Influence of the platform in multicoordinate ligands for actinide partitioning

Article abstract of DOI:10.1039/b704667g

Multicoordinate ligands based on the trityl, C-pivot, and CTV platforms and the ligating groups CMPO, DGA, PICO, and MPMA were synthesized and studied for their extraction properties. The extraction efficiencies of these multicoordinate ligands are largel

Full text of DOI:10.1039/b704667g

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www.rsc.org/njc | New Journal of Chemistry
Influence of the platform in multicoordinate ligands for actinide
partitioning
Henk H. Dam, David N. Reinhoudt and Willem Verboom*
Received (in Montpellier, France) 28th March 2007, Accepted 1st May 2007
First published as an Advance Article on the web 5th June 2007
DOI: 10.1039/b704667g
Multicoordinate ligands based on the trityl, C-pivot, and CTV platforms and the ligating groups
CMPO, DGA, PICO, and MPMA were synthesized and studied for their extraction properties.
The extraction efficiencies of these multicoordinate ligands are largely influenced by the properties
of the platform. The DAm values follow the order CTV6 4 trityl E C-pivot 4 CTV3 4 CTV0
with a maximum for CTV6CMPO of DAm = 30 (SAm/Eu = 1.4, cL = 10ꢀ4 M, 3 M HNO3).
There is a strong relationship between the DAm values, increasing in the order of CTV0CMPO
o CTV3CMPO o CTV6CMPO, and the ‘mobility’ of their CMPO groups. The SAm/Eu values
are less influenced by the platform and range between 0.2 and 2.0, though they can reverse under
the influence of the HNO3 concentration (CTV6PICO SAm/Eu = 0.7 at 0.001 M HNO3 to 1.2 at
0.01 M HNO3) or by changing the platform (CTV(0, 3 or 6)MPMA from SAm/Eu = 0.4 to 1.6 for
tritMPMA both at 0.001 M HNO3). For the CMPO derivatives the SAm/Eu values are most
consistent, ranging from 1.4 to 1.8.
phenylmalonamide)9 are described. Multicoordinate ligands
Introduction
based on these ligating groups and the calix[4, 6, and 8]arene
and cavitand platforms are known.4 In contrast to these
platforms, the ones described here are functionalized with
three ligating groups. This number matches the 1 : 3 metal :
ligand stoichiometry that was found for CMPO groups that
are not preorganized.5
Minor actinides i.e. Np, Am, and Cm are responsible for the
long-term radiotoxicity of HLLW (High Level Liquid Waste)
nuclear waste. The radiotoxicity of these long-lived (t1/2
=
102–106 years) nuclides can be reduced via transmutation into
short-lived (t1/2 = 101 years) nuclides or stable nuclides.
Separation (partitioning–transmutation strategy (P & T))1,2
of these actinides from the relatively harmless lanthanides is
essential to success in the transmutation process.
Results and discussion
In current industrial separation processes, trivalent Am and
Cm will always be extracted together with lanthanides and this
complicates the transmutation.3 Improvement of the efficiency
of the actinide (An(III))–lanthanide (Ln(III)) separation will
therefore increase the feasibility of the currently impractical
waste reprocessing.
A strategy to obtain Am3+ ligands having both high SAm/Eu
(separation) and DAm (distribution) ratios is by preorganizing
existing ‘hard oxygen donor’ ligating groups onto a platform.
The advantage of using such multicoordinate ligands contain-
ing hard donor atoms is that the increase in SAm/Eu value
coincides with generally high DAm values which are retained at
higher acidities (3 M HNO3). Very recently this strategy has
been reviewed.4
Here the Am3+ and Eu3+ extraction properties of multi-
coordinate ligands based upon the trityl, cyclotriveratrylene
(CTV), and C-pivot platforms (Chart 1) and four known
Am3+ ligating groups viz. CMPO (diphenyl carbamoyl-
methyl)phosphine oxide),5,6 PICO (picolinamide),7 DGA
(N,N0-dimethyl diglycoldiamide),8 and MPMA (N-methyl-N-
Synthesis
Trityl based multicoordinate ligands. The trityl (triphenoxy-
methane) platform can be conformationally locked, such that
the three hydroxyl groups point into the same direction, by
substituting the m-position of the benzene ring with a (steri-
cally) bulky group (Chart 1).10 It has been shown that the trityl
platform is able to tightly place ligating groups together to
provide a good fit for the complexation of Eu3+ 10
Due to the
.
bulky tert-butyl groups the hydroxyl groups of 4 are sterically
hindered and consequently are less reactive. By reaction of
these phenol moieties with the reactive chloroacetonitrile and
subsequent reduction with LiAlH4 trityl 6 can be obtained in
two steps in an overall yield of 68% as reported in the
literature.10 Optionally, trityl 5 was reduced to 6 using BH3
in refluxing THF. Due to the –(CH2)2– spacer the connecting
points (amino moieties) are less sterically crowded, and in
addition the reactivity is increased as compared to the original
hydroxyl groups (Scheme 1).
Trityl 6 was functionalized with the CMPO, DGA, and
PICO ligating groups by reaction with their p-nitrophenol
activated esters (Scheme 2). The MPMA ligating group was
connected to the trityl by using an activated amide coupling,
since the syntheses of its p-nitrophenol activated ester was
Laboratory of Supramolecular Chemistry and Technology, Mesa+
Research Institute for Nanotechnology, University of Twente, P. O.
Box 217, 7500 AE Enschede, The Netherlands. E-mail:
w.verboom@utwente.nl
1
unsuccessful. In the H NMR spectra the triplets of the two
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Chart 1 3D representations of the trityl, CTV, and C-pivot platforms.
Scheme 1
–CH2– groups of the spacer in the multicoordinate ligands
7–CMPO, 7–DGA, 7–PICO, and 7–MPMA are often broad
and poorly resolved due to their close proximity and the
sterically crowded environment.
–(CH2)3– spacers, and the 13–CTV6 platform equipped with
–(CH2)6– spacers which results in very mobile ligating groups
(Chart 2).
The amine CTV 813 (Chart 2) and the phenolic CTV 914
were prepared via the well known perchloric acid catalyzed
condensation of 3,4-disubstituted benzyl derivatives according
to literature procedures.15,16 For the latter condensation reac-
tion the perchloric acid was diluted with MeOH. The phenolic
CTV 9 was used as starting compound for the synthesis of
CTVs 11 (Scheme 3) and 13 (Scheme 4). Reaction of 9 with
tert-butyl-N-(3-bromopropyl)carbamate gave the BOC pro-
tected CTV 10 in 86% yield. The BOC groups were cleaved
using TFA to give the TFA-salt 11a upon precipitation from
Et2O. The salt was used in subsequent reactions since depro-
tonation of the salt using 1 M NaOH to its amine form 11
reduces the yield to 77%.
CTV based multicoordinate ligands. The stable crown isomer
of the CTV (cyclotriveratrylene, also called cycloveratril)
macrocycle has its functional groups oriented towards one
side of the molecule and can be functionalized with three
ligating groups.11,12 The length of the –(CH2)n– spacer be-
tween the ligating groups and the platform determines the
mobility and consequently the degree of preorganization of the
ligating groups. Three CTV platforms having different
–(CH2)n– spacer lengths were synthesized. These include the
8–CTV0 platform which induces a rather tight preorganiza-
tion of its ligating groups, the 11–CTV3 platform having
Scheme 2
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Chart 2 Synthesis of multicoordinate ligands based on the 8–CTV0, 11–CTV3, and 13–CTV6 platforms.
The synthesis of CTV 12 was performed by reaction of 9
with 6-bromohexanenitrile using caesium carbonate as a base
to give CTV 12 in 91% yield. Firstly, the reduction of 12 to its
amine CTV 13 was attempted using BH3 in refluxing THF.
However, the decomposition of the CTV 13-BH3 adduct was
very difficult, resulting in low yields. Raney-cobalt in combi-
nation with 7 bar of H2 at room temperature was successful
and gave CTV 13 in 93% yield.
of the C3-symmetric C-pivot platform 3 is relatively simple
(Chart 1). The synthesized C-pivot platform 20 consists of a
central C-atom on which a tert-butylphenyl group is con-
nected and three CMPO ligating groups connected by
–(CH2)3– spacers. The C-pivot platform 17 was prepared in
three steps, starting from the commercially available tris-
(2-cyanoethyl)nitromethane, as described in the literature.17
Reaction of the free amine in 17 with 4-tert-butylbenzoyl
chloride gave the C-pivot 18 in 47% yield. Deprotection of
the BOC groups in 18 with TFA afforded the TFA salt of
C-pivot 19. This salt was subsequently reacted with the
p-nitrophenol activated ester of CMPO to give the required
pivCMPO ligand 20 in 59% yield (Scheme 5).
