Heteroditopic rhenium(I) and ruthenium(II) bipyridyl calix[4]arene receptors for binding cation-anion ion pairs

Article abstract of DOI:10.1039/b008576f

New heteroditopic ion pair receptors that contain rhenium(I) and ruthenium(II) bipyridyl amide anion recognition sites covalently linked to a lower rim calix[4]arene tetraester alkali metal cation binding site have been prepared and shown to bind alkali m

Full text of DOI:10.1039/b008576f

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Heteroditopic rhenium(I) and ruthenium(II) bipyridyl calix[4]arene
receptors for binding cation–anion ion pairs
James B. Cooper,a Michael G. B. Drewb and Paul D. Beer*,a
a Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford,
South Parks Road, Oxford, UK OX1 3QR
b Department of Chemistry, University of Reading, Whiteknights, Reading, UK RG6 2AD
Received 24th October 2000, Accepted 15th December 2000
First published as an Advance Article on the web 26th January 2001
New heteroditopic ion pair receptors that contain rhenium() and ruthenium() bipyridyl amide anion recognition
sites covalently linked to a lower rim calix[4]arene tetraester alkali metal cation binding site have been prepared
and shown to bind alkali metal (Liϩ, Naϩ)–halide (BrϪ, IϪ) ion pair species. Proton NMR titration studies reveal the
lower rim ester co-bound alkali metal cation significantly enhances the strength of bromide and iodide binding in
acetonitrile solutions with the largest positive co-operative binding effect of sixtyfold observed with bromide and
the lithium complex of one receptor. Solid/liquid extraction experiments show two of the receptors are capable of
solubilising NaCl and NaOAc in dichloromethane solutions.
Stimulated by the need to design new selective extraction and
transportation reagents for metal salt species of environmental
and biological importance, ion pair recognition, the simul-
taneous binding of cationic and anionic guest species by ditopic
receptors, is a rapidly developing new field of coordination
chemistry.1–13 Novel co-operative and allosteric metal salt
complexing behaviour whereby the binding of the metal
cation charged guest can enhance, through electrostatic and
conformational effects, the subsequent coordination of the
pairing anion has been demonstrated by a number of ditopic
crown ether functionalised boron,1 uranyl,2 polyammonium,3
amide,6–12 urea11 and amide4,13–urea calix[4]arene5 based
Fig. 1 Design of ion pair receptor.
receptor systems. In addition such systems have recently been
University of Wales, Swansea. Elemental analyses were per-
shown to solubilise and transport alkali metal salts across
lipophilic membranes.10 We have established that charged or
formed at the Inorganic Chemistry Laboratory, University of
Oxford.
neutral transition metal organometallic and coordination
amide containing receptor systems can selectively bind and
sense anions.14 Covalently linking the known lower rim ester-
functionalised calix[4]arene alkali-metal cation coordinating
moiety15 with a transition metal amide anion recognition group
also at the lower rim will create new heteroditopic calix[4]arene
based receptors capable of simultaneous binding of metal
cation–anion ion pairs (Fig. 1). This calix[4]arene lower rim
heteroditopic receptor design for ion pair recognition (Fig. 1)
contrasts our recently reported heteroditopic bis(calix[4]arene)
rhenium() bipyridyl and ferrocene receptor molecules which
were shown co-operatively to bind iodide anion at the upper
rim via complexation of two alkali metal cations at the two
lower rims.13 We report here the syntheses and anion/cation
coordination chemistry of new heteroditopic rhenium() and
ruthenium() bipyridyl calix[4]arene receptors which display up
to sixtyfold co-operative enhancement of halide anion binding
in the presence of a co-bound alkali metal cation.
Solvent and reagent pretreatment
Where necessary, solvents were purified prior to use and stored
under nitrogen. Acetonitrile and dichloromethane were distilled
from calcium hydride, tetrahydrofuran was distilled from benzo-
phenone ketyl. Unless stated otherwise, commercial grade
chemicals were used without further purification. Calix[4]arene
tetraester 1,15 Boc protected diamines16 and 4-chlorocarbonyl-
4Ј-methyl-2,2Ј-bipyridine 817 were prepared according to liter-
ature procedures.
Syntheses
25-[(Carboxy)methoxy]-26,27,28-tri[(ethoxycarbonyl)meth-
oxy]calix[4]arene 2. Calix[4]arene tetraester 1 (1 g, 1.30 mmol)
was dissolved in CH2Cl2 (50 ml) and stirred with conc. HNO3
(65%, 1 ml) for 3 h. Water (50 ml) was added and the mixture
stirred for 15 minutes. The phases were separated and the
solvent was removed under reduced pressure. The residue was
stirred in diethyl ether and the solvent removed under vacuum
Experimental
Instrumentation
1
to give the product as a white solid (0.91 g, 94% yield). H
NMR (300 MHz, CDCl3): δ 1.32 (m, 9H, OCH2CH3), 3.32
(d (J = 13), 2H, CCH2C), 3.35 (d (J = 13), 2H, CCH2C), 4.21–
4.32 (m, 6H, OCH2CH3), 4.44 (d (J = 16), 2H, COCH2O),
4.72 (s, 2H, COCH2O), 4.73 (d (J = 13), 4H, CCH2C), 4.92
(d (J = 16), 2H, COCH2O), 4.95 (s, 2H, COCH2O), 5.02
Nuclear magnetic resonance spectra were obtained on Bruker
AM300 and Varian-Unity 500 instruments using the solvent
deuterium signal as internal reference, fast atom bombardment
(FAB) mass spectra at the EPSRC mass spectrometry service,
392
J. Chem. Soc., Dalton Trans., 2001, 392–401
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b008576f

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(d (J = 13), 4H, CCH2C) and 6.48–7.14 (m, 12H, ArH)
Microanalysis: C42H44O12ؒ0.5H2O requires C 67.28, H 6.05%;
found C 67.39, H 5.93%,
CONHCH2). Microanalysis: C51H62N2O13 requires C 65.92, H
6.95, N 3.02%; found C 65.86, H 7.18, N 2.93%.
General synthesis of unprotected amines: 25-[(1-aminoethyl-
carbamoyl)methoxy]-26,27,28-tri[(ethoxycarbonyl)methoxy]-
calix[4]arene 4. Compound 4a (1.00 g, 0.97 mmol) was
dissolved in CH2Cl2 (25 ml) and stirred with an excess of tri-
fluoroacetic acid (TFA) (1 ml) for 1 h. HCl (1 M, 25 ml) was
added and the mixture stirred for 15 minutes. The phases were
separated and the CH2Cl2 layer was washed with water (2 × 25
ml). The phases were separated and the organic phase was dried
over MgSO4. After filtration the solvent was removed under
25-[(Chlorocarbonyl)methoxy]-26,27,28-tri[(ethoxycarb-
onyl)methoxy]calix[4]arene 3. Compound 2 (1.00 g, 1.35 mmol)
was refluxed in oxalyl chloride for 2 hours. Excess of oxalyl
chloride was removed under reduced pressure and the acid
chloride used without further purification or analysis.
General synthesis of calix[4]arene protected amides: 25-[1-
(tert-Butoxycarbonylamino)ethylcarbamoylmethoxy]-26,27,28-
1
reduced pressure to give the product (0.9 g, 98% yield). H
tri[(ethoxycarbonyl)methoxy]calix[4]arene 4a. Compound
3
NMR (300 MHz, CDCl3): δ 1.87–1.32 (m, 9H, OCH2CH3), 3.24
(d (J = 14), 2H, CCH2C), 3.26 (d (J = 13.5), 2H, CCH2C), 3.34
(br s, 2H, NHCH2CH2), 3.75 (br s, 2H, CH2CH2NH3ϩ), 4.13–
4.28 (m, 6H, OCH2CH3), 4.36 (s, 2H, COCH2O), 4.52 (s, 2H,
COCH2O), 4.52–4.96 (m, 6H, CCH2C, COCH2O), 4.99
(d (J = 15), 2H, COCH2O), 6.25–6.87 (m, 12H, Ar H) and 8.84
(br t, 1H, NH). Microanalysis: C44H50N2O11ؒHClؒCF3CO2Hؒ
H2O requires C 58.07, H 5.72, N 2.94%; found C 58.36, H 5.60,
N 2.60%.
(1.02 g, 1.34 mmol) was stirred in dry CH2Cl2 (25 ml) with an
excess of dry triethylamine (1 ml) for 30 minutes. Mono-Boc
protected ethylenediamine (0.5 g, 3.1 mmol, 2.2 equivalents)
was added in dry CH2Cl2 (25 ml) and the mixture stirred over-
night. 1 M HCl (25 ml) was added and the mixture stirred for
15 minutes. The phases were separated and the solvent was
removed from the organic phase to give the product as a white
solid (1.09 g, 91% yield). 1H NMR (300 MHz, CDCl3): δ 1.16–
1.25 (m, 9H, OCH2CH3), 1.33 (s, 9H, C(CH3)3), 3.19 (br
d (J = 13.5), 4H, CCH2C), 3.30–3.32 (m, 2H, NHCH2CH2NH),
3.46–3.50 (m, 2H, NHCH2CH2NH), 4.08–4.20 (m, 6H,
OCH2CH3), 4.33 (s, 2H, COCH2O), 4.46 (s, 2H, COCH2O),
4.53 (d (J = 15), 2H, COCH2O), 4.62 (d (J = 14), 4H, CCH2C),
4.92 (d (J = 16), 2H, COCH2O), 5.33 (br s, 1H, NHCOO), 6.21
(d (J = 7.5), 2H, m-H of Ar), 6.34 (d (J = 7), 2H, m-H of Ar),
6.44 (t (J = 7), 2H, p-H of Ar), 6.72 (t (J = 7), 2H, p-H of Ar),
6.77–6.87 (m, 4H, m-H of Ar), 8.45 (s, 1H, CONHCH2).
