Anion effects in selective bifunctional metal salt extractants based on aza-thioether macrocycles: Co-operative cation-anion binding?

Article abstract of DOI:10.1039/b210391p

The binding of AgX salts (X = NO₃^-, BF ₄^- and ClO₄^-) to [15]aneS ₂ON₂-(CH₂CONHCONH-^tBu)₂ (L¹) has been assessed by ¹H NMR spectroscopy. ¹H NMR titration studies of AgX with L¹ and related ligands are interpreted in terms of a range of metal-salt binding interactions. Anion binding occurs via a switching mechanism whereby co-ordination of a metal cation to L¹ breaks internal hydrogen-bonding to allow anions to bind to the inner urea hydrogen site on the attached pendant arm. No anion binding occurs in the absence of a bound metal ion. Crystal structures of two complexes L·AgNO₃ confirm this feature [for N-H ... ONO ₂, N ... O = 2.866(5)-2.940(5) A in L¹· AgNO₃], but also show chelate binding of the amide O-donor of the acylurea pendant arm to Ag¹ in the solid state. Two-phase metal extraction studies with AgX salts and L¹ confirm that the anion plays an important role, although it is likely that solubility of the resulting metal complexes in the organic phase is the predominant factor. A range of related amide substituted macrocycles has also been prepared and anion binding interactions appear strongest with those ligands containing the highest number of amide/urea units. At high anion concentrations, and in the presence of Ag', all of the ligands participate in anion-ligand interactions. The Royal Society of Chemistry 2003.

Full text of DOI:10.1039/b210391p

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Anion effects in selective bifunctional metal salt extractants based
on aza-thioether macrocycles: co-operative cation–anion binding?†
Mark W. Glenny, Alexander J. Blake, Claire Wilson and Martin Schröder*
School of Chemistry, The University of Nottingham, University Park, Nottingham,
UK NG7 2RD
Received 22nd October 2002, Accepted 9th January 2003
First published as an Advance Article on the web 23rd April 2003
The binding of AgX salts (X = NO3Ϫ, BF4Ϫ and ClO4Ϫ) to [15]aneS2ON2–(CH2CONHCONH–tBu)2 (L1) has been
assessed by 1H NMR spectroscopy. 1H NMR titration studies of AgX with L1 and related ligands are interpreted
in terms of a range of metal–salt binding interactions. Anion binding occurs via a switching mechanism whereby
co-ordination of a metal cation to L1 breaks internal hydrogen-bonding to allow anions to bind to the inner urea
hydrogen site on the attached pendant arm. No anion binding occurs in the absence of a bound metal ion. Crystal
structures of two complexes LؒAgNO3 confirm this feature [for N–H ؒ ؒ ؒ ONO2, N ؒ ؒ ؒ O = 2.866(5)–2.940(5) Å in
L1ؒAgNO3], but also show chelate binding of the amide O-donor of the acylurea pendant arm to Ag in the solid
state. Two-phase metal extraction studies with AgX salts and L1 confirm that the anion plays an important role,
although it is likely that solubility of the resulting metal complexes in the organic phase is the predominant factor.
A range of related amide substituted macrocycles has also been prepared and anion binding interactions appear
strongest with those ligands containing the highest number of amide/urea units. At high anion concentrations,
and in the presence of Ag, all of the ligands participate in anion–ligand interactions.
and an acylurea unit for metal and anion co-ordination,
Introduction
respectively, is effective for binding metal salts in the solid
state.17 The structure of AgNO3ؒ[12]aneS3N–CH2C(O)NHC-
(O)NH–tBu clearly shows the Ag ion co-ordinated inside the
Crown thioethers are now a well studied class of ligands with a
large body of associated work in the literature.1 Their co-ordin-
ation chemistry is diverse and results in many stable transition
metal complexes2 with unusual co-ordination geometries
and/or oxidation states for the metal centres.1,3 Their ability to
behave as selective metal extraction agents for ‘soft’ metal ions
such as mercury4 has also been reported. In contrast to pure
thioether macrocycles, the chemistry of aza-thioether macro-
cycles has been relatively neglected, although the parent macro-
Ϫ
[12]aneNS3 cavity and the NO3 anion interacting with the
amide functionality on the pendant arm. One of the problems
with molecules of this type, designed to interact with substrates
via hydrogen-bonding, is that there exists an inherent tendency
to form intramolecular hydrogen-bonds. This has been noted
in particular with other systems containing urea function-
alities10c,18 and is apparent in the systems described here. Inter-
actions of this type must be overcome if a heteroditopic host
is to function as an ion-pair receptor where intermolecular
hydrogen-bonding to anions is a key function. We report herein
structural examples of AgNO3ؒreceptor complexes and seek
to address some of the issues surrounding the action of the
receptors in solution.
cycles [9]aneNS2,5 [15]aneNS4,6 [12]aneN2S2 and several other
7
mixed-donor macrocycles8 have been reported. In addition, a
number of N-aryl substituted aza-thioether macrocycles are
known, some of which demonstrate selective Ag extraction and
transport.9 Incorporation of a secondary amine group directly
into the thioether macrocyclic ring allows facile functional-
isation and this is where our interest in these molecules
originates. Combining the ability of thioether macrocycles to
co-ordinate ‘soft’ metal ions, even under acidic conditions, with
anion binding sites allows the potential preparation of bifunc-
tional molecules for the binding and extraction of metal salts.
We have therefore targeted the synthesis of functional hetero-
ditopic molecules which can co-ordinate both the cation and
anion(s) of a metal salt and act as an ion-pair receptor. A few
species of this type already exist10 and may show co-operative
ion-pair binding where the complexation of the cation acts as a
switch for selective anion co-ordination.11 It is not uncommon
for these types of systems to utilise the well established co-
ordinative ability of hosts such as crown ethers and calixarenes
combined with anion receptors such as Schiff-base supported
uranyls,12 amides,1b,2,13 boryls14 and zinc porphyrins.15 These
compounds are generally only useful for the tandem com-
plexation of Group 1 halides and hydrogen phosphates and are
not applicable to the extraction of transition metal salts. How-
ever, Tasker and co-workers have recently reported16 the use of
zwitterionic salen-type ligands for binding transition metal
salts.
Results and discussion
Aza-thioether host ligands, L1–L10 (Fig. 1), were prepared by
reaction of the parent macrocycles with pre-formed anion bi-
nding units, e.g. 1-tert-butyl-3-(chloroacetyl)urea, N-tert-butyl-
2-chloroacetamide and N-phenyl-2-chloroacetamide (Fig. 2).
The resulting heteroditopic ligands were complexed with AgX
salts (X = NO3Ϫ, BF4Ϫ and ClO4Ϫ) and characterised by NMR
and infrared spectroscopy, mass spectrometry, elemental analy-
sis and, in some cases, by single crystal X-ray diffraction.
The AgNO3 complex of the acylurea derivatised macrocycle
[15]aneS2ON2–(CH2CONHCONH–tBu)2 (L1) was obtained by
reaction of the macrocycle with AgNO3 in MeCN solution.
