Syntheses and structures of three new copper(II) coordination polymers involving 2, 2-(4, 6-dinitro-1, 3-phenylenedioxy)diacetic acid

Article abstract of DOI:10.1002/zaac.201100292

Three copper(II) coordination polymers, namely, {[CuL(H₂O) ₂]·4H₂O}_n(1), [CuL(H₂O)(DMF)] _n(2), and [CuL(2, 2′-bipy)(DMSO)]·DMSO (3) [H ₂L = 2, 2′-(4, 6-dinitro-1, 3-phenyl-enedioxy)diacetic acid] were synthesized in different solvents (H₂O, DMF, and DMSO). X-ray single crystal diffraction studies show that both complexes 1 and 3 belong to triclinic crystal system and P space group and complex 2 belongs to the monoclinic crystal system and P2₁/c space group. In three complexes, all the central Cu^II ions coordinate with the ligand, forming a square pyramidal configuration. Both complexes 1 and 2 show similar 1D chain-like structure and the chains are further connected by hydrogen bonds, forming 3D frameworks. Complex 3 exhibits a 0D structure due to the introduction of the ligand 2, 2′-bipy. In addition, the luminescence properties of these complexes were investigated. Copyright

Full text of DOI:10.1002/zaac.201100292

ARTICLE
DOI: 10.1002/zaac.201100292
Syntheses and Structures of Three New Copper(II) Coordination Polymers
Involving 2,2-(4,6-Dinitro-1,3-phenylenedioxy)diacetic Acid
Dong-Sheng Ma,*[a] Xiu-Mei Zhang,[a] Pei-Jiang Liu,[a] and Shuai Zhang[a]
Keywords: Crystal structure; Coordination complex; Copper; Fluorescence
Abstract. Three copper(II) coordination polymers, namely, P21/c space group. In three complexes, all the central CuII ions coordi-
{[CuL(H2O)2]·4H2O}n(1), [CuL(H2O)(DMF)]n(2), and [CuL(2,2Ј- nate with the ligand, forming a square pyramidal configuration. Both
bipy)(DMSO)]·DMSO (3) [H2L = 2,2Ј-(4,6-dinitro-1,3-phenyl-en-
complexes 1 and 2 show similar 1D chain-like structure and the chains
edioxy)diacetic acid] were synthesized in different solvents (H2O, are further connected by hydrogen bonds, forming 3D frameworks.
DMF, and DMSO). X-ray single crystal diffraction studies show that Complex 3 exhibits a 0D structure due to the introduction of the ligand
¯
both complexes 1 and 3 belong to triclinic crystal system and P1 space 2,2Ј-bipy. In addition, the luminescence properties of these complexes
group and complex 2 belongs to the monoclinic crystal system and were investigated.
and effect of different solvents in the synthesis of copper-con-
1. Introduction
taining complexes.
Many functional coordination polymers with carboxylic li-
Herein, we report the syntheses, structures, and luminescent
gands have been synthesized due to their strong coordination
properties of three new copper coordination polymers in dif-
abilities and diverse coordination modes. To date, most of the
ferent solvents (water, DMF, and DMSO) by the reaction of
efforts have been focused on the rigid aromatic carboxylic li-
the ligand and copper(II). It is found that three solvents are all
gands, which can easily form hydrogen bonds and π–π interac-
coordinated with copper. Complex {[CuL(H2O)2]·4H2O}n (1)
tions.[1–4] Among those, studies on coordination polymers with
achieved from water and complex [CuL(H2O)(DMF)]n (2)
flexible aromatic carboxylic ligands are rare, probably because
achieved from DMF exhibit the similar 1D infinite chain struc-
they have greater deformation ability in coordination process
tures. Complex [CuL(2,2Ј-bpy)(DMSO)]·DMSO (3) achieved
and could adopt diverse configurations according to different
from DMSO shows 0D structure due to the presence of 2,2Ј-
coordinating environments, thus increasing the difficulty to
bipyridine as a second ligand.
