Helical ribbons of cadmium(II) and zinc(II) dicarboxylates with bipyridyl-like chelates - Syntheses, crystal structures and photoluminescence

Article abstract of DOI:10.1002/ejic.200300061

Four mixed-ligand complexes of [M(mpa)(phen)]_n [M = Cd (1) or Zn (2) and mpa = m-phthalate and phen = 1,10-phenanthroline) and [M ₂(mpa)₂(2,2′-bpy)₂]_n [M = Zn (3) of Cd (4) and 2,2′-bpy = 2,2′-bipyrid

Full text of DOI:10.1002/ejic.200300061

FULL PAPER
Helical Ribbons of Cadmium(II) and Zinc(II) Dicarboxylates with Bipyridyl-
Like Chelates ؊ Syntheses, Crystal Structures and Photoluminescence
Ling-Yun Zhang,[a] Gao-Feng Liu,[a] Shao-Liang Zheng,[a] Bao-Hui Ye,[a] Xian-
Ming Zhang,[a] and Xiao-Ming Chen*[a]
Keywords: Coordination polymers / Cadmium / Zinc / N ligands / Pi interactions
Four mixed-ligand complexes of [M(mpa)(phen)]n [M = Cd
(1) or Zn (2) and mpa = m-phthalate and phen = 1,10-phen-
anthroline) and [M2(mpa)2(2,2Ј-bpy)2]n [M = Zn (3) or Cd (4)
and 2,2Ј-bpy = 2,2Ј-bipyridine] have been synthesized and
helical chains. While 3 and 4 crystallize in the triclinic space
group P1. The one-dimensional ribbons are assembled into
three-dimensional networks by π−π stacking interactions.
They all show strong blue photoluminescence and are stable
¯
their crystal structures have been established by single-crys- in air up to ca. 402, 371, 365 and 370 °C, respectively.
tal X-ray diffraction. They all consist of one-dimensional rib-
bons featuring dinuclear units. Both 1 and 2 crystallize iso-
morphously in the monoclinic space group P2/c and feature
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
bpy)2]n [M ϭ Zn (3) or Cd (4) and 2,2Ј-bpy ϭ 2,2Ј-bipyri-
dine], which exhibit different structures compared to the re-
lated CuII complexes,[7,8] all of which show blue lumi-
nescence.
The construction of supramolecular architectures is cur-
rently of great interest owing to their intriguing network
topologies and potential functions such as adsorption, ion
exchange, shape-selective catalysis, non-linear and magnetic
materials.[1Ϫ3] The strategies for design and tailor-making
of such supramolecular architectures with dicarboxylate
spacers such as terephathlate, malate, oxalate, 4,4Ј-oxybis-
(benzoic acid) are currently interesting. Recently, we and
Results and Discussion
Characterization
The IR spectrum of 1 shows characteristic bands of the
others have reported some interesting polymeric architec- dicarboxylate groups in the usual region at 1564 and 1515
tures containing linear, nonlinear flexible and V-shaped di- cmϪ1 for the asymmetric stretching and at 1400 cmϪ1 for
carboxylates together with bipyridyl-like ligands.[4Ϫ11] Chel- the symmetric stretching. The separations (∆) between
ating bipyridyl-like ligands such as 1,10-phenanthroline and νasym(CO2) and νsym(CO2) are at 164 and 115 cmϪ1, which
2,2Ј-bipyridine are important in maintaining the one di- are attributed to the existence of both bridging and chelate
mensionality of the coordination polymers and may provide modes of the carboxylate groups, respectively (Scheme 1,
potential supramolecular recognition sites for πϪπ aro- a).[18] For 2, the bands are at 1614 and 1558 cmϪ1 for the
matic stacking interactions to form interesting supramol- asymmetric stretching and at 1397 cmϪ1 for the symmetric
ecular structures such as double-stranded helices and mo- stretching; the ∆ values are at 217 and 161 cmϪ1, and are
lecular zippers.[7,8]
attributable to the co-existence of the monodentate and
On the other hand, polynuclear d10 metal complexes are bridging modes (Scheme 1, b). For 3, the bands of the di-
very attractive in that they not only exhibit intriguing struc- carboxylate units are shown at 1562 and 1532 cmϪ1 for the
tures but also photoluminescent properties.[12Ϫ17] As a se- asymmetric stretching and at 1431 cmϪ1 for the symmetric
quel to our previous reports on a series of d10 complexes, stretching; the ∆ values are at 131 and 101 cmϪ1, which are
which show strong luminescent properties,[4,5,14Ϫ16] we now attributed to co-existence of the bridging and chelate modes
describe four one-dimensional coordination polymers (Scheme 1a, c). Whereas for 4, the characteristic bands and
[M(mpa)(phen)]n [M ϭ Cd (1) or Zn (2); mpa ϭ m-phthal- ∆ values are very similar to those found for 1, indicating
ate and phen ϭ 1,10-phenanthroline] and [M2(mpa)2(2,2Ј- that the carboxylate groups exhibit both a bridging and
chelate mode. The IR spectra indicate that the mpa carb-
[a]
oxylate groups function in different coordination modes,
consistent with the crystal structures of 1, 2, 3 and 4.
