Synthesis, crystal structures and photoluminescent properties of three novel cadmium(II) compounds constructed from 5-sulfoisophthalic acid (H 3SIP)

Article abstract of DOI:10.1002/ejic.200600532

Hydrothermal reactions of Cd(NO₃)₂ and NaH ₂SIP (5-sulfo-isophthalic acid monosodium salt) at pH = 2 and 7 produce [Cd₂(μ₂-OH₂)₂(HSIP) ₂(H₂O)₆] (1) and [Cd₅(μ ₂-OH)₂(μ₃-OH)₂(SIP) ₂(H₂O)₅]_n (2), respectively. A similar hydrothermal reaction in the presence of dpp [1,3-bis(4-pyridyl)propane] yields {[Cd₃(SIP)₂(dpp)₆]·4(H ₂O)}_n (3). Single-crystal X-ray diffraction reveals that compound 1 has a discrete dinuclear structure with the [Cd₂(μ ₂-OH₂)₂] unit. Polymer 2 features an inorganic layer, which has centrosymmetric 12- and 24-membered rings composed of chair-shaped [Cd₄(μ₃-OH)₂] units and Cd(μ₂-OH)₂(CO₂) units, and is interconnected by SIP into a 3D framework. Complex 3 contains a 1D ladder-like [Cd ₄(SIP)₄]_n unit with four cadmium atoms co-planar, which is interconnected by dpp into a 2D nanosized layered structure. In the solid state, compounds 1 and 3 exhibit blue-violet photoluminescence with maxima at 436 and 409 nm upon excitation at 342 and 350 nm, respectively. However, compound 2 shows photoluminescence with the maximum at 306 nm upon excitation at 270 nm. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200600532

FULL PAPER
DOI: 10.1002/ejic.200600532
Synthesis, Crystal Structures and Photoluminescent Properties of Three Novel
Cadmium(II) Compounds Constructed from 5-Sulfoisophthalic Acid (H3SIP)
Qing-Yan Liu,[a] Yu-Ling Wang,[b] and Li Xu*[a]
Keywords: Cadmium compounds / Hydrothermal synthesis / Crystal structures / Photoluminescent properties
Hydrothermal reactions of Cd(NO3)2 and NaH2SIP (5-sulfo-
isophthalic acid monosodium salt) at pH = 2 and 7 produce
[Cd2(µ2-OH2)2(HSIP)2(H2O)6] (1) and [Cd5(µ2-OH)2(µ3-
OH)2(SIP)2(H2O)5]n (2), respectively. A similar hydrothermal
reaction in the presence of dpp [1,3-bis(4-pyridyl)propane]
yields {[Cd3(SIP)2(dpp)6]·4(H2O)}n (3). Single-crystal X-ray
diffraction reveals that compound 1 has a discrete dinuclear
structure with the [Cd2(µ2-OH2)2] unit. Polymer 2 features an
inorganic layer, which has centrosymmetric 12- and 24-mem-
bered rings composed of chair-shaped [Cd4(µ3-OH)2] units
and Cd(µ2-OH)2(CO2) units, and is interconnected by SIP into
a 3D framework. Complex 3 contains a 1D ladder-like
[Cd4(SIP)4]n unit with four cadmium atoms co-planar, which
is interconnected by dpp into a 2D nanosized layered struc-
ture. In the solid state, compounds 1 and 3 exhibit blue-violet
photoluminescence with maxima at 436 and 409 nm upon ex-
citation at 342 and 350 nm, respectively. However, compound
2 shows photoluminescence with the maximum at 306 nm
upon excitation at 270 nm.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Introduction
including diverse electronic properties and coordination
The design and construction of metal–organic frame- geometries of the metal ions as well as versatile functions
works (MOFs) has been one of the most active areas of of organic ligands.[5–7] Consequently, a wide variety of coor-
materials research in recent years. The intense interest in dination architectures with interesting structures and de-
these materials is driven by their potential applications as sired properties have been prepared through judicious
functional materials (catalysis, magnetism, electric conduc- choice of organic ligands and metal ions.[8–11] Recently, 5-
tivity and nonlinear optics) and intriguing structural diver- sulfoisophthalic acid (H3SIP) has been successfully used to
sities.[1–4] Assembly of these metal–organic coordination investigate the lanthanide contraction effect[12] and the co-
polymers allows for a wide choice of various parameters ordination polymer chemistry of a main group metal
Scheme 1. Coordination modes of 5-sulfoisophthalic acid observed in compounds 1–3.
[a] State Key Laboratory of Structural Chemistry, Fujian Institute (Pb2+),[13] because of its multiple coordinating modes and
of Research on the Structure of Matter, Chinese Academy of
the sensitivity of the sulfonate group to the surrounding
Sciences,
chemical environment. In this contribution, SIP will serve
as a probe to examine the coordination polymer chemistry
of the late transition metal Cd2+. Three novel (SIP)Cd com-
pounds, [Cd2(µ2-OH2)2(HSIP)2(H2O)6] (1), [Cd5(µ2-OH)2-
(µ3-OH)2(SIP)2(H2O)5]n (2) and {[Cd3(SIP)2(dpp)6]·
4(H2O)}n (3), will be described with regard to syntheses,
crystal structures, and IR spectroscopic and photolumines-
Fuzhou, Fujian 350002, P. R. China
Fax: +86-591-83705045
E-mail: xli@fjirsm.ac.cn
qyliu@fjirsm.ac.cn
[b] College of Chemistry and Chemical Engineering, Jiangxi Nor-
mal University,
Nanchang, Jiangxi 330022, P. R. China
Fax: +86-791-8120387
E-mail: ylwangchem@gmail.com
Eur. J. Inorg. Chem. 2006, 4843–4851
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4843

Q.-Y. Liu, Y.-L. Wang, L. Xu
FULL PAPER
cent properties. Two unprecedented bridging coordination C2 axis passing through O7 and O7A (for symmetry code
modes of SIP (Scheme 1, b and c) are observed in polymer see Table 1). The two CdII atoms are linked by two bridging
2.