predict the structures of coordination polymers. However,
these characteristics could make them easily adjust the coordi-
nating orientation to accommodate the coordination environ-
ment.[5–8] Therefore, polymers with novel structures and prop-
erties could probably be built by adopting flexible aromatic
carboxylic ligands as building blocks,[9–12] which may have
potentially applications in separation, catalysis, optics, and
electrical conductivity, magnetism and bionics etc.[13–16]
Copper chemistry is well-documented through structural and
magnetic characterization of different varieties of mono-, di-,
and polynuclear complexes. Copper coordination polymers are
widely used in many fields such as application in the synthesis
of catalysts in heterogeneous and homogeneous reactions,
functional materials (super conductive materials, magnetic ma-
terials, ceramic materials and electronic materials etc.) and
metal enzyme models.[17–23] On the other hand, solvents can
also effect the formation of the crystal structure.[24–27] Taking
2. Experimental Section
2.1. Materials and Measurements
All commercially available chemicals are of reagent grade and were
used as received without further purification. Elemental analyses for
C, H, and N were carried out with a Vario EL III elemental analyzer.
account of the above, our aim was to explore constructing rules The IR spectra were recorded with a Bruker tensor 27 FT-IR spectro-
photometer in the 4000–400 cm–1 region by using KBr pellets. The
* Prof. Dr. D.-S. Ma
luminescent spectra were taken with a Perkin Elmer Corporation
Model Fluorescence Spectrometer LS 55 PL. 1H NMR spectra was
performed with a Bruker AV300 MHz equipment. The melting point
was taken on a WRS-2 microscopic meting point meter of Shanghai
precision & scientific instrument Co., Ltd.
E-Mail: rwws8828@sina.com
[a] School of Chemistry and Materials Science
Heilongjiang University
74 XueFu Road, NanGang District
Harbin 150080, P. R. China
236
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Z. Anorg. Allg. Chem. 2012, 638, (1), 236–241

Copper(II) Coordination Polymers Involving 2,2-(4,6-Dinitro-1,3-phenylenedioxy)diacetic Acid
m, 1197 m, 1082 m, 1047 m, 925 m, 853 m, 834 m, 824 m, 740 m,
713 m, 606 w cm–1.
2.2. Synthesis of 2,2Ј-(4,6-Dinitro-1,3-phenylenedioxy)-
diacetic Acid (H2L)
2.3.2 Synthesis of [CuL(H2O)(DMF)]n (2)
The ligand (H2L) was synthesized following the references
method.[28,29] A mixture of chloroacetic acid (51.60 g, 0.54 mol), so-
dium hydroxide (36.30 g, 0.90 mol), resorcin (20.00 g, 0.18 mol) was
dissolved in distilled water (200 mL) with stirring. The solution was
heated to reflux for 6 h, and the pH value was adjusted to about 2.0
by using 25% hydrochloric acid. After cooling to room temperature,
yellow precipitate (10.80 g, 27%) was obtained. Subsequently, all of
the above yellow products were dissolved in concentrated sulfuric acid
(100 mL) with stirring, and a mixture of nitric acid (9.45 g, 0.15 mol)
and sulfuric acid (20.58 g, 0.21 mol) was dropped into the above solu-
tion with keeping the reaction temperature under 0 °C for 1 h. After-
wards, the mixed solution was kept stirring about 5 h at room tempera-
ture. The mixture was poured into water (500 mL), the crude product
was obtained (37%). The product was obtained by recrystallization
from water. Elemental analysis: C10H8N2O10: calcd. C 37.99; H 2.55;
N 8.86%; found: C 37.87; H 2.64; N 8.93%. Melting point: 214.8–
215.8 °C. UV (solvent: MeOH): 289 nm, [squ ] = 2.42ϫ103 mol L–
1 cm–1. FT-IR (KBr): ν˜ = 3558 m, 3468 m, 2927 m, 1772 s, 1741 s,
1614 s, 1596 s, 1520 m, 1426 m, 1244 s, 1220 s, 1085 m, 1064 s, 917
w, 871 w, 834 w, 814 m, 719 m, 662 w cm–1. 1H NMR ([D6]DMSO):
5.10 (s, 4 H, CH2), 7.14 (s, 1 H), 8.66 (s, 1 H), 13.29 (s, 2 H) ppm.
The preparation of complex 2 was similar to that of 1 except that the
DMF was used instead of water as solvent. Yield 36%. Elemental
analysis: C13H15Cu1N3O12: calcd. C 33.26; H 3.20; N 8.96%; found:
C 33.00; H 3.22; N 8.64%. FT-IR (KBr): ν˜ = 3429 s, 2921 w, 2843
w, 1615 s, 1519 m, 1385 m, 1356 m, 1281 m, 1194 w, 1079 w, 1041
w, 915 w, 834 w, 703 w cm–1.
