Three new alkaline earth coordination compounds based on 5-(2-pyrimidyl)tetrazole-2-acetic acid

Article abstract of DOI:10.1016/j.ica.2014.08.058

Reactions of Hpymtza (Hpymtza = 5-(2-pyrimidyl)tetrazole-2-acetic acid) with MCl₂(M = Mg(II), Sr(II), Ba(II)), produced three new coordination compounds, [Mg(H₂O)₆]·2pymtza·H₂O (1), [Sr(pymtza)₂(H₂O)₂]·4H₂O (2), [Ba(pymtza)₂(H₂O)₄]·H₂O (3), These compounds were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Compound 1 shows a mononuclear structure while 2 and 3 reveal 1-D structures via bridging pymtza as linker. Furthermore, the luminescent properties of 1-3 were investigated at room temperature in the solid state.

Full text of DOI:10.1016/j.ica.2014.08.058

Inorganica Chimica Acta 423 (2014) 430–434
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Three new alkaline earth coordination compounds based
on 5-(2-pyrimidyl)tetrazole-2-acetic acid
⇑
⇑
Jian Hua Zou, Han Jie Cui, Bo Xu, Da Liang Zhu, Qiao Yun Li , Gao Wen Yang , Yong Chun Hua
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:
Received 13 July 2014
Received in revised form 17 August 2014
Accepted 18 August 2014
Available online 16 September 2014
Reactions of Hpymtza (Hpymtza = 5-(2-pyrimidyl)tetrazole-2-acetic acid) with MCl2 (M = Mg(II), Sr(II),
Ba(II)), produced three new coordination compounds, [Mg(H2O)6]Á2pymtzaÁH2O (1), [Sr(pymtza)2(H2O)2]-
Á4H2O (2), [Ba(pymtza)2(H2O)4]ÁH2O (3), These compounds were characterized by elemental analysis, IR
spectroscopy and single-crystal X-ray diffraction. Compound 1 shows a mononuclear structure while 2
and 3 reveal 1-D structures via bridging pymtza as linker. Furthermore, the luminescent properties of
1–3 were investigated at room temperature in the solid state.
Keywords:
Hpymtza
Ó 2014 Elsevier B.V. All rights reserved.
Alkaline earth metal
Crystal structure
Luminescence
1. Introduction
5-(2-pyrimidyl)tetrazole-2-acetic acid ligand (Hpymtza), a new
tetrazole-containing carboxylate ligand (Scheme 1), have been less
From the view point of crystal engineering, the shapes of the
organic ligands are very important in forming the final structures
of the coordination frameworks. One of the important characteris-
tics of an organic compound used as a ligand is its diverse
coordination modes, molecular rigidity and flexibility, and to
determine the orientation of the binding sites [1,2]. As versatile
building clusters, carboxylate-tetrazole compounds have been
employed extensively as multidentate chelating or bridging linkers
because of both the carboxylate and tetrazole group being able to
participate in mono-, bi-,and multidentate coordination modes
with central metal ions, so they can be used as linkers to design
and construct varied structural and functional coordination com-
plexes and therefore greatly increase the chances of their potential
industrial applications in the field of heterogeneous catalysis, opti-
cal properties, magnetism and luminescence. Among multitudi-
nous tetrazole-containing carboxylate ligands, tetrazolate-
5-acetic acid [3], tetrazolate-5-formic acid [4], tetrazole-1-acetic
acid [5], 5-aminotetrazole-1-acetic acid [6], 5-(2-pyrazinyl)tetra-
zole-2-acetic acid [7], 5-(2-pyridyl)tetrazole-2-acetic acid [8],
5-[N-acetato(3-pyridyl)]tetrazole [9], 5-[N-acetato(4-pyridyl)]
tetrazole [10], 5-[(4-nitryl)phenyl] tetrazole-1-acetato [11], etc.,
have proven to be good candidates for the construction of novel
coordination compounds. However, the compounds based on
studied, to the best of our knowledge. The Hpymtza ligand simul-
taneously comprises N atoms of pyrimidine and tetrazole rings and
O atoms of carboxylate which should display more flexible coordi-
nation fashionsand, and the –CH2– spacer between the tetrazole
ring and carboxylate group offers flexible orientations of the car-
boxylate arm, allowing the formation of varied framework struc-
tures. In this paper, we describe the synthesis, crystal structures
and luminescent properties of the three new coordination com-
pounds [Mg(H2O)6]Á2pymtzaÁH2O (1), [Sr(pymtza)2(H2O)2]Á4H2O
(2), [Ba(pymtza)2(H2O)4]ÁH2O (3).
