Metal complexation of calix[4]azacrown derivatives - Evidence for communication between upper and lower functionalised rims

Article abstract of DOI:10.1002/ejic.200601000

The coordination chemistry of calix[4]azacrowns obtained from the reaction of a diester calix[4]arene with diethylenetriamine provided unusual copper(II) and manganese(II) complexes in which calix[4]azacrown acts as a bidentate N,O-donor ligand, in some cases, but as a unidentate N-donor ligand, in other cases. The first example of a binuclear ruthenium(II)/manganese(II) complex, involving the calix[4]arene framework as the bridging ligand, is also reported. The calix[4]arene framework consists of a bipyridyl unit connected at the upper rim of the calix[4]arene, through an amide linkage, and an azacrown unit at the lower rim, also connected through amide groups. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200601000

FULL PAPER
DOI: 10.1002/ejic.200601000
Metal Complexation of Calix[4]azacrown Derivatives – Evidence for
Communication Between Upper and Lower Functionalised Rims
[a]
[b]
[b,c]
[a]
Tammy L. Gernon,[b,c]
Andrew D. Bond, Bernadette S. Creaven, Denis F. Donlon,
[
c]
John McGinley,* and Hans Toftlund
Dedicated to the memory of Des Cunningham[†]
Keywords: Calix[4]arene / Macrocyclic ligands / Heterometallic compounds / Copper(II) / Manganese(II) / Ruthenium(II) /
EPR spectroscopy
The coordination chemistry of calix[4]azacrowns obtained
from the reaction of a diester calix[4]arene with diethyl-
enetriamine provided unusual copper(II) and manganese(II)
complexes in which calix[4]azacrown acts as a bidentate
N,O-donor ligand, in some cases, but as a unidentate N-do-
nor ligand, in other cases. The first example of a binuclear
ruthenium(II)/manganese(II) complex, involving the ca-
lix[4]arene framework as the bridging ligand, is also re-
ported. The calix[4]arene framework consists of a bipyridyl
unit connected at the upper rim of the calix[4]arene, through
an amide linkage, and an azacrown unit at the lower rim,
also connected through amide groups.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
Introduction
Calix[4]arenes are versatile host molecules for supra- numerous elaborate structures.[1] Double calix[4]arenes,[2]
molecular chemistry, which have been incorporated into for example, have been constructed covalently through
Figure 1. Calix[4]azacrowns.
[
3]
upper rim/upper rim linkage, lower rim/lower rim link-
[
4]
[5]
age or upper rim/lower rim linkage, and also nonco-
[
a] Department of Physics and Chemistry, University of Southern
[
6]
valently through hydrogen bonding. Incorporation of a
crown ether into a rigid calix[4]arene creates a new type of
supramolecular host, with interesting prospects for binding
Denmark,
5
230 Odense M, Denmark
[
[
b] Department of Applied Science, Institute of Technology,
Tallaght, Dublin 24, Ireland
[
7]
c] Department of Chemistry, National University of Ireland May- metal ions. The family of calix[4]azacrowns combine ca-
nooth,
lix[4]arenes with azaethylene chains attached to the pheno-
lic oxygen atoms by acetamido groups, which serve both as
covalent linking functions and as potential chelating
Maynooth, Co. Kildare, Ireland
[†] Our teacher, mentor and friend who passed away on September
1
8, 2006.
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749

J. McGinley et al.
FULL PAPER
groups. The first calix[4]azacrowns of type 1 (Figure 1) were arene (diester calix[4]arene),[9a,23] which was then stirred for
prepared by reaction of either a calix[4]arene dimethyl ester 72 h with either diethylenetriamine or tris(2-aminoethyl)-
or calix[4]arene diacyl chloride derivative with the appropri- amine in a methanol/toluene solvent mixture to give the
ate diamine and were shown by FAB-mass spectrometry to cyclic amides 2 and 3 as white solids in good yield, similar
2
+
2+
2+
2+
2+
[24]
complex divalent (Be , Mg , Ca , Sr , Ba ) and tri- to that described by Bitter et al.
The IR spectra of 2
3
+
3+
3+
3+
3+
[8]
–1
valent (Sc , Y , In , Gd , Bi ) metal cations.
