmÀ3) of Co(II), Ni(II), Cu(II),
Zn(II), Cd(II), Ag(I) and Pb(II) nitrate. Transport experiments
were performed over 24 h against a back gradient of protons,
maintained by buffering the source and receiving phases at pH
4.9 and 3.0, respectively. A common feature of all four studies
based on 14–16 and 20 is that, within experimental error, sole
transport selectivity for Ag(I) was observed (Table 2) under the
conditions employed.
Transport efficiency/selectivity across bulk liquid mem-
branes has long been known to be influenced by a range of
often interdependent factors.28 For example, slow kinetics
and/or thermodynamic stabilities that are either too low to
permit uptake of a metal into the organic phase, or too high to
The solution behaviour of 13 with Ag(I) salts was investi-
gated by 1H-NMR spectroscopy (Table 1). Addition of
AgNO3 to a solution of 13 in MeCN leads initially to an
upfield shift for the N(15)–H proton from dH 9.01 in 13 to dH
8.65 on addition of 0.4 equivalents of AgNO3. This upfield
shift reflects the breaking of the internal H-bonding in free 13
Fig. 12 Binding of AgNO3 to 13.
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Table 2 Transport flux data for Ag(I) from seven-metal competitive
transport across a bulk chloroform membrane employing 14–16 and
20 as ionophores (25 1C)ab
Ionophore
Ag(I) J/mol per 24 hc
14
15
16
20
a
159
82
147
54
b
Values are the mean from duplicate experiments. The correspond-
ing J values for Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) were all 0
c
(within experimental error). All J values are Â10À7
.
allow its loss to the receiving phase, will all inhibit transport
efficiency and also affect selectivity. Because of the possible
interplay of subtleties such as these, it is often difficult to
analyse in detail observed transport behaviour. Although this
situation pertains to the present study, it is still possible to note
the following observations. Although 15 and 16 differ only by
the change of one donor in the macrocyclic ring (from oxygen
to sulfur), the substituted S3N2 derivative 16 yields a signifi-
cantly higher flux for Ag(I) transport, presumably reflecting
the expected higher affinity of its donor set for Ag(I) relative to
the OS2N2-donor set of 15. A comparable transport rate to
that for 16 was found for the smaller macrocyclic derivative,
14, showing that the additional oxygen donor in 15 (relative to
14) in fact leads to a reduction in transport efficiency. The
remaining compound, 20, differs from the other three macro-
cyclic derivatives in that it incorporates a S3N-donor set and
contains only one pendant arm with a single amide function-
ality: it shows the poorest Ag(I) transport rate.
Fig. 14 Extraction of pertechnetate with pendant aza-thioethers 15,
23, 24, 26 and 27. [NaTcO4] = 1 Â 10À4 M; pH = 7.4 (HEPES/NaOH
buffer); [ligand] = 1 Â 10À3 M in CHCl3.
the overall extraction behaviour under the conditions em-
ployed. Unfortunately, because of the high distribution ratios
with the low applied ligand concentrations employed [2.5 Â
10À4 –1.5 Â 10À3 M], no information could be obtained about
the composition of the extracted complexes from these experi-
ments, although the single crystal X-ray structure of the 1 : 1
complex [Ag(25)(SCN)] has been reported previously and
shows a solid-state co-ordination pattern that involves binding
to all macrocyclic donor atoms along with a sulfur from the
SCNÀ ligand.29 The stability of selected metal complexes with
unsubstituted macrocycles employing mixed S2ON2-donor
systems (including 25) has also been reported30 and confirms
that such species show strong affinity for Ag(I) [and Cu(II)]
relative to the other five transition and post-transition metal
ions investigated.
Liquid–liquid extraction studies
The new thia-aza crown compounds were also tested as
extractants for liquid–liquid extraction of a series of different
metal ions using an extraction system based upon metal
salt–picric acid–buffer–H2O/ligand–CHCl3. Fig. 13 shows an
overview of the extraction behaviour of the ligands studied
towards Ag(I) at comparable experimental conditions. Con-
sistent with the membrane transport studies above, the thia-
aza crowns show a high affinity for Ag(I) and extract it almost
quantitatively even at low ligand concentrations. Conversion
of secondary amines to tertiary ones has no marked effect on
Additional experiments were performed involving extrac-
tion from an aqueous source phase buffered at pH 5.2 and
containing equimolar concentrations of Co(II), Ni(II), Cu(II),
Zn(II), Cd(II) and Pb(II) >cM(NO ) = 1 Â 10À4 M] into a
3 2
CHCl3 phase incorporating ligand 25 (cligand = 5 Â 10À3 M).
This ligand shows only high extraction of Pb(II) (55%) under
the conditions used here. Very low extraction levels were
observed for other divalent transition metal ions, even for
Ni(II), which has been shown to form a metal complex of
composition [Ni(25)(NO3)](NO3) in the solid-state.31 How-
ever, the five-fold higher ligand concentration used in this
experiment, in comparison with the Ag(I) extraction by 25
confirms the pronounced preference for Ag(I) by these types of
ionophores.
In addition to the above cation extraction studies, the
solvent extraction behaviour of the ligands 15, 23, 24, 26,
À
and 27 was also examined towards the TcO4 anion. We
wished to probe whether 15, 23 and 24 incorporating hydro-
gen-bonding side arms would afford a pronounced interaction
with the anion. However, as shown in Fig. 14, the ligands 15,
23 and 24 show only a very weak extraction of this oxoanion
into the organic phase whereas higher extraction was observed
for the benzyl and nitrobenzyl substituted ligands 26 and 27.
