Heterodinuclear ruthenium(II) bipyridyl-transition metal dithiocarbamate macrocycles for anion recognition and sensing

Article abstract of DOI:10.1016/j.tet.2004.08.058

New heterodinuclear ruthenium(II) bipyridyl-transition metal dithiocarbamate macrocycles have been prepared in good yields via metal directed self-assembly and shown to recognise anions. ¹H NMR anion titration studies reveal the nature of the b

Full text of DOI:10.1016/j.tet.2004.08.058

Tetrahedron 60 (2004) 11227–11238
Heterodinuclear ruthenium(II) bipyridyl-transition metal
dithiocarbamate macrocycles for anion recognition and sensing
*
Michelle D. Pratt and Paul D. Beer
Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, Oxford OX1 3QR, UK
Received 22 January 2004; revised 23 June 2004; accepted 19 August 2004
Available online 23 September 2004
Abstract—New heterodinuclear ruthenium(II) bipyridyl-transition metal dithiocarbamate macrocycles have been prepared in good yields
via metal directed self-assembly and shown to recognise anions. H NMR anion titration studies reveal the nature of the bipyridyl amide
1
metal dithiocarbamate spacer unit in the respective dinuclear metal macrocycle influences significantly the strength of chloride and bromide
complexation in DMSO solutions. Luminescence spectroscopy was used to sense anions in polar organic solutions via notable emission
enhancement and quenching of the respective ruthenium(II) bipyridyl groups in the receptors.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
assembly4 in producing novel heterodinuclear ruthenium(II)
bipyridyl-transition metal dithiocarbamate macrocyclic
receptors.
Anionic species are well known to play numerous funda-
mental roles in biology and chemical processes and their
detrimental effects as environmental pollutants is of
growing concern.1 In view of this, there is intense current
interest being shown in the design and syntheses of
receptors that are proficient at detecting anions in
solution.1,2 By incorporating redox- and photo-active
transition metal inorganic signalling probes into various
acyclic, macrocyclic and calixarene ligand frameworks, we
have produced a series of selective spectral and electro-
chemical responsive reagents for anions.2a,3 In an effort to
construct new types of luminescent responsive receptors for
anion recognition, we report here the synthesis of hetero-
dinuclear ruthenium(II) bipyridyl-transition metal dithio-
carbamate macrocycles using metal directed self-assembly.
Recently, the dithiocarbamate (dtc) moiety has proven to be
a useful structural motif lending itself to the metal directed
assembly of a range of structures including nano-sized
resorcarene-based assemblies,5 catenanes,6 assorted macro-
cycles7 and cyptands.8 The dithiocarbamate ligand is simple
to prepare via reaction of carbon disulfide with a secondary
amine in the presence of base. Consequently, bipyridyl
ligands were functionalised initially with secondary amines,
and after chelation to the ruthenium(II) bis(bipyridyl)
moiety, transition metal directed self-assembly using the
dithiocarbamate ligand produced the target heterodinuclear
macrocycles.
Reductive amination of 4,40-diformyl-2,20-bipyridyl 1 with
butylamine afforded the bis amine 2 in 92% yield
(Scheme 1). Condensation of 4,40-bis(chlorocarbonyl)-
2,20-bipyridine 3 with 2 equiv of N-butyl-ethane-1,2-
diamine 4 produced the bis-amide-amine bipyridyl deriva-
tive 5 in quantitative yield (Scheme 2). Amide-amine
bipyridyl compound 9 was similarly prepared by conden-
sation of 4,40-bis(chlorocarboxyl)-2,20-bipyridine 3 with
2 equiv of a Boc-protected diamine (Scheme 3), which was
obtained from 4-nitrobenzaldehyde (see Section 6).
2. Synthesis
We have exploited the positively charged ruthenium(II)
bipyridyl moiety in the construction of a variety of acyclic
and macrocyclic receptors for anion sensing.2a,3 The
preparation of these latter macrocyclic systems can be
problematic as their synthesis requires high dilution
conditions and often yields are moderate. These synthetic
problems may be over come by applying metal directed self-
Refluxing the appropriate bipyridyl amine derivative with
cis-Ru(bpy)2Cl2 in aqueous ethanol solution followed by
Sephadex column chromatography eluting with acetonitrile/
methanol (95:5) and addition of excess NH4PF6 produced
Keywords: Anion sensing; Ruthenium; bpy; Macrocycle; Luminescence;
Metal directed self-assembly.
* Corresponding author. Tel.: C44-1865285142; fax: C44-1865272690;
e-mail: paul.beer@chem.ox.ac.uk
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.08.058

11228
M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
Scheme 1.
Scheme 2.
Scheme 3.
the respective ruthenium(II) complexes 10–12 in good
yields (69–80%, Scheme 4).
macrocycles 16–21 were investigated by a variety of
spectroscopic techniques.
One-pot macrocyclisation with 2 equiv of carbon disulfide,
KOH and transition metal acetate salt in acetonitrile/water
(9:1) or THF/water (9:1) solutions gave the target hetero-
dinuclear receptors 13–21 in good yields (48–95%,
Scheme 5). These macrocyclic systems were characterised
by 1H NMR spectroscopy (for diamagnetic derivatives),
electrospray mass spectrometry (ESMS) and elemental
analysis (see Section 6). No evidence from ESMS was
seen for dimeric or higher oligomeric structures.
3.1. NMR titrations
Solubility problems at NMR concentrations dictated that all
titration experiments were undertaken in d6-DMSO. The
addition of tetrabutylammonium anion salts to d6-DMSO
solutions of diamagnetic transition metal containing recep-
tors, in general, resulted in significant downfield pertur-
bations of the respective bipyridyl H3 and amide receptor
protons. EQNMR9 analysis of the resulting titration curves
suggested 1:1 receptor/anion stoichiometry in the majority
of cases and the calculated stability constant values are
shown in Table 1. Unfortunately with dihydrogen phosphate
and acetate anions, precipitation problems during the
titration experiment thwarted quantitative binding analysis
for the majority of the receptors.
3. Anion coordination studies
The interactions of anions with acyclic ruthenium(II)
bipyridyl receptors 11 and 12 and their corresponding