and 3 exhibit a strong C=O signal at 1678 and 1681 cm
We have previously reported upper- and lower-rim func- respectively (compared to 1746 cm–1 in the starting diester
tionalised calix[4]arenes, capable of binding transition- calix[4]arene), indicative of the amide functional group, to-
–1
metal and alkali-metal salts, as well as ligands capable of gether with a sharp N–H signal at 3372 and 3399 cm ,
[9]
attachment to calix[4]arenes. One such calix[4]arene con- which is not present in the spectrum of the starting diester
tained picolyl groups.[ In extending this theme, we tar- derivative. The H NMR spectrum suggests that the calix-
9c]
1
geted the design of calix[4]azacrowns and, in particular, the [4]arene molecules in 2 and 3 adopt a distorted cone confor-
[
25]
calix[4]arenes 2 and 3 which are capped by a diamide bridge mation:
a pair of AB-type doublets is observed for the
at the 1,3-position on the lower rim. diastereotopic methylene protons at δ = 4.16 and 3.36 ppm
Transition-metal ions which are covalently linked to each in 2 and at δ = 4.17 and 3.39 ppm in 3, respectively, com-
other through a ligand system are of interest and impor- pared to δ = 4.43 and 3.30 ppm for the corresponding sig-
tance for a variety of purposes.[
10–17]
They can be used for nals in the starting diester calix[4]arene.
studies into light-induced energy and electron transfer, as
well as model systems for the development of supramolec-
ular compounds which are capable of performing useful
light induced processes such as photochemical devices. In-
deed, the conversion of light energy into chemical energy is
of current interest with particular focus on the development
of efficient solar energy conversion schemes. To observe
such transfer processes between the metal centres, they must
be linked by a bridging ligand. These ligands have varied
from chelating units linked by either flexible or rigid chains
or by rod-like spacers.[
14,18–21]
More recently, the cage com-
pound 1,12-dicarba-closo-dodecaborane, known as p-car-
borane, has been used as the linker molecule.[
22]
These
linker or spacer molecules determine the spatial arrange-
ment of the whole molecule while their chemical properties
are important in influencing the spectroscopic and redox
properties of the two metal centres as well as determining
the rate of the electron/electron transfer process. We have
focused our efforts on the construction of polynuclear com-
plexes in which a photoactive and redox-active metal are
[
9a]
linked by bridges based on a calix[4]arene derivative. Ex-
tensive functionalisation has been carried out at both the
upper and lower rims of the calix[4]arene. A calix[4]arene,
with appropriate functionalisation at both the wide and
narrow rims, is capable of maintaining a well-defined dis-
tance between two metal centres positioned at each rim. By
the simple modification of the synthesis of the function-
alised calix[4]arene, this distance can be easily altered. To
the best of our knowledge, there has been no report of a
calix[4]arene derivative as a spacer molecule in energy/elec-
tron transfer reactions.
Scheme 1. Reagents and conditions: (i) K
MeCN, reflux, 18 h; (ii) diethylenetriamine, MeOH, toluene, 48 h;
2 3
CO , ethyl bromoacetate,
(
iii) tris(2-aminoethyl)amine, MeOH, toluene, 48 h.
1H NMR studies have previously indicated that macro-
cycles of this type show interesting binding proper-
[
7c,7d,26]
ties;
for example, while the tetra(p-tert-butyl)calix-
[
4]azacrown 1 does not extract transition-metal ions, the
Results and Discussion
corresponding 1,3-dimethoxy-p-tert-butylcalix[4]azacrown
extracts Cu ions selectively with respect to Co and Ni
ions.
2+
2+
2+
Lower-Rim Complexes
[
7c,7d]
Complexation behaviour of 2 towards alkaline-
The method used for preparation of lower-rim function- earth and transition-metal ions has been recently de-
[
26]
alised calix[4]azacrown (2) is shown in Scheme 1. Base-pro- scribed
and the X-ray crystal structure of the complex
moted reaction of p-tert-butylcalix[4]arene with ethyl bro- with Mg2 revealed that the metal ion was not bound to
moacetate in acetonitrile produced the diester 5,11,17,23- any of the nitrogen atoms, but lay outside of the crown
tetra-tert-butyl-25,27-bis(ethoxycarbonylmethyloxy)calix[4]- loop, forming a coordination polymer through metal–oxy-
+
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Metal Complexation of Calix[4]azacrown Derivatives
FULL PAPER
gen bonds to carbonyl O atoms from different calix[4]arene
entities. Oueslati et al.[ found that metal extraction did
not occur on attempted complexation of 2 with copper,
nickel and cobalt picrates. Instead, crystals were formed in
which a water molecule lies within the crown loop of 2 and
picric acid accepts a hydrogen bond from this water mole-
cule. In an effort to understand the binding, or lack thereof,
7d]
2
+
of Cu to calix[4]azacrowns, we undertook complexation
reactions of 2 and 3 with various copper(II) salts, as well
as investigating the complexation behaviour of MnCl2.
Figure 2. Molecular structure of 4 (H atoms omitted).