Thermogravimetric analysis (TGA) was performed on
polycrystalline samples in air. There was no decomposition
School of Chemistry and Chemical Engineering, Sun Yat-Sen
University,
Guangzhou 510275, China
Fax: (internat.) ϩ 86-20/84112245
E-mail: cescxm@zsu.edu.cn
Eur. J. Inorg. Chem. 2003, 2965Ϫ2971
DOI: 10.1002/ejic.200300061
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2965

L.-Y. Zhang, G.-F. Liu, S.-L. Zheng, B.-H. Ye, X.-M. Zhang, X.-M. Chen
FULL PAPER
Scheme 1. Coordination modes of mpa: (a) chelate-bidentate, (b) monodentate-bidentate and (c) chelating bis(bidentate)
˚
up to ca. 402, 371, 365 and 370 °C for 1, 2, 3 and 4, respec- 2.453(4), Cd1ϪO3 ϭ 2.331(4) A, O3ϪCd1ϪO4 ϭ 55.2(1)°]
tively, suggesting that the products are more stable than the to furnish a highly distorted octahedral geometry. Two CdII
related ones synthesized by the conventional solution atoms related by a twofold axis are bridged by a pair of the
method, at room temperature.[17]
mpa µ-carboxylate ends into
a
dinuclear unit
˚
˚
[Cd1···Cd1A ϭ 3.99 A]. A face-to-face distance of 3.51 A
between a pair of phen ligands coordinated to the two CdII
atoms is observed, showing significant intramolecular
πϪπ interactions.
Crystal Structures
Complexes 1, 2, 3 and 4 all consist of one-dimensional
ribbons. Both 1 and 2 crystallize isomorphously in the mon-
oclinic space group P2/c, while 3 and 4 crystallize in the
In fact, the V-shaped mpa ligand acts in the chelate-bi-
dentate coordination mode (see Scheme 1, a) to link the ad-
¯
triclinic space group P1 (see Tables 1 and 2).
In the crystal structure of 1, there is one CdII atom, one jacent CdII atoms into one-dimensional helical ribbons with
˚
mpa ligand and one phen ligand in each independent crys- a pitch of 9.55 A running along the c axis (Figure 2, a).
tallographic unit. As shown in Figure 1, each CdII atom in Pairs of phen ligands are alternately attached to both sides
1
is primarily coordinated by two nitrogen atoms of the ribbon; the adjacent zigzag ribbons are packed
˚
[Cd1ϪN1
ϭ
2.395(4), Cd1ϪN2
ϭ
2.377(5) A, through intercalation of the lateral phen ligands (face-to-
˚
N2ϪCd1ϪN1 ϭ 70.5(2)°] of a chelating phen ligand, two face distance 3.32 A), in the zipper-like fashion, into two-
oxygen atoms of two µ-carboxylate ends of two mpa ligands dimensional networks parallel to the bc plane. Adjacent
˚
[Cd1ϪO2A
ϭ
2.255(4), Cd1ϪO1B
ϭ
2.301(4) A, ribbons
also
have
strong
intermolecular
πϪπ
O2AϪCd1ϪO1B ϭ 99.7(2)°] and two oxygen atoms of one interactions[19Ϫ23] between the mpa phenyl rings in an offset
˚
chelating carboxylate end of one mpa ligand [Cd1ϪO4 ϭ fashion with a face-to-face distance of ca. 3.38 A, which
Table 1. Crystallographic data for 1Ϫ4
1
2
3
4
Empirical formula
Formula mass
Temperature [K]
Crystal color and form
Crystal system
C20H12CdN2O4
456.72
293
colorless prisms
monoclinic
P2/c (no. 13)
8.391(6)
10.681(8)
19.10(2)
C20H12N2O4Zn
409.69
293
pale-yellow blocks
monoclinic
P2/c (no. 13)
8.730(4)
C36H24N4O8Zn2
771.33
293
C36H24Cd2N4O8
865.39
228
pale-yellow blocks
triclinic
colorless blocks
triclinic
¯
¯
Space group
P1 (no. 2)
P1 (no. 2)
˚
a [A]
9.44(1)
9.425(2)
10.267(2)
18.649(4)
74.03(3)
85.93(3)
64.15(3)
1558.8(6)
2
˚
b [A]
10.34(1)
18.57(2)
11.40(1)
16.98(1)
100.07(1)
94.02(1)
110.50(1)
1670(2)
˚
c [A]
α [°]
β [°]
γ [°]
100.73(2)
99.65(2)
3
˚
Volume [A ]
1682(2)
4
1.803
1.329
1652(2)
4
1.647
1.517
Z
2
Dcalcd. [Mg/m3]
Absorption coefficient [mmϪ1
F(000)
1.534
1.496
784
1.844
1.428
856
]
904
832
Crystal size [mm]
θmax [°]
0.30 ϫ 0.25 ϫ 0.20
26.0
3554
3321
245
0.35 ϫ 0.33 ϫ 0.27
28.0
2938
2685
245
0.50 ϫ 0.40 ϫ 0.35
26.0
6572
6553
452
0.52 ϫ 0.48 ϫ 0.42
28.31
10180
7385
452
Reflections collected
Independent reflections
Number of parameters
Goodness-of-fit on F2
1.053
1.060
1.038
1.179
Final R indices [I Ն 2σ(I)][a][b]
R indices (all data)[a][b]
R1 ϭ 0.0455,
wR2 ϭ 0.1226
R1 ϭ 0.0621,
wR2 ϭ 0.1331
0.947 and Ϫ0.849
R1 ϭ 0.0538,
wR2 ϭ 0.1370
R1 ϭ 0.0707,
wR2 ϭ 0.1491
0.631 and Ϫ0.836
R1 ϭ 0.0651,
wR2 ϭ 0.1537
R1 ϭ 0.1247,
wR2 ϭ 0.1837
0.502 and Ϫ0.845
R1 ϭ 0.0342,
wR2 ϭ 0.0827
R1 ϭ 0.0392,
wR2 ϭ 0.0939
0.882 and Ϫ0.623
Ϫ3
˚
Largest peak and hole [e·A
]
[a]
[b]
2
2 2
2 2 1/2
R1 ϭ (Fo Ϫ Fc)/Fo. wR2 ϭ [w(Fo Ϫ Fc ) /w(Fo ) ]
.
