Synthesis, structures and magnetic properties of nicotinato-copper(II) complexes with polybenzimidazole and polyamine ligands

Article abstract of DOI:10.1016/j.ica.2010.09.038

Four novel nicotinato-copper(II) complexes containing polybenzimidazole and polyamine ligands were synthesized with formula [Cu₂(bbma) ₂(nic)₂](ClO₄)₂·CH ₃OH·0.5H₂O (1), [Cu

Full text of DOI:10.1016/j.ica.2010.09.038

Inorganica Chimica Acta 365 (2011) 309–317
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Inorganica Chimica Acta
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Synthesis, structures and magnetic properties of nicotinato-copper(II) complexes
with polybenzimidazole and polyamine ligands
⇑
Feng-Mei Nie , Fei Lu, Shuang-Yan Wang, Mei-Ye Jia, Zhi-Yun Dong
Department of Chemistry, 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:
Four novel nicotinato-copper(II) complexes containing polybenzimidazole and polyamine ligands were
synthesized with formula [Cu2(bbma)2(nic)2](ClO4)2ꢀCH3OHꢀ0.5H2O (1), [Cu2(dien)2(nic)2](ClO4)2ꢀ
2CH3OH (2), [Cu(ntb)(nic)]ClO4ꢀH2O (3) and [Cu(tren)(nic)]BPh4ꢀCH3OHꢀH2O (4), in which bbma is
bis(benzimidazol-2-yl-methyl)amine, dien is diethylenetriamine, ntb is tris(2-benzimidazolylmethyl)-
amine, tren is tris(2-aminoethyl)amine and nic is nicotinate anion. All of the complexes were character-
ized by elemental analysis, IR and X-ray diffraction analysis. Complexes 1 and 2 contain centrosymmetric
dinuclear entity with the two Cu(II) atoms bridged by two nicotinate anions in an anti-parallel mode. The
CuꢀꢀꢀCu separation is 7.109 Å for 1 and 6.979 Å for 2. Complexes 3 and 4 are mononuclear with nicotinate
coordinated to Cu(II) ion by the carboxylate O atom in 3 and the pyridine N atom in 4. All of the com-
plexes exhibit abundant hydrogen bonds to form 1D chain for 1, 3, 4 and 2D network for 2. Magnetic sus-
ceptibility measurements over the 2–300 K range reveal very weak ferromagnetic interaction between
the two Cu(II) ions in 1 and antiferromagnetic interaction in 2 mediated by nicotinate ligand, with J value
to be 0.15 and ꢁ0.19 cmꢁ1, respectively.
Received 22 July 2010
Received in revised form 19 September
2010
Accepted 22 September 2010
Available online 29 September 2010
Keywords:
Copper(II) complex
Nicotinic acid
Crystal structure
Magnetic property
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
pyl)oxamide) [14], azide [5] and isonicotinic acid [21] as coligands.
But nicotinato-copper(II) complexes by using polybenzimidazole
Nicotinic acid plays an important role in the metabolism of the
living cells and possesses very interesting pharmaceutical proper-
ties [1,2]. It can also be used to transmit magnetic interactions.
Therefore, much interest has been directed towards their metal
complexes [3–8]. Nicotinic acid, namely 3-pyridinecarboxylic acid,
is one of the three isomers of pyridine monocarboxylic acid. It has
potential coordination sites involving the nitrogen atom of the pyr-
idine and the carboxylate oxygen atoms. It can coordinate with
copper(II) atom via one or two O atoms of carboxylate group or
the pyridine N atom or both of them. At the same time, the pyri-
dine N atom and carboxylate group of nicotinate can also serve
as hydrogen bond accepter. This makes it a good candidate to con-
struct novel multidimensional structures through its versatile
and polyamine as terminal ligands have rarely been reported
[13], and the investigation of magnetic interaction mediated by
nicotinate anion is relatively less [5,8,11,14,17,20].
Polybenzimidazole and polyamine terminal ligands have long
been used in coordination chemistry [23–25]. These ligands can
differ both in the lengths of the arms and the nature of N-donor
atoms on each arm. Tris(2-benzimidazolylmethyl)amine (ntb)
and bis(benzimidazol-2-yl-methyl)amine (bbma) contain aromatic
N-donor atoms on their arms, while tris(2-aminoethyl)amine
(tren) and diethylenetriamine (dien) contain aliphatic N-donor
atoms. They are widely used to prepare a variety of metal com-
plexes to model the active site structures of some relevant metal-
loenzymes. Compared to Cu(II) complexes of polyamine tren and
dien, the crystallograpically characterized Cu(II) complexes of ntb
and bbma are relatively less. Except two isophthalato-bridged
dinuclear copper(II) complexes of ntb and bbma, only mononuclear
copper(II) complexes have been obtained and structurally charac-
terized [26].
Weare interestedin the preparation of copper(II)nicotinatecom-
plexes with polybenzimidazole and polyamine terminal ligands for
the following reasons. First we would like to see how the structural
change of the terminal ligands with aromatic benzimidazole side
arms (ntb, bbma) or aliphatic side arms (tren, dien) influence the
coordination behavior of nicotinate as coligand. Second, the nicoti-
nato-copper(II) complexes of these ligands may afford versatile
coordination modes, hydrogen bonds and p–p interactions.
