A novel organic-inorganic hybrid material with fluorescent emission: [Cd(PT)(H2O)]n (PT = phthalate)

Article abstract of DOI:10.1039/b211358a

The novel organic-inorganic hybrid material [Cd(PT)(H₂O)]_n (1; PT = phthalate) has been hydrothermally synthesized. The X-ray diffraction study reveals that 1 exhibits an interesting two-dimensional (2D) honeycomb framework constructed from [CdO₇] single helical chains linked via oxygen atoms of the PT ligands, which adopt the μ₆-bridging coordination mode. A study of the physical properties of 1 demonstrates that it exhibits a strong fluorescent emission in the solid state at room temperature.

Full text of DOI:10.1039/b211358a

View Article Online / Journal Homepage / Table of Contents for this issue
A novel organic-inorganic hybrid material with fluorescent emission:
[Cd(PT)(H2O)]n (PT = phthalate)y
Shutao Wang,a Yu Hou,a Enbo Wang,*ab Yangguang Li,a Lin Xu,a Jun Peng,a Shuxia Liua and
Changwen Hua
a
Institute of Polyoxometalate Chemistry, Department of Chemistry, Northeast Normal
University, Changchun, 130024, P. R. China. E-mail: wangenbo@public.cc.jl.cn;
Fax: +86 431 568 4009
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
b
Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China
Received (in Montpellier, France) 18th November 2002, Accepted 18th February 2003
First published as an Advance Article on the web 29th May 2003
The novel organic-inorganic hybrid material [Cd(PT)(H2O)]n (1; PT ¼ phthalate) has been hydrothermally
synthesized. The X-ray diffraction study reveals that 1 exhibits an interesting two-dimensional (2D) honeycomb
framework constructed from [CdO7] single helical chains linked via oxygen atoms of the PT ligands, which
adopt the m6-bridging coordination mode. A study of the physical properties of 1 demonstrates that it exhibits a
strong fluorescent emission in the solid state at room temperature.
Organic-inorganic hybrid compounds with extended struc-
tures are currently of considerable interest owing to their
intriguing structural motifs and unique electro-conductive,
optical and magnetic properties, as well as three-dimensional
(3D) porosity.1–10 This kind of hybrid materials combines
the unique characteristics of both inorganic and organic sub-
units; furthermore, the extended structures improve and/or
strengthen some interesting physical properties. In this
family, metal carboxylates have been extensively studied.3
By selecting suitable bi-, tri- and tetracarboxylic ligands
and metal ions, clusters, or other building blocks, chemists
have obtained some exciting results.4,5,8–10 The research on
metal benzene dicarboxylic ligands is one of the most active
areas. Generally, benzene dicarboxylic ligands can be of three
structural types (see Scheme 1): (i) linear (180ꢀ) 1,4-dicar-
boxylic ligand; (ii) 1,3-dicarboxylic ligand with a large angle
(ca. 120ꢀ) between the two carboxyl groups; (iii) 1,2-dicar-
boxylic ligand with a small angle (ca. 60ꢀ) between the two
carboxyl groups. It is noteworthy that many reports are con-
cerned with the multi-dimensional compounds constructed by
metal ions and 1,4-dicarboxylic ligands, while the extended
compounds composed of 1,3- and 1,2-dicarboxylic ligands
have rarely been reported. The possible reason may lie in
the differences in stereo orientation of these ligands. How-
ever, the variety of coordination modes11–14 of phthalate
may also provide the possibility to prepare new metal phtha-
late with diverse topological structures and potentially inter-
esting physical properties.
Scheme 1 Schematic representation of three structural types of ben-
zene dicarboxylic ligands.
of open-framework cadmium oxalates and succinates have
been observed,15 however, few cadmium benzene dicarboxyl-
ates with extended structures are known to date.16 To the
best of our knowledge, no cadmium phthalate with a multi-
dimensional structure has been synthesized hitherto. In this
paper, we report a novel two-dimensional (2D) cadmium
phthalate, [Cd(PT)(H2O)]n (1; PT ¼ phthalate), which exhi-
bits a strong fluorescent emission in the solid state at room
temperature.
