Syntheses, crystal structures, and magnetic properties of two new 1D molecular solids based on Ni(mnt)2 ion

Article abstract of DOI:10.1016/j.ica.2005.03.028

Two novel ion-pair complexes, 1-(4′-bromo-2′-fluorobenzyl) isoquinolinium-bis(maleonitrile dithiolato)nickel(III), [BrFBzIQl] ? Ni(mnt)₂ ? 0.5MeCN (1) and 1-(4′-bromo-2′- flourobenzyl)-quinolinium-bis(maleonitriledithiolato)nickel(III), [BrFBzQ

Full text of DOI:10.1016/j.ica.2005.03.028

Inorganica Chimica Acta 358 (2005) 2680–2686
www.elsevier.com/locate/ica
Syntheses, crystal structures, and magnetic properties of two new
1D molecular solids based on Ni(mnt)2 ion
*
Chunlin Ni, Yizhi Li, Dongbin Dang, You Song, Zhaoping Ni, Qingjin Meng
State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing University, 22 Hankou Road, 210093 Nanjing, PR China
Received 13 October 2004; accepted 14 March 2005
Available online 18 April 2005
Abstract
Two novel ion-pair complexes, 1-(40-bromo-20-fluorobenzyl)isoquinolinium-bis(maleonitriledithiolato)nickel(III), [BrFBzIQ-
l] Æ Ni(mnt)2 Æ 0.5MeCN (1) and 1-(40-bromo-20-flourobenzyl)-quinolinium-bis(maleonitriledithiolato)nickel(III), [BrFBzQl] Æ
Ni(mnt)2 (2) have been characterized structurally and magnetically. The anions and cations of 1 stack into columns in the solid state,
ꢁ
˚
respectively; and the Ni(III) ions form uniform stacking column with the Niꢀ ꢀ ꢀNi distances 4.061 A within a NiðmntÞ column
2
through intermolecular Niꢀ ꢀ ꢀS, Sꢀ ꢀ ꢀS, Niꢀ ꢀ ꢀNi or pꢀ ꢀ ꢀp interactions, while 2 forms 1D column of alternating between cations
and anions via the hydrogen bonds, Cꢀ ꢀ ꢀN, Cꢀ ꢀ ꢀN, Nꢀ ꢀ ꢀC, and pꢀ ꢀ ꢀp interactions. The changes of coupling constants were observed
in these two complexes at 85 K for 1 and 70 K for 2. It is interesting that 1 undergoes a transition from antiferromagnetic to fer-
romagnetic phase and 2 does counter to that of 1.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Maleonitriledithiolate; Isoquinolinium; Quinolinium; Nickel(III) complex; Crystal structure; Magnetic properties
1. Introduction
into wellꢁ-segregated columns in the solid state, and
ions form deal 1D magnetic chain of
NiðmntÞ
2
In recent years, the design of new molecule-based
ꢁ
s = 1/2 through intermolecular Niꢀ ꢀ ꢀS, Sꢀ ꢀ ꢀS, Niꢀ ꢀ ꢀNi
or pꢀ ꢀ ꢀp interactions; (2) these ion-pair complexes exhi-
bit versatile magnetic properties such as ferromagnetic
ordering, magnetic transition from ferromagnetic cou-
pling to diamagnetism, meta-magnetism and spin-Pei-
erls-like transitions; (3) theꢁtopology and size of the
materials based on NiðmntÞ blocks has gained an in-
2
creased interest due to their novel magnetic properties
[1–7]. Especially, the discovery of NH4 Æ Ni(mnt)2ÆH2O
with ferromagnetic ordering has led to new develop-
ment of Ni(mnt)2 chemistry [8]. Our contribution to
this field is to have developed a new class of ion-pair
complexes [RbzPy][Ni(mnt)2] (RbzPy+ = benzylpyridi-
nium derivative) [9–15], the prominent features of the
complexes can be described as follows: (1) the signifi-
cant structural feaꢁture of these ion-pair complexes is
countercation in NiðmntÞ
complex may play an
2
important role in controlling the stacking pattern of
anions and cations, which further influence the mag-
netic properties of these complexes. Our continuing re-
search with [Ni(mnt)2]ꢁ complexes is to find more
suitable multifunctional organic cations to tune the
crystal stacking structure of [Ni(mnt)2] anion, and
establish a relationship between the magnetic interac-
tions and the stacking pattern of anions or cations.
