Four structurally diverse coordination complexes based on a new flexible ligand

Article abstract of DOI:10.1007/s11243-014-9816-y

Four new coordination compounds, namely mononuclear [Zn(pyrtza) ₂(H₂O)₂] (1), binuclear [Ni(pyrtza)(H ₂O)₂Cl]₂ (2), 1D [Cd(pyrtza)₂] (3), and 2D [Mn(pyrtza)Cl] (4), were synthesized by the reactions of Hpyrtza (Hpyrtza = 5-(2-pyrimidyl) tetrazole-2-acetic acid) with MCl₂ (M = Zn(II), Ni(II), Cd(II), Mn(II)) in the presence of KOH under solvothermal conditions. The compounds were characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. The luminescence properties of the complexes were investigated at room temperature in the solid state. Graphical Abstract: Four new coordination compounds, namely mononuclear [Zn(pyrtza) ₂(H₂O)₂] (1), binuclear [Ni(pyrtza) (H ₂O)₂Cl]₂ (2), 1D [Cd(pyrtza)₂] (3), and 2D [Mn(pyrtza)Cl] (4), were synthesized [Hpyrtza = 5-(2-pyrimidyl) tetrazole-2-acetic acid]. The luminescence properties of the complexes were investigated at room temperature in the solid state.[Figure not available: see fulltext.]

Full text of DOI:10.1007/s11243-014-9816-y

Transition Met Chem (2014) 39:421–429
DOI 10.1007/s11243-014-9816-y
Four structurally diverse coordination complexes based on a new
flexible ligand
•
Wu Xiang Li Jian Hua Zou Bing Bing Wang
•
•
•
Shan Li Gao Wen Yang Qiao Yun Li
•
•
•
Bo Qiu Da Liang Zhu
Received: 13 January 2014 / Accepted: 10 March 2014 / Published online: 1 April 2014
Ó Springer International Publishing Switzerland 2014
Abstract Four new coordination compounds, namely
mononuclear [Zn(pyrtza)2(H2O)2] (1), binuclear [Ni(pyr-
tza)(H2O)2Cl]2 (2), 1D [Cd(pyrtza)2] (3), and 2D [Mn(pyr-
tza)Cl] (4), were synthesized by the reactions of Hpyrtza
(Hpyrtza = 5-(2-pyrimidyl) tetrazole-2-acetic acid) with
MCl2 (M = Zn(II), Ni(II), Cd(II), Mn(II)) in the presence of
KOH under solvothermal conditions. The compounds were
characterized by elemental analysis, IR spectroscopy, and
single-crystal X-ray diffraction. The luminescence proper-
ties of the complexes were investigated at room temperature
in the solid state.
acid (Htza) [4, 14–19], 5-(2-pyridyl) tetrazole-2-acetic acid
(Hpytza) [20], and 5-[N-acetato(3-pyridyl)] tetrazole (a3-
pytz) [21] have received much attention in that they have
proven to be good candidates for the construction of novel
coordination compounds. We have now synthesized another
tetrazole-carboxylate ligand, 5-(2-pyrimidyl)tetrazole-2-ace-
tic acid (Hpyrtza, Scheme 1), which, to the best of our
knowledge, has not been reported before. The selection of this
ligand arises from several considerations as follows: First, the
Hpyrtza ligandincludes both nitrogen atoms in the pyrimidine
and tetrazole rings and carboxylate oxygens, as well as the
classic N–N0 chelating 2,20bipy core, and is therefore very
likely to display a variety of coordination modes. Also, the –
CH2– spacer between the tetrazole ring and carboxylate group
offers flexible orientations of the carboxylate arm, allowing
the formation of various framework structures. Finally, the
abundant nitrogen and oxygen atoms may participate in
hydrogen bonds, stabilizing the resulting supramolecular
assemblies [1, 2]. In this paper, four new coordination com-
poundsdisplayingfour different coordinationmodes of pyrtza
(Scheme 2) are described, namely [Zn(pyrtza)2(H2O)2] (1),
[Ni(pyrtza)(H2O)2Cl]2 (2), [Cd(pyrtza)2] (3), and [Mn(pyr-
tza)Cl] (4). These complexes were obtained by reacting
Hpyrtza with MCl2 where M = Zn(II), Ni(II), Cd(II), Mn(II).
The characterization, X-ray crystal structures, and lumines-
cence properties of the complexes are described.
