Luminescent complexes of Re(I) and Ru(II) with appended macrocycle groups derived from 5,6-dihydroxyphenanthroline: Cation and anion binding

Article abstract of DOI:10.1039/b416293e

A range of ligands in which a macrocydic unit is fused to a 1,10-phenanthroline unit has been prepared starting from 5,6- dihydroxyphenanthroline. The ligands are L¹ in which the pendant ligand is 18-crown-6; L², in which the pendant

Full text of DOI:10.1039/b416293e

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F U L L P A P E R
Luminescent complexes of Re(I) and Ru(II) with appended
macrocycle groups derived from 5,6-dihydroxyphenanthroline:
cation and anion binding
a
b
b
a
a
Theodore Lazarides, Thomas A. Miller, John C. Jeffery, Tanya K. Ronson, Harry Adams
a
and Michael D. Ward*
Department of Chemistry, University of Sheffield, Sheffield, UK S3 7HF.
a
E-mail: m.d.ward@sheffield.ac.uk; Fax: 0114 2229346; Tel: 0114 2229346
School of Chemistry, University of Bristol, Cantock’s Close, Bristol, UK BS8 1TS
b
Received 21st October 2004, Accepted 3rd December 2004
First published as an Advance Article on the web 5th January 2005
A range of ligands in which a macrocyclic unit is fused to a 1,10-phenanthroline unit has been prepared starting from
1
2
5
,6-dihydroxyphenanthroline. The ligands are L in which the pendant ligand is 18-crown-6; L , in which the pendant
3
1
2
ligand is benzo-24-crown-8; and L , in which the macrocycle contains two carboxamide units. Ligands L and L
can bind Group 1 and 2 metal cations in their crown-ether cavities; L contains two H-bond (amide) donors and is
suitable for anion-binding. Luminescent complexes of the form [Ru(bipy)
3
2
+
2−
2
L] , [ReL(CO)
3
Cl] and [RuL(CN)
4
]
were
prepared and some were structurally characterised; their interactions with various guest species were investigated by
1
2
+
luminescence and NMR spectroscopy. For complexes with the crown ethers (L and L ), binding of K was
1
2−
rather weak, but the electrostatic effect due to the charge on the host complex was clear with [RuL (CN)
4
2+
]
binding
+
1
2+
K more strongly than [Ru(bipy)
2
L ] . Binding to the pendant crown ethers was much stronger with Ba , and both
1
2
2+
[
ReL (CO)
binding constants of 4.5 × 10 M for [ReL (CO)
Ru(bipy) L ] and [ReL (CO) Cl], due to their H-bond donor sites, showed binding of dihydrogenphosphate to the
macrocycle. Whereas [ReL (CO)
3
Cl] and [ReL (CO)
3
4
Cl] showed substantial luminescence quenching in MeCN on addition of Ba ions, with
−1
1
2+
5
−1
2
2+
3
Cl]/Ba and 1.3 × 10 M for [ReL (CO)
3
Cl]/Ba . Complexes
3
2+
3
[
2
3
3
−
−1
3
Cl] showed 1 : 1 binding with (H
L ] showed 1 : 2 binding, with microscopic association constants of ca. 1 × 10 and 1.6 × 10 M in
MeCN. The fact that K > K suggests a cooperative interaction whereby binding of the first anion makes binding of
the second one easier to an extent which overcomes electrostatic effects, and a model for this is proposed which also
2
PO
4
) in dmso with a binding constant of 65 M ,
3
2+
6
6
−1
[
Ru(bipy)
2
2
1
3
2+
accounts for the substantial increase in luminescence from [Ru(bipy)
2
L ] (5-fold enhancement) when the second
Cl] undergo complete luminescence quenching and
−
3
2+
3
(
H
2
PO
4
) anion binds. Both [Ru(bipy)
2
L ] and [ReL (CO)
3
a change in colour to near-black in the presence of (anhydrous) fluoride in MeCN, probably due to deprotonation of
the carboxamide group. These changes are however irreversible on a long timescale and lead to slow decomposition.
Introduction
hydroxyl groups, which can be used as the basis of a macrocycle
synthesis, are as close as possible to the phenanthroline site
so the electronic interaction between reporter group and the
macrocyclic site should be strong. Attachment of the NN
chelating site of the new phenanthroline/crown ligands to
Complexes in which a macrocyclic binding site are pendant
from a metal complex unit which is photochemically or elec-
trochemically active have been of enduring interest as sensors,
with binding of a guest to the macrocyclic unit inducing a
perturbation of the primary metal centre which results in a
2+
2+
a {Ru(bipy)
2
}
fragment afforded a series of [Ru(bipy) ]
3
derivatives with a pendant crown-ether which showed a weak
1–3
change in its redox potential or luminescence properties.
2+
electrochemical response in the presence of Ba cations in
Most commonly the guest species (analyte) in the macrocycle
is a metal cation, although more recently anionic guests have
received much attention because of their ability to associate
with macrocycles by hydrogen-bonding.1f ,1g,1h Molecules of this
nature are often based on bridging ligands which contain
macrocyclic crown-ether or aza-crown-ether components linked
to a polypyridyl unit, which reflects the fact that the ions often
used as analytes are Group IA or IIA cations which bind well
to crown-ether ligands, and the reporter group displaying the
desired redox and/or luminescent response is based on a metal-
MeCN solution.
In this paper we describe more extensive studies on complexes
with ligands of this series. Two different types of macrocycle
(purely crown ether, or crown ether/amide) have been attached
to the phenanthroline skeleton, with the former showing effec-
tive binding of Group I and Group II metal cations, and the
latter showing effective binding of various anions, in both cases
with a substantial change in luminescence of the reporter group.
Metal polypyridyl units with different charges (2−, 0, 2+) have
been examined as possible reporter groups, in order to optimise
electrostatic effects on binding of guest cation or anions to the
macrocycle units.
3
polypyridyl complex. Clearly it is desirable that the electronic
interaction between reporter group and macrocyclic binding site
should be as large as possible; this may be achieved by either
using a conjugated bridge between the sites, or by having them
as close together as possible.
Results and discussion
We described in a recent communication the facile syntheses of
a new series of ditopic phenanthroline/crown-ether ligands de-
rived from 5,6-dihydroxy-1,10-phenanthroline in which the two
Synthesis and characterisation
The complexes discussed in this paper are shown in Scheme 1
and are based on two different ligand sets. Ligands L and L
contain 18-crown-6 and benzo-24-crown-8 units respectively
fused to the phenanthroline core; ligand L in contrast contains
4
1
2
metal-ion binding sites are directly fused. 5,6-Dihydroxy-1,10-
5
phenanthroline (dhphen) is a particularly appealing starting
3
material for the construction of ligands of this type—containing
linked polypyridyl and macrocyclic units—because the reactive
a macrocyclic ring incorporating four ether and two amide
5
2 8
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5

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Scheme 1
1
groups. L was prepared from dhphen in a single step, by reaction
of dhphen with pentaethyleneglycol-ditosylate, as described in
4
2
3
our initial communication. The syntheses of L and L are
summarised in Scheme 1 and follow recently published routes
6
used to prepare similar macrocycles (benzo-crowns and amide-
containing crowns ) without pendant phenanthroline units.