A number of copper(II) complexes of nicotinate with discrete
mononuclear unit [9–12], dinuclear unit [13] and extended
polymeric 1D, 2D and 3D [5,8,12–22] structures have been re-
ported and characterized. Some of these complexes contain dien
(diethylenetriamine) [9–11,13], bipy (2,20-bipyridine) [8,16], phen
(1,10-phenanthroline) [15], trans-oxap, trans-oxen (H2oxen =
N,N0-bis(2-aminoethyl)oxamide, H2oxap = N,N0-bis(2-aminopro-
⇑
Corresponding author. Tel./fax: +86 10 68903033.
E-mail address: niefm@mail.cnu.edu.cn (F.-M. Nie).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.09.038

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F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 309–317
half an hour, a methanol (50 ml) solution of NaClO4ꢀH2O (0.140 g,
1 mmol) was added dropwise to this solution. The mixture was re-
fluxed for 3 h and then filtered and left for slow evaporation. Blue
block crystals were formed after a week. Yield: 350 mg (60%). Anal.
Calc. for Cu2C45H43N12O13.5Cl2 (1165.89 g/mol): C, 46.35; H, 3.72;
N, 14.42. Found: C, 46.36; H, 4.05; N, 13.98%. IR (KBr pellet):
3431 (br, s) (for H-bonded water molecules), 3263(sh, s), 2923(s),
1600(s), 1588(s), 1491(w), 1474(m), 1456(m), 1377(s), 1279(m),
1111(s), 1094(s), 742(s) (for out-of-plane bending vibrations of
the o-disubstituted phenyl rings of the bbma ligand).
N
O
N
O
N
O
Cu
Cu
Cu Cu
O
bO
O
c
a
Scheme 1. Bonding modes of nicotinate anion in the four copper(II) complexes.
intermolecular interactions such as hydrogen bonds and p–p inter-
actions to form interesting supramolecular coordination assembly.
Third, we would like to investigate the magnetic interaction medi-
ated by nicotinate anion. In this paper, two novel dinuclear nicotina-
to-copper(II) complexes [Cu2(bbma)2(nic)2](ClO4)2ꢀCH3OHꢀ0.5H2O
(1), [Cu2(dien)2(nic)2](ClO4)2ꢀ2CH3OH (2) and two mononuclear
complexes [Cu(ntb)(nic)]ClO4ꢀH2O (3) and [Cu(tren)(nic)]BPh4ꢀ
CH3OHꢀH2O (4) were synthesized and characterized. In the above
four complexes, nicotinate coordinates to Cu(II) in three bonding
2.4.2. Preparation of [Cu2(dien)2(nic)2](ClO4)2ꢀ2CH3OH (2)
To a methanol solution (10 ml) of Cu(ClO4)2ꢀ6H2O (0.185 g,
0.5 mmol) was added a methanol solution (10 ml) of sodium nico-
tinate (0.073 g, 0.5 mmol). Sky-blue precipitate formed. Then a
methanol solution (10 ml) of diethylenetriamine (0.052 g,
0.5 mmol) was added under stirring to give dark blue solution. Vio-
let crystals suitable for X-ray structure determination were ob-
tained after one week by slow evaporation of the filtrate. Yield:
165 mg (81%). Elemental analysis shows that two lattice methanol
molecules were replaced by two water molecules during storage in
air. Anal. Calc. for Cu2C20H38N8O14Cl2 (812.56 g/mol): C, 29.56; H,
4.71; N, 13.79. Found: C, 29.90; H, 4.74; N, 13.92%. IR (KBr pellet):
3423(br, s), 3341(br, s), 3273(br, s), 2960(s), 1619(s), 1569(m),
1462(m), 1385(s), 1260(m), 1096(s), 762(m), 623(s).
modes which could be described as
l2-N, O chelating mode in 1
and 2 (see Scheme 1a), one carboxylate O atom in 3 (see
Scheme 1b) and the pyridine N atom in 4 (see Scheme 1c). The mag-
netic susceptibility measurements at variable temperature over the
2–300 K range for 1 and 2 suggested very weak ferromagnetic cou-
pling interaction of the two Cu(II) ions for 1 but weak antiferromag-
netic coupling interaction in 2.
2.4.3. Preparation of [Cu(ntb)(nic)]ClO4ꢀH2O (3)
2. Experimental
A
methanol solution (15 ml) of Cu(ClO4)2ꢀ6H2O (0.185 g,
0.5 mmol) was added to a methanol solution (15 ml) of ntb
(0.204 g, 0.5 mmol) and sodium nicotinate (0.073 g, 0.5 mmol).
The mixture was refluxed for 6 h. The resulting solution was al-
lowed to stand in air at room temperature. After 10 h, green crys-
tals were formed. The products were filtered and washed with cold
methanol and dried in vacuo over P4O10. Yield: 284 mg (80%). Anal.
