Anion binding and luminescent sensing using cationic ruthenium(II) aminopyridine complexes

Article abstract of DOI:10.1002/chem.200800772

The synthesis of a series of ruthenium(II) based anion sensors of the type [Ru(η⁶-C₆H₄MeCHMe₂)-Cl(L) ₂][BF₄] (2) is reported in which ligand L represents a series of substituted pyridinylmethyl-amine derivatives. The carbazole based ligand L³ exhibits a fluorescent intraligand charge-transfer (ILCT) state that is quenched by ligand-to-metal charge transfer (LMCT) upon coordination to ruthenium in the 1:1 complex [Ru(η⁶-C ₆H₄MeCHMe₂)Cl₂(L³)] (1c). The 1:2 complex 2c is fluorescent, however, and acts as a fluorescent anion sensor because of the mixing of an anion-dependent charge-transfer component into the excited state. The 1:2 complexes of type 2 all exhibit interesting low symmetry ¹H NMR spectra that also are a useful handle on anion complexation. The electronic structures of L³, 1c and 2c have been probed by time-dependent DFT calculations.

Full text of DOI:10.1002/chem.200800772

DOI: 10.1002/chem.200800772
Anion Binding and Luminescent Sensing using Cationic Ruthenium(II)
Aminopyridine Complexes
Sara Jane Dickson,[a] Martin J. Paterson,[b] Charlotte E. Willans,[a]
Kirsty M. Anderson,[a] and Jonathan W. Steed*[a]
Abstract: The synthesis of a series of
(LMCT) upon coordination to rutheni-
um in the 1:1 complex [Ru(h6-
C6H4MeCHMe2)Cl2(L3)] (1c). The 1:2
complex 2c is fluorescent, however,
and acts as a fluorescent anion sensor
because of the mixing of an anion-de-
pendent charge-transfer component
into the excited state. The 1:2 com-
plexes of type 2 all exhibit interesting
low symmetry 1H NMR spectra that
also are a useful handle on anion com-
plexation. The electronic structures of
L3, 1c and 2c have been probed by
time-dependent DFT calculations.
ruthenium(II) based anion sensors of
the
type
[BF4] (2) is reported in which
[Ru(h6-C6H4MeCHMe2)-
G
ACHTREUNG
ligand L represents a series of substi-
tuted pyridinylmethyl–amine deriva-
tives. The carbazole based ligand L3 ex-
hibits a fluorescent intraligand charge-
transfer (ILCT) state that is quenched
by ligand-to-metal charge transfer
Keywords: anion binding · density
functional calculations
· fluores-
cence · ruthenium · sensors
Introduction
studies.[30,31] In the presence of an anionic ligand a molecular
cleft can be created in which the single overall positive
charge on the metal fragment complements monovalent
anions bound within a binding pocket engineered by ligand
design. In the present paper we report the synthesis, struc-
ture, anion binding and fluorescent properties of a series of
such metal-based receptors. Part of this workhas appeared
in a preliminary communication.[32]
Metal ions are important structural and signalling elements
in anion-binding and sensing systems.[1–10] The metal may
play either i) a structural role,[11–15] ii) it may form a key com-
ponent of the anion binding site[3,16,17] or iii) it may act as
part of a redox, luminescent or colourimetric reporter
group.[7,10,18–23] Generally inert metal-containing fragments
such as metallocenes, arene complex of d6 metals, or tris(bi-
pyridyl) type complexes have been used predominantly in a
reporting role.[9,10,24,25] More recently there has been a trend
toward self-assembling systems in which a more labile
metal, along with the anion and a series of multifunctional
ligands together form a complex under thermodynamic con-
trol.[26–29] Within this context the semilabile (arene)rutheni-
Results and Discussion
Synthesis and characterisation: Ligands L1–L5 were pre-
pared by reaction of the appropriate pyridine carboxalde-
hyde with the relevant amine. The simple synthetic proce-
dure involves a condensation step followed by the reduction
of the imine, using NaBH4, to produce a secondary amine.
Reactions were carried out in 1,2-dichloroethane at reflux
for 6 h and products were fully characterised. Reaction of li-
um(II) piano stool type complexes represent a readily syn-
thesised scaffold that has proved useful in anion binding
[a] S. J. Dickson, Dr. C. E. Willans, Dr. K. M. Anderson, Prof. J. W. Steed
Department of Chemistry, Durham University
South Road, Durham, DH1 3LE (UK)
Fax : (+44)191-384-4737
E-mail: jon.steed@durham.ac.uk
[b] Dr. M. J. Paterson
Department of Chemistry
School of Engineering and Physical Sciences
Heriot-Watt University, Edinburgh, EH14 4AS (UK)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200800772.
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Chem. Eur. J. 2008, 14, 7296 – 7305

FULL PAPER
1
ion was confirmed by H NMR spectroscopy. In DMSO, the
formation of a further chiral product from 3 was observed
1
by H NMR spectroscopy that lacked the very low field res-
onance assigned to the NH proton in 3. This product most
likely arises from displacement of the secondary amine by
the coordinating solvent to give chiral [Ru(h6-
C6H4MeCHMe2)Cl
A
G
G
1
In the H NMR spectra there is a significant difference in
the chemical shift values for the NH resonance of the free li-
gands compared to adducts of 1 and to cations of type 2.
For example, the NH resonance in the free ligand L2, occurs
at d=4.92 ppm, in the mono-adduct 1b at d=5.94 ppm and
in the monocationic host 2b at d=6.67 ppm. In addition to
effects arising from the coordination to the Ru(II) centre
the downfield chemical shift of this resonance suggests en-
hanced hydrogen bonding in 2b compared to the free ligand
and 1b, and presumably arises from hydrogen bonding to
À
the BF4 ion.
1
Interestingly, the H NMR spectra of complexes 2a–c all
exhibit an AB quartet resonance assigned to the methylene
gands L1–L4 with the chloro-bridged dimer [{Ru(h6-
C6H4MeCHMe2)Cl
(m-Cl)}2],[33] gave mono-adducts of type
protons, Ha,a’ and Hb,b’, for example, in 2a at d=4.40 and
2
A
4.32 ppm, with J=17.2 Hz, consistent with geminal coupling
[Ru(h6-C6H4MeCHMe2)Cl2(L)] (L=L1–L4, compounds 1a–
d) similar to known analogous compounds.[34] Further reac-
tion of these mono-adducts with one equivalent of AgBF4
and an additional ligand in methanol/acetone (1:1, v/v) sol-
vent mixture gave monocationic Ru(II) complexes [Ru(h6-
(in some cases further split by vicinal coupling to NH). Al-
though this splitting is also observed in 3 it is not evident in
1
the H NMR spectra of the free ligands or monoadducts of
type 1. As compounds 2a–c are not chiral (no splitting of
the p-cymene ligand resonances is observed), the inequiva-
lence of protons Ha and Hb must arise from the fact that the
molecule is point group Cs and Ha and Hb are not related to
one another by the mirror symmetry of the molecule. In-
stead, the mirror plane relates Ha to Ha’ and Hb to Hb’ and
hence Ha and Hb are diastereotopic. Note that the protons
are diastereotopic even without invoking any restricted rota-
tion, for example arising from intramolecular NH···Cl or
CH···Cl hydrogen bonding—indeed molecular models sug-
gest that any such association is unfeasible. In principle dia-
stereotopic protons should also be observed for the para
isomer 2d (prepared as a control), however, only a broad
doublet resonance (NH coupling) is observed for the meth-
ylene protons, which are perhaps too far away from the
metal centre for the magnetic inequivalence to be observed.
A dilution study on compound 2a in CDCl3 shows that the
NH and methylene resonances remain essentially unchanged
across the concentration range 1.9–31.0 moldmÀ3 ruling out
any intermolecular association as an alternative explanation
of the magnetic inequivalence.
C6H4MeCHMe2)Cl(L)2]
[BF4] (L=L1–L4, compounds 2a–d).
