Slow magnetization dynamics in a six-coordinate Fe(ii)-radical complex

Article abstract of DOI:10.1039/C9DT00558G

A new paramagnetic ligand, betaDTDA, and its coordination complex with Fe(hfac)₂ are reported (betaDTDA = 4-(benzothiazol-2′-yl)-1,2,3,5-dithiadiazolyl; hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-). The neutral radical betaDTDA is the first dithiadiazolyl ligand designed to include an electropositive sulphur moiety outside the thiazyl heterocycle, increasing the capacity for supramolecular, structure-directing electrostatic contacts and enabling new pathways for magnetic exchange. The Fe(hfac)₂(betaDTDA) complex is composed of a hs-Fe(ii) center with the three bidentate ligands arranged about the ion in a distorted octahedral 6-coordinate environment. The magnetic properties of crystalline Fe(hfac)₂(betaDTDA) are consistent with strong antiferromagnetic (AF) coupling between the metal and ligand moments, giving rise to a well-defined S_total = 3/2 ground state that is the only thermally populated state below 40 K. Below 4 K, this complex exhibits slow relaxation of the magnetization detected by ac susceptibility measurements consistent with a single-molecule magnet (SMM) behaviour.

Full text of DOI:10.1039/C9DT00558G

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M. B. Mills, E. Song, D. V. Soldatov, P. D. Boyle, M. Rouzieres, R. Clerac and K. Preuss, Dalton Trans., 2019,
DOI: 10.1039/C9DT00558G.
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Efficient extraction of sulfate from water using
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ARTICLE
Slow magnetization dynamics in a six-coordinate Fe(II)-radical
complex†
Carolyn A. Michalowicz,a Michelle B. Mills,a Ellen Song,a Dmitriy V. Soldatov,a Paul D. Boyle,b
Received 00th January 20xx,
Accepted 00th January 20xx
Mathieu Rouzières,c,d Rodolphe Clérac,c,d and Kathryn E. Preuss*a
DOI: 10.1039/x0xx00000x
A new paramagnetic ligand, betaDTDA, and its coordination complex with Fe(hfac)2 are reported (betaDTDA = 4-
(benzothiazol-2-yl)-1,2,3,5-dithiadiazolyl; hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato-). The neutral radical betaDTDA is
the first dithiadiazolyl ligand designed to include an electropositive sulphur moiety outside the thiazyl heterocycle,
increasing the capacity for supramolecular, structure-directing electrostatic contacts and enabling new pathways for
magnetic exchange. The Fe(hfac)2(betaDTDA) complex is comprised of a hs-Fe(II) center with the three bidentate ligands
arranged about the ion in a distorted octahedral 6-coordinate environment. The magnetic properties of crystalline
Fe(hfac)2(betaDTDA) are consistent with strong antiferromagnetic (AF) coupling between the metal and ligand moments,
giving rise to a well-defined Stotal = 3/2 ground state that is the only thermally populated state below 40 K. Below 4 K, this
complex exhibits slow relaxation of the magnetization detected by ac susceptibility measurements consistent with a single-
molecule magnet (SMM) behaviour.
www.rsc.org/
Introduction
The design of molecule-based materials with technologically
relevant properties, especially magnetic properties, has
attracted a great deal of interest in recent decades. The
potential for novel functionalities or novel combinations of
functionalities, accessible using well-established synthetic
protocols, make molecule-based designs particularly appealing.
The flexibility of design in molecule-based materials also allows
for incorporation of other attractive qualities, such as solubility
in organic media and volatility at low temperature.
