Synthesis, crystal structure, and fluorescence properties of a novel coordination polymer [Zn(L)(4,4'-bipyridine)(H2O)] n ·(H2O) 4

Article abstract of DOI:10.1134/S1070328412050028

In this work, a novel and rare coordination polymer, [Zn(L)(Bipy)(H ₂O)] _n ·(H₂O) ₄ (H ₂L-sphe-nylpropylmalonate acid, Bipy-4,4'-bipyridine), has been synthesized and characterized by elemental analysis, FT-IR spectroscopy, and solid fluorimetry studies. In the crystal, the Zn²⁺ ion of the complex is hexa-coordinated in a slightly distorted octahedral configuration forming the unit structure, 2D structure, and 3D framework. The supramolecular architecture was constructed by a unit of (H₂O) ₄ discrete water cluster. Besides, the coordination polymer displays strong emission spectra due to the metal-to-ligand charge-transfer transition, having potential applications as fluorescent materials. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S1070328412050028

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2012, Vol. 38, No. 6, pp. 386–391. © Pleiades Publishing, Ltd., 2012.
Synthesis, Crystal Structure, and Fluorescence Properties
of a Novel Coordination Polymer
1
[Zn(L)(4,4'ꢀBipyridine)(H2O)]n · (H2O)4
E. J. Gao*, R. S. Wang, L. Lin, S. H. Liu, T. D. Sun, and M. C. Zhu
Coordination Chemistry Laboratory, Shenyang University of Chemical Technology, Shenyang, Liaoning, 110142 P.R. China
*eꢀmail: ejgao@yahoo.com.cn
Received March 10, 2011
Abstract—In this work, a novel and rare coordination polymer, [Zn(L)(Bipy)(H2O)]n · (H2O)4 (H2L—spheꢀ
nylpropylmalonate acid, Bipy—4,4'ꢀbipyridine), has been synthesized and characterized by elemental analꢀ
ysis, FTꢀIR spectroscopy, and solid fluorimetry studies. In the crystal, the Zn2+ ion of the complex is hexaꢀ
coordinated in a slightly distorted octahedral configuration forming the unit structure, 2D structure, and 3D
framework. The supramolecular architecture was constructed by a unit of (H2O)4 discrete water cluster.
Besides, the coordination polymer displays strong emission spectra due to the metalꢀtoꢀligand chargeꢀtransꢀ
fer transition, having potential applications as fluorescent materials.
DOI: 10.1134/S1070328412050028
1
INTRODUCTION
In this paper, we successfully designed and syntheꢀ
sized novel coordination polymer
[Zn(L)(Bipy)(H2O)]n 4H2O ( (L—phenylpropyꢀ
lmalonate) including isolated (H2O)4 cluster units.
The crystal structure, synthesis, and characterization
are also discussed in this work.
a
In recent years, coordination polymers or suꢀ
pramolecular architectures with different dimensionꢀ
alities have captured interest of researchers. Owing to
their intriguing construction from weak interactions,
⋅
I)
such as
π–π
ꢀstacking, hydrogen bonds, ion–π interꢀ
action, and hydrophobing interactions. The supramoꢀ
lecular compounds have become the extensive focus of
magnetism, molecular absorption, catalysis, electrical
conductivity, hostꢀguest chemistry, etc. [1–5]. Meanꢀ
while, these extended coordination polymers have
molecular topological structures [6–8]. Many topoꢀ
logical structures of coordination polymers have been
constructed from the basis of N,Nꢀbidentate ligands,
such as 4,4'ꢀbipyridine (Bipy), 2,2'ꢀbipyridine, and
4,4'ꢀtrimethylenedipyridine [8–10]. Bipy with aroꢀ
matic rings is an organic molecule with a rigid strucꢀ
ture, with which it is suitable for emission fluoresꢀ
cence. Compared to organic luminescent materials,
metalꢀorganic coordination polymers have the advanꢀ
tages of high luminescence efficiency and excellent
stability [11]. Benzenealkyl dicarboxylate shows exꢀ
cellent performances during and after coordination of
the complexes and the potential applications in bioꢀ
logical activity and synthesis of new drugs [12]. Howꢀ
ever, to our best of knowledge, benzenealkyl dicarboxꢀ
ylates as ligands are relatively less [11, 12]. Although
many Zn(II) complexes have been reported, those
with benzenealkyl dicarboxylate and Bipy are still surꢀ
prisingly rare.