At the pH 7.4 employed for these experiments, it is expected
that each of the ligands be present in its protonated form.32 It
thus appears that the higher lipophilicity present in 26 and 27
Fig. 13 Extraction of Ag(I) with pendant aza-thioethers 15, 23, 24
and 25. [AgNO3] = 1 Â 10À4 M; pH = 5.2 (MES/NaOH buffer);
[ligand] = 1 Â 10À3 M in CHCl3; [HPic] = 5 Â 10À3 M.
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relative to the amide-containing species 15, 23, and 24 dom-
inates in this case and more than compensates for any
tendency for the pendant arm functional groups in the latter
systems to assist in anion uptake.
Membrane transport
The transport experiments employed a concentric cell design
in which the aqueous source phase (10 cm3) and receiving
phase (30 cm3) were separated by a chloroform phase (50 cm3).
Details of the cell design have been reported elsewhere.34 In
each experiment all three phases were stirred separately at
10 rpm using stirring paddles for the receiving phase and
propellers for the source and organic phases. Each paddle or
propeller was coupled to a single (geared) synchronous motor,
and the cell was enclosed by a water jacket and thermostatted
at 25 1C. The aqueous source phase consisted of a sodium
acetate–acetic acid buffer solution (pH 4.9 Æ 0.1) containing
an equimolar mixture of the metal ions, each at a concentra-
tion of 10À2 mol dmÀ3. The chloroform phase contained the
macrocycle at 10À3 mol dmÀ3. The receiving phase consisted
of a buffer solution of sodium formate–formic acid (pH 3.0 Æ
0.1). All transport runs were terminated after 24 h and atomic
absorption spectroscopy was used to determine the amount of
each metal ion transported into the receiving phase during this
period (using a Varian Spectra AA-800 spectrometer). The
transport results are quoted as the average values obtained
from duplicate runs; transport fluxes (J values) are in mol per
24 h and represent mean values measured over 24 h. J values
equal to or less than B15 Â 10À7 mol per 24 h are zero within
experimental error and were ignored in the analysis of the
results.
Conclusions
We have prepared in good yield a range of derivatised macro-
cycles where the pendant arm(s) contain potential hydrogen-
bonding moieties comprising urea and amide functions. We
envisage that these and related systems will find applications as
selective metal salt extractants from, for example, dilute waste
streams for the recovery of toxic and/or precious metals.
Reaction of the parent macrocycles with a range of substrates
has been investigated and the solid-state structures examined.
The structures demonstrate that hydrogen-bonding involving
the pendant arms is strong and, where there is more than one
amide N–H unit, intramolecular hydrogen-bonding is the
dominant influence controlling the conformations of the pen-
dant arms. The majority of the donor atoms in the macro-
cycles were found to be exo-dentate in the solid-state, but
NMR spectral data suggest flexibility in the macrocyclic rings
in solution. The crystal structure of [Ag(18)(NO3)] demon-
strates that in the solid-state there is significant hydrogen-
bonding between the macrocyclic amide arm and the nitrate
anion, indicating that these systems may act as heteroditopic
receptors for metal salts. The hydrogen-bonding network
appears to be disrupted in acetonitrile solution where strong
competitive solvation of the cationic moiety probably inhibits
any interaction with the anion. Membrane and liquid–liquid
extraction experiments have shown that these systems are
highly selective for Ag(I) over a range of other metal ions.
Liquid–liquid solvent extraction
The liquid–liquid extraction experiments were performed at
23 Æ 11C in microcentrifuge tubes (2 mL) by means of
mechanical shaking. The phase ratio V(org) : V(w) was 1 : 1
(0.5 mL each). A shaking time of 30 min was chosen because in
all cases the extraction equilibrium was reached during this
period. After extraction, all samples were centrifuged and the
phases separated. The metal concentration in both phases was
determined using g-radiation measurements of 110mAg radio-
isotopes in a NaI(Tl) scintillation counter (Cobra II/Canberra-
Packard). For the competitive extraction experiments the
metal concentration in the aqueous phase was determined by
ICP-OES spectroscopy (Optima 3000/Perkin Elmer) accord-
ing to standard conditions (viewing height: 9 mm, Ar plasma
gas flow: 15.0 l minÀ1, Ar auxiliary gas flow: 0.5 l minÀ1, Ar
nebulizer gas flow: 0.8 l minÀ1; solution uptake rate: 0.1 ml
minÀ1; wavelengths-Ag: 328.068 nm; Cd: 214.438 nm; Co:
228.616 nm; Ni: 231.604 nm; Cu: 324.754 nm; Pd: 340.458 nm;
Pb: 220.353 nm and Zn: 202.548 nm, integration time: 60 s
each). The determination of the anion concentration in both
phases was carried out radiometrically by b-radiation mea-
surements of 99Tc in a liquid scintillation counter (LS 6000
LL/Beckman).
Experimental
Materials and methods
All reagents and solvents were purchased from commercial
sources and were used as received unless stated otherwise.
Aza-thioether macrocycles were prepared according to the
literature.9,10,13 Benzoylisocyanate was prepared according to
the literature procedure.33 4-Nitrobenzoylisocyanate was pre-
pared in a similar fashion to that of benzoyl isocyanate using
toluene as the solvent. 1-tert-Butyl-3-(chloroacetyl)urea and
1-phenyl-3-(chloroacetyl)urea were prepared by heating at
reflux tert-butylurea or phenylurea with chloroacetylchloride
in benzene. N-tert-Butyl-2-chloroacetamide and N-phenyl-2-
chloroacetamide were prepared by adding chloroacetylchlo-
ride slowly to excess tert-butylamine or aniline respectively in
toluene at 0 1C. Elemental analyses (C, H, N) were carried out
by the by the Analytical Department of the School of Chem-
istry, University of Nottingham. 1H-NMR and 13C-NMR
spectra were recorded on a Bruker AX300 FT-NMR spectro-
meter. Chemical shifts are referenced with respect to the
residual protio solvent. Mass spectra were recorded on a
Finnigan MAT TSQ-700 at the EPSRC National Service,
University of Wales, Swansea.