A
The new complexes were fully characterised by elemental
analysis, ESI-MS, IR spectroscopy (nujol) and 1H and
13C{1H} NMR spectroscopy. For compound 2c it proved very
difficult to remove traces of [Ru(h6-C6H4MeCHMe2)Cl-
A
G
N
nature of its 1H NMR spectrum), which was present as a
ꢀ10% impurity in the samples studied. In contrast to L1–L4,
the reaction of [{Ru(h6-C6H4MeCHMe2)Cl(m-Cl)}2] with L5
U
(1:1 ratio of L5/Ru) did not result in a product of type 1, but
gave a cationic chelate complex [Ru(h6-C6H4MeCHMe2)-
A
which retain two chloride ligands in the mass spectrum, the
ES+ mass spectrum of 3 shows a peakat m/z=455 assigned
1
to the molecular cation. The H NMR spectrum of 3 pro-
vides clear evidence for the chirality of the metal centre
with separate signals for the diastereotopic methyl groups
on the isopropyl substituent, a characteristic diastereotopic
AA’BB’ pattern for the p-cymene aromatic ring, and a dou-
blet of doublets for the methylene protons of L5. In contrast,
Attempts were made to characterise the new complexes
by X-ray crystallography, however in every case crystals
were not forthcoming. However, changing the p-cymene
ligand for hexamethylbenzene by reaction of L1 with [{Ru-
1
analysis of the H NMR spectra of type 1 compounds does
not show diastereotopic splitting, thus confirming that the
metal centre is not chiral. The chemical shift of the NH res-
onance at d=11.50 ppm in 3 is also very significantly differ-
ent from compounds of type 1 in which the NH resonance
occurs at dꢀ4–6 ppm (d=4.40 ppm in compound 1a, for ex-
ample). The ionic nature of 3 was confirmed by counter
anion metathesis with NaBPh4 in methanol, which gave a
A
ACHTREUNG
AHCTREUNG
characterised by X-ray crystallography. The structure is
shown in Figure 1 and comprises the usual piano-stool ge-
ometry with two terminal chloride ligands and a single uni-
precipitate of [Ru(h6-C6H4MeCHMe2)Cl(k-N,N’-L5)]
The 1:1 ratio between the complex cation in 3 and BPh4
A
ACHTREUNG
À
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J. W. Steed et al.
ous workon 3-aminopyridine derivatives, which showed the
formation of compounds in which a single anion is sand-
wiched between two hosts.[31] The inclusion of this second
equilibrium resulted in a much improved fit to the titration
data compared to a 1:1 model alone. Job plot analysis of 2a
binding BrÀ also confirmed the 2:1 host/guest stoichiometry
and an ESI mass spectrum of 2a in the presence of half an
equivalent of NBu4Br gave a peakat m/z 1357, correspond-
ing to [(2a)2Br]+. In contrast, the Job plot for the analogous
chloride complex suggested a 1:1 stoichiometry despite the
fact that a better fit to the titration data was obtained for
the model including both 1:1 and 2:1 complexes (Figure 2).
The fact that the second binding constant is small may ex-
plain the anomaly.
Figure 1. X-ray crystal structure of [Ru
(h6-C6Me6)Cl2(L1)] (4) showing
the NH···Cl hydrogen bonding, N···Cl 3.436(3) Š (50% displacement el-
lipsoids).
A
NH proton is engaged in a single NH···Cl interaction[35–37] to
an adjacent molecule.
Anion binding: The anion complexation ability of the new
1
host complexes 2a, 2b and 2c was determined by H NMR
spectroscopic titration with the tetrabulylammonium salts of
a number of common anions in CDCl3. Anion binding by 1a
and 1b was also studied as a control. Anion binding con-
stants for the formation of 1:1 and 2:1 host/guest complexes
are given in Table 1. The use of both 1:1 and 2:1 stoichiome-
try models for complexes 2a and 2b is consistent with previ-
Table 1. Anion binding constants (log b) for 1:1, 1:2 and 2:1 host/guest
+
complexes in CDCl3 at 208C. Anions added as NBu4 salts, host concen-
Figure 2. Titration data showing chemical shift changes of the pyridyl-H
resonances for 2a.
tration 0.006 moldmÀ3 (hyphen indicates not measured).
log b
Anion
ClÀ
1a
1b
2a
2b
2c[b]
ꢀ0
b11
b11
b11
b11
Binding by hosts 2a and 2b is strongest with chloride, the
most densely charged anion, followed by H2PO4 in the case
À
2.00(2)
3.64(3)
b21
4.04(3)
b21
3.95(3)
b12
of 2a and acetate, the most basic anions, followed by bro-
mide and then the relatively charge-diffuse nitrate anion.
There is a significant enhancement in all binding constants
on moving to the nitro-substituted host 2b consistent with
the electron withdrawing nature of the nitro substituent and
consequent increased H-bond acidity of the secondary
6.01(9)
b11
6.66(9)
b11
7.03(4)
b11
BrÀ
–
–
–
–
–
–
–
3.28(2)
b21
3.71(3)
b21
3.38(3)
b12
5.32(9)
b11
6.30(9)
b11
5.69(9)
b11
À
NO3
ꢀ0
–
2.06(14)
b21
3.44(4)
b21
3.23(6)
À
amine NH protons. Titrations were attempted with HSO4
À
3.92(7)
b11
6.11(9)
b11
and H2PO4 with 2b, but resulted in precipitation. Unlike
À
MeCO2
b11
2a and 2b, a 1:1 and 2:1 host/guest model fitted the data for
2c very poorly. However, a model involving the binding of
two anions by a single host gave good agreement to the
data. It is likely that the much larger size of the carbazole
substituent prevents two hosts from encapsulating a single
anion in this case. In terms of affinity, however, the com-
pound proved similar to 2a and 2b with modest selectivity
for chloride and acetate. Nitrate binding is relatively weak
and inclusion of a 1:2 complex in the model did not result in
any significant improvement in the fit. The control com-
pounds of type 1 proved to have essentially no anion affini-
ty, highlighting the importance of the charge and anion che-
late effect in hosts 2 despite the need to compete with the
3.53(10)
b21
2.06[a]
b11
3.40[a]
b21
5.11[a]
b11
4.14(2)
b21
3.41(2)
b12
7.11(12)
6.20(2)
–
À
[c]
HSO4
–
À
[c]
H2PO4
–
–
3.67(11)
b21
6.18(15)
b11
1.94[a]
b21
2.19[a]
À
CF3SO3
ꢀ0
b11
ꢀ0
2.30(7)
b21
4.54(5)
À
[a] Large error. [b] Corrected for the presence of [Ru(h6-
BF4 counterion in the latter compounds. Virtually no dis-
C6H4MeCHMe2)Cl
(H2O)
(k-N-L3)]
[BF4]. [c] Precipitate.
placement of the unidentate pyridyl ligands was observed
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Binding and Sensing using Ruthenium Complexes
FULL PAPER
during the titrations even in the presence of nucleophilic
anions such as ClÀ, in contrast to previous workon 3-amino-
pyridine derivatives.[31] The possible displacement of L3 by
one equivalent of chloride in 2a to give 1a was studied as a
function of time. After one hour, a very small amount of 1a
is evident (ꢀ2%), After 5 h about a 10% conversion is ob-
served rising to 40% of the mixture after ꢀ40 h. The anion-
binding equilibria are summarised in Scheme 1.
Figure 3. 1H NMR spectra of the methylene region of host 2a in CDCl3
À
as
a
function of a) added NBu4+BrÀ and b) added NBu4+CF3SO3
(bottom to top 0, 0.2, 0.5, 1.0 and 5.0 equivalents of anion).