The CTV based multicoordinate ligands (Chart 2) were
synthesized by reaction of the amino terminated CTVs with
either the activated ester of the respective ligand (CMPO,
DGA and PICO) or via an activated amide coupling (MPMA).
The reaction of CTV0 with the activated ester of PICO yielded
an insoluble product which could not be purified.
Extraction results
C-Pivot based multicoordinate ligands. In contrast to the
Ideally the organic solvent for actinide solvent extraction
processes should be stable, have a low water-miscibility, a
previously mentioned trityl and CTV platforms the structure
Scheme 3
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Scheme 4
relatively low vapor pressure, and no significant harmful
effects on the environment.18,19 The extraction efficiency of
ligands is directly related to the solubility of the ligand–metal
complex in the organic phase. Strongly coordinating polar
solvents dissolve metal complexes generally better. This results
normally in significantly higher DAm values, whereas the
SAm/Eu values are less easily affected by changing the solvent.
The effects of several solvents on the extraction efficiency of
Am3+ and Eu3+ using 7–tritCMPO and 16–CTV6CMPO
were examined (Table 1).
benzene20 gave satisfactory extraction results, and all prepared
ligands could be dissolved in it, this solvent was chosen as the
organic phase in the extraction experiments.
Extraction properties of the CTV, trityl, and C-pivot based
ligands. The extraction data of the CTV based multicoordinate
ligands are summarized in Table 2. The CTV platform is very
rigid, ligating groups directly connected to it (Chart 2) are
rather constricted in their movements. Due to a rigid preorga-
nization of the ligating groups the DS of complex formation
will be less negative which is advantageous for the extraction
process. A rigid conformation leaves, however, little room for
rearrangement of the ligating groups. The latter is probably
the origin of the very low extraction efficiencies of the CTV0
ligands. However, a large increase of the extraction efficiency
is observed upon elongation of the ꢀ(CH2)n– spacer to n = 3
and 6. For lower rim CMPO-functionalized calix[4]arenes a
similar increase in extraction on elongation of the ꢀ(CH2)n–
Table 1 shows that there is a wide variety in the DAm values
(0.1–30), whereas the SAm/Eu values stay between 0.8–1.7.
Nitrobenzene, the most polar solvent of this series, gives the
highest extraction efficiency for 16–CTV6CMPO. Despite that
n-octanol is rather apolar, the DAm values for the ligands
measured in this solvent are also relatively high. This can be
explained by the ability of n-octanol to form hydrogen bonds
and having a strongly coordinating oxygen atom. Since nitro-
Scheme 5
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Table
1
DAm and SAm/Eu values of ligands 7–tritCMPO and
Table 2 DAm and SAm/Eu values of the ligands based on the CTV0,
CTV3, and CTV6 platforms, cL = 10ꢀ2 M at 0.001 and 3 M HNO3
16–CTV6CMPO (cL = 10ꢀ3 M, 3 M HNO3) in six different sol-
vents18,19
HNO3
10ꢀ3
HNO3
Dipole
moment/ Dielectric
TritylCMPO CTV6CMPO
M
3 M
10ꢀ3 M 3 M
Ligand
Ligand
DAm SAm/Eu DAm SAm/Eu
Solvent
C m
constant
DAm
DEu
SAm/Eu
CTV0CMPO
1.26
0.89
1.4
0.08 CTV0PICO
0.05
1.6
nd
nd
nd
nd
Nitrobenzenea
Dichloroethane
n-Octanol
Tetrachloroethane 1.30
Dichloromethane 1.14
4.22
1.83
1.76
34.78
10.36
10.34
8.20
8.93
4.89
2.8 1.3
5.3 1.6
30 1.3
5.8 1.6
21
1.1
8.1 0.8
2.5 1.5
1.2 1.3
23
4.6
2.7 1.5
0.1 1.7
1.2
1
DAm
DEu
SAm/Eu
CTV3CMPO 440
440
2.95 CTV3PICO
1.95
1.5
o0.02 o0.01
0.07 o0.01
o0.3
Chloroform
1.15
a
cL = 10ꢀ4 M.
DAm
DEu
SAm/Eu
CTV6CMPOb
CTV0DGA
CTV3DGA
CTV6DGA
59
36
1.6
1.38 CTV6PICO
1.02
1.4
0.37 o0.01
0.53 o0.01
0.7
DAm
DEu
SAm/Eu
nda
nda
nda
nda
CTV0MPMA
0.09 o0.01
0.34 o0.01
0.3
spacer has been observed.21 The increased ‘mobility’ of the
ligating groups allows for a more optimal bond geometry and
hence the formation of stronger ligand–metal cation bonds.
From the log D vs. log [L] curves of the CTV–CMPO ligands
(Fig. 1 and 2; vide infra) it can be concluded that CTV6CMPO
is significantly more and CTV0CMPO significantly less effi-
cient in extracting Am3+ as compared to the other ligands,
stressing the influence of the –(CH2)n– spacer. From Tables 2
and 3 the following order of Am3+ extraction efficiencies can
be observed for the CMPO ligands: CTV6CMPO 4 tritCM-
PO E pivCMPO 4 CTV3CMPO 4 CTV0CMPO. The
ligands have comparable SAm/Eu values, ranging from 1.4 to
1.8. The platform is thus mostly influencing the extraction
efficiencies.
DAm
DEu
SAm/Eu
4.8
7.0
0.7
0.15 CTV3MPMA
0.72
0.21
0.28 o0.01
0.69 o0.01
0.4
DAm
DEu
SAm/Eu
21.4
440
o0.5
0.75 CTV6MPMA
3.5
0.21
0.76 o0.01
2.12 o0.01
0.4
a
b
nd (not determined). Major precipitation. [L] = 10ꢀ5 M.
The extraction equilibrium constant depends on the concen-
trations of the species in solution expressed as eqn (2).
½MLnðNO3Þxꢂ
In contrast to the CMPO derivatives all DGA derivatives
have selectivities for Eu3+ over Am3+ up to a SEu/Am of 5,
which is known for DGA multicoordinate ligands.22 Surpris-
ingly, the CTV3- and CTV6PICO ligands also have selectivity
for Eu3+. The calix[n]arene-PICO ligands studied by Casnati
et al. have SAm/Eu values ranging from 2 to 14 at the same
HNO3 concentration.23 The three MPMA multicoordinate
ligands based on the CTV scaffold have selectivity for Eu3+
at 0.001 M HNO3. Comparison of these extraction results with
those of tritylMPMA in Table 2 shows that changing the
platform from CTV to trityl results in a change in the Am3+
selectivity of the MPMA derivatives at 0.001 M HNO3.
Significant differences in the Am/Eu selectivity can thus be
obtained by simply changing the platform. At higher acidities
the CTV-MPMA ligands do not extract Am3+ and Eu3+ any
more (Table 4), whereas the tritylMPMA does extract at 3 M
HNO3. The tritylMPMA ligand is a more efficient extractant
than its CTV analogues, therefore its competition with proto-
nation is stronger resulting in an observable extraction at
3 M HNO3.
Kex
¼
ð2Þ
x
n
½Mxþꢂ½NOꢀ3 ꢂ ½Lꢂ
The distribution ratio D is defined as the ratio of the total
amount of metal extracted in the organic layer and the total
amount in the aqueous layer (eqn (3)).
½MLnðNO3Þxꢂ
DM
¼
ð3Þ
½Mxþꢂ
Eqn (3) can also be written as eqn (4).
ꢀ x
ꢀ
logDM = log(Kex[NO3 ] ) + nlog[L]
(4)
According to eqn (4) there is a linear relationship between the
logarithmic function of D and the logarithmic function of the
ligand concentration. The slope of the resulting plot should be
equal to the number of ligand molecules per metal cation in
the extracted species. The ‘‘free’’ CMPO ligand has a metal to
ligand stoichiometry of 1 : 3.5 Therefore, a stoichiometry of
1 : 1 can be assumed for multicoordinating ligands having
three CMPO groups. However, due to several factors, like
changes in the flexibility or steric environment of the ligating
groups different stoichiometries may be obtained. The log DM
vs. log [L] graphs of the ligands CTV0CMPO, CTV3CMPO,
and CTV6CMPO are shown in Fig. 1 and that of tritCMPO
and pivCMPO in Fig. 2. CTV6CMPO and CTV3CMPO have
similar slopes of 1.3, the closest stoichiometry being a 4 : 5
metal to ligand ratio. The complexes could thus be oligomeric
in nature; however, the values of the slopes give the approx-
imate overall composition of the extracted species. Whether
the species is a single complex, oligomeric, or polymeric
cannot be deduced from these experiments. In principle, the
Stoichiometry of complexation. The complexation stoichio-
metries of the complexes of the CMPO ligands were deduced
using the following method.