In this paper, we report the syntheses, structures and
magnetic properties of two novel ion-pair complexes,
that the NiðmntÞ ions and [RbzPy]+ cations stack
2
*
Corresponding author. Tel.: +86 25 83597266; fax: +86 25
83314502.
E-mail address: njuchem1024@163.com (Q. Meng).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.03.028

C. Ni et al. / Inorganica Chimica Acta 358 (2005) 2680–2686
2681
+
N
[BrFBzIQl]2[Ni(mnt)2] (973 mg, 1 mmol) and the mix-
ture was stirred for 1 h. MeOH (90 cm3) was then added,
and the mixture allowed to stand overnight, 590 mg of
black micro-crystals formed were filtered off, washed
with MeOH and dried in vacuum.Yield:87.2%. Anal.
Calc. for C24H12N5NiBrFS4 Æ 0.5CH3CN: C, 44.37; H,
2.01; N, 11.38. Found: C, 44.50; H, 2.12; N, 11.29 %.
IR (KBr, cmꢁ1): 3068(m), 3054(m), 2204(m), 1642(s),
1606(s), 1579(s), 1535(s), 1487(vs), 1158(s), 878(s),
577(m).
Br
(a)
CH2
CH2
F
F
+
N
Br
(b)
Fig. 1. The structures of [BrFBzIQl]+ (a) and [BrFBzQl]+ (b) cations.
[BrFBzIQl] Æ Ni(mnt)2 Æ 0.5MeCN (1) ([BrFBzIQl]+ = 1-
(40-bromo-20-fluorobenzyl)isoquinolinium) and [BrFBz-
Ql] Æ Ni(mnt)2 (2) ([BrFBzIQl]+ = 1-(40-bromo-20-fluo-
robenzyl)quinolinium). Interestingly, for these two
ion-pairs complexes, although all components of anion
and cation are same except that one is isoquinolinium
derivative and the other is quinolinium derivative (Fig.
1), the structures and properties of the two complexes
are very different.
2.3. Synthesis of [BrFBzQl][Ni(mnt)2] (2)
The procedure for preparing 2 is similar to that for 1.
Yield: 90.5%. Anal. Calc. for C24H12N5NiBrFS4: C,
43.93; H, 1.84; N, 10.67. Found: C, 44.06; H, 1.98; N,
10.52%. IR (KBr, cmꢁ1): 3091(m), 3058(m), 2210(m),
1625(s), 1606(s), 1587(s), 1527(s), 1483(vs), 1160(s),
884(s), 592(m).
The black single crystals suitable for the X-ray struc-
ture analysis were obtained by evaporating the MeCN
and i-PrOH (v/v = 1:1) mixed solution of 1 and 2 for
about two weeks at room temperature.
2. Experimental
4-Bromo-2-fluorobenzyl bromide, isoquinoline and
quinoline were purchased from Aldrich and were used
without further purification. 1-(40-bromo-20-fluoroben-
zyl)isoquinolinium bromide ([BrFBzIQl]Br) and 1-(40-
bromo-20-fluorobenzyl)quinolinium bromide ([BrFBz-
Ql]Br) were prepared by the literature method [16].
Disodium maleonitriledithiolate (Na2mnt) was synthe-
sized by a published procedure [17].
2.4. Instrumental procedures
Elemental analyses of C, H, and N were run on a
Model 240 Perkin–Elmer CHN instrument. IR spectra
were recorded on an IF66V FT-IR (400–4000 cmꢁ1 re-
gion) spectrophotometer in KBr pellets. Magnetic sus-
ceptibility data on powder sample were collected over
the temperature range of 2–300 K using a Quantum De-
sign MPMS-5S super-conducting quantum interference
device (SQUID) magnetometer and diamagnetic correc-
tions were made using Pascalꢀs constants.
