Investigation of the crystal structures and magnetic features of two bis(dithiolato)nickelate salts with flexible organic cations

Article abstract of DOI:10.1007/s11243-021-00452-w

Two bis(dithiolato)nickel salts with different flexible ammonium counterions, [Et₃MeN][Ni(dmit)₂] (1) and [(i-Bu)Et₃N][Ni(dmit)₂] (2) (dmit^2? = 2-thioxo-1,3-dithiole-4,5-dithiolate, Et₃MeN⁺ = triethylmethylammonium, (i-Bu)Et₃N⁺ = triethylisobutylammonium), are prepared and identified by powder X-ray diffraction (PXRD) patterns and single-crystal X-ray diffraction. Salt 1 crystallizes in the triclinic space group P???1 at 293?K. The anions and cations in 1 form alternating layered arrangements along the a-axis direction. Salt 2 belongs to the monoclinic crystal system and space group P2₁/n. The anions and cations in 2 form separate columnar stacks along bc-plane direction. The neighboring anions are stacked as dimers in the anion columnar stacks of 2. The magnetic features of salts 1 and 2 show 1D alternating spin chain magnetic exchange behavior, and the magnetic experimental data are well fitted through a spin chain magnetic model. The difference in the crystal structures and magnetic properties between the two new salts 1 and 2 fully demonstrates that the magnetic properties are dependent on the alignment of the [Ni(dmit)₂]^? anions, which are related to the flexible organic cations. Graphical abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s11243-021-00452-w

Transition Metal Chemistry
https://doi.org/10.1007/s11243-021-00452-w
Investigation of the crystal structures and magnetic features of two
bis(dithiolato)nickelate salts with ꢀexible organic cations
Xuan‑Rong Chen1 · Zhen‑Min Zhang · Min Luo · Hang Liu · Jia‑Yi Yuan
1
1
1
1
Received: 4 December 2020 / Accepted: 24 February 2021
©
The Author(s), under exclusive licence to Springer Nature Switzerland AG 2021
Abstract
Two bis(dithiolato)nickel salts with diferent ꢀexible ammonium counterions, [Et MeN][Ni(dmit) ] (1) and [(i-Bu)Et N]
3
2
3
2
−
+
+
[
Ni(dmit) ] (2) (dmit =2-thioxo-1,3-dithiole-4,5-dithiolate, Et MeN =triethylmethylammonium, (i-Bu)Et N =trieth-
2
3
3
ylisobutylammonium), are prepared and identiꢁed by powder X-ray difraction (PXRD) patterns and single-crystal X-ray
difraction. Salt 1 crystallizes in the triclinic space group P − 1 at 293 K. The anions and cations in 1 ꢂorm alternating layered
arrangements along the a-axis direction. Salt 2 belongs to the monoclinic crystal system and space group P2 /n. The anions
1
and cations in 2 ꢂorm separate columnar stacks along bc-plane direction. The neighboring anions are stacked as dimers in
the anion columnar stacks oꢂ 2. The magnetic ꢂeatures oꢂ salts 1 and 2 show 1D alternating spin chain magnetic exchange
behavior, and the magnetic experimental data are well ꢁtted through a spin chain magnetic model. The diference in the
crystal structures and magnetic properties between the two new salts 1 and 2 ꢂully demonstrates that the magnetic properties
−
are dependent on the alignment oꢂ the [Ni(dmit) ] anions, which are related to the ꢀexible organic cations.
2
Introduction
has been reported in many bis(dithiolate) metal complexes
14–20].
[
−
Metal bis-1,2-dithiolene complexes have been increasingly
studied in recent decades [1–7]. In recent years, some novel
properties, such as ion conductivity and dielectric proper-
[M(dmit) ] complexes are well-known metal bis-
2
1,2-dithiolene complexes with unusual magnetic proper-
ties and conducting properties [21–33]. Investigations on
−
ties, have been ꢂound in these complexes [8–13]. Planar
[M(dmit) ] complexes have ꢂocused on obtaining unusual
2
−
[
M(dithiolate) ] monoanions are easily aligned into colum-
physicochemical properties by introducing appropriate cati-
2
nar stacks to ꢂorm a 1D magnetic chain with spin–lattice
interactions between neighboring anions. Thereꢂore, spin-
Peierls-type magnetic behavior is commonly observed and
ons. First, Nakamura’s group [34–41] reported an interesting
−
[Ni(dmit) ] system by introducing a metal crown ether cat-
2
ion, with the system showing novel magnetic and conduct-
ing properties and ꢂerroelectricity. Some researchers have
II
III
introduced Fe or Mn cations with spin crossover behavior
−
into the [Ni(dmit) ] system to obtain novel molecular mag-
2
*
Xuan-Rong Chen
nets with spin transition and magnetic bistability [42–51].
