Fully fluorinated imidodiphosphinate shells for visible- and NIR-emitting lanthanides: Hitherto unexpected effects of sensitizer fluorination on lanthanide emission properties

Article abstract of DOI:10.1002/chem.200700087

In this paper we demonstrate that the effect of aromatic C - F substitution in ligands does not always abide by conventional wisdom for ligand design to enhance sensitisation for visible lanthanide emission, in contrast with NIR emission for which the same effect coupled with shell formation leads to unprecedented long luminescence lifetimes. We have chosen an imidodiphosphinate ligand, N-{P,P-di-(pentafluorophinoyl)}-P,P-dipentafluoro-phenylphosphinimidic acid (HF₂₀tpip), to form ideal fluorinated shells about all visible- and NIR-emitting lanthanides. The shell, formed by three ligands. comprises twelve fully fluorinated aryl sensitiser groups, yet no-high energy X - H vibrations that quench lanthanide emission. The synthesis, full characterisation including X-ray and NMR analysis as well as the photo-physical properties of the emissive complexes [Ln(F₂₀tpip)₃], in which Ln = Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb, Y, Gd, are reported. The photophysical results contrast previous studies, in which fluorination of alkyl chains tends to lead to more emissive lanthanide complexes for both visible and NIR emission. Analysis of the fluorescence properties of the HF₂₀tpip and [Gd-(F₂₀tpip)₃] reveals that there is a low-lying state at around 715 nm that is responsible for partially quenching of the signal of the visible emitting lanthanides and we attribute it to a π - σ* state. However, all visible emitting lanthanides have long lifetimes and unexpectedly the [Dy(F₂₀tpip)₃] complex shows a lifetime of 0.3 ms, indicating that the elimination of high-energy vibrations from the ligand framework is particularly favourable for Dy. The NIR emitting lanthanides show strong emission signals in powder and solution with unprecedented lifetimes. The luminescence lifetimes of [Nd(F₂₀tpip)₃], [Er(F₂₀tpip)₃] and [Yb(F₂₀tpip)₃] in deuteurated acetonitrile are 44, 741 and 1111 μs. The highest value observed for the [Yb(F₂₀tpip)₃] complex is more than half the value of the Yb ion radiative lifetime.

Full text of DOI:10.1002/chem.200700087

FULL PAPER
DOI: 10.1002/chem.200700087
6308
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Chem. Eur. J. 2007, 13, 6308 – 6320

FULL PAPER
Fully Fluorinated Imidodiphosphinate Shells for Visible- and NIR-Emitting
Lanthanides: Hitherto Unexpected Effects of Sensitizer Fluorination on
Lanthanide Emission Properties
Peter B. Glover,[a] Andrew P. Bassett,[a] Peter Nockemann,[b] Benson M. Kariuki,[a]
Rik Van Deun,[b] and Zoe Pikramenou*[a]
Abstract: In this paper we demonstrate
characterisation including X-ray and
NMR analysis as well as the photo-
physical properties of the emissive
signal of the visible emitting lantha-
nides and we attribute it to a p–s*
state. However, all visible emitting lan-
thanides have long lifetimes and unex-
ꢀ
that the effect of aromatic C F substi-
tution in ligands does not always abide
by conventional wisdom for ligand
design to enhance sensitisation for visi-
ble lanthanide emission, in contrast
with NIR emission for which the same
effect coupled with shell formation
leads to unprecedented long lumines-
cence lifetimes. We have chosen an
imidodiphosphinate ligand, N-{P,P-di-
(pentafluorophinoyl)}-P,P-dipentafluoro-
phenylphosphinimidic acid (HF20tpip),
to form ideal fluorinated shells about
all visible- and NIR-emitting lantha-
nides. The shell, formed by three li-
gands, comprises twelve fully fluorinat-
ed aryl sensitiser groups, yet no-high
complexes [Ln(F20tpip)3], in which
A
Ln=Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb,
Y, Gd, are reported. The photophysical
results contrast previous studies, in
which fluorination of alkyl chains tends
to lead to more emissive lanthanide
complexes for both visible and NIR
emission. Analysis of the fluorescence
properties of the HF20tpip and [Gd-
pectedly the [Dy(F20tpip)3] complex
G
shows a lifetime of 0.3 ms, indicating
that the elimination of high-energy vi-
brations from the ligand framework is
particularly favourable for Dy. The
NIR emitting lanthanides show strong
emission signals in powder and solution
with unprecedented lifetimes. The lu-
A
minescence lifetimes of [Nd
A
lying state at around 715 nm that is re-
sponsible for partially quenching of the
[Er(F20tpip)3] and [Yb(F20tpip)3] in
A
ACHTREUNG
deuteurated acetonitrile are 44, 741
and 1111 ms. The highest value ob-
served for the [Yb(F20tpip)3] complex
R
Keywords: lanthanides
·
ligand
is more than half the value of the Yb
ion radiative lifetime.
design · luminescence · photochem-
istry · supramolecular chemistry
ꢀ
energy X H vibrations that quench
lanthanide emission. The synthesis, full
Introduction
Self-assembly of ligands around lanthanide ions is a power-
ful strategy to obtain architectures in which the steric and
electronic properties of the ligands control the lanthanide
coordination environment. Lanthanide helices,[1–5] wheels,[6–8]
starbust shapes,[9] hairpins,[10] racks,[11,12] rotaxanes,[13]
squares[14] and other high-dimensional architectures[15–21]
have been prepared. When luminescent lanthanides are in-
troduced into these architectures, new properties can be ex-
plored for materials and sensing applications.[10,22–27] Opti-
mising ligand design to target efficient sensitisation along
with long lanthanide emission lifetimes is of particular inter-
est in the design of lanthanide probes in luminescence imag-
ing of cells.[28] We have been interested in the assembly of
shells around the metal using imidodiphosphinates as bind-
[a] P. B. Glover, A. P. Bassett, Dr. B. M. Kariuki, Dr. Z. Pikramenou
School of Chemistry, The University of Birmingham
Edgbaston B15 2TT (UK)
Fax : (+44)121-414-4446
E-mail: z.pikramenou@bham.ac.uk
[b] Dr. P. Nockemann, Dr. R. V. Deun
Katholieke Universiteit Leuven
Department of Chemistry, Celestijnenlaan 200F
3001 Leuven (Belgium)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author. It contains NMR
spectra of ligand and complexes, additional UV/Vis, emission and lu-
minescence spectra are available.
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6309

Z. Pikramenou et al.
ing sites that allow a choice of “remote” sensitiser units.[29–31]
A key strategy to achieve long luminescence lifetimes in lan-
ꢀ
thanide complexes is to eliminate X H groups with high-
energy vibrations from the ligand design. Luminescence is
ꢀ
also quenched when solvent molecules containing X H
groups (e.g. water and most common organic solvents) are
directly coordinated to the lanthanide. Thus the “ideal”
ligand design (not yet achieved) for long lifetimes should be
Scheme 1.