EXPERIMENTAL
Materials and measurements. Ligand L was preꢀ
pared according to a previously published method
with some modifications [13]. Other chemicals were
purchased from commercial sources and came into
use without further purification. Element analysis (C,
H, and N) were performed with a model Finnigan
EA 1112 instrument. IR spectra were run as KBr pelꢀ
lets with a Nicolet IRꢀ470 instrument.
Synthesis of the L
propanol and 7 mL of pyridine were mixed, stirred,
and heated to 65 C, and then 10 mL of thionyl chloꢀ
ride was added to the mixture. The mixture was stirred
and heated at 115 C under reflux for 1.5 h, after which
.
A total of 10 mL of
β
ꢀphenylꢀ
°
°
it was cooled to room temperature, and the white solid
appeared. The water was added to the stirring mixture.
The organic phase was separated directly from the reꢀ
action mixture with a separating funnel. The comꢀ
bined organic phases were dried, and the solvent was
removed. The phenylpropylchlorine was separated by
vacuum distillation under conditions of 142–143
and was then added to a mixture of sodium ethoxide
and dipropylmalonate (water bath at a constant temꢀ
perature of 60 C) under reflux for 4 h. The phenylproꢀ
pylmalonate was obtained by vacuum distillation unꢀ
°C
°
1
The article is published in the original.
386

SYNTHESIS, CRYSTAL STRUCTURE, AND FLUORESCENCE PROPERTIES
387
Table 1. Crystal data and structure refinement parameters
for
der conditions of 172–174°C and then was hydroꢀ
lyzed. After about 30 min, the white solid was
obtained, extracted, and recrystallized. L was obtained
I
1
Parameter
Value
in 32.4% yield. H NMR (300 MHz, DMSOꢀd6,
δ,
ppm): 1.53 (m., 2H, H3), 1.76 (m., 2H, H2), 2.52 (m.,
2H, H1), 2.66 (t., 1H, CH2CH2CH2CHPh), 7.18
(b.m., 5H, Ph).
Empirical formula
Formula weight
Crystal system
Space group
C22H30N2O9Zn
531.85
Synthesis of complex I. The concentration of all reꢀ
agents was 10 mmol L–1. An aqueous solution (10 mL)
containing 1 mmole of H2L was added dropwise into
10 mL of an aqueous solution containing 1 mmole of
Zn(NO3)2 with stirring and the mixture was allowed to
react for 5 h at room temperature. Then 10 mL of Bipy
(1 mmol) dissolved in 40% (v/v) ethanol was added,
and the reaction was continued to occur for 15 h. Afꢀ
terwards, the pH of the mixture was adjusted to 4.52 by
the addition of an aqueous solution of HCl. Light colꢀ
orless transparent solution was obtained by filtration,
and the solution was filtered and kept in air. After a few
days, the resulting colorless transparent crystals were
obtained, and then filtered off, washed with ethanol.
Monoclinic
P21/c
a
, Å
, Å
11.4565(13)
25.345(3)
8.6199(10)
102.898(2)
2439.7(5)
4
b
c
, Å
β
V
Z
, deg
IR (ν
, cm–1): 3428 m, 2925 m, 1719 m, 1611 s, 1582 s,
1416 s, 138 s, 1213 m, 1072 m, 811 m, 698 m, 643 m.
, Å3
For C22H30N2O9Zn (
anal. calcd., %: C, 49.49;
Found, %: C, 49.57;
M = 533.88)
H, 5.66;
H, 5.72;
N, 5.25.
N, 5.15.
ρcalcd, g cm–3
1.448
Xꢀray structure determination. Singleꢀcrystal data of
complex were collected at 293 K in a range of 1.61
< 26.04 on a Brucker Smart 1000 CCD diffractoꢀ
meter with Mo radiation ( = 0.71073 ).
