Synthesis, hydrogen-bonded 1D structure, and abrupt spin transition between high-spin (HS) and an ordered [HS-HS-HS-LS] of a mononuclear iron(III) complex [FeIII(Him)2(4-MeOhapen)]CF3SO3 (Him = imidazole, 4-MeOh

Article abstract of DOI:10.1016/j.ica.2015.09.031

A SCO iron(III) complex [Fe^III(Him)₂(4MeOhapen)]CF₃SO₃ was synthesized, where Him = imidazole and 4-MeOhapen = N,N′-bis(2-oxy-4-methoxyacetophenylidene)ethylenediamine. Fe^III ion has an octahedral coo

Full text of DOI:10.1016/j.ica.2015.09.031

Inorganica Chimica Acta 439 (2016) 49–54
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, hydrogen-bonded 1D structure, and abrupt spin transition
between high-spin (HS) and an ordered [HS–HS–HS–LS] of a
III
mononuclear iron(III) complex [Fe (Him) (4-MeOhapen)]CF SO
(
(
2
3
3
0
Him = imidazole, 4-MeOhapen = N,N -bis-
2-oxy-4-methoxyacetophenylidene)ethylenediamine)
a
a
a
a
a
Kyohei Miyano , Takahiro Nishida , Hiromasa Ono , Daisuke Hamada , Takeshi Fujinami ,
a,
⇑
b
Naohide Matsumoto , Yukinari Sunatsuki
a
Department of Chemistry, Faculty of Science, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555, Japan
Department of Chemistry, Faculty of Science, Okayama University, Tsushima-naka 1-1, Okayama 700-8530, Japan
b
a r t i c l e i n f o
a b s t r a c t
III
Article history:
Received 19 June 2015
Received in revised form 3 September 2015
Accepted 24 September 2015
Available online 9 October 2015
2 3 3
A SCO iron(III) complex [Fe (Him) (4MeOhapen)]CF SO was synthesized, where Him = imidazole and
4
0
III
-MeOhapen = N,N -bis(2-oxy-4-methoxyacetophenylidene)ethylenediamine. Fe ion has an octahedral
coordination geometry with N donor atoms of the equatorial tetradentate ligand (4-MeOhapen)
and two nitrogen atoms of two imidazoles (Him) at the axial positions. The adjacent cations are bridged
2 2
O
ꢀ
ꢀ
3
by CF
3
SO
3
ion through NHꢁ ꢁ ꢁO hydrogen bonds between Him and CF
3
SO
to give a one-dimensional
III
chain structure {[Fe (Him)
2
(4MeO-hapen)]CF SO } . The magnetic susceptibility measurements
3 3 11
Keywords:
Iron(III)
Spin crossover
Imidazole
showed that complex exhibits an abrupt spin transition between a single HS phase and a symmetry-
breaking [HS–HS–HS–LS] phase and another transition around 80 K. The single-crystal X-ray analyses
at 296 and 150 K revealed the structures at a single HS and [HS–HS–HS–LS] states.
Ó 2015 Elsevier B.V. All rights reserved.
N
2
O
2
Schiff-base ligand
Hydrogen bonds
D structure
1
1
. Introduction
Spin crossover (SCO) phenomenon is an inter-conversion
especially ‘‘hapen-type” ligand gives a favorable conformation
which makes a large torsion of O–Fe–O angle during the spin tran-
sition from HS to LS state due to the steric repulsion between en
between high-spin (HS) and low-spin (LS) states by external per-
(ethylenediamine moiety) and methyl group of o-hydroxyace-
tophenone moieties (hapen = N,N -bis(2-oxyacetophenylidene)-
ethylenediamine) [8]. (2) Intermolecular hydrogen bond via axial
imidazole group gives a positive effect to induce abrupt spin tran-
sition [9]. (3) The steric requirements from methoxy group of
hapen ligand and counter anion modify the assembly structure to
0
turbations, such as temperature, pressure, and light irradiation
III
[
1]. Among the SCO complexes reported so far, FeII and Fe com-
plexes have been the most intensively studied [1]. It is well known
that Fe sites in some heme proteins exhibit SCO behavior [2] and as
their model compounds iron porphyrin and macrocyclic complexes
have been extensively studied [3]. As a simple model compound
for some heme proteins, Nishida in 1975 first synthesized a family
influence the SCO property [8,9].
