Abnormal conformation change of an asymmetrical triaryltriazole before and after its coordination

Article abstract of DOI:10.1016/j.molstruc.2011.07.017

A new asymmetrical substituted triaryltriazole ligand, 3-(p-methoxyphenyl)- 4-(p-bromophenyl)-5-(2-pyridyl)-1,2,4-triazole (L) and its complexes, trans-[MnL₂(NCS)₂] (1) and trans-[CuL₂(ClO ₄)₂] (2), h

Full text of DOI:10.1016/j.molstruc.2011.07.017

Journal of Molecular Structure 1002 (2011) 159–166
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Abnormal conformation change of an asymmetrical triaryltriazole before
and after its coordination
a,
Guo-Ping Shen a, Jian Zhao a, Jing-Jing Jiang a, Qin Liu b, Xuan Shen a, Yan Xu a, Dun-Ru Zhu a, , Xiao-Qin Liu
⇑
⇑
a College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, Nanjing 210009, PR China
b Department of Applied Chemistry, Nanjing University of Finance & Economics, Nanjing 210003, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 June 2011
Received in revised form 6 July 2011
Accepted 9 July 2011
Available online 20 July 2011
A new asymmetrical substituted triaryltriazole ligand, 3-(p-methoxyphenyl)-4-(p-bromophenyl)-5-(2-
pyridyl)-1,2,4-triazole (L) and its complexes, trans-[MnL2(NCS)2] (1) and trans-[CuL2(ClO4)2] (2), have
been successfully synthesized and characterized by UV, IR, ESI-MS, elemental analyses and single-crystal
X-ray diffraction methods. In the structure, two L ligands are mainly stabilized by two kinds of intermo-
lecular
pꢀ ꢀ ꢀp interactions. In the complexes, each L ligand involves a chelating bidentate coordination
mode via N atom of pyridyl group and one N atom of the triazole. Both complexes show a distorted octa-
hedron containing two trans-coordinated anions in 1 with NCSꢁ but in 2 with ClO4ꢁ. The dihedral angle
between the pyridyl and triazole ring in the free L ligand, 1 and 2 is 0.8(2)°, 12.8(2)° and 9.3(2)°, respec-
tively, which represents the first example that the triazole–pyridyl twist angle in the complexes of any
triaryltriazole is larger than that in the free L ligand.
Keywords:
Syntheses
Triazole
Crystal structures
Complexes
Ó 2011 Elsevier B.V. All rights reserved.
Conformation change
1. Introduction
2. Experimental section
During the past two decades, triaryltriazoles ligands have at-
tracted considerable attention in coordination chemistry due to
their possessing rich and versatile coordination modes [1] and
interesting spin-crossover properties in their iron(II) complexes
[2,3]. All kinds of mononuclear [1], dinuclear [4,5] and trinuclear
metal complexes [6] with triaryltriazoles ligands have been re-
ported to date. Generally, in the free triaryltriazole, the three aryl
rings are not coplanar with the central triazole ring. The X-ray
crystal structure analyses of the free triaryltriazoles revealed that
the dihedral angles between the pyridyl and triazole ring in all
cases are in the range of 16.3(3)–50.1(3)° (Table 3) [1,7–19]. In
the complexes of any triaryltriazole, however, the triazole–pyridyl
twist angle becomes always smaller in favor of coordination
(Table 4) [2–4,6,19–23]. Herein we report a very unusual example
that conformation change of a new asymmetrical 3,4,5-tri-substi-
tuted triaryltriazole, 3-(p-methoxyphenyl)-4-(p-bromophenyl)-5-
(2-pyridyl)-1,2,4-triazole (L), is abnormal before and after its
coordination, that is, the pyridyl and triazole ring is almost in a
plane in the free L ligand but is not in its two mononuclear com-
plexes, trans-[MnL2(NCS)2] (1) and trans-[CuL2(ClO4)2] (2). The sin-
gle crystal structures and spectral properties of L, 1 and 2 have
been systematically studied.