2966
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Inorg. Chem. 2003, 2965Ϫ2971

Helical Ribbons of Cadmium(II) and Zinc(II) Dicarboxylates with Bipyridyl-Like Chelates
FULL PAPER
˚
Table 2. Selected bond lengths [A] and angles [°]; symmetry codes:
(A) x, Ϫy, z ϩ 1/2, (B) Ϫx, Ϫy, Ϫz, for 1 and 2, (A) Ϫx, Ϫy, Ϫz
ϩ 1, (B) x, y ϩ 1, z, for 3, (A) Ϫx, Ϫy ϩ 2, Ϫz ϩ 1, (B) x ϩ 1, y
Ϫ 1, z ϩ 1, for 4
1
Cd(1)ϪO(3)
Cd(1)ϪO(2A)
Cd(1)ϪO(1B)
2.331(4) Cd(1)ϪO(4)
2.255(4) Cd(1)ϪN(1)
2.301(4) Cd(1)ϪN(2)
2.453(4)
2.395(4)
2.377(5)
O(2A)ϪCd(1)ϪO(1B) 99.7(2)
O(2A)ϪCd(1)ϪO(3) 100.6(2)
O(3)ϪCd(1)ϪN(2)
O(2A)ϪCd(1)ϪN(1) 169.7(2)
137.4(1)
O(1B)ϪCd(1)ϪO(3)
94.7(1)
O(1B)ϪCd(1)ϪN(1)
O(3)ϪCd(1)ϪN(1)
N(2)ϪCd(1)ϪN(1)
O(1B)ϪCd(1)ϪO(4)
N(2)ϪCd(1)ϪO(4)
79.2(2)
89.7(2)
70.5(2)
146.9(1)
85.4(1)
O(2A)ϪCd(1)ϪN(2) 101.4(2)
O(1B)ϪCd(1)ϪN(2) 116.9(2)
O(2A)ϪCd(1)ϪO(4)
O(3)ϪCd(1)ϪO(4)
N(1)ϪCd(1)ϪO(4)
99.2(2)
55.2(1)
86.7(2)
Figure 1. Perspective view of the coordination environments of the
metal atoms with atomic labels in 1
2
Zn(1)ϪO(3)
Zn(1)ϪO(1B)
Zn(1)ϪO(2A)
O(3)ϪZn(1)ϪO(1B)
2.026(3) Zn(1)ϪN(2)
2.033(4) Zn(1)ϪN(1)
2.045(3)
2.175(4)
2.218(4)
97.4(2)
O(2A)ϪZn(1)ϪN(2)
O(3)ϪZn(1)ϪN(1)
O(1B)ϪZn(1)ϪN(1)
92.9(2)
92.5(2)
83.4(2)
O(3)ϪZn(1)ϪO(2A) 101.8(2)
O(1B)ϪZn(1)ϪO(2A) 96.2(2)
O(3)ϪZn(1)ϪN(2)
O(1B)ϪZn(1)ϪN(2)
131.4(2)
127.0(2)
O(2A)ϪZn(1)ϪN(1) 165.6(1)
N(2)ϪZn(1)ϪN(1)
76.2(2)
3
Zn(1)ϪO(1)
Zn(1)ϪO(2)
Zn(1)ϪO(6)
Zn(1)ϪO(5A)
Zn(1)ϪN(1)
Zn(1)ϪN(2)
2.454(5) Zn(2)ϪO(7)
2.066(4)
2.391(5)
2.012(5)
2.469(5)
2.165(6)
2.086(5)
101.0(2)
152.3(2)
106.4(2)
98.3(2)
105.9(2)
77.7(2)
98.4(2)
59.7(2)
92.4(2)
2.085(4 Zn(2)ϪO(8)
2.095(5) Zn(2)ϪO(4B)
2.039(4) Zn(2)ϪO(3B)
2.165(5) Zn(2)ϪN(3)
2.198(6) Zn(2)ϪN(4)
O(5A)ϪZn(1)ϪO(2) 103.8(2)
O(5A)ϪZn(1)ϪO(6) 105.5(2)
O(2)ϪZn(1)ϪO(6)
O(4B)ϪZn(2)ϪO(7)
O(4B)ϪZn(2)ϪN(4)
O(7)ϪZn(2)ϪN(4)
O(4B)ϪZn(2)ϪN(3)
O(7)ϪZn(2)ϪN(3)
N(4)ϪZn(2)ϪN(3)
O(4B)ϪZn(2)ϪO(8)
O(7)ϪZn(2)ϪO(8)
N(4)ϪZn(2)ϪO(8)
N(3)ϪZn(2)ϪO(8)
93.6(2)
O(5A)ϪZn(1)ϪN(1) 103.5(2)
O(2)ϪZn(1)ϪN(1)
O(6)ϪZn(1)ϪN(1)
O(5A)ϪZn(1)ϪN(2)
O(2)ϪZn(1)ϪN(2)
O(6)ϪZn(1)ϪN(2)
N(1)ϪZn(1)ϪN(2)
151.1(2)
88.6(2)
85.9(2)
96.9(2)
162.3(2)
75.5(2)
159.8(2)
O(5A)ϪZn(1)ϪO(1) 158.6(2)
O(4B)ϪZn(2)ϪO(3B) 57.9(2)
O(2)ϪZn(1)ϪO(1)
O(6)ϪZn(1)ϪO(1)
N(1)ϪZn(1)ϪO(1)
N(2)ϪZn(1)ϪO(1)
58.2(2)
88.3(2)
93.1(2)
85.1(2)
O(7)ϪZn(2)ϪO(3B)
N(4)ϪZn(2)ϪO(3B)
N(3)ϪZn(2)ϪO(3B)
O(8)ϪZn(2)ϪO(3B)
151.0(2)
95.1(2)
97.4(2)
101.0(2)
4
Cd(1)ϪO(1)
Cd(1)ϪO(2)
Cd(1)ϪO(6)
Cd(1)ϪO(5A)
Cd(1)ϪN(1)
Cd(1)ϪN(2)
O(5A)ϪCd(1)ϪO(2)
2.281(3) Cd(2)ϪO(7)
2.524(3) Cd(2)ϪO(8)
2.246(2) Cd(2)ϪO(4B)
2.252(3) Cd(2)ϪO(3A)
2.379(3) Cd(2)ϪN(3)
2.333(3) Cd(2)ϪN(4)
2.245(2)
2.559(3)
2.247(3)
2.285(3)
2.325(3)
2.332(3)
90.7(1)
93.9(1)
105.9(1)
88.6(1)
176.65(9)
70.89(9)
140.0(1)
54.40(8)
79.96(9)
125.06(8)
Figure 2. Perspective views of the two-dimensional networks paral-