ꢀ
a ligand with no X H bonds and which excludes solvent co-
ordination to the lanthanide. To try to achieve such an ideal
design, we chose to use a fully fluorinated imidodiphosphi-
nate ligand, N-(P,P-dipentafluorophinoyl)-P,P-dipentafluor-
ophenyl-phosphinimidic acid (HF20tpip). This ligand pro-
vides an ideal framework placing twelve “remote” aryl sen-
sitisers about the lanthanide forming a shell and having no
CH, NH or OH oscillators in the ligand structure. Although,
elimination of high-energy vibrations has been adapted pre-
viously in ligand design, the combination of sensitiser units
lated by using a modified procedure[44–46] and then reacted
with hexamethyldisilazane and hydrogen peroxide to afford
the pure HF20tpip. HF20tpip has been fully characterised by
spectroscopic techniques and single-crystal X-ray diffraction.
The crystal structure of the ligand indicates that the enol-
type form of the ligand is present and also contains hexane
solvent molecules. Both the P=O bond lengths are equal at
1.503 Š and the angle between them (that is, O1=P1···P2=
ꢀ
O2) is 43.818, and the P N bond lengths are almost identical
ꢀ
with aromatic C F substitution and the ability of ligands to
at 1.553 and 1.555 Š. This short bond length is indicative of
a degree of electron delocalisation around the binding unit,
and is consistent to those found for other imidodiphosphi-
nate type ligands.[30] The proton is disordered between the
two oxygen atoms and hydrogen bonding occurs between
pairs of ligand molecules related by inversion, with an
O1···O1’ distance of 2.43 Š (Figure 1 left). The two mole-
form shells around the metal has not been previously report-
ed, hitherto the unexpected luminescence behaviour. Ap-
proaches to eliminate high-energy vibrations in ligand struc-
tures have shown to be effective for improving sensitisation
properties in NIR and visible emission, although the ligands
either leave the metal coordinatively unsaturated or do not
ꢀ
carry sensitiser units. Approaches involved alkyl chain C F
substitution of diketonate ligands,[32–38] deuteration of
podand structures[39] and sulfonylaminate binding sites[40,41]
with no sensitiser unit. Our studies not only demonstrate the
importance of the fluorinated shell structure around the lan-
thanide formed by the assembly of three ligands for all the
emitting lanthanides, but also provide an understanding of
ꢀ
the effect of aromatic C F substitution in the ligand struc-
ture on the photophysical properties of all emitting lantha-
nides. Indeed, we demonstrate that aromatic fluorination is
not suited for sensitisation properties of the visible emitting
lanthanides, which is in contrast with the effect of fluorinat-
ed alkyl chains in diketonate complexes. During the course
of our work,[42] a communication reported the Er complex
of the fluorinated tpip ligand albeit with a dual lifetime that
would be unexpected in a pure single molecular species[43]
and a shorter lifetime to that determined herein.
Figure 1. Left: A pair of molecules in the crystal structure of HF20tpip
showing hydrogen bonding between two molecules. Right: a segment of
the crystal structure viewed down the b axis.
We have prepared and studied the photophysical proper-
ties of the visible and near infra-red emitting complexes of
III
EuIII, TbIII, S m , DyIII, NdIII, ErIII, YbIII, YIII and GdIII. The
analysis of their photophysical properties, allows the evalua-
tion of ligand design for optimum sensitiser function based
on the aromatic fluorine substituents.
cules also interact through p–p contact between rings sepa-
rated by approximately 3–4 Š, although they are not paral-
lel; the dihedral angle being 14.768. These pairs interact
with neighbouring molecules through edge–face and edge–
Results and Discussion
ꢀ
edge (F F) contacts to form cages that are occupied by the
Preparation and characterisation of HF20tpip and [Ln-
hexane solvent (Figure 1 right).
A
The 31P NMR spectrum of HF20tpip shows one phospho-
rus environment with a resonance at d=ꢀ9.0 ppm. The
chemical shift of the resonance is comparable with literature
values of fluorinated triarylphosphanes[47,48] and it appears
N-(P,P-dipentafluorophinoyl)-P,P-dipentafluorophenyl-phos-
phinimidic acid (HF20tpip) was prepared in two steps
(Scheme 1). Bromodipentafluorophenylphosphane was iso-
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Photochemistry
FULL PAPER
Table 1. Refinement and crystallographic data for complexes 1–7.
at a lower frequency in compar-
ison to Htpip, indicating that
the phosphorus is more shield-
1
2
3a
3b
formula
C73H4F60N3NdO7P6
296
C73H4F60N3O7P6S
296
m
73H4CEuF60N3 O7P6
C74H6EuF60N3O7P6
ed by the presence of the per- T [K]
293
296
system
space group
triclinic
trigonal
triclinic
P1
triclinic
P1
fluorinated aromatic groups.
¯
¯
¯
¯
P1
R3
The 19F NMR spectrum of
HF20tpip has three resonances
corresponding to the three
unique fluorine environments
in the ligand, with a ratio of
2:1:2 (Supporting Information)
a [Š]
b [Š]
c [Š]
a [8]
b [8]
g [8]
Z
14.6917(8)
15.2185(8)
20.6561(10)
88.497(4)
90.112(4)
64.491(4)
2
4166.3(4)
1.997
0.053
25.5464(6)
25.5464(6)
22.3700(6)
90.0
90.0
120.0
14.6815(12)
15.2316(12)
20.6436(18)
88.104(6)
89.913(5)
64.220(5)
2
14.6612(2)
15.2824(2)
20.6461(3)
87.993(1)
89.819(1)
64.605(1)
2
6
with characteristic 3J
(F,F) cou-
N
V [Š3]
12643.2(5)
1.961
0.063
4154.2(6)
2.009
4176.0(1)
2.009
plings of 20 Hz. In the 1calcd [gcmꢀ3
]
13C NMR spectrum three dou-
R1
0.057
0.113
wR2
0.137
0.151
0.139
0.305
ꢀ
blets for the three C F environ-
4
5
6
7
ments appear with the charac-
1
formula
T [K]
system
space group
a [Š]
b [Š]
c [Š]
a [8]
C72F60GdN3O6P6
298
monoclinic
P2/n
12.3581(3)
14.1063(2)
23.7628(4)
90.0
C72DyF60N3O6P6
296
C72ErF60N3O6P6
296
C72F60N3O6P6Yb
296
teristic 250 Hz J
A
while a doublet triplet is as-
signed to the carbon atom di-
monoclinic
P2/n
12.4095(11)
14.0521(10)
23.6822(16)
90.0
monoclinic
P2/n
triclinic
P1
¯
rectly bonded to the phospho-
12.4381(2)
13.9971(2)
23.6157(4)
90.0
90.679(1)
90.0
16.152(5)
16.149(5)
23.216(8)
86.262(10)
70.495(11)
60.111(9)
2
1
rus atoms with a 140 Hz J
(P,C)
coupling and two 2J
(C,F) cou-
A
plings of 18 Hz. The absorption
spectrum of HF20tpip in ethanol
shows an absorbance band at
b [8]
g [8]
90.645(1)
90.0
89.388(5)
90.0
Z
2
2
2
V [Š3]
1calcd [gcmꢀ3
R1
4142.2(2)
1.993
0.036
4129.5(5)
2.003
0.035
4111.1(1)
2.016
4911(3)
1.692
lmax =268 nm
(e=
3800 molꢀ1 dm3 cmꢀ1).
