M. Mazzanti et al.
system is also particularly well suited for the self-assembly
of larger cluster structures by using template cations,[19] and
work in this direction is in progress.
Experimental Section
Synthesis of [Eu((S)-Phbipox)2]OTf: Triethylamine (20.2 mL) was added
to a solution of (S)-Phbipox (50 mg 0.145 mmol) in anhydrous methanol
(2 mL). The resulting solution was stirred for 2 h and a solution of Eu-
Figure 6. Molecular models built from the structures of the D and L in 4
showing the sterical constraints preventing the formation of the hetero-
chiral trinuclear complexes [(LLL)-{Eu((S)-Phbipox)2}3]+3 (created by
using the MERCURY 2.2 program).
ACHTUNGRTEN(NUGN OTf)3 (0.0725 mmol) in methanol (1 mL) was then added. The resulting
solution was stirred at room temperature for an hour. Diisopropylether
was then added to afford a white microcrystalline solid precipitate that
was filtered and dried for two weeks at 408C under vacuum (87% yield).
1H NMR for the (L)-[Eu((S)-Phbipox)2]+ species (500 MHz, CD3CN,
À108C): d=0.45 (0.4H, brt; Hc), 3.42 (0.4H, brt; Ha), 2.71(0.4H, brt;
Hb), 6.07 (0.4H, brd; H6), 6.21(0.8H, brs; Hd), 6.50 (0.4H, brs; H3), 7.21
(0.8H, brs; He), 7.42 (0.4H, brd; H2), 7.50 (0.4H, brt; Hf), 7.95 (0.4H,
brd; H1), 8.72 (0.4H, brt; H5), 8.50 (0.4H, d, J=5.7 Hz; H4); 1H NMR
in methanol with excitation at 279 and 340 nm varied be-
tween 20(2) and 28(1)% depending of the concentration
used (6–7 mm). Circularly polarised luminescence studies
+3
for the (DDD)-[Eu((S)-Phbipox)2]3 species (500 MHz, CD3CN, À108C):
*: À25.18 (1H, brt; Hc), À7.83 (1H, brd; H6), À5.92 (1H, brt; Hb), 1.53
(1H, brt; Ha), 3.99 (1H, brt; H5), 6.34 (1H, d, J=6.6 Hz; H3), 7.42 (1H,
brd; H4), 9.54 (1H, brt; Hf), 10.24 (2H, brt; He), 11.12 (1H, brt; H2),
11.35 (1H, d, J=6.1 Hz; H2), 13.57 (2H, brs; Hd); &:À14.21 (1H, brt;
Hc), 0.33 (1H, brt; Hb), 2.15 (1H, brd; H3), 3.28 (1H, brt; H2), 6.50(1H,
brs; Ha), 8.07 (1H, d, J=7.9 Hz; H4), 89.54 (2H, brt; H5), 9.83 (3H, brt,
H1; He), 10.37 (2H, brs; Hd), 10.68 (1H, brt; Hf), 19.78 (1H, brs; H6);
MS (ES+) CD3OD: m/z=841.1 [Eu((S)-Phbipox)2]+; MS (ES+) CD3CN:
ACTHNUTRGNEUNG
m/z=841.3 [Eu((S)-Phbipox)2]+, 335 [{Eu3((S)-Phbipox)6}(OTf)]2+; ele-
mental analysis calcd (%) for [Eu((S)-Phbipox)2]OTf·1.26Et3NOTf3
(C49.82H46.9N7.26O12.78F6.78S2.26Eu, Mw =1305.23): C 45.85, H 3.32, N 7.89;
found: C 45.85, H 3.62, N 7.79;
Crystal data for 4: C172.50H148Eu4F12N24O45.50S4; Mr =4249.23; crystal size=
0.20ꢃ0.15ꢃ0.15 mm3; orthorhombic; space group P212121; a=
17.3481(10), b=32.1765(15), c=32.4386(12) ꢂ; a=b=g=908; V=
18107.3(15) ꢂ3; Z=4; 1calcd =1.559 mgmÀ3
;
m=1.510 mmÀ1
;
l=
0.71073 ꢂ; T=150 (2) K; 3.028<2qmax<23.258; 42715 reflections col-
lected; 25589 unique reflections (Rint =0.0459); R1 =0.05031, wR2 =
0.1001 [I>2s(I)]; R1 =0.0806, wR2 =0.1058 (all data); residual electron
density=1.515 eAÀ3
.
CCDC-763804 contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge
The figure graphics were generated by using the MERCURY 2.2 pro-
gram supplied with the Cambridge Structural Database.[22] Further exper-
imental details, including ligand synthesis, X-ray crystallography and
mass spectroscopy are given in the Supporting Information.
Figure 7. Normalised emission spectra of [Eu((S)-Phbipox)2]OTf at
a) 7 mm in CD3OD, b) 7 mm in CH3CN, c) 26 mm in CH3CN.
will be carried out in future work to investigate the influ-
ence of the concentration and of chirality on the photophys-
ical properties.[23]
Acknowledgements
In summary, we have reported a rare enantiopure trinu-
clear europium complex obtained in a novel concentration-
dependent self-assembly process promoted by a new (S)-
PhbipoxÀ ligand. We have shown that selective homochiral
recognition occurs, probably as a result of sterical interac-
tion, during the self-assembly of the bis-ligand monomeric
complexes to yield the final trinuclear species. Some selec-
tivity was also found in the self-assembly of the two ligands
around the europium centre to afford the L and D mono-
meric isomers.
This research was carried out in the frame of the EC COST Action D-38
“Metal-Based Systems for Molecular Imaging Applications”. We thank
Lydia Ouadah for ligand synthesis, Colette Lebrun and Pierre A. Bayle
for their help with the spectroscopic characterisations.
Keywords: chirality · cluster compounds · lanthanides ·
luminescence · N,O ligands · self-assembly
Future studies will be directed to tune the ligand bulk and
cation size with the objective of increasing the stereoselec-
tivity of the self-assembly of the monomeric complex. This
[2] S. Faulkner, J. L. Matthews, Comprehensive Coordination Chemistry
II, Vol. 9, Elsevier, Oxford, 2004.
6162
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 6159 – 6163