Synthesis of 1-(1-ferrocenylethyl)-pyridinium chloride and its hybrid materials with lindquist ype polyoxometalates

Article abstract of DOI:10.1016/j.jorganchem.2010.04.033

A new ferrocene derivative, 1-(1-ferrocenylethyl)-pyridinium (fep = CpFeCp-CH(CH₃)-Py⁺) chloride, and two charge ransfer salts (CTSs) based on the cationic fep donor and Lindqvist ype polyoxometalate acceptors, [fep]₂[Mo₆O₁₉] (1) and [fep] ₂[W₆O₁₉] (2), were synthesized. fepCl was characterized by elemental analysis, IR spectroscopy and ¹H NMR and the two CTSs were characterized by elemental analysis, IR spectroscopy, UV-vis diffuse reflectance spectrum, cyclic voltammetry, fluorescence spectrum and single crystal X-ray diffraction. X-ray crystallographic studies of the brownish red CTSs 1 and 2 reveal that they are isostructural and crystallize in the monoclinic space group P2₁/n. In salts 1-2, fep and polyoxoanions are cocrystallized by Coulombic forces, and there also exist the complex C-H?π and π?π stacking interactions between the adjacent fep cations and C-H?O hydrogen bonds between the adjacent fep cations and polyanions. The UV-vis diffuse reflectance spectra indicate the presence of a broad charge ransfer band between 500 and 850 nm for 1-2, and CT character of 1 and 2 is also confirmed by the Mulliken correlation between the CT transition energies and the reduction potentials of the polyoxometalate acceptors. Two new hybrid materials based on 1-(1-ferrocenylethyl)-pyridinium donor and Lindqvist ype polyoxometalate acceptors were synthesized in high yields and their UV-vis diffuse reflectance spectra indicate the presence of a broad charge ransfer band between 500 and 850 nm.

Full text of DOI:10.1016/j.jorganchem.2010.04.033

Journal of Organometallic Chemistry 695 (2010) 1863e1868
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of 1-(1-ferrocenylethyl)-pyridinium chloride and its hybrid materials
with lindquist-type polyoxometalates
,
,
a
b
Yujuan Niu a, Xiaoyu Ren a, Bin Yin a, Danjun Wang a b, Ganglin Xue a , Huaiming Hu , Feng Fu ,
*
Jiwu Wang b
a Key Laboratory of Synthetic and Natural Functional Molecule Chemistry (Ministry of Education), Shaanxi Key Laboratory of Physico-Inorganic Chemistry, Department of Chemistry,
Northwest University, Xi’an 710069, China
b Shaanxi Key Laboratory of Chemical Reaction Engineering, Yanan University, Yan’an, Shaanxi 716000, China
a r t i c l e i n f o
a b s t r a c t
A new ferrocene derivative, 1-(1-ferrocenylethyl)-pyridinium (fep ¼ CpFeCpeCH(CH3)ePyþ) chloride,
and two charge-transfer salts (CTSs) based on the cationic fep donor and Lindqvist-type polyoxometalate
acceptors, [fep]2[Mo6O19] (1) and [fep]2[W6O19] (2), were synthesized. fepCl was characterized by
elemental analysis, IR spectroscopy and 1H NMR and the two CTSs were characterized by elemental
analysis, IR spectroscopy, UVevis diffuse reflectance spectrum, cyclic voltammetry, fluorescence spec-
trum and single crystal X-ray diffraction. X-ray crystallographic studies of the brownish red CTSs 1 and 2
reveal that they are isostructural and crystallize in the monoclinic space group P21/n. In salts 1e2, fep and
Article history:
Received 2 February 2010
Received in revised form
22 April 2010
Accepted 30 April 2010
Available online 6 May 2010
Keywords:
Charge-transfer salts
Ferrocene
polyoxoanions are cocrystallized by Coulombic forces, and there also exist the complex CeH/
p and
p
/p
stacking interactions between the adjacent fep cations and CeH/O hydrogen bonds between the
adjacent fep cations and polyanions. The UVevis diffuse reflectance spectra indicate the presence of
a broad charge-transfer band between 500 and 850 nm for 1e2, and CT character of 1 and 2 is also
confirmed by the Mulliken correlation between the CT transition energies and the reduction potentials of
the polyoxometalate acceptors.