III
A family of the complexes [Fe (Him)
2
(hapen)]Y would give
III
III
of Fe complexes [Fe B
2
L]BPh
4
with salen-type N
2
O
2
ligand L and
interesting SCO properties with hysteresis and multi-step. In this
ꢀ
III
III
two axial monodentate ligand B, and counter anion BPh
4
study, we synthesized a Fe complex [Fe (Him)
2
(4-MeOhapen)]
ꢀ
0
(
BPh
4
= tetraphenylborate) [4]. Later, Matsumoto, Murray, and
CF
3
SO
3
, where 4-MeOhapen denotes N,N -bis(2-oxy-4-methoxy-
III
III
0
0
Real synthesized SCO Fe complexes [Fe B
Schiff-base ligands L , monodentate ligand B , and various counter
anion Y [5–7]. These studies demonstrated that (1) A favorable
2
L ]Y with analogous
acetophenylidene)ethylenediamine). The complex has a hydro-
0
0
ꢀ
gen-bonded 1D structure bridged by CF
3
SO
3
anion, and shows a
0
spin transition between HS and ordered [HS–HS–HS–LS] phases.
Such symmetry breaking-phase transition attract much attention
conformation of the planar ligand L’ can induce SCO property and
[
10]. We report here the synthesis, SCO property, and crystal
structures at HS and [HS–HS–HS–LS] states (Scheme 1).
⇑
Corresponding author. Tel./fax: +81 96 342 3390.
E-mail address: naohide@aster.sci.kumamoto-u.ac.jp (N. Matsumoto).
http://dx.doi.org/10.1016/j.ica.2015.09.031
020-1693/Ó 2015 Elsevier B.V. All rights reserved.
0

5
0
K. Miyano et al. / Inorganica Chimica Acta 439 (2016) 49–54
2
. Experimental
120 °C for 60 min and then cooled from 120 °C to room tempera-
ture. Magnetic susceptibilities were measured by a Quantum
2.1. General
Design MPMS-XL5 magnetometer in the temperature range of
ꢀ1
5
–300 K at the 2 K min
under an applied magnetic field of
All reagents and solvents used in this study are commercially
0.5 T. The calibration was performed with palladium metal. Corrections
for diamagnetism were applied using Pascal’s constants [11].
available from Tokyo Kasei Co., Ltd., Tokyo, Japan and Wako Pure
Chemical Industries, Ltd., Osaka, Japan, and were used without
further purification. All of the synthetic procedures were
performed in air.
2.4. Crystallographic data collection and structure analyses
X-ray diffraction data were collected using a Rigaku RAXIS
RAPID imaging plate diffractometer using graphite monochro-
2
2
.2. Preparation of materials
.2.1. Preparations of H (4-MeOhapen) and precursor iron(III)
mated Mo K
a radiation (k = 0.71073 Å). The temperature of the
crystal was maintained at the selected value by means of a Rigaku
cooling device within an accuracy of ±2 K. The X-ray diffraction
data were collected at 296, and 150 K. After the data collection at
296 K, the crystal was cooled from 296 to 200 K with the cooling
2
III
complex [Fe Cl(4-MeOhapen)]ꢁH
2
O
0
The ligand, N,N -bis(4-methoxy-2-hydroxyacetophenylidene)
2
ethylenediamine, abbreviated as H (4-MeOhapen), was prepared
ꢀ1
according to the general synthetic procedure of salen-type Schiff-
base ligand [8]. To a solution of 4-methoxy-2-hydroxyacetophe-
none (0.1 mol, 16.62 g) in 50 mL of methanol was added a solution
of ethylenediamine (0.05 mol, 3.01 g) in 50 mL of methanol, and
the mixture was stirred for 30 min on a hot-plate and cooled to
room temperature. Yellow crystals precipitated were collected by
suction filtration, washed with a small amount of methanol and
rate of 3 K min , and then the crystal was cooled slowly from
ꢀ1
200 to 150 K at the rate of 0.1 K min . The crystal was kept at
150 K for one day, and the data collection was started. The X-ray
diffraction data collected after quick cooling showed a poor quality
to determine the crystal structure. The data were corrected for Lor-
entz, polarization and absorption effects. The structures were
solved by a direct method, and expanded using the Fourier tech-
nique. Hydrogen atoms were fixed at the calculated positions
and refined using a riding model. All calculations were performed
using the CrystalStructure crystallographic software package [12].
