Slow magnetic relaxation in Ni-Ln (Ln = Ce, Gd, Dy) dinuclear complexes

Article abstract of DOI:10.1039/c9dt02122a

Three new isomorphous complexes [Ni(o-van-en)LnCl₃(H₂O)] [H₂(o-van-en) = N,N′-ethylene-bis(3-methoxysalicylaldiminate; Ln = Ce (1), Gd (2), Dy (3)] were prepared by a stepwise reaction using mild conditions and were struct

Full text of DOI:10.1039/c9dt02122a

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Slow magnetic relaxation in Ni–Ln (Ln = Ce, Gd,
Dy) dinuclear complexes†
Cite this: DOI: 10.1039/c9dt02122a
Anna Vráblová, a,b Milagros Tomás, *c Larry R. Falvello, b Ľubor Dlháň,d
e
Ján Titiš, e Juraj Černák *a and Roman Boča
Three new isomorphous complexes [Ni(o-van-en)LnCl3(H2O)] [H2(o-van-en) = N,N’-ethylene-bis(3-
methoxysalicylaldiminate; Ln = Ce (1), Gd (2), Dy (3)] were prepared by a stepwise reaction using mild
conditions and were structurally characterised as dinuclear molecules in which Ni and Ln are coordinated
by the compartmental Schiff base ligand (o-van-en)= and doubly bridged by O atoms. While the nickel(II)
centre is diamagnetic within the N2O2 square-planar coordination of the Schiff base ligand, the lanthanide
atoms are octa-coordinated to give an {LnCl3O5} chromophore with a fac-arrangement of the chlorido
ligands. AC magnetic measurements revealed that all three complexes, including the nominally isotropic
Gd(III) system, show field induced slow magnetic relaxation with two or three relaxation channels: at T =
1.9 K the low-frequency relaxation time is τLF(1) = 0.060 s at BDC = 0.5 T, τLF(2) = 0.37 s at BDC = 0.3 T,
and τLF(3) = 1.29 s at BDC = 0.15 T.
Received 20th May 2019,
Accepted 17th August 2019
DOI: 10.1039/c9dt02122a
rsc.li/dalton
(QTM) due to non-negligible magnetic exchange interactions
between lanthanide and transition metal ions.5 A recent study
Introduction
Since the identification of the first single-molecule magnet on 3d–4f complexes with diamagnetic 3d metal ions such as
(SMM) {Mn12} in 1993,1 research on this phenomenon has zinc(II) or cobalt(III) showed an enhancement of the Ueff barrier
continued apace and has also been extended to lanthanide in comparison to their mononuclear lanthanide analogues;6 it
based materials.2 As early as 2004, heteronuclear 3d–4f com- was suggested that the presence of a diamagnetic 3d cation
plexes were observed to display slow magnetic relaxation.3 The near the lanthanide central atom, with a monatomic O bridge,
advantage of transition metal and lanthanide complexes lies induces a large charge polarisation on the bridging oxygen
in a fusion of the properties of both. In fact, the magnetic atom that favours an increase in the Ueff barrier. This obser-
study of complexes comprising transition metals and vation suggests a new strategy in designing 3d–4f complexes
lanthanides dates back to 1985, when Gatteschi et al. observed with diamagnetic 3d ions.5,7–10
unexpected ferromagnetic coupling between copper(II) and
gadolinium(III) ions.4
Regarding the 4f elements, heavy lanthanide ions were
widely used for the preparation of SMM materials due to their
More recent research has yielded a few examples of a sig- large angular momentum J and large magnetic anisotropy.11–13
nificant reduction in quantum tunnelling magnetization However, a recent study of light lanthanide ions revealed sur-
prising magnetic behaviour for cerium(III).14 Despite the small
magnetic moment, which arises from its small angular
momentum J and small Landé g factor, the spin–orbit coup-
ling is strong enough to create significant magnetic anisotropy
and thus an energy barrier between the two orientations of the
magnetization. The first cerium(III) based SMM was reported
in 2013 15 and later other cerium(III) complexes were reported
to be SMMs.16–19
aDepartment of Inorganic Chemistry, Institute of Chemistry, P. J. Šafárik University
in Košice, Moyzesova 11, Košice, Slovakia. E-mail: juraj.cernak@upjs.sk
bInstituto de Ciencia de Materiales de Aragón (ICMA), Departamento de Química
Inorgánica, University of Zaragoza–CSIC, E-50009 Zaragoza, Spain
cCentro de Quimica y Materiales de Aragón (CEQMA-ISQCH), Departamento de
Química Inorgánica, Pedro Cerbuna 12, University of Zaragoza–CSIC, E-50009
Zaragoza, Spain. E-mail: milagros.t@csic.es
dInstitute of Inorganic Chemistry, Slovak University of Technology, 812 37 Bratislava,
Slovakia
Among the lanthanide ions, the case of gadolinium(III)
complexes represents another breakthrough in the theory of
slow relaxation of magnetization. Despite its essentially isotro-
pic ground state with L = 0, several materials have been
reported for which magnetic anisotropy around the gadoli-
nium(III) centre was induced by local coordination, magnetic
exchange coupling or electron density donation.20–29 These
eDepartment of Chemistry, FPV, University of SS Cyril and Methodius, 917 01
Trnava, Slovakia
†Electronic supplementary information (ESI) available: X-ray structure analysis,
synthetic, crystallographic and physical data. CCDC 1916431–1916433. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c9dt02122a
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materials containing gadolinium(III) may be considered as
members of a new class of SMMs with the highest known spin
state (4f7) for a single ion.