Polyoxometalates
Reflectance spectra
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
containing the cationic ferrocenyl donor CpFeCpCH2Nþ(CH3)3 and
polyoxometalate acceptors of the Lindqvist structural type
Polyoxometalates (POMs) or metal oxide clusters are versatile in
many aspects, and in recent years new efforts have been made to
explore their applications in catalysis, medicine, and material
sciences [1,2], which is based on the ability of POMs to act as
electron reservoirs as well as the extreme variability of their
molecular properties, including size, shape, charge, charge density,
redox potential, acidity, solubility and so on [3,4]. In particular, the
potentialities of molecular materials of these metal oxide clusters
are exemplified by the POMs in their use as electron-accepting
moieties in charge-transfer materials prepared by cocrystallization
with electron-rich organic donors, such as tetrathiafulvalene and
their derivatives via an initial electron-transfer [5]. The ferrocene
and its derivatives are an excellent type of organicmetallic electron
donors, and recent years some charge-transfer salts (CTSs) based on
ferrocene-type donor and POM acceptor have been synthesized and
structurally characterized [6e13]. The first charge-transfer salt
([M6O19
]
2ꢀ) (M ¼ Mo, W) was reported by Professor Kochi in 1995
[10], and he revealed the relevant charge-transfer interactions
between POM acceptors and organic donors in the
[C5H5FeC5H4CH2N(CH3)3]2M6O19 (M ¼ Mo, W) by the UVevis
diffuse reflectance spectrum and time-resolved (laser-flash) spec-
troscopic method. Recently, our group reported the charge-transfer
salts based on the cationic ferrocenyl donor CpFeCpCH2Nþ(CH3)3
and Keggin-type acceptors, [CpFeCpCH2N(CH3)3]4[PMo12O40]$
CH3CN and [CpFeCpCH2N(CH3)3]4[GeMo12O40] [8], in which the
Keggin polyanion {PMo12O40} was reduced to ꢀ4 from the original
4ꢀ
ꢀ3, and [GeMo12O40
]
remains its original oxidation state. The
charge-transfer salts composed of cationic donors and anion
acceptors can be described as outer-sphere (OS) charge-transfer
complexes [14] in which the main interaction between the cation
and anion are coulomb force, and the charge-transfer transitions
are highly related to the contacts interactions between the cation
and anion, and also to the structures and composition of cationic
donor and polyoxometalate acceptors. In this direction, we have
recently utilized cationic ferrocenylmethylpyridinium donor
* Corresponding author. Tel.: þ86 29 8830 2604; fax: þ86 29 8830 3798.
E-mail address: xglin707@163.com (G. Xue).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.04.033

1864
Y. Niu et al. / Journal of Organometallic Chemistry 695 (2010) 1863e1868
Table 1
Crystallographic parameters and refinement details for [fep]2[Mo6O19] (1) and
[fep]2[W6O19] (2).
Compounds
1
2
Formula
C
34H36Fe2Mo6N2O19 C34H36Fe2W6N2O19
M, g molꢀ1
1463.99
P21/n
1991.45
P21/n
Space group
a, Å
b, Å
c, Å
A
12.4674(11)
13.6294(12)
14.0077(13)
90
12.516(2)
13.681(2)
14.053(2)
90
B
G
V, Å3
114.681(1)
90
2162.8(3)
2
2.248
2.409
10,541
3834
287
114.705(3)
90
2186.1(6)
2
Z
dcalc, g cmꢀ3
3.025
m
, mmꢀ1
16.436
10,774
3878
263
0.932
Total reflns
Indep reflns
Parameters
GOF
1.180
R1 (l > 2
wR2 (l > 2
R1 (all data)
wR2 (all data)
s
(l))
(l))
0.0252
0.0763
0.0319
0.0966
0.569, ꢀ0.920
0.0378
0.0948
0.0612
0.1151
1.565, ꢀ1.323
s
Fig. 1. ORTEP diagram of the asymmetric unit of 1 with the atomic numbering scheme
and 30% thermal ellipsoids. H atoms are omitted for clarity.