M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
11229
Scheme 4.
Table 1 shows that all three receptors containing ethyl
spacer units connecting the ruthenium(II) bipyridyl amide
unit to the respective secondary amine or transition metal
dithiocarbamate complex 11, 16 and 18 display the
selectivity preference ClKOBrKOIK, which suggests the
chloride anion is of complementary size to the receptors’
cavity. These halide binding results contrast those of 19 and
21 where weak binding of all three halide anions is
observed. Presumably, the aryl group containing macro-
cyclic cavity sterically hinders halide complexation.
Acyclic receptor 12 complexes BrK with similar strength
to 11, 16 and 18. However, the stability of the ClK complex
is significantly reduced in comparison.
transition observed with [Ru(bpy)3]2C. The majority of the
electronic transitions associated with the transition metal
dithiocarbamate complexes are hidden beneath the ruthe-
nium(II) bipyridyl absorptions. The addition of anions to
acetonitrile solutions of the respective receptors resulted in
small perturbations of the electronic spectrum. In some
cases isosbestic points were observed (Fig. 1). However,
attempts to determine quantitative binding data using
Spectfit10 proved problematic.
3.3. Luminescence spectroscopy
The ability of [Ru(bpy)3]2C to act as a luminescent receptor
unit is well established.2 The emission spectra of all
receptors displayed a single broad emission maximum
which is red-shifted relative to Ru(bpy)3 PF6 (Table 3).
Again the amide substituents on the bipyridyl motif can
explain the energy decrease of the MLCT excited state. It is
interesting to note that the relative emission intensities of
the heterodinuclear macrocycles vary greatly depending
3.2. UV–visible
The electronic spectral characteristics of the receptors are
shown in Table 2, where as noted previously,2a the electron
withdrawing characteristics of the amide groups causes a
lower energy MLCT transition compared to the MLCT

11230
M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
Scheme 5.
upon the nature of the transition metal dtc complex. The
presence of redox-active transition metals nickel(II) 16 and
copper(II) 17, causes luminescence quenching of the
Ru(bpy)23C units. Figure 2 shows that the emission intensity
for zinc(II) dtc containing macrocycle 18 is much larger
than that of acyclic ruthenium(II) bipyridyl receptor 11 and
that emission quenching is clearly observed with 16 and 17
relative to 11. The effects of addition of anions in the
luminescence spectra of the receptors were investigated in
acetonitrile for 11, 16–18 and in DMSO for 12, 19–21 due to
solubility differences.
3.4. Emission binding studies in acetonitrile
The effect of anion addition on the emission spectra
depended on the receptor in question. For 11 there was
typically a marked increase in the intensity of the emission
upon addition of chloride, bromide, iodide, and acetate with

M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
Table 1. Anion stability constant values K (MK1) in DMSO-d6
M(dtc)2 MZ
H2POK4
11231
AcOK
ClK
BrK
IK
a
11
12
16
18
19
21
—
—
Ni
Zn
Ni
Zn
1000
b
900
245
1000
920
!10
!10
120
180
190
140
!10
!10
20
!10
0
0
!10
!10
a
b
a
b
b
990
b
b
b
Errors estimated to be %10%, tempZ298 K.
a
EQNMR8 could not fit data.
Precipitation occurred.
b
Table 2. UV–visible characterisation data in CH3CN at 1.25!10K5
M
Compound
MLCT
Wavelength (nm)
LC
MLCT
3/103 MK1 cmK1
Wavelength (nm)
3/103 MK1 cmK1
Wavelength (nm)
3/103 MK1 cmK1
[Ru(bpy)3]2C
244
245
246
245
245
245
246
244
254
27.2
180.0
20.6
45.9
24.2
41.6
49.7
28.7
41.0
287
287
288
288
287
288
288
287
286
79.8
75.6
46.8
72.9
53.3
89.6
79.5
55.2
75.8
450
454
451
454
454
454
456
445
455
14.3
75.2
8.2
14.0
11.0
17.5
12.6
10.5
12.6
10
11
13
14
15
16
17
18
Figure 1. UV–visible titration of 16 and AcOK in CH3CN.
a concomitant hypsochromic shift in the emission lmax
(Table 4). For example, the addition of excess chloride to 11
caused a 47% increase in intensity and a 4.5 nm blue shift in
the emission maximum (Fig. 3). The hypsochromic shift
indicates that the MLCT state moves to higher energy in the
presence of an anion. The MLCT dp* state has the electron
formally residing on the bipyridine ligand, and this
configuration is presumably less favourable when a
negatively charged guest binds to the amide bipyridine
group. The emission enhancement is probably due to the
binding of an anion causing the receptor molecule to
become more structurally rigid, by restricting its vibrational
and rotational modes. This limits the pathways for
radiationless decay, and hence increases the observed
emission intensity.11
Table 3. Emission data in CH3CN except for compounds marked ‘*’ were
in DMSO, 1.25!10K5 M, lexcit at maxima of MLCT
Receptor
M(dtc)2 MZ
Wavelength
(nm)
Intensity (arbi-
trary units)
[Ru(bpy)3]
[PF6]2
20
597
56
In contrast, macrocycle 18 displayed significant decreases in
emission intensity on addition of anions. The luminescence
quenching observed upon anion addition to the macrocyclic
receptor is more difficult to explain. One possible cause of
luminescence quenching is if the symmetry of the molecule
is altered upon complexation, destabilising the 3MLCT
excited state. Thus the emission would be quenched, and an
intensity decrease would be observed. This effect might also
cause a change in the energy levels involved, which would
be observed as a shift in the wavelength of the emission
maximum.12 Disappointingly, only small increases in
—
603
631
639
604
623
625
625
630
630
635
638
214
87
202
10
24
220
3
21
—
—
Ni
Cu
Zn
Ni
Cu
Zn
Cu
Zn
22*
23
24
25
26
27
13
29
214
119
206
30*
31*

11232
M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
Figure 2. Emission spectra of 11 and 16–18 in CH3CN, 1.25!10K5 M.
Table 4. Percentage change in emission maxima intensity in CH3CN and change in wavelength maxima upon addition of excess anions
Anion
AcOK
H2POK4
,
ClK
BrK
IK
(11)
C64%
K12.5
K65%
K12.0
C39%
K2.5
K88%
K2.0
C47%
K4.5
K45%
K5.5
C38%
K3.0
K30%
K4.5
C7%
K3.0
K30%
K3.5
Dlmax (nm)
(18)
Dlmax (nm)
Figure 3. Luminescence titration of 11 with ClK in CH3CN, 1.25!10K5 M.
emission intensity upon addition of anions to macrocycles
16 and 17 were observed.
receptors 11 and 18 with dihydrogen phosphate could not be
determined due to the complexity of the emission responses,
and acetate was bound strongly by both receptors.
Specfit10 analysis of the titration data enabled stability
constants to be determined (Table 5). The stability constants
in acetonitrile for receptor 11 are all very high in this solvent
and are quoted as log b1O6, which is approaching the upper
limit for log b1 values by Specfit.10 The halide anions
(chloride, bromide and iodide) were all bound by receptor
11 with similarly large stability constants, whereas macro-
cycle 18 showed a selectivity trend ClKOBrKOIK, as seen
in the 1H NMR titration experiments. Stability constants for
3.5. Emission binding studies in DMSO
The anion emission titration studies for receptors 12 and
19–21 were conducted in DMSO, due to their poor
solubility in acetonitrile. Addition of anions to the
ruthenium(II) receptor 12 in DMSO resulted in small
increases in the emission intensity and slight hypsochromic
shifts. However, the changes in the emission intensity in