water molecules to form the rhomboidal [Cd2(µ2-OH2)2]
core with a Cd–O distance of 2.412(1) Å and O(7)–Cd(1)–
O(7A) bond angle of 75.48(8)°. Each cadmium ion is
bonded to two bridging water molecules, three terminal
water molecules and one HSIP2– dianion through the che-
lating carboxylate group. The Cd–O distances range from
2.412(1) to 2.567(3) Å, which is consistent with those found
in comparable structures.[16–19] The uncoordinated carbox-
ylate group is protonated for charge balance, as suggested
by the strong absorption at 1710 cm–1.[20] As shown in Fig-
ure 2a, a 3D supramolecular framework is formed through
three types of hydrogen bonds between (a) coordinated
water molecules and sulfonate oxygen atoms [O(7)···O(5B)
2.732(2) Å, O(8)···O(6C) 2.832(2) Å and O(9)···O(6D)
2.808(2) Å]; (b) coordinated water molecules and carboxyl-
ate oxygen atoms [O(9)···O(4B) 2.867(3) Å]; and (c) a car-
boxylate group and a carboxylate oxygen atom [O(3)···
O(2E) 2.581(3) Å]. Of particular interest is the infinite
tape formed by hydrogen bonds between the [Cd2(µ2-OH2)2-
(H2O)2] units and the sulfonate groups along the crystallo-
graphic b axis (Figure 2b). The hydrogen-bonded tape fea-
tures an eight-membered ring [the bridging H2O(7), O(5)
and their equivalents], which is nearly perpendicular to the
[Cd2(µ2-OH2)2] plane (95.7°). The tape is strengthened by
the O(8)···O(6C) hydrogen bonds, as shown in Figure 2b.
The 3D supramolecular structures are further stabilised by
π–π interactions between the parallel aromatic rings in an
off-set fashion with a face-to-face distance of 3.44(2) Å and
a centre-to-centre distance of 3.66(3) Å. This indicates that
noncovalent interactions can play a crucial role in con-
structing the whole packing.
Results and Discussion
Preparation of the Compounds
Hydrothermal synthesis is widely employed to produce
new materials with diverse structural architectures, but is
still a kind of black box. This method can minimise the
problems associated with ligand solubility and enhance the
reactivity of reactants in favour of efficient molecular build-
ing during the crystallisation process. There are a variety of
hydrothermal parameters such as reaction time, tempera-
ture, pH value, templates and molar ratio of reactants, and
small changes in one or more of these parameters can have
a profound influence on the final reaction outcome. Com-
pounds 1 and 2, with very different structures, were ob-
tained from similar reactions but at different pH values, in-
dicating that the hydrothermal reaction outcome of the Cd/
H3SIP system is pH-dependent. We also notice that N-con-
taining auxiliary ligands such as dpp [1,3-bis(4-pyridyl)-
propane] are also able to tune the framework structures. At
a ratio of Cd/SIP/dpp = 3:2:6, the 2D polymer 3 is
formed. Reducing the corresponding ratio to 3:2:2 results
in the 1D compound {[Cd(SIP)(dpp)(H2O)3]·0.5Cd(H2O)6·
5H2O}n,[14] indicating that the reaction products are ratio-
dependent. The preparative reactions were carried out at
different temperatures (140 °C, 160 °C and 180 °C) to ex-
amine the temperature dependence of their solid structures.
X-ray diffraction analyses of these reaction products indi-
cate that the same results were obtained under these reac-
tion temperatures although the purity and yields were
slightly different, indicative of the thermodynamic nature of
the hydrothermal reactions.[15]
Crystal Structure of [Cd5(µ2-OH)2(µ3-OH)2(SIP)2(H2O)5]n
(2)
Crystal Structure of [Cd2(µ2-OH2)2(HSIP)2(H2O)6] (1)
The dinuclear structure of 1 is shown in Figure 1; it has
Compound 2 contains five unique CdII ions, four of
a crystallographically imposed C2h symmetry, which has the which are six-coordinate and one [Cd(3)] five-coordinate.
Figure 1. ORTEP drawing of 1 with 40% probability displacement ellipsoids. Hydrogen atoms are shown as small spheres of arbitrary
radii.
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Novel Cadmium(II) Compounds Constructed from 5-Sulfoisophthalic Acid
FULL PAPER
As shown in Figure 3, Cd(1) has a distorted octahedral co- Table 1. (continued).