diethyl ether, and dried in vacuo. Precursor iron(III) complex
III
[
H
Fe Cl(4-MeOhapen)]ꢁH
2
O
was prepared by the reaction of
(8.1 g, 0.05 mol), and
2
(4-MeOhapen) (17.8 g, 0.05 mol), FeCl
3
trimethylamine (10.1 g, 0.1 mmol) with 1:1:2 in methanol accord-
III
ing to the method applied for [Fe Clsalen] [5b]. Black precipitates
3
. Results and discussion
were collected by suction filtration and washed with diethyl ether.
Yield: 20.3 g (92%).
III
3
.1. Synthesis and characterization of iron(III) complex [Fe (Him)
2
(
4-MeOhapen)]CF SO
3
3
III
2
CF
.2.2. Preparation of iron(III) complex [Fe (Him)
2
(4-MeOhapen)]
The FeIII complex [Fe (Him) (4-MeOhapen)]CF SO was pre-
III
3
SO
To a suspension of [Fe Cl(4-MeOhapen)]ꢁH
3
2 3 3
III
2
O (1 mmol, 0.44 g)
pared according to the synthetic procedure applied for the synthesis
of [Fe (Him) (4-MeOhapen)]PF [8b]. The precursor Fe complex
III
III
in 30 mL of methanol was added an excess of imidazole (10 mmol,
.68 g), and the mixture was stirred for 10 min on a hot-plate and
then filtered. To the filtrate was added a solution of NaCF SO
1 mmol, 0.17 g) in 5 mL of methanol. The resulting solution was
2
6
III
0
[Fe Cl(4-MeOhapen)]ꢁH
2
O was obtained by mixing the ligand
3
3
2
H (4-MeOhapen), iron(III) chloride anhydrate, and triethylamine
III
III
(
in a 1:1:2 M ratio in methanol. The Fe complex [Fe (Him)
(4-MeOhapen)]CF SO was obtained as well grown black plate-like
crystals by mixing [Fe Cl(4-MeOhapen)]ꢁH
NaCF SO in a 1:10:1 M ratio in methanol. The C, H, and N
elemental analyses agreed with the formula [Fe (Him)
(4-MeOhapen)]CF SO The thermogravimetric analysis (TGA)
2
allowed to stand for a few days, during which time black plate-like
crystals precipitated, and they were collected by suction filtration,
washed with small amount of diethyl ether, and dried in air.
3
3
III
2
O, imidazole, and
3
3
III
Black plate crystals were obtained. Yield: 0.172 g (25%). Anal. Calc.
2
III
for [Fe (Him)
2
(4-MeOhapen)]CF
3
SO
3
(C26
H
30
N
6
O
4
3
FeCF SO
3
): C,
3
3
.
4
6.63; H, 4.35; N, 12.08. Found: C, 46.83; H, 4.34; N, 12.09%.
.3. Physical measurements
Elemental analyses (C, H, and N) were carried out at the Center
detected no crystal solvent. Thermochromic behaviors in the
solution and solid states are shown in Fig. 1. The ethanol solution
of the compound showed a visible thermochromism from orange
red at room temperature to dark green–blue at liquid nitrogen
temperature. Red and green–blue colors are typical colors for HS
2
III
for Instrumental Analysis of Kumamoto University. Thermogravi-
metric analysis (TGA) was measured on a TG/DTA6200 (Seiko
Instrument Inc.). The sample of ca. 2 mg was heated from room
and LS states with this type of Fe complexes, respectively. In the
solid state, brown color of the ground sample at room temperature
changed to
a black brown at liquid-nitrogen temperature,
ꢀ1
temperature to 120 °C in the heating mode at 2 °C min , kept at
suggesting an incomplete SCO in the solid state.
Fig. 1. (a) Thermochromism of [FeIII(Him)
(4-MeOhapen)]CF SO at room (left) and
2 3 3
liquid nitrogen (right) temperatures in the diluted ethanol solutions. (b) Ther-
mochromism of the ground sample at room (left) and liquid nitrogen (right)
temperatures in the solid state.
Scheme 1. Structure of [FeIII(Him) (4-MeOhapen)]+.