M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
11233
Table 5. Stability constants determined by Specfit10 in CH3CN at receptor
concentrations of 1.25!10K5 M (TempZ298 K)
study of the 2,20-bpy reductions was rendered impossible
(Table 7).
log b1 11
log b1 18
For all receptors the ruthenium(II/III) redox wave was
observed at w1.0 V. For 11 the first bipyridyl ligand centred
reduction is assigned to the 4,40-amide-substituted bipyr-
idyl. The electron withdrawing amide group means that
this bipyridyl group is easier to reduce than its neighbouring
ones. The anodic shifts in the copper(II/III) couple for the
ruthenium macrocycles 14 and 17 compared to Cu(Et2dtc)2
may be a result of the close proximity of the positively
charged ruthenium(II) centre. All four systems investigated
displayed quasi-reversible behaviour for both the ruthenium
(II/III) couple and the copper(II/III) redox couples (for
receptors 14 and 17).
AcOK
H2POK4
ClK
O6
O6
a
a
O6
O6
O6
5.72G0.07
5.04G0.04
4.76G0.06
BrK
IK
a
Specfit10 could not fit data.
DMSO were much less than those observed in CH3CN for
compound 11. This is to be expected due to the competitive
nature of DMSO.13 Addition of anions to the macrocycles
19–21 caused only small decreases in emission intensity.
The only anion to cause significant changes in the emission
spectra was dihydrogen phosphate. For this anion stability
constants could be determined with a 1:1 stoichiometry and
are given in Table 6. The zinc(II) macrocycle 21 displayed
an enhanced binding affinity for dihydrogen phosphate
compared to its acyclic analogue 12.
The addition of dihydrogen phosphate to receptor 10 caused
a small cathodic shift for the first bipyridyl reduction wave
(10 mV), but addition of acetate, chloride, bromide, and
iodide caused little change (!5 mV). Addition of anions to
11 also caused modest cathodic shifts of w10 mV for the
first bipyridyl wave. The shift was approximately the same
for addition of all anions, and little discrimination was
shown. For both receptors 10 and 11, no shifts were
observed for the ruthenium(II/III) couple or the second and
third bipyridyl reduction couples on the addition of anions.
Electrochemical studies on [Ru(bpy)3][(PF6)2] showed no
perturbations upon addition of anions to either the
ruthenium(II/III) oxidation wave, or the bipyridyl reduction
waves.
Table 6. Stability constants determined by Specfit10, in DMSO at receptor
concentrations of 1.25!10K5 M (TempZ298 K)
log b1 12
4.2G0.1
log b1 21
5.28G0.06
H2POK4
4. Electrochemical investigations
Cathodic shifts occur because the complexation of anions
increases the negative charge density adjacent to the binding
site.17 This in turn inhibits the reduction of the redox centre
and so a greater formal reduction potential is required to add
more electrons. As noted in previous systems, the fact that
no shifts were observed for the second or third bipyridyl
reduction couples or for the ruthenium(II/III) couple lends
support to the hypothesis that the binding of anionic guests
is centred in the vicinity of the substituted bipyridyl groups
in solution.
The electrochemical properties of 10, 11 and copper(II) dtc
containing receptors 14 and 17 were investigated using
cyclic and square wave voltammetry with tetrabutylammo-
nium tetrafluoroborate as supporting electrolyte. As
expected the electrochemical data for 10 and 11 are similar
to Ru(bpy)23C, displaying four redox waves assigned to a
metal centred Ru(II)/(III) oxidation and three ligand centred
bipyridyl reduction processes (Table 7). The electrochemi-
cal properties of copper(II) dithiocarbamate complexes are
well-documented undergoing reversible one-electron oxi-
dation and reduction redox processes.14–16
Electrochemical investigations of the macrocycles 14 and
17 and Cu(Et2dtc)2 upon addition of anions revealed no
perturbations of the ruthenium(II/III) redox wave. However,
significant cathodic shifts were observed in the copper(II/
III) redox wave (Table 8). The addition of dihydrogen
phosphate to macrocycle 14 resulted in a shift of 40 mV.
This shift was considerably larger than the shift observed for
Cu(Et2dtc)2 (!10 mV). Receptor 14 showed little inter-
action with acetate. However, the large cathodic shift in the
copper(II/III) redox potential of Cu(Et2dtc)2 upon addition
The copper(II/III) couple in macrocycles 14 and 17 is
compared to the copper(II/III) couple in the model com-
pound, copper(II) diethyl dithiocarbamate (Cu(Et2dtc)2).
The electrochemical investigations of 14 and 17 were
limited to an electrochemical window of C1.25–0 V, in
order to avoid decomposition of the macrocycles. Under
more reducing conditions precipitation was observed and
irreproducible results were noted. Thus assignment and
Table 7. Electrochemical data for 10, 11, 14, 17 in CH3CN/0.1 M TBABF4, Ag/AgNO3 reference electrode
First 2,20-bpy
reduction E1/2/V
Second 2,20-bpy
reduction E1/2/V
Third 2,20-bpy
reduction E1/2/V
Complex
Ru(II/III) couple E1/2
V
/
Cu(II/III) couple E1/2/
V
[Ru(bpy)3]2C
10
11
14
17
Cu(Et2dtc)2
C1.03
C1.02
C1.03
C1.00
C1.02
—
K1.61
K1.60
K1.51
—
—
—
K1.82
K1.83
K1.80
—
—
—
K2.12
K2.12
K2.10
—
—
—
—
—
—
C0.29
C0.20
C0.19
E1/2Z(EpaCEpc)/2.