Analytical data indicated that the 1:1 complex, L1ؒAgNO3,
1
had been isolated and H NMR titration of L1 with AgNO3
(between 0.125 and 0.875 mol fraction of silver nitrate) con-
firmed the formation of a 1:1 complex in deuterated MeCN
solution.19 The signals for the macrocyclic methylene hydrogens
adjacent to sulfur atoms are observed to shift downfield in the
1H NMR spectrum of the complex (d3-MeCN) by 0.1 ppm with
respect to the free ligand, while the pendant arm methylene
hydrogen signal is shifted downfield by 0.32 ppm. While these
shifts are indicative of metal ion binding to the macrocycle, our
main interest was centred on the urea functionality and whether
the NO3Ϫ anion interacts to any degree with the urea hydrogens.
We have already demonstrated that our component-based
system, which contains both an aza-thioether macrocyclic unit
† Based on the presentation given at Dalton Discussion No. 5, 10–12th
April 2003, Noordwijkerhout, The Netherlands.
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1941

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Fig. 1 Structures of ligands L1–L10.
Fig. 3 Crystal structure of L1 showing the twisted conformation of
the pendant arms, intramolecular hydrogen-bonding and exo arrange-
ment of the N and S donor atoms. Displacement ellipsoids are drawn at
the 50% probability level.
Ϫ
hydrogen-bond to the NO3 anion formed. It is usual for
anion–amide/urea interactions to result in a downfield shift of
1
the urea hydrogen signals in H NMR spectra,20 the degree of
1
shift indicating the strength of the interaction. The H NMR
spectrum of L1ؒAgNO3 in d3-MeCN shows that one of the
acylurea hydrogen signals is shifted downfield by 0.33 ppm with
respect to the free ligand while the other urea hydrogen signal is
shifted upfield by 0.20 ppm. The observation of a downfield
shift is consistent with an anion–urea interaction; however, the
magnitude of the shift indicates that the interaction may be a
weak one, while the upfield shift of the other urea hydrogen
signal indicates weakening or breaking of an existing hydrogen-
bond.
Fig. 2 Synthesis of ligands L1–L10.
In all of the receptors we have prepared so far, internal
hydrogen-bonds are consistently observed between the macro-
cyclic nitrogen atom and urea or amide hydrogen atoms in the
pendant group. In the systems containing acylurea pendant
groups, such as L1, an additional intramolecular hydrogen-
bond exists between the outermost urea hydrogen and the acyl
oxygen thus holding the urea in a twisted conformation, i.e.
hydrogens pointing in opposite directions (Fig. 2). A crystal
structure of L1 (Fig. 3) was obtained and clearly shows the pres-
ence of both types of hydrogen-bond. In order for anion
binding to the urea to occur in L1ؒAgNO3, at least one of the
intramolecular hydrogen-bonds must be broken and a new
Owing to the exo arrangement of the donor atoms in L1
(Fig. 3), reorganisation of the donors to an endo conformation
is necessary to accommodate a metal cation. If, as is likely, the
macrocyclic N-donors bind the metal ion the hydrogen-bonds
to the urea moieties which are present in the free ligand will be
broken upon coordination. This then is the necessary mechan-
ism whereby the previously unavailable inner urea hydrogens
are released to interact with anions in solution (Fig. 4). This is
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1942

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Table 1 1H NMR chemical shifts (ppm) of L1ؒAgX complexes (d3-MeCN)
Entry
Experiment
NHinner
NHouter
CH2 pendant
1
2
3
4
5
6
7
8
9
10
11
12
13
L1
9.09
8.26
8.41
9.42
9.09
9.52
8.56
8.51
8.26
8.80
9.20
8.26
8.26
8.22
7.99
8.00
8.02
8.22
8.38
8.02
8.02
7.99
8.04
8.12
7.99
7.99
3.21
3.34
3.37
3.53
3.21
3.25
3.39
3.38
3.34
3.43
3.40
3.34
3.34
L1 ϩ AgBF4
L1 ϩ AgClO4
L1 ϩ AgNO3
L1 ϩ n-Bu4NO3
L1 ϩ n-Bu4N(Ar)a
L1 ϩ AgNO3 ϩ 3 equiv. n-Bu4BF4
L1 ϩ AgNO3 ϩ 8 equiv. n-Bu4BF4
L1 ϩ AgBF4 ϩ 1 equiv. n-Bu4NO3
L1 ϩ AgBF4 ϩ 3 equiv. n-Bu4NO3
L1 ϩ AgBF4 ϩ 13 equiv. n-Bu4NO3
L1 ϩ AgBF4 ϩ 2 equiv. AgNO3
L1 ϩ AgNO3 ϩ 2 equiv. AgBF4
a Ar = 4-nitrobenzoate.
basis of the reorganisation mechanism involving binding of Ag
and disruption of internal hydrogen-bonding. This then allows
us to use the chemical shift of the inner urea hydrogens in the
L1ؒAgBF4 complex as a base value to compare the relative
strengths of other anion interactions with the receptor. Upfield
shifts of 0.68 and 0.22 ppm for the inner and outer hydrogens,
respectively, were also observed upon addition of AgClO4 to L1.
However, the shift for the inner urea hydrogen is less than that
observed in the presence of AgBF4, indicating that a weak
interaction may exist between ClO4Ϫ and the inner urea hydro-
gens. Examination of the chemical shift data (Table 1) of the
outer urea hydrogen in all three complexes L1ؒAgX (X = BF4 ,
Ϫ
Ϫ
Ϫ
Fig. 4 Proposed rearrangement whereby co-ordination of Ag()
releases previously unavailable urea hydrogens for hydrogen-bonding to
anions.
ClO4 and NO3 ) shows that it is almost invariant in the pres-
ence of different anions, δ 8.00 0.02. This is clear evidence
that this outer hydrogen is taking very little part in interactions
with the anions.
consistent with the downfield shift observed in the NMR spec-
trum of L1ؒAgNO3. Although this mechanism does not explain
the upfield shift of the remaining outer urea signal, the fact that
only one urea hydrogen appears to be involved in an interaction
is consistent with the twisted conformation observed in the
solid state of the free ligand being maintained in solution.
To elucidate the solution dynamics of the system, 1H
NMR titration experiments with AgBF4, AgClO4, n-Bu4NNO3,
n-Bu4NBF4 and n-Bu4N(4-nitrobenzoate) in deuterated MeCN
were conducted. Addition of n-Bu4NNO3 (10-fold excess) to L1
afforded no shift of the urea hydrogens, whereas addition of
one equivalent of n-Bu4N(4-nitrobenzoate)21 produced sig-
nificant downfield shifts (0.43 and 0.16 ppm, respectively, for
the inner and outer hydrogens). The observation of downfield
shifts for both urea hydrogens in the latter experiment indicates
that the twisted conformation of the pendant group can be
altered by the presence of a strongly binding substrate. Import-
antly, however, no hydrogen-bonds appear to be broken or
With this evidence in mind it would appear that the
downfield shift of the inner urea hydrogens observed in L1ؒ
AgNO3 indicates that NO3Ϫ is bound much more strongly than
Ϫ
ClO4 . It should, therefore, be possible to carry out titration
experiments to determine anion binding constants by firstly
preparing the complex L1ؒAgBF4 and titrating this with tetra-
alkylammonium salts of the anions of interest. Preliminary
experiments carried out to test this using L1ؒAgBF4 resulted in
downfield shifts of the inner urea hydrogen signal on addition
Ϫ
of NO3 . However, this was complicated by the outcome of
analogous experiments carried out by titrating L1ؒAgNO3 with
n-Bu4NBF4, which resulted in upfield shifts of the inner urea
hydrogens. Upfield shifts were also observed upon addition of
AgBF4 to L1ؒAgNO3, whereas no shift was observed when
AgNO3 was added to L1ؒAgBF4. This suggests that despite the
appearance of stronger anion binding in the case of L1ؒAgNO3,
the complex L1ؒAgBF4 appears to be more stable under certain
conditions. It is not easy to interpret these results in a simple
manner because of the various competing equilibria occurring
in solution, although by careful choice of metal salt and the use
of certain assumptions the results become more meaningful.
