Syntheses, structures and luminescent properties of a dimer and an one-dimensional chain coordination polymer with the flexible bis(triazole) and hydroxybenzoate ligands

Article abstract of DOI:10.1016/j.molstruc.2006.10.028

Two novel complexes [Zn(phba)₂(btp)]₂ (1) and [Cd(phba)₂(btp)(H₂O)]_n (2) have been synthesized by using 1,3-bis(1,2,4-triazol-1-yl)propane (btp) and 4-hydroxybenzoate (phba). 1 contains the neutral dimer Zn₂(btp)₂ metallacycle, while 2 forms the one-dimensional zigzag chain structure. 1 and 2 exhibit blue luminescent emissions at 402 and 394 nm, respectively, excited at 340 nm in the solid state at room temperature.

Full text of DOI:10.1016/j.molstruc.2006.10.028

Journal of Molecular Structure 837 (2007) 263–268
www.elsevier.com/locate/molstruc
Syntheses, structures and luminescent properties of a dimer
and an one-dimensional chain coordination polymer with the
flexible bis(triazole) and hydroxybenzoate ligands
a
a,
a
Gui Yin a,b, Yuping Zhang , Baolong Li *, Yong Zhang
a
College of Chemistry and Chemical Engineering, Key Laboratory of Organic Synthesis of Jiangsu Province, Suzhou University, Suzhou 215123, PR China
b
School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, PR China
Received 12 September 2006; received in revised form 25 October 2006; accepted 27 October 2006
Available online 8 December 2006
Abstract
Two novel complexes [Zn(phba)2(btp)]2 (1) and [Cd(phba)2(btp)(H2O)]n (2) have been synthesized by using 1,3-bis(1,2,4-triazol-1-
yl)propane (btp) and 4-hydroxybenzoate (phba). 1 contains the neutral dimer Zn2(btp)2 metallacycle, while 2 forms the one-dimensional
zigzag chain structure. 1 and 2 exhibit blue luminescent emissions at 402 and 394 nm, respectively, excited at 340 nm in the solid state at
room temperature.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: 1,3-Bis(1,2,4-triazol-1-yl)propane; Hydroxybenzoate; Zinc complex; Cadmium complex; Dimeric complex; One-dimensional chain
1. Introduction
with their potential application in the material science.
Recently, we reported the crystal structures of a series of
transition metal coordination polymers with the flexible
bis(triazole) ligands such as 1,2-bis(1,2,4-triazol-1-yl)eth-
ane [20–23] and 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene
[24,25].
On the other hand, although salicylate has been widely
employed for the synthesis of the coordination compounds
[26,27]. 4-Hydroxybenzoate, the isomer of salicylate, was
rarely studied to date [28]. The combination of the flexible
ligand 1,3-bis(1,2,4-triazol-1-yl)propane (btp) and 4-
hydroxybenzoate (phba) can give rise to novel complexes.
In the present paper, we report the preparation, crystal
The design and construction of the coordination poly-
mers and polynuclear complexes has attracted great atten-
tion in recent years for their potential application as well as
the variety of architectures and topologies [1–9]. The selec-
tion of the ligands is undoubtedly the key point in the syn-
thesizing of the coordination polymers and polynuclear
complexes.
1,2,4-Triazole and its derivatives are very interesting
ligands because they combine the coordination geometry
of both pyrazole and imidazole with regard to the arrange-
ment of their three heteroatoms. A large number of mono-
nuclear, oligonuclear and polynuclear transition metal
complexes of 1,2,4-triazole derivatives have been synthe-
sized and characterized due to their magnetic properties
and novel topologies [10–15]. However the complexes of
the flexible bis(triazole) ligands have not been well exploit-
ed up to now [16–19]. Our interest is to study the coordina-
tion chemistry of 1,2,4-triazole and its derivatives together
structure and luminescent properties of
a
dimer
[Zn(phba)2(btp)]2 (1) and an one-dimensional zigzag chain
coordination polymer [Cd(phba)2(btp)(H2O)]n (2).
2. Experimental
2.1. Materials and general methods
*
The flexible ligand 1,3-bis(1,2,4-triazol-1-yl)propane
(btp) was synthesized according to the literature method
Corresponding author.
E-mail address: libaolong@suda.edu.cn (B. Li).
0022-2860/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.10.028