chenxr@yctu.edu.cn
In addition, ammonium organic cations can be introduced
Zhen-Min Zhang
into the [M(dmit) ] system to obtain a series oꢂ molecu-
2
2
031264406@qq.com
lar conductors, and their crystal structures and electrical
properties have been intensively investigated in reported
research papers [52–56]. However, the magnetic properties
Min Luo
002951937@qq.com
1
Hang Liu
830080690@qq.com
oꢂ these molecular conductors with ammonium cations as
1
−
counterions have rarely been studied. The [M(dmit) ] salts
2
Jia-Yi Yuan
587457343@qq.com
usually show structural phase transitions in their high-tem-
perature phase (HTP) and in low-temperature phase (LTP)
due to the disorder–order transitions oꢂ ammonium cations,
accordingly exhibiting magnetic phase transitions due to
2
1
School oꢂ Chemistry and Environmental Engineering
and Instrumental Analysis Center, Yancheng Teachers
University, 2# Xiwang Road, Yancheng 224007,
People’s Republic oꢂ China
Vol.:(0
1
123456789)
3

Transition Metal Chemistry
the disorder–order transitions oꢂ the organic cations and the
structural phase transitions oꢂ the complexes.
Found: C, 31.51; N, 2.25; H, 3.93%. IR bands (KBr pellet,
−
1
cm ) [63]: 1342 (ν ), 1058(ν ).
C=C
C=S
In previous studies, our group ꢂocused on investigating
Single crystals were obtained through by slowly evaporat-
ing oꢂ the acetone solution oꢂ powdered samples oꢂ 1 and 2
at ambient temperature ꢂor 7−14 days. The phase purities oꢂ
1 and 2 were determined through their PXRD patterns, and
the experimental and simulated XRD patterns were consist-
ent, as displayed in Figs. S4 and S5.
−
[
Ni(dmit) ] salts by incorporating ꢀexible organic cations
2
as counterions, such as pyridinium cations [57–59], imida-
zole cations and ammonium cations. Recently, we achieved a
bis(dithiolate)nickel salt [Et (n-Pr)N][Ni(dmit) ] [60], which
3
2
showed a magnetic transition with large thermal hysteresis.
This magnetic transition resulted ꢂrom a structural phase
transition with a lattice symmetry increase ꢂrom HTP to LTP.
Physical measurements
−
To expand the research on [Ni(dmit) ] salts, we
2
chose more ꢂlexible organic cations ꢂor use with the
C, H and N elemental analyses were perꢂormed on a Perki-
nElmer 2400 II Elementar Vario analytic instrument. IR
−
[
Ni(dmit) ] building blocks to obtain novel molecular
2
−
1
solids with magnetic ꢂeatures. In this paper, we present
spectra oꢂ 1 and 2 were recorded ꢂrom 4000 to 400 cm on
a Bruker Vertex 80 Fourier Transꢂorm Inꢂrared Spectrometer
aꢂter mixing the powdered samples with solid KBr. PXRD
data were collected on a Bruker D8 difractometer with a Cu
Kα radiation source (λ =1.5418 Å) with a scanning range
the crystal structures and magnetic ꢂeatures oꢂ two new
−
salts, [Ni(dmit) ] with triethylmethylammonium and
2
triethylisobutylammonium.
−
1
oꢂ 5 to 50° and a scanning rate oꢂ 2° min . Thermogravi-
metric analyses oꢂ the powdered samples oꢂ 1 and 2 were
perꢂormed on a NETZSCH STA 449F5 thermogravimetric
analyzer, and the samples (~5 mg ꢂor 1 and 2) were placed
in an Al O crucible ꢂor heating ꢂrom 30 to 800 °C. Mag-
Experimental
Materials
2
3
netic property measurements oꢂ 1 and 2 were collected with
a Quantum Design MPMS-XL superconducting quantum
interꢂerence device (SQUID) magnetometer using powdered
samples (~60 mg) ꢂrom 1.8 to 400 K under a magnetic ꢁeld
oꢂ 10,000 Oe.