]
0.029
0.14
The lanthanide complexes of
wR2
0.092
0.093
0.076
0.31
HF20tpip
were
prepared
p–p contact occurs within a single complex unit between
rings separated by a distance of approximately 3–4 Š, al-
though they are not parallel (the dihedral angle is about
20.188). The arrangement of ligands leaves a gap on one
side of the complex, which accommodates a molecule of
methanol that is coordinated to the lanthanide cation
(Figure 2d). The contacts between neighbouring complex
units are mainly between the fluorine atoms, with some
slightly less than the combined van der Waals radii. For
Scheme 2.
ꢀ
(Scheme 2) by addition the desired lanthanide chloride into
a solution of the ligand in hot alcohol in a 1:3 ratio either in
the presence or absence of a base. We found that, unlike the
Htpip reactions, the presence of base did not make any dif-
ference in isolation of the complexes, due to the acidic
nature of the proton in HF20tpip.
The crystallographic data for the complexes (1–7) are
shown in Table 1. The seven complexes fall into four types
of structures as described below.
1, the Nd O distances are in the range 2.375(4)–
2.432(4) Š for the ligand and 2.469(5) for methanol. One
O=P···P=O torsion angle (1.40(1)8) is less than the other
two (9.59(1), 8.95(1)8). For 3a and 3b, the Eu O distan-
ces are in the range 2.330(4)–2.391(4) Š and 2.327(7)–
2.403(6) Š for the ligand and 2.433(5) and 2.398(10) for
the coordinated solvent, respectively.
ꢀ
2) The structure of Sm (2) complex consists of the molecu-
lar unit co-crystallised with methanol. The complex unit
has threefold symmetry and the oxygen atoms coordinate
to the cation in propeller-like or distorted trigonal anti-
1) In the structures of the Nd (1), and Eu (3a and 3b), the
cation coordination and crystal packing are similar. This
is reflected by the similar unit cell parameters (Table 1)
and the three complexes are shown in Figure 2a–c. Thus,
the details of just one will be described. In the structure
of 1, the Nd is coordinated by a methanol molecule in
addition to the three F20tpip ligands (Figure 2a). Close
ꢀ
prism geometry (Figure 3 top) with an Sm O distance of
2.329(4) Š. For the ligand, the O=P···P=O torsion angle
ꢀ
is ꢀ1.96(1)8. Within the cluster unit, all C6F5 units are
involved in edge–face interactions as either donor or ac-
ceptor. The occluded solvent does not coordinate to the
cation, but is contained in cylindrical cages formed by
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6311

Z. Pikramenou et al.
two molecular units linked
by edge-to-face interactions
along the c axis.
3) In the crystal, the complex
units for Gd (4), Dy (5) and
Er (6) cations have twofold
symmetry and are not sol-
vated Figure 4a–c. The three
complexes are isostructural
with similar unit cell param-
eters
and
symmetry
(Table 1). For the ligand, the
O=P···P=O angles are about
ꢀ0.4 and ꢀ128 within the
cluster and the coordination
around the metal is propel-
ler shaped with bonds in the
range
2.286(2)–2.290(2) Š
for Gd, 2.258(2)–2.263(2) Š
for Dy and 2.2315(16)–
2.241(15) Š for Er. The mo-
lecular units interact with
neighbours mainly through
F···F contacts, edge-to-face
interactions and interactions
of p–p type also occur (Fig-
ure 4d).
4) In the structure obtained for
7, the Yb ion is not coordi-
nated by solvent and has a
distorted octahedral geome-
Figure 2. The complexes of a) 1, b) 3a, c) 3b and d) a space filling representation of 1 with the methanol mole-
cule omitted to show the slot it occupies
ꢀ
try (Figure 5 top) with Yb
O distances in the range 2.18(2)–2.28(2) Š. For the
ligand, the O=P···P=O torsion angles are ꢀ0.3.37(3),
ꢀ3.35(3) and ꢀ4.29(3)8. In a manner similar to the struc-
ture of 2, complex units interact through edge-to-face
contacts to form stacks along the c axis (Figure 5
bottom). Cylindrical cages are also formed in this struc-
ture, but no solvent was found in this case. However, the
calculated density is very low when compared to the
structures of other complexes. This, combined with the
fact that the quality of data was low, suggests that there
is likely to be solvent, most likely disordered, in the
cages.
A detailed 19F and 31P NMR study of the [Ln
(F20tpip)3] com-
A
plexes (Ln=Y, Nd, Sm, Eu, Tb, Dy, Er, Yb) has been car-
ried out. A summary of the NMR data of the complexes is
given in Table 2.
The phosphorus atoms are the closest to the lanthanide
ion and consequently offer much useful information on the
properties of the [Ln(F20tpip)3] complexes. Upon coordina-
G
tion of F20tpip to YIII, the 31P resonance of the ligand moves
downfield from d=ꢀ9 to ꢀ3 ppm, indicative of the de-
shielding effect of the phosphorus atoms upon coordination
to the lanthanide ion. The 31P NMR spectra of the [Ln-
Figure 3. Top: The molecular unit of 2. Bottom: a pair of units enclosing
a solvent position.
A
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Chem. Eur. J. 2007, 13, 6308 – 6320

Photochemistry
FULL PAPER
The presence of three sets of
resonances for the twenty fluo-
rine atoms of each complex in-
dicates that all of the aromatic
rings are equivalent in solution.
III
In the NdIII, S m , EuIII and YIII
complexes the resonances are
sharp revealing 3J
(F,F) cou-
A
plings in the order of 20 Hz,
consistent with fluorine atoms
in aromatic compounds. The 19F
resonances observed in the
analogous TbIII, DyIII, ErIII and
YbIII complexes are broad, ob-
scuring their multiplicity, which
is an effect of the different lan-
thanide paramagnetism.
The 13C NMR spectrum of
[Sm(F20tpip)3] in [D6]acetone
A
allows complete assignments
with all the expected informa-
tion (Supporting Information).
Four distinct resonances are ob-
served that correspond to the
four unique carbon environ-
ments in the complex. The 1J-
(C,F) coupling of approximate-
ly 250 Hz splits the signals of
Figure 4. Complexes a) 4, b) 5, c) 6 and d) a pair of molecules with a p–p interaction for a pair of rings show-
ing overlap of 1/3 of a ring.
ꢀ
the three C F carbons into
three doublets. The signal for
the carbon atom directly
bonded to the phosphorus atom
1
2
the presence one phosphorus environment for the six phos-
phorus atoms of the complexes and confirm the equivalence
splits with a 144 Hz J
(P,C) coupling and two J
G
plings of 18 Hz to give a doublet–triplet pattern. In the rest
of the ligands. The 31P chemical shifts of [Ln
A
of the 13C NMR spectra of the [Ln
ACHTREUNG
divide into three groups with respect to the [Y
U
ited solubility hampered the observation of some signals, in
particular those of the quaternary carbons.