2.1. Materials and measurements
Melting points were determined using an X4 digital microscopic
melting point apparatus and are uncorrected. Elemental analyses
for M2+ (M = Mn, 1; Cu, 2) were performed on a Zeeman inductively
coupled plasma (ICP) spectrometer, while the C, H, N analyses were
carried out with a Thermo Finnigan Flash 1112A elemental ana-
lyzer. FT-IR spectra were recorded on a Nicolet 380 FT-IR instru-
ment using KBr disks in the range of 4000–400 cmꢁ1. UV–vis
spectra were recorded on a Perkin–Elmer Lambda 35 spectrometer
at r.t. in acetonitrile solution. 1H NMR spectra were measured on a
Bruker AM 500 MHz spectrometer at ambient temperature in
CDCl3. Chemical shifts are reported in parts per million (ppm)
downfield from tetramethylsilane (TMS). Electrospray ionization
mass spectrum (ESI-MS) was recorded with a Finnigan mat APISSQ
710 mass spectrometer, with MeOH on the mobile phase; the flow
rate of the mobile phase was 0.2 cm3 minꢁ1. The spray voltage was
4.5 kV and the capillary voltage was 28.7 V. The capillary temper-
ature was 200 °C. All chemicals used were of analytical grade,
and solvents were purified by conventional methods.
2.2. Synthesis of L
⇑
The ligand, 3-(p-methoxyphenyl)-4-(p-bromophenyl)-5-(2-
pyridyl)-1,2,4-triazole (L) was prepared by condensation of
Corresponding authors. Tel.: +86 25 83587717; fax: +86 25 83172261.
E-mail address: zhudr@njut.edu.cn (D.-R. Zhu).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.07.017

160
G.-P. Shen et al. / Journal of Molecular Structure 1002 (2011) 159–166
Table 1
Crystal data and structure refinement for L, 1 and 2.
Compounds
L
1
2
Empirical formula
Formula weight
Crystal system
Space group
a (Å)
C
20H15BrN4O
C42H30Br2MnN10O2S2
985.64
Monoclinic
P21/c
14.518(3)
9.1784(16)
16.189(3)
101.503(2)
2114.0(6)
2
C40H30Br2Cl2CuN8O10
1076.98
Monoclinic
P21/c
8.9069(12)
30.698(4)
8.1360(10)
108.797(2)
2105.9(5)
2
407.27
Monoclinic
C2/c
13.934(3)
11.277(2)
22.920(5)
93.558(3)
3594.6(13)
8
b (Å)
c (Å)
b (°)
V (Å3)
Z
Dc (g cmꢁ3
)
1.505
2.304
1648
1.548
2.351
990
1.698
2.611
1078
l
(mmꢁ1
F (0 0 0)
)
Crystal size (mm)
h range
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
0.16 ꢂ 0.14 ꢂ 0.08
1.78–25.50
11,048
3331 [Rint = 0.0298]
3331/0/235
1.041
0.26 ꢂ 0.16 ꢂ 0.12
1.43–26.00
13,315
4085 [Rint = 0.0619]
4085/0/268
0.962
0.24 ꢂ 0.14 ꢂ 0.10
1.33–25.50
15,269
3901 [Rint = 0.0521]
3901/174/325
1.029
R/wR [I > 2
R/wR (all data)
Max., Min.
r
(I)]
0.0348/0.0914
0.0629/0.1103
0.248, ꢁ0.372
0.0455/0.0962
0.1134/0.1151
0.525, ꢁ0.556
0.0452/0.1095
0.0885/0.1307
0.637, ꢁ0.351
D
q
(e Åꢁ3
)
Table 2
Selected bond distances (Å) and angles (°) for L, 1 and 2.