2. Experimental
2.1. Materials and methods
In this study, 5-(2-pyrimidyl)tetrazole was prepared by [2 + 3]
cycloaddition, by treating 2-cyanopyrimidine with NaN3 in toluene
in the presence of triethylammonium chloride. The reaction of 5-
(2-pyrimidyl)tetrazole with chloroacetic acid in methanolic potas-
sium hydroxide solution gave mostly H(tetrazole)-substituted
products (Kpymtza), which was further purified by adjusting the
pH to
2 with HCl, forming the corresponding acid product
(Hpymtza). Other chemicals were commercially available reagents
of analytical grade and used without further purification. The ele-
mental analysis for C, H and N were performed on a Carlo-Erba
EA1110 CHNO-S microanalyzer. The IR spectra were recorded
(4000–400 cmÀ1) on a NICOLET 380 spectrometer with pressed
⇑
Corresponding authors. Tel./fax: +86 512 52251842 (Q.Y. Li). Tel.: +86 512
52251846; fax: +86 512 52251842 (G.W. Yang).
E-mail addresses: liqiaoyun61@126.com (Q.Y. Li), ygwsx@126.com (G.W. Yang).
http://dx.doi.org/10.1016/j.ica.2014.08.058
0020-1693/Ó 2014 Elsevier B.V. All rights reserved.

J.H. Zou et al. / Inorganica Chimica Acta 423 (2014) 430–434
431
Table 2
KBr pellets. The photoluminescent spectra were performed on a
Selected bond distances (Å) and angles (°) for 1–3.
Hitachi F4600 spectrofluorometer.
C14H24MgN12O11 (1)
Mg(1)–O(5)
Mg(1)–O(3)
O(5)–Mg(1)–O(3)
O(5)–Mg(1)–O(4)
O(3)–Mg(1)–O(3A)
2.0597
2.1020
92.3
90.1
87.7
Mg(1)–O(4)
2.0870
2.2. Synthesis of [Mg(H2O)6]Á2pymtzaÁH2O (1)
O(5)–Mg(1)–O(4A)
O(4)–Mg(1)–O(3)
O(4)–Mg(1)–O(3A)
89.9
90.1
89.9
A mixture of MgCl2Á6H2O (0.0406 g, 0.2 mmol) and Hpymtza
(0.0824 g, 0.4 mmol) in mixture of EtOH (6 ml) and water (2 mL)
was adjusted to pH 6 with NaOH(0.5 mol/L) and sealed in a
25 mL telfon-lined stainless steel container, which was heated at
120 °C for 48 h. After the sample was cooled to room temperature,
colorless block crystals 1 were obtained. For 1, yield: 53% based on
Mg. Anal. Calc. for C14H24MgN12O11: C, 29.99; H, 4.31; N, 29.98.
Found: C, 30.22; H, 4.20; N, 29.61%. IR (KBr, cmÀ1): 3431(s),
1625(s), 1570(m), 1435(m), 1385(s), 1315(m), 1199(w), 1130(w),
1083(w), 920(s), 827(w), 741(w), 645(w), 647(m), 588(w).