The general extraction equilibrium in solution can be
expressed as eqn (1), where a solid line denotes the species in
24
the organic phase:
M
xþ þ xNO3ꢀ þ nLÐMLnðNO3Þx
ð1Þ
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Fig. 1 Plots of log DAm vs. log [L] at 3 M HNO3.
complexes could thus also exist as a mixture of 1 : 1 and 2 : 3
metal to ligand species. The slope of the log D vs. log [L] line of
CTV0MPO is 0.8, which indicates a reversed stoichiometry of
a 5 : 4 metal to ligand ratio with regard to the previous two
ligands. Complexes are formed in which the ligands bind on
average to more than one metal. These observations seem
peculiar since the latter is unlikely for rigid ligands such as
CTV0CMPO and the metal to ligand ratio of more than 1 is
unexpected for the more flexible CTV3CMPO and
CTV6CMPO ligands. It should, however, be kept in mind
that complexes with a saddle geometry are in principle
possible.11 This geometry allows a ‘more than one metal
bonding’ for the CTV0CMPO ligand.
Effect of nitric acid on the extraction. The effect of the HNO3
concentration in the aqueous phase on the extraction behavior
was studied for tritCMPO, pivCMPO, and all CTV6 deriva-
tives (Table 4). The extraction efficiencies are influenced by a
combined HNO3 salting out effect and protonation of the
ligand, dependent on its basicity. The extraction behavior of
CTV6DGA is irregular upon changing the acidity. The max-
imum at 0.001 M HNO3 is decreasing to a minimum between
0.1–1 M HNO3 followed by a maximum at 3 M HNO3,
whereupon it decreases again as a result of the opposing effects
previously mentioned. For both the PICO and MPMA deri-
vatives a fast decrease in extraction is observed; at 0.1 M
HNO3 there is no significant metal extraction any more. For
PICO derivatives this is understandable considering the easily
protonated pyridine nitrogen atom. Malonamides preorga-
nized on a tripodal C-pivot, having a –(CH2O(CH2)3)– spacer,
or trialkylbenzene platforms have a small selectivity towards
Am3+ with regard to Eu3+ and have an increase in extraction
efficiency ongoing from 1 to 3 M HNO3.25,26 The combined
effects of the protonation of the ligating groups and the
differences in preorganization of the CTV6 platform may be
the reason for the opposite extraction behavior of the
CTV6MPMA ligand.
The corresponding slopes of pivCMPO are 1.5, suggesting a
2 : 3 metal to ligand stoichiometry for the complexes. For
tritCMPO the slope is not linear over the whole concentration
range. The line starts with a slope of about 0.7, indicating a
3 : 2 metal to ligand stoichiometry, at approximately
[L] = 3 ꢃ 10ꢀ4 M. Than a region can be recognized where
the slope is zero, which means that the distribution ratio is
independent of the ligand concentration. Here most probably
a structural reorganization of the extracted species takes place
which is completed at [L] E 2 ꢃ 10ꢀ3 M where the slope
becomes 0.7 again. For all the CMPO derivatives the stoichio-
metries of their Am3+ as compared to their Eu3+ complexes
are the same.
The phosphoryl oxygen in CMPO extractants is protonated
under the conditions of nuclear waste treatment (B3 M
HNO3).27,28 The extraction efficiency of this type of ligand
Fig. 2 Plots of log DAm vs. log [L] at 3 M HNO3.
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Table 3 DAm and SAm/Eu values of the ligands based on the trityl and C-pivot platforms at 0.001 and 3 M HNO3
HNO3
10ꢀ3
HNO3
HNO3
Liganda
Ligandb
M
3 M
10ꢀ3
M
3 M
Liganda
10ꢀ3
M
3 M
DAm
DEu
SAm/Eu
TritylCMPO
10.7
6.25
1.7
2.8
1.8
1.6
TritylPICO
4100
4100
o0.01c
o0.01c
pivCMPO
63
41
1.5
0.11
0.06
1.8
DAm
DEu
SAm/Eu
a
TritylDGA
4100
4100
13.2
36
0.4
TritylMPMA
5.8
3.68
1.6
1.35
5.97
0.2
b
c
[L] = 10ꢀ4 M. [L] = 10ꢀ1 M. Major precipitation.
largely depends on the basicity of the carbonyl and phosphoryl
oxygens and is regulated by their substituents. The platform
also influences the behavior of the multicoordinate ligand
towards the HNO3 concentration.4 From Table 4 it can
be seen that CTV6CMPO gives a regular decrease in extrac-
tion efficiency from 0.001 M to 6 M HNO3. A similar,
though somewhat faster decrease in extraction efficiency is
observed for the pivCMPO ligand. TritCMPO exhibits a
totally different behavior; there is a maximum extraction
observed at 0.01 M HNO3 and a minimum at around 1 M
HNO3 from which it goes up again. In contrast, when the trityl
is preorganized with CMPO groups at the ‘opposite’ side of
the molecule it results in a strong decrease in extraction upon
increasing the HNO3 concentration.29 The origin of these
differences in extraction behavior is not known in detail.
However, it is probably related to an interplay of the salting
out effect and the protonation of the ligating groups, which
determines the competitive behavior of the multicoordinate
ligand between the protons and metal ions. For most ligands
the SAm/Eu values change only slightly, except for the
CTV6DGA and CTV6PICO ligand. For the former ligand
the selectivity for Eu3+ is almost tripled, going from 0.01 M to
3 M HNO3 and for the latter it is reversed from 0.001 M to
0.01 M HNO3. It is unlikely that this behavior is originating
from changes in the aqueous phase, since it is not observed for
the other ligands.
Conclusions
Three different platforms, of which one platform has three
different –(CH2)n– spacer lengths, were successfully synthe-
sized and functionalized with Am3+ ligating groups resulting
in fifteen new ligands. The extraction efficiencies of these
multicoordinate ligands are largely governed by the properties
of the platform. Their SAm/Eu values range between 0.2 and 2.0
and are, for the non CMPO ligands, largely dependent on the
HNO3 concentration. The DAm values differ much more and
follow the order CTV6 4 trityl E C-pivot 4 CTV3 4 CTV0
with a maximum for CTV6CMPO of DAm = 30 (SAm/Eu = 1.4,
cL = 10ꢀ4 M, 3 M HNO3). The rigid preorganization of
ligating groups on the CTV0 platform did not result in
increased SAm/Eu values. The CMPO derivatives have
Table 4 DAm and SAm/Eu values from ligands tritCMPO, pivCMPO, and the CTV6 based ligands at varying HNO3 concentrations
[HNO3]/M
0.001
0.003
13.2
8.71
1.5
0.01
18.6
9.12
2.0
0.03
3.24
2.04
1.6
0.1
0.62
0.38
1.6
1
3
6
Ligand
[L]/M
10ꢀ4
tritCMPO
DAm
DEu
SAm/Eu
12.0
7.76
1.5
0.27
0.16
1.7
2.82
1.82
1.5
13.2
9.55
1.4
pivCMPO
10ꢀ4
10ꢀ5
10ꢀ2
10ꢀ2
10ꢀ2
DAm
DEu
SAm/Eu
63.1
40.7
1.6
31.6
21.4
1.5
13.2
11.2
1.2
9.12
7.59
1.2
1.58
1.12
1.4
0.13
0.08
1.6
0.11
0.06
1.8
0.04
0.03
1.3
CTV6CMPO
CTV6DGA
CTV6PICO
DAm
DEu
SAm/Eu
58.9
36.3
1.6
nda
20.4
15.5
1.3
nda
5.75
3.80
1.5
1.55
1.05
1.5
1.38
1.02
1.4
0.06
0.05
nd
nda
nda
nda
nda
DAm
DEu
SAm/Eu
21.4
440
o0.5
nd
nd
nd
5.73
9.11
0.6
nd
nd
nd
o0.01
o0.01
nd
o0.01
o0.01
nd
0.75
3.5
0.2
0.14
0.73
0.2
DAm
DEu
SAm/Eu
0.37
0.53
0.7
nd
nd
nd
0.20
0.17
1.2
nd
nd
nd
o0.02
o0.02
nd
o0.02
o0.02
nd
o0.01
o0.01
nd
o0.01
o0.01
nd
CTV6MPMA
DAm
DEu
SAm/Eu
0.76
2.12
0.4
nd
nd
nd
0.04
0.11
0.4
nd
nd
nd
o0.02
o0.02
nd
o0.02
o0.02
nd
o0.01
o0.01
nd
o0.01
o0.01
nd
a
nd (not determined).
ꢁc
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comparable SAm/Eu values, ranging from 1.4 to 1.8, and so the
platform is thus mostly influencing the extraction efficiencies.
The threefold preorganization of platforms with CMPO
groups5 did not result in improved extraction properties.