Some considerable effort has been extended to produce
strictly dinuclear 3d–4f molecular complexes30–32 to serve as
building blocks for the further preparation and study of poly-
nuclear clusters33–36 and polymers.37–39 A related fact in the
context of the present work is that salen-type Schiff bases orig-
inating from o-vanillin and related aldehydes have been used
in coordination chemistry due to their ability to form com-
plexes with
a rich variety of geometries and structural
dimensions.40
In what follows we describe the preparation, chemical and
structural characterization and magnetic properties of three
isomorphous dinuclear [Ni(o-van-en)Ln(H2O)Cl3] complexes
[Ln = Ce (1), Gd (2), Dy (3); H2L = H2(o-van-en) = N,N′-ethylene-
bis(3-methoxysalicylaldiminate)]. The choice of Ce(III), Dy(III)
and Gd(III) was designed to expose the main differences in the
magnetic behaviours of a light lanthanide ion, a heavy lantha-
nide ion and the lanthanide ion with a spherical orbital
ground state, respectively.
Results and discussion
Synthesis and identification
Scheme 1 Schematic representation of the synthetic route for prepa-
ration of 1, 2 and 3.
The three complexes [Ni(o-van-en)LnCl3(H2O)] [Ln = Ce (1), Gd
(2), Dy (3)] were first synthesized in microcrystalline form
using mild solution techniques in a modification of the
method of Costes and co-workers.41 The synthetic procedure is
depicted in Scheme 1. The products were characterized using
chemical analysis and IR spectroscopy; the observed absorp-
tion bands are listed in the ESI.† The imine group absorption,
ν(CvN), observed slightly above 1600 cm−1, can be considered
as a characteristic band. In the IR spectrum of the ligand, this
vibration was observed at 1631 cm−1 which agrees with the
reported value of 1628 cm−1 reported for the same Schiff
base,42 and is similar to the value of 1625 cm−1 for a related
Schiff base L [L = N,N′-bis((E)-3-phenylallylidene)-3-methyl-1,2-
phenylenediamine].43 The ligand bonded in the complex
[CdLX2] (X = Cl, Br, I, SCN) exhibits a shift of 1–7 cm−1 to
lower wavenumbers. In the spectra of the complexes 1, 2 and 3
nuclear molecules of [Ni(o-van-en)Ce(H2O)Cl3] (Fig. 1). The
Ni(II) atom is coordinated in square-planar form by the N2O2
donor set of the potentially ditopic ligand (o-van-en)2−. The Ce
(III) central atom is octa-coordinated by four oxygen atoms
from the (o-van-en)2− ligand, one aqua and three chlorido
ligands, yielding an {LnCl3O5} chromophore (Fig. 1).
Calculations using the program SHAPE44 indicate that the
coordination polyhedron is close to a bicapped (O1 and O4)
trigonal prism [Fig. S2;† the same holds for the Dy(III) and
Gd(III) complexes]. It is significant (vide infra) that the three
chlorido ligands form a single face of the polyhedron.
Analogous
[Ni(o-van-en)Ln(NO3)3]·(CH3)2CO
heterodi-
nuclear complexes with auxiliary nitrato ligands and contain-
the vibration ν(CvN) was observed at 1622–1623 cm−1
.
Recrystallization of these microcrystalline products or reac-
tion by diffusion techniques yielded single crystals of 1–3. The
phase identities of the microcrystalline products with the
corresponding single-crystal samples were established by
LeBail refinement using the powder diffraction patterns for all
three samples (see Fig. S1†).
Crystal structures
Compounds 1–3 are isomorphous, so we will limit our descrip-
tion and discussion to complex 1 with the corresponding geo-
metric parameters of 2 and 3 given in parentheses. We note
that all three crystal structures were studied at room tempera-
Fig. 1 Molecular structure of [Ni(o-van-en)Ce(H2O)Cl3]; thermal ellip-
ture. The crystal structure of 1 consists of neutral heterodi- soids are drawn with 50% probability.
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ing various lanthanide atoms have been reported;45,46 but to with higher nuclearity, i.e., Tr2Ln2 compounds in which some
our knowledge no analogous complexes with other 3d of the chlorido ligands act as bridges between the lanthanide
elements with auxiliary chlorido ligands have been studied. centers.47,56
On the other hand, eight analogous heterodinuclear com-
There are four dinuclear molecules per unit cell of 1 (and
plexes containing chlorido ligands were reported with modi- likewise for 2 and 3). The packing of the complex molecules is
fied Schiff base ligands.34,47–51 An interesting example is the governed by medium-strength hydrogen bonds of the O–H⋯Cl
complex [NiCl2(o-van-bu)YbCl(H2O)3] with a hexacoordinated type yielding a chain-like supramolecular structure running
Ni(II) central atom (donor set Cl2O2N2).48
along the a axis with additional, weaker Car–H⋯Cl, NvC–
The observed Ni–N and Ni–O as well as the Ce–O bond dis- H⋯Cl type hydrogen bonds and weak π–π stacking interactions
tances are similar to those reported in the analogous com- of the aromatic rings of the neighbouring chains forming
plexes [Ni2(o-van-en)2Ce(NO3)2](NO3),52 ([Cu(o-van-en)Gd(NO3)3]· supramolecular layers in the ab plane (Fig. S3 and Table S2†).
0.25H2O,53 [Co(o-van-en)(CH3COO)2Dy(NO3)2]54) (Table 1). The There are only close contacts of the C–H⋯Cl type between
Ln–Cl bond distances in 1 are in the range of 2.717(2)–2.802(2) planes, involving methyl and methylene groups of the ligand.
Å [2.630(3)–2.714(3) Å for 2 and 2.6005(10)–2.6955(9) Å for 3],
DC magnetic data
which can be compared to the average Ce–Cl distance of
2.7467 Å (2.6829 Å for Gd–Cl and 2.6357 Å for Dy–Cl) found in
the CSD.55 The CSD further reveals that in all Ni–Ln (Ln = Ce,
Gd, Dy) with Ln–Ni distances shorter than 5 Å the two metal
atoms are bridged by monatomic O bridges, and the mean
values of the Ni–Ln distances are 3.58 Å, 4.53 and 4.45 Å for
Ce–Ni, Gd–Ni and Dy–Ni, respectively. In our compounds 1–3
the observed Ln–Ni distances are significantly shorter than the
corresponding calculated mean values (Table 1). The remain-
ing geometric parameters in all three complexes exhibit
expected values.