2

K. Miyano et al. / Inorganica Chimica Acta 439 (2016) 49–54
51
3.2. Temperature-dependence of magnetic properties
3.3. Crystal structure
The magnetic susceptibility (
was measured in the temperature range 5–300 K under an applied
magnetic field of 0.5 T at a sweep rate of 2 K min . The magnetic
susceptibility was measured while lowering the temperature from
v
M
) of the polycrystalline sample
The X-ray diffraction analyses were measured at 296 and 150 K.
The crystallographic data are listed in Table 1. Relevant coordina-
tion bond distances and angles, and hydrogen-bond distances are
given in Table 2. At 296 K, compound crystallized in a monoclinic
ꢀ1
3
00 to 5 K in the first run. Subsequently, the magnetic susceptibil-
ity was measured while raising the temperature from 5 to 300 K in
the second run. The T vs. T plots are shown in Fig. 2, in which the
T vs. T plots for the cooling and warming modes are drawn as
blue and red colors, respectively. The experimental T vs. T pro-
file can be examined in terms of the spin-only values of the HS
space group C2/c (No. 15) with Z = 8, and the unique crystallo-
III
(4-MeOhapen)]+ and one
graphic unit consists of one [Fe (Him)
2
ꢀ
v
M
CF
3
SO
4
anion. At 150 K compound crystallized in a triclinic space
v
M
group P 1ꢀ (No. 2) with Z = 8, and the unique crystallographic
III
+
v
M
unit consists of four cations [Fe (Him) (4-MeOhapen)] and four
CF SO anions. It demonstrates that the crystal system and space
3
2
ꢀ
4
S = 5/2) and LS (S = 1/2) states of FeIII ions with the 3d electronic
configuration; the theoretical spin-only T values for the HS
S = 5/2) and LS (S = 1/2) states are 4.37 and 0.375 cm mol K,
respectively.
On lowering the temperature from 300 K, the
5
(
ꢀ
group change from monoclinic C2/c at 296 K to P1 at 150 K.
v
M
3
ꢀ1
(
3
.3.1. Structure at 296 K
The molecular structure of the [Fe (Him)
with the atom numbering scheme at 296 K is shown in Fig. 3. The
III
+
2
(4-MeOhapen)] part
M
v T value has a
3
ꢀ1
constant value of ca. 4.64 cm mol K above 200 K and then
decreases abruptly at around 190 K to reach a plateau region of ca.
3
above 200 K is compatible with 4.37 cm mol K of the spin-only
HS value. The
region below 180 K is comparable to the estimated value of
3
III
Fe ion has an octahedral coordination environment with N
donor atoms of the equatorial tetradentate ligand 4-MeOhapen
and N donor atoms of two imidazoles at the axial positions. The
Fe–N(imine) (2.107(3), 2.092(4) Å), Fe–N(imdazole) (2.151(5),
.184(5) Å) and Fe–O (1.877(3), 1.897(3) Å) coordination bond
2 2
O
3
ꢀ1
3
ꢀ1
.5 cm mol K below 180 K. The
v
M
T value of ca. 4.64 cm mol
K
3
ꢀ1
ꢀ1
2
3
v
M
T value of ca. 3.5 cm mol K at the plateau
2
3
ꢀ1
distances and the angle of O–Fe–O (100.5(1)°) at 296 K are consis-
.37 cm mol K corresponding to 3/4 HS (S = 5/2) and 1/4 LS
III
tent with the reported bond lengths for HS Fe complexes with
(S = 1/2) species, i.e. [HS–HS–HS–LS] phase. The spin-transition
similar Schiff-base ligands [6c,7,8]. Fig. 3(b) shows the orientations
of the two imidazole rings, in which the two imidazole rings are
oriented nearly along the two N–Fe–O diagonals. The saturated
five-memberd chelate ring takes gausche conformation, as C9
and C10 atoms deviate by +0.14 and ꢀ0.30 Å from the mean plane
defined by Fe, N1, and N2, showing a gauche conformation.
temperature T1/2 assigned between 4HS and HS–HS–HS–LS states
is evaluated to be T1/2" = 193 K and T1/2; = 192 K, respectively.
Though it looks that the compound has a small hysteresis at the
fast scan rate of 2 K min , the scan rate dependence can give the
more detailed mechanism of the spin transition as observed in
the literatures [13].
