Construction of six new coordination complexes with 5-(3-pyridyl) tetrazole-2-acetato

Article abstract of DOI:10.1016/j.ica.2014.07.034

Six new complexes with 3-pytza ligand (3-pytza = 5-(3-pyridyl) tetrazole-2-acetato), [Sr(3-pytza)₂(H₂O)₂]_n·nH₂O (1), [Zn(3-pytza)₂(H₂O)₂]_n·2nH₂O (2), [Cu(3-pytza)₂(H₂O)]_n·2nH₂O (3), [Pb(3-pytza)₂]_n(4), [Eu(3-pytza)₂Cl(H₂O)₂]_n(5), [Tb(3-pytza)₂Cl(H₂O)₂]_n(6) have been synthesized. These compounds were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. The X-ray analysis reveals that these compounds display 1D or 2D structures. Furthermore, the luminescent properties of 1-6 were investigated at room temperature in the solid state.

Full text of DOI:10.1016/j.ica.2014.07.034

Inorganica Chimica Acta 423 (2014) 87–94
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Construction of six new coordination complexes
with 5-(3-pyridyl) tetrazole-2-acetato
⇑
⇑
Jian-Hua Zou, Da-Liang Zhu, He Tian, Fei Fei Li, Fei Fei Zhang, Gao-Wen Yang , Qiao-Yun Li ,
Yun Xia Miao
Jiangsu Laboratory of Advanced Functional Materials, Department of Chemistry and Materials Engineering, Changshu Institute of Technology, Changshu 215500, Jiangsu, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Six new complexes with 3-pytza ligand (3-pytza = 5-(3-pyridyl) tetrazole-2-acetato), [Sr(3-pytza)2(H2-
O)2]nꢀnH2O (1), [Zn(3-pytza)2(H2O)2]nꢀ2nH2O (2), [Cu(3-pytza)2(H2O)]nꢀ2nH2O (3), [Pb(3-pytza)2]n (4),
[Eu(3-pytza)2Cl(H2O)2]n (5), [Tb(3-pytza)2Cl(H2O)2]n (6) have been synthesized. These compounds were
characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. The X-ray anal-
ysis reveals that these compounds display 1D or 2D structures. Furthermore, the luminescent properties
of 1–6 were investigated at room temperature in the solid state.
Received 17 February 2014
Received in revised form 9 May 2014
Accepted 10 July 2014
Available online 1 August 2014
Keywords:
Crystal structure
3-pytza
Ó 2014 Elsevier B.V. All rights reserved.
Luminescence
1. Introduction
candidates for the construction of new coordination compounds.
However, the compounds based on 5-(3-pyridyl) tetrazole-2-ace-
The design and construction of coordination compounds with
unique structural motifs and unique chemical as well as physical
properties has been given considerable attention in either coordi-
nation chemistry or material chemistry [1]. On the one hand, from
the point view of crystal engineering, ligands are often designed in
order to form specific lattice structures, that is to say, the shapes
and symmetry of the organic ligands are vital to form the unique
structures of the coordination topologies. One of the important
characteristics of an organic compound used as a ligand is its
diverse coordination modes, molecular rigidity and flexibility
which may determine the orientation of the binding sites [2]. On
the other hand, many objective factors, such as the ligand-to-metal
ratio, the solvent system, the pH values and the temperature can
inevitably influence the final structures of our targeted molecules.
As versatile building blocks, carboxylate–tetrazole organic ligands,
for instance, tetrazolate-5-acetic acid (H2tza) [3], tetrazolate-5-for-
mic acid (Htzf) [4], tetrazole-1-acetic acid (Htza) [5], 5-aminotet-
razole-1-acetic acid (Hatza) [6], 5-(2-pyrazinyl) tetrazole-2-acetic
acid (Hpztza) [7], 5-(2-pyridyl) tetrazole-2-acetic acid (Hpytza)
[8], 5-[N-acetato(3-pyridyl)] tetrazole (a3-ptz) [9], 5-[N-aceta-
to(4-pyridyl)] tetrazole (a4-ptz) [10], 5-[(4-nitryl)phenyl] tetra-
zole-1-acetato (nptza) [11], etc. have proven to be good
tato potassium salt ligand (K3-pytza), a new tetrazole-containing
carboxylate ligand, to the best of our knowledge, has only been
reported with Sm [12]. In this paper, we have further our investi-
gation to treat 3-pytza potassium salt with several metal ions,
ranging from the s-block element Sr(II), the ds-block ones Zn(II),
Cu(II), the p-block one Pb(II) to the f-block ones, Eu(III), Tb(III).