Thus, L was prepared by high-dilution reaction of dhphen with
the ditosylate B, and L was prepared from dhphen in two steps,
7
2
3
by reaction with ethyl bromoacetate to give diester C, followed
by reaction with the diamine NH
2
(CH
2
)
2
O(CH
2
)
2
O(CH
2
)
2
3
NH
2
to give the cyclic diamide. Following preparation of L , our
intention had been to reduce the amide units to amines to
make mixed N,O-donor aza-crown units for binding metal ions,
but attempts at reduction with hydride-based reducing agents
1
Fig. 1 Molecular structure of [Re(CO)
3
Cl(L )]·0.5H
2
O (lattice water
molecule not shown).
such as LiAlH proved messy and resulted in decomposition.
4
However, the amide groups were effective at hydrogen-bonding
3
to anions (see below) so ligand L , originally intended as an
intermediate, proved to be valuable in its own right.
1
2−
+
The series of complexes [Ru(CN) (L )] (as its PPN salt),
4
1
1
2+
[Re(CO)
3
Cl(L )] and [Ru(bipy) (L )] (as its hexafluorophos-
2
phate salt) was prepared in order to investigate electro-
static effects on the binding of guest cations in the macro-
2
cyclic site. [Re(CO)
3
Cl(L )] was prepared as an alternative to
1
[
Re(CO) Cl(L )] as a neutral host with a different cavity size
3
for binding large ions. The complexes were characterised on
2
Fig. 2 Molecular structure of [Re(CO)
3
Cl(L )].
1
the basis of H NMR spectrometry and mass spectrometry (see
1
Experimental section). The crystal structures of [Re(CO)
3
Cl(L )]
tion from aqueous acetonitrile allowed isolation of needle-like
crystals which were very hygroscopic and rapidly delicquesced
as soon as they were removed from the mother liquor. Con-
sequently the crystals diffracted very weakly and structural
determination is of poor quality (R1 ≈ 14% based on the data
2
and [Re(CO) Cl(L )] are shown in Figs. 1 and 2; crystallographic,
3
data collection and refinement details are summarised in Table 1,
and selected bond distances and angles are collected in Table 2.
In both cases the {Re(phen)(CO) Cl} unit adopts the usual
3
◦
near-octahedral geometry with a fac-tricarbonyl arrangement
with 2h < 40 ), and no table of bond distances and angles is
8
and unremarkable individual bond distances and angles, and
included, but the gross structure of the complex is clear. The
the macrocycles are approximately preorganised for metal-ion
geometry of the RuN core (Fig. 3) is unremarkable. In the
6
9
binding, as is typical of crown ethers.
macrocyclic unit, the two amide groups are oriented such that
the two NH groups are directed towards the same face of the
3
3
The complexes [Re(CO)
3
Cl(L )] and [Ru(bipy)
2
(L )](PF
)
6 2
1
˚
were also prepared, and gave H NMR and mass spectrometric
macrocycle, with N(7) and N(8) being separated by ca. 4.5 A;
data in agreement with their formulations (see Experimental
the disposition of these could allow them to act as H-bond
donors simultaneously to a single receptor, as has been shown by
Beer and co-workers where a macrocycle containing two amide
3
section). Although crystals of [Ru(bipy)
2
(L )](PF
6
2
) could not
be obtained, conversion to the chloride salt and recrystallisa-
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6
5 2 9

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a
Table 1 Crystal, data collection and refinement details for the crystal structures
1
2
2
3
Complex
[Re(CO)
3
Cl(L )]·0.5H
2
O
[Re(CO)
3
Cl(L )]
[Re(CO)
3
Cl(L )Na(H
2
O)
2
][PF
6
]
[Ru(bipy)
2
(L )]Cl
2
·6H
2
O
Formula
Molecular weight
Crystal system
Space group
k/A˚
C
729.14
Monoclinic
C2/c
0.71073
100(2)
25.0812(17)
16.5695(11)
12.9281(9)
90
93.9390(10)
90
5360.0(6)
8
25
H
27ClN
2
O
9.5Re
C
33
H
34ClN
2
O
11Re
C
33
H
38ClF
6
N
2
NaO13PRe
42 2 8
C H52Cl N O12Ru
856.27
Monoclinic
P2 /c
1.54178
100(2)
21.4640(7)
13.3917(4)
11.4092(4)
90
97.565(2)
90
1060.26
Monoclinic
C2/c
1032.89
Triclinic
¯
1
P1
0.71073
100(2)
17.908(4)
17.748(4)
27.982(6)
90
95.70(3)
90
8849(3)
8
0.71073
150(2)
T/K
a/A˚
9.411(8)
b/A˚
c/A˚
13.877(12)
19.278(17)
85.394(16)
83.010(15)
74.521(16)
2405(4)
◦
a/
b/
◦
◦
c /
V/A˚
3
3250.91(18)
4
1.750
Z
2
−
3
q/g cm
1.807
1.592
1.426
Crystal size/mm
l/mm
0.25 × 0.12 × 0.10
0.5 × 0.2 × 0.005
0.3 × 0.2 × 0.05
0.5 × 0.1 × 0.1
−
1
4.691
8.628
2.936
0.504
Data, restraints, parameters
Final R1, wR2
6176, 78, 375
0.0317, 0.0675
5068, 25, 428
0.0672, 0.1571
10159, 330, 578
0.0793, 0.2398
6253, 1, 526
0.141, 0.410
a
The value of R1 is based on selected data with I>2r(I); the value of wR2 is based on all data.
from the dhphen unit, which are directly attached to the strongly
2
+
electron-withdrawing {Ru(bipy)
2
(phen)} unit. Support for this
1
1
is provided by the H NMR spectra of [Ru(bipy)
2
(L )](PF
6
) and
2
1
[
Re(CO)
to these oxygen atoms are considerably more deshielded than all
of the other CH groups, indicating that the oxygen atom to
3
Cl(L )], in which the signals of the CH groups attached
2
2
which they are attached is relatively electron deficient compared
to the others. Additional structural evidence for this is discussed
later.
1
The comparison between [Ru(bipy)
2
(L )](PF
6
)
2
and [Re(CO) -
3
1
Cl(L )] shows however that the loss of the 2+ charge in the
3
+
Fig. 3 Molecular structure of [Ru(bipy)
2
(L )]Cl
2
·6H
2
O (anions and
latter case results in a binding constant for K that is about
lattice solvent molecules not shown).
1
2−
four times higher. Moving further to [Ru(CN)
4
(L )] , whose
+
2
− charge should stabilise the K adduct by a comparable
groups formed two hydrogen-bonds to a single chloride guest.3j,10
+
amount, required a change of solvent since addition of K
3
1
In [Ru(bipy)
2
(L )]Cl
2
this is not occurring, at least in the solid
ions to a solution of (PPN)
immediate precipitation of K
however gave an association constant for K of 125 M ,
in contrast to a value of 92 M for [Re(CO)
MeCN. That binding of K to [Ru(CN)
2
[Ru(CN)
4
(L )] in MeCN resulted in
1
state. One of the chloride ions, Cl(1), is interacting with four
2
[Ru(CN)
4
(L )]. Use of methanol
+
−1
lattice water molecules (O · · · Cl non-bonded distances of 3–
˚
−1
1
+
3
.3 A); Cl(2) however is interacting with the amide group of
3
Cl(L )]/K in
˚
+
1
2−
N(8), with a Cl(2) · · · N(8) separation of 3.21 A indicative of a
4
(L )] is stronger than it
Cl(L )], even with a change in solvent from MeCN
1
single NH · · · Cl hydrogen-bond.
is to [Re(CO)
3
to MeOH, shows that the electrostatic effect of a 2− charge
on the host complex more than overcomes the much greater
competitive effect of MeOH as solvent. The low absolute values
Effect of complex charge on binding of cationic guests
To investigate the effect of the charge on the overall complex on
guest binding in the crown ethers, we measured the binding
+
for the K binding constants across the whole series however
precludes their effective use as luminescent sensors for singly-
charged metal ions. For this reason we next examined binding
+
constants of K ions for the 18-crown-6 site of complexes
1
2+
1
1
2−
[
Ru(bipy)
2
(L )] , [Re(CO)
3
Cl(L )] and [Ru(CN)
4
(L )] using
2+
of Ba ions to the macrocycles.