Scheme 1. Anion binding by complexes 2 forms both 1:1 and 2:1 host/
guest complexes.
ence of chloride takes hours to days (see above). The mag-
netic equivalence is also unlikely to occur by anion associa-
tion to form a transient 20-electron complex since this
would not result in increased symmetry in any case other
than ClÀ binding. In our view the most likely explanation is
chloride loss to form a transient 16-electron complex in
which the two pyridyl ligands can become co-planar. We
suggest therefore strong anion association in hosts 2 leading
to increased lability of the coordinated chloride ligand as a
result of electrostatic repulsion, such that in the presence of
tightly bound anions XÀ the complex is rapidly interconvert-
Surprisingly, on addition of strongly bound anions, the res-
onances assigned to the diastereotopic methylene protons
1
Ha and Hb in the H NMR spectra of compounds 2a, 2b and
2c gradually collapsed to a singlet. In contrast, weakly inter-
À
acting anions such as CF3SO3 do not affect the appearance
of the resonance even after the addition of a fivefold excess,
Figure 3. Generally the 1H NMR spectroscopic resonances
assigned to the methylene protons Ha and Hb of the nitro
host 2b coalesced into a singlet with less added anion than
for 2a. In both cases (2b and 2a) the anion/host ratio re-
quired is approximately inversely proportional to the anion
binding constant. For example compound 2a gives a singlet
methylene resonance after the addition of only 0.4 equiva-
lents of ClÀ, whereas 0.8 equivalents of acetate and two
equivalents of nitrate are required to achieve coalescence. It
tookmore equivalents still to collapse the AB quartet to a
singlet for 2c than for both 2a and 2b, thus the loss of the
geminal coupling appears to correspond with the strength of
interaction with the anions in each case. To remove the in-
equivalence of protons Ha and Hb in complexes of type 2,
anion binding must either induce a time-averaged plane of
symmetry running along the N-Ru-N axis or involve tempo-
rary dissociation of the pyridyl ligand. The latter explana-
tion seems relatively unlikely because we have shown that
the displacement of the ligand to regenerate 1a in the pres-
ing between the 18-electron [Ru(h6-C6H4MeCHMe2)Cl
3)2]+·XÀ [Ru(h6-
and the transient 16-electron
C6H4MeCHMe2)
(L1–3)2]2+·XÀ·ClÀ. Sixteen electron Ru(II)
G
AHCTREUNG
intermediates are well known in the substitution chemistry
of 6-coordinte 18 electron species.[38] We present this explan-
ation tentatively since we cannot rule out the possibility that
anion binding induces a conformational change that moves
the methylene group just far enough away from the metal
centre on average to render the splitting unobservable even
though the methylene protons remain formally inequivalent.
Such a situation appears to be the case for the para isomer
2d which does not exhibit splitting despite the formal mag-
netic inequivalence of the methylene protons.
Photophysical binding studies: The carbazole derivative 2c
was designed as a fluorescent anion chemosensor. The free
ligand L3 in acetonitrile exhibits a single band in its UV/Vis
spectrum at l=377 nm and in its fluorescence spectrum a
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J. W. Steed et al.
broad emission centred on l=430 nm. To understand the
photophysical properties of the system we undertooktime-
dependent DFT calculations, which suggested that the first
excited state of the ligand gives rise to a broad band at
about l=350 nm (l=377 nm observed in acetonitrile) and
involve charge transfer from the carbazole to the pyridyl
group. The dominant single particle–hole configuration (ci =
0.690) of the first excited state is seen in Figure 4 and can be
ascribed to intraligand charge transfer (ILCT).
shift to shorter wavelength (l=447 nm for ClÀ, BrÀ and
À
MeCO2À; l=456 nm for NO3 ), but not to the same wave-
length as the free ligand (l=430 nm), Figure 6. In each case
Figure 6. Emission spectrum of 2c (1.03”10À4 m, MeCN, lex =375 nm)
upon addition of up to 10 mole equivalents of tetrabutyl ammonium ace-
tate. The arrows indicate emission after an increase in molar equivalents.
The equivalents were increased in a stepwise approach: 0, 0.5, 1, and in
integer steps from 2–10.
Figure 4. Electronic transition to the dominant configuration of the first
excited state of L4.
Coordination of L3 to ruthenium(II) to give 1c results in
complete quenching of this ILCT emission and the complex
is essentially non-emissive, even though both 1c and 2c give
rise to a similar absorption at l=377 nm (with a significant-
ly higher extinction coefficient for 2c). Titration of 1c with
NBu4+ClÀ does not result in any restoration of the fluores-
cence. Complex 2c, however, exhibits a broad emission at
longer wavelength (l=474 nm) compared to the free ligand
(Figure 5).
changes were complete after addition of one equivalent of
anion. This suggests that the quenching is a result of solely
the 1:1 complex. The chemical shift data obtained by NMR
spectroscopic titration strongly suggests that hydrogen bond-
ing of a pyridyl CH group (Figure 2) as well as the amine
NH donor to these anions, and hence the interaction of
anions with the pyridyl unit, may reduce its electron accept-
or ability, and hence lower the emission wavelength.
The structural and electronic properties of 1c, 2c and
2c·ClÀ were also probed by time-dependent DFT calcula-
tions using benzene as a model for p-cymene. In the case of
1c the calculations indicate a broad absorption band around
l=350 nm assignable to an ILCT transition very similar to
that observed in the free ligand L3 consistent with the ob-
served similarity in their absorption spectra. In 1c there are
three electronic states which give rise to this broad band.
States 2 and 3 (see the Supporting Information) are domi-
nated by ILCT configurations. State 1 is an interesting
mixed state consisting of two dominant configurations in-
volving a charge redistribution around the metal centre with
some ligand-to-metal charge transfer (LMCT) component.
State 1 (Figure 7) also has a significant (cꢀ0.1) component
of ILCT character similar to states 2 and 3. Thus, although
absorption gives rise to a similar ILCT band in L3 and 1c,
state mixing in 1c means that the system can relax in a state
involving a ruthenium d-orbital. This LMCT state is tenta-
tively assigned as the non-emissive state.
Figure 5. Fluorescent emission spectra (1.03”10À4 m, MeCN, lex =375 nm)
of L3, 1c and 2c.
The ability of 2c to act as a fluorescent anion sensor was
probed by spectrofluorimetric titration with a number of dif-
ferent anions in acetonitrile. Addition of the non-coordinat-
For the two-arm host 2c in the absence of anions there
are two states contributing to the absorption band around
l=377 nm. Similarly to 1c these are localised on the carba-
zole ligands, although there is no metal-based LMCT com-
ponent unlike 1c, consistent with the observed emission of
2c. The calculations also reproduce the observed twofold in-
crease in absorbance of 2c compared to 1c. The structure of
À
ing CF3SO3 resulted in a slight increase in the emission in-
tensity, but no change in wavelength (see the Supporting In-
formation), consistent with the fact that this anion is ex-
tremely weakly bound by these types of host. In contrast,
À
À
addition of ClÀ, BrÀ, NO3 and MeCO2 all resulted in par-
tial quenching of the fluorescence (factor of ꢀ2.5) and a
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Binding and Sensing using Ruthenium Complexes
FULL PAPER
Figure 9. Charge transfer state involving ClÀ ion in 2c·ClÀ.
Conclusion
A new series of coordination compound hosts have been
synthesised. Compounds 2a and 2b bind a range of anions
À
with modest selectivity for ClÀ, H2PO4 and acetate, forming
both 1:1 and 2:1 host/guest complexes. These compounds
display remarkable anion-dependent diastereotopic NMR
spectra allowing for a novel means to monitor anion bind-
ing. Compound 2c behaves differently forming 1:1 and 1:2
complexes with anions. Compound 2c exhibits significant
changes in its fluorescence upon binding coordinating
anions, whereas weakly bound anions do not affect the emis-
sion. Time dependent DFT calculations suggest that absorp-
tion and hence emission in these systems involves an ILCT
process that is quenched in 1c by mixing with metal-based
orbitals in an LMCT process. This mixing does not occur in
2c but anion binding does result in quenching via a charge-
transfer state. These versatile coordination compounds thus
represent interesting and potentially tuneable fluorescent
anion sensors.
Figure 7. The first of three states giving rise to the observed l=377 nm
(calcd l=362 nm) absorption in 1c. The MLCT component allows non-
radiative decay and hence no fluorescence is observed.