All AR chemicals were used without ꢂurther puriꢁcation.
4
,5-Di(thiobenzoyl)-1,3-dithiole-2-thione (dmit(COPh) )
2
[
61] and (Et MeN)Cl, [(i-Bu)Et N]Br [62] were prepared
3 3
according to the published method.
Preparation of [Et MeN][Ni(dmit) ] (1)
3
2
Reꢀnement X‑ray crystallography
Sodium methoxide was prepared by placing 210 mg oꢂ
sodium metal in 20 mL oꢂ methanol, and then this sodium
methoxide was dropwise added into a methanol (20 mL)
Single crystals oꢂ 1 and 2 were selected and mounted on
a glass capillary, and difraction intensity data were col-
lected at 293 and 100 K by a Bruker AXS SMART diꢂ-
ꢂractometer equipped with a CCD area detector and Mo Kα
solution oꢂ dmit(COPh) (815 mg, 2 mmol) in a nitrogen
2
atmosphere at room temperature. Aꢂter stirring ꢂor 30 min,
the mixture gradually became a dark red solution. Then,
NiCl ·6H O (240 mg, 1 mmol), (Et MeN)Cl (162 mg,
(
λ=0.71073 Å) radiation [64, 65]. The structures oꢂ 1 and
2
were solved using the direct method and reꢁned with the
2
2
3
SHELX-2014 [66] by the ꢂull-matrix least-squares proce-
1
mmol) and I (128 mg, 0.5 mmol) were added to the
2
2
dure on F . All nonhydrogen atoms were anisotropically
above mixed solution, producing a dark green precipitate
aꢂter approximately 2 h. The dark green precipitate was
collected by vacuum ꢁltration, washed with methanol and
dried in vacuum. Yield: 70%. Anal. Calc. ꢂor C H NNiS :
reꢁned, and hydrogen atoms were introduced at calculated
positions. The crystallographic details oꢂ the data collection
and structure reꢁnements oꢂ 1 and 2 at 293 K and 100 K are
summarized in Table 1 and Table 2.
13
18
10
C, 27.51; N, 2.47; H, 3.20%. Found: C, 27.09; N, 2.21;
−
1
H, 3.16%. IR bands (KBr pellet, cm ) [63]: 1349(ν ),
C=C
Calculation of overlap integral within anion–anion
pairs
1
057(ν ).
C=S
Preparation of [(i‑Bu)Et N][Ni(dmit) ] (2)
The intermolecular overlap integrals were calculated ꢂor
3
2
two neighboring [Ni(dmit) ] anions (considered as a dimer)
2
A procedure similar to 1 was used ꢂor the preparation oꢂ
using Multiwꢂn program [67], and the SOMO oꢂ each
[
[
(i-Bu)Et N][Ni(dmit) ] (2), but instead oꢂ [Et MeN]Cl,
[Ni(dmit) ] anion in the selected dimer was used as the
3
2
3
2
(i-Bu)Et N]Br (152 mg, 1 mmol) was used. Yield: 75%.
basis ꢂunction ꢂor the calculation oꢂ intermolecular overlap
3
Anal. Calc. ꢂor C H NNiS : C, 31.52; N, 2.30; H, 3.97%.