lel to the bc plane (a) and the ac plane (b) in 1; the arrow in (b)
highlights the intermolecular πϪπ interaction between the mpa
phenyl rings; the face-to-face distances for the πϪπ interactions are
87.3(1)
O(4B)ϪCd(2)ϪO(7)
O(4B)ϪCd(2)ϪN(4)
138.58(9) O(7)ϪCd(2)ϪN(4)
84.6(1) O(4B)ϪCd(2)ϪN(3)
131.56(9) O(7)ϪCd(2)ϪN(3)
O(5A)ϪCd(1)ϪO(6) 117.1(1)
O(2)ϪCd(1)ϪO(6)
O(5A)ϪCd(1)ϪN(1)
O(2)ϪCd(1)ϪN(1)
O(6)ϪCd(1)ϪN(1)
O(5A)ϪCd(1)ϪN(2) 133.8(1)
O(2)ϪCd(1)ϪN(2)
˚
˚
˚
x1 ϭ 3.51 A, y1 ϭ 3.32 A and z1 ϭ 3.38 A
86.1(1)
N(4)ϪCd(2)ϪN(3)
O(4B)ϪCd(2)ϪO(8)
also extend the ribbons into two-dimensional networks
(Figure 2, b) in another direction parallel to the ab plane.
Therefore, these ribbons are in fact stacked through two
different kinds of aromatic πϪπ stacking interactions, be-
tween phen ligands and mpa ligands, into a three-dimen-
sional architecture in the lattice.
83.13(9) O(7)ϪCd(2)ϪO(8)
99.00(9) N(4)ϪCd(2)ϪO(8)
69.27(9) N(3)ϪCd(2)ϪO(8)
O(6)ϪCd(1)ϪN(2)
N(1)ϪCd(1)ϪN(2)
O(5A)ϪCd(1)ϪO(1) 100.2(1)
O(4B)ϪCd(2)ϪO(3A) 123.2(1)
O(2)ϪCd(1)ϪO(1)
O(6)ϪCd(1)ϪO(1)
N(1)ϪCd(1)ϪO(1)
N(2)ϪCd(1)ϪO(1)
54.08(8) O(7)ϪCd(2)ϪO(3A) 94.6(1)
87.3(1)
173.14(9) N(3)ϪCd(2)ϪO(3A)
109.9(1) O(8)ϪCd(2)ϪO(3A)
N(4)ϪCd(2)ϪO(3A) 137.5(1)
88.6(1)
82.64(9)
In the crystal structure of 2, each ZnII atom is primarily
coordinated by two nitrogen atoms [ZnϪN ϭ 2.175(4) or
Eur. J. Inorg. Chem. 2003, 2965Ϫ2971
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L.-Y. Zhang, G.-F. Liu, S.-L. Zheng, B.-H. Ye, X.-M. Zhang, X.-M. Chen
FULL PAPER
Figure 3. Perspective view of the coordination environments of the
metal atoms with atomic labels in 2
˚
2.218(4) A] from a chelating phen ligand and three oxygen
˚
atoms [ZnϪO ϭ 2.026(3)Ϫ2.045(3) A] from two µ-car-
boxylate ends and one monodentate carboxylate end of
three mpa ligands in a distorted trigonal arrangement, in
which the N1 and O2A atoms occupy the axial positions
and the pendant carboxy O4 atom has no significant inter-
˚
action with Zn1 [Zn1···O4 ϭ 2.675(4) A] (Figure 3). The
˚
intradinuclear Zn···Zn distance (3.933 A) and the face-to-
˚
face distance (3.52 A) between the two phen ligands are
similar to those found in 1.
All the mpa ligands in 2 exhibit the monodentate-biden-
tate coordination mode (Scheme 1, b), and the pitch of the
˚
helical ribbon is 9.29 A, being shorter than that in 1. These
differences may be attributed to the radius of the CdII atom
being larger than that of the ZnII atom, resulting in differ-
ent coordination environments. On the other hand, adjacent
ribbons in 2 are packed in a highly similar fashion to 1
through the πϪπ stacking interactions between the lateral
˚
phen ligands with face-to-face distances of ca. 3.29 A and
between the mpa phenyl rings with face-to-face distances of
˚
ca. 3.35 A, into a three-dimensional network in the solid.