L
1
2
N1AC1
N1AC5
1.343(4)
1.313(4)
Mn1AN1
Mn1AN2
Mn1AN5
N2AN3
O1AC14
Br1AC18
N5AC21
S1AC21
N1AMn1AN2
N1AMn1AN5
N2AMn1AN5
N5AC21AS1
Mn1AN5AC21
C11AO1AC14
2.256(3)
2.220(3)
2.173(4)
1.374(4)
1.400(5)
1.894(4)
1.154(5)
1.620(5)
73.2(2)
88.6(2)
91.7(2)
178.7(4)
166.2(4)
117.7(4)
Cu1AN1
Cu1AN2
Cu1AO5
N2AN3
O1AC14
Br1AC18
2.052(3)
1.966(2)
2.434(3)
1.373(3)
1.421(4)
1.888(3)
N2AN3
O1AC14
Br1AC18
1.387(4)
1.425(4)
1.898(3)
C1AN1AC5
N3AN2AC6
C6AN4AC7
116.4(3)
108.3(2)
105.5(2)
O5ACu1AN1
O5ACu1AN2
N1ACu1AN2
88.1(2)
91.6(2)
80.0(1)
O1AC11AC12
C11AO1AC14
125.0(3)
118.2(2)
Cu1AO5ACl1
C11AO1AC14
135.6(3)
117.6(3)
4,40-dibromophenylphosphazoanilide (1.786 g, 4.8 mmol) with
N-(p-methoxyphenylcarbonyl)-N0-(2-pyridylcarbonyl)hydrazine
(1.085 g, 4.0 mmol) in o-dichlorobenzene at 190 °C for 5 h [11],
yield 0.982 g (60%), m.p. 219–222 °C. Single crystals of the L
ligand suitable for X-ray diffraction study were obtained from
anhydrous ethanol upon slow evaporation at ambient tempera-
ture. Elemental analyses: found (%): C, 58.79; H, 3.66; N, 13.83.
was isolated, washed with H2O and EtOH, and dried in vacuo to
yield 0.165 g (83.7%) of the complex. The light-yellow single
crystals suitable for X-ray diffraction were obtained by evaporation
from an ethanol solution. Elemental analyses: found (%): Mn, 5.95;
C, 51.27; H, 2.83; N, 13.91. C42H30Br2MnN10O2S2 Calcd. (%):
Mn, 5.57; C, 51.18; H, 3.07; N, 14.21. UV (nm): k = 313, 332. IR
(cmꢁ1):
m = 3070.8(w), 2967.8(w), 2066.8(vs), 1611.3(m), 1600.3(m),
C
20H15BrN4O Calcd. (%): C, 58.98; H, 3.71; N, 13.76. UV (nm):
1578.8(m), 1489.8(s), 1250.2(s), 1067.6(m), 1023.8(m), 845.2(m),
637.4(w). ESI-MS: m/z = 927.58, 837.25, 431.42.
k = 228, 281. IR (cmꢁ1):
m
= 3058.9(w), 2958.5(w), 2835.5(w),
1613.7(m), 1587.3(m), 1567.1(m), 1493.5(s), 1474.6(s), 1282.1(s),
1067.5(m), 1029.1(s), 999.4(m). 1H NMR d: 3.80 (s, 3H),
6.82–6.85 (d, 2H), 7.09–7.13 (d, 2H), 7.21–7.23 (t, 1H), 7.35–7.38
(d, 2H), 7.50–7.56 (d, 2H), 7.74–7.77 (t, 1H), 8.16–8.18 (d, 1H),
8.32–8.33 (d, 1H). ESI-MS: m/z = 409.2.
2.4. Synthesis of trans-[CuL2(ClO4)2] (2)
Complex 2 was obtained in a yield of 91.2% by a procedure
similar to complex 1 but using Cu(NO3)2ꢀ3H2O and NaClO4ꢀH2O
instead of MnCl2ꢀ6H2O and KSCN, respectively. Blue single crystals
suitable for X-ray analysis were obtained from ethanol upon slow
evaporation. Elemental analyses: found (%): Cu, 6.25; C, 44.68; H,
2.3. Synthesis of trans-[MnL2(NCS)2] (1)
A solution of MnCl2ꢀ6H2O (0.040 g, 0.20 mmol) and anhydrous
ethanol (5 cm3) was added dropwise to a stirring solution of L
(0.163 g, 0.40 mmol) in boiling anhydrous ethanol (10 cm3). The
resulting solution was mixed with an EtOH solution containing
KSCN (0.039 g, 0.40 mmol). The light-yellow powder that formed
2.63; N, 10.19.
44.61; H, 2.81; N, 10.40. UV (nm): k = 319, 338, 647. IR (cmꢁ1):
= 3081.8(w), 2975.6(w), 1611.5(m), 1604.5(m), 1582.5(m),
1501.0(s), 1261.2(m), 1109.2(s), 1067.4(s), 1022.2(m), 926.7(w),
622.4(m). ESI-MS: m/z = 915.00, 837.17, 642.92, 431.33.