The observed extraction results are comparable to that of
CMPO-functionalized cavitands6b and lower rim CMPO-func-
tionalized calix[4]arenes.30 Only the upper rim CMPO-func-
tionalized calix[4]arenes in which the CMPO groups are
directly connected to the phenyl rings (similar to
CTV0CMPO) have a significant higher extraction efficiency
1 M solution in THF) was refluxed in dry THF (500 mL total)
for 16 h. Concentrated HCl (25 mL) was added and the
mixture was refluxed for 30 min. The mixture was basified
with NaOH (aq) to pH B10. Most of the solvent was
evaporated under reduced pressure and the crude product
was taken up into CH2Cl2 (200 mL). The aqueous layer was
washed with CH2Cl2 (3 ꢃ 50 mL) and dried with MgSO4.
Evaporation of the solvent afforded 17.8 g of a white powder,
which was purified by recrystallization from MeOH giving 6 as
white crystals. Yield 14.5 g (95%); mp 155–157 1C. The results of
the analytical analysis (1H NMR, 13C NMR, and mass spectro-
metry) corresponded with the data described in literature.10
and selectivity for Am3+ 31
These superior extraction proper-
.
ties thus most likely result from a combination of the electro-
nic effect of the phenyl substituents and a preferential
preorganization of the CMPO groups by the calix[4]arene.
The extraction efficiencies of the multicoordinate ligands
with the DGA, MPMA, and PICO ligating groups are lower
than that of the CMPO analogues. All the multicoordinate
ligands based on the DGA ligating groups have a selectivity
for Eu3+ up to SEu/Am = 5. These values are comparable to
those published for a DGA-functionalized trityl.22
Tris(3,5-di-tert-butyl-2-(((N,N-dimethyl-3-oxapentanamide)-
amino)ethoxy)phenyl)methane (7–tritDGA). A solution of trityl
6 (0.40 g, 0.53 mmol) and the p-nitrophenol activated ester of
DGA (0.46 g, 1.64 mmol) in CHCl3 (30 mL) was refluxed for
2 d. The solvent was evaporated under reduced pressure and
the crude product was taken up into CH2Cl2 (30 mL). The
organic layer was washed with 1 M NaOH (7 ꢃ 20 mL) and
H2O (20 mL) and dried with MgSO4. Evaporation of the
solvent afforded 0.52 g of the crude product as a yellowish
powder. Trituration with Et2O gave 7–tritDGA as a white
solid. Yield 0.39 g (50%); mp 158 1C; FAB-MS: m/z 1188.0
([M + H]+, calc. 1187.8); 1H NMR d: 7.90 (t, 3H, J = 6.0 Hz,
NH), 7.30 (d, 3H, J = 2.1 Hz, PhH), 7.19 (d, 3H, J = 2.4 Hz,
PhH), 6.52 (s, 1H, CH), 4.32 (s, 6H, OCH2C(O)), 4.12 (s, 6H,
OCH2C(O)), 3.78 (br t, 6H, OCH2), 3.54 (br t, 6H, CH2NHO),
2.99 (s, 9H, CH3), 2.97 (s, 9H, CH3), 1.36 (s, 27H, C(CH3)3),
1.23 (s, 27H, C(CH3)3); 13C NMR d: 170.1, 169.0, 153.0, 144.9,
141.9, 137.3, 127.0, 122.5, 71.2, 70.5, 69.8, 39.7, 37.7, 36.0,
35.6, 35.5, 34.5, 31.5, 31.4. Anal. Calc. for C67H106N6O12:
C, 67.76; H, 9.00; N, 7.08. Found: C, 67.69; H, 8.91; N, 6.99%.
The results also show that protonation of the ligands has
significant influences on their extraction behavior. SAm/Eu
values can reverse, for instance for CTV6PICO from SAm/Eu
= 0.7 at 0.001 M HNO3 to 1.2 at 0.01 M HNO3. The DAm
values change significantly for all ligands upon a change in the
HNO3 concentration.
Experimental
General information and instrumentation
All moisture-sensitive reactions were carried out under an
argon atmosphere. The solvents and all reagents were ob-
tained from commercial sources and used without further
purification. Solvents were dried according to standard pro-
cedures and stored over molecular sieves. 1H NMR and
13C NMR spectra were recorded on a Varian Unity INOVA
(300 MHz) spectrometer. 1H NMR chemical shift values
(300 MHz) are reported as d using the residual solvent signal
as an internal standard (CDCl3, d 7.257). 13C NMR chemical
shift values (75 MHz) are reported as d using the residual
solvent signal as an internal standard (CDCl3, d 77.0). Fast
atom bombardment (FAB) mass spectra were recorded with
a Finnigan MAT 90 spectrometer. Matrix-assisted laser
desorption ionization (MALDI) TOF mass spectra were re-
corded using a Perkin Elmer/PerSpective Biosystems Voyager-
DE-RP MALDI-TOF mass spectrometer. Elemental analyses
were performed using a Carlo Erba EA1106 instrument.
Analytical TLC was performed using Merck prepared plates
(silica gel 60 F-254 on aluminium). Merck silica gel (40–63 mm)
was used for flash chromatography. Column chromatography
was carried out on Merck silica gel 60 (230–400 mesh).
Compounds 4 and 5,10 the activated esters of CMPO,32
DGA,33 PICO,23 and MPMA9 were synthesized according to
literature procedures.
Tris(3,5-di-tert-butyl-2-(((pyridine-2-carbonyl)amino)ethoxy)-
phenyl)methane (7–tritPICO). A solution of trityl 6 (0.50 g,
0.66 mmol) and picolinic acid pentafluorophenyl ester (0.59 g,
2.04 mmol) in CHCl3 (30 mL) was refluxed for 2 d. The solvent
was evaporated under reduced pressure and the crude product
was taken up into CH2Cl2 (30 mL). The organic layer was
washed with 1 M NaOH (7 ꢃ 20 mL) and H2O (20 mL) and
dried with MgSO4. Evaporation of the solvent afforded 0.64 g
of the crude product which was subjected to column chroma-
tography (SiO2, eluent EtOAc) giving 7–tritPICO as a white
powder. Yield 0.56 g (80%); mp 85–86 1C; FAB-MS:
m/z 1073.6 ([M + H]+, calc. 1073.7); 1H NMR d: 8.55
(d, 3H, J = 5.7 Hz, PhH), 8.12 (d, 3H, J = 4.5 Hz, PhH),
7.72 (t, 3H, J = 9.6 Hz, PhH), 7.39 (t, 3H, J = 9.6 Hz, PhH),
7.29–7.34 (m, 3H, PhH), 7.19 (d, 3H, J = 1.4 Hz, PhH), 6.65
(s, 1H, CH), 3.86–3.92 (m, 6H, OCH2), 3.60 (t, 6H, J = 5.1 Hz,
CH2NHO), 1.30 (s, 27H, C(CH3)3), 1.23 (s, 27H, C(CH3)3);
13C NMR d: 164.2, 153.0, 149.8, 147.9, 144.9, 142.1, 137.4,
127.1, 125.9, 122.6, 122.1, 70.7, 39.9, 37.7, 35.5, 34.5, 31.5,
31.3. Anal. Calc. for C67H88N6O6 ꢄ 0.25CH2Cl2: C, 73.83; H,
8.15; N, 7.68. Found: C, 73.82; H, 8.10; N, 7.62%.
Tris(3,5-di-tert-butyl-2-((N-phenyl-N-methylmalonamido)-
ethoxy)phenyl)methane (7–tritMPMA). A solution of trityl 6
(0.50 g, 0.66 mmol), N-phenyl-N-methylmalonic acid (0.42 g,
2.2 mmol), and DCC (0.41 g, 2.0 mmol) in THF (40 mL) was
Syntheses
Tris(3,5-di-tert-butyl-2-aminoethoxyphenyl)methane (6). A
solution of trityl 5 (15.0 g, 20.1 mmol) and BH3 (121 mL,
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stirred for 3 d at rt. The suspension was cooled to ꢀ18 1C and
the white precipitate was filtered off. The filtrate was evapo-
rated under reduced pressure and the crude product was taken
up into Et2O (50 mL). The organic layer was washed with
NaHCO3 (3 ꢃ 20 mL) and H2O (2 ꢃ 20 mL) and dried with
MgSO4. Evaporation of the solvent afforded 0.84 g of the
crude product as a white foam. This was subjected to column
chromatography (SiO2, eluent EtOAc) to give 7–tritMPMA as
a white solid. Yield 0.45 g (83%); mp 172–173 1C; FAB-MS:
m/z 1283.9 ([M + H]+, calc. 1283.8); 1H NMR d: 8.26 (s, 3H,
NH), 7.30–7.42 (m, 10H, PhH), 7.22–7.24 (m, 8H, PhH), 7.15
(d, 3H, J = 2.1 Hz, PhH), 6.42 (s, 1H, CH), 3.64 (br t, 6H,
OCH2), 3.48 (br t, 6H, CH2NHO), 3.28 (s, 9H, CH3), 3.17 (s,
(50 mL). The organic layer was washed with H2O (3 ꢃ 30 mL),
1 M HCl (3 ꢃ 10 mL), and dried with MgSO4. The solvent was
removed under reduced pressure. Trituration (Et2O) gave 12
as a white solid. Yield 1.60 g (91%); mp 113–117 1C; MALDI-
TOF-MS: m/z 693.8 ([M + H]+, calc. 693.4); 1H NMR d: 6.83
(s, 3H, ArH), 6.82 (s, 3H, ArH), 4.75 (d, 3H, J = 13.9 Hz,
ArCHHAr), 3.91–4.06 (m, 6H, ArOCH2), 3.82 (s, 9H,
ArOCH3), 3.53 (d, 3H, J = 13.9 Hz, ArCHHAr), 2.35
(t, 6H, J = 7.0 Hz, CH2CN), 1.82 (q, 6H, J = 6.8 Hz,
ArOCH2CH2), 1.59–1.75 (m, 12H, CH2CH2); 13C NMR d:
148.4, 147.2, 132.4, 132.0, 119.6, 115.7, 114.1, 69.0, 56.4, 36.5,
28.5, 25.4, 25.2, 17.1. Anal. Calc. for C42H51N3O6: C, 72.70;
H, 7.41; N, 6.06. Found: C, 72.74; H, 7.49; N, 6.09%.