NMR titrations. In each case, in a suitable solvent, addition
+
of K ions resulted in a clear shift of the signals for the crown
2
+
1
2
Binding of Ba to [Re(CO)
3
Cl(L )] and [Re(CO)
3
Cl(L )]
ether protons, which could be used as the basis for a stability
constant titration. In every case the data fitted nicely to a 1 : 1
On the basis of the above results we initially examined the
1
2−
2+
binding isotherm, as expected.
In MeCN, titration of [Ru(bipy)
host/guest system [Ru(CN) (L )] /Ba , reasoning that use of
4
1
2+
+
2
(L )](PF
6
)
2
with KPF
6
gave
Ba in place of K would help to overcome the inherently
−
1
+
an association constant of just 23 M . Free 18-crown-6 binds
weak binding of K , and that use of the 2− charged host
+
6
−1
K ions in methanol with K ≈ 10 M , and benzo-18-crown-6
system would also optimise the binding constant for electro-
derivatives have been shown by Beer and co-workers to bind
static reasons. However insoluble precipitates of (presumably)
+
−1
1
K ions with association constants of ca. 1000 M in a mixed
Ba[Ru(CN)
4
(L )] were obtained in all solvents. We therefore used
3d
1
dmso/MeCN (1 : 1) solvent system.
the next-best system, i.e. the neutral complexes [Re(CO)
3
Cl(L )]
−
1
2
2+
Accordingly, a value as low as 23 M in a relatively non-
competitive solvent (MeCN) is surprising, and some of this may
be ascribed to the 2+ charge on the host complex which will
and [Re(CO)
3
Cl(L )], to see if they would bind Ba sufficiently
strongly to give a clear change in the luminescence of the host
at low concentrations, and these experiments were successful.
+
2+
electrostatically destabilise the K adduct. The neutral complex
Fig. 4 shows the effects of addition of portions of Ba ions
1
−1
1
[
Re(CO)
3
Cl(L )] gave a binding constant of 92 M . The effects
on the UV/Vis and luminescence spectra of [Re(CO)
3
Cl(L )]
of charge are immediately apparent, but the binding constant is
still low compared to 18-crown-6. We ascribe this to the poor
electron-donating ability of the two oxygen atoms, originally
in MeCN. See Table 3 for details of relevant UV/Vis and
luminescence spectral data. The UV/Vis spectrum shows some
minor changes in the UV region but the MLCT absorption
5
3 0
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6

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◦
Table 2 Selected bond distances ( A˚ ) and angles ( ) for the crystal
structures
1
[
Re(CO)
3
Cl(L )]·0.5H
2
O
a
Re–C(31)
Re–C(30)
Re–C(32)
1.905(12) Re–Cl(A)
1.916(5) Re–Cl
1.916(5) C(31)–O(31)
1.918(19) C(31A)–O(31A)
2.172(3)
2.176(3)
89.1(5)
89.7(5)
88.78(19)
90.4(5)
2.379(11)
2.4604(19)
1.165(12)
1.158(18)
1.154(5)
a
Re–C(31A)
Re–N(1)
Re–N(2)
C(30)–O(30)
C(32)–O(32)
C(32)–Re–N(2)
N(1)–Re–N(2)
C(31)–Re–Cl
C(30)–Re–Cl
C(32)–Re–Cl
N(1)–Re–Cl
N(2)–Re–Cl
1.147(6)
C(31)–Re–C(30)
C(31)–Re–C(32)
C(30)–Re–C(32)
C(31)–Re–N(1)
C(30)–Re–N(1)
C(32)–Re–N(1)
C(31)–Re–N(2)
C(30)–Re–N(2)
97.43(16)
75.99(13)
176.8(5)
92.10(14)
93.33(14)
86.47(10)
81.69(10)
97.83(17)
173.39(16)
96.8(4)
171.43(16)
2
[
Re(CO)
3
Cl(L )]
b
Re–C(42)
Re–C(41)
Re–C(43)
Re–C(43A)
Re–N(8)
1.941(11) Re–Cl(A)
1.959(12) Re–Cl
2.316(10)
2.421(4)
1.124(13)
1.137(13)
1.16(2)
1.16(3)
95.6(6)
75.9(3)
92.5(3)
89.6(3)
179.5(6)
87.1(2)
1.967(19) C(41)–O(41)
b
1.97(3)
2.185(8)
2.187(8)
91.1(5)
87.9(7)
90.1(6)
173.7(4)
95.2(4)
92.6(6)
97.8(4)
169.7(4)
C(42)–O(42)
C(43)–O(43)
C(43A)–O(43A)
C(43)–Re–N(1)
N(8)–Re–N(1)
C(42)–Re–Cl
C(41)–Re–Cl
C(43)–Re–Cl
N(8)–Re–Cl
Re–N(1)
C(42)–Re–C(41)
C(42)–Re–C(43)
C(41)–Re–C(43)
C(42)–Re–N(8)
C(41)–Re–N(8)
C(43)–Re–N(8)
C(42)–Re–N(1)
C(41)–Re–N(1)
1
2+
Fig. 4 Spectroscopic titration of [Re(CO)
3
Cl(L )] with Ba in MeCN
−5
(
concentration, 1.4 × 10 M). Top: UV/Vis spectral changes during
the titration. Bottom: luminescence changes during the titration. Inset:
plot of the luminescence titration data (points) showing the fit to a 1 : 1
N(1)–Re–Cl
84.7(2)
2
binding isotherm (solid line). [Re(CO)
see main text).
3
Cl(L )] shows similar behaviour
(
2
c
[
Re(CO)
3
Cl(L )Na(H
2
O)
2
][PF
6
]
Table 3 UV-Vis and luminescence spectroscopic data for the Ru and
Re(1)–C(43)
Re(1)–C(42)
Re(1)–C(41)
Re(1)–N(1)
Re(1)–N(8)
Re(1)–Cl(1)
1.916(12) Na(1)–O(21)
1.949(14) Na(1)–O(24)
2.436(10)
2.614(10)
2.62(2)
Re complexes
d
2.06(2)
Na(1)–O(31A)
d
Complex
UV-Vis
max/nm (10 e/M cm
Luminescence
2.156(8)
2.162(9)
2.513(4)
Na(1)–O(31B)
Na(1)–O(34)
Na(1)–O(37)
Na(1)–O(200)
Na(1)–O(100)
2.81(6)
2.372(12)
2.462(9)
2.308(10)
2.43(2)
96.3(6)
75.4(3)
−3
−1
−1
k
)
kmax/nm
1
[
[
[
[
[
[
ReCl(CO)
ReCl(CO)
ReCl(CO)
3
3
3
(L )]
288(25.0) 330(6.1) 390(3.8)
288(25.0) 330(6.5) 390(3.6)
285(28.0) 327(6.0) 386(4.2)
285(63.5) 422(12.4) 451(15.0) 608
285(64.0) 422(12.0) 451(15.5) 607
285(59.5) 426(12.0) 451(14.0) 609
606
606
608
2
(L )]
C(43)–Re(1)–C(42)
C(43)–Re(1)–C(41)
C(42)–Re(1)–C(41)
C(43)–Re(1)–N(1)
C(42)–Re(1)–N(1)
C(41)–Re(1)–N(1)
C(43)–Re(1)–N(8)
C(42)–Re(1)–N(8)
86.1(5)
89.5(6)
90.4(6)
99.5(4)
173.6(4)
92.8(5)
172.3(4)
98.8(4)
C(41)–Re(1)–N(8)
N(1)–Re(1)–N(8)
C(43)–Re(1)–Cl(1)
C(42)–Re(1)–Cl(1)
C(41)–Re(1)–Cl(1) 176.8(5)
N(1)–Re(1)–Cl(1)
N(8)–Re(1)–Cl(1)
3
(L )]
1
2+
Ru(bipy)
Ru(bipy)
Ru(bipy)
2
2
2
(L )]
(L )]
(L )]
90.3(3)
92.8(4)
2
2+
2+
3
84.1(3)
83.6(4)
better fit expected in the former case, may be ascribed to the
electronic effect mentioned above: the two O atoms directly
attached to the phenanthroline unit in the 18-crown-6 unit,
a
Cl and carbonyl group C(31)/O(31) are mutually disordered, with
the minor components (18% site occupancy) being Cl(A) and
C(31A)/O(31A). Bond angles are only given for atoms in the major
2
+
which must necessarily be used in binding to the Ba ion, are
electron deficient and poor donors. In contrast, the 24-crown-
b
2+
disorder component [Cl, C(31) and O(31)]. Cl and carbonyl group
8 unit is too large for all eight O atoms to be required for Ba
C(43)/O(43) are mutually disordered, with the minor components (23%
site occupancy) being Cl(A) and C(43A)/O(43A). Bond angles are only
given for atoms in the major disorder component [Cl, C(43) and O(43)].