C40H30Br2Cl2CuN8O10 Calcd. (%): Cu, 5.90; C,
m

G.-P. Shen et al. / Journal of Molecular Structure 1002 (2011) 159–166
161
Table 3
Triazole–pyridyl twist angle (°) for the known triaryltriazoles.
Structure
La
R1
R2
R3
R4
X
Py/Trz
Reference
L
OCH3
CH3
Cl
Br
H
H
H
CH3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
N
0.8(2)
This work
[7]
[8]
R2
X
L1
L2
L3
L4
L5
L6
L7
L8
L9
L10
OCH3
OCH3
H
CH3
CH3
Cl
Cl
Cl
Cl
H
46.2(2)
35.1(1)
36.0(2)
28.1(2)
No data
23.7(2)
43.4(1)
18.5(3)
16.3(3)
No data
R4
R3
H
[9]
[10]
[20]
[11]
[12]
[11]
[11]
[21]
Cl
N
OCH3
CH3
Cl
Br
H
R1
N
N
N
H
H
L11
L12
L13
L14
L15
L16
L17
L18
L19
L20
L21
L22
L23
H
H
H
H
H
H
H
H
H
H
H
H
H
i-Pr
t-Bu
OCH3
OEt
CH3
H
CH3
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Cl
H
H
H
H
H
H
H
H
N
H
H
H
29.8(2), 43.7(2)
25.0(3), 33.3(3)
26.9(1), 47.9(1)
20.1(1), 30.0(1)
32.0(3), 48.0(3)
35.9(3), 36.8(3)
36.5(2), 50.1(3)
30.1(2), 32.7(2)
No data
[13]
[14]
[1]
[15]
[16]
[17]
[18]
[1]
[19]
[1]
[1]
[19]
[19]
R2
X
R4
R3
H
CH3
CH3
H
H
H
N
R1
N
N
N
N
Cl
Br
H
26.9(1), 28.7(1)
28.1(2), 46.8(2)
No data
H
Cl
No data
a
L4 = 3-(4-pyridyl)-4-(p-methylphenyl)-5-(2-pyridyl)-1,2,4-triazole; L23 = 4-pyrrolyl-3,5-di(2- pyridyl)-1,2,4-triazole.
Table 4
Triazole–pyridyl twist angle (°) for complexes of any triaryltriazoles.
Complexes
Py/Trz
Reference
[MnL2(NCS)2]/[CuL2(ClO4)2]
[MnL52(NCS)2]/
12.8(2)/9.3(2)
11.2(3)/2.9(3)
This work
[20]
[CoL52(H2O)(EtOH)](ClO4)2ꢀH2O
[MnL62(NCS)2]
13.2(1)
11.1(2)
10.3(3)
5.9(2)
10.6(3),
35.2(3)
2.2(2), 3.4(2)
11.6(3),
14.8(3)
16.7(2),
33.9(2)
Our worka
Our worka
Our worka
[21]
[FeL82(NCSe)2]
[FeL92(NCS)2]
[CuL102(ClO4)2]ꢀMeCN
[FeL112(NCS)2]
Our worka
[Ni2L132Cl2(H2O)2]Cl2ꢀ7H2O
[4]
[3]
[FeL152(NCS)2]
[FeL162(NCS)2]
[3]
[Fe3L184(NCS)6]
19.6(1)-31.5(1) [6]
4.3(2)-45.4(1)
12.5(2),
[FeL193](BF4)2ꢀ3.6MeCNꢀEt2O
[19]
[FeL203(NCS)2]
Our worka
Fig. 1. Projection of the structure of L with the atomic labeling system. Hydrogen
atoms are omitted for clarity.
15.5(2)
[CoL212(NCS)2]
9.4(8), 13.5(8)
4.0(2)-30.0(2)
6.1(2), 24.7(2)
6.7(4), 10.4(3)
[22]
[19]
[23]
[23]
[FeL223](BF4)2ꢀMeCNꢀEt2O
[CoL232(DMF)2](ClO4)2
[Co2L232(DMF)2(H2O)2](ClO4)4ꢀ0.5Et2O
were located from a difference map and refined isotropically. Crys-
tallographic data are summarized in Table 1. The selected bond
lengths and angles for L, 1 and 2 are listed in Table 2. CCDC for L,
1 and 2 are 822,798, 822,799, 822,800, respectively.
a
Unpublished results.