When 2,2Ј-bpy, an aromatic chelate ligand of smaller size,
was used instead of phen, different ribbons were formed in
3 and 4 under similar reaction conditions. As illustrated in
Figure 4 (a), there are two different metal coordination en-
vironments in 3. Zn1 is coordinated by two oxygen atoms
of one chelating carboxylate end of one mpa ligand
˚
[Zn1ϪO1
ϭ
2.454(5), Zn1ϪO2
ϭ
2.085(4) A,
O1ϪZn1ϪO2 ϭ 58.2(2)°], two oxygen atoms of two µ-car-
boxylate ends of two mpa ligands [Zn1ϪO5A ϭ 2.039(4),
Figure 4. Perspective views of the coordination environments of the
metal atoms with atomic labels (a), the one-dimensional ribbon
running along the b axis (b) and the three-dimensional network (c)
in 3
˚
Zn1ϪO6 ϭ 2.095(5) A, O5AϪZn1ϪO6 ϭ 105.5(2)°] and
two nitrogen atoms of a chelate 2,2Ј-bpy ligand [Zn1ϪN1 ϭ
˚
2.165(5), Zn1ϪN2 ϭ 2.198(6) A, N1 ϪZn1ϪN2 ϭ 75.5(2)°]
to furnish a highly distorted octahedral environment,
The Zn1 atom in 3 is bridged by two µ-carboxylate ends
whereas Zn2 is ligated by four oxygen atoms of two chelat- to a crystallographically equivalent ZnII atom to generate a
˚
ing carboxylate ends of two mpa ligands [Zn2ϪO ϭ dinuclear unit [Zn1···Zn1A ϭ 4.324 A] (Figure 4, a). The
˚
2.012(5)Ϫ2.469(5) A, O3BϪZn2ϪO4B
ϭ
57.9(2), distance of Zn1···Zn1A is longer than in 2, which may be
O7ϪZn2ϪO8 ϭ 59.7(2)°] and two nitrogen atoms of a che- attributed to the different coordination geometry and the
late 2,2Ј-bpy ligand [Zn2ϪN4 ϭ 2.086(5), Zn2ϪN3 ϭ orientation of the two 2,2Ј-bpy ligands around the two ZnII
˚
2.165(6) A, N3 ϪZn2ϪN4 ϭ 77.7(2)°] to complete a highly atoms. The dinuclear units are interconnected to the
distorted octahedral geometry.
mononuclear Zn2 sites, furnishing one-dimensional ribbons
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Helical Ribbons of Cadmium(II) and Zinc(II) Dicarboxylates with Bipyridyl-Like Chelates
FULL PAPER
along the b axis, which exhibit large rings each comprising
four bridging V-shaped mpa ligands, two dinuclear units
and two mononuclear units. The ribbon is decorated by
2,2Ј-bpy ligands in four different orientations (Figure 4, b).
In fact, the V-shaped mpa ligands in 3 exhibit two different
modes, chelate-bidentate (Scheme 1, a) and chelating
bis(bidentate) (Scheme 1, c). The bridging bidentate ends of
the chelate-bidentate mpa ligands contribute to the forma-
tion of the dinuclear units, whereas the chelate ends are
connected to both the mono- and dinuclear ZnII sites. The
2,2Ј-bpy ligands are orientated outwards of the ribbon and
thus play an important role in packing adjacent ribbon
chains into three-dimensional networks (Figure 4, c)
through πϪπ stacking interactions (face-to-face distance ca.
˚
3.56 or 3.62 A). It should be pointed out that the πϪπ
stacking interactions for mpa ligands in 3 are insignificant
compared to those of 1 and 2.
In the crystal structure of 4, there are two CdII atoms,
two mpa ligands and two phen ligands in each independent
crystallographic unit. Cd1 is coordinated by two oxygen
atoms from one chelating carboxylate end of one mpa li-
˚
gand [Cd1ϪO1 ϭ 2.281(3), Cd1ϪO2 ϭ 2.524(3) A,
O1ϪCd1ϪO2 ϭ 54.08(8)°], two oxygen atoms of two µ-
carboxylate ends of two mpa ligands [Cd1ϪO5A ϭ
˚
2.252(3), Cd1ϪO6 ϭ 2.246(2) A, O5AϪCd1ϪO6 ϭ
117.1(1)°] and two nitrogen atoms of a chelate 2,2Ј-bpy li-
˚
gand [Cd1ϪN1 ϭ 2.379(3), Cd1ϪN2 ϭ 2.333(3) A,
N1ϪCd1ϪN2 ϭ 69.27(9)°] to furnish a highly distorted oc-
tahedral coordination. Similarly to Cd1, Cd2 is also coordi-
nated in a highly distorted octahedral geometry (see
Table 2). The two crystallographically independent CdII
atoms are each bridged by two µ-carboxylate ends to its
crystallographically equivalent CdII atom to generate a di-
nuclear unit (Figure 5, a). Such dinuclear units are further
Figure 5. Perspective views of the coordination environments of the
metal atoms (a) and the two-dimensional ribbons (b) in 4; the face-
˚
to-face distances for the πϪπ interactions are x2 ϭ 3.48 A, y2
ϭ
˚
˚
3.64 A and z2 ϭ 3.47 A
extended by the bridging mpa ligands into one-dimensional combination of V-shaped mpa ligands with chelating phen
helical ribbons with a pitch of 9.71 A running along the and 2,2Ј-bpy ligands along with the CuII ions generated
˚
¯
(111) direction, which are decorated by 2,2Ј-bpy ligands at single-stranded helical chains, namely [Cu2(mpa)2(phen)2-
both sides. Since the pair of 2,2Ј-bpy ligands are orientated (H2O)]n and [Cu(mpa)(2,2Ј-bpy)]n·2nH2O.[7] In contrast,
in opposite directions of the dinuclear unit, the geometry using CdII or ZnII atoms in place of CuII atoms under simi-
of the unit is hence different, concomitant with larger intra- lar reaction conditions, the one-dimensional ribbons of 1Ϫ4
˚
dinuclear metalϪmetal distances (Cd1···Cd1A ϭ 4.364 A, comprising dinuclear units were isolated. These obser-