Comparison of the IR spectrum of 6 and 7 with that of 4
reveals slight differences in the spectra. The differences sug-
Copper(II) Complexes
Complexation reactions of 2 and 3 were carried out in gest that the mode of complexation of the calixazacrown
MeOH at reflux temperature, using copper(II) acetate hy- derivative is not determined solely by the metal ion (al-
drate, copper(II) chloride dihydrate and copper(II) perchlo- though this clearly will have some bearing), but is also influ-
rate hexahydrate, respectively, in each case in a 1:1 ratio. enced by the anion and its coordinating ability. The more
Intense blue solutions were obtained in all cases and most strongly complexing acetate anion remains bound to Cu2
of the solvent had to be removed under reduced pressure in 4, while the weakly complexing perchlorate anions may
before precipitation occurred. For the reaction involving 2 be less likely to do so in 6 and 7. Elemental analyses of
with copper(II) acetate, a blue/green complex 4 was ob- both 6 and 7 suggest the presence of one perchlorate anions
+
tained, which was shown by X-ray diffraction to be Cu(2) - per Cu2 ion as well as the presence of only one calix[4]-
+
2
2
+
(
CH CO ) (MeOH) (Figure 2). The Cu ion is not com- azacrown unit, requiring that the ligands of 2 and 3 be neu-
3 2 2 2
plexed within the calix[4]azacrown, but instead is bound to tral, possibly using the lone pairs on the nitrogen atoms in
two such units through interactions with the lone pairs on the ring to bind Cu2 internally in the calixazacrown loop.
the NH of the crown ring and the C=O groups of the amide Furthermore, the metal complexes crystallise along with a
units. Thus, 2 acts as a bidentate N,O-donor ligand. The molecule of methanol in both cases. To date, we have not
complex is centrosymmetric, and Cu2+ adopts a typical been able to obtain suitable crystals of 6 or 7 to establish
+
[
4+2] distorted octahedral geometry. The Cu–N and Cu– this conclusively.
O(acetate) bond lengths are 2.052(4) and 1.957(3) Å, For the complexation reaction of 2 with copper(II) chlo-
respectively, while the axial Cu–O=C distances are ride, a mixture of green 8 and blue 9 solids was obtained
.715(3) Å. The monomeric nature of the copper acetate when the reaction was allowed to proceed for 120 min. On
2
unit, in contrast to the bridging structures, usually associ- decreasing the reaction time to 20 min, the major product
ated with simple copper(II) acetate salts,[ may be attrib- was 8. The green material 8 has an IR spectrum similar
uted to the steric bulk of the calix[4]azacrown ligand, which to that of 4 (with the exception of the carbonyl stretching
prevents further association. The coordinated amine group frequency due to the acetate group). This suggests that 8
of 2 retains its proton, forming an N–H···O hydrogen bond comprises of copper(II) chloride bound between two calix-
to the unbound O atom of the acetate group. An O–H···O azacrown ligands in a similar manner to the copper(II) ace-
hydrogen bond is also formed from the phenolic OH group tate complex 4. Since 8 is the major product obtained from
of 2 to the acetate group. In the solid state, MeOH mole- the reaction after only a the short time period, complex-
cules form O–H···O hydrogen bonds to the Cu-bound and ation of copper(II) chloride by 2 appears to be the initial
unbound C=O groups of the amide bridge. The infrared outcome. When the reaction proceeds for a longer time, the
spectrum of 4 shows two bands in the carbonyl region, as blue solid 9 is formed. Single crystals of 9 were obtained
27]
–1
was expected from the X-ray crystal structure, at 1690 cm , from the mother liquor after 90 min reaction, and single-
[
28]
representative of an amide carbonyl bond, and also at crystal X-ray analysis
1
confirmed that cleavage of the
–
1
578 cm , representing the acetate carbonyl group. The re- amide bonds had occurred, resulting in the simple copper-
action of 3 with copper(II) acetate also results in a green diethylenetriamine complex shown in Figure 3. This com-
solid 5 which showed similar bands in the infrared spec- plex can also be obtained by direct reaction of diethylenetri-
trum, particularly in the carbonyl region at 1676 and amine with copper(II) chloride dihydrate in a 1:1 ratio.[
29]
–
1
1
555 cm suggesting that the acetate was binding to the Cleavage of amide bonds by copper(II) chloride has been
–1
[30]
copper in an analogous manner. A broad band at 3360 cm
described previously. On repeating the reaction, we were
was also evident implying that the copper was bonding to also able to obtain the calix[4]arene di-acid derivative[
31]
3
through the pendant amine. Elemental analysis on this that is formed in the cleavage reaction. We have only ob-
compound also suggested a 1:2 metal/ligand complex as ob- served the formation of 9 when the reaction mixture is
served in 4. heated for long periods of time. This suggests that the green
The complexation reactions of 2 and 3 with copper(II) complex 8 is relatively stable, and that it requires a consider-
perchlorate hexahydrate gave the green complexes 6 and 7. able amount of energy before the cleavage reaction pro-
Eur. J. Inorg. Chem. 2007, 749–756
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751

J. McGinley et al.
FULL PAPER
ceeds. One probable mechanism for this process involves are occupied by water molecules. Elemental analyses and
2
+
Cu moving from being externally coordinated (in the the infrared spectra of these complexes support this hypo-
manner of 4) to being internally coordinated, with this thesis.
movement allowing the amide bonds to cleave.