2.1. Synthesis of [BrFBzIQl]2[Ni(mnt)2] and
[BrFBzQl]2[Ni(mnt)2]
These two compounds were prepared by the direct
combination of NiCl2Æ6H2O, Na2mnt and [BrFBzIQl]Br
or [BrFBzQl]Br in H2O in 1:2:2 molar ratio. The brown
precipitate that formed was filtered off, washed with
water and dried under vacuum. Yield: 91%. Anal. Calc.
for [BrFBzIQl]2[Ni(mnt)2] (C40H24N5NiBr2F2S4): C,
49.35; H, 2.48; N, 8.63. Found: C, 49.21, H, 2.54, N,
8.49%. IR (KBr, cmꢁ1): 3096(m), 3036(m), 2216(m),
2196(vs), 1643(s), 1606(s), 1578(s), 1513(s), 1475(vs),
1149(s), 880(s), 580(m). Yield: 87%. Anal. Calc. for
[BrFBzQl]2[Ni(mnt)2] (C40H24N5NiBr2F2S4): C, 49.35;
H, 2.48; N, 8.63. Found: C, 49.29, H, 2.61, N, 8.56%.
IR (KBr, cmꢁ1): 3079(m), 3057(m), 2214(m), 2194(vs),
1625(s), 1606(s), 1576(s), 1529(s), 1481(vs), 1150(s),
885(s), 595(m).
2.5. Crystal structure determination
Crystals with dimensions 0.20 · 0.20 · 0.3 mm for 1
and 0.30 · 0.30 · 0.4 mm for 2 were selected for index-
ing and intensity data collections at 293(2) K on a Bru-
ker Smart APEX CCD area detector using graphite-
˚
monochromated Mo Ka radiation (k = 0.71073 A) by
x scan mode within the angular range 1.9 < h < 26.0
for 1 and 2.0 < h < 25.0 for 2, respectively. Space
group, lattice parameters, and other relevant informa-
tion are listed in Table 1. The structures were solved
by direct methods and refined on F2 by full-matrix
least-squares, employing Brukerꢀs SHELXTL [18]. All
non-hydrogen atoms were refined with anisotropic ther-
mal parameters. All H atoms were placed in calculated
positions, assigned fixed isotropic displacement param-
eters 1.2 times the equivalent isotropic U value of the
attached atom, and allowed to ride on their respective
parent atoms.
2.2. Synthesis of [BrFBzIQl][Ni(mnt)2] (1)
A MeCN solution (20 cm3) of I2 (160 mg, 0.62 mmol)
was slowly added to a MeCN solution (50 cm3) of

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C. Ni et al. / Inorganica Chimica Acta 358 (2005) 2680–2686
Table 1
Crystal data and structure refinement for 1 and 2
Compounds
1
2
Empirical formula
C24H12N5NiBrFS4 Æ C24H12N5NiBrFS4
0.5CH3CN
Formula weight
T (K)
676.77
293(2)
656.25
293(2)
˚
Wavelength (A)
0.71073
orthorhombic
Pca21
0.71073
triclinic
Crystal system
Space group
Unit cell dimensions
ꢀ
P1
˚
a (A)
21.346(3)
17.960(2)
7.417(1)
90
7.430(2)
10.229(3)
17.243(5)
86.35(1)
86.34(1)
77.56(1)
1275.4(6)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
90
Fig. 2. ORTEP plot (30% probability ellipsoids) showing the molec-
ular structure of 1.