Experimental
Materials and general methods
All chemicals were commercially available and used without
further purification. Elemental analyses (C, H and N) were
carried out on a Perkin–Elmer 240 CHN elemental analyzer.
FT-IR spectra were recorded in the range of 400–4000 cmꢁ1
on an Alpha Centaurt FT/IR spectrophotometer using KBr
pellets. Thermogravimetric data were collected on a Perkin–
Elmer TGA7 instrument in flowing nitrogen at a heating rate
of 10 ꢀCꢂminꢁ1. The diffuse reflectance UV-vis spectrum
(BaSO4 pellet) was obtained with a Varian Cary 500 UV-
vis NIR spectroscopy. Excitation and emission spectra were
obtained on a SPEX FL-2T2 spectrofluorometer equipped
with a 450 W xenon lamp as the excitation source. Lumi-
nescence lifetimes were measured with a SPEX 1934D phos-
Cadmium compounds with organic acids show interesting
optical properties, especially fluorescence. Recently, cad-
mium carboxylates with extended frameworks have received
much attention because of their excellent fluorescent proper-
ties, besides their interesting structural topologies. A series
y Electronic supplementary information (ESI) available: figures show-
ing the metal-oxygen framework of 1 and its XPS, IR, UV-vis spectra
and the decay of the luminescence, as well as the fluorescent excitation
and emission spectra of PT. See http://www.rsc.org/suppdata/nj/b2/
b211358a/
phorimeter using
a 7 W pulsed xenon lamp as the
excitation source. All measurements were performed at room
temperature.
1144
New J. Chem., 2003, 27, 1144–1147
DOI: 10.1039/b211358a
This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2003

View Article Online
Hydrothermal synthesis
The title compound 1 was hydrothermally synthesized under
autogeneous pressure. An aqueous mixture (7 cm3) containing
KH(PT) (0.204 g, 1 mmol), Cd(NO3)2ꢂ4H2O, (0.462 g, 1.5
mmol), and oxalic acid (0.126 g, 1 mmol) was neutralized to
pH 6.5 with 2 M KOH aqueous alkali under continuous stir-
ring and then sealed in a Parr teflon-lined stainless steel vessel
(15 mL), which was heated to 160 ꢀC for 120 h. After slowly
cooling at 5 ꢀCꢂhꢁ1 to ambient temperature, colorless block-
like crystals of the complex [Cd(PT)(H2O)]n (1) were mechani-
cally separated from the white powder and washed by water
(yield: ca. 40% based on Cd). Anal. calcd for C8H6CdO5 : C:
32.62; H: 2.06%; found: C: 32.57; H: 2.19%. FT-IR (cmꢁ1):
3439(m), 3348(s), 3248(m), 1643(m), 1580(vs), 1550(vs),
1491(s), 1446(m), 1417(s), 1290(w), 1158(w), 1087(w),
1039(w), 967w, 877(m), 842(m), 798(m), 764(m), 735(m),
703(m), 657(m), 553(w), 453(w).
X-Ray crystallography
Fig. 1 ORTEP drawing of 1 showing the local coordination environ-
ment of Cd(II) with thermal ellipsoids at 50% probability.