Introduction
Metal–organic frameworks (MOFs), especially those based
on N-heterocyclic carboxylic acids with both nitrogen and
oxygen atoms which have good coordinating properties [1, 2],
have attracted interestnot only due to theirintriguingdiversity
of structures, but also their potential commercial applications
as multifunctional materials, in the area of magnetism [3, 4],
heterogeneous catalysis [5, 6], photochemistry [7–9], ferro-
electrics [10], dielectrics [11], etc. Typical of N-heterocyclic
carboxylic acids and tetrazole-carboxylate ligands such as
tetrazolate-5-acetic acid (H2tza) [12, 13], tetrazole-1-acetic
W. X. Li ꢀ J. H. Zou ꢀ B. B. Wang ꢀ S. Li ꢀ
G. W. Yang (&) ꢀ Q. Y. Li (&) ꢀ B. Qiu ꢀ D. L. Zhu
Jiangsu Laboratory of Advanced Functional Materials,
Department of Chemistry and Materials Engineering, Changshu
Institute of Technology, Changshu 215500, Jiangsu,
People’s Republic of China
Experimental
Materials and methods
Apart from the ligand, all the other chemicals were com-
mercially available reagents of analytical grade and used
without further purification. The elemental analysis for C,
e-mail: ygwsx@126.com
Q. Y. Li
e-mail: liqiaoyun61@126.com
123

422
Transition Met Chem (2014) 39:421–429
(s), 1,527 (m), 1,392 (s), 1,348 (m), 1,271 (w), 1,043 (s),
1,032 (w), 1,007 (m), 998 (m), 827 (m).
Synthesis of the complexes
Scheme 1 Structural formula of the Hpyrtza ligand
A mixture of Hpyrtza (0.0824 g, 0.4 mmol) and ZnCl2
(0.0260 g, 0.2 mmol) for 1, NiCl2ꢀ6H2O (0.2 mmol,
0.0476 g) for 2, CdCl2ꢀ2.5H2O (0.2 mmol, 0.0456 g) for 3,
and MnCl2ꢀ4H2O (0.2 mmol, 0.0396 g) for 4 was dissolved
in a mixture of EtOH (6 mL) and water (2 mL); then, the
pH was adjusted to 6 with KOH (0.5 mol/L), and the
mixture was sealed in a 25 mL telfon-lined stainless steel
container, which was heated at 120 °C for 48 h, and then,
the complex was cooled to room temperature. Colorless
block crystals 1–4 were obtained. For 1, yield: 48 % based
on Zn. Anal. Calcd. for C14H14N12O6Zn: C, 32.9; H, 2.8;
N, 32.8 %. Found: C, 32.7; H, 2.8; N, 33.1 %. IR (KBr,
cm-1): 3,424 (s), 1,673 (s), 1,629 (s), 1,573 (s), 1,382 (s),
1,302 (m), 1,201 (w), 1,059 (w), 824 (m), 742 (m), 674 (w),
640 (w), 526 (w). For 2, yield: 48 % based on Ni. Anal.
Calcd. for C14H18Cl2N12Ni2O8: C, 25.1; H, 2.7; N, 25.1 %.
Found: C, 25.4; H, 2.6; N, 25.4 %. IR (KBr, cm-1): 3,381
(s), 1,639 (s), 1,589 (s), 1,563 (s), 1,489 (m), 1,458 (m),
1,411 (m), 1,390 (s), 1,306 (w), 1,200 (w), 1,144 (w), 824
(m), 729 (w), 683 (w), 650 (w). For 3, yield: 41 % based on
Cd. Anal. Calcd. for C14H10CdN12O4: C, 32.2; H, 1.9; N,
32.2 %. Found: C, 32.4; H, 2.0; N, 32.0 %. IR (KBr,
cm-1): 3,468 (s), 1,629 (s), 1,564 (m), 1,398 (s), 1,319 (m),
1,247 (m), 1,163 (w), 1,140 (w), 1,099 (w), 925 (s), 833
(w), 723 (w), 636 (w), 647 (m), 589 (w). For 4, yield: 46 %
based on Mn. Anal. Calcd. for C7H5ClMnN6O2: C, 28.5; H,
H, and N was obtained on a Perkin-Elmer 2400 microan-
alyzer. The IR spectra were recorded (4,000–400 cm-1) on
a NICOLET 380 spectrometer with pressed KBr pellets.