2c was also optimised in the presence of a ClÀ ion. The cal-
culated geometry of the resulting complex is shown in
Figure 8. The NH···ClÀ and pyridyl CH···ClÀ hydrogen
bonded contacts in the theoretical structure compare well
Experimental Section
General procedure for 1H NMR spectroscopic experiments: 1H NMR
spectroscopic titration experiments were carried out by using Varian
Mercury 400 spectrometer running at 400 MHz, at room temperature. All
chemical shifts are report in ppm. A specific concentration of host, typi-
cally 0.5–1.5 mm, was made up in a single NMR tube in CDCl3 (0.5 mL).
The anions, as their tetrabutylammonium salts, were made up to 1 mL,
five times the concentration of the host, with CDCl3. 10 mL aliquots of
the guest were added to the NMR tube and the spectra were recorded
after each addition. Results were analysed by using HypNMR 2006.[40,41]
General procedure for UV/Vis spectroscopic experiments: UV/Vis titra-
tion experiments were carried out using a UNICAM UV/Vis spectrome-
ter (UV2–100), which is PC-controlled by means of Vision software, at
room temperature. A specific concentration (as indicated in Figure cap-
tions) of host in acetonitrile (3.0 mL) was made up in a single quartz cuv-
ette. The anions, as their tetrabutylammonium salts, were made up to
300 mL, 10 times the concentration of the host, in acetonitrile. 15 mL ali-
quots of the guest were added to the cuvette, with a path length of 1 cm
and the spectra were recorded after each addition.
Figure 8. DFT calculated geometry for the 1:1 complex 2c·ClÀ (CH hy-
drogen atoms omitted for clarity).
with the observed chemical shift changes, upon ClÀ binding
in solution and with relevant crystallographic data on relat-
ed compounds.[39] For the 2c·ClÀ system, the absorption
band consists mostly of carbazole localised transitions in a
similar way to the case when the anion is absent, however,
interestingly one strongly absorbing state in the l=370 nm
region consists of charge transfer from a chloride p-orbital
to an orbital localised over the central metal and pyridyl li-
gands. This provides a mechanism for the anion to quench
the ILCT process, Figure 9.
General procedure for fluorescence experiments: Fluorescence titration
experiments were carried out by using a Fluoromax-3, which is PC-con-
trolled, at room temperature. A specific concentration of host (as indicat-
ed in Figure captions) was made up in a single quartz cuvette, with a
path length of 1 cm, in the acetonitrile (3.0 mL). The anions, as their tet-
rabutylammonium salts, were made up to 300 mL, 10 times the concentra-
tion of the host, in acetonitrile. 15 mL aliquots of the guest were added to
the cuvette, the sample was excited at l=375 nm, and spectra were re-
corded after each addition.
Chem. Eur. J. 2008, 14, 7296 – 7305
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7301

J. W. Steed et al.
DFT calculations: Geometry optimizations were performed by using the
B3LYP functional in conjunction with the following basis: the Stuttgart–
Dresden effective core potential (SDD) on the Ruthenium, the 4-31G
basis on all carbon, nitrogen and hydrogen atoms, the 6-311+G(2d) basis
on the chloride ions. If a guest ClÀ was present the basis was further aug-
mented with a diffuse set of s and p functions on the peripheral hydrogen
atoms. The time-dependent calculations were performed with an enlarged
basis of 6-31G(d) on all atoms except ruthenium and chlorine, for which
the basis was as above. Although the full conformational space was not
sampled, preliminary computations were performed for each system to
ensure the most sensible host–guest binding conformation. Minima were
confirmed as such by using analytical frequency calculations. All compu-
tations were performed by using the Gaussian program.[42]
9-Ethyl-N-[(pyridine-3-yl)methyl]-9H-carbazol-3-amine (L3): 3-Amino-9-
ethylcarbazole (9.60 g, 46 mmol) and 3-pyridinecarboxaldehyde (5.00 g,
47 mmol) were dissolved in dry 1,2-dichloroethane, and magnesium sul-
fate (5.00 g) was added. The solution was placed under reflux for 6 h
whilst stirring. After this time the solution was filtered to remove magne-
sium sulfate, and then concentrated under reduced pressure to yield a
brown oil. The product was washed with diethyl ether, and the brown
solid impurities removed by filtration. The diethyl ether was removed
under reduced pressure to yield the imine as darkyellow oil. 1H NMR
(CDCl3, 400 MHz): d=8.92 (d, J=1.6 Hz, 1H; Py-H), 8.53 (dd, J=4.8,
1.6 Hz, 1H; Py-H), 8.49 (s, 1H; CH=N), 8.15 (dt, J=7.7, 1.6 Hz, 1H; Ar-
H), 7.97 (ddd, J=8.0, 0.4, 1.2 Hz, 1H; Ar-H), 7.91 (dd, J=2.0, 1.2 Hz,
1H; Ar-H), 7.33 (m, 2H; Ar-H), 7.11 (dt, J=7.2, 1.2 Hz, 1H; Py-H), 4.15
(q, J=7.2 Hz, 2H; CH2), 1.26 ppm (t, J=7.2 Hz, 3H; CH3); 13C{1H}-
NMR (CDCl3, 125 MHz): d=153.7, 153.2, 142.0, 133.5, 123.0, 122.7,
122.5, 118.9, 118.0, 107.8, 107.7, 36.7, 12.8 ppm. The imine (2.15 g,
7.18 mmol) was dissolved in methanol, and whilst stirring NaBH4 (2.69 g,
71.8 mmol) was added until the solution ceased to effervesce. The solu-
tion was stirred for a further 2 h. 50:50 HCl/H2O was added until the so-
lution was pH 3, and then 2m NaOH was added until the solution was
pH 9. The product was extracted using dichloromethane. The organic
layer was dried over MgSO4, and then filtered. The solvent was evaporat-
ed under reduced pressure, and the product, re-crystallised from di-
chloromethane and hexane. Yield: 1.26 g, 4.18 mmol, 58%; 1H NMR
(CDCl3, 400 MHz): d=8.72 (d, J=2.0 Hz, 1H; Py-H), 8.56 (dd, J=5.0,
1.5 Hz, 1H; Py-H), 8.02 (d, J=7.5 Hz, 1H; Ar-H), 7.60 (d, J=7.5 Hz,
1H; Py-H), 7.46 (t, J=7.5 Hz, 1H; Py-H), 7.37 (m, 2H; Ar-H), 7.27 (m,
2H; Ar-H), 7.20 (t, J=7.5 Hz, 1H; Ar-H), 6.90 (dd, J=8.5, 2.0 Hz, 1H;
Py-H), 4.44 (s, 2H; CH2), 4.30 (q, J=7.5 Hz, 2H; CH2), 4.05 (brs, 1H;
NH), 1.40 ppm (t, J=7.5 Hz, 3H; CH3); 13C{1H}-NMR (CDCl3,
125 MHz):149.3, 148.7, 135.4, 125.5, 123.6, 122.5, 118.1, 114.5, 109.3,
N-[(Pyridin-3-yl)methyl]benzenamine (L1): Aniline (2.05 g, 21 mmol)
and 3-pyridine carboxaldehyde (2.35 g, 22 mmol) were dissolved in dry
1,2-dichloroethane (250 mL), and magnesium sulfate (3.0 g, 25 mmol)
was added. The solution was placed under reflux for 6 h whilst stirring.