2.3.3 Synthesis of [CuL(2,2Ј-bipy)(DMSO)]·DMSO (3)
The preparation of complex 3 was similar to that of 1 except that the
DMSO was used instead of water as solution, and the 2,2Ј-bipy was
used as the second ligand. Yield 59%. Elemental analysis:
C24H26Cu1N4O12S2: calcd. C 41.74, H 3.27; N 9.12%; found: C 41.59;
H 3.15; N 9.46%. FT-IR (KBr): ν˜ = 3424 m, 1640 s, 1599 s, 1522 m,
1468 w, 1441 w,1402 m, 1357 m, 1271 s, 1198 w, 1102 w, 1078 m,
1032 m, 918 w, 835 m, 790 m, 773 m, 745 w, 732 w, 697 m, 605 w
cm–1.
2.4. X-ray Crystallography
Single-crystal X-ray diffraction data for complexes 1–3 were collected
with a Rigaku R-AXIS RAPID imaging plate diffractometer with
graphite-monochromated Mo-Kα (λ = 0.71073 Å) at 291 K. Empirical
absorption corrections based on equivalent reflections were applied.
The structures of complexes 1–3 were solved by direct methods and
refined by full-matrix least-squares methods on F2 using SHELXS-97
crystallographic software package.[30,31] All non-hydrogen atoms were
refined anisotropically. The hydrogen atoms of the L and 2,2Ј-bipy
molecules were placed in calculated positions and treated as riding on
their parent. The crystal parameters, data collection, and refinement
results for 1–3 are summarized in Table 1. Selected bond lengths and
angles are listed in Table 2.
2.3. Synthesis of the Complexes
2.3.1 Synthesis of {[CuL(H2O)2]·4H20}n (1)
H2L (0.06 g, 0.20 mmol) and copper nitrate (0.04 g, 0.20 mmol) were
dissolved in distilled water (20 mL) with stirring. Afterwards, the pH
value was adjusted to about 7 with the aqueous solution of sodium
hydroxide (20%). The mixture was stirred for 2 h and the blue precipi-
tate was filtered off. The filtrate was left at room temperature for sev-
eral days; dark blue crystals suitable for X-ray diffraction were ob-
tained in 43% yield. Elemental analysis: C10H18Cu1N2O16: calcd. C
24.70; H 3.70; N 5.76%; found: C 24.42; H 3.74; N 5.79%. FT-IR
(KBr): ν˜ = 3435 s, 2071 w, 1519 m, 1446 m, 1426 m, 1405 m, 1361
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Table 1. Crystallographic data for complexes 1–3.
1
2
3
Empirical formula
Formula weight
C10H18CuN2O16
485.81
C13H15CuN3O12
468.82
C24H26CuN4O12S2
690.15
Crystal system
Space group
triclinic
P1
monoclinic
P21/c
triclinic
P1
¯
¯
a /Å
b /Å
c /Å
α /°
6.9075(14)
8.9797(18)
16.179(3)
84.54(3)
84.73(3)
71.43(3)
945.0(3)
2
6.7169(13)
26.680(5)
10.486(2)
90
106.25(3)
90
9.728(4)
10.696(5)
14.163(9)
94.58(2)
93.25(2)
90.009(16)
1466.6(13)
2
β /°
γ /°
V /Å3
1804.0(6)
2
Z
T /K
291(2)
1.707
1.241
291(2)
1.726
1.283
291(2)
1.563
0.955
dcalcd /mg·m–3
μ /mm–1
F(000)
498
956
710
Reflections collected
Rint
8773
0.0819
1.062
0.0544, 0.1395
0.0764, 0.1712
17554
0.0495
1.083
0.0420, 0.1082
0.0575, 0.1159
13899
0.0267
1.073
0.0438, 0.1209
0.0567, 0.1330
Goodness-of-fit on F2
b)
R1a), wR2 [I Ͼ 2σI)]
R1, wR2 (all data)
2
2 2
2 2 1/2
a) R1 = (Σ||Fo|–|Fc|)/Σ|Fo|. b) wR2 = [Σw(Fo –Fc ) / Σw (Fo ) ]
.
Z. Anorg. Allg. Chem. 2012, 236–241
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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237

D.-S. Ma, X.-M. Zhang, P.-J. Liu, S. Zhang
ARTICLE
Table 2. Selected bond lengths /Å and angles /° of complexes 1–3.