The crystal determination for compound 1 was performed
on a Bruker Smart Apex CCD diffractometer with Mo-Ka
˚
radiation (l ¼ 0.71073 A) at 293(2) K in the range of
2.80ꢀ < y < 28.04ꢀ using the o-scan technique. An empirical
absorption correction was applied. The structure was solved
by direct methods using the program SHELXS-97 and refined
by full-matrix least-squares methods on F2 using the
SHELXL-97 program package.17 All of the non-hydrogen
atoms were refined anisotropically. Positions of the hydrogen
atoms attached to carbon atoms were located from difference
maps. The two H atoms of the water molecule could not be
located on the difference Fourier maps owing to the presence
of the very heavy Cd atoms. The large peak near the Cd atom
is caused by the ‘‘truncated tail’’ effect. Crystal data are sum-
marized in Table 1.
center in the asymmetric unit. As shown in Fig. 1, the local
coordination environment around the Cd(II) ion in 1 exhibits
a distorted pentagonal bipyramid geometry with two bidentate
chelating carboxylates and one monodentate carbonate in the
equatorial plane and with the other monodentate carbonate
and one water molecule in the axial positions. In detail, the
seven-coordination environment of Cd is as follows: four
oxygen atoms of the different PT ligands coordinate with the
Cd(II) ion in different bidentate chelating modes. The Cd–O
˚
distances (2.327–2.435 A) are quite similar to normal Cd–
18
OCO distances (2.251–2.879 A). The Cd–O (2.253 A) and
˚
˚
˚
the Cd–OW (2.327 A) distances in the apical positions are
CCDC reference number 195535. See http://www.rsc.org/
suppdata/nj/b2/b211358a/ for crystallographic files in CIF
or other electronic format.
slightly shorter than those in the equatorial positions, indicat-
ing that Cd(II) ions display an oblate pentagonal bipyramidal
coordination geometry.
It is noteworthy that each PT ligand adopts the uncommon
m6-bridging mode16 to connect with 4 Cd(II) ions. Overall, the
two carboxyl groups of the PT ligands exhibit three coordina-
tion modes with the Cd atoms, as shown in the Scheme 2. One
carboxyl group adopts a bidentate 1,3-chelating mode; the
other one exhibits a bidentate bridging mode. Furthermore,
both carboxyl groups show the bidentate 1,6-chelating mode.
Based on these coordination modes of PT, an interesting 2D
Cd–O–Cd inorganic framework is formed (see Fig. 2). It is also
notable that the 2D inorganic layer consists of Cd–O–Cd sin-
gle helix chains [see Fig. S1 in the Electronic Supplementary
Information (ESI)y] via corner-sharing oxygen atoms. (CdO7)
pentagonal bipyramids connect to each other alternately via
shared corners and shared edges to form left-hand single helix
chains. Furthermore, oxygen atoms (O3) of the phthalate
ligand link the single helices to produce a Cd–O–Cd inorganic
layer. As a result, these layers show a honeycomb framework
Results and discussion
Description of the crystal structure
The single crystal X-ray diffraction study reveals that com-
pound 1 consists of a 2D covalently bonded honeycomb fra-
mework built-up from cadmium(II), phthalate and water
molecules. There is only one crystallographically unique Cd
Table 1 Crystal data and structure refinement of 1
Molecular formula
M
C8H6CdO5
294.53
293(2)
T/K
˚
l/A
Crystal system
0.71073
Orthorhombic
Pbca
˚
with cavity dimensions of 9.49 ꢃ 5.79 A, filled with coordi-
Space group
˚
nated water molecules.
a/A
˚
9.2775(8)
7.7207(6)
23.449(2)
1679.6(2)
8
b/A
˚
In the packing arrangement of 1 (see Fig. 3), the adjacent 2D
undulated layers are parallel to each other and construct a 3D
structure via short C–Hꢂ ꢂ ꢂC interactions between aromatic
c/A
3
˚
U/A
Z
m/mmꢁ1
2.590
9197
Reflections collected
Independent reflections
R1 [I ꢄ 2s(I)]
Rint
1981
0.0322
0.0686
0.0814
wR2 [I ꢄ 2s(I)]
R1 (all data)
wR2 (all data)
0.0363
0.0840
Scheme 2 The coordination modes of the phthalate ligands in 1.