ꢀ1
Fig. 4 shows a one-dimensional (1D) chain structure at 296 K.
On decreasing the temperature further at the scan speed of
ꢀ
ꢀ
1
The anion CF
3
SO
3
plays as a linker by two of three oxygen atoms
2
K min , the
ing a spin transition from HS–HS–HS–LS phase to an unidentified
phase. In the warming mode, the T vs. T plots show a shallow
M
v T vs. T plots show a shoulder at ca. 80 K, suggest-
ꢀ
of CF
3
SO
3
, and the two oxygen atoms O(5) and O(7) are hydro-
gen-bonded to two imidazole groups of two adjacent cations
v
M
III
+
[
2
Fe (Him) (4-MeOhapen)] to produce a one-dimensional chain
minimum around ca. 80 K and the profile is not accord with that
in the cooling mode. This behavior around 80 K is just a kinetic
structure. The cation–anion hydrogen-bond distances between an
ꢀ
imidazole nitrogen atom and anion CF
=
3
SO
3
are O(5)ꢁ ꢁ ꢁN(4)
effect that depends on the scan rate. The dip in the
recorded in the warming mode is caused by the release of the
kinetic arrest, as observed in {[Zn1ꢀxFex(bbtr) ](ClO
x = 0.02–1, bbtr = 1,4-di(1,2,3-triazol-1-yl)-butane) [14].
vT curve
2.917(8) Å and O(7)ꢁ ꢁ ꢁN(6)⁄ = 2.799(9) (* denotes the corre-
sponding atom of the adjacent unit; ꢀ1/2 + x, 1/2 ꢀ y, 1/2 + z).
3
4 2 1
) }
There is no interchain hydrogen bonds less than 3.1 Å. Due to the
(
chirality of the gauche conformation of the five-membered chelate
III
ring, there are two possible species of d- and k-[Fe (Him)
2
+
(
4-MeOhapen)] . Within a chain, adjacent cations are related by
III
(4-MeOhapen)]+ species
c-glide plane so that d- and k-[Fe (Him)
are linked via CF
2
ꢀ
3
SO
3
are in the range of 2.074(12)–2.180 ion and
arranged alternately (Fig. 4).
Table 1
Crystallographic data of [FeIII(Him)
(4-MeOhapen)]CF
FeF
695.47
monoclinic
C2/c (No.15)
296
2
3 3
SO at 296 and 150 K.
Formula
Formula weight
Crystal system
Space group
T (K)
C
27
H
30
6
N O
7
3
S
triclinic
P 1ꢀ (No. 2)
150
a (Å)
b (Å)
c (Å)
20.692(1)
17.4343(7)
18.1663(8)
90
113.014
90
6031.9(5)
8
1.539
17.124(3)
18.526(3)
20.508(3)
79.743(3)
89.315(4)
65.348(4)
5804(2)
8
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
calc (g cmꢀ3)
1.592
6.679
0.1462, 0.3415
ꢀ
1
l
(mm
)
6.428
0.0567, 01,832
Fig. 2.
v
M
T vs. T plots of [FeIII(Him)
2
(4-MeOhapen)]CF
3
SO
3
, in which the data in the
a
b
R , Rw
cooling and warming modes are drawn as blue and red colors, respectively. (For
interpretation of the references to color in this figure legend, the reader is referred
to the web version of this article.)
a
R =
Rw = [
R
||F
R
o
| ꢀ |F
c o
||/R|F |.
| ꢀ |F
b
2
2
2
2 2
w(|F
o

5
2
K. Miyano et al. / Inorganica Chimica Acta 439 (2016) 49–54
Table 2
Coordination bond distances, angles, and hydrogen bond distances of [FeIII(Him)
applied to all cations and anions. Similar to the 1D structure at
96 K, the complex at 150 K has a similar one dimensional
structure, in which four cations are arrayed as the repeating unit
(–Aa–Bb–Cc–Dd–) . Based on the Fe–N and Fe–O bond distances
2
(4-
2
MeOhapen)]CF
3
SO
3
at 296 and 150 K.