1
Cu(1)–O(12)
Cu(1)–O(11)
1.931(4)
1.957(3)
Cu(1)–O(5)#1
Cu(1)–O(1)
1.947(3)
2.344(2)
Cu(1)–O(1)#2
1.971(3)
O(12)–Cu(1)–O(5)#1
O(12)–Cu(1)–O(11)
O(5)#–Cu(1)–O(1)
O(5)#1–Cu(1)–O(11)
O(11)–Cu(1)–O(1)
89.84(14)
176.28(13)
101.10(10)
90.72(13)
90.78(11)
O(12)–Cu(1)–O(1)
92.73(13)
88.33(13)
178.10(12)
91.09(12)
79.47(11)
O(12)–Cu(1)–O(1)#2
O(5)#1–Cu(1)–O(1)#2
O(11)–Cu(1)–O(1)#2
O(1)#2–Cu(1)–O(1)
Symmetry codes: #1 x+1, y, z #2 –x+2, –y+2, –z
2
Cu(1)–O(1)
Cu(1)–O(11)
Cu(1)–O(4)#2
O(1)–Cu(1)–O(11)
O(1)–Cu(1)–O(4)#1
O(11)–Cu(1)–O(12)
O(4)#–Cu(1)–O(12)
O(4)#1–Cu(1)–O(4)#2
1.922(2)
Cu(1)–O(4)#1
Cu(1)–O(12)
1.959(2)
1.966(2)
1.958(3)
2.322(2)
90.84(11)
174.58(9)
165.77(10)
89.58(9)
80.43(8)
O(11)–Cu(1)–O(4)#1
O(1)–Cu(1)–O(12)
O(1)–Cu(1)–O(4)#2
O(11)–Cu(1)–O(4)#2
O(12)–Cu(1)–O(4)#2
88.12(10)
92.70(10)
94.45(8)
97.88(10)
95.58(9)
Symmetry codes: #1 –x, –y+1, –z #2 x + 1, y, z
3
Cu(1)–O(1)
Cu(1)–O(11)
Cu(1)–N(3)
O(1)–Cu(1)–O(5)
N(4)–Cu(1)–N(3)
O(1)–Cu(1)–N(3)
O(5)–Cu(1)–N(3)
O(5)–Cu(1)–O(11)
1.963(2)
Cu(1)–N(4)
Cu(1)–O(5)
2.006(2)
1.969(2)
2.232(2)
2.010(2)
88.83(9)
80.54(10)
171.67(9)
95.35(9)
94.66(9)
O(5)–Cu(1)–N(4)
O(1)–Cu(1)–N(4)
O(1)–Cu(1) –O(11)
N(4)–Cu(1)–O(11)
N(3)–Cu(1)–O(11)
168.76(9)
94.01(9)
89.97(9)
96.22(10)
96.86(10)
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting the de-
pository numbers CCDC-734886, CCDC-744660, and CCDC-734887
dinated by three oxygen atoms of three carboxylate groups of
three L ligands and two oxygen atoms of two water molecules,
resulting in a square pyramid type with τ = 0.03.[32] The basal
plane of pyramid is defined by two oxygen atoms (O5, O1i,
where i = 2–x, 2–y, z) of two L ligands and two water molecu-
lar oxygen atoms (O11, O12), whereas the apical site is occu-
pied by O1 from L ligand, with the Cu1–O1 being almost per-
pendicular to the least-squares plane. In many cases, the nitro
groups of benzene ring do not take part in the coordination
with central metal ions, which also exist in these three com-
plexes reported herein.
The molecule can be seen as a dimer of two nearly square-
planar monomeric units, which are related to each other by an
inversion center located in the middle of the dimer through
two bridging oxygen groups, O1 and its symmetry equivalent
O1i. The result is a tightly bound pair of CuO5 nuclei, with
the distance of copper cations Cu1 and Cu1i at 3.327(1) Å
from each other.
In the crystal structure of complex 1, two carboxylic groups
of L ligand exhibit two kinds of coordination modes, that is,
O5 bridges two neighboring CuII ions into dimer, whereas O1
only coordinates to one CuII ion. In addition, the two carboxyl-
ate groups of L ligand do not locate in a plane with the central
benzene ring with the dihedral angles between the carboxylate
groups and the benzene ring of 72.56(3)° to 81.52(3)°, which
is much larger than those found in free H2L ligands (nearly
0°).[28,29]
(Fax:
+44-1223-336-033;
E-Mail:
deposit@ccdc.cam.ac.uk,
http://www.ccdc.cam.ac.uk).