264
G. Yin et al. / Journal of Molecular Structure 837 (2007) 263–268
Table 1
[18]. All other reagents and solvents employed were com-
mercially available and used as received without further
purification. The C, H, N microanalyses were carried out
with a Perkin-Elmer 240C analyser. IR spectra were
obtained for KBr pellets on a Nicolet 170SX FT-IR spec-
trophotometer in the 4000–400 cmÀ1 region. The lumines-
cence measurements were carried out in the solid state at
room temperature and the spectra were collected with a
Perkin-Elmer LS50B spectrofluorimeter.
Crystallographic data for 1 and 2
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C42H40N12O12Zn2
1035.60
193(2)
0.71073
Monoclinic
P21/c
10.750(2)
19.234(3)
11.432(3)
90
114.071(4)
90
2158.3(7)
2
1064
1.594
C21H22CdN6O7
582.85
193(2)
0.71073
Triclinic
P1
9.9743(12)
11.0238(7)
11.2144(9)
66.090(8)
77.431(9)
83.062(9)
1099.51(17)
2
˚
˚
a (A)
˚
b (A)
˚
c (A)
a
b (ꢁ)
2.2. Preparation of the complexes
c
3
˚
V (A )
2.2.1. [Zn(phba)2(btp)]2 (1)
A
Z
25 mL water/MeOH solution (1:1 v/v) of
F (000)
588
1.760
1.051
Zn(NO3)26H2O (0.5 mmol) was added to one leg of an
‘‘H-shaped’’ tube, and a 25 mL water/MeOH (1:1 v/v)
q[g.cmÀ3
]
l[mmÀ1
]
1.191
solution
of
1,3-bis(1,2,4-triazol-1-yl)propane
(btp)
Crystal size [mm]
h range for data
collection (ꢁ)
0.38 · 0.31 · 0.19
3.05–25.34
0.40 · 0.28 · 0.15
3.17–25.35
(0.5 mmol) and sodium 4-hydrogenbenzoate (1.0 mmol)
was added to the other leg of the tube. Colourless crystal
1 (yield: 37%) were obtained after about two months. Anal.
Calcd. for C42H40N12O12Zn2 (1): C, 48.71; H, 3.89; N,
16.23%. Found: C, 48.57; H, 3.74; N, 16.01. IR data
(cmÀ1): 3241 m, 3141 m, 1605 s, 1536 s, 1505 m, 1454 m,
1397 s, 1273 m, 1243 m, 1219 m, 1165w, 1135 m, 1095w,
996w, 857w, 787 m, 671w, 641 m, 417w.
Index ranges
À12 6 h 6 12,
À22 6 k 6 23,
À13 6 l 6 12
À10 6 h 6 12,
À12 6 k 6 13,
À13 6 l 6 13
Refinement method Full-matrix least-
Full-matrix least-
squares on F2
squares on F2
3940[R(int) = 0.0337]
Independent
reflections
Parameter
3981[R(int) = 0.0180]
308
324
Max. and min.
transmission
Goodness of fit S
Final R1 and wR2
[I > 2r(I)]
0.8053 and 0.6603
0.8582 and 0.6785
2.2.2. [Cd(phba)2(btp)(H2O)]n (2)
1.095
0.0366 and 0.0855
1.014
0.0204 and 0.0519
The synthesis procedure of 2 was similar to the synthesis
of 1, except that Cd(NO3)2.6H2O was instead of