The photoluminescence spectra were recorded on a Hitachi
F4600 spectrofluorometer.
Synthesis of Hpyrtza
5-(2-Pyrimidyl)tetrazole (Hpyrtz) was prepared by a
[2 ? 3] cycloaddition reaction, involving a treatment of
2-cyanopyrimidyl with NaN3 in toluene in the presence of
triethylammonium chloride [22, 23]. A mixture of chloro-
acetic acid (4.73 g, 0.05 mol), Hpyrtz (7.40 g, 0.05 mol),
and potassium hydroxide (5.61 g, 0.10 mol) in methanol
(100 mL) were refluxed for 24 h at 70 °C. After cooling to
room temperature, the precipitate was filtered off and
washed with 2 9 30 mL of methanol; then, it was dis-
solved in distilled water (30 mL), and the pH of the solu-
tion was adjusted to 2 with concentrated HCl (12 mol/L),
giving 5-(2-pyrimidyl)tetrazole-2-acetic acid (Hpyrtza) as
a powder. Yield: 63 % (based on Hpyrtz). Anal. Calcd for
C7H6N6O2: C, 40.8; H, 2.9; N, 40.8 %. Found: C, 40.5; H,
2.8; N, 40.9 %. IR (KBr, cm-1): 3,494 (w), 1,632 (s), 1,579
Scheme 2 Coordination modes of the Hpyrtza ligand
123

Transition Met Chem (2014) 39:421–429
423
Table 1 Crystallographic data for 1–4
Compound
1
2
3
4
Empirical formula
Formula mass
Crystal system
Space group
C14H14ZnN12O6
511.74
C14H18Ni2Cl2N12O8
670.68
C14H10CdN12O4
522.75
C7H5ClMnN6O2
295.56
Triclinic
P¯ı
Triclinic
P¯ı
Monoclinic
C2/c
Monoclinic
P21/c
˚
a (A)
9.0171(18)
14.017(3)
16.705(3)
77.15(3)
81.30(3)
89.61(3)
2,034.1(7)
4
6.6754(13)
8.9528(18)
11.607(2)
80.35(3)
85.21(3)
69.47(3)
640.2(2)
1
15.660(3)
8.6131(17)
13.637(3)
11.817(2)
13.030(3)
6.9683(14)
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
95.95(3)
105.39(3)
3
˚
V (A )
1,829.5(6)
4
1,034.4(4)
4
Z
T/K
calcd (g/cm3)
l (mm-1
291(2)
291(2)
291(2)
1.898
291(2)
1.898
D
1.671
1.740
)
1.270
1.744
1.249
1.533
Reflections collected
17,371
6,620
9,266
10,540
2,360(0.0486)
1,955
Unique reflections (Rint
)
7,145(0.0820)
4,633
2,912(0.0397)
2,273
2,097(0.0513)
1,865
No. observations (I [ 2.00 r (I))
No. variables
Ra, wRb
GOFc
595
166
141
154
0.0825, 0.1839
1.082
0.0503, 0.1111
1.084
0.0329, 0.0666
1.072
0.0525, 0.1244
1.025
3
˚
D/qmax (e/A )
0.476
0.951
0.533
1.503
3
˚
D/qmin (e/A )
-0.516
-0.388
-0.546
-1.345
a
R = ||Fo| - |Fc|/|Fo|
Rw = {w(Fo2 - Fc2)2/w(F2o)2}1/2
b
c
GOF = {w((F2o - F2c)2)/(n - p)}1/2, where n number of reflections and p total numbers of parameters refined
1.7; N, 28.4 %. Found: C, 28.6; H, 1.8; N, 28.6 %. IR
(KBr, cm-1): 3,424 (s), 1,653 (s), 1,617 (s), 1,579 (m),
1,480 (m), 1,435 (m), 1,409 (m), 1,322 (w), 1,306 (w),
1,270 (w), 912 (m), 824 (m), 742 (w), 679 (w), 641 (w),
592 (w).
parameters related to the non-H atom to which they were
bonded. Crystallographic data are summarized in Table 1,
and selected bond lengths and angles are listed in Table 2.
Hydrogen-bonding parameters are given in Table 3.