ordination geometry with the equatorial positions taken up
by one chelating carboxylate group [O(10A) and O(11A)],
Compound 3
Cd(1)–O(5)
2.317(2)
2.338(3)
2.539(2)
2.300(3)
2.356(3)
82.75(10)
90.22(9)
89.78(9)
129.70(9)
53.47(7)
86.42(10)
83.89(9)
84.90(8)
84.37(9)
167.37(10)
Cd(1)–N(1)
2.372(3)
2.302(2)
2.346(2)
2.351(3)
Cd(1)–N(3)
Cd(2)–O(3B)
Cd(2)–N(5)
Cd(2)–N(6D)
N(1)–Cd(1)–N(3)
N(1)–Cd(1)–O(5)
N(1A)–Cd(1)–O(5)
O(1)–Cd(2)–N(5)
O(3B)–Cd(2)–O(4B)
N(6D)–Cd(2)–O(1)
N(6D)–Cd(2)–O(4B)
N(4C)–Cd(2)–O(1)
N(4C)–Cd(2)–O(4B)
N(4C)–Cd(2)–O(6D)
Cd(2)–O(1)
Cd(2)–O(4B)
Cd(2)–N(4C)
Table 1. Selected bond lengths [Å] and bond angles [°] of 1–3.[a]
N(1)–Cd(1)–N(3A)
N(3)–Cd(1)–O(5)
97.25(10)
95.57(9)
84.43(9)
84.90(8)
91.42(8)
83.31(9)
91.61(10)
85.97(9)
95.33(10)
Compound 1
N(3A)–Cd(1)–O(5)
O(1)–Cd(2)–O(4B)
N(5)–Cd(2)–O(3B)
N(6D)–Cd(2)–O(3B)
N(6D)–Cd(1)–N(5)
N(4C)–Cd(2)–O(3B)
N(4C)–Cd(1)–N(5)
Cd(1)–O(1)
Cd(1)–O(7)
2.265(2)
2.4121(13) Cd(1)–O(8)
Cd(1)–O(2)
2.567(3)
2.284(2)
Cd(1)–O(9)
2.2683(18)
O(1)–Cd(1)–O(2)
O(1)–Cd(1)–O(8)
O(7)–Cd(1)–O(7A)
O(9)–Cd(1)–O(8)
O(9)–Cd(1)–O(2)
O(7)–Cd(1)–O(2)
Cd(1)–O(7)–Cd(1A)
52.45(8)
163.71(9)
75.48(8)
81.13(6)
78.00(6)
123.84(4)
104.52(8)
O(1)–Cd(1)–O(7)
83.93(5)
107.82(6)
85.73(7)
83.21(5)
143.84(8)
108.51(11)
O(1)–Cd(1)–O(9)
O(9)–Cd(1)–O(7)
O(7)–Cd(1)–O(8)
O(2)–Cd(1)–O(8)
O(9)–Cd(1)–O(9A)
[a] Symmetry transformation for equivalent atoms: Compound 1:
A: –x, –y + 1, –z + 2. Compound 2: A: x + 1, y, z – 1; B: –x, –y
+ 2, –z + 1; C: –x – 1, –y + 3, –z + 1; D: –x, –y + 2, –z + 2; E:
–x – 1, –y + 3, –z + 2; F: –x – 1, –y + 2, –z + 2. Compound 3:
A: –x – 1, –y + 1, –z + 1; B: x – 1, y, z; C: –x – 1, –y, –z + 1; D:
x, y + 1, z.
Compound 2
Cd(1)–O(1)
Cd(1)–O(16)
Cd(1)–O(11A)
Cd(2)–O(2)
Cd(2)–O(16C)
Cd(2)–O(18)
Cd(3)–O(3)
Cd(3)–O(18)
Cd(3)–O(20)
Cd(4)–O(20)
Cd(4)–O(22)
Cd(4)–O(22D)
Cd(5)–O(22)
Cd(5)–O(8E)
Cd(5)–O(4F)
O(1)–Cd(1)–O(16)
O(10A)–Cd(1)–O(11A)
O(15)–Cd(1)–O(16)
O(15)–Cd(1)–O(10A)
O(5B)–Cd(1)–O(1)
O(5B)–Cd(1)–O(10A)
O(16C)–Cd(2)–O(16)
O(18)–Cd(2)–O(6B)
O(2)–Cd(2)–O(16)
O(2)–Cd(2)–O(18)
O(17)–Cd(2)–O(16)
O(17)–Cd(2)–O(18)
O(3)–Cd(3)–O(12)
O(12)–Cd(3)–O(18)
O(19)–Cd(3)–O(12)
O(20)–Cd(2)–O(3)
O(20)–Cd(3)–O(18)
O(13)–Cd(4)–O(22)
O(22D)–Cd(4)–O(22)
O(13)–Cd(4)–O(20)
O(21)–Cd(4)–O(20)
O(13)–Cd(4)–O(9E)
O(21)–Cd(4)–O(9E)
O(4B)–Cd(5)–O(8E)
O(8E)–Cd(5)–O(22)
O(14)–Cd(5)–O(4F)
O(14)–Cd(5)–O(8E)
O(23)–Cd(5)–O(4F)
O(23)–Cd(5)–O(8E)
Cd(1)–O(16)–Cd(2C)
Cd(2)–O(18)–Cd(3)
Cd(4)–O(22)–Cd(5)
Cd(5)–O(22)–Cd(4D)
2.258(3)
2.198(2)
2.317(3)
2.315(3)
2.260(2)
2.200(3)
2.260(2)
2.201(3)
2.182(3)
2.237(2)
2.286(2)
2.235(2)
2.193(2)
2.270(2)
2.309(3)
118.75(9)
54.97(9)
97.29(10)
85.45(13)
90.71(9)
84.97(11)
81.20(8)
90.15(11)
78.61(9)
Cd(1)–O(15)
Cd(1)–O(10A)
Cd(1)–O(5B)
Cd(2)–O(16)
Cd(2)–O(17)
Cd(2)–O(6B)
Cd(3)–O(12)
Cd(3)–O(19)
Cd(4)–O(13)
Cd(4)–O(21)
Cd(4)–O(9E)
Cd(5)–O(14)
Cd(5)–O(23)
Cd(5)–O(3F)
2.327(3)
2.405(3)
2.445(2)
2.276(2)
2.398(4)
2.412(2)
2.432(2)
2.287(3)
2.416(2)
2.276(3)
2.345(2)
2.517(2)
2.279(3)
2.507(2)
one monodentate carboxylate oxygen atom [O(1)] and one
µ3-hydroxy oxygen atom [O(16)]. The axial positions are oc-
cupied by one water molecule [O(15)] and one sulfonate
oxygen atom [O(5B)] from the third SIP ligand. The angles
formed by the equatorial atoms range from 54.97(9)°
[O(10A)–Cd(1)–O(11A)] to 118.75(9)° [O(1)–Cd(1)–O(16)],
indicative of a serious distortion of the [CdO6] octahedron.