An important class of molecule-based magnetic material
that is currently receiving significant attention is the single-
molecule magnet (SMM). SMMs exhibit slow dynamics of their
magnetization induced by different types of relaxation
mechanisms such as quantum tunnelling (QTM), Orbach-type
(thermally activated), Raman or direct processes. This property
makes them potential candidates for applications in quantum
computing and spintronic devices.1 The first materials identified
as SMMs were polynuclear complexes of transition metal ions.2
Current work more focussed on mononuclear SMMs of f-
elements is yielding some of the most exciting advancements
for example with Orbach-like processes with extremely large
energy barriers.3 Now, with a more fully developed understand-
Figure 1. Line drawing and ORTEP representation of an excerpt of the crystal structure
depicting Fe(hfac)2(betaDTDA); thermal ellipsoids at 50%; colour code: H, white sphere
and C, black; N, blue; S, orange; O, red; F, green; Fe, brown ellipsoids.
ding of SMM structure/property relationships, mononuclear 3d
transition metal complexes are also being targeted and have
been shown to exhibit SMM behaviour.4 However,
mononuclear transition metal SMMs are significantly less
widely reported than other systems.
In general, the design of molecule-based materials requires
rational manipulation of the molecular structure to optimize
material properties (e.g., magnetic, electric, or mechanical
properties). One approach to the design of new materials with
interesting magnetic properties is to develop paramagnetic
ligands for coordination to metal centres. Coordinating radical
ligands to metal ions can result in strong magnetic exchange
between the metal- and the ligand-based moments,5
potentially increasing the net magnetic moment, providing an
effective pathway for coupling between multiple coordinated
metal centres, or engendering controllable intramolecular
redox processes. In 3d transition metal complexes, exchange
coupling with coordinated radical ligands tends to be strong and
a. Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1,
Canada. Email: kpreuss@uoguelph.ca
b. Department of Chemistry, Western University, London, Ontario N6A 3K7, Canada.
c. CNRS, CRPP, UMR 5031, F-33600 Pessac, France.
d. Univ. Bordeaux, CRPP, UMR 5031, F-33600 Pessac, France.
† Electronic Supplementary Information (ESI) available: synthetic details for the
preparation of 2-cyanobenzothiazole; crystallographic details and tables; additional
figures and magnetic measurement details. See DOI: 10.1039/x0xx00000x
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the nature of the exchange coupling is readily predicted using a
simple orbital overlap approach.6
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DOI: 10.1039/C9DT00558G
Paramagnetic ligands have been developed from a variety
of heterocyclic organic radicals.7,8 We find the 1,2,3,5-
dithiadiazolyl (DTDA) radical particularly appealing because
paramagnetic DTDA-based ligands are able to participate in
numerous intermolecular interactions as a result of their
molecular and electronic structure. DTDAs often participate in
pancake bonding9 through overlap of their singly occupied
molecular orbitals (SOMOs). Manipulation of pancake bonding
as a supramolecular synthon has led to interesting SMM
behaviour10 and magnetic switchability11 in solid state metal
Figure 2. Excerpts from the crystal structure of Fe(hfac)2(betaDTDA) illustrating the -
stacking of the betaDTDA ligands and supramolecular S⋯O contacts, viewed from two
complexes of DTDA ligands. Design of DTDA ligands with R- different positions; for clarity, only O atoms of hfac ligands are shown; colour code: H,
white; C, grey; N, blue; S, yellow; O, red; F, green; Fe, dark red.
groups that can participate in other types of intermolecular
interactions has led to supramolecular pairs with a high spin
ground state,12 magnetic ordering,13,14 and isomerization in the
solid state.15 Directional electrostatic interactions, such as
sigma hole bonds,16 enable crystal engineering that influences
the magnetic properties of metal-radical complexes by creating
new intermolecular exchange pathways.12,13 We have
analysis). Slow re-sublimation of the isolated product under
static vacuum (10-1 Torr, 115 °C) yields crystals suitable for
analysis by single crystal X-ray diffraction.