Cd2···Cd2A ϭ 4.181 A) compared to that in 1. These geo- vations may be attributed to the fact that the CuII has a
˚
metric differences may be attributed to the significant intra- greater tendency towards square-planar coordination tend-
molecular πϪπ stacking interactions in 1. The V-shaped ency than the CdII and ZnII atoms and the fact that CdII
mpa ligands in 4 exhibit uniquely the chelate-bidentate co- and ZnII atoms have a tendency to form dinuclear struc-
ordination mode (Scheme 1, a). Adjacent ribbons are in- tural units in the presence of the aromatic chelates. Actually,
tercalated in a zipper fashion into two-dimensional layers in
[Cu2(mpa)2(phen)(H2O)]n
and
[Cu(mpa)(2,2Ј-
through the πϪπ stacking interactions between the 2,2Ј-bpy bpy)]n·2nH2O as well as other related coordination poly-
ligands with face-to-face distances of ca. 3.47Ϫ3.64 A (Fig- mers,[7] the one-dimensional chains are based on mononu-
˚
ure 5, b), and the layers are further packed into a three- clear structural units featuring primarily a square-planar
dimensional network by van der Waals interactions. Similar geometry, compared to those in 1, 2, 3 and 4. Therefore the
to 3, there are no significant πϪπ stacking interactions from dinuclear structural units in 1, 2, 3 and 4 represent new
the mpa ligands.
examples of building blocks among the dicarboxylate-
In our previous reports, we have shown that appropriate bridged one-dimensional coordination polymers. On the
combinations of nonlinear flexible/V-shaped dicarboxylates other hand, different aromatic chelates also have a signifi-
with chelating phen can furnish interesting one-dimensional cant effect on the structures, as evidenced by the fact that
supramolecular structures such as molecular zippers as well the structure of 3 is significantly different from that of 1
as single- and double-stranded helices.[7,8] In particular, a and 2.
Eur. J. Inorg. Chem. 2003, 2965Ϫ2971
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L.-Y. Zhang, G.-F. Liu, S.-L. Zheng, B.-H. Ye, X.-M. Zhang, X.-M. Chen
FULL PAPER
Photoluminescence
solid state at room temperature. The enhancement and sig-
nificant blue-shift (up to 400 nm)[30] of the luminescence of
The solid-state photoluminescent spectra of 1, 2, 3 and 4
at room temperature are depicted in Figure 6. Complexes 1
and 2 both exhibit intense blue photoluminescence with an
emission maximum at ca. 423 and 420 nm upon excitation
at 317 and 334 nm, respectively. According to the previous
observations,[4,16,24Ϫ29] these emission bands would be as-
signed to the emission of ligand-to-metal charge transfer
(LMCT). Whereas there are two intense emission maxima
at ca. 397 and 413 nm for 3, and ca. 405 and 422 nm for 4
upon excitation at ca. 347 and 355 nm, respectively. The
peaks at 413 and 422 nm would be assigned to the emission
of LMCT,[4,5,26,28,29] while the peaks at 397 and 405 nm
would be distributed to the intraligand emission from the
2,2Ј-bpy ligand.[5,30] It is known that the free 2,2Ј-bpy mol-
ecule displays a weak luminescence at ca. 530 nm in the
the 2,2Ј-bpy ligand compared to that of the free 2,2Ј-bpy
molecule may therefore be attributed to the chelating of the
2,2Ј-bpy ligand to the metal ion, which effectively increases
the rigidity of the ligand and reduces the loss of energy by
radiationless decay of the intraligand emission excited
state.[24]
Conclusion
We have synthesized four stable one-dimensional ribbon-
like coordination polymers under hydrothermal conditions,
which show new dinuclear structural units as building
blocks among the dicarboxylate-bridged one-dimensional
coordination polymers as well as interesting photoluminesc-
ent properties. Compared to our previous one-dimensional
copper() analogues, it has been found that different coor-
dinations may have a very significant effect on the struc-
tures of the one-dimensional chains. Different combinations
of nonlinear flexible/V-shaped dicarboxylates with chelating
phen and 2,2Ј-bpy ligands in the presence of different metal
ions, such as Cu, Cd and Zn, can furnish different one-
dimensional supramolecular structures, such as molecular
zippers, single- and double-stranded helices,[7,8] as well as
helical ribbons.
Experimental Section
General Remarks: All chemicals were commercially available and
used as received without further purification. The C, H and N mic-
roanalyses were carried out with a PerkinϪElmer 240 elemental
analyzer. The FT-IR spectra were recorded from KBr pellets in the
range 4000Ϫ400 cmϪ1 with a Nicolet 5DX spectrometer. All the
excitation and emission spectra were measured with an Aminco
Bowman Series 2 with a xenon arc lamp as the excitation light
source for the solid-state samples. Thermogravimetric analysis
(TGA) data were collected with a PerkinϪElmer TGS-2 analyzer
in air at a heating rate of 10 °C minϪ1
.