Syntheses
[12]aneS3N–CONHCOPh (1). To a solution of [12]aneNS3
(0.47 g, 2.10 mmol) in 1,2-dichloroethane (25 mL) was added
benzoylisocyanate (0.37 g, 2.52 mmol) with the formation of
white precipitate. The mixture was heated at reflux for 1 h and
the white precipitate filtered, washed with dichloromethane,
hexane and then dried under reduced pressure to afford 0.58 g
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(75%) of white powder. Anal. calc. for C16H22N2O2S3: C,
51.86; H, 5.98; N, 7.56%. Found: C, 51.69; H, 5.85; N, 7.50%.
1H-NMR (CDCl3): d (ppm) = 2.92 (m, 8H, CH2), 2.98 (m,
4H, CH2), 3.62 (m, 4H, CH), 7.48 (t, 2H, Ph), 7.55 (t, 1H, Ph),
7.88 (d, 2H, Ph), 9.04 (s, 1H, NH). 13C-NMR (CDCl3): d
(ppm) = 28.37 (CH2), 29.90 (CH2), 31.73 (CH2), 49.63 (CH2),
127.78 (CH), 128.77 (CH), 132.79 (CH), 133.19 (Cquat), 153.96
(CO), 166.18 (CO). IR (cmÀ1) 3186 (nNH), 1709 (nCO), 1651
(nCO). FAB+-MS m/z (C16H22N2O2S3, 370): 371 (M + H+).
50.06; H, 5.76; N, 7.72%. 1H-NMR (CDCl3): d (ppm) =
2.80–3.13 (m, 12H, CH2), 3.99 (m, 4H, CH2), 7.21–7.52 (m,
5H, Ph), 9.02 (s, 1H, NH). 13C-NMR (CDCl3): d (ppm) =
29.50 (CH2), 30.44 (CH2), 32.97 (br, CH2), 55.13 (CH2),
125.24 (CH), 125.73 (CH), 128.77 (CH), 139.79 (Cquat),
184.02 (CS). IR (cmÀ1) 3192 (nNH), 1525 (nCS). FAB+-MS
m/z (C15H22N2S4, 358): 359 (M + H+).
[12]aneS3N–CONHPhNO2-4 (6). Using the same procedure
as outlined for the preparation of 1 in toluene, [12]aneNS3
(0.154 g, 0.689 mmol) and 4-nitrophenylisocyanate (0.113 g,
0.689 mmol) afforded 0.22 g (82%) of the product as an off-
white solid after concentration and cooling. Anal. calc. for
C15H21N3O3S3: C, 46.49, H, 5.46; N, 10.84%. Found: C,
46.51; H, 5.43; N, 10.57%. 1H-NMR (CDCl3): d (ppm) =
2.84–3.04 (m, 12H, CH2), 3.65 (m, 4H, CH2), 7.56 (d, 2H, Ph),
8.19 (d, 2H, Ph), 9.01 (s, 1H, NH). FAB+-MS m/z
(C15H21N3O3S3, 387): 388 (M + H+).
[12]aneS3N–CSNHCOPh (2). Using the same procedure as
outlined for the preparation of 1, [12]aneNS3 (0.27 g, 1.21
mmol) and benzoyl isothiocyanate (0.17 mL, 1.27 mmol)
afforded 0.30 g (64%) of the product as a pale yellow crystal-
line solid after concentration and slow cooling. Anal. calc. for
C16H22N2OS4: C, 49.71, H, 5.74; N, 7.25%. Found: C, 49.01;
H, 5.63; N, 7.01%. 1H-NMR (CDCl3): d (ppm) = 2.81 (s, 8H,
CH2), 3.06 (m, 4H, CH2), 3.82 (s, br, 2H, CH), 4.18 (s, br, 2H,
CH), 7.50 (t, 2H, Ph), 7.62 (t, 1H, Ph), 7.86 (d, 2H, Ph), 8.35 (s,
1H, NH). 13C-NMR (CDCl3): d (ppm) = 25.43 (CH2), 26.04
(CH2), 31.37 (CH2), 51.46 (CH2), 52.14 (CH2), 127.83 (CH),
129.00 (CH), 132.24 (CH), 133.26 (Cquat), 163.99 (CO), 181.39
(CS). IR (cmÀ1) 3326 (nNH), 1689 (nCO), 1522 (nCS). FAB+-
MS m/z (C16H22N2OS4, 386): 387 (M + H+).
[12]aneS3N–CONHCOPhNO2-4 (7). Using the same proce-
dure as outlined for the preparation of 1, [12]aneNS3 (0.125 g,
0.560 mmol) and 4-nitrobenzoylisocyanate (0.107 g, 0.560
mmol) afforded 0.14 g (60%) of product as a brown solid.
Further product was obtained by concentrating the solution.
The product was sparingly soluble in common solvents. Anal.
calc. for C16H21N3O4S3: C, 46.25; H, 5.09; N, 10.11%. Found:
[12]aneS2ON–CONHCOPh (3). To a solution of [12]ane-
NOS2 (0.177 g, 0.854 mmol) in dichloromethane (15 mL) was
added benzoylisocyanate (0.126 g, 0.854 mmol) and the mix-
ture stirred at room temperature for 30 minutes after which
time the solvent was removed. The resulting waxy solid was re-
crystallised from dichloromethane-diethyl ether to give 0.18 g
(60%) of the product as a white crystalline solid. Anal. calc.
for C16H22N2O3S2: C, 54.21; H, 6.26; N, 7.90%. Found: C,
53.97; H, 6.26; N, 7.76%. 1H NMR (CDCl3): d (ppm) = 2.78
(m, 4H, CH2), 2.98 (m, 4H, CH2), 3.75 (m, 8H, CH), 7.46 (t,
2H, Ph), 7.56 (t, 1H, Ph), 7.81 (d, 2H, Ph), 8.10 (s, 1H, NH).