Ruthenium(II)/Manganese(II) Complexes
We have previously investigated the complexation of cop-
per(I) to a pyridyl derivative of a calix[4]arene and were able
to oxidise the metal centre while retaining complexation.[
Retention of this bonding is important, because if energy
or electron transfer occurs from one rim to the other, then
a change in the oxidation state of the metal at the lower
rim must happen. Thus, it is essential that the metal–ligand
9c]
Figure 3. Molecular structure of the cleavage product 9.
bonding is retained at the lower rim. To achieve a scaffold
capable of holding two different metals at different coordi-
nation sites, we have functionalised both the upper and
lower rim of a calix[4]arene (Scheme 2); the synthesis of 13
The complexation reaction of 3 with copper(II) chloride
results only in a single green complex 10. The infrared spec-
trum of this compound was very similar to that obtained
for 8 which suggested that the copper was bonded to the
free amine of the calix[4]azacrown. Microanalysis suggested
the presence of only one chloride anion which would mean
that the calix[4]azacrown was acting as a unidentate ligand
through loss of a proton from the pendant amine group.
The remaining coordination sites about the copper atom
were occupied by water molecules. There was no evidence
in this case of any cleavage reactions occurring or of two
calix[4]azacrown units bonding to the copper atom.
[9a]
has been reported previously.
Manganese(II) Complexes
As in the case of the copper complexations described
above, the complexation reactions of 2 and 3 with manga-
nese(II) chloride tetrahydrate were carried out in MeOH at
reflux temperature, respectively, in each case in a 1:1 ratio.
Brown solutions were obtained in both cases and most of
the solvent had to be removed under reduced pressure be-
fore precipitation occurred. Compound 11 crystallises with
a molecule of methanol present as solvent of crystallisation.
Elemental analyses for 11 and 12 suggest the presence of
only one chloride anion which would mean that the calix-
[
4]azacrown 3, in each case, was acting as a unidentate li-
gand through loss of a proton from the pendant amine
group. The remaining coordination sites about the metal
atom were occupied by water molecules.
II
The EPR spectra of the Mn complexes without any
functionalisation on the upper rim (11–12) were obtained
as glasses in dimethylformamide (DMF) at 120 K. Both
spectra were almost identical, showing jagged six-line spec-
tra; the six-line spectrum in each case arising from the fact
Scheme 2. Reagents and conditions: (i) diethylenetriamine, MeOH,
toluene, 48 h; (ii) tris(2-aminoethyl)amine, MeOH, toluene, 48 h.
II
that Mn has I = 5/2. These spectra indicate that the coor-
II
dination of Mn is very similar in each case. We believe
The bis(bipy) diester calix[4]arene 13 was treated with
that the manganese atom is bonded to the amine nitrogen 0.5 equiv. of either diethylenetriamine or tris(2-aminoethyl)-
[
24]
of the azacrown ring, either NH or NH depending on the amine in methanol/toluene
to give the calix[4]azacrown
2
II
calix[4]arene derivative 2 or 3, similar to the bonding of derivatives 14 and 15. The Ru complexes 16 and 17 were
the copper metal in the X-ray crystal structure of 4. The prepared by reacting 14 or 15 with 1.1 equiv. of Ru(bipy)-
[
32]
remaining coordination sites around the manganese metal Cl4
in refluxing absolute ethanol and, on cooling, a
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Metal Complexation of Calix[4]azacrown Derivatives
FULL PAPER
brown solid precipitated in each case and recrystallised ever, a substantial increase in the signals for a RuIII species,
from chloroform. These solids were kept in the dark during which indicated that the oxidation had occurred only at the
II
the filtering and drying stages and were stored at room tem- Ru sites. The samples were then warmed to 273 K and re-
1
perature in the dark. All efforts to obtain H NMR spectra cooled to 120 K. This was to allow any energy or electron
of both 16 and 17 failed in all solvents, due to lack of solu- transfer to occur. On recording the spectra again, the spec-
bility in the deuterated solvents. Elemental analyses for tra looked identical to the initial partially oxidised spectra.
both products showed the presence of three molecules of However, closer examination revealed that the intensity of
II
II
II
III
chloroform. The Ru /Mn complexes 18 and 19 were pre- both the Mn and Ru species had decreased by ca. 30%,
II
pared by the reaction of the appropriate Ru complexes 16 indicating that either energy or electron transfer was occur-
or 17 with manganese(II) chloride tetrahydrate in refluxing ring from the Mn centre to the Ru centre, with conse-
II
III
II
III
methanol. Elemental analyses for 18 and 19 suggest the quent oxidation of the Mn to Mn , an EPR-silent species.