integrals, which is obtained by DFT calculation using the
1
6
24
10
1
3

Transition Metal Chemistry
Table 1 Crystallographic data and structural reꢁnement data oꢂ 1 and
Table 2 Crystallographic data and structural reꢁnement data oꢂ 1 and
2 at 100 K
2
at 293 K
Compound
1
2
Compound
1
2
Temperature (K)
Chemical ꢂormula
Formula weight
Wavelength (Å)
CCDC numbers
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
293
293
Temperature (K)
Chemical ꢂormula
Formula weight
Wavelength (Å)
CCDC numbers
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
100
100
C H NNiS
C H NNiS
C H NNiS
C H NNiS
1
3
18
10
16 24
10
13 18
10
16 24
10
567.59
0.71073
2,023,007
Triclinic
P − 1
7.4366(8)
12.4959(13)
12.5215(12)
90.255(3)
98.229(3)
102.877(3)
1121.8(2)/2
1.680
609.65
0.71073
2,023,008
Monoclinic
567.59
609.65
0.71073
2,063,631
Monoclinic
0.71073
2,063,630
Triclinic
P − 1
7.2683(11)
12.3593(19)
12.6112(19)
89.814(4)
97.765(4)
103.634(4)
1090.4(3)/2
1.729
P2 /n
P2 /n
1
1
8.3368(15)
27.159(5)
11.782(2)
90
102.293(5)
90
8.2469(2)
27.5517(5)
11.3808(2)
90
101.674(2)
90
γ (°)
γ (°)
3
3
V (Å )/Z
2606.6(8)/4
1.554
V (Å )/Z
2532.41(9)/4
1.599
ρ (g×cm−3)
ρ (g×cm−3)
F (000)
582
1.795
1.67–27.51
− 8≤h≤9
1682
1.551
2.84–27.56
− 10≤h≤10
− 35≤k≤35
− 15≤l≤15
0.0331
F (000)
582
1.847
2.912–27.635
− 9≤h≤9
− 16≤k≤16
− 16≤l≤16
0.0480
1260
1.597
1.478–30.172
− 11≤h≤10
− 37≤k≤36
− 15≤l≤14
0.0424
Abs. coef. (mm−1)
θ Ranges (data collection°)
Index range
Abs. coef. (mm−1)
θ Ranges (data collection°)
Index range
−
−
16≤k≤16
14≤l≤16
Rint
0.0398
Rint
Independent reꢀections/
5128/0/230
6001/0/258
Independent reꢀections/
4880/6/230
6544/0/258
restraints/parameters
restraints/parameters
Reꢁned method
Full-matrix least-squares on F2
1.099
Reꢁned method
Full-matrix least-squares on F2
1.204
2
2
Goodness oꢂ ꢁt on F
1.028
Goodness oꢂ ꢁt on F
1.052
R , wR [I>2σ(I)]
R1 =0.0355
R1 =0.0379
R , wR [I>2σ(I)]
R1 =0.0758
R1 =0.0304
1
2
1
2
wR =0.0875
wR =0.0799
wR =0.2106
wR =0.0702
2
2
2
2
R , wR [all data]
R1 =0.0481
R1 =0.0613
R , wR [all data]
R1 =0.0798
R1 =0.0407
1
2
1
2
wR =0.0936
wR =0.0888
wR =0.2123
wR =0.0741
2
2
2
2
Residual (e nm−3
)
0.508/− 0.749
0.537/− 0.343
Residual (e nm−3
)
1.997/− 1.014
0.553/− 0.350
ꢀ
ꢂ
ꢀ
ꢂ
ꢃ
ꢃ
ꢃ
ꢃ
R
=
Σ ꢁF ꢁ − ꢁF ꢁ ∕Σ F
,
R
=
Σ ꢁF ꢁ − ꢁF ꢁ ∕Σ F
,
1
o
c
ꢃ
oꢃ
1
o
c
ꢃ
oꢃ
ꢀ
ꢄ
ꢀ
ꢄ
ꢁ
ꢃ
ꢁ
ꢃ
1∕2
ꢁ
ꢃ
ꢁ
ꢃ
1∕2
2
2
2
2
2
2
2
2
2
2
ꢂ
ꢂ
ꢂ
ꢂ
− F
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
− F
ꢂ
ꢂ
ꢂ
ꢂ
ꢂ
wR =Σw
F
∕Σw
F
wR =Σw
F
∕Σw
F
2
oꢂ
cꢂ
oꢂ
2
oꢂ
cꢂ
oꢂ
+
−
basis set oꢂ B3LYP/6-31G* ꢂor C, N and S elements, the
relativistic efective core potential basis set oꢂ lanl2dz ꢂor
Ni element by Gaussian 09 program [68], and the deꢂault
values oꢂ convergence criteria are set. Each dimer structure
was extracted ꢂrom the single crystal structure oꢂ 1 and 2 at
1 contains one (Et MeN) cation and one [Ni(dmit) ] anion.
3
2
−
The [Ni(dmit) ] anion is square planar, the Ni–S bond
2
length is between 2.1518(6) and 2.1748(6) Å, and the oxi-
+
dation state oꢂ nickel is 3 . The bond distance and bond
−
angles in the [Ni(dmit) ] moieties, listed in Table S1, are
2
−
2
93 and 100 K.
comparable to those in other reported [Ni(dmit) ] analogs
2
+
[
53–56]. The alkyl chain oꢂ (Et MeN) cations is ordered
3
at 293 K ꢂor 1, and the bond length and angle values in the
alkyl chains are comparable to those in other ammonium
cations [48–52].