13C NMR (CDCl3): d (ppm) = 31.02 (CH2), 32.83 (CH2),
73.60 (CH2), 77.20 (CH2), 127.76 (CH), 128.68 (CH), 132.62
1
C, 45.70; H, 4.85; N, 10.16%. H-NMR (CDCl3): d (ppm) =
2.91 (m, 12H, CH2), 3.65 (m, 4H, CH2), 8.02 (d, 2H, Ph), 8.32
(d, 2H, Ph), 9.55 (s, 1H, NH). IR (cmÀ1) 3205 (nNH), 1703
(nCO), 1652 (nCO). FAB+-MS m/z (C16H21N3O4S3, 415): 416
(M + H+).
[12]aneS2N2–(CONHCOPh)2 (8). Using the same procedure
as outlined for the preparation of 1, [12]aneN2S2 (0.18 g, 0.872
mmol) and benzoylisocyanate (0.257 g, 1.74 mmol) afforded
0.43 g (100%) of the very poorly soluble product as a white
solid. Anal. calc. for C24H28N4O4S2: C, 57.58; H, 5.64; N,
11.19%. Found: C, 56.24; H, 5.61; N, 10.80%. 1H-NMR
(C6D6): d (ppm) = 2.77 (s, 4H, CH2), 2.91 (t, 4H, CH2),
3.60 (m, 4H, CH2), 3.89 (s, 4H, CH2), 7.39–7.64 (m, 10H), 8.25
(s, 2H). IR (cmÀ1) 3243 (nNH), 1700 (nCO), 1651 (nCO).
FAB+-MS m/z (C24H28N4O4S2, 500): 501 (M + H+).
(CH), 133.20 (Cquat), 153.49 (CO), 166.63 (CO). IR (cmÀ1
)
3190 (nNH), 1688 (nCO), 1651 (nCO). FAB+-MS m/z
(C16H22N2O3S2, 354): 355 (M + H+).
[12]aneS3N–CONHPh (4). Using the same procedure as
outlined for the preparation of 1, [12]aneNS3 (0.050 g, 0.224
mmol) and phenylisocyanate (0.027 g, 0.227 mmol) afforded
0.067 g (87%) of the product as a white solid. Anal. calc. for
C15H22N2OS3: C, 52.59, H, 6.47; N, 8.18%. Found: C, 52.44;
[12]aneS2N2–(CSNHCOPh)2 (9). Using the same procedure
as outlined for the preparation of 1, [12]aneN2S2 (0.107 g,
0.518 mmol) and benzoylisothiocyanate (0.14 mL, 1.04 mmol)
afforded 0.179 g (65%) of product as an insoluble white solid.
Anal. calc. for C24H28N4O2S4: C, 54.11; H, 5.30; N, 10.52%.
Found: C, 53.54; H, 5.22; N, 10.40%. Due to the very low
solubility of the sample, no NMR data were obtained. IR
(cmÀ1) 3350 (nNH), 3287 (nNH), 1684 (nCO), 1668 (nCO),
1527 (nCS). FAB+-MS m/z (C24H28N4O4S2, 532): 533
(M + H+).
1
H, 6.19; N, 7.74%. H NMR (CDCl3): d (ppm) = 2.77–3.01
(m, 12H, CH2), 3.62 (m, 4H, CH2), 7.07 (t, 1H, Ph), 7.28 (t,
2H, Ph), 7.41 (d, 2H, Ph), 8.25 (s, 1H, NH). 13C NMR
(CDCl3): d (ppm) = 30.31 (CH2), 30.39 (CH2), 33.29 (CH2),
52.18 (CH2), 119.51 (CH), 123.00 (CH), 129.01 (CH), 139.03
(Cquat), 156.69 (CO). IR (cmÀ1) 3279 (nNH), 1640 (nCO).
EI-MS m/z (C15H22N2OS3, 342): 342 (M+ꢁ).
[12]aneS2N2–(CONHCOPhNO2-4)2 (10). Using the same
procedure as outlined for the preparation of 1, [12]aneN2S2
(0.158 g, 0.766 mmol) and 4-nitrobenzoylisocyanate (0.294 g,
1.53 mmol) afforded 0.221 g (49%) of product as a brown
solid. Further product was obtained by concentrating the
solution. The product was sparingly soluble in common
solvents. Anal. calc. for C24H26N6O8S2: C, 48.81; H, 4.44;
[12]aneS3N–CSNHPh (5). Using the same procedure as
outlined for the preparation of 1, [12]aneNS3 (0.052 g, 0.233
mmol) and phenylisothiocyanate (0.032 g, 0.237 mmol) af-
forded 0.071 g (85%) of the product as a white solid. Anal.
calc. for C15H22N2S4: C, 50.24, H, 6.18; N, 7.81%. Found: C,
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N, 14.23%. Found: C, 48.18; H, 4.45; N, 13.86%. IR (cmÀ1
)
pressure. Anal. calc. for C22H42N6O4S2 Á CH2Cl2, C, 48.16;
H, 7.72; N, 14.98%. Found: C, 48.26; H, 7.68; N, 14.89%. 1H-
NMR (CDCl3): d (ppm) 1.38 (s, 18H, CMe3), 2.67–2.95 (m,
16H, CH2), 3.19 (s, 4H, CH2), 8.18 (br, s, 2H, NH), 9.12 (br, s,
2H, NH). 13C-NMR (CDCl3): d (ppm) = 28.89 (CMe3), 31.33
(CH2), 50.83 (CH2), 52.26 (CH2), 53.35 (CMe3), 54.28 (CH2),
58.59 (CH2), 74.34 (CH2), 151.89 (CO), 172.09 (CO). FAB+-
MS m/z (C22H42N6O4S2, 518): 519 (M + H+).