After this time the solution was filtered to remove the magnesium sul-
fate, and the solution concentrated under reduced pressure to yield the
product as an orange oil. 1H NMR (CDCl3, 400 MHz): d=8.88 (d, J=
1.9 Hz, 1H; Py-H), 8.56 (dd, J=4.6, 1.9 Hz, 1H; Py-H), 8.34 (s, 1H;
CH), 8.14 (dt, J=7.8, 1.9 Hz, 1H; Py-H), 7.32–7.08 ppm (m, 6H; Py-H,
Ar-H), 13C{1H}-NMR (CDCl3, 100 MHz,): d=157.1, 152.0, 151.4, 150.9,
134.8, 131.8, 129.2, 126.5, 123.7, 120.8, 43.5 ppm. The resulting imine was
dissolved in methanol, and whilst stirring NaBH4 (5.03 g, 13 mmol) was
added until the solution ceased to effervesce. The solution was stirred for
a further 2 h. 50:50 HCl/H2O was added until the solution was pH 3, and
then 2m NaOH was added until the solution was pH 9. The product was
extracted using dichloromethane. The organic layer was dried over
MgSO4, and then filtered. The solvent was evaporated under reduced
pressure, and the product extracted, as a white crystalline solid and re-
crystallised with dichloromethane and hexane. Yield: 3.15 g, 17 mmol,
77%; 1H NMR (CDCl3, 400 MHz): d=8.53 (dd, J=5.0, 1.0 Hz, 1H; Py-
H), 8.39 (d, J=1.5 Hz, 1H; Py-H), 7.71 (d, J=7.5 Hz, 1H; Py-H), 7.27
(m, 1H; Ar-H), 7.20 (t, J=8.0 Hz, 2H; Ar-H), 6.76 (t, J=7.5 Hz, 1H;
Py-H), 7.64 (d, J=8.0 Hz, 2H; Ar-H), 4.36 (s, 2H; CH2), 4.19 ppm (brs,
1H; NH); 13C{1H}-NMR (CDCl3, 125 MHz): d=149.4, 148.9, 135.2, 129.6,
108.4, 103.8, 47.4, 37.5, 13.9 ppm; MS
(ES+): m/z: 302 [M+]; elemental
G
analysis calcd (%) for: C 79.70, H 6.35, N 13.94; found: C 79.76, H 6.38,
N 14.03.
N-[(Pyridin-4-yl)methyl]benzenamine (L4): Aniline (5.35 g, 57 mmol)
and 4-pyridine carboxaldehyde (6.2 g, 57 mmol) were dissolved in dry
1,2-dichloroethane, and magnesium sulfate (6.84 g, 57 mmol) was added.
The solution was placed under reflux for 6 h. whilst stirring. The solution
was filtered to remove magnesium sulfate, and then concentrated under
reduced pressure to yield a yellow oil. The intermediate imine was
washed with diethyl ether, and the yellow solid impurities removed by fil-
tration. The diethyl ether was removed under reduced pressure to yield
the imine as white powder (6.58 g, 36 mmol, 63%). 1H NMR (CDCl3,
500 MHz): d=8.76 (dd, J=4.5, 2.0 Hz, 2H; Py-H), 8.46 (s, 1H; CH), 7.76
(dd, J=4.5, 2.0 Hz, 2H; Py-H), 7.43 (t, J=7.5 Hz, 2H; Ar-H), 7.32–
7.23 ppm (m, 3H; Ar-H); 13C{1H}-NMR (CDCl3, 125 MHz): d=158.2,
123.8, 118.3, 113.2, 46.0 ppm; MS
(ES+): m/z: 185 [M+]; elemental analy-
N
sis calcd (%) for C12H12N2: C 78.23, H 6.57, N 15.21; found: C 78.15, H
6.56, N 15.20; IR: n˜ =3258 cmÀ1 (s).
4-Nitro-N-[(pyridine-3-yl)methyl]benzenamine
(L2):
4-Nitroaniline
(13.60 g, 65 mmol) and 3-pyridine carboxaldehyde (6.93 g, 65 mmol) were
dissolved in dry 1,2-dichloroethane, and magnesium sulfate (5.00 g) was
added. The solution was placed under reflux for 6 h whilst stirring. After
this time the solution was filtered to remove magnesium sulfate, and then
concentrated under reduced pressure. The product was washed with di-
ethyl ether, and the diethyl ether was removed under reduced pressure
to yield the impure imine as darkyellow solid. 1H NMR (MeOD,
400 MHz): d=8.78 (d, J=2.4 Hz, 1H; Py-H), 8.58 (dd, J=4.8, 1.6 Hz,
1H; Py-H), 8.08 (d, J=2.0 Hz, 2H; ArH), 7.53 (dd, J=8.4, 5.6 Hz, 1H;
Py-H), 7.45 (s, 1H; Py-H), 6.77 (d, J=2.0 Hz, 2H; ArH), 6.29 ppm (s,
150.84, 129.5, 127.3, 122.5, 121.2 ppm; MS
(ES+): m/z: 183 [M+]; elemen-
N
tal analysis calcd (%) for C12 H10N2: C 79.10, H 5.53, N 15.37; found: C
78.01, H 5.53, N 15.14. The imine (6.0 g, 33 mmol) was dissolved in meth-
anol, and whilst stirring NaBH4 (6.1 g, 165 mmol) was added until the so-
lution ceased to effervesce. The solution was stirred for a further 2 h.
50:50 HCl/H2O was added until the solution was pH 3, and then 2m
NaOH was added until the solution was pH 9. The product was extracted
using dichloromethane. The organic layer was dried over MgSO4, and
then filtered. The solvent was evaporated under reduced pressure, and
the product re-crystallised from dichloromethane and hexane. Yield:
4.9 g, 26.6 mmol, 81%; 1H NMR (CDCl3, 500 MHz): d=8.54 (dd, J=4.5,
1.5 Hz, 2H; Py-H), 7.29 (dd, J=4.5, 1.5 Hz, 2H; Py-H), 7.17 (dd, J=7.0,
1.5 Hz, 2H; Ar-H), 6.75 (tt, J=7.5, 1.0 Hz, 1H; Ar-H), 6.58 (dd, J=9.0,
1.5 Hz, 2H; Ar-H), 4.37 ppm (s, 2H; CH2); 13C{1H}-NMR (CDCl3,
1H; CH); MS
(ES+): m/z: 228 [M+]. The imine (7.0 g, 30.0 mmol) was
N
dissolved in methanol, and whilst stirring NaBH4 (6.0 g, 162.0 mmol) was
added until the solution ceased to effervesce. The solution was stirred for
a further 2 h. 50:50 HCl/H2O was added until the solution was pH 3, and
then 2m NaOH was added until the solution was pH 9. The product was
extracted using dichloromethane. The organic layer was dried over
MgSO4, and then filtered. The solvent was evaporated under reduced
pressure, and the product re-crystallised from dichloromethane and
hexane. Yield: 4.4 g, 19.1 mmol, 62%; 1H NMR (CDCl3, 500 MHz): d=
8.63 (s, 1H; Py-H), 8.57 (d, J=5.0 Hz, 1H; Py-H), 8.09 (dd, J=7.0,
2.0 Hz, 2H; Ar-H), 7.67 (dd, J=8.0, 2.0 Hz, 1H; Py-H), 7.30 (dd, J=8.0,
5.0 Hz, 1H; Py-H), 6.59 (dd, J=7.0, 2.0 Hz, 2H; Ar-H), 4.92 (s, 1H;
NH), 4.47 ppm (d, J=6.0 Hz, 2H; CH2); 13C{1H}-NMR (CDCl3,
125 MHz): d=149.6, 149.3, 135.2, 126.6, 124.0, 111.72, 45.4 ppm; MS-
125 MHz): d=150.2, 129.6, 122.3, 118.2, 113.1, 47.3 ppm; MS(ES+): m/z:
U
185 [M+]; elemental analysis calcd (%) for C12 H10N2: C 78.23, H 6.57, N
15.21; found: C 78.00, H 6.57, N 15.20.
N-[(Pyridin-2-yl)methyl]benzenamine (L5): Aniline (10.7 g, 0.11 mol) and
2-pyridine carboxaldehyde (12.3 g, 0.11 mol) were dissolved in dry 1,2-di-
chloroethane (500 mL), and magnesium sulfate (13.2 g, 0.11 mol) was
added. The solution was placed under reflux for 6 h. whilst stirring. The
solution was filtered to remove the magnesium sulfate, and concentrated
under reduced pressure to yield the intermediate imine product as a
A
62.60, H 5.25, N 18.25; found: C 62.40, H 4.80, N 18.38; IR: n˜ =
3239 cmÀ1 (s).