ꢀꢀ3
Difference in peak and hole, e A
for the dry pressed disk samples using a Shimazu UV-2550 spec-
trophotometer, equipped with an integrating sphere coated with
polytetrafluoroethylene (PTFE). Absorption spectra were referenced
to barium sulfate. Cyclic voltammetry (CV) studies were carried out
in acetonitrile solution at ambient temperatureunder the protection
of N2 using an EG & G 273A apparatus undercomputercontrol (M270
software). The source, mounting, and polishing of the glassy carbon
(GC, 3 mm diameter) have been described [16]. SCE (saturated
calomel electrode) was as the reference electrode, and a platinum
wire as the counter electrode, NBu4Br was the supporting electro-
lyte, and the scan rate was 100 mV sꢀ1. Luminescent spectra were
measured at room temperature on a Hitachi F4500 fluorescence
spectrophotometer. Magnetic measurements were carried out using
a Quantum Design MPMS-XL SQUID magnetometer.
(CpFeCpeCH2ePyþ) as cations to obtain four new outer-sphere
charge-transfer complexes, [CpFeCpeCH2ePy]2[Mo6O19],
[CpFeCpeCH2ePy]2[W6O19], [CpFeCpeCH2ePy]4[W10O32 and
(NBu4)[CpFeCpeCH2ePy]2[PMo12O40] [13]. In these salts, the fer-
rocenylmethylpyridinium (CpFeCpeCH2ePyþ) and the poly-
oxoanions are cocrystallized by Coulombic forces, and there also
]
exist the complex CeH/
the adjacent ferrocenylmethylpyridinium cations. The orbital
overlap between the -donor plane of the pyridyl ring and one
oxygen facet of the acceptor octahedron in the solid state is
observed in salts [CpFeCpeCH2ePy]2[Mo6O19 and
p and p/p stacking interactions between
p
]
[CpFeCpeCH2ePy]2[W6O19]. As a part of our continuing efforts to
find new and more suitable cationic donor to tune the crystal
stacking structure of charge-transfer complexes based on ferro-
cenyl cationic donors and polyoxometalate acceptors, herein we
report the synthesis of a new cationic ferrocenyl containing pyr-
idinium group, 1-(1-ferrocenylethyl)-pyridinium chloride, and its
CTSs with Lindquist-type polyoxometalates.
2.2. Synthesis of 1-(1-ferrocenylethyl)-pyridinium chloride (fepCl)
A solution of 46.2 g (0.2 mol) of acetylferrocene [17] in 200 ml of
ethanol was added dropwise, at room temperature, to a solution of
2. Experimental
2.1. General methods
(NBu4)2M6O19 (M ¼ Mo or W) was prepared according to the
literature [15]. The solvents used in preparations of fepCl
(fep ¼ CpFeCpeCH(CH3)ePyþ) were all dried, especially THF was
distilled from Na and pyridine was distilled from NaOH just prior to
use, other starting materials were AR grade and used as purchased.
1H NMR spectra were recorded on a Varian INOVA-400 MHz spec-
trometer with TMS as an internal standard. IR spectra were obtained
on an EQUINOX55 IR spectrometer with KBr pellets. Solid state
diffuse reflectance spectra between 300 and 850 nm were obtained
CH3
CH3
Cl
N
N
(NBu4)2M6O19.