New J. Chem., 2003, 27, 1144–1147
1145

View Article Online
Fig. 4 The TG curve of 1.
chelating and bridging carboxylate groups. The values of Dn
for 1 suggest that the carboxylate groups coordinate to the
metal atoms in multiple monodentate (197 cmꢁ1) and bidentate
(45 cmꢁ1) fashions,20b consistent with the results of the X-ray
analysis.
Fig. 2 A ball-and-stick representation of the 2D honeycomb struc-
ture of 1, showing water molecules OW filling in the cavities (the long-
˚
est distance between opposite Cd atoms is 9.492 A and the shortest
˚
distance is 5.788 A).
The TG curve of compound 1 (see Fig. 4) can be divided into
two weight loss steps. The first step occurs in the range 150–
220 ꢀC, attributed to the removal of coordinated H2O. The
observed weight loss (5.94%) is in agreement with the calculated
value (6.11%). The second step occurs in the range 280–500 ꢀC,
corresponding to the decomposition of PT ligands. The
observed weight loss in this step (50.23%) compares well with
the calculated value (50.32%). The residue is CdO.
Compound 1 exhibits a strong fluorescent emission (see
Fig. 5). The solid state diffuse reflectance UV-vis spectrum
(Fig. S4 in ESIy) of 1 shows two intense bands at 243 and
274 nm, assigned to the intraligand p-p* transitions of phtha-
late ligand. The emission of 1 [lmax ¼ 407 nm, t ¼ 0.021 ms
(see Fig. S6 in ESIy); the short luminescence should be assigned
to fluorescence] is neither MLCT (metal-to-ligand charge
transfer) nor LMCT (ligand-to-metal charge transfer) in nat-
ure and can probably be assigned to intraligand fluorescent
emission, since free phthalic acid exhibits a similar fluorescent
emission at lmax ¼ 345 nm (Fig. S5 in ESIy). In comparison to
the free phthalic acid molecule, a bathochromic shift in 1
was observed, undoubtedly owing to the deprotonation of
the ligand during the formation of the 2D honeycomb
framework.21
groups of the phthalate ligands projecting perpendicularly
beyond the inorganic layers (the distance and angle of C–
ꢀ
˚
Hꢂ ꢂ ꢂC is 2.836 A and 153.27 , respectively) instead of the
ordinary p-p interactions observed in other layered struc-
tures.7a Both benzene motifs between adjacent phthalates are
not parallel (the angle is ca. 70ꢀ). Short C–Hꢂ ꢂ ꢂC interactions
are also found between intra-layer neighboring aromatic
˚
groups (the distance of C–Hꢂ ꢂ ꢂC is 2.858 A and the angle is
153.47ꢀ). These short interactions enhance the stability of the
compound and lead to a higher dimensional structure with
tunnels parallel to the b axis.
Bond valence calculations (Cd, 1.73) suggested that all Cd
atoms are in the +2 oxidation state.19 This result is also sup-
ported by the XPS measurement of the compound. The XPS
spectrum (Fig. S2 in ESIy) in the energy region of Cd3d3/2
and Cd3d5/2 shows one peak at 405.6eV, attributable to Cd2+
.
IR, TG and fluorescence properties
The IR spectrum of 1 (Fig. S3 in ESIy) shows several bands
in the nasym(CO2) and nsym(CO2) region at 1643, 1580, 1491
cmꢁ1 and 1446, 1417 cmꢁ1, respectively. The absence of strong
peaks around 1720 cmꢁ1 indicates that all carboxyl groups are
deprotonated.20a The absorptions at lower frequencies (1643–
1491 cmꢁ1) can be attributed to deformation vibrations of the
In conclusion, the successful isolation of 1 provides the first
example of a cadmium phthalate with an extended structure, in
which the phthalate ligands show interesting coordination
modes. Compound 1 exhibits strong fluorescent emission and
may be an excellent candidate for potential photoactive mate-
rials. Further research is going on to prepare novel metal
Fig. 3 View along the b axis of 1. Phthalate ligands project above
and below into the interlamellar region and there regularly exists some
small cavities along the b axis direction. All H atoms are omitted for
clarity.