Although molecular compounds with Ln–Cl bonds are
known, these represent only about 6% of all molecular lantha-
nide complexes.55 Those in which the lanthanide is bonded to
three terminal chlorido ligands are just around 1%. For com-
parison, the number of molecular lanthanide compounds with
three coordinated NO3− groups is more than five times that with
three Cl− ligands. Nevertheless, given the large number of mole-
cular Ln compounds that have been characterized, there are
some 400 compounds in the latter class – Ln–Cl3(terminal). The
only eight heterodinuclear Tr–Ln complexes with Schiff bases
similar to the one in compounds 1–3 and with chlorido
ligands bonded to the lanthanide metal that have been struc-
turally characterized have only one or two chlorido ligands
bonded to the lanthanide,34,47–51 not three as in compounds
1–3. Also, two related compounds with three Cl− ligands
bonded to the same lanthanide metal have been found, but
In compounds 1–3 the central Ni(II) atom is in a square planar
environment formed by four oxygen donor atoms. Thus, it is
magnetically silent, except for some temperature-independent
magnetism arising from the presence of low-lying excited
states. The lanthanide Ln(III) centres bear orbital and spin
2
angular momentum and the ground multiplet is F5/2 for
8
6
Ce(III), S7/2 for Gd(III) and H15/2 for Dy(III), with the magneto-
gyric ratios gJ = 6/7, 2 and 4/3, respectively. Thus the magneti-
zation per formula unit should saturate to M1 = Mmol/(NAμB) =
gJ·J = 6/7 × 5/2 = 15/7, 2 × 7/2 = 7, and 4/3 × 15/2 = 10. The high-
temperature limit of the effective magnetic moment, based
upon the magnetic susceptibility, is μeff/μB = gJ[J(J + 1)]1/2
=
(6/7)(5/2 × 7/2)1/2 = 2.54, 2 × (7/2 × 9/2)1/2 = 7.94, and (4/3)
(15/2 × 17/2)1/2 = 10.6.
The DC magnetic data for 1 are shown in Fig. 2. Clearly
visible linear dependence of the effective magnetic moment
between T = 9–300 K indicates some temperature-independent
paramagnetism as expected for the Ni(II) centre in a square
planar environment: χTIP = 6 × 10−9 m3 mol−1. With the above
correction the room-temperature effective magnetic moment
(the high-temperature limit) adopts a value of μeff = 2.36μB,
that is not far from the single ion value (2.54). The magnetiza-
tion data at T = 2.0 and B = 7 T, M1 = 1.0, is much lower relative
to isolated multiplet 2F5/2 for Ce(III) (2.1).
Owing to the effect of the crystal field, the six-fold
2
degenerate ground atomic multiplet F5/2 |R′3:J;MJ〉 = |5/2; 1/2,
Table 1 Selected geometric parameters in 1, 2 and 3 with their s.u.’s
1
2
3
Ln–Cl1
Ln–Cl2
Ln–Cl3
Ln–O1
Ln–O2
Ln–O3
Ln–O4
Ln–O5
Ni–O2
Ni–O3
Ni–N1
Ni–N2
Ln⋯Ni
2.717(2)
2.802(2)
2.789(2)
2.710(5)
2.485(5)
2.469(5)
2.697(5)
2.518(5)
1.843(5)
1.843(5)
1.827(6)
1.829(7)
3.4876(10)
2.630(3)
2.714(3)
2.709(3)
2.658(7)
2.396(7)
2.385(7)
2.650(7)
2.393(6)
1.842(7)
1.833(7)
1.816(9)
1.825(9)
3.3959(14)
2.6005(10)
2.6940(9)
2.6955(9)
2.654(2)
2.364(3)
2.343(2)
2.648(2)
2.376(3)
1.843(2)
1.842(2)
1.834(3)
1.836(3)
3.3735(5)
Fig. 2 DC magnetic data for 1. Solid lines – fitted. Colored circles – TIP
corrected data.
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3/2, 5/2〉 is split into three crystal-field multiplets (Kramers
doublets)
within
the
respective
double
group:
ꢀ
ꢁ
R′3 : J; MJ crysꢀta!l field jG′ : Γ′; γ′i. The magnetic data was fitted
assuming that only the lowest Kramers doublet is thermally
populated. Then the effective Hamiltonian in use is
ꢀ
Ĥeaff ¼ μBBðgezff Ĵzeff cos θa þ gexfyf Ĵxeff sin θaÞ
ð1Þ
with Jeff = 1/2; a denotes grids distributed uniformly over the
meridian. To this end, the optimization routine converged to
eff
the following set of magnetic parameters: g = 0.80(19), gzeff
=
xy
4.50(1), and the molecular-field correction (operative at low
temperature) zj/hc = –0.27 cm−1. Large gz and small gxy are
typical values for the anisotropic lanthanide ions.
Fig. 4 DC magnetic data for 3. Dashed lines are visual guides.
Ab initio calculations for 1 gave the values g{0.035, 0.251,
3.880} that support the magnetic data analysis. The first
excited Kramers doublet lies 300 cm−1 above the ground one
and its thermal population at T = 300 K is only 9%.
The DC magnetic data for 2 confirms the behaviour of the
8S7/2 ground term (Fig. 3): the effective magnetic moment is
case, the higher terms of the series of the crystal field potential
will also contribute
þk
X
X
ˆm
Bmk ꢁ Ok ðJz; J+
ˆ ˆ
Þ
ð2Þ
ˆ
V ¼
m¼0
k¼0;2;4;6
where Ômk (Ĵz,Ĵ ) are the appropriate equivalent operators. The
almost constant over the whole temperature range with μeff
=
6
sixteen members of the H15/2 multiplet are then split into
7.8–7.9μB; the magnetization per formula unit at B = 7.0 T and
T = 2.0 K saturates to M1 = 6.6. This data is consistent with an
isotropic g-factor slightly below 2.0. The data fitting to the
Curie law and the Brillouin function gave g = 1.952(6). A super-
position of the magnetization data vs. BT−1 confirms an
invisible magnetic anisotropy of 2.
eight Kramers doublets.