CH3CN
M6O19
Fe
Fe
(M=Mo,W)
2
Fig. 2. A representation showing the linkages of hydrogen bonding between the
polyoxoanions and the ferrocenyl cations in 1, H atoms are omitted for clarity.
Scheme 1.

Y. Niu et al. / Journal of Organometallic Chemistry 695 (2010) 1863e1868
1865
2.3. Synthesis of [CpFeCpeCH(CH3)ePy]2[Mo6O19] (1)
A solution of fepCl (0.33 g, 1 mmol) in acetonitrile (10 ml) was
added dropwise to an acetonitrile (20 ml) solution of (NBu4)2
-
Mo6O19 (0.68 g, 0.5 mmol). The mixture was left stirring at room
temperature and then filtered. The filtrate was slowly evaporated
at ambient conditions. Within 2 days, brownish red block crystals
of 1 were isolated in about 55% (based on (NBu4)2Mo6O19).
Elemental analysis (%) calcd for C34H36O19Fe2N2Mo6: C 27.9, H
2.49, N 1.91; found: C 27.3, H 1.86, N 2.06; IR (KBr): 3073.6 (m),
1330.7 (m), 1242.4 (m), 1126.9 (s), 955.6 (vs), 903.4 (s), 796.2 (vs),
675.2 (s).
2.4. Synthesis of [CpFeCpeCH(CH3)ePy]2[W6O19] (2)
The synthetic procedure for 2 is similar to that of 1 except for
using (NBu4)2W6O19 (0.95 gꢂ, 0.5 mmol) instead of (NBu4)2Mo6O19
.
The brownish red block crystals of 2 were isolated in about 75%
(based on (NBu4)2W6O19). Elemental analysis (%) calcd for
C34H36O19Fe2N2W6: C 20.5, H 1.82, N 1.41; found: C 20.1, H 1.74, N
1.38; IR (KBr): 3075.9 (s), 1330.9 (m) 124,205 (m), 1129.2 (s), 974.5.0
(vs), 880.2 (s), 809.9 (vs), 678.7 (s).
Fig. 3. Projection of the crystal structure of 1 along b direction showing the layers of
ꢁ
the organic donor and inorganic acceptor alternatively arranged in (10ı) plane and
pyridyl rings penetrate into the anion layers. H atoms are omitted for clarity.
30.4 g (0.8 mol) of sodium borohydride in 200 ml of water. The
reaction mixture was stirred overnight at room temperature, then
poured into water and vacuum filtration, washed and dried, the
product 1-hydroxyethylferrocene were obtained [18].
2.5. Crystal structure determination
A solution of PCl3 (0.1 ml, 1 mmol) in THF (5 ml) was added
dropwise to a THF (20 ml) solution of (1-hydroxyethyl)ferrocene
(0.23 g, 1 mmol) and pyridine (0.1 ml, 1 mmol) at 0 ꢁC. The mixture
was left stirring for 1 h at this temperature, the ice bath was
removed and the mixture left to stir at room temperature for 3 h.
The yellow precipitate formed was filtered off and recrystallisation
from CH2Cl2, yield: 55.2%. Elemental analysis (%) calcd for
C17H18ClFeN: C 62.3, H 5.54, N 4.27; found: C 62.0, H 5.75, N 4.14; IR
(KBr): 3051(s), 1628(s), 1483(s), 1382(m), 1339(m), 1248(m), 1130
A selected crystal of compounds 1e2 was respectively mounted
on a glass fiber capillary which was put on a BRUKER SMART APEX
II CCD diffractometer equipped with graphite monochromatic
radiation and used for data collection. Data were collected at 293
(2) K using MoK
a
radiation (
l
¼ 0.71073 Å). The structure were
solved by direct methods (SHELXTL-97) and refined by the full-
matrix-block least-squares method on F2. All non-hydrogen atoms
were refined with anisotropic displacement parameters. Hydrogen
atoms were included at calculated positions and refined with
a riding model. A summary of the crystal data, experimental
details, and refinement results for the structure of 1e2 are listed in
Table 1. The CCDC reference numbers are CCDC 762166 for 1 and
762167 for 2.