3209 (nNH), 1700 (nCO), 1651 (nCO). FAB+-MS m/z
(C24H26N6O8S2, 590): 591 (M + H+).
[15]aneS2ON2–(CONHCOPh)2 (11). Using the same proce-
dure as outlined for the preparation of 1, [15]aneN2OS2 (0.273
g, 1.09 mmol) and benzoylisocyanate (0.321 g, 2.18 mmol)
afforded 0.58 g (98%) of the product after crystallisation from
the reaction mixture by trituration with hexane. Anal. calc. for
C26H32N4O5S2: C, 57.33; H, 5.92; N, 10.29%. Found: C,
57.58; H, 5.96; N, 9.68%. 1H-NMR (CDCl3): d (ppm) =
2.79 (m, 4H, CH2), 3.01 (m, br, 4H, CH2), 3.63 (m, 4H, CH),
3.77 (m, 8H, CH), 7.46 (m, 6H, Ph), 7.81 (t, 4H, Ph), 9.05 (s,
2H, NH). 13C-NMR (CDCl3): d (ppm) = 31.17 (CH2), 31.97
(CH2), 43.41 (CH2), 49.55 (CH2), 72.12 (CH2), 127.29, 128.09
(CH), 128.39 (CH), 132.46 (CH), 132.84 (Cquat), 133.24
(Cquat), 154.00 (br, CO), 166.98 (CO). IR (cmÀ1) 3232
(nNH), 1713 (nCO), 1652 (nCO). FAB+-MS m/z
(C26H32N4O5S2, 544): 545 (M + H+).
[12]aneS2ON2–(CH2CONHCONH–tBu)2 (15). Using the
same procedure as outlined for the preparation of 12,
[15]aneN2OS2 (0.945 g, 3.78 mmol) and 1-tert-butyl-3-
(chloroacetyl)urea (1.45 g, 7.55 mmol) afforded 1.49 g (67%)
of the product as white solid after drying under reduced
pressure. Anal. calc. for C24H46N6O5S2, C, 51.22; H, 8.24;
1
N, 14.93%. Found: C, 50.88; H, 8.12; N, 14.52%. H-NMR
(CDCl3): d (ppm) 1.34 and 1.35 (s, 18H, CMe3), 2.79 (m, 16H,
CH2), 3.17 (s, 4H, CH2), 3.70 (m, 4H, CH2), 8.19 (br, s, 2H,
NH), 9.19 (br, s, 2H, NH). 13C-NMR (CDCl3): d (ppm) =
28.80 (CMe3), 30.09 (CH2), 31.87 (CH2), 50.70 (CMe3), 51.99
(CH2), 55.33 (CH2), 59.36 (CH2), 73.00 (CH2), 151.20 (CO),
172.48 (CO). IR (cmÀ1) 3289 br (nNH), 1715 (nCO), 1552
(nCO). FAB+-MS m/z (C24H46N6O5S2, 562): 563 (M + H+).
[12]aneS2ON–CH2CONHCONH–tBu (12). To a suspension
of K2CO3 (0.33 g, 2.39 mmol), and KI (0.63 g) in CH3CN (30
mL) was added [12]aneNOS2 (0.33 g, 1.59 mmol) and 1-tert-
butyl-3-(chloroacetyl)urea (0.31 g, 1.59 mmol) and the mixture
heated at reflux for 3 h. The solvent was removed and the
resulting solid extracted with dichloromethane and washed
with water, brine and finally dried over MgSO4. After filtra-
tion and removing the solvent the product was obtained as
white solid (0.35 g, 60%) which was recrystallised from
methanol. Anal. calc. for C15H29N3O3S2 Á H2O, C, 47.22; H,
8.14; N, 11.01% Found: C, 47.58; H, 7.78; N, 10.55%. 1H-
NMR (CDCl3): d (ppm) 1.37 (s, 9H, CMe3), 2.72 (m, 4H,
CH2), 2.84 (m, 8H, CH2), 3.76 (m, 4H, CH2), 3.21 (s, 2H,
CH2), 8.21 (br, s, 1H, NH), 9.32 (br, s, 1H, NH). 13C-NMR
(CDCl3): d (ppm) = 28.86 (CMe3), 29.10 (CH2), 30.86 (CH2),
50.69 (CMe3), 52.58 (CH2), 59.68 (CH2), 74.34 (CH2), 151.09
(CO), 172.94 (CO). IR (cmÀ1) 3250 (nNH), 1716 (nCO), 1652
(nCO). FAB+-MS m/z (C15H29N3O3S2, 363): 364 (M + H+).