Microanalysis: C49H58N2O13ؒH2O requires C 65.30, H 6.72,
N 3.11%; found C 65.03, H 6.30, N 3.59%.
25-[(1-Aminopropylcarbamoyl)methoxy]-26,27,28-tri[(ethoxy-
carbonyl)methoxy]calix[4]arene 5. Compound 5a (2.00 g, 1.92
mmol) was treated as for 4 to give the product as a white solid
1
(1.93 g, 95% yield). H NMR (500 MHz, CDCl3): δ 1.19–1.35
(m, 9H, OCH2CH3), 2.05–2.17 (m, 2H, CH2CH2CH2), 3.03 (br
s, 2H, NHCH2CH2), 3.24 (d (J = 13.5), 2H, CCH2C), 3.25 (d
(J = 14), 2H, CCH2C), 3.57 (br q, 2H, CH2CH2NH), 4.11–4.26
(m, 6H, OCH2CH3), 4.47 (s, 2H, COCH2O), 4.51 (s, 2H,
COCH2O), 4.53 (d (J = 16.5), 2H, COCH2O), 4.62 (d (J = 14),
2H, CCH2C), 4.65 (d (J = 14.5), 2H, CCH2C), 4.93 (d
(J = 16.5), 2H, COCH2O), 6.35 (d (J = 7.5), 2H, m-H of Ar),
6.44–6.47 (m, 3H, m-, p-H of Ar), 6.53 (t (J = 7.5), 1H, p-H
of Ar), 6.72 (t (J = 7.5), 2H, p-H of Ar), 6.76–6.79 (m, 4H,
m-H of Ar), 8.45 (br s, 3H, NH3ϩ) and 8.81 (t (J = 6.5 Hz), 1H,
CONHCH2). Microanalysis: C45H52N2O11ؒ2CF3CO2Hؒ2H2O
requires C 55.40, H 5.60, N 2.64%; found C 55.35, H 5.54,
N 2.89%.
25-[1-(tert-Butoxycarbonylamino)propylcarbamoylmethoxy]-
26,27,28-tri[(ethoxycarbonyl)methoxy]calix[4]arene 5a. Method
as above Compound 3 (1.74 g, 2.29 mmol) was treated with
mono-Boc protected 1,3-diaminopropane (0.8 g, 4.6 mmol,
2 equivalents) to give the product as a white solid (2.18 g,
97% yield). 1H NMR (300 MHz, CDCl3): δ 1.23–1.32 (m,
9H, OCH2CH3), 1.42 (s, 9H, C(CH3)3), 1.76–1.81 (m, 2H,
CH2CH2CH2), 3.17–3.19 (m, 2H, NHCH2CH2), 3.26 (d
(J = 14), 4H, CCH2C), 3.49–3.51 (m, 2H, CH2CH2NH),
4.12–4.24 (m, 6H, OCH2CH3), 4.36 (s, 2H, COCH2O), 4.50
(s, 2H, COCH2O), 4.61 (d (J = 16.5), 2H, COCH2O), 4.69
(d (J = 13.5), 2H, CCH2C), 4.71 (d (J = 13.5), 2H, CCH2C),
4.97 (d (J = 16), 2H, COCH2O), 5.41 (br s, 1H, NHCOO), 6.23
(d (J = 7.5), 2H, m-H of Ar), 6.35–6.38 (m, 3H, m-, p-H of Ar),
6.48 (t (J = 7), 1H, p-H of Ar), 6.81 (t (J = 7), 2H, p-H of Ar),
6.88–6.91 (m, 4H, m-H of Ar) and 8.39 (s, 1H, CONHCH2).
Microanalysis: C50H60N2O13ؒ2H2O requires C 64.36, H 6.91,
N 3.00%; found C 64.54, H 6.85, N 3.78%.
25-[(1-Aminobutylcarbamoyl)methoxy]-26,27,28-tri[(ethoxy-
carbonyl)methoxy]calix[4]arene 6. Compound 6a (2.00 g, 1.92
mmol) was treated as for 4 to give the product as a white solid
1
(1.85 g, 91% yield). H NMR (500 MHz, CDCl3): δ 1.17–1.31
(m, 9H, OCH2CH3), 1.70–1.73 (m, 4H, CH2CH2CH2CH2),
2.98–2.30 (m, 2H, NHCH2CH2), 3.23 (d (J = 14), 4H, CCH2C),
3.41–3.42 (m, 2H, CH2CH2NH), 4.09–4.22 (m, 6H,
OCH2CH3), 4.28 (s, 2H, COCH2O), 4.46 (s, 2H, COCH2O),
4.58 (d (J = 17), 2H, COCH2O), 4.63 (d (J = 14.5), 2H,
CCH2C), 4.67 (d (J = 14.5), 2H, CCH2C), 4.96 (d (J = 16.5), 2H,
COCH2O), 6.15 (d (J = 7.5), 2H, m-H of Ar), 6.28–6.32 (m, 3H,
m-, p-H of Ar), 6.43 (t (J = 7.5), 1H, p-H of Ar, 6.81 (t (J = 7 Hz),
2H, p-H of Ar), 6.89–6.92 (m, 4H, m-H of Ar), 8.19 (br s,
3H, NH3ϩ) and 8.58 (s, 1H, CONHCH2). Microanalysis:
C46H55N2O11ؒ2CF3CO2Hؒ2H2O requires C 55.81, H 5.71, N
2.60%; found C 55.96, H 5.24, N 3.30%.
25-[1-(tert-Butoxycarbonylamino)butylcarbamoylmethoxy]-
26,27,28-tri[(ethoxycarbonyl)methoxy]calix[4]arene 6a. Method
as above Compound 3 (1.06 g, 1.39 mmol) was treated with
mono-Boc protected 1,4-diaminobutane (0.40 g, 2.13 mmol,
1.5 equivalents). The product was purified by column chrom-
atography on silica eluted with 1:1 CH2Cl2–ethyl acetate; after
removal of the solvent this gave the product as a white solid
25-[(1-Aminophenylcarbamoyl)methoxy]-26,27,28-tri[(eth-
oxycarbonyl)methoxy]calix[4]arene 7. 1,2-Diaminobenzene
(12.85 g, 118 mmol, 100 equivalents) was dissolved in dry
CH2Cl2 (500 ml) and stirred with an excess of NEt3 (3 ml).
Compound 3 (0.97 g, 1.18 mmol, 1 equivalent) in dry CH2Cl2
(250 ml) was added dropwise over 1 h. The mixture was stirred
overnight. 2 M HCl (250 ml) was added and the mixture stirred
for 2 h. The phases were separated and the solvent was removed
from the organic phase under reduced pressure. The residue was
dissolved in CHCl3, filtered and the solvent removed under
reduced pressure. The residue was dissolved in MeCN, filtered
and the solvent removed under reduced pressure. The residue
1
(0.83 g, 65% yield). H NMR (300 MHz, CDCl3): δ 1.17–1.25
(m, 9H, OCH2CH3), 1.35 (s, 9H, C(CH3)3), 1.44–1.50 (m, 2H,
CH2CH2CH2CH2), 1.57–1.63 (m, 2H, CH2CH2CH2CH2), 3.05–
3.11 (m, 2H, NHCH2CH2), 3.19 (d (J = 14), 4H, CCH2C), 3.36–
3.40 (m, 2H, CH2CH2NH), 4.03–4.20 (m, 6H, OCH2CH3), 4.29
(s, 2H, COCH2O), 4.44 (s, 2H, COCH2O), 4.53–4.71 (m, 7H,
COCH2O, CCH2C, NHCOO), 4.90 (d (J = 16), 2H, COCH2O),
6.16 (d (J = 7.5), 2H, m-H of Ar), 6.28–6.32 (m, 3H, m-, p-H
of Ar), 6.42 (t (J = 7), 1H, p-H of Ar), 6.74 (t (J = 7), 2H, p-H
of Ar), 6.81–6.85 (m, 4H, m-H of Ar) and 8.30 (s, 1H,
J. Chem. Soc., Dalton Trans., 2001, 392–401
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was dissolved in Et2O, filtered and the solvent removed under
reduced pressure to give the product as a yellow powder (0.72 g,
69% yield). 1H NMR (500 MHz, CDCl3): δ 1.12 (t (J = 7.5), 6H,
OCH2CH3), 1.27 (t (J = 7.5), 3H, OCH2CH3), 3.25 (d (J = 14),
2H, CCH2C), 3.32 (d (J = 14), 2H, CCH2C), 3.95–3.98 (m, 4H,
OCH2CH3), 4.21 (q (J = 7), 2H, OCH2CH3), 4.57 (d (J = 16.5),
2H, COCH2O), 4.60 (s, 2H, COCH2O), 4.61 (s, 2H, COCH2O),
4.69 (d (J = 14), 2H, CCH2C), 4.84 (d (J = 14), 2H, CCH2C),
4.93 (d (J = 16.5), 2H, COCH2O), 6.35 (d (J = 7.5), 2H, m-H of
Ar), 6.44–6.47 (m, 3H, m-, p-H of Ar), 6.53 (t (J = 7.5), 1H, p-H
of Ar), 6.73–6.78 (m, 3H, m-, p-H of Ar), 6.81 (d (J = 8.5), 1H,
o-H of Ar), 6.84 (d (J = 7.5), 4H, m-H of Ar), 7.08 (t (J = 7),
1H, m-H of Ar), 7.29 (d (J = 8 Hz), 1H, o-H of Ar) and 9.79
(s, 1H, CONHC). Microanalysis: C48H54N2O11ؒH2O requires C
67.59, H 6.62, N 3.28%, found C 67.71, H 5.73, N 3.38%.