Cd(5) has a similar coordination environment to that of
Cd(1). Cd(2) also has a distorted [CdO6] octahedral coordi-
nation geometry in which a pair of symmetrically related
µ3-hydroxy oxygen atoms [O(16) and O(16C)], a µ2-hydroxy
oxygen atom [O(18)] and a sulfonate oxygen atom [O(6B)]
form the equatorial plane. The water molecule [O(17)] and
the carboxylate oxygen atom [O(2)] occupy the apical posi-
tions. The coordination environment of Cd(4) is similar to
that of Cd(2) but the terminal water molecule [O(21)] is
located at the equatorial plane and the µ2-hydroxy oxygen
atom [O(20)] occupies the apical position. The Cd(3) atom
is coordinated by one µ2-hydroxy oxygen atom [O(18)], a
sulfonate oxygen atom [O(12)] and one carboxylate oxygen
atom [O(3)] in an equatorial plane, and the other µ2-hy-
droxy oxygen atom [O(20)] and the water molecule [O(19)]
in the apical positions to complete its trigonal-bipyramidal
coordination environment. The Cd–O distances range from
2.182(3) to 2.517(2) Å, as listed in Table 1. Two crystallo-
graphically unique SIP ligands exhibit two different coordi-
nation modes (Scheme 1, b and c). One SIP (b) acts as a
hexadentate ligand with the bidentate sulfonate and carbox-
ylate groups, and one µ2-η2:η1 carboxylate group (one oxy-
gen atom bridges two metal atoms, the other connects one
metal atom and the carboxylate group coordinates to two
metal atoms). The other SIP ligand also adopts a hexaden-
tate bridging coordination mode through its one bidentate
carboxylate group, one chelate carboxylate group and the
tridentate sulfonate group. To the best of our knowledge,
O(1)–Cd(1)–O(11A)
O(16)–Cd(1)–O(10A)
O(15)–Cd(1)–O(1)
O(15)–Cd(1)–O(11A)
O(5B)–Cd(1)–O(16)
O(5B)–Cd(1)–O(11A)
O(6B)–Cd(2)–O(16)
O(16C)–Cd(2)–O(18)
O(2)–Cd(2)–O(16C)
82.70(9)
101.87(9)
99.84(12)
93.96(11)
79.69(8)
84.72(10)
174.23(9)
93.27(11)
92.43(9)
108.43(11) O(2)–Cd(2)–O(6B)
82.08(9)
90.06(15)
84.41(15)
103.64(8)
121.49(11) O(19)–Cd(3)–O(3)
73.32(9)
92.98(9)
O(17)–Cd(2)–O(16C)
O(17)–Cd(2)–O(6B)
O(3)–Cd(3)–O(18)
100.81(16)
84.14(15)
129.41(11)
78.58(9)
92.68(11)
98.00(9)
82.07(10)
92.43(9)
100.88(9)
110.23(9)
79.23(8)
O(19)–Cd(3)–O(18)
O(20)–Cd(3)–O(12)
101.49(11) O(13)–Cd(4)–O(21)
100.35(8)
83.20(8)
82.62(9)
88.06(10)
77.61(9)
92.88(10)
83.71(9)
120.34(9)
85.51(9)
87.58(9)
97.71(11)
102.12(11) Cd(1)–O(16)–Cd(2)
124.45(11) Cd(2)–O(16)–Cd(2C)
142.54(16) Cd(3)–O(20)–Cd(4)
105.06(9)
121.22(10) Cd(3)–O(3)–Cd(5F)
O(22D)–Cd(4)–O(21)
O(22)–Cd(4)–O(20)
O(22D)–Cd(4)–O(20)
O(22)–Cd(4)–O(9E)
O(22D)–Cd(4)–O(9E)
O(3F)–Cd(5)–O(4F)
O(3F)–Cd(5)–O(22)
O(14)–Cd(5)–O(3F)
O(14)–Cd(5)–O(22)
O(23)–Cd(5)–O(3F)
O(23)–Cd(5)–O(22)
89.83(9)
54.08(8)
97.64(8)
79.74(8)
78.12(8)
94.46(11)
94.77(10)
105.56(9)
98.80(8)
111.16(11)
96.80(8)
Cd(4)–O(22)–Cd(4D)
121.56(10)
Eur. J. Inorg. Chem. 2006, 4843–4851
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Q.-Y. Liu, Y.-L. Wang, L. Xu
FULL PAPER
Figure 2. (a) 3D porous supramolecular open framework of 1 viewed along the c axis. (b) [Cd2(µ2-OH2)2] cores bridged by sulfonate
groups through hydrogen bonds to form a 1D tape.
Figure 3. ORTEP drawing of 2 with 40% probability displacement ellipsoids.
neither type of coordination mode of the SIP ligands is ob- (O16) as a metal linker bridges the neighbouring three Cd
served in the reported SIP complexes.
atoms to generate a chair-shaped tetranuclear [Cd4(µ3-
The 3D framework structure shown in Figure 4a is con- OH)2] cluster with Cd(2), O(16) and their equivalents re-
structed by inorganic oxide layers pillared by the SIP li- lated by an inversion centre defining a plane and with the
gands, reminiscent of reported metal biphosphonate com- two Cd(1) atoms above and below the [Cd2(µ3-OH)2] plane.
pounds.[21,22] The inorganic oxide layer contains two types The Cd(1)–O(16), Cd(2)–O(16) and Cd(2C)–O(16) dis-
of chair-like [Cd4(µ3-OH)2] cluster units formed by Cd(1)/ tances are 2.198(2), 2.276(2) and 2.260(2) Å, respectively,
Cd(2) and Cd(4)/Cd(5), respectively, and features two types with surrounding angles of 105.56(9)°, 124.45(11)° and
of centrosymmetric rings: 12-membered (A) and 24-mem- 98.80(8)° for Cd(1)–O(16)–Cd(2), Cd(1)–O(16)–Cd(2C) and
bered (B). As shown in Figure 4b, each µ3-hydroxy group Cd(2)–O(16)–Cd(2C), respectively. The chair-shaped
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Novel Cadmium(II) Compounds Constructed from 5-Sulfoisophthalic Acid
FULL PAPER
Figure 4. (a) 3D structure of 2 (the polyhedral presentation indicates the coordination environments for the Cd centre). (b) Perspective
view of the 2D metal–oxide inorganic layer featuring the chair-shaped [Cd4(µ3-OH)2] clusters and two types of large rings.