Results and discussion
Crystal structures
As shown in Fig. 1b, the anions and cations in 1 ꢂorm
an alternating chain arrangement along the a axis direc-
tion. The neighboring cations are arranged in centrosym-
metric styles (Fig. 1c); there are only van der Waals ꢂorces
1
crystallizes in the triclinic crystal system with space group
P − 1 at 293 K. As depicted in Fig. 1a, an asymmetric unit oꢂ
1
3

Transition Metal Chemistry
Fig. 1 a Molecular structure oꢂ 1 with displacement ellipsoids at a
clarity) ꢂor 1 at 293 K; c cation layer; d anion layers, in which the
Ni…Ni distance between the adjacent superimposed anions is irregu-
lar; and e charge-assisted H-bonds between the cations and anions
2
0% probability level at 293 K (hydrogen atoms omitted ꢂor clarity);
b packing diagram showing alternating layered arrangements oꢂ the
anions and cations along the a axis direction (H atoms omitted ꢂor
−
between the adjacent cations in the a layer. The anionic layer
is constructed by π-type anion dimers, in which two ani-
ons are related to each other through an inversion center
and stacked in transverse and longitudinal ofset modes. In
the anion columnar stacks, the Ni…Ni distance between
dimers in the [Ni(dmit) ] anions. As displayed in Fig. 1e,
2
charge-assisted H-bonds are ꢂormed between the cations
and anions, with the distances d
=2.9658(8),
C8#1-H8C#1…S1#2
d
= 2.9417(7), d
= 3.4767(26),
C7#1…S1#3
C9#1-H9B#1…S8#4
dC7#1-H7A#1…S4#5 = 2.9797(7) and the symmetry codes
#1 = − 1 + x, y, − 1 + z, #2 = 1 − x, 1 − y, − z, #3 = − x,
1 − y, − z, #4=− x, 1 − y, 1 − z, #5=− 1+x, y, − 1+z, and
the adjacent superimposed anions is irregular, d = 4.255
1
and d =4.083 Å in an anion stack (reꢂ. Figure 1d). There
2
are no obvious S…S contacts between the neighboring
1
3

Transition Metal Chemistry
these interatomic distances are less than the sum oꢂ the van
der Waals radii oꢂ an H (C) atom and S atom.
2 crystallizes in the monoclinic crystal system
with space group P2 /n at 293 K. The asymmetric
1
+
1
also crystallizes in the triclinic crystal system with
unit oꢂ 2 is composed oꢂ one [(i-Bu)Et N] cation and
3
−
space group P − 1 at 100 K in the low-temperature phase.
As depicted in Fig. 2a, an asymmetric unit oꢂ 1 also con-
one [Ni(dmit) ] anion, as depicted in Fig. 3a. The
2
−
[Ni(dmit) ] anion is square planar, the Ni–S bond length
2
+
−
tains one (Et MeN) cation and one [Ni(dmit) ] anion.
is between 2.1576(8) and 2.1719(8) Å, and the oxidation
3
2
+
The corresponding bond distance and bond angles in the
state oꢂ nickel is 3 . The bond parameters oꢂ 2 listed in
−
[
Ni(dmit) ] moieties, listed in Table S1, are comparable to
Table S2 are rather similar to those in 1. As displayed in
Fig. 3b, the anions and cations in 2 are arranged in the
style oꢂ columnar stacks along the a-axis direction. The
anions are arranged in two diferent styles, ꢂorming a zig-
zag chain arrangement viewed along the a + c direction
(reꢂ. Figure 4a). As depicted in Fig. 4b, c, the neighboring
2
1
1
at 293 K. As shown in Fig. 2b, the anions and cations in
ꢂorm an alternating chain arrangement along the a axis
direction. It is noted that the crystal structure at 100 K in
the low-temperature phase is nearly similar to that at 293 K
in the high-temperature phase.