Steady-state luminescence studies of [Ln(F20tpip)3] in the
N
visible and NIR regions, in which Ln=Eu, Tb, Sm, Dy, Nd,
Er, Yb: Upon excitation of the ligand absorption band at
270 nm, characteristic narrow band red, green, pink and
the [Er
(F20tpip)3]. The shifts of the SmIII, TbIII, DyIII and
A
YbIII complexes remain similar to that of the YIII complex.
This can be explained by the paramagnetic shift being a
combination of the pseudocontact and contact shifts.[49,50] In
the NMR spectra of complexes of paramagnetic metal ions,
there are two main additive contributing interactions to the
chemical shifts of the ligand nuclei with the paramagnetic
nucleus: contact and pseudocontact. The contact shift for a
nucleus is determined by covalent bonding interactions
transferring unpaired electron density onto the ligand. This
effect is most pronounced with ligand nuclei that are very
close to the metal ion. The pseudocontact shift arises from
through space interaction of the unpaired electron and the
nuclear magnetic dipole.[49]
III
yellow emission is observed for the EuIII, TbIII, S m and
DyIII complexes, respectively (Figure 6). The emission pro-
files of [Ln(F20tpip)3] in acetonitrile closely resemble those
U
of the analogous tpip and Metpip complexes,[30] indicating a
similar coordination environment in solution. The emission
spectra of powder samples of the TbIII and DyIII complexes
also show intense emission with similar profiles, indicating
no major changes in the coordination environment of the
complexes between the solid state and solution. In the case
of the EuIII complex, a study of the single crystal allowed
7
observation of a further splitting on the 5D0! F2 hypersensi-
tive band, giving three bands centred at 609, 613 and
619 nm. The splitting of the band is a result of the low-sym-
metry environment around the metal ion (Figure 7). Howev-
er, in all the solutions of the visible-emitting lanthanides, we
The 19F spectra of the [Ln
(F20tpip)3] complexes are very
A
similar to each other, with the three resonances in a 2:1:2
ratio at similar chemical shifts (Supporting Information).
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Z. Pikramenou et al.
Figure 5. Top: complex 7. Bottom: a pair of molecules with the cage posi-
tion highlighted.
Figure 6. The corrected emission spectra of the visible emitting com-
plexes in acetontitrile, lexc =270 nm. Top: [Tb(F20tpip)3] (a) and [Dy-
N
7
A
-
4
6
Table 2. NMR data for [Ln(F20tpip)3] in [D6]acetone.
A
Bottom: [Sm
N
A
d (19F)
d (31P)
ꢀ3.2
4
6
-
5
7
3
based D0! FJ (J=0, 1, 2, 3, 4) transitions, respectively.
[Y
G
ꢀ133.6 (d, J
G
3
ꢀ148.3 (t, J
G
3
ꢀ162.1 (dd, J
3
[Nd
ꢀ133.7 (d, J
7.4
ꢀ3.7
3
ꢀ149.0 (t, J
(F,F)=20 Hz, 4F; p-Ar CF)
ꢀ162.3 (m, 8F; m-Ar CF)
3
[Sm
ꢀ133.5 (d, J
3
ꢀ148.8 (t, J
A
ꢀ162.2 (m, 8F; m-Ar CF)
3
[Eu
ꢀ132.9 (d, J
ꢀ39.4
ꢀ11.5
ꢀ3.1
3
ꢀ148.8 (t, J
(F,F)=20 Hz, 4F; p-Ar CF)
ꢀ162.2 (m, 8F; m-Ar CF)
ꢀ131.8 (br, 8F; o-Ar CF)
ꢀ149.2 (br, 4F; p-Ar CF)
ꢀ162.9 (br, 8F; m-Ar CF)
ꢀ129.7 (br, 8F; o-Ar CF)
ꢀ149.0 (br, 4F; p-Ar CF)
ꢀ162.5 (br, 8F; m-Ar CF)
ꢀ133.0 (br, 8F; o-Ar CF)
ꢀ148.0 (br, 4F; p-Ar CF)
ꢀ161.9 (br, 8F; m-Ar CF)
ꢀ134.6 (br, 8F; o-Ar CF)
ꢀ147.5 (br, 4F; p-Ar CF)
ꢀ161.9 (br, 8F; m-Ar CF)
[Tb(F20tpip)3]
A
[Dy(F20tpip)3]
G
[Er
A
ꢀ46.6
ꢀ0.26
[Yb(F20tpip)3]
A
Figure 7. Single crystal luminescence of [Eu(F20tpip)3], corrected for
PMT response, lexc =270 nm.
G
also observed a background fluorescence band at lmax
around 390 nm (Supporting Information). At the first in-
stance we attributed the band to ligand fluorescence (the
band is also present in the free ligand) as a result of incom-
plete energy transfer from the ligand to the lanthanide ion.
To confirm that the signal at 390 nm was due to the bound
6314
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Chem. Eur. J. 2007, 13, 6308 – 6320

Photochemistry
FULL PAPER
ligand and not free dissociated ligand, we examined the
excitation spectra of all three complexes show a band with
lmax =272 nm, in agreement with the absorption spectra cor-
responding to the ligand p–p* absorption band. The spectra
emission of [Eu(F20tpip)3] upon addition of H2O and D2O.
G
Were the F20tpip ligand to be bound to the lanthanide more
weakly than the tpip one (due to the withdrawing properties
of the twenty fluorine atoms) addition of water would influ-
ence the ligand dissociation process. Upon addition of H2O
there is decrease in the lanthanide signal; however, this de-
crease does not take place upon addition of D2O (Support-
ing Information). The relevant intensity ratio of the bands
remains constant. These results established the stability of
the complexes in the presence of water and further analysis
of the H2O/D2O effect is performed by time-resolved lumi-
nescence studies.
of [Eu
A
T
E
The photophysical properties of [Nd
A
A
ACHTREUNG
as in the solid state, have been explored. No ligand fluores-
cence could be observed at 700 nm. Excitation in the ligand-
centred band at 272 nm of the [Nd(F20tpip)3] complex results
A
in the typical lanthanide-centred emission of the trivalent
neodymium ion, showing three distinct peaks, corresponding
Figure 9. Excitation (solid line) and absorption (dotted line) spectra of
[Eu(F20tpip)3] in acetonitrile, lem =610 nm.
4
4
4
4
to the F3/2! I9/2 transition at 875 nm, the F3/2! I11/2 transi-
ACHTREUNG
4
4
tion at 1055 nm and the F3/2! I13/2 transition at 1325 nm
(Figure 8). The dominant band in this spectrum is the well-
and [Nd(F20tpip)3] (Supporting Information) are presented.
N
These results demonstrate that energy transfer takes place
from the pentafluorophenyl groups of the ligand to the lan-
thanide ion and that it is the dominant sensitisation pathway
for the visible and NIR emitting lanthanides.