26,27,28-Tri[(ethoxycarbonyl)methoxy]-25-[1-(4Ј-methyl-
[2,2Ј-bipyridine-4-carboxamido)butylcarbamoylmethoxy]-
c alix[4]arene 11. Prepared by an analogous method to that for
compound 9. Compound 6 (0.72 g, 8.46 mmol) was treated with
4-chlorocarbonyl-4Ј-methyl-2,2Ј-bipyridine (0.27 g, 1.17 mmol)
to give the product as a pale yellow solid (0.99 g, 84% yield). 1H
NMR (500 MHz, CDCl3): δ 1.21 (t (J = 7), 6H, OCH2CH3),
1.25 (t (J = 7), 3H, OCH2CH3), 1.73–1.79 (m, 4H, CH2CH2-
CH2CH2), 2.69 (s, 3H, CCH3), 3.22 (d (J = 13.5), 2H, CCH2C),
3.24 (d (J = 13.5), 2H, CCH2C), 3.48 (q (J = 6.5), 2H,
NHCH2CH2), 3.54 (q (J = 6.5), 2H, CH2CH2NH), 4.09–4.21
(m, 6H, OCH2CH3), 4.37 (s, 2H, COCH2O), 4.48 (s, 2H,
COCH2O), 4.59 (d (J = 16.5), 2H, COCH2O), 4.67 (d (J = 14),
4H, CCH2C), 4.94 (d (J = 16.5), 2H, COCH2O), 6.23 (d (J = 8),
2H, m-H of Ar), 6.36 (d (J = 8), 2H, m-H of Ar), 6.37
(t (J = 7.5), 1H, p-H of Ar), 6.47 (t (J = 8), 1H, p-H of Ar), 6.77
(t (J = 7.5), 2H, p-H of Ar), 6.84 (d (J = 6.5), 2H, m-H of Ar),
6.86 (d (J = 7.5), 2H, m-H of Ar), 7.11 (t (J = 5), 1H, bipy H),
7.29 (t (J = 5), 1H, NH), 7.77 (dd (J = 5), 1H, bipy H), 8.22 (s,
1H, bipy H3), 8.41 (d (J = 5), 1H, bipy H), 8.44 (t (J = 6.5), 1H,
NH), 8.66 (s, 1H, bipy H3) and 8.75 (d (J = 5.5 Hz), 1H, bipy H).
Microanalysis: C58H62N4O12ؒCH3CO2CH2CH3ؒ2H2O requires C
65.83, H 6.59, N 4.95%; found C 65.90, H 6.97, N 4.47%.
General synthesis of calix[4]arene bipyridyl amides: 26,27,28-
tri[(ethoxycarbonyl)methoxy]-25-[1-(4Ј-methyl-2,2Ј-bipyridine-
4-carboxamido)ethylcarbamoylmethoxy]calix[4]arene 9. 4-
Chlorocarbonyl-4Ј-methyl-2,2-bipyridine 8 (0.27 g, 1.17 mmol,
1.5 equivalents) was stirred in dry CH2Cl2 (25 ml) with dry
triethylamine (1 ml) for 30 min. Compound 4 (0.64 g, 0.78
mmol) in dry CH2Cl2 with dry triethylamine (1 ml) was added
and the mixture stirred overnight. HCl (1 M, 50 ml) was added
and the mixture stirred for 15 min. The phases were separated
and the organic phase was extracted with saturated K2CO3
solution (50 ml). The solvent was removed from the organic
phase and the residue purified by silica column chromatography
eluted with 10% ethyl acetate in CH2Cl2 to remove side
products and then pure ethyl acetate to remove the product.
The solvent was removed to give the product as a pale yellow
solid (0.65 g, 85% yield). 1H NMR (500 MHz, CD3CN): δ 1.20
(t (J = 7), 6H, OCH2CH3), 1.24 (t (J = 7), 3H, OCH2CH3), 2.43
(s, 3H, CCH3), 3.20 (d (J = 13.5), 2H, CCH2C), 3.24 (d
(J = 13.5), 2H, CCH2C), 3.63 (br s, 4H, NHCH2CH2NH),
4.12–4.21 (m, 6H, OCH2CH3), 4.39 (s, 2H, COCH2O), 4.52
(d (J = 16.5), 2H, COCH2O), 4.55 (s, 2H, COCH2O), 4.62 (d
(J = 13.5), 2H, CCH2C), 4.68 (d (J = 13.5), 2H, CCH2C), 4.93
(d (J = 16), 2H, COCH2O), 6.41–6.47 (m , 3H, Ar H), 6.50–6.55
(m, 3H, Ar H), 6.70 (t (J = 7.5), 2H, p-H of Ar), 6.76 (d (J = 7.5),
2H, m-H of Ar), 6.83 (d (J = 7.5), 2H, m-H of Ar), 7.22
(d (J = 4), 1H, bipy H), 7.66 (dd (J = 5), 1H, bipy H), 7.91 (br s,
1H, NH), 8.21 (s, 1H, bipy H3), 8.36 (br s, 1H, NH), 8.45 (d
(J = 4.5), 1H, bipy H), 8.67 (d (J = 5.5 Hz), 1H, bipy H) and 8.69
(s, 1H, bipy H3). Microanalysis: C56H58N4O12ؒH2O requires
C 67.46, H 5.62, N 6.07%; found C 67.49, H 5.36, N 6.08%.
FAB-MS [MHϩ]: m/z = 979.
26,27,28-Tri[(ethoxycarbonyl)methoxy]-25-[1-(4Ј-methyl-
[2,2Ј-bipyridine-4-carboxamido)phenylcarbamoylmethoxy]-
calix[4]arene 12. Prepared by an analogous method to that
of compound 9. Compound 7 (0.66 g, 0.79 mmol) was treated
with 4-chlorocarbonyl-4Ј-methyl-2,2Ј-bipyridine (0.25 g, 1.08
mmol) to give the product as a pale brown solid (0.62 g, 80%
yield). 1H NMR (500 MHz, CDCl3): δ 1.09 (t (J = 7), 6H,
OCH2CH3), 1.25 (t (J = 7), 3H, OCH2CH3), 2.42 (s, 3H, CCH3),
3.23 (d (J = 14), 2H, CCH2C), 3.24 (d (J = 14), 2H, CCH2C),
3.87–3.98 (m, 4H, OCH2CH3), 4.20 (q (J = 7), 2H, OCH2CH3),
4.48 (s, 2H, COCH2O), 4.56 (d (J = 16.5), 2H, COCH2O), 4.64
(d (J = 13.5), 2H, CCH2C), 4.69 (s, 2H, COCH2O), 4.79
(d (J = 13.5), 2H, CCH2C), 5.01 (d (J = 16.5), 2H, COCH2O),
6.11 (d (J = 8), 2H, m-H of Ar), 6.28–6.30 (m, 3H, m-, p-H of
Ar), 6.43 (t (J = 7), 1H, p-H of Ar), 6.81 (t (J = 7), 2H, p-H of
Ar), 6.88 (t (J = 7), 2H, m-H of Ar), 6.95 (t (J = 7), 2H, m-H
of Ar), 7.07 (d (J = 5), 1H, bipy H), 7.18 (t (J = 7.5), 1H, m-H of
Ar), 7.37 (t (J = 7.5), 1H, m-H of Ar), 7.47 (d (J = 7.5), 1H, o-H
of Ar), 7.77 (d (J = 5), 1H, bipy H), 8.12 (d (J = 8), 1H, o-H of
Ar), 8.20 (s, 1H, bipy H3), 8.31 (d (J = 5), 1H, bipy H), 8.78
(d (J = 5 Hz), 1H, bipy H), 8.84 (s, 1H, bipy H3), 9.77 (s, 1H,
NH) and 10.24 (s, 1H, NH). Microanalysis: C60H58N4O12ؒH2O
requires C 68.95, H 5.79, N 5.36%; found C 69.10, H 5.87, N
5.51%.
