Tetranuclear NIR luminescent Schiff-base Zn-Nd complexes

Article abstract of DOI:10.1039/b710204f

With the simple dinuclear Zn-Nd complex [ZnNdL(H₂O)(NO ₃)₃] (1) (H₂L = N,N′-bis(3- methoxysalicylidene)ethylene-1,2-diamine) as the precursor, tetranuclear [Zn₂Nd₂L₂(4,4′-bpy)(NO₃) ₆]·Et₂O (2) and [Zn₂Nd₂L ₂(4,4′-bpe)]·2H₂O (3) (4,4′-bpy = 4,4′-bipyridine, 4,4′-bpe = trans-bis(4-pyridyl)ethylene) complexes are formed: suitable choice of bidentate linkers could construct multinuclear heterometallic 3d-4f Schiff-base complexes with improved luminescent properties, and the controlling of linker character shows a potentially effective way to the fine-tuning properties of NIR luminescence from Nd ions. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/b710204f

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Tetranuclear NIR luminescent Schiff-base Zn–Nd complexesw
Xingqiang Lu
Wai-Yeung Wong, Wai-Kwok Wong* and Richard A. Jones
¨
,*ab Weiyu Bi, Wenli Chai, Jirong Song, Jianxin Meng,
a
a
a
b
b
b
c
Received (in Gainesville, FL, USA) 4th July 2007, Accepted 29th August 2007
First published as an Advance Article on the web 7th September 2007
DOI: 10.1039/b710204f
0
With the simple dinuclear Zn–Nd complex [ZnNdL(H O)(NO ) ] (1) (H L = N,N -bis-
2
3 3
2
(
3-methoxysalicylidene)ethylene-1,2-diamine) as the precursor, tetranuclear [Zn Nd L -
2 2 2
0
0
0
0
(
4,4 -bpy)(NO ) ] ꢀ Et O (2) and [Zn Nd L (4,4 -bpe)] ꢀ 2H O (3) (4,4 -bpy = 4,4 -bipyridine,
3
6
2
2
2
2
2
0
4
,4 -bpe = trans-bis(4-pyridyl)ethylene) complexes are formed: suitable choice of bidentate linkers
could construct multinuclear heterometallic 3d–4f Schiff-base complexes with improved
luminescent properties, and the controlling of linker character shows a potentially effective way to
the fine-tuning properties of NIR luminescence from Nd ions.
1
2c
multinuclear 3d–4f complexes.
It is noticeable that in the
Introduction
above 3d–4f heterometallic complexes, the axial position of the
Much recent effort has been devoted to luminescent lanthanide
ꢁ
12a,f
ꢁ 12c,e
ꢁ
or NO
3
3
12e,g
d ions was occupied by anions (OAc ,
Cl
solvates from different reaction conditions,
which may lead to partial luminescent quenching with OH
solvates such as EtOH or H O around the 4f ions. If replaced
(
Ln) complexes with long-lived and characteristic line like
1
emission bands (near UV to visible and NIR regions),
12b,e,g
)
2
or H O
2
because of their potential applications in bioassays, medicine
3
2
4
and materials science. The limit of low absorption coefficients
due to the parity forbidden f–f transitions for these lanthanide
by axial groups with rigid multidentate linkers of stronger
coordination ability, polynuclear 3d–4f complexes should be
obtained, which could effectively extend the electronic con-
jugation of the whole molecule, and endow multi-chromo-
phores to increase the rate of the energy-transfer process,
leading to better luminescent properties than that of the
dinuclear complexes. Herein, with the simple dinuclear Zn–Nd
5
ions, has led to considerable exploration of suitable chromo-
6
phores, with intense and tunable absorption maxima in the
visible region, to act as sensitizers of luminescence from
lanthanides in complex systems. Several recent investigations
7
have focused on organic dyes and d-block metal complexes
8
9
10
11
(
i.e. Cr(III), Ru(II), Pt(II), Re(I) or Os(II) ), which display
2 3 3
complex [ZnNdL(H O)(NO ) ] (1) as the precursor, we report
absorption bands in the near-UV or visible ranges, and have
been demonstrated to effectively transfer energy to the lantha-
nide ions indirectly.
