Synthesis, crystal structure and magnetic properties of a nickel(III) maleonitriledithiolate complex using 1-methyl-3-benzylbenzimidazolium cation

Article abstract of DOI:10.1016/j.molstruc.2005.03.002

A new ion-pair complex, 1-methyl-3-benzylbenzimidazolium bis(maleonitrile-dithiolato)nickelate(III), has been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray crystallography. In solid state, the Ni(mnt)₂^-

Full text of DOI:10.1016/j.molstruc.2005.03.002

Journal of Molecular Structure 743 (2005) 197–200
www.elsevier.com/locate/molstruc
Synthesis, crystal structure and magnetic properties
of a nickel(III) maleonitriledithiolate complex using
1-methyl-3-benzylbenzimidazolium cation
Dongbin Danga, Chunlin Nia, Yan Baia, Zhengfang Tiana,
a
Lili Wen , Qingjin Meng , Song Gao
a,
b
*
aState Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing University, 210093 Nanjing, People’s Republic of China
bState Key Laboratory of Rare Earth Materials Chemistry and Applications, Peking University, Beijing 100871, People’s Republic of China
Received 2 February 2005; revised 27 February 2005; accepted 1 March 2005
Available online 6 April 2005
Abstract
A new ion–pair complex, 1-methyl-3-benzylbenzimidazolium bis(maleonitrile-dithiolato)nickelate(III), has been synthesized and
characterized by elemental analysis, IR spectroscopy and X-ray crystallography. In solid state, the Ni(mnt)K2 anions and [MeBzBzim]C
cations are alternately stacked and form a one-dimensional (1D) column through p–p interactions between the plane of Ni(mnt)K2 and the
neighbored benzimidazole ring. The p–p interactions between adjacent cations and the weak interactions between adjacent anions further
give rise to a three-dimensional supermolecular structure. The variable temperature magnetic susceptibilities investigation indicates that the
p–p stacking interactions result in an antiferromagnetic exchange coupling between Ni(III) ions of the complex and the Neel temperature
(TN) at 5.0 K is observed.
q 2005 Elsevier B.V. All rights reserved.
Keywords: 1-Methyl-3-benzylbenzimidazolium; Bis(maleonitrile-dithiolato)nickelate(III) complex; X-ray structure; Magnetic properties
1. Introduction
transition and so on [6–12]. Our strategy is using
benzylbenzimidazolium derivative (Scheme 1) as counter
ion instead of benzylpyridinium derivative, because that the
structure and electronic property of benzimidazole differs
from that of pyridine. And this change is anticipated to
affect the crystal structure and obtain complexes with a new
type of stacking structure and fancy magnetic properties.
Herein, we report the synthesis, structure and magnetic
properties of a nickel(III) mnt complex using 1-methyl-3-
benzylbenzimidazolium cation.
Transition metal complexes of maleonitriledithiolate
(mnt) continue to attract great interest because of their
potential and developed applications in the fields of
conducting and magnetic materials, dyes, non-linear optics,
catalysis and others [1–5]. Their high charge density
associated with the delocalized planar p-system makes
them have access to a diverse number of stacking modes and
possess interesting resultant physical properties. Previous
work on a series of complexes formed by [M(mnt)]nK and
benzylpyridinium derivative have shown varying counter-
ions which lead to versatile magnetic exchange properties
containing ferromagnetic ordering at 2 K, peculiar magnetic
transition from ferromagnetic coupling to diamagnetism or
from paramagnetic to diamagnetism, spin-Peierls-like
2. Experimental
2.1. Materials and the general procedures
All chemicals and solvents were reagent grade, and were
used without further purification. Benzylbenzimidazole
[13], disodium maleonitriledithiolate (Na2mnt) [14] were
synthesized following the published procedures. 1-Methyl-
3-benzylbenzimidazolium iodide ([MeBzBzim](I) was
*
Corresponding author. Tel.: C86 25 83597266; fax: C86 25 83314502.
E-mail address: mengqj@nju.edu.cn (Q. Meng).
0022-2860/$ - see front matter q 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2005.03.002

198
D. Dang et al. / Journal of Molecular Structure 743 (2005) 197–200
Table 1
Crystal data and structure refinement for 2
Chemical formula
Formula weight
Temperature (K)
Wavelength
C23H15N6NiS4
562.36
N
293(2)
˚
0.71073 A
Crystal system
Space group
Triclinic
N
R1
P1
˚
Unit cell dimensions
aZ7.468(2) A, aZ86.90(1)8
R2
Scheme 1. Benzylbenzimidazolium derivative cations.
˚
bZ10.003(2) A, bZ79.80(1)8
cZ16.572(4) A, gZ79.58(1)8
1200.9(5)
˚
3
˚
Volume, A
Z
2
Density (calculated)
Absorption coefficient
Diffractometer/scan
F(000)
1.555 g cmK3
1.181 mmK1
obtained by mixing methyl iodide and benzylbenzimidazole
in acetone and refluxed for 5 h.
Simens SMART/CCD area detector
574
q range for data collection
Index ranges
2.07–25.49
2.1.1. [MeBzBzim]2[Ni(mnt)2] 1
K8%h%9, K12%k%12, K15%l%20
6224
Reflections collected
Independent reflections
Absorption correction
Refinement method
Data/restraints/parameters
Goodness of fit on F2
Final R indices [IO2s(I)]
R indices (all data)
Largest diff. peak and hole
This compound was prepared by the direct combination
of 1:2:2 mol equiv of NiCl2$6H2O, Na2mnt and
[MeBzBzim]I in H2O. A red precipitate given was filtered
off, washed by water and dried under vacuum. Yield: 90%
(Found: C, 57.98; H, 3.82; N, 14.33. Calc. for C
38H30N8NiS4: C, 58.10; H, 3.85; N, 14.26%).
4365 [RintZ0.0795]
None
Full-matrix least-squares on F2
4365/0/308
1.004
R1Z0.0487, wR2Z0.1033
R1Z0.0676, wR2Z0.1092
˚
0.582 and K0.331 e A
K3
2.1.2. [MeBzBzim][Ni(mnt)2] 2
A MeCN solution (10 cm3) of I2 (150 mg, 0.59 mmol)
was slowly added to a MeCN solution (20 cm3) of
[MeBzBzim]2[Ni(mnt)2] (785 mg, 1.0 mmol), and stirred
for 15 min. MeOH (90 cm3) was then added, and the
mixture allowed to stand overnight. The microcrystals
formed were filtered off, washed with MeOH and dried in
vacuum. Yield: 87%. (Found: C, 49.05; H, 2.73; N, 15.01.
Calc. for C23H15N6NiS4: C, 49.13; H, 2.69; N, 14.94%). IR
(cmK1): 3133(w), 3072(m), 2208(vs), 1630(w), 1564(m),
1491(w), 1456(m), 747(s), 696(m).
were selected for X-ray structure measurement. All
measurements were made on a Siemens Smart CCD area
detector equipped with graphite-monochromated Mo Ka
˚
radiation (lZ0.71073 A) by uK2q scan mode. The
structure was solved by direct methods and expanded
using Fourier techniques. The non-hydrogen atoms were
refined anisotropically. All H atoms were placed in
calculated positions, assigned fixed isotropic displacement
parameters 1.2 times the equivalent isotropic U value of the
attached atom, and allowed to ride on their respective parent
atoms. All calculations were performed using the Bruker’s
SHELXTL program [15]. Space group, lattice parameters,
and other relevant information are listed in Table 1.
2.2. Physical measurements
Elemental analyses for carbon, hydrogen and nitrogen
were performed on a Perkin–Elmer 240 analytical instru-
ment. Infrared spectra were obtained with KBr pellets in
4000–400 cmK1 region, using an IFS66VFT-IR spectro-
photometer. Magnetic susceptibility data on crushed single
crystals were collected over the temperature range 2–300 K
using a Quantum Design MPMS-5S super-conducting
quantum interference device (SQUID) magnetometer, and
the experimental data were corrected for diamagnetism of
the constituent atoms estimated from Pascal’s constants.
3. Results and discussion
In the IR spectrum of complex 2, n(C–H) bands of
aromatic rings are exhibited at 3072, 3132, 747 and
696 cmK1. The very strong characteristic band due to the
n(CbN) of nitrile groups is seen at 2208 cmK1. Bands at
1455 and 1563 cmK1 can be assigned to n(CaN) and
n(CaC) of the benzimidazole ring and phenyl ring. Bands at
1491 cmK1 can be assigned to n(CaC) of mnt.
2.3. Structure determination of 2
Complex 2 crystallizes in the triclinic space group P1.
An ORTEP diagram of a formula unit with the atom
numbering scheme is depicted in Fig. 1. The relevant bond
lengths and bond angles are listed in Table 2. The
asymmetry unit consists of a [MeBzBzim]C cation and a
[Ni(mnt)2]K anion. For the anion, the nickel atom exhibits
Crystal structure determination suitable size single
crystals of the title compound 2 were obtained upon slow
evaporation of acetonitrile solution of the compound at
room temperature. A dark-red single crystal of complex 2,
having approximate dimensions 0.20!0.15!0.12 mm3,

D. Dang et al. / Journal of Molecular Structure 743 (2005) 197–200
199
Fig. 1. ORTEP drawing of complex 2 with the atom-numbering scheme.
square-planar geometry with four sulfur atoms. The five-
membered nickel-containing ring are slightly puckered, as
that have been found for other [M(mnt)2]nK structures [16].
The average S–Ni–S bond angle within the five-membered
ring is 87.27(4)8. The average Ni–S bond distance is
˚
˚
2.141(1) A. The average S–C bond distance is 1.719(3) A.
To compare with that of [Ni(mnt)2]K complex with
pyridinium [4–8], Ni–S bond distances are slightly shorter
and C–S bond distances are slightly longer. The anion is not
completely planar and the CN groups bend away from the
plane defined by four sulfur atoms. C(4)–N(2) and
C(5)–N(3) bend to one side of the plane, while C(1)–N(1)
and C(8)–N(4) bend to the other side. The CN group with
the large deviation is C(4)–N(2) and the deviations from the
Fig. 2. The packing diagram for complex 2 as viewed along the
crystallographic a-axis.
further gives rise to a three-dimensional supermolecular
structure. The shortest atom–atom distances are 3.53, 3.52,
˚
3.44 and 3.75 A for S(1)–N(3A), N(1)–N(4B), N(3)–C(8C)
and N(4)–C(5D), respectively (the symmetry codes, A:
x, 1Cy, z; B: Kx, 1Ky, Kz; C: 1Kx, Ky, Kz; D: Kx, Ky,
Kz). The weak magnetic interactions between Ni(III) ions
through the exchange pathways of p–p interactions are
expected from the structural point.
˚
˚
S4 plane are 0.119 A for N(2), and 0.077 A for C(4),
respectively. The cation, [MeBzBzim]C, adopts a confor-
mation where the benzene ring and benzimidazole ring are
twist to the reference plane C(17)–C(18)–N(6). The dihedral
angles are 110.38 for benzene and 90.28 for benzimidazole,
respectively.
The magnetic properties of the 2 have been investigated at
a field of 2 kOe in the temperature range 2–300 K. As
illustrated in Fig. 4, the magnetic susceptibility, cm, increases
as the temperature is decreased, till reaching a maximum of
0.018 emu molK1 at ca. 7.0 K and then sharply goes down to
In solid state, the [Ni(mnt)2]K anions and [MeBzBzim]C
cations are alternately stacked as revealed by the projection
along the crystallographic a-axis, and form one-dimensional
columns through p–p interactions between the plane of
[Ni(mnt)2]K and the neighbored benzimidazole ring
(Fig. 2). The distances between the center of benzimidazole
ring and the plane of neighboring [Ni(mnt)2]K alternate
˚
between 3.53 and 3.50 A within a column. Then this column
and one of the adjacent columns form an infinite super-
molecular ladder framework through the p–p interactions
between benzene rings of the cations as shown in Fig. 3
(For the overlapping pair of benzene rings, the centroid–
˚
centroid distance is 3.72 A.), and the existence of weak
interactions between the neighbored [Ni(mnt)2]K anions
Table 2
˚
The relevant bond lengths (A) and bond angles (8) for 2
Ni(1)–S(4)
Ni(1)–S(1)
S(1)–C(2)
S(3)–C(6)
2.135(1)
2.140(1)
1.718(4)
1.716(3)
Ni(1)–S(3)
Ni(1)–S(2)
S(2)–C(7)
S(4)–C(3)
2.139(1)
2.151(1)
1.730(3)
1.712(4)
S(4)–Ni(1)–S(3)
S(3)–Ni(1)–S(1)
S(3)–Ni(1)–S(2)
85.83(4)
178.45(4)
92.82(4)
S(4)–Ni(1)–S(1)
S(4)–Ni(1)–S(2)
S(1)–Ni(1)–S(2)
92.63(4)
178.63(4)
88.72(4)
Fig. 3. View of supermolecular ladder framework in complex 2 showing the
p–p stacking interactions.

200
D. Dang et al. / Journal of Molecular Structure 743 (2005) 197–200
4. Supplementary material
0.020
0.016
0.012
0.008
0.004
0.000
0.025
0.020
0.015
0.010
0.005
0.000
CCDC 262186 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/conts/retrieving.html
(or from the Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ, UK; fax: C44 1223
336033).
T
T
0
10
20
30
40
50
60
T/ K
Acknowledgements
0
50
100
150
200
250
300
Financial support from the National Natural Science
Foundation (No. 20490218), The Center of Analysis and
Determination of Nanjing University are acknowledged.
T / K
Fig. 4. Plot of cm versus T for 2. The solid line represents the best fit; inset:
plot of dcmT/dT versus T for 2.
the value of 0.011 emu molK1 at 2.0 K. The value of cmT at
300 K is 0.38 emu K molK1, which is slightly larger than that
of a spin-only value (SZ1/2) per formula unit. With
decreasing temperature, the cmT value first decreases slightly
till reaching 0.33 emu K molK1 at 50 K, and then
decreases rapidly below this temperature till reaching
0.02 emu K molK1 at 2 K. The Neel temperature (TN) of
complex 2, which may be estimated from the sharp peak of
d(cmT)/dT at 5.0 K shown in the inset of Fig. 3 [17,18]. The
magnetic data above 10 K can be fitted well to the Curie–
Weiss law with CZ0.42 emu K molK1, qZK10.6 K, and
References
[1] P.I. Clemenson, Coord. Chem. Rev. 106 (1990) 171.
[2] N. Robertson, L. Cronin, Coord. Chem. Rev. 227 (2002) 93.
´
[3] A.T. Coomber, D. Beljonne, R.H. Friend, J.L. Bredas, A. Charlton,
N. Robertson, A.E. Underhill, M. Kurmoo, P. Day, Nature 380
(1996) 144.
[4] A.E. Pullen, C. Faulmann, K.I. Pokhodnya, P. Cassoux,
M. Tokumoto, Inorg. Chem. 37 (1998) 6714.
[5] T. Waters, X.B. Wang, X. Yang, L. Zhang, R.A.J. O’Hair, L.S. Wang,
A.G. Wedd, J. Am. Chem. Soc. 126 (2004) 5119.
[6] X.M. Ren, Q.J. Meng, Y. Song, C.L. Lu, C.J. Hu, X.Y. Chen,
Z.L. Xue, Inorg. Chem. 41 (2002) 5931.
P
P
the agreement factor RZ (combsKcmcalc)2/ (cmobs)2Z
2.58!10K8. The negative value of Weiss temperature
indicates that the antiferromagnetic exchange coupling
between Ni(III) ions dominates the magnetic properties of
the complex.
[7] X.M. Ren, Q.J. Meng, Y. Song, C.S. Lu, C.J. Hu, X.Y. Chen, Inorg.
Chem. 41 (2002) 5686.
[8] J.L. Xie, X.M. Ren, Y. Song, W.W. Zhang, W.L. Liu, C. He,
Q.J. Meng, Chem. Commun. 2002; 2346.
[9] J.L. Xie, X.M. Ren, Y. Song, Y. Zou, Q.J. Meng, J. Chem. Soc.,
Dalton Trans. 2002; 2868.
In this work, a new ion–pair complex, 1-methyl-3-
benzylbenzimidazolium bis(maleonitrile-dithiolato)nicke-
late(III), has been synthesized. The X-ray structure
characterization shows the Ni(mnt)K2 anions and [MeBzB-
zim]C cations are alternately stacked. The p–p stacking
interactions and the weak interactions between adjacent
anions give rise to a three-dimensional supermolecular
structure. The variable temperature magnetic suscepti-
bilities investigation indicates that the antiferromagnetic
exchange coupling between Ni(III) ions through the
exchange pathways of p–p stacking interactions dominates
the magnetic properties of the complex and the Neel
temperature (TN) at 5.0 K is observed.
[10] J.L. Xie, X.M. Ren, C. He, Y. Song, Q.J. Meng, R.K. Kremer,
Y.G. Yao, Chem. Phys. Lett. 396 (2003) 41.
[11] C.L. Ni, D.B. Dang, Y. Song, S. Gao, Y.Z. Li, Z.P. Ni, Z.F. Tian,
L.L. Wen, Q.J. Meng, Chem. Phys. Lett. 396 (2003) 353.
[12] X.M. Ren, H. Okudera, R.K. Kremer, Y. Song, C. He, Q.J. Meng,
P.H. Wu, Inorg. Chem. 43 (2004) 2569.
[13] Y. Kikugawa, Synthesis 1981; 124.
[14] A. Davison, R.H. Holm, Inorg. Synth. 10 (1967) 8.
[15] SHELXTL, Version 5.10, Structure Determination Software Programs,
Bruker Analytical X-ray Systems Inc., Madison, WI, USA.
[16] K.W. Plumlee, B.M. Hoffman, J.A. Ibers, J. Chem. Phys. 63 (1975)
1926.
[17] M.E. Fisher, Proc. R. Soc. (London) A254 (1960) 66.
[18] M.E. Fisher, Philos. Mag. 7 (1962) 1731.