X-ray crystallography
Results and discussion
Single-crystal X-ray crystal data were collected on a Rigaku
SCX mini CCD diffractometer equipped with graphite-
Structure of complex 1
˚
monochromated Mo-Ka radiation (k = 0.071073 A). The
Complex 1 crystallizes in triclinic space group P¯ı, and the
asymmetric unit contains two [Zn(pyrtza)2(H2O)2] mole-
cules. The molecular geometries of the two independent
[Zn(pyrtza)2(H2O)2] molecules are almost the same. As
shown in Fig. 1, each Zn center is coordinated by two
oxygen atoms from two pyrtza ligands and two water
ligands, forming a distorted tetrahedral coordination
geometry. The pyrtza anion in 1 acts as a monodentate
ligand, coordinating via one of its carboxylate-O atoms
[Scheme 2(I)], thereby giving a mononuclear structure. For
intensity data were collected by the x scan technique and
were reduced using the Crystal-Clear program [24], and an
absorption correction (multi-scan) was applied. The reflec-
tion data were also corrected for Lorentz and polarization
effects. The structures were solved by direct methods and
refined on F2 by full-matrix least squares using SHELXTL
[25]. All the non-hydrogen atoms were located from the
Fourier maps and were refined anisotropically. All H atoms
were refined isotropically, with the isotropic vibration
123

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Transition Met Chem (2014) 39:421–429
Table 2 Selected bond
˚
C14H14ZnN12O6 (1)
Zn(1)–O(5)
distances (A) and angles (°) for
1–8
1.929(5)
1.958(4)
1.937(4)
1.956(5)
120.4(2)
114.6(2)
97.2(2)
Zn(1)–O(7)
1.932(5)
1.958(4)
1.940(5)
1.957(4)
97.9(2)
Zn(1)–O(10)
Zn(1)–O(9)
Zn(2)–O(1)
Zn(2)–O(3)
Zn(2)–O(12)
Zn(2)–O(11)
O(5)–Zn(1)–O(7)
O(7)–Zn(1)–O(10)
O(7)–Zn(1)–O(9)
O(1)–Zn(2)–O(3)
O(3)–Zn(2)–O(12)
O(3)–Zn(2)–O(11)
O(5)–Zn(1)–O(10)
O(5)–Zn(1)–O(9)
O(10)–Zn(1)–O(9)
O(1)–Zn(2)–O(12)
O(1)–Zn(2)–O(11)
O(1)–Zn(2)–O(11)
115.6(2)
112.07(19)
98.0(2)
119.4(2)
116.7(2)
98.7(2)
115.7(2)
108.96(19)
C14H18Ni2Cl2N12O8 (2)
Ni(1)–O(4)
2.0512(18)
2.085(3)
2.115(3)
91.86(7)
91.90(9)
92.38(10)
96.75(10)
85.89(11)
93.51(6)
176.83(8)
91.27(9)
Ni(1)–O(3)
2.0654(17)
2.112(3)
Ni(1)–O(1)
Ni(1)–N(5A)
Ni(1)–N(1A)
Ni(1)–Cl(1)
2.4035(15)
88.24(9)
O(4)–Ni(1)–O(3)
O(3)–Ni(1)–O(1)
O(3)–Ni(1)–N(5A)
O(4)–Ni(1)–N(1A)
O(1)–Ni(1)–N(1A)
O(4)–Ni(1)–Cl(1)
O(1)–Ni(1)–Cl(1)
N(1A)–Ni(1)–Cl(1)
14H10CdN12 O4 (3)
Cd(1)–O(1)
O(4)–Ni(1)–O(1)
O(4)–Ni(1)–N(5)A
O(1)–Ni(1)–N(5A)
O(3)–Ni(1)–N(1A)
N(5A)–Ni(1)–N(1A)
O(3)–Ni(1)–Cl(1)
N(5A)–Ni(1)–Cl(1)
174.26(9)
87.76(12)
171.03(10)
78.86(12)
90.69(6)
90.29(9)
C
2.341(2)
2.525(3)
Cd(1)–O(2)
2.489(2)
2.472(2)
92.31(8)
77.15(11)
54.00(7)
113.20(8)
88.40(10)
101.23(8)
66.24(8)
81.09(7)
Cd(1)–N1(A)
