Metal-to-ligand charge-transfer sensitisation of near-infrared emitting lanthanides in trimetallic arrays M2Ln (M = Ru, Re or Os; Ln = Nd, Er or Yb)

Article abstract of DOI:10.1039/b500849b

The new pro-ligand 4-methyl-4'-(carbonylaraino(2-(tert-butoxycarbonylamino) ethyl))-2,2'-bipyridyl (L¹) has been prepared and used to synthesise the complex fac-Re^ICl(CO)₃(L¹) 1 and the complex salts [M^II(bipy)₂(L¹)](PF ₆)₂ (M = Ru^II 8 or Os^II 15). Deprotection with trifluoroacetic acid affords the amine-functionalised derivatives fac-Re^ICl(CO)₃(L²) 2, [M ^II(bipy)₂(L²)](PF₆)₂ (M = Ru^II 9 or Os^II 16) which react with the dianhydride of diethylenetriamine pentaacetic acid (DTPA) to give the binuclear complex {fac-Re^ICl(CO)₃}₂(L³) 3 and the complex salts [{M^II(bipy)₂}₂(L ³)](PF₆)₄ (M = Ru^II 10 or Os ^II 17). The latter react with salts Ln(OTf)₃ to afford a series of 12 heterotrimetallic compounds that contain a lanthanide (Ln) ion in the DTPA binding site; {fac-Re^ICl(CO)₃}₂(L ³)Ln^III (Ln = Nd 4, Er 5, Yb 6 or Y 7) and [{M ^II(bipy)₂}₂(L³)Ln ^III](PF₆)(OTf)₃ (M = Ru^II, Ln = Nd 11, Er 12, Yb 13 or Y 14; M = Os^II, Ln = Nd 18, Er 19, Yb 20 or Y 21). All of these trimetallic species display absorption bands ascribed to metal-to-ligand charge-transfer (MLCT) excitations, and luminescence measurements show that these excited states can be used to sensitise near-infrared emission from Ln^III (Ln = Nd, Er or Yb) ions. Single crystal X-ray structures of L^I and [Ru^II(bipy) ₂(L²H)](H₂PO₄)₃· (CH₃)₂CO·0.8H₂O were obtained, the latter revealing the presence of H₂PO₄^- counter anions, the source of which is presumed to be hydrolysis of PF₆ ^- ions. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b500849b

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F U L L P A P E R
Metal-to-ligand charge-transfer sensitisation of near-infrared
emitting lanthanides in trimetallic arrays M2Ln (M = Ru, Re or
Os; Ln = Nd, Er or Yb)
Simon J. A. Pope, Benjamin J. Coe,* Stephen Faulkner* and Rebecca H. Laye
Department of Chemistry, The University of Manchester, Oxford Road, Manchester, UK M13
9PL. E-mail: b.coe@man.ac.uk, stephen.faulkner@man.ac.uk
Received 19th January 2005, Accepted 14th February 2005
First published as an Advance Article on the web 10th March 2005
The new pro-ligand 4-methyl-4ꢀ-(carbonylamino(2-(tert-butoxycarbonylamino)ethyl))-2,2ꢀ-bipyridyl (L1) has been
prepared and used to synthesise the complex fac-ReICl(CO)3(L1) 1 and the complex salts [MII(bipy)2(L1)](PF6)2 (M =
RuII 8 or OsII 15). Deprotection with trifluoroacetic acid affords the amine-functionalised derivatives
fac-ReICl(CO)3(L2) 2, [MII(bipy)2(L2)](PF6)2 (M = RuII 9 or OsII 16) which react with the dianhydride of
diethylenetriamine pentaacetic acid (DTPA) to give the binuclear complex {fac-ReICl(CO)3}2(L3) 3 and the complex
salts [{MII(bipy)2}2(L3)](PF6)4 (M = RuII 10 or OsII 17). The latter react with salts Ln(OTf)3 to afford a series of 12
heterotrimetallic compounds that contain a lanthanide (Ln) ion in the DTPA binding site;
{fac-ReICl(CO)3}2(L3)LnIII (Ln = Nd 4, Er 5, Yb 6 or Y 7) and [{MII(bipy)2}2(L3)LnIII](PF6)(OTf)3 (M = RuII, Ln =
Nd 11, Er 12, Yb 13 or Y 14; M = OsII, Ln = Nd 18, Er 19, Yb 20 or Y 21). All of these trimetallic species display
absorption bands ascribed to metal-to-ligand charge-transfer (MLCT) excitations, and luminescence measurements
show that these excited states can be used to sensitise near-infrared emission from LnIII (Ln = Nd, Er or Yb) ions.
Single crystal X-ray structures of L1 and [RuII(bipy)2(L2H)](H2PO4)3·(CH3)2CO·0.8H2O were obtained, the latter
−
−
revealing the presence of H2PO4 counter anions, the source of which is presumed to be hydrolysis of PF6 ions.
complexes {fac-ReICl(CO)3}2(L3)LnIII in which the LnIII ion is
Introduction
bound in a diethylenetriamine pentaacetic acid (DTPA)-derived
coordination environment with the ReI tricarbonyl moieties held
in close proximity.19 We have now extended this methodology to
include related assemblies containing [MII(bpy)3]2+ (M = Ru or
Os) chromophores, the latter of which represent the first reported
examples of covalently linked OsII–LnIII complexes.
Much attention has recently focused on electronic and optical in-
vestigations of ligand-bridged multinuclear, and often lumines-
cent, transition metal complexes.1 Usually, such studies involve
chromophores comprising polypyridyl complexes of d-block
metal ions such as ReI, RuII or OsII. However, investigations
of luminescence from f-block lanthanide (Ln) complexes have
recently gained momentum, largely motivated by the potential
for applications in time-resolved immunoassays and biological
imaging.2 Improvements in the sensitivity of such techniques can
be achieved by exploiting the long-lived emissions derived from
Ln ions.3
Results and discussion
Synthesis and characterization
The synthesis of the Boc-protected pro-ligand, L1, has been de-
scribed previously in a preliminary communication.19 Scheme 1
shows the preparation of L1 and complexes such as described
in this communication. The 1H NMR spectrum of L1 in CDCl3
includes six bpy signals and broadened NH resonances at 5.11
and 7.65 ppm, the former attributed to the Boc amide moiety.
Deprotection of uncomplexed L1 with trifluoroacetic acid (TFA)
results in unacceptably low product yields and long reac-
tion times. However, complexation to form fac-ReICl(CO)3(L1)
(1) followed by deprotection affords fac-ReICl(CO)3(L2) (2) in
Lanthanides such as neodymium,4 ytterbium5 and erbium6
have low energy excited states which emit in the near-infrared
(NIR) region, outside the range of biological absorption. A
wide variety of sensitising chromophores can be applied to
such ions, including complexes of d-block transition metals
which display metal-to-ligand charge-transfer (MLCT) excited
states. A number of examples of luminescent mixed d/f com-
plexes have been reported recently, including systems which
use [RuII(bpy)3]2+ (bpy = 2,2ꢀ-bipyridyl),7 PtII,8 ferrocenyl7
or PdII-porphyrin9 complexes as covalently-linked sensitising
chromophores, the majority of which are stable in protic
solvents. Assemblies incorporating ReI-based sensitisers have
also been studied, but dissociation in protic solvents means
that their potential for applications in assays is severely
restricted.8c,10 Other existing d/f hybrid complexes include CrIII-
containing helicates,11 hairpin-shaped DNA-intercalating PtII
2,2ꢀ:6ꢀ,2ꢀꢀ-terpyridyl (tpy) derivatives,12 a CuII-detecting 1,10-
phenanthroline species,13 a self-assembled FeII bis(tpy) complex
for magnetic resonance imaging,14 [RuII(bpy)3]2+-functionalised
calixarenes as Ln sensors,15 and RuII 4,4ꢀ-bipyridyl-containing
molecular squares.16 Sensitised NIR luminescence has also been
observed in a coordination polymer containing co-crystallised
[RuII(bpy)(CN)4]2− units and YbIII centres.17
1
high yield as the TFA adduct. Comparison of the H NMR
spectrum of 1 in CDCl3 with that of L1 reveals a general
downfield shift of the bpy protons induced by complexation.