Preparation of [Cd(mpa)(phen)]n (1): A mixture of Cd(NO3)2·9H2O
(1.0 mmol), H2mpa (0.5 mmol), phen (1.0 mmol), NaOH
(1.0 mmol) and water (10 mL) was stirred in air for 15 min, then
transferred and sealed in a 23-mL Teflon-lined reactor, which was
heated at 160 °C for 5 d and then cooled to room temperature at
a rate of 5 °C hϪ1. Colorless prisms were obtained, washed with
deionized water and absolute ethanol (yield Ͼ 40% based on Cd).
C20H12CdN2O4 (456.72): calcd. C 52.59, H 2.65, N 6.13; found C
52.70, H 2.59, N 6.20. IR (KBr, cmϪ1): ν˜ ϭ 3417 s, 3169 s, 1979
w, 1615 s, 1564 s, 1515 m, 1481 w, 1400 s, 1145 m, 1102 m, 1049
w, 909 w, 859 s, 825 w, 783 m, 729 s and 635 m. TGA analysis of
1 shows a weight loss starting at ca. 402 °C.
Preparation of [Zn(mpa)(phen)]n (2): Complex 2 was prepared as for
1. Pale yellow blocks of 2 were obtained, washed with deionized
water and absolute ethanol (yield
Ͼ 60% based on Zn).
C20H12N2O4Zn (409.69): calcd. C 58.63, H 2.95, N 6.84; found C
58.58, H 2.88, N 6.90. IR (KBr, cmϪ1): ν˜ ϭ 3433 s, 3334 m, 3193
m, 3000 w, 1614 s, 1558 m, 1515 m, 1453 m, 1397 s, 1271 w, 1168
m, 1098 w, 850 s, 782 m, 744 w, 723 s, 592 m and 528 w. Decompo-
sition of the polymeric framework of 2 began at ca. 371 °C.
Figure 6. The excitation and emission spectra of 1Ϫ4 in the solid
state at room temperature; the solid lines represent 1 and the dash-
dot ones represent 2 in (a); the solid lines represent 4 and the dash-
dot ones represent 3 in (b)
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Helical Ribbons of Cadmium(II) and Zinc(II) Dicarboxylates with Bipyridyl-Like Chelates
FULL PAPER
[3]
P. J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem. Int. Ed.
1999, 38, 2638Ϫ2684.
J. Tao, M.-L. Tong, J.-X. Shi, X.-M. Chen, S. W. Ng, Chem.
Commun. 2000, 2043Ϫ2044.
X.-M. Zhang, M.-L. Tong, M.-L. Gong, X.-M. Chen, Eur. J.
Inorg. Chem. 2003, 138Ϫ142.
D.-F. Sun, R. Cao, Y. Liang, Q. Shi, W.-P. Su, M.-C. Hong, J.
Chem. Soc., Dalton Trans. 2001, 2335Ϫ2340.
X.-M. Chen, G.-F. Liu, Chem. Eur. J. 2002, 8, 4811Ϫ4817.
G.-F. Liu, B.-H. Ye, Y.-H. Ling, X.-M. Chen, Chem. Commun.
2002, 1442Ϫ1443.
M. J. Plater, M. R. St. J. Foreman, R. A. Howie, J. M. S. Ska-
kle, S. A. McWilliam, E. Coronado, C. J. G. Garcia, Polyhedron
2001, 20, 2293Ϫ2303.
S.-L. Zheng, M.-L. Tong, X.-L. Yu, X.-M. Chen, J. Chem.
Soc., Dalton Trans. 2001, 586Ϫ592.
J. Tao, M.-L. Tong, X.-M. Chen, J. Chem. Soc., Dalton Trans.
2000, 3669Ϫ3674.
Preparation of [Zn2(mpa)2(2,2Ј-bpy)2]n (3):
A
mixture of
Zn(NO3)2·9H2O (1.0 mmol), H2mpa (0.5 mmol), 2,2Ј-bpy
(1.0 mmol), NaOH (1.0 mmol) and water (10 mL) was stirred in air
for 15 min, then transferred and sealed in a 23-mL Teflon-lined
reactor, which was heated at 160 °C for 5 d and then cooled to
room temperature at a rate of 5 °C hϪ1. Colorless prisms were
obtained, washed with deionized water and absolute ethanol (yield
Ͼ 35% based on Zn). C36H24N4O8Zn2 (771.33): calcd. C 56.05, H
3.14, N 7.26; found C 56.11, H 3.01, N 7.33. IR (KBr, cmϪ1): ν˜ ϭ
3424 s, 3108 s, 3069 s, 1902 w, 1943 w, 1612 s, 1562 s, 1532 s, 1431
s, 1383 s, 1159 m, 1074 m, 1020 m, 934 w, 849 m, 827 m, 750 m,
658 s, and 583 m. TGA analysis of 3 shows a weight loss starting
at ca. 365 °C.
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
Preparation of [Cd2(mpa)2(2,2Ј-bpy)2]n (4): Complex 4 was prepared
as for 3. Colorless blocks of 4 were obtained, washed with deion-
ized water and absolute ethanol (yield Ͼ 50% based on Zn).
C36H24Cd2N4O8 (856.39): calcd. C 49.96, H 2.80, N 6.47; found C
49.88, H 2.85, N 6.54. IR (KBr, cmϪ1): ν˜ ϭ 3414 s, 3109 m, 3050
m, 1602 s, 1552 s, 1474 m, 1436 s, 1381 s, 1314 m, 1247 w, 1154 m,
1078 m, 1016 s, 908 w, 827 m, 727 m, 717 s, and 652 w. Decompo-
sition of the polymeric framework of 4 began at ca. 370 °C.
P. C. Ford, E. Cariati, J. Bourassa, Chem. Res. 1999, 99,
3625Ϫ3648.