Cd(1)–N(6A)
O(1B)–Cd(1)–O(1)
O(1)–Cd(1)–N(6C)
O(1B)–Cd(1)–O(2)
N(6C)–Cd(1)–O(2)
O(1B)–Cd(1)–O(2B)
O(1B)–Cd(1)–N(1A)
N(6C)–Cd(1)–N(1A)
O(2)–Cd(1)–N(1A)
N(1C)–Cd(1)–N(1A)
164.83(10)
75.72(8)
O(1)–Cd(1)–N(6C)
N(6C)–Cd(1)–N(6A)
O(1)–Cd(1)–O(2)
N(6A)–Cd(1)–O(2)
O(2)–Cd(1)–O(2B)
O(1)–Cd(1)–N(1A)
N(6A)–Cd(1)–N(1A)
O(2)–Cd(1)–N(1C)
140.99(7)
136.64(7)
54.00(7)
81.86(8)
135.90(8)
82.29(8)
156.74(11)
C7H5ClMnN6O2 (4)
Mn (1)–O(2B)
2.144(6)
2.322(6)
2.515(2)
84.5(2)
Mn (1)–O(1A)
2.188(5)
2.372(6)
2.573(2)
94.5(2)
Mn (1)–N(4)
Mn (1)–N(5)
Mn (1)–Cl(1)
Mn (1)–Cl (1C)
O(2B)–Mn (1)–O(1A)
O(1A)–Mn (1)–N(4)
O(1A)–Mn (1)–N(5)
O(2B)–Mn (1)–Cl(1)
N(4)–Mn (1)–Cl(1)
O(2B)–Mn (1)–Cl(1)
N(4)–Mn (1)–Cl(1C)
Cl(1C)–Mn (1)–Cl(1)
O(2B)–Mn (1)–N(4)
O(2B)–Mn (1)–N(5)
N(4)–Mn (1)–N(5)
O(1A)–Mn (1)–Cl(1)
N(5)–Mn (1)–Cl(1)
O(1A)–Mn (1)–Cl(1)
N(5)–Mn (1)–Cl(1C)
91.6(2)
155.3(2)
70.9(2)
76.4(2)
106.77(19)
158.12(17)
98.49(17)
80.80(18)
90.99(7)
95.24(16)
90.61(16)
172.05(16)
98.67(16)
Symmetry code For 2 A: 1 - x,
2 - y, 2 - z; For 3 A: -x, -y,
1 - z; : B: -x, y, 1.5 - z; C: x,
-y, 0.5 ? z; For 4 A: 1 - x, -
y, 2 - z; B:1 - x, -0.5 ? y,
1.5 - z; C: x, -0.5-y, -0.5 ? z
the pyrtza ligand coordinated with Zn(1), the dihedral
angles between the pyrimidyl and tetrazolyl ring planes are
3.5° and 3.3°, respectively, and those between the
tetrazolyl ring and the plane of the carboxylate group plane
are 87.8° and 90.2°, respectively. For the pyrtza ligand
coordinated with Zn(2), the dihedral angles between the
123

Transition Met Chem (2014) 39:421–429
425
˚
Table 3 Hydrogen-bonding geometry (A and °) for 1–4
D–HꢀꢀꢀA
D–H HꢀꢀꢀA DꢀꢀꢀA
D–HꢀꢀꢀA
C14H14ZnN12O6 (1)
O(9)–H(9A)ꢀꢀꢀO(7)#1
O(10)–H(10B)ꢀꢀꢀO(5)#2
O(11)–H(11B)ꢀꢀꢀO(3)#3
0.96
0.96
0.96
2.44
2.44
2.40
2.39
2.54
2.43
2.46
2.45
2.43
3.282(7)
3.277(7)
3.225(7)
3.230(7)
146
145
144
145
O(12)–H(12B)ꢀꢀꢀO(1) #4 0.96
C(3)–H(3A)ꢀꢀꢀN(7)#5
C(6)–H(6A)ꢀꢀꢀO(5)#6
C(13)–H(13A)ꢀꢀꢀO(7)
0.93
0.97
0.97
3.464(10) 174
3.345(8)
3.363(8)
3.353(8)
3.339(8)
157
155
154
156
C(20)–H(20A)ꢀꢀꢀO(1) #7 0.97
C(27)–H(27A)ꢀꢀꢀO(3)
14H18Ni2Cl2N12O8 (2)
O(3)–H(3A)ꢀꢀꢀO(2)
0.97
C
0.85
0.85
0.86
0.85
1.81
2.41
2.42
1.95
2.6347
3.1628
3.1628
2.6818
163
149
147
143
O(3)–H(3B)ꢀꢀꢀCl(1)#1
O(4)–H(4A)ꢀꢀꢀCl(1)#1
O(4)–H(4B)ꢀꢀꢀO(2)#2
14H10CdN12 O4 (3)
C(2)–H(2C)ꢀꢀꢀO(1)#1
C(6)–H(6B)ꢀꢀꢀO(2)#2
C
0.93
0.97
2.44
2.34
3.248(4)
3.315(3)
145
179
C7H5ClMnN6O2 (4)
C(2)–H(2B)ꢀꢀꢀO(1)#1
0.97
2.59
3.416(10) 144
Fig. 2 The 3D network of
interactions
1
formed by hydrogen bonding
Symmetry codes for 1: #1: 1 - x, -y, 1 - z; #2: -x, -y, 1 - z; #3:
1 - x, -1-y, 1 - z; #4: -x, -1-y, 1 - z; #5: 1 - x, -1-y, -z; #6:
x, -1?y, z; #7: x, 1 ? y, z. For 2: #1: 1 - x, 2 - y, 1 - z; #2: -1?x,