3. Results and Discussion
3.1 Structure Description
Recently, we have reported two types of the crystal structure
of H2L.[28,29] The only difference of the two compounds is the
number of the lattice water molecules, which influences the
formation of the hydrogen bonding and the stacking fashion of
the molecules. From the reported results, one can find that the
hydrogen bonds between lattice water molecules and organic
components are able to strongly influence the arrangements
of the whole molecules. So, what will happen when different
solvents were used in the synthesis of coordination complexes?
Herein, we used copper as coordination metal and H2L as li-
gand to carry out reactions in H2O, DMF, and DMSO and
obtained three different inorganic-organic hybrid complexes.
3.1.1 Crystal Structure of Complex 1
Figure 1 presents a ball-and-stick view of the crystal struc-
ture of complex 1. The asymmetric unit consists of one CuII
cation, one L ligand, two coordinated water molecules, and
four lattice water molecules. The central CuII ion is five-coor- infinite chainlike structure along a axis, as shown in Figure 1b.
Another structural feature of complex 1 is that it has an
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Copper(II) Coordination Polymers Involving 2,2-(4,6-Dinitro-1,3-phenylenedioxy)diacetic Acid
Figure 1. (a) Molecular structure of complex 1; (b) 1D ladder chain of complex 1; (c) 2D hydrogen-bonding net of complex 1. Symmetry
codes:I = 1+x, y, –z; II = 2–x, 2–y, –z.
Meanwhile, the interchain weak C–H···O hydrogen bonding ions in a bridging fashion. Thus, the copper atoms are infi-
C9–H9A···O7ii (where ii = 2–x, 3–y, –z) links the chains to nitely linked by L ligands to generate a one-dimensional chain.
form a 2D structure with (001) plane. In the packing arrange- The nearest Cu···Cu distance between adjacent chains is
ment of complex 1, the adjacent 2D layers form a 3D frame- 10.486(3) Å. Figure 2c shows the 3D supramolecular frame-
work by O–H···O hydrogen bonding of lattice water molecules work constructed by hydrogen bonding.
(Figure 1c).
3.1.3 Crystal Structure of Complex 3
3.1.2 Crystal Structure of Complex 2
Different from complex 1, complex 3 does not form a 1D
Single crystal X-ray diffraction analysis indicates that Cu1 coordination chain due to the introduction of 2,2Ј-bipy. The
in complex 2 is also in a square pyramid coordination environ- asymmetric unit of complex 3 consists of one CuII ion, one
ment with τ = 0.15 (Figure 2a), involving three oxygen atoms 2,2Ј-bipy ligand, one L ligand, one coordinated DMSO, and
(O1, O4iii, O4iv, where iii = –x, 1–y, –z; iv = 1+x, y, z) from one free DMSO molecules. The arrangement around the cen-
three different L ligands and two oxygen atoms (O11, O12) tral metal atom is close to square pyramidal (Figure 3a) with
from water molecules. The basal of the pyramid is defined by two of the basal positions occupied by the two nitrogen atoms
O1, O11, O12, and O4iii, whereas the apical site is occupied (N3, N4) of 2,2Ј-bipy ligand and the other ones by two oxygen
by O4iv. The O–Cu–O angles range from 80.43(8)° to atoms (O1, O5) of two different carboxylate groups of the
174.59(9)°. It should be noted that no water was added in the same L ligand, whereas the axial position is occupied by the
synthesis of complex 2, the coordinated water molecule per- oxygen atom (O11) of the coordinated DMSO molecule (τ =
haps comes from the reactants or undried DMF solvent.
0.05). The four basal atoms are very nearly coplanar, their
As shown in Figure 2b, complex 2 is also a 1D coordination maximum deviation from the mean plane not exceeding
polymer consisting of double metal atoms with the distance of 0.0350(11) Å. The central copper atom is displaced from this
Cu···Cu in dimer of 3.277(1) Å. In complex 2, all carboxyl plane by a distance of 2.379(2) Å towards the axial O11 atom.
groups are completely deprotonated, in agreement with the IR In complexes 1 and 2, the axial positions of central metal ion’s
data, in which no absorption peaks around 1731–1651 cm–1 pyramid coordination environment are occupied by the oxygen
for –COOH were observed. Similar with complex 1, the coor- atoms of L ligands, while it is occupied by DMSO oxygen
dination modes of two carboxylate groups in L ligand are dif- atom for complex 3.