Six new coordination compounds, namely, [Sr(3-pytza)2(H2O)2]n-
ꢀnH2O(1), [Zn(3-pytza)2(H2O)2]nꢀ2nH2O (2), [Cu(3-pytza)2(H2O)]n-
ꢀ2nH2O (3), [Pb(3-pytza)2]n (4), [Eu(3-pytza)2Cl(H2O)2]n (5),
[Tb(3-pytza)2Cl(H2O)2]n (6) were obtained. The 3-pytza ligand in
1–6 shows four different coordination modes (Scheme 1). Herein
we report their synthesis, crystal structures and luminescent prop-
erties along with the synthetic conditions on the formation of such
complexes.
2. Experimental
2.1. Materials and instruments
5-(3-pyridyl) tetrazole (designated as H3-pytz) was prepared by
[2+3] cycloaddition reactions, by treating 3-cyanopyridine with
NaN3 in toluene in the presence of triethylammonium chloride.
The reaction of H3-pytz with ethyl bromoacetate in methanolic
potassium hydroxide solution gave mostly H(tetrazole)-substi-
tuted products 5-(3-pyridyl) tetrazole-2-acetato potassium salt
(K3-pytza) [13]. All chemicals were obtained from commercial
⇑
Corresponding authors. Tel.: +86 512 52251846; fax: +86 512 52251842
(G.-W. Yang). Tel./fax: +86 512 52251842 (Q.-Y. Li).
E-mail addresses: ygwsx@126.com (G.-W. Yang), liqiaoyun61@126.com
(Q.-Y. Li).
http://dx.doi.org/10.1016/j.ica.2014.07.034
0020-1693/Ó 2014 Elsevier B.V. All rights reserved.

88
J.-H. Zou et al. / Inorganica Chimica Acta 423 (2014) 87–94
Scheme 1. The coordination modes of the 3-pytza ligand in 1–6.
sources and used without further purification. The elemental anal-
yses for C, H and N were performed with a PE2400 elemental ana-
lyzer. The IR spectra were obtained on a NICOLET380 spectrometer
using KBr disks in the range 4000–400 cmꢁ1. Photoluminescent
analyses were performed on an F-4600 fluorescence spectrometer.
Single crystal X-ray diffraction was carried out by a Rigaku SCX-
mini-CCD diffractometer.
2.4. Synthesis of [Eu(3-pytza)2Cl(H2O)2]n (5) and
[Tb(3-pytza)2Cl(H2O)2]n (6)
A mixture of EuCl3ꢀ6H2O (0.0366 g, 0.1 mmol) or TbCl3ꢀ6H2O
(0.0373 g, 0.1 mmol) and K3-pytza (0.0486 g, 0.2 mmol) in mixture
of EtOH (5 mL) and water (2 mL) was sealed in a 25 mL teflon-lined
stainless steel container, which was heated at 120 °C for 48 h. After
the sample was cooled to room temperature, the colorless block
crystals 5 or 6 was obtained. For 5, yield: 34% based on Eu. Anal.
Calc. for C16H16ClEuN10O6: C, 30.42; H, 2.55; N, 22.17. Found: C,
30.24; H, 2.59; N, 22.33%. IR (KBr, cmꢁ1): 3343(s), 1611(s),
1573(s), 1449(s), 1419(s), 1393(m), 1377(m), 1313(w), 1197(w),
1037(m), 827(w), 752(w), 731(w), 637(m), 581(w). For 6, yield:
38% based on Tb. Anal. Calc. for C16H16ClTbN10O6: C, 30.09; H,
2.52; N, 21.93. Found: C, 29.80; H, 2.62; N, 21.67%. IR (KBr,
cmꢁ1): 3343(s), 3280(s), 1613(s), 1574(s), 1450(s), 1419(s),
1394(m), 1378(m), 1313(w), 1198(w), 1038(m), 827(w), 752(w),
732(w), 638(m), 582(w).
2.2. Synthesis of [Sr(3-pytza)2(H2O)2]nꢀnH2O (1) and [Zn(3-
pytza)2(H2O)2]nꢀ2nH2O (2)
A mixture of Sr(NO3)2 (0.0211 g, 0.1 mmol) or Zn(NO3)2ꢀ6H2O
(0.0298 g, 0.1 mmol) and K3-pytza (0.0486 g, 0.2 mmol) in mixture
of EtOH (3 mL) and water (6 mL) was heated at 80 °C for 4 h with
stirring, then cooled to the room temperature and filtered, the col-
orless block crystals 1 or 2 was obtained. For 1, yield: 55% based on
Sr. Anal. Calc. for C16H18N10O7Sr: C, 34.94; H, 3.30; N, 25.47. Found:
C, 35.22; H, 3.42; N, 25.64%. IR (KBr, cmꢁ1): 3491(s), 3334(m),
1639(s), 1600(s), 1530(m), 1438(s), 1400(s), 1378(m), 1310(m),
1155(w), 1025(w), 825(m), 752(w), 732(w), 631(w), 585(w). For
2, yield: 58% based on Zn. Anal. Calc. for C16 H20N10O8 Zn: C,
35.21; H, 3.69; N, 25.66. Found: C, 35.47; H, 3.77; N, 25.89%. IR
(KBr, cmꢁ1): 3456(s), 3298(m), 1635(s), 1619(m), 1538(m),
1443(m), 1379(s), 1302(s), 1204(m), 1155(m), 1104(m), 1064(m),
1047(m), 824(w), 755(w), 673(w), 640(w), 522(w).