C14H22SrN12O10 (2)
Sr(1)–O(1)
Sr(1)–O(2)
Sr(1)–O(3A)
2.663
2.772
2.852
Sr(1)–O(1C)
Sr(1)–O(3)
Sr(1)–O(4)
2.526
2.748
2.537
93.942
113.243
65.281
73.509
146.461
73.155
139.910
99.873
137.725
146.555
O(1)–Sr(1)–O(1B)
O(1)–Sr(1)–O(2)
O(1)–Sr(1)–O(3)
O(1)–Sr(1)–O(4)
O(1C)–Sr(1)–O(2)
O(1C)–Sr(1)–O(3)
O(1C)–Sr(1)–O(4)
O(2)–Sr(1)–O(3)
O(2)–Sr(1)–O(4)
O(3)–Sr(1)–O(4)
138.437
47.770
143.855
87.600
73.096
68.615
130.804
96.164
72.143
81.719
O(1)–Sr(1)–O(1C)
O(1)–Sr(1)–O(2B)
O(1)–Sr(1)–O(3A)
O(1C)–Sr(1)–O(1D)
O(1C)–Sr(1)–O(2B)
O(1C)–Sr(1)–O(3A)
O(2)–Sr(1)–O(2B)
O(2)–Sr(1)–O(3A)
O(3)–Sr(1)–O(3A)
O(3A)–Sr(1)–O(4)
2.3. Synthesis of [Sr(pymtza)2(H2O)2]Á4H2O (2) and
[Ba(pymtza)2(H2O)4]ÁH2O (3)
C14H20BaN12O9 (3)
Ba(1)–O(4)
Ba(1)–O(3)
Ba(1)–N(6)
2.793
2.938
3.034
70.20
Ba(1)–O(2B)
Ba(1)–N(1)
2.834
3.008
An identical procedure to that of 1 was followed to prepare 2
and 3, respectively, except that MgCl2Á6H2O was replaced by SrCl2-
Á6H2O or BaCl2Á2H2O. Colorless crystals of 2 and 3 were obtained.
For 2, yield: 55% based on Sr. Anal. Calc. for C14H22N12O10Sr: C,
27.75; H, 3.66; N, 27.74. Found: C, 27.91; H, 3.54; N, 27.53%. IR
(KBr, cmÀ1): 3474(s), 1610(s), 1570(m), 1391(s), 1309(m),
1247(m), 1161(w), 1130(w), 1087(w), 921(s), 824(w), 710(w),
635(w), 640(m), 585(w). For 3, yield: 63% based on Ba. Anal. Calc.
for C14H20BaN12O9: C, 26.37; H, 3.16; N, 26.36. Found: C, 26.18;
H, 3.22; N, 26.23%. IR (KBr, cmÀ1): 3477(s), 1607(s), 1571(m),
1382(s), 1310(m), 1190(w), 1160(w), 1130(w), 1079(w), 918(m),
819(m), 739(w), 677(w), 635(m), 589(w).
O(2C)–Ba(1)–O(4A)
O(2C)–Ba(1)–N(6A)
O(2C)–Ba(1)–O(2B)
O(2C)–Ba(1)–N(1)
O(2C)–Ba(1)–O(3A)
O(4A)–Ba(1)–N(6A)
N(6)–Ba(1)–O(3A)
O(4A)–Ba(1)–N(1)
O(4A)–Ba(1)–O(3A)
N(1A)–Ba(1)–N(6A)
O(3)–Ba(1)–N(6)
N(1A)–Ba(1)–N(6)
N(6A)–Ba(1)–O(3)
N(6A)–Ba(1)–N(6)
O(2C)–Ba(1)–N(1A)
O(2C)–Ba(1)–O(3)
O(2C)–Ba(1)–O(4)
O(2C)–Ba(1)–N(6)
O(4A)–Ba(1)–N(1A)
O(4A)–Ba(1)–O(3)
O(4A)–Ba(1)–O(4)
O(4A)–Ba(1)–N(6)
N(1A)–Ba(1)–O(3)
O(3)–Ba(1)–O(3A)
N(1A)–Ba(1)–N(1)
N(1A)–Ba(1)–O(3A)
N(6A)–Ba(1)–O(3A)
N(6A)–Ba(1)–N(1)
68.34
105.41
129.48
65.21
70.64
143.53
67.79
75.11
74.21
67.73
168.49
96.06
121.34
159.39
109.46
55.76
77.84
74.28
119.87
125.05
54.94
137.62
129.1
72.28
147.28
137.62
129.12
2.4. X-ray crystallography
Symmetry code for 1 A: Àx, 2 À y, 1 À z; for 2 A: 0.5 + x, À0.5 À y, 0.5 À z; B: x,
À0.5 À y, z; C: À0.5 + x, y, 0.5 À z; D: À0.5 + x, À0.5 À y, 0.5 À z; For 3 A: À2 À x, y,
1.5 À z; B: À1 À x, y, 1.5 À z; C: À1 + x, y, z.