26,27,28-Tri[(ethoxycarbonyl)methoxy]-25-[1-(4Ј-methyl-
[2,2Ј-bipyridine-4-carboxamido)propylcarbamoylmethoxy]calix-
[4]arene 10. Compound 10 was prepared by an analogous
method to that for 9. Compound 5 (2.13 g, 2.34 mmol) was
treated with 4-chlorocarbonyl-4Ј-methyl-2,2Ј-bipyridine (1.10 g,
4.72 mmol) to give the product as a pale yellow solid (1.25 g,
General synthesis of the rhenium receptors: tricarbonyl-
chloro{26,27,28-tri[(ethoxycarbonyl)methoxy]-25-[1-(4Ј-methyl-
2,2Ј-bipyridine-4-carboxamido)ethylcarbamoyl)methoxy]-
calix[4]arene} rhenium(I) L1. Pentacarbonyl rhenium chloride
(0.12 g, 0.33 mmol, 1.1 equivalents) was refluxed in dry THF
(20 ml) for 30 minutes. Compound 9 (0.30 g, 0.30 mmol) was
added and the mixture refluxed overnight. The solvent was
removed under reduced pressure and the resulting residue
purified by silica column chromatography eluting with ethyl
acetate and collecting the second orange band. The solvent was
removed and the residue purified by silica column chrom-
atography eluting with THF and collecting the fraction that
moved. The solvent was removed and the residue purified
by silica column chromatography eluting with MeCN and
collecting the orange second fraction. The solvent was removed
under reduced pressure and the residue dissolved in the
minimum of CH2Cl2. Addition of hexane resulted in a yellow
precipitate which was filtered off and dried to give the product
1
54% yield). H NMR (500 MHz, CD3CN): δ 1.18 (t (J = 7.5),
6H, OCH2CH3), 1.23 (t (J = 7), 3H, OCH2CH3), 1.89 (qnt,
(J = 6.5), 2H, CH2CH2CH2), 2.44 (s, 3H, CCH3), 3.26
(d (J = 14), 2H, CCH2C), 3.26 (d (J = 13.5), 2H, CCH2C),
3.47–3.51 (m, 4H, NHCH2CH2CH2NH), 4.12–4.19 (m, 6H,
OCH2CH3), 4.41 (s, 2H, COCH2O), 4.57 (s, 2H, COCH2O),
4.61 (d (J = 16.5), 2H, COCH2O), 4.62 (d (J = 13.5), 2H,
CCH2C), 4.70 (d (J = 13.5), 2H, CCH2C), 4.93 (d (J = 16), 2H,
COCH2O), 6.44–6.49 (m, 3H, Ar H), 6.55 (br s, 3H, Ar H),
6.74 (t (J = 7.5), 2H, p-H of Ar), 6.85 (d (J = 7.5), 2H, m-H of
Ar), 6.88 (d (J = 7.5), 2H, m-H of Ar), 7.24 (d (J = 5), 1H, bipy
H), 7.72 (d (J = 5), 1H, bipy H), 7.98 (br t, 1H, NH), 8.20 (br t,
1H, NH), 8.27 (s, 1H, bipy H3), 8.50 (d (J = 5), 1H, bipy H),
8.74 (s, 1H, bipy H3) and 8.75 (d (J = 5.5 Hz), 1H, bipy H).
Microanalysis: C57H60N4O12ؒH2O requires C 67.69, H 6.18,
N 5.54%; found C 67.65, H 6.05, N 5.37%.
1
as a yellow powder (0.11 g, 28% yield). H NMR (300 MHz,
CD3CN): δ 1.22–1.28 (m, 9H, OCH2CH3), 2.55 (s, 3H, CCH3),
3.16–3.31 (m, 4H, CCH2C), 3.67 (br s, 4H, NHCH2CH2NH),
394
J. Chem. Soc., Dalton Trans., 2001, 392–401

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4.16–4.24 (m, 6H, OCH2CH3), 4.44 (m, 10H, COCH2O,
CCH2C), 4.93 (d (J = 16.5), 1H, COCH2O), 4.94 (d (J = 16.5),
1H, COCH2O), 6.46–6.82 (m, 12H, Ar H), 7.48 (d (J = 6), 1H,
bipy H), 7.84 (d (J = 5), 1H, bipy H), 8.06 (s, 1H, NH), 8.30 (s,
1H, bipy H3), 8.41 (s, 1H, NH), 8.66 (s, 1H, bipy H3), 8.86
(d (J = 5.5), 1H, bipy H) and 9.02 (d (J = 5.5 Hz), 1H, bipy H).
Microanalysis: C59H58ClN4O15ReؒH2O requires C 54.39, H
4.64, N 4.30%; found C 53.89, H 4.82, N 4.16%. FAB-MS: m/z
1250, [M Ϫ Cl]ϩ, 1285, [MH]ϩ, and 1308, [M ϩ Na]ϩ.
(J = 13.5), 1H, CCH2C), 4.78 (d (J = 13.5), 1H, CCH2C), 4.96
(d (J = 16.5), 1H, COCH2O), 4.99 (d (J = 16), 1H, COCH2O),
6.26 (d (J = 7.5), 2H, m-H of Ar), 6.41 (t (J = 7), 1H, p-H of
Ar), 6.45 (d (J = 8), 2H, m-H of Ar), 6.55 (t (J = 7.5), 1H, p-H
of Ar), 6.74–6.87 (m, 6H, Ar H), 7.25 (t (J = 7.5), 1H, Ar H),
7.38 (d (J = 6), 1H, bipy H), 7.43 (t (J = 8), 1H, Ar H), 7.97
(d (J = 5), 1H, bipy H), 8.15 (d (J = 8.5), 1H, Ar H), 8.17 (s, 1H,
bipy H3), 8.81 (s, 1H, bipy H3), 8.90 (d (J = 5.5), 1H, bipy H),
9.13 (d (J = 5.5 Hz), 1H, bipy H), 10.29 (s, 1H, NH) and 10.55
(s, 1H, NH). Microanalysis: C63H58ClN4O15ReؒH2O requires
C 56.02, H 4.48, N 4.15; found C 55.84, H 4.61, N 4.13%.
FAB-MS: m/z = 1334, Mϩ, 1357, [M ϩ Na]ϩ; 1299, [M Ϫ Cl]ϩ.
Tricarbonylchloro{26,27,28-tri[(ethoxycarbonyl)methoxy]-25-
[1-(4Ј-methyl-[2,2Ј-bipyridine-4-carboxamido)propylcarbamoyl-
methoxy]calix[4]arene}rhenium(I) L2. Prepared by an analo-
gous method to that for L1. Pentacarbonyl rhenium chloride
(0.27 g, 0.75 mmol) was treated with compound 10 (0.62 g,
0.63 mmol) and the products purified as for L1; the receptor
General synthesis of ruthenium(II) receptors: bis(2,2Ј-
bipyridyl){26,27,28-tri[(ethoxycarbonyl)methoxy]-25-[1-(4Ј-
methyl-[2,2Ј-bipyridine-4-carboxamido)ethylcarbamoylmeth-
oxy]calix[4]arene}ruthenium(II) L5. Bis(2,2Ј-bipyridyl)ruthen-
ium() dichloride (0.17 g, 0.33 mmol) was dissolved in 1:1
water–ethanol (10 ml) and stirred for 30 min before being
brought to reflux for 1 h. Compound 9 (0.30 g, 0.31 mmol) in
ethanol (10 ml) was added and the mixture refluxed overnight.
The solvent was removed and the residue purified by column
chromatography on Sephadex LH-20 eluted with acetonitrile.
The last bright red fraction was collected and the solvent
removed. The residue was stirred in water (20 ml) and an excess
of ammonium hexafluorophosphate (0.5 g, 1.8 mmol). The
resulting precipitate was filtered off, washed with copious water
to remove excess of ammonium hexafluorophosphate and dried
to give the product as an orange powder (0.08 g, 26% yield). 1H
NMR (500 MHz, CD3CN): δ 1.17–1.21 (m, 6H, OCH2CH3),
1.23 (t (J = 7), 3H, OCH2CH3), 2.53 (s, 3H, C(CH3)3), 3.18
(d (J = 13.5), 1H, CCH2C), 3.19 (d (J = 13.5), 1H, CCH2C),
3.28 (d (J = 13.5), 2H, CCH2C), 3.63–3.64 (m, 4H, NHCH2-
CH2NH), 4.09–4.14 (m, 4H, OCH2CH3), 4.18 (q (J = 7), 2H,
OCH2CH3), 4.48 (s, 2H, COCH2O), 4.50 (d (J = 12.5), 1H,
CCH2C), 4.53 (d (J = 12.5), 1H, CCH2C), 4.61 (s, 2H,
COCH2O), 4.65 (d (J = 13.5), H, CCH2C), 4.67 (d (J = 16.5),
2H, COCH2O), 4.88 (d (J = 16.5), 2H, COCH2O), 6.44–6.49
(m, 4H, Ar H), 6.60–6.76 (m, 8H, Ar H), 7.26 (d (J = 6), 1H,
bipy H), 7.33–7.41 (m, 4H, bipy H), 7.54 (d (J = 5.5), 1H, bipy
H), 7.58 (d (J = 5.5), 1H, bipy H), 7.69–7.71 (m, 3H, bipy H),
7.79 (d (J = 6), 1H, bipy H), 8.01–8.08 (m, 4H, bipy H), 8.09 (s,
1H, NH), 8.39 (s, 1H, NH), 8.43 (s, 1H, bipy H3), 8.48 (m, 5H,
bipy H) and 8.75 (s, 1H, bipy H3). Microanalysis: C76H74F12-
N8O12P2Ruؒ2H2O requires C 53.12, H 4.57, N 6.52%; found C
53.00, H 5.18, N 6.36%. FAB-MS: m/z 1537, [M Ϫ PF6]ϩ;
1392, [Mϩ Ϫ 2PF6]ϩ.