2.5. Single crystal structures determination
Suitable single crystals of complexes 1–6 were mounted on a
Rigaku SCXmini-CCD diffractometer equipped with a graphite-
monochromated Mo K
a radiation (k = 0.71073 Å) at 291 K. All
absorption corrections were performed using the CrystalClear pro-
grams. The crystal structures of 1–6 were solved by direct methods
and refined on F2 by full-matrix least-squares using anisotropic
displacement parameters for all non-hydrogen atoms [14a]. For
1–6, important crystal data and collection and refinement param-
eters are summarized in Table 1S, and selected bond lengths and
angles are given in Table 1. Hydrogen-bonding parameters are
given in Table 2S.
2.3. Synthesis of [Cu(3-pytza)2(H2O)]nꢀ2nH2O (3) and [Pb(3-pytza)2]n
(4)
A mixture of Cu(ClO4)2ꢀ6H2O (0.0370 g, 0.1 mmol) or Pb(ClO4)2-
ꢀ6H2O (0.0514 g, 0.1 mmol) and K3-pytza (0.0486 g, 0.2 mmol) in
water (9 mL) was heated at 90 °C for 8 h with stirring, then cooled
to the room temperature and filtered, the block crystals 3 (blue) or
4 (colorless) was obtained. For 3, yield: 45% based on Cu. Anal. Calc.
for C16H18CuN10O7: C, 36.54; H, 3.45; N, 26.63. Found: C, 36.28; H,
3.51; N, 26.73%. IR (KBr, cmꢁ1): 3353(s), 3255(m), 1609(s), 1567(s),
1473(m), 1440(s), 1418(s), 1378(m), 1306(m), 1196(m), 1036(m),
823(m), 730(w),679(w), 637(w), 577(w). For 4, yield: 61% based
on Pb. Anal. Calc. for C16H12N10O4Pb: C, 31.22; H, 1.97; N, 22.76.
Found: C, 31.48; H, 2.10; N, 22.59%. IR (KBr, cmꢁ1): 1607(s),
1440(s), 1420(s), 1390(s), 1296(m), 1204(m), 1152(m), 1057(m),
1005(m), 924(w), 821(m), 731(w), 678(w), 588(w).
3. Results and discussions
3.1. Syntheses consideration and general characterizations
In this work, we selected 3-pytza ligand with both flexible car-
boxylate group and rigid tetrazolyl and pyridyl rings to construct
metal coordination architectures in order to explore the influence
of metal ions and the synthesis conditions in forming such com-
plexes. Besides, s-block element Sr(II), p-block one Pb(II), ds-block
ones Zn(II), Cu(II) and especially the f-block ones, Eu(III), Tb(III)
which are more likely to display different coordination numbers
and geometries when coordinated to the same ligand due to their
different ionic radii and coordination abilities, therefore,

J.-H. Zou et al. / Inorganica Chimica Acta 423 (2014) 87–94
89
Table 1
O(1A)–Tb(1)–O(1)
O(2C)–Tb(1)–Cl(1)
171.94(13)
78.30(13)
O(3)–Tb(1)–Cl(1)
O(1)–Tb(1)–Cl(1)
145.04(7)
94.03(7)
Selected bond distances (Å) and angles (°) for 1–6.
[Sr(3-pytza)2 (H2O)2]nꢀnH2O (1)
Symmetry code for 1 A: ꢁ1 ꢁ x, 1 ꢁ y, ꢁ1 ꢁ z; B: ꢁx, 1 ꢁ y, ꢁ1 ꢁ z. For 2 A: 1 ꢁ x, ꢁy,
ꢁz; B: 1 ꢁ x, 1 ꢁ y, ꢁ1 ꢁ z; C: x, ꢁ1 + y, 1 + z. For 3 A: 1 ꢁ x, ꢁ0.5 + y, 2 ꢁ z; B: ꢁx,
0.5 + y, ꢁz. For 4 A: x, 1.5 ꢁ y, ꢁ0.5 + z; B: x, 1.5 ꢁ y, 0.5 + z. For 5 A: ꢁx, y, 0.5 ꢁ z; B:
x, ꢁy, 0.5 + z; C: ꢁx, ꢁy, ꢁz. For 6 A: 1 ꢁ x, y, 0.5 ꢁ z; B: x, ꢁy, ꢁ0.5 + z; C: 1 ꢁ x, ꢁy,
1 ꢁ z.