Zn(NO3)26H2O. Anal. Calcd. for C21H22CdN6O7 (2): C,
43.28; H, 3.80; N, 14.42%. Found: C, 43.21; H, 3.74; N,
14.35. IR data (cmÀ1): 3386s, 3118vs, 1698w, 1598s,
1528s, 1505s, 1443m, 1389s, 1281s, 1243s, 1165m, 1104m,
1034w, 934w, 857m, 795m, 749m, 702w, 656m, 625m,
548w.
R1 and wR2 indices 0.0419 and 0.0884
(all data)
0.0225 and 0.0532
Largest diff. Peak
0.330 and À0.471
0.578 and À0.444
À3
˚
and hole (e A
)
Table 2
2.3. X-ray crystallography
˚
Selected bond lengths (A) and angles (ꢁ) for 1 and 2
1
All data collections were performed at the temperature
of 193(2) K on a Rigaku Mercury CCD diffractometer with
the x-scan technique. The structures were solved by direct
methods and refined with the full-matrix least-squares tech-
nique using the SHELXS-97 and SHELXL-97 programs
[29]. Anisotropic thermal parameters were assigned to all
non-hydrogen atoms. The hydrogen atoms from btp and
phba ligands were generated geometrically. The hydrogen
atoms from water molecules were obtained from difference
Fourier maps. The crystallographic data for 1 and 2 are
listed in Table 1. The selected bond lengths and angles
for 1 and 2 are listed in Table 2.
Zn(1)–O(1)
Zn(1)–O(4)
Zn(1)–N(6A)
O(2)–Zn(1)–O(1)
O(4)–Zn(1)–O(2)
N(6A)–Zn(1)–O(2)
N(3)–Zn(1)–O(1)
O(4)–Zn(1)–N(3)
2.153(2)
1.9839(17) Zn(1)–N(3)
2.064(2)
Zn(1)–O(2)
2.152(2)
2.066(2)
60.74(8)
161.02(8)
91.61(8)
107.80(8)
96.37(8)
O(4)–Zn(1)–O(1)
100.54(8)
143.96(8)
103.95(8)
92.86(9)
95.36(8)
N(6A)–Zn(1)–O(1)
O(4)–Zn(1)–N(6A)
N(3)–Zn(1)–O(2)
N(6A)–Zn(1)–N(3)
2
Cd(1)–O(1)
Cd(1)–O(4)
Cd(1)–N(3)
O(2)–Cd(1)–O(1)
N(6A)–Cd(1)–O(1)
2.4841(14) Cd(1)–O(2)
2.2916(14) Cd(1)–O(7)
2.2574(16) Cd(1)–N(6A)
2.3054(14)
2.4502(17)
2.2572(16)
142.67(5)
54.57(5)
95.41(5)
N(3)–Cd(1)–O(1)
N(3)–Cd(1)–O(2)
91.03(5)
N(6A)–Cd(1)–O(2) 149.95(5)
N(3)–Cd(1)–N(6A) 117.27(6)
3. Results and discussion
O(4)–Cd(1)–O(7)
O(4)–Cd(1)–O(2)
N(6A)–Cd(1)–O(4)
O(2)–Cd(1)–O(7)
N(6A)–Cd(1)–O(7)
159.74(6)
88.28(5)
89.07(6)
88.08(6)
84.17(6)
O(4)–Cd(1)–O(1)
N(3)–Cd(1)–O(4)
O(7)–Cd(1)–O(1)
N(3)–Cd(1)–O(7)
82.38(5)
113.75(6)
79.28(6)
86.24(6)
In the IR spectra, the conspicuous carboxylate stretch-
ing at 1605, 1505, 1454 and 1397 cmÀ1 in 1, 1598, 1505,
1443 and 1389 cmÀ1 in 2. 1 and 2 both present two groups
of the antisymmetric ma(COO) and symmetric stretching
Symmetry codes: A Àx + 1, Ày + 1, Àz + 1 for 1; A x, y, z À 1 for 2.