1
was isolated as a yellow powder (0.16 g, 26% yield). H NMR
(500 MHz, DMSO-d6): δ 1.15 (t (J = 7), 6H, OCH2CH3),
1.20 (t (J = 7.5), 3H, OCH2CH3), 1.86 (qnt (J = 7.5), 2H,
CH2CH2CH2), 2.56 (s, 3H, C(CH3)3), 3.23 (d (J = 14), 4H,
CCH2C), 3.32–3.38 (m, 2H, NHCH2CH2), 3.39–3.43 (m, 2H,
CH2CH2NH), 4.05–4.11 (m, 4H, OCH2CH3), 4.14 (q (J = 7),
2H, OCH2CH3), 4.30 (s, 2H, COCH2O), 4.52 (s, 2H, COCH2O),
4.60–4.68 (m, 6H, COCH2O, CCH2C), 4.91 (d (J = 16.5), 2H,
COCH2O), 6.30 (d (J = 7.5), 2H, m-H of Ar), 6.37–6.40 (m,
3H, Ar H), 6.46 (t (J = 7), 1H, p-H of Ar), 6.73 (t (J = 7.5), 2H,
p-H of Ar), 6.83–6.87 (m, 4H, m-H of Ar), 7.61 (d (J = 5.5), 1H,
bipy H), 7.99 (dd (J = 5.5), 1H, bipy H), 8.14 (t (J = 6), 1H,
NH), 8.67 (s, 1H, bipy H3), 8.86 (d (J = 5.5), 1H, bipy H), 8.93
(s, 1H, bipy H3) and 9.10–9.13 (m, 2H, bipy H, NH). Micro-
analysis: C60H60ClN4O15Reؒ4H2O requires C 52.57, H 5.00, N
4.09%; found C 52.12, H 4.65, N 4.13%. ES-MS: m/z 1264,
[M Ϫ Cl]ϩ; 1299, [MH]ϩ.
Tricarbonylchloro{26,27,28-tri[(ethoxycarbonyl)methoxy]-25-
[1-(4Ј-methyl-[2,2Ј-bipyridine-4-carboxamido)butylcarbamoyl-
methoxy]calix[4]arene}rhenium(I) L3. Prepared by an analo-
gous method to that for L1. Pentacarbonyl rhenium chloride
(0.23 g, 0.62 mmol) was treated with compound 11 (0.52 g, 0.52
mmol) and the products purified as for L1; L3 was isolated as
a yellow powder (0.10 g, 14% yield). 1H NMR (500 MHz,
DMSO-d6): δ 1.16 (t (J = 7), 6H, OCH2CH3), 1.22 (t (J = 7), 3H,
OCH2CH3), 1.73–1.79 (m, 4H, CH2CH2CH2CH2), 2.60 (s, 3H,
CCH3), 3.23 (d (J = 13.5), 2H, CCH2C), 3.25 (d (J = 13.5), 2H,
CCH2C), 3.50 (m, 2H, NHCH2CH2), 3.56 (m, 2H, CH2CH2-
NH), 4.09–4.21 (m, 6H, OCH2CH3), 4.36 (s, 2H, COCH2O),
4.48 (s, 2H, COCH2O), 4.58–4.70 (m, 6H, COCH2O, CCH2C),
4.94 (d (J = 16.5), 2H, COCH2O), 6.26 (d (J = 8), 2H, m-H of
Ar), 6.35 (d (J = 8), 2H, m-H of Ar), 6.37 (t (J = 7.5), 1H, p-H
of Ar), 6.44 (t (J = 8), 1H, p-H of Ar), 6.77 (t (J = 7.5), 2H, p-H
of Ar), 6.83 (d (J = 6.5), 2H, m-H of Ar), 6.86 (d (J = 7.5), 2H,
m-H of Ar), 7.61 (d (J = 5), 1H, bipy H), 7.97 (dd (J = 5), 1H,
bipy H), 8.09 (t (J = 5), 1H, NH), 8.65 (s, 1H, bipy H3), 8.85
(d (J = 5), 1H, bipy H), 8.95 (s, 1H, bipy H3), 9.08 (d (J = 5.5),
1H, bipy H) and 9.14 (t (J = 6.5 Hz), 1H, NH). Microanalysis:
C61H62ClN4O15Reؒ3H2O requires C 53.60, H 5.01, N 4.10%;
found C 53.80, H 5.25, N 4.19%. ES-MS: m/z 1278, [M Ϫ Cl]ϩ;
1313, [MH]ϩ.
Bis(2,2Ј-bipyridyl){26,27,28-tri[(ethoxycarbonyl)methoxy]-
25-[1-(4Ј-methyl-2,2Ј-bipyridine-4-carboxamido)propylcarb-
amoylmethoxy]calix[4]arene}ruthenium(II) L6. Prepared by
an analogous method to that for L5. Bis(2,2Ј-bipyridyl)-
ruthenium() dichloride (0.25 g, 0.48 mmol) was treated with
compound 10 (0.40 g, 0.40 mmol). The initial reaction product
was purified by chromatography on Sephadex LH-20 eluted
with acetonitrile. The solvent was removed and the residue
redissolved in the minimum of CH2Cl2. Addition of diethyl
ether (100 ml) resulted in a precipitate, which was filtered off
and dried to give the product as the chloride salt, an orange
Tricarbonylchloro{26,27,28-tri[(ethoxycarbonyl)methoxy]-25-
[1-(4Ј-methyl-2,2Ј-bipyridine-4-carboxamido)phenylcarbamoyl-
methoxy]calix[4]arene}rhenium L4. Prepared by an analogous
method to that for L1. Pentacarbonyl rhenium chloride (0.30 g,
0.29 mmol) was treated with compound 12 (0.15 g, 0.41 mmol).
The product was isolated as a yellow powder (0.27 g, 69%
yield). 1H NMR (300 MHz, CD3CN): δ 1.12–1.18 (m, 6H,
OCH2CH3), 1.28 (t (J = 7), 3H, OCH2CH3), 2.59 (s, 3H, CCH3),
3.28 (br dd, 2H, CCH2C), 3.93–4.03 (m, 4H, OCH2CH3), 4.23
(q (J = 7), 2H, OCH2CH3), 4.53 (d (J = 16.5), 1H, COCH2O),
4.57 (d (J = 16), 1H, COCH2O), 4.58 (s, 2H, COCH2O), 4.65
(d (J = 13.5), 2H, CCH2C), 4.69 (s, 2H, COCH2O), 4.76 (d
1
powder (0.35 g, 57% yield). H NMR (500 MHz, CD3CN): δ
1.12–1.14 (m, 6H, OCH2CH3), 1.21 (t (J = 7), 3H, OCH2CH3),
2.53 (s, 3H, C(CH3)3), 3.24 (d (J = 13.5), 4H, CCH2C), 3.40–
3.52 (m, 4H, NHCH2CH2CH2NH), 4.04–4.10 (m, 4H,
OCH2CH3), 4.17 (q (J = 7), 2H, OCH2CH3), 4.33 (s, 2H,
COCH2O), 4.53 (s, 2H, COCH2O), 4.62–4.70 (m, 4H,
COCH2O, CCH2C), 4.74 (d (J = 13.5), 2H, CCH2C), 4.96
(d (J = 16), 2H, COCH2O), 6.35–6.40 (m , 3H, Ar H), 6.46–6.48
(m, 3H, Ar H), 6.75 (t (J = 7), 2H, p-H of Ar), 6.87–6.91 (m, 4H,
m-H of Ar), 7.23 (d (J = 6), 1H, bipy H), 7.33–7.40 (m, 4H,
bipy H), 7.51 (d (J = 5), 1H, bipy H), 7.70–7.74 (m, 5H, bipy H),
J. Chem. Soc., Dalton Trans., 2001, 392–401
395

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7.83 (d (J = 5), 1H, bipy H), 8.01–8.07 (m, 4H, bipy H), 8.20
(br s, 1H, NH), 8.58–8.60 (m, 4H, bipy H), 9.47 (s, 1H, bipy
H3), 10.08 (s, 1H, bipy H3) and 10.19 (br s, 1H, NH). Micro-
analysis: C77H76Cl2N8O12Ruؒ6H2O requires C 58.33, H 5.55,
N 7.07%; found C 58.57, H 5.23, N 7.09%.
s, 3H, Ar H), 6.65–6.72 (m, 4H, m-H of Ar), 6.83–6.86 (m, 2H,
p-H of Ar), 7.27 (d (J = 5.5), 1H, bipy H), 7.31–7.44 (m, 6H,
ArH, bipy H), 7.54–7.56 (m, 2H, Ar H), 7.65 (d (J = 5), 1H,
bipy H), 7.67–7.74 (m, 4H, bipy H), 7.87 (d (J = 5), 1H, bipy H),
7.99–8.08 (m, 5H, bipy H), 8.40 (s, 1H, bipy H3), 8.47–8.50 (m,
4H, bipy H), 8.87 (s, 1H, bipy H3), 9.84 (s, 1H, NH) and 9.91 (s,
1H, NH). Microanalysis: C80H74F12N8O12P2Ruؒ2H2O requires
C 54.39, H 4.45, N 6.34%; found C 54.66, H 4.24, N 6.16%.