y, z. For 3: #1: -2-x, 1 - y, 1 - z; #2: -1?x, y, z; #3: x, -1?y,
z. For 4: #1: 1 - x, -y, 1 - z
There are hydrogen bonding interactions present between
the water ligand and carboxylate oxygen atom [O(9)–
H(9A)ꢀꢀꢀO(7), O(10)–H(10B)ꢀꢀꢀO(5), O(11)–H(11B)ꢀꢀꢀO(3),
O(12)–H(12B)ꢀꢀꢀO(1)], between the C–H group of the py-
rimidyl ring and the tetrazolyl nitrogen atom [C(3)–
H(3A)ꢀꢀꢀN(7), C(6)–H(6A)ꢀꢀꢀO(5)], and between the C–H
group of the acetato group and the carboxylate oxygen
atom [C(13)–H(13A)ꢀꢀꢀO(7), C(20)–H(20A)ꢀꢀꢀO(1), C(27)–
H(27A)ꢀꢀꢀO(3)]. Adjacent [Zn(pyrtza)2(H2O)2] molecules
are linked together through hydrogen-bonding interactions
to generate a 3-D network structure (Fig. 2).
Structure of complex 2
Single-crystal X-ray analysis reveals that 2 is centrosym-
metric and crystallizes in triclinic space group P¯ı, and the
asymmetric unit contains one [Ni(pyrtza) (H2O)2Cl]2 mol-
ecule. The perspective view of 2 is shown in Fig. 3. The Ni
atom presents a slightly distorted octahedral geometry and
was defined by two nitrogen atoms and one carboxylate
group oxygen atom from two different pyrtza ligands, a
chlorine anion, and two oxygen atoms of two coordinated
water molecules. The Ni–N(O) bond lengths from
Fig. 1 The coordination environment of the Zn atom in complex 1
Hydrogen atoms are omitted for clarity
˚
2.0512(18) to 2.115(3) A are in the range observed in the
related analogous complexes [26]. Two neighboring Ni
centers are bridged by two tridentate bridging pyrtza ligands
[Scheme 2(II)] to form a binuclear structure with the NiꢀꢀꢀNi
pyrimidyl and tetrazolyl ring planes are 6.6° and 0.6°,
respectively, and those between the tetrazolyl ring and the
carboxylate group plane are 94.3° and 87.9°, respectively.
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Transition Met Chem (2014) 39:421–429
Fig. 3 The binuclear structure
of complex 2, showing the
coordination environment of the
Ni atom
Fig. 4 The 2D network of
complex 2 formed by hydrogen
bonding interactions extending
along the ac plane
˚
distance of 6.9440(15) A. The dihedral angle between the
Structure of complex 3
pyrimidyl and tetrazolyl ring planes is 1.3° and that of the
tetrazolyl ring and the carboxylate group plane is 93.4°. In
complex 2, there are hydrogen bonding interactions
between the coordinated water molecule and the carboxyl-
ate group oxygen atom of the pyrtza ligands, [O(3)–
H(3A)ꢀꢀꢀO(2), O(4)–H(4B)ꢀꢀꢀO(2)] and between the coor-
dinated water molecule and chlorine atom [O(3)–
H(3B)ꢀꢀꢀCl(1), O(4)–H(4A)ꢀꢀꢀCl(1)]. The adjacent binuclear
complexes are further connected through the hydrogen
bonding interactions, forming a 2-D structure (Fig. 4).