Fig. 5 shows the various equilibria involved in ion-pair binding
for a neutral ligand with a Ag salt in non-aqueous solvents. If
the metal salt is soluble in the solvent used then K1 can be
ignored. Likewise, if the metal is assumed to be always bound
to the receptor, which is highly likely given the high selectivity
of thioethers for Ag, then K2, K3, K4 and K6 can all be ignored.
This leaves only K5, which we are interested in and would like to
measure, and ion-pairing as the major equilibrium processes in
solution.
Ϫ
formed upon addition of NO3 to L1. This is in accord with
the mechanism requiring metal-induced reorganisation of the
macrocycle to release the inner urea hydrogens and allow anion
binding to occur. Hence, this system involves an ion-switch
resulting in co-operative binding of the metal salt. There also
appears to be very little aggregation of the molecules in MeCN
solution, the only shift observed in the 1H NMR spectrum of L1
upon 100-fold dilution being a downfield shift of 0.06 ppm for
the inner urea hydrogens. This represents further evidence that
the twisted structure of the free receptor incorporating strong
intramolecular hydrogen-bonding is maintained in solution.
Addition of one equivalent of AgBF4 to L1 results in both
urea hydrogen signals shifting upfield (0.83 and 0.23 ppm
respectively for the inner and outer hydrogens), whereas addi-
tion of an 8-fold excess has no further major effect on the
1
Further examination of the higher field region of the H
NMR spectrum where the macrocyclic methylene signals occur
provides further insight into the differences in binding of the
different anions. Two distinct patterns are observed for the
macrocyclic methylene hydrogens: one is common to both L1ؒ
AgBF4 and L1ؒAgClO4, and the other is observed for L1ؒ
Ϫ
observed chemical shift. Assuming negligible urea–BF4 inter-
actions, the direction and magnitude of shift of the inner urea
hydrogens in the complex L1ؒAgBF4 can be understood on the
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
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Fig. 5 Equilibria involved in silver salt ion-pair binding with neutral
ligands.
Fig. 7 Proposed anion interactions with acylurea substituted macro-
cycles (single pendant arm and condensed view of macrocycle shown
for simplicity).
competing anions, which must be accompanied by some type of
reorganisation, will be favourable if the overall entropy of the
system is increased [eqns. (1) and (2)].
L1ؒAgNO3 ϩ xsAgϩ ϩ xsBF4
Ϫ
L1ؒAgϩ ϩ xsBF4Ϫ ϩ xsAgϩ ϩ NO3
(1)
(2)
Ϫ
L1ؒAgNO3 ϩ xsn-Bu4Nϩ ϩ xsBF4
Ϫ
L1ؒAgϩ ϩ xsBF4Ϫ ϩ xsn-Bu4Nϩ ϩ NO3
Ϫ
While the mechanism for this type of rearrangement is not
obvious, the driving force may be related to the amount of ion-
pairing between the various species in solution. Previous studies
have shown that in polar aprotic solvents, AgNO3 is more
highly ion-paired than AgBF4; and likewise, for the tetraalkyl-
Ϫ
ammonium salts, NO3 salts appear to be more highly ion-
paired.22 Thus, release of NO3 on addition of anions to
Ϫ
L1ؒAgNO3 may reflect the greater ion-pairing of NO3 salts.
Ϫ
However, without calorimetric measurements the entropic and
enthalpic contributions are difficult to establish.
The exact structure of L1ؒAgNO3 in solution is difficult to
ascertain due to the number of possible donors. Thus, macro-
cyclic N-, O- and S-donors, acyl O-, urea H-centres, anion and
solvent may all play a role. Fortunately, a single crystal of L1ؒ
AgNO3 suitable for X-ray diffraction was obtained by slow dif-
fusion of Et2O into a solution of the complex in MeCN. Based
on the solution NMR data, we might have expected to observe
1
Fig. 6 Macrocyclic methylene resonances in the H NMR spectra of
L1ؒAgNO3 (top) and L1ؒAgBF4 (bottom).
AgNO3 (Fig. 6). In addition, the signal attributed to the pendant
arm methylene units of the L1ؒAgNO3 complex is shifted
an interaction between a NO3 anion and the Ag and urea
Ϫ
Ϫ
Ϫ
considerably downfield compared with the BF4 and ClO4
centres. This, however, is not observed yet the infrared spectrum
of the compound displays a peak at 1384 cmϪ1 (νNO) which is
unshifted from that of AgNO3 (KBr disc).
complexes. Both of these observations are consistent with the
co-ordination about Ag and/or the conformation of the ligand
being different in the presence of different anions. There
are several types of interaction that an anion may have with a
heteroditopic ligand such as L1, and these are shown schematic-
ally in Fig. 7 with D representing little or no interaction of the
anion with the complex cation. On the basis of the previous
discussion and of the changes in chemical shift upon titration
of the complexes with anions, we believe that the complex L1ؒ
AgNO3 is best represented by A or B, whereas L1ؒAgClO4 is
compatible with B or C. We assign D as a default structure to
L1ؒAgBF4. Obviously these are the extreme situations in solu-
tion and two or more of these structures may be in equilibrium,
yet this proposal does offer an explanation to the previously
puzzling order in stability of the complexes. On purely entropic
The crystal structure of L1ؒAgNO3 shows the asymmetric
unit (Fig. 8) to consist of two independent complexes linked
through two Ag–S bonds [Ag(1)–S(1) and Ag(2)–S(4);
3.1453(17) and 2.7343(15) Å, respectively (see Table 2)]. There
is a hydrogen-bond between a urea hydrogen on one com-
plex unit and a macrocyclic oxygen on the other [for N(5)–
H(5A) ؒ ؒ ؒ O(6), N ؒ ؒ ؒ O = 2.867(5) Å]. The structural core is
shown in Fig. 9. All outer urea hydrogens are involved in intra-
molecular hydrogen-bonding to the acyl oxygen of the same
pendant arm, while the inner urea hydrogens, except H(5A)
which is involved in intermolecular bonding, interact with
Ϫ
NO3 oxygen atoms [for N(3)–H(3A) ؒ ؒ ؒ O(1A), N(9)–
H(9C) ؒ ؒ ؒ O(5A) and N(11)–H(11A) ؒ ؒ ؒ O(6A), N ؒ ؒ ؒ O
2.867(5), 2.940(5) and 2.866(5) Å, respectively]. This is consist-
Ϫ
grounds, release of the NO3 anion upon the introduction of
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1944

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Fig. 8 Crystal structure of L1ؒAgNO3 showing hydrogen-bonding between urea hydrogens and nitrate anions and intramolecular hydrogen-bonds.
All non-urea hydrogens have been omitted for clarity and displacement ellipsoids are shown at the 50% probability level.