K. R. Kyle, C. K. Ryu, J. A. Dibenedetto, P. C. Ford, J. Am.
Chem. Soc. 1991, 113, 2954Ϫ2965.
W. Clegg, D. R. Harbron, C. D. Homan, P. A. Hunt, J. R.
Little, B. P. Straughan, Inorg. Chim. Acta 1991, 186, 51Ϫ60.
M.-L. Tong, X.-M. Chen, B.-H. Ye, L.-N. Ji, Angew. Chem.
Int. Ed. 1999, 38, 2237Ϫ2240.
J. Tao, J.-X. Shi, M.-L. Tong, X.-X. Zhang, X.-M. Chen, Inorg.
Chem. 2001, 40, 6328Ϫ6330.
S.-L. Zheng, M.-L. Tong, S.-D. Tan, Y. Wang, J.-X. Shi, Y.-X.
Tong, H.-K. Lee, X.-M. Chen, Organometallics 2001, 20,
5319Ϫ5325.
K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, John Wiley & Sons, New York, 1986.
M.-L. Tong, H.-J. Chen, X.-M. Chen, Inorg. Chem. 2000, 39,
2235Ϫ2238.
S.-L. Zheng, M.-L. Tong, R.-W. Fu, X.-M. Chen, S. W. Ng,
Inorg. Chem. 2001, 40, 3562Ϫ3569.
X-ray Crystallographic Study: A summary of the crystal data for 1,
2, 3 and 4 is given in Table 1. Selected bond lengths and angles are
listed in Table 2. Drawings were produced with SHELXTL. The
intensity data of 1, 2 and 3 were collected with a Siemens R3m
diffractometer using the ω-scan technique with graphite-monochro-
[18]
[19]
[20]
[21]
˚
mated Mo-Kα (λ ϭ 0.71073 A) radiation at room temperature and
the intensity data of 4 were collected with a Bruker Apex CCD
diffractometer with the graphite-monochromated Mo-Kα (λ ϭ
˚
0.71073 A) radiation at 228 K in the ω-2θ scan mode. Lorentz-
polarization and absorption corrections were applied.[31] The struc-
tures were solved with direct methods and refined with a full-matrix
least-squares technique using the SHELXS-97 and SHELXL-97
programs,[32,33] respectively. Anisotropic thermal parameters were
assigned to all non-hydrogen atoms. The organic hydrogen atoms
X.-M. Zhang, M.-L. Tong, S.-H. Feng, X.-M. Chen, J. Chem.
Soc., Dalton Trans. 2001, 2069Ϫ2070.
[22]
[23]
C. Janiak, J. Chem. Soc., Dalton Trans. 2000, 3885Ϫ3896.
M.-L. Tong, Y.-M. Wu, S.-L. Zheng, X.-M. Chen, T. Yuen, C.-
L. Lin, X.-Y. Huang, J. Li, New J. Chem. 2001, 25, 1482Ϫ1485.
H. Yersin, A. Vogler (Eds.), Photochemistry and Photophysics
of Coordination Compounds, Springer, Berlin, 1987.
V. W.-W. Yam, K. K.-W. Lo, Chem. Soc. Rev. 1999, 28,
323Ϫ334.
˚
were generated geometrically (CϪH 0.96 A); the aqua hydrogen
[24]
[25]
[26]
[27]
[28]
atoms were located from difference maps and refined with isotropic
temperature factors. Analytical expressions of neutral-atom scat-
tering factors were employed, and anomalous dispersion correc-
tions were incorporated.[34] CCDC-212917 (1), -212918 (2), -212919
(3), -212920 (4) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge
H. Kunkely, A. Vogler, J. Chem. Soc., Chem. Commun. 1990,
1204Ϫ1205.
R. Bertoncello, M. Betinelli, M. Casarin, A. Gulino, E. Tond-
ello, A. Vittadini, Inorg. Chem. 1992, 31, 1558Ϫ1565.
J.-C. Dai, X.-T. Wu, Z.-Y. Fu, C.-P. Cui, S.-M. Wu, W.-X. Du,
L.-M. Wu, H.-H. Zhang, R.-Q. Sun, Inorg. Chem. 2002, 41,
1391Ϫ1396.
W. Chen, J.-Y. Wang, C. Chen, Q. Yue, H.-M. Yuan, J.-S. Chen,
S.-N. Wang, Inorg. Chem. 2003, 42, 944Ϫ946.
G. Qian, M. Wang, Mater. Lett. 2002, 56, 71Ϫ75.
A. C. T. North, D. C. Phillips, F. S. Mathews, Acta Crystallogr.,
Sect. A 1968, 24, 351Ϫ356.
G. M. Sheldrick, SHELXS-97, Program for X-ray Crystal
Structure Solution, Göttingen University, Germany, 1997.
G. M. Sheldrick, SHELXL-97, Program for X-ray Crystal
Structure Refinement, Göttingen University, Germany, 1997.
International Tables for X-ray Crystallography, vol. C, Tables
4.2.6.8 and 6.1.1.4, Kluwer Academic Publisher, Dordrecht,
1992.
CB2 1EZ, UK; Fax: (internat.)
deposit@ccdc.cam.ac.uk].
ϩ 44-1223/336-033; E-mail:
[29]
[30]
[31]
Acknowledgments
[32]
[33]
[34]
This work was supported by the NSFC (no. 20131020) and the
Ministry of Education of China (no. 01134).
[1]
O. M. Yaghi, H. Li, C. David, D. Richardson, T. L. Groy, Acc.
Chem. Res. 1998, 31, 474Ϫ484.
[2]
S. R. Batten, R. Robson, Angew. Chem. Int. Ed. 1998, 37,
1460Ϫ1494.
Received January 30, 2003
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