2
96 K
150 K
A
1
Fe
B
C
D
and O–Fe–O bond angles, the spin states of four cations are easily
assigned to LS–HS–HS–HS for A–B–C–D. The Fe–N and Fe–O bond
distances B, C and D are in the range of 2.074(12)–2.180(11), 2.088
(10)–2.215(9), and 2.094(12)–2.175(10), respectively, and the
O–Fe–O bond angles are around 100°. These values are close to
Fe–N1
Fe–N2
Fe–N3
Fe–N5
Fe–O1
Fe–O2
2.107(3)
2.092(4)
2.151(5)
2.184(5)
1.877(3)
1.897(3)
2.134
1.905(14) 2.106(12) 2.114(15) 2.106(13)
1.905(10) 2.074(12) 2.088(10) 2.094(12)
1.982(10) 2.142(10) 2.169(9)
2.134(10)
2.175(10)
1.875(9)
2.002(9)
1.876(8)
2.180(11) 2.215(9)
1.861(10) 1.915(8)
III
the values at 296 K and are in the expected range for HS Fe
1.885(12) 1.894(10) 1.899(12) 1.898(10)
III
complexes. Thus the Fe centers of B, C and D are in the HS state.
<Fe–N>
1.949
2.126
2.147
2.127
O1–Fe–O2
O1–Fe–N1
O1–Fe–N3
O1–Fe–N5
O2–Fe–N2
O2–Fe–N3
O2–Fe–N5
N1–Fe–N2
O(5)ꢁ ꢁ ꢁN(4)
100.52(11) 85.4(4)
101.1(4)
87.7(5)
91.7(4)
90.4(4)
88.6(5)
89.3(4)
89.4(5)
82.7(5)
101.6(5)
89.2(5)
89.2(4)
90.5(4)
87.8(5)
90.4(5)
88.0(5)
81.5(5)
100.6(4)
87.5(5)
93.4(4)
87.7(4)
89.5(5)
89.7(4)
90.6(4)
82.4(5)
The corresponding values of cation A are in the range of
1.905(10)–2.002(9) and 85.4(4)°, indicating that the cation A is in
the LS state. The X-ray analysis confirmed an ordered
88.49(13)
93.73(15)
87.82(15)
89.53(11)
90.01(13)
90.25(13)
81.41(13)
2.917(8)
93.3(5)
89.0(4)
87.9(4)
93.7(5)
90.1(5)
87.7(5)
87.7(5)
[
HS–HS–HS–LS] phase at 150 K. The single HS state at 296 K was
converted to symmetry-breaking [HS–HS–HS–LS] state at
a
150 K, accompanying a crystallographic phase transition from
ꢀ
monoclinic C2/c to triclinic P1. Though both at 296 and 150 K,
2.718(15) 2.808(14) 2.827(15) 2.808(14)
2.903(14) 2.878(14) 2.873(14) 2.891(14)
ꢀ
the complex has a similar 1D structure bridged by CF
3
SO
3
ion, a
O(7)ꢁ ꢁ ꢁN(6)* 2.799(9)
significant difference is found in the sequence of the gauche
conformation of saturated five-membered chelate ring. While
(
(
a) *; ꢀ1/2 + x, 1/2 ꢀ y, 1/2 + z.
b) Interchain hydrogen bonds at 150 K.
III
+
2
d- and k-[Fe (Him) (4-MeOhapen)] species along the chain are
aꢁ ꢁ ꢁd, 2.995(11); bꢁ ꢁ ꢁc, 3.037(11); N(C)ꢁ ꢁ ꢁO, 3.033(16).