Field scan of the AC susceptibility
The AC susceptibility data was acquired at the field amplitude of
BAC = 0.38 mT and depending upon the external magnetic field
BDC, temperature, and the frequency f of the oscillating field.
The first scan for a variable magnetic field, fixed low temp-
erature T = 2.0 K, and a set of four representative frequencies
f = 1.1, 11, 111, and 1116 Hz is shown in Fig. 5. It is seen that
the out-of-phase susceptibility χ″ is zero at BDC = 0, which is
traditionally explained as an effect of the fast magnetic tunnel-
ling. With the applied external field, the out-of-phase suscepti-
bility rises to a maximum and then attenuates at higher fields.
The position of the maximum slightly depends upon the fre-
quency of the oscillating field. The subsequent data measure-
ments were done at the external field for which the out-of-
The DC magnetic data for 3 is shown in Fig. 4. The effective
magnetic moment displays the high-temperature (HT) limit of
μeff = 12.15μB that decreases only slightly down to T ∼ 60 K;
then it decreases more rapidly to 11.1μB at the lowest tempera-
ture of the measurements. The observed HT limit is somewhat
higher than that expected for a single Dy(III) ion (10.6). This
might be due to the presence of low-lying excited states of the
cooperating Ni(II) centre. More surprising is the saturation
value of the magnetization M1(J) = 7.9 at T = 2.0 and B = 7.0 T,
which differs substantially from the single-ion expectation
(M1 = 10). This can arise in a partial quenching of the orbital
angular momentum of the Dy(III) centre by the asymmetric
ligand field of the {DyO4O′Cl3} chromophore. Another reason
could be the zero-field splitting of the ground crystal-field mul-
tiplet inherent to an anisotropic ion such as Dy(III). In such a
phase susceptibility component displays a maximum: BDC
0.1 or 0.5, 0.3, and 0.15 T for 1 through 3.
=
Temperature scan of the AC susceptibility
Temperature evolution of the AC susceptibility components for
a set of frequencies varying between f = 0.1 and 1500 Hz at a
selected external field BDC is shown in Fig. S4 (see ESI†). It can
be concluded that the samples 1 through 3 show field induced
slow magnetic relaxation typical for single ion magnets (SMM).
On heating, the in-phase susceptibility components for various
frequencies tend to merge at the critical temperature (ca. 10, >7,
and 7 K); at the same time the out-of-phase component vanishes
since then the system behaves as an ordinary paramagnet.
Frequency scan of the AC susceptibility for 3, Ni–Dy complex
The same data sets have been rearranged to the frequency
dependence of the AC susceptibility components for a set of
temperatures.
Fig. 3 DC magnetic data for 2. Solid lines – fitted.
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τ(LF) = 1/(2πfmax) ∼ 0.995 s. Both, in-phase and out-of-phase
susceptibilities were fitted simultaneously by employing the
three-set Debye model, as explained in the ESI.† Using the
resulting relaxation parameters (thermal susceptibilities χTk
,
distribution parameters αk, and relaxation times τk, k = 1–3),
the convoluted susceptibility components are drawn as solid
lines in Fig. 6. It is evident that these lines pass through the
experimental points and this is also supported by the statisti-
cal analysis in the ESI.†
At low temperature the HF component recovers only a tail;
however, with increasing temperature the LF component
decays progressively in favor of the HF one; the IF component
balances in-between. At temperature T > 5 K, the IF component
cannot be fitted satisfactorily and then only a two-set Debye
model is applicable. At the lowest measurement temperature,
T = 1.9 K, the mole fractions of the individual relaxation
species are x(LF) = 0.49, x(IF) = 0.28, and x(HF) = 0.23, respect-
ively. At the same time, the three relaxation times are τ(LF) =
1.29 s, τ(IF) = 74 ms, and τ(HF) = 964 μs. In contrast, at T =
6.3 K, x(LF) = 0.13 and x(HF) = 0.87 hold true.
In Fig. 7, the Argand diagram is shown; it is a convolution
of three distorted semicircles (arcs) of different height, posi-
tion and width. Also an Arrhenius-like plot ln τ vs. T−1 is
shown on the right for the individual relaxation processes. The
three highest-temperature points for the HF relaxation channel
have been fitted by a straight line in order to get parameters
for the Orbach relaxation process τ = τ0 exp(Ueff/kBT): Ueff/kB
65 K and τ0 = 1.9 × 10−10 s.
=
The temperature evolution of the HF relaxation time can be
represented by various graphs as shown in Fig. S5 (see ESI†).
The dependence ln τ vs. ln T at its two edges can be recovered
by straight lines: ln τ = –8.81 + 11.3(ln T) at the highest temp-
eratures, and ln τ = –Dτ at the lowest temperatures. Therefore,
the whole dataset has been fitted via the equation
Fig. 5 AC magnetic data for 1, 2, and 3. Field scans for a set of frequen-
cies at low temperature.
τꢀ1 ¼ CT n þ Dτ
ð3Þ
For 3, it is evident (Fig. 6) that the out-of-phase component
consists of three contributions: low-frequency (LF), intermedi-
ate-frequency (IF), and the high-frequency (HF). For the lowest-
temperature measurements (T = 1.9 K) the LF component
dominates with the peak-position at fmax ∼ 0.16 Hz. Then the
corresponding relaxation time is estimated to be as long as
where the first term refers to the Raman process and the
second one the quantum tunnelling process. The optimization
routine gave n = 10.8(3), C = 3.6(16) × 10−4 K−n s−1, and
Fig. 7 Argand diagram (left) and the Arrhenius-like plot (right) for 3.