Fig. 5 Fluorescent excitation and emission spectra of 1 in the solid
state at room temperature.
1146
New J. Chem., 2003, 27, 1144–1147

View Article Online
´
(a) C. Livage, C. Egger and G. Ferey, Chem. Mater., 1999, 11,
8
9
phthalates with extended structures and explore their various
physical properties.
´
1546; (b) C. Livage, C. Egger and G. Ferey, Chem. Mater.,
2001, 13, 410; (c) C. Serre, F. Millange, J. Marrot and G. Ferey,
´
´
Chem. Mater., 2002, 14, 2409; (d ) F. Serpaggi and G. Ferey,
J. Mater. Chem., 1998, 8, 2737.
(a) Y. J. Kim and D.-Y. Jung, Inorg. Chem., 2000, 39, 1470; (b)
Y. J. Kim, E. W. Lee and D. Y. Jung, Chem. Mater., 2001, 13,
2684; (c) E. W. Lee, Y. J. Kim and D. Y. Jung, Inorg. Chem.,
2002, 41, 501.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (20171010).
10 P. M. Forster and A. K. Cheetham, Angew. Chem., Int. Ed., 2002,
41, 457.
11 (a) R. C. Squire, S. M. J. Aubin, K. Folting, W. E. Streib,
G. Christou and D. N. Hendrickson, Inorg. Chem., 1995,
34, 6463; (b) E. K. Brechin, R. O. Gould, S. G. Harris, S. Parsons
and R. E. P. Winpenny, J. Am. Chem. Soc., 1996, 118, 11 293; (c)
E. K. Brechin, S. G. Harris, S. Parsons and R. E. P.
Winpenny, Chem. Commun., 1996, 1439; (d ) J. C. Dai,
X. T. Wu, Z. Y. Fu, C. P. Cui, S. M. Hu, W. X. Du,
L. M. Wu, H. H. Zhang and R. Q. Sun, Inorg. Chem., 2002, 41,
1391.
References
1
(a) M. Eddaoudi, D. B. Moler, H. L. Li, B. L. Chen, T. M.
Reineke, M. O’Keeffe and O. M. Yaghi, Acc. Chem. Res., 2001,
´
34, 319; (b) A. K. Cheetham, G. Ferey and T. Loiseau, Angew.
Chem., 1999, 111, 3466; A. K. Cheetham, G. Ferey and T.
Loiseau, Angew. Chem., Int. Ed., 1999, 38, 3269; (c) R. Robson,
´
J. Chem. Soc., Dalton Trans., 2002, 3735; (d ) G. Ferey,
Chem. Mater., 2001, 13, 3084.
´
12 (a) M. B. Cingi, C. Guastini, A. Musati and M. Nardelli, Acta
Crystallogr., Sect. B, 1970, 26, 1836; (b) C. K. Prout, J. R.
Carruthers and F. J. C. Rossotti, J. Chem. Soc., 1971, 3350; (c)
N. V. Gerbeleu, Y. A. Simonov, G. A. Timko, P. N. Bourosh,
J. Lipkowski, S. G. Baka, D. I. Saburov and M. D. Mazus, Russ.
J. Inorg. Chem., 1999, 44, 1191; (d ) R. C. Squire, S. M. J. Aubin,
K. Folting, W. E. Streib, D. N. Hendrickson and G. Christou,
Angew. Chem., Int. Ed. Engl., 1995, 34, 887.
13 (a) M. B. Cingi, A. M. M. Lanfredi, A. Tiripicchio and M. T.
Camellini, Acta Crystallogr., Sect. B, 1977, 33, 659; (b) M. B.