Absorption coefficient, mm–1
Crystal size, mm
1.060
I
°
°
<
θ
K
λ
Å
α
0.10
×
0.08 × 0.06
The structure was solved using direct methods with
the fullꢀmatrix leastꢀsquares technique using the
SHELXLꢀ97 program [14, 15]. All nonꢀhydrogen
atoms were refined anisotropically. Hydrogen atoms
were located from different Fourier maps. Crystal data
θ
Range for data collection,
1.61–26.04
1112
deg
F
(000)
and structure refinement for complex
I are summaꢀ
rized in Table 1. Selected bond lengths and bond
angles are listed in Table 2. The coordinates of the
atoms and the thermal parameters were deposited with
the Cambridge Crystallographic Data Centre
(no. 815303; deposit@ccdc.cam.ac.uk or http://www.
ccdc.cam.ac.uk).
Scan mode
Limiting indices
ϕ
and
ω
scans
–13
≤
h
≤
14, –31
≤
k ≤ 25,
–10 ≤ l ≤ 7
Reflections collected/unique
Refinement parameters
Goodnessꢀofꢀfit on F2
11177/4754
312
RESULTS AND DISCUSSION
The base structure of polymer complex
I
as shown
is
in Fig. 1. As can be seen, the Zn2+ ion of complex
I
1.036
hexacoordinated in a slightly distorted octahedral
configuration. Each Zn2+ ion is sixꢀcoordinated by
two nitrogen atoms from two Bipy molecules, three
oxygen atoms from two L ligands, and one coordiꢀ
nated water molecule.
Besides, each L provides two oxygen atoms (O(3
O(4
)) to bidentate chelating one Zn2+ ion, and each
L also provides one oxygen atom (O(2)) bridging one
Final
indices (all data)
Δρmax Δρmin
Å–3
R
indices (
I
> 2
σ(I
))
R
1 = 0.0650, wR2 = 0.1751
1 = 0.1229, wR2 = 0.2060
2.058 and –0.899
R
R
A),
A
/
, e
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2012

388
GAO et al.
Table 2. Selected bond lengths (Å) and bond angles (deg) for structure
I
*
Bond
d
, Å
Bond
d, Å
Zn(1)–N(1)
Zn(1)–O(1)
Zn(1)–O(3)#1
2.201(5)
2.097(4)
2.067(4)
Zn(1)–N(2)#2
Zn(1)–O(2)
2.141(5)
2.101(4)
2.093(4)
Zn(1)–O(4)#1
Angle
ω
, deg
Angle
ω
, deg
O(4)#1Zn(1)O(3)#1
O(3)#1Zn(1)O(1)
O(3)#1Zn(1)O(2)
O(4)#1Zn(1)N(2)#2
O(1)Zn(1)N(2)#2
O(4)#1Zn(1)N(1)
O(1)Zn(1)N(1)
86.22(17)
172.55(17)
81.48(16)
92.85(18)
90.19(19)
85.67(18)
89.97(19)
178.5(2)
O(4)#1Zn(1)O(1)
O(4)#1Zn(1)O(2)
O(1)Zn(1)O(2)
86.41(17)
166.65(17)
105.96(17)
89.09(18)
92.13(18)
90.56(18)
89.26(18)
O(3)#1Zn(1)N(2)#2
O(2)Zn(1)N(2)#2
O(3)#1Zn(1)N(1)
O(2)Zn(1)N(1)
N(2)#2Zn(1)N(1)
#1
#2
* Symmetry transformations used to generate equivalent atoms:
x, –y
+ 3/2,
z
+ 1/2;
x + 1, y, z.
Zn(Bipy)(H2O) entities including isolated (H2O)4 clusꢀ are in turn bridged by Bipy nitrogen atoms via two
ter units, resulting in a 1D chain as shown in Fig. 2.
Additionally, along direction, the fragments of
Zn(L)(H2O) formed from L molecules and Zn2+ ions
Zn–N coordination bonds affording a 2D structure of
the complex, as shown in Fig. 3a. There is C–H⋅⋅⋅π
x
ꢀ
stacking interactions in the complex as shown in Fig. 3b.
N(2A)
N
C
N
C
N(2)
C
C
N(1A)
O(1
N(1)
A)
Zn
Zn(1
A)
O(2)
O
C
O(5)
O(2)
O(3A)
O
C
Zn(1)
O(1)
O(5A)
O(4)
O(4)
O(3)
Fig. 1. Basic structure of the complex (H atoms were omitted for clarity).
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SYNTHESIS, CRYSTAL STRUCTURE, AND FLUORESCENCE PROPERTIES
389
N
x
N
z
y
C
C
O
O
O
Zn
Zn
O
Fig. 2. 1D polymeric chain of the coordination polymer (H atoms were omitted for clarity).