arrayed alternately at 296 K, the gauche conformations at 150 K
are [k, k, k, d]11 or its symmetry related [d, d, d, k]11 for
3
.3.2. Structure at 150 K
A crystal was cooled from room temperature to 150 K and
[
HS(D)ꢀHS(C)ꢀHS(B)ꢀLS(A)]11 (Fig. 5). During the spin transition
from 4HS (described as [HS(D)ꢀHS(C)ꢀHS(B)ꢀHS(A)]11) to 3HS
1LS ([HS(D)ꢀHS(C)ꢀHS(B)ꢀLS(A)]11), the conformations of the
five membered chelate rings change from [k(D), d(C), k(B)d(Α)] at
96 K to [k(D), k(C), k(B), d(Α)] at 150 K, in which the conformation
maintained at the temperature for one day, and then the X-ray
diffraction experiment was started. The complex crystallized into
a triclinic space group P1 with Z = 8 at 150 K, indicating that the
crystal underwent a structural phase transition. The crystallo-
graphic data is added to the data at 296 K in Table 1. The unique
crystallographic unit consists of four [Fe (HIm)
cations noted as A, B, C, and D and four CF SO anions noted as
a, b, c, and d. The relevant bond distances and angles of four
cations are added to the corresponding values of the cation at
2
+
ꢀ
2
of C changes from d to k, in addition to the spin state change of A
from HS to LS. Owing to the conformation change of C and the spin
III
+
2
(4-MeOhapen)]
change of A, hydrogen bonding manner from CF
SO
ꢀ
ion c is
3
3
ꢀ
3 3
significantly affected, as shown in Fig. 6. At 296 K, there is no inter-
chain hydrogen bonds. On the other hand, as seen in Fig. 6, at 150 K
inerchain contacts have been found between c and b and between
a and d. Further interchain hydrogen bonds between c and
96 K in Table 2, where the same atom numbering system is
Fig. 3. (a) ORTEP drawing of [FeIII(Him)
(4-MeOhapen)]+ with the atom numbering scheme at 296 K. (b) View of the complex-cation projected on the planar tetradentate
2
ligand, showing the orientations of two imidazole rings and two methoxy groups.
ꢀ
of [FeIII(Him)
Fig. 4. 1D chain structure bridged by CF
3
SO
3
2
(4-MeOhapen)]CF
3
SO
3
at 296 K. The chain runs along the b-axis and within a chain d- and k-species are alternately
arrayed.

K. Miyano et al. / Inorganica Chimica Acta 439 (2016) 49–54
53
ꢀ
of [FeIII(Him)
at 150 K. The crystallographic unique unit of four [FeIII (HIm)
(4-MeOhapen)]+ cations (A, B,
Fig. 5. 1D chain structure bridged by CF
3
SO
3
2
(4-MeOhapen)]CF
3
SO
3
2
ꢀ
C, and D) and four CF
3
SO
3
anions (a, b, c, and d). Their saturated five membered chelate rings take d, k, d, k conformations for A, B, C, and D.
ꢀ
ꢀ
3
Fig. 6. Stacking manner of adjacent 1D chains and the interchain interaction through CF
3
SO
3
ions. Interchain contact via. CF
3
SO
ion is not found in the HS phase at 296 K, but
ꢀ
CF
3
SO
3
ions show inter-chain contact at 150 K.
imidazole is found, in which the imidazole forms bifurcated
hydrogen bonds [15]. It can be described that this unusual
one-dimensional structure. The magnetic susceptibility indicates
another spin-transition from [HS–HS–HS–LS] to an unidentified
state around 80 K. The present result suggests that multi-step spin
transition with all the spin states can be observed for this type of
one-dimensional complexes.
[
HS–HS–HS–LS] phase is stabilized by the structural change of
the coordination environment and the combination of d- and
ꢀ
k-conformation, and interchain interaction via CF
3
SO
3
. Symmetry
breaking-phase transition has been observed for several com-
pounds [10].
Acknowledgments
3 3 6
The CF SO and PF salts at the HS states have an isomorphous
structure and showed a similar one-dimensional structure con-
structed by hydrogen-bonds between the anion and axial imidazole
T. Fujinami was supported by the Research Fellowship for
Young Scientists of the Japan Society for the Promotion of Science,
KAKENHI 00248556.
[
8b]. The 1D structure should be related to abrupt and multi-step
SCO properties. These two anions have a C symmetry at the
3
bridging moiety and can give one-dimensional structure. Within a
one-dimensional chain, the adjacent SCO sites are well separated
and the structural change (bond distance and coordination
geometry) due to the spin transition can be transmitted along the
Appendix A. Supplementary material
CCDC 1407204 and 1407205 contains the supplementary
III
chain. The CF
3
SO
3
salt exhibit an abrupt spin transition between a
crystallographic data for [Fe (Him)
2
(4-MeOhapen)]CF
3
SO
3
at 296
single HS phase and a symmetry-breaking [HS–HS–HS–LS] phase
and another spin transition around 80 K. On the other hand, the
PF salt shows an abrupt one-step spin transition. The abruptness
6
should be brought from the hydrogen-bonded 1D structure.
Interchain interaction through anion gives another cooperative
effect on the SCO properties.
and 150 K. 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 http://dx.doi.org/
10.1016/j.ica.2015.09.031.
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