presence of only one chloride anion which would mean that Importantly, this suggests that the two metals are in com-
the calix[4]azacrowns 16 and 17, in each case, were acting munication with each other, despite the fact that there is no
as a unidentate ligand through loss of a proton from the direct pathway between them, since they are not attached
pendant amine group. The remaining coordination sites to the same benzene ring. More unprecedented was that
about the metal atom were occupied by water molecules. the result could be observed using the relative slow EPR
Furthermore, in both cases, two molecules of chloroform spectroscopy technique, instead of having to use transient
were also present as solvent of crystallisation, the chloro- spectroscopy with nanoseceond laser flash photolysis. This
form being present from the washing of the solid to remove would indicate that the charge recombination reaction in
any unreacted calix[4]azacrown scaffold. Interestingly, the this case is very slow, implying that the charge-separation
two metal centres are not directly connected through the between the metal species is close to an optimum distance.
same aromatic ring of the calix[4]arene. This is simply due
to the synthetic path chosen. The first step in the function-
alisation process is the etherification reaction at the lower Conclusions
rim, which has a dual role; firstly, it protects two of the
We have shown that binding of copper(II) and manga-
phenol groups on the narrow rim while conferring cone
nese(II) to calixazacrowns can be achieved, and that the
conformation on the molecule, and secondly, it directs the
particular mode of coordination appears to be influenced
functionalisation of the wide rim opposite the remaining
by the coordination ability of the associated anion. We have
free hydroxy groups of the narrow rim. It is this second
also synthesised mixed metal complexes with ruthenium(II)
function which does not allow a direct connection between
at the upper rim of our calix[4]arene scaffold and manga-
both metal centres.
nese(II) at the lower rim. Furthermore, initial EPR studies
of these complexes indicate that the metals are able to com-
tained as glasses in DMF at 120 K. Both spectra were al-
The EPR spectra of the complexes 18 and 19 were ob-
III
municate with each other, although they are not bound to
the same aromatic ring of the calix[4]arene structure. We
are currently examining the amide cleavage reaction in more
detail and also looking at the coordination chemistry of
other transition metals with 2 and 3, as well as carrying out
transient spectroscopy on the mixed metal species in an ef-
fort to understand the communication processes being un-
dertaken.
most identical. Some very small peaks for Ru were ob-
served, which was not unexpected as it was impossible to
keep the sample under light-free conditions at all times dur-
ing the preparation of the sample for the experiment. The
very similar, jagged six-line spectra for 18 and 19 indicate
II
that the coordination of Mn is very similar in both com-
plexes. We believe that, in both cases, the Mn atom is
bonded to one nitrogen atom from the azacrown unit and
that the remaining five coordination sites of the manganese
are occupied by water molecules. These results are similar
to those observed by Berg et al., where they had synthesised
Experimental Section
1H and 13C NMR (δ in ppm; J in Hz) spectra were recorded with
either a JEOL JNM-LA300 FT-NMR spectrometer or a Bruker
Avance 300 MHz spectrometer using saturated CDCl3 solutions
2
+
[
Ru(bipy)3] complexes covalently attached to bis(picolyl-
amine) or tris(picolylamine) functional groups to which
II
[33]
Mn could be attached.
II
II
4
The Ru /Mn complexes 18 and 19 were partially oxi- with Me Si reference, unless indicated otherwise, with resolutions
III
II
–1
dised to obtain the mixed valence Ru /Mn complexes. of 0.18 Hz and 0.01 ppm, respectively. Infrared spectra (cm ) were
recorded as KBr discs or liquid films between KBr plates with a
The reactions were preformed using ammonium cerium(IV)
Nicolet Impact 410 FT-IR. All UV/Vis spectra were recorded on a
nitrate as the oxidant in a 3:1 mixture of DMF and meth-
anol, similar to that described by Ghirotti et al.[22] Dimeth-
Shimadzu UV-160A spectrometer. Melting point analysis was car-
ried out using a Stewart Scientific SMP 1 melting point apparatus
and are uncorrected. The EPR spectra were recorded either at
room temperature or in frozen glass at 120 K using a Bruker EMX
spectrometer operating at the X-band. Microanalysis was carried
out at the Microanalytical Laboratory of either University College,
ylformamide was one of the two solvents in which these
compounds would dissolve, the other was methyl sulfoxide.