Sr(1)–O(1)
2.732
2.480
2.749
2.569
Sr(1)–O(2)
Sr(1)–O(1A)
Sr(1)–O(4B)
Sr(1)–O(6)
2.719
2.586
2.650
2.535
Sr(1)–O(3)
Sr(1)–O(3B)
Sr(1)–O(5)
O(1)–Sr(1)–O(2)
O(1)–Sr(1)–O(1A)
O(1)–Sr(1)–O(4B)
O(1)–Sr(1)–O(6)
O(2)–Sr(1)–O(1)
O(2)–Sr(1)–O(4B)
O(2)–Sr(1)–O(6)
O(3)–Sr(1)–O(3B)
O(3)–Sr(1)–O(5)
O(1A)–Sr(1)–O(3B)
O(1A)–Sr(1)–O(5)
O(3B)–Sr(1)–O(4B)
O(3B)–Sr(1)–O(6)
O(4B)–Sr(1)–O(6)
47.8
O(1)–Sr(1)–O(3)
O(1)–Sr(1)–O(3B)
O(1)–Sr(1)–O(5)
O(2)–Sr(1)–O(3)
O(5)–Sr(1)–O(6)
O(2)–Sr(1)–O(5)
O(3)–Sr(1)–O(1A)
O(3)–Sr(1)–O(4B)
O(3)–Sr(1)–O(6)
O(1A)–Sr(1)–O(4B)
O(1A)–Sr(1)–O(6)
O(3B)–Sr(1)–O(5)
O(4B)–Sr(1)–O(5)
107.0
66.1
115.2
80.7
110.9
77.3
93.7
66.4
94.2
140.6
80.9
144.8
137.3
97.6
74.7
164.2
82.9
112.2
168.7
162.2
93.0
77.5
88.5
complexes with diverse structures and properties were acquired.
Products of 1–6 suitable for single crystal X-ray diffraction analysis
cannot be obtained by changing the reaction conditions, regardless
of the ligand-to-metal ratio or the solvent system, either. However,
it is worthwhile to point out that crystallographic cell data (a, b, c,
a, b, c) are identical to those of complexes 1 and 2 when we sub-
stitute MCl2 for M(NO3)2 (M = Sr, Zn) to prepare compounds 1
and 2 under the same conditions, which indicates the product
structures weakly depend on the nature of the metal counter
anion. In addition, we cannot obtain 3 and 4 by means of MCl2 or
M(NO3)2 (M = Pb, Cu) under similar conditions. Otherwise, in the
process of preparing compounds 5 and 6, only when reacting the
ligand and metal salts in the solvent system with less water can
we obtain crystals with high quality.
Compounds 1–6 are all air stable. All general characterizations
were carried out with crystal samples. The elemental analysis
showed that the components of these complexes were well in
accordance with the results of the structural analysis. For 1–6,
the characteristic bands of carboxylate groups appeared in the
usual region at 1600–1639 cmꢁ1 for the antisymmetric stretching
vibrations and at 1377–1450 cmꢁ1 for the symmetric stretching
vibrations [15]. The absence of any strong absorption bands around
1720 cmꢁ1 confirm complete deprotonation of the carboxyl groups
of the pytza ligand during the reactions. In addition, the strong and
broad band centered at 3255–3491 cmꢁ1 for the compounds
except compound 4 are attributed to the O–H stretching vibration
of the free or bonded water molecule in the compounds. These are
in accordance with the results of the X-ray diffraction analysis.