3
˚
Volume (A )
2843.5(6)
4
Z
Dcalc (mg/m3)
Absorption coefficient
(mmꢁ1
1.581
2.413
1.709
2.686
)
Table 2
Selected bond lengths, bond angles and dihedral angles for 1 and 2
F(000)
Crystal size (mm3)
1352
654
0.3 · 0.2 · 0.2
14122
5329 (0.075)
0.4 · 0.3 · 0.3
6382
4417 (0.035)
Compounds
1
2
Reflections collected
Independent reflections
˚
Bond length (A)
Ni(1)–S(1)
Ni(1)–S(3)
2.138(2)
2.140(2)
2.141(1)
2.142(1)
2.141(2)
2.130(2)
2.137(2)
2.136(2)
(Rint
Refinement method
)
full-matrix least-
squares on F2
full-matrix least-
squares on F2
4417/0/325
Ni(1)–S(2)
Ni(1)–S(4)
Data/restraints/parameters 5329/0/354
Goodness-of-fit on F2
1.030
1.018
Bond angles (ꢁ)
S(1)–Ni(1)–S(2)
S(1)–Ni(1)–S(4)
S(3)–Ni(1)–S(4)
S(2)–Ni(1)–S(3)
Final R indices [I > 2r (I)] R1 = 0.0532,
wR2 = 0.1223
R1 = 0.0567,
wR2 = 0.1079
R1 = 0.1014,
wR2 = 0.1019
92.25(5)
87.17(5)
92.53(5)
88.05(5)
88.62(6)
92.71(6)
86.00(6)
92.67(6)
Final R indices (all data)
R1 = 0.0912,
wR2 = 0.1290
Dihedral angles (ꢁ)
Benzene–C(19)–C(18)–N(5) plane
Isoquinoline–C(19)–C(18)–N(5) plane
88.8
94.9
81.6
100.9
3. Results and discussion
3.1. Crystal structure of 1
The complex 1 crystallizes in the orthorhombic space
group Pca21. An ORTEP view with non-hydrogen
atomic labeling is shown in Fig. 2. Selected bond
lengths, bond angles, and dihedral angles for 1 are listed
nearest Niꢀ ꢀ ꢀS and Sꢀ ꢀ ꢀS distances are 3.493 and
˚
3.821 A, respectively; and the Niꢀ ꢀ ꢀNi distance is
˚
4.061 A, while the closest Niꢀ ꢀ ꢀNi separation between
˚
anion columns is 14.392 A, which is significantly longer
in Table 2. There are a NiðmntÞ anion, a [BrFBzIQl]+
than the distance of Niꢀ ꢀ ꢀNi separation within a column.
ꢁ
2
ꢁ
cation and a half of MeCN in the asymmetric unit cell.
ꢁ
Therefore, the NiðmntÞ anion chain can be considered
2
The Ni(1) of the NiðmntÞ anion exhibits the square-
as a 1D uniform magnetic one (Fig. 3(a)). In a
[BrFBzIQl]+ cation column, the adjacent cations stack
into a boat-type conformation (Fig. 3(b)). The isoquin-
oline rings are not completely parallel with respect to
each other (the dihedral angle of 3.8), and the average
contact distance of atoms of an isoquinoline ring to
2
planar coordination geometry. The Ni–S bond distance
and the S–Ni–S bond angle within the five-membered
rings are in good agreement with those found in
NiðmntÞ
complexes [19]. The [BrFBzIQl]+ cation
ꢁ
2
adopts a conformation where both the phenyl and iso-
quinoline rings are twisted to the C(19)–C(18)–N(5) ref-
erence plane. The dihedral angles that isoquinoline ring
and phenyl ring make with the reference plane are 88.8ꢁ
and 94.9ꢁ, respectively. An interesting structural feature
of 1 is the presence of the completely segregated stack
˚
neighboring one is 3.605 A. Therefore, the cations form
1D chain through pꢀ ꢀ ꢀp interactions between isoquino-
line rings. It is worth noting that the intermolecular
hydrogen bonds between anions, cations and solvents
MeCN (as shown in Fig. 3(c)) play important roles in
crystal packing and stability, and the corresponding dis-
tances and angles of H-bonding contacts are summa-
rized in Table 3.
columns of NiðmntÞ ꢁanions and [BrFBzIQl]+ cation
2
as revealed by the projectꢁion along the crystallographic
c-axis. Within a NiðmntÞ anions stacking column, the
2

C. Ni et al. / Inorganica Chimica Acta 358 (2005) 2680–2686
2683
described above for 1. Selected bond distances, bond an-
gles, and dihedral angles are summarized in Table 2. The
stacking pattern of 2 is significantly different from that
of 1, the alternating stacking of anions and cations
forms a 1D chain through pꢀ ꢀ ꢀp interactions between
ꢁ
the quinoline rings and the planes of NiðmntÞ ions
2
(Fig. 4(a)). The distance betweeꢁn quinoline rings and
˚
those of the planes of NiðmntÞ ions is 3.570 A, and
2
the quinoline rings are not completely parallel with the
ꢁ
planes of NiðmntÞ (the dihedral angle of 3.1ꢁ). The
2
(a)
chains grow along the a axis through the molecular
interactions involving the hydrogen bonds beꢁtween the
nitrogen atoms [N(1) and N(2)] of NiðmntÞ and the
2
carbon atoms [C(16) and C(17)] (Table 4), and inter-
˚
˚
˚
chain Cꢀ ꢀ ꢀN(3.445 A), Cꢀ ꢀ ꢀC(3.614 A), Nꢀ ꢀ ꢀN(3.806 A)
ꢁ
interactions between NiðmntÞ
anions (Fig. 4(b)).
