Two anionic [CuI6X7]nn- (X=Br and I) chain-based organic-inorganic hybrid solids with N-substituted benzotriazole ligands

Article abstract of DOI:10.1016/j.jssc.2010.03.007

Solvothermal reactions of the flexible ligand 1,6-Bi(benzotriazole)hexane with CuI and KI or CuBr and KBr in ethanol generate two hybrid compounds, namely, {(HETA)[(Cu₆I₇)(ETA)₂]}_n(1) and {K(Cu₆Br₇)(BBTH)}_n(2) (ETA=N-ethylbenzotriazole, HETA=protonated N-ethylbenzotriazole, BBTH=1,6-bi(benzotriazole)hexane). In 1, two [Cu₃I₄] vertex missing cubane-like subunits link each other by sharing one I atom to give a [Cu₆I₇] cluster, which further form novel 1D [Cu₆I₇]_n^n- anionic chain. Two in-situ generated ETA ligands finished the 4-coordinated environments of copper centers and another one discrete protonated ETA ligand keeps the charge neutrality for 1. In complex 2, bowl-shaped [Cu₅Br₄] clusters and rhomboid [Cu₂Br₂] dimers link each other to generate a [Cu₆Br₇]_n^n- 1D chain. BBTH ligands complete the tetrahedral spheres of Cu(I), and 7-coordinated K atoms further extend the 1D chain motifs to a 2D hybrid layer of 2. The UV-vis diffuse reflectance spectrum and luminescence measurements show that compound 1 and 2 both are potential semiconductor and photoluminescence materials.

Full text of DOI:10.1016/j.jssc.2010.03.007

ARTICLE IN PRESS
Journal of Solid State Chemistry 183 (2010) 1150–1158
Contents lists available at ScienceDirect
Journal of Solid State Chemistry
journal homepage: www.elsevier.com/locate/jssc
I
nꢀ
7 n
Two anionic [Cu X ]
(X¼Br and I) chain-based organic–inorganic hybrid
6
solids with N-substituted benzotriazole ligands
Ã
Xia Gao, Quan-Guo Zhai, Shu-Ni Li, Rui Xia, Hai-Juan Xiang, Yu-Cheng Jiang, Man-Cheng Hu
Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi’ an, Shaanxi 710062, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Solvothermal reactions of the flexible ligand 1,6-Bi(benzotriazole)hexane with CuI and KI or CuBr and
Received 8 November 2009
Received in revised form
KBr in ethanol generate two hybrid compounds, namely, {(HETA)[(Cu I )(ETA) ]} (1) and {K(Cu Br )
6
7
2
n
6
7
(
BBTH)}
zotriazole)hexane). In 1, two [Cu
I atom to give a [Cu
n
(2) (ETA¼N-ethylbenzotriazole, HETA¼protonated N-ethylbenzotriazole, BBTH¼1,6-bi(ben-
1
March 2010
I
3 4
] vertex missing cubane-like subunits link each other by sharing one
Accepted 8 March 2010
Available online 12 March 2010
nꢀ
6
I
7
] cluster, which further form novel 1D [Cu
6
7
I ]
n
anionic chain. Two in-situ
generated ETA ligands finished the 4-coordinated environments of copper centers and another one
Keywords:
5 4
discrete protonated ETA ligand keeps the charge neutrality for 1. In complex 2, bowl-shaped [Cu Br ]
CuI
nꢀ
clusters and rhomboid [Cu
2
Br
2
] dimers link each other to generate a [Cu
6
Br
7
]
n
1D chain. BBTH ligands
CuBr
complete the tetrahedral spheres of Cu(I), and 7-coordinated K atoms further extend the 1D chain
motifs to a 2D hybrid layer of 2. The UV–vis diffuse reflectance spectrum and luminescence
measurements show that compound 1 and 2 both are potential semiconductor and photoluminescence
materials.
N-Ethylbenzotriazole
1
,6-Bi(benzotriazole)hexane
Organic–inorganic hybrid solid
&
2010 Elsevier Inc. All rights reserved.
1
. Introduction
neutral (a¼b), cationic (a 4b) and anionic (aob) aggregates.