48.3
112.2
70.3
[Zn(3-pytza)2(H2O)2]nꢀ2nH2O (2)
Zn(1)–O(5)
2.0793(17)
Zn(1)–N(5A)
Zn(1)–N(5)
2.213(3)
2.213(3)
Zn(1)–O(1B)
Zn(1)–O(1C)
O(5)–Zn(1)–O(1B)
O(5)–Zn(1)–O(1C)
O(5)–Zn(1)–N(5A)
O(1B)–Zn(1)–N(5A)
2.083(2)
2.213(2)
90.50(8)
89.50(8)
87.49(9)
90.18(9)
O(5)–Zn(1)–O(5A)
O(1B)–Zn(1)–O(1C)
O(5A)–Zn(1)–N(5A)
O(1C)–Zn(1)–N(5A)
180.00(7)
180.0
92.51(9)
89.82(9)
[Cu(3-pytza)2(H2O)]nꢀ2nH2O (3)
Cu(1)–O(2)
1.961(7)
Cu(1)–O(3)
Cu(1)–N(5A)
Cu(1)–N(5B)
O(2)–Cu(1)–N(10B)
O(2)–Cu(1)–N(5A)
N(5A)–Cu(1)–N(10B)
O(3)–Cu(1)–O(5)
N(5A)–Cu(1)–O(5)
1.990(7)
2.042(8)
2.042(8)
90.8(3)
92.9(3)
168.4(4)
87.1(3)
Cu(1)–N(10B)
Cu(1)–O(5)
2.038(8)
2.283(7)
O(1)–Cu(1)–O(3)
O(3)–Cu(1)–N(10B)
O(3)–Cu(1)–N(5A)
O(2)–Cu(1)–O(5)
N(10B)–Cu(1)–O(5)
176.4(3)
89.4(3)
87.7(3)
89.3(3)
96.1(3)
95.0(3)
[Pb(3-pytza)2]n (4)
Pb(1)–O(1A)
Pb(1)–O(3B)
Pb(1)–N(5)
Pb(1)–O(3A)
O(1A)–Pb(1)–O(3B)
O(3B)–Pb(1)–N(10)
O(3B)–Pb(1)–N(5)
O(4B)–Pb(1)–O(3B)
O(4B)–Pb(1)–O(1A)
O(2A)–Pb(1)–O(1A)
O(2A)–Pb(1)–N(5)
N(5)–Pb(1)–N(10)
2.408(7)
2.440(7)
2.756(9)
2.440(7)
77.9(3)
82.6(3)
79.9(3)
48.88
125.94
49.77
100.03
157.01
Pb(1)–O(2A)
Pb(1)–O(4B)
Pb(1)–N(10)
2.8145
2.8525
2.688(9)
O(1A)–Pb(1)–N(10)
O(1A)–Pb(1)–N(5)
O(4B)–Pb(1)–N(10)
O(4B)–Pb(1)–N(5)
O(4B)–Pb(1)–O(2A)
O(2A)–Pb(1)–O(3B)
O(2A)–Pb(1)–N(10)
86.7(3)
75.2(3)
78.55
100.56
156.29
124.57
77.90
3.2. Crystal structure of [Sr(3-pytza)2(H2O)2]nꢀnH2O(1)
Compound 1 crystallizes in monoclinic space group P21/c and
the asymmetric unit contains one [Sr(3-pytza)2(H2O)2]nꢀnH2O mol-
ecule. As shown in Fig. 1, the Sr(II) center is eight-coordinated by
six carboxylate-O atoms from four 3-pytza ligands and two O
atoms from two water molecules, forming a distorted square-
antiprism coordination geometry. Two neighboring Sr(II) ions are
bridged by two carboxylate groups from two 3-pytza ligands in a
[Eu(3-pytza)2Cl(H2O)2]n (5)
Eu(1)–O(3)
Eu(1)–O(3A)
Eu(1)–O(2B)
Eu(1)–O(2)
2.384(7)
2.384(7)
2.441(6)
2.851(6)
Eu(1)–O(1)
Eu(1)–O(1A)
Eu(1)–Cl(1)
2.438(7)
2.438(7)
2.626(4)
l1,1,3-COO bridging mode [Scheme 1-I], forming a 1-D chain
O(3)–Eu(1)–O(3A)
O(3)–Eu(1)–O(1)
O(3)–Eu(1)–O(2B)
O(1A)–Eu(1)–O(2B)
O(2B)–Eu(1)–O(2C)
O(1)–Eu(1)–Cl(1)
O(3)–Eu(1)–O(2A)
O(2B)–Eu(1)–O(2A)
O(1)–Eu(1)–O(2)
O(2)–Eu(1)–Cl(1)
69.1(3)
94.3(2)
129.7(2)
74.0(2)
156.2(4)
94.91(16)
73.4(2)
112.62(19)
47.7(2)
O(3)–Eu(1)–O(1A)
O(1A)–Eu(1)–O(1)
O(3A)–Eu(1)–O(2B)
O(1)–Eu(1)–O(2B)
O(3)–Eu(1)–Cl(1)
O(2B)–Eu(1)–Cl(1)
O(1)–Eu(1)–O(2A)
O(3)–Eu(1)–O(2)
O(2B)–Eu(1)–O(2)
O(2A)–Eu(1)–O(2)
77.5(2)
170.2(3)
72.6(2)
108.1(2)
145.47(16)
78.11(19)
135.4(2)
131.6(2)
61.4(2)
extending along the a axis with Srꢀ ꢀ ꢀSr distance of 4.4592 Å and
the Srꢀ ꢀ ꢀSrꢀ ꢀ ꢀSr bite angle of 131.1° (Fig. 2). In 1, hydrogen bonding
interactions exist between the coordinated water molecule and the
oxygen atom of the non-coordinated water [O(5)–H(5A)ꢀ ꢀ ꢀO (7)
2.813 Å/139°] and between the coordinated water molecule and
the nitrogen atom of the tetrazole ring [O(6)–H(6A)ꢀ ꢀ ꢀN(4)
3.043 Å/136°]. The adjacent chains are linked together through
hydrogen bonding interactions, to form a 3-D supramolecular
framework (Fig. S1).