Straight line – high-temperature limit of the Arrhenius equation referring
to the Orbach process. Solid curve – fitted using Raman and quantum
tunneling processes.
Fig. 6 AC magnetic data for 3. Solid lines – fitted by the extended
three-set Debye model.
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Dτ = 1.0(1) × 103 s−1. This means that the high-temperature at T = 1.9 K and BDC = 0.5 T becomes τ(LF) = 60.3(5) ms as com-
limit of the high-frequency relaxation process can be equally pared to 18.7(11) ms at BDC = 0.1 T. A successful data fitting
reproduced by the Raman process itself. A value of n = 12 has requires the two-set Debye model for T > 3.5 K. SIM behaviour
been found for a Co(II) compound.57
of the Ce(III) ions has been reviewed recently.14 For instance,
AC susceptibility studies of single-molecule magnet behaviour
in polynuclear assembly of Ce(III) with polymolybdates reveal a
two-channel slow relaxation with the relaxation times τ = 6009
and 217 μs at T = 1.9 K and BDC = 0.02 T.18 There is a sizable
field influence since at BDC = 0.14 T the relaxation times merge
to τ = 605 μs.
Frequency scan of the AC susceptibility for 1, Ni–Ce complex
The frequency dependence of the AC susceptibility com-
ponents for 1 is shown in Fig. 8. For T = 1.9 K the well-devel-
oped peak of χ″ at f ∼ 10 Hz implies the relaxation time τ(LF) ∼
16 ms. This is much shorter relative to 3. However, the peak is
slightly asymmetric with an arm, and its reliable fit requires a
two-set Debye model where the HF component is also con-
sidered. On heating the peak is shifted to higher frequencies
but for T > 4 K the two-set model becomes unstable; then the
single-set model has been applied for higher temperatures.
The resulting relaxation parameters are listed in the ESI†
along with statistical analysis.
Frequency scan of the AC susceptibility for 2, Ni–Gd complex
The frequency dependence of the AC susceptibility com-
ponents for the Gd compound 2 is shown in Fig. 10. In this
case the two-set Debye model reproduces the experimental
data with well separated branches. The existence of slow relax-
ation is unexpected in the case of the isotropic gadolinium
centre. Even more surprising is the Arrhenius-like plot drawn
in Fig. 11 where the HF relaxation time is only slightly temp-
erature dependent between 1.9 and 6.5 K. Moreover, the HF
branch shows a “strange” behaviour (Fig. S6†): on cooling the
relaxation time passes through a maximum and then it is shor-
tened: τ(HF) = 223 μs at T = 3.9 as compared to τ(HF) = 120 μs
at T = 1.9 K.
The Argand diagram and the Arrhenius-like plot for 1 are
displayed in Fig. 9. In this case the LF relaxation time was
fitted via eqn (3) giving n = 6.59(7), C = 174(22) × 10−4 K−n s−1
,
and Dτ = 51(1) s−1. At the same time the parameters of the
Orbach relaxation process are Ueff/kB = 43 K and τ0 = 3.1 × 10−7 s.
As expected, the external magnetic field has a visible effect
on the relaxation behaviour of 1 (see ESI†): the relaxation time
The strange behaviour has been observed recently in Cu(II),
Ni(II), Co(II), and Mn(II) complexes showing distorted octa-
Fig. 8 AC magnetic data for 1. Solid lines – fitted by the extended two-
set Debye model.
Fig. 10 AC magnetic data for 2. Solid lines – fitted by the extended
two-set Debye model.
Fig. 9 Argand diagram (left) and the Arrhenius-like plot (right) for 1.
Full circles – single-set Debye model; solid curve – fitted with Raman &
tunneling process; dashed – three-point linear extrapolation for the
Orbach process.
Fig. 11 Argand diagram (left) and the Arrhenius-like plot (right) for 2.
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hedral geometry.58–61 It was possible to reproduce such data by than in the above-mentioned compounds [Ln2(mq)4Cl6]. From
using a phenomenological equation
Fig. 12, it can be seen that in compounds 1–3 the chlorido
ligands are in what can be called fac-configuration – that is,
concentrated in the same part of the coordination sphere,
while the other compounds present a more symmetrical distri-
bution; that has to affect the electron distribution in the
coordination sphere.
τꢀ1 ¼ CT n þ EτT ꢀk
ð4Þ
that contains the conventional Raman term (parameters C and
n > 0), along with the “strange” term (parameters Eτ and k > 0).
Linear fits for the truncated data allowed bracketing starting
values for data fitting via eqn (4); the final parameters are: n =
1.18(26), C = 4.7(26) × 102 K−n s−1, Eτ = 2.4(3) × 104 Kk s−1, and
k = 1.7(2). Two slow relaxation processes have also been
described for several Gd(III) compounds.20,22,23,28,29 For
instance, for a Gd(III)EDTA chelate compound,29 the values of
Ueff = 6.1 K (τ = 4 × 10−2 s) and Ueff = 84 K (τ = 8 × 10−7 s) were
reported (BDC = 0.45 T).
Conclusions
Using mild chemical conditions a new kind of 3d–4f dinuclear
NiLn Schiff base compound, [Ni(o-van-en)LnCl3(H2O)] (Ln =
Ce, Gd, Dy) was prepared and structurally characterized. In all
three complexes the square four-coordinated nickel(II) atom
and octacoordinated Ln(III) atom (donor set O5Cl3) are located
in the neighbouring compartments provided by the Schiff base
ligand and linked by two monatomic O bridges. The coordi-
nation of the Ln atom is highly unsymmetrical with all chlor-
ido ligands situated in a “fac” fashion. AC susceptibility
measurements reveal that all three complexes show field sup-
ported slow magnetic relaxation. This result in the case of the
Gd(III) compound suggests a need for further detailed mag-
netic studies, in the field of SMM, of complexes with the chlor-
ido ligands concentrated in a face of the coordination polyhe-
dron. AC magnetic measurements revealed that all three com-
plexes, including the nominally isotropic Gd(III) system, show
field induced slow magnetic relaxation with two or three relax-
ation channels: at T = 1.9 K the low-frequency relaxation time
is τLF(1) = 0.060 s at BDC = 0.5 T, τLF(2) = 0.37 s at BDC = 0.3 T,
and τLF(3) = 1.29 s at BDC = 0.15 T.