[15]aneS3N2–(CH2CONHCONH–tBu)2 (16). Using the
same procedure as outlined for the preparation of 12,
[15]aneN2S3 (0.46 g, 1.74 mmol) and 1-tert-butyl-3-
(chloroacetyl)urea (0.67 g, 3.48 mmol) afforded 0.66 g (66%)
of the product as a white solid after chromatography on silica-
60 (dichloromethane–methanol 10 : 1 eluent) and drying under
reduced pressure. Large crystals were obtained by recrystalli-
sation from 1,2-dichloroethane/hexane. Anal. calc. for
C24H46N6O4S3, C, 49.80; H, 8.01; N, 14.52%. Found: C,
1
49.79; H, 7.99; N, 14.43%. H-NMR (CDCl3): d (ppm) 1.36
(s, 18H, CMe3), 2.81 (m, 20H, CH2), 3.22 (s, 4H, CH2), 8.19
(br, s, 2H, NH), 9.29 (br, s, 2H, NH). 13C-NMR (CDCl3): d
(ppm) = 28.81 (CMe3), 29.96 (CH2), 32.54 (CH2), 32.83
(CH2), 50.75 (CMe3), 52.76 (CH2), 55.36 (CH2), 58.64
(CH2), 151.29 (CO), 172.41 (CO). IR (cmÀ1) 3287, 3232
(nNH), 1712 (nCO), 1550 (nCO). FAB+-MS m/z
(C24H46N6O4S3, 578): 579 (M + H+).
[12]aneS3N–CH2CONHCONH–tBu (13). To a suspension
of K2CO3 (1.60 g, 11.5 mmol), and KI (5 mg) in CH3CN (50
mL) was added [12]aneNS3 (1.46 g, 6.54 mmol) and 1-tert-
butyl-3-(chloroacetyl)urea (1.26 g, 6.54 mmol) and the mixture
heated at reflux for 2.5 h. The solvent was removed and the
resulting solid extracted with dichloromethane, concentrated
and triturated with diethyl ether to afford 0.159 g (64%) of the
product as a white powder after isolation by filtration, wash-
ing with diethyl ether and drying under reduced pressure.
Anal. calc. for C15H29N3O2S3, C, 47.46; H, 7.70; N, 11.07%.
[12]aneS2ON–CH2CONHCONHPh (17). Using the same
procedure as outlined for the preparation of 12, [12]aneNOS2
(0.268 g, 1.29 mmol) and 1-phenyl-3-(chloroacetyl)urea (0.275
g, 1.29 mmol) afforded 0.66 g (66%) of the product as an
orange solid after chromatography on silica-60 (dichloro-
methane–methanol 20 : 1 eluent) and drying under reduced
pressure. Anal. calc. for C17H25N3O3S2, C, 53.24; H, 6.57; N,
10.96%. Found: C, 52.79; H, 6.18; N, 10.61%. 1H-NMR
(CDCl3): d (ppm) 2.75 (m, 4H, CH2), 2.93 (m, 8H, CH2),
3.32 (s, 2H, CH2), 3.81 (m, 4H, CH2), 7.09 (t, 1H, Ph), 7.32 (t,
2H, Ph), 7.53 (d, 2H, Ph), 9.83 (br, s, 1H, NH), 10.35 (br, s,
1H, NH). 13C-NMR (CDCl3): d (ppm) = 29.36 (CH2), 30.85
(CH2), 52.75 (CH2), 59.57 (CH2), 73.98 (CH2), 120.02 (Cquat),
123.96 (CH), 128.78 (CH), 137.18 (Cquat), 149.87 (CO), 173.48
(CO). IR (cmÀ1) 3239 (nNH), 1712 (nCO), 1683 (nCO).
FAB+-MS m/z (C17H25N3O3S2, 383): 384 (M + H+).
1
Found: C, 47.13; H, 7.49; N, 10.91%. H-NMR (CDCl3): d
(ppm) 1.39 (s, 9H, CMe3), 2.67 (m, 4H, CH2), 2.78 (m, 4H,
CH2), 2.83 (s, 8H, CH2), 3.18 (s, 2H, CH2), 8.16 (br, s, 1H,
NH), 8.98 (br, s, 1H, NH). FAB+-MS m/z (C15H29N3O2S3,
379): 380 (M + H+).
[12]aneS2N2–(CH2CONHCONH–tBu)2 (14). Using the
same procedure as outlined for the preparation of 12,
[12]aneN2S2 (0.27 g, 1.31 mmol) and 1-tert-butyl-3-(chloro-
acetyl)urea (0.50 g, 2.62 mmol) afforded 0.39 g (57%) of the
product as a pale-yellow solid after drying under reduced
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[12]aneS3N–CH2CONH–tBu (18). Using the same proce-
dure as outlined for the preparation of 12, [12]aneNS3
(0.0498 g, 0.424 mmol) and N-tert-butyl-2-chloroacetamide
(0.0635 g, 0.424 mmol) afforded 0.13 g (91%) of the product as
a white crystalline solid. An analytically pure sample was
obtained by recrystallisation from a dichloromethane–hexane
mixture. Anal. calc. for C14H28N2OS3, C, 49.96; H, 8.38; N,
8.32%. Found: C, 49.64; H, 8.44; N, 8.33%. 1H NMR
(CDCl3): d (ppm) 1.38 (s, 9H, CMe3), 2.69 (m, 8H, CH2),
2.83 (m, 8H, CH2), 2.96 (s, 2H, CH2), 7.22 (br, s, 1H, NH).%.
1H-NMR (d3-MeCN): d (ppm) 1.35 (s, 9H, CMe3), 2.67 (s, br,
8H, CH2), 2.78 (s, br, 8H, CH2), 2.88 (s, 2H, CH2), 7.18 (br, s,
1H, NH). 13C-NMR (CDCl3): d (ppm) = 27.31 (CH2), 28.36
(CH2), 28.72 (CMe3), 29.50 (CH2), 50.94 (CMe3), 53.05 (CH2),
59.26 (CH2), 169.36 (CO). IR (cmÀ1) 3252 (nNH), 3079
(nNH), 1646 (nCO), 1572 (nCO). FAB+-MS m/z
(C14H28N2OS3, 336): 337 (M + H+).