The lanthanide emission quantum yields were found to be
0.1% for [Eu
A
G
N
and in the [Sm
AHCTREUNG
calculate a value. The signals were weak compared to the
reference compounds and this may attribute to big error
values in the measurements. The ligand-based emission of
isoabsorptive solutions of [Eu
tonitrile was monitored upon excitation at 270 nm. A de-
crease of ligand emission in [Eu(F20tpip)3] of around 40%
A
AHCTREUNG
indicates that the energy is transferred from the ligand to
the EuIII centre. However, the low quantum yields for [Eu-
Figure 8. Corrected emission spectrum of [Nd
(F20tpip)3] (dotted line) and [Yb(F20tpip)3] (dashed line) in dry acetoni-
trile, lexc =272 nm. Emission intensities are not to scale.
A
G
ACHTREUNG
A
ACHTREUNG
ACHTREUNG
AHCTREUNG
deactivation processes in the case of F20tpip complexes or to
a change of the triplet state level of the ligand. We have ex-
cluded the possibility of the presence of other ligand-to-
metal charge-transfer states that may provide deactivating
pathways due to the lack of any additional bands in the UV/
Vis absorption spectra and the fact that both Eu and Tb
with different redox properties seemed to be affected. We
have also excluded excimer formation based on dilution and
solvent effects. To determine the triplet state of F20tpip, we
4
4
known F3/2! I11/2 transition used in Nd/YAG laser applica-
tions. The emission spectrum of the [Er(F20tpip)3] complex
(Figure 8, dotted line) shows that the same sensitisation pro-
cess as discussed for the [Nd(F20tpip)3] complex is valid for
AHCTREUNG
AHCTREUNG
[Er
N
G
4I13/2! I15/2 transition at 1535 nm with some fine structure.
4
The emission spectrum of the [Yb(F20tpip)3] complex in dry
R
acetonitrile (Figure 8) contains one band corresponding to
2
2
the F5/2! F7/2 transition. This band is split into three com-
ponents, the strongest of which is centred at 970 nm, but
two weaker components can also be observed, one at
994 nm and another one at 1042 nm.
The excitation spectra of all complexes were recorded by
monitoring the strongest emission band in each case. The
examined the 77 K emission spectrum of the [Gd(F20tpip)3]
G
complex (Figure 10). To our surprise, two bands were ob-
served at 375 and 715 nm. These bands are also present at
the room-temperature emission of the [Gd
(F20tpip); however, in the spectrum of the latter the bands
are slightly blue shifted (at 360 and 700 nm) with the low-
A
ACHTREUNG
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6315

Z. Pikramenou et al.
nide, the effect of deuteration is much more pronounced
ꢀ
ꢀ
due to the replacement of C H bond oscillators with C D
oscillators. The difference in lifetime between acetone and
[D6]acetone coordination is more pronounced; the lifetime
is more than doubled for the [Eu
ACHTREUNG
creased by a factor of over three for [Dy
AHCTREUNG
ꢀ
ditional contributing factor is the higher number of C H vi-
brations in acetone than acetonitrile in close proximity to
the lanthanide centre. This is supported by the close proxim-
ity of solvent molecules in the crystal structure of [Eu-
A
N
does not include coordinated solvent molecules, there is
enough openness in the structure for coordination in solu-
Figure 10. The emission spectrum of [Gd(F20tpip)3] at 77 K, in MeOH/
EtOH 20:80, lexc =270 nm. *=scattered light.
A
ꢀ
tion. It is also likely that the presence of C H solvent bonds
in the outer coordination sphere of [Dy
A
a slightly larger quenching effect on the luminescence life-
time because of the smaller energy gap (ꢁ7,900 cmꢀ1),[55]
between the lowest excited state (4F9/2), and highest J
ground state (6F3/2), of the DyIII(aq) ion. The trend is not fol-
energy band being much smaller in intensity relative to the
high-energy band (Supporting Information). These results
would support the presence of a low-lying ligand-based state
which is responsible for an intraligand process that affects
the sensitisation of the visible lanthanide emission. The
high-energy band can be attributed to the singlet state of
the ligand, in agreement with previous reports on photo-
physical properties of fluorinated benzenes.[51] It is worth
noting that DFT calculations support an additional singlet
state for pentafluorobenzene with ps* character, lying lower
in energy than the pp* state.[51] In chloro- and bromoben-
zenes, dual phosphorescence has been observed at 400 and
500 nm assigned to the pp* and ps* states, respectively.[52]
The triplet state of fluorobenzenes is less well explored due
to the weak signal of emission and reports are limited on
studies of single-substituted fluorobenzene.[53,54] Based on
our results and the aforementioned reports we attribute the
low-energy ligand emission to a p-s* state.
lowed for [Tb(F20tpip)3], in which only a small increase in
A
lifetime in going from acetone to [D6]acetone is observed.
To calculate the number of coordinated solvent molecules[56]
we examined the effect of the luminescence lifetimes of
upon addition of H2O and D2O aliquots (Table 4).
Table 4. Luminescence lifetimes of the EuIII 5D0 level in [Eu
ACHTREUNG
and the TbIII 5D4 level in [Tb
ACHTREUNG
lexc =355 nm.
Solvent
t [ms]
[Eu
[Eu
[Eu
C
dry CH3CN
1.5
0.6
1.5
1.8
0.9
1.9
dry CH3CN + H2O[a]
dry CH3CN + D2O[a]
dry CH3CN
[Tb
[Tb
[Tb
ACHTREUNG
A
dry CH3CN + H2O[a]
dry CH3CN + D2O[a]
AHCTREUNG
[a] [H2O] and [D2O]=10 moldmꢀ3
.
Time-resolved luminescence studies of visible and NIR
emitting [Ln
ACHTREUNG
A
G
A
The application of Equation (1) to the lifetime values
(Table 4), in which q=number of coordinated solvent mole-
cules, A is a proportionality constant (AEu =1.05, ATb =4.2),
kH2O is the observed decay rate (msꢀ1) in an aqueous
sured in a variety of solvents, and are presented along with
their corresponding radiative rate constants in Table 3. All
CH3CN solution, and kCH CN is the observed decay rate
Table 3. Luminescence lifetimes in ms at room temperature of the EuIII
3
(msꢀ1) in dry CH3CN, gives values for [Eu
(F20tpip)3] and
G
(5D0), TbIII (5D4), and DyIII (4F9/2) levels in [Ln
(F20tpip)3], (Ln=Eu, Tb,
A
[Tb
A
Dy), and lexc =355 nm.
Acetonitrile [D3]Acetonitrile Acetone [D6]Acetone
q ¼ AðkH OꢀkCH CN
Þ
ð1Þ
2
3
[Eu
[Tb(F20tpip)3] 1.8
[Dy(F20tpip)3] 0.3
G
1.6
2.0
0.3
1.2
1.9
0.09
3.0
1.9
0.3
U
A modified version of Equation (1) has been proposed[57]
taking into account the quenching contribution by outer
sphere solvent molecules. The calculated values for [Eu-
lifetime traces can be fitted satisfactorily to a monoexponen-
tial decay profile. The lifetime of the SmIII complex could
not be obtained accurately due to the weakness of the
signal.