The resonance associated with the Boc amide proton remains
at ca. 5.1 ppm, whilst the other NH signal shifts downfield by
0.7 ppm. Treatment of 2 with 0.5 equiv. of DTPA dianhydride
at room temperature in the presence of triethylamine yields
the dinuclear complex {fac-ReICl(CO)3}2(L3) [Re2(L3) (3)]. The
latter reacts readily with the appropriate Ln triflate salts to
afford heterotrinuclear complexes {fac-ReICl(CO)3}2(L3)LnIII
[Re2(L3)Ln where Ln = Nd (4), Er (5), Yb (6), or Y (7)]. We
have used analogous procedures to form trinuclear assemblies
containing RuII or OsII bis(bpy) units; Ru2(L3)Ln [Ln = Nd (11),
Er (12), Yb (13), or Y (14)] and Os2(L3)Ln [Ln = Nd (18), Er
(19), Yb (20), or Y (21)]. These compounds were synthesized
via the intermediates [MII(bpy)2(L1)](PF6)2 [M = Ru (8) or
Os (15)], [MII(bpy)2(L2)](PF6)2 [M = Ru (9) or Os (16)] and
We have recently shown how self-assembly can be used
to screen MLCT chromophores for use as Ln sensitisers,18
and also reported the synthesis of kinetically stable trinuclear
1 4 8 2
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0
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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show only minor deviations from those of their homobimetallic
precursors, confirming the proposed formulations. In addition,
the heterotrinuclear complexes were studied via IR, UV-vis. and
luminescence spectroscopies and mass spectrometry. MALDI
mass spectra proved invaluable in the characterisation of these
Scheme 1 Synthesis of Re2(L3)Ln complexes.
[{MII(bpy)2}2(L3)](PF6)4 [M2(L3); M = Ru (10) or Os (17)]. For
the synthesis of 15, heating in ethylene glycol at 90 ◦C was used
because L1 decomposes under reflux in this solvent.
The new homonuclear RuII/OsII complex salts 8–10 and 15–17
were fully characterised by using a wide range of spectroscopic
1
and analytical techniques. The H NMR spectra of the Boc-
protected complexes in 8 and 15 again include signals for the
two amide protons, in addition to complex aromatic regions
due to the three bpy ligands. The deprotected complexes in 2,
9 and 16 show no NH2 signals in CD3COCD3, and an amide
resonance is observed only for 16. The RuII/OsII homodinuclear
species 10 and 17 give very similar 1H NMR spectra in D2O, the
primary point of interest being the observation of three methyl
resonances, indicating the presence of diastereoisomers.
In general, the electronic absorption spectra of the red
coloured RuII compounds show a broad band at 450 nm assigned
to a 3MLCT excitation and more intense bands at 290 and
245 nm attributed to intra-bpy p→p* transitions. In contrast, for
the OsII compounds, a number of broad transitions between 350
and 600 nm are ascribed as 3MLCT in nature. Typical examples
of these spectra are shown in Fig. 1. Both electrospray and
MALDI mass spectrometry are applicable to the monometallic
compounds, but corresponding data could not be obtained for
the heavy bimetallic species 10 and 17. However, 1H NMR
spectra and CHN analyses verify the formulations of the latter
complexes.
Formation of the heterotrinuclear lanthanide species yielded
hygroscopic solids that were isolated by using standard Schlenk
techniques. Elemental analyses afforded low C and N but
high H percentages, indicative of extensive hydration. The
1H NMR spectra of the YIII-containing species 7, 14 and 21
Fig. 1 Top: Absorption spectra for the dinuclear compounds: Re2(L3)
(3, grey, 1 × 10−4 M), Ru2(L3) (10, thin, 7 × 10−6 M) and Os2(L3) (17,
thick, 3 × 10−5 M). Bottom: Normalised emission spectra: 3 (grey, kex
340 nm), 10 (thin, kex 450 nm) and 17 (thick, kex 490 nm). All spectra
recorded in methanol.
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0
1 4 8 3

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Fig. 2 MALDI mass spectrum (alpha) of [6 − Cl]+. Top: theoretical isotopic distribution. Bottom: experimental.
complexes, and Fig. 2 shows a representative example of
such a spectrum. In general, the RuII/OsII heterotrinuclear
compounds show very broad clusters, with the appropriate
isotopic distributions, corresponding to sequential loss of three
OTf groups, and in one case also a PF6 unit.
Electronic absorption and emission spectra of the com-
plexes M2(L3) (M = Re, Ru or Os) are shown in Fig. 1. Excitation
of a methanol solution of Ru2(L3) (10) at 450 nm results in
intense emission at 630 nm with a lifetime of 309 ns, charac-
teristic of such complex chromophores. In similar fashion, the
luminescence behaviour of Os2(L3) (17) is typical of compounds
of this type, with a broad intense band at 745 nm observed
in methanol following excitation at 490 nm. As expected, the
emission lifetime for 17 is an order of magnitude shorter than
that of its RuII analogue 10.
When compared with 10, a number of changes in the emissive
characteristics are observed for the heterotrinuclear species
Ru2(L3)Ln. In each case, the MLCT emission maximum shifts
to lower energy, with a peak at 637 nm. In addition, the MLCT
emission lifetime decreases, most markedly in Ru2(L3)Nd (11,
s = 240 ns). Both the shift in kmax(em) and the shortening of s
are indicative of MLCT→Ln ET. Further information on the
ET processes is obtained from the Ln NIR emission bands.
Excitation at either 337 or 450 nm results in Ln-based emissions
in all cases, both in methanol and d4-methanol. Generally, the
MLCT-based emission is intense throughout the NIR region.
However, in the cases of Ru2(L3)Ln [Ln = Nd (11) or Er (12)]
the luminescence is Ln-dominated at the respective detection
wavelengths of 1340 or 1530 nm. For 11, the emissive decay
Photophysical studies
The photoexcitation behaviour of the ReI complexes 1–6 has
been described previously in a preliminary communication.3
Briefly, 337 nm excitation of 3 gives rise to an intense, short-
lived emission at kmax = 625 nm, which is characteristic of
+
such fac-{ReI(CO)3bpy} chromophores. Formation of the
heterotrinuclear LnIII complexes causes ca. 30% attenuation of
this MLCT-derived emission, accompanied by small decreases
in the emission lifetime. Measurements of the LnIII-derived
emissions from the complexes Re2(L3)Ln [Ln = Nd (4), Er (5) or
Yb (6)] in methanol and d4-methanol confirm that the observed
quenching of the ReI MLCT luminescence arises from energy
transfer (ET) to the LnIII centres. Luminescence lifetimes (s) and
other data are shown in Table 1. Time-gating or fitting to a
double exponential decay were used to extract s values in the
cases where the LnIII emission spectrum is convoluted with that
from the MLCT states.
Table 1 Photophysical data for the compounds M2(L3) (M = Re, Ru or Os) and M2(L3)Ln (Ln = Nd, Er, Yb or Y)
i
Compound
kmax(em)/nm
s(CH3OH)/nsa
s(CD3OD)/nsa
kd/nmb
s(CH3OH)/ns
s(CD3OD)/ns
qc
k(ET)/(106 s−1
)
M luminescence
Ln luminescence
3 Re2(L3)d
625
625
625
625
611
630
637
637
637
632
745
757
757
757
750
13
10
12
13
24
309
240
275
294
264
34
27
11
16
17
18
318
306
281
308
310
40
4 Re2(L3)Ndd
5 Re2(L3)Erd
6 Re2(L3)Ybd
7 Re2(L3)Y
1340
1530
980
237
—
1882
512
540
8303
0.3
—
0.7
58.3
41.7
35.3
10 Ru2(L3)
11 Ru2(L3)Nd
12 Ru2(L3)Er
13 Ru2(L3)Yb
14 Ru2(L3)Y
17 Os2(L3)
1340
1530
980
176e, 219
—
207,e 498
203,e 852
308,g 7391
0.3
—
—
0.38
—
—
f
—
18 Os2(L3)Nd
19 Os2(L3)Er
20 Os2(L3)Yb
21 Os2(L3)Y
26
24
26
31
35
31
36
31
1340
1530
980
26,h 272
—
35,h 545
31,h 1164
5326
0.1
—
—
6.2
9.4
6.2
f
—
a Re MLCT lifetimes measured at 800 nm; Ru/Os MLCT lifetimes measured at 1200 nm. b Detection wavelength for Ln emission. c Inner-sphere
hydration number. d Data taken from ref. 19. e Rise time lifetime component. f Emission decay from Yb too weak relative to MLCT signal. g Bi-
exponential fit using Ru MLCT and Yb-based lifetimes. h Bi-exponential fit using Os MLCT and Ln-based lifetimes. i Calculated using k(ET) =
1/s2 − 1/s1 where s1 is the partially quenched MLCT lifetime and s2 is the unquenched MLCT lifetime of the Y analogue.