7302
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 7296 – 7305

Binding and Sensing using Ruthenium Complexes
FULL PAPER
yellow oil. 1H NMR (CDCl3, 500 MHz): d=8.49 (d, J=5.0 Hz, 1H; Ar-
H), 8.46 (s, 1H; CH), 8.99 (d, J=7.5 Hz, 1H; Py-H), 7.48 (dt, J=7.5,
1.0 Hz, 1H; Py-H), 7.22 (t, J=7.5 Hz, 2H; Py-H), 7.14 (d, J=7.0 Hz, 2H;
Ar-H), 7.06 ppm (m, 7.09–7.04 Hz, 2H; Ar-H); 13C{1H}-NMR (CDCl3,
100 MHz): d=151.1, 149.8, 136.6, 129.4, 126.9, 125.2, 121.9, 121.3 ppm;
128.5, 125.9, 125.5, 124.5, 123.8, 122.5, 120.5, 118.4, 115.0, 109.7, 108.8,
103.3, 97.5, 83.2, 82.2, 46.5, 37.8, 30.8, 22.4, 18.1, 14.1 ppm; MS(ES+):
N
m/z: 559 [M+]; elemental analysis calcd (%) for C30H33N3Cl2Ru: C 59.30,
H 5.47, N 6.92; found: C 59.18, H 5.61, N 6.79; IR: n˜ =3379 cmÀ1 (w,
NH).
MS
(ES+): m/z: 183 [M+]. The imine was dissolved in methanol, and
A
[Ru(h6-p-cymene)(N-{(pyridin-4-yl)methyl}benzenamine)Cl2]
(1d):
[Ru(h6-p-cymene)Cl2]2 (0.8 g, 1.3 mmol) and L4 (0.5 g, 2.7 mmol) were
dissolved in toluene (100 mL), previously degassed for 1 h and left to stir
at room temperature for 1 h. During this time a yellow/orange precipitate
formed. The solid was collected by filtration, washed with toluene and
dried in the air for 18 h (0.69 g, 1.41 mmol, 52%). 1H NMR (CDCl3,
500 MHz): d=8.87 (d, J=6.5 Hz, 2H; Py-H), 7.3–7.1 (m, 4H; Py-H, Ar-
H), 6.73 (t, J=8.0 Hz, 1H; Ar-H), 6.51 (d, J=8.0 Hz, 2H; Ar-H), 5.41 (d,
J=6.0 Hz, 2H; Ar-H), 5.21 (d, J=6.0 Hz, 2H; Ar-H), 4.49 (s, 1H; NH),
4.36 (s, 2H; CH2), 2.97 (sept, J=7.0 Hz, 1H; CH), 2.09 (s, 3H; CH3),
1.29 ppm (d, J=7.0 Hz, 6H; CH3); 13C{1H}-NMR (CDCl3, 125 MHz): d=
154.7, 147.3, 129.6, 129.3, 123.0, 118.3, 113.1, 103.8, 97.2, 82.9, 82.5, 46.7,
whilst stirring NaBH4 (12.2 g, 0.33 mol) was added until the solution
ceased to effervesce. The solution was stirred for a further 2 h. 50:50
HCl/H2O was added until the solution was pH 3, and then 2m NaOH was
added until the solution was pH 9. The product was extracted using di-
chloromethane. The organic layer was dried over MgSO4, and then fil-
tered. The solvent was evaporated under reduced pressure, and the prod-
uct extracted, as a white crystalline solid and recrystallised with from di-
chloromethane and diethylether. Yield: 6.5 g, 35 mmol, 32%; 1H NMR
(CDCl3, 400 MHz): d=8.61 (d, J=4.5 Hz, 1H; Ar-H), 7.62 (dt, J=8.0,
1.5 Hz, 1H; Py-H), 7.34 (d, J=8.0 Hz, 1H; Py-H), 7.23–7.17 (m, 3H; Py-
H, Ar-H), 6.76 (t, J=7.5 Hz, 1H; Ar-H), 7.69 (d, J=7.5 Hz, 2H; Ar-H),
4.66 (s, 1H; NH), 4.47 ppm (s, 2H; CH2); 13C{1H}-NMR (CDCl3,
125 MHz): d=158.9, 137.0, 129.6, 122.4, 121.9, 117.8, 113.3, 49.5 ppm;
30.9, 22.5, 18.4; MS
(ES+): m/z: 490 [M+]; elemental analysis calcd (%)
G
for C22H26N2Cl2Ru: C 53.88, H 5.34, N 5.71; found: C 54.43, H 5.40, N
MS
(ES+): m/z: 185 [M+]; elemental analysis calcd (%) for C12H12N2: C
A
4.99; IR: n˜ =3315 cmÀ1 (w, NH).
78.23, H 6.52, N 15.20; found: C 77.99, H 6.52, N 15.21.
[Ru(h6-p-cymene)(N-{(pyridin-3-yl)methyl}benzenamine)2Cl]
[BF4] (2a):
R
[Ru(h6-p-cymene)(N-{(pyridine-3-yl)methyl}benzenamine)Cl2]
(1a):
Compound 1a (0.4 g, 0.8 mmol) and silver tetrafluoroborate (0.16 g,
0.8 mmol) were dissolved in 50:50 MeOH/acetone (50 mL), previously
degassed for 1 h and left to stir at room temperature for 20 min. The sil-
ver(I) chloride was removed through celite and L1 (0.15 g, 0.8 mmol) was
added to the filtrate, which was then stirred for a further 4 h. The solvent
was removed under reduced pressure to yield a crude orange solid, which
was re-crystallised from CH2Cl2 and C6H14. The orange solid was filtered
[Ru(h6-p-cymene)Cl2]2 (0.4 g, 0.64 mmol) and L1 (0.24 g, 1.3 mmol) were
dissolved in toluene (100 mL), previously degassed for 1 h and left to stir
at room temperature for 1 h. During this time an orange precipitate
formed. The solid was collected by filtration, washed with toluene and
dried in the air for 18 h (0.57 g, 1.2 mmol, 89%). 1H NMR (CDCl3,
400 MHz): d=8.95 (s, 1H; Py-H), 8.89 (d, J=5.6 Hz, 1H; Py-H), 7.69 (d,
J=8.0 Hz, 1H; Py-H), 7.22 (dd, J=8.0, 5.6 Hz, 1H; Py-H), 7.15 (t, J=
8.0 Hz, 2H; Ar-H), 6.73 (t, J=8.0 Hz, 1H; Ar-H), 6.57 (d, J=8.0 Hz,
2H; Ar-H), 5.29 (d, J=4.8 Hz, 2H; Ar-H), 5.03 (d, J=4.8 Hz, 2H; Ar-
H), 4.40 (brs, 1H; NH), 4.38 (s, 2H; CH2), 2.85 (sept, J=6.8 Hz, 1H;
CH), 1.94 (s, 3H; CH3), 1.22 ppm (d, J=6.8 Hz, 6H; CH3); 13C{1H}-NMR
(CDCl3, 125 MHz): d=154.1, 153.4, 136.9, 136.5, 129.6, 124.5, 118.4,
1
and washed with C6H14, and dried in air (0.3 g, 0.4 mmol, 56%). H NMR
(CDCl3, 400 MHz): d=8.76 (s, 2H; Py-H), 8.38 (d, J=5.8 Hz, 2H; Py-
H), 7.54 (d, J=7.6 Hz, 2H; Py-H), 7.0 (m, 6H; Ar-H), 6.55 (t, J=7.6 Hz,
2H; Py-H), 6.42 (d, J=7.6 Hz, 4H; Ar-H), 5.37 (brs, 2H; NH), 5.29
(AA’BB’, J=6.2 Hz, 4H; Ar-H), 4.40 and 4.32 (AB, J=17.2 Hz, 4H;
CH2), 2.28 (sept, J=6.8 Hz, 1H; CH), 1.59 (s, 3H; CH3), 0.83 ppm (d, J=
6.8 Hz, 6H; CH3); 13C{1H}-NMR (CDCl3, 125 MHz): d=154.1, 151.2,
139.0, 138.1, 129.5, 125.1, 117.3, 112.9, 102.6, 102.4, 90.5, 81.2, 44.5, 30.9,
113.4, 103.6, 97.4, 83.0, 82.4, 45.1, 30.8, 22.5, 18.3 ppm; MS(ES+): m/z:
A
489 [M+]; elemental analysis calcd (%) for C22H26N2Cl2Ru: C 53.88, H
5.34, N 5.71; found: C 53.71, H 5.34, N 5.62; IR: n˜ =3352 cmÀ1 (w, NH).