FAB-MS: m/z 1585, [M Ϫ PF6]ϩ; 1440, [Mϩ Ϫ 2PF6]ϩ.
The chloride salt (0.14 g, 0.09 mmol) was stirred in water
(20 ml) and an excess of ammonium hexafluorophosphate (0.5 g,
1.8 mmol). The resulting precipitate was filtered off, washed
with copious water to remove excess of ammonium hexafluoro-
phosphate and dried to give the product as an orange powder
(0.16 g, 98% yield) 1H NMR (500 MHz, DMSO-d6): δ 1.10–1.13
(m, 6H, OCH2CH3), 1.19 (t (J = 7), 3H, OCH2CH3), 1.82
(qnt (J = 7), 2H, CH2CH2CH2), 2.54 (s, 3H, C(CH3)3), 3.24 (br d
(J = 14), 4H, CCH2C), 3.32–3.35 (m, 2H, NHCH2CH2), 3.39
(q (J = 6), 2H, CH2CH2NH), 4.04–4.09 (m, 4H, OCH2CH3),
4.14 (q (J = 7), 2H, OCH2CH3), 4.29 (s, 2H, COCH2O),
4.52 (s, 2H, COCH2O), 4.59–4.69 (m, 6H, COCH2O, CCH2C),
4.89 (d (J = 16.5), 2H, COCH2O), 6.30 (d (J = 7.5), 2H, m-H of
Ar), 6.37–6.40 (m, 3H, Ar H), 6.47 (t (J = 7), 1H, p-H of Ar),
6.73 (t (J = 7.5), 2H, p-H of Ar), 7.40 (d (J = 5.5), 1H, bipy H),
7.47–7.53 (m, 4H, bipy H), 7.57 (d (J = 5.5), 1H, bipy H), 7.69–
7.77 (m, 4H, bipy H), 7.85 (d (J = 6), 1H, bipy H), 8.12–8.18 (m,
5H, bipy H, NH), 8.76 (s, 1H, bipy H3), 8.83 (br d (J = 7.5), 4H,
bipyH),9.00(brt(J = 5.5Hz),1H,NH)and9.04(s,1H,bipyH3).
Microanalysis: C77H76F12N8O12P2Ruؒ3H2O requires C 52.83,
H 4.72, N 6.40%; found C 52.61, H 4.47, N 6.39%. FAB-MS;
m/z 1551, [M Ϫ PF6]ϩ; 1406, [M Ϫ 2PF6]ϩ.
Crystallography
Crystal data for L4. C63H58ClN4O15Re, M = 1332.78, mono-
clinic, space group P21/a, Z = 4, a = 15.947(17), b = 23.90(3),
c = 16.640(19) Å, β = 96.77(1)Њ, U = 6298 Å3, 17787 reflections
(10509) independent, R(int) = 0.0649 collected with Mo-Kα
radiation using the MARresearch Image Plate System at room
temperature. Data analysis was carried out with the XDS
program.18 The structure was solved using direct methods with
SHELXS 86.19 The non-hydrogen atoms were refined with
anisotropic thermal parameters apart from a few carbon atoms
in CO2Et groups which had high thermal motion and for which
dimensions were constrained. Hydrogen atoms were included
in geometric positions and given thermal parameters equivalent
to 1.2 times those of the atom to which they were attached.
The structure was refined on F 2 using SHELXL20 with 733
parameters to R1 0.0961, wR2 0.2500 for 4314 data with
I > 2σ(I) and R1 0.2151, wR2 0.3055 for all data.
CCDC reference number 186/2309.
See http://www.rsc.org/suppdata/dt/b0/b008576f/ for crystal-
lographic files in .cif format.
Bis(2,2Ј-bipyridyl){26,27,28-tri[(ethoxycarbonyl)methoxy]-
25-[1-(4Ј-methyl-2,2Ј-bipyridine-4-carboxamido)butylcarbamoyl-
methoxy]calix[4]arene}ruthenium(II) hexafluorophosphate L7.
Prepared by an analogous method to that for L5. Bis(2,2Ј-
bipyridyl)ruthenium() dichloride (0.15 g, 0.29 mmol) was
treated with compound 11 (0.20 g, 0.20 mmol) to give the
product as (the hexafluorophosphate salt) an orange powder
1H NMR titrations
A solution of the receptor (500 µl) was prepared at a concen-
tration typically of the order of 0.01 mol dmϪ3 in deuteriated
1
1
(0.07 g, 27% yield). H NMR (500 MHz, DMSO-d6): δ 1.16
acetonitrile. The initial H NMR spectrum was recorded and
(t (J = 7), 6H, OCH2CH3), 1.20 (t (J = 7), 3H, OCH2CH3), 1.58
(br s, 4H, CH2CH2CH2CH2), 2.53 (s, 3H, C(CH3)3), 3.23 (br d
(J = 14), 4H, CCH2C), 3.28–3.30 (m, 2H, CH2CH2NH), 4.07–
4.10 (m, 4H, OCH2CH3), 4.14 (q (J = 7), 2H, OCH2CH3), 4.27
(s, 2H, COCH2O), 4.52 (s, 2H, COCH2O), 4.61 (d (J = 16.5),
2H, COCH2O), 6.64 (d (J = 13), 4H, CCH2C), 4.87 (d
(J = 16.5), 2H, COCH2O), 6.32 (d (J = 7.5), 2H, m-H of Ar),
6.38–6.42 (m , 3H, Ar H), 6.48 (t (J = 7.5), 1H, p-H of Ar), 6.70
(t (J = 7.5), 2H, p-H of Ar), 6.80 (d (J = 7.5), 2H, m-H of Ar),
6.83 (d (J = 7.5), 2H, m-H of Ar), 7.40 (d (J = 6), 1H, bipy H),
7.46–7.54 (m, 4H, bipy H), 7.57 (d (J = 6), 1H, bipy H), 7.69–
7.72 (m, 3H, bipy H), 7.75 (d (J = 5), 1H, bipy H), 7.81 (d
(J = 6), 1H, bipy H), 8.08 (t (J = 6), 1H, NH), 8.13–8.19 (m, 4H,
bipy H), 8.75 (s, 1H, bipy H3), 8.83–8.85 (m, 4H, bipy H), 8.98
(t (J = 6 Hz), 1H, NH) and 9.04 (s, 1H, bipy H3). Microanalysis:
C78H78F12N8O12P2Ruؒ2H2O requires C 53.64, H 4.73, N 6.42%;
found C 53.44, H 4.61, N 6.37%. FAB-MS: m/z 1565,
aliquots of anion were added by gas-tight syringe from a solu-
tion made such that 1 mol equivalent was added in 20 µl. After
each addition and mixing the spectrum was recorded again and
changes in the chemical shift of certain protons were noted.
The result of the experiment was a plot of displacement in
chemical shift as a function of the amount of added anion,
which was subjected to analysis by curve-fitting since the shape
is indicative of the stability constant for the complex. The com-
puter program EQNMR21 was used which requires the con-
centration of each component and the observed chemical shift
(or its displacement) for each data point. Typically these
titration experiments were repeated three times with at least
fifteen data points in each experiment.
Results and discussion
Syntheses of lower rim mono-amine calix[4]arene synthons
[M Ϫ PF6]ϩ, 711, [M Ϫ 2PF6]2ϩ
.
The new lower rim mono-amine ester substituted calix[4]arene
derivatives 4–7 were prepared according to Scheme 1. The
reaction of the tetraester 115 with 65% HNO3 in dichloro-
methane led to selective hydrolysis of one of the esters to give
the monoacid 2 in almost quantitative yield. Refluxing 2
with oxalyl chloride produced the triester monoacid chloride
3 which on condensation with the appropriate Boc protected
alkyl diamine16 followed by addition of trifluoroacetic acid
in dichloromethane gave the new lower rim mono-amine
calix[4]arene synthons 4–6 in very good yields (Scheme 1).
The addition of a large excess of 1,2-diaminobenzene to 3 in
dichloromethane afforded the calix[4]arene aryl linked amine 7
in 69% yield (Scheme 2).