ferent: one carboxylate group adopts a unidentate coordination
The coordination types of L ligand in complex 3 are also
mode with one CuII ion, whereas the other one links two CuII different with those in complexes 1 and 2. In complexes 1
Z. Anorg. Allg. Chem. 2012, 236–241
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239

D.-S. Ma, X.-M. Zhang, P.-J. Liu, S. Zhang
ARTICLE
Figure 2. (a) Molecular structure of complex 2; (b) 1D ladder chain of complex 2; (c) 3D packing diagram of complex 2. Symmetry codes: I
= –x, 1–y, –z; II = –1–x, 1–y, –z.
Figure 3. (a) Molecular structure of complex 3; (b) 3D packing diagram of complex 3.
and 2, the two carboxyl groups of L ligand display different intramolecular hydrogen bonding C9–H9B···O12vi (where vi
coordination modes with copper atoms: one carboxyl group = –x, 1 –y, 1 –z) and intermolecular hydrogen bonding C24–
only coordinates to one copper atom with unidentate mode, H24B···O11 into an infinite chain along [100] direction.
whereas the other one coordinates to two copper atoms in μ2-
In the three complexes reported herein, the solvent mole-
bridging fashion. In complex 3, the two carboxyl groups of L cules (H2O, DMF, and DMSO) coordinate with the central CuII
ligand exhibit the same coordination type and both link with ions by oxygen atoms in similar fashion. The coordinated sol-
one copper atom in unidentate fashion, which is also responsi- vent molecules have no influence in the formation of 1D
ble for the zero-dimensional crystal structure of complex 3.
chains in complexes 1 and 2, whereas they influence the dis-
In addition, the crystal structure of complex 3 is stabilized tance of neighboring chains: due to the larger volume of DMF
by intra and intermolecular hydrogen bonding (Figure 3b). comparing with H2O, the distance of nearest chains in complex
Firstly, the intermolecular hydrogen bonds C17–H17···O2i, 1 is 8.980(2) Å, which is slightly smaller than that of 10.48
C18–H18···O4v (where v = –x, –y, –z) link the two groups (3) Å in complex 2. In addition, the coordination of solvent
into dimer; secondly, these dimers are further connected by molecules with central metal ions stabilizes the crystal struc-
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Copper(II) Coordination Polymers Involving 2,2-(4,6-Dinitro-1,3-phenylenedioxy)diacetic Acid
ture, on the other hand, it also prevents the metal ions to coor- atoms and prevents the formation of high dimensional com-
dinate with more L ligands to form a higher dimensional net- plex. The luminescent curves of complexes 1–3 and H2L indi-
work.
cate that the good planar can increase the luminescent inten-
sities in coordination complexes.
3.2 Luminescent Properties
References
The emission spectra of complexes 1–3 and H2L in solid
state at room temperature were investigated. As shown in Fig-
ure 4, H2L shows a strong fluorescent emission at 460 nm,
which is different with that of the benzene ring (254 nm). The
red shift is perhaps caused by the introduction of nitro groups.
Complexes 1–3 show similar luminescent spectra with H2L
except for the intensities. The emissions can probably be as-
signed to the interligand (π–π*) fluorescent emission because
similar emission under the same conditions are observed for
the free H2L. It is clear that the coordination bonds signifi-
cantly influence the luminescence intensities of three com-
plexes. For complexes 1 and 3, due to the enhanced structural
rigidity and reduced fluorescence quenching effect.[33,34] the
luminescent intensities are stronger than that of free H2L. The
luminescent intensity of complex 2 is weaker than that of free
H2L perhaps due to the existence of solvent molecule DMF,
which destroys the coplanar of the complex.
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Figure 4. Fluorescent spectra of ligand and complexes 1–3.
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ligand. In all of the three complexes, solvent molecules coordi-
nate with centered metal atoms through oxygen atoms. For
complexes 1 and 2, due to the existence of nitro groups in L
ligands, the large steric hindrances make the copper ions only
coordinating with L ligands at one side and form a 1D chain-
like structure. In addition, there are abundant hydrogen bonds
in the complexes, which link the chains into 3D supramolec-
ular network. For complex 3, the existence of the second li-
gand, 2,2Ј-bipy, occupies the coordination sites of copper
Received: June 30, 2011
Published Online: November 29, 2011
Z. Anorg. Allg. Chem. 2012, 236–241
© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
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