= 30.68 (CH2), 31.13 (CH2), 53.19 (CH2), 60.05 (CH2), 73.61
(CH), 119.43 (Cquat), 123.84 (CH), 128.74 (CH), 137.92 (Cquat),
169.53 (CO). IR (cmÀ1) 3220 (nNH), 1686 (nCO), 1600 (nCO).
FAB+-MS m/z (C16H24N2O2S2, 340): 341 (M + H+).
[15]aneS2ON2–(CH2CONHPh)2 (22). Using the same pro-
cedure as outlined for the preparation of 12, [15]aneN2OS2
(0.192 g, 0.767 mmol) and N-phenyl-2-chloroacetamide (0.260
g, 1.53 mmol) afforded 0.23 g (58%) of the product as pale
yellow oil after chromatography on silica-60 (dichloromethane
–methanol 40 : 1 eluent) and drying under reduced pressure.
Anal. calc. for C26H36N4O3S2 Á 0.2CH2Cl2, C, 58.96; H, 6.87;
1
N, 10.50%. Found: C, 59.28; H, 6.64; N, 11.02%. H-NMR
(CDCl3): d (ppm) 2.83 (m, 12H, CH2), 2.96 (m, 4H, CH2), 3.20
(s, 4H, CH2), 3.75 (m, 4H, CH2), 7.07 (t, 2H, Ph), 7.28 (t, 4H,
Ph), 7.60 (d, 4H, Ph), 9.29 (br, s, 2H, NH). 13C-NMR
(CDCl3): d (ppm) = 30.09 (CH2), 32.14 (CH2), 52.12 (CH2),
55.10 (CH2), 60.32 (CH2), 71.49 (CH2), 119.40 (Cquat), 123.99
[15]aneS3N2–(CH2CONH–tBu)2 (19). Using the same pro-
cedure as outlined for the preparation of 12, [15]aneN2S3
(0.0763 g, 0.286 mmol) and N-tert-butyl-2-chloroacetamide
(0.086 g, 0.573 mmol) afforded 0.12 g (85%) of the product as
a white wax. After chromatography on silica-60 (dichloro-
methane–methanol 10 : 1 eluent) and drying under reduced
pressure, the product obtained appeared pure by NMR spec-
troscopy. Anal. calc. for C22H44N4O2S3 Á CH3OH, C, 52.04; H,
9.22; N, 10.68% Found: C, 52.56; H, 8.71; N, 10.09%. 1H-
NMR (CDCl3): d (ppm) 1.31 (s, 18H, CMe3), 2.62–2.80 (m,
20H, CH2), 2.94 (s, 4H, CH2), 7.06 (br, s, 2H, NH). 13C-NMR
(CDCl3): d (ppm) = 28.70 (CMe3), 30.40 (CH2), 32.83 (CH2),
50.67 (CMe3), 52.28 (CH2), 54.98 (CH2), 60.15 (CH2), 169.50
(CO). FAB+-MS m/z (C22H44N4O2S3, 492): 493 (M + H+).
(CH), 128.74 (CH), 137.48 (Cquat), 168.68 (CO). IR (cmÀ1
)
3300 (nNH), 1678 (nCO), 1598 (nCO). FAB+-MS m/z
(C26H36N4O3S2, 516): 517 (M + H+).
[15]aneS3N2–(CH2CONHPh)2 (23). Using the same proce-
dure as outlined for the preparation of 12, [15]aneN2S3 (0.215
g, 0.807 mmol) and N-phenyl-2-chloroacetamide (0.274 g, 1.62
mmol) afforded 0.30 g (70%) of the product as a white solid
after washing with acetone and drying under reduced pressure.
Anal. calc. for C26H36N4O2S3, C, 58.61; H, 6.81; N, 10.52%.
1
Found: C, 58.41; H, 6.52; N, 10.35%. H-NMR (CDCl3): d
(ppm) 2.90 (m, 20H, CH2), 3.24 (s, 4H, CH2), 7.10 (t, 2H, Ph),
7.32 (t, 4H, Ph), 7.63 (d, 4H, Ph), 9.29 (br, s, 2H, NH). 13C-
NMR (CDCl3): d (ppm) = 31.03 (CH2), 33.13 (CH2), 33.20
(CH2), 52.45 (CH2), 55.15 (CH2), 60.00 (CH2), 119.52 (Cquat),
124.43 (CH), 128.96 (CH), 137.62 (Cquat), 168.64 (CO). IR
(cmÀ1) 3291 (nNH), 3256 (nNH), 1685 (nCO), 1597 (nCO).
FAB+-MS m/z (C26H36N4O2S3, 532): 533 (M + H+).
[12]aneS3N–CH2CONHPh (20). Using the same procedure
as outlined for the preparation of 12, [12]aneNS3 (0.133 g,
0.595 mmol) and N-phenyl-2-chloroacetamide (0.101 g, 0.595
mmol) afforded 0.17 g (80%) of the product as pale yellow wax
after chromatography on silica-60 (dichloromethane–metha-
nol 40 : 1 eluent) and drying under reduced pressure. Anal.
calc. for C16H24N2OS3, C, 53.89; H, 6.78; N, 7.86%. Found:
C, 54.00; H, 6.53; N, 7.65%. 1H-NMR (CDCl3): d (ppm)
2.64–2.84 (m, 16H, CH2), 3.17 (s, 2H, CH2), 7.07 (t, 1H, Ph),
7.30 (t, 2H, Ph), 7.67 (d, 2H, Ph), 9.41 (br, s, 1H, NH). 13C-
NMR (CDCl3): d (ppm) = 27.52 (CH2), 28.35 (CH2), 29.52
(CH2), 58.66 (CH2), 119.35 (Cquat), 123.96 (CH), 128.73 (CH),
137.59 (Cquat), 168.32 (CO). IR (cmÀ1) 3225 (nNH), 1685
(nCO), 1601 (nCO). FAB+-MS m/z (C16H24N2OS3, 356):
357 (M + H+).