binding and the guest ion could be coordinated in such a way
that the two weak O-donors are not used.
2
+
c
Although we could not obtain crystals of the Ba adduct of
Due to the disorder of the crown ether ring, bond angles around the Na
2
d
[Re(CO) Cl(L )], we have two pieces of structural evidence to
atom are not given. O(31) is disordered over two sites, with the major
component [O(31A)] having 67% site occupancy.
3
support the assertion that the O atoms directly attached to the
phenanthroline unit are particularly poor ligands. Fig. 5 shows
maximum (350–400 nm region) is very little affected. The
3
characteristic luminescence, from the MLCT state of the Re-
diimine chromophore, is however significantly quenched in
2
+
MeCN solution by addition of the Ba ions. The quenching
is not complete, with a reduction in luminescence intensity
2
+
of ca. 50% occurring when a large excess of Ba ions is
added, and a slight red-shift in the emission maximum to
6
20 nm. From these data, which fit well to a 1 : 1 binding
4
−1
isotherm, an association constant of 4.5 × 10 M for the
Re(CO) Cl(L )]/Ba system in MeCN was obtained. A similar
experiment for the [Re(CO)
very similar results, with approximately 50% quenching of the
1
2+
[
3
2
2+
3
Cl(L )]/Ba system in MeCN gave
3
2+
MLCT luminescence on Ba binding, and a binding constant
Fig. 5 Bond distances (in A˚ ) around the encapsulated Li+ ion of a
Ru(II) complex with a pendant 15-crown-5 unit (data taken from ref. 4);
note the particularly long bonds to O(72) and O(84).
5
−1
2+
of 1.3 × 10 M was determined. The fact that binding of Ba
to the 18-crown-6 is weaker than to the 24-crown-8, despite the
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6
5 3 1

View Article Online
a structure which we recall from our earlier communication
4
+
on this work, in which a Li ion occupies a 15-crown-5 ring
1
fused to a phenanthroline unit in the same way as used for L
and L ; the Li–O bonds to O(72) and O(84) are considerably
2
longer than the other three. We have also obtained crystals of
2
[
[
Re(CO)
Re(CO)
3
Cl(L )Na(H
2
O)
2
](PF ) (Fig. 6), by crystallisation of
6
2
3
Cl(L )] from an MeCN solution containing NaPF .
6
+
The Na guest ion is bound to one side of the 24-crown-
ring, interacting with five of the O-donor atoms but not
8
with O(15) and O(40), the atoms directly attached to the
phenanthroline ring. There are also two axial water ligands.
The crown ether backbone is considerably disordered, and only
the major component is shown in Fig. 6, but it is clear that the
+
Na guest prefers not to ligate to the oxygen atoms from the
dhphen unit in this case. Taken together, this structure and the
one shown in Fig. 5 confirm that the two O atoms originating
from the dhphen unit in these crown ligands are poor donors.
2
+
Nonetheless, Ba binds sufficiently strongly to the neutral hosts
to give a clear modulation of luminescence intensity at low
−
5
concentrations (≈10 M).
Fig. 7 Differing modes of binding of dihydrogenphosphate to com-
3
plexes of L . (a) NMR titration data (based on the shift of the amide
3
−2
N–H signal) for addition of [Bu
in dmso. The solid line is the calculated fit to a 1 : 1 binding isotherm.
b) Luminescence titration data for addition of [Bu N][H PO ] to
4 2 4 3
N][H PO ] to [Re(CO) Cl(L )] (10 M)
(
4
2
4
3
−5
[
Ru(bipy)
2
(L )][PF
6
]
2
(10 M) in MeCN. The solid line is the calculated
−
fit to a 1 : 2 Ru : [H
2
PO
4
]
binding isotherm.
6
−1
binding constants derived from these data are K
1
= 1.9 × 10 M
2
3 2 2 6
Fig. 6 Molecular structure of [Re(CO) Cl(L )Na(H O) ][PF ] (anion
5
−1
and K
2
= 7.8 × 10 M . Starting with an arbitary luminescence
not shown); atoms with hollow bonds are those involved in the disorder.
Only the major component of disorder is shown.
intensity of 1 in the absence of dihydrogenphosphate, the data
also show that binding the first anion only results in a slight
decrease of luminescence to 0.8 units, whereas binding the
second results in a strong increase in luminescence intensity to
a limiting value of 5.5 times the original intensity.
3
Anion binding to complexes of L
3
3
The complexes [Re(CO)
3
Cl(L )] and [Ru(bipy)
2
(L )](PF
6
)
2
con-
With two equivalent and independent binding sites we expect
tain a pair of amide hydrogen-bond donors in the macrocyclic
substituent which, as has been demonstrated by numerous
that K
1
= 4K
2
, because the first binding event can occur at
either of two equivalent binding sites; any significant deviation
from this signals an interaction between the two events such
that binding of the first guest enhances (or diminishes) binding
of the second. Taking this statistical factor of 4 into account,
we see that the two ‘microscopic’ binding constants are K
3j,10–12
groups,
can be effective at binding of anionic guests. We
found that these complexes showed strong interactions with the
−
anions dihydrogenphosphate (H
2
PO
4
) and fluoride.
3
−5
mic
A solution of [Re(CO)
showed no significant changes in absorption and lumines-
cence behaviour on addition of (Bu N)(H PO ). However at
higher concentrations, in an NMR experiment, addition of
3
Cl(L )] in dmso or MeCN (ca. 10 M)
1
=
6
−1
mic
6
−1
0.5K
1
≈ 1 × 10 M , and K
2
= 2K ≈ 1.6 × 10 M , with
2
4
2
4
the second being slightly higher than the first. This is surprising;
it might be expected that binding the first dihydrogenphosphate
anion would substantially reduce the likelihood of a second one
binding for electrostatic reasons, especially in view of the results
3
(
Bu
4
N)(H
2
PO
4
) to [Re(CO) Cl(L )] in dmso resulted in a steady
3
shift of the amide NH protons to higher field. The titration data
nicely fitted a 1 : 1 binding isotherm [Fig. 7(a)] from which an
12
described above, and by others, which show that electrostatic
factors can have a significant effect on guest binding. Note that
there is no possibility of fitting this binding curve to a 1 : 1
host : guest model, which gives a completely differently-shaped
response [cf. Fig. 7(a)].