2
Therefore, the weak magnetic interactions between
Ni(III) ions through Cꢀ ꢀ ꢀN, Cꢀ ꢀ ꢀC, Nꢀ ꢀ ꢀN exchange
pathways are expected.
3.3. Magnetic properties of 1 and 2
(b)
The temperature-dependent molar magnetic suscepti-
bilities of 1 and 2 were measured in a magnetic field of
1000 Oe in the range of 2–300 K. For 1, the vmT value
at 300 K is 0.374 emu K molꢁ1, a value which is as ex-
pected for NiIII (s = 1/2) magnetically isolated. As the
temperature is lowered, the vmT product first smoothly
decreases, exhibits a minimum of 0.253 emu K molꢁ1
at 85 K, then increases sharply to reach a very high va-
lue (1.83 emu K molꢁ1) at 2 K (Fig. 5). Its magnetic
behavior may be divided into two parts on their depen-
dence on temperature. Above 85 K, the temperature
dependence of reciprocal susceptibility ðvꢁm1Þ follows
the Curie–Weiss law with a negative Weiss constant
h = ꢁ80.4 K, indicating an overall antiferromagnetic
interaction between Ni(III) ions. Below 85 K, there is
a rise in vmT as T decrease is characteristic of a magnetic
system with dominant ferromagnetic interaction
between Ni(III) ions. The magnetic data in low-temper-
ature region (T < 85 K) can be well fitted by the Curie–
Weiss law with the fitting parameters being
C = 0.53 emu K molꢁ1, h = 2.23 K (the insets of Fig.
5). The ac susceptibility measurements performed in
the temperature range 2–10 K, at Hac = 2 Oe and fre-
quency of 111 Hz, show both in-phase (v0) and out-of-
phase (v00) signals at low temperature. The lack of peaks
in both v0 and v00 versus T curves suggests that long-
range ferromagnetic ordering is absent above 2 K.
The weak ferromagnetic coupling behavior below
85 K is confirmed by the dependence of isothermal mag-
netization at 2, 5, 10 and 50 K, respectively (Fig. 6). The
magnetization at 2 K increases very rapidly before the
field reaches 1 kOe, above which the magnetization sat-
urates rapidly upon increasing the field. The saturation
(c)
Fig. 3. Side view of the anions (a) and cations (b) stack and
intermolecular contacts between anions and cations (c) of 1.
Table 3
Hydrogen bonds for 1
D–Hꢀ ꢀ ꢀA
d(Dꢀ ꢀ ꢀH) d(Hꢀ ꢀ ꢀA) d(Dꢀ ꢀ ꢀA) (DHA)
C(9)–H(9)ꢀ ꢀ ꢀN(3)#1
0.93
C(11)–H(11)ꢀ ꢀ ꢀN(4)#1 0.93
C(14)–H(14)ꢀ ꢀ ꢀN(1)#2 0.93
2.54
2.52
2.56
2.53
3.444(10) 164.0
3.256(16) 137.0
3.421(11) 154.0
3.047(12) 114.0
C(25)–H(25)ꢀ ꢀ ꢀF(1)#3
0.93
Symmetry transformations used to generate equivalent atoms: #1:
x ꢁ 1/2, ꢁy, z + 1. #2: x ꢁ 1/2, ꢁy + 1, z. #3: x + 1/2, ꢁy + 1, z.
3.2. Crystal structure of 2
The coordination geometry of anion and the confor-
mation of cation in 2 are essentially identical to those

2684
C. Ni et al. / Inorganica Chimica Acta 358 (2005) 2680–2686
(a)
(b)
Fig. 4. Side view of the anions and cations stack and intermolecular contacts between anions and cations of 2.
magnetization is 1070 emu G molꢁ1, significantly smal-
ler than the saturation value (5585 emu G molꢁ1) ex-
pected for Ni(III) species. On the contrary, the
magnetization at 5, 10 and 50 K increases slowly as
the magnetic field increases. This weak ferromagnetism
of 1 arises from the presence of a spin-canted structure
in the ferromagnetic state. It is well-known that spin
canting may arise from two mechanisms: single-ion
magnetic anisotropy and antisymmetric exchange [20–
26]. The results of the structural analysis of 1 indicate
that a center of inversion is absent in a Pca21 space
group; the antisymmetric exchange would account for
the spin canting observed.