2.5. X-ray data collection and structure determination
Table 5
The well-shaped single crystals of L, 1 and 2 were selected for X-
ray diffraction study. The unit cell parameters and intensity data
were collected at 293(2) K on a Bruker SMART CCD diffractometer
with a detector distance of 5 cm and frame exposure time of 8 s
The hydrogen bonding geometry and p–p stacking interactions of L.
DAHꢀ ꢀ ꢀA
DAH (Å)
Hꢀ ꢀ ꢀA (Å)
2.56
2.56
3.04
Dꢀ ꢀ ꢀA (Å)
3.446(4)
3.431(4)
3.568(4)
DAHꢀ ꢀ ꢀA (°)
159
156
116
Dihedral angle
0.86
1.98
C3AH3Aꢀ ꢀ ꢀN2a
0.93
0.93
0.96
centꢀ ꢀ ꢀcent
3.632
3.751
C13AH13Aꢀ ꢀ ꢀN3b
using a graphite-monochromated Mo Ka (k = 0.71073 Å) radiation.
C14AH14Cꢀ ꢀ ꢀ
p
The structures were all solved by direct methods and refined on F2
by full-matrix least squares procedures using SHELXTL software
[24]. All non-hydrogen atoms were anisotropically refined. Atoms
O2, O3, O4 and O5 of one ClOꢁ4 anion in 2 were found to be highly
disordered with an occupancy of 0.807(3) for O2, O3, O4 and O5,
and 0.193(3) for O2A, O3A, O4A and O5A, respectively. All H atoms
p
p
p
ꢀ ꢀ ꢀ
(trz)ꢀ ꢀ ꢀ
(py)ꢀ ꢀ ꢀ
p
interaction
p
p
(trz)c
(py)c
a
b
c
Symmetry codes: 3/2 ꢁ x, 1/2 + y, ꢁ1/2 ꢁ z.
Symmetry codes: 1 ꢁ x, y, ꢁ1/2 ꢁ z.
Symmetry codes: 1 ꢁ x, y, 3/2 ꢁ z.

162
G.-P. Shen et al. / Journal of Molecular Structure 1002 (2011) 159–166
Table 6
The hydrogen bonding geometry and
p–p stacking interactions of 1.
DAHꢀ ꢀ ꢀA
DAH (Å)
Hꢀ ꢀ ꢀA (Å)
Dꢀ ꢀ ꢀA (Å)
DAHꢀ ꢀ ꢀA (°)
C3AH3Aꢀ ꢀ ꢀS1a
0.93
0.96
0.93
0.93
2.836
2.863
2.692
2.942
3.559(5)
3.555(5)
3.484(4)
3.769(5)
135
130
143
149
C14AH14Bꢀ ꢀ ꢀS1b
C20AH20Aꢀ ꢀ ꢀO1c
C4AH4Aꢀ ꢀ ꢀ
p
a
b
c
Symmetry codes: x, y ꢁ 1, z.
Symmetry codes: 1 ꢁ x, 2 ꢁ y, ꢁz.
Symmetry codes: x, 1.5 ꢁ y, 0.5 + z.
phenyl rings, one pyridyl group and one triazole ring. The pyridyl
and triazole ring is almost in a plane with a dihedral angle of
0.8(2)°, which has not been observed in all the free triaryltriazole
ligands [1,7–19] (Table 3). The central 1,2,4-triazole ring is ori-
ented at dihedral angles of 89.4(1)° and 86.9(2)° with respect to
the p-methoxyphenyl ring and the p-bromophenyl ring, respec-
tively. It is noticeable that two L ligands are mainly stabilized by
two kinds of intermolecular
p p interactions. One strong offset
ꢀ ꢀ ꢀ
face-to-face
p p interaction exists between two central triazole
ꢀ ꢀ ꢀ
rings containing N4 and N4c (1 ꢁ x, y, 3/2 ꢁ z), respectively, with
a centroid–centroid distance of 3.632 Å and a dihedral angle of
0.86°. Another
p p interaction exists between two neighboring
ꢀ ꢀ ꢀ
pyridyl rings containing N1 and N1c (1 ꢁ x, y, 3/2 ꢁ z), respectively,
Fig. 2. The crystal packing of L showing the hydrogen bonding and
p stacking
with a centroid–centroid distance of 3.751 Å and a dihedral angle
interactions.
of 1.98°. In addition, there are also one CAHꢀ ꢀ ꢀ
p interaction and
two CAHꢀ ꢀ ꢀN hydrogen bonds in the L ligand (Table 5 and Fig. 2).