The unit cell of complex 3 consists of half a Cd atom, one
pyrtza ligand in crystallographically independent
a
asymmetric unit, with monoclinic space group C2/c. Each
Cd center is coordinated by four nitrogen atoms (N1A,
N6A, N1C, N6C) from two pyrtza ligands and four oxy-
gen atoms (O1, O2, O1B, O2B) from two carboxylate
groups of other pyrtza ligands (Fig. 5). The interatomic
˚
Cd–O[2.341(2),
Cd–N[2.472(2),
2.525(3) A]
and
˚
2.489(2) A] bond distances are similar to those found in
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Transition Met Chem (2014) 39:421–429
427
Fig. 5 The 1D chain structure of complex 3, showing the coordination environment of the Cd atom. Hydrogen atoms are omitted for clarity
Fig. 6 The 3D network of
complex 3 formed by hydrogen
bonding interactions
the related Cd complexes, such as [Cd(pztza)2]ꢀ2(CH3OH)
[26]. Each pyrtza ligand displays a quadridentate chelating
mode [Scheme 2(III)], chelating the Cd center via py-
rimidyl N1 and tetrazolate N6 with a five-membered
chelating ring and the other Cd atom via the carboxylate
atoms O1 and O2 with a four-membered chelate ring,
generating a 1-D network with the CdꢀꢀꢀCd distance of
dihedral angle between the pyrimidyl and tetrazolyl ring
planes is 14.8° and that of the tetrazolyl ring and the
carboxylate group plane is 96.7°. There are hydrogen
bonding interactions between the C–H group of the
primidyl ring and the carboxylate oxygen atom [C(2)–
H(2C)ꢀꢀꢀO(1), C(6)–H(6B)ꢀꢀꢀO(2)]. The adjacent 1D chains
are further connected through hydrogen bonding interac-
tions, generating a 3-D supramolecular network (Fig. 6).
˚
7.6233 A and a CdꢀꢀꢀCdꢀꢀꢀCd bite angle of 126.87°. The
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Transition Met Chem (2014) 39:421–429
Fig. 9 The emission spectra of complexes 1, 3, 4 and free Hpyrtza at
room temperature in the solid state
is six-coordinated by two carboxylate O atoms from two
pyrtza ligands, two nitrogen atoms from one pyrtza ligand,
and two chloride ligands, forming a distorted octahedral
coordination geometry (Fig. 7). Neighboring Mn atoms are
doubly bridged by one carboxylate group from a pyrtza
ligand in a l1,3-COO bridging mode and one chloride
ligand in a l1,1-Cl bridging mode. Each pyrtza ligand
adopts a quadridentate coordination mode to connect three
manganese centers [Scheme 2(IV)], giving rise to a 2-D
network extending along the bc plane (Fig. 8). The dihe-
dral angle between the pyrimidyl and tetrazolyl ring planes
is 11.3° and that of the tetrazolyl ring and the carboxylate
group is 61.7°. Within the 2-D layer, one hydrogen bonding
interaction is found between the C–H group of the car-
boxylate group and the oxygen atom of the carboxylate
group [C(2)–H(2B) ꢀꢀꢀO(1)].
Fig. 7 The coordination environment of the Mn atom in complex 4.
Hydrogen atoms are omitted for clarity
Luminescence properties
In view of their potential applications in the photochem-
istry area, we have investigated the luminescence proper-
ties of these coordination compounds at room temperature
in the solid state. Complexes 1 and 3 exhibit photolumi-
nescences, with emission maxima at 452 and 454 nm,
respectively, upon excitations at 375 nm (Fig. 9). This
fluorescent emission could be tentatively assigned to the
intraligand transitions, because a similar emission at
443 nm upon excitation at 375 nm was also observed for
the free ligand. Generally, the intraligand fluorescence
emission wavelength is determined by the energy gap
between the p and p* molecular orbitals of the free ligand,
which is related to the extent of p conjugation [27–29]. In
contrast, compound 2 shows a much lower level of lumi-
nescence. Complex 4 does not exhibit any detectable
Fig. 8 The 2D network of complex 4 extending along the bc plane
Structure of complex 4
Complex 4 is dimeric and crystallizes in monoclinic space
group P21/c, and the asymmetric unit contains one
[Mn(pyrtza)Cl] unit. In complex 4, each [Mn(pyrtza)Cl]2
pair is centrosymmetrically disposed, and each Mn center
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Transition Met Chem (2014) 39:421–429
429
2. Ye BH, Tong ML, Chen XM (2005) Coord Chem Rev 249:545
3. Dong WW, Zhao J, Xua L (2008) J Solid State Chem 181:
1149–115181
4. He F, Tong ML, Yu XL, Chen XM (2005) Inorg Chem 44:
559–565
emission, and this can be explained by the factor that this
complex contains nickel, whose low d–d transition quen-
ches luminescence. Therefore, luminescence in such com-
plex is very rare.