Crystal Structures
developed
a number of thiazyl radical ligands with
A dark brown prismatic crystal of betaDTDA, grown by
sublimation under static vacuum (10-1 Torr, 120 °C), was
selected for single crystal X-ray analysis. Diffraction data were
collected at 150 K. BetaDTDA crystallizes in P21/c with two
molecules in the asymmetric unit (Figure S1; Table S1).† The
two molecules form a pancake-bonded (betaDTDA)2 dimer,
with a cis-cofacial arrangement of the thiazyl rings, which is
common for DTDA radicals in the solid state.23 Bond lengths and
angles of the thiazyl rings, and distances between the pancake-
bonded pair (Table S2),† are comparable to those observed for
other pancake-bonded DTDA radicals. Close S+···N- contacts
between thiazyl S and N atoms of the pancake-bonded
(betaDTDA)2 pairs define arrays of molecules along [001]
(Figure S1; Table S2).† Further S+···N-, S···S, and S···C contacts,
involving the thiazyl and benzothiazole sulphur atoms, are
electronegative substituents on the R-group, but have not until
recently pursued the effect of incorporating regions of partial
positive charge density into the DTDA R-group.
Herein, we report
a new DTDA radical ligand, 4-
(benzothiazol-2´-yl)-1,2,3,5-dithiadiazolyl (betaDTDA), and its
coordination complex with the Fe(hfac)2 fragment (Figure 1).
Magnetic measurements of Fe(hfac)2(betaDTDA) indicate
strong antiferromagnetic (AF) coupling between the metal- and
the ligand-based magnetic moments. This complex also exhibits
slow relaxation of magnetization below 4 K in agreement with
SMM properties.
Results and Discussion
Synthesis
present in multiple directions. The incorporation of
a
benzothiazole sulphur atom clearly contributes to the
formation of a dense 3-dimensional network of contacts.
Red crystals of Fe(hfac)2(betaDTDA) were grown by slow
sublimation under static vacuum (10-1 Torr, 115 °C). The metal
complex crystallizes in P21/c with one molecule in the
asymmetric unit (Figure 1; Table S1).† The slightly distorted
octahedral coordination geometry is consistent with a typical 6-
coordinate hs-Fe(II) centre (Table S3).† Coordinated betaDTDA
ligands are not involved in pancake bonding, however multiple
other non-covalent contacts are present. Contacts between
BetaDTDA is prepared from the corresponding 2-
benzothiazolecarbonitrile, betaCN, following a modification of
well-established general procedures,17,18 and is isolated by
sublimation, yielding X-ray quality crystalline material. BetaCN
is not commercially available, but is readily prepared from 2-
aminothiophenol using standard organic synthetic protocols
(Scheme
S1).†
In
the
first
step,
ethyl
2-
benzothiazolecarboxylate is produced by refluxing 2-
aminothiophenol with diethyl oxalate.19 The corresponding
amide is afforded by reaction of the ethyl carboxylate with
aqueous ammonia.20 Conversion of the amide to betaCN is then
achieved by dehydration using POCl3.21 Isolation of white,
crystalline betaCN in high yield is achieved by sublimation of the
crude product (10-2 Torr, 60 °C).
Fe(hfac)2(betaDTDA) is prepared by stoichiometric reaction
of betaDTDA with Fe(hfac)2(THF)2.22 Sublimation of the crude
product under vacuum (10-5 Torr, 120 °C) yields pure, crystalline
material, suitable for bulk analysis (magnetometry, elemental
electropositive
benzothiazole
sulphur
atoms
and
electronegative hfac oxygen atoms support arrays wherein the
nearly planar radical ligands form slipped -stacks in [001], with
a distance of ca. 3.5 Å between ligand planes (Figure 2). Non-
covalent S···O contacts have been identified as an important
factor in the stability of a wide range of solid state structures,24
and are likely to be a significant structure-directing interaction
in Fe(hfac)2(betaDTDA) as well. Additional close contacts within
the slipped -stacks include those between hfac fluorine atoms
and thiazyl sulphur atoms, and between hfac fluorine atoms and
2 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C9DT00558G
Figure 3. Temperature dependence of the T product for Fe(hfac)2(betaDTDA) ( is
defined as M/H per mole of complex) at 0.1 T; open circles indicate measured data
points; red and green lines represent best fits as described in text. Inset: magnetization
as a function of applied field between 1.85 and 8 K. The solid lines correspond to the
complete model discussed in the text.