(s), 1055(m), 1031(m), 828(s), 755(s), 730(s) and 681(s) cmꢀ1
.
1H
NMR [DMSO-d6, 400 MHz]: 9.10(2H, py), 8.55 (1H, py), 8.13 (2H,
d
py), 5.61 (1H, CH), 4.58 (2H, Cp H), 4.32 (2H, Cp H), 4.26 (5H, Cp H),
1.38 (3H, CH3), 3.36 (H2O) and 2.51 (DMSO).
Fig. 4. A view of the interactions between adjacent ferrocenyl units in 1. The blue short distance between two adjacent pyridyl rings show
p/
p
stacking interactions and the light
blue short distance between the hydrogen atom of pyridyl and the bare Cp ring of another adjacent ferrocenyl unit show CeH/p interactions. (For interpretation of the references
to color in this figure legend, the reader is referred to the web version of this article.)

1866
Y. Niu et al. / Journal of Organometallic Chemistry 695 (2010) 1863e1868
Table 2
are linked via pairs of CeH/
atoms of pyridyl and Cp rings of one molecule and the bare Cp ring of
the next in the plane, and there also exist stacking interaction
p interactions between the hydrogen
Characteristic absorptions arising from polyoxoanions (cmꢀ1).
p/p
Compound
nas(MeOa)
nas(MeOb)
nas(MeOc)
between the neighboring pyridyl rings in (101) plane with the mean
interplanar separation of 3.583 Å (Fig. 4).
1
955
957
974
973
903
884
880
877
796
800
806
811
675
662
678
667
[NBu4]2[Mo6O19
2
[NBu4]2[W6O19
]
]
3.2. IR spectra
The absorption peaks in the range 1100ꢀ500 cmꢀ1 arising from
the polyoxoanions for [NBu4]2[Mo6O19], [NBu4]2[W6O19], salts 1
and 2 are compared in Table 2. The nas(MeOa) vibration frequencies
for 1 and 2 have slightly changes of 1e2 cmꢀ1 compared with
[NBu4]2[Mo6O19] and [NBu4]2[W6O19], however the frequencies of
nas(MeOb) and nas(MeOc) present larger change, particularly the
nas(MeOc) for 1 and 2 have blue shifts of 11 and 13 cmꢀ1, respec-
tively. These results indicate that the polyanions in compounds 1
and 2 still maintain the basic Lindquist structure but are distorted
owing to the interactions among the ferrocenyl cations and the
framework oxygen atoms of polyoxometalates.
3. Results and discussion
3.1. Synthesis and crystal structures
The CTSs 1e2 were synthesized by reaction of the correspond-
ing Lindquist anions [NBu4]2[M6O19] (M ¼ Mo, W) with fepCl in
CH3CN solution (Scheme 1). When the yellow dilute acetonitrile
solution of fepCl was mixed with the (Bu4N)2[M6O19] (M ¼ Mo, W)
acetonitrile solution, the color of reaction mixture changed from
yellow to brown. The remarkable color change suggests that the
electronic interaction between the cationic ferrocenyl donor and
the POM acceptor has occurred [19,20]. Using (NBu4)4Mo8O26
3.3. Electronic absorption spectra
instead of (NBu4)2Mo6O19 to react in the same conditions, we got
4ꢀ
the same product 1 in high yield (58%). This is because [Mo8O26
]
and [Mo6O19
]
2ꢀ can transform mutually in some conditions [21,22].
UVevis absorption spectra were obtained by the diffuse reflec-
tance technique [10,23]. The reflectance electronic spectra of the
compounds 1, 2 and startingmaterialsfepCl, [NBu4]2[M6O19] (M¼ Mo,
W) are compared in Fig. 5. It is noticeable that the starting materials
Salts 1 and 2 are isostructural and crystallize in the monoclinic
space group P21/n, therefore only the structure of 1 is discussed here.