The oxidation was monitored using EPR spectroscopy. On
cooling the partially oxidised sample, no decrease in the
signal intensity of the six-line region of the spectra, associ- Dublin or the National University of Ireland Cork. Standard
II
ated with the Mn signals, was observed. There was, how- Schlenk techniques were used throughout. Starting materials were
Eur. J. Inorg. Chem. 2007, 749–756
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753

J. McGinley et al.
FULL PAPER
commercially obtained and used without further purification. The
resulting brown solution was stirred for 2 h. The solution was al-
lowed to stand and, after several days, a brown powder precipi-
tated, which was collected by filtration and dried.
synthesis of compounds 4-tert-butylcalix[4]arene,[
34]
5,11,17,23-
[
9a,23]
tetra-tert-butyl-25,27-diethoxycarbonylmethyloxycalix[4]arene,
calix[4]azacrown 2,
[
35]
and 5,17-di-tert-butyl-11,23-bis[(4Ј-methyl-
3
11: Brown solid, yield 0.39 g (75%). C53H82ClMnN O12 (1043.62):
2
,2Ј-bipyridin-4-yl)carbonylamino]-25,27-bis(ethoxycarbonylmeth-
calcd. C 61.00, H 7.92, N 4.03; found C 61.19, H 8.15, N 4.48;
[
9a]
II
[32]
oxy)calix[4]arene (13) and Ru (bipy)Cl
4
have been described
–1
m.p. 220 °C (dec.). IR (KBr): ν˜ max = 3343 (NH) cm , 1680 (amide
in the literature previously.
–1
C=O) cm .
Synthesis of Calix[4]azacrown 3: A solution of diester calix[4]arene
2.0 g, 2.5 mmol) and tris(2-aminoethyl)amine (2.26 mL,
5.1 mmol) in a mixture of methanol (25 mL) and toluene (25 mL)
was stirred at room temperature for 3 d. After this time, the solu-
tion was concentrated under reduced pressure. The solid residue
was suspended in methanol and filtered to give a white solid.
1
4
2: Brown solid, yield 0.40 (76%). C54H83ClMnN O11 (1054.65):
(
1
calcd. C 61.50, H 7.93, N 5.31; found C 61.99, H 7.55, N 5.74;
m.p. 220 °C (dec.). IR (KBr): ν˜ max = 3357 (NH) cm , 1667 (amide
C=O) cm .
–1
–1
Synthesis of Extended Calix[4]azacrown 14: A solution of the
bis(bipy) calix[4]arene 13 (0.4 mmol) and diethylenetriamine
74 4 6
Calix[4]azacrown 3: Yield 1.23 g (56.4%). C54H N O (875.19):
calcd. C 74.10, H 8.52, N 6.40; found C 74.25, H 8.40, N 6.43;
(
1.6 mmol) in a mixture of methanol (20 mL) and toluene (20 mL)
was stirred at room temperature for 5 d. After this time, the solu-
tion was concentrated under reduced pressure. The solid residue
was dissolved in methanol, recrystallised and filtered to give a white
solid.
m.p. 262–264 °C. IR (KBr): ν˜ max = 3390 (NH), 1680 (amide C=O)
–
1
1
cm . H NMR (300 MHz, CDCl
CONHCH ), 7.12 (s, 4 H, Ar-H), 6.70 (s, 4 H, Ar-H), 6.33 (s, 2 H,
OH), 4.48 (s, 4 H, OCH
CO), 4.18 (d, 1J = 13.0 Hz, 4 H, Ar-
3
): δ = 8.29 (br. t, 2 H,
2
2
1
68 71 9 8
Calix[4]azacrown 14: Yield 0.26 g (67%). C H N O (1142.35):
calcd. C 71.50, H 6.26, N 11.04; found C 71.39, H 6.04, N 11.09;
m.p. 250 °C (dec.). IR: (KBr): ν˜ max = 3400 (NH, OH), 1671 (amide
3
C=O) cm . H NMR (300 MHz, CDCl ): δ = 8.89 (d, J = 7.2 Hz,
CH
a
H
b
-Ar), 3.52 (m, 6 H, CH
2
), 3.39 (d, J = 13.0 Hz, 4 H, Ar-
CH
a
H
b
-Ar), 2.95 (m, 6 H, CH ), 1.33 (s, 18 H, tBu), 0.88 (s, 18 H,
2
tBu) ppm.
–
1
1
1
General Synthesis of Copper(II) Complexes 4–10: To a solution of
the calix[4]azacrown (0.5 mmol) in chloroform (5 mL) was added
the appropriate copper(II) salt (0.5 mmol) in methanol (5 mL) and
the resulting blue solution was heated to reflux for 2 h. On cooling,
the solution was allowed to stand and, after several days, either a
powder or crystals appeared, which was collected by filtration and
dried.
1
2
H, 6-H), 8.78 (s, 2 H, 3-H), 8.59 (d, J = 7.2 Hz, 2 H, 6Ј-H), 8.35
(
s, 2 H, 3Ј-H), 8.20 (s, 2 H, OH), 8.05 (br. t, 2 H, CONHCH ),
2
1
1
7
7
4
.94 (d, J = 7.2 Hz, 2 H, 5-H), 7.52 (s, 4 H, Ar-H), 7.23 (d, J =
.2 Hz, 2 H, 5Ј-H), 6.79 (s, 4 H, Ar-H), 6.28 (s, 1 H, NH), 4.47 (s,
1
H, OCH
2
CO), 4.21 (d, J = 14.0 Hz, 4 H, Ar-CH
a
H
b
-Ar), 3.55
-Ar), 2.94
3
), 0.96 (s, 18 H, tBu) ppm.