Bis(2,2Ј-bipyridyl){26,27,28-tri[(ethoxycarbonyl)methoxy]-
25-[1-(4Ј-methyl-2,2Ј-bipyridine-4-carboxamido)phenylcarb-
amoylmethoxy]calix[4]arene}ruthenium(II) hexafluorophosphate
L8. Prepared by an analogous method to that for L5. Bis(2,2Ј-
bipyridyl)ruthenium() dichloride (0.10 g, 0.19 mmol) was
treated with compound 12 (0.10 g, 0.97 mmol) to give the
product as an orange powder (0.08 g, 46% yield). 1H NMR (500
MHz, CD3CN): δ 1.04–1.08 (m, 6H, OCH2CH3), 1.22 (t (J = 7),
3H, OCH2CH3), 2.50 (s, 3H, CCH3), 3.14 (d (J = 13.5), 2H,
CCH2C), 3.28 (d (J = 13.5), 2H, CCH2C), 3.87–3.96 (m, 4H,
OCH2CH3), 4.17 (q (J = 7), 2H, OCH2CH3), 4.47 (d (J = 16.5),
1H, COCH2O), 4.52 (d (J = 16.5), 1H, COCH2O), 4.58–4.61
(m, 4H, COCH2O, CCH2C), 4.68 (s, 2H, COCH2O), 4.73
(d (J = 13.5), 1H, CCH2C), 4.74 (d (J = 13.5), 1H, CCH2C),
4.85–4.91 (m, 2H, COCH2O), 6.24–6.32 (m, 3H, Ar H), 6.58 (br
Receptor syntheses and characterisation
Condensation reactions of the appropriate lower rim mono-
396
J. Chem. Soc., Dalton Trans., 2001, 392–401

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Scheme 1
doublets, H1a and H1b, H3a and H3b being no longer equivalent.
This is consistent with a lowering of symmetry involving
the ruthenium() bipyridyl amide substituent being held
asymmetrically by intramolecular hydrogen bonds with respect
to the symmetry plane. Interestingly in the more polar solvent
DMSO-d6 this asymmetry is removed indicating that hydrogen
bonding has been disrupted. Evidence for intramolecular
hydrogen bonding occurring in the solid state is discussed below
with the X-ray structural investigation of L4.
X-Ray structural investigation of receptor L4
Crystals of L4 suitable for structural determination were grown
from dilute acetonitrile solutions of the receptor. The structure
is shown in Fig. 3 together with the atomic numbering scheme.
The Re atom has a distorted octahedral environment being
bonded to three mutually cis carbonyl groups (1.92(2)–1.99(2)
Å), two nitrogen atoms of a substituted bipyridyl (Re–N(l)
2.138(10), 2.179(12) Å) and a chlorine atom (Re–Cl 2.438(5) Å).
The bipyridyl group is linked to a calix[4]arene by a diamide
linkage whose conformation is fixed via an intramolecular
hydrogen bond between N(161)–H and O(153) of 2.726 Å. The
conformation of the calix[4]arene is a C2 distorted cone. The
four phenyl rings intersect the plane of the four methylene
groups at angles of 103.3, 36.5, 105.2 and 36.1Њ. As can be seen
clearly in the Figure rings 1 and 3 are tilted so that the atoms at
the top of the cone C(13) and C(33) are closer together than
atoms at the bottom rim C(16) and C(36). The position of the
calix[4]arene is adjacent to the diamide linkage to facilitate an
intramolecular hydrogen bond between N(154)–H and O(253)
of 2.938 Å. N(154) is also in close proximity to O(150) at
2.669 Å. There is an additional intermolecular hydrogen bond
in the unit cell, between N(154) and O(100) (0.5 Ϫ x, Ϫ0.5 ϩ y,
Ϫz) at 3.059 Å.
Scheme 2
amine calix[4]arene derivative with 4-chlorocarbonyl-4Ј-methyl-
2,2Ј-bipyridine 817 gave the ethyl 9, propyl 10, butyl 11 and aryl
12 linked compounds in 85%, 54%, 84% and 80% yields respect-
ively (Scheme 3). Complexation reactions with Re(CO)5Cl in
THF produced the new rhenium() bipyridyl calix[4]arene
receptors L1–L4 as orange-yellow solids. The ruthenium()
bipyridyl calix[4]arene receptors L5–L8 were prepared by reac-
tion of the bipyridyl calix[4]arene derivatives with Ru(bipy)2Cl2
in aqueous ethanol solution followed by addition of an excess
of ammonium hexafluorophosphate (Scheme 3). All these new
Ion pair binding studies
Receptors L1–L8 are designed simultaneously to bind a cation
and anion ion pair such that the presence of a co-bound alkali
metal cation would enhance the strength of anion binding via
favourable electrostatic interactions and preorganisation effects.
The difficulty with investigating simultaneous cation and anion
binding is that there are many competing equilibria processes
involved (Fig. 4). The number of equilibria shown in Fig. 4 can
be simplified and reduced if the following assumptions and
considerations of choice of metal salt, ion pair guest species
and solvent medium are taken into account. The anion stability
constant K2 of the receptor can be determined independently
and the titration experiment repeated in the presence of a
1
receptors were characterised by H NMR spectroscopy, FAB
mass spectrometry and elemental analysis (see Experimental
section).
It is noteworthy that the 1H NMR spectra of L1–L8 in
CD3CN gave evidence for the existence of intramolecular
hydrogen bonds between the carbonyl oxygens and amide-
NH groups of the lower rim substituents. For example Fig. 2
displays a comparison of the 1H NMR spectra of the methylene
proton region for compound 9 and L5. 9 exhibits the expected
splitting pattern, four pairs of doublets, for the calixarene
methylene protons. The spectrum for L5 contains six pairs of
J. Chem. Soc., Dalton Trans., 2001, 392–401
397

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Fig. 2 Comparison of the 1H NMR methylene region for compound 9 and L5 in CD3CN solution.
Scheme 3
stoichiometric amount of metal cation. If it is assumed that any
solution K3 and precipitation of the salt K1. The assumption
metal cation present in solution is fully bound to the receptor,
K5 can then be determined. Comparison of K2 and K5 therefore
gives the enhancement of anion binding as a consequence of
the co-bound metal cation. However, consideration must also
be given to both the competing process of ion pairing in
that the metal cation is fully bound by the receptor ignores
these competing equilibria which will be responsible for any
apparent decreases in strength of anion binding when the ‘free’
metal cation is present in solution. Precipitation of the ion pair
salt (K1) is of particular concern and it is therefore prudent to
398
J. Chem. Soc., Dalton Trans., 2001, 392–401

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Fig. 3 The structure of L4 with ellipsoids at 20% probability.
1
by H NMR titration experiments in CD3CN solution. The
addition of tetrabutylammonium bromide and iodide salts
to CD3CN solutions of the receptors resulted in significant
downfield perturbations of the bipy H3a, H3b and amide
NHa2 protons whereas those of NHa1, were observed to move
marginally upfield (Fig. 5), which indicates that anion binding
is occurring near the bipyridyl group involving amide NHa2 but
not NHa1 which perhaps continues to form an intramolecular
hydrogen bond with a carboxyl ester group of the lower rim.
EQNMR21 analysis of the resulting titration curves (e.g. Fig. 5)
gave stability constant values for 1:1 solution anion complexes
shown in Tables 1 and 2. All the receptors complex bromide
anion more strongly than iodide and as a consequence of the
positively charged ruthenium() metal centre, which leads
to additional attractive electrostatic interactions with
the bromide anion, L5–L8 display larger magnitudes of halide
stability constants in comparison to those of the neutral
rhenium receptors L1–L4.
Fig. 4 Equilibria involved in ion pair binding.
The addition of LiClO4 and NaClO4 to L1–L8 caused the
lower rim calixarene ester methylene receptors protons to
broaden initially and sharpen again after one equivalent
suggesting strong complexes of 1:1 stoichiometry are being
formed in solution. Interestingly significant upfield shifts of up
to ∆δ = 1.5 ppm were also observed for both the amide protons
on alkali metal cation addition which indicates that lower rim
metal cation binding disrupts the amide–carbonyl ester intra-
molecular hydrogen bonding interactions noted previously.
Fig. 5 Proton NMR titration curves of L5 with IϪ in CD3CN.
1
Repeating the bromide and iodide H NMR titrations in the
ensure the metal salt itself is soluble in the chosen solvent
medium. As a consequence solution ion pairing will then be the
only major equilibrium process to compete with anion binding
by the metal bound receptor.
presence of one equivalent of lithium or sodium alkali metal
cation caused all four amide and bipy H3 proton resonances of
the respective receptors to be significantly shifted downfield and
the EQNMR determined stability constant values are also pre-
sented in Tables 1 and 2. Clearly both Tables show that with all
receptors there is a significant increase in the strength of brom-
ide and iodide binding when the alkali metal is co-bound with
the largest anion enhancement of sixtyfold being exhibited by
L4Liϩ and bromide (Table 1). This positive co-operative binding
of halide anion may be attributed to mutual electrostatic alkali
metal cation–anion attraction, preorganisation effects and
increased strength of hydrogen bonding to the bound anion as
Proton NMR alkali metal cation and halide anion binding studies
Taking into account the above, the knowledge that lower rim
ester functionalised calix[4]arenes are known strongly to
complex alkali metal cations,15 which will minimise competing
ion pairing interactions, and receptor–alkali metal salt solu-
bility properties, the lithium, sodium cation and bromide,
iodide anion coordination properties of L1–L8 were investigated
J. Chem. Soc., Dalton Trans., 2001, 392–401
399

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Table 1 Stability constants for bromide and iodide binding in the
presence and absence of alkali metal cations by rhenium receptors
L1–L4 in CD3CN
presence of alkali metal cation the relative increase of charge
is larger for the neutral rhenium receptors (neutral to ϩ1)
compared to the dicationic ruthenium systems (ϩ2 to ϩ3).