5. Li QY, Chen DY, He MH, Yang GW, Shen L, Zhai C, Shen W,
Gu K, Zhao JJ (2012) J Solid State Chem 190:196–201
6. Yang GW, Chen DY, Zhai C, Tang XY, Li QY, Zhou F, Miao
ZF, Jin JN, Ding HD (2011) Inorg Chem Commun 14:913–915
7. Lia ZY, Dai JW, Qiu HH, Yue ST, Liu YL (2010) Inorg Chem
Commun 10:13452–13455
8. Li QY, Yang GW, Tang XY, Ma YS, Yao W, Zhou F, Chen J,
Zhou H (2010) Cryst Growth Des 10:165–170
9. Huang YG, Wu BL, Yuan DQ, Xu YQ, Jiang FL, Hong MC
(2007) Inorg Chem 46:1171–1176
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13:250
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Einaga Y (2008) Chem Commun 1753–1755
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Conclusions
In summary, we have reported four new complexes of
Hpyrtza with Zn(II), Ni(II), Cd(II), and Mn(II), respec-
tively. Although Hpyrtza and Hpztza (Hpztza = 5-(2-pyr-
azinyl)tetrazole-2-acetic acid) are isomeric, the complexes
of Hpyrtza reported in this paper are different from those
with Hpztza [24]. Furthermore, the four complexes of
Hpyrtza show different conformations of the ligand, dem-
onstrating that Hpyrtza is a flexible ligand with a variety of
coordination modes. Using the same synthesis, conditions
gave a wide variety of structures, ranging from mononu-
clear and binuclear to 1D and 2D networks, which may be
assigned to the different transition metals used and making
the structures unpredictable [24]. Inspired by these obser-
vations, we are currently exploring other complexes with
Hpyrtza to acquire more fascinating structures and poten-
tial applications.
17. Yang HY, Li LK, Wu J, Hou HW, Xiao B, Fan YT (2009) Chem
Eur J 15:4049
18. Zhang XQ, Yu Q, Bian HD, Bao XG, Liang HJ (2009) Coord
Chem 62:2108
19. Dong WW, Zhao J, Xu L, Solid J (2008) State Chem 181:1149
20. Li QY, Yang GW, Tang XY, Ma YS, Zhou F, Liu W, Chen J,
Zhou H (2010) Inorg Chem Commun 13:254
21. Shen L, Yang J, Ma YS, Tang XY, Yang GW, Li QY, Zhou F,
Miao ZF, Fei XW, Huang JW (2011) J Coord Chem 64:431
22. Koguro K, Oga T, Mitsui S, Orita R (1998) Synthesis. 910
23. Demko ZP, Sharpless KB (2001) J Org Chem 66:7945
24. CrystalClear R (2005) Rigaku Corporation, Tokyo, Japan
25. Sheldrick GM (2008) Acta Cryst A64:112
26. Yang J, Shen L, Yang GW, Li QY, Shen W, Jin JN, Zhao JJ, Dai
J (2012) J Solid State Chem 186:124
27. Wua MF, Zheng FK, Xu G, Wua AQ, Li Y, Chen HF, Guo SP,
Chen F, Liu ZF, Guo GC, Huang JS (2010) Inorg Chem Commun
13:250
Supplementary material
Crystallographic data for the structural analysis have been
deposited with Cambridge Crystallographic Data Centre,
CCDC reference numbers 948319-948322 (1–4, respec-
tively). These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.
ccdc.cam.ac.uk/data_request/cif.
Acknowledgments We greatly appreciate the financial support
from College Students’ Innovation and Entrepreneurship Training
Program of Jiangsu Province (201310333010Z).
28. Li X, Wu BL, Niu CY, Niu YY, Zhang HY (2009) Cryst Growth
Des 9:3423
29. Perkovic MW (2000) Inorg Chem 39:4962
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