in Fig. 7, which is in agreement with the magnetic nature
of a weak ferromagnetism mentioned above. Further
measurement revealed that 1 is a soft magnet with no
detectable hysterisis at 2 K in the magnetization. It is
ꢁ
worth mentioning that the NiðmntÞ complexes show-
2
ing magnetic transition at about 85 K from antiferro-
magnetic to ferromagnetic interaction in molecule
solids are very rare. As far as we know, only two exam-
ples for the transition were reported before. Compared
with NH4 Æ Ni(mnt)2 Æ H2O [8], the title complex com-
prises a large organic cation [BrFBzIQl]+ and oþrganic
solvent MeCN instead of inorganic ion NH4 and
H2O of NH4 Æ Ni(mnt)2 Æ H2O.
The magnetic behavior of a weak ferromagnetic cou-
pling due to spin-canting should be quite field dependent
[27]. In order to confirm the occurrence of spin-canting
for 1, the magnetization values were measured at differ-
ent temperature and values of the applied field as shown
1.0
2.0
0.8
0.6
1.6
0.4
1.2
0.8
0.4
0.0
0.2
0.0
m
χ
Table 4
Hydrogen bonds for 2
T
0
20
40
60
80
D–Hꢀ ꢀ ꢀA
d(Dꢀ ꢀ ꢀH) d(Hꢀ ꢀ ꢀA) d(Dꢀ ꢀ ꢀA) (DHA)
m
χ
T / K
C(16)–H(16)ꢀ ꢀ ꢀN(2)#1
0.93
0.93
2.58
2.50
2.49
2.49
3.426(9)
3.230(8)
3.448(7)
3.254(9)
152.0
135.0
171.0
139.0
C(17)–H(17)ꢀ ꢀ ꢀN(1)#1
C(18)–H(18)aꢀ ꢀ ꢀN(4)#2 0.97
C(24)–H(24)ꢀ ꢀ ꢀN(3)#3
0.93
0
50
100 150 200 250 300
T / K
Symmetry transformations used to generate equivalent atoms: #1:
ꢁx + 1, ꢁy + 1, ꢁz + 1. #2: x, y + 1, z. #3: ꢁx + 1, ꢁy, ꢁz.
a = x + 1, y, z.
Fig. 5. vmT and vm (inset) vs. T plots for 1.

C. Ni et al. / Inorganica Chimica Acta 358 (2005) 2680–2686
2685
1200
1000
800
600
400
200
0
0.40
0.35
0.30
0.25
0.006
0.005
0.004
0.003
0.002
0.001
0.000
0.20
0.15
0.10
0.05
0.00
2K
5K
10K
50K
m
χ
M
T
m
χ
50
100 150 200 250 300
T / K
0
50
100 150 200 250 300
T / K
0
10000 20000 30000 40000 50000
H / G
Fig. 8. vmT and vm (inset) vs. T plots for 2.
Fig. 6. Field dependence of magnetization of
temperatures.
1 at different
sensitive to not only the overlap fashion of neighboring
ꢁ
700
NiðmntÞ anions but also intermolecular contacts, and
2
200G
1000G
5000G
small structural change can result in large changes in the
ꢁ
600
500
400
300
200
100
0
materials properties of the NiðmntÞ complexes due to
2
the subtle interplay between ferromagnetic and antifer-
romagnetic components of intermolecular interactions
[5,6]. The theoretical studies have also suggested that
no simple correlation of magnetic coupling is possible
with few structural parameters due to extensꢁive delocal-
M
ization of the electron density in NiðmntÞ unit, and
2
several shorter contact distances such as Niꢀ ꢀ ꢀNi,
Niꢀ ꢀ ꢀS, Sꢀ ꢀ ꢀS, Sꢀ ꢀ ꢀN, and Cꢀ ꢀ ꢀN play significant roles
in the super-exchange pathway [8,32]. Therefore, the dif-
ferent magnetic transitions for 1 and 2 may be
understood.
0
5
10
15
20
25
30
35
T / K
Fig. 7. The magnetization data for 1 as a function of temperature at
different external fields.