The asymmetric unit of 1 is composed from half of [Mo6O19
2ꢀ
]
and
did not show any absorption at l > 500 nm and the diffuse reflectance
one fep cation and the ratio is 1:2 (Fig.1). Each anionwith the MoeOa,
MoeOb and MoeOc average distances of 1.679, 1.924 and 2.316 Å,
respectively, is surrounded by twelve adjacent fep units, and there
spectrum of CTS 1 in the solid state (Fig. 5a) showed a broad strong
absorption band from 350 to 800 nm. Spectral (digital) subtraction of
the component spectra (i.e. of [NBu4]2[Mo6O19] and fepCl, individu-
ally) of salt 1 in the solid state yielded the difference spectrum (Fig. 5a
inset) consisting of a very climbing band from 500 to beyond 800 nm,
the result is comparable with those of reported charge-transfer salts
[10,13]. The diffuse reflectance spectrum of the salt 2 in the solid state
(Fig. 5b) is similar to CTS 1, but it showed a little difference, the
climbing band starts from 350 nm and it has downtrend at 750 nm. In
accord with Mulliken theory [24e26], the new (visible) absorption
bands should be ascribed to charge-transfer transitions between the
cationic ferrocenyl donor and the POM acceptors.
existseveralshortcontacts amongthe[Mo6O19]
2ꢀ polyoxoanions and
the fep cations and the nearest C/O distances are in the range of
3.069 (5)e3.569(6) Å, which shows the presence of interactions
between the polyoxoanions and the ferrocenyl via Coulombic forces
and CH/O hydrogen bonds (Fig. 2). Fig. 3 shows the packing of the
compound in solid state along b direction, the layers of polyoxoanions
ꢁ
and ferrocenyl cations are alternatively arranged in (10ı) plane, and
pyridyl rings penetrate into the anion layers with the closest C/O
distance of 3.069(5) Å. The ferrocene unit displays the typical sand-
wichgeometrywiththe twoCprings innearlyeclipsedconformation.
The average dihedral angle between the two Cp rings is only 0.81, in
other words the two Cp rings in each ferrocene moiety are almost
3.4. Cyclic voltammetry
parallel, which is smaller than 3.5 in [CpFeCpCH2N(CH3)3]2[M6O19
]
ꢁ
(M ¼ Mo,W) [10]. In (10ı) plane the closest Fe/Fe distance between
Cyclic voltammetry of the CTSs 1, 2 and the starting materials
are showed in Fig. 6. In the range ꢀ1.5e1.0 V, CTS 1 exhibits two
the neighboring ferrocenyl cationsis 7.229Å, adjacent ferrocene units
a
b
300
400
500
600
700
800
Wavelength/nm
500
600
700
800
Wavelength/nm
300
400
500
600
700
800
300
400
500
600
700
800
Wavelength/nm
Wavelength/nm
Fig. 5. Charge-transfer absorption spectra of CTs 1 (a) and 2 (b) (dd) dispersed in barium sulfate in comparison with the absorption spectra of [NBu4]2[M6O19] (M ¼ Mo, W)
(———), respectively, and fepCl (...). The inset elicits the charge-transfer band by the spectral (digital) subtraction of [NBu4]2[M6O19] and fepCl individually from 1 to 2,
respectively.