The geometry and the electron density of the coordination
sites has been proved to exert a very important influence on
the SMM behaviour of lanthanide ions. There are few studies
of the influence of ions and since the number of chlorido
derivatives is smaller than for instance, nitrato, the studies
reported about the influence of the chlorido ligands in the
SMM behaviour are very rare and it may require more research.
The magnetic study on the [Ln2(mq)4X6](EtOH)2 (Fig. 12,
left) (mq = 8-hydroxy-2-methylquinoline) compounds which
have been prepared for Ln = Dy, with X = NO3 or Cl− shows
−
that for these compounds the energy barrier is higher when X
= Cl− (NO3−: Δ/kB = 40.0 K and Cl−: Δ/kB = 102.4 K).62 We note
that for Ln = Gd, X = NO3−, Cl−, no slow relaxation was
observed. However, a recent study on [Ln(tpm)X3]·yMeCN63
(tpm = tris(3,5-dimethyl-pyrazolyl)methane) shows that at zero
DC field, no significant out-of-phase susceptibility was
−
detected for Ln = Dy or Er, none for X = NO3 nor X = Cl−, but
under applied fields, it was observed for Ln = Dy and NO3− but
not for Cl−, while for Ln = Er, the situation was the opposite,
Experimental
Syntheses
−
indicating that NO3 in this case is a more suitable anion for
obtaining SMM with Dy while Cl− is a better anion for Er. No
such comparative information for Ln = Gd has been reported,
to our knowledge.
Ethylenediamine, o-vanillin, NiCO3, GdCl3·6H2O, CeCl3·7H2O,
DyCl3·6H2O, ethanol and diethyl ether, all of analytical grade,
were purchased from commercial sources and used as
received.
All three of our compounds, including the Gd(III) one, with
three Cl− ligands and under applied external field, show slow
relaxation. We note that the location of the three coordinated
chlorido atoms in our compounds (Fig. 12, right) is different
Synthesis of the ligand H2(o-van-en). For the synthesis of
H2(o-van-en)
a modification of the previously reported
method35 was used. Ethylenediamine (0.1 cm3, 1.5 mmol) was
added to 50 cm3 of an ethanol solution of o-vanillin (0.4542 g,
3 mmol). The mixture was placed in a boiling flask and refluxed
for 5 hours. The final solution was filtered and left for crystalliza-
tion. After a few hours, dark yellow crystals of the product
appeared. The crude product was filtered and washed with 2 ml
of diethylether. Yield: 90%. Purity and identity of the product
were checked by CHN analysis, IR, UV-Vis, 1H and 13C NMR spec-
troscopies. The corresponding analytical data for H2(o-van-en) as
well as for complexes 1, 2 and 3 are listed in ESI.†
Synthesis of [Ni(o-van-en)Ce(H2O)Cl3] (1). Solid H2(o-van-en)
(2 g, 6 mmol) and nickel(II) carbonate (0.7 g, 6 mmol) were
added to 100 cm3 of water and heated in an open beaker. After
one hour of reaction the resulting brown microcrystalline
Fig. 12 Left: [Ln2(mq)4Cl6] showing the disposition of the Cl− ligands.
Right: Molecular drawing of compounds 1–3 showing the “fac” disposi-
tion of the three clorido ligands.
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product (crude nickel complex) was separated by filtration, crystal used for data collection, two domains were indexed and
washed with 2 ml of ethanol and dried in air. The dry product data integration was conducted simultaneously for both. The
was used in the next step of the synthesis without further puri- structures for 1, 2 and 3 were solved using SHELXT.64
fication. Solid CeCl3·7H2O (0.3 g, 0.8 mmol) was dissolved in Refinement based on intensities was performed using
10 cm3 of ethanol and the resulting clear solution was added SHELXL-2014/7.65 All non-hydrogen atoms were refined anisotro-
to the brown ethanol solution of [Ni(o-van-en)] (50 cm3 of pically. Hydrogen atoms were located in difference Fourier maps.
ethanol). After 15 min of stirring, the orange microcrystalline For the final refinement, H atoms bound to C were placed at cal-
complex [Ni(o-van-en)Ce(H2O)Cl3] (1) was separated by fil- culated positions and refined as riders with Uiso(H) = 1.2Ueq(C)
tration and washed three times with 2 ml of ethanol. Single for non-methyl
H
and with Uiso(H)
=
1.5Ueq(C) for
crystals suitable for X-ray analysis were obtained by recrystalli- methyl H. Using the program CALC-OH the positions of the
zation of the microcrystalline complex using room temperature water hydrogen atoms for the O1 aqua ligand were found; their
diffusion of a MeOH solution into iPrOH.
isotropic thermal parameters were tied with the parent atom
Synthesis of [Ni(o-van-en)Gd(H2O)Cl3] (2). The same pro- [Uiso(H) = 1.2Ueq(O)].66 For compound 1 the final refinement was
cedure was used as for the Ce(III) complex with the modifi- conducted using data from both domains. The structure figures
cation that instead of CeCl3·7H2O, GdCl3·6H2O (0.3 g, were drawn using Diamond.67 Crystal data and final parameters
0.8 mmol) was used. Single crystals of [Ni(o-van-en)Gd(H2O) for the structure refinements are summarized in Table S1† and
Cl3] (2) were obtained by crystallization using diffusion of a possible hydrogen bonds are given in Table S2.†
MeOH solution of GdCl3 into an iPrOH solution of [Ni(o-van-
Ab initio calculations
en)] at room temperature.