4. Conclusions
Although 2 shows a magnetic coupling constant
change around 70 K (Fig. 8), the magnetic exchange
behavior of 2 is significantly different from that of 1.
Above 70 K, 2 exhibits Curie–Weiss behavior with a
Curie constant of 0.355 emu K molꢁ1 and Weiss temper-
ature of 4.20 K, which indicates weak ferromagnetic
coupling (the inset of Fig. 8). Below 70 K, 2 exhibits
antiferromagnetic interaction with a negative Weiss tem-
ꢁ
Two novel ion-pair complexes containing NiðmntÞ
2
anion have been structurally characterized and their
magnetic behaviors investigated. The stacking pattern
of 1 is significantly different from those of its analogies
[RbzPy][Ni(mnt)2] [9–15]. The crystal cell of 1 has half
of one CH3CN molecular, and [BrFBzIQl]+ cations
stack into a column via pꢀ ꢀ ꢀp interactions between iso-
quinoline rings. The H-bonding interactions between
anions, cations and solvents MeCN play an important
role in crystal stacking and stability. The first example
which shows ferromagnetic interaction in the metal
dithiolene complexes is the charge-transþfer salt contain-
ing inorganic cation inorganic ion NH4 and inorganic
molecular H2O, NH4 Æ Ni(mnt)2 Æ H2O [8]. This salt is
an insulator with localized spins that exhibits long-range
ferromagnetic order below 4.5 K. It is interesting that
similar magnetic behaviors were obtained when we use
organic cation [BrFBzIQl]+ or [BrFBzPy]+ instead of
perature of ꢁ7.92 K and
a Curie constant of
0.493 emu K molꢁ1. The theoretic calculations [28–30]
and experimental determination [31] had shown that
about 0.15 of the unpaired electron resides on ligand
ꢁ
C and N atoms of NiðmntÞ anion, while the rest re-
2
sides in the NiS4 core, so the weak magnetic interactions
between Ni(III) ions of 2 through Cꢀ ꢀ ꢀN, Cꢀ ꢀ ꢀC, Nꢀ ꢀ ꢀN
exchange pathways are expected.
The change of magnetic coupling constant is with ref-
erence to the variations in intermolecular contacts as the
temperature is lowered [8]. As for complexes containing
ꢁ
þ
NiðmntÞ anion, the previous studies hꢁave shown that
NH4 in NH4 Æ Ni(mnt)2 Æ H2O. The system containing
2
[BrFBzPy]+ shows long-range ferromagnetic order
the magnetic coupling between NiðmntÞ anions is very
2

2686
C. Ni et al. / Inorganica Chimica Acta 358 (2005) 2680–2686
[11] J.L. Xie, X.M. Ren, Y. Song, W.W. Zhang, W.L. Liu, C. He,
Q.J. Meng, Chem. Commun. (2002) 2346.
below 2.8 K [12], while the magnetic order was not ob-
tained in 1, probably because the temperature is too
low. The stack of 2 is very unique and its magnetic ex-
change mechanism may involve H-bonding, pꢀ ꢀ ꢀp,
Cꢀ ꢀ ꢀN, Cꢀ ꢀ ꢀC, Nꢀ ꢀ ꢀN interactions that differ signifi-
cantly from that of 1. To the best of our knowledge, re-
ports on the mnt2ꢁ acting as the H-bonding acceptor are
very rare [24].
[12] J.L. Xie, X.M. Ren, Y. Song, Y. Zou, Q.J. Meng, J. Chem. Soc.
Dalton Trans. (2002) 2868.
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41 (2002) 5686.
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Ni, W.L. Liu, Q.J. Meng, Y.G. Yao, Eur. J. Inorg. Chem. (2003)
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[15] J.L. Xie, X.M. Ren, Y. Song, W.J. Tong, C.S. Lu, Y.G. Yao,
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Acknowledgments
[17] A. Davison, R.H. Holm, Inorg. Synth. 10 (1967) 8.
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The authors are grateful for the financial support
from the National Natural Science Foundation of China
(Nos. 20171022, 20490210). The Center of Analysis and
Determination of Nanjing University is acknowledged.
[19] X.M. Ren, C.S. Lu, P.H. Wu, Q.J. Meng, J. Chem. Crystallogr.
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