A
G
It is evident from these results that solvent coordination
affects the lifetime of the complexes. In the cases in which
the solvent molecules coordinate strongly with the lantha-
A
ACHTREUNG
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Chem. Eur. J. 2007, 13, 6308 – 6320

Photochemistry
FULL PAPER
values for the EuIII and TbIII are relatively large, 12300 and
ꢁ14800 cmꢀ1 respectively; hence, only high-energy vibra-
tional states of (solvent or ligand) bond oscillators will
match well and therefore be able to quench the lanthanide
excited state effectively. For this reason the effect in the life-
ꢀ
C F bonds. The fluorination of the shell was designed to
ꢀ
eliminate all high-energy C H bonds in the resultant com-
plexes, which would otherwise operate to deactivate f–f-
based lanthanide luminescence. Indeed the effect is more
pronounced in the case of NIR-emitting complexes.
ꢀ
Powders and solutions of [Nd
A
G
times is not pronounced in replacing C H vibrations in tpip
ꢀ
and [Yb(F20tpip)3] display long luminescence lifetimes
R
with C F in F20tpip Eu and Tb complexes. Conversely, the
(Table 5). All decay curves were monoexponential with
energy difference values for a group of lanthanides, which
includes NdIII (DEꢁ5500 cmꢀ1), SmIII (DEꢁ7400 cmꢀ1),
DyIII (DEꢁ7900 cmꢀ1), ErIII (DEꢁ6500 cmꢀ1) and YbIII (DE
ꢁ10000 cmꢀ1), are considerably smaller. For these lantha-
nides it is possible that low-energy vibrational states of bond
oscillators quench effectively the excited states. This is sup-
ported by our results in which the enhancement of lumines-
Table 5. Luminescence lifetimes t in ms of the NdIII (4F3/2), ErIII (4I13/2),
and YbIII (2F5/2) levels in [Ln(F20tpip)3], (Ln=Nd, Er, Yb).[a]
G
[Nd
G
[Er
G
powder
solution
46
44
316
741
cence lifetimes is so pronounced for [Dy
NIR-emitting complexes [Nd(F20tpip)3], [Er
[Yb(F20tpip)3], in contrast with the respective tpip com-
plexes.
ACHTREUNG
[a] All lifetimes are measured at room temperature, lexc =266 nm, c=
10ꢀ5 m. All samples were prepared under nitrogen atmosphere. CD3CN
was used as the solvent.
A
ACHTREUNG
AHCTREUNG
good fittings, which confirms the presence of a single spe-
ꢀ
cies. Deuterated acetonitrile was chosen to provide a C H
vibration-free environment around the lanthanide.
Conclusions
ꢀ
The observed NIR lifetimes represent a substantial and
unprecedented increase for Nd, Er or Yb coordination com-
pounds in solution and solid state. The highest value is ob-
We have demonstrated that aromatic C F substitution in an
imidodiphosphinate binding site leads to complexes with un-
paralleled photophysical behaviour in the NIR and visible
region. The HF20tpip ligand provides a ligand framework
served for the [Yb(F20tpip)3] complex and is more than half
A
the value of the radiative lifetime.[58] The increase in the lu-
minescence decay rate from solution to powder samples, ap-
parent for Er and Yb cases, is in agreement with our previ-
ous results in the case of tpip complexes.[29] We have attrib-
uted this to crystal lattice vibration or cross relaxation
mechanisms operational in solid state. The steep increase in
lifetimes from the tpip[29] to the F20tpip shells, indicates that
structure that leads to stable, luminescent [Ln(F20tpip)3]
complexes for all lanthanides and provides a ligand frame-
G
ꢀ
work, with no high-energy X H vibrations and aryl sensitis-
er groups, that is able to assemble in a shell arrangement
around the metal. The single-crystal structures of the com-
ꢀ
plexes show intermolecular F F interactions that may lead
to the design of new materials and exploration of new appli-
cations. The fluorinated shell formed about the lanthanide
ion is shown to allow solvent access on the lanthanide coor-
dination sphere, possibly due to the increased polarity of the
shell, in contrast with the non-fluorinated, hydrophobic tpip
complexes. All of the visible- and NIR-emitting complexes
show luminescence that is sensitised by the ligand p–p*
state, demonstrated by excitation spectroscopy. The
HF20tpip possesses a low-lying p–s* energy state that affects
its sensitiser properties, in particular in the case of the visi-
ꢀ
the C H vibrations in close proximity to the primary and
secondary sphere dramatically quench the NIR emission;
ꢀ
hence, replacement by C F is favourable for the emission
properties. The solution quantum yields for NIR-emitting
complexes can be estimated from F=t/tR to be 18% for
Nd, 5% for Er and 56% for Yb, in which tR =0.25 ms
(NdIII), 14 ms (ErIII) and 2 ms (YbIII).
The fluorinated imidodiphosphinate shell is effective for
protection of the lanthanide and has been shown to lead to
longer lifetimes of the NIR lanthanides than other deuteu-
rated or fluorinated ligands.
ble emitting complexes [Ln(F20tpip)3] Ln=Eu, Tb, Sm and
E
ꢀ
Dy. This effect is attributed to the multiple aromatic C F
In summary, it is clear that
the effect of the vibrational os-
ꢀ
cillations (aromatic C F vs C-
H) is different for each case of
a visible or NIR emitting lan-
thanide complex. The ability of
bond oscillations to efficiently
quench f–f transitions depends
primarily upon how closely the
emissive states of the lantha-
nide and the highest energy-
level state of the bond oscilla-
III
ꢀ
ꢀ
Scheme 3. Representation of the vibrational energy quanta of C H and C F bonds and the Ln low-lying
tors are matched. The DE energy electronic levels.
Chem. Eur. J. 2007, 13, 6308 – 6320
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www.chemeurj.org
6317

Z. Pikramenou et al.
Materials: Starting materials were of reagent grade, obtained from Al-
drich or Avocado, and used without further purification, unless otherwise
stated. Bromopentafluorobenzene (98%) was obtained from Avocado
substitution and has not been previously observed in visible-
emitting lanthanide complexes of fluorinated diketones. The
emission properties of the Dy complex are enhanced to a
greater extent in comparison with the rests of the visible
and dried with 4 Š molecular sieves prior to use. Lanthanide(III) chlor-
G
ides were obtained from Aldrich or Acros (99.9%) and used as received.
Deuterated solvents were obtained from Goss Scientific and used as re-
ceived. Anhydrous solvents, when required, were freshly distilled over
the appropriate drying agents under dinitrogen. Reactions requiring an-
hydrous conditions were performed under dinitrogen using standard
Schlenk and vacuum line techniques. For the photophysical studies
CH3CN was dried over P2O5 (5% w/v) and freshly distilled prior to use,
[D6]acetone, [D3]acetonitrile and acetone used in photophysical studies
were dried over 3 Š molecular sieves.