3. Results and discussion
We think that it is these intermolecular and intramolecular hydro-
gen bonds and
dral angle of the pyridyl and triazole ring.
p p stacking interactions that determine the dihe-
ꢀ ꢀ ꢀ
3.1. Syntheses
The asymmetrical 3,4,5-triaryl-substituted 1,2,4-triazole ligand
(L) reacts with M2+ (M = Mn and Cu) ion and the anion (NCSꢁ and
ClOꢁ4 ) in molar ratio 2:1:2 to obtain two neutral mononuclear
hexacoordinate complexes, trans-[MnL2(NCS)2] (1) and trans-
[CuL2(ClO4)2] (2), which are stable in air. Yields of complexes 1
and 2 are 83.7% and 91.2%, respectively. The elemental analyses
were satisfactory and indicate that each complex contains one me-
tal ion, two tꢁriaryltriazole ligands, and two coordinated anions (1:
NCSꢁ, 2: ClO4 ).
3.3. Crystal structure of 1
A projection of the structure of 1 is presented in Fig. 3, together
with the atomic labeling system. Complex 1 crystallizes in the
monoclinic space group P21/c and there is an inversion center at
the Mn(II) atom. Each Mn(II) atom adopts a distorted [MnN6]
octahedral geometry coordinated by four nitrogen atoms from
two L ligands in the equatorial plane and two nitrogen atoms from
two NCSꢁ ions in the axial positions. This feature is also different
from that found in
a mononuclear Mn(II) complex with
3.2. Crystal structure of L
asymmetrical 3,5-disubstituted 1,2,4-triazole, cis-[MnL02(NCS)2]
[25] [L0 = 3-methyl-4-(p-bromophenyl)-5-(2-pyridyl)-1,2,4-tria-
zole] where the two NCSꢁ anions are in the cis arrangement. Each
L ligand coordinates to Mn(II) atom via N1 atom of the pyridyl ring
and N2 atom of the triazole, which is similar to the coordination
modes in the related Mn(II) complexes [20,26–27]. The MnAN
A perspective view of L with the atom-numbering scheme is
shown in Fig. 1. Both bond lengths and angles in L are comparable
with those reported for the related structures [1,7–19]. The X-ray
structure analysis indicates that L consists of two substituted
Fig. 3. Projection of the structure of 1 with the atomic labeling system. Hydrogen atoms are omitted for clarity.

G.-P. Shen et al. / Journal of Molecular Structure 1002 (2011) 159–166
163
Fig. 4. The crystal packing of 1 viewed along the b-axis showing the hydrogen bonding.
Fig. 5. Projection of the structure of 2 with the atomic labeling system. Hydrogen atoms are omitted for clarity.
bond lengths are within the normal ranges observed for the octa-
hedral Mn(II) complexes [20,26]. However, the MnANtrz bond
length is 0.036 Å shorter than MnANpy one. The same feature
has been observed in the analogous Mn(II) complexes with
trans-NCSꢁ groups [20,26]. The NCSꢁ groups are almost linear
[N5AC21AS1 178.7(4)°], whereas the MnANC(S) linkages are a
little bent [Mn1AN5AC21 166.2(4)°]. The L ligand in 1 is non-pla-
nar. The triazole ring makes dihedral angles of 12.8(2)°, 50.3(2)°
and 75.4(2)° with the pyridyl ring, p-methoxyphenyl ring and
p-bromophenyl ring, respectively. It is noticeable that on coordi-
nation, the triazole–pyridyl twist angle becomes larger than
that observed in the free L ligand. This phenomenon has not been
observed in the complexes with triaryltriazole ligands [2–4,6,
19–23] (Table 4). Due to existence of a dihedral angle (76.8(2)°)
between the pyridyl ring and the p-bromophenyl ring in the L
Table 7
The hydrogen bonding geometry and p–p stacking interactions of 2.