22.6, 17.6 ppm; MS
A
[Ru(h6-p-cymene)(4-nitro-N-{(pyridin-3-yl)methyl}benzenamine)2Cl]-
(%) for C34H38N4ClRuBF4: C 56.25, H 5.28, N 7.72; found: C 55.86, H
5.22, N 7.63; IR: n˜ =3421 (w, NH), 1062 cmÀ1 (s, BF4À).
[BF4] (1b): [{Ru(h6-p-cymene)Cl2}2] (1.0 g, 1.6 mmol) and L2 (0.8 g,
[Ru(h6-p-cymene)(4-nitro-N-{(pyridin-3-yl)methyl}benzenamine)2Cl]-
3.2 mmol) were dissolved in toluene (100 mL), previously degassed for
1 h and left to stir at room temperature for 1 h. During this time a
yellow/orange precipitate formed. The solid was collected by filtration,
washed with toluene and dried in the air for 18 h (1.2 g, 2.24 mmol,
68%). 1H NMR (CDCl3, 500 MHz): d=8.76 (d, J=6.4 Hz, 1H; Py-H),
8.74 (s, 1H; Py-H), 7.95 (d, J=8.8 Hz, 2H; Ar-H), 7.45 (d, J=6.4 Hz,
1H; Py-H), 7.07 (t, J=6.4 Hz, 1H; Py-H), 6.44 (d, J=8.8 Hz, 2H; Ar-H),
5.94 (s, 1H; NH), 5.30 (d, J=5.6 Hz, 2H; Ar-H), 5.09 (d, J=5.6 Hz, 2H;
Ar-H), 4.15 (s, 2H; CH2), 2.81 (sept, J=6.8 Hz, 1H; CH), 1.61 (s, 3H;
CH3), 1.18 ppm (d, J=6.8 Hz, 6H; CH3); 13C{1H}-NMR (CDCl3,
125 MHz): d=153.8, 153.3, 152.8, 138.5, 136.8, 126.5, 124.5, 111.8 103.9,
A
(0.2 g, 0.9 mmol) and L2 (0.2 g, 0.8 mmol) were dissolved in 50:50
MeOH/acetone (50 mL), previously degassed for 1 h and left to stir at
room temperature for 20 min. The silver(I) chloride was removed
through celite. The solvent volume was reduced under reduced pressure
and the product recrystallised in the freezer from a MeOH/acetone/dieth-
yl ether solvent mixture overnight. During this time an orange solid
formed and was collected by filtration and washed with diethyl ether
(0.1 g, 0.2 mmol, 33%). 1H NMR (CDCl3, 500 MHz): d=8.84 (s, 2H; Py-
H), 8.54 (d, J=5.5 Hz, 2H; Py-H), 7.98 (d, J=9.0 Hz, 4H; Ar-H), 7.63
(d, J=5.5 Hz, 2H; Py-H), 7.12 (t, J=5.5 Hz, 2H; Py-H), 6.67 (s, 2H;
NH), 6.49 (d, J=9.0 Hz, 4H; Ar-H), 5.47 (d, J=6.0 Hz, 2H; Ar-H), 5.44
(d, J=6.5 Hz, 2H; Ar-H), 4.57 and 4.49 (ABX, J=7.0, 17.0 Hz, 4H;
CH2), 2.30 (sp, J=7.0 Hz, 1H; CH), 1.56 (s, 3H; CH3), 0.85 ppm (d, J=
7.0 Hz, 6H; CH3); 13C{1H}-NMR (CDCl3, 125 MHz): d=153.7, 152.6,
151.9, 138.4, 138.1, 137.4, 126.4, 125.2, 111.6, 102.8, 102.3, 90.2, 44.2, 30.8,
97.3, 82.9, 82.5, 44.1, 30.9, 22.4, 18.4 ppm; MS
(ES+): m/z: 535 [M+]; ele-
G
mental analysis calcd (%) for C22H25N3O2Cl2Ru: C 49.35, H 4.71, N 7.85;
found: C 50.39, H 4.70, N 8.92; IR: n˜ =3238 cmÀ1 (w, NH) (persistent
contamination by ꢀ20% L2).
[Ru(h6-p-cymene)(9-ethyl-N-{(pyridine-3-yl)methyl}-9H-carbazol-3-ami-
ne)Cl2] (1c): [{Ru(h6-p-cymene)Cl2}2] (0.50 g, 0.8 mmol) and L3 (0.50 g,
1.7 mmol) were dissolved in toluene (100 mL), previously degassed for
1 h and left to stir at room temperature for 1 h. During this time an
orange precipitate formed. The solid was collected by filtration, washed
with toluene and dried in the air for 18 h (0.97 g, 1.3 mmol, 76%).
1H NMR (CDCl3, 400 MHz): d=8.94 (s, 1H; Py-H), 8.80 (d, J=7.6 Hz,
1H; Py-H), 7.87 (d, J=8.0 Hz, 1H; Ar-H), 7.68 (d, J=7.6 Hz, 1H; Py-
H), 7.34 (t, J=7.6 Hz, 1H; Py-H), 7.3–7.1 (m, 5H; Ar-H) 6.80 (d, J=
8.0 Hz, 1H; Ar-H), 5.13 (d, J=6.0 Hz, 2H; Ar-H), 4.86 (d, J=6.0 Hz,
2H; Ar-H), 4.39 (s, 2H; CH2), 4.35 (brs, 1H; NH), 4.22 (q, J=7.6 Hz,
2H; CH2), 2.68 (sept, J=7.0 Hz, 1H; CH), 1.74 (s, 3H; CH3), 1.29 (t, J=
7.6 Hz, 3H; CH3), 1.04 ppm (d, J=7.0 Hz, 6H; CH3); 13C{1H}-NMR
(CDCl3, 125 MHz): d=154.5, 153.3, 140.5, 138.1, 137.1, 136.8, 129.3,
22.4, 17.7 ppm; MS
(ES+): m/z: 815 [M+]; elemental analysis calcd (%)
N
for C34H36N6O4ClRuBF4: C 50.04, H 4.45, N 10.30; found: C 50.35, H
4.86, N 10.38; IR: n˜ =3390 (w, NH), 1061 cmÀ1 (s, BF4).
[Ru(h6-p-cymene)(9-ethyl-N-{(pyridine-3-yl)methyl}-9H-carbazol-3-
amine)2Cl][BF4] (2c): Compound 1c (0.5 g, 0.7 mmol) and silver tetra-
R
fluoroborate (0.15 g, 0.8 mmol) were dissolved in 50:50 MeOH/acetone
(50 mL), previously degassed for 1 h and left to stir at room temperature
for 20 min. The silver(I) chloride was removed through celite and L3
(0.25 g, 0.8 mmol) was added to the filtrate, which was then stirred for a
further 4 h. The solvent was removed under reduced pressure to yield a
crude orange oil. The oil was washed with ethanol and re-crystallised
from CH2Cl2 and C6H14. The green solid was filtered and washed with
Chem. Eur. J. 2008, 14, 7296 – 7305
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7303

J. W. Steed et al.
C6H14, and dried in air. (0.13 g, 0.1 mmol, 19%). 1H NMR (CDCl3,
400 MHz): d=8.96 (s, 2H; Py-H), 8.48 (d, J=5.5 Hz, 2H; Py-H), 7.88 (d,
J=7.5 Hz, 2H; Ar-H), 7.39 (t, J=7.5 Hz, 2H; Ar-H), 7.11 (t, J=7.5 Hz,
2H; Ar-H), 7.6–6.9 (m, Py-H, 12H; Ar-H), 5.31 (AA’BB’, 4H; Ar-H),
4.54 and 4.46 (AB, J=16.5 Hz, 4H; CH2), 4.21 (4q, J=7.0 Hz, H; CH2),
2.13 (sept, J=6.5 Hz, 1H; CH), 1.46 (s, 3H; CH3), 1.33 (t, J=7.0 Hz,
6H; CH3), 0.54 ppm (d, J=6.5 Hz, 6H; CH3); 13C{1H}-NMR (CDCl3,
125 MHz): d=153.9, 151.3, 140.4, 140.2, 139.0, 138.2, 133.9, 125.7, 125.7,
125.1, 123.7, 122.6, 120.6, 118.3, 114.6, 109.7, 109.0, 108.5, 103.0, 102.8,
1.420 gcmÀ3, F000 =1064, SMART 6k, MoKa radiation, l=0.71073 Š, T=
120(2) K, 2qmax =58.48, 19681 reflections collected, 6518 unique (Rint
=
0.0599). Final GooF=0.992, R1=0.0380, wR2=0.0755, R indices based
on 5580 reflections with I>2s(I) (refinement on F2), 268 parameters, 2
restraints. Lorentz polarisation and absorption corrections were applied.
101.9, 90.6, 80.7, 45.5, 37.7, 30.6, 22.0, 17.4, 14.2 ppm; MS
ACHTREUNG
Acknowledgement
[M+ÀBF4]; IR: n˜ =3409 (w, NH), 1060 cmÀ1 (s, BF4).
[Ru(h6-p-cymene)(N-{(pyridin-4-yl)methyl}benzenamine)2Cl]
ACHTREUNG
We thankthe EPSRC and the Leverhulme Trust for funding and for pro-
vision of computing facilities.
Compound 1d (0.4 g, 0.8 mmol), silver tetrafluoroborate (0.2 g,
0.9 mmol) and L4 (0.2 g, 0.8 mmol) were dissolved in 50:50 MeOH/ace-
tone (50 mL), previously degassed for 1 h and left to stir at room temper-
ature for 20 min. The silver(I) chloride was removed through celite. The
solvent volume was reduced under reduced pressure and the product was
collected as an orange oil. 1H NMR (CDCl3, 500 MHz): d=8.85 (d, J=
6.5 Hz, 4H; Py-H), 7.41 (d, J=6.5 Hz, 4H; Py-H), 7.08 (t, J=7.5 Hz, 4H;
Ar-H), 6.67 (t, J=7.5 Hz, 2H; Ar-H), 6.47 (d, J=7.5 Hz, 4H; Ar-H), 5.84
(d, J=6.0 Hz, 2H; Ar-H), 5.59 (d, J=6.0 Hz, 2H; Ar-H), 4.57 (s, 2H;
NH), 4.36 (d, J=2.0 Hz, 4H; CH2), 2.55 (sept, J=7.0 Hz, 1H; CH), 1.68
(s, 3H; CH3), 1.11 ppm (d, J=7.0 Hz, 6H; CH3); 13C{1H}-NMR (CDCl3,
125 MHz): d=154.1, 154.0, 147.3, 129.6, 124.7, 118.3, 113.1, 103.5, 102.0,
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88.4, 82.3, 46.7, 31.0, 22.5, 17.9 ppm; MS
liable elemental analysis was not obtained because of the oily nature of
A
the product.
[Ru(h6-p-cymene)
A
(3):
[{Ru(h6-p-cymene)Cl2}2] (0.80 g, 1.3 mmol) and L5 (0.40 g, 2.2 mmol)
were dissolved in toluene (100 mL), previously degassed for 1 h and left
to stir at room temperature for 1 h. During this time an orange precipi-
tate formed. The solid was collected by filtration, washed with toluene
and dried in the air for 18 h (0.52 g, 1.1 mmol, 82%). 1H NMR (CDCl3,
500 MHz): d=11.50 (s, 1H; NH), 8.95 (d, J=6.5 Hz, 1H; Py-H), 8.03 (d,
J=7.5 Hz, 2H; Ar-H), 7.82 (t, J=6.5 Hz, 1H; Py-H), 7.40 (t, J=6.5 Hz,
1H; Py-H), 7.39(d, J=6.5 Hz, 1H; Py-H), 7.38 (t, J=7.5 Hz, 2H; Ar-H),
7.22 (t, J=7.5 Hz, 1H; Ar-H), 6.40 (d, J=5.5 Hz, 1H; Ar-H), 5.49 (d, J=
6.5 Hz, 1H; Ar-H), 5.34 (d, J=6.5 Hz, 1H; Ar-H), 4.84 (d, J=5.5 Hz,
1H; Ar-H), 4.55 (dd, J=15.0, 5.0 Hz, 1H; CH2), 4.30 (dd, J=15.0,
10.0 Hz, 1H; CH2) 2.80 (q, J=7.0 Hz, 1H; CH), 2.25 (s, 3H; CH3), 1.15
(d, J=7.0 Hz, 3H; CH3), 0.65 ppm (d, J=7.0 Hz, 3H; CH3); 13C{1H}-
NMR (CDCl3, 125 MHz): d=162.0, 153.1, 149.3, 139.5, 129.4, 126.9,
125.1, 122.1, 121.8, 105.5, 96.4, 86.3, 85.3, 84.4, 83.4, 58.7, 30.0, 24.0,
19.2 ppm; MS
A
for C22H24N2Cl2Ru: C 53.88, H 5.34, N 5.71, Cl, 14.46; found: C 53.52, H
5.42, N 5.69, Cl 14.19; IR: n˜ =3382 cmÀ1 (w, NH).
[Ru(h6-p-cymene)
A
U
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([3]
A
ACHTREUNG
ne)Cl]Cl (0.02 g, 0.041 mmol) was dissolved in methanol, and added to a
solution of NaBPh4 (0.014 g, 0.041 mmol) in methanol. A yellow precipi-
tate was formed immediately, and collected by filtration (0.026 g,
0.032 mmol, 79%); elemental analysis calcd (%) for C46H46N2BClRu: C
71.36, H 5.99, N 3.62; found: C 71.09, H 6.00, N 3.57.
[Ru(h6-hexamethylbenzene)(N-{(pyridine-3-yl)methyl}benzenamine)Cl2]
(4): [{Ru
(h6-C6Me6)Cl2}2] (0.1 g, 0.15 mmol) and L1 (0.049 g. 0.27 mmol)
A
were stirred in dry toluene (20 mL) at room temperature overnight. Over
this time a darkred solid precipitates from solution, and is collected by
filtration. The crude product was then washed with toluene, and the pure
red solid is collected by filtration (0.089 g, 0.096 mmol, 64%). 1H NMR
(CDCl3, 400 MHz): d=8.71 (s, 1H; Py-H), 8.62 (d, J=6.0 Hz, 1H; Py-
H), 7.60 (d, J=6.0 Hz, 1H; Py-H), 7.17 (dd, J=6.0, 1.8 Hz, 1H; Py-H),
7.09 (t, J=7.5 Hz, 2H; Ar-H) 6.65 (t, J=7.5 Hz, 1H; Ar-H), 6.51 (d, J=
7.5 Hz, 2H; Ar-H) 4.32 (s, 3H; NH, CH2), 1.80 ppm (s, 18H; C6Me6); ele-
mental analysis calcd (%) for C24H30Cl2N2Ru: C 55.60, H 5.83, N 5.40;
found C 54.90, H 5.72, N 4.85.
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Crystallographic data: C24H30Cl2N2Ru, Mr =518.47, yellow block, 0.30”
0.10”0.10 mm, monoclinic, space group Cc (No. 9), a=15.291(4), b=
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7304
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Chem. Eur. J. 2008, 14, 7296 – 7305

Binding and Sensing using Ruthenium Complexes
FULL PAPER
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Received: April 23, 2008
Published online: July 9, 2008
Chem. Eur. J. 2008, 14, 7296 – 7305
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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7305