the syntheses, structures and photophysical properties of
0
two Zn–Nd tetranuclear complexes [Zn
0
2
Nd
2
L
2
(4,4 -bpy)-
(
NO
3
)
6
] ꢀ Et
2
O (2) and [Zn
2
Nd
2
L
2
(4,4 -bpe)] ꢀ 2H
2
O (3), which
1
2
Our past research has focused on the use of compart-
mental salen-type Schiff-base ligands, to bind both 3d Zn(II)
and 4f Nd(III), Yb(III) or Er(III) ions. These heterometallic
systems, as suitable chromophores, can act as antennae or
sensitizers for NIR lanthanide luminescence, and the p-con-
jugation of those salen-type Schiff-base ligands helps to en-
hance luminescent properties. In the view of fine-tuning of
their NIR properties, three effective routes are adopted: (1)
change of spacers or (2) electronic properties of the substitu-
ents on the flanking phenyl rings of the Schiff-base ligands to
0
0
are formed from different bidentate (4,4 -bpy or 4,4 -bpe)
linkers to connect with the two Zn–Nd salen-type Schiff-base
architecture units on the axial positions of Zn ions; and their
NIR luminescent characteristics can be effectively fine-tuned
as a function of the linkage.
Results and discussion
NMR
1
2g
extend the conjugation of the complexes,
and (3) of the
As shown in Scheme 1, reaction of an equimolar amount of
H L, Zn(OAc) ꢀ 2H O and Nd(NO ) ꢀ 6H O in absolute etha-
functional bridge from OH to other anionic groups, to obtain
2
2
2
3 3
2
nol afforded dinuclear precursor 1 in a good yield of ca. 80%.
0
Further reaction of 1 with the second 4,4 -bipyridyl ligand
0 0
a
Department of Chemical Engineering, Shaanxi Key Laboratory of
4
,4 -bpy or 4,4 -bpe in 2 : 1 ratio in DMF–EtOH resulted in
Physico-inorganic Chemistry, Northwest University, Xi’an 710069
Shaanxi, China. E-mail: lvxq@nwu.edu.cn
Department of Chemistry, Hong Kong Baptist University, Waterloo
the formation of tetranuclear 2 or 3, respectively.
b
Unchanged NMR spectroscopic results (as shown in ESI,w
Road, Kowloon Tong, Hong Kong, China. E-mail:
wkwong@hkbu.edu.hk
Department of Chemistry and Biochemistry, The University of Texas
3
Fig. 1s) reveals that complexes 1–3 are stable in CD OD
1
c
solution at room temperature for up to one month. The H
NMR spectra of 2 or 3 show large shifts (d from 14.22 to
ꢁ6.70 ppm for 2, 14.31 to ꢁ7.87 ppm for 3) of the resonances
to high fields in the neodymium compounds due to the
lanthanide-induced shift. Two down-field signals (d 14.22
and 13.25 ppm for 2; d 14.31 and 13.27 ppm for 3) are assigned
at Austin, 1 University Station A5300, Austin, 78712-0165, TXUSA
w Electronic supplementary information (ESI) available: Table 1s:
˚
Interatomic distances (A) and bond angles (1) with esds for complexes
1
and 3. Fig. 1s: H NMR spectra of complexes 1–3 in CD
2
3
OD at
room temperature. Fig. 2s: View of the stacking of 2. Fig. 3s: View of
the stacking of 3. See DOI: 10.1039/b710204f
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New J. Chem., 2008, 32, 127–131 | 127

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˚
in 2 and 3 are 3.544(2) and 3.581(2) A, respectively, slightly
1
2
longer than those of previous Zn–Nd Schiff-base complexes,
in which the apical position of Zn ions was occupied by
ꢁ
ꢁ
O atoms from solvates (H O) or anions (OAc or NO3 ),
2
0
instead of N atoms from the 4,4 -bipyridyl ligands in
complexes 2 and 3.
0
0
The change of 4,4 -bipyridyl linker length from 4,4 -bpy to
0
4
,4 -bpe leads to a significant change of the conjugation
extension in the two tetranuclear complexes. In 2, the Znꢀ ꢀ ꢀZn
0
˚
separation from bridged 4,4 -bpy is 11.221(2) A, and as shown
in ESI,w Fig. 2s, no appreciable aromatic p–p stacking inter-
actions are present, though various complementary inter-
molecular C–Hꢀ ꢀ ꢀO (C11–H11ꢀ ꢀ ꢀO13 and C20–H20ꢀ ꢀ ꢀO8)
hydrogen bonds were generated to lead to the formation
of a multi-dimensional hydrogen bonded framework. For 3,
Scheme 1 Controlled design of tetranuclear heterometallic 3d–4f
complexes.