[Cd4(µ3-OH)2] cluster formed by Cd(4)/Cd(5) has a similar with approximate dimensions of 3.8ϫ4.9 Å2, which is com-
geometry to that of the [Cd4(µ3-OH)2] cluster formed by posed of Cd(3), Cd(4) and Cd(5) atoms and their equiva-
Cd(1)/Cd(2), with Cd(5)–O(22), Cd(4)–O(20) and Cd(4)– lents linked by two µ3-OH, two µ2-OH and two carboxylate
O(22) bond lengths of 2.193(2), 2.286(2) and 2.237(2) Å, groups. It also contains a large 24-membered ring (B) with
respectively, and surrounding angles of 105.06(9)°, approximate dimensions of 4.7 ϫ 14.3 Å2. The inorganic
121.22(10)° and 96.80(8)° for Cd(4)–O(22)–Cd(5), Cd(5)– oxide layer is linked by the carboxylate and sulfonate
O(22)–Cd(4D) and Cd(4)–O(22)–Cd(4D), respectively. groups of the SIP ligands to form a 3D pillared framework.
There are several compounds containing a chair-shaped tet-
ranuclear cadmium cluster,[23–25] but those with two cap-
ping µ3-OH groups are rare. It is even more interesting that
the [Cd4(µ3-OH)2] cluster units are interconnected by the
Crystal Structure of {[Cd3(SIP)2(dpp)6]·4(H2O)}n (3)
Cd(3)(µ2-OH)2(CO2) unit into an unusual inorganic oxide
As shown in Figure 5, 3 contains two crystallographically
layer. Although cadmium cluster units have been known to independent cadmium ions; Cd(1) lies on the crystallo-
be present in coordination polymers,[6,26–28] such cluster- graphic inversion centre. Both Cd2+ ions are octahedrally
based inorganic layers as subunits of a coordination poly- coordinated but their coordination environments are dif-
mer are still scarce. The layer has a 12-membered ring (A) ferent. Cd(1) is coordinated to four equatorial pyridine ni-
Eur. J. Inorg. Chem. 2006, 4843–4851
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Q.-Y. Liu, Y.-L. Wang, L. Xu
FULL PAPER
trogen atoms [Cd–N = 2.372(3) and 2.338(3) Å] in a square- co-planar. The 1D ladder can also conveniently be regarded
planar arrangement and two apical sulfonate oxygen atoms as resulting from two antiparallel [Cd(SIP)]n single chains
from two trans-SIP ligands [Cd–O = 2.317(2) Å]. Cd(2) is bridged by Cd(1) (Figure 6).
coordinated by one chelating and one monodentate carbox-
Compound 3 contains one monodentate [N(1)···N(2)]
ylate group from two different SIP ligands, and one pyri- and two bridging dpp ligands [N(3)···N(4) and N(5)···N(6)].
dine nitrogen atom in equatorial positions with Cd–O dis- The flexible dpp ligand can adopt several conformations
tances of 2.346(2), 2.539(2) and 2.302(2) Å, respectively, based on the orientations of the CH2 groups, such as TT,
and a Cd–N distance of 2.300(3) Å. The axial positions are TG, GG and GGЈ (T = trans; G =gauche ), with quite dif-
taken up by two other pyridine nitrogen atoms, with Cd– ferent N···N separations (6.7–10.1 Å).[29,30] In the present
N distances of 2.351(3) and 2.356(3) Å. As illustrated in case, the monodentate dpp has a conformation of TG with
Figure 6, the SIP ligands interconnect the Cd2+ ions in co- an N···N distance of 8.9 Å and the bridging ones adopt TT
ordination mode d (Scheme 1) into an infinite ladder struc- conformation with an N···N separation of 9.5 Å. The 1D
ture along the a axis, which features the cyclic [Cd4(SIP)4] ladders are connected by the bridging dpp ligands to form
unit with dimensions of 7.5ϫ12.8 Å2. It is interesting that a 2D nanolayer with a thickness of about 1.5 nm, as shown
the four Cd ions [Cd(1), Cd(2), Cd(1A) and Cd(2A)] are in Figure 7; the cavity is filled in by the monodentate dpp.
Figure 5. ORTEP drawing of 3 with 35% probability displacement ellipsoids.
Figure 6. 1D ladder structure in compound 3 featuring the cyclic [Cd4(SIP)4] unit.
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Novel Cadmium(II) Compounds Constructed from 5-Sulfoisophthalic Acid
FULL PAPER
which is similar to that of the analogue {[Cd(SIP)(H2O)3]·
[17]
0.5(H2en)(H2O)}n
(412 nm), can be assigned to ligand-
to-metal charge transfer (LMCT). This is consistent with
the fact that the CdII or ZnII coordination complexes with
aromatic carboxylate ligands may possess an LMCT photo-
luminescent property.[34–36] In the case of 2, the emission at
306 nm upon excitation at 270 nm is similar to that of the
free H3SIP ligand. This indicates that the emission band of
2 is an intraligand transition. The further lifetime measure-
ments at room temperature of each emission maximum give
results of 0.61, 18 and 0.56 ns for compounds 1, 2 and 3,
respectively. The lifetime of 2 is significantly longer than
those of 1 and 3. This is consistent with the fact that metal
hydroxide (or oxide) clusters usually have longer emission
lifetimes[35] because the µ2/µ3-OH ligands can tighten the
whole framework and thus result in weaker vibrations.