ꢀ
lanthanides by C F substitution. The ligand framework is
shown to be ideal for the NIR-emitting lanthanides. The
NIR-emitting complexes [Ln(F20tpip)3] with Ln=Nd, Yb
C
and Er show unprecedented long lifetimes that will un-
doubtedly lead to exciting application of NIR complexes in
imaging applications and luminescent materials. The [Yb-
A
Bromodipentafluorophenylphosphane: The preparation was carried out
in a N2 atmosphere in dry conditions. A solution of bromopentafluoro-
benzene (10.0 g, 5.05 mL, 40.5 mmol) in dry diethyl ether was added
dropwise to a suspension of Mg turnings (1.07 g, 44.0 mmol) in dry dieth-
yl ether (10 mL), at a rate to keep the solution under a gentle reflux. A
small crystal of iodine was used to initiate the reaction. The solution was
then heated under reflux for 2 h. The resulting dark brown solution was
transferred slowly through a canula to a solution of phosphorus tribro-
mide (1.7 mL, 4.7 g, 18.0 mmol) in dry diethyl ether (6 mL) on a salt-ice
bath. The solution was stirred for 1 h, after which anhydrous benzene
(30 mL) was added. The diethyl ether was removed under reduced pres-
sure giving a large amount of precipitate. The solution was filtered under
N2 and the benzene removed at reduced pressure giving a thick brown
liquid. The crude product was purified by distillation at 0.1 Torr with the
desired fraction coming over at 100–1048C to yield the desired product
as a thick golden oil (4.35 g, 9.8 mmol, 54%). 31P{1H} NMR (121 MHz,
CDCl3): d=12.8 ppm (quint, 3J (P,F)=36 Hz); 19F{1H} NMR (282 MHz,
than half the value of the radiative ion lifetime. The results
ꢀ
show that the elimination of high-energy X H vibrations in
the ligand structure and elimination of solvent coordination
are two factors particularly important for the yellow emis-
sion of Dy and the NIR emission of Nd, Yb and Er lantha-
nides.
Experimental Section
Equipment: 1H, 13C, 19F{1H} and 31P{1H} NMR spectra were recorded on
Bruker AC300, AV300, AV400 and DRX 500 spectrometers. Orthophos-
phoric acid was used as an external reference for 31P{1H} shifts, and
CCl3F was as the external reference for 19F shifts. Elemental analyses
were performed by the CHN microanalysis services at University of
London. Fast atom bombardment mass spectra (FAB MS) were mea-
sured on a VG ZabSpec machine by using a Cs neutral atom beam. Elec-
trospray mass spectra were recorded on a Micromass LC-TOF machine.
UV/Vis absorption spectra were recorded on a Shimadzu UV-3101PC
UV/Vis/NIR and Perkin–Elmer Lambda 17 spectrometers. All measure-
ments were carried out at room temperature (ꢁ208C) unless otherwise
stated. Luminescence experiments of the visible-emitting lanthanide com-
plexes were carried out on a Photon Technology Instruments emission
spectrometer previously described.[59] Emission spectra were corrected
for the PMT response. Excitation spectra were corrected for lamp re-
sponse. Lifetime spectra were carried out by using a Photon Technology
Instruments system equipped with Continuum Surelite SSP Nd-YAG
laser, using the 355 nm harmonic excitation light.[30] The data for the life-
time studies were recorded on a LeCroy 9350 AM 500 MHz oscilloscope,
as an average of 500 shots and analysed using a non-linear least-squares
iterative technique (Marquardt–Levenberg algorithm).
CDCl3): d=ꢀ127.9 (m, 4F; o-Ar CF), ꢀ146.2 (tt, 3J
A
4J
(F,F)=4 Hz, 2F; p-Ar CF), ꢀ159.1 ppm (m, 4F; m-Ar CF). In a previ-
ous publication the only spectroscopic analysis reported is 31P NMR spec-
trum, which agrees with our result.[44,62] Mass spectrometry was not at-
tempted due to the air and moisture sensitivity of the compound.
N-(P,P-Dipentafluorophinoyl)-P,P-dipentafluorophenylphosphinimidic
acid (HF20tpip): Hexamethyldisilazane (0.82 mL, 0.63 g, 3.9 mmol) was
added to
a solution of bromodipentafluorophenylphosphane (5.14 g,
11.6 mmol) in toluene (20 mL). The solution was heated under reflux for
5 h then the byproduct Me3SiBr removed by distillation. The resulting
brown solution was cooled on an ice bath for 10 min and hydrogen per-
oxide (1.1 g, 11.6 mmol, 35% in water) in THF (9 mL) was slowly added
dropwise. The contents of the flask were added to diethyl ether
(100 mL). The solution was filtered and the solvent removed. The crude
product was separated on silica 90 using hexane/ethyl acetate/acetic acid
(50:50:1) to give the product as a pale cream solid (0.98 g, 1.3 mmol,
33%). HF20tpip crystals were grown by slow evaporation of the chroma-
The steady-state luminescence spectra and the lifetime measurements in
the NIR were done on an Edinburgh Instruments FS920P near-infrared
spectrometer, with a 450W xenon lamp as the steady-state excitation
source, a double excitation monochromator with 1800 lines per mm, an
emission monochromator with 600 lines per mm and a liquid nitrogen
cooled Hamamatsu R5509–72 near infrared photomultiplier tube. For the
lifetime measurements, the setup includes a Nd/YAG laser, equipped
with 2nd, 3rd and 4th harmonic options (allowing laser excitation at 532,
355 and 266 nm, respectively). Repetition rate is 10 Hz, pulse width is 3–
5 ns. A maximum value of an error of 15% is estimated for all lifetime
measurements.
tography solutions. 31P{1H} NMR (121 MHz, [D6]acetone): d=ꢀ9.0 ppm
3
(s); 19F{1H} NMR (282 MHz, [D6]acetone): d=ꢀ134.8 (d, J
A
8F; o-Ar CF), ꢀ148.9 (t, 3J
(F,F)=20 Hz, 4F; p-Ar CF), ꢀ162.8 ppm (br,
N
3J(F,F)=21 Hz, 8F; m-Ar CF); 13C NMR (75 MHz, [D6]acetone): d=149
R
(d, 1J
139 (d, 1J
2J(C,F)=18 Hz, 4C; Cquat); accurate MS(EIS +): m/z: calcd for [M+
A
N
AHCTREUNG
AHCTREUNG
+Na]: 799.9061; found: 799.9066; UV/Vis (ethanol): lmax (loge)=268 nm
(3.6); elemental analysis calcd (%) for C24F20NO2P2H·1.5H2O: C 35.8, H
0.5, N 1.7; found: C 35.9, H 0.5, N 1.7.
Crystallographic data: C24HF20NO2P2·0.25
G
For the determination of X-ray crystal structures, intensity data were col-
lected on Brüker SMART 6000 diffractometers equipped with CCD de-
tectors using CuKa radiation l=1.54178 Š). The images were interpreted
and integrated with the program SAINT.[60] SHELX97 was used for solu-
tion and refinement.[61] The structures were solved by direct methods and
refined by full-matrix least-squares methods on F2. Non-hydrogen atoms
were refined anisotropically and the riding mode was used for hydrogen
atoms. CCDC-634236–634244 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_
request/cif.
rhombic, space group Pbcn, a=12.3361(4), b=22.0894(6), c=
21.9459(6) Š, V=5980.2(3) Š3, Z=8, 1calcd =1.774 gcmꢀ3, F
(000)=3124,
m=2.782 mmꢀ1, R1=0.0512 [2sF], wR=0.148 for 4142 independent re-
flections.