Calc. for C30H27ClCuN8O7 (710.59 g/mol): C, 50.71; H, 3.83; N,
15.77. Found: C, 50.74; H, 3.82; N, 15.25%. IR (KBr pellet):
3423(br, s), 3193(s), 2923(s), 1625(s), 1595(m), 1544(m),
1491(w), 1474(m), 1453(s), 1370(s), 1277(m), 1120(s), 743(s) (for
out-of-plane bending vibrations of the o-disubstituted phenyl
rings of the ntb ligand).
2.1. Materials
All chemicals including diethylenetriamine, tris(2-aminoethyl)-
amine were purchased from commercial sources and used as
received without further purification. Sodium nicotinate was pre-
pared by reacting nicotinic acid with a stoichiometric amount of
NaOH in water. The blue solid Cu(nic)2ꢀ2H2O was prepared by
the reaction of CuSO4ꢀ5H2O and sodium nicotinate at the ratio of
1:2 in water.
Caution! Salts of perchlorate and their metal complexes are
potentially explosive and should be handled with great care and
in small quantities.
2.4.4. Preparation of [Cu(tren)(nic)]BPh4ꢀCH3OHꢀH2O (4)
2.2. Physical measurements
A methanol solution (20 ml) of tren (0.36 g, 0.25 mmol) and
Cu(nic)2ꢀ2H2O (0.086 g, 0.25 mmol) in methanol solution (30 ml)
were mixed to give a blue solution and stirred for half an hour.
NaBPh4 (0.085 g, 0.25 mmol) in methanol solution (10 ml) was
added. The mixture was stirred overnight and then filtered. Slow
evaporation of the filtrate yielded blue chunk crystals after one
week. Yield: 105 mg (64%). Elemental analysis shows that half a
lattice water molecule and one lattice methanol molecule were lost
during storage in air. Anal. Calc. for CuC36H43N5O2.5B (660.11 g/
mol): C, 65.50; H, 6.56; N, 10.61. Found: C, 65.70; H, 6.41; N,
10.61%. IR (KBr pellet): 3431(br, s), 3330(s), 3282(s), 2886(s),
1628(s), 1479(m), 1451(w), 1427(m), 1369(s), 737(s).
Elemental analyses for C, H and N were performed using Ele-
mental Vario MICRO CUBE (Germany) elemental analytical instru-
ment, IR spectra were recorded as KBr pellets on Bruker TENSOR 27
FT-IR spectrometer in the range of 4000–400 cmꢁ1. The magnetic
measurement was carried out with a Quantum Design MPMS-7
SQUID magnetometer in the temperature range of 2–300 K and
in a field of 1000 Oe. Diamagnetic correction for the constituent
atoms was made by using Pascal’s constants.
2.3. Preparation of ligands
The ligand tris(2-benzimidazolylmethyl)amine (ntb) was syn-
thesized following the literature method and bis(benzimidazol-2-
yl-methyl)amine (bbma) was prepared according to published
procedures [27,28].
2.5. X-ray structural analysis
Crystals of 1 and 4 were mounted on Bruker Smart 1000 area
detector and the Rigaku Saturn724+ diffractometer at 273(2) and
93(2) K, respectively. Single-crystal X-ray diffraction data for 2
and 3 were collected on a Rigaku RAXIS-RAPID single-crystal dif-
fractometer at 293(2) K. All of the diffractometers are equipped
2.4. Preparation of complexes
2.4.1. Preparation of [Cu2(bbma)2(nic)2](ClO4)2ꢀCH3OHꢀ0.5H2O (1)
A methanol solution (50 ml) of bbma (0.277 g, 1 mmol) was
added to a stirred solution (100 ml) of Cu(nic)2ꢀ2H2O (0.345 g,
1 mmol) in methanol with the formation of a blue solution. After
with graphite-monochromated Mo Ka radiation (k = 0.71073 Å).
Empirical absorption correction was made for the collected reflec-
tions [29]. All of the structures were solved with direct method by
using SHELXS-97 [30] and refined on F2 by full-matrix least-squares

F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 309–317
311
Table 1
Crystallographic data and structure refinement for 1–4.