1 4 8 4
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0

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lifetimes are typical of NdIII species with lifetimes of ca. 200–
500 ns. However, a relatively long rise time (ca. 200 ns in each
case) is observed, indicating that ET is probably rather inefficient
for this particular system. From the decay lifetimes an approxi-
mate inner-sphere hydration number (q = 290(kCH3OH–kCD3OD) −
0.4) was calculated and for 11 q = 0.3, which is entirely consistent
with an octadentate coordination environment. Time-resolved
emission spectroscopy clearly shows the superimposition of the
longer-lived NdIII component on the tail of the shorter-lived
MLCT contribution (Fig. 3). The ErIII analogue (12) is emissive
in d4-methanol at 1530 nm with a long lifetime just below
a microsecond. Again, the decay is preceded by a relatively
long rise time of 203 ns, indicating inefficient MLCT→ErIII
ET. The emission spectrum for Ru2(L3)Yb (13) is more difficult
to interpret, since the tail of the MLCT luminescence is still
intense at the YbIII emission wavelength of 980 nm. However, in
d4-methanol the YbIII lifetime is sufficiently long (microsecond
domain) that a tail fit can be applied to the decay and a
lifetime obtained via reconvolution methods. Unfortunately, the
emission spectrum of 13 in methanol is dominated by the MLCT
signal, precluding extraction of the YbIII-based signal.
Fig. 4 Fitted decay, detector response and residual for Os2(L3)Nd (18)
in CD3OD (kex = 337 nm, kem = 1340 nm).
Yb) reveals some general observations. The MLCT lifetimes
increase in the order Re < Os ꢁ Ru. The NdIII compounds
(4, 11 and 18) all have very similar lifetimes for Ln NIR
emission, but their ErIII counterparts (5, 12 and 19) show a
significant variation in s at 1530 nm. The lifetime of Os2(L3)Er
(19) is over twice that of its ReI analogue (5), with the RuII
species (12) being intermediate. As expected, none of these ErIII
compounds produces any detectable emission in methanol, due
to efficient quenching by both C–H and O–H oscillators. The
YbIII complexes (6, 13 and 20) are the most difficult to analyse in
the NIR region due to overlapping emissions from both d- and
f-metal components. However, Re2(L3)Yb (6) provides the most
information in this regard, due to the favourable, short lifetime
of the MLCT chromophore and the apparent efficiency of ET.
To provide a more accurate reference complex, particularly
in terms of ligand conformation, a non-luminescent Ln ion,
YIII, was also introduced into the DTPA-like binding site to
afford 7, 14 and 21. Interestingly, in each case quite a significant
modulation of the MLCT emission occurs when compared with
the M2(L3) species, suggesting that conformational effects are
important. For Ru2(L3)Y (14) and Os2(L3)Y (21), the emission
maximum shows a small red-shift, whereas for Re2(L3)Y (7) the
shift is to higher energy. In the ReI and OsII species, the MLCT
luminescence lifetimes of the YIII complexes are all longer than
those observed for the corresponding complexes with emissive
Ln ions, suggesting that ET is reasonably efficient. The rate of
ET can be approximated by using k(ET) = 1/s1 − 1/s2 (where
s1 is the donor lifetime of the YIII complex, and s2 the donor
lifetime of the Ln complex) and the resulting values are reported
in Table 1. It is clear from these values that the efficiency of ET
in the ReI complexes is an order of magnitude better than that in
the analogous OsII species. The RuII lifetimes appear to be more
variable, but the lack of significant quenching of the donor state
suggests inefficient ET for these species.
Fig. 3 Time resolved emission spectrum of Ru2(L3)Nd (11) in CD3OD
(kex = 337 nm).
The Os2(L3)Ln species also show attenuation of the MLCT
emission when compared with 17, with red-shifted emission
maxima at 757 nm and shortened s values. Analysis of the
luminescence spectra again reveals that the MLCT emission
extends throughout the NIR region. Hence, in most cases the
MLCT lifetime is convoluted with that of the longer-lived
Ln emissive state. Thus, for Os2(L3)Nd (18), dual exponential
analyses of the lifetime measurements in methanol and d4-
methanol give typical values for the NdIII-centred emission and
MLCT luminescence (Fig. 4). Treatment of the NdIII lifetimes
using the Horrocks equation gives a q value of approximately
zero, consistent with the coordination environment of the Ln
ion. For Os2(L3)Er (19), the ErIII-based emission has a lifetime
greater than one microsecond in d4-methanol. The complex
Os2(L3)Yb (20) is more difficult to analyse because of the
proximity of the intense MLCT luminescence (757 nm) and
the (relatively) weak YbIII emission (980 nm). At 980 nm, the
spectra are dominated by MLCT emission, in similar fashion
to the RuII analogue 13. However, in d4-methanol the long-lived
tail of the spectrum can be fitted to a lifetime of microsecond
order and thus is clearly YbIII in origin. Although the YbIII
signal is shrouded by MLCT emission in methanol, it is clear
from the spectral characteristics of the MLCT emission that
MLCT→YbIII ET is occurring.
Perhaps the most intriguing aspect of these d–f hybrids is
the comparison of the apparent ET efficiencies in the RuII and
ReI complexes. The emission decays for Ru2(L3)Ln [Ln = Nd
(11) or Er (12)] show a relatively long rise time feature (ca.
200 ns) prior to Ln decay. However, for the corresponding ReI
compounds 4 and 5, the grow-in is essentially instantaneous
(< 5 ns, and beyond the resolution of the detector). Long grow-in
features tend to indicate inefficient intramolecular ET, whereas
short times correspond with efficient processes. The interesting
3
point here is that the energies of the donor MLCT states are
very similar for the RuII and ReI systems (15 700 cm−1 and
16 000 cm−1, respectively) and thus the thermodynamic proxim-
ity to accessible Ln excited states is the same for both systems.
The presence of saturated ethylene linkers within L3 suggests
that the ET mechanism is predominantly Fo¨rster, and therefore
dominated by through space dipole–dipole interactions. Given
Direct comparison of the luminescence properties of the
compounds M2(L3)Ln (M = Ru, Re or Os; Ln = Nd, Er or
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0
1 4 8 5

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the similarity in the energies of the MLCT states, the spatial
proximity of the donor and acceptor states will therefore be
the primary factor determining ET efficiency. As indicated by
the results obtained with the YIII complexes (see above), the
observed differences may be due to conformational effects. In
the RuII complexes the electrostatic repulsion between the 2 + d-
metal units may expand the structure, increasing d(Ln · · · Ru).
By contrast, the neutral ReI centres will not experience such
electrostatic effects. Another potentially significant difference is
the spatial structures of the MLCT excited states. In the RuII
complexes, each metal is coordinated to three p-accepting bpy
groups, and although the amide-functionalised one is expected
to possess the lowest energy p* orbitals, MLCT to all three
ligands undoubtedly occurs. In contrast, the ReI centres have
only one bpy ligand, which is part of L3 and in close proximity to
the Ln ion. It seems likely that the differences in ET efficiencies
between the RuII and ReI complexes M2(L3)Ln (Ln = Nd or
Er) can be attributed to a combination of MLCT excited state
structures and conformational influences.
Fig.
6
Structural representation of [RuII(bipy)2(L2H)](H2PO4)3·
(CH3)2CO·0.8H2O (50% probability ellipsoids; counterions and lattice
solvent molecules omitted for clarity).
of which suggests that the terminal amine of the ligand is
protonated.