0
The existence of CQC of 4,4 -bpe endows extended electronic
conjugation of the tetranuclear molecule system, and increases
to the pyridyl protons of complexed linkers, shifted down-field
0
˚
relatively compared with free 4,4 -bpy (d 7.82 and 8.69 ppm)
the distance of the Znꢀ ꢀ ꢀZn separation (13.295(2) A).
0
or 4,4 -bpe (d 7.48, 7.73 and 8.74 ppm). The signals of the
A detailed examination of the crystal packing of 3 revealed
˚
coordinated ligand (d from 11.77 to ꢁ5.36 ppm for 2 and d
weak aromatic p–p stacking (3.751(5) A), which
from 11.77 to ꢁ5.17 ppm for 3) are significantly spread relative
together with complementary intermolecular C–Hꢀ ꢀ ꢀO
(C11–H11ꢀ ꢀ ꢀO7) hydrogen bonds (as shown in ESI,w Fig.
3s), cause the close stacking of the multi-dimensional network.
The solvate molecules of 2 and 3 are not bound to the
framework and they exhibit no observable interactions with
the host structure.
to those of the free H L Schiff base (d from 8.42 to 3.82 ppm)
2
and in diamagnetic 1 (d from 11.72 to ꢁ5.07 ppm).
Crystallography
The X-ray crystal structure analysis unambiguously revealed
the tetranuclear 3d–4f structures for complexes 2 and 3. Fig. 1
and 2 show the molecular structure of 2 or 3 in the asymmetric
unit: two independent dimers lie about the inversion center,
Photophysical properties
The UV-Vis absorption spectra of complexes 1–3 in MeOH
solution at room temperature are shown in Fig. 3. Similar
ligand-centered solution absorption spectra (204, 228, 271 and
348 nm) are observed, red-shifted upon coordination to
the metal ions compared with that (226, 248 and 337 nm) of
0
0
0
and one 4,4 -bipyridyl linker (4,4 -bpy for 2, 4,4 -bpe for 3)
bridges the two Zn ions. Each Zn(II) ion lies in a five-
coordinate environment and adopts a distorted square pyra-
midal geometry, where the inner N
2 2
O core from the Schiff-
base H L ligand comprises the basal plane, and one N atom
2
2
the free Schiff-base ligand H L. The smaller molar absorption
0
from the 4,4 -bipyridyl ligand occupies the apical position.
Each Nd(III) ion is ten-coordinated, composed of the outer
O O cavity of the Schiff-base H L ligand and six O atoms
coefficients of complex 2 in the same condition (solvent and
concentration), should be attributed to the larger p-system
of complex 3. At room temperature in MeOH solution, the
emission spectra of complexes 1–3 are shown in Fig. 4:
2
2
2
from three bidentate nitrate anions. The average length of
Zn–O (phenolic), Nd–O (phenolic, methoxy or nitrate) or
Zn–N bonds (as shown in ESI,w Table 1s) is in the normal
range and comparable to those of other dinuclear Zn–Nd
3
+
the typical NIR emission bands of Nd
(4F3/2 - 4IJ/2,
J = 9, 11, 13), show no shifts but obvious differences of
relative intensity. The emissions at 863 nm must be assigned
to the 4F3/2 - 4I9/2, 1060 nm to 4F3/2 - 4I11/2 and 1328 nm to
1
2a,g
Schiff-base complexes.
The Zn–Nd distances of each dimer
Fig. 1 Perspective drawing of compound 2; H atoms and solvates are omitted for clarity.
1
28 | New J. Chem., 2008, 32, 127–131
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Fig. 2 Perspective drawing of compound 3; H atoms and solvates are omitted for clarity.