Y. Niu et al. / Journal of Organometallic Chemistry 695 (2010) 1863e1868
1867
a
b
80
80
40
0
II'
40
II'
I'
I'
0
II
II
I
-40
-80
-40
I
-80
1.0
0.5
0.0
-0.5
-1.0
-1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
Potential/V
Potential/V
Fig. 6. Cyclic voltammetry of CTSs 1 (a) and 2 (b) in 1 ꢃ 10ꢀ4 mol/L acetonitrile solution and 0.1 mol/L NBu4Br as the supporting electrolyte.
b
a
7000
5600
4200
2800
1400
0
6000
5000
4000
3000
2000
1000
0
300
350
400
450
500
330
360
390
420
450
480
Wavelength/nm
Wavelength/nm
Fig. 7. Emission spectra of the charge-transfer salts 1 (a) and 2 (b) (dd), and the corresponding POMs (———).
redox pairs (see Fig. 6a), which could be assigned to fep and
on the cationic ferrocenylethylpyridinium donor and Lindqvist-
type polyoxometalate acceptors, [fep]2[Mo6O19 (1) and
[fep]2[W6O19 (2), were synthesized. X-ray crystallographic
studies of the crystalline materials reveal that there exist
extensive CeH/ and stacking interactions between the
adjacent fep cations, and CeH/O hydrogen bonds between the
adjacent fep cations and polyanions. The electronic spectra of
the 1 and 2 show the charge-transfer absorption band between
the cationic ferrocenyl donor and the POM acceptors, and CT
character of 1 and 2 is also confirmed by the Mulliken correlation
between the CT transition energies and the reduction potentials
of the polyoxometalate acceptors. Novel charge-transfer salts
could be expected by modulating the ferrocene derivative donors
and POMs.
2ꢀ
Mo6O systems, respectively. Emid value of redox pair for fep in the
]
19
charge-transfer salt 1 is 0.409 V compared with 0.374 V of free fep
cation, and that of the pair for Mo6O19 are ꢀ0.365 V compared with
ꢀ0.445 V of [NBu4]2[Mo6O19]. 2 also shows two redox pairs at 0.474
and ꢀ0.909 V (see Fig. 6b), which could be assigned to fep and
]
p
p/p
2ꢀ
2ꢀ
cluster
W6O systems, higher than ꢀ0.923 of parent [W6O19
]
19
and that of fepCl respectively. The closer value of the reduction
wave to that of donor CpFeCpeCH(CH3)ePyþ for [Mo6O19
]
2ꢀ
than
[W6O19
]
2ꢀ system indicated the more pronounced charge-transfer
absorption for 1 than 2, which is consistent with the spectral
extension from 500 nm to the long waves of the hexamolybdate CT
salt 1 relative to the hexatungstate analogue 2 in the UVevis
absorption spectra [10].
3.5. Fluorescence properties
Acknowledgements
The photoluminescent properties of POMs and salts 1e2 were
investigated in the solid state at room temperature (Fig. 7). Exci-
tation at 280 nm leads to broad fluorescence signals with the
emission peaks at about 394, 399 nm for 1 and 2, respectively,
which may mainly be attributed to O2p to Mo4d (or W5d) charge-
transfer. The emission bands of 1 and 2 are compared to that of the
corresponding POMs and exhibit the weakened fluorescence
signals, the obviously distinct suggests the strongly interactions
between the ferrocenyl donor to POM acceptors.
This work was supported by the National Natural Science
Foundation of China (20973133), the Education Commission of
Shaanxi Province (09JK783) and National Training Fund for the
Basic Sciences (J083417/J0104).
Appendix. Supplementary material
CCDC 762166 and 762167 contain the supplementary crystal-
lographic 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.
4. Conclusion
In summary,
a
new ferrocene derivative, 1-(1-ferroceny-
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.jorganchem.2010.04.033.
lethyl)-pyridinium chloride, and two charge-transfer salts based

1868
Y. Niu et al. / Journal of Organometallic Chemistry 695 (2010) 1863e1868
[13] H.S. Xu, Z.F. Li, B. Liu, G.L. Xue, H.M. Hu, F. Fu, J.W. Wang, Cryst. Growth Des. 10
References
(2010) 1096e1103.
[14] S.V. Rosokha, J.K. Kochi, Acc. Chem. Res. 41 (2008) 641e653.