Single crystal X-ray crystal data were collected on a Rigaku SCX
mini CCD diffractometer equipped with a graphite-monochromated
Table 1
Crystallographic data for 1–3.
Table 3
Hydrogen-bonding geometry (Å and °) for 1–3.
Compound
1
2
3
Empirical formula
Formula mass
Crystal system
Space group
a (Å)
C
14H24MgN12O11 C14H22SrN12O10 C14H20BaN12O9
D–HÁ Á ÁA
D–H
HÁ Á ÁA
DÁ Á ÁA
D–HÁ Á ÁA
560.76
monoclinic
C2/c
22.230(4)
6.8685(14)
18.949(4)
606.06
637.75
C14H24MgN12O11 (1)
O(3)–H(3C)Á Á ÁO(1)#1
O(4)–H(4B)Á Á ÁN(5)#2
O(4)–H(4C)Á Á ÁO(2)#3
O(6)–H(6C)Á Á ÁO(1)#4
orthorhombic
P nma
monoclinic
P2/c
0.96
0.96
0.96
0.85
2.02
2.14
1.84
2.25
2.7451
3.0396
2.7102
3.005
130
155
149
149
7.2919(15)
37.309(8)
9.0444(18)
10.276(2)
7.0256(14)
18.098(6)
b (Å)
c (Å)
C14H22SrN12O10 (2)
a
(°)
O(3)–H(3A)Á Á ÁO(5)
O(4)–H(4A)Á Á ÁO(5)#1
O(5)–H(5A)Á Á ÁO(6)
O(5)–H(5B)Á Á ÁO(6)#1
O(6)–H(6C)Á Á ÁO(2)#2
O(6)–H(6D)Á Á ÁN(5)#3
0.85
0.85
0.85
0.85
0.85
0.85
2.11
2.14
2.14
1.81
1.84
2.15
2.8972
2.8503
2.9587
2.6192
2.6956
2.8631
153
141
164
158
169
141
b (°)
122.00(3)
115.21(2)
c
(°)
V (Å3)
2453.6(12)
4
291(2)
1.518
0.152
11969
2460.6(9)
4
1182.1(5)
2
Z
T (K)
291(2)
1.636
291(2)
1.792
Dcalcd (g cmÀ3
)
C14H20BaN12O9 (3)
l
(mmÀ1
)
2.265
1.751
O(3)–H(3C)Á Á ÁN (5)#1
O(4)–H(4B)Á Á ÁO(1)#2
O(4)–H(4C)Á Á ÁO(3)#3
O(5)–H(5B)Á Á ÁO(1)
0.91
0.90
0.88
0.76
2.02
2.05
2.06
2.10
2.9042
2.8958
2.8915
2.844
164
158
159
168
Reflections collected
Unique reflections
14454
2856(0.1066)
10954
2705 (0.0529)
2809 (0.0828)
(Rint
No. observations
(I > 2.00 (I))
)
1785
1782
2481
r
Symmetry codes for 1: # 1: 0.5 À x, 1.5 + y, 0.5 À z; #2: À0.5 + x, 0.5 + y, z; #3:
0.5 À x, 0.5 + y, 0.5 À z; #4: 1 À x, 1 + y, 0.5 À z. For 2: #1: 0.5 + x, y, À0.5 À z; #2:
À0.5 + x, y, À0.5 À z; #3: À1 + x, y, z. For 3: #1: À2 À x, 1 À y, 1 À z; #2: À1 + x, y, z;
#3: x, À1 + y, z.