Table 2 Selected bond lengths (Å), angles (Њ) for L1ؒAgNO3
Ag(1)–N(7)
Ag(1)–N(8)
Ag(1)–O(9)
Ag(1)–S(1)
Ag(1)–S(3)
Ag(1)–S(4)
2.610(3)
2.495(3)
2.505(3)
3.1453(17)
2.6014(14)
2.5495(13)
Ag(2)–N(1)
Ag(2)–N(2)
Ag(2)–S(1)
Ag(2)–S(2)
Ag(2)–S(4)
Ag(2)–O(2)
2.454(3)
2.555(4)
2.7069(14)
2.6700(14)
2.7343(15)
2.708(3)
N(7)–Ag(1)–N(8)
N(7)–Ag(1)–O(9)
N(7)–Ag(1)–S(1)
N(7)–Ag(1)–S(3)
N(7)–Ag(1)–S(4)
N(8)–Ag(1)–O(9)
N(8)–Ag(1)–S(1)
N(8)–Ag(1)–S(3)
N(8)–Ag(1)–S(4)
O(9)–Ag(1)–S(1)
O(9)–Ag(1)–S(3)
O(9)–Ag(1)–S(4)
S(1)–Ag(1)–S(4)
S(1)–Ag(1)–S(3)
S(3)–Ag(1)–S(4)
71.19(11)
90.57(10)
97.06(9)
151.25(8)
79.83(8)
68.74(11)
146.71(9)
80.87(8)
136.28(8)
80.69(8)
85.43(8)
144.79(8)
67.21(4)
110.29(5)
118.36(4)
N(1)–Ag(2)–N(2)
N(1)–Ag(2)–O(2)
N(1)–Ag(2)–S(1)
N(1)–Ag(2)–S(2)
N(1)–Ag(2)–S(4)
N(2)–Ag(2)–O(2)
N(2)–Ag(2)–S(1)
N(2)–Ag(2)–S(2)
N(2)–Ag(2)–S(4)
O(2)–Ag(2)–S(1)
O(2)–Ag(2)–S(2)
O(2)–Ag(2)–S(4)
S(1)–Ag(2)–S(2)
S(1)–Ag(2)–S(4)
S(2)–Ag(2)–S(4)
73.94(12)
67.62(11)
132.70(9)
79.63(9)
152.42(9)
98.70(11)
76.56(8)
151.98(8)
106.30(9)
153.90(7)
79.29(8)
85.37(8)
116.85(4)
71.80(4)
Fig. 9 Crystal structure of L1ؒAgNO3 showing the central core.
Hydrogen-bonding of H(5A) to the adjacent macrocyclic oxygen and
the long Ag(1)–S(1) interaction are clearly visible. All non-urea
hydrogens have been omitted for clarity and displacement ellipsoids are
shown at the 50% probability level.
101.40(5)
Ag(1)–S(1)–Ag(2) 101.32(5)
Ag(1)–S(4)–Ag(2) 118.20(5)
ent with the solution NMR data where only the inner urea
hydrogens take part in anion binding. Both complex units are
six co-ordinate with severely distorted octahedral geometries
about Ag, which is bound to both macrocyclic N-donors and
three S-donors, two of which are bridging. Significantly, an acyl
O-donor from two separate acylurea pendant arms binds to a
single Ag centre with the remaining two acyl O-donors
involved in intramolecular hydrogen-bonding to the outer urea
hydrogens within the pendant unit. The observed upfield shift
for the outer hydrogens by NMR spectroscopy in solution upon
complexation is therefore consistent with carbonyl binding to
the encapsulated Ag ion and concomitant weakening of the
internal hydrogen-bonds at the outer urea centres. The macro-
cyclic ether O-centre is not involved in any close contacts with
the Ag ions. Co-ordination of carbonyl moieties to Ag is fairly
common and many structures containing this fragment have
been reported23 with Ag–O bond distances ranging from 2.194
to 2.995 Å,24 placing the bonds in this structure at the upper end
of this range. Binding of the acyl O-donor can therefore be
superimposed onto the binding modes suggested in A–D
(Fig. 7), the solid-state structure suggesting that mode B may
predominate in solution. The intramolecular Ag–S bond dis-
tances range from 2.5495(13) to 2.7069(14) Å and are typical
values for thioether crowns,25 which are also known to form
clusters and oligomers with Ag in the solid state.26 A combin-
ation of stereochemical flexibility for both the Ag ion25,27 and
the macrocyclic ring is most likely responsible for the unusual
structure observed in the solid state.
The related macrocycle, [15]aneS3N2–(CH2CONHCONH–
tBu)2 (L2), where a sulfur donor replaces the ether oxygen in L1,
produces very similar results to those found for L1 with all the
Ag salts used. In all cases the direction and magnitude of shift
upon addition of these salts to L2 in d3-MeCN parallel that of
L1, indicating that this ligand also functions as a heteroditopic
ion-pair receptor for AgNO3 and AgClO4. Presumably, there-
fore, AgNO3 binds to L2 in a similar fashion to that proposed
for L1ؒAgNO3. L2 was treated with one equivalent of AgBF4 in
deuterated MeCN to give L2ؒAgBF4. Titration of L2ؒAgBF4
with n-Bu4NNO3, between 0.125 and 0.875 mole fraction of
Ϫ
NO3 , produced downfield shifts of the inner urea hydrogens as
Ϫ
expected. Preparation of a Job plot19 showed the NO3 com-
plex to be of 1:1 stoichiometry and the binding constant for
Ϫ
NO3 anion with L2ؒAgϩ was determined as 49
1 MϪ1 by
using the program EQNMR.28 This value is fairly large con-
sidering that anion binding is taking place in MeCN, and that
there is no preorganisation of the ligand. A highly preorganised
macrocyclic anion receptor, containing three thiourea units, has
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1945

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Fig. 10 Crystal structure of L2ؒAgNO3 showing hydrogen-bonding between urea hydrogens and nitrate anions and intramolecular hydrogen-bonds.
All non-urea hydrogens have been omitted for clarity and displacement ellipsoids are shown at the 50% probability level.
Table 3 Selected bond lengths (Å), angles (Њ) for L2ؒAgNO3
co-ordination number of Ag in this complex, although the
remaining Ag–S(2) distance is more typical at 2.568(4) Å.