1
(
(
m, 4 H, CH
m, 4 H, CH
2
), 3.47 (d, J = 14.0 Hz, 4 H, Ar-CH
a b
H
2
), 2.49 (s, 6 H, CH
4
6
: Blue solid, yield 0.39 g (84%). C112H160CuN O20 (1974.04):
Synthesis of Extended Calix[4]azacrown 15: A solution of 13
0.5 mmol) and diethylenetriamine (2.0 mmol) in a mixture of
methanol (15 mL) and toluene (15 mL) was stirred at room tem-
perature for 5 d. After this time, the solution was concentrated un-
der reduced pressure. The solid residue was dissolved in methanol,
recrystallised and filtered to give a white solid.
calcd. C 68.14, H 8.17, N 4.26; found C 67.78, H 8.00, N 4.43;
m.p. 179–180 °C. IR (KBr): ν˜ max = 3360 (NH), 1690 (amide C=O)
(
–1
–1
–1
cm , 1578 (COOasym) cm , 1448 (COOsym) cm .
Green/blue solid, yield 0.42 g (88%).
1932.01): calcd. C 69.62, H 8.03, N 5.80, found C 69.78, H 8.00,
N 5.43; m.p. 179–180 °C. IR (KBR): ν˜ max = 3360 (NH), 1690
5:
112 6 16
C H154CuN O
(
Calix[4]azacrown 15: Yield 0.21 g (44%); m.p. 200 °C (dec.).
–1
–1
–1
(amide C=O) cm , 1578 (COOasym) cm , 1448 (COOsym) cm .
C
70
H
76
N
10
O
8
(1185.42): calcd. C 70.92, H 6.46, N 11.82; found C
6
: Green solid, yield 0.42 g (86%). C53 72ClCuN 11 (1026.15):
H
3
O
71.39, H 6.04, N 11.59. IR (KBr): ν˜ max = 3360 (NH, OH), 1666
–
1
1
1
calcd. C 62.03, H, 7.07, N 4.09; found C 61.93, H 6.98, N 4.32;
m.p. 200 °C (dec.). IR (KBr): ν˜ max = 3359 (NH), 1677 (amide
3
(amide C=O) cm . H NMR (300 MHz, CDCl ): δ = 8.85 (d, J
1
= 7.2 Hz, 2 H, 6-H), 8.80 (s, 2 H, 3-H), 8.55 (d, J = 7.2 Hz, 2 H,
–1
–1
1
C=O), 1109 (ClO
: Green solid, yield 0.41 g (78%). C55
calcd. C 61.78, H 7.22, N 5.24, found C 62.19, H 6.83, N 5.32;
4
) cm , 625 (ClO
4
) cm .
2
6Ј-H), 8.31 (s, 2 H, 3Ј-H), 8.13 (br. t, 2 H, CONHCH ), 7.92 (d, J
=
(
7.2 Hz, 2 H, 5-H), 7.53 (s, 4 H, Ar-H), 7.30 (s, 2 H, OH), 7.18
7
H77ClCuN
4
O11 (1069.22):
d, 1J = 7.2 Hz, 2 H, 5Ј-H), 6.84 (s, 4 H, Ar-H), 4.52 (s, 4 H,
1
OCH
H, CH
CH ), 2.50 (s, 6 H, CH
2
CO), 4.18 (d, J = 14.0 Hz, 4 H, Ar-CH
a
H
b
-Ar), 3.53 (m, 6
-Ar), 2.76 (m, 6 H,
3
), 0.97 (s, 18 H, tBu) ppm.
–1
m.p. 212 °C (dec.). IR (KBr): ν˜ max = 3355 (NH) cm , 1668 (amide
C=O) cm , 1110 (ClO
1
2
a b
), 3.46 (d, J = 14.0 Hz, 4 H, Ar-CH H
–1
–1
–1
4
) cm , 625 (ClO
4
) cm .
2
8
: Green solid, yield 0.38 g (85%). C104
H
138Cl
2
CuN O12 (1798.69):
6
General Synthesis of Ruthenium(II) Complexes 16 and 17: To a solu-
calcd. C 69.45, H 7.73, N 4.67; found C 69.68, H 7.36, N 5.01;
m.p. 150 °C (dec.). IR (KBr): ν˜ max = 3340 (NH), 1678 (amide C=O)
tion of the calix[4]azacrown 14 or 15 (0.185 mmol) in absolute etha-
II
nol (20 mL) was added Ru (bipy)Cl
4
(0.37 mmol) in absolute etha-
–1
cm .