Fig. 2 a Molecular structure oꢂ 1 with displacement ellipsoids at a 50% probability level at 100 K (hydrogen atoms omitted ꢂor clarity); b pack-
ing diagram showing alternating layered arrangements oꢂ the anions and cations along the a axis direction ꢂor 1 at 100 K
Fig. 3 a Asymmetric unit with thermal ellipsoids drawn at a 30% probability level ꢂor 2 at 293 K; b packing diagram showing the arrangement
oꢂ separated columnar stacks along the c-axis direction oꢂ 2 at 293 K
1
3

Transition Metal Chemistry
Fig. 4 a Anions in the manner oꢂ two diferent styles, ꢂorming a zigzag chain arrangement and the b, c neighboring anions stacked as dimers in
the anion columnar stacks oꢂ 2 at 293 K
anions are stacked as dimers in the anion columnar stacks.
There exist only short interatomic lateral S…S contacts
between the anion columnar stacks, which are less than the
sum oꢂ the van der Waals radii oꢂ two S atoms.
parameters oꢂ 2 at 100 K listed in Table S2 are rather similar
to those in 2 at 293 K. As displayed in Fig. 5b, the anions
and cations in 2 are arranged in the style oꢂ columnar stacks
along the a-axis direction. It is noted that the crystal struc-
ture oꢂ 2 at 100 K in the low-temperature phase is also simi-
lar to that at 293 K in the high-temperature phase.
2
also crystallizes in the monoclinic crystal system
with space group P2 /n at 100 K. The asymmetric unit
1
+
oꢂ 2 is also composed oꢂ one [(i-Bu)Et N] cation and
3
−
one [Ni(dmit) ] anion, as depicted in Fig. 5a. The bond
2
Fig. 5 a Asymmetric unit with thermal ellipsoids drawn at a 50% probability level ꢂor 2 at 100 K; b packing diagram showing the arrangement
oꢂ separated columnar stacks along the c-axis direction oꢂ 2 at 100 K
1
3

Transition Metal Chemistry
Magnetic properties
coupling between the neighboring anions oꢂ Pair I and Pair
2
II. Besides, the calculated overlap integral S oꢂ Pair I and
In a spin system in which the magnetic behavior is domi-
nated by AFM coupling, the magnetic exchange constant,
Pair II at 293 K is identical to those at 100 K ꢂor 1 and 2,
demonstrating that magnetic exchange interaction between
the neighboring anions is almost similar in the low-temper-
ature phase and in the high-temperature phase.
J , between two spins may be described as
AF
2
(
2t)
On the basis oꢂ the crystal structure analysis, a co-ꢂacial
π-type dimer exists with two types oꢂ neighboring Ni⋅⋅⋅Ni dis-
tances in the anion column stacks ꢂor 1 and 2, as a result, the
salts 1 and 2 probably show the magnetic behavior oꢂ an S=½
alternating spin chain in both phases. Consequently, an S=½
antiꢂerromagnetic (AFM) Heisenberg linear chain model was
chosen ꢂor the analysis oꢂ magnetic susceptibility data oꢂ 1 and
JAF
∝
(1)
Ueff
where the symbol t is the transꢂer integral between two spin
sites, which is proportional to the overlap integral (S) oꢂ the
interacting magnetic orbitals, and U represents the efec-
ef
tive on-site Coulomb repulsion and this is nearly constant ꢂor
a deꢁned magnetic solid. Consequently, the J is directly
AF
2
in both phases. The spin Hamiltonian may be written as that
2
proportional to S oꢂ the interacting magnetic orbitals. As
in Eq. (2) ꢂor the Heisenberg alternating linear chain
n∕2
described in the section oꢂ the crystal structures oꢂ 1 and 2 at
2
93 K and 100 K, the crystal structures oꢂ 1 and 2 at 293 K
ꢀ
̂
H = −2J
̂
̂
̂ ̂
are similar to those at 100 K. Furthermore, the [Ni(dmit) ]
[S2j−1S2j + ꢀS2jS2j+1]
(2)
2
i=1
anions in 1 and 2 ꢂorm an alternating chain in the stacks, and
AFM coupling is probably between the neighboring anions
in the spin chain. Thereꢂore, we calculated the overlap inte-
gral between the neighboring anions oꢂ 1 and 2 at 293 and
where J and αJ represent the exchange constants between a
spin and its leꢂt neighbor, and between a spin and its right
neighbor, respectively. For an AFM exchange system (J<0
and 0 ≤ α ≤ 1), in the exteme, when α= 0, the alternating
linear chain model is simpliꢁed to the dimer model with
pairwise interactions. When α=1 the alternating linear chain
model reduces to the regular linear-chain model [69, 70].