As found in the structure of L1ؒAgNO3, the inner acylurea
hydrogens in L2ؒAgNO3 are involved in hydrogen-bonding
Ag–N(1)
Ag–N(2)
Ag–O(1)
Ag–O(3)
2.510(10)
2.471(10)
2.600(8)
Ag–S(1)
Ag–S(2)
Ag–S(3)
2.928(3)
2.568(4)
2.822(4)
Ϫ
interactions with NO3 anions of adjacent molecules [for
2.872(10)
N(3)–H(3C) ؒ ؒ ؒ O(1A) and N(5)–H(5C) ؒ ؒ ؒ O(2A), N ؒ ؒ ؒ O
2.926(14) and 2.917(15) Å, respectively] and the twisted con-
formation of the pendant arms is also observed. The hydrogen-
N(1)–Ag–S(1)
N(1)–Ag–S(2)
N(1)–Ag–S(3)
N(1)–Ag–N(2)
N(2)–Ag–S(1)
N(2)–Ag–S(2)
N(2)–Ag–S(3)
S(1)–Ag–S(2)
S(1)–Ag–S(3)
S(2)–Ag–S(3)
146.5(2)
134.4(2)
76.3(3)
74.2(3)
73.3(2)
146.7(2)
92.4(3)
78.95(10)
112.70(10)
81.60(11)
N(1)–Ag–O(1)
N(1)–Ag–O(3)
N(2)–Ag–O(1)
N(2)–Ag–O(3)
O(1)–Ag–O(3)
O(1)–Ag–S(1)
O(1)–Ag–S(2)
O(1)–Ag–S(3)
O(3)–Ag–S(1)
O(3)–Ag–S(2)
O(3)–Ag–S(3)
84.6(3)
62.3(3)
68.8(3)
131.5(3)
86.3(3)
76.5(2)
122.0(2)
156.3(2)
141.5(2)
81.7(2)
96.8(2)
Ϫ
bonds between urea groups and NO3 anions in this complex
are also typical for this kind of interaction, with values for
other structurally characterised examples usually lying in the
range 2.8–3.0 Å.33 As for L1ؒAgNO3, the NO3Ϫ stretching mode
in the IR spectrum of L2ؒAgNO3 is found at the same position
as that in AgNO3 (1384 cmϪ1).
Comparison of the bifunctionalised macrocycles L1 and L2
with related monofunctionalised ligands, containing only one
pendant unit, e.g. [12]aneS2ON–CH2CONHCONH–tBu (L10,
Fig. 1), indicates that anion binding is diminished when the
number of urea hydrogens available to bind anions is reduced.
A more thorough investigation of related tweezer-type anion
a binding constant for NO3 of 17.1 0.4 MϪ1 in DMSO,29
whereas a tweezer-type receptor containing only two (amide)
Ϫ
Ϫ
hydrogen-bonding sites has a binding constant for NO3 of
27 1.4 MϪ1 in CHCl3.30
receptors has suggested that the degree of NO3 binding is
Ϫ
Reaction of L2 with AgNO3 in MeCN and subsequent slow
diffusion of Et2O into a solution of the complex afforded small
colourless crystals suitable for X-ray diffraction. The crystal
structure of L2ؒAgNO3 shows the complex to be monomeric
with a seven co-ordinate Ag ion (Fig. 10). In L2ؒAgNO3,
both acyl oxygen atoms of the pendant arms are found to co-
ordinate to the encapsulated metal [Ag–O(1) 2.600(8), Ag–O(3)
2.872(10) Å (see Table 3)], the presence of the additional
S-donor in L2 inhibiting the formation of a dimer via bridging
sulfur centres in the solid state as observed in L1ؒAgNO3.
Potentially vacant co-ordination sites on one side of the metal
cation are filled by the acyl O-donors. Given the small but
highly dependent upon the number of hydrogen-bond donors,
with every additional hydrogen-bond adding around 2–3 kJ
molϪ1 to the free energy of complexation.30 Difficulties in
isolating a pure Ag complex product were experienced with
this particular ligand, which was used only in NMR titration
experiments. Substitution of the urea tert-butyl end group for a
phenyl group, as in [12]aneS2ON–CH2CONHCONHPh (L3),
results in the urea hydrogen resonances shifting downfield for
1
the free ligand by more than 1 ppm in the H NMR spectrum
due to inductive effects. Addition of AgNO3 to L3 results in a
large upfield shift for the outer urea hydrogen and a smaller
shift of the inner hydrogen, although upon addition of excess
AgNO3 the inner hydrogen signal begins to shift downfield
toward the value found for the free ligand. This suggests that as
the anion concentration is increased, anion binding becomes
more pronounced. No evidence was found for the presence of
LؒAgNO3 ion-pairs in the electrospray mass spectra for any
of the complexes.
1
significant upfield shift of the urea hydrogens in the H NMR
spectra of both L1ؒAgNO3 and L2ؒAgNO3, it is likely that this
Ag–O(acyl) interaction is also present in solution (MeCN), thus
weakening the intramolecular hydrogen-bond between this
oxygen and the nearby urea hydrogen centres.
Of the three main stereochemistries for seven co-ordinate
complexes – pentagonal bipyramidal, capped trigonal prismatic
and capped octahedral,31 all of which are very similar in energy
with a variety of intermediate structures available32 – the com-
plex L2ؒAgNO3 is probably best described as a slightly twisted
capped trigonal prism. One trigonal face consists of N(1), O(1)
and O(3), the other comprises S(1), S(2) and S(3) with N(2) as
the capping atom. Two of the Ag–S bond distances are long
[Ag–S(1) and Ag–S(3); 2.928(3) and 2.822(4) Å, respectively]
and lie well into the upper quartile of Ag–S distances in
thioether complexes.25 This may be a result of the high
Since the studies described so far indicated that the outer
urea hydrogen centres do not participate in anion binding
interactions, ligands were prepared which contain a single
amide function in the pendant arm (Fig. 1): [15]aneS3N2–
(CH2CONH–tBu)2 (L4), [12]aneS3N–CH2CONH–tBu (L5),
[15]aneS3N2–(CH2CONHPh)2
(L6),
[15]aneS3N2–CH2-
CONHPh (L7), [12]aneS3N–CH2CONHPh (L8) and [12]ane-
S2ON–CH2CONHPh (L9). The AgNO3 complexes of all six
ligands were prepared in an analogous manner to L1ؒAgNO3
and all showed upfield shifts in their amide hydrogen signals.
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1946

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However, small downfield shifts were observed with higher
L:AgNO3 ratios indicating possible anion–amide interactions
at high anion concentrations. Aggregation of the ligands does
not appear to be significant in MeCN solution since the pos-
cated by solution dynamics where, in the presence of competing
anions, new equilibria are established which act to reduce the
stability of the metal salt complexes formed. This is especially
noticeable with L1ؒAgNO3 where, despite the apparently large
anion binding strength, other factors take precedence in solu-
tion to form complexes where anion binding does not play a
predominant role in the overall complex stability. Both solution
and solid-state structural data are consistent with the inner
hydrogen of the acylurea pendant arms contributing to anion
binding, while an additional novel binding of the acyl O-donor
is confirmed in the solid state. The ligands are highly effective at
complexing Ag salts as shown by extraction studies, although
the effect of different anions on extraction ability is marked and
is probably related to the solubility of the resulting metal salt
complex in the organic phase.
1
ition and appearance of the signals in the H NMR spectrum
do not change to any great extent on dilution. The use of
Ϫ
IR spectroscopy to identify interactions of NO3 with the
ligands was not conclusive. This is due in part to the signifi-
cant changes which occur to the hydrogen-bonding network
upon Ag co-ordination, but it also appears that the hydrogen-
bonding observed in the crystal structure is too weak to have
Ϫ
a significant effect on the position of the NO3 stretching
frequency.