76.70(16)
153.4(3)
[Tb(3-pytza)2Cl(H2O)2]n (6)
Tb(1)–O(3)
Tb(1)–O(3A)
Tb(1)–O(1)
Tb(1)–O(1A)
2.350(3)
2.350(3)
2.397(3)
2.397(3)
Tb(1)–O(2)
Tb(1)–O(2C)
Tb(1)–Cl(1)
2.389(4)
2.389(4)
2.643(2)
3.3. Crystal structure of [Zn(3-pytza)2(H2O)2]nꢀ2nH2O (2)
ꢀ
Compound 2 crystallizes in the triclinic space group P1 and the
O(3)–Tb(1)–O(3A)
O(3A)–Tb(1)–O(2C)
O(3)–Tb(1)–O(1A)
O(3)–Tb(1)–O(1)
69.91(14)
72.34(14)
96.19(11)
77.11(9)
O(3)–Tb(1)–O(2C)
O(2C)–Tb(1)–O(2B)
O(2C)–Tb(1)–O(1A)
O(2C)–Tb(1)–O(1)
129.48(14)
156.6(3)
106.81(12)
74.89(13)
asymmetric unit contains half of [Zn(3-pytza)2(H2O)2]nꢀ2n2H2O
molecule. As shown in Fig. 3, each Zn(II) center lies on an inversion
center and is coordinated by two carboxylate-O atoms from two

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J.-H. Zou et al. / Inorganica Chimica Acta 423 (2014) 87–94
Fig. 1. The coordination environment of Sr atom in 1. Hydrogen atoms are omitted for clarity.
Fig. 2. The 1-D chain structure of 1. Hydrogen atoms are omitted for clarity.
Fig. 3. The 1-D chain structure of 2, showing the coordination environment of Zn atom. Hydrogen atoms are omitted for clarity.
3-pytza ligands, two pyridyl-N atoms from two 3-pytza ligands
and two O atoms from two water molecules, forming a slightly dis-
torted octahedral geometry. Each 3-pytza ligand adopts a biden-
tate bridging coordination mode [Scheme 1-II], binding to two
molecule and the nitrogen atom of the tetrazole ring [O(7)–
H(7A)ꢀ ꢀ ꢀN(4) 2.8501 Å/166°] and between the non-coordinated
water molecule and the oxygen atom of the carboxylate
group[O(7)–H(7B)ꢀ ꢀ ꢀO(1) 2.7414 Å/164°]. The adjacent 1-D chains
are further connected through hydrogen bonding interactions, to
construct a 3-D framework (Fig. S2).
Zn(II) atoms via pyridyl-N and carboxylate-O, generating a 1-D
0
polymeric chain with the Znꢀ ꢀ ꢀZn distance of 10.7342 ÅA and the
Znꢀ ꢀ ꢀZnꢀ ꢀ ꢀZn bite angle of 180.00° (Fig. 3). In 2, hydrogen bonding
interactions exist between the coordinated water molecule and the
oxygen atom of the carboxylate group [O(5)–H(5B)ꢀ ꢀ ꢀO(2)
2.7148 Å/124°], between the non-coordinated water molecule
and the oxygen atom of the solvent water molecule [O(3)–
H(5C)ꢀ ꢀ ꢀO(7) 2.6487 Å/170°], between the non-coordinated water
3.4. Crystal structure of [Cu(3-pytza)2(H2O)]nꢀ2nH2O (3)
Single-crystal X-ray diffraction analysis reveals that compound
3 crystallizes in monoclinic space group P21 and the asymmetric
unit contains one [Cu(3-pytza)2(H2O)]nꢀ2n2H2O molecule. As

J.-H. Zou et al. / Inorganica Chimica Acta 423 (2014) 87–94
91
Fig. 4. The 2-D layered structure of 3, showing the coordination environment of Cu atom. Hydrogen atoms are omitted for clarity.