3
+
4
F
3/2 - 4I13/2 transition of Nd . Due to the limitation of
nuclearity species (Zn Nd
2
2
)
with two chromophores
our equipment, the excitation spectra and the NIR lumines-
1
cent lifetime could not be measured. The free H L ligand,
could effectively increase the luminescent properties of their
complexes. Moreover, the route to multinuclear formation,
completely avoids luminescent quenching from OH-
2
0
4
,4 -bipyridyl linkers and Nd(NO3)3 do not exhibit
1
2c
NIR luminescence under the same conditions, and the
ligand-centered fluorescence of complexes 1–3 in the
visible region is almost quenched in solution at room tem-
perature, which suggests that the energy transfer from the
antenna (3d Zn complexes) to lanthanide ions takes place
containing bridges or solvents. Especially for the superior
luminescent complexes 2 and 3, the function of the linkers
at the axial position of Zn ions endows the adjustment
of whole conjugation extension to some extent, which should
1
4
be due to the larger size of spectral overlap between the
same broad ligand-centered emission spectra (donor) and
the Nd-centered narrow line absorption spectrum (acceptor),
and may be a new way to make better use of fine-tuning
sensitizers to lanthanide ions. With respect to their lumines-
cent properties in the solid state, similar NIR emission
spectra are observed, and well resemble their characteristics
in dilute solution. Differences of relative intensities of
complexes 1–3 in the solid state from those in solution, further
demonstrates that the directional close stacking of crystal
molecules has a significant effect on their luminescence besides
high nuclearity.
1
3
efficiently.
It is noteworthy that the relative intensities of the
three compound transitions are structured, both in dilute
MeOH solution and in the solid state. In solution, almost
identical NIR emission spectra were obtained, and the relative
emission intensities of complexes 2 or 3 at 1060 nm were ca. 1.6
or 2.6 times to that of the dinuclear Zn–Nd precursor 1, and
ca. 1.3 or 1.7 times to that of the pyridine adduct of 1,
when compared the relative intensity using solutions with
their concentrations adjusted to give the same absorbance
values at 337 nm, which indicates that the emission
should result from the Zn–Nd bimetallic species, and higher
Fig. 4 NIR emission spectra of 1 (solid line), 2 (dotted line) and 3
ꢁ5
Fig. 3 UV-Vis spectra of 1 (solid line), 2 (dotted line) and 3 (dashed
ꢁ
(dash-dot-dot line) in MeOH solution at 2 ꢃ 10
M at room
5
line) in MeOH solution at 2 ꢃ 10 M at room temperature.
temperature.
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1
65.58; H, 6.06; N, 8.63%. H NMR (270 MHz, CD
Conclusion
3
OD): d
(
ppm) 8.42 (2H), 6.91 (4H), 6.71 (2H), 3.96 (4H), 3.82 (6H).
0
In conclusion, suitable choice of 4,4 -bipyridyl linkers re-
2
placing axial bound H
+
2
O solvates of 3d Zn
ions from the
dinuclear precursor could construct tetranuclear heterometal-
lic Zn–Nd complexes, with extended molecular conjugation,
and more chromophores, leading to better luminescent pro-
perties than those of dinuclear complexes. The controlling of
function from the linkage shows a potentially effective way to
the fine-tuning of luminescent properties in 3d–4f Schiff-base
coordination complexes in the future.
[ZnNdL(H
(0.033 g, 0.10 mmol) in absolute ethanol (5 ml),
Zn(OAc) O (0.022 g, 0.10 mmol) was added and heated
ꢀ 2H
under reflux for 5 h. A solution of Nd(NO O (0.044 g,
2 3 3 2
O)(NO ) ] (1). To a stirred suspension of H L
2
2
)
3
ꢀ 6H
3
2
0.10 mmol) in absolute ethanol (2 ml) was then added and the
mixture was refluxed for another 3 h. The clear yellow solution
was then cooled to room temperature and volatile materials
were removed under reduced pressure to give the product in
ca. 77% yield. Calc. for C18
N, 9.46%. Found: C, 28.38; H, 2.66; N, 9.33%. H NMR (270
MHz, CD OD): d (ppm) 11.72 (1H), 9.41 (1H), 8.35 (1H), 8.02
20 14 5
H O N ZnNd: C, 29.22; H, 2.72;
1
Experimental
3
All chemicals were commercial products of reagent grade and
were used without further purification. Elemental analyses
were performed on a Perkin-Elmer 240C elemental analyzer.