Extraction of silver
Owing to the high affinity of the ligands for Ag and the appar-
ent structural changes in the presence of different anions, we
were interested in the effect that this may have on the ability of
the ligands to extract different Ag salts in a two phase aque-
ous–organic system. Extraction studies were carried out with L2
Experimental
Aza-thioether parent macrocycles were prepared in our labor-
atory and all other reagents and solvents were purchased from
commercial sources and used as received unless stated other-
wise. Complexes of AgNO3 were prepared by adding an MeCN
solution of AgNO3 to a solution of the appropriate ligand dis-
solved in MeCN (or an MeCN–CH2Cl2 mixture). In a typical
procedure AgNO3 (0.2 mmol) in MeCN (2 mL) was added to L
(0.2 mmol) in MeCN (2 mL) and the mixture heated gently
for one minute. Slow diffusion of diethyl ether into the result-
ing mixture afforded a white precipitate after several days
(yield >80%). In some circumstances the product is insoluble
in the reaction medium and was isolated by filtration or centri-
fugation. Diffraction-quality crystals were grown by slow diffu-
sion of diethyl ether into MeCN or methanolic solutions of the
complexes.
and AgX salts (X = NO3 , BF4Ϫ and ClO4 ) with the apparatus
described in the Experimental section which contains an aque-
ous source phase and an organic receiving phase. After 2 h the
Ag remaining in the source phase was analysed by AAS and the
amount of Ag extracted in the presence of different anions
expressed as a percentage occupancy of the ligand. Distribution
coefficients were not determined from these experiments as the
Ag concentration was deliberately kept higher than that of the
ligand. The results are plotted in Fig. 11.
Ϫ
Ϫ
Metal extraction
The extraction apparatus consisted of vials (30 mL capacity)
containing 10 mL of an unbuffered aqueous source phase (AgX
and NaX, X = NO3 , BF4 and ClO4 ; [Ag] = 4.2 mmol LϪ1
with total anion concentration at 50 mmol LϪ1) and an organic
receiving phase (1,2-dichloroethane, 5 mL) containing L1 (0.038
mmol). The vials were shaken at 700 rpm (IKA Vibrax-VXR)
for 120 min and the source phase analysed by AAS for remain-
ing Ag. All values are mean values of duplicate runs.
Ϫ
Ϫ
Ϫ
Fig. 11 Graph showing effect of anion on Ag() extraction using L2.
It can be seen that AgNO3 is extracted least, whereas similar
amounts of Ag are extracted in the presence of the poorly co-
Ϫ
Ϫ
ordinating anions BF4 and ClO4 . This is in accord with the
stabilities of the various complexes in the presence of excess
metal salt but, owing to the different solvents used, it is more
likely a reflection of the solubility of the metal complexes in the
organic phase. The amount of bleeding of metal complex into
the aqueous phase was not determined although this should be
minimal since the complexes show low solubility in water.
Extraction experiments with L1 gave similar results and in the
presence of acids (HNO3 or HBF4) the amount of Ag extracted
was reduced by less than 10%, reflecting the lack of protonation
sites in the ligands which bind metal cations effectively via
S-donors even at low pH.
X-Ray structure analyses
A summary of the crystal data and refinement parameters for
L1, L1ؒAgNO3 and L2ؒAgNO3 is given in Table 4. Data for L1ؒ
AgNO3 were collected on an Nonius KappaCCD area detector.
Data for L1 and L2ؒAgNO3 were collected on a Bruker
SMART1000 CCD area detector. Crystals were cooled using
Oxford Cryosystems open-flow nitrogen cryostats.34 Data were
corrected for Lorentz and polarisation effects and absorption
corrections were also applied. The structures were solved by
direct methods35 and subsequent difference-Fourier syntheses.36
All non-H atoms, except those in disordered residual ether
molecules in L2ؒAgNO3, were refined anisotropically and all H
atoms were placed at calculated positions and thereafter refined
with Uiso(H) = 1.2Ueq(C). The structure of L1 contains a dis-
ordered dichloromethane solvent molecule which was modelled
over two sites that were found to be occupied in the ratio 80:20.
The crystal of L2ؒAgNO3 decayed suddenly during acquisition
and a decay correction was applied. The partially-occupied
Et2O solvent molecule is also disordered and has been modelled
over two sites with occupancies 0.3 and 0.2 and the application
of geometric restraints.
Conclusions
A switching mechanism has been identified in these systems
whereby a hydrogen-bond between the macrocyclic N-centre
and a urea or amide hydrogen is disrupted upon co-ordination
of Ag() ions and subsequent hydrogen-bonding to anions, via
the ‘free’ pendant unit, is then allowed. Such a co-operative
effect between cation and anion binding sites is of great interest
given the relative simplicity of the ligand design, and shows
how systems based on simple components can produce effective
results. In the absence of a bound metal ion internal hydrogen-
bonding appears to be stronger than intermolecular hydrogen-
bonding. It appears that better anion binding can be expected
with ligands containing more urea/amide units. This is compli-
CCDC reference numbers 195912–195914.
See http://www.rsc.org/suppdata/dt/b2/b210391p/ for crystal-
lographic data in CIF or other electronic format.
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1947

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Table 4 Crystal data and structure determination details
Compound
Formula
M
L1
L1ؒAgNO3
C48H92Ag2N14O16S4
1465.34
L2ؒAgNO3
C26H51AgN7O7.50S3
785.79
C25H48Cl2N6O5S2
647.71
Crystal system
Space group
Triclinic
P1
Triclinic
P1
Triclinic
P1
¯
¯
¯
a/Å
b/Å
c/Å
α/Њ
10.3080(7)
10.3129(7)
16.9116(11)
88.351(1)
84.537(1)
72.061(1)
1702.6(3)
2
12.8639(3)
15.5509(4)
17.1342(7)
93.6089(12)
96.4705(12)
110.9970(16)
3159.85(17)
2
9.662(4)
11.141(4)
18.973(7)
77.451(5)
79.171(5)
82.495(4)
1949.4(13)
2
β/Њ
γ/Њ
U/Å3
Z
T /K
150(2)
0.354
17399
7793, 0.016
0.0678 [5620 I > 2σ(I )]
0.180
150(2)
0.826
46416
14123, 0.125
0.0539 [7759 I > 2σ(I )]
0.120
150(2)
0.725
8277
5968, 0.053
0.103 [4772 I > 2σ(I )]
0.271
µ(Mo-Kα)/mmϪ1
Reflections collected
Unique reflections, Rint
R1
wR2 (all data)
L1, [12]aneS2ON2–(CH2CONHCONH–tBu)2. To a suspen-
sion of K2CO3 (1.5 g, 10.86 mmol), and KI (0.8 g, 4.82
mmol) in CH3CN (50 mL) was added [15]aneN2OS2 (0.945 g,
3.78 mmol) and 1-tert-butyl-3-(chloroacetyl)urea (1.45 g,
7.55 mmol) and the mixture heated at reflux for 3 h. The solvent
was removed and the resulting solid extracted with dichloro-
methane and washed with water, brine and finally dried over
MgSO4. After filtration and evaporation of the solvent, the
product was obtained as a white solid (1.49 g, 67%). Recrystal-
lisation from dichloromethane–hexane mixtures, or chromato-
graphy (silica gel, dichloromethane–3% methanol eluent)
affords a purer product. Anal. calc. for C24H46N6O5S2: C, 51.22;
(CH), 137.18 (Cquat), 149.87 (CO), 173.48 (CO). IR (cmϪ1) 3239
(νNH), 1712 (νCO), 1683 (νCO). FABϩ-MS m/z (C17H25N3O3S2,
383): 384 (M ϩ Hϩ).
L4, [15]aneS3N2–(CH2CONH–tBu)2. Using the same pro-
cedure as outlined above for the preparation of L1, [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 spectro-
scopy. Anal. calc. for C22H44N4O2S3: C, 53.62; H, 9.00; N, 11.37.