Based on Eq. (3), the molar magnetic susceptibility as a
ꢂunction oꢂ temperature ꢂor an S=½ Heisenberg antiꢂerro-
magnetic linear chain, deduced ꢂrom the cluster approach,
can be expressed as
1
00 K. The calculated overlap integrals oꢂ anion–anion pairs
are summarized in Table 3. The calculated overlap integral
2
S oꢂ Pair II at 293 K ꢂor 1 is 72.9, which is higher than
1
9.3 oꢂ Pair I, indicating a stronger AFM coupling between
the neighboring anions oꢂ Pair II than Pair I. However, the
2
calculated overlap integral S oꢂ Pair II at 293 K ꢂor 2 is
9
9, near to 70.1 oꢂ Pair I, showing commensurate AFM
2
2
Ng ꢁ
2
Table 3 The calculated overlap integral (S) and S within anion–
anion pairs at 293 and 100 K ꢂor 1 and 2
2
B
A + Bx + cx
2
1 + Dx + Ex + Fx
ꢀchain
=
⋅
(3)
3
k T
B
1
where x =|J|/k T and J ≤ 0. The Eq. (3) has two sets oꢂ
B
parameters A − F ꢂor the alternating-exchange linear spin
chain [70]. The experimental molar magnetic susceptibil-
ity in both phases is given in Eq. (4) iꢂ the paramagnetic
impurity, originating ꢂrom the lattice deꢂects, molecular dia-
magnetism oꢂ atoms core and the possible van Vleck-type
temperature-independent paramagnetism, arising ꢂrom the
coupling oꢂ the ground and excited states through a magnetic
Temperature
293 K
100 K
S (10–3)
–
3
2
–6
2
–6
Anion–anion pairs
S (10 )
S (10 )
S (10 )
Pair I
− 4.39
19.3
− 4.60
8.96
21.2
ꢁ
eld [69], are ꢂurther considered.
Pair II
8.54
72.9
80.3
C
ꢀm = ꢀchain
+
+ ꢀ0
(4)
T − ꢁ
2
The temperature-dependent magnetic susceptibility oꢂ 1
measured ꢂrom 2 to 400 K in the cooling and heating process
is displayed in Fig. 6, where the molar magnetic suscepti-
bility data are processed through a diamagnetic correction
Temperature
Anion–anion pairs
Pair I
293 K
S (10 )
8.37
100 K
S (10 )
8.76
− 9.98
–
3
2
–6
–3
2
–6
using Pascal’s constants [71]. In the χ − T plot oꢂ 1, the
S (10 )
70.1
S (10 )
76.7
m
compound shows a simple Curie–Weiss-type paramagnetic
behavior in the low-temperature region (approximately
Pair II
− 9.95
99.0
99.6
1
3

Transition Metal Chemistry
–
4
−1
θ=− 0.28943 K, and χ =− 1.1×10 emu·mol , and the
0
2
square oꢂ the correlation coeꢃcient R = 0.996 ꢂor 1. The
−
magnetic impurity ꢂrom uncoupled [Ni(dmit) ] anions is
2
estimated to be approximately 8.89% based on the ꢁtted C
value in 1.
The χ − T plot oꢂ 2 ꢂrom 2 to 300 K during the cool-
m
ing process is displayed in Fig. 8, and the molar magnetic
susceptibility data were processed similar to 1. In the
whole temperature region, the χ value reaches a maximum
m
at ~ 175 K, and a large Curie–Weiss tail is also observed
below ~ 50 K, indicating simple Curie–Weiss-type para-
magnetism behavior due to magnetic impurities arising
ꢂrom lattice deꢂects. Based on the crystal structure analysis,
the anions and cations in 2 ꢂorm columnar stacks along the
a-axis direction. As a result, we used the 1D Heisenberg
alternating spin chain magnetic model to analyze the mag-
netic behavior oꢂ 2.