No. Variables
164
0.0950, 0.2007
1.108
174
165
Ra, wRb
0.0578, 0.1345
0.905
0.0339, 0.1034
0.828
Goodness-of-fit
(GOF)c
D
D
/
/
qmax (e/Å3)
qmin (e/Å3)
0.550
À0.440
0.476
0.746
Mo K radiation (k = 0.071073 Å). The intensity data were collected
a
À0.459
À0.817
P
P
by the x scan technique and were reduced using Crystal-Clear pro-
a
b
c
R = ||Fo| À |Fc|/ |Fo|.
P
P
gram [12,13]. An empirical absorption correction based on scans
was applied. The structure was solved by the direct methods and
refined by full matrix least-squares on F2 using SHELXTL [14]. All
Rw = { w(Fo2 À Fc2)2/ w(F2o)2}1/2
.
P
Goodness-of-fit = { [w((Fo2 À F2c)2)/(n–p)}1/2, where n = number of reflections
and p = total numbers of parameters refined.

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J.H. Zou et al. / Inorganica Chimica Acta 423 (2014) 430–434
non-hydrogen atoms were refined anisotropically and the hydrogen
atoms were included in the final stage of the refinement on calcu-
lated positions bonded to their carrier atoms. Crystallographic data
are summarized in Table 1, selected bond lengths and angles are
listed in Table 2. Hydrogen-bonding parameters are given in Table 3.
pymtza ligand is not coordinated to Mg(II), resembling the previ-
ously reported [Mg(H2O)6]Á(a4-ptz)2Á2H2O, and the Mg–O bond
lengths[2.0597–2.1020 Å] (Table 2) are in agreement with the lit-
erature values for Mg–O(W) complexes [15]. It should be noted
that all coordinated O atoms belong to the water molecules of
crystallization and thus none of the nitrogen and oxygen atoms
of the pymtza ligand is coordinated. Neighboring [Mg(H2O)6]-
3. Results and discussion
Á2pymtzaÁH2O molecules are held together through the
p–p
stacking interactions between the pyrimidyl and tetrazole rings
(3.7044 and 3.6281 Å) from neighboring pymtza ligands (Fig. 2)
and four kinds of hydrogen bonding interactions between the guest
water molecule and the oxygen atom of the carboxylate group
[O(3)—H(3C)Á Á ÁO(1) 2.7451Å/130° O(4)–H(4C)Á Á ÁO(2) 2.7102 Å/
149°, O(6)–H(6C)Á Á ÁO(1) 3.005 Å/149°] and between the guest
water molecule and the nitrogen atom of the pyrimidyl
ring[O(4)–H(4B)Á Á ÁN(5) 3.0396 Å/155°] to form a 3-D supramolec-
ular network. (Table 3, Fig. 1S).
3.1. Crystal structure of [Mg(H2O)6]Á2pymtzaÁH2O (1)
Complex 1 consists of neutral mononuclear structure, and crys-
tallizes in the monoclinic space group C2/c and the asymmetric
unit contains one-half of [Mg(H2O)6]2+ ion, one pymtza ligand,
and half of guest water molecule. As is shown in Fig. 1, The Mg(II)
center is coordinated by six O atoms, forming a slightly distorted
octahedron coordination geometry. It is interesting that the
3.2. Crystal structure of [Sr(pymtza)2(H2O)2]Á4H2O (2)
Single crystal X-ray analysis reveals that complex 2 crystallizes
in the orthorhombic space group Pnma. The perspective view of 2
is shown in Fig. 3, the Sr(II) center is connected to six oxygen atoms
(O1, O2, O1B, O2B, O1C and O2D) from four pymtza ligands, three
oxygen atoms (O3, O3A, O4) of three water molecules. The feature
of 2 is its unusual nine-coordinate tricapped trigonal prism
Scheme 1. Schematic drawing for the Hpymtza ligand.
Fig. 1. The coordination environment of Mg(II) of complex 1.