Found: C, 52.56; H, 8.71; N, 10.09%. 1H NMR (CDCl3):
δ (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): δ (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). FABϩ-MS m/z
(C22H44N4O2S3, 492): 493 (M ϩ Hϩ).
1
H, 8.24; N, 14.93. Found: C, 50.88; H, 8.12; N, 14.52%. H
NMR (CDCl3): δ (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): δ (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 (cmϪ1) 3289 br (νNH), 1715 (νCO), 1552
(νCO). FABϩ-MS m/z (C24H46N6O5S2, 562): 563 (M ϩ Hϩ).
L5, [12]aneS3N–CH2CONH–tBu. Using the same procedure
as outlined above for the preparation of L1, [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,
L2, [15]aneS3N2–(CH2CONHCONH–tBu)2. Using the same
procedure as outlined above for the preparation of L1,
[15]aneN2S3 (0.46 g, 1.74 mmol) and 1-tert-butyl-3-(chloro-
acetyl)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 recrystallis-
ation from 1,2-dichloroethane–hexane. Anal. calc. for C24H46-
N6O4S3: C, 49.80; H, 8.01; N, 14.52. Found: C, 49.79; H, 7.99;
1
8.32. Found: C, 49.64; H, 8.44; N, 8.33%. H NMR (CDCl3):
δ (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): δ (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): δ (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 (cmϪ1) 3252 (νNH), 3079 (νNH), 1646
(νCO), 1572 (νCO). FABϩ-MS m/z (C14H28N2OS3, 336): 337
(M ϩ Hϩ).
1
N, 14.43%. H NMR (CDCl3): δ (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): δ (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
(cmϪ1) 3287, 3232 (νNH), 1712 (νCO), 1550 (νCO). FABϩ-MS
m/z (C24H46N6O4S3, 578): 579 (M ϩ Hϩ).
L6, [15]aneS3N2–(CH2CONHPh)2. Using the same procedure
as outlined above for the preparation of L1, [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. Found: C, 58.41; H, 6.52; N, 10.35%. 1H NMR (CDCl3):
δ (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): δ (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 (cmϪ1) 3291
(νNH), 3256 (νNH), 1685 (νCO), 1597 (νCO). FABϩ-MS m/z
(C26H36N4O2S3, 532): 533 (M ϩ Hϩ).
L3, [12]aneS2ON–CH2CONHCONHPh. Using the same
procedure as outlined above for the preparation of L1,
[12]aneNOS2 (0.268 g, 1.29 mmol) and 1-phenyl-3-(chloro-
acetyl)urea (0.275 g, 1.29 mmol) afforded 0.66 g (66%) of the
product as an orange solid after chromatography on silica-60
(dichloromethane–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): δ (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). 13
C
NMR (CDCl3): δ (ppm) 29.36 (CH2), 30.85 (CH2), 52.75 (CH2),
59.57 (CH2), 73.98 (CH2), 120.02 (Cquat), 123.96 (CH), 128.78
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1948

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L7, [15]aneS3N2–CH2CONHPh. A solution of N-phenyl-2-
chloroacetamide (0.295 g, 1.74 mmol) in MeCN (30 mL) was
added dropwise to a rapidly stirred suspension of K2CO3
(0.240 g, 1.74 mmol) in MeCN (40 mL) containing [15]aneN2S3
(0.463 g, 0.174 mmol) which was heated at 50 ЊC. After the
addition was complete the mixture was stirred at 50 ЊC over-
night and the solvent was evaporated, water added and the
products 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-di-
chloroethane–hexane mixture. Anal. calc. for C18H29N3OS3: C,
54.10; H, 7.31; N, 10.51. Found: C, 54.46; H, 7.19; N, 10.12%.
1H NMR (CDCl3): δ (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 (cmϪ1) 3290 (νNH), 3205 (νNH), 1669
(νCO), 1598 (νCO). FABϩ-MS m/z (C18H29N3OS3, 399): 400
(M ϩ Hϩ).
S–CH2), 3.52 (s, 4H, CH2), 3.65 (m, 4H, N–CH2), 8.09 (br, s,
2H, NH), 9.45 (br, s, 2H, NH). 13C NMR (d3-MeCN): δ (ppm)
29.12 (CMe3), 33.00 (CH2), 35.41 (CH2), 51.28 (CMe3), 55.02
(CH2), 55.21 (CH2), 55.50 (CH2), 68.43 (CH2), 152.45 (CO),
173.87 (CO). IR (KBr disc, cmϪ1) 3311 m,1715 s, 1556 s 1384 vs,
1202 s, 1110 m, 798 m, 630 m. FABϩ-MS m/z (C24H46AgN6O5S2,
669): 669 (LAgϩ).
[15]aneS3N2–(CH2CONHCONH–tBu)2ؒAgNO3 [L2ؒAgNO3].
Anal. calc. for C24H46AgN7O7S3: C, 38.50; H, 6.19; N, 13.09.
1
Found: C, 38.69; H, 6.07; N, 12.55%. H NMR (d3-MeCN):
δ (ppm) 1.32 (s, 18H, CMe3), 2.74–2.92 (m, 20H, macrocyclic
CH2), 3.38 (s, 4H, CH2), 8.02 (br, s, 2H, NH), 8.44 (br, s, 2H,
NH). IR (KBr disc, cmϪ1) 3300 m, 1700 s, 1665 s, 1555 s, 1507 s,
1384 vs, 1255 s, 1197 m, 1100 m, 1020 m. FABϩ-MS m/z
(C24H46AgN6O4S3, 685): 685 (LAgϩ).
[12]aneS2ON–CH2CONHCONHPhؒAgNO3 [L3ؒAgNO3].
Anal. calc. for C17H25AgN4O6S2ؒH2O: C, 35.73; H, 4.76; N,
9.80. Found: C, 35.08; H, 4.33; N, 9.65%. 1H NMR (d3-MeCN):
δ (ppm) 2.84 (m, 12H, S–CH2), 3.45 (s, 2H, CH2), 3.63 (br, s,
4H, N–CH2), 7.12 (t, 1H, Ar), 7.35 (t, 2H, Ar), 7.49 (d, 2H, Ar),
9.04 (br, s, 1H, NH), 10.17 (br, s, 1H, NH). IR (KBr disc, cmϪ1)
3261 m, 1718 vs, 1685 s, 1601 s, 1554 s, 1384 vs, 1324 s, 1217 s,
1116 m, 1024 m, 757 m, 695 m. FABϩ-MS m/z (C17H25-
AgN3O3S2, 490): 490 (LAgϩ).
L8, [12]aneS3N–CH2CONHPh. Using the same procedure as
outlined above for the preparation of L1, [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–methanol,
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): δ (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): δ (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 (cmϪ1) 3225 (νNH), 1685 (νCO), 1601 (νCO). FABϩ-MS m/z
(C16H24N2OS3, 356): 357 (M ϩ Hϩ).