11234
M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
Table 8. Cathodic shifts in Cu(II/III) redox wave upon addition of 5 equiv
of anion in CH3CN/0.1 M TBABF4
spectra were recorded on a Perkin Elmer Lamba 6 UV–
visible Spectrometer. Measurements were conducted at
25 8C using a 1!1 cm rectangular quartz cuvette. UV–
visible spectra were recorded on a PE Lamba 6 spectro-
meter. Electrochemical studies were performed on a
Princeton Applied Research potentiastat/galvanostat model
273 using a glassy carbon working electrode, a platinum
counter electrode and an Ag/AgNO3 reference electrode
(0.33 VG10 mV vs SCE). Kemet diamond sprays (1 mm
and 0.25 mm) were used to polish the working electrode.
Cu(II/III) couple DE
(mV)
Cu(Et2dtc)2
14
17
a
a
H2POK4
AcOK
!10
60
40
!10
a
Precipitation occurred.
of acetate anions may imply there is a coordinative
interaction between the copper(II) centre and the anion.
4,40-Diformyl-2,20-bipyridine 1,18 4,40-bis(carboxy)-2,20-
bipyridine 3,19 and 4,40-bis(chlorocarbonyl)-2,20-bipyridine
4,18 were prepared according to literature procedures.
Unfortunately, no significant changes in oxidation poten-
tials were observed on addition of bromide or iodide to 14 or
17. At the concentrations used for the electrochemical
experiments, addition of dihydrogen phosphate and acetate
anions to receptor 17 caused precipitation, hindering further
investigation.
6.10.1. 4,40-Bis(butylaminomethyl)-2,20-bipyridine, 2.
4,4 -Diformyl-2,20-bipyridine (0.20 g, 0.9 mmol) and n-
butylamine (0.13 g, 1.8 mmol) were dissolved in toluene
(100 ml). The mixture was refluxed under nitrogen for
45 min using Dean–Stark apparatus and then the solvent
was removed to yield an orange oil. This was dissolved in
MeOH (100 ml) and a fivefold excess of NaBH4 was
cautiously added and stirred for 1 h under nitrogen. HCl (aq)
(2 M) was added carefully until pHZ1. The mixture was
made basic (pHZ11) by the addition of KOH (aq) (2 M).
The product was extracted into CH2Cl2 (4!50 ml) and
dried over K2CO3. Solvent removal and drying in vacuo
yielded a yellow oil (0.27 g, 92%).
5. Conclusions
A series of new 4,40-amide-secondary amine substituted
ruthenium(II) bipyridyl derivatives were prepared initially,
which on applying metal directed self-assembly, using the
dithiocarbamate ligand, produced novel heterodinuclear
ruthenium(II) bipyridyl-transition metal dithiocarbamate
macrocycles in good yields. A variety of spectroscopic
and electrochemical techniques were employed to investi-
gate their anion recognition and sensing capabilities. It is
noteworthy that the nature of the spacer unit in the
respective dinuclear metal macrocycles crucially dictates
the strength of chloride and bromide binding in DMSO
solutions with ethyl spacer containing macrocyclic recep-
tors 16 and 18 forming much stronger complexes than the
corresponding aryl linked systems 19 and 21. Although
UV–visible absorption spectroscopy proved largely insen-
sitive to anion complexation, the luminescence spectra of
the receptors were significantly perturbed on anion binding.
Both anion complexation induced emission enhancement
and quenching effects were noted, respectively, with 11
and 18.
1H NMR in CDCl3 (d/ppm): 0.85 (t, 6H, 3JZ7.2 Hz, CH3),
1.30 (m, 4H, 3JZ7.2 Hz, CH2CH3), 1.45 (m, 4H, 3JZ7.2 Hz,
CH2CH2CH3), 2.58 (t, 4H, 3JZ7.2 Hz, NCH2CH2), 3.83 (s,
4H, bpyCH2NH), 7.27 (d, 2H, 3JZ4.8 Hz, bpy-H5,50), 8.27
3
(s, 2H, bpy-H3,30), 8.56 (d, 2H, JZ4.8 Hz, bpy-H6,60).
13C NMR in CDCl3 (d/ppm): 14.67 (CH3), 23.50 (CH2),
32.23 (CH2), 50.03 (CH2NH), 53.43 (bpyCH2), 120.71
(bpy-C), 123.27 (bpy-C), 139.01 (bpy-C), 149.34 (bpy-C),
150.77 (bpy-C).
ESMS: m/z 327.3 [MCH]C.
6.1.2. 4,40- Bis-[(2-butylamino-ethyl-carbamoyl] 2,20-
bipyridine, 5. N-Butyl-ethane-1,2-diamine (0.2 g,
1.7 mmol) was dissolved in CH2Cl2 (30 ml) under a
nitrogen atmosph0ere. To this rapidly stirred solution, a
solution of 4,4 -di(chlorocarbonyl)-2,20-bipyridine 4
(0.24 g, 0.8 mmol) dissolved in CH2Cl2 (30 ml) was added
dropwise. A white precipitate formed immediately, but the
solution was stirred for a further 15 min to ensure com-
pletion of the reaction. The product was filtered, washed
with H2O (2!15 ml), Et2O (2!15 ml) and dried in vacuo
to give a highly insoluble white solid in quantitative yield
(0.38 g).
Voltammetric studies revealed modest anion induced
cathodic shifts of the respective first bipyridyl reduction
redox couple of acyclic receptors 10 and 11, whereas a
significant cathodic perturbation of the copper(II)/(III) dtc
redox couple of 14 was noted with dihydrogen phosphate
anion addition.
6. Experimental
6.1. General
3
NMR spectra were recorded on a Varian Mercury 300 or a
Varian Unity Plus machine 500. FAB Mass spectrometry
was carried out by the EPSRC mass spectrometry service,
Swansea. Elemental analyses were performed by the
Inorganic Chemistry Laboratory Microanalysis Service
and electrospray mass spectrometry (ESMS) were per-
formed on a Micromass ESI-TOF in the Inorganic
Chemistry Department, University of Oxford. Fluorescence
1H NMR in DMSO-d6 (d/ppm): 0.82 (t, 6H, JZ3.9 Hz,
CH3), 1.28 (m, 4H, CH2CH3), 1.52(m, 4H, CH2CH2CH3),
2.65 (m, 4H, NHCH2CH2CH2CH3), 2.81 (m, 4H, CH2NH),
3.54 (m, 4H, CH2NHCO), 7.88 (m, 2H, bpy-H5,50), 8.76 (s,
2H, bpy-H3,30), 8.83 (m, 2H, bpy-H6,60), 9.14 (m, 2H,
CONH).
ESMS: m/z 441.6 [MCH]C, 463.6 [MCNa]C.

M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
11235
6.1.3. Butyl-(4-nitro-benzyl)-amine, 6. 4-Nitrobenzalde-
ESMS: m/z 301.2 [MCNa]C.
hyde (2 g, 13 mmol) and n-butylamine (0.96 g, 13 mmol)
were dissolved in toluene (100 ml). The mixture was
refluxed under nitrogen for 45 min using Dean–Stark
apparatus and the solvent was removed to yield an orange
oil. This was dissolved in MeOH (100 ml) and a five-fold
excess of NaBH4 was added cautiously and stirred for 1 h
under nitrogen. HCl (aq) (2 M) was added carefully until
pHZ1 and then NaOH (aq) (2 M) until pHZ11. The
product was extracted into CH2Cl2 (4!50 ml) and dried
over K2CO3. Solvent removal and drying in vacuo yielded a
yellow oil (1.76 g, 65% yield).
6.1.6. 4,400 Bis-[(4-butylaminomethyl-phenyl)-carba-
moyl]-2,20-bipyridine, 9. (4-Amino-benzyl)- butyl-carba-
mic acid tert-butyl ester 8 (4.88 g, 1.7 mmol) was dissolved
in CH2Cl2 (30 ml) under a nitrogen atmosphere. To this a
solution of 4,40-di(chlorocarbonyl)-2,20-bipyridine (2.03 g,
8.0 mmol) dissolved in CH2Cl2 (30 ml) was added drop-
wise. An orange precipitate formed immediately, but the
solution was stirred for a further 15 min to ensure
completion of the reaction. The product was filtered,
washed with H2O (2!15 ml), Et2O (2!15 ml) and dried
in vacuo to give an orange solid (5.88 g, 96% yield).
Interestingly during this reaction the amine protecting group
(Boc) was removed to yield the free amine.
1H NMR in CDCl3 (d/ppm): 0.81 (t, 3H, 3JZ7.2 Hz, CH3),
1.19 (m, 2H, 3JZ7.2 Hz, CH2CH3), 1.40 (m, 2H, 3JZ7.2 Hz,
CH2CH2CH3), 3.11 (m, 2H, NHCH2CH2), 4.43 (s, 2H,
ArCH2), 7.30 (d, 2H, 3JZ7.8 Hz, Ar-H), 8.10 (d, 2H,
3JZ7.8 Hz, Ar-H).
1H NMR in DMSO-d6 (d/ppm): 0.93 (t, 6H, CH3), 1.22 (m,
4H, CH2CH3), 1.43 (m, 4H, CH2CH2CH3), 3.15 (m, 4H,
NHCH2CH2), 4.37 (s, 4H, ArCH2), 7.20 (d, 4H, 3JZ7.8 Hz,
ESMS: m/z 209.1 [MCH]C.
3
Ar-H), 7.75 (d, 4H, Ar-H), 8.03 (d, 4H, JZ7.2 Hz, bpy-
H5,50), 8.094 (m, 4H, bpy-H6,60 and CONH), 10.86 (s, 2H,
bpy-H3,3 ).
6.1.4. Butyl-(4-nitro-benzyl)-carbamic acid tert-butyl
ester, 7. Bis-(tert-butoxycarbonyl)anhydride (0.27,
1.2 mmol) was dissolved in 30 ml of dioxane. This was
added, over 2 1/2 h, to butyl-(4-nitro-benzyl)-amine (0.2 g,
1.1 mmol) (which was dissolved in 30 ml of dioxane). The
solution was stirred for 30 min, after which time the solvent
was removed in vacuo giving a white semi-solid. H2O
(50 ml) was added and the product was extracted into
CH2Cl2 (3!50 ml), dried with MgSO4, filtered and reduced
in vacuo leaving a clear, viscous oil (0.25 g, 74% yield).
ESMS: m/z 565.7 [MCH]C.
6.1.7. Ruthenium(II) (4,40-bis(butylaminomethyl)-2,20-
bipyridine)bis(2,20-bipyridin0e)-bis(hexafluorophos-
phate), 10. cis-Dichlorobis(2,2 -bipyridine)ruthenium(II)
(0.12 g, 0.2 mmol) and 4,40-bis-(butylaminomethyl)-2,20-
bipyridine 2 (0.09 g, 0.2 mmol) were dissolved in EtOH/
H2O (50:50) (50 ml) and refluxed for 18 h. The solvent was
removed in vacuo leaving a shiny deep purple solid. The
crude product was purified by column chromatography on
Sephadexw LH-20, eluting with MeCN to remove excess
[Ru(bpy)2Cl2] and then 5% MeOH in MeCN to obtain the
product. Solvent removal gave a deep purple shiny, flaky
solid. It was noted that for this and all subsequent ruthenium
compounds that there was a thin0 green band, between the
purple of the cis-dichlorobis(2,2 -bipyridine)ruthenium(II)
and the red of the product, attributed to a ruthenium(III)
complex. The chloride counteranion was exchanged for
hexafluorophosphate by dissolving the chloride salt in the
minimum amount of MeOH and adding a saturated solution
of NH4PF6 (aq). This gives the hexafluorophosphate salt as a
precipitate, which can be removed by filtration, washed with
H2O, then Et2O and dried under vacuum to yield a red solid
(typically 90–94% conversion from the chloride salt). The
red solid was isolated and dried under vacuum (0.16 g, 80%
yield).
1H NMR in CDCl3 (d/ppm): 0.85 (t, 3H, 3JZ7.8 Hz,
CH2CH3), 1.23 (m, 4H, 3JZ6.6 Hz, CH2CH2CH3), 1.44 (s,
9H, C(CH3)3), 3.14 (m, 2H, NBocCH2CH2), 4.46 (s, 2H,
ArCH2), 7.34 (d, 2H, 3JZ8.4 Hz, Ar-H), 8.13 (d, 2H,
3JZ8.1 Hz, Ar-H).
13C NMR in CDCl3 (d/ppm): 13.95 (CH3), 20.14 (CH2),
28.52 ((CH3)3C), 30.5 (CH2), 47.34 (CH2), 67.24
(ArCH2N), 80.24 ((CH3)3C), 123.88 (Ar-C), 128.22 (Ar-C),
128.26 (Ar-C), 147.32 (Ar-C).
ESMS: m/z 331.2 [MCNa]C.
6.1.5. (4-Amino-benzyl)- butyl-carbamic acid tert-butyl
ester, 8. The nitro compound 7 (6.20 g, 0.018 mol) was
reduced using Raney Nickel, 10 atm, 50 8C, 1 h in EtOH.
The solvent was removed and the product purified by
column chromatography on silica eluting with CH2Cl2 to
give the amine (3.62 g, 72% yield).
1H NMR in CD3CN (d/ppm): 0.94 (t, 6H, 3JZ7.0 Hz, CH3),
1.40 (m, 4H, 3JZ7.5 Hz, CH2CH3), 1.63 (m, 4H, 3JZ7.5 Hz,
CH2CH2CH3), 2.96 (m, 4H, 3JZ7 Hz, NCH2CH2), 4.22 (s,
4H, bpyCH2NH), 7.44 (m, 6H, bpy-He and bpy-H5,50), 7.75
1H NMR in CDCl3 (d/ppm): 0.80 (t, 3H, 3JZ6.9 Hz, CH3),
1.11 (m, 4H, 3JZ6.6 Hz, CH2CH2CH3), 1.39 (s, 9H,
CCH3), 3.03 (br s, 2H, NH2), 3.68 (m, 2H, NBocCH2CH2),
3
(m, 6H, bpy-H6,60 and bpy-Hf), 8.09 (t, 4H, JZ7.8 Hz,
bpy-Hd), 8.52 (d, 6H, 3JZ7.8 Hz, bpy-Hc), 8.59 (s, 2H, bpy-
H3,30).
3
4.21 (s, 2H, ArCH2), 7.15 (d, 2H, JZ8.1 Hz, Ar-H), 7.26
3
(d, 2H, JZ7.8 Hz, Ar-H).
13C NMR in CD3CN (d/ppm): 13.44 (CH3), 20.04 (CH2),
30.27 (CH2), 48.83 (CH2NH), 50.59 (bpyCH2), 124.56
(bpy-C), 125.01 (bpy-C), 127.87 (bpy-C), 127.92 (bpy-C),
138.19 (bpy-C), 151.76 (bpy-C), 151.85 (bpy-C), 152.03
(bpy-C), 157.07 (bpy-C), 157.17 (bpy-C).
13C NMR in CDCl3 (d/ppm): 13.98 (CH3), 20.16 (CH2),
28.61 ((CH3)3C), 30.21 (CH2), 45.85 (CH2), 67.15
(ArCH2N), 79.27 ((CH3)3C), 115.08 (Ar-C), 128.10 (Ar-C),
129.33 (Ar-C), 146.14 (Ar-C).

11236
M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
Elemental analysis: found: C 44.7%, H 4.8%, N 10.4%.
MALDI: m/z 978.2 [MK2PF6]C, 1122.8 [MKPF6]C.
Calculated (C40H46N8RuP2F12$2H2O): C 45.0%, H 4.7%, N
10.5%.
6.2. General method for synthesis of macrocycles, 13–15
The macrocyclic receptors were synthesised in a one pot
reaction. To a stirred solution of the respective ruthenium
(II) receptor 10 in 10 ml MeCN/H2O mixture (9:1) was
added an excess of KOH(aq) (1 M). Two equivalents of
carbon disulphide were dropped into the solution and the
mixture stirred for 10 min allowing formation of the
potassium dithiocarbamate salt. This salt was not isolated
but reacted in situ by the addition of 1 equiv of nickel,
copper, or zinc (II) acetate. The mixture was stirred
overnight. Addition of water precipitated the product. The
mixture was stirred for a further 2 h before it was filtered
and dried to give the macrocycles.
ESMS: m/z 739.9 [MK2PF6]C, 884.9 [MKPF6]C, 1029.9
[M]C.
6.1.8. Ruthenium(II) 4,40- bis-[(2-butylamino-ethyl-
carbamoyl] 2,20-bipyridine bis(2,20-bipyridine)-bis(hexa-
fluorophosphate), 11. Procedure as for receptor 10,
using cis-dichlorobis(2,20-bipyridine)ruthenium(II) (0.19 g,
0.36 mmol) and 4,40-bis-[(2-butylamino-ethyl-carbamoyl]
2,20-bipyridine 5 (0.16 g, 0.36 mmol) The hexafluorophos-
phate salt was then isolated (0.29 g, 71% yield).
1H NMR in CD3CN (d/ppm): 0.96 (t, 6H, 3JZ7.2 Hz, CH3),
1.42 (m, 4H, 3JZ7.5 Hz, CH2CH3), 1.66 (m, 4H, 3JZ7.0 Hz,
CH2CH2CH3), 3.07 (t, 4H, 3JZ8.0 Hz, NHCH2CH2
6.2.1. Nickel(II) macrocycle, 13. Procedure outlined above
using receptor 10 (0.12 g, 0.1 mmol) and 1 equiv of
nickel(II) acetate tetrahydrate. Red/brown solid (0.06 g,
48%).
3
CH2CH3), 3.28 (t, 4H, JZ5.1 Hz, CH2NHCH2CH2CH2),
3.71 (m, 4H, 3JZ7.0 Hz, CONHCH2), 7.44 (m, 4H,
3JZ5.7 Hz, bpy-He), 7.73 (m, 6H, bpy-H5,50 and bpy-Hf),
7.96 (d, 2H, 3JZ6.0 Hz, bpy-H6,60), 8.10 (m, 4H, 3JZ6.0 Hz,
bpy-Hd), 8.55 (m, 6H, bpy-Hc and 2CONH), 9.04 (s, 2H,
bpy-H3,30).
1H NMR in CD3CN (d/ppm): 0.87 (br m, 6H, CH3), 1.32 (m,
3
4H, CH2CH3), 1.62 (br m, 4H, JZ7.5 Hz, CH2CH2CH3),
(obscured by solvent, NCH2CH2), 5.69 (dd, 4H, 3JZ6.3 Hz,
4JZ1.5 Hz, bpyCH2N), 7.43 (m, 6H, bpy-H6,60 and bpy-
3
13C NMR in CD3CN (d/ppm): 13.24 (CH3), 19.74 (CH2),
28.15 (CH2), 37.41 (CH2), 48.57 (CH2), 48.92 (CH2),
124.97 (bpy-C), 125.66 (bpy-C), 126.20 (bpy-C), 128.33
(bpy-C), 138.80 (bpy-C), 141.97 (bpy-C), 152.28 (bpy-C),
153.30 (bpy-C), 157.21 (bpy-C), 157.34 (bpy-C), 158.10
(bpy-C), 165.76 (CO).
He), 7.73 (t, 2H, JZ7.5 Hz, bpy-Hf), 8.09 (m, 6H, bpy-
3
H5,50 and bpy-Hd), 8.55 (d, 4H, JZ7.5 Hz, bpy-Hc), 8.99
(s, 2H, bpy-H3,30).
Elemental analysis: found: C 39.9%, H 3.7%, N 8.8%.
Calculated (C42H42N8RuS4NiP2F12$2H2O): C 39.6%, H
3.6%, N 8.8%.
Elemental analysis: found: C 43.2%, H 5.0%, N 11.1%.
Calculated (C44H52N10RuO2P2F12$4H2O): C 43.5%, H
5.0%, N 11.5%.
ESMS: m/z 474.2 [MK2PF6]2C
.
6.2.2. Copper(II) macrocycle, 14. Procedure outlined
above using receptor 10 (0.12 g, 0.1 mmol) and 1 equiv of
copper(II) acetate monohydrate. Brown solid (0.077 g,
62%).
ESMS: m/z 427.2 [MK2PF6]2C, 500.2 [MKPF6]2C, 573.2
[M]2C
.
6.1.9. Ruthenium(II) (4,40 bis-[(4-butylaminomethyl-
phenyl)-carbamoyl]-2,20-bipyridine) bis(2,20-bipyri-
dine)-bis(hexafluorophosphate), 12. Procedure as for
receptor 10 using cis-dichlorobis(2,20-bipyridine)ruthenium
(II) (0.85 g, 1.6 mmol) and 4,40 bis-[(4-butylaminomethyl-
phenyl)-carbamoyl]-2,20-bipyridine 9 (1.25 g, 1.6 mmol)
The product was isolated as a deep purple shiny, flaky
solid. (1.40 g, 69% yield).
NMR broad, paramagnetic.
Elemental analysis: found: C 38.3%, H 3.4%, N 8.6%.
Calculated (C42H42N8RuS4CuP2F12$2H2O): C 39.6%, H
3.4%, N 8.8%.
ESMS: m/z 476.5 [MK2PF6]2C
.
3
1H NMR in CD3CN (d/ppm): 0.94 (t, 6H, JZ5 Hz, CH3),
1.39 (m, 4H, CH2CH3), 1.46 (m, 4H, CH2CH2CH3), 3.05 (t,
4H, 3JZ7.8 Hz, NHCH2CH2), 4.17 (s, 4H, ArCH2NH), 7.32
(d, 2H, bpy-H5,50), 7.56 (m, 4H, 3JZ5.4 Hz, bpy-He), 7.77
(d, 2H, 3JZ5.4 Hz, bpy-H6,60), 7.88 (m, 4H, bpy-Hf), 7.96
(m, 4H, bpy-Hd), 8.19 (m, 8H, bpy-Hc and ArH), 8.91 (m,
2H, bpy-H3,30 and ArH), 10.09 (br s, 1H, NHCO), 10.44 (br
s, 1H, NHCO).
6.2.3. Zinc(II) macrocycle, 15. Procedure outlined above
using receptor 10 (0.12 g, 0.1 mmol) and 1 equiv of zinc(II)
acetate dihydrate. Red/brown solid (0.09 g, 72%).
1H NMR in CD3CN (d/ppm): 0.85 (br m, 6H, CH3), 1.25 (m,
3
4H, CH2CH3), 1.65 (br m, 4H, JZ7.5 Hz, CH2CH2CH3),
3.97 (m, 4H, 3JZ6.3 Hz, NCH2CH2), 5.69 (dd, 4H,
3JZ6.3 Hz, 4JZ1.5 Hz, bpyCH2N), 7.31 (d, 2H, 3JZ
4.2 Hz, bpy-H6,60), 7.40 (m, 4H, 3JZ5.5 Hz, bpy-He), 7.61
Elemental analysis: found: C 39.7%, H 4.1%, N 10.5%.
3
3
(t, 2H, JZ5.1 Hz, bpy-Hf), 7.76 (dd, 4H, JZ20.0 Hz,
4JZ4.5 Hz, bpy-H5,50), 8.05 (m, 4H, bpy-Hd), 8.50 (d, 4H,
3JZ7.5 Hz, bpy-Hc), 8.69 (s, 2H, bpy-H3,30).
Calculated (C54H56F12N10O2P2Ru$3H2O): C 49.0%, H
4.7%, N 10.6%.

M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
11237
Elemental analysis: found: C 43.5%, H 3.9%, N 8.8%.
(C42H42N8RuS4ZnP2F12): C 42.0%, H 3.8%, N 8.5%.
Calculated (C46H50F12N10O2P2RuZn$3/2H2O): C 40.1%, H
3.8%, N 10.2%.
ESMS: m/z 535.2 [MK2PF6]2C
.
ESMS: m/z 440.1 [MKCS2–2PF6]2C, 478.0 [MK2PF6]2C
955.2 [MK2PF6]C.
,
6.2.8. Nickel(II) macrocycle, 19. Procedure given above,
using ruthenium receptor 12 (0.1 g, 0.07 mmol) and 1 equiv
of nickel(II) acetate tetrahydrate. The product was isolated
as red/brown coloured solid (0.095 g, 95% yield).
6.2.4. Macrocycles, 16–21. General procedure the same as
for macrocycles 13–15, but in a THF/H2O (9:1) mix.
1H NMR in DMSO-d6 (d/ppm): 0.82 (t, 6H, JZ7.5 Hz,
3
6.2.5. Nickel(II) macrocycle, 16. Procedure given above,
using ruthenium receptor 11 (0.08 g, 0.08 mmol) and
1 equiv of nickel(II) acetate tetrahydrate. The product was
isolated as red/brown coloured solid (0.03 g, 62% yield).
CH3), 1.20 (m, 4H, CH2CH3), 1.49 (m, 4H, CH2CH2CH3),
3.29 (m, 4H, NBocCH2CH2), 4.77 (s, 4H, bpyCH2), 7.30 (d,
2H, bpy-H5,50), 7.55 (br m, 2H, bpy-Hd) 7.78 (m, 10H, Ar
and bpy-Hc), 7.97 (br m, 2H, bpy-H6,60), 8.19 (br m, 2H,
bpy-He), 8.87 (br m, 2H, bpy-Hf), 9.38 (br s, 2H, CONH).
3
1H NMR in DMSO-d6 (d/ppm): 0.90 (t, 6H, JZ7.5 Hz,
CH3), 1.29 (m, 4H, CH2CH3), 1.53 (m, 4H, CH2CH2CH3),
2.94 (br m, 4H, NHCH2CH2CH2CH3), 3.10 (br m, 4H,
CH2NHCH2CH2CH2), 3.60 (m, 4H, CONHCH2), 7.74 (m,
4H, 3JZ4.5 Hz, bpy-He), 7.84 (d, 4H, 3JZ4.5 Hz, bpy-Hf),
7.84 (d, 3JZ5.4 Hz, 2H, bpy H5,50), 7.97 (d, 2H, 3JZ5.4 Hz,
bpy-H6,60), 8.20 (m, 4H, 3JZ6.3 Hz, bpy-Hd), 8.86 (d, 4H,
3JZ6.3 Hz, bpy Hc), 9.15 (s, 2H, bpy-H3,30), 9.25 (s, 2H,
CONH).
Elemental analysis: found: C 44.0%, H 4.1%, N 9.4%.
Calculated (C56H54N10O2NiRuS4P2F12$3H2O): C 43.9%, H
4.0%, N 9.2%.
MALDI: m/z for PF6 salt, 1186.2 [MK2PF6]C, 1331.6
[MKPF6]C.
Elemental analysis: found: C 40.4%, H 4.4%, N 9.8%.
6.2.9. Copper(II) macrocycle, 20. Procedure given above,
using ruthenium receptor 12 (0.1 g, 0.07 mmol) and 1 equiv
of copper(II) acetate monohydrate. The product was isolated
as brown solid (0.09 g, 91% yield).
Calculated (C46H50F12N10O2P2RuNi$H2O): C 40.3%, H
3.8%, N 10.2%.
ESMS: m/z 531.2 [MK2PF6]2C, 1207.1 [MKPF6]C.
NMR broad, paramagnetic.
6.2.6. Copper(II) macrocycle, 27. Procedure given above,
using ruthenium receptor 21 (0.2 g, 0.18 mmol) and 1 equiv
of copper (II) acetate monohydrate. The product was
isolated as brown solid (0.14 g, 59% yield).
Elemental analysis: found: C 43.7%, H 4.0%, N 8.8%.
Calculated (C56H54N10O2CuRuS4P2F12.3H2O): C 43.8%, H
3.9%, N 9.1%.
MALDI: m/z for PF6 salt, 595.3 [MK2PF6]2C, 1191.6 [MK
NMR broad, paramagnetic.
2PF6]C.
Elemental analysis: found: C 38.2%, H 4.1%, N 9.3%.
6.2.10. Zinc(II) macrocycle, 21. Procedure given above,
using ruthenium receptor 12 (0.1 g, 0.07 mmol) and 1 equiv
of zinc (II) acetate dihydrate. The product was isolated as
red/brown coloured solid (0.058 g, 56%).
Calculated (C46H50F12N10O2P2RuCu$3H2O): C 39.1%, H
4.0%, N 9.9%.
ESMS: m/z 533.6 [MK2PF6]2C
.
1H NMR in DMSO-d6 (d/ppm): 0.84 (t, 6H, CH3), 1.26 (m,
4H, CH2CH3), 1.66 (m, 4H, CH2CH2CH3), 3.29 (m, 4H,
NHCH2CH2), 5.01 (s, 4H, bpyCH2), 7.33 (br m, 2H, bpyH-
5,50), 7.51 (br m, 2H, bpy-Hd) 7.74 (m, 10H, Ar and bpy-
Hc), 7.89 (br m, 2H, bpy-H6,60), 8.15 (m, 2H, bpy-He), 8.83
(m, 2H, bpy-Hf), 9.29 (br s, 2H, bpy-H3,30), 10.75.(br s, 2H,
NHCO).
6.2.7. Zinc(II) macrocycle, 18. Procedure given above,
using ruthenium receptor 11 (0.2 g, 0.18 mmol) and 1 equiv
of zinc (II) acetate dihydrate. The product was isolated as
red/brown coloured solid (0.13 g, 55% yield).
3
1H NMR in DMSO-d6 (d/ppm): 0.85 (t, 6H, JZ7.5 Hz,
CH3), 1.24 (m, 4H, CH2CH3), 1.65 (m, 4H, CH2CH2CH3),
3.70 (br m, 4H, NHCH2CH2CH2CH3), 3.79 (br m, 4H,
CH2NHCH2CH2CH2), 3.97 (m, 4H, CONHCH2), 7.50 (br
Elemental analysis: found: C 43.6%, H 3.9%, N 9.0%.
3
m, 4H, bpy-He), 7.72 (d, 4H, JZ4.5 Hz bpy-Hf), 7.82 (d,
3
2H, bpy H5,50), 7.95 (d, 2H, JZ5.7 Hz, bpy-H6,60), 8.18
Calculated (C56H54N10O2ZnRuS4P2F12$3H2O): C 43.7%, H
3.9%, N 9.1%.
(m, 4H, 3JZ7.5 Hz, bpy-Hd), 8.84 (m, 4H, 3JZ6.3 Hz, bpy
Hc), 9.12 (s, 2H, bpy-H3,30), 9.32 (s, 2H, CONH).
MALDI: m/z for PF6 salt, 607.2 [MK2PF6CH2O]2C,
1193.4 [MK2PF6]C.
Elemental analysis: found: C 39.7%, H 4.1%, N 9.3%.

11238
M. D. Pratt, P. D. Beer / Tetrahedron 60 (2004) 11227–11238
1
7. Protocol for H NMR titrations
3. (a) Beer, P. D. Chem. Commun. 1996, 689. (b) Beer, P. D.;
Cadman, J. New J. Chem. 1999, 23, 347. (c) Beer, P. D.; Hayes,
E. J. Coord. Chem. Rev. 2003, 240, 167.
A solution of the receptor (500 ml) was prepared at a
concentration typically of the order of 0.01 mol dmK3 in
dueterated dimethyl sulfoxide. The initial 1H NMR
spectrum was recorded and aliquots of anion were added
by gas-tight syringe from a solution made such that
1 mol equiv was added in 20 ml. 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 the 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
computer program EQMNR9 was used which requires the
concentration of each component and the observed chemical
shift (or its displacement) for each data point. Typically
these titrations experiments were repeated three times with
at least fifteen data points in each experiment.
4. (a) Saalfrank, R. W.; Bernt, I. Curr. Opin. Solid State Mater.
Sci. 1998, 3, 407. (b) Fujita, M. Chem. Soc. Rev. 1998, 27, 417.
(c) Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. Rev. 2000,
100, 853.
5. Fox, O. D.; Drew, M. G. B.; Beer, P. D. Angew. Chem. Int., Ed.
Engl. 2000, 39, 136.
6. Padilla-Tosta, M. E.; Fox, O. D.; Drew, M. G. B.; Beer, P. D.
Angew. Chem. Int., Ed. Engl. 2001, 40, 4235.
7. (a) Beer, P. D.; Berry, N.; Drew, M. G. B.; Fox, O. D.; Padilla-
Tosta, M. E.; Patell, S. Chem. Commun. 2001, 199. (b) Berry,
N. G.; Pratt, M. D.; Fox, O. D.; Beer, P. D. Supramol. Chem.
2001, 13, 677.
8. (a) Beer, P. D.; Cheetham, A. G.; Drew, M. G. B.; Fox, O. D.;
Hayes, E. J.; Rolls, T. D. Dalton Trans. 2003, 4, 603. (b) Beer,
P. D.; Berry, N. G.; Cowley, A. R.; Hayes, E. J.; Oates, E. C.;
Wong, W. W. H. Chem. Commun. 2003, 19, 2408.
9. Hynes, M. J. J. Chem. Soc. Dalton Trans. 1993, 311–312.
10. Binstead, R.A.; Zuberbu¨hler, A.D. Specfit Global Analysis,
version 2.90X; Binstead, R.A. Specfit, 32, 2000.
11. Beer, P. D.; Szemes, F.; Balzani, V.; Sala, C. M.; Drew,
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´
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