Fig. 5. The 1-D chain structure of 4, showing the coordination environment of Pb atom.
shown in Fig. 4, each Cu(II) center in a trigonal bipyramidal geom-
etry is surrounded by two carboxylate-O atoms from two 3-pytza
ligands [14b], two pyridyl-N atoms from two 3-pytza ligands and
one O atom from one water ligand. Each 3-pytza ligand adopts a
bidentate bridging coordination mode [Scheme 1-II], binding to
two Cu(II) atoms via pyridyl-N and carboxylate-O, generating a
2-D layer network, which contains a square grid with a Cu(II) at
each corner and an 3-pytza ligand at each edge connecting with
two Cu(II). The edge lengths are unequal, with 11.1036 and
12.1456 Å. The diagonal lengths of the square grid are 17.9090
and 14.7170 Å, and the angles of the square are 74.58° and
83.01° and 100.67°. In 3, hydrogen bonding interactions exist
between the coordinated water molecule and the oxygen atom of
the non-coordinated water molecule [O(5)–H(5A)ꢀ ꢀ ꢀO(7)
2.7562 Å/155°], between the coordinated water molecule and oxy-
gen atom of the carboxylate group [O(5)–H(5B)ꢀ ꢀ ꢀO(4) 2.966(11) Å/
135°], between the non-coordinated water molecule and the oxy-
gen atom of the carboxylate group [O(6)–H(6A)ꢀ ꢀ ꢀO(4)
2.844(13) Å/158°, O(6)–H(6B)ꢀ ꢀ ꢀO(1) 2.810(14) Å/159°], between
the non-coordinated water molecule and the nitrogen atom of
the tetrazole ring [O(7)–H(7A)ꢀ ꢀ ꢀN(4) 3.0750 Å/159°] and between
the non-coordinated water molecule and the oxygen atom of the
non-coordinated water [O(7)–H(7B)ꢀ ꢀ ꢀO(6) 3.0134 Å/134°]. The
adjacent 2-D layers are held together via hydrogen bonding inter-
actions, to construct a 3-D framework (Fig. S3).
3.5. Crystal structure of [Pb(3-pytza)2]n (4)
Compound 4 consists of one Pb(II), two 3-pytza ligands in the
crystallographic asymmetric unit, with monoclinic space group
P21/c. Each Pb(II) is coordinated by four oxygen atoms from two
3-pytza ligands and two nitrogen atoms from other two 3-pytza
ligands (Fig. 5). Each 3-pytza ligand exhibits a chelating-bridging
coordination mode [Scheme 1-III], chelating the Pb(II) via carbox-
ylate-O(O1 and O2) with a four-membered chelating ring, and
binding to other Pb(II) atom via pyridyl-N, generating a 1-D net-
work with the Pbꢀ ꢀ ꢀPb distance of 10.4159 Å and the Pbꢀ ꢀ ꢀPbꢀ ꢀ ꢀPb
bite angle of 173.368°. In 4, non-classic hydrogen bonding interac-
tions exist between –CH2– and the oxygen atom of the carboxylate
group [C(2)–H(2B)ꢀ ꢀ ꢀO(4) 3.254(14) Å/154°, C(10)–H(10A)ꢀ ꢀ ꢀO(2)
3.183(14) Å/160°] and between the pyridyl C–H group and the
nitrogen atom of the tetrazole ring [C(5)–H(5)ꢀ ꢀ ꢀN(9)
3.311(16) Å/149°]. The adjacent 1-D chains are connected together
by the hydrogen bonding interactions to construct a 3-D frame-
work (Fig. S4).
3.6. Crystal structure of [Eu(3-pytza)2Cl(H2O)2]n (5)
The X-ray structure analysis reveals that compound 5 shows an
1-D double chain. Compound 5 crystallizes in monoclinic space
group C2/c. As shown in Fig. 6, each Eu(III) center is nine-coordi-

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J.-H. Zou et al. / Inorganica Chimica Acta 423 (2014) 87–94
Fig. 6. The coordination environment of Eu atom in 5. Hydrogen atoms are omitted
for clarity.
nated by six O atoms from four 3-pytza ligands and two O atoms
from two water molecules and a Cl anion, forming a distorted
monocapped square antiprism coordination geometry. The 3-pytza
ligand chelates one Eu(III) ion via two carboxylate-O atoms while
simultaneously binds to a second Eu(III) ion via one carboxylate-
O atom[Scheme 1-I], thus compound 5 forms a 1-D chain structure
extending along the c axis with neighboring Euꢀ ꢀ ꢀEu distance of
4.5599 Å and the Euꢀ ꢀ ꢀEuꢀ ꢀ ꢀEu bite angle of 150.533° (Fig. 7). The
bond distances of O1–C1 and O2–C1 are 1.222 and 1.256 Å, respec-
tively. The difference may arise from the different coordination
modes of the two oxygen atoms, O(1) only connects to one Eu(III)
while O(2) links to two independent Eu(III) centers in a bridging
mode. In 5, hydrogen-bonding interactions exist between the
Fig. 8. The coordination environment of Tb atom in 6. Hydrogen atoms are omitted
for clarity.
coordinated water molecule and the chloride anion [O(3)–
H(3A)ꢀ ꢀ ꢀCl(1) 3.096 Å/165°] and between the coordinated water
molecule and the nitrogen atom of the pyridyl ring [O(3)–
H(3B)ꢀ ꢀ ꢀN (5) 2.739 Å/155°]. The neighboring 1-D chains of 5 are
held together through hydrogen-bonding interactions, generating
a 3-D network (Fig. S5).