DAHꢀ ꢀ ꢀA
DAH (Å)
Hꢀ ꢀ ꢀA (Å)
Dꢀ ꢀ ꢀA (Å)
DAHꢀ ꢀ ꢀA (°)
144
143
124
134
154
164
148
147
142
Dihedral angle
0.0
C1AH1Aꢀ ꢀ ꢀN3a
C2AH2Aꢀ ꢀ ꢀO2b
C3AH3Aꢀ ꢀ ꢀO5c
C4AH4Aꢀ ꢀ ꢀO3Ac
C12AH12Aꢀ ꢀ ꢀO4d
C14AH14Bꢀ ꢀ ꢀO1e
C16AH16Aꢀ ꢀ ꢀO2f
0.93
0.93
0.93
0.93
0.93
0.96
0.93
0.93
2.31
2.59
2.55
2.72
2.67
2.74
2.79
3.07
2.82
3.117(4)
3.373(5)
3.166(4)
3.427(1)
3.526(5)
3.673(5)
3.614(5)
3.886(3)
3.601(5)
C4AH4Aꢀ ꢀ ꢀ
p
p
C9AH9Aꢀ ꢀ ꢀ
0.93
p
p
ꢀ ꢀ ꢀ
p
interaction
centꢀ ꢀ ꢀcent
p
3.694
ꢀ ꢀ ꢀ
p
(py)ꢀ ꢀ ꢀ
p
(py)g
4.139
a
b
c
d
e
f
Symmetry codes: 2 ꢁ x, ꢁy, 2 ꢁ z.
Symmetry codes: 3 ꢁ x, ꢁy, 2 ꢁ z.
Symmetry codes: x, y, z ꢁ 1.
ligand, there is an intramolecular edge-to-face CAHꢀ ꢀ ꢀ
tion involving C4AH4A and the p-bromophenyl ring
= 149°). The crystal structure
p interac-
Symmetry codes: x ꢁ 1, y, z.
(H4Aꢀ ꢀ ꢀ
p
= 2.942 Å and C4AH4Aꢀ ꢀ ꢀ
p
Symmetry codes: x, 1/2 ꢁ y, z ꢁ ½.
Symmetry codes: x ꢁ 1, y, z ꢁ 1.
Symmetry codes: ꢁx, ꢁy, 1 ꢁ z.
is further stabilized by weak intermolecular CAHꢀ ꢀ ꢀS and CAHꢀ ꢀ ꢀO
g
hydrogen bonds (Table 6 and Fig. 4). These intramolecular and

164
G.-P. Shen et al. / Journal of Molecular Structure 1002 (2011) 159–166
Fig. 6. The crystal packing of 2 viewed along the a-axis showing the hydrogen bonding.
Fig. 7. View of one offset face-to-face
ring in 2.
pꢀ ꢀ ꢀp stacking interaction for two parallel pyridyl rings and two edge-to-face CAHꢀ ꢀ ꢀp stacking interactions for p-bromophenyl
intermolecular interactions may result in the larger dihedral angle
of the pyridyl and triazole ring in 1.
[29,30]. The CuAO distance is 2.435(3) Å, indicating the involve-
ment of two ClOꢁ4 ions in the coordination [31], which is similar
to that found in trans-[CuL02(ClO4)2] [28]. The coordination mode
of L ligand in 2 is similar to that found in 1 and the L ligand is also
non-planar. The triazole ring makes dihedral angles of 9.3(2)°,
25.2(2)° and 74.2(2)° with the pryidyl ring, p-methoxyphenyl ring
and p-bromophenyl ring, respectively. Once again, the triazole–
pyridyl twist angle of the triaryltriazole in 2 is larger than that
observed in the free L ligand. This abnormal conformation change
may due to the existence of intermolecular and intramolecular
3.4. Crystal structure of 2
Fig. 5 presents the structure of 2 with its atom numbering
system. The crystal structure consists of a [CuL2]2+ cation and
two ClOꢁ4 anions. The Cu(II) atom in 2 is also in a distorted
octahedral geometry coordinated by four nitrogen atoms from
two L ligands and two oxygen atoms from two ClOꢁ4 anions in
the axial positions. The CuAN bond lengths are within the normal
ranges observed for a octahedral Cu(II) complex [28]. However, the
CuANtrz bond length is 0.085 Å shorter than CuANpy. The same
feature has been observed in the similar Cu(II) complexes
hydrogen bonds and
pꢀ ꢀ ꢀp stacking interactions in 2 (vide infra).