1
2
3
4
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
Space group
a (Å)
C
35H38Cl2N12Cu2O2
C22H42Cl2Cu2N8O14
840.62
C30H27ClCuN8O7
710.59
C37H48BCuN5O4
701.15
988.13
0.30 ꢂ 0.25 ꢂ 0.20
0.40 ꢂ 0.46 ꢂ 0.12
monoclinic
P21/n (no. 14)
14.9542(5)
7.3680(3)
15.7904(5)
90
102.483(1)
90
1698.7(1)
1.643
0.48 ꢂ 0.30 ꢂ 0.20
0.47 ꢂ 0.27 ꢂ 0.27
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1 (no. 2)
P1 (no. 2)
P1 (no. 2)
11.097(4)
11.154(4)
11.288(4)
75.588(6)
81.124(6)
66.315(6)
1236.9(7)
1.618
9.8515(8)
12.3343(10)
13.3912(12)
83.116(5)
80.226(3)
77.856(3)
1561.7(2)
1.511
9.7084(13)
11.0230(15)
17.112(2)
75.391(4)
79.695(5)
79.227(5)
1724.0(4)
1.351
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
qcalc (g cmꢁ3
Z
)
1
2
2
2
F(0 0 0)
l
618
1.051
868
1.484
730
0.846
742
0.681
(mmꢁ1
)
Tmax/Tmin
0.8174/0.7434
1.2904/0.7751
1.0958/0.8962
0.8391/0.7416
hkl range
ꢁ13 to 7
ꢁ19 to 19
ꢁ9 to 9
ꢁ11 to 12
ꢁ15 to 15
ꢁ17 to 17
2.19–27.44
10788
ꢁ9 to 12
ꢁ13 to 7
ꢁ14 to 14
ꢁ20 to 22
3.06–27.49
14229
ꢁ12 to 13
2.66–24.02
5155
ꢁ20 to 20
2.12–27.48
7254
h Range (°)
Measured reflections
Unique reflections (Rint
Observed reflections I > 2r(I)
)
4353 (0.0264)
2978
3899 (0.0182)
3104
6916 (0.0237)
5690
7594 (0.0209)
6685
Data/restraints/parameters
Goodness-of-fit
4353/0/354
1.044
3899/0/238
1.039
6916/0/425
1.036
7594/3/443
0.997
R1/wR2 (I > 2
r
(I))
0.0602/0.1281
0.1011/0.1447
0.601/ꢁ0.349
0.0339/0.0889
0.0456/0.0931
0.629/ꢁ0.396
0.0462/0.1224
0.0568/0.1285
0.814/ꢁ0.613
0.0380/0.0846
0.0434/0.0878
0.617/ꢁ0.343
R1/wR2 (all data)
Resid. el. dens. (e Åꢁ3
)
Table 2
The IR spectral bands (cmꢁ1) for complexes 1–4.
Complex
m
(N–H),
m
(O–H)
m
as(COOꢁ)
m
s(COOꢁ)
D
m
(COOꢁ)
m(Cl–O)
1
3431
3263
3423
3341
3423
3193
3431
3330
1600
1588
1619
1569
1625
1595
1628
1479
1377
1385
1370
1369
223
234
255
259
1111
1096
1120
—
2
3
4
‘‘—” Means complex 4 contain no perchlorate anions.
techniques using the SHELXL-97 program [31]. The non-hydrogen
atoms were subjected to anisotropic refinement and the hydrogen
atoms were located geometrically. In complex 1, O(8) atom of the
water molecule was assigned with occupancy to be 0.5 and the
hydrogen atoms on it were not located. In complex 2, the disor-
dered C(4) atom of dien including H atoms on it were located at
two sites with a total occupancy of 1. The detailed crystallographic
data and structure refinement parameters for 1–4 are summarized
in Table 1.
3. Results and discussion
Fig. 1. Cation structure of complex 1 (30% probability thermal ellipsoids).
3.1. Synthesis and characterization
NaBPh4 used as the source of counter anions. All of the four com-
plexes are soluble in DMF and DMSO. Complexes 1 and 3 contain-
ing bbma and ntb can slightly dissolve in methanol but are
insoluble in water. Complexes 2 and 4 containing dien and tren
as main ligands can dissolve in methanol and water in some
extent.
3.1.1. Synthesis and the solubility of the complexes
The synthetic procedures used to prepare the four complexes
can be divided into two categories: the first pathway is based
on the reaction of Cu(ClO4)2ꢀ6H2O, dien or ntb ligand and sodium
nicotinate in the ratio of 1:1:1, while the second one involves the
reaction of Cu(nic)2ꢀ2H2O with bbma or tren and NaClO4ꢀH2O or

312
F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 309–317
Table 3
3.2. Description of the structures
Selected bond lengths (Å) and angles (°) for complex 1.
3.2.1. [Cu2(bbma)2(nic)2](ClO4)2ꢀCH3OHꢀ0.5H2O (1)
Cu(1)–N(2)
Cu(1)–N(4)
Cu(1)–O(1)
2.008(4)
1.997(4)
2.362(4)
Cu(1)–N(1)
Cu(1)–N(6)#1
2.021(5)
2.013(4)
2+
Complex 1 contains one dinuclear [Cu2(bbma)2(nic)]2 cation,
two perchlorate anions, one lattice methanol and half a disordered
water molecules. The cation structure of 1 is shown in Fig. 1; se-
lected bond lengths and angles are given in Table 3.
N(4)–Cu(1)–N(2)
N(2)–Cu(1)–N(6)#1
N(2)–Cu(1)–N(1)
N(4)–Cu(1)–O(1)
N(6)#1–Cu(1)–O(1)
160.12(16)
97.53(15)
80.98(18)
94.19(16)
91.98(14)
N(4)–Cu(1)–N(6)#1
N(4)–Cu(1)–N(1)
N(6)#1–Cu(1)–N(1)
N(2)–Cu(1)–O(1)
N(1)–Cu(1)–O(1)
100.60(16)
80.82(19)
178.46(19)
93.26(16)
88.5(3)
In the centrosymmetric dinuclear cation, the two Cu(II) are
bridged by two anions of nicotinic acids through the pyridyl nitro-
gen atom and one of the carboxylate oxygen atoms in an anti-
parallel bridging way [13] and the CuꢀꢀꢀCu separation is 7.109 Å.