Cingi, A. M. M. Lanfredi, A. Tiripicchio and M. T. Camellini,
Acta Crystallogr., Sect. B, 1978, 34, 134; (c) M. B. Cingi, A. M.
M. Lanfredi, A. Tiripicchio and M. T. Camellini, Acta Crystal-
logr., Sect. B, 1978, 34, 406; (d ) M. B. Cingi, A. M. M. Lanfredi,
A. Tiripicchio and M. T. Camellini, Acta Crystallogr., Sect. B,
1978, 34, 412.
2
(a) C. T. Chen and K. S. Suslick, CoorD. Chem. Rev., 1993, 128,
293; (b) X. H. Bu, W. Chen, S. L. Lu, R. H. Zhang, D. Z. Liao,
W. M. Bu, M. Shionoya, F. Brisse and J. Ribas, Angew. Chem.M
Int. Ed., 2001, 40, 3210; (c) W. B. Lin, O. R. Evans, R. G. Xiong
and Z. Y. Wang, J. Am. Chem. Soc., 1998, 120, 13 272; (d ) S. T.
Wang, Y. G. Li, E. B. Wang, G. Y. Luan, C. W. Hu, N. H. Hu
and H. Q. Jia, J. Solid State Chem., 2002, 167, 402; (e) Y. G.
Li, H. Zhang, E. B. Wang, N. Hao, C. W. Hu, Y. Yan and D.
Halld, New J. Chem., 2002, 26, 1619.
(a) B. Moulton and M. J. Zaworotko, Chem. Rev., 2001, 101,
1629; M. J. Zaworotko, Chem. Commun., 2001, 1; (b) K. T.
Holman, A. M. Pivovar, J. A. Swift and M. D. Ward, Acc. Chem.
Res., 2001, 34, 107; (c) M. Kondo, T. Okubo, A. Asami, S. Noro,
T. Yoshitomi, S. Kitagawa, T. Ishii, H. Matsuzaka and K. Seki,
Angew. Chem., Int. Ed., 1999, 38, 140; (d ) L. Pan, X. Huang, J.
Li, Y. Wu and N. Zheng, Angew. Chem., Int. Ed., 2000, 39, 527;
(e) P. J. Hagrman, D. Hagrman and J. Zubieta, Angew. Chem.,
Int. Ed., 1999, 38, 2638; ( f ) D. Braga, F. Grepioni and G. R.
Desiraju, Chem. Rev., 1998, 98, 1375; (g) L. R. MacGillivray,
R. H. Groeneman and J. L. Atwood, J. Am. Chem. Soc., 1998,
120, 2676.
3
14 (a) R. E. Norman, R. C. Holz, S. Menage, C. J. O’Connor, J. H.
Zhang and L. Que, Inorg. Chem., 1990, 29, 4629; (b) I. Krstanovic,
L. Karanovic and D. Stojakovic, Acta Crystallogr., Sect. C,
1985, 41, 43; (c) H. Endres, Z. Anorg. Allg. Chem., 1984,
513, 78.
15 (a) P. A. Prasad, S. Neeraj, S. Natarajan and C. N. Rao, Chem.
Commun., 2000, 1251; (b) R. Waidhyanathan, S. Natarajan and
C. N. Rao, Chem. Mater., 2001, 13, 3524; (c) R. Waidhyanathan,
S. Natarajan and C. N. Rao, Inorg. Chem., 2002, 41, 5226; (d ) R.
Waidhyanathan, S. Natarajan and C. N. Rao, Cryst. Growth Des.,
2003, 3, 47.
16 (a) H. K. Fun, S. S. S. Raj, R. G. Xiong, J. L. Zuo, Z. Yu and
X. Z. You, J. Chem. Soc., Dalton Trans., 1999, 1915; (b) R. L.
Rardin, W. B. Tolman and S. J. Lippard, New J. Chem., 1991,
15, 417.