Fig. 7. The 1-D chain structure of 5. Hydrogen atoms are omitted for clarity.

J.-H. Zou et al. / Inorganica Chimica Acta 423 (2014) 87–94
93
Fig. 9. The 1-D chain structure of 6. Hydrogen atoms are omitted for clarity.
Fig. 10. The emission spectrums of 1, 2, 4 and K3-pytza at room temperature in the
solid state (kex = 347 nm for K3-pytza ligand; kex = 361 nm for 1; kex = 351 nm for 2;
kex = 370 nm for 4).
Fig. 11. The emission spectrums of 5 at room temperature in the solid state
(kex = 394 nm).
3.8. Fluorescence properties
3.7. Crystal structure of [Tb(3-pytza)2Cl(H2O)2]n (6)
The luminescence properties of free K3-pytza ligand and com-
plexes 1–6 were investigated at room temperature in solid state
(Figs. 10–12). Compounds 1 and 2 exhibit photoluminescence with
maximum emissions at 443(1) and 453(2) nm upon excitations at
363(1), 351(2) nm, respectively. These fluorescent emissions could
be tentatively assigned to the intraligand fluorescences emission,
because a similar emission at 450 nm upon excitation at 347 nm
was also observed for the free ligand K3-pytza (Fig. 10). Generally,
the intraligand fluorescence emission wavelength is determined by
Complex 6 crystallizes in monoclinic space group C2/c and the
asymmetric unit contains half of [Tb(3-pytza)2Cl(H2O)2]n molecule.
Each Tb(III) in 6 is seven-coordinated by four carboxylate-O atoms
from four 3-pytza ligands, two O atoms from two water molecules
and a Cl atom, forming a distorted pentagonal bipyramid coordina-
tion geometry (Fig. 8). Two neighboring Tb(III) are doubly bridged
by two carboxylate groups from two 3-pytza ligands in a l1,3-COO
bridging mode[Scheme 1-IV], displaying a 1-D chain extending
along the c axis with the Tbꢀ ꢀ ꢀTb distance of 4.600 Å and the
Tbꢀ ꢀ ꢀTbꢀ ꢀ ꢀTb bite angle of 149.66° (Fig. 9). In 6, hydrogen bonding
interactions exist between the coordinated water molecule and the
chloride anion [O(3)–H(3A)ꢀ ꢀ ꢀCl(1) 3.1320 Å/171°] and between
the coordinated water molecule and the nitrogen atom of the pyr-
idyl ring [O(3)–H(3B)ꢀ ꢀ ꢀN(5) 2.7327 Å/158°]. The neighboring 1-D
chains are further connected through these hydrogen bonding
interactions, forming a 3-D framework (Fig. S6).
the energy gap between the
p
and p⁄ molecular orbitals of the free
conjugation [16]. How-
ligand, which is related to the extent of
p
ever, compound 3 has no fluorescent emission in that copper has
low energy d–d transitions. Upon excitation at 370 nm, compound
4 exhibits a emission peak at 504 nm, which may arise from the
Pb2+ lone pair to ligand charge transfer [17]. In addition, the emis-
sion spectras of compounds 5 and 6 exhibit the characteristic emis-
sion of Eu3+ and Tb3+, respectively. For 5, four characteristic peaks

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J.-H. Zou et al. / Inorganica Chimica Acta 423 (2014) 87–94
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To the best of our knowledge, we are the first to investigate
coordination compounds containing 3-pytza. The structure varia-
tion from the 1-D double chain to the 2-D framework may be
attributed to the difference of the central ions and versatile coordi-
nation modes of the 3-pytza ligand. The XRD analysis shows that
the products are pure (Supplementary material). Our research
results indicate that, 3-pytza ligand with both flexible carboxylate
group and rigid tetrazole and pyridyl ring is versatile agent to con-
struct metal coordination architectures. As a promising new type
of multifunctional ligand, 3-pytza has a great potential in the field
of coordination compounds, and further endeavors for exploration
of 3-pytza complexes are underway in our work group.
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We greatly appreciate the financial support from the 14th Chal-
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Entrepreneurship Training Program of Jiangsu Province and the
Start Grant from CSLG.
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CCDC 962771–962776 contains the supplementary crystallo-
graphic data for 1–6. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.ica.2014.07.034.