Synthesis, characterization and crystal structures of supramolecular complexes of copper(II)(2,2′-biimidazole) induced by inorganic counter anions

Article abstract of DOI:10.1016/j.poly.2009.05.052

Four new complexes [Cu(H₂biim)₂(H₂O)](NO₃) ₂ (1), [Cu(H₂biim)₂](ClO₄)₂· 2DMSO (2), [Cu(H₂biim)₂] [I_0.36·(NO₃)_0.64]₂ (3) and {[Cu(H₂biim)₂(H₂O)](SiF₆)} ·H₂O (4) (H₂biim = 2,2′-biimdazole, DMSO = dimethyl sulfoxide) have been synthesized and characterized by X-ray diffraction. The different inorganic anions NO₃^-, ClO₄^-, [I_0.36·(NO₃)_0.64]^- and SiF₆^{2 -} in these complexes lead to different 3D structures. Among them, complex 3 has an interesting 3D porous structure with two [I_0.36·(NO₃)_0.64]^- ions as guests in the cavity. Compound 4 was obtained by the reaction of Cu(BF₄)₂ with H₂biim in water in glass bottle. The robust hydrogen bond of typeV R₂¹(7) played a key role in the formation of SiF₆^{2 -} in complex 4.

Full text of DOI:10.1016/j.poly.2009.05.052

Polyhedron 29 (2010) 317–327
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, characterization and crystal structures of supramolecular complexes
of copper(II)(2,20-biimidazole) induced by inorganic counter anions
a
a
a
b
a,
Qiong-Hua Jin a, , Li-Li Zhou , Li-Jun Xu , Yuan-Yuan Zhang , Cun-Lin Zhang , Xiao-Ming Lu
*
*
a Department of Chemistry, Capital Normal University, Beijing 100048, PR China
b Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics,
Capital Normal University, Beijing 100048, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 31 May 2009
Four new complexes [Cu(H2biim)2(H2O)](NO3)2 (1), [Cu(H2biim)2](ClO4)2ꢀ2DMSO (2), [Cu(H2biim)2]
[I0.36ꢀ(NO3)0.64
]
(3) and {[Cu(H2biim)2(H2O)](SiF6)}ꢀH2O (4) (H2biim = 2,20-biimdazole, DMSO = dimethyl
2
sulfoxide) have been synthesized and characterized by X-ray diffraction. The different inorganic anions
NO3ꢁ, ClO4ꢁ, [I0.36ꢀ(NO3)0.64
]
ꢁ and SiF6 in these complexes lead to different 3D structures. Among them,
2ꢁ
Keywords:
complex 3 has an interesting 3D porous structure with two [I0.36ꢀ(NO3)0.64
]
ꢁ ions as guests in the cavity.
Supramolecular complexes
Copper complexes
Biimidazole
Compound 4 was obtained by the reaction of Cu(BF4)2 with H2biim in water in glass bottle. The robust
hydrogen bond of typeV R21(7) played a key role in the formation of SiF6 in complex 4.
2ꢁ
Crystal structures
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
[Cu(H2biim)2(H2O)](NO3)2 (1), [Cu(H2biim)2] (ClO4)2ꢀ2DMSO (2),
[Cu(H2biim)2] [I0.36ꢀ(NO3)0.64 2 (3), {[Cu(H2biim)2(H2O)](SiF6)}ꢀH2O
]
Supramolecular polymers have received much attention due to
their structural diversities and potential applications as new mate-
rials. The assembly of supramolecular complexes depends on many
factors such as the nature of the metal, ligand, counterion and sol-
vent. The consideration and utilization of the coordination bonds of
(4). These four complexes have different 3D structures, due to
the diverse type of robust hydrogen bonds, such as type I, II,V
R21(7) and type III, IV R22(9), formed by different inorganic anions
with H2biim and solvent molecules. Among them, complexꢁ3 has
an interesting 3D porous structure with two [I0.36ꢀ(NO3)0.64
] ions
a transition metal ion, intermolecular hydrogen bonds and
p–p
as guests in the cavity. Thanks to this special structure, it has the
potential application as the supramolecular material. In complex
packing interactions also help to control the molecular arrange-
ment [1–4]. 2,20-Biimidazole(H2biim) is an excellent candidate
for building a supramolecular structure involving directed hydro-
gen bonding interactions. H2biim exists in the reported compounds
in multifold forms, such as (1) neutral ligand H2biim [3]; (2) anion
ligand Hbiimꢁ [5,6]; (3) biim2ꢁ [7]; (4) cation H3biim+ [8] and (5)
H4biim2+ [9] (Scheme 1). The uncoordinated N–H groups in H2biim
and its ions participate in various hydrogen bonds with counter an-
ions or other acceptors. Hydrogen bond is regarded as robust
power in the construction of supramolecular polymers. Hydrogen
bond also provides useful information to understand the compli-
cated process in biological systems [10].
Recently, the authors in [6] discuss the role of counter anions in
crystal packing of Ag–H2biim complexes. A few Cu–H2biim com-
plexes containing inorganic anions, such as [Cu(H2biim)2(H2O)]-
SO4ꢀ3H2O [3], [Cu(H2biim)2]Cl2 [11] and [Cu(H2biim)2]Br2 [12]
have been reported, but the role of counter anions has not been
studied fully. Here we report the synthesis and characterization
of four new Cu(II)–H2biim complexes with inorganic counter ions,
2ꢁ
4, the unexpected anion SiF6 was not directly coming from the
2ꢁ
starting materials, just like SiF6
in [Cd(H2biim)3]2SiF6(BF4)2ꢀ
2ꢁ
6EtOH [13] and I2SO2 in [Pt(depe)2]I2SO2 [14].
2. Experimental
2.1. Materials and measurements
All chemicals were obtained from commercial sources and used
without further purification. Elemental analyses (C, H, N) were per-
formed on a Vario EL analyzer. Infrared spectra were recorded on a
Brucker EQUINOX 55 FT-IR spectrometer photometer as KBr pellets
in the 4000–400 cmꢁ1. Thermal analyses were formed on a Netzsch
STA 449C instrument, with a heating rate of 10 °C/min in nitrogen.
2.2. Synthesis of complexes 1–4
2.2.1. [Cu(H2biim)2(H2O)](NO3)2 (1)
A mixture of Cu(NO3)2ꢀ3H2O (0.2416 g, 1 mmol) and H2biim
(0.2680 g, 2 mmol) in water (30 ml) was refluxed for 3 h and a clear
solution was obtained. The mixture was concentrated under
* Corresponding authors.
E-mail address: jinqh@mail.cnu.edu.cn (Q.-H. Jin).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.05.052

318
Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
2.2.3. [Cu(H2biim)2] [I0.36ꢀ(NO3)0.64 2
] (3)
A
mixture of Cu(NO3)2ꢀ4H2O (0.3080 g, 1 mmol) and KI
(0.1660 g, 1 mmol) in water (10 ml) was stirred for 30 min and
H2biim (0.2680 g, 2 mmol) was added to the mixture which was
refluxed for 1 h. The resulting solution was filtered and allowed
to evaporate slowly at room temperature. After one week, dark
green crystals were formed. Anal. Calc. for C12H12 0.72N9.30O3.84Cu:
I
C, 28.62; H, 2.38; N, 25.88 Found: 28.62; H, 2.41; N, 25.88%. IR
(KBr disc, v/cmꢁ1): 3128s, 1636w, 1528s, 1416s, 1385vs, 1339s,
1301s, 1178s, 1136s, 1099s, 1051m, 1004m, 939w, 870w, 821w,
770s, 714w, 685s, 507m, 445m.
2.2.4. {[Cu(H2biim)2(H2O)](SiF6)}ꢀH2O (4)
Cu(BF4)2ꢀ6H2O (0.1186 g, 0.5 mmol) was dissolved in 30 ml of
water and H2biim (0.1340 g, 1 mmol) was added to the resulting
solution. The mixture was refluxed for 6 h and a clear solution
was obtained. The mixture was concentrated under vacuum to
a volume of 20 ml. The resulting solution was filtered and the fil-
trate was left in air to evaporate to form crystals of 4 after two
Scheme 1.
ꢁ
vacuum to a volume of 10 ml. The resulting solution was filtered
and allowed to evaporate slowly at room temperature. After three
days, dark green crystals were formed. Anal. Calc. for C12H14N10O7Cu:
C, 30.50; H, 3.14; N, 29.71. Found: C, 30.38; H, 2.95; N, 29.54%. IR
(KBr disc, v/cmꢁ1): 3445m, 3122s, 2996s, 2760w, 2456w, 1764w,
1620w, 1525s, 1385s, 1324s, 1250w, 1179s, 1134s, 1095s,
1003m, 940w, 915w, 803m, 763s, 682s, 507w, 446w.
months. The BF4 ions reacted with the glass container and
2ꢁ
formed SiF6 species, which crystallized with the Cu compound
as observed by X-ray analysis. Anal. Calc. for C12H16F6N8O2SiCu:
C, 28.24; H, 3.14; N, 21.96. Found: C, 28.61; H, 3.26; N, 21.68%.
IR (KBr disc; v/cmꢁ1): 3494m, 3421m, 3278s, 3167m, 3148m,
1676w, 1634w, 1528s, 1429s, 1385m, 1324w, 1249w, 1178m,
1134m, 1115w, 1098s, 1002w, 850w, 832w, 751vs, 684s, 651w,
505w, 474s, 443m.
2.2.2. [Cu(H2biim)2](ClO4)2ꢀ2DMSO (2)
A mixture of Cu(ClO4)2ꢀ6H2O (0.3705 g, 1 mmol) and H2biim
(0.2680 g, 2 mmol) in EtOH (30 ml) was refluxed for 6 h and the
green colored precipitated product was obtained. The precipitate
was dissolved in solution of EtOH/DMSO with the volume ratio
of 1:1 (10/10 ml). The resulting solution was filtered and allowed
to evaporate in a refrigerator. After a week, green crystals were
formed. Anal. Calc. for C16H24N8O10S2Cl2Cu: C, 28.05; H, 3.55; N,
16.40. Found: C, 27.95; H, 3.49; N, 3.49%. IR (KBr disc, v/cmꢁ1):
3431m, 3123s, 2998s, 2761w, 1630w, 1527m, 1429m, 1324m,
1179s, 1120s, 1093s, 1019w, 999w, 947w, 854w, 764s, 682, 627s,
446w.
2.3. Crystal structure determination and refinement
Crystals of 1–4 suitable for single-crystal X-ray diffraction were
mounted on a Bruker SMART diffractometer equipped with a CCD
area detector with graphite monochromator situated in the inci-
dent beam for data collection. The determination of unit cell
parameters and data collections were performed with Mo Ka radi-
ation (k = 0.71073 Å). All data were corrected by the semi-empiri-
cal method using the SADABS program. The program SAINT [15] was
used for integration of the diffraction profiles.
Table 1
Crystallographic data for complexes 1–4.
Complex
1
2
3
4
Formula
Mr
C12H14N10O7Cu
473.87
C16H24N8O10S2Cl2
Cu
C12H12I0.72N9.30O3.84
u
C
C12H16N8O2SiF6Cu
509.96
Temperature (K)
Crystal system
Space group
Crystal size (mm)
a (Å)
273(2)
monoclinic
Cc
0.12 ꢂ 0.10 ꢂ 0.06
19.6043(18)
6.8193(6)
14.2812(13)
90
113.5410(10)
90
1750.3(3)
4
1.798
25.04
686.99
triclinic
P1
502.86
monoclinic
P2(1)/c
0.43 ꢂ 0.32 ꢂ 0.18
13.7856(13)
6.8603(8)
18.7785(19)
90
107.286(2)
90
1695.7(3)
4
1.970
25.01
298(2)
monoclinic
P2(1)/c
0.23 ꢂ 0.20 ꢂ 0.12
10.5177(11)
9.6204(9)
17.971(2)
90
95.1750(10)
90
1811.0(3)
4
1.870
25.01
0.42 ꢂ 0.39 ꢂ 0.17
7.1160(10)
10.2731(13)
10.3289(15)
113.464(2)
97.1830(10)
91.5360(10)
684.77(16)
1
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
h Range (°)
1.666
25.00
F(0 0 0)
964
351
988
1028
Data/restraint/parameters
Reflections collected
Independent reflections
Goodness-of-fit on F2
Rint
1551/1/141
4407
1551
1.125
0.0191
2372/0/208
3569
2372
1.078
0.0118
26.41
8110
2995
1.044
3194/0/272
8825
3194
1.072
0.0263
0.0376
R1[I > 2
r(I)]
0.0264
0.0334
0.0323
0.0275
wR2[I > 2
r
(I)]
0.0655
0.0876
0.0765
0.0611
R1 (all data)
0.0294
0.0419
0.0462
0.0409
wR2 (all data)
0.0670
0.257, ꢁ0.321
0.0960
0.416, ꢁ0.351
0.0833
0.489, ꢁ0.367
0.0684
0.263, ꢁ0.281
Residuals (e Åꢁ3
)

Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
319
Table 2
Selected bond length (Å) and angles (°) for 1–4.
Complex 1
Cu(1)–N(3)
Cu(1)–N(1)#1
N(3)–Cu(1)–N(1)
N(3)#1–Cu(1)–N(1)#1
N(3)#1–Cu(1)–O(4)
1.9994(17)
2.0306(18)
82.23(7)
82.23(7)
90.76(6)
Cu(1)–N(3)#1
Cu(1)–O(4)
N(3)#1–Cu(1)–N(1)
N(1)–Cu(1)–N(1)#1
N(1)–Cu(1)–O(4)
1.9994(17)
2.207(3)
97.39(7)
151.05(11)
104.47(6)
Cu(1)–N(1)
2.0306(18)
178.49(11)
97.39(7)
90.76(6)
104.47(6)
N(3)–Cu(1)–N(3)#1
N(3)–Cu(1)–N(1)#1
N(3)–Cu(1)–O(4)
N(1)#1–Cu(1)–O(4)
Complex 2
Cu(1)–N(1)
N(3)–Cu(1)–N(1)#1
Cl(1)-O(1)
2.021(2)
82.23(9)
1.410(3)
Cu(1)–N(3)
N(3)#1–Cu(1)–N(3)
O(30)–Cl(1)–O(2)
2.018(2)
80.00(9)
52.6(15)
N(3)–Cu(1)–N(1)
N(1)#1–Cu(1)–N(1)
O(30)–Cl(1)–O(20)
97.77(9)
180.00(11)
114(2)
Complex 3
Cu(1)–N(1)
2.000(3)
Cu(1)–N(7)
2.004(3)
Cu(1)–N(3)
2.006(3)
Cu(1)–N(5)
N(7)–Cu(1)–N(3)
N(3)–Cu(1)–N(5)
2.012(3)
178.01(13)
97.89(12)
N(1)–Cu(1)–N(7)
N(1)–Cu(1)–N(5)
98.56(12)
166.17(13)
N(1)–Cu(1)–N(3)
N(7)–Cu(1)–N(5)
82.14(11)
81.88(12)
Complex 4
Cu(1)–N(5)
Cu(1)–N(1)
N(5)–Cu(1)–N(3)
N(7)–Cu(1)–N(1)
N(7)–Cu(1)–O(1)
2.012(2)
2.028(2)
97.13(8)
97.32(8)
95.49(7)
Cu(1)–N(7)
Cu(1)–O(1)
N(7)–Cu(1)–N(3)
N(3)–Cu(1)–N(1)
N(3)–Cu(1)–O(1)
2.023(2)
2.2304(18)
167.78(8)
81.53(8)
96.73(8)
Cu(1)–N(3)
2.025(2)
81.66(8)
169.03(9)
94.87(8)
96.10(8)
N(5)–Cu(1)–N(7)
N(5)–Cu(1)–N(1)
N(5)–Cu(1)––O(1)
N(1)–Cu(1)–O(1)
All structures were solved by direct methods using the SHELXS
program of the SHELXTL-97 package and refined with SHELXL [16].
Metal atom centers were located from the E-maps and other
non-hydrogen atoms were located in successive difference Fourier
syntheses. The final refinements were performed by full matrix
least-squares methods with anisotropic thermal parameters for
non-hydrogen atoms on F2. All the hydrogen atoms were first
found in difference electron density maps, and then placed in the
Table 3
Hydrogen bonding interactions (Å) and angles (°) for complexes 1–4.
D–H
d(D–H)
d(Hꢀ ꢀ ꢀA)
\DHA
d(Dꢀ ꢀ ꢀA)
A
Symmetry
Complex 1
N(2)–H(7)
N(2)–H(7)
N(4)–H(8)
N(4)–H(8)
O(4)–H(4)
O(4)–H(4)
O(4)–H(4)
0.860
0.860
0.860
0.860
0.8499(11)
0.8499(11)
0.8499(11)
2.03
2.64
2.06
2.52
1.926(6)
2.55(3)
2.600(15)
147.1
127.8
146.0
124.7
170(3)
126(3)
153(3)
2.788(3)
3.2354(18)
2.816(3)
3.096(3)
2.767(2)
3.126(2)
3.381(2)
O(3)#2
O(4)#3
O(3)#2
O(2)#4
O(1)#5
O(3)#5
N(9)#5
[ꢁx + 1, y, ꢁz + 3/2]
[x, ꢁy + 1, z ꢁ 1/2]
[ꢁx + 1, ꢁy + 2, ꢁz + 1]
[ꢁx + 3/2, y + 1/2, ꢁz + 3/2]
[ꢁx + 1, y + 1, ꢁz + 3/2]
Complex 2
N2–H2
N2–H2
0.860
0.860
2.356
2.410
129.86
142.55
2.981
3.137
O1
O5
[x, y, zꢁ1]
[ꢁx + 1, ꢁy + 1, ꢁz]
Complex 3
N2–H2
N2–H2
N4–H4
N4–H4
N4–H4
N4–H4
N6–H6
N6–H6
N6–H6
N8–H8
N8–H8
N8–H8
N8–H8
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.860
2.189
2.857
2.020
2.437
2.630
2.630
2.255
2.615
2.834
2.179
2.447
2.657
2.657
139.04
154.11
173.98
129.62
156.86
156.86
147.25
112.53
155.77
153.64
142.45
162.23
162.23
2.894
3.650
2.876
3.058
3.437
3.437
3.015
3.050
3.635
2.974
3.173
3.486
3.486
O5_b
I2_a
O6_b
O5_b
I2_a
N10_b
O1_b
O4_b
I1_a
O3_b
O1_b
N9_b
I1_a
[ꢁx, ꢁy + 1, ꢁz + 1]
[ꢁx, ꢁy + 1, ꢁz + 1]
[ꢁx, ꢁy + 1, ꢁz + 1]
[ꢁx, ꢁy + 1, ꢁz + 1]
[ꢁx, ꢁy + 1, ꢁz + 1]
[ꢁx, ꢁy + 1, ꢁz + 1]
[ꢁx + 1, y + 1/2, ꢁz + 3/2]
[ꢁx + 1, y + 1/2, ꢁz + 3/2]
[ꢁx + 1, y + 1/2, ꢁz + 3/2]
[ꢁx + 1, y + 1/2, ꢁz + 3/2]
[ꢁx + 1, y + 1/2, ꢁz + 3/2]
[ꢁx + 1, y + 1/2, ꢁz + 3/2]
[ꢁx + 1, y + 1/2, ꢁz + 3/2]
Complex 4
N2–H2
N2–H2
N4–H4
N4–H4
N6–H6
N6–H6
N8–H8
N8–H8
O1–H1A
O1–H1B
O2–H2A
O2–H2A
O2–H2B
O2–H2B
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.860
0.850
0.850
0.850
0.850
0.850
0.850
2.047
2.167
1.996
2.462
2.108
2.335
2.193
2.305
1.905
2.030
1.988
2.519
2.132
2.348
144.68
147.03
145.37
128.67
135.69
122.22
130.77
143.56
172.45
172.62
173.68
114.39
145.06
133.04
2.793
2.926
2.747
3.074
2.789
2.887
2.831
3.040
2.749
2.875
2.834
2.972
2.870
2.993
F2
F3
F2
O2
F6
F5
F6
O1
F3
O2
F1
F6
F5
F2
[ꢁx + 1, ꢁy + 1, ꢁz + 1]
[ꢁx + 1, ꢁy + 1, ꢁz + 1]
[ꢁx + 1, ꢁy + 1, ꢁz + 1]
[x, ꢁy + 3/2, z + 1/2]
[ꢁx + 2, y + 1/2, ꢁz + 1/2]
[ꢁx + 2, ꢁy + 1, ꢁz + 1]
[x, ꢁy + 3/2, z + 1/2]
[ꢁx + 1, ꢁy + 1, ꢁz + 1]
[x ꢁ 1, y, z]
[x ꢁ 1, y, z]
[ꢁx + 1, y + 1/2, ꢁz + 1/2]
[ꢁx + 1, y + 1/2, ꢁz + 1/2]

320
Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
calculated sites and included in the final refinement in the riding
model approximation with displacement parameters derived from
the parent atoms to which they were bonded. Further crystallo-
graphic data and experimental details for the structural analyses
of all complexes are summarized in Table 1, and selected bond
lengths and angles with their estimated standard deviations and
the hydrogen bonds for complexes 1–4 are summarized in Tables
2 and 3, respectively.
mixed solvent DMSO and EtOH. When CuNO3 and KI were used
in the presence of 2 equiv. of H2biim in water, compound 3 was
isolated. When Cu(BF4)2 was treated with 2 equiv. of H2biim in
water, interestingly, compound 4 including unexpected anion
2ꢁ
SiF6 was obtained after two months of evaporation. We agree
2ꢁ
with the literature [13] that the anion SiF6 was generated by
ꢁ
the reaction of BF4 with the glass container. The long time of
ꢁ
crystals growing was also important for all BF4 to be changed to
ꢁ
2ꢁ
SiF62ꢁ, while BF4 and SiF6 coexist in [Cd(H2biim)3]2- SiF6(BF4)2ꢀ
6EtOH.
3. Results and discussion
3.2. Crystal structures of the complexes
3.1. Synthesis of the complexes
3.2.1. [Cu(H2biim)2(H2O)](NO3)2 (1)
The synthesis reactions of preparing complexes 1–4 are sum-
marized in Scheme 2. To obtain the four compounds, it was impor-
tant to take into account the ratio of starting materials, the nature
of the solvent and the counter anions. The reaction of CuNO3 with 2
equiv. of H2biim in water gave rise to complex 1. Complex 2 could
be prepared by the reaction of CuClO4 with 2 equiv. of H2biim in
EtOH, its crystals were obtained by recrystallization from the
The crystal structure of complex 1 indicates that the unit cell
consists of one [Cu(H2biim)2(H2O)]2+ cation and two NO3 anions.
ꢁ
The structure of the cation [Cu(H2biim)2(H2O)]2+ in 1 is similar to
that in [Cu(H2biim)2(H2O)]SO4ꢀ3H2O [3] and 4 (Fig 4a). The coordi-
nation environment around CuII can be described as a distorted
square pyramidal geometry. Four nitrogen atoms of two chelating
Scheme 2.
Scheme 3.
Fig. 1a. 1D zigzag chains of 1 along a-axis.

Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
321
H2biim ligands form the basal plane of the pyramidal, and the
metal deviates from this plane by 0.267 Å. These two H2biim
molecules are not coplanar with the dihedral angle of 29.16°, and
the two imidazole rings are close to coplanarity with the dihedral
angle of 7.63°. In the cation species, the Cu–N bond distances
[Cu1–N3 = 1.9994(17) Å, Cu1–N1 = 2.0306(18) Å] are shorter than
the Cu–O distance [2.207(3) Å], which agree with the bond lengths
of Cu–N and Cu–O in [Cu(H2biim)2(H2O)]SO4ꢀ3H2O[3], respectively.
The molecules [Cu(H2biim)2(H2O)](NO3)2 form infinite 1D zig-
zag chains along the a-axis through hydrogen bonds involving
the N–H groups of H2biim ligands, water molecules and all the
of [Cu(H2biim)2]2+ in 2 is similar to that in 3 (Fig. 3a). The metal
center allows the formation of a distorted square-planar with four
nitrogen atoms of two chelating H2biim ligands. The Cu–N bond
distances [Cu–N1 = 2.021(2) and Cu–N3 = 2.018(2) Å] are similar
to those in the compound of [Cu(H2biim)2]Cl2 [10][Cu–N11 =
2.010(2), Cu–N31 = 2.036(2) Å]. These distances are observed for
H2biim–Cu complexes retrieved from the CSD [17]. The bite angle
[N(3)#1–Cu(1)–N(3) = 80.00(9)°] generated by the chelating
H2biim is in the range registered in the CSD so far (N–Cu–N:
78.6–81.4°).
Packing is controlled to a great extent by the ability of coordi-
ꢁ
NO3 anions. Each nitrate anion forms robust hydrogen bond of
nated H2biim to form hydrogen bonds with counter ions and
R21(7) (Scheme 3) (Nꢀ ꢀ ꢀO = 2.788(3) and 2.816(3) Å,
solvent molecules. As shown in Fig. 2a, where all anions ClO4
ꢁ
type
I
N–Hꢀ ꢀ ꢀO = 146.0° and 147.1°) with each H2biim ligand. Each nitrate
anion further accepts a hydrogen bond from a coordinated water
molecule, with a short O4ꢀ ꢀ ꢀO1 separation of 2.767(2) Å and
O4–H4ꢀ ꢀ ꢀO1 segment close to linearity (170(3)°). Two adjacent
[Cu(H2biim)2(H2O)](NO3)2 units are further connected to each
other via the hydrogen bonds of O4–H4ꢀ ꢀ ꢀO1 resulting in a 1D
zigzag chains along the a-axis (Fig. 1a). A similar pattern is found
locally in the complex [Zn(H2biim)2(H2O)](NO3)2 [3]. The extensive
are omitted for clarity, the packing of the units [Cu(H2biim)2]2+ is
an infinite step-like chain along b-axis. Two DMSO molecules and
ꢁ
two ClO4 anions are located at two sides of the cation, the hydro-
gen bonds are formed between the N–H donors of H2biim and the
oxygen atoms from DMSO or ClO4ꢁ. The uncoordinated perchlorate
oxygen O1 acts as an acceptor for one of the N–H groups of a
H2biim ligand with N2ꢀ ꢀ ꢀO1 distance 2.981 Å and N2–H2ꢀ ꢀ ꢀO1
angle 129.86°. The other connection involves the oxygen of DMSO
molecule with both the N–H groups (N2ꢀ ꢀ ꢀO5 = 3.137 N2–
H2ꢀ ꢀ ꢀO5 = 142.55°, N4ꢀ ꢀ ꢀO5 = 2.757, N4–H4ꢀ ꢀ ꢀO5 = 154.16°). There
hydrogen bonds and p–p interactions between the infinite chains
are responsible for the supramolecular open framework structure
of 1 along the crystallographic b-axis, as depicted in Fig. 1b.
are two weak contacts which further stabilize the complex, one
ꢁ
is Cuꢀ ꢀ ꢀS (DMSO) (3.448 Å), the other is Cuꢀ ꢀ ꢀO(SiF62ꢁClO4
)
3.2.2. [Cu(H2biim)2](ClO4)2ꢀ2DMSO (2)
(2.700 Å). These chains are further assembled into a 3D framework
The asymmetric unit of complex 2 consists of one [Cu(H2biim)2]2+
by mutilple hydrogen bonds, weak interactions and
tions between H2biim ligands (Fig. 2b).
p–p interac-
ꢁ
cation, two ClO4 anions, and two DMSO molecules. The structure
Fig. 1b. Supramolecular framework structure of 1 along b-axis.

322
Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
3.2.3. [Cu(H2biim)2] [I0.36ꢀ(NO3)0.64 2
]
(3)
[Cu(1)–N(1) = 2.000(3), Cu(1)–N(7) = 2.004(3), Cu(1)–N(3) = 2.006(3)
and Cu(1)–N(5) = 2.012(3) Å] are similar to those in complex 2.
The bite angle [N(7)–Cu(1)–N(5) = 81.88(12)°] generated by the
Complex 3 ꢁconsists of one [Cu(H2biim)2]2+ cation and two
[I0.36ꢀ(NO3)0.64
]
anions (Fig. 3a). The Cu–N bond distances
Fig. 2a. Step-like chain of [Cu(H2biim)2] (ClO4)2ꢀ2DMSO unit along the b-axis. All ClOꢁ were omitted for clarity.
4

Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
323
Fig. 2b. Packing along b-axis. All O atoms in ClOꢁ4 were disordered.
Fig. 3a. ORTEP drawing of [Cu(H2biim)2] [I0.36ꢀ(NO3)0.64
] (3).
2

324
Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
chelating of the H2biim is found in the upper limit of the range
registered in the CSD so far (N–Cu–N: 78.6–81.4°) [17]. In
[I0.36ꢀ(NO3)0.64]ꢁ, Iꢁ ion and N atom locate in the same position
(occupied 36% by Iꢁ and 64% by NO3ꢁ), which can be seen from
assisted hydrogen bonds N–Hꢀ ꢀ ꢀI, N–Hꢀ ꢀ ꢀN, N–Hꢀ ꢀ ꢀO as well as
two types of weak interactions Oꢀ ꢀ ꢀCu (2.772 Å) and Iꢀ ꢀ ꢀCu
(3.190 Å) to form a zigzag chain along a-axis (Fig 3b). Four types
of robust hydrogen bond synthons, namely type I, II R21(7), type
III, IV R22(9) (Scheme 3) are found in complex 3. The type II
R21(7) synthon is formed by the the Iꢁ ion with N–H groups of
H2biim, and the type IV R22(9) synthon might be formed through
the induction of the type II R21(7) synthon. To our knowledge,
the hydrogen bond of type IV R22(9) has not been reported before.
The adjacent chains are interlinked by multiple hydrogen bonds
the fact that N(H2biim)ꢀꢀꢀN(NO3ꢁ) and N(H2biim)ꢀ ꢀ ꢀI have the same
distances, and Iꢁ ion does not connect with any O atoms of NO3
.
ꢁ
Each building unit [Cu(H2biim)2]2+ in complex 3 links with O
atoms, N atoms and Iꢁ anions of [I0.36ꢀ(NO3)0.64
]
via charge-
ꢁ
and
p–p interactions between H2biim ligands to form the 3D
porous framework along b-axis (Fig. 3c). Each cavity is of the scale
ꢁ
4.2 ꢂ 13.2 Å with two clathrate [I0.36ꢀ(NO3)0.64
]
inside. This inter-
esting structure makes the complex possess potential application
as the supramolecular material.
3.2.4. {[Cu(H2biim)2(H2O)] SiF6}ꢀH2O (4)
Complex 4 consists of a [Cu(H2biim)2(H2O)]2+ cation, a SiF6
2ꢁ
anion and one lattice-water molecule (Fig. 4a). The coordination
environment of CuII ion in 4 is very similar to that of complex 1.
The CuII ion is displaced from the [Cu(H2biim)2]2+ plane by
0.204 Å. The dihedral angle of the two chelating H2biim ligands
is 12.29°, while the two imidazole rings are close to coplanarity
with the dihedral angle of 2.61°. The Cu–N bond distances are in
2ꢁ
the range of 2.012(2)–2.028(2) Å. Unlike the SiF6
in
[Cd(H2biim)3]2SiF6(BF4)2ꢀ6EtOH [13], where all the six Si–F bond
2ꢁ
distances are equal, the anion SiF6
in 4 has different Si–F
distances which are in the range of 1.6621(18)–1.7087(17) Å.
Each building block [Cu(H2biim)2(H2O)]2+ is connected to two
2ꢁ
2ꢁ
SiF6 anions and each SiF6 is connected with two [Cu(H2biim)2
(H2O)]2+ cations via hydrogen bonds of type R21(7) and
step-like infinite chain along c-axis
V
O1–H1Aꢀ ꢀ ꢀF3 to form
a
(Fig. 4b). In the chain, all the aqua ligands are arranged in the same
direction (either above or below the [Cu(H2biim)2]2+ plane). The
chains are further assembled in a head-to-head or a tail-to-tail fash-
ion by N8–H8ꢀ ꢀ ꢀO1 hydrogen bonds which are constructed by the
2ꢁ
coordinated water and the N–H group of H2biim. The SiF6 anions
are also connected with lattice water molecules through hydrogen
bonds O2–H2Aꢀ ꢀ ꢀF1, O2–H2Bꢀ ꢀ ꢀF5 and O2–H2Bꢀ ꢀ ꢀF2. The hydrogen
bonds formed by SiF62ꢁ with other acceptors in 4 are different from
those in [Cd(H2biim)3]2SiF6(BF4)2ꢀ6EtOH [11]. The coordinated
water molecule in [Cu(H2biim)2(H2O)]2+ is connected with
lattice water through hydrogen bond O1–H1Bꢀ ꢀ ꢀO2. The cation
[Cu(H2biim)2(H2O)]2+
,
the anion SiF6
and lattice water are
2ꢁ
connected by multiple hydrogen bonds as well as p–p interactions
between H2biim and H2biim to form a 3D framework (Fig. 4c).
3.3. Discussion of the structures and the strange change of anions
In complexes 1–4, all the inorganic counter anions NO3ꢁ, ClO4
ꢁ
,
ꢁ
2ꢁ
[I0.36ꢀ(NO3)0.64
]
and SiF6
are uncoordinated. Different anions
induce the cation building blocks to form different 3D structures
because of their different charge, size and ability of forming
ꢁ
hydrogen bond with other acceptors. In 1, NO3 induces the
molecule to form an infinite line along the a-axis and then further
ꢁ
form a 3D framework. In 2, ClO4 and DMSO induce the molecule
to form an infinite step-like chain along b-axis, and further form a
ꢁ
3D structure. The anions NO3ꢁ, ClO4 are directly coming from the
starting mateꢁrials Cu(NO3)2 and Cu(ClO4)2. For
3 and 4,
are obtained by unusual change of
2ꢁ
[I0.36ꢀ(NO3)0.64
]
and SiF6
inorganic anions, which will be discussed in the following.
ꢁ
In 3, the existence of unexpected [I0.36ꢀ(NO3)0.64
]
might be
attributed to robust hydrogen bonds of type I–IV and the weak
interaction Iꢀ ꢀ ꢀCu, which is similar to the weak interaction Brꢀ ꢀ ꢀCu
in [Cu(H2biim)2] Br2 [12] and the weak interaction Iꢀ ꢀ ꢀS in [Pt
ꢁ
Fig. 3b. 1D zigzag chains of 3 along a-axis.
(depe)2] I2SO2 [14]. [I0.36ꢀ(NO3)0.64
]
helps compound 3 to form

Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
325
ꢁ
Fig. 3c. Hydrogen-bonded porous structure of 3 along b-axis with two [I0.36ꢀ(NO3)0.64
] as guest in the cavity.
Fig. 4a. ORTEP drawing of {[Cu(H2biim)2(H2O)] SiF6}ꢀH2O (4).
ꢁ
an infinite chain along a-axis resulting in an interesting 3D
porous structure. The porous structure does not appear in 1,
was reported that hydrogen bonds between the F atom of BF4
and the N–H group of H2biim with the unfavorable angle N–HꢀꢀꢀF
(about 120°) cannot directly affect the crystal stability [13].
We suppose that the reaction mechanism of generating
[Cu(H2biim)2]Cl2 and [Cu(H2biim)2]Br2.
2ꢁ
In 4, the appearance of SiF6
should be due to the robust
ꢁ
2ꢁ
hydrogen bonds of type V and hydrogen bond O–H(H2O)ꢀ ꢀ ꢀF. The
[I0.36ꢀ(NO3)0.64
] and SiF6 related to the fact that Cu(II) bonded-
H2biim plays a role of catalyst and the catalyst property might be
attribute to the hydrogen bonds.
anion SiF6 can induce [Cu(H2biim)2(H2O)]2+ to form a step-like
2ꢁ
infinite chain along c-axis resulting in a stable 3D structure. It

326
Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
Fig. 4b. Aquo ligands in the step-like chains of 4 in head-to-head and tail-to-tail arrangement along c-axis.
3.4. Thermal analysis
4. Conclusion
The thermal stability of 1, 3 and 4 was examined by thermal
analysis (TGA). Because the CuClO4 is an exploder, we cannot get
the TGA data of complex 2. The TG experiments of the powder
samples of 1 and 4 were carried out from 20 to 500 °C. The
weight loss of ꢃ4.8% for 1 and ꢃ9.11% for 4 in the range of
37–185 °C corresponds to the loss of the coordinated water
molecule of crystallization for 1 (3.8% calc.), the coordinated
and lattice water molecule for 4 (7.06% calc.). The weight loss till
270 °C could be associated with the sublimation of the H2biim
ligand (56.54% calc. for 1 and 53.28% calc. for 4). The residue
species are CuNO3 for 1 and CuSiF6 for 4, respectively. The ther-
mal decomposition behavior of complex 3 is studied from 20 to
1000 °C. The weight loss at 274 °C corresponds to the loss of the
This paper confirms the important role of inorganic counter an-
ions in Cu(II) chemistry, especially those which can form hydrogen
ꢁ
bonds like NO3ꢁ, ClO4ꢁ, [I0.36ꢀ(NO3)0.64
]
and SiF62ꢁ. Hydrogen
bonds are believed to play a key role in the generation of unex-
pected anion SiF6 and [I0.36ꢀ(NO3)0.64]ꢁ. The catalytic properties
2ꢁ
seem to be related to the formation of hydrogen bonds between
the Cu-bonded H2biim with the inorganic anions and solvent, such
as type I, II, V R21(7) and type III, IV R22(9) synthons. Our results
may help people understand the action of copper enzymes such
as the catalytic mechanism in biological systems and the design
of new supramolecular materials.
Supplementary data
H2biim ligand (ꢃ53.28% calc.). The residue of Cu[I0.36ꢀ(NO3)0.64 2
]
is decomposed at temperature of 567 °C (13.92% calc.) and the
CCDC 702994, 707792, 713515 and 711330 contain the supple-
mentary crystallographic data for compounds 1–4. These data can
last residue is Cu2O.

Q.-H. Jin et al. / Polyhedron 29 (2010) 317–327
327
Fig. 4c. 3D framework of 4 along b-axis.
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be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223 336
033; or e-mail: deposit@ccdc.cam.ac.uk.
Acknowledgements
This work has been supported by the National Science Founda-
tion of China (Grant No. 20871085), the Committee of Education of
Beijing Foundation of China (Grant No. KM200610028006), the
Project sponsored by SRF for ROCS and SEM, the subsidy of Beijing
Personnel Bureau, National Keystone Basic Research Program (973
Program) under Grant Nos. 2007CB310408, 2006CB302901, State
Key Laboratory of Functional Materials for Informatics, Shanghai
Institute of Microsystem and Information Technology, Chinese
Academy of Sciences.
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