17 (a) G. M. Sheldrick, SHELXL97, Program for Crystal Structure
Refinement, University of Go¨ttingen, Germany, 1997; (b) G. M.
Sheldrick, SHELXL97, Program for Crystal Structure Solution,
University of Go¨ttingen, Germany, 1997.
18 W. Clegg, J. T. Cressey, A. Mccamley and B. P. Straughan, Acta
Crystallogr., Sect. C, 1995, 51, 234.
4
(a) H. Li, M. Eddaoudi, M. O’Keeffe and O. M. Yaghi, Nature
(London), 1999, 402, 276; T. M. Reineke, M. Eddaoudi, M. Fehr,
D. Kelley and O. M. Yaghi, J. Am. Chem. Soc., 1999, 121, 1651;
(b) L. Pan, N. Zheng, Y. Wu, S. Han, R. Yang, X. Huang and
J. Li, Inorg. Chem., 2001, 40, 828; (c) Z. L. Huang, M. Drillon,
N. Masciocchi, A. Sironi, J. T. Zhao, P. Rabu and P. Panissod,
Chem. Mater., 2000, 12, 2805; (d ) A. Dimos, A. Michaelides
and S. Skoulika, Chem. Mater., 2000, 12, 3256.
(a) O. M. Yaghi, H. Li and T. L. Groy, J. Am. Chem. Soc., 1996,
118, 9096; (b) S. S. Y. Chui, S. M. F. Lo, J. P. H. Charmant, A. G.
Orpen and I. D. Williams, Science, 1999, 283, 1148; (c) S. O. H.
Gutschke, M. Molinier, A. K. Powell, R. E. P. Winpenny and
P. T. Wood, Chem. Commun., 1996, 823; (d ) S. O. H. Gutschke,
D. J. Price, A. K. Powell and P. T. Wood, Angew. Chem., Int. Ed.,
2001, 40, 1920; (e) A. Dimos, A. Michaelides and S. Skoulika,
Chem. Mater., 2000, 12, 3256.
5
19 I. D. Brown and D. Altermatt, Acta. Crystallogr., Sect. B, 1985,
41, 244.
20 (a) Q. Shi, R. Cao, D. F. Sun, M. C. Hong and Y. C. Liang, Poly-
hedron, 2001, 20, 3287; (b) S. G. Baca, Y. A. Simonov, N. V.
Gerbeleu, M. Gdaniec, P. N. Bourosh and G. A. Timco, Poly-
hedron, 2001, 20, 831.
21 (a) Z. F. Chen, R. G. Xiong, J. Zhang, X. T. Chen, Z. L. Xue and
X. Z. You, Inorg. Chem., 2001, 40, 4075; (b) J. Zhang, W. B. Lin,
Z. F. Chen, R. G. Xiong, B. F. Abrahams and H. K. Fun,
J. Chem. Soc., Dalton Trans., 2001, 1806.
6
7
(a) L. Xu, Y. Q. Sun, E. B. Wang, E. H. Shen, Z. R. Liu, C. W.
Hu, Y. Xing, Y. H. Lin and H. Q. Jia, New J. Chem., 1999, 23,
1041; (b) L. Xu, Y. Q. Sun, E. B. Wang, E. H. Shen, Z. R. liu,
C. W. Hu, Y. Xing, Y. H. Lin and H. Q. Jia, J. Solid State Chem.,
1999, 146, 533.
(a) Y. Lu, E. B. Wang, M. Yuan, G. Y. Luan, Y. G. Li, H. Zhang,
C. W. Hu, Y. Yao, Y. Qin and Y. Chen, J. Chem. Soc., Dalton
Trans., 2002, 3029; (b) M. Yuan, Y. G. Li, E. B. Wang, Y. Lu,
C. W. Hu, N. H. Hu and H. Q. Jia, J. Chem. Soc., Dalton Trans.,
2002, 14, 2916.
New J. Chem., 2003, 27, 1144–1147
1147