G. Yin et al. / Journal of Molecular Structure 837 (2007) 263–268
265
frequency ms(COO). The 1605 and 1454 cmÀ1 absorptions
for 1 are assigned to monodentate mode of COO because
the calculated D value is 151 cmÀ1, which is compared with
that 144 cmÀ1 of the free CH3COOÀ [30]. The 1505 and
1397 cmÀ1 absorptions are assigned to bisdentate mode
of COO because the calculated D value is 108 cmÀ1, which
is obviously smaller than 144 cmÀ1 of the free CH3COOÀ.
The 1598 and 1443 cmÀ1 absorptions (the calculated D val-
ue is 155 cmÀ1) are attributed to the monodentate COO,
and 1505 and 1389 cmÀ1 absorptions (the calculated D val-
ue is 116 cmÀ1) are assigned to bisdentate COO for 2. 1 and
2 both contain monodentate and bisdentate COO coordi-
nation modes which is confirmed by X-ray diffraction anal-
ysis. The triazole ring vibrations appear at 1536 and
1273 cmÀ1 for 1, 1528 and 1281 cmÀ1 for 2 [17,18]. The
high frequency absorptions 3241 and 3141 cmÀ1 for attrib-
uted to the O–H stretching vibrations of phba molecule for
1. The strong peaks from 3118 to 3386 cmÀ1 for 2 are
assigned to the coordinated water molecule and OH group
of phba molecule.
structure with a 1:1 metal-to-ligand ratio. Each zinc(II)
center in 1 is in a fiver-coordinated distorted square-pyra-
midal geometry, coordinated by three oxygen atoms from
˚
two phba molecules [Zn(1)–O(1) 2.153(2) A; Zn(1)–O(2)
˚
˚
2.152(2) A; Zn(1)–O(4) 1.9839(17) A] and one nitrogen
˚
atom from one btp molecule [Zn(1)–N(6A) 2.064(2) A] in
the plane positions, and one nitrogen atom from the other
˚
btp molecule [Zn(1)–N(3) 2.066(2) A] in the axial position.
Two phba molecules act as the different coordination
modes. The COO group of one phba molecule acts as che-
lating coordination mode [O(1) and O(2)] to one zinc(II)
atom, the COO group of the other phba molecule exhibits
as monodentate coordination mode [O(4)]. The btp mole-
cules show the anti-gauche conformation. The dihedral
angle between two triazole rings is 64.0ꢁ. The ZnÁ Á ÁZn sep-
˚
aration via the bridging ligand btp in 1 is 10.116 A, very
˚
closer to the metal-metal separation 10.447 A in the report-
ed btp ligand complex [Co(btp)2(NCS)2] [19].
There are hydrogen bonding interactions between the
hydrogen atoms of hydroxy groups of two phba molecules
and the uncoordination N(2) atom of triazole ring and
O(5) atom of the COO group of the adjacent dimers (Table
3 Fig. 2).
The crystal structure of 1 is made of neutral dimer
metallacycle. In each dimer metallacycle, as shown in
Fig. 1, two zinc(II) centers are connected by two btp mol-
ecules, resulting in a discrete Zn2(btp)2 20-membered
metallacycle which represents the smallest closed cyclic
The crystal structure of 2 is made of one-dimensional
zigzag chain (Fig. 3), which is different from the dimer
structure of 1. The coordination geometry of the Cd(II)
atom in 2 is distorted octahedral; it is coordinated by two
nitrogen atoms from the triazole rings of two symmetry-re-
˚
lated btp ligands [Cd(1)–N(3) 2.2574(16) A; Cd(1)–N(6A)
˚
2.2572(16) A] and two oxygen atoms from one COO group
˚
of phba molecule [Cd(1)–O(1) 2.4841(14) A; Cd(1)–O(2)
˚
2.3054(14) A] in the equatorial plane, and two oxygen
˚
atoms from one phba molecule [Cd(1)–O(4) 2.2916(14) A]
˚
and one water molecule [Cd(1)–O(7) 2.4502(17) A] in the
axial positions.
Two phba molecules in 2 also act as the different coor-
dination modes (the chelating and monodentate coordina-
tion modes) similar to that in 1. Each btp molecule in 2
coordinates to two Cd(II) atoms through its two triazole
nitrogen atoms, thus acting as a bridging bidentate ligand
to link two Cd(II) atoms and form a one-dimensional zig-
zag chain. The btp molecules also exhibit the anti-gauche
conformation. The dihedral angle between two triazole
rings is 21.6ꢁ, different from the dihedral angle 64.0ꢁ in 1.
The CdÁ Á ÁCd distance separated by btp bridge is
Table 3
˚
Hydrogen bonding parameters (A, ꢁ) for 1
D–HÁ Á ÁA
d(D–H)
d(HÁ Á ÁA)
2.00
1.78
2.26(3)
2.01(3)
d(DÁ Á ÁA)
Æ(DHA)
O(3)–H(3B)Á Á ÁN(2)i
O(6)–H(6C)Á Á ÁO(5)ii
O(7)–H(2W)Á Á ÁN(2)
O(7)–H(1W)Á Á ÁO(1)
0.84
0.84
0.72(3)
0.77(3)
2.797(3)
2.606(3)
2.941(3)
2.770(2)
159.0
167.8
160(3)
167(3)
Symmetry transformations used to generate equivalent atoms: i, x + 1,
Ày + 3/2, z + 1/2; ii x, Ày + 1/2, z À 1/2.
Fig. 1. The dimeric structure of 1. Symmetry code: A Àx + 1, Ày + 1,
Àz + 1.