X-Ray structural determinations
The pro-ligand L1 was re-crystallised from a concentrated
methanolic solution at room temperature to give colourless,
prismatic single crystals suitable for X-ray diffraction. A struc-
ture analysis performed on one of these crystals confirmed the
proposed formulation. As represented in Fig. 5, the structure is
stabilised by significant p-stacking between the bpy rings (p–p
Conclusion
A range of heterotrimetallic complexes has been prepared
in which the MLCT state of a d-block metal chromophore
acts as an effective sensitiser for NIR luminescence from Ln
ions. The lessons learned from these systems are important
for the development of NIR luminescence for imaging and
assay. In particular, it is worth noting that short-lived MLCT
luminescence is much easier to separate from long-lived Ln
emissions, suggesting that ReI and OsII bpy complexes are much
more promising as sensitisers when compared with related RuII
species.
˚
contacts of 3.37 and 3.33 A), accompanied by intermolecular
hydrogen bonding between the amide protons and amide
carbonyl groups of the ethylenediamine linker (distances of
˚
2.908 and 2.858 A). The packing is sufficiently compact that no
lattice solvent molecules are evident in the unit cell. Salt 9 was
dissolved in acetone and allowed to stand at 4 ◦C for 6 months,
resulting in the formation of several orange block crystals. Fig. 6
shows a representation of the cationic component of 9. The
structure solution reveals the counter anions in the unit cell to
be H2PO4−, presumably a consequence of PF6− hydrolysis. Such
hydrolysis has been observed previously in various other sys-
tems, including a ZnII complex of 1-(2-hydroxyethyl)-1,4,7,10-
tetraazacyclododecane20 and a CuII complex of 1,3,5-tris(1,4,7-
Experimental
Materials and procedures
All new compounds are air-stable both in the solid state and
solution. However, several compounds are hygroscopic and stan-
dard inert-atmosphere techniques were used throughout. The
triazacyclonon-1-ylmethyl)benzene.21 There are six H2PO4 an-
−
starting materials cis-RuII(bpy)2Cl2,22 cis-OsII(bpy)2Cl2 and
23
ions and two complex cations per unit cell, the charge balancing
N-(tert-butoxycarbonyl)-1,2-diaminoethane24 were synthesised
according to the literature.
General physical measurements
Infrared spectra were recorded as solids using an ATR (Atten-
uated Total Reflectance)-fitted Bruker Equinox 55 spectrometer
over the range 4000–800 cm−1 for 64 scans. Mass spectra were
obtained using positive or negative electrospray in acetonitrile
solutions on a Micromass Platform II, or by MALDI using
methanol solutions with an ALPHA matrix on a Micromass
Tofspec2. Electronic absorption spectra were obtained on a
double-beam Cary Varian 500 Scan UV-vis-NIR spectropho-
1
1
tometer as methanol solutions. H and 13C{ H} NMR spectra
were recorded on a Bruker Avance 400 MHz spectrometer at
298 K. CHN analyses were performed by the Microanalytical
Laboratory, University of Manchester using a Carlo Erba
Instruments CHNS-O EA 1108 Elemental Analyser.
Crystallography
Crystal data and data collection and refinement parameters
for compounds [RuII(bipy)2(L2H)](H2PO4)3·(CH3)2CO·0.8H2O
and L1 are given in Table 2, selected bond lengths and angles in
Table 3.
Fig. 5 Structural representations of L1. Top: packing diagram. Bottom:
with 50% probability ellipsoids.
Data collection and processing. Data were collected with
a Bruker Smart APEX CCD area detector equipped with an
1 4 8 6
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0

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Table 2 Crystal, data collection and refinement details for the two crystal structures
[RuII(bipy)2(L2H)](H2PO4)3·(CH3)2CO·0.8H2O
L1
Formula
M
C37H46.6N8O14.8P3Ru
C19H24N4O3
356.42
1034.20
Triclinic
P1
Crystal system
Triclinic
¯
Space group
P1
˚
a/A
10.7974(14)
12.1158(16)
17.545(2)
106.729(2)
95.920(2)
91.912(2)
2181.6(5)
2
5.0564(15)
5.6297(18)
16.199(5)
87.396(5)
83.943(5)
84.685(6)
456.3(2)
1
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
U/A
Z
T/K
100(2)
0.543
100(2)
0.090
l/mm−1
Reflections collected
Independent reflections (Rint
Final R1, wR2 [I>2r(I)]
(all data)
6167
4716
0.0829, 0.2346
0.1056, 0.2560
2011
1610
0.0716, 0.1801
0.0895, 0.2006
)
a The structures were refined on Fo using all data.
2
Oxford Cryosystems low temperature device25 using Mo-Ka
radiation and x scans. Data were corrected for Lorentz and
polarisation factors. Absorption corrections were applied to all
data.
crude acid chloride derivative was then reacted without further
purification. The residue was redissolved in dry acetonitrile
(10 cm3) with triethylamine (1 cm3) under a nitrogen atmosphere
and an acetonitrile (5 cm3) solution of N-(tert-butoxycarbonyl)-
1,2-diaminoethane (0.748 g, 4.67 mmol) was added dropwise
via a syringe. This mixture was allowed to stir at room
temperature for 24 h. The solvents were removed in vacuo
and the product redissolved in dichloromethane and subjected
to aqueous washings. The organic layers were collected and
evaporated to dryness yielding a light brown solid. This crude
product was then placed on a silica gel column and eluted
with dichloromethane/methanol (initially 99 : 1, followed by
95 : 5). The main yellow band was collected and evaporated to
afford the product as a very pale pink (indicative of trace FeII
contamination), mildly hygroscopic solid: yield 1.21 g (70%). dH
(CDCl3) 1.45 (9 H, s, tBu), 2.35 (3 H, s, Me), 3.36 (2 H, m, CH2),
3.54 (2 H, m, CH2), 5.11 (1 H, s br, NHBoc), 7.12 (1 H, s, bpy),
7.65 (1 H, s br, NH), 7.74 (1 H, d, J 5.7, bpy), 8.20 (1 H, s, bpy),
8.48 (1 H, d, J 5.5, bpy), 8.65 (1 H, s, bpy), 8.72 (1 H, d, J 5.8,
bpy). mmax 3343m, 3296m, 3053w, 2983w, 2940w, 1691s, 1645s,
1594m, 1536s, 1446m, 1387m, 1362m, 1335m, 1269m, 1251m,
1169s, 1098w, 1070w, 1037w cm−1 (Found: C, 62.79; H, 7.00; N,
15.04. Calc. for C19H24N4O3·0.5MeOH: C, 62.89; H, 7.04; N,
15.04%). ES+-MS: m/z 379 ([M + Na]+), 357 ([M + H]+).
Structure analysis and refinement. Both structures were
solved by direct methods using SHELXS-97. Both struc-
tures were completed by iterative cycles of DF-syntheses
and full-matrix least squares refinement. In compound L1
all non-H atoms were refined anisotropically. In compound
[RuII(bipy)2(L2H)](H2PO4)3·(CH3)2CO·0.8H2O all non-H atoms
were refined anisotropically except the disordered O atoms
belonging to the (H2PO4)− groups and the disordered solvent
molecules (an acetone molecule and water molecule). In both
structures difference Fourier syntheses were employed in posi-
tioning idealised hydrogen atoms and were allowed to ride on
their parent C or N-atoms. All refinements were against F2 and
used SHELX-97.26
CCDC reference numbers 263036 and 263037.
See http://www.rsc.org/suppdata/dt/b5/b500849b/ for cry-
stallographic data in CIF or other electronic format.
Syntheses
4-Methyl-4ꢀ -(carbonylamino(2-(tert-butoxycarbonylamino)-
ethyl))-2,2ꢀ-bipyridyl L1. 4-Methyl-2,2ꢀ-bipyridyl-4ꢀ-carboxylic
acid (1.0 g, 5.05 mmol) was suspended in dichloromethane
(10 cm3) and SOCl2 (10 cm3) added dropwise whilst stirring.
The mixture was stirred at room temperature for 6 h and then
evaporated to dryness in vacuo, giving a white residue. This
fac-ReICl(CO)3(L1) 1. A solution of L1·0.5MeOH (100 mg,
0.268 mmol) and ReICl(CO)5 (101 mg, 0.279 mmol) in chloro-
form (15 cm3) was heated under reflux for 6 h. The mixture was
then evaporated to dryness in vacuo, giving an orange residue.