There are five kinds of intermolecular and intramolecular
hydrogen bond interactions in the structure of 2 (Table 7), which
is significantly associated with the closer crystal packing. These

G.-P. Shen et al. / Journal of Molecular Structure 1002 (2011) 159–166
165
respectively, and p-bromophenyl ring (H4Aꢀ ꢀ ꢀ
C4AH4Aꢀ ꢀ ꢀ = 147°; H9Aꢀ ꢀ ꢀ
(Fig. 6). Notably, an offset face-to-face
between two parallel pyridyl rings with a plane-plane distance of
3.694 Å and a centroid–centroid distance of 4.139 Å (Fig. 7).
p
= 3.07 Å and
p
p
= 2.82 Å and C9AH9Aꢀ ꢀ ꢀ
p = 142°)
L
1
p–p
interaction exists
These extensive hydrogen bonds and
p–p stacking interactions
assemble the cation units and ClOꢁ4 anions into
dimensional structure.
a three-
3.5. IR spectrum
2
The IR spectrum of free L shows two medium bands at 1587.3
and 1567.1 cmꢁ1, attributable to the pyridyl ring vibrations. Upon
pyridine coordination to a metal the higher band is shifted by
about 15 wavenumbers [27]. So in the spectrum of the complex
1 (or 2), a band at 1600.3 (or 1604.5) (m) and 1578.8 (or
1582.5) cmꢁ1 (m) can be assigned to the coordinated pyridyl ring
(Fig. 8). This means that in 1 and 2, each L ligand uses one pyridyl
nitrogen and one triazole nitrogen for chelate binding. In 1, a very
strong band at 2066.8 cmꢁ1 is assigned to C„N stretching vibra-
tions of two trans-oriented thiocyanate groups [4]. In 2, the bands
due to the perchlorate anions are around 1109.2 (s), 926.7 (w),
1650
1625
1600
1575
1550
Wavenumbers (cm-1)
Fig. 8. IR spectra of L, 1 and 2 in the region of characteristic bands of pyridyl ring
(1650–1550 cmꢁ1).
hydrogen bond interactions include: (1) between pyridyl ring and
triazole ring [C1AH1Aꢀ ꢀ ꢀN3a]; (2) between two methoxy groups
[C14AH14Aꢀ ꢀ ꢀO1e]; (3) between pyridyl ring and ClOꢁ4 anion
[C2AH2Aꢀ ꢀ ꢀO2b, C3AH3Aꢀ ꢀ ꢀO5c, C4AH4Aꢀ ꢀ ꢀO3Ac]; (4) between
p-bromophenyl ring and ClO4ꢁ anion [C16AH16Aꢀ ꢀ ꢀO2f]; (5) be-
tween p-methoxyphenyl ring and ClOꢁ4 anion [C12AH12Aꢀ ꢀ ꢀO4d].
Different from 1, there are two kinds of intramolecular edge-to-
622.4 cmꢁ1 (m), which can be assigned as the IR-allowed
IR-forbidden mode and the nondegenerate ClO3 symmetrical
m mode,
m
bending frequency, respectively [32]. These features are in agree-
ment with the results of X-ray analyses. In addition, the stretching
vibrations of C(Ph)ABr bond at 1067.5, 1067.6 and 1067.4 cmꢁ1 are
attributed to L, 1 and 2, respectively.
face CAHꢀ ꢀ ꢀ
p interactions in 2 involving C4AH4A and C9AH9A,
Fig. 9. Positive ion ESI-MS of L (a), 1 (b) and 2 (c) in methanol solution.

166
G.-P. Shen et al. / Journal of Molecular Structure 1002 (2011) 159–166
3.6. UV–vis spectrum
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of 2 and three main peaks were observed. The base peak at m/z
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4. Conclusions
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Acknowledgments
This work was funded by the National Nature Science Founda-
tion of China (Nos. 20771059, 20971068 and 20976082) and the
Natural Science Foundation of Jiangsu Province (BK2008371).
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