Figure 4. Temperature (left) and frequency (right) dependence of the real (χ, top) and
imaginary (χ, bottom) parts of the ac susceptibility between 10 and 10000 Hz and
between 1.85 and 6 K, respectively, for Fe(hfac)2(betaDTDA) in zero dc field. Solid lines
are visual guides for the eye.
aromatic
H atoms. Multiple contacts between -stacks
tropy, which is not uncommon for hs-Fe(II).
contribute to a dense 3-dimensional network. Of particular note
is a contact between a fluorine atom and both sulphur atoms of
a neighbouring thiazyl ring (Figure S2),† the geometry of which
is similar to that commonly observed between sulphur atoms
and electronegative moieties in DTDAs25 and in metal
complexes of DTDA radical ligands.26 The geometry of this
contact can be rationalized using calculated electrostatic
potential surfaces which indicate significant partial positive
charge between the two S atoms, in the plane of the  system.25
Based on the crystal structure, the complex can be viewed
magnetically as a hetero-spin pair composed of an SFe = 2 Fe(II)
and an Srad = ½ betaDTDA radical. The intramolecular exchange
interaction can thus be modelled on the basis of an isotropic
spin Heisenberg Hamiltonian:
퐻 = ― 2퐽
(
푆퐹푒 ⋅ 푆푟푎푑
)
+ 푔푎푣휇퐵
(
푆퐹푒 + 푆푟푎푑 ⋅ 퐻{Fatila, 2016 #2014}
)
푆
where J is the Fe(II) – radical coupling constant and are the
푖
spin operators (with SFe = 2 and Srad = ½). The theoretical
expression of the magnetic susceptibility can be estimated by
applying the van Vleck equation27 in the weak field
Magnetic Properties
Magnetic susceptibility data collected on a crystalline sample of
betaDTDA confirm that it is diamagnetic over the measured
temperature range (1.85 K – 350 K; Figure S3),† consistent with
pancake bonding observed in the crystal structure (150 K).
The magnetic susceptibility of a polycrystalline sample of
Fe(hfac)2(betaDTDA) was measured at an applied field of 0.1 T,
between 1.85 and 300 K (Figure 3). The T product at room
temperature is 3.22 cm3 K mol-1, close to the expected value for
an ideal Curie system comprised of one Srad = 1/2 betaDTDA
ligand and one SFe = 2 hs-Fe(II) ion (C = 3.375 cm3 K mol-1 for giso
= 2), and consistent with the absence of pancake bonding in the
Fe(hfac)2(betaDTDA) crystal structure. Upon cooling, the T
product decreases, indicating dominant antiferromagnetic (AF)
coupling interactions between the spins of the hs-Fe(II) metal
centre and the radical ligand. The T product reaches a value of
2.3 cm3 K mol-1 at ~45 K and remains relatively constant upon
further cooling, until ~25 K. Below 25 K, the value of T
decreases, reaching a minimum of 1.42 cm3 K mol-1 at 1.85 K.