Table 3 Selected bond lengths and angles of the two crystal structures
[RuII(bipy)2(L2H)](H2PO4)3(CH3)2CO·0.8H2O
L1
Ru1–N1
Ru1–N2
Ru1–N5
2.058(7)
2.042(8)
2.050(7)
Ru1–N6
Ru1–N7
Ru1–N8
2.053(8)
2.054(7)
2.058(7)
C1–N1
C1–C5
C1–C6
C2–N1
C2–C3
C3–C4
C4–C5
C4–C11
C6–N2
C6–C10
C7–N2
C7–C8
C8–C9
1.338(7)
1.404(6)
1.487(6)
1.328(8)
1.380(7)
1.393(8)
1.376(8)
1.501(7)
1.333(7)
1.395(7)
1.329(7)
1.390(7)
1.392(8)
C9–C10
C9–C12
C12–O1
C12–N3
C13–C14
C13–N3
C14–N4
C15–O2
C15–N4
C15–O3
C16–O3
C16–C17
C16–C19
C16–C18
1.386(8)
1.508(7)
1.228(7)
1.323(7)
1.450(8)
1.459(6)
1.456(7)
1.219(12)
1.342(12)
1.359(7)
1.462(8)
1.508(9)
1.512(10)
1.516(8)
N1–Ru1–N2
N1–Ru1–N5
N1–Ru1–N6
N1–Ru1–N8
N5–Ru1–N2
N5–Ru1–N6
N5–Ru1–N8
N8–Ru1–N6
78.5(3)
88.8(3)
95.6(3)
95.9(3)
94.7(3)
78.7(3)
173.2(3)
95.8(3)
N6–Ru1–N2
N7–Ru1–N2
N7–Ru1–N6
N7–Ru1–N8
N7–Ru1–N5
N7–Ru1–N1
N8–Ru1–N2
171.4(3)
93.5(3)
92.8(3)
79.0(3)
97.1(3)
170.6(3)
91.2(3)
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0
1 4 8 7

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This crude product was purified on an alumina column, eluting
with dichloromethane/methanol (99 : 1). The main yellow band
was collected and evaporated to afford the desired product as a
light orange–yellow solid: yield 0.134 g (76%). dH (CDCl3) 1.47
296 (13 800), 241 (19 500) nm. MALDI-MS: broad clusters at
m/z 1609 ([M − Cl]+), 1577 ([M − 2Cl]+), 1446 ([M − Cl − Er]+).
{fac-ReICl(CO)3}2(L3)YbIII 6. Method as for 4, but using
YbIII(OTf)3 (8 mg, 0.013 mmol) to afford a light yellow solid:
yield 21 mg (98%). dH (CD3OD) −59, −56, −55, −47, −28, −24,
−22, −17, −16, −14, −6, 13, 21, 23, 25, 27, 28, 32, 36, 40, 43,
45, 48, 61, 66, 100. mmax 3293w (v br), 3088w, 2954w, 2022s (CO),
1889s (br, CO), 1624s, 1586s, 1550m, 1484w, 1441m, 1410m,
1274s, 1236s, 1162s, 1098m, 1027s cm−1. kmax (e/mol−1 dm3 cm−1)
379 (3800), 295 (12 500), 243 (17 900) nm. MALDI-MS: broad
clusters at m/z 1615 ([M − Cl]+), 1583 ([M − 2Cl]+), 1446 ([M −
Cl–Yb]+).
t
(9 H, s, Bu), 2.50 (3 H, s, Me), 3.38–3.76 (4 H, m, CH2), 5.14
(1 H, br, NHBoc), 7.32 (1 H, d, J 5.6, bpy), 7.91 (1 H, d, J 5.1,
bpy), 8.15 (1 H, s, bpy), 8.35 (1 H, br s, NH), 8.65 (1 H, s, bpy),
8.84 (1 H, d, J 5.1, bpy), 9.07 (1 H, d, J 5.6, bpy). mmax 3334w
(br), 3051w, 2978w, 2936w, 2017s (CO), 1939s (CO), 1913s (CO),
1867s, 1766s, 1716m, 1669m, 1645m, 1623w, 1517m, 1485m,
1451m, 1409m, 1365m, 1309m, 1236m, 1163m, 1029m cm−1
(Found: C, 39.79; H, 3.22; N, 8.19. Calc. for C22H24N4ClO6Re:
C, 39.91; H, 3.65; N, 8.46%). ES−-MS: m/z 660 ([M − 2H]−).
fac-ReICl(CO)3(L2) 2. Trifluoroacetic acid (2 cm3) was
added dropwise to a solution of 1 (50 mg, 0.076 mmol) in
dichloromethane (5 cm3). The mixture was stirred at room
temperature for 2 h. The solvents were removed in vacuo and
the product precipitated from acetone with diethyl ether and
filtered using Schlenk apparatus to afford the desired product
as a yellow solid: yield 49 mg (89%). dH (CD3COCD3) 2.64
(3 H, s, Me), 3.84–4.06 (2 H, m, CH2), 4.09 (2 H, m, CH2), 7.65
(1 H, dd, J 5.6, 1.0, bpy), 8.20 (1 H, dd, J 5.8, 1.6, bpy), 8.80
(1 H, s, bpy), 8.94 (1 H, d, J 5.6, bpy), 9.21 (1 H, d, J 5.8, bpy),
9.30 (1 H, s, bpy). mmax 3074w (v br), 2019s (CO), 1915s (br, CO),
1867s, 1769w, 1671m, 1623m, 1551m, 1484m, 1449m, 1412m,
1336m, 1307m, 1280w, 1238w, 1198m, 1130m, 1109m, 1076m,
1030w cm−1. kmax (e/mol−1 dm3 cm−1) 381 (2300), 297 (8400),
240sh (12400) nm (Found: C, 32.57; H, 2.09; N, 8.14. Calc. for
C17H16N4ClO4Re·1.5CF3CO2H: C, 32.77; H, 2.41; N, 7.64%).
ES+-MS: m/z 568 ([M − Cl + MeCN]+), 527 ([M − Cl]+).
{fac-ReICl(CO)3}2(L3) 3. A solution of 2·1.5CF3CO2H
(50 mg, 0.068 mmol) in dry acetonitrile (5 cm3) with a few drops
of NEt3 and diethylenetriamine pentaacetic dianhydride (12 mg,
0.034 mmol) was stirred at room temperature for 24 h. The
solution was concentrated and the hygroscopic yellow product
precipitated by the addition of diethyl ether, filtered off and
washed with diethyl ether: yield 42 mg (81%). dH (CD3OD) 2.51
(6 H, s, Me), 2.87–3.75 (26 H, m, CH2), 7.41 (2 H, d, J 5.6, bpy),
7.88 (2 H, m, bpy), 8.44 (2 H, s, bpy), 8.67 (2 H, d, J 5.6, bpy),
8.83 (2 H, d, J 5.3, bpy), 9.01 (2 H, d, J 5.3, bpy). mmax 3273w
(br), 3054w, 2980w, 2019s (CO), 1885s (br, CO), 1717m, 1623m
(br), 1543m, 1483m, 1383m, 1308m, 1236m, 1198m, 1137m,
1033m cm−1. kmax (e/mol−1 dm3 cm−1) 378 (5000), 292 (17100),
243 sh (22400) nm (Found: C, 37.87; H, 3.70; N, 9.76. Calc.
for C48H51N11Cl2O16Re2·2H2O: C, 38.00; H, 3.65; N, 10.15%).
MALDI-MS: m/z 1446 ([M − Cl]+), 1411 ([M − 2Cl]+), 1382
([M − 2Cl − CO]+), 1358 ([M − 2Cl − 2CO]+).
{fac-ReICl(CO)3}2(L3)YIII 7. Method as for 4, but using
YIII(OTf)3 (7 mg, 0.013 mmol) to afford a light yellow solid:
yield 21 mg (100%). dH (CD3OD) 2.49, 2.50, 2.54 (6H, s, Me),
2.99–3.72 (26H, m, CH2), 7.45 (2H, m, bpy), 7.86 (2H, d, J 5.6,
bpy), 8.42 (2H, m, bpy), 8.71–8.89 (4H, m, bpy), 9.05 (2H, m,
bpy). mmax 3334m (br), 3087w, 2890w, 2024s (CO), 1895s (CO),
1626m, 1585m, 1551m, 1456w, 1410w, 1376w, 1240s, 1166s,
1097m, 1028s cm−1. kmax (e/mol−1 dm3 cm−1) 378 (4800), 295
(16 100), 245 (22 500) nm. MALDI-MS: broad clusters at m/z
1533 ([M − Cl]+), 1497 ([M − 2Cl]+).