6H, CH3), 1.28 (s, 27H, C(CH3)3), 1.18 (s, 27H, C(CH3)3); 13
C
2,7,12-Trimethoxy-3,8,13-tris(aminohexyloxy)-10,15-dihy-
dro-5H-tribenzo[a,d,g]cyclononene (13–CTV6). To a suspen-
sion of 11 (0.51 g, 0.73 mmol) in MeOH (30 mL) was added
a small quantity of NH3 and RaneyCo. The mixture was
hydrogenated under 7 bar H2 in an autoclave at rt for 18 h.
The active hydrogen was removed from the catalyst by flush-
ing with argon and the solvent was removed under reduced
pressure. The crude product was taken up in CHCl3 (50 mL)
and the mixture was filtered over hyflo and dried with MgSO4.
Removing of the solvent afforded 13–CTV6. Yield 0.48 g
(93%); mp 111–113 1C; MALDI-TOF-MS: m/z 707.2 ([M +
2H]+, calc. 707.5); 1H NMR d: 6.83 (s, 3H, ArH), 6.81 (s, 3H,
ArH), 4.73 (d, 3H, J = 13.6 Hz, ArCHHAr), 3.89–4.04 (m,
6H, ArOCH2), 3.81 (s, 9H, ArOCH3), 3.52 (d, 3H, J = 13.9
Hz, ArCHHAr), 2.67 (t, 6H, J = 6.6 Hz, CH2NH2), 1.79 (q,
NMR d: 168.1, 167.3, 153.0, 144.8, 143.2, 141.9, 137.3, 130.0,
128.2, 127.1, 127.0, 122.5, 70.5, 40.5, 40.2, 37.9, 37.6, 35.4,
34.5, 31.4, 31.4. Anal. Calc. for C79H106N6O9: C, 73.81; H,
8.32; N, 6.55. Found: C, 73.79; H, 8.41; N, 6.49%.
2,7,12-Trimethoxy-3,8,13-tris(N-Boc-aminopropoxy)-10,15-
dihydro-5H-tribenzo[a,d,g]cyclononene (10). A suspension of 9
(0.50 g, 1.22 mmol), tert-butyl-N-(3-bromopropyl)carbamate
(1.17 g, 4.9 mmol), and Cs2CO3 (2.39 g, 7.34 mmol) was stirred
in CH3CN (50 mL) for 18 h at 55 1C. The solvent was removed
under reduced pressure and the residue was taken up in CHCl3
(50 mL). The precipitate was filtered off over hyflo gel and the
solvent was removed under reduced pressure. Trituration of
the crude product with hexane–diisopropyl ether and drying
in vacuo gave 10 as a white powder. Yield 0.93 g (86%); mp
136–139 1C; MALDI-TOF-MS: m/z 879.7 ([M]+, calc. 879.5);
1H NMR d: 6.83 (s, 3H, ArH), 6.81 (s, 3H, ArH), 5.38 (s, 3H,
NH), 4.75 (d, 3H, J = 13.9 Hz, ArCHHAr), 4.06–4.13 (m, 3H,
ArOCHH), 3.94–4.01 (m, 3H, ArOCHH), 3.83 (s, 9H,
ArOCH3), 3.53 (d, 3H, J = 13.9 Hz, ArCHHAr), 3.30–3.32
6H,
J = 7.0 Hz, ArOCH2CH2), 1.33–1.52 (m, 18H,
CH2CH2CH2); 13C NMR d: (CD3OD) 149.5, 148.5, 134.3,
134.2, 116.9, 115.5, 70.5, 57.1, 42.0, 37.0, 31.8, 30.5, 27.8, 27.1.
Anal. Calc. for C42H63N3O6: C, 71.46; H, 8.99; N, 5.95.
Found: C, 71.49; H, 8.97; N, 5.93%.
(m, 6H, CH2NH), 1.96 (m, 6H, CH2), 1.43 (s, 27H, CH3); 13
C
2,7,12-Trimethoxy-3,8,13-tris((diphenylphosphoryl)acetamido)-
10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (14–CTV0CMPO).
A suspension of 8 (0.15 g, 0.37 mmol) and the p-nitrophenyl
activated ester of CMPO (0.47 g, 1.22 mmol) in toluene (20
mL) was refluxed for 18 h. The solvent was evaporated under
reduced pressure and the crude product was taken up into
CHCl3 (20 mL). The organic layer was washed with 1 M
NaOH (3 ꢃ 20 mL) and H2O (20 mL) and dried with Na2SO4.
Removal of the solvent, followed by column chromato-
graphy (SiO2, eluent 7.5% EtOH in CH2Cl2) afforded
14–CTV0CMPO. Yield 0.31 g (73%); mp 164–167 1C;
NMR d: 156.1, 148.4, 147.0, 132.6, 131.7, 115.5, 113.5, 78.9,
68.5, 56.1, 38.8, 36.5, 29.4, 28.5. Anal. Calc. for C48H69N3O12:
C, 65.51; H, 7.90; N, 4.77. Found: C, 65.53; H, 7.84; N, 4.74%.
2,7,12-Trimethoxy-3,8,13-tris(ammoniopropoxy)-10,15-dihy-
dro-5H-tribenzo[a,d,g]cyclononene (11a–CTV3). A solution of
10 (0.93 g, 1.06 mmol) and TFA (12 mL) in CH2Cl2 (12 mL)
was stirred for 3 h at rt, after which it was quenched by the
addition of Et2O (20 mL). The precipitate was filtered off,
washed extensively with Et2O and dried in vacuo to afford
11a–CTV3 as a white solid. Yield 0.94 g (97%); HRM, FAB-
MS: m/z 919.851 ([M–2H+], calc. 919.820); 1H NMR d:
(CD3OD) 7.08 (s, 3H, ArH), 7.05 (s, 3H, ArH), 4.73–4.83
(m, 3H, ArCHHAr), 4.07–4.23 (m, 6H, ArOCH2), 3.84 (s, 9H,
ArOCH3), 3.59 (d, 3H, J = 13.9 Hz, ArCHHAr), 3.18 (t, 6H,
J = 6.6 Hz, CH2N), 2.11 (q, 6H, J = 6.0 Hz, CH2); 13C NMR
d: (CD3OD) 149.5, 147.6, 135.1, 133.9, 117.4, 114.9, 69.6, 56.7,
39.7, 36.8, 28.0.
1
MALDI-TOF-MS: m/z 1132.9 ([M + H]+, calc. 1132.4); H
NMR d: 9.30 (s, 3H, NH), 8.25 (s, 3H, ArH), 7.68–7.80 (m,
12H, PhH), 7.39–7.57 (m, 18H, PhH), 6.84 (s, 3H, ArH), 4.68
(d, 3H, J = 13.6 Hz, ArCHHAr), 3.80 (s, 9H, ArOCH3), 3.54
(d, 3H, J = 13.2 Hz, ArCHHAr), 3.44 (d, 3H, J = 12.8 Hz,
COCHHP), 3.43 (d, 3H, J = 12.8 Hz, COCHHP); 13C NMR
d: 162.4, 162.3, 147.4, 135.3, 132.3, 131.0, 130.8, 130.7, 128.9,
128.7, 126.2, 121.1, 111.7, 56.1, 40.8, 40.0, 36.3. Anal. Calc. for
C66H60N3O9P3: C, 70.02; H, 5.34; N, 3.71. Found: C, 70.33; H,
5.36; N, 3.78%.