In contrast to the extensively investigated neutral species, the
structural and luminescent aspects of anionic or cationic copper (I)
halide aggregates remain rarely explored due to synthetic
and calculating difficulties [25–30]. On the other hand, organic
species, with versatile binding modes and features can be used to
transfer energy or electron, enhance spinorbital coupling as well as
impart chemical reactivity or chirality [23,24,31–37]. As a result,
rigid or flexible multidentate nitrogen-donor ligands usually act as
organic connectors to link these copper halide motifs to form
extended organic–inorganic hybrid architectures. Thus, the design
of organic ligands is a useful way of manipulating the hybrid
structures.
The current increasing attention and powerful driving force in
the organic–inorganic hybrid materials not only originate from
their fascinating properties in material science, medicine, cata-
lysis, etc., but also from their intriguing variety of architectures
and their diversity of electronic structures and topologies [1–11].
In those materials, the inorganic component may confer useful
optical or magnetic properties and thermal stability, while the
organic component offers the potential for a range of polariz-
abilities and structural diversification. The combination of these
two kinds of components results in the characteristics of diverse
structural chemistry and novel physical properties [12–16].
Among these types of hybrid compounds reported so far,
copper(I) halides have been widely investigated due to their rich
photoluminescent properties and intriguing topology [17,18].
Copper(I) tends to form a variety of coordination compounds with
halides, ranging from 0D complexes to 3D frameworks with
structural moieties such as rhomboid Cu2 ꢁ 2 dimers, cubane or
In the context of our research interest on the coordination
chemistry of polyazaheteroaromatic ligands, we recently reported
on the influence of the spacer length of
alkane organic ligands on the solid state structures of CuX-based
hybrid coordination polymers. Novel {Cu3 ꢁ 3 ladder-like chain
and {Cu8 ꢁ 8 ribbons have been firstly presented [24]. Moreover,
a,o-bis(benzotriazole)-
}
n
}
n
step-cubane Cu4 ꢁ 4 tetramers, zigzag [CuX]
n
chains, and hexagonal
the increasing dimensionality from 1-D to 3-D indicates that the
spacer length and isomerism of the bis(benzotriazole)alkane
ligands play an essential role in formation of the framework of
these hybrid materials. In order to further our investigations, 1,
[
Cu6 ꢁ 6]
n
grid chains [19–24]. It should be noted that the rich
aꢀb
n
] species is basically caused
structural variation in the [(Cu
a b
X )
by the ligating versatility of the halide anions, constructing diverse
6-bi(benzotriazole)hexane (BBTH) with much longer alkane
spacer is selected. To the best of our knowledge, neither
hydro(solvo)thermal nor solution methods have been used to
synthesize any compounds containing BBTH ligand. In other
words, no investigation about hybrid materials constructed from
Ã
Corresponding authors. Fax: +86 29 85307774.
E-mail addresses: zhaiqg@snnu.edu.cn (Q.-G. Zhai),
hmch@snnu.edu.cn (M.-C. Hu).
0022-4596/$ - see front matter & 2010 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2010.03.007

ARTICLE IN PRESS
X. Gao et al. / Journal of Solid State Chemistry 183 (2010) 1150–1158
1151
BBTH ligand has been reported to date. Herein, using BBTH ligand
under solvothermal reactions with CuI and KI or CuBr and KBr in
ethanol generate two novel hybrid compounds, namely,
1371(w), 1322(m), 1216(s), 1158(w), 1127(w), 1086(w), 997(w),
747(s).
{
(HETA)[(Cu
6
I
7
)(ETA)
2
]}
n
(1) and {K(Cu
6
Br
7
)(BBTH)}
n
(2) (ETA¼
2.4. Crystal structure determination
N-ethyl-benzotriazole, HETA¼protonated N-ethylbenzotriazole,
BBTH¼1,6-bi(benzotriazole)-hexane). Furthermore, these two
compounds have been characterized by X-ray single-crystal
diffractions, X-ray powder diffractions (XRPD), FT-IR, elemental
analysis, TG/DTA, UV-vis diffuse reflectance spectra, and solid-
state and solution photoluminescence measurements.
Suitable single crystals of 1 and 2 were carefully selected
under an optical microscope and glued to thin glass fibers.
Crystallographic data for all compounds were collected with a
Siemens Smart CCD Diffractometer with graphite-monochro-
˚
mated Mo Ka radiation (l¼0.71073 A) at T¼298(2) K. Absorption
corrections were made using the SADABS program [39]. The
structures were solved using the direct method and refined by
2
2
. Experimental
full-matrix least-squares methods on F by using the SHELXL-97
program package [40]. All non-hydrogen atoms were refined
anisotropically. Positions of the hydrogen atoms attached to
carbon and oxygen atoms were fixed at their ideal positions.
Crystal data as well as details of data collection and refinements
for 1 and 2 are summarized in Table 1. Selected bond lengths and
angles are listed in Table 2.
2
.1. Materials and physical measurements
The ligand 1,6-Bi(benzotriazole)hexane was synthesized ac-
cording to a literature method [38]. Other reagents and solvents
employed were commercially available and used without further
purification. The Fourier-transform infrared spectra (KBr pellets)
were recorded using a Nicolet Avatar 360 FT–IR Spectrometer in
the range of 4000–400 cm . C, H, and N elemental analyses were
performed using an Elementar Vario EL III elemental analyzer.
X-ray powder diffraction data were recorded on a Rigaku Multi-
Flex diffractometer with a scan speed of 0.05–0.21/min. Thermal
stability studies were carried out using a NETSCHZ STA–449C
thermoanalyzer under a nitrogen atmosphere (40–1000 1C range)
at a heating rate of 10 1C/min. UV–vis diffuse reflectance spectra
were obtained with a Lamdba 900 UV–vis–NIR spectrophotometer
at room temperature. Initially, the 100% line flatness of the
ꢀ
1
3. Results and discussion
3.1. Syntheses
Complexes 1 and 2 were both synthesized by BBTH ligand, CuI
and KI or CuBr and KBr in ethanol solvent with the identical
reaction temperature and reaction time. However, only mono-N-
ethylbenzotriazole ligands were found in the ultimate products of
compound 1. It is noted that the kind of anions that linked with
metal cations is a key factor to affect the formation of the
resulting products as well as the formation mechanism. It is well
known that iodide ions are a stronger nucleophile than bromine
ions. That is to say, iodine ions take place nucleophilic substitu-
tion reaction easily compared with bromine ions. On the basis of
the above theory and some literature reports [19], we can
tentatively speculate the formation mechanism of 1 as depicted
in Scheme 1: benzotriazole acquired by the rupture of the BBTH
4
spectrophotometer was set using barium sulfate (BaSO ). A
powder crystal sample of the compound was mounted on the
sample holder. The thickness of the sample was much larger than
the individual crystal particles. The solid-state and solution
fluorescence spectra all were measured with a Cary Eclipse
fluorescence spectrophotometer at room temperature. The ex-
citation slit and emission slit were both 2.5 nm.
6 7 2 n
2.2. Synthesis of {(HETA)[(Cu I )(ETA) ]} (1)
Table 1
Crystal data and structure refinements for compounds 1 and 2.
A mixture of CuI (0.190 g, 1.0 mmol), BBTH (0.161 g, 0.5 mmol),
Compound
1
2
KI (0.166 g, 1.0 mmol) and ethanol (10 mL) was stirred for 30 min
in a 25 mL Teflon-lined reactor then sealed the reactor. The
reactor was heated in an oven to 180 1C for 120 h and then cooled
Empirical formula
fw
C
24
H
28Cu
6
I
7
N
9
C
18 7 6 6
H20Br Cu KN
1712.09
1300.11
Monoclinic
P2 /m
ꢀ
1
to room temperature at a rate of 2.5 1C h . Yellow block-shaped
crystals of 1 were obtained by filtration, washed with ethanol, and
dried in air (Yield: ca. 0.12 g, 32% based on Cu). Anal. Calcd. (%) for
Cryst syst
Space group
a ( A˚ )
Monoclinic
C2/c
1
2
0.886(2)
1.0602(13)
7.9590(10)
19.140(2)
b ( A˚ )
c ( A˚ )
1
C
1
1
1
24 6 7 9
H28Cu I N (%): C 16.84, H 1.65, N 7.36; Found (%): C 17.01, H
ꢀ
1
21.071(3)
10.1109(14)
.58, N 7.26. FT-IR (KBr pellet, cm ): 2973(m), 2925(m),
602(m), 1494(w), 1446(s), 1380(m), 1316(s), 1241(s), 1194(s),
069(s), 1030(w), 750(s).
a
b
g
V (A˚
(deg)
(deg)
(deg)
90
90
109.50(2)
90
100.98(10)
90
3
4588.2(9)
1512.0(3)
)
Z
4
2
2
.3. Synthesis of {K(Cu
6
Br
7
)(BBTH)}
n
(2)
T (K)
calcd(g cm
298(2)
2.479
298(2)
2.856
ꢀ
3
D
)
ꢀ
1
m
(mm
F(0 0 0)
for data collection (deg)
)
7.468
13.553
1216
A
mixture of CuBr (0.215 g, 1.5 mmol), BBTH (0.161 g,
3120
0
.5 mmol), KBr (0.119 g, 1.0 mmol) and ethanol (10 mL) was
y
2.05–25.02
11 804/4038
0.0707
257
2.05–25.02
7608/2756
0.0534
197
stirred for 30 min in a 25 mL Teflon-lined reactor then sealed
the reactor. The reactor was heated in an oven to 180 1C for 120 h
and then cooled to room temperature at a rate of 2.5 1C h
Yellow block-shaped crystals of 2 were obtained by filtration,
washed with ethanol, and dried in air (Yield: ca. 0.132 g, 45%
based on Cu). Anal. Calcd. (%) for C18
1
Reflections collected/unique
R(int)
ꢀ
1
Parameters
.
2
GOF on F
0.990
1.027
a
R
R
1
, wR
2
[I42
(all data)
d
(I)]
0.0506, 0.1342
0.0772, 0.1510
1.409, ꢀ1.404
0.0431, 0.0873
0.0741, 0.0968
1.066, ꢀ1.054
1
, wR
2
H20Cu
6
Br
7
KN
6
(%): C 16.63, H
˚
ꢀ3
)
qfin(max/min) (e A
.55, N 6.46; Found (%): C 16.72, H 1.42, N 6.50. FT-IR (KBr pellet,
ꢀ
1
a
¼P
P
¼[P
2
o
2
c
2
P
2 2 0.5
) ]
cm ): 3075(w), 2934(m), 2954(w), 1613(w), 1491(w), 1441(m),
R
1
(|F
o
|ꢀ|F
c
|)/ |F
o
|, wR
2
w(F
–F
) / w(F
o
.

ARTICLE IN PRESS
1
152
X. Gao et al. / Journal of Solid State Chemistry 183 (2010) 1150–1158
Table 2
Selected bond lengths [ A˚ ] and angles [1] for compounds 1 and 2.
1
Cu(1)–N(3)
Cu(1)–I(1)
Cu(1)–I(2)
Cu(1)–I(3)
N(1)–C(2)
N(1)–C(7)
N(3)–C(1)
N(4)–C(10)
2.043(9)
Cu(2)–I(4)#1
Cu(2)–I(1)#2
Cu(2)–I(1)
Cu(2)–I(2)
N(4)–C(15)
N(6)–C(9)
2.6109(17)
2.6404(16)
2.7016(17)
2.7479(17)
1.44(6)
Cu(3)–N(2)
Cu(3)–I(4)
Cu(3)–I(2)#1
Cu(3)–I(3)
N(2)–N(3)
N(4)–N(5)
N(5)–N(6)
2.066(9)
2.6263(16)
2.6501(18)
2.6677(14)
1.372(14)
1.458(16)
1.376(13)
1.50(6)
2.6130(17)
2.6465(17)
2.7557(16)
1.291(12)
1.44(5)
1.38(6)
C(15)–C(16)
N(1)–N(2)
1.50(5)
1.44(6)
1.366(13)
N(3)–Cu(1)-I(1)
N(3)–Cu(1)-I(2)
I(1)–Cu(1)-I(2)
N(3)–Cu(1)-I(3)
I(1)–Cu(1)-I(3)
I(2)–Cu(1)-I(3)
112.7(3)
101.4(3)
117.90(6)
103.0(3)
107.47(6)
113.38(6)
I(4)#1–Cu(2)–I(1)#2
I(4)#1–Cu(2)–I(1)
I(1)#2–Cu(2)–I(1)
I(4)#1–Cu(2)–I(2)
I(1)#2–Cu(2)–I(2)
I(1)–Cu(2)–I(2)
114.42(6)
112.58(6)
106.40(5)
108.76(6)
102.18(6)
112.09(6)
N(2)–Cu(3)–I(4)
N(2)–Cu(3)–I(2)#1
I(4)–Cu(3)–I(2)#1
N(2)–Cu(3)–I(3)
I(4)–Cu(3)–I(3)
112.4(3)
108.4(3)
111.86(6)
101.5(3)
111.56(6)
110.68(6)
I(2)#1–Cu(3)–I(3)
Symmetry transformations used to generate equivalent atoms: #1—x, y, ꢀz+1/2; #2—x, ꢀy+1, ꢀz.
2
Cu(1)–N(3)
Cu(1)–Br(3)#1
Cu(1)–Br(3)
Cu(1)–Br(4)
Cu(2)–N(2)
Cu(2)–Br(1)
Cu(2)–Br(4)
Cu(2)–Br(2)
1.999(6)
Cu(3)–Br(4)#2
Cu(3)–Br(5)
Cu(3)–Br(3)#3
Cu(3)–Br(2)
K(1)–Br(1)
2.3829(16)
2.3921(16)
2.5745(17)
2.7912(19)
3.183(3)
K(1)–Br(5)#5
C(7)–N(1)
3.553(3)
1.454(9)
1.54(5)
2.4708(14)
2.4926(14)
2.6704(15)
2.035(6)
C(7)–C(11)#2
C(8)–C(9)
1.52(4)
C(9)–C(10)
C(10)–C(11)
1.529(18)
1.51(4)
2.4031(14)
2.5017(15)
2.6510(16)
K(1)–Br(2)#5
K(1)–Br(3)#4
K(1)–Br(4)
3.316(3)
3.5053(14)
3.619(2)
N(3)–Cu(1)–Br(3)#3
N(3)–Cu(1)–Br(3)
Br(3)#3–Cu(1)–Br(3)
N(3)–Cu(1)–Br(4)
Br(3)#3–Cu(1)–Br(4)
Br(3)–Cu(1)–Br(4)
119.54(19)
113.04(19)
110.48(5)
100.62(19)
107.00(5)
104.33(5)
N(2)–Cu(2)–Br(1)
N(2)–Cu(2)–Br(4)
Br(1)–Cu(2)–Br(4)
N(2)–Cu(2)–Br(2)
Br(1)–Cu(2)–Br(2)
Br(4)–Cu(2)–Br(2)
124.11(18)
102.20(18)
113.49(6)
106.52(18)
100.01(5)
110.03(5)
Br(4)#1–Cu(3)–Br(5)
Br(5)–Cu(3)–Br(3)#4
Br(4)#1–Cu(3)–Br(2)
Br(5)–Cu(3)–Br(2)
125.29(7)
104.02(6)
109.13(6)
100.97(6)
101.44(5)
112.97(6)
Br(3)#4–Cu(3)–Br(2)
Br(4)#1–Cu(3)–Br(3)#4
Symmetry transformations used to generate equivalent atoms: #1—x, ꢀy+1/2, z; #2—xꢀ1, y, z; #3—x, ꢀy, ꢀz; #4—x, y+1/2, ꢀz; #5—x+1, y, z.
Scheme 1. Suggested mechanism of the in-situ generation of ETA ligands in 1 under solothermal reaction.
ligand while C
2
H
5
I formed by the nucleophilic substitution
supramolecular structure consisting of 1D anionic organic–
n+
reaction of strong nucleophilic iodine ions and ethanol solvent
under high temperature and autogenous pressure, both of which
react to produce mono-N-alkylated heterocycles simultaneously.
The reactants and in-situ mono-N-ethylbenzotriazole ligand self-
assemble to produce hybrid coordination polymer 1 by the effects
of kinetic and thermodynamic stabilities. The solvothermal
reactions are simultaneous C–N bond rupture, N-alkylated and
self-assembly processes, which is similar to the situation
previously reported by Wu et al. [19] and Yao et al. [41]. When
bromides were used instead of iodides under the same reaction
conditions, we successfully synthesized complex 2, a unique
hybrid solid with BBTH ligands. To the best of our knowledge,
coordination polymers based on the ligand reported here is
exclusive to date.
inorganic hybrid [(Cu
6
I
7
)(ETA)
2
]
n
chains and disordered proto-
nated HETA organic cations. As shown in Fig. 1, there exist three
independent four-coordinated copper centers. The coordination
environment around Cu(1) is completed by three iodine atoms
and one nitrogen atom from ETA ligand, with the distances
˚
˚
Cu(1)–N(3)¼2.043(9) A, Cu(1)–I(1)¼2.6263(16) A, Cu(1)–I(2)¼
˚
˚
2.6501(18) A and Cu(1)–I(3)¼2.6677(14) A, respectively. The
corresponding bond angles around Cu(1) are in the range of
101.4(3)–117.90(6)1. The Cu(2) atom coordinated by four iodine
˚
atoms with the Cu–I bonds are of 2.6109(17)–2.7479(17) A, and
the corresponding bond angles are in the range of 102.18(6)–
114.42(6)1. Just like Cu(1), the residue Cu(3) center is also
tetracoordinated to three iodine atoms and one nitrogen atom
˚
from ETA ligand (Cu(3)–N(2)¼2.066(9) A, Cu(3)–I¼2.6130(17)–
˚
2
1
.7557(16) A). The corresponding bond angles are in the range of
+
01.5(3)–121.4(3)1. As depicted in Fig. 2, three independent Cu
and four I atoms link each other to form a unique vertex missing
ꢀ
3.2. Description of crystal structures
cubane-like [Cu
of 2.683(2)–2.7632(19) A, which are comparable to those found in
the structurally characterized compounds based on [Cu
3 4
I ] subunit. The Cu–Cu distances are in the range
˚
X-ray single-crystal diffraction analysis shows that complex 1
crystallizes in the monoclinic space group C2/c, and shows a
4 4
I ]

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X. Gao et al. / Journal of Solid State Chemistry 183 (2010) 1150–1158
1153
Fig. 1. View of the coordination environments of the copper atoms in compound 1 [Symmetry codes: A,—x, 1–y, –z; B,—x, y, 0.5–z].
Fig. 2. View of the 1D organic–inorganic hybrid chain in compound 1.
cubane-like clusters [24,42–45]. Two [Cu
connected by a joint I(3) atom, forming a [Cu
3
I
4
]
subunits are
] unit, which
BBTH ligand. As shown in Fig. 3, the Cu(1) center is
tetracoordinated to three bromine atoms and one nitrogen atom
6
I
7
˚
further link each other to construct a 1D inorganic chain structure.
It is noted that adjacent [Cu ] motifs take the anti-conformation,
using Cu(2) and I(1) atoms to form a [Cu
distance between diagonal copper atoms is about 3.2 A. Thus, four
independent iodine atoms are of three kinds of bridging modes:
from BBTH ligand, with the distances of Cu–N¼1.999(6) A and
˚
6
I
7
Cu–Br¼2.4708(14)–2.6704(15) A, respectively. The corresponding
2
I
2
] parallelogram and the
˚
bond angles around Cu(1) are in the range of 100.62(19)–
119.54(19)1. The Cu(2) atom also coordinates to three Br atoms
˚
and one N atom from benzotriazole (Cu–N¼2.035(6) A, Cu–Br¼
˚
m
2
–I(4),
m
3
–I(1),
m
3
–I(2) and
m
4
–I(3). To the best of our knowledge,
2.4031(14)–2.6510(16) A, N/Br–Cu–Br¼100.01(5)–124.11(18)1).
nꢀ
this anionic [Cu
6
I
7
]
n
inorganic chain is unprecedented in the
The residue 4-coordinated tetrahedral Cu(3) atom are linked to
four Br atoms with Cu–Br bonds and Br–Cu–Br angles of
chemistry of copper halides. Moreover, the residual coordination
positions of Cu(1) and Cu(3) are occupied by two nitrogen atoms
from the same ETA ligand to form the organic–inorganic hybrid
anionic chain structure of compound 1 (Fig. 2). This linkage
˚
2.3829(16)–2.7912(19) A and 100.97(6)–125.29(7)1. Moreover,
atom, it is common
heptacoordinated to seven bromine atoms. The K–Br bond
with regard to the unique
K
˚
generates [Cu
2
˚
N
2
I] five-membered rings with copper separations
of about 3.56 A, which effectively ‘ease’ the repulsion of metal ions
and is usually found for many triazoles of which the N -position is
chains are packed
interactions (center-to-center distance
lengths are in the range of 3.183(3)–3.619(2) A and the
corresponding bond angles are in the range of 66.99(2)–
157.24(8)1. Two Cu(2) and two Cu(3) centers are firstly linked
by five Br atoms (one Br(1), one Br(2), two Br(4) and one Br(5))
4
n+
substituted [46]. The hybrid [(Cu
via very weak
between benzotriazole rings of about 4.3 A) to give a 3D porous
6
I
7
)(ETA)
2
]
n
ꢀ
p–p
to give a novel bowl-shaped [Cu
4
Br
5
]
anionic motif, which
Br ] units linking
–Br(2) atoms. The bowl size
˚
can also be regarded as four neutral [Cu
2
2
supramolecular framework with channel dimensions of about
each other through sharing one
m
4
2
2
˚
˚
1
2 ꢁ 19 A , which is fully occupied by the disordered HETA
is about 6 ꢁ 5 A and neighbor Cu centers are separated for
˚
2.9413(17)–3.1753(17) A. Moreover, two Cu(1) atoms are
organic cations (Figure S1).
The use of bromides generated complex 2, which crystallizes in
connected by two Br(3) to generate another [Cu
2
Br
]
2
] units with
ꢀ
˚
the monoclinic space group P2
1
/m and contains three indepen-
Cu–Cu distance of 2.8299(15) A. Then, the [Cu
4
Br
5
2 2
and [Cu Br ]
dent copper(I) atoms, one K atom, five bromine anions and half of
subunits link each other via Br(4) and Br(3) atoms to form a

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X. Gao et al. / Journal of Solid State Chemistry 183 (2010) 1150–1158
Fig. 3. View of the coordination environments for compound 2 [Symmetry codes: A—x, 0.5+y, ꢀz; B—1ꢀx, 0.5+y, ꢀz; C—1ꢀx, ꢀy, ꢀz; D—x, ꢀy, ꢀz; E—x, 0.5ꢀy, z;
F—1+x, y, z].
Fig. 4. View of 1D inorganic ribbon structure (left) and 2D hybrid layer (right) in compound 2.
ꢀ
unique 1D [Cu
6
Br
7
]
anionic chain as depicted in Fig. 4 (left). Just
] motifs in compound 1, the
orientation of two adjacent bow-shaped [Cu Br units is
opposite. Furthermore, as shown in Fig. 4 (right), these 1D
inorganic chains are connected by heptacoordinated K atoms to
6 7
like the anti-arrangement of [Cu I
4
5
]
6 7
give a 2D neutral inorganic [KCu Br ] layer. In this layer, five

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X. Gao et al. / Journal of Solid State Chemistry 183 (2010) 1150–1158
1155
independent bromine atoms are of
m
3
(Br(1) and Br(5)),
m
4
(Br(3)
through strong aromatic
benzotriazole rings from adjacent layers, with a center-to-center
p
–
p
stacking interactions between
and Br(4)) and (Br(2)) bridging modes, respectively. Just like
m
5
˚
the 1D organic–inorganic hybrid chain of 1, the unoccupied
benzotriazole N atoms finish the tetrahedral sphere of Cu(1) and
Cu(2) centers using the pyrazole-like bridging mode, which
distance of about 3.6 A.
generates
separations of about 3.33 A. Thus, each BBTH ligand takes the
cisoid-configuration and acts as -bridge to link four copper
atoms as depicted in Figure S2 (a). To the best of our knowledge, it
is the first example that 1,6-Bi(benzotriazole)hexane was utilized
to construct hybrid coordination polymers. The BBTH ligands
a
[Cu
2
N
2
Br] five-membered rings with copper
3.3. XRPD, FT-IR and TG/DTA
˚
m
4
As shown in Figure S3, complexes 1 and 2 were characterized
via X-ray powder diffraction (XRPD) at room temperature. The
XRPD pattern measured for the as-synthesized samples were
basically in consistent with the XRPD patterns simulated from the
respective single-crystal X-ray data using the Mercury 1.4 program,
which indicate the purity of samples 1 and 2. Whats more, on the
basis of the XRPD results it can be established that the single
crystal selected is a representative of the bulk compound.
alternately distribute on the two sides of the inorganic [KCu
layer to give the 2D organic–inorganic hybrid network (Figure S2
b) and (c)) for compound 2. Ultimately, adjacent 2D hybrid layers
was packed to present a 3D hybrid framework as shown in Fig. 5,
6 7
Br ]
(
Fig. 5. View of 3D supramolecular architecture packed through strong aromatic
p
–p
stacking interactions between benzotriazole rings from adjacent hybrid layers for 2.
Fig. 6. Optical absorption spectra for solid samples of 1 and 2.

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X. Gao et al. / Journal of Solid State Chemistry 183 (2010) 1150–1158
Since BBTH ligand has been ruptured during the synthesis
Due to the importance of thermal stability for organic–
inorganic hybrid materials, complexes 1 and 2 were studied by
thermal analysis under an air atmosphere from 40 to 1000 1C
(Figure S5). The weight loss curve of complex 1 shows that it is
stable up to ca. 150 1C. There are two weight loss steps occurred
between 150 and 900 1C. The first weight loss observed between
150 and 330 1C, resulted from the decomposition of ETA ligand
(exptl: 23.7%, calcd: 24.8%). The second weight loss corresponded
to the loss of iodine anions (exptl: 54.2%, calcd: 53.9%). The
weight loss curve of complex 2 shows that it is stable up to ca.
330 1C, over the range 330–400 1C, a sharp weight loss was due to
the decomposition of BBTH (exptl: 25.8%, calcd: 24.6%). In the
temperature range 400–950 1C, a mild weight loss process is
ascribed to the sublimation of CuBr. This conclusion is supported
by the value of the second weight loss (exptl: 69.4%, calcd: 71.4%).
of complex 1, we should only select benzotriazole (BTA)
as the comparison instead of BBTH ligand, when the FT-IR spectra
of hybrid complex 1 was studied (Figure S4 (a)). Three absorption
ꢀ
1
bands at 2973, 1446 and 1380 cm
are attributed to the flex
ꢀ
1
vibration of methyl, while one absorption band at 2925 cm
is attributed to the flex vibration of methylene among
complex 1, which indicates the rupture of the ligand and the
existence of methyl and methylene. Whats more, the framework
vibrations of phenyl and triazole rings are both in the range of
ꢀ
1
ꢀ1
1
200–1600 cm . The difference in the range of 1000–1300 cm
shows that nitrogen atoms of benzotriazole rings have coordi-
nated with copper atoms. The FT-IR spectra of BBTH
ligand and hybrid complex 2 are similar to each other as
shown in Figure S4 (b). Two absorption bands at 2934 and
ꢀ
1
ꢀ1
2
854 cm
(2937 and 2859 cm
for BBTH) are attributed to the
flex vibration of methylene. The framework vibrations of
ꢀ
1
phenyl and triazole rings are in the range of 1200–1600 cm
The slightly difference in the range of 1000–1300 cm
.
3.4. Study of optical band gap
ꢀ
1
shows
that nitrogen atoms of benzotriazole rings have coordinated with
copper atoms.
In order to explore the conductivity of the two compounds 1
and 2, the measurements of diffuse reflectivity for powder crystal
Fig. 7. Solid state (a) and solution (b and c) emission spectra of 1 and 2.

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X. Gao et al. / Journal of Solid State Chemistry 183 (2010) 1150–1158
1157
samples were used to obtain their band gap (E
g
). The band gap
Supplementary material
E
g
was determined as the intersection point between the energy
axis and the line extrapolated from the linear portion of the
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Center (CCDC) (E-mail: deposit@ccdc.ca-
m.ac.uk) as supplementary materials and the CCDC reference
numbers is 750885 for 1 and is 750886 for 2.
absorption edge in a plot of Kubelka–Munk function F against
2
energy E [47,48]. Kubelka–Munk function, F¼(1–R) /2R, was
converted from the recorded diffuse reflectance data, where
R is the reflectance of an infinitely thick layer at a given
wavelength. The F versus E plots for the compounds are shown
Acknowledgment
g
in Fig. 6, and the E values assessed from the steep absorption
edge is 2.37 and 2.57 eV, respectively, which indicate that both
hybrid compounds are potential semiconductor materials. It
should be noted that these band gap sizes are significantly
smaller than that of CuBr and CuI (2.89 eV for CuBr and 2.95 eV for
CuI) (Fig. 6) [49].
This work was supported by the National Natural Science
Foundation of China (grant Nos. 20801033 and 20871079), the
Natural Science Foundation of Shaanxi Province (2009JQ2003),
the Youth Foundation of School of Chemistry and Materials
Science, and the Innovation Funds of Graduate Programs, Shaanxi
Normal University.
3.5. Photoluminescence properties
It is well know that the copper(I) halide complexes with both
Appendix A. Supplementary data
discrete and multi-dimensional structure show excellent lumi-
nescence properties [50–55]. Thus, we reported herein the
photoluminescence of the two compounds in the solid state
under room temperature. To understand more thoroughly the
nature of these emission bands, the luminescence of BBTH was
also investigated. The intraligand emission of the free BBTH was
observed at 442 nm along with a shoulder band at 420 nm
The online version of this article contains additional supple-
mentary data. Please visit doi:10.1016/j.jssc.2010.03.007
References
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