[RuII(bpy)2(L1)](PF6)2 8.
A
solution of L1·0.5MeOH
(100 mg, 0.268 mmol) and cis-RuIICl2(bpy)2·2H2O (146 mg,
0.281 mmol) in ethanol (10 cm3) was heated at 70 ◦C for
24 h. The reaction progress was monitored via TLC. The
mixture was then evaporated to dryness in vacuo, giving a red
residue. This crude product was purified on a silica column,
eluting with acetonitrile/water/sat. aq. KNO3 (14 : 2 : 1).
The main red band was collected, treated with excess aqueous
NH4PF6 and extracted with dichloromethane to give upon
evaporation a dark red solid. This solid was then redissolved in
dichloromethane, residual KNO3 removed by filtration and the
solution evaporated to dryness to afford the dark red product:
t
yield 211 mg (71%). dH (CD3COCD3) 1.35 (9 H, s, Bu), 2.60
(3 H, s, Me), 3.32 (2 H, m, CH2), 3.52 (2 H, m, CH2), 6.11 (1 H,
t br, NHBoc), 7.40 (1 H, d, J 5.3, bpy), 7.48–7.57 (4 H, m, bpy),
7.78 (1 H, d, J 5.8, bpy), 7.82 (1 H, dd, J 5.8, 1.7, bpy), 7.90–7.97
(3 H, m, bpy), 7.98 (1 H, s, bpy), 8.10 (1 H, m, bpy), 8.15 (4 H, m,
bpy), 8.26 (1 H, br t, NH), 8.68 (1 H, s, bpy), 8.74 (4 H, d, J 8.1,
bpy), 8.97 (1 H, s, bpy). mmax 3649w, 3435w, 3082w, 2924w, 1700m,
1665m, 1620m, 1604m, 1538m, 1465m, 1446m, 1424m, 1365m,
1239m, 1161m, 1025m, 819s cm−1. kmax (e/mol−1 dm3 cm−1) 454
(13 000), 287 (50 500), 246 (22 900) nm (Found: C, 42.84; H, 3.79;
N, 9.75. Calc. for C39H40N8F12O3P2Ru·0.5CH2Cl2: C, 43.04; H,
3.75; N, 10.17%). ES+-MS: m/z 915 ([M − PF6]+), 769 ([M −
2PF6]+).
{fac-ReICl(CO)3}2(L3)NdIII 4. To a solution of 3·2H2O
(20 mg, 0.014 mmol) in methanol (10 cm3) was added NdIII(OTf)3
(8 mg, 0.014 mmol). The mixture was stirred at 50 ◦C for 24 h.
The solvent volume was then reduced to a minimum and the
yellow product precipitated by the addition of diethyl ether,
filtered off and washed with diethyl ether: yield 19 mg (87%). dH
(CD3OD) −2 (br), 1.2, 2–3 (m, br), 3.2, 3.3–4.5 (m, br), 7–11
(m, br). mmax 3292w (br), 3078w, 2980w, 2023s (CO), 1893s (br,
CO), 1624m, 1579m, 1553m, 1485w, 1442w, 1410w, 1276s, 1236s,
1164s, 1118m, 1098m, 1027s cm−1. kmax (e/mol−1 dm3 cm−1)
379 (3200), 296 (10800), 242 (15200) nm. MALDI-MS: broad
clusters at m/z 1587 ([M − Cl]+), 1555 ([M − 2Cl]+), 1446 ([M −
Cl − Nd]+).
{fac-ReICl(CO)3}2(L3)ErIII 5. Method as for 4, but using
ErIII(OTf)3 (8 mg, 0.013 mmol) to afford a light yellow solid:
yield 20 mg (90%). dH (CD3OD) −62, −54, −40, −34, −28,
−26, −20, 24, 28, 30, 33, 35, 42, 54, 58, 63, 80, 114. mmax
3294w (br), 3089w, 2967w, 2022s (CO), 1890s (br, CO), 1624s,
1586m, 1550m, 1484m, 1442m, 1410m, 1275s, 1235s, 1224s,
1163s, 1096m, 1027s cm−1. kmax (e/mol−1 dm3 cm−1) 380 (4100),
[RuII(bpy)2(L2)](PF6)2 9. To a solution of 8·0.5CH2Cl2
(50 mg, 0.045 mmol) in dichloromethane (2 cm3) was added
a few drops of trifluoroacetic acid. The mixture was stirred at
room temperature for 2 h. The solvents were removed in vacuo
and the product precipitated from acetone with diethyl ether
and filtered using Schlenk apparatus to afford a dark red solid:
yield 46 mg (95%). dH (CD3COCD3) 2.57 (3 H, s, Me), 3.31 (1 H,
m, CHH), 3.75–3.90 (2 H, m, CH2), 4.03 (1 H, s, CHH), 7.41
(1 H, m, bpy), 7.52–7.60 (4 H, m, bpy), 7.83 (1 H, dd, J 5.6,
1.6, bpy), 7.92 (1 H, m, bpy), 8.00–8.25 (8 H, m, bpy), 8.80–8.95
(5 H, m, bpy), 9.39 (1 H, d, J 8.6, bpy), 9.94 (1 H, m, bpy).
mmax 3641w (br), 3342w (br), 3090w, 1662m, 1621m, 1601m,
1541m, 1466m, 1446m, 1425m, 1373m, 1240w, 1163w, 1026w,
815s cm−1. kmax (e/mol−1 dm3 cm−1) 454 (10 400), 287 (48 600),
246 (18 600) nm (Found: C, 40.33; H, 2.98; N, 10.10. Calc. for
C34H32N8F12OP2Ru·CF3CO2H: C, 40.27; H, 3.10; N, 10.44%).
MALDI-MS: m/z 815 ([M − PF6]+), 670 ([M − 2PF6]+).
[{RuII(bpy)2}2(L3)](PF6)4 10. A solution of 9·CF3CO2H
(20 mg, 0.019 mmol) in dry acetonitrile (5 cm3) with a few
drops of NEt3 and diethylenetriamine pentaacetic dianhydride
1 4 8 8
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0

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(3 mg, 0.008 mmol) was stirred at room temperature for 24 h.
The solution was concentrated and the dark red hygroscopic
product precipitated by addition of diethyl ether, filtered off
and washed with dichloromethane then acetone: yield 19 mg
(100%). dH (D2O) 2.53, 2.55, 2.59 (6 H, 3s, Me), 2.82–4.09
(26 H, m, CH2), 7.13 (2 H, m, bpy), 7.23 (8 H, m, bpy), 7.41
(2 H, m, bpy), 7.49 (2 H, m, bpy), 7.62 (8 H, m, bpy), 7.80 (10
H, m, bpy), 8.38 (2 H, m, bpy), 8.45 (8 H, m, bpy), 8.69 (2 H,
m, bpy). mmax 3268w (br), 3071w, 2927w, 1660m, 1603m, 1542m,
1465m, 1445m, 1424m, 1375s, 1300m, 1239m, 1199m, 1163m,
1134s, 1065m, 836s cm−1. kmax (e/mol−1 dm3 cm−1) 455 (9800), 289
(43 300), 245 (17 100) nm (Found: C, 43.89; H, 3.76; N, 11.53.
Calc. for C82H83N19F24O10P4Ru2: C, 43.26; H, 3.67; N, 11.69%).
484 (12800), 375 (9800), 288 (39 800), 246 (26 100) nm (Found:
C, 42.15; H, 3.68; N, 9.07. Calc. for C39H40N8F12O3OsP2·C7H8:
C, 42.72; H, 3.71; N, 9.38%). MALDI-MS: broad clusters at
m/z 1004 ([M − PF6]+), 859 ([M − 2PF6]+).