Alternatively, the positive charge on the ruthenium receptor
may via unfavourable electrostatic interactions disfavour lower
rim ester alkali metal cation binding, thus a relatively greater
proportion of unbound metal cations is present in solution to
compete with anion binding by ion pairing, reducing the
enhancement of anion complexation. Tables 1 and 2 also reveal
that alkyl chain length variation has little effect on the strength
of halide anion binding. However, the enhancement of anion
binding with a co-bound cation for the ruthenium receptors in
particular (Table 2) is dependent on the alkyl spacer being
greatest for the propyl linked receptor L6 with the butyl linked
receptor L7 exhibiting the lowest enhancement values.
Moreover, although the rigid aryl linked receptors L4, L8 form
comparatively weaker halide complexes than the alkyl linked
analogues, alkali metal coordination leads to the largest
co-operative amplifications of anion binding of up to sixtyfold
for L4 with co-bound lithium cation and bromide anion guest.
This may be a consequence of co-bound alkali metal cation
induced aryl linked receptor preorganisation and intra-
molecular hydrogen bond disruption which especially favours
subsequent halide anion complexation.
Metal
Relative
Receptor
Anion
cationa
Kb/MϪ1
enhancementc
L1
L1
L1
L1
L1
L2
L2
L2
L2
L2
L3
L3
L3
L3
L4
L4
L4
L4
L4
IϪ
None
Liϩ
15
200
215
50
IϪ
13.3
14.3
IϪ
Naϩ
None
Liϩ
BrϪ
BrϪ
IϪ
1110
22.2
d
None
IϪ
Liϩ
220
IϪ
Naϩ
None
Liϩ
280
BrϪ
BrϪ
IϪ
d
1185
d
None
IϪ
Liϩ
e
d
e
BrϪ
BrϪ
IϪ
None
Liϩ
None
10
205
220
40
IϪ
Liϩ
20.5
22.0
IϪ
Naϩ
None
Liϩ
BrϪ
BrϪ
2400
60.0
a Titration carried out in the presence of one equivalent of alkali
metal perchlorate salt. b Determined at 298 K; errors estimated to be
р 5%. c Relative anion binding enhancement, K(Mϩ)/K (free receptor).
d EQNMR could not determine a stability constant from the titration
data. e Partial precipitation prevented a stability constant from being
determined.
Alkali metal salt extraction experiments
Having demonstrated that these ditopic receptors with a co-
bound metal cation co-operatively bind anions in solution, it
was of interest to investigate whether solid alkali metal salts
could be extracted and solubilised into organic solvents. Alkali
metal salt solid/liquid extraction experiments were performed
with rhenium receptor L1 and ruthenium receptor L6. Each
receptor was dissolved in CD2Cl2 and stirred with an excess of
Table 2 Stability constants for bromide and iodide binding in
the presence and absence of alkali metal cations by ruthenium receptors
L5–L8 in CD3CN
1
Metal
Relative
solid NaCl and NaOAc for 12 hours. After filtration the H
Receptor
Anion
cationa
Kb/MϪ1
enhancementc
NMR spectra revealed two sets of resonances which corre-
sponded to the salt complex and free receptor. The salt complex
resonances were characterised notably by significant downfield
perturbations of the bipy H3 and amide NHa protons, and by
perturbations of the calixarene aromatic and lower rim ester
protons. The percentage extraction was determined by relative
integration of equivalent protons and revealed L1 extracted
60% and L6 55% of both sodium salts. It is noteworthy that on
repeating the extraction experiments with NH4OAc no signifi-
cant changes were observed in the 1H NMR spectra suggesting
the metal cation binding ability of the heteroditopic receptor is
of paramount importance in the alkali metal salt extraction
process.
L5
L5
L5
L5
L5
L6
L6
L6
L6
L6
L7
L7
L7
L7
L7
L8
L8
L8
L8
L8
IϪ
None
Liϩ
60
310
335
230
1260
65
350
460
250
2410
75
175
270
275
620
20
170
270
130
1540
IϪ
5.2
5.6
IϪ
Naϩ
None
Liϩ
BrϪ
BrϪ
IϪ
5.5
None
IϪ
Liϩ
5.4
7.1
IϪ
Naϩ
None
Liϩ
BrϪ
BrϪ
IϪ
9.6
None
IϪ
Liϩ
2.3
3.6
IϪ
Naϩ
None
Liϩ
BrϪ
BrϪ
IϪ
2.3
None
Conclusions
IϪ
Liϩ
8.5
13.5
IϪ
Naϩ
None
Liϩ
A series of new heteroditopic rhenium() and ruthenium()
bipyridyl calix[4]arene receptors that simultaneously complex
alkali metal cation–anion ion pairs at the calixarene lower
rim have been synthesized. Proton NMR halide anion titration
investigations in the absence and presence of lithium and
sodium cations reveal the lower rim ester co-bound alkali metal
cation significantly enhances the strength of bromide and
iodide binding, with the largest positive co-operative anion
binding effect of sixtyfold being displayed by [LiL4]ϩ and brom-
ide. It is noteworthy that with iodide the greatest enhancement
of binding for all receptors is with the co-bound sodium cation
which correlates with the known selectivity preference of lower
rim tetrasubstituted ethyl ester for this alkali metal cation.
Interestingly the degree of halide binding enhancement for the
neutral rhenium() receptors L1–L4 is considerably larger than
for the charged ruthenium() receptors L5–L8 which may
be attributable to unfavourable electrostatic effects leading to
a relatively higher proportion of ‘free’ metal cations being
available in solution to compete with anion binding via ion
BrϪ
BrϪ
11.8
a Titration carried out in the presence of one equivalent of alkali metal
perchlorate salt. b Determined at 298 K; errors estimated to be р 5%.
c Relative anion binding enhancement, K(Mϩ)/K (free receptor).
a result of metal cation complexation removing lower rim
ester–amide intramolecular hydrogen bonding. Interestingly
the degree of enhancement of iodide binding for all receptors is
greatest in the presence of co-bound sodium which correlates
with this metal cation being known to form highly stable and
selective complexes with lower rim tetrasubstituted ethyl ester
calix[4]arenes.15 It is also noteworthy that when comparing
Tables 1 and 2 the degree of halide binding enhancements for
the neutral rhenium receptors are much larger than for the
charged ruthenium receptors. This may be rationalised by
considering the relative charge increases of the rhenium versus
ruthenium receptors on alkali metal cation binding. In the
400
J. Chem. Soc., Dalton Trans., 2001, 392–401

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7 M. M. G. Antonisse and D. N. Reinhoudt, Chem. Commun., 1998,
1495.
8 I. Stibor, D. S. M. Hafeed, P. Lhotak, J. Hodacova, J. Koca and
M. Cayan, Gazz. Chim. Ital., 1997, 127, 673.
pairing. Alkali metal salt solid/liquid extraction experiments
reveal L1 and L6 to solubilise NaCl and NaOAc by up to 60%
in dichloromethane solutions.
9 P. D. Beer, P. K. Hopkins and J. D. McKinney, Chem. Commun.,
1999, 1253; D. J. White, N. Lang, H. Miller, S. Parsons, S. Coles and
P. Tasker, Chem. Commun., 1999, 2077.
10 A. J. Chrisstoffels, F. de Jong, D. N. Reinhoudt, S. Sivelli,
L. Gazzola, A. Casnati and R. Ungaro, J. Am. Chem. Soc., 1999,
125, 10142.
11 N. Teramae, K. Shigemon and S. Nishizawa, Chem. Lett., 1999,
1185.
12 M. J. Deetz, M. Shang and B. D. Smith, J. Am. Chem. Soc., 2000,
122, 6201.
Acknowledgements
We thank the EPSRC for a studentship (to J. B. C.) and for use
of the mass spectrometry service at the University of Wales,
Swansea. The University of Reading and EPSRC are gratefully
acknowledged for funding towards the crystallographic image
plate system.
13 J. B. Cooper, M. G. B. Drew and P. D. Beer, J. Chem. Soc., Dalton
Trans., 2000, 2721.
14 P. D. Beer, Chem. Commun., 1996, 689; P. D. Beer, Acc. Chem. Res.,
1998, 31, 71; P. D. Beer, P. A. Gale and G. Z. Chen, J. Chem. Soc.,
Dalton Trans., 1999, 1897.
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