[Ln(F20tpip)3] with Ln=Y, Nd, Sm, Eu, Gd, Tb, Dy, Er, Yb: LnCl3·xH2O
A
(0.017 mmol, 1 equiv) in ethanol (2 mL) followed by a solution of potassi-
um hydroxide in methanol (0.17 mL, 0.017 mmol, 0.1m) were added to a
stirring solution of HF20tpip (40 mg, 0.052 mmol, 3 equiv) in hot ethanol.
The solution was heated under reflux for 1 h and allowed to cool to room
temperature. The resulting white precipitate was collected by filtration,
6318
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Chem. Eur. J. 2007, 13, 6308 – 6320

Photochemistry
FULL PAPER
washed with methanol, and then dried under vacuum to give the corre-
acknowledges a Research Grant of the Fund for Scientific Research—
Flanders (FWO; project 1.5.099.06).
sponding [Ln(F20tpip)3]. Typical yields 60–95%. Single crystals for X-ray
G
diffraction and solid-state luminescence studies were grown from solu-
tions of the complex in methanol with 10% acetone. The same prepara-
tion without the addition of bases was successfully attempted where Ln=
Y, Eu, Tb, Dy.
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Chem. Int. Ed. 2005, 44, 7954.
[2] S. Floquet, M. Borkovec, G. Bernardinelli, A. Pinto, L. A. Leuthold,
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[Y
N
[Nd
(F20tpip)3]: 31P{1H} NMR (121 MHz, [D6]acetone): d=7.4 ppm (s);
19F{1H} NMR (282 MHz, [D6]acetone): d=ꢀ133.7 (d, J=19 Hz, 8F; o-Ar
CF), ꢀ149.0 (t, J=20 Hz, 4F; p-Ar CF), ꢀ162.3 ppm (m, 8F; m-Ar CF);
MS(ES +): m/z: 2496 [M++Na]; UV/Vis (acetonitrile): lmax (loge)=
272 nm (4.1); elemental analysis calcd (%) for C72F60N3NdO6P6: C 35.0,
H 0.0, N 1.7; found: C 34.9, H 0.0, N 1.9.
[Sm
A
19F{1H} NMR (282 MHz, [D6]acetone): d=ꢀ133.5 (d, J
(F,F)=19 Hz, 8F;
o-Ar CF), ꢀ148.8 (t, 3J
(F,F)=20 Hz, 4F; p-Ar CF), ꢀ162.2 ppm (m, 8F;
ACHTREUNG
A
m-Ar CF); 13C NMR (75 MHz, [D6]acetone): d=149 (d, 1J
257 Hz; Ar CF), 146 (d, 1J
C
ACHTREUNG
C); MS(FAB +): m/z: 2480 [M++H], 1704 [M+ꢀC24F20NP2O2]; UV/Vis
(acetonitrile): lmax (loge)=272 nm (4.1); elemental analysis calcd (%) for
C72F60N3O6P6Sm: C 34.9, H 0.0, N 1.7; found: C 35.0, H 0.0, N 1.7.
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2005, 44, 6140.
[Eu
N
(F,F)=20 Hz, 8F;
o-Ar CF), ꢀ148.8 (t, 3J
(F,F)=20 Hz, 4F; p-Ar CF), ꢀ162.2 ppm (m, 8F;
E
m-Ar CF); MS(ESI +): m/z: 2496 [M++Na]; UV/Vis (acetonitrile): lmax
(loge)=272 nm (4.2); elemental analysis calcd (%) for C72EuF60N3O6P6:
C 34.9, H 0.0, N 1.7; found: C 35.1, H 0.0, N 1.8.
[Gd
(F20tpip)3]: MS(FAB +): m/z: 2509 [M++Na], 2487 [M++H], 1710
G
[M+ꢀC24F20NP2O2]; UV/Vis (acetonitrile): lmax (loge)=272 nm (4.1); el-
emental analysis calcd (%) for C72F60GdN3O6P6: C 34.8, H 0.0, N 1.7;
found: C 34.8, H 0.0, N 1.9.
[Tb
A
(brs); 19F{1H} NMR (282 MHz, [D6]acetone): d=ꢀ131.8 (br, 8F; o-Ar
CF), ꢀ149.2 (br, 4F; p-Ar CF), ꢀ162.9 ppm (br, 8F; m-Ar CF); MS
(ESI+): m/z: 2511 [M++Na]; UV/Vis (acetonitrile): lmax (loge)=272 nm
(4.1); elemental analysis calcd (%) for C72F60N3O6P6Tb: C 34.8, H 0.0, N
1.7; found: C 35.0, H 0.0, N 1.7.
[Dy
(F20tpip)3]: 31P{1H} NMR (121 MHz, [D6]acetone): d=ꢀ3.1 ppm
(brs); 19F{1H} NMR (282 MHz, [D6]acetone): d=ꢀ129.7 (br, 8F; o-Ar
CF), ꢀ149.0 (br, 4F; p-Ar CF), ꢀ162.5 ppm (br, 8F; m-Ar CF); MS
(FAB+): m/z: 2493 [M++H], 1716 [M+ꢀC24F20NP2O2]; UV/Vis (acetoni-
trile): lmax (loge)=272 nm (3.9); elemental analysis calcd (%) for
C72DyF60NO6P6: C 34.7, H 0.0, N 1.7; found: C 34.8, H 0.0, N 1.8.
[Er
A
(brs); 19F{1H} NMR (282 MHz, [D6]acetone): d=ꢀ133.0 (br, 8F; o-Ar
CF), ꢀ148.0 (br, 4F; p-Ar CF), ꢀ161.9 ppm (br, 8F; m-Ar CF); MS
(FAB+): m/z 2497 [M++H], 1720 [M+ꢀC24F20NP2O2]; UV/Vis (acetoni-
trile): lmax (loge)=272 nm (4.1); elemental analysis calcd (%) for
C72ErF60NO6P6: C 34.6, H 0.0, N 1.7; found: C 34.7, H 0.0, N 1.6.
[Yb
(F20tpip)3]: 31P{1H} NMR (121 MHz, [D6]acetone): d=ꢀ0.26 ppm
(brs); 19F{1H} NMR (282 MHz, [D6]acetone): d=ꢀ134.6 (br, 8F; o-Ar
CF), ꢀ147.5 (br, 4F; p-Ar CF), ꢀ161.9 ppm (br, 8F; m-Ar CF); MS
(FAB+): m/z 2502 [M+]; UV/Vis (acetonitrile): lmax (loge)=272 nm
(4.1); elemental analysis calcd (%) for C72F60NO6P6Yb: C 34.5, H 0.0, N
1.7; found: C 34.6, H 0.0, N 1.9.
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Acknowledgement
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We wish to thank EPSRC and the University of Birmingham for support.
R.V.D. is a postdoctoral fellow of the FWO-Flanders and he gratefully
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Received: January 19, 2007
Published online: June 15, 2007
6320
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Chem. Eur. J. 2007, 13, 6308 – 6320