[15] W.G. Klemperer, in: A.P. Ginsberg (Ed.), Inorganic Synthesis, vol. 27, Wiley,
New York, 1990, p. 71.
[16] B. Keita, Y.W. Lu, L. Nadjo, R. Contant, M. Abbessi, J. Canny, M. Richet, J.
Electroanal. Chem. 477 (1999) 146e157.
[17] P.J. Graham, R.V. Lindsey, G.W. Parshall, M.L. Peterson, G.M. Whitman, J. Am.
Chem. Soc. 79 (1957) 3416e3420.
[18] P.J. Swarts, M. Immelman, G.J. Lamprecht, S.E. Greyling, J.C. Swarts, S. Afr. J.
Chem. 50 (1997) 208e216.
[19] M. Che, M. Fournier, J.P. Launay, J. Chem. Phys. 71 (1979) 1954e1960.
[20] C. Sanchez, J. Livage, J.P. Launay, M. Fournier, Y. Jeannin, J. Am. Chem. Soc. 104
(1982) 3194e3202.
[21] J. Kang, J.A. Nelson, M. Lu, B.H. Xie, Zh.H. Peng, D.R. Powel, Inorg. Chem. 43
(2004) 6408e6413.
[22] Y. Zhu, L.Sh. Wang, J. Hao, Z.Ch. Xiao, Y.G. Wei, Y. Wang, Cryst. Growth Des. 9
(2009) 3509e3518.
[23] P. Le Maguerès, S.M. Hubig, S.V. Lindeman, P. Veya, J.K. Kochi, J. Am. Chem.
Soc. 122 (2000) 10073e10082.
[1] M.T. Pope, Heteropoly and Isopoly Oxometalates. Springer-Verlag, Berlin,
1983.
[2] M. Clemente-León, E. Coronado, C.J. Gómez-García, E. Martinez-Ferrero, J.
Clust. Sci. 13 (2002) 381e407.
[3] L. Ouahab, Chem. Mater. 9 (1997) 1909e1926.
[4] E. Coronado, J.R. Galán-Mascarós, C. Giménez-Saiz, C.J. Gómez-García, Adv.
Mater. Opt. Electron. 8 (1998) 61e76.
[5] E. Coronado, C.J. Gómez-García, Chem. Rev. 98 (1998) 273e296.
[6] P. Le Maguerès, L. Ouahab, S. Golhen, D. Grandjean, O. Penǎ, J.C. Jegaden, C.
J. Gómez-García, P. Delhaès, Inorg. Chem. 33 (1994) 5180e5187.
[7] S. Golhen, L. Ouahab, D. Grandjean, P. Molinié, Inorg. Chem. 37 (1998)
1499e1506.
[8] Z.F. Li, B. Liu, H.S. Xu, G.L. Xue, H.M. Hu, F. Fu, J.W. Wang, J. Organomet. Chem.
694 (2009) 2210e2216.
[9] W.B. Yang, C.Z. Lu, C.D. Wu, Y.Q. Yu, Q.Z. Zhang, S.M. Chen, J. Clust. Sci. 14
(2003) 421e430.
[10] P.L. Veya, J.K. Kochi, J. Organomet. Chem. 488 (1995) C4eC8.
[11] X.M. Liu, G.L. Xue, H.M. Hu, Q.C. Gao, F. Fu, J.W. Wang, J. Mol. Struct. 787
(2006) 101e105.
[12] Z.F. Li, R.R. Cui, B. Liu, G.L. Xue, H.M. Hu, F. Fu, J.W. Wang, J. Mol. Struct. 920
(2009) 436e440.
[24] R. Foster, Organic Charge-Transfer Complexes. Academic, New York, 1969.
[25] R.S. Mulliken, J. Am. Chem. Soc. 74 (1952) 811e824.
[26] R.S. Mulliken, W.B. Person, Molecular Complexes. A Lecture and Reprint
Volume. Wiley, New York, 1969.