[15]aneS3N2–CH2CONHPh (24). A solution of N-phenyl-2-
chloroacetamide (0.295 g, 1.74 mmol) in acetonitrile (30 mL)
was added dropwise to a rapidly stirred suspension of K2CO3
(0.240 g, 1.74 mmol) in acetonitrile (40 mL) containing
[15]aneN2S3 (0.463 g, 0.174 mmol) at 50 1C. After the addition
was complete the mixture was stirred at 50 1C overnight and
the solvent was evaporated, water added and the products
were extracted into dichloromethane and purified by column
chromatography on silica-60 (dichloromethane–methanol 14 :
1 eluent) to afford 0.3 g (43%). An analytically pure sample
was obtained by recrystallisation from a 1,2-dichloroethane
–hexane mixture. Anal. calc. for C18H29N3OS3, C, 54.10; H,
1
[12]aneS2ON–CH2CONHPh (21). Using the same proce-
dure as outlined for the preparation of 12, [12]aneNOS2 (0.158
g, 0.762 mmol) and N-phenyl-2-chloroacetamide (0.129 g,
0.762 mmol) afforded 0.18 g (70%) of the product as pale
yellow wax after chromatography on silica-60 (dichloromethane
–methanol 12 : 1 eluent) and drying under reduced pressure.
Anal. calc. for C16H24N2O2S2, C, 56.44; H, 7.10; N, 8.23%.
Found: C, 57.59; H, 7.20; N, 8.09%. 1H-NMR (CDCl3): d
(ppm) 2.75 (m, 4H, CH2), 2.80–2.96 (m, 8H, CH2), 3.26 (s, 2H,
CH2), 3.78 (m, 4H, CH2), 7.10 (t, 1H, Ph), 7.31 (t, 2H, Ph), 7.71
(d, 2H, Ph), 9.78 (br, s, 1H, NH). 13C-NMR (CDCl3): d (ppm)
7.31; N, 10.51%. Found: C, 54.46; H, 7.19; N, 10.12%. H-
NMR (CDCl3): d (ppm) 2.83 (m, 20H, CH2), 3.25 (s, 2H,
CH2), 7.11 (t, 1H, Ph), 7.32 (t, 2H, Ph), 7.72 (d, 2H, Ph), 9.71
(br, s, 1H, NH). IR (cmÀ1) 3290 (nNH), 3205 (nNH), 1669
(nCO), 1598 (nCO). FAB+-MS m/z (C18H29N3OS3, 399): 400
(M + H+).
[Ag([12]aneS3N–CH2CONH-tBu)(NO3)][Ag(18)(NO3)]. To
18 (0.0233 g, 0.0692 mmol) in dichloromethane (0.5 mL) was
added AgNO3 (0.0118 g, 0.0692 mmol) in acetonitrile (1 mL)
and the mixture was heated gently until the white precipitate
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that formed had dissolved. The solution was allowed to cool
slowly and yielded the product (0.025 g, 71%) as a white
crystalline solid. Crystals suitable for X-ray diffraction were
grown by slow diffusion of Et2O into an acetonitrile solution
of [Ag(18)(NO3)]. Anal. calc. for C14H28AgN3O4S3, C, 33.20;
1
H, 5.57; N, 8.30%. Found: C, 33.20; H, 5.22; N, 8.08%. H-
NMR (d3-MeCN): d (ppm) 1.30 (s, 9H, CMe3), 2.86 (s, br,
16H, CH2), 3.02 (s, 2H, CH2), 6.53 (br, s, 1H, NH). IR (cmÀ1
)
3282 (nNH), 1657 (nCO), 1560 (nCO). FAB+-MS m/z
(C14H28AgN2OS3, 443): 443 (LAg+).
The synthesis of 25 has been reported previously.35
X-ray structure analyses
A summary of the crystal data and refinement parameters for
[12]aneS3N–CONHCOPh (1), [12]aneS3N–CSNHCOPh (2),
[12]aneS2ON–CONHCOPh (3), [12]aneS2ON–CH2CONH-
CONH-tBu (12), [12]aneS2ON2–(CH2CONHCONH-tBu)2
(15),10 [15]aneS3N2–(CH2CONHPh)2 (23) and [Ag(18)(NO3)]
is given in Table 3. The crystals were cooled using an Oxford
Cryosystems open-flow nitrogen crysostat.36 Data for 2 were
collected on a Stoe Stadi-4 four-circle diffractometer using o–y
scans while data for 1, 3, 12, 23 and [Ag(18)(NO3)] were
collected on a Bruker SMART1000 CCD area detector using
o scans. Data were corrected for Lorentz and polarisation
effects and absorption corrections were also applied. The
structures were solved by direct methods and subsequent
difference-Fourier syntheses.37,38 All non-H atoms were re-
fined anisotropically38 and all H-atoms were placed at calcu-
lated positions and thereafter refined riding on their parent
atoms with Uiso(H) = 1.2 Ueq(C). CCDC reference numbers
195912 and 607523–607528. For crystallographic data in CIF
or other electronic format see DOI: 10.1039/b609180f.
Acknowledgements
We thank the EPSRC and The University of Nottingham for
support, and the EPSRC National Mass Spectrometry service
at The University of Wales, Swansea for mass spectra. MS
gratefully acknowledges receipt of a Royal Society Wolfson
Merit Award and of a Royal Society Leverhulme Trust Senior
Research Fellowship. LFL acknowledges the Australian Re-
search Council for support.
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