[OsII(bpy)2(L2)](PF6)2 16. To a solution of 15·C7H8 (80 mg,
0.067 mmol) in dichloromethane (5 cm3) was added a few
drops of trifluoroacetic acid. The mixture was stirred at room
temperature for 2 h. The solvents were removed in vacuo and the
product precipitated from acetone with diethyl ether and filtered
using Schlenk apparatus to afford a dark green solid: yield 68 mg
(97%). dH (CD3COCD3) 2.68 (3 H, s, Me), 3.85 (2 H, m, CH2),
4.00 (2 H, m, CH2), 7.34 (1 H, dd, J 5.8, 1.0, bpy), 7.48 (4 H, m,
bpy), 7.76 (1 H, d, J 6.0, bpy), 7.81 (1 H, dd, J 6.1, 1.8, bpy), 7.90–
8.05 (9 H, m, bpy), 8.83 (4 H, m, bpy), 8.92 (1 H, s, bpy), 9.47
(1 H, d, J 1.5, bpy), 10.09 (1 H, br, NH). mmax 3077w (v br), 1666m,
1620m, 1546m, 1463m, 1447m, 1422m, 1291s, 1176s, 1131s,
1022s, 827s cm−1. kmax (e/mol−1 dm3 cm−1) 594 (2600), 483 (9600),
374 (7100), 291 (49 000), 246 (20 400) nm (Found: C, 35.35;
H, 2.88; N, 8.43. Calc. for C34H32N8F12OOsP2·2CF3CO2H: C,
35.75; H, 2.68; N, 8.78%). MALDI-MS: broad clusters at m/z
906 ([M − PF6]+), 762 ([M − 2PF6]+).
[{RuII(bpy)2}2(L3)NdIII](PF6)(OTf)3 11. To a solution of 10
(20 mg, 0.009 mmol) in methanol (10 cm3) was added NdIII(OTf)3
(5 mg, 0.008 mmol). The mixture was stirred at 50 ◦C for 24 h.
The solvent volume was then reduced to a minimum and the dark
red product precipitated by the addition of diethyl ether, filtered
off and washed with diethyl ether: yield 17 mg (87%). mmax 3267w,
2976w, 2910w, 1601m, 1546m (br), 1483, 1465m, 1446m, 1410w,
1242s, 1224s, 1153s, 1028s, 836s cm−1. kmax (e/mol−1 dm3 cm−1)
455 (4400), 288 (19 300), 248 (7800) nm. MALDI-MS: broad
clusters at m/z 2283 ([M − OTf]+), 2133 ([M − 2OTf]+), 1982
([M − 3OTf]+).
[{RuII(bpy)2}2(L3)ErIII](PF6)(OTf)3 12. Method as for 11,
but using ErIII(OTf)3 (5 mg, 0.008 mmol) to afford a dark
red solid: yield 18 mg (92%). mmax 3084w, 1631m, 1545m,
1466m, 1447m, 1241s, 1158s, 1028s, 913m, 836s cm−1. kmax
(e/mol−1 dm3 cm−1) 454 (6700), 287 (25 300), 246 (11 700) nm.
MALDI-MS: broad clusters at m/z 2307 ([M − OTf]+), 2157
([M − 2OTf]+), 2009 ([M − 3OTf]+).
[{RuII(bpy)2}2(L3)YbIII](PF6)(OTf)3 13. Method as for 11,
but using YbIII(OTf)3 (5 mg, 0.008 mmol) to afford a dark
red solid: yield 16 mg (81%). mmax 3267w, 3069w, 1637m (br),
1543m, 1465m, 1446m, 1372w, 1244s, 1224s, 1157s, 1137s, 1028s,
841m cm−1. kmax (e/mol−1 dm3 cm−1) 456 (12 800), 287 (43 300),
246 (24 070) nm. MALDI-MS: broad clusters at m/z 2308 ([M −
OTf]+), 2159 ([M − 2OTf]+).
[{RuII(bpy)2}2(L3)YIII](PF6)(OTf)3 14. Method as for 11, but
using YIII(OTf)3 (5 mg, 0.009 mmol) to afford a dark red solid:
yield 16 mg (75%). dH (D2O) 2.49 (br), 2.52 (6 H, s, Me), 2.81–
4.25 (26 H, m, CH2), 7.24 (2H, d, J 4.3 Hz, bpy), 7.34 (8 H,
m, bpy), 7.55 (2 H, d, J 4.0 Hz, bpy), 7.63 (2H, d, J 4.8 Hz,
bpy), 7.78 (8 H, m, bpy), 7.93–8.08 (10 H, m, bpy), 8.44 (2H, s,
bpy), 8.50 (8H, d, J 7.8 Hz, bpy), 8.68–8.80 (2 H, m, bpy). mmax
3358w, 3084w, 1654m, 1544m, 1466m, 1447m, 1375m, 1251s,
1225s, 1158s, 1107m, 1028s, 840m cm−1. kmax (e/mol−1 dm3 cm−1)
456 (23 600), 288 (110 500), 246 (43 900) nm. MALDI-MS:
broad clusters at m/z 2075 ([M − 2OTf]+), 1926 ([M − 3OTf]+),
1783 ([M − 3OTf–PF6]+).
[{OsII(bpy)2}2(L3)](PF6)4 17. A solution of 16·2CF3CO2H
(40 mg, 0.031 mmol) in dry acetonitrile (5 cm3) with a few
drops of NEt3 and diethylenetriamine pentaacetic anhydride
(6 mg, 0.017 mmol) was stirred at room temperature for 24 h.
The solution was concentrated and the dark green hygroscopic
product precipitated by addition of diethyl ether, filtered off and
washed with diethyl ether: yield 27 mg (70%). dH (D2O) 2.57,
2.59, 2.63 (6 H, 3s, Me), 3.06–3.97 (26 H, m, CH2), 7.18 (2 H, s,
bpy), 7.28 (8 H, m, bpy), 7.46 (2 H, s, bpy), 7.55 (2 H, s, bpy), 7.68
(8 H, m, bpy), 7.85 (10 H, m, bpy), 8.51 (10 H, m, bpy), 8.75 (2 H,
m, bpy). mmax 3266w, 3073w, 1648m (br), 1542m, 1462m, 1446m,
1421m, 1368m, 1308m, 1237m, 1199m, 1169m, 1098m, 1022s,
841m cm−1. kmax (e/mol−1 dm3 cm−1) 604 (2100), 483 (7600), 373
(5600), 291 (17 500), 247 (13 800) nm (Found: C, 39.62; H, 3.97;
N, 10.70. Calc. for C82H83N19F24O10Os2P4: C, 40.12; H, 3.41; N,
10.84%).
[{OsII(bpy)2}2(L3)NdIII](PF6)(OTf)3 18. To a solution of 17
(20 mg, 0.008 mmol) in methanol (10 cm3) was added NdIII(OTf)3
(5 mg, 0.008 mmol). The mixture was stirred at 50 ◦C for 24 h.
The solvent volume was then reduced to a minimum and the
dark green product precipitated by the addition of diethyl ether,
filtered off and washed with diethyl ether: yield 17 mg (81%).
mmax 3276w, 3076w, 1605m (br), 1547m, 1463m, 1447m, 1423m,
1243s, 1223s, 1152s, 1027s, 838m cm−1. kmax (e/mol−1 dm3 cm−1)
608 (1000), 485 (3600), 373 (2600), 291 (13700), 247 (6900) nm.
MALDI-MS: broad clusters at m/z 2463 ([M − OTf]+), 2313
([M − 2OTf]+), 2164 ([M − 3OTf]+), 2016 ([M − 3OTf–PF6]+).
[{OsII(bpy)2}2(L3)ErIII](PF6)(OTf)3 19. Method as for 18,
but using ErIII(OTf)3 (5 mg, 0.008 mmol) to afford a dark
green solid: yield 15 mg (71%). mmax 3077w, 1606m (br), 1546m,
1463m, 1447m, 1423m, 1244s, 1223s, 1153s, 1027s, 840m cm−1.
kmax (e/mol−1 dm3 cm−1) 602 (1100), 483 (4000), 371 (2900), 290
(12 000), 248 (7500) nm. MALDI-MS: broad clusters at m/z
2484 ([M − OTf]+), 2332 ([M − 2OTf]+), 2184 ([M − 3OTf]+).
[OsII(bpy)2(L1)](PF6)2 15.