The decrease in T below 25 K can be attributed to either weak
AF interactions between complexes or the hs-Fe(II) magnetic
anisotropy or both effects. The field dependence of the
magnetization measured at various temperatures between 1.85
and 8 K is shown in Figure 3 (inset). At the highest applied field
(7 T), the magnetization is still well below that expected for an
Stotal = 3/2 unit (3 B), consistent with significant magnetic aniso-
approximation:
5퐽
푁푔2푎푣휇2
퐵10 + 35푒푘 푇
퐵
휒Fe ― rad
=
5퐽
4푘퐵푇
2 + 3푒푘 푇
퐵
with the parameters having the usual meanings. In order to fit
the data for the T product below 25 K, inter-complex
interaction have been introduced in the frame of the mean-field
theory. The following definition of mean-field susceptibility,

MF, has been used:
휒Fe ― rad
2푧퐽′
푁푔2푎푣휇2퐵
휒MF
=
1 ―
휒Fe ― rad
where Fe-rad is the susceptibility of the non-interacting
complex, z is the number of nearest neighbours, and J is the
magnetic interaction between two neighbouring complexes.28
A very good fit of the data collected at 0.1 T down to 1.85 K has
been achieved, with the following parameters: gav = 2.2(1), J/kB
= -62(2) K and zJ/kB = -0.62(5) K. The remarkably large
intramolecular interactions stabilize the Stotal = 3/2 ground state
which is separated from the first Stotal = 5/2 excited state by
315 K, explaining the observed plateau of the T product
between 25 and 45 K. The zJ term, which is introduced in the
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above model as mean-field intermolecular interactions, is also
phenomenologically taking into account the effects of hs-Fe(II)
magnetic anisotropy. In order to evaluate the role of the
magnetic anisotropy on the low temperature magnetic data,
the T vs T and M vs. H data below 45 K have been fitted to a
Conclusions
View Article Online
DOI: 10.1039/C9DT00558G
4-(benzothiazol-2´-yl)-1,2,3,5-
Neutral
radical
ligand
dithiadiazolyl (betaDTDA) has been designed to possess an
electropositive sulphur atom (external to the thiazyl ring) that
can participate in electrostatic interactions. The solid state
structure of the Fe(hfac)2(betaDTDA) complex is dominated by
-stacking of coordinated betaDTDA ligands, supported by
electrostatic contacts between benzothiazole sulphur atoms
and neighbouring hfac oxygen atoms. Short contacts between
thiazyl sulphur atoms and hfac fluorine atoms, in a geometry
typical for DTDAs, also contribute to the dense, three-
dimensional network of contacts. Magnetic measurements of
Fe(hfac)2(betaDTDA) indicate strong antiferromagnetic (AF)
coupling between the radical and Fe(II) ion moments, which
stabilizes a well-defined Stotal = 3/2 ground state. At low
temperature (<4 K), Fe(hfac)2(betaDTDA) exhibits slow
dynamics of the magnetization consistent with SMM behaviour.
Stotal
Hamiltonian:
퐻 = 퐷푆2푡표푡푎푙,푧 + 푔푎푣휇퐵푆푡표푡푎푙 ⋅ 퐻{Fatila, 2016 #2014}
= 3/2 macrospin model considering the following
The T product and magnetization data are simultaneously
well-reproduced29 (solid green line for the T vs. T data) by this
approach, leading to gav = 2.22(5) and D/kB = +8.9(4) K. Even if
the value of the D parameter needs to be taken with caution as
the presence of intermolecular interactions cannot be ruled
out, this analysis shows that the magnetic anisotropy of the hs-
Fe(II) centre is relevant to describe the magnetic ground state
of the Fe(hfac)2(betaDTDA) complex. With these preliminary
analyses in hand, a more general approach to model the
magnetic properties of this complex was considered using the
following Hamiltonian:
Experimental
퐻 = ― 2퐽
푔퐹푒푆퐹푒 + 푔푟푎푑푆푟푎푑
(
푆퐹푒 ⋅ 푆푟푎푑
)
+ 퐷퐹푒푆2퐹푒,푧
General Considerations. All reactions and manipulations were
performed under inert atmosphere and using anhydrous
solvents, unless stated otherwise. Anhydrous solvents were
dispensed from refillable solvent kegs, filled by Caledon Labs,
from an LC-SPS solvent purification system equipped with dry-
packed columns of 3 Å molecular sieves. Reagents were
purchased from Strem, Sigma-Aldrich, and Alfa Aesar and used
without further purification unless otherwise noted.