2,7,12-Trimethoxy-3,8,13-tris(nitrilohexyloxy)-10,15-dihy-
dro-5H-tribenzo[a,d,g]cyclononene (12). A suspension of 9
(1.04 g, 2.54 mmol), 6-bromohexanenitrile (2.68 g, 15.2 mmol),
and Cs2CO3 (4.96 g, 15.2 mmol) in CH3CN (50 mL) was
stirred at 55 1C for 18 h. The solvent was removed under
reduced pressure and the residue was taken up in CH2Cl2
2,7,12-Trimethoxy-3,8,13-tris(N,N-dimethyl-3-oxaglutaramido)-
10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (14–CTV0DGA). A
suspension of 8 (0.13 g, 0.31 mmol) and the p-nitrophenol ester
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of DGA (0.49 g, 1.85 mmol) in toluene (15 mL) was refluxed
for 18 h. The solvent was evaporated under reduced pressure
and the crude product was taken up into CHCl3 (20 mL). The
organic layer was washed with 1 M NaOH (3 ꢃ 20 mL) and
H2O (20 mL) and dried with MgSO4. Removal of the solvent,
followed by column chromatography (SiO2, eluent 10% EtOH
in CH2Cl2) afforded 14–CTV0DGA. Yield 0.20 g (62%); mp
143–145 1C; MALDI-TOF-MS: m/z 835.0 ([M + H]+, calc.
NH + PhH), 6.87 (s, 3H, ArH), 6.82 (s, 3H, ArH), 4.77 (d,
3H, J = 13.9 Hz, ArCHHAr), 3.73–3.94 (m, 6H, ArOCH2),
3.81 (s, 9H, ArOCH3), 3.55 (d, 3H, J = 13.9 Hz, ArCHHAr),
3.28–3.32 (m, 12H, CH2N + CH2P), 1.81 (q, 6H, J = 6.2 Hz,
CH2CH2CH2); 13C NMR d: 164.9, 148.2, 146.9, 132.5, 132.2,
132.0, 130.9, 130.7, 128.8, 128.7, 128.5, 115.3, 113.9, 67.3, 56.5,
39.6, 37.3, 36.4, 28.8. Anal. Calc. for C75H78N3O12P3: C,
68.96; H, 6.02; N, 3.22. Found: C, 69.03; H, 5.94; N, 3.17%.
1
835.4); H NMR d: 8.85 (s, 3H, NH), 8.41 (s, 3H, ArH), 6.96
(s, 3H, ArH), 4.77 (d, 3H, J = 13.6 Hz, ArCHHAr), 4.28
(s, 6H, NHCOCH2O), 4.16 (d, 6H, COCH2O), 3.87 (s, 9H,
ArOCH3), 3.63 (d, 3H, J = 13.6 Hz, ArCHHAr), 2.97 (s, 18H,
NCH3); 13C NMR d: 168.0, 166.7, 147.2, 135.5, 131.3, 125.4,
121.0, 111.7, 71.3, 69.7, 56.0, 36.0, 35.5. Anal. Calc. for
C42H54N6O12: C, 60.42; H, 6.52; N, 10.07. Found: C, 60.28;
H, 6.46; N, 9.94%.
2,7,12-Trimethoxy-3,8,13-tris((N,N-dimethyl-3-oxaglutara-
mido)propoxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene
(15–CTV3DGA). To a suspension of 11a (0.30 g, 0.37 mmol)
in CHCl3 (25 mL) was added Et3N (0.32 mL, 2.23 mmol). The
mixture was heated to 40 1C under stirring until the reactants
were dissolved. To this solution was added the p-nitrophenyl
activated ester of DGA (0.59 g, 2.23 mmol) and the mixture
was stirred for 18 h at 50 1C. The mixture was allowed to cool
to rt and washed with 1 M NaOH (3 ꢃ 20 mL). The organic
layer was dried with MgSO4 and the solvent was removed
2,7,12-Trimethoxy-3,8,13-tris(N-phenyl-N-methylmalonamido)-
10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (14–CTV0MPMA).
A solution of N-phenyl-N-methylmalonic acid (0.48 g, 2.5
mmol) and DCC (0.52 g, 2.5 mmol) in CHCl3 (8 mL) was
stirred for 1 h at rt. Subsequently, CTV0 8 (0.17 g, 0.42 mmol)
and a solution of Et3N (0.25 g, 2.5 mmol) in CHCl3 (7 mL)
were added and the resulting mixture was stirred at 60 1C for
18 h. After cooling, the precipitate was removed by filtration
and the filtrate was washed with H2O (10 mL), 1 M HCl
(2 ꢃ 10 mL), and brine (3 ꢃ 10 mL) and dried with MgSO4.
The solvent was evaporated under reduced pressure and the
crude product was taken up into CH2Cl2 (10 mL). The formed
precipitate was removed by filtration and the filtrate was
purified by column chromatography (SiO2, eluent 3% EtOH
in CH2Cl2) followed by preparative TLC affording
14–CTV0MPMA. Yield 0.10 g (27%); mp 181–184 1C;
MALDI-TOF-MS: m/z 931.9 ([M + H]+, calc. 931.4); 1H
NMR d: 9.91 (s, 3H, NH), 8.36 (s, 3H, ArH), 7.34–7.45 (m,
9H, PhH), 7.17 (d, 6H, J = 7.0 Hz, PhH), 6.92 (s, 3H, ArH),
4.74 (d, 3H, J = 13.6 Hz, ArCHHAr), 3.88 (s, 3H, ArOCH3),
3.60 (d, 3H, J = 13.9 Hz, ArCHHAr), 3.31 (s, 9H, NCH3),
3.20 (s, 3H, COCHHCO), 3.19 (s, 3H, COCHHCO); 13C
NMR d: 168.4, 163.7, 147.4, 143.1, 135.2, 131.2, 130.1,
128.4, 127.1, 126.1, 121.1, 111.7, 56.1, 41.8, 37.6, 36.5. Anal.
Calc. for C54H54N6O9: C, 69.66; H, 5.85; N, 9.03. Found: C,
69.77; H, 5.83; N, 9.10%.
under
(SiO2, eluent 20% EtOH in CH2Cl2 followed by rinsing
with AcOH–MeOH–CH2Cl2 3.5 10 86.5) afforded
reduced
pressure.
Column
chromatography
:
:
15–CTV3DGA. Yield 0.30 g (78%); mp 94–96 1C; MALDI-
TOF-MS: m/z 1009.0 ([M + H]+, calc. 1008.5); 1H NMR
d: 7.83 (t, 3H, J = 5.5 Hz, NH), 6.86 (s, 3H, ArH), 6.82 (s, 3H,
ArH), 4.71 (d, 3H, J = 13.9 Hz, ArCHHAr), 4.16 (s, 6H,
NHCOCH2O), 3.94–4.09 (m, 12H, ArOCH2 + COCH2O),
3.80 (s, 9H, ArOCH3), 3.41–3.54 (q + d, 9H, CH2NH +
ArCHHAr), 2.75 (s, 9H, NCH3), 2.74 (s, 9H, NCH3), 2.02
(q, 6H, J = 6.3 Hz, CH2CH2CH2); 13C NMR d: 169.5, 168.5,
148.5, 147.0, 132.6, 131.9, 116.1, 113.9, 71.8, 69.7, 67.8, 56.3,
36.3, 35.5, 35.2, 29.2. Anal. Calc. for C51H72N6O15: C, 60.70;
H, 7.19; N, 8.33. Found: C, 60.78; H, 7.12; N, 8.40%.
2,7,12-Trimethoxy-3,8,13-tris((pyridine-2-carbonylamino)-
propoxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (15–
CTV3PICO). To a suspension of 11a (0.23 g, 0.40 mmol)
in CHCl3 (15 mL) was added Et3N (0.32 mL, 2.23 mmol).
The mixture was heated to 40 1C under stirring until the
reactants were dissolved. To this solution was added the
pentafluorophenol activated ester of PICO (0.69 g, 2.38
mmol) and the mixture was stirred for 18 h at 50 1C. The
mixture was allowed to cool to rt and washed with 1 M
NaOH (3 ꢃ 10 mL). The organic layer was dried with
MgSO4 and the solvent was removed under reduced pres-
sure. Column chromatography (SiO2, eluent 2%–3.5%
EtOH in CH2Cl2) afforded 15–CTV3PICO as a white solid.
Yield 0.31 g (88%); mp 61–64 1C; MALDI-TOF-MS: m/z
895.6 ([M + H]+, calc. 895.4); 1H NMR d: 8.50 (d, 3H,
J = 4.0 Hz, PhH), 8.28 (s, 3H, NH), 8.18 (d, 3H, J = 8.1 Hz,
PhH), 7.82 (t, 3H, J = 8.4 Hz, PhH), 7.39 (t, 3H, J = 6.2 Hz,
PhH), 6.90 (s, 3H, PhH), 6.81 (s, 3H, H), 4.74 (d, 3H,
J = 13.6 Hz, ArCHHAr), 4.07–4.76 (m, 6H, ArOCH2),
3.74 (s, 9H, ArOCH3), 3.82 (d, 3H, J = 13.9 Hz, ArCH-
HAr), 2.12 (q, 6H, J = 6.4 Hz, CH2CH2CH2); 13C NMR
d: 164.4, 148.5, 148.1, 147.9, 146.8, 137.1, 132.6, 131.7,
125.9, 121.9, 116.1, 113.6, 67.5, 56.0, 36.6, 36.3, 29.2. Anal.