Fig. 6 Plots oꢂ χm versus T ꢂor 1 (the blue squares: experimental data
oꢂ the magnetic susceptibility during the cooling process; red circles:
experimental data oꢂ the magnetic susceptibility during the heating
process). (Color ꢁgure online)
As shown in Fig. 8, the best ꢂit is obtained ꢂor the
magnetic susceptibility data ꢂrom 2 to 300 K, providing
the ꢂollowing parameters: α = 0.18115, J/k = 157.5 K,
B
−
1
below 75 K). This type oꢂ paramagnetism is due to mag-
netic impurities, which originate ꢂrom uncoupled spins oꢂ
lattice deꢂects.
g = 1.91, C = 0.02524 emu K mol , θ = − 2.9794 K, and
–
4
−1
χ =− 5.7×10 emu·mol , and the square oꢂ the correla-
0
2
tion coeꢃcient R =0.998 ꢂor 2. The magnetic impurity ꢂrom
−
As shown in Fig. 6, the χ values gradually increase as
uncoupled [Ni(dmit) ] anions is estimated to be approxi-
m
2
the temperature increases in the high-temperature region
mately 6.73% based on the ꢁtted C value in 2.
(
above 150 K), showing the magnetic character oꢂ a Heisen-
berg alternating linear chain.
We used a 1D Heisenberg alternating spin chain mag-
netic model [Eq. (4)] to ꢁt the temperature-dependent mag-
netic susceptibility oꢂ 1. As displayed in Fig. 7, the variable
temperature magnetic susceptibility ꢂrom 1.8 to 400 K was
Conclusions
In summary, two nickel-bis-1,2-dithiolene salts with diꢂ-
ꢂerent ꢂlexible ammonium organic cations, [Et MeN]
3
ꢁ
tted to Eq. (4), providing the ꢂollowing parameters ꢂor 1:
[Ni(dmit) ] (1) and [(i-Bu)Et N][Ni(dmit) ] (2), were
2
3
2
−
1
α = 0.22394, ∆/k = 354.3 K, C = 0.03332 emu·K·mol ,
synthesized and characterized by IR spectroscopy, PXRD
B
and single-crystal X-ray difraction. The two salts showed
Fig. 7 Black circles are the experimental data oꢂ χ , and the red line
Fig. 8 Temperature-dependent χm oꢂ 2 ꢂrom 2 to 300 K (the black cir-
cles are the experimental data, and the red line represents the ꢁtting
curve through the spin dimer ꢁtting model). (Color ꢁgure online)
m
represents the ꢁt using the 1D Heisenberg alternating spin chain
equation ꢂor 1
1
3

Transition Metal Chemistry
diferent crystal structures due to the geometric nature oꢂ
the counterions in the crystals. 1 crystallized in the triclinic
crystal system, and the space group belonged to be P − 1.
The anions and cations in 1 ꢂormed an alternating layered
arrangement, while 2 crystallized in the monoclinic space
14. Duan HB, Ren XM, Meng QJ (2010) Coord Chem Rev 254:1509
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5. Ren XM, Meng QJ, Song Y, Lu CS, Hu CJ, Chen XY (2002) Inorg
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1
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columnar stacks. The temperature-dependent magnetic sus-
ceptibilities oꢂ salts 1 and 2 demonstrated spin chain mag-
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(1829) Cryst Growth Des 2020:20
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Appl ACS (2020) Mater Interꢂaces 12:28129
1. Kusamoto T, Yamamoto HM, Tajima N, Oshima Y, Yamashita S,
Kato R (2012) Inorg Chem 51:11645
Appendix A: Supplementary data
2. Han YK, Seo DK, Kang H, Kang W, Noh DY (2004) Inorg Chem
4
3:7294
CCDC 2,023,007, 2,023,008, 2,063,630 and 2,063,631
contain the supplementary crystallographic data oꢂ 1 and 2.
These data can be obtained ꢂree oꢂ charge via http://www.
ccdc.cam.ac.uk/conts/retrieving.html, or ꢂrom the Cam-
bridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; ꢂax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article, including the IR spectra and PXRD results,
can be ꢂound in the Supporting Inꢂormation.
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chi M, Misaki Y, Hosokoshi Y, Inoue K, Azuma N (2004) Inorg
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Supplementary Information The online version contains supplemen-
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Acknowledgements The authors thank the National Natural Science
Foundation oꢂ China (Grant No. 21801218) and the Natural Science
Foundation oꢂ the Jiangsu Higher Education Institutions oꢂ China
1. Kato R, Cui HB, Tsumuraya T, Miyazaki T, Suzumura Y (2017)
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