LiN(TMS)2·Et2O was prepared from LiN(TMS)2 in large quantities
following a literature procedure.17 SbPh3 from Sigma was
recrystallized from hot acetonitrile prior to use. 2-
Cyanobenzothiazole (betaCN) was prepared following slight
modifications of literature procedures, as described in the
Supplementary Information.† NMR spectra were collected at
the University of Guelph using Bruker instruments (frequency
as indicated). Infrared spectra (KBr pressed pellet or KBr plate)
were recorded on a Nicolet 4700 FTIR spectrometer at 4 cm-1
resolution and ambient temperature. Elemental analyses were
performed by MHW Laboratories in Phoenix, AZ, USA.
4-(Benzothiazol-2´-yl)-N,N,N'-tris(trimethylsilyl)amidine.
2-Cyanobenzothiazole (1.49 g, 9.31 mmol) was added to a clear,
colourless solution of LiN(SiMe3)2·Et2O (2.30 g, 9.53 mmol) in
anhydrous diethyl ether (100 mL). After 3 hours of stirring the
resulting dark purple solution, trimethylsilylchloride (1.4 mL, 11
mmol) was added. The reaction mixture was left to stir for 12
hours at room temperature before it was filtered in situ to
remove LiCl byproduct. The solvent was removed in vacuo from
the red filtrate to obtain a dark red waxy solid which was used
immediately, without purification, in the next step; crude yield
3.2 g (87%). FTIR (KBr, cm-1): 3279 (w), 3066 (w), 2955 (s), 2898
(m), 1942 (w), 1786 (w), 1641 (s), 1603 (m), 1561 (m), 1498 (m),
1456 (w), 1410 (m), 1348 (w), 1314 (s), 1282 (w), 1251 (s), 1205
(s), 1154 (w), 1124 (m), 1096 (m), 1055 (s), 965 (s), 932 (m), 888
(w), 840 (s), 758 (s), 729 (m), 711 (m), 687 (m), 659 (w), 638 (w),
619 (w), 582 (w), 434 (s).
+ 휇퐵
(
)
⋅ 퐻{Fatila, 2016 #2014}
A converging numerical fit of the experimental data is only
achieved (solid red line for the T vs. T data and solid lines for
the M vs. H data) when using as initial values the ones obtained
in the above simplified models and fixing grad = 2.0.29 The
following set of parameters are found, gFe = 2.17(5), J/kB = -
61.1(6) K and DFe/kB = +6.3(2) K, confirming the values found
with the simplified approaches. It is worth mentioning that
2
2
(
)
퐸퐹푒 푆퐹푒,푥 ― 푆퐹푒,푦
adding a transverse anisotropy term (
) in the
above Hamiltonian or intermolecular magnetic interactions (zJ')
does not improve the experimental-theory agreement. A
relatively large DFe value is indeed expected (typically up to
30 K) for a non-Kramer hs ions like an S = 2 Fe(II) centre.30
Considering the presence of
a significant magnetic
anisotropy in this complex, the ac susceptibility was also
measured in zero dc-field as a function of ac frequency at
various temperatures (1.83 – 5.5 K) and as a function of
temperature at various ac frequencies (10 – 10000 Hz). As
shown in Figure 4, plots of the temperature and frequency-
dependence of the in-phase () and out-of-phase () ac
susceptibility in zero dc field reveal the slow dynamics of the
magnetization below 4 K. Unfortunately, the relaxation time
cannot be estimated from these measurements as there is no
clear maximum in the out-of-phase ac susceptibility at the
lowest temperature we are capable of measuring and as the
relaxation process is not of Debye nature (Figure S4).† The
application of a dc-field up to 1 T does not slow the relaxation
process and therefore even under dc-field it is not possible to
evaluate the relaxation time of this system with our
instruments. Nevertheless, Fe(hfac)2(betaDTDA) is one of
comparatively few mononuclear transition metal – radical
complexes31 and a rare example of a 6-coordinate Fe(II)
complex8,32 that exhibits observable slow dynamics of the
magnetization consistent with a SMM behaviour.