(a)
(b)
x
x
y
y
z
z
N
N
O
O
Zn
O
O
O
N
N
Fig. 3. 2D layer structure of the complex (a); C–H⋅⋅⋅πꢀstacking interactions in the complex (b). H atoms were omitted for clarity.
The distances between H(13) and the benzene ring are complicated 3D stacked structure as illustrated in
Fig. 4a.
It is well known that the vast Hꢀbond network
3.39 Å, respectively, and these are shorter than 3.8 Å
normally found for intermolecular C–H⋅⋅⋅π interacꢀ
formed is based on water clusters, which often appear
in the complex crystals [18–22]. In this paper, four
water molecules (O(1w), O(2w), O(3w), and O(4w))
formed a discrete water cluster with the oxygen atoms,
which come from L (O(5)) and coordinated water
molecules (O(1)), resulting in the discrete 1D chain of
water cluster formed by a unit of (H2O)4. As illustrated
tions [16, 17].
Interestingly, the presence of four lattice water
molecules, one carboxyl oxygen atom, and one coorꢀ
dinated water molecule in each structure unit leads to
a complicated hydrogen bonding system. Finally, the
2D layers were connected by hydrogen bonding interꢀ
actions (as shown in Fig. 4b), forming a numerous in Fig. 4c, the O···O distance in the water cluster of the
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 38
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390
GAO et al.
(a)
x
y
x
y
x
(c)
Zn
(b)
Zn
Zn
z
y
O
C
O
Rotate
O
O
O
Zn
Zn
Zn
Fig. 4. 3D structure of the coordination polymer (2D layers connected by hydrogenꢀbonding interactions) (a); 1D chain of the
discrete water cluster in complex ormed by a unit of (H O) in different directions (b), (c).
I
2
4
complex ranges from 2.618 to 2.941 Å with an average cence with an emission peak at 465 nm upon excitaꢀ
distance of 2.8 Å, which is appropriate to those tion at 369 nm. The phenylpropylmalonate (L) shows
observed in the ice phase (2.77–2.84 Å) and shorter fluorescence with a weak emission peak at 305 nm
than those in liquid water (2.854 Å) [23, 24].
upon excitation at 263 nm. The complex exhibits the
fluorescence emission maximum at 545 nm upon
excitation at 510 nm. Compared to the emission specꢀ
trum of Bipy (λem = 465 nm), the emission peak of
The IR spectrum of complex
I was observed as a
broad band centered at 3428 cm–1 that may be asꢀ
signed to O–H stretching of the water cluster [25]. The
complex
I
has shifted 80 nm (Δλem = 80 nm). The
is assigned to the ligandꢀtoꢀ
weak
full carboxyl group coordination modes for the metal
ions [26]. The
(C–N) peak displayed at 1213 cm–1 and
δ
(C=O) absorption band at 1719 cm–1 exhibits
emission of complex
I
metal chargeꢀtransfer transition [29–31].
δ
the other strong absorption peak observed at 1161–
1582 cm–1 can be attributed to stretching of the aroꢀ
matic ring [27, 28].
ACKNOWLEDGMENTS
We gratefully acknowledge the Natural Science
The solidꢀstate fluorescence property of a complex Foundation of China (nos. 20971090 and 21171118),
powder was measured at room temperature and emisꢀ the Science and Technology Projects Fund of Shenꢀ
sion spectrum is given in Fig. 5. Bipy shows fluoresꢀ yang City (no. F10ꢀ215ꢀ1ꢀ00), and the Foundation of
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SYNTHESIS, CRYSTAL STRUCTURE, AND FLUORESCENCE PROPERTIES
391
500
3
400
300
200
100
0
2
1
250
300
350
400 450
Wavelength, nm
500
550
600
Fig. 5. Roomꢀtemperature solidꢀstate emission spectra: L (1), Bipy (2), and complex (3).
15. Sheldrick, G.M., SHELXSꢀ97, Program for Crystal
Structure Refinement, G ttingen (Germany): Univ. of
ttingen.
Educational Department of the Liaoning Province
(no. L2010430).
ö
G
ö
16. Nishio, M., Umezawa, Y., Honda, K., et al., CrystEngꢀ
Comm., 2009, vol. 11, p. 1757.