Each Cu(II) atom is coordinated with three N atoms of bbma and
one N atom of the first nicotinate defining the base and one O atom
from the carboxylate group of the second nicotinate occupying the
apex of the pyramid in a distorted square pyramidal geometry. The
Symmetry transformations used to generate equivalent atoms: #1 ꢁx + 1, ꢁy + 2,
ꢁz + 1.
3.1.2. Spectroscopy
The most relevant absorption bands in the IR spectra of 1–4 are
listed in Table 2. There are two absorption bands in the range of
3200–3500 cmꢁ1 for all of the four complexes, these bands corre-
spond to N–H and O–H stretching vibrations and indicate the pres-
ence of the NH groups of ntb, the lattice water or methanol
molecules in the complexes. The bands around 1111–1120 cmꢁ1
in 1, 3 and 1096 cmꢁ1 in 2 are due to the ionic perchlorate groups
[32,33]. Each of the four complexes exhibits the typical carboxylate
Addison
ramidal geometry and
[35]. The equatorial bond angels are in the range of 80.82(19)–
100.60(16)° and the bond angles for the apex O(1) with the four
s
value of 1 is 0.30, where
s = 1 for perfect trigonal bipy-
s
= 0 for perfect square pyramidal geometry
N
atoms in equatorial plane are in the range of 88.5(3)–
94.19(16)°, which are all deviated from the ideal value of 90°.
The four basal Cu(II)–N bond distances are in the range of
1.997(4)–2.021(5) Å. The axial Cu(1)–O(1) is 2.362(4) Å, which is
longer than the normal Cu(II)–carboxylate oxygen bond length.
This feature is frequently found in Cu(II) crystal chemistry and
characterized with square-pyramidal configuration [26]. It is noted
that the O(4) atom of perchlorate makes very weak interaction
with Cu(1)–O(4) bond distance of 2.695 Å, which is close to the re-
ported nicotinate–copper(II) complexes with the same coordina-
tion feature [13].
As shown in Fig. 2, 1D chain structure is formed by intermolec-
ular H-bond interactions between the NH group of benzimidazole
from bbma and the uncoordinated carboxylate oxygen atom of nic-
otinate (N(3)ꢀꢀꢀO(2) = 2.743(6) Å, \N(3)–H(3)–O(2) = 152°). The 1D
stretching frequencies
s(COOꢁ) of nicotinate (Table 2). The two bands at about
1600 cmꢁ1 are assigned to the antisymmetric stretching frequen-
cies
as(COOꢁ) and the band around 1370 cmꢁ1 contributed to
symmetric stretching frequencies
s(COOꢁ). The difference be-
m
as(COOꢁ) which split into two bands and
m
m
m
tween the antisymmetric stretching and symmetric stretching
gives information on the carboxylate bonding mode for the com-
plexes. The
D
m
(COOꢁ) values for 1–4 are from 223 to 259 cmꢁ1
,
which are typical for unidentate bonded carboxylate group of nic-
otinate [34]. These findings are also consistent with the X-ray anal-
ysis results.
Fig. 2. The 1D chain connected through hydrogen bonding interactions in 1.
Fig. 3. Cation structure of complex 2 (30% probability thermal ellipsoids).

F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 309–317
313
Table 4
3.2.2. [Cu2(dien)2(nic)2](ClO4)2ꢀ2CH3OH (2)
Selected bond lengths (Å) and angles (°) for complex 2.
As can be seen for 1, complex 2 has the same type of coordina-
tion structure with complex 1 but different terminal ligand. Com-
plex 2 comprised of a centrosymmetric [Cu2(dien)2(nic)2]2+ cation,
two perchlorate anions and two lattice methanol molecules. The
cation structure of 2 is shown in Fig. 3, selected bond distances
and angles are summarized in Table 4.
Cu(1)–N(2)
Cu(1)–N(3)
Cu(1)–O(1)
2.0103(18)
2.0233(19)
2.2398(16)
Cu(1)–N(1)
Cu(1)–N(4)
2.022(2)
2.0234(17)
N(2)–Cu(1)–N(4)
N(2)–Cu(1)–O(1)
N(4)–Cu(1)–O(1)
N(2)–Cu(1)–N(1)
N(4)–Cu(1)–N(1)
178.44(8)
88.22(7)
90.36(7)
84.78(8)
94.75(8)
N(2)–Cu(1)–N(3)
N(4)–Cu(1)–N(3)
O(1)–Cu(1)–N(3)
N(1)–Cu(1)-N(3)
O(1)–Cu(1)–N(1)
84.83(8)
96.39(8)
115.62(8)
144.57(9)
97.79(9)
In the cation structure of 2, two nicotinate anions bridge the
adjacent Cu(II) through both the pyridine N and the carboxylate
O atoms to form a dinuclear copper complex in an anti-parallel
bridging way. The CuꢀꢀꢀCu distance is 6.979 Å, which is shorter than
that of complex 1 (7.109 Å) and nearly the same as that found in
[Cu2(dien)2(nic)2](BF4)2ꢀ2MeOH [13]. Each Cu(II) is coordinated
by three N atoms of dien, one pyridine N atom of the first nicotin-
ate and one carboxylate O atom from another nicotinate in a dis-
chain is further expanded to a two-dimensional (2D) structure (see
Fig. S1) by the stacking interactions between the benzene ring
and the imidazole ring of the neighboring bbma, forming a 2D net-
work structure (with the centroid-to-centroid distance to be
3.759 Å, Cg1 = C11–C12–C13–C14–C15–C16, Cg2 = C10–N4–C11–
C16–N5).
p–p
torted trigonal bipyramidal geometry with
The trigonal plane is defined by two terminal nitrogen atoms
s value to be 0.56.