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4-(Benzothiazol-2´-yl)-1,2,3,5-dithiadiazolium
ARTICLE
cm; 15-25 mg) under nitrogen. Prior to experiments, the field-
chloride.
View Article Online
DOI: 10.1039/C9DT00558G
dependent magnetization was measured at 100 K in order to
Excess sulphur monochloride (4 mL, 50 mmol) was added to a
red solution of crude 4-(benzothiazol-2´-yl)-N,N,N'-
tris(trimethylsilyl)amidine (3.2 g, 8.1 mmol) in CH2Cl2 (20 mL) ,
forming a bright orange precipitate. The orange slurry was
stirred for 16 hours at room temperature, and the bright orange
solid product was collected by filtration. The crude product was
used without further purification; crude yield 2.3 g (>100% due
to S8 byproduct). FTIR (KBr, cm-1): 3060 (w), 1685 (w), 1550 (w),
1507 (s), 1384 (s), 1316 (m), 1131 (s), 878 (s), 847 (m), 840 (m),
778 (s), 705 (m), 541 (w).
confirm the absence of any bulk ferromagnetic impurities. The
magnetic data were corrected for the diamagnetic
contributions from the sample (Fe(hfac)2(betaDTDA) only) and
sample holder.
Conflicts of interest
The authors declare no conflicts of interest.
4-(Benzothiazol-2-yl)-1,2,3,5-dithiadiazolyl. Triphenylan-
timony (1.02 g, 2.01 mmol) was added to an orange slurry of
crude 4-(benzothiazol-2´-yl)-1,2,3,5-dithiadiazolium chloride
(1.41 g, 5.15 mmol) in acetonitrile (35 mL). The resulting dark
purple slurry was stirred for 30 minutes at room temperature.
The slurry was then filtered in vacuo to afford a dark purple
powder. The product was purified by dynamic vacuum
sublimation (10-2 Torr; 120 °C) using a temperature gradient
tube furnace. Sublimation under static vacuum (10-1 Torr; 120
°C) was then used to grow crystals suitable for X-ray
crystallography. Sublimed yield 0.66 g (54% from nitrile). FTIR
(KBr, cm-1): 1552 (w), 1508 (m), 1451 (w), 1355 (m), 1301 (m),
1115 (s), 1059 (m), 902 (s), 833 (s), 813 (s), 797 (s), 765 (s), 754
(s), 724 (m), 687 (w), 498 (s), 425 (w). Anal. Calcd. for C8H4N3S3:
C, 40.31; H, 1.69; N, 17.63%. Found: C, 40.48; H, 2.00; N, 17.38%.
EPR (toluene, 25 °C) five-line pattern consistent with exchange
between coupling to two equivalent 14N nuclei; aN = 5.026 G, g
= 2.010.
Acknowledgements
K.E.P. and E.S. acknowledge support from the Natural Sciences
and Engineering Research Council (NSERC) of Canada in the
form of a Discovery Grant (DG) and an Undergraduate Summer
Research Award (USRA), respectively. M. B. M. acknowledges
support from the Government of Ontario in the form of an
Ontario Graduate Scholarship. R.C. and M.R. thank the
University of Bordeaux, the Région Nouvelle Aquitaine, the
CNRS, the MOLSPIN COST action CA15128, and the GdR MCM-
2: Magnétisme et Commutation Moléculaires for financial
support. D.V.S. thanks the Canada Foundation for Innovation
(CFI) for funding the X-ray diffractometer.
Notes and references
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DOI: 10.1039/C9DT00558G
Mononuclear 6-coordinate hs-Fe(II)-radical complex exhibits single-molecule magnet behaviour