Infrared spectra were recorded on a Nicolet Nagna-IR 550
(1H), 7.91 (1H), 7.70 (1H), 3.85 (1H), 3.64 (1H), 2.99 (1H),
2.85 (1H), 1.15 (3H), 0.29 (1H), ꢁ3.45 (1H), ꢁ5.17 (3H). IR
ꢁ
1
(KBr, cm ): 3422 (br), 2933 (w), 1635 (s), 1607 (m), 1457 (vs),
1386 (m), 1344 (s), 1281 (vs), 1220 (m), 1074 (m), 1030 (m), 966
(m), 855 (w), 785 (w), 737 (m), 639 (w).
ꢁ
1
spectrophotometer in the region 4000–400 cm using KBr
1
pellets. H NMR spectra were recorded on a JEOL EX270
3
spectrometer in CD OD at room temperature. Electronic
0
.
Zn L Nd (4,4 -bpy)(NO ) ] Et O (2). To a solution of 1
2 2 2 3 6 2
[
absorption spectra in the UV/Vis region were recorded with
a Hewlett Packard 8453 UV/Vis spectrophotometer, and
steady-state visible fluorescence on a pico-N2 laser system
0
(
74 mg, 0.10 mmol) in absolute ethanol (4 ml) was added 4,4 -
bpy (7.8 mg, 0.05 mmol) and the mixture was refluxed for 2 h.
Then 2 ml absolute DMF was added to give a clear yellow
solution. Diethyl ether was allowed to diffuse slowly into this
solution at room temperature and pale yellow single crystals
were obtained in three weeks. Yield: 46 mg (55%). Calc. for
(
PLT Time Master) with lex = 337 nm. NIR emission was
detected by a liquid-nitrogen cooled INSb IR detector (EG &
G) with a preamplifier and recorded by a lock-in amplifier
system. The third harmonic, 355 nm line of a Nd-YAG laser
C
50
H
49
N
12
O
27Zn
2
Nd
2
: C, 35.98; H, 2.96; N, 10.07%. Found:
(
Quantel Brilliant B), was used as the excitation light source.
1
C, 38.13; H, 3.05; N, 9.96%. H NMR (270 MHz, CD
3
OD): d
ppm) 14.22 (1H), 13.25 (1H), 11.77 (1H), 10.60 (1H), 8.91
1H), 8.23 (1H), 8.01 (1H), 7.96 (1H), 7.90 (1H), 4.64 (1H),
(
(
Syntheses
0
H L: N,N -bis(3-methoxysalicylidene)ethylene-1,2-diamine.
2
3.61 (1H), 3.35 (1H) 2.99 (1H), 2.85 (1H), 2.71 (1H), 1.19 (3H),
Schiff base H L was obtained from o-vanilin (6.3 g, 40 mmol)
2
0.20 (1H), ꢁ0.42 (1H), ꢁ1.40 (1H), ꢁ3.56 (1H), ꢁ5.36 (3H),
ꢁ
1
and 1,2-diaminoethane (1.4 ml, 20 mmol) according to a well-
1
ꢁ6.70 (1H). IR (KBr, cm ): 3435 (w), 2939 (w), 1638 (s), 1610
(m), 1461 (vs), 1392 (m), 1318 (s), 1277 (vs), 1218 (s), 1074 (m),
1030 (m), 958 (w), 849 (w), 820 (w), 737 (m), 639 (w).
5
established procedure from the literature. Yield: 5.0 g, 76%.
Calc. for C18 : C, 65.84; H, 6.14; N, 8.53%. Found: C,
20 4 2
H O N
Table 1 Crystal data and refinement for complexes 2 and 3
Compound
2
3
Empirical formula
M
C
50
H
49
1669.23
N
12Nd
2
O
27Zn
2
48 50 2 2
C H N12Nd O28Zn
1662.22
Triclinic
Crystal system
Space group
Triclinic
ꢀ
ꢀ
P1 (no. 2)
9.5651(5)
10.5104(6)
16.2462(9)
77.6550(10)
80.6800(10)
74.2530(10)
1527.92(15)
1
P1 (no. 2)
9.1671(14)
10.4152(16)
16.667(3)
92.882(3)
100.841(3)
104.315(3)
1506.5(4)
1
˚
a/A
˚
b/A
˚
c/A
a/1
b/1
g/1
3
˚
V/A
Z
D
ꢁ3
c
/g cm
1.814
0.31 ꢃ 0.25 ꢃ 0.21
1.832
0.35 ꢃ 0.31 ꢃ 0.23
Crystal size/mm
m(Mo-Ka)/mm
T/K
ꢁ1
2.542
293(2)
2.579
293(2)
Data/restraints/parameters
Quality-of-fit indicator
6658/0/422
1.028
6121/0/415
0.948
Final R indices [I 4 2s(I)]
R
wR
1
= 0.0256
= 0.0680
= 0.0281
= 0.0690
R
wR
2
R
1
1
= 0.0595
= 0.1322
= 0.1145
2
wR = 0.1600
2
R indices (all data)
R
1
wR
2
1
30 | New J. Chem., 2008, 32, 127–131
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0
.