Fig. 2. The p–p .
stacking interaction and hydrogen bonds in complex 1, showing the supramolecular bonds around the Mg(H2O)62+

J.H. Zou et al. / Inorganica Chimica Acta 423 (2014) 430–434
433
structure (SrO9). The Sr-O bond length from 2.526 to 2.852 Å are
carboxylate groups from two pymtza ligands in a
l1,1,3-COO bridg-
observed in the range of related analogous complexes [15,16].
Compared to 1 in which pymtza is thoroughly uncoordinated, in
complex 2, two neighboring Sr(II) ions are bridged by two
ing mode and one water molecule in a l1,1-H2O bridging mode,
forming a 1-D chain extending along the a axis with a SrÁ Á ÁSr dis-
tance of 4.0282 Å and a SrÁ Á ÁSrÁ Á ÁSr bite angle of 129.6° (Fig. 4).
Adjacent 1-D chains are held together through six kinds of hydro-
gen bonding interactions between the uncoordinated water mole-
cule and the oxygen atom of the uncoordinated water molecule
[O(3)–H(3A)Á Á ÁO(5) 2.8972 Å/153° O(4)–H(4A)Á Á ÁO(5) 2.8503 Å/
141°,
O(5)–H(5A)Á Á ÁO(6)
2.9587 Å/164°,
O(5)–H(5B)Á Á ÁO(6)
2.6192 Å/158°], between the uncoordinated water molecule and
the oxygen atom of the carboxylate group [O(6)–H(6C)Á Á ÁO(2)
2.6956Å/169°] and between the uncoordinated water molecule
and the nitrogen atom of the tetrazole ring [O(6)–H(6D)Á Á ÁN(5)
2.8631 Å/141°], generating a 2-D network (Table 3, Fig. 2S).
3.3. Crystal structure of [Ba(pymtza)2(H2O)4]ÁH2O (3)
The X-ray crystallographic analysis shows that compound 3
crystallizes in the monoclinic space group P2/c and features a
1-D chain structure. As is shown in Fig. 5, each Ba(II) center is
Fig. 3. The coordination environment of Sr(II) of complex 2. Hydrogen atoms are
omitted for clarity.
Fig. 5. The coordination environment of Ba(II) of complex 3. Hydrogen atoms are
omitted for clarity.
Fig. 6. The p–p stacking interaction between neighboring 1D chains in complex 3.
Hydrogen atoms are omitted for clarity.
Fig. 4. The 1D chain structure of 2 extending along the a axis. (a) View from the ab
plane (b) view from the bc plane. Hydrogen atoms are omitted for clarity.
Fig. 7. The emission spectra of complexes 1–3 and Hpymtza at room temperature
in the solid state.

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J.H. Zou et al. / Inorganica Chimica Acta 423 (2014) 430–434
ten coordinated by two nitrogen atoms from the tetrazole ring (N1,
N1A), two nitrogen atoms from the pyrimidyl ring (N6, N6A), two
oxygen atoms of the carboxylate group (O2B.O2C), four oxygen
atoms of the coordinated water molecules (O3, O3A, O4, O4A), dis-
playing a distorted bicapped square-antiprism coordination geom-
etry. Compared to 1 and 2, pymtza adopts a chelating mode via its
two nitrogen atoms while only one of the carboxylate oxygen
atoms is coordinated, which may be ascribed to the larger radius
of the barium. The Ba–O(N) distance falls in the range
2.793–3.034 Å which was similar to those reported in the related
Ba(II) complexes [16]. Thus, complex 3 forms an unusual 1-D chain
structure along the a axis with a BaÁ Á ÁBa distance of 10.276 Å. and a
BaÁ Á ÁBaÁ Á ÁBa bite angle of 180°. Adjacent 1-D chains are further
Appendix A. Supplementary material
CCDC 948316–948319 contains the supplementary crystallo-
graphic data for 1–3. 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 associated with
this article can be found, in the online version, at http://dx.doi.
org/10.1016/j.ica.2014.08.058.