These observations clearly reveal the structure-dependent
photoluminescent properties of coordination polymers.
Figure 7. Perspective view of the 2D structure of 3. Lattice water
molecules and monodentate dpp molecules omitted for clarity.
FTIR Spectra
The FTIR spectra of 1 and 3 exhibit broad absorptions
centred at 3498 and 3399 cm–1 for 1 and 3, respectively, be-
cause of the existence of water molecules in the structures.
The O–H stretching vibrations of the water molecules and
hydroxy group in 2 appear at 3435 and 3159 cm–1. The IR
spectra of 1–3 display the typical stretching bands of car-
boxylate groups between 1400 and 1622 cm–1. The charac-
teristic band at 1710 cm–1 in 1 is attributable to the proton-
ated carboxylate group of H3SIP ligand. The absorptions
in the region 1000–1230 cm–1 in 1–3 are typical for the sul-
fonate groups. The strong absorptions at about 620 cm–1 in
1–3 can be assigned to the S–O stretching vibrations.
Photoluminescent Properties
Metal–organic frameworks (MOFs) are promising pho-
toluminescent materials because of their high thermal sta-
bility, and structure- and metal-dependent emission. The
combination of organic linkers and metal centres in coordi-
nation polymers provides an efficient route to a new type
of photoluminescent materials with potential applications
as light-emitting diodes (LEDs). The d10 metal compounds
have been shown to exhibit interesting photoluminescent
properties.[31–33] In the present work, we have examined the
Figure 8. Solid-state emission photoluminescent spectra of 1–3 at
room temperature.
Conclusions
In conclusion, hydrothermal reactions of the Cd/H3SIP
photoluminescent properties of 1–3 and the free H3SIP li- system are pH-dependent. Incomplete deprotonation of the
gand in the solid state at room temperature. Free NaH2SIP H3SIP ligand occurs under acidic conditions, leading to
displays a photoluminescent emission at 320 nm upon exci- lowered connectivity of the SIP ligand and the formation
tation at 286 nm.[17] Compound 1 exhibits a broad photolu- of the discrete dinuclear compound 1. The ligand is fully
minescent emission centred at 436 nm upon excitation at deprotonated under neutral or basic conditions, ac-
342 nm and 3 displays an emission at 409 nm upon exci- companied by the formation of the hydroxy-bridged cad-
tation at 350 nm (Figure 8). The emissions of 1 (436 nm) mium clusters 2. In 2, the chair-like [Cd4(µ3-OH)2] cluster
and 3 (409 nm) occur at much longer wavelengths than that units are interconnected by the [Cd(µ2-OH)2(CO2)] unit
of the free ligand (320 nm). Such a large bathochromic shift into an unprecedented inorganic oxide layer, which is pil-
indicates that the aromatic rings of the ligand effectively lared by the SIP3– ligand into a 3D framework structure.
interact with the metal ion and/or with each other through Two unprecedented coordination modes are observed in
π-stacking interactions, as described above. In other words, compound 2. The addition of the auxiliary ligand dpp leads
the π-electrons of the aromatic rings are delocalised over to the 2D structure of 3 containing a cyclic [Cd4(SIP)4] unit
the Cd2+ ion and/or the neighbouring ligand. With the with the Cd atoms co-planar. Compounds 1–3 display dif-
above concerns in mind, the fluorescence emission of 1 may ferent photoluminescent emissions at room temperature, in-
tentatively be assigned to the formation of the [Cd2(µ2- dicating structure-dependent photoluminescent properties
OH2)2] cluster, which compares to our recently reported of the Cd/SIP coordination polymers and thus potential ap-
(SIP)lead compound.[13] The emission peak of 3 at 409 nm, plication in LED technology.
Eur. J. Inorg. Chem. 2006, 4843–4851
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FULL PAPER
1615 s, 1569 w, 1553 m, 1400 s, 1216 w, 1182 s, 1106 m, 1044 s, 858
w, 833 w, 707 w, 673 m, 620 m, 447 w cm–1.
Experimental Section
General Remarks: All chemicals were purchased commercially and
used without further purication, including 5-sulfoisophthalic acid
monosodium salt (Alfa) and 1,3-bis(4-pyridyl)propane (Acros). El-
emental analyses were carried out with an Elementar Vario EL III
analyser and IR spectra (KBr pellets) were recorded with a Perkin–
Elmer Spectrum One. Fluorescent spectra were measured at room
temperature with an Edinburgh FL-FS90 TCSPC system. All com-
plexes were synthesised by a hydrothermal method under autoge-
nous pressure.