: Blue solid, yield 0.18 g (88%). C
C 22.86, H 6.23, N 19.99; found C 22.87, H 5.84, N 19.90; m.p.
nol (20 mL) and the resulting brown solution was heated to reflux
for 3 h. On cooling, a brown precipitate resulted in each case. The
precipitate was collected by filtration, dried and stored in the dark.
9
8 2 2 6
H26Cl Cu N O (420.33): calcd.
–1
1
60 °C (dec.). IR (KBr): ν˜ max = 3240 (NH) cm .
1
6: Red/brown solid, yield 0.32 g (83%). C91
(2156.8): calcd. C 50.68, H 4.21, N 8.44; found C 50.78, H 4.00, N
8.73; m.p. Ͼ 300 °C. IR (KBr): ν˜ = 3385 (NH, OH), 1663
13 8 2
H90Cl13N O Ru
1
0: Green solid, yield 0.24 g (80%). C54 84ClCuN O11 (1064.26):
H
4
calcd. C 60.94, H 7.96, N 5.26; found C 60.42, H 7.47, N 5.64;
m.p. 160 °C (dec.). IR (KBr): ν˜ max = 3340 (NH, OH), 1681 (C=O
amide) cm .
max
–
1
(amide C=O) cm .
–1
1
7: Red/brown solid, yield 0.30 g (76%). C93H95Cl13N O Ru
14 8 2
General Synthesis of Manganese(II) Complexes 11–12: To a solution
of the calix[4]azacrown (0.5 mmol) in chloroform (5 mL) was added
manganese(II) chloride (0.5 mmol) in methanol (10 mL) and the
(2180.8): calcd. C 50.78, H 4.32, N 8.91; found C 50.48, H 4.01, N
8.43; m.p. Ͼ 300 °C. IR (KBr): ν˜ max = 3385 (NH, OH), 1661
–
1
(amide C=O) cm .
754
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 749–756

Metal Complexation of Calix[4]azacrown Derivatives
FULL PAPER
General Synthesis of Ruthenium(II)/Manganese(II) Complexes 18
and 19: To a solution of the ruthenium(II) calix[4]azacrown 16 or
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1
7 (0.11 mmol) in methanol (10 mL) was added manganese(II)
chloride tetrahydrate (0.11 mmol) in methanol (10 mL) and the re-
sulting brown solution was stirred at room temperature for 2 h.
During the course of the reaction, a dark brown solid precipitated
in each case. The precipitate was collected by filtration, washed
with CHCl
3
, dried and stored in the dark.
8: Brown solid, yield (62%). C90
8.76, H 4.46, N 8.21; found C 48.21, H 4.39, N 8.72; m.p. Ͼ
ˇ
[
[
[
5] See, for example, a) V. Stasný, I. Stibor, H. Dvo rˇ áková, P.
1
4
3
2
H98Cl11MnN13O13Ru : calcd. C
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–
1
00 °C: IR (KBr): ν˜ max = 3374 (NH, OH), 1662 (amide C=O) cm .
1
9: Brown solid, yield 0.14 g (57%). C92 13Ru
H
103Cl11MnN14
O
2
(2216.9): calcd. C 48.89, H 4.59, N 8.68; found C 49.19, H 4.63, N
9
.17; m.p. Ͼ 300 °C. IR (KBr): ν˜ max = 3378 (NH, OH), 1660
–1
(
amide C=O) cm .
X-ray Crystallography: Crystal data for 4: C112
1974.00, monoclinic, a = 12.2259(8) Å, b = 24.0471(17) Å, c =
6
H160CuN O20, M
=
3
1
9.5251(13) Å, β = 101.262(3)°, U = 5629.8(7) Å , T = 180(2) K,
–1
1 α
space group P2 /n, Z = 2, µ(Mo-K ) = 0.261 mm . 66796 reflec-
tions measured, 9751 unique (Rint = 0.0913) which were used in all
calculations. The final R = 0.0824, wR (all data) = 0.2874, good-
ness-of-fit on F = 1.09. Data were collected at 180(2) K with a
Bruker Nonius X8 APEX II diffractometer,
correction was applied.
1
2
2
[
36]
and a multi-scan
[37]
2
The structures were refined against F
[
38]
using all data.
tions and refined using a riding model.
Hydrogen atoms were placed at calculated posi-
[
CCDC-616020 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[
Acknowledgments
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The authors are grateful to the Technological Sector Research Pro-
gramme, Strand I (2002–2005), under the European Social Fund
Operational Programme for Industrial Development, the PhD con-
tinuation of IT Tallaght and the Enterprise Ireland, International
Collaboration Fund for financial assistance. A. D. B. is grateful to
the Danish Natural Sciences Research Council and the Carlsberg
Foundation for provision of the X-ray equipment.
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 749–756