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linked together through the
p–p stacking interactions between
the pyrimidyl and tetrazole rings from neighboring pymtza ligands
(3.5125 Å) (Fig. 6) and four types of hydrogen bonding interaction
between the coordinated water molecule and the nitrogen atom of
the pyrimidyl group [O(3)–H(3C)Á Á ÁN (5) 2.9042 Å/164°], between
the guest water molecule and the oxygen atom of carboxylate
group [O(4)–H(4B)Á Á ÁO(1) 2.8958 Å/158°, O(5)–H(5B)Á Á ÁO(1)
2.844 Å/168°] and between the coordinated water molecule and
the oxygen atom of the guest water [O(4)–H(4C)Á Á ÁO(3) 2.8915 Å/
159°], affording a 3-D network (Table 3, Fig. 3S).
(b) A. Rodríguez-Diéguez, A. Salinas-Castillo, A. Sironi, J.-M. Seco, E. Colacio,
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3.4. Luminescent properties
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The luminescent properties of 1–3 were measured at room tem-
perature in the solid state. Complexes 1–3 exhibit photolumines-
cence with emission maximum at 426 (1), 424 (2), 441 (3) nm
upon excitations at 367 nm (1), 370 nm (2), 372 nm (3), respec-
tively (Fig. 7). These fluorescent emissions could be tentatively
assigned to the intraligand fluorescence emission, because a simi-
lar emission at 443 nm upon excitation at 375 nm was also
observed for the free ligand Hpymtza. Compared to the ligand, blue
shifts of 17, 19, 2 nm for complexes 1–3 are observed, respectively,
which are well in accordance to the compounds previously
reported [15,18]. The intensity of compound 2 is stronger than that
of Hpymtza, corresponding to other Sr-tetrazole-carboxylate com-
plexes [19]. However, that of 1 or 3 is a little weaker than the
ligand, which is considered to mainly arise from the coordination
mode of the ligand and the distinctness of their structures
[8b,15]. Generally, the intraligand fluorescence emission
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wavelength is determined by the energy gap between the
p⁄ molecular orbitals of the free ligand, which is related to the
extent of conjugation [17-19].
p and
p
(b) Q.-Y. Li, G.-W. Yang, Y.-S. Ma, M.-J. Li, Y. Zhou, Inorg. Chem. Commun. 11
(2008) 795.
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4. Conclusions
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362 (2009) 1723.
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Chem. 65 (2012) 2657.
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F. Chen, Z.-F. Liu, G.-C. Guo, J.-S. Huang, Inorg. Chem. Commun. 13 (2010)
250;
In summary, we have reported three new compounds formed
by Hpymtza and Mg(II), Sr(II), Ba(II), respectively. The strong coor-
dination abilities of flexible carboxylate group and nitrogen atoms
of the pyrimidyl ring endow Hpymtza with different coordination
modes. Our research results indicate that, as a promising new type
of multifunctional ligand, Hpymtza has a great potential in the
field of coordination polymers, and further endeavors for explora-
tion of other complexes are underway in our workgroup.
(b) X. Li, B.-L. Wu, C.-Y. Niu, Y.-Y. Niu, H.-Y. Zhang, Cryst. Growth Des. 9 (2009)
3423.
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Acknowledgments
[19] (a) Q.-Y. Li, F. Zhou, C. Zhai, L. Shen, X.-Y. Tang, J. Yang, G.-W. Yang, Z.-F. Miao,
J.-N. Jin, W. Shen, Inorg. Chem. Commun. 14 (2011) 843;
(b) J.-H. Zou, D.-L. Zhu, H. Tian, F.-F. Li, F.F. Zhang, G.-W. Yang, Q.-Y. Li, Y.-X.
Miao, Inorg. Chim. Acta 423 (2014) 87–94;
The authors wish to appreciate the financial support from 14th
Challenge Cup for Domestic College Students, College Students’
Innovation and Entrepreneurship Training Program of Jiangsu
Province and the Start Grant from CSLG.
(c) J. Yang, Y.-T. Min, Y. Chen, J. Wang, H. Tian, L. Shen, Y.-S. Zhai, G.-W. Yang,
J-.H. Zou, Q.-Y. Li, H.-J. Cui, Inorg. Chim. Acta 419 (2014) 73.