Synthesis of {[Cd3(SIP)2(dpp)6]·4(H2O)}n (3): A mixture of CdII ni-
trate tetrahydrate (0.0231 g, 0.075 mmol), 5-sulfoisophthalic acid
monosodium salt (0.0134 g, 0.05 mmol), 1,3-bis(4-pyridyl)propane
(0.0297 g, 0.15 mmol), triethylamine (0.01 mL) and water (15 mL)
was heated at 160 °C for 4 d. Colourless rod-like crystals of 3 were
obtained when cooling to room temperature at 5 °C/h. The crystals
were recovered by filtration, washed with distilled water and dried
in air (yield: 0.023 g, 46% based on Cd). C94H98Cd3N12O18S2
(2085.16): calcd. C 54.02, H 4.73, N 8.05; found C 54.03, H 4.71,
Synthesis of [Cd2(µ-OH2)2(HSIP)2(H2O)6] (1): A mixture of CdII
nitrate tetrahydrate (0.0616 g, 0.2 mmol), 5-sulfoisophthalic acid
monosodium salt (0.0536 g, 0.2 mmol), triethylamine (0.01 mL)
and water (15 mL) (pH = 2) was heated at 160 °C for 4 d. Colour-
less plate-like crystals of 1 were obtained when cooling to room
temperature at 5 °C/h. The crystals were recovered by filtration,
washed with distilled water and dried in air (yield: 0.05 g, 63%
based on Cd). C16H24Cd2O22S2 (857.27): calcd. C 22.33, H 2.81;
N 8.02. IR (KBr pellet): ν = 3399 s, 2943 s, 1612 s, 1560 w, 1502
˜
w, 1428 s, 1364 s, 1224 m, 1199 m, 1103 m, 1068 w, 1042 m, 1015
m, 925 w, 846 w, 811 m, 781 w, 728 m, 624 m, 576 w, 515 w, 448
w cm–1.
X-ray Crystallographic Study: X-ray diffraction data of compounds
1–3 were collected with a Rigaku Mercury CCD diffractometer
equipped with graphite-monochromated Mo-Ka radiation (λ =
0.71073 Å). CrystalClear software was used for data reduction and
empirical absorption correction.[37] The structures were solved by
the direct methods and successive Fourier difference syntheses, and
refined by the full-matrix least-squares method on F2 (SHELXTL
found C 22.31, H 2.76. IR (KBr pellet): ν = 3498 s, 1710 s, 1622 s,
˜
1580 w, 1552 s, 1436 w, 1371 s, 1231 s, 1187 s, 1118 s, 1047 s, 999
w, 857 w, 768 m, 731 w, 673 m, 624 m, 580 w cm–1.
Synthesis of [Cd5(µ2-OH)2(µ3-OH)2(SIP)2(H2O)5]n (2): A mixture Version 5.1[38]). The H atoms bonded to C atoms and N atoms
of CdII nitrate tetrahydrate (0.0616 g, 0.2 mmol), 5-sulfoisophthalic
acid monosodium salt (0.0536 g, 0.2 mmol), triethylamine
were assigned to calculated positions and refined using a riding
model [C–H = 0.93 Å, Uiso(H) = 1.2Uiso(C); N–H = 0.89 Å, Uiso(H)
(0.05 mL) and water (15 mL) (pH = 7) was heated at 160 °C for = 1.2Uiso(N)]; H atoms bonded to O atoms were located from dif-
4 d. Colourless prism-like crystals of 2 were obtained when cooling
to room temperature at 5 °C/h. The crystals were recovered by fil-
tration, washed with distilled water and dried in air (yield: 0.013 g,
11% based on Cd). C16H20Cd5O23S2 (1206.44): calcd. C 15.82, H
ference maps except for one lattice water oxygen atom of com-
pound 3, which could not be located. The R1 values are defined as
R1 = Σ||Fo| – |Fc||/Σ|Fo| and wR2 = {Σ[w(Fo – Fc ) ]/Σ[w(Fo2)2]}1/2
.
2
2 2
Details of the crystal parameters, data collection and refinement
are summarised in Table 2, and selected bond lengths and bond
1.66; found C 15.76, H 1.63. IR (KBr pellet): ν = 3435 s, 3159 s,
˜
Table 2. Crystallographic data for compounds 1–3.
1
2
3
Empirical formula
Formula mass
Temperature [K]
Crystal size [mm]
Crystal system
Space group
Z
a [Å]
b [Å]
c [Å]
α [°]
C16H24Cd2O22S2
857.27
293(2)
0.40ϫ0.28ϫ0.05
monoclinic
C2/m
C16H20Cd5O23S2
1206.44
293(2)
C94H98Cd3N12O18S2
2085.16
293(2)
0.38ϫ0.30ϫ0.20
triclinic
0.45ϫ0.25ϫ0.10
triclinic
¯
P1
2
¯
P1
1
2
23.104(6)
6.8756(11)
8.7315(18)
90
107.007(14)
90
1326.4(5)
2.146
1.860
8.16570(10)
12.0452(2)
15.2366(3)
78.749(5)
85.824(6)
72.229(5)
1399.56(4)
2.863
10.2233(15)
12.842(2)
19.073(3)
101.562(4)
99.637(5)
104.124(6)
2316.5(6)
1.495
β [°]
γ [°]
V [Å3]
Dcalcd. [g/cm3]
µ [mm–1]
3.988
0.801
Measured reflections
Independent reflections
Observed reflections [I Ͼ 2σ(I)]
Parameters
F(000)
Completeness [%]
2θ range [°]
h/k/l ranges
5133
1645
1581
136
848
99.7
3.10–27.49
–29/29
–8/8
–6/11
0.0258
0.0208
0.0550
10722
6286
5828
464
1144
97.8
3.19–27.48
–10/10
–9/15
–18/19
0.0164
0.0267
0.0705
1.798/–1.372
18047
10479
9017
584
1066
98.5
3.06–27.48
–13/12
–13/16
–24/24
0.0225
Rint
R1 (obsd. refl.)
wR2 (all refl.)
0.0439
0.0980
1.246/–0.598
Largest diff. peak/hole [e/Å3]
0.390/–0.728
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Novel Cadmium(II) Compounds Constructed from 5-Sulfoisophthalic Acid
FULL PAPER
[16] Z. M. Sun, J. G. Mao, Y. Q. Sun, H. Y. Zeng, A. Clearfield,
Inorg. Chem. 2004, 43, 336–341.
[17] Q. Y. Liu, L. Xu, Inorg. Chem. Commun. 2005, 8, 401–405.