Synthesis of [Ni(o-van-en)Dy(H2O)Cl3] (3). For the synthesis
of the complex [Ni(o-van-en)Dy(H2O)Cl3] the same procedure
was used as for the Ce(III) complex with the modification that
instead of CeCl3·7H2O, DyCl3·6H2O (0.3 g, 0.8 mmol) was
used. Crystals of [Ni(o-van-en)Dy(H2O)Cl3] (3) were obtained by
recrystallization using diffusion of a methanol solution of the
microcrystalline product into iPrOH with a temperature gradi-
ent of from 70 °C at the bottom of the beaker to room tempera-
ture at the top of the solution.
Ab initio calculations were performed with ORCA 4.1.2 compu-
tational package using the experimental geometry of complex
under study.68 The relativistic effects were included in the cal-
culations with second-order Douglas–Kroll–Hess (DKH)69 pro-
cedure together with the scalar relativistic contracted version
of def2-SV(P) basis function for all elements, except Ce atom.
For Ce, the SARC2-DKH-QZVP basis function was used.70 The
calculations were based on state average complete active space
self-consistent field (SA-CASSCF) wave functions. The active
space of the CASSCF calculations comprised of one electron in
seven metal-based f-orbitals. The state averaged approach was
used, in which 7 doublet states were equally weighted. The
spin–orbit effects have been included through quasi-degener-
ate perturbation theory in which an approximation to the
Breit–Pauli form of the spin–orbit coupling operator (SOMF)
was utilized.71
Physical measurements
Elemental analyses (C, H, N) were performed on a PerkinElmer
2400 Series II CHNS/O analyser. Infrared spectra were recorded
on a PerkinElmer Spectrum 100 CsI DTGS FTIR Spectrometer
with UATR 1 bounce-KRS-5 in the range of 4000–300 cm−1
.
Powder X-Ray data were collected using a RIGAKU D/max 2500
diffractometer equipped with a copper rotating anode, operat-
ing at 40 kV and 80 mA, with a graphite monochromator.
Measurements were made for 2θ from 2.5° to 40° in steps of
0.02° with a rate of 1 s per step. The magnetic susceptibility
(determined as χ = M/H) was taken at B = 0.1 T using a SQUID
magnetometer (Quantum Design, MPMS-XL7) in the tempera-
ture range from 1.9 to 300 K. Raw susceptibility data was cor-
rected for the diamagnetic contribution. The magnetization
data was acquired at low temperature T = 2.0 and 4.6 K until
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
BDC = 7.0 T. The AC susceptibility data was taken at the applied Financial support from Slovak grant agencies (APPV-18-0016
external fields using the amplitude of the oscillating field and VEGA 1/0063/17) is gratefully acknowledged, as is support
BAC = 0.38 mT for a set of temperatures and for 22 frequencies from the Ministerio de Ciencia, Innovación y Universidades
between f = 0.1 to 1500 Hz.
(Spain, Grants MAT2015-68200-C2-1-P and PGC2018-093451-
B-I00), the European Union Regional Development Fund,
FEDER), the Diputación General de Aragón, Project M4,
Crystallography
X-ray experiments were carried out on a four-circle κ-axis E11_17R and the support of the publication fee by the CSIC
Xcalibur2 diffractometer equipped with a Sapphire3 CCD Open Access Publication Support Initiative through its Unit of
detector (Oxford Diffraction). The CrysAlis software package Information Resources for Research (URICI). Also, this work was
[Oxford Diffraction 2006 CrysAlisPro CCD and CrysAlisPro supported by the project NFP313010V954 of call OPVaI-VA/DP/
RED] was used for data collection and reduction. Crystals of 2018/1.1.3-07. AV thanks the National Scholarship Programme of
compound 1 were found to exhibit multiple domains. For the the Slovak Republic and grant VVGS-PF-2018-777.
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22 A. J. Calahorro, I. Oyarzabal, B. Fernández, J. M. Seco,
T. Tian, D. Fairen-Jimenez, E. Colacio and A. Rodríguez-
Diéguez, Dalton Trans., 2016, 45, 591.
23 V. Tkáč, A. Orendáčová, R. Tarasenko, E. Čižmár,
M. Orendáč, K. Tibenská, A. G. Anders, S. Gao, V. Pavlík
and A. Feher, J. Phys.: Condens. Matter, 2013, 25, 506001.
References
1 R. Sessoli, D. Gatteschi, A. Caneschi and M. A. Novak,
Nature, 1993, 365, 141.
2 N. Ishikawa, M. Sugita, T. Ishikawa, S. Koshihara and
Y. Kaizu, J. Am. Chem. Soc., 2003, 125, 8694.
3 S. Osa, T. Kido, N. Matsumoto, N. Re, A. Pochaba and 24 M. J. Martínez-Pérez, S. Cardona-Serra, C. Schlegel,
J. Mrozinski, J. Am. Chem. Soc., 2004, 126, 420.
4 A. Bencini, C. Benelli, A. Caneschi, R. L. Carlin, A. Dei and
D. Gatteschi, J. Am. Chem. Soc., 1985, 107, 8128.
F. Moro, P. J. Alonso, H. Prima-García, J. M. Clemente-Juan,
M. Evangelisti, A. Gaita-Ariño, J. Sesé, J. van Slageren,
E. Coronado and F. Luis, Phys. Rev. Lett., 2012, 108, 247213.
5 S. K. Langley, D. P. Wielechowski, V. Vieru, N. F. Chilton, 25 V. Chandrasekhar, B. M. Pandian, R. Azhakar, J. J. Vittal
B. Moubaraki, B. F. Abrahams, L. F. Chibotaru and
K. S. Murray, Angew. Chem., Int. Ed., 2013, 52, 12014.
6 M. Fondo, J. Corredoira-Vázquez, A. Herrera-Lanzós,
A. M. García-Deibe, J. Sanmartín-Matalobos, J. M. Herrera,
E. Colacio and C. Nuñez, Dalton Trans., 2017, 46, 17000.
7 S. K. Langley, N. F. Chilton, L. Ungur, B. Moubaraki,
and R. Clérac, Inorg. Chem., 2007, 46, 5140.