17. Gao, E.J., Liu, H.Y., Zhu, M.C., et al., Russ. J. Coord.
Chem., 2009, vol. 35, p. 915.
18. Choudhury, S.R., Jana, A.D., Colacio E., and
Lee, H.M., Cryst. Growth Des., 2007, vol. 7, p. 212.
19. Infantes, L., Chisholm, J., and Motherwell, S., Crystꢀ
EngComm., 2003, vol. 5, p. 480–486.
20. Beatty, A.M., CrystEngComm., 2001, vol. 51, p. 1.
21. Gao, E.J., Su, M., Zhang, M., et al., Z. Anorg. Allg.
Chem., 2010, vol. 636, p. 1565.
REFERENCES
1. Pas
án, J., Sanchiz, J., Lloret, F., et al., CrystEngComm.,
2007, vol. 9, p. 478.
2. Cheetham, A.K., Rao, C.N.R., and Feller, R.K., Chem.
Commun., 2006, vol. 46, p. 4780.
3. Ma, B.Q., Sun, H.L., and Gao, S., Inorg. Chem., 2005,
vol. 44, p. 837.
4. Liu, J.Q., Wang, Y.Y., Liu, P., and Wu, W.P., Inorg.
Chem. Commun., 2007, vol. 10, p. 343.
5. Huang, H., Yu, S.Y., Liu, H.B., and Shi, M., Polyheꢀ
22. Quiñonero, D., Deya, P.M., and Carranza, M.P., Dalꢀ
ton Trans., 2010, vol. 39, p. 794.
23. Lu, J., Yu, J.H., Chen, X.Y., et al., Inorg Chem., 2005,
vol. 44, p. 5978.
dron., 2004, vol. 23, p. 55.
6. Robson, R., J. Chem. Soc,. 2000, p. 3735.
7. Huang, X.C., Zhang, J.P., Lin, Y.Y., et al., Chem. Comꢀ
mun., 2004, vol. 9, p. 1100.
8. Janiak, C., DaltonTrans., 2003, vol. 14, p. 2781.
9. Ma, B.Q., Gao, S., Sun H.L., and Xu, G.X., J. Chem.
Soc., 2001, p. 130.
10. Gao, E.J., Guo, M.J., Zhang, Y.X., et al., Russ. J. Coord.
Chem., 2010, vol. 36, p. 923.
11. Amiri, M.G., Mahmoudi, G., Morsali, A., et al., Crystꢀ
EngComm., 2007, vol. 9, p. 686.
12. Gao, E.J., Zhu, M.C., Liu, L., et al., Inorg. Chem.,
2010, vol. 49, p. 3261.
13. Sun, Y.Z., Xu, D.J., Si, Z.L., et al., Shenyang Inst.
Chem. Technol., 1997, vol. 11, p. 183.
14. Sheldrick, G.M., SHELXSꢀ97, Program for Crystal
24. Gao, E.J., Huang, Y., Zhu, M.C., and Wang, L., Inorg.
Chem. Commun., 2009, vol. 12, p. 872.
25. Ghosh, S.K. and Bharadwaj, P.K., Inorg. Chem., 2004,
vol. 43, 6887.
26. Dai, P.X., Yang, E.C., Wang, X.G., and Zhao, X.J.,
Z. Anorg. Allg. Chem., 2008, vol. 634, p. 1581.
27. Zhang, L.P. and Zhu, L.G., CrystEngComm., 2006,
vol. 8, p. 815.
28. Garcia, H.C., Diniz, R., and Yoshidab, M.I., CrystEngꢀ
Comm., 2009, vol. 11, p. 881.
29. BiingꢀChiau Tzeng, BoꢀSo Chen, ShihꢀYang Lee,
et al., New J. Chem., 2005, vol. 29, p. 1254.
30. Allendorf, M.D., Bauer, C.A., Bhakta R.K., and Houꢀ
ka, R.J.T., Chem. Soc. Rev., 2009, vol. 38, p. 330.
31. Sapchenko, S.A., Dybtsev, D.N., Samsonenko D.G.,
and Fedin, V.P., New J. Chem., 2010, vol. 34, p. 2445.
Structure Solution, G
öttingen (Germany): Univ. of
Göttingen, 1997.
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