Fig. 4. The 2D structure interacted through Hydrogen bonding interactions in 2.

314
F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 309–317
\O(3)–H(3)–O(2) = 168(5)°] to connect the adjacent dinulcear cat-
ion units forming a 2D network structure as shown in Fig. 4.
3.2.3. [Cu(ntb)(nic)]ClO4ꢀH2O (3)
Complex 1 consists of a [Cu(ntb)(nic)]+ cation, one perchlorate
and one disordered water molecule. The cation structure of 3 is de-
picted in Fig. 5. Relevant bond distances and angles are presented
in Table 5.
The central Cu(II) is coordinated by four nitrogen atoms of ntb
and one carboxylate O atom of nicotinate. The geometry around
Cu(II) can be described as distorted trigonal bipyramidal as re-
vealed by the magnitude of the trigonality index
s of 0.62. The
three benzimidazole N(21), N(31) and N(41) atoms of ntb make
up the trigonal plane. The amine N(1) atom of ntb and the O(1)
atom of nicotinate are in the axial positions with the axial angle
of O(1)–Cu(1)–N(1) is 172.43(8)°. The Cu(II) deviates from the tri-
gonal plan towards O(1) by 0.385 Å. The distortion of the coordina-
tion environment of Cu(II) can be illustrated by the deviation of the
equatorial angles from 120°. The bond angles of the equatorial
plane N(21)–Cu(1)–N(31), N(31)–Cu(1)–N(41), N(41)–Cu(1)–
N(21) are 135.05(9)°, 102.77(9)° and 112.65(9)°, respectively. The
bond angles of tertiary amine N(1) with the three benzimidazole
N atoms [N(21)–Cu(1)–N(1), N(31)–Cu(1)–N(1) and N(41)–Cu(1)–
N(1)] are in the range of 78.62(8)–81.23(8)°, which is in part due
to the straining nature of ntb.
Fig. 5. Cation structure of complex 3 (30% probability thermal ellipsoids).
Table 5
Selected bond lengths (Å) and angles (°) for complex 3.
Cu(1)–N(21)
Cu(1)–N(41)
Cu(1)–O(1)
2.014(2)
2.122(2)
1.9392(18)
Cu(1)–N(1)
Cu(1)–N(31)
2.157(2)
2.038(2)
The bond distances of Cu(II) and the benzimidazole N atoms are
2.014(2) Å for Cu(1)–N(21), 2.038(2) Å for Cu(1)–N(31) and
2.122(2) Å for Cu(1)–N(41). They are shorter than the Cu(1)–amine
N(1) bond distance 2.157(2) Å, which is also observed in other cop-
per(II) complexes of ntb [32,39–41]. This is in part due to the great-
O(1)–Cu(1)–N(21)
N(21)–Cu(1)–N(31)
N(21)–Cu(1)–N(41)
O(1)–Cu(1)–N(1)
N(31)–Cu(1)–N(1)
96.64(8)
135.05(9)
112.65(9)
172.43(8)
81.23(8)
O(1)–Cu(1)–N(31)
O(1)–Cu(1)–N(41)
N(31)–Cu(1)-N(41)
N(21)–Cu(1)–N(1)
N(41)–Cu(1)–N(1)
105.86(8)
96.95(8)
102.77(9)
79.65(8)
78.62(8)
er
p
-bonding ability of benzimidazole pendants compared to
-donors, and in part to the
alkylamines, which is exclusively
r
straining nature of the tripodal ligand [23]. Except the coordination
of four nitrogen atoms of ntb to Cu(II), the fifth coordination is
from nicotinate. Nicotinate coordinated to Cu(II) via the carboxyl-
ate O atom with Cu(1)–O(1) bond length of 1.9392(18) Å.
Intermolecular H-bond of type N–HꢀꢀꢀO [N(22)ꢀꢀꢀO(2) =
2.736(3) Å, \N(22)–H(22A)ꢀꢀꢀO(2) = 142°] between the NH group
of ntb and the uncoordinated carboxylate oxygen atom of nicotin-
ate connected the two adjacent molecules to form a double molec-
N(1), N(3) and the O(1) with bond lengths Cu(1)–N(1) = 2.022(2),
Cu(1)–N(3) = 2.0233(19) Å, and Cu(1)–O(1) = 2.2398(16) Å. The ax-
ial sites were occupied by N(2) and N(4) atoms with bond dis-
tances of Cu(1)–N(2) and Cu(1)–N(4) to be 2.0103(18) and
2.0234(17) Å, similar Cu(1)–N(2) bond length is also found in other
copper(II) complexes of dien [36–38] and more approximate to
that of [Cu2(dien)2(nic)2](BF4)2ꢀ2MeOH [13]. Bond angles in the tri-
gonal plane are in the range of 97.79(9)–144.57(9)°, which deviate
significantly from 120° of the ideal trigonal bipyramid. The axial
bond angle is 178.44(8)° for N(2)–Cu(1)–N(4).
ular unit, which is also stabilized by p–p stacking interaction from
the imidazole ring and the imidazole ring of adjacent benzimid-
azole with the centroid-to-centroid distance to be 3.601 Å
(Cg1 = Cg2 = C22–N21–C28–C23–N22). The double molecular units
are further connected via H-bond of type N–HꢀꢀꢀN [N(42)ꢀꢀꢀN(11) =
2.785(3) Å, \N(42)–H(42A)ꢀꢀꢀN(11) = 166°] between the NH group
of ntb and the nitrogen atom of nicotinate to form 1D chain struc-
ture as shown in Fig. 6.
The lattice methanol molecule is H-bonded to the NH2 group of
dien [N(3)ꢀꢀꢀO(3) = 2.989(3) Å, \N(3)–H(3)–O(3) = 173°] and the
uncoordinated carboxlylate
O
atom [O(3)ꢀꢀꢀO(2) = 2.782(3) Å,
Fig. 6. The 1D chain connected through hydrogen bonding interactions in 3.

F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 309–317
315
structure of 4 is shown in Fig. 7, main bond distances and angles
are listed in Table 6.
The Cu(II) is coordinated by four N atoms of tren and the pyri-
dine N atom of nicotinate in distorted trigonal bipyramidal geom-
etry with
s value of 0.84, which is comparable to the reported
Cu(II) complexes of tren [33,43–46]. The equatorial plane is de-
fined by three primary amine nitrogen atoms N(2), N(3) and N(4)
of tren and the axial positions are occupied by the tertiary amine
N(1) and pyridine N(5) atoms. The Cu(II) lies 0.209 Å below the
equatorial plane toward N(5). The equatorial Cu–N bond distances
are 2.0655(16) Å for Cu(1)–N(2), 2.0907(16) Å for Cu(1)–N(3), and
2.1144(15) Å for Cu(1)–N(4). The axial bond distances are
2.0437(16) Å for Cu(1)–N(1) and 2.0087(16) Å for Cu(1)–N(5)(pyr-
idine). The equatorial bond angles are 105.96(6)° for N(3)–Cu(1)–
N(4), 124.09(6)° for N(4)–Cu(1)–N(2) and 126.91(6)° for N(2)–
Cu(1)–N(3). The bond angles of tertiary amine N(1) with the three
primary amine N atoms are in the range of 83.59(6)–84.89(6)°. The
striking feature of complex 4 is that nicotinate coordinates to Cu(II)
via the pyridine N atom not the carboxylate O atom as that found
in complex 3 Fig. 7.
Intermolecular H-bond of type N–HꢀꢀꢀO [N(4)ꢀꢀꢀO(1) = 2.946(2) Å,
\N(4)–H(4)ꢀꢀꢀO(1) = 146°] between the NH2 group of tren and one
of the uncoordinated carboxylate oxygen atoms of nicotinate con-
nected the two neighboring molecules to form a double molecular
unit (Table 7). The adjacent double molecular units are further
bridged by intermolecular H-bond of type O–HꢀꢀꢀO [O(4)ꢀꢀꢀO(2) =
2.815(2) Å, \O(4)–H(7)ꢀꢀꢀO(2) = 167(2)° and O(4)ꢀꢀꢀO(1) = 2.827(2) Å,
\O(4)–H(4)ꢀꢀꢀO(1) = 174.8(19)°] through two water molecules to
form 1D chain structure as shown in Fig. 8.
Fig. 7. Cation structure of complex 4 (30% probability thermal ellipsoids).
Table 6
Selected bond lengths (Å) and angles (°) for complex 4.
3.3. Magnetic measurements
Cu(1)–N(5)
Cu(1)–N(2)
Cu(1)–N(4)
2.0087(16)
2.0655(16)
2.1144(15)
Cu(1)–N(1)
Cu(1)–N(3)
2.0437(16)
2.0907(16)
The molar magnetic susceptibility vM and effective magnetic
moment of 1 and 2 were measured in the temperature range of
2–300 K in the field of 1000 Oe. The plots of vM and leff versus T
for 1 and 2 are shown in Fig. 9 and Fig. 10. As shown in Fig. 9,
N(5)–Cu(1)–N(1)
N(1)-Cu(1)–N(2)
N(1)–Cu(1)–N(3)
N(5)–Cu(1)–N(4)
N(2)–Cu(1)–N(4)
177.34(6)
84.89(6)
84.12(6)
98.97(6)
124.09(6)
N(5)–Cu(1)–N(2)
N(5)–Cu(1)–N(3)
N(2)–Cu(1)–N(3)
N(1)–Cu(1)-N(4)
N(3)–Cu(1)–N(4)
94.21(6)
94.45(6)
126.91(6)
83.59(6)
105.96(6)
the value of leff for 1 is 2.67 B.M. at room temperature. Upon cool-
ing, it increases slowly and reaches to a maximum value of
2.71 B.M. at 2 K. This result supports the presence of weak ferro-
magnetic coupling interaction between the adjacent Cu(II) ions in
1. The value of leff is 2.75 B.M. for 2 at room temperature. It
decreases slowly between 40 and 300 K as the temperature
The 1D chain is further expanded to a two-dimensional (2D)
structure through H-bond interactions involving the NH groups
of ntb, the water molecules and perchlorate anions as shown in
Fig. S2. Similar hydrogen bond interaction was also found in com-
plex [Mn(ntb)(nic)]ClO4ꢀH2O [42].
decreases, the value of leff then decreases much faster and reaches
to 2.62 B.M. at 2 K. These features are characteristic of the occur-
rence of weak antiferromagnetic interaction between the Cu(II)
ions in 2. The experimental magnetic data for the two complexes
have been fitted by using the Bleany–Bowers expression derived
3.2.4. [Cu(tren)(nic)]BPh4ꢀCH3OHꢀH2O (4)
Complex 4 is composed of one [Cu(tren)(nic)]+ cation, one
BPh4ꢁ, one methanol and one lattice water molecules. The cation
through the Hamiltonian H=ꢁ2JSCu1SCu2 [Eq. (1)], where J is the ex-
ˆ
ˆ
ˆ
change coupling parameter, the parameters N, b and K in Eq. (1)
Table 7
Selected hydrogen bond parameters for 1–4.
D–HꢀꢀꢀA
d(D–H)
d(HꢀꢀꢀA)
d(DꢀꢀꢀA)
\(DHA)
Symmetry codes
Complex 1
N(3)–H(3)ꢀꢀꢀO(2)
Complex 2
0.86
1.95
2.743(6)
152
ꢁx + 1, ꢁy + 2, ꢁz + 2
1/2 + x, 3/2 ꢁ y, 1/2 + z
N(3)–H(3D)ꢀꢀꢀO(3)
0.90
0.77(5)
2.09
2.03
2.989(3)
2.782(3)
173
168(5)
O(3)–H(3E)ꢀꢀꢀO(2)
Complex 3
N(22)–H(22A)ꢀꢀꢀO(2)
0.86
0.86
2.00
1.94
2.736(3)
2.785(3)
142
166
1 ꢁ x, 1 ꢁ y, ꢁz
x, ꢁ1 + y, z
N(42)–H(42A)ꢀꢀꢀN(11)
Complex 4
N(4)–H(04B)ꢀꢀꢀO(1)
O(4)–H(40A)ꢀꢀꢀO(2)
O(4)–H(40B)ꢀꢀꢀO(1)
0.92
0.84(2)
0.842(16)
2.14
1.99(2)
1.987(16)
2.946(2)
2.815(2)
2.827(2)
146
167(2)
174.8(19)
1 ꢁ x, ꢁy, 1 ꢁ z
2ꢁx, ꢁy, 1 ꢁ z

316
F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 309–317
Fig. 8. The 1D chain connected through hydrogen bonding interactions in 4.
romagnetic coupling interaction between the adjacent Cu(II) ions
mediated by the bridging nicotinate anions in complex 2. Such
weak magnetic coupling interaction may be resulted from the long
CuꢀꢀꢀCu separation in 1 and 2 [8].
ꢀ
ꢁ
2Ng2b2
KT
1
vM
¼
þ Na
ð1Þ
3 þ expðꢁ2J=KTÞ
4. Conclusion
In this work, two dinuclear nicotinato-copper(II) complexes
[Cu2(bbma)2(nic)2](ClO4)2ꢀCH3OHꢀ0.5H2O (1), [Cu2(dien)2(nic)2]-
(ClO4)2ꢀ2CH3OH (2) and two mononuclear complexes [Cu(ntb)-
(nic)]ClO4ꢀH2O (3) and [Cu(tren)(nic)]BPh4ꢀCH3OHꢀH2O (4) were
synthesized and characterized, in which nicotinate ligand exhibits
three types of bonding modes, namely, l2-N, O chelating mode in 1
and 2, by one carboxylate O atom in 3 and the pyridine N atom in 4.
Magnetic susceptibility measurements for 1 and 2 show very weak
ferromagnetic interaction of the two Cu(II) ions for 1 but weak
antiferromagnetic interaction in 2.
Fig. 9. Plots of vM (O) and leff (D) vs. T for complex 1. The solid line corresponds to
the theoretical best fit.
Acknowledgments
This study was supported by Beijing Natural Science
Foundation (Grant No. 2092010), Beijing Municipal Education
Commission Research Program (KM200810028009) and the
Scientific Research Foundation for Returned Overseas Chinese
Scholars, Beijing Municipal Government.
Appendix A. Supplementary material
CCDC 777725, 777726, 777727 and 777728 contain the supple-
mentary crystallographic data for complexes 1, 2, 3 and 4, respec-
tively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.ica.2010.
09.038.
Fig. 10. Plots of
the theoretical best fit.
vM (O) and leff (D) vs. T for complex 2. The solid line corresponds to
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