[18] J. Tao, X. Yin, Z. B. Wei, R. B. Huang, L. S. Zheng, Eur. J.
Inorg. Chem. 2004, 125–133.
[19] X. Li, R. Cao, W. H. Bi, D. Q. Yuan, D. F. Sun, Eur. J. Inorg.
Chem. 2005, 3156–3166.
angles are listed in Table 1. CCDC-609221 to -609223 (for 1–3)
contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
[20] L. J. Bellamy, The Infrared Spectra of Complex Molecules,
Wiley, New York, 1958.
[21] E. V. Bakhmutova, X. Ouyang, D. G. Medvedev, A. Clearfield,
Inorg. Chem. 2003, 42, 7046–7051.
[22] Z. M. Sun, J. G. Mao, Y. Q. Sun, H. Y. Zeng, A. Clearfield,
New J. Chem. 2003, 27, 1326–1330.
[23] M. Weidenbruch, M. Herrndorf, A. Schäfer, S. Pohl, W. Saak,
J. Organomet. Chem. 1989, 361, 139–145.
Acknowledgments
We gratefully acknowledgement the financial support of the “One
Hundred Talents Program” of the Chinese Academy of Sciences
and the National Science Foundation of China (Grant No.
20473092).
[24] S. Boulmaaz, R. Papiernik, L. G. H. Vaissermann, J. C. Daran,
Polyhedron 1992, 11, 1331–1336.
[25] D. C. Liles, M. McPartlin, P. A. Tasker, H. C. Lip, L. F. Lin-
doy, J. Chem. Soc., Chem. Commun. 1976, 549–551.
[1] B. Moulton, M. J. Zaworotko, Chem. Rev. 2001, 101, 1629–
1658.
[2] O. R. Evans, R. Xiong, Z. Wang, G. K. Wong, W. Lin, Angew. [26] W. B. Lin, Z. Y. Wang, L. Ma, J. Am. Chem. Soc. 1999, 121,
Chem. 1999, 111, 557–559; Angew. Chem. Int. Ed. 1999, 38,
536–538.
[3] M. Eddaoudi, D. B. Moler, H. L. Li, B. L. Chen, T. M. Rein-
eke, M. O’Keeffe, O. M. Yaghi, Acc. Chem. Res. 2001, 34, 319–
330.
11249–11250.
[27] X. Xue, X. S. Wang, L. Z. Wang, R. G. Xiong, B. F. Abrahams,
X. Z. You, Z. L. Xue, C. M. Che, Inorg. Chem. 2002, 41, 6544–
6546.
[28] S. LulinЈski, I. Madura, J. Serwatowski, J. Zachara, Inorg.
Chem. 1999, 38, 4937–4941.
[29] L. Carlucci, G. Ciani, D. W. v. Gudenberg, D. M. Proserpio,
Inorg. Chem. 1997, 36, 3812–3813.
[30] M. F. Tabellion, S. R. Seidel, A. M. Arif, P. J. Stang, J. Am.
Chem. Soc. 2001, 123, 11982–11990.
[31] P. C. Ford, A. Vogler, Acc. Chem. Res. 1993, 26, 220–226.
[32] C. M. Che, S. W. Lai, Coord. Chem. Rev. 2005, 249, 1296–1309.
[33] R. Bertoncello, M. Bettinelli, M. Casarin, A. Gulino, E. Tond-
ello, A. Vittadini, Inorg. Chem. 1992, 31, 1558–1565.
[34] G. A. Crosby, R. G. Highland, K. A. Truesdell, Coord. Chem.
Rev. 1985, 64, 41–52.
[4] C. D. Wu, W. B. Lin, Angew. Chem. Int. Ed. 2005, 44, 1958–
1961.
[5] S. Kitagawa, R. Kitaura, S. I. Noro, Angew. Chem. Int. Ed.
2004, 43, 2334–2375.
[6] O. R. Evans, W. B. Lin, Acc. Chem. Res. 2002, 35, 511–522.
[7] C. N. R. Rao, S. Natarajan, R. Vaidhyanathan, Angew. Chem.
Int. Ed. 2004, 43, 1466–1496.
[8] J. P. Zhang, Y. Y. Lin, X. C. Huang, X. M. Chen, J. Am. Chem.
Soc. 2005, 127, 5495.
[9] G. H. Li, Z. Shi, X. M. Liu, Z. M. Dai, S. H. Feng, Inorg.
Chem. 2004, 43, 6884–6886.
[10] Y. M. Song, T. Zhou, X. S. Wang, X. N. Li, R. G. Xiong, Cryst.
Growth Des. 2006, 6, 14–17.
[11] X. H. Bu, M. L. Tong, H. Chang, S. Kitagawa, S. R. Batten,
Angew. Chem. Int. Ed. 2004, 43, 192–195.
[35] S. L. Zheng, J. H. Yang, X. L. Yu, X. M. Chen, W. T. Wong,
Inorg. Chem. 2004, 43, 830–838.
[36] B. Valeur, Molecular Fluorescence: Principles and Applications,
Wiley-VCH, Weinheim, 2002.
[12] Q. Y. Liu, L. Xu, Eur. J. Inorg. Chem. 2005, 3458–3466.
[13] Q. Y. Liu, L. Xu, Eur. J. Inorg. Chem. 2006, 1620–1628.
[14] Q. Y. Liu, L. Xu, CrystEngComm 2005, 7, 87–89.
[15] R. M. Barrer, Hydrothermal Chemistry of Zeolite, Academic
Press, London, 1982.
[37] CrystalClear, version 1.3, Rigaku Corp., 2000.
[38] G. M. Sheldrick, SHELXS 97, Program for Crystal Structure
Solution, University of Göttingen, 1997.
Received: June 8, 2006
Published Online: October 19, 2006
Eur. J. Inorg. Chem. 2006, 4843–4851
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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