Calc. for C51H54N6O9: C, 68.44; H, 6.08; N, 9.39. Found: C,
68.34; H, 5.99; N, 9.39%.
2,7,12-Trimethoxy-3,8,13-tris(((diphenylphosphoryl)acetami-
do)propoxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (15–
CTV3CMPO). To a suspension of 11a (0.30 g, 0.37 mmol) in
CHCl3 (25 mL) was added Et3N (0.32 mL, 2.23 mmol). The
mixture was heated to 40 1C under stirring until the reactants
were dissolved. To this solution was added the p-nitrophenyl
activated ester of CMPO (0.85 g, 2.23 mmol) and the mixture
was stirred for 18 h at 50 1C. The mixture was allowed to cool
to rt and washed with 1 M NaOH (3 ꢃ 20 mL). The organic
layer was dried with MgSO4 and the solvent was removed
under reduced pressure. Column chromatography (SiO2, elu-
ent 6.5%–7.5% EtOH in CH2Cl2) afforded 15–CTV3CMPO.
Yield 0.23 g (49%); mp 99–103 1C; MALDI-TOF-MS:
m/z 1305.6 ([M]+, calc. 1305.5); 1H NMR d: 7.61–7.76
(m, 12H, PhH), 7.4–7.47 (m, 12H, PhH), 7.22–7.25 (m, 9H,
ꢁc
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2,7,12-Trimethoxy-3,8,13-tris((N-phenyl-N-methylmalona-
mido)propoxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene
(15–CTV3MPMA). A solution of N-phenyl-N-methylmalonic
acid (0.31 g, 1.6 mmol) and DCC (0.34 g, 1.6 mmol) in CHCl3
(5 mL) was stirred for 1 h at rt. Subsequently, a solution of 11a
(0.25 g, 0.27 mmol) and Et3N (0.22 mL, 1.6 mmol) in CHCl3
(5 mL) was added and the resulting mixture was stirred at
60 1C for 48 h. After cooling, the precipitate was removed by
filtration and the filtrate was washed with H2O (10 mL), brine
(10 mL), 1 M HCl (2 ꢃ 10 mL), and dried with MgSO4. The
solvent was evaporated under reduced pressure and the crude
product was purified by column chromatography (SiO2, eluent
5%–7.5% EtOH in CH2Cl2) giving 15–CTV3MPMA as a
white solid. Yield 0.27 g (89%); mp 82–87 1C; MALDI-
TOF-MS: m/z 1105.3 ([M + H]+, calc. 1105.5); 1H NMR
d: 7.85 (br s, 3H, NH), 7.29–7.42 (m, 9H, PhH), 7.16 (d, 6H, J
= 7.0 Hz, PhH), 6.87 (s, 3H, ArH), 6.84 (s, 3H, ArH), 4.74 (d,
3H, J = 13.6 Hz, ArCHHAr), 3.94–4.10 (m, 6H, ArOCH2),
3.80 (s, 9H, ArOCH3), 3.54 (d, 3H, J = 13.9 Hz, ArCHHAr),
3.44 (q, 6H, J = 6.2 Hz, CH2NH), 3.26 (s, 9H, NCH3), 3.05 (s,
163–164 1C; MALDI-TOF-MS: m/z 1134.8 ([M]+, calc.
1134.6); 1H NMR d: 7.60 (s, 3H, NH), 6.82 (s, 3H, ArH),
6.81 (s, 3H, ArH), 4.73 (d, 3H, J = 13.6 Hz, ArCHHAr), 4.20
(s, 6H, NHCOCH2), 4.05 (s, 6H, COCH2), 3.89–4.00 (m, 6H,
ArOCH2), 3.80 (s, 9H, ArOCH3), 3.51 (d, 3H, J = 13.6 Hz,
ArCHHAr), 3.28 (q, 6H, J = 6.6 Hz, CH2NH), 2.89 (s, 9H,
NCH3), 2.81 (s, 9H, NCH3), 1.78 (q, 6H, J = 7.0 Hz,
ArOCH2CH2), 1.56 (q, 6H, J = 7.1 Hz, CH2CH2N),
1.35–1.48 (m, 12H, CH2CH2); 13C NMR d: 169.3, 168.6,
148.2, 147.3, 132.0, 131.9, 115.3, 114.0, 71.9, 69.7, 69.2, 56.3,
38.8, 36.4, 35.5, 35.4, 29.3, 29.1, 26.6, 25.7. Anal. Calc. for
C60H90N6O15; C, 63.47; H, 7.99; N, 7.40. Found: C, 63.44;
H, 8.03; N, 7.33%.
2,7,12-Trimethoxy-3,8,13-tris(((pyridine-2-carbonyl)amino)-
hexyloxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene (16–
CTV6PICO). A suspension of 13 (0.45 g, 0.64 mmol) and
the pentafluorophenol activated ester of PICO (0.33 g,
2.12 mmol) in CHCl3 (10 mL) was stirred for 18 h at 50 1C.
The mixture was allowed to cool to rt and washed with 1 M
NaOH (3 ꢃ 10 mL). The organic layer was dried with MgSO4
and the solvent was removed under reduced pressure. Column
chromatography (SiO2, eluent 6% EtOH in CH2Cl2) afforded
6H, COCH2CO), 2.00 (q, 6H, J = 6.2 Hz, CH2CH2CH2); 13
C
NMR d: 168.4, 166.3, 148.5, 146.9, 143.1, 132.6, 131.9, 130.0,
128.3, 127.0, 116.0, 113.9, 67.7, 56.3, 40.7, 37.4, 36.9, 36.4,
29.1. Anal. Calc. for C63H72N6O12: C, 68.46; H, 6.52; N, 7.60.
Found: C, 68.52; H, 6.53; N, 7.64%.
16–CTV6PICO. Yield 0.28
g (43%); mp 134–135 1C;
1
MALDI-TOF-MS: m/z 1021.2 ([M + H]+, calc. 1021.5); H
NMR d: 8.50 (d, 3H, J = 3.3 Hz, PhH), 8.18 (d, 3H, J = 7.7
Hz, PhH), 8.04 (br s, 3H, NH), 7.81 (t, 3H, J = 7.7 Hz, PhH),
7.37 (t, 3H, J = 6.0 Hz, PhH), 6.82 (s, 3H, ArH), 6.80 (s, 3H,
ArH), 4.73 (d, 3H, J = 13.6 Hz, ArCHHAr), 3.88–4.03
(m, 6H, ArOCH2), 3.79 (s, 9H, ArOCH3), 3.43–3.53 (m, 9H,
ArCHHAr+CH2NH), 1.78–1.80 (m, 6H, ArOCH2CH2),
1.63–1.67 (m, 6H, CH2CH2NH), 1.47–1.48 (m, 12H,
CH2CH2); 13C NMR d: 164.1, 150.0, 148.2, 147.9, 147.2,
137.2, 132.0, 131.9, 125.9, 122.0, 115.3, 114.0, 69.2, 56.2,
39.2, 36.4, 29.5, 29.1, 26.6, 25.7. Anal. Calc. for
C60H72N6O9: C, 70.57; H, 7.11; N, 8.23. Found: C, 70.60; H,
7.13; N, 8.24%.
2,7,12-Trimethoxy-3,8,13-tris(((diphenylphosphoryl)acetami-
do)hexyloxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene
(16–CTV6CMPO). A suspension of 13 (0.45 g, 0.64 mmol)
and the p-nitrophenyl activated ester of CMPO (0.81 g, 2.12
mmol) in CHCl3 (10 mL) was stirred at 50 1C for 18 h. The
reaction mixture was washed with 1 M NaOH (3 ꢃ 10 mL)
and H2O (10 mL). The mixture was dried with MgSO4. The
solvent was evaporated under reduced pressure and the crude
product was purified by column chromatography (SiO2, eluent
10% EtOH in CH2Cl2) to afford 16–CTV6CMPO. Yield
0.52
g
(56%); mp 179–180 1C; MALDI-TOF-MS:
m/z 1431.4 ([M]+, calc. 1431.6); 1H NMR d: 7.69–7.76 (m,
12H, PhH), 7.46–7.52 (m, 18H, PhH), 7.34 (s, 3H, NH), 6.82
(s, 6H, ArH), 4.74 (d, 3H, J = 13.6 Hz, ArCHHAr), 3.84–3.98
(m, 6H, ArOCH2), 3.80 (s, 9H, ArOCH3), 3.53 (d, 3H,
J = 13.9 Hz, ArCHHAr), 3.29 (d, 6H, J = 12.5 Hz, CH2CO),
3.19 (q, 6H, J = 6.5 Hz, CH2NH), 1.70 (q, 6H, J = 6.9 Hz,
ArOCH2CH2), 1.30–1.45 (m, 18H, CH2CH2CH2); 13C NMR
d: 164.6, 148.2, 147.1, 132.6, 132.0, 132.0, 130.9, 130.7, 130.1,
129.0, 128.8, 115.3, 113.8, 69.1, 56.3, 39.8, 38.0, 36.4, 29.1,
26.4, 25.6. Anal. Calc. for C84H96N3O12P3: C, 70.43; H, 6.75;
N, 2.93. Found: C, 70.46; H, 6.76; N, 2.95%.