26 M. Orendáč, L. Sedláková, E. Čižmár, A. Orendáčová, A. Feher,
S. A. Zvyagin, J. Wosnitza, W. H. Zhu, Z. M. Wang and S. Gao,
Phys. Rev. B: Condens. Matter Mater. Phys., 2010, 81, 214410.
27 P. I. Girginova, L. C. J. Pereira, J. T. Coutinho, I. C. Santos
and M. Almeida, Dalton Trans., 2014, 43, 1897.
L. F. Chibotaru and K. S. Murray, Inorg. Chem., 2012, 51, 28 A. Arauzo, A. Lazarescu, S. Shova, E. Bartolomé, R. Cases,
11873.
J. Luzón, J. Bartolomé and C. Turta, Dalton Trans., 2014,
43, 12342.
8 A. Upadhyay, S. K. Singh, C. Das, R. Mondol, S. K. Langley,
K. S. Murray, G. Rajaraman and M. Shanmugam, Chem. 29 R. J. Holmberg, L. T. A. Ho, L. Ungur, I. Korobkov,
Commun., 2014, 50, 8838.
L. F. Chibotaru and M. Murugesu, Dalton Trans., 2015, 44,
9 A. Upadhyay, C. Das, S. Vaidya, S. K. Singh, T. Gupta,
20321.
R. Mondol, S. K. Langley, K. S. Murray, G. Rajaraman and 30 T. D. Pasatoiu, J.-P. Sutter, A. M. Madalan, F. Z. C. Fellah,
M. Shanmugam, Chem. – Eur. J., 2017, 23, 4903. C. Duhayon and M. Andruh, Inorg. Chem., 2011, 50, 5890.
10 W.-B. Sun, P.-F. Yan, S.-D. Jiang, B.-W. Wang, Y.-Q. Zhang, 31 T. D. Pasatoiu, C. Tiseanu, A. M. Madalan, B. Jurca,
H.-F. Li, P. Chen, Z.-M. Wang and S. Gao, Chem. Sci., 2016,
7, 684.
C. Duhayon, J.-P. Sutter and M. Andruh, Inorg. Chem., 2011,
50, 5879.
11 Z. Jin, J. Bai, T. Wei, F. Li, C. Song, X. Luo and L. Xu, New J. 32 J.-P. Costes, F. Dahan, C. Duhayon and A. J. Mota,
Chem., 2017, 41, 13490. Polyhedron, 2015, 96, 51.
12 G. A. Kostin, A. O. Borodin, N. V. Kuratieva, 33 A. S. Dinca, S. Shova, A. E. Ion, C. Maxim, F. Lloret,
A. S. Bogomyakov and A. A. Mikhailov, Inorg. Chim. Acta,
2018, 479, 135.
13 S. P. Petrosyants, A. B. Ilyukhin, N. N. Efimov,
M. Julve and M. Andruh, Dalton Trans., 2015, 44, 7148.
34 X. Feng, W. Zhou, Y. Li, H. Ke, J. Tang, R. Clérac, Y. Wang,
Z. Su and E. Wang, Inorg. Chem., 2012, 51, 2722.
A. V. Gavrikov and V. M. Novotortsev, Inorg. Chim. Acta, 35 X.-C. Huang, C. Zhou, H.-Y. Wei and X.-Y. Wang, Inorg.
2018, 482, 813. Chem., 2013, 52, 7314.
14 F. Pointillart, O. Cador, B. Le Guennic and L. Ouahab, 36 L. Jiang, B. Liu, H.-W. Zhao, J.-L. Tian, X. Liu and S.-P. Yan,
Coord. Chem. Rev., 2017, 346, 150. CrystEngComm, 2017, 19, 1816.
15 S. Hino, M. Maeda, K. Yamashita, Y. Kataoka, M. Nakano, 37 H. J. Im and S. W. Lee, Polyhedron, 2015, 101, 48.
T. Yamamura, H. Nojiri, M. Kofu, O. Yamamuro and 38 D. Visinescu, A. M. Madalan, M. Andruh, C. Duhayon,
T. Kajiwara, Dalton Trans., 2013, 42, 2683.
16 S. Hino, M. Maeda, Y. Kataoka, M. Nakano, T. Yamamura
and T. Kajiwara, Chem. Lett., 2013, 42, 1276.
17 J. J. Le Roy, I. Korobkov, J. E. Kim, E. J. Schelter and
M. Murugesu, Dalton Trans., 2014, 43, 2737.
J.-P. Sutter, L. Ungur, W. Van den Heuvel and
L. F. Chibotaru, Chem. – Eur. J., 2009, 15, 11808.
39 D. Visinescu, I.-R. Jeon, A. M. Madalan, M.-G. Alexandru,
B. Jurca, C. Mathonière, R. Clérac and M. Andruh, Dalton
Trans., 2012, 41, 13578.
18 A. B. Khélifa, M. S. Belkhiria, G. Huang, S. Freslon, 40 M. Andruh, Dalton Trans., 2015, 44, 16633.
O. Guillou and K. Bernot, Dalton Trans., 2015, 44, 16458.
19 S. K. Singh, T. Gupta, L. Ungur and G. Rajaraman, Chem. –
Eur. J., 2015, 21, 13812.
41 J.-P. Costes, F. Dahan, A. Dupuis and J.-P. Laurent, Inorg.
Chem., 1997, 36, 3429.
42 B. N. Ghose, J. Chem. Eng. Data, 1984, 29, 237.
20 D. C. Izuogu, T. Yoshida, H. Zhang, G. Cosquer, K. Katoh, 43 Z. Saedi, E. Hