Syntheses, crystal structures, and magnetic properties of Ni(mnt)2-based molecular solids containing substituted isoquinolinium

Article abstract of DOI:10.1016/j.ica.2006.04.041

Two novel ion-pair complexes, [RBzIQl]⁺[Ni(mnt)₂]^- (mnt^2- = maleonitriledithiolate, [RBzIQl]⁺ = 4-R-benzylisoquinolinium; R = H (1), Cl (2)) have been characterized structurally and magnetically. The Ni (mnt)₂^- anions and [BzIQl]⁺ cations of 1 form 1D column of alternating between cations and anions via π?π stacking interaction between Ni(mnt)₂ plane and isoquinoline ring, and the Ni(mnt)₂ anions between adjacent columns exist C?N, C?N, and N?N interaction. The anions and cations of 2 stack into well-segregated columns in the solid state; and the Ni(III) ions form a 1D zigzag chain in a Ni(mnt)₂ column through intermolecular Ni?S, S?S, Ni?Ni or π?π interactions. The chain is uniform in 2 with the Ni?Ni distances of 3.784 A?. Magnetic susceptibility measurements for these complexes in the temperature range 1.8-300 K show that 1 exhibits antiferromagnetic coupling behavior, and 2 exhibits unusual magnetic phase transitions around 45 K. The overall magnetic behavior for 2 indicates the presence of antiferromagnetic interaction in the high-temperature phase (HT) and spin gap in the low-temperature phase (LT).

Full text of DOI:10.1016/j.ica.2006.04.041

Inorganica Chimica Acta 359 (2006) 3927–3933
www.elsevier.com/locate/ica
Syntheses, crystal structures, and magnetic properties
of Ni(mnt)2-based molecular solids containing
substituted isoquinolinium
a,b,
a
a
a
a
Chunlin Ni
*, Zhengfang Tian , Zhaoping Ni , Dongbin Dang , Yizhi Li ,
a
a,
*
You Song , Qingjin Meng
a
State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing University, 210093 Nanjing, PR China
Department of Applied Chemistry, Centre of Inorganic Functional Materials, South China Agricultural University, Wushan, Tianhe District,
Guangzhou, Guangdong 510642, PR China
b
Received 26 January 2006; received in revised form 22 April 2006; accepted 30 April 2006
Available online 5 May 2006
Abstract
Two novel ion-pair complexes, [RBzIQl]+[Ni(mnt)2]ꢀ (mnt2ꢀ = maleonitriledithiolate, [RBzIQl]+ = 4-R-benzylisoquinolinium;
R = H (1), Cl (2)) have been characterized structurally and magnetically. The NiðmntÞ2 anions and [BzIQl]+ cations of 1 form 1D col-
ꢀ
umn of alternating between cations and anions via pꢁ ꢁ ꢁp stacking interaction between Ni(mnt)2 plane and isoquinoline ring, and the
Ni(mnt)2 anions between adjacent columns exist Cꢁ ꢁ ꢁN, Cꢁ ꢁ ꢁN, and Nꢁ ꢁ ꢁN interaction. The anions and cations of 2 stack into well-seg-
regated columns in the solid state; and the Ni(III) ions form a 1D zigzag chain in a Ni(mnt)2 column through intermolecular Niꢁ ꢁ ꢁS,
˚
Sꢁ ꢁ ꢁS, Niꢁ ꢁ ꢁNi or pꢁ ꢁ ꢁp interactions. The chain is uniform in 2 with the Niꢁ ꢁ ꢁNi distances of 3.784 A. Magnetic susceptibility measure-
ments for these complexes in the temperature range 1.8–300 K show that 1 exhibits antiferromagnetic coupling behavior, and 2 exhibits
unusual magnetic phase transitions around 45 K. The overall magnetic behavior for 2 indicates the presence of antiferromagnetic inter-
action in the high-temperature phase (HT) and spin gap in the low-temperature phase (LT).
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Maleonitriledithiolate; Isoquinolinium; Nickel(III) complex; Crystal structure; Antiferromagnetic coupling; Spin gap
1. Introduction
Recently, we have developed a surprising new class of
ion-pair complexes [RbzPy][Ni(mnt)2] (RbzPy+ = ben-
zylpyridinium derivative) [12–19] and found that the signif-
icant structural feature of these ion-pair complexes is that
the Ni(mnt)2 ions and [RbzPy]+ cations stack into well-seg-
regated columns in the solid state, and Ni(mnt)2 ions form
ideal 1D magnetic chains of S = 1/2 through intermolecu-
lar Niꢁ ꢁ ꢁS, Sꢁ ꢁ ꢁS, Niꢁ ꢁ ꢁNi or pꢁ ꢁ ꢁp interactions. These ion-
pair complexes exhibit versatile magnetic properties such as
ferromagnetic ordering, magnetic transition from ferro-
magnetic to diamagnetic coupling, meta-magnetism, and
spin-Peierls-like transitions. One of the advantages of using
substituted benzylpyridinium as countercation is that the
topology and size of the countercation in Ni(mnt)2 com-
plex may play an important role in controlling the stacking
In the past few years, a considerable number of molecu-
lar solids based on M(dithiolene)2 as building blocks have
been investigated due to their novel properties such as mag-
netism, conducting, and non-linear optics [1–10]. Espe-
cially, the discovery of the first Ni(mnt)2 complex with
ferromagnetic ordering, NH4 Æ Ni(mnt)2 Æ H2O [11], has
led to new development of Ni(mnt)2 chemistry, and
prompted us to investigate the magnetic interaction in sim-
ple ionic complexes composed of Ni(mnt)2 anions.
*
Corresponding authors. Tel.: +86 20 85280318; fax: +86 20 85282366.
E-mail address: scauchemnicl@163.com (C. Ni).
0020-1693/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.04.041

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C. Ni et al. / Inorganica Chimica Acta 359 (2006) 3927–3933
pattern of anions and cations, which further influence the
magnetic properties of these complexes. Our continuing
research with [Ni(mnt)2]ꢀ complexes is to find more suit-
able multifunctional organic cations to tune the crystal
stacking structure of the [Ni(mnt)2] anion, and establish a
relationship between the magnetic interactions and the
stacking pattern of anions or cations. The structure of iso-
quinoline is similar to pyridine, but its electronic conjugat-
ing system is larger than that of the latter. We have
introduced substituted benzylisoquinolinium into the
Ni(mnt)2 system and obtained two newly prepared
Ni(mnt)2-based molecular solids: [BzIQl][Ni(mnt)2] (1)
2.3. Synthesis of [ClBzIQl][Ni(mnt)2] (2)
The procedure for preparing 2 is similar to that for 1.
Yield: 87%. Anal. Calc. for C24H13N5NiClS4 Æ 0.75CH3C-
N Æ 0.5H2O (2): C, 48.34; H, 2.58; N, 12.71. Found: C,
48.50; H, 2.73; N, 12.54%. IR (KBr, cmꢀ1): IR spectrum
(cmꢀ1): m(CN), 2207.5 s; m(C@C) of mnt2ꢀ, 1445.3 s. Yield:
85%.
The black single crystals suitable for the X-ray structure
analysis were obtained by evaporating the MeCN and i-
PrOH (v/v = 1:1) mixed solution of 1 and 2 about two
weeks at room temperature.
and
[ClBzIQl][Ni(mnt)2] Æ 0.75MeCN Æ 0.5 H2O
(2).
Although these molecular solids show antiferromagnetic
coupling behavior, 2 exhibit unusual spin-gap around
60 K. To the best of our knowledge, a spin gap system
the Ni(mnt)2 complex is very rare.
2.4. Instrumental procedures
Elemental analyses of C, H, and N were run on a Model
240 Perkin–Elmer C H N instrument. IR spectra were
recorded on an IF66V FT-IR spectrophotometer in
4000–400 cmꢀ1 region as KBr pellets. Magnetic susceptibil-
ity data on polycrystals sample was collected over the tem-
perature range of 1.8–300 K using a Quantum Design
MPMS-5S super-conducting quantum interference device
(SQUID) magnetometer, and diamagnetic corrections were
made using Pascal’s constants.
2. Experimental
Benzyl bromide, 4-chlorobenzyl bromide, and isoquino-
line were purchased from Aldrich and were used without
further purification. 1-Benzylisoquinolinium bromide
([BzIQl]Br) and 1-(40-chlorobenzyl)isoquinolinium bro-
mide ([ClBzIQl]Br) were prepared by the literature meth-
ods [20]. Disodium maleonitriledithiolate (Na2mnt) was
synthesized by a published procedure [21].
Table 1
Crystal data and structure refinement for 1 and 2
Compounds
1
2
2.1. Synthesis of [BzIQl]2[Ni(mnt)2] and
[ClBzIQl]2[Ni(mnt)2]
Empirical formula
C
24H14N5NiS4
C24H13N5NiClS4 Æ 0.75
CH3CN Æ 0.5H2O
633.59
Formula weight
559.35
293(2)
0.71073
triclinic
These two compounds were prepared by the direct com-
bination of NiCl2 Æ 6H2O, Na2mnt and [BzIQl]Br or
[ClBzIQl]Br in H2O in 1:2:2 molar ratio. The brown precip-
itate that formed was filtered off, washed with water and
dried under vacuum. Yield: 85%. Anal. Calc. for [BzIQl]2-
[Ni(mnt)2] (C40H28N6NiS4): C, 61.62; H, 3.62; N, 10.78.
Found: C, 61.51; H, 3.74; N, 10.69%. IR spectrum
(cmꢀ1): m(CN), 2202.6 s; m(C@C) of mnt2ꢀ, 1450.3 s. Yield:
91% Anal. Calc. for [ClBzIQl]2[Ni(mnt)2] (C40H26N6-
NiCl2S4): C, 56.62; H, 3.09; N, 9.90. Found: C, 56.57; H,
3.13; N, 9.86%. IR spectrum (cmꢀ1): m(CN), 2196.0 s;
m(C@C) of mnt2ꢀ, 1444.7 s.
T (K)
Wavelength (A)
293(2)
˚
0.71073
monoclinic
P21/c
18.669(4)
23.580(5)
7.234(2)
90
99.89(1)
90
3137.2(13)
4
Crystal system
ꢀ
Space group
P1
˚
a (A)
7.216(1)
11.042(2)
15.840(1)
93.34(3)
98.10(3)
105.80(3)
1196.1(4)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
Density (calculated)
(Mg/m3)
1.553
1.342
Absorption coefficient
1.184
0.996
(mmꢀ1
)
F(000)
570
1290
0.40 · 0.35 · 0.20
16748
2.2. Synthesis of [BzIQl][Ni(mnt)2] (1)
Crystal size (mm3)
0.60 · 0.50 · 0.30
11471
4197 (0.021)
Reflections collected
Independent reflections
(Rint
A MeCN solution (20 cm3) of I2 (160 mg, 0.62 mmol)
was slowly added to a MeCN solution (50 cm3) of
[BzIQl]2[Ni(mnt)2] (780 mg, 1 mmol) and the mixture was
stirred for 1 h. MeOH (90 cm3) was then added, and the
mixture allowed to stand overnight, 466 mg of black
micro-crystals formed were filtered off, washed with MeOH
and dried in vacuum.Yield: 83%. Anal. Calc. for
C24H14N5NiS4: C, 51.53; H, 2.52; N, 12.52. Found: C,
51.50; H, 2.61; N, 12.46%. IR spectrum (cmꢀ1): m(CN),
2208.5 s; m(C@C) of mnt2ꢀ, 1451.3 s.
6131 (0.034)
)
Refinement method
full-matrix
least-squares on F2 least-squares on F2
4197/0/307
1.011
full-matrix
6131/0/361
1.065
Data/restraints/
parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R1 = 0.0308,
wR2 = 0.0626
R1 = 0.0334
wR2 = 0.0638
R1 = 0.0576,
wR2 = 0.1120
R1 = 0.0992
wR2 = 0.1196
Final R indices (all data)

C. Ni et al. / Inorganica Chimica Acta 359 (2006) 3927–3933
3929
Table 2
Selected bond lengths, bond angles and dihedral angles for 1 and 2
Compounds
1
2
˚
Bond length (A)
Ni(1)–S(1)
Ni(1)–S(2)
Ni(1)–S(3)
Ni(1)–S(4)
S(1)–C(2)
S(2)–C(3)
S(3)–C(6)
S(4)–C(7)
2.152(1)
2.152(1)
2.150(1)
2.152(1)
1.723(3)
1.722(2)
1.723(3)
1.723(2)
2.144(1)
2.141(1)
2.141(1)
2.139(1)
1.744(3)
1.701(3)
1.699(4)
1.699(4)
Bond angles (ꢁ)
S(1)–Ni(1)–S(2)
S(1)–Ni(1)–S(4)
S(2)–Ni(1)–S(3)
S(3)–Ni(1)–S(4)
92.63(4)
87.11(4)
87.57(4)
92.69(5)
92.84(4)
87.10(4)
87.78(4)
92.26(4)
Fig. 1. ORTEP plot (30% probability ellipsoids) showing the molecule
structure of 1.
Dihedral angles (ꢁ)
CAr–CH2–NPy and UAr
91.7
96.3
75.7
66.1
65.3
97.6
C
Ar–CH2–NPy and UIQI
UAr and UIQI
phenyl ring make with the reference plane are 96.3ꢁ and
ꢀ
91.7ꢁ (Table 2), respectively. The NiðmntÞ2 anions and
[BzIQl]+ cations are alternately stacked as revealed by the
projection along the crystallographic a-axis (Fig. 2) and
form a column through pꢁ ꢁ ꢁp interactions between the iso-
2.5. Crystal structure determination
Crystals with dimensions 0.2 · 0.3 · 0.4 mm for 1 and
0.30 · 0.35 · 0.4 mm for 2 were selected for indexing and
intensity data collections at 293(2) K on a Bruker Smart
APEX CCD area detector using graphite-monochromated
ꢀ
quinoline rings and the planes of NiðmntÞ2 ions (Fig. 3a).
The nearest distance between isoquinoline rings and the
ꢀ
˚
Ni(III) of the planes of NiðmntÞ2 ions is 3.632 A, and
the isoquinoline riꢀngs are not completely parallel with the
plane of NiðmntÞ2 anion (the dihedral angle of 2.0ꢁ). As
shown in Fig. 2, there are two significant interactions
between adjacent columns. One is pꢁ ꢁ ꢁp interactions of
benzene rings of cations between column A and column
A0 (Fig. 3a), and the contact distances of C(9), C(10) and
C(11) atoms to the centre of neighboring benzene ring
˚
Mo Ka radiation (k = 0.71073 A) by x scan mode within
the angular range 1.8 < h < 26.0 for 1 and 1.7 < h < 26.0
for 2, respectively. Space group, lattice parameters, and
other relevant information are listed in Table 1, and
selected bond lengths, bond angles, and dihedral angles
for 1 and 2 are listed in Table 2. The structures were solved
by direct methods and refined on F2 by full-matrix least-
squares, employing Bruker’s SHELXTL [22]. All non-hydrogen
atoms were refined with anisotropic thermal parameters.
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.
˚
are 3.824, 3.582 and 3.750 A, respectively. The other is
ꢀ
Cꢁ ꢁ ꢁN, Cꢁ ꢁ ꢁC, and Nꢁ ꢁ ꢁN interactions of NiðmntÞ2 anions
between column A and column B and two overlap modes
B
A′
3. Results and discussion
3.1. Crystal structures
Crystallographic data for 1 and 2 are listed in Table 1.
An ORTEP view of 1 with non-hydrogen atomic labeling
is shown ꢀin Fig. 1. An asymmetric unit of 1 includes one
NiðmntÞ2 anion and one [BzIQl]+ cation, The Ni(1) of
ꢀ
the NiðmntÞ2 anion exhibits the square-planar coordina-
tion geometry. The Ni–S bond distances and the S–Ni–S
bond angles (Table 2) within the fivꢀe-membered rings agree
well with those found in NiðmntÞ2 complexes comprised
of benzylpyridinium derivatives [18]. The [BzIQl]+ cation
adopts a conformation where both the phenyl and isoquin-
oline rings are twisted to the C(14)–C(15)–N(5) reference
plane. The dihedral angles that the isoquinoline ring and
B′
A
Fig. 2. The packing diagram of a unit cell for 1 as viewed along a-axis.

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C. Ni et al. / Inorganica Chimica Acta 359 (2006) 3927–3933
ꢀ
An asymmetric unit of 2 contains one NiðmntÞ2 anion
and one [ClBzIQl]+ cation, half and quarter of acetonitrile
molecule, and half of water molecule. The water molecule
is disordered, and the occupancies of both O(1) and O(2)
are 25%. The coordination geometry of anion and the con-
formation of cation in 2 are essentially identical to those
described above for 1 (the Ni–S band distances and the
S–Ni–S bond angle and the dihedral angles that the iso-
quinoline ring and phenyl ring make with the reference
plane C(14)–C(15)–N(5) are listed in Table 2), while the
stacking pattern of anions and cations for 2 (Fig. 4) are sig-
nificantly different from those of 1.ꢀThe Ni(III) ions form a
1D zigzag chain within a NiðmntÞ2 column through inter-
molecular Niꢁ ꢁ ꢁS, Sꢁ ꢁ ꢁS, Niꢁ ꢁ ꢁNi or pꢁ ꢁ ꢁp interactions
(Fig. 5a), and the overlap mode of adjacent anions is
(a)
ꢀ
Mode M
shown in Fig. 6. Within a NiðmntÞ2 anions stacking col-
umn, the nearest Niꢁ ꢁ ꢁS and Sꢁ ꢁ ꢁS distances are 3.585
˚
˚
and 3.788 A, respectively; the Niꢁ ꢁ ꢁNi distance is 3.785 A,
while the closest Niꢁ ꢁ ꢁNi separation between anion col-
˚
umns is 14.392 A, which is significantly longer than the dis-
tance of Niꢁ ꢁ ꢁNi separation within a column. Therefore,
Mode N
(b)
Fig. 3. (a) The pꢁ ꢁ ꢁp interactions between the isoquinoline rings and the
planes of NiðmntÞ2ꢀ ions in column A and the pꢁ ꢁ ꢁp interactions of cations
between column A and column A0 for 1. (b) Modes of overlapping of
[Ni(mnt)2]ꢀ anions between column A and column B for 1.
of adjacent anions are expected (Fig. 3b). For mode M, the
contacts of C(1)ꢁ ꢁ ꢁC(1A), C(1)ꢁ ꢁ ꢁN(1A), N(1)ꢁ ꢁ ꢁC(2A),
˚
and N(1)ꢁ ꢁ ꢁC(3A) are 3.813, 3.737, 3.737, and 3.594 A,
respectively; and the nearest contact for mode N is
˚
3.454 A. The weak magnetic interactions between Ni(III)
ions through Cꢁ ꢁ ꢁN, Cꢁ ꢁ ꢁC, Nꢁ ꢁ ꢁN exchange pathways
Fig. 4. The packing diagram of a unit cell for 2 as viewed along a-axis.
are expected from the structural point.
(a)
(b)
Fig. 5. (a) Side view of the anions stack of 2 showing the alternating space linear-chain of [Ni(mnt)2]ꢀ. (b) Boat-type conformation of the cations in 2.

C. Ni et al. / Inorganica Chimica Acta 359 (2006) 3927–3933
3931
0.08
0.07
0.06
0.05
0.35
0.30
0.25
0.20
0.15
0.10
0.04
T
m
0.03
m
0
50 100 150 200 250 300
0.02
0.01
T (K)
Fig. 6. Mode of overlapping of [Ni(mnt)2]ꢀ anions for 2.
0.00
ꢀ
0
50
100 150 200 250 300
T (K)
the NiðmntÞ2 anion chain can be considered as a 1D uni-
(a)
form magnetic one. In a [ClBzIQl]+cation column, the
adjacent cations stack into a boat-type conformation
through pꢁ ꢁ ꢁp interactions between isoquinoline rings
(Fig. 5b), which is significantly different form that of the
[RBzPy]+ system [23]. The isoquinoline rings are nearly
parallel with respect to each other, and the contact distance
C(18), C(19), and C(20) atoms to centre of the neighboring
0.035
0.030
0.025
0.020
0.015
0.010
0.005
0.000
0.005
0.004
Tmax= 45.0 K
0.003
0.002
0.001
0.000
-0.001
˚
isoquinoline rings are 3.862, 3.482, and 3.692 A.
By comparing the structures of 1 and 2, we conclude
that the stacking and overlapping modes are different when
we have changed the p-substituted group in the benzene,
and the Cl group favors separated columnar molecular
stacking. In addition, some intermolecular contacts of
hydrogen bonds were found between the adjacent cationic
and anionic columns (Table 3), which play important roles
in the molecular stacking and stabilizing.
m
0
50 100 150 200 250 300
T (K)
0
50
100 150 200 250 300
T (K)
(b)
Fig. 7. (a) Plots of vm vs. T for 1 (inset: plots of vmT vs. T) (b) Plots of vm
vs. T for 2 (inset: plots of dvmT vs. dT). The solid line is reproduced from
the theoretical calculations and detailed fitting procedure described in the
text.
3.2. Magnetic properties of 1 and 2
The temperature dependence of the magnetic suscepti-
bilities for 1 and 2 were measured under an applied field
of 2000 Oe in the temperature range 1.8–300 K. The plots
of vm versus T for 1 and 2 are shown in Fig. 7 with vm being
the magnetic susceptibility per nickel atom corrected by the
diamagnetic contribution. For the complexes 1 and 2,
the overall magnetic behaviors correspond to a paramag-
netic system with an antiferromagnetic coupling interac-
tion. At 300 K, the vmT values of 1 and 2 are 0.347,
0.362 emu K molꢀ1, the values are slightly lower than the
expected for magnetically isolated Ni(III) ions. As the tem-
perature is lowered, the vm value of 2 varies in a complex
way (Fig. 7b): it increases slightly from 0.00120 emu molꢀ1
at 300 K to 0.00336 emu molꢀ1 at 60 K, then decreases
abruptly to a minimum (0.00287 emu molꢀ1 at 30 K) and
finally increases to 0.0314 emu molꢀ1 again upon further
cooling to 1.8 K. It is worthy to note that the vm values
decrease exponentially at 60 K for 2, indicating that 2
exhibits the characteristics of a spin gap system [24]. On
increase of temperature back to the original temperature,
the same vm–T curves are obtained without hysteresis effect
being detected. These findings indicate that 2 undergoes a
reversible phase transition and the phase transition temper-
ature (ꢂ45 K) is evaluated as the temperature at the max-
imum of the d(vmT)/dT derivative (inset of Fig. 7b).
Table 3
Hydrogen bonds for 1 and 2
D–Hꢁ ꢁ ꢁA
Complex 1
d(Dꢁ ꢁ ꢁH) d(Hꢁ ꢁ ꢁA) d(Dꢁ ꢁ ꢁA) \(DHA)
C(16)–H(16)ꢁ ꢁ ꢁ N(4)#1
0.93
0.93
2.43
2.57
3.349(4)
3.340(4)
168.0
141.0
C(23)–H(23)ꢁ ꢁ ꢁ N(1)#2
Complex 2
C(9)–H(9)ꢁ ꢁ ꢁN(1)#3
0.93
2.53
2.60
2.59
3.449(5)
3.424(7)
3.447(5)
169.0
143.0
152.0
C(15)–H(15B)ꢁ ꢁ ꢁN(6)#4 0.97
C(17)–H(17A)ꢁ ꢁ ꢁN(4)#5 0.93
The magnetic susceptibility data of 1 were quantitatively
analysed by the Curie–Weiss law with a Curie constant of
0.42 emu K molꢀ1 and a negative Weiss constant h =
ꢀ4.2 K, indicating an overall antiferromagnetic interaction
Symmetry transformations used to generate equivalent atoms: #1: x,
y ꢀ 1, z; #2: x, y, z + 1; #3: x, ꢀy + 1/2, z + 1/2; #4: ꢀx + 1, y ꢀ 1/2,
ꢀz + 3/2; #5: x + 1, ꢀy +1/2, z + 1/2.

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C. Ni et al. / Inorganica Chimica Acta 359 (2006) 3927–3933
between Ni(III) ions (Fig. 7a). The theoretical calculations
[25–27] and experimental determination [28] had shown
that about 0.15 of the unpaiꢀred electron resides on ligand
C and N atoms of NiðmntÞ2 anion, while the rest resides
in the NiS4 core, so this weak magnetic interactions
between Ni(III) ions of 1 through Cꢁ ꢁ ꢁN, Cꢁ ꢁ ꢁC, Nꢁ ꢁ ꢁN
exchange pathways are expected.
Acknowledgements
The authors are grateful for the financial support from
the National Natural Science Foundation of China (No.
20490218) and the president’s foundation of South China
Agricultural University (No. 2005K092).
The magnetic susceptibilities of 2 may be estimated by
the formula vm = [aexp(ꢀD/kBT)]/T + C/T + v0, where a
is a constant value corresponding to the dispersion of exci-
tation energy, D is the magnitude of the spin gap, v0 con-
tributes from the core diamagnetism and the possible
Van Vleck paramagnetism, and the other symbols have
their usual meanings [29], The best fit curve is shown in
Fig. 7b, and the corresponding parameters are given as fol-
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,
C = 5.6 · 10ꢀ2 emu K molꢀ1, and R = 2.3 · 10ꢀ4 (R is
P
2
2
defined as
ðvcmalc ꢀ vombsdÞ =ðvombsdÞ ). The origins of the
phase transition for 2 is attributed to cooperative interac-
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[Ni(mnt)2]ꢀ anions [30], pꢁ ꢁ ꢁp stacking interactions
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In this paper, two novel ion-pair complexes containing
the NiðmntÞ2 anion have been structurally characterized
ꢀ
and their magnetic behaviors investigated. 1 forms 1D
alternating column of cations and anions via pꢁ ꢁ ꢁp stacking
interactions between the Ni(mnt)2 plane and isoquinoline
ring, and the Ni(mnt)2 anions between adjacent columns
exhibit Cꢁ ꢁ ꢁN, Cꢁ ꢁ ꢁN, and Nꢁ ꢁ ꢁN interaction. The anions
and cations of 2 stack into well-separated uniform columns
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chain within a Ni(mnt)2-column through intermolecular
Niꢁ ꢁ ꢁS, Sꢁ ꢁ ꢁS, Niꢁ ꢁ ꢁNi or pꢁ ꢁ ꢁp interactions. Magnetic sus-
ceptibility measurements show that 1 exhibits antiferro-
magnetic coupling behavior, and 2 exhibits unusual
magnetic phase transitions around 45 K. The overall mag-
netic behavior for 2 indicates the presence of antiferromag-
netic interaction in the high-temperature phase (HT) and
spin gap in the low-temperature phase (LT).
5. Supplementary materials
The detailed crystallographic data for 1 and 2 have been
deposited at the Cambridge Crystallographic Data Center
as supplementary publication No. CCDC 260424 and
No. CCDC 260425. Copies of the data may be obtained
free of charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: +44 1223 336033; deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
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