2,7,12-Trimethoxy-3,8,13-tris((N-phenyl-N-methylmalona-
mido)hexyloxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene
(16–CTV6MPMA). A solution of N-phenyl-N-methylmalonic
acid (0.50 g, 2.6 mmol) and DCC (0.53 g, 2.6 mmol) in CHCl3
(8 mL) was stirred for 1 h at rt. Subsequently, a solution of 13
(0.30 g, 0.43 mmol) and Et3N (0.36 mL, 2.6 mmol) in CHCl3
(7 mL) was added and the resulting mixture was stirred at
60 1C for 48 h. After cooling, the precipitate was removed by
filtration and the filtrate was washed with H2O (10 mL), brine
(10 mL), 1 M HCl (2 ꢃ 10 mL), and dried with MgSO4. The
solvent was evaporated under reduced pressure and the crude
product was purified by column chromatography (SiO2, gra-
dient elution 3.5–4% EtOH in CH2Cl2) to give
16–CTV6MPMA. Yield 0.32 g (60%); mp 150–154 1C;
2,7,12-Trimethoxy-3,8,13-tris((N,N-dimethyl-3-oxaglutara-
mido)hexyloxy)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene
(16–CTV6DGA). A suspension of 13 (0.45 g, 0.64 mmol) and
the p-nitrophenyl activated ester of DGA (0.56 g, 2.12 mmol)
in CHCl3 (10 mL) was stirred at 50 1C for 18 h. The reaction
mixture was washed with 1 M NaOH (3 ꢃ 10 mL) and H2O
(10 mL). The mixture was dried with MgSO4. The solvent was
evaporated under reduced pressure and the crude product was
purified by column chromatography (SiO2, eluent 12% EtOH
in CH2Cl2) to give 16–CTV6DGA. Yield 0.37 g (52%); mp
1
MALDI-TOF-MS: m/z 1231.9 ([M + H]+, calc. 1231.7); H
NMR d: 7.86 (br s, 3H, NH), 7.31–7.43 (m, 9H, PhH), 7.15 (d,
6H, J = 7.0 Hz, PhH), 6.83 (s, 3H, ArH), 6.81 (s, 3H, ArH),
4.73 (d, 3H, J = 13.6 Hz, ArCHHAr), 3.88–4.02 (m, 6H,
ArOCH2), 3.80 (s, 9H, ArOCH3), 3.52 (d, 3H, J = 13.9 Hz,
ArCHHAr), 3.21–3.27 (m, 15H, NCH3, NCH2), 3.05 (s, 6H,
COCH2CO), 1.79 (q, 6H, J = 6.8 Hz, ArOCH2CH2),
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1.38–1.59 (m, 18H, CH2CH2CH2); 13C NMR d: 168.8, 165.9,
148.3, 147.3, 142.9, 132.0, 131.9, 130.0, 128.3, 126.9, 115.3,
114.0, 69.2, 56.3, 40.2, 39.2, 37.4, 36.4, 29.3, 29.1, 26.7, 25.7.
Anal. Calc. for C72H90N6O12: C, 70.22; H, 7.37; N, 6.82.
Found: C, 70.13; H, 7.34; N, 6.90%.
with the appropriate aqueous solution (0.25 mL) at ambient
temperature (22–24 1C) for 60 min for equilibration in a 2 mL
screw cap vial. Subsequently, the two layers were separated by
centrifugation (5 min, 1600 rpm). 0.15 mL of each layer was
pipetted out into vials and positioned for g-ray measurement.
The gamma-activity was determined by measuring for 1 h with
a Germanium High Purity Ge(HP)-detector. The reported DM
values are the averages of at least two experiments. The errors
in the extraction percentages of the duplicate experiments are
less than 4%. In the region 5% 4 E 4 95% the error in the
DM values is larger since, for example, an extraction of
95 ꢅ 1% results in a DM of 19 ꢅ 5.
4-tert-Butylbenzamido-4-tert-butyloxycarbonylaminopropyl-
1,7-bis(tert-butyloxycarbonylamino)heptane (18). A solution of
17 (1.94 g, 3.9 mmol), tert-butylbenzoyl chloride (0.76 g,
3.9 mmol), and Et3N (5.4 mL, 38.7 mmol) was stirred in
toluene (40 mL) at 90 1C for 5 h. Part of the solvent was
evaporated under reduced pressure, whereupon the residue
was slowly cooled to ꢀ20 1C. White crystals were formed
which were filtered off and washed with hexane (2 ꢃ 20 mL)
giving C-pivot 18. Yield 1.2 g (47%); mp 174–176 1C; FAB-
MS: m/z 663.5 ([M + H]+, calc. 663.5); 1H NMR d: 7.65
(d, 2H, J = 8.4 Hz, PhH), 7.42 (d, 2H, J = 6.6 Hz, PhH), 5.65
(s, 1H, NH), 4.64 (s, 3H, NH), 3.07–3.13 (q, 6H, J = 6.3 Hz,
CH2NH), 1.76–1.82 (m, 6H, CH2CH2CH2), 1.39–1.50 (m, 6H,
CCH2CH2), 1.42 (s, 27H, OC(CH3)3), 1.33 (s, 9H, C(CH3)3);
13C NMR d: 166.8, 156.1, 154.9, 132.4, 129.0, 128.2, 79.2, 40.8,
34.9, 32.3, 31.1, 28.4, 23.9. Anal. Calc. for C36H62N4O7: C,
65.23; H, 9.43; N, 8.45. Found: C, 65.24; H, 9.36; N, 8.48%.
Tracer solutions. In each extraction between 200 Bq and 600
Bq of 241Am and 152Eu, depending on the DM values of the
ligands, was used. Where necessary, the concentration of Eu3+
was adjusted by addition of a stable isotope of europium. The
241Am and 152Eu isotopes were used from NRG (Nuclear
Research & Consultancy Group) stock.
Acknowledgements
This research is supported by the Technology Foundation
STW, applied science division of NWO and the technology
program of the Ministry of Economic Affairs. We gratefully
acknowledge the Fuels, Actinides and Isotopes (FAI) depart-
ment at the Nuclear Research & Consultancy Group (NRG)
in the Netherlands for providing the radionuclear facilities.
Especially we would like to thank Tanja Tomasberger and
Marco Ooijevaar for their support and work on the measure-
ments.
4-tert-Butylbenzamido-4-(((diphenylphosphoryl)acetamido)
propylamino)-1,7-bis((diphenylphosphoryl)acetamido)heptane
(20–pivCMPO). To a solution of C-pivot 18 (2.80 g, 4.2 mmol)
in CH2Cl2 (10 mL) was added TFA (10 mL) and the resulting
solution was stirred for 1 h at rt. The solution was quenched
by the addition of Et2O (60 mL) whereupon a precipitate was
formed. The precipitate was filtered off, washed extensively
with Et2O and dried in vacuo to give 2.7 g (91%) of the TFA
salt of 4-tert-butylbenzamido-4-aminopropyl-1,7-heptanedi-
amine 19 as a white foam. HRM, FAB-MS: m/z 725.620
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([M ꢀ 2H+], calc. 725.614); H NMR d: (CD3OD) 6.31 (d,
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(m, 34H, PhH), 5.45 (s, 1H, NH), 3.68–3.75 (q, 6H, J = 7.0 Hz,
CH2NH), 3.50 (d, 6H, J = 12.6 Hz, C(O)CH2P(O)), 3.15 (s,
3H, NH), 1.51–1.54 (m, 6H, CH2CH2CH2), 1.34 (s, 9H,
C(CH3)3), 1.21–1.26 (t, 6H, J = 6.9 Hz, CCH2CH2); 13C
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128.7, 126.7, 125.3, 58.3, 39.7, 39.4, 38.5, 34.8, 32.1, 31.2.
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Found: C, 69.44; H, 6.56; N, 5.18%.
¨
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ꢁc
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1632 | New J. Chem., 2007, 31, 1620–1632