A
solution of L1·0.5MeOH
(100 mg, 0.268 mmol) and cis-OsIICl2(bpy)2 (162 mg,
0.282 mmol) in ethylene glycol (5 cm3) was heated at 90 ◦C
for 24 h. The mixture was allowed to cool and excess aqueous
NH4PF6 added affording a black precipitate. This solid was col-
lected on a fine porosity sinter and then purified using alumina
column chromatography, eluting with toluene/acetonitrile (1
: 1). The principle green band was collected and the solvent
removed to afford a dark green solid: yield 124 mg (39%). dH
[{OsII(bpy)2}2(L3)YbIII](PF6)(OTf)3 20. Method as for 18,
but using YbIII(OTf)3 (5 mg, 0.008 mmol) to afford a dark
green solid: yield 16 mg (76%). mmax 3357w, 3085w, 2988w, 1620m
(br), 1550m, 1464m, 1448m, 1423m, 1248s, 1224s, 1157s, 1100m,
1027s, 841m cm−1. kmax (e/mol−1 dm3 cm−1) 598 (3700), 484
(6600), 374 (5000), 287 (64300) nm. MALDI-MS: broad clusters
at m/z 2487 ([M − OTf]+), 2337 ([M − 2OTf]+), 2187 ([M −
3OTf]+).
[{OsII(bpy)2}2(L3)YIII](PF6)(OTf)3 21. Method as for 18, but
using 16 (15 mg, 0.006 mmol) and YIII(OTf)3 (3 mg, 0.006 mmol)
to afford a dark green solid: yield 13 mg (91%). dH (D2O)
2.57(br), 2.60, 2.62 (6 H, 3s, Me), 2.82–4.21 (26 H, m, CH2), 7.16
t
(CD3COCD3) 1.38 (9 H, s, Bu), 2.35 (3 H, s, Me), 3.36 (2 H,
m, CH2), 3.53 (2 H, m, CH2), 6.46 (1 H, br t, NH), 7.37 (1 H,
d, J 5.1, bpy), 7.45–7.55 (4 H, m, bpy), 7.79 (2 H, d, J 5.8,
bpy), 7.90–8.05 (8 H, m, bpy), 8.10 (1 H, m, bpy), 8.81 (4 H, m,
bpy), 9.00 (2 H, m, bpy and NH), 9.35 (1 H, s, bpy). mmax 3648w,
3429w, 3086w, 2976w, 1697m, 1665m, 1622m, 1536m, 1463m,
1448m, 1423m, 1366m, 1313m, 1265m, 1241m, 1163m, 1126m,
1069m, 1024m, 828s cm−1. kmax (e/mol−1 dm3 cm−1) 589 (3600),
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0
1 4 8 9

View Article Online
(2 H, s, bpy), 7.26 (8 H, m, bpy), 7.41 (2 H, m, bpy), 7.53 (2 H,
m, bpy), 7.60–7.74 (8 H, m, bpy), 7.76–7.93 (10 H, m, bpy),
8.41 (2 H, s, bpy), 8.49 (8 H, s, bpy), 8.66–8.76 (2 H, m, bpy).
mmax 3354w, 3086w, 2988w, 1634m (br), 1551m, 1464m, 1448m,
1424m, 1252s, 1224s, 1157s, 1103m, 1028s, 922w, 840m cm−1.
kmax (e/mol−1 dm3 cm−1) 590 (2700), 485 (9200), 456 (8900),
373 (7000), 291 (48 900), 246 (19 700) nm. MALDI-MS: broad
clusters at m/z 2404 ([M − OTf]+), 2257 ([M − 2OTf]+), 2106
([M − 3OTf]+), 1957 ([M − 3OTf–PF6]+).
2 S. Faulkner and J. L. Matthews, in Comprehensive Coordination
Chemistry II, ed. J. A. McCleverty and T. J. Meyer, Pergamon Press,
Oxford, 2004, vol. 9, pp. 913–944.
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4 A. Beeby and S. Faulkner, Chem. Phys. Lett., 1997, 266, 116.
5 A. Beeby, S. Faulkner and J. A. G. Williams, J. Chem. Soc., Dalton
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6 M. H. V. Werts, J. W. Verhoeven and J. W. Hofstraat, J. Chem. Soc.,
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7 S. I. Klink, H. Keizer and F. C. J. M. Van Veggel, Angew. Chem., Int.
Ed., 2000, 39, 4319.
Luminescence measurements
The luminescence properties of the RuII, ReI and OsII compo-
nents were determined using a Perkin-Elmer LS55 fluorimeter.
In the case of the NdIII, ErIII and YbIII complexes, the sample
was excited using a pulsed nitrogen laser (PTI-3301, 337 nm)
or a nitrogen pumped dye laser (PTI-330, 520 nm), operating
at 10 Hz. Light emitted perpendicular to the excitation beam
was focused onto the slits of a monochromator (PTI120), which
was used to select the appropriate wavelength. The growth and
decay of the luminescence at selected wavelengths was detected
using a germanium photodiode (Edinburgh Instruments, EI–P)
and recorded using a digital oscilloscope (Tektronix TDS220)
before being transferred to a PC for analysis. Time-resolved
emission spectra (TRES) were obtained by measuring the
growth and decay of the luminescence at each of a series of
wavelengths. Luminescence lifetimes were obtained by iterative
reconvolution of the detector response (obtained by using a
scatterer) with exponential components for growth and decay
of the metal-based luminescence, using a spreadsheet running
in Microsoft Excel. The details of this approach have been
discussed elsewhere.4,5 Fitting to a double exponential decay
yielded no improvement in fit, as judged by minimisation of
residual squared and reduced v2, except where indicated.
8 (a) N. M. Shavaleev, L. P. Moorcraft, S. J. A. Pope, Z. R. Bell, S.
Faulkner and M. D. Ward, Chem. Commun., 2003, 1134; (b) N. M.
Shavaleev, L. P. Moorcraft, S. J. A. Pope, Z. R. Bell, S. Faulkner and
M. D. Ward, Chem. Eur. J., 2003, 9, 5283; (c) N. M. Shavaleev, G.
Accorsi, D. Virgili, Z. R. Bell, T. Lazarides, G. Calogero, N. Armaroli
and M. D. Ward, Inorg. Chem., 2005, 44, 61.
9 A. Beeby, R. S. Dickins, S. FitzGerald, L. J. Govenlock, D. Parker,
J. A. G. Williams, C. L. Maupin, J. P. Riehl and G. Siligardi, Chem.
Commun., 2000, 1183.
10 N. M. Shavaleev, Z. R. Bell and M. D. Ward, J. Chem. Soc., Dalton
Trans., 2002, 3925.
11 D. Imbert, M. Cantuel, J.-C. G. Bu¨nzli, G. Bernardinelli and C.
Piguet, J. Am. Chem. Soc., 2003, 125, 15698; S. G. Telfer, N. Tajima,
R. Kuroda, M. Cantuel and C. Piguet, Inorg. Chem., 2004, 43, 5302.
12 P. B. Glover, P. R. Ashton, L. J. Childs, A. Rodger, M. Kercher, R. M.
Williams, L. De Cola and Z. Pikramenou, J. Am. Chem. Soc., 2003,
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13 T. Gunnlaugsson, J. P. Leonard, K. Se´ne´chal and A. J. Harte, Chem.
Commun., 2004, 782.
14 R. Ruloff, G. van Koten and A. E. Merbach, Chem. Commun., 2004,
842.
15 P. D. Beer, F. Szemes, P. Passaniti and M. Maestri, Inorg. Chem.,
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16 D. Guo, C.-Y. Duan, F. Lu, Y. Hasegawa, Q.-J. Meng and S.
Yanagida, Chem. Commun., 2004, 1486.
17 T. A. Miller, J. C. Jeffery, M. D. Ward, H. Adams, S. J. A. Pope and
S. Faulkner, Dalton Trans., 2004, 1524.
18 S. J. A. Pope, B. J. Coe, S. Faulkner, E. V. Bichenkova, X. Yu and
K. T. Douglas, J. Am. Chem. Soc., 2004, 126, 9490.
19 S. J. A. Pope, B. J. Coe and S. Faulkner, Chem. Commun., 2004, 1550.
20 T. Koike, S. Kajitani, I. Nakamura, E. Kimura and M. Shiro, J. Am.
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Acknowledgements
We thank the EPSRC for support (grant GR/S04949) and the
Ramsay Memorial Trust and The University of Manchester for
a Ramsay Centenary Fellowship (Dr R. H. Laye).
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1 4 9 0
D a l t o n T r a n s . , 2 0 0 5 , 1 4 8 2 – 1 4 9 0