] 2H
[
Zn
2
L
2
Nd
2
(4,4 -bpe)(NO
3
)
6
2
O (3). To a solution of 1
0
4 (a) A. Beeby, R. S. Dickins, S. Faulkner, D. Parker and J. A. G.
Williams, Chem. Commun., 1997, 1401; (b) S. I. Klink, G. A.
Hebbink, L. Grave, F. C. J. M. van Veggel, D. N. Reinhoudt, L.
H. Slooff, A. Polman and J. W. Hofstraat, J. Appl. Phys., 1999, 86,
(
74 mg, 0.10 mmol) in absolute ethanol (4 ml) was added 4,4 -
bpe (9.2 mg, 0.05 mmol) and the mixture was refluxed for 2 h.
Then 2 ml absolute DMF was added to give a clear yellow
solution. Diethyl ether was allowed to diffuse slowly into this
solution at room temperature and pale yellow single crystals
were obtained in two weeks. Yield: 51 mg (61%). Calc. for
1
181; (c) A. Beeby, R. S. Dickins, S. FitzGerald, L. J. Govenlock,
C. L. Maupin, D. Parker, J. P. Riehl, G. Siligardi and J. A. G.
Williams, Chem. Commun., 2000, 1183.
5
6
7
W. T. Carnall, in Handbook on the Physics and Chemistry of Rare
Earths, ed. K. A. Gschneidner and L. Eyring, Jr, Elsevier,
Amsterdam, 1987, vol. 3, p. 171.
C
48
H
50
N
12
O
28Zn
2
Nd
C, 34.76; H, 3.07; N, 10.24%. H NMR (270 MHz, CD
d (ppm) 14.31 (1H), 13.27 (1H), 11.77 (1H), 8.65 (1H), 8.26
1H), 8.01 (1H), 7.94 (1H), 7.68 (1H), 7.53 (1H), 5.20 (1H),
.78 (1H), 3.65 (1H), 3.54 (1H), 3.11 (1H), 3.01 (1H), 2.79
1H), 1.28 (3H), 0.31 (1H), ꢁ0.50 (1H), ꢁ2.69 (1H), ꢁ3.46
2
: C, 34.68; H, 3.03; N, 10.11%. Found:
1
(a) N. Sabbatini, M. Guardigli and J.-M. Lehn, Coord. Chem. Rev.,
3
OD):
1
2
¨
993, 123, 201; (b) J.-C. G. Bunzli and C. Piguet, Chem. Soc. Rev.,
005, 34, 1048.
(
(a) B. S. Harrison, T. J. Foley, A. F. Knefely, J. K. Mwaura, G. B.
Cunningham, T.-S. Kang, M. Bouguettaya, J. M. Boncella, J. R.
Reynolds and K. Schanze, Chem. Mater., 2004, 16, 2938; (b) G. A.
Hebbink, D. N. Reinhoudt and F. C. J. M. van Veggel, Eur. J.
4
(
(
ꢁ1
1H), ꢁ5.17 (3H), ꢁ6.71 (1H), ꢁ7.87 (1H). IR (KBr, cm ):
Org. Chem., 2001, 4101; (c) S. Faulkner, M.-C. Carrie, S. J. A.
´
3
1
463 (br), 2936 (w), 1666 (s), 1616 (vs), 1582 (m), 1550 (m),
458 (vs), 1389 (s), 1303 (vs), 1232 (s), 1194 (s), 1096 (w), 1073
Pope, J. Squire, A. Beeby and P. G. Sammes, Dalton Trans., 2004,
1405; (d) B. P. Burton-Pye, S. L. Heath and S. Faulkner, Dalton
Trans., 2005, 146.
(
w), 1082 (w), 965 (m), 846 (w), 734 (m), 510 (w).