[15]aneS3N2–(CH2CONH–tBu)2ؒAgNO3 [L4ؒAgNO3]. Anal.
calc. for C22H44AgN5O5S3: C, 39.87; H, 6.69; N, 10.57. Found:
1
C, 39.46; H, 6.65; N, 10.55%. H NMR (d3-MeCN): δ (ppm)
1.32 (s, 18H, CMe3), 2.67–2.91 (m, 20H, macrocyclic CH2), 3.04
(s, 4H, CH2), 6.58 (br, s, 2H, NH). IR (KBr disc, cmϪ1) 3310 m,
1700 s, 1669 s, 1559 s, 1540 s, 1457 s, 1384 vs, 1327 s, 1228 s,
1120 m, 1050 m. FABϩ-MS m/z (C22H44AgN4O2S3, 599): 599
(LAgϩ).
L9, [12]aneS2ON–CH2CONHPh. Using the same procedure
as outlined above for the preparation of L1, [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 (dichloro-
methane–methanol, 12:1 eluent) and drying under reduced
pressure. Anal. calc. for C16H24N2O2S2: C, 56.44; H, 7.10; N,
[12]aneS3N–CH2CONH–tBuؒAgNO3 [L5ؒAgNO3].
Anal.
calc. for C14H28AgN3O4S3: C, 33.20; H, 5.57; N, 8.30. Found: C,
33.20; H, 5.22; N, 8.08%. 1H NMR (d3-MeCN): δ (ppm) 1.30 (s,
9H, CMe3), 2.87 (br, s, 16H, macrocyclic CH2), 3.02 (s, 2H,
CH2), 6.56 (br, s, 1H, NH). IR (KBr disc, cmϪ1) 3283 m, 1658 s,
1559 s, 1457 m, 1384 vs, 1330 s, 1265 m, 1219 m, 1110 m,
1037 w, 931 m, 905 m, 825 w. FABϩ-MS m/z (C14H28AgN2OS3,
443): 443 (LAgϩ).
1
8.23. Found: C, 57.59; H, 7.20; N, 8.09%. H NMR (CDCl3):
δ (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): δ (ppm)
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 (cmϪ1) 3220 (νNH), 1686 (νCO), 1600 (νCO).
FABϩ-MS m/z (C16H24N2O2S2, 340): 341 (M ϩ Hϩ).
[15]aneS3N2–(CH2CONHPh)2ؒAgNO3 [L6ؒAgNO3].
Anal.
calc. for C26H36AgN5O5S3: C, 44.44; H, 5.16; N, 9.06. Found: C,
43.50; H, 5.28; N, 9.27%. 1H NMR (d3-MeCN): δ (ppm)
2.88 (m, 20H, macrocyclic CH2), 3.39 (s, 4H, CH2), 7.08 (t, 2H,
Ar), 7.25 (t, 4H, Ar), 7.55 (d, 4H, Ar), 9.02 (br, s, 2H, NH).
IR (KBr disc, cmϪ1) 3258 m, 3133 m, 1700 s, 1676s, 1617 s,
1599 s, 1550 s, 1499 s, 1444 s, 1384 vs, 1315 s, 1249 s, 1200 s,
1104 m, 759 m, 693 m. FABϩ-MS m/z (C26H36AgN4O2S3, 639):
639 (LAgϩ).
L10, [12]aneS2ON–CH2CONHCONH–tBu. Using the same
procedure as outlined above for the preparation of L1,
[12]aneNOS2 (0.33 g, 1.59 mmol) and 1-tert-butyl-3-(chloro-
acetyl)urea (0.31 g, 1.59 mmol) afforded 0.35 g (60%) of the
product as a white solid. Recrystallisation by slow evaporation
from methanol affords a more pure product. Anal. calc. for
C15H29N3O3S2: C, 49.56; H, 8.04; N, 11.56. Found: C, 47.58; H,
7.78; N, 10.55%. 1H NMR (CDCl3): δ (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): δ (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 (cmϪ1) 3250 (νNH), 1716
(νCO), 1652 (νCO). FABϩ-MS m/z (C15H29N3O3S2, 363): 364
(M ϩ Hϩ).
[15]aneS3N2–CH2CONHPhؒAgNO3 [L7ؒAgNO3]. Anal. calc.
for C18H29AgN4O4S3ؒH2O: C, 36.80; H, 5.32; N, 9.54. Found: C,
36.19; H, 4.91; N, 9.30%. 1H NMR (d3-MeCN): δ (ppm) 2.76–
3.02 (m, 20H, macrocyclic CH2), 3.44 (s, 2H, CH2), 7.15 (t, 1H,
Ar), 7.37 (t, 2H, Ar), 7.62 (d, 2H, Ar), 9.23 (br, s, 1H, NH). IR
(KBr disc, cmϪ1) 3257 m, 1685 s, 1617 s, 1597 s, 1540, 1491 s,
1444 s, 1384 vs, 1318 s, 1245 s, 1150 m, 1020 m, 761 m, 697 m.
FABϩ-MS m/z (C18H29AgN3OS3, 506): 506 (LAgϩ).
[12]aneS3N–CH2CONHPhؒAgNO3 [L8ؒAgNO3]. Anal. calc.
for C16H24AgN3O4S3: C, 36.50; H, 4.60; N, 7.98. Found: C,
36.58; H, 4.47; N, 8.09%. 1H NMR (d3-MeCN): δ (ppm) 2.88 (s,
16H, macrocyclic CH2), 3.35 (s, 2H, CH2), 7.12 (t, 1H, Ar), 7.34
(t, 2H, Ar), 7.57 (d, 2H, Ar), 8.66 (br, s, 1H, NH). IR (KBr disc,
cmϪ1) 3290 m, 1685 s, 1597 s, 1540 s, 1497 s, 1444 s, 1384 vs,
[15]aneS2ON2–(CH2CONHCONH–tBu)2ؒAgNO3-
[L1ؒAgNO3]. Anal. calc. for C24H46AgN7O8S2: C, 39.34; H,
6.33; N, 13.38. Found: C, 39.35; H, 6.25; N, 13.10%. 1H NMR
(d3-MeCN): δ (ppm) 1.31 (s, 18H, CMe3), 2.71–2.96 (m, 16H,
D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
1949

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1327 s, 1256 s, 1112 m, 1037 m, 759 m, 733 m, 697 m. FABϩ-MS
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m/z (C16H24AgN2OS3, 463): 463 (LAgϩ).
[12]aneS2ON–CH2CONHPhؒAgNO3 [L9ؒAgNO3].
Anal.
calc. for C16H24AgN3O5S2: C, 37.65; H, 4.74; N, 8.23. Found: C,
37.47; H, 4.61; N, 8.42%. 1H NMR (d3-MeCN): δ (ppm) 2.77–
2.90 (m, 16H, macrocyclic CH2), 3.31 (s, 2H, CH2), 7.13 (t, 1H,
Ar), 7.35 (t, 2H, Ar), 7.55 (d, 2H, Ar), 8.75 (br, s, 1H, NH). IR
(KBr disc, cmϪ1) 3290 m, 1685 s, 1664 s, 1603 s, 1551 s, 1499 s,
1449 s, 1384 vs, 1359 s, 1256 s, 1110 s, 1015 m, 762 m. FABϩ-MS
m/z (C16H24AgN2O2S2, 447): 447 (LAgϩ).
Acknowledgements
We thank the EPSRC, The University of Nottingham, the
EPSRC National Mass Spectrometry Service at the University
of Swansea and the EPSRC National Service for Crystallo-
graphy at the University of Southampton.
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D a l t o n T r a n s . , 2 0 0 3 , 1 9 4 1 – 1 9 5 1
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