266
G. Yin et al. / Journal of Molecular Structure 837 (2007) 263–268
Fig. 2. The cell packing of 1.
Fig. 3. Viewing the one-dimensional zigzag chain of 2. Symmetry codes: A x, y, z À 1; B x, y, z À 2.
˚
11.214 A, equal to the c axis translation, which is small
hydroxy groups and the coordination water molecules,
and the carboxylato-oxygen atoms of coordinated phba
and the nitrogen atom of triazole ring [Table 4]. The C8–
C13 phenyl ring and his symmetry-related C8–C13
(1 À x, 1 À y, Àz) phenyl ring are absolutely parallel with
˚
longer than the ZnÁ Á ÁZn distance (10.447 A) in 1.
It is interesting that the hydrogen bonding and p–p
stacking interactions play an important role in the forma-
tion of crystal structure. There are intramolecular hydro-
gen bonding interactions between the hydrogen atoms of
˚
the centeriod-to-centeriod distance 4.138 A and plane

G. Yin et al. / Journal of Molecular Structure 837 (2007) 263–268
267
Table 4
Hydrogen bonding parameters (A, ꢁ) for 2
˚
2
1
D–HÁ Á ÁA
d(D–H)
d(HÁ Á ÁA)
d(DÁ Á ÁA)
2.668(2)
2.665
2.941(3)
2.770(2)
Æ(DHA)
O(3)–H(3B)Á Á ÁO(4)a
O(6)–H(6C)Á Á ÁO(2)b
O(7)–H(2W)Á Á ÁN(2)c
O(7)–H(1W)Á Á ÁO(1)d
0.84
1.83
179.6
171.7
160(3)
167(3)
0.84
1.83
2
0.72(3)
0.77(3)
2.26(3)
2.01(3)
1
Em
Symmetry transformations used to generate equivalent atoms: a, Àx + 1,
Ày + 1, Àz; b, Àx + 1, Ày, Àz + 1; c, Àx + 2, Ày + 1, Àz + 1; d, Àx + 2,
Ày + 1, Àz.
Ex
250
300
350
400
450
500
550
˚
distance 3.186 A; the C15–C20 phenyl ring and his symme-
Wavelength (nm)
try-related C15–C20 (1 À x, 1 À y, 1 À z) phenyl ring are
Fig. 5. Solid state emission and excitation spectra of 1 and 2 at room
temperature.
absolutely parallel with the centeriod-to-centeriod distance
˚
˚
4.029 A and plane distance 3.446 A; the C1/C2/N1-N3 tri-
azole ring and his symmetry-related C1/C2/N1/N3 (2 À x,
1 À y, 1 À z) triazole ring are absolutely parallel with the
imately 402 and 394 nm, respectively, upon excitation at
340 nm (Fig. 5). This emission is neither metal-to-metal
charge transfer (MLCT) nor ligang-to-metal transfer
(LMCT) in nature since the Zn(II) and Cd(II) are difficult
to oxidize or to reduce to its d10 configuration. Compara-
bly, free phba and btp molecule in the solid state displays
the emission band centered at about 395 and 410 nm,
respectively, when excited at 340 nm. The luminescence
emissions of 1 and 2 might therefore probably be assigned
˚
centeriod-to-centeriod distance 4.252 A and plane distance
˚
3.011 A, exhibiting obvious p–p stacking interactions inter-
phenyl rings and inter-triazole rings. The cell packing of 2
is shown in Fig. 4.
Previously Albada and coworkers reported two cop-
per(II) complexes {[Cu(btp)2(CH3CN)(H2O)] (CF3SO3)2}n
and {[Cu(btp)2(CH3CN)2](ClO ) } with two-dimensional
4 2 n
to the intraligand (p–p*) emission (combination of p–p
transition of phba and btp) [31,32].
On the basis of this work, further syntheses and struc-
tural studies of novel coordination polymers with flexible
bis(triazole) ligands are also under way in our laboratory.
network [18], and Zhao and coworkers synthesized a cobal-
t(II) complex [Co(btp)2(NCS)2]n with one-dimensional
double chain structure [19]. Compared the structure of 1
with 2, the coordination geometry of the Cd(II) is six-coor-
dination, in distorted octahedral, while the coordination
environment of Zn(II) is a five-coordinated distorted
square-pyramidal geometry, because the water molecule
is coordinated to Cd(II) atom but there is no water in 1.
Zn(II) complex 1 is the neutral dimer Zn2(btp)2 metallacy-
cle, while Cd(II) complex 2 forms the one-dimensional zig-
zag chain structure through the btp bridges.
*
Acknowledgments
This work was supported by the Natural Science Foun-
dation of Jiangsu Province (No. BK2006049) and Funds of
Key Laboratory of Organic Synthesis of Jiangsu Province,
PR China (No. KJS0612).
Measurement of the solid state luminescence spectra of 1
and 2 reveals a strong blue emission maximum at approx-
Fig. 4. The cell packing of 2.

268
G. Yin et al. / Journal of Molecular Structure 837 (2007) 263–268
[15] J.P. Zhang, X.M. Chen, Chem. Commun. (2006) 1689.
Appendix A. Supplementary data
[16] Effendy, F. Marchetti, C. Pettinari, R. Pettinari, B.W. Skelton, A.H.
White, Inorg. Chem. 42 (2003) 112.
[17] L.F. Tang, Z.H. Wang, J.F. Chai, W.L. Jia, Y.M. Xu, J.T. Wang,
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Reedijk, Eur. J. Inorg. Chem. (2000) 121.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/
j.molstruc.2006.10.028.
[19] Q.H. Zhao, H.F. Li, X.F. Wang, Z.D. Chen, New J. Chem. 26 (2002)
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