8
¨
(a) D. Imbert, M. Cantnuel, J.-C. G. Bunzli, G. Bernardinelli and
C. Piguet, J. Am. Chem. Soc., 2003, 125, 15698; (b) S. Torelli, D.
Crystal structure determination. Single crystals of 2 and 3 of
Imbert, M. Cantuel, G. Bernardinelli, S. Delahaye, A. Hauser,
¨
J.-C. G. Bunzli and C. Piguet, Chem.–Eur. J., 2005, 11, 3228.
9 (a) S. I. Klink, H. Keizer and F. C. J. M. van Veggel, Angew.
Chem., Int. Ed., 2000, 39, 4319; (b) D. Guo, C.-Y. Duan, F. Lu,
Y. Hasegawa, Q.-J. Meng and S. Yanagida, Chem. Commun.,
suitable dimensions were mounted onto thin glass fibers. All
the intensity data were collected at 298 K on a Bruker
SMART CCD diffractometer (Mo-Ka radiation,
.71073 A) in F and o scan modes. Structures were solved
by Patterson methods followed by difference Fourier synth-
l =
˚
0
2
004, 1486.
1
0 (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) P. B. Glover, P.
R. Ashton, L. J. Childs, A. Rodger, M. Kercher, R. M. Williams,
L. D. Cola and Z. Pikramenou, J. Am. Chem. Soc., 2003, 125,
eses, and then refined by full-matrix least-squares techniques
2 16a
against F using SHELXTL. All other non-hydrogen atoms
were refined with anisotropic thermal parameters. Absorption
1
corrections were applied using SADABS.
6b
All hydrogen
9
918; (d) H.-B. Xu, L.-X. Shi, E. Ma, L.-Y. Zhang, Q.-H. Wei and
atoms were placed in calculated positions and refined isotro-
pically using a riding model. Crystallographic data and refine-
ment parameters for the complexes are presented in Table 1.
Relevant atomic distances and bond angles are collected in
ESI,w Table 1s.
CCDC reference number 652822 (for 2) and 652823 (for 3).
For crystallographic data in CIF or other electronic format
see DOI: 10.1039/b710204f
Z.-N. Chen, Chem. Commun., 2006, 1601.
1 S. J. A. Pope, B. J. Coe, S. Faulkner and R. H. Laye, Dalton
Trans., 2005, 1482.
12 (a) W.-K. Wong, H. Liang, W.-Y. Wong, Z. Cai, K.-F. Li and
K.-W. Cheah, New J. Chem., 2002, 26, 275; (b) W.-K. Lo,
W.-K. Wong, J.-P. Guo, W.-Y. Wong, K.-F. Li and K.-W. Cheah,
Inorg. Chim. Acta, 2004, 357, 4510; (c) X.-P. Yang, R. A. Jones, V.
Lynch, M. M. Oye and A. L. Holmes, Dalton Trans., 2005, 849; (d)
X.-P. Yang and R. A. Jones, J. Am. Chem. Soc., 2005, 127, 7686;
1
(
e) W.-K. Wong, X.-P. Yang, R. A. Jones, J. H. Rivers, V. Lynch,
W.-K. Lo, D. Xiao, M. M. Oye and A. L. Holmes, Inorg. Chem.,
2006, 45, 4340; (f) X.-P. Yang, R. A. Jones, Q.-Y. Wu, M. M. Oye,
W.-K. Lo, W.-K. Wong and A. L. Holmes, Polyhedron, 2006, 25,
271; (g) W.-K. Lo, W.-K. Wong, W.-Y. Wong, J.-P. Guo, K.-T.
Yeung, Y.-K. Cheng, X.-P. Yang and R. A. Jones, Inorg. Chem.,
Acknowledgements
We thank Hong Kong Grants Council and Natural Science
Foundation (2007B03) of Shaanxi Province for financial
support.
2
006, 45, 9315; (h) X.-P. Yang, R. A. Jones, W.-K. Wong, M. M.
Oye and A. L. Holmes, Chem. Commun., 2006, 1836.
3 S. Petoud, S. M. Cohen, J.-C. G. Bunzli and K. N. Raymond,
J. Am. Chem. Soc., 2003, 125, 13324.
4 D. L. Foster, J. Chem. Phys., 1953, 21, 836.
1
1
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This journal is ꢂc the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2008
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