Binding of the dihydrogenphosphate anion to metal com-
plexes with two pendant carboxamide H-bonding sites has
been studied by the groups of Beer3 and Reinhoudt.
−
1
association constant of 65 M was determined. Reinhoudt mea-
sured association constants for binding of dihydrogenphosphate
to various neutral metal complex hosts containing two pendant
3
4
−1
carboxamide units, and obtained values in the range 10 –10 M
11
in dmso. In these cases however the dihydrogenphosphate was
associated not only by two hydrogen bonds, but also a weak
coordinate bond between the anion and an electron-deficient
metal centre, so it is reasonable that our value should be rather
j
11
2
+
Beer has extensively examined [Ru(bipy)
3
]
derivatives with
lower.
The complex [Ru(bipy)
two pendant amides, similar in essence to our complex
3
3
3j
2
(L )](PF
6
)
2
was expected to be a better
[Ru(bipy)
2
(L )](PF
6
)
2
;
Reinhoudt’s group examined neutral
host for anions, because of its positive charge. A luminescence
uranyl-salophen complexes with a pair of pendant carboxamide
groups. Both observed that in the solid state, complexes of
3
11
titration of [Ru(bipy)
2
(L )](PF
6
)
2
in MeCN with (Bu
4
N)(H
2
PO
4
)
showed somewhat unusual behaviour [Fig. 7(b)]. Initially, ad-
dition of small amounts of the dihydrogenphosphate anion
resulted in a slight decrease in the Ru-based luminescence in-
tensity, but as additional portions were added the luminescence
increased considerably. These data could be satisfactorily fitted
by assuming stepwise formation of a 1 : 2 host : guest adduct,
with binding of the second equivalent of dihydrogenphosphate
causing a large increase in the luminescence intensity. The two
their host compounds with dihydrogenphosphate anions showed
that two anions could be associated with each host because
of hydrogen-bonding between the anions. In each case, one
dihydrogenphosphate anion is held close to the host by multiple
hydrogen-bonding interactions to amide groups; the second
dihydrogenphosphate anion does not however interact directly
with the host complex, but forms a double H-bond with the
externally-directed pair of oxygen atoms on the first guest anion
5
3 2
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6

View Article Online
(
such hydrogen-bonded polymerisation of dihydrogenphosphate
complete quenching of luminescence. Weakly-solvated fluoride
ion in MeCN is known to be strongly basic, and we ascribe this
behaviour to deprotonation of the carboxamide NH groups to
generate anionic sites. The intense colour which appears in the
visible spectrum is due to a new transition at around 600 nm
(Fig. 9), which appears as a low-energy tail on the MLCT
transition; this may be ascribed to a ligand-to-ligand charge-
transfer band from the deprotonated amide unit (HOMO)
to the adjacent phenanthroline p* orbital (LUMO). Loss of
13
is known in the solid state in other cases). This behaviour is
sketched in Fig. 8(a). Both groups observed that in solution,
titration experiments showed only 1 : 1 binding between complex
host and dihydrogenphosphate guest, and that this 1 : 1 binding
resulted in perturbation of the amide N–H protons on the host;
thus it is clear that in the cases examined the first of these binding
events (directly to the host by interaction with the carboxamide
protons) occurs, but the second (‘piggy-back’ binding of the
second dihydrogenphosphate to the first) does not.
3
luminescence occurs because the MLCT state is no longer the
lowest in energy but will quickly collapse to the non-emissive
LLCT state. On a short timescale, these changes were reversible;
addition of a few drops of MeOH to one of the reactions
reversed the effect, with immediate loss of the dark colour and
regeneration of the UV/Vis spectrum of the starting complex,
as the strongly solvated fluoride ion is no longer a good base and
the complex re-protonates. Gale and Sessler have exploited the
basicity of fluoride in aprotic solvents in colorimetric fluoride
sensors based on oligopyrroles which, in the same way, are
deprotonated by fluoride ion resulting in intense colours for
14
the resultant anions.
3
Fig. 9 Shifts in the UV/Vis spectrum of [Ru(bipy)
2
(L )][PF
6
]
2
in MeCN
−
Fig. 8 Possible modes of binding of two [H
2
PO
4
]
guests to one host
−5
(
10 M) on addition of portions of Bu
4
NF (the order of spectra
with two carboxamide units. Mode (a) has been described in refs. 3j and
1; mode (b) is proposed to be operating for [Ru(bipy)
is light grey–medium grey–dark grey as more fluoride is added); the
3
1
2 6 2
(L )][PF ] in
dark grey curve shows the presence of a new low-energy transition at
MeCN.
3
ca. 600 nm. The luminescence of [Ru(bipy)
2
(L )][PF
6
]
2
is completely
quenched during the titration.
3
Complex [Ru(bipy)
2
(L )](PF
6
2
) is therefore unusual, not only
because two separate binding events for dihydrogenphosphate
can be seen in the UV/Vis and luminescence titration, but
also because the second has a higher microscopic binding
constant than the first. This indicates a cooperative effect
whereby association of the first anion facilitates binding of the
second to an extent which overcomes the expected electrostatic
repulsion between the two anions. Fig. 8(b) shows a possible
explanation. The first anion associates with one carboxamide
by hydrogen-bond formation in the usual way. The second
anion however can hydrogen-bond not only to the second
amide, but also to the first anion, completing a relatively rigid
cyclic H-bonded structure (which may also involve additional
OH · · · O interactions between the dihydrogenphosphates and
the ether oxygen atoms of the macrocycle). Although this model
is speculative, it does account for the presence of two binding
It was not possible however to extract meaningful equilibrium
constants from these data for three reasons. Firstly, establish-
ment of equilibrium was slow, with changes in UV/Vis and
luminescence spectra taking minutes to complete after addition
of a sample of fluoride. Secondly, the spectroscopic titration
curves did not fit a simple 1 : 1, 1 : 2 or 2 : 1 host : guest
model. Gale observed similar behaviour during the interaction
of amidopyrroles with fluoride and suggested that it could be
due to a multi-step sequence of events in which deprotonation
15
occurs after initial binding of the fluoride anion. Finally,
over a timescale of many minutes or longer, the reaction was
irreversible; a dark solution of either complex treated with
fluoride and stored under N showed complete decolouration
2
overnight, indicating destruction of the original complex.
events with K
2
> K . It also accounts nicely for the lumi-
1
Conclusions
nescence behaviour, which shows a substantial enhancement
of luminescence only following binding of the second anion;
completion of a cyclic hydrogen-bonded array will make the
complex considerably more rigid and reduce the number of
The 5,6-dihydroxyphenanthroline unit is a convenient reagent
which lends itself to the synthesis of macrocycles (here, crown
ethers and mixed crown ether/amide macrocycles) which incor-
porate an externally-directed phenanthroline site for attachment
to metal ions which have the capability to signal binding of
guest species in the macrocycle. The reporter group and the
macrocyclic host unit are necessarily close together, maximising
the likelihood of a strong response. A limitation is that the two
O atoms which are directly connected to the phenanthroline unit
are electron deficient and rather poor donors, giving low binding
3
vibrational modes available for quenching of the MLCT excited
state, whereas one anion on its own will have little effect.
Attempts to probe this further by NMR spectroscopy were
not successful because at the higher concentrations required
3
2+
the [Ru(bipy) (L )] /dihydrogenphosphate adduct precipitated
2
from solution.
Both [Re(CO)
a strong interaction with fluoride ion (but not chloride, which
showed no effect). Titration of either complex in MeCN with
3
3
3
Cl(L )] and [Ru(bipy)
2
(L )](PF
6
2
) also showed
+
constants for e.g. K binding in the 18-crown-6 unit. Compar-
+
1
2+
1
ison of K binding to [Ru(bipy)
2
(L )] , [Re(L )(CO) Cl] and
3
1
2−
dry Bu
4
NF resulted in a colour change to near-black and the
[Ru(L )(CN)
4
]
shows however a clear increase in the binding
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6
5 3 3

View Article Online
1
strength as the charge on the host becomes more negative.
was added to precipitate crude K
2
[Ru(CN) (L )] which was
4
1
2
[
Re(L )(CO)
3
Cl] and [Re(L )(CO)
3
Cl] show strong binding to
collected by filtration and washed with copious amounts of
acetone. The crude material was purified by chromatography
on Sephadex LH-20 with methanol as the eluant; the second
2
+
Ba ions in MeCN; the binding is signalled by an approximately
5
and [Ru(bipy)
3
3
ꢀC
0% loss of the MLCT luminescence intensity. [Re(L )(CO)
3
Cl]
3
2+
1
2
(L )] bind dihydrogenphosphate by hydrogen-
orange band was collected to yield pure orange K
2
1
[Ru(CN)
4
(L )]
+
1
bonding to the carboxamide NH protons; the neutral complex
in 22% yield. ESMS: m/z 736.4 ([K
(MeOH-d ): d 9.65 (2H, dd; phen), 8.59 (2H, dd; phen), 7.77
(2H, dd; phen), 4.43 (4H, m; CH ), 4.07 (4H, m; CH ), 3.83 (4H,
m; CH ), 3.77 (4H, s; CH ).
This complex was converted to the bis(triphenylphosphine)-
3
Ru(CN)
4
(L )] ). H NMR
3
−1
[
Re(L )(CO)
3
Cl] binds one guest anion (K = 65 M in dmso),
4
3
2+
whereas [Ru(bipy)
constants in MeCN (K
indicating a cooperative interaction whereby binding of the first
anion facilitates binding of the second. Binding of two dihydro-
genphosphate anions to [Ru(bipy)
5-fold) increase in luminescence intensity, possibly because of
formation of a rigid hydrogen-bonded structure which inhibits
2
(L )] binds two, with microscopic binding
2
2
mic
6
−1
mic
6
−1
1
= 1 × 10 M ; K
2
= 1.6 × 10 M )
2
2
1
iminium salt [PPN]
2
[Ru(CN) (L )], which is much more soluble
in organic solvents, by the following method. A solution
of bis(triphenylphosphine)iminium chloride (PPNCl) (98 mg,
0.17 mmol) in warm water (10 cm ) was added to an aqueous
(L )] (50 mg, 0.072 mmol) in water
(10 cm ). A red precipitate formed which was filtered over
4
3
2+
2
(L )] is signalled by a large
(
3
3
3
1
vibrational relaxation of the MLCT state. [Re(L )(CO)
and [Ru(bipy)
3
Cl]
solution of K
2
[Ru(CN)
4
3
2+
3
2
(L )] also interact with fluoride ions which
ꢀ
C
deprotonate the carboxamide groups, causing a strong colour
change and complete loss of luminescence; however the process
is irreversible and leads to slow decomposition of the complexes.
Celite , washed with water, and left to dry. The precipitate
was washed through the filter with acetonitrile and evaporated
to dryness in vacuo. This solid (purple when very dry) was
recrystallised from acetonitrile/diethyl ether, and the resultant
solid was washed with diethyl ether after filtration. Finally it
Experimental
ꢀ
C
was purified by chromatography on Sephadex LH-20 with
1
General details
methanol as the eluant, to yield pure red [PPN]
2
[Ru(CN)
4
(L )]
(
99 mg, 0.064 mmol; 89% yield for conversion from the
The following compounds were prepared according to the
potassium salt). MALDI-MS (negative ion mode): m/z 620.1
1
4
1
4
literature procedures: L , [Ru(bipy)
2
(L )][PF
6
]
2
, 5,6-dihydroxy-
1
−
[
Ru(CN) (L )] . MALDI-MS (positive-ion mode): m/z 538
4
5
phenanthroline, 1,2-bis(9-hydroxy-1,4,7-trioxanonyl)benzene
+
1
[
C
30
H
25
P
2
N
2
] . H NMR (MeOH-d
4
): d 9.95 (2H, dd; phen),
16
17
(
compound A in Scheme 1), and [Ru(bipy)
reagents were purchased from the usual commercial sources
Aldrich, Lancaster, Avocado) and used as received. K Ru(CN)
was kindly loaned by Johnson Matthey.
2
Cl
2
]·2H
2
O. Other
+
8
7
.27 (2H, dd; phen), 7.70 (12H, m; phenyl protons of PPN ),
.48 (ca. 50H, m; 48 phenyl protons of PPN+ and 2H from
(
4
6
phenanthroline), 4.42 (4H, m; CH
4H, m; CH ), 3.72 (4H, s; CH ).
2
), 4.01 (4H, m; CH ), 3.80
2
(
2
2
The following instruments were used for standard spectro-
1
scopic and analytical studies. For H NMR spectra, Bruker AC
2
50 or Bruker AMX 400 spectrometers; FAB mass spectra, a
1,2-Bis(9-p-tolylsulfonyloxy-1,4,7-trioxanonyl)benzene, B. The
di-alcohol A (1.5 g, 4 mmol), Et N (4.1g, 40 mmol) and a
catalytic amount of 4-dimethylaminopyridine were dissolved in
VG AutoSpec spectrometer; electrospray mass spectra, a Waters
LCT spectrometer; MALDI mass spectra, a Bruker Reflex III
3
TM
3
◦
spectrometer; UV/Vis spectra, a Cary-50 spectrophotometer;
luminescence spectra, a Perkin-Elmer LS-50B spectrometer
equipped with a red-sensitive Hamamatsu R-928 photomulti-
plier.
Calculations of association constants from UV/Vis, lumines-
cence or NMR spectroscopic titration data were performed with
the programs NMRTit-HG (for 1 : 1 host : guest complexes) and
NMRTit-HGG (for 1 : 2 host : guest complexes) kindly provided
dry CH
2
Cl
2
(15 cm ). The solution was cooled down to 0 C
and a solution of p-tosyl chloride (3.8 g, 20 mmol) dissolved
3
in dry CH
2
Cl (30 cm ) was added dropwise over a 3 h period.
2
The reaction mixture was then allowed to warm up to ambient
3
temperature before being stirred overnight. 5 N HCl (40 cm )
was then added and the organic phase was separated and washed
3
3
with 2 N HCl (2 × 50 cm ) and saturated brine (50 cm ). The
organic phase was then dried over MgSO and the solvent
4
18
by Prof. C. A. Hunter of the University of Sheffield.
was removed to afford a dark yellow oil. The crude product
was purified by column chromatography (silica gel: gradient
elution starting with neat CH
CH Cl /ethyl acetate) to give the desired compound as a pale
yellow oil (1.8 g, 66%). H-NMR (CDCl
4H, d), 6.91 (4H, s), 4.14 (8H, m), 3.8–3.6 (16H, m). EIMS:
2
Cl
2
and slowly changing to 1 : 1
Preparations
2
2
1
1
[
Re(CO)
3
Cl(L )]. A mixture of L (56 mg, 0.13 mmol) and
1
3
): d 7.80 (4H, d), 7.32
3
Re(CO)
5
Cl (49 mg, 0.13 mmol) in dry toluene (20 cm ) was
(
◦
heated to 80 C with stirring under N
2
for 2 h to give a dark
+
m/z 683 (M ).
yellow solution. After evaporation of the solvent the crude
product was purified by chromatography on silica using CH Cl
thf (9 : 1) as eluent to give the pure product (33 mg, 42%).
2
2
/
2
Ligand L . A suspension of ditosylate B (1.0 g, 1.46 mmol)
+
1
and 5,6-dihydroxyphenanthroline (0.31 g, 1.46 mmol) in dry
FABMS: m/z 743, (M + Na) . H NMR (MeCN-d
3
): d 9.30
2H, dd, phen), 8.90 (2H, dd, phen), 7.93 (2H, dd, phen), 4.49 m
4H, m; CH ), 3.95 m (4H, m; CH ), 3.69 m (4H, m; CH ), 3.62 s
4H, s; CH ). Anal. found C, 41.5; H, 3.7; N, 3.9%. Required for
3
DMF (200 cm ) was added dropwise over a period of 3 days
(
(
(
3
to a stirred suspension of Cs
2
CO
3
in dry DMF (100 cm ) at
2
2
2
◦
8
0 C. After the addition was complete, the mixture was stirred
2
◦
at 80 C for a further 3 days. The system was kept under a
dry N atmosphere. The resulting mixture was allowed to cool,
and filtered; the filtrate was evaporated to dryness. The residue
was triturated with CH Cl and filtered again to remove the
remaining salts. The filtrate was then washed with a 10% w/v
C
25
H
26
N
2
O
9
ClRe: C, 41.7; H, 3.6; N, 3.9%.
2
1
[
PPN]
2
[Ru(CN)
4
(L )]. To degassed aqueous methanol
3
1
(
(
40 cm , 1 : 1) was added L (90 mg, 0.22 mmol), K
CN) O (103 mg, 0.22 mmol) and concentrated H SO
three drops, to give a pH of between 3 and 4). The solution was
stirred at reflux overnight, during which time it became orange.
4
Ru-
(ca.
2
2
6
·3H
2
2
4
3
K
2
CO
over MgSO
brown oil was subjected to column chromatography (flash silica
3
solution (2 × 50 cm ) and the organic phase was dried
4
before the removal of the solvent. The resulting
It was then cooled and neutralised (K
2
CO
3
), and the solvent
2
removed in vacuo. The orange solid residue was dissolved in
gel: CH
a dark yellow oil (0.55 g, 68%). H-NMR (CDCl
d; phen), 8.61 (2H, d; phen), 7.61 (2H, dd; phen), 6.90 (4H, s;
2
Cl /MeOH 9 : 1) to afford the desired compound L as
2
3
3
1
water (5 cm ), and methanol (50 cm ) was added to precipitate
unreacted K Ru(CN) O (white powder) which was filtered
·3H
off; the filtrate solution was evaporated to dryness. The orange
3
): d 9.10 (2H,
4
6
2
C
6
H
4
), 4.46 (4H, m; CH
2
), 4.16 (8H, m; CH
2
), 4.0 − 3.8 (12H,
3
3
+
solid was, again, dissolved in water (5 cm ), and acetone (20 cm )
m; CH
2
). EIMS: m/z 550 (M ).
5
3 4
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6

View Article Online
2
2
+
6
[
Ru(bipy)(L )][PF
6
]
2
.
A mixture of L (0.20 g, 0.36 mmol)
(M − 2PF
) . Anal. found: C, 43.3; H, 3.7; N, 9.4%. Required
and [Ru(bipy)
2
Cl
2
]·2H
2
O (0.19 g, 0.36 mmol) in degassed
for C42
H
40
N
4
O
6
RuP
2
F
12·H
2
O: C, 43.4; H, 3.6; N, 9.6%.
3
ethanol (70 cm ) was heated to reflux under dry nitrogen for
h. The solvent was removed by evaporation and the crude
product was subjected to column chromatography on silica gel
acetonitrile/sat. aq. NaNO /H O, 25 : 2 : 1). The major orange
band was collected and the complex was precipitated with
aqueous NH PF . The product was extracted from the aqueous
suspension with several portions of CH Cl . The combined
organic extracts were dried over MgSO and the solvent was
removed to afford the pure complex (0.19 g, 43%). H-NMR
CD Cl ): d 8.78 (2H, d; phen), 8.50 (4H, m; bipy), 8.08 (2H,
3
3
[
Re(CO)
3
Cl(L )]. A mixture of L (0.12 g, 0.27 mmol) and
2
3
[
Re(CO)
5
Cl] (0.100 g, 0.27 mmol) in degassed toluene (25 cm )
◦
was heated to 70 C under dry nitrogen for 12 h. The solvent was
removed and the crude product was purified by chromatography
on Sephadex LH20 using MeCN as eluent. The intense yellow
(
3
2
4
6
1
band was collected (0.10 g, 37%). H NMR (CD
3
CN): d 9.31
2
2
(
(
2H, d; phen), 8.93 (2H, d; phen), 7.90 (2H, dd; phen), 7.30
2H, br t; CONH), 4.78 (4H, s; OCH CO), 3.60 (8H, m;
OCH+CH OCH ), 3.45 (4H, m; NHCH ). ESMS: m/z 711
M − Cl) . High resolution ESMS: Calcd for C25 Re,
11.1101; Found: 711.1132.
4
1
2
CH
2
2
2
2
2
(
2
2
(
7
H
24
N
4
O
9
m; bipy), 7.98 (2H, m; bipy), 7.87 (2H, d; phen), 7.82 (2H, d;
bipy), 7.57 (2H, dd; phen), 7.53 (2H, d; bipy), 7.43 (2H, m;
bipy), 7.22 (2H, m; bipy), 6.79 (4H, m; C
6
H ), 4.51 (4H, m;
4
X-Ray crystallography
Crystals for X-ray diffraction studies were grown from the
CH closest to phen), 4.00–3.50 (20H, m; CH
2
2
). FAB-MS: m/z
+
+
+
1
2
292 [M + K] , 1276 [M + Na] , 1110 [M − PF
6
] , 964 [M −
+
1
PF
6
] . Anal. found: C, 43.0; H, 3.6; N, 5.9%. Required for
following solvents: [Re(CO)
3
Cl(L )]·0.5H
2
O and [Re(CO)
3
-
2
3
C
50
H
50
N
6
O
8
RuP
2
F
12·2CH
2
Cl
2
: C, 42.8; H, 4.0; N, 5.8%.
Cl(L )], CH
2
Cl
2
/hexane; [Ru(bipy)
2
(L )]Cl
2
·6H O, MeCN/
2
2
water; [Re(CO)
3
Cl(L )Na(H
2
O)
2
](PF ), MeCN/diethyl ether.
6
2
2
[
Re(CO)
3
Cl(L )]. A mixture of L (0.20 g, 0.36 mmol) and
For each complex a suitable crystal was coated with hydrocarbon
oil and attached to the tip of a glass fibre, which was then
3
[
Re(CO)
5
Cl] (0.130 g, 0.36 mmol) in degassed CHCl (50 cm )
3
was heated to reflux under dry nitrogen overnight. The solvent
was removed by evaporation and the crude product was purified
by column chromatography on alumina (CH
transferred to the diffractometer under a stream of cold N
2
.
The diffractometer was a Bruker-AXS PROTEUM instrument
2
Cl
2
/thf, 9 : 1). The
2
(
Cu radiation from a rotating anode source) for [Re(CO) Cl(L )],
3
intense yellow band was collected and the solvent removed to
and a Bruker-AXS SMART (Mo radiation) for the other three
crystals. Details of the crystal parameters, data collection and re-
finement for each of the structures are collected in Table 1. After
1
give the pure complex (0.11g, 36%). H-NMR (CD
2
Cl
2H, d; phen), 8.40 (2H, d; phen), 7.71 (2H, dd; phen), 6.78
4H, br s; C ), 4.46 (4H, m; CH closest to phen), 3.97 (4H,
), 3.88 (4H, m; CH
2
): d 9.14
(
(
6
H
4
2
data collection, in each case an empirical absorption correction
m; CH
CH
2
2
), 3.70 (4H, m, CH
2
), 3.61 (8H, m;
19
(
SADABS) was applied, and the structures were then solved by
+
+
2
). FAB-MS: m/z 879 [M + Na] , 821 [M − Cl] . Anal.
2
conventional direct methods and refined on all F data using the
SHELX suite of programs. In all cases non-hydrogen atoms
Found C, 46.0; H, 3.7; N, 3.3%. Required for C33
C, 46.3; H, 4.0; N, 3.3%.
H
34
N
2
O11ClRe:
20
were refined with anisotropic thermal parameters; hydrogen
atoms were included in calculated positions and refined with
3
Ligand L . Part 1: synthesis of diester C. A suspension of 5,6-
isotropic thermal parameters.
dihydroxyphenanthroline (1.55 g, 7.3 mmol), K
ethyl bromoacetate (2.68 g, 16 mmol) and a catalytic amount of
triethylbenzylammonium chloride in dry acetonitrile (40 cm )
was heated to reflux under a dry nitrogen atmosphere for 16 h.
After completion of the reaction, the solid suspension was
filtered while hot to remove inorganic salts. The solvent was
then removed under reduced pressure and the crude product
2
CO (3.74 g),
3
1
The structures of [Re(CO)
3
Cl(L )]·0.5H
2
O and [Re(CO) -
3
2
3
Cl(L )] both had disorder between the Cl ligand and one CO
ligand which could successfully be resolved; site occupancies are
1
given in the footnotes to Table 2. In [Re(CO)
3
Cl(L )]·0.5H
2
O,
the lattice water molecule lies on a special position. In both of
these complexes, restraints were used to keep the Re–C, C–O and
Re–Cl bond distances involving the disordered CO/Cl ligands
sensible, and also to ensure that the thermal parameters of the
disordered atoms were similar between the two sites.
was recrystallised from toluene and diethyl ether (yield 1.9 g,
1
6
8%). H NMR (CDCl
3
): d 1.30 (6H, t; OCH
2
CH ), 4.25 (4H,
3
q; OCH
2
CH
3
), 4.93 (4H, s; OCH
2
CO), 7.65 (2H, m; phen), 8.75
3
+
For [Ru(bipy) (L )]Cl ·6H O, as noted in the text, the crystals
(
2H, d; phen), 9.15 (2H, d; phen). ESMS: m/z 385 (MH ). Anal.
2
2
2
were unstable and diffracted weakly; the quality of the refine-
found: C, 62.1; H, 5.2; N, 7.2%. Required for C20
H
20
N
2
6
O : C,
◦
ment (R1 ≈ 14% based on data with 2hmax = 40 ) is sufficient
6
2.5; H, 5.2; N; 7.3%.
Part 2: synthesis of L . A solution of diester C (1.00 g,
3
to establish the gross connectivity, but a detailed discussion of
bond distances/angles is not appropriate.
2
.6 mmol) and 1,8-diamino-3,6-dioxa-octane (0.43 g, 2.8 mmol)
2
3
[Re(CO)
3
Cl(L )Na(H
2
O)
2
](PF ) displayed some disorder of
6
in ethanol (30 cm ) was heated to reflux for 48 h. The
solvent was removed under reduced pressure and the crude
product was purified by silica gel chromatography using MeOH
the macrocycle backbone, which could be modelled reasonably
successfully. In the macrocyclic backbone, a short section
consisting of atoms O(31), C(32) and C(33) were disordered over
two sites with occupancies of 0.67 and 0.33. Some of the other
atoms in the macrocycle show rather large thermal ellipsoids
indicative of disorder between two closely-spaced components,
but attempts to split these atoms into two components were not
successful, resulting in unrealistic C–C and C–O separations.
The hexafluorophosphate anion shows disorder for four of the
F atoms in a square plane [i.e. rotation about the ordered F(3)–
P(1)–F(6) axis] with site occupancies for the two components of
0.6 and 0.4. The atoms associated with the macrocycle, including
the encapsulated Na atom and its water ligands, all have slightly
higher than usual thermal parameters reflecting the fact that
the model used for the disorder of the flexible macrocycle
is an approximation. Numerous restraints were used in the
final refinement, to keep both the geometry and the thermal
behaviour of the disordered components of the macrocycle and
the hexafluorophosphate anion sensible.
containing 3% aqueous NH solution, to afford the macrocyclic
3
3
1
diamide L (0.44 g, 38%). H NMR (DMSO-d
6
): d 9.10 (2H,
d; phen), 8.65 (2H, d; phen), 8.25 (2H, br t; CONH), 7.35
3
8
(
2H, dd; phen H /H ), 4.65 (4H, s; OCH
2
CO), 3.60 (8H, m;
2
CH
2
OCH
2
CH
2
OCH
2
), 3.45 (4H, m; NHCH ). ESMS: m/z 441
+
(
MH ).
3
3
[
Ru(bipy)(L )][PF
6
]
2
.
A mixture of L (0.12 g, 0.27 mmol)
O (0.14 g, 0.27 mmol) in degassed
and [Ru(bipy)
2
Cl
2
]·2H
2
3
ethanol (30 cm ) was heated to reflux under dry nitrogen for
h. The solvent was removed and the crude product was
purified by column chromatography (silica gel: acetonitrile/sat.
aq. KNO /H O, 12 : 2 : 1). The major orange band was collected
and the complex was precipitated with aqueous NH PF . The
product was extracted from the aqueous suspension with several
portions of CH Cl . The combined organic extracts were dried
over MgSO
2
3
2
4
6
2
2
4
and the solvent was removed to afford the pure
+
complex (0.12 g, 39%). FABMS: m/z 999 (M − PF
6
) , 854
CCDC reference numbers 253589–253592.
D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6
5 3 5

View Article Online
See http://www.rsc.org/suppdata/dt/b4/b416293e/ for cry-
stallographic data in CIF or other electronic format.
4 C. R. Rice, A. Guerrero, R. L. Paul, Z. R. Bell, G. R. Motson, J. C.
Jeffery and M. D. Ward, New J. Chem., 2001, 25, 185.
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6
W. Paw and R. Eisenberg, Inorg. Chem., 1997, 36, 2287.
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Acknowledgements
7
We thank EPSRC for a project studentship (to T. L.) and
Johnson Matthey for the loan of ruthenium salts. We are grateful
to Prof. C. Hunter for assistance with calculation of the stability
constant values for cation and anion binding.
7
957; (b) J. Jurczak, T. Stankiewicz, P. Salanski, S. Kasorzyk and P.
Lipkowski, Tetrahedron, 1993, 49, 1478.
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D a l t o n T r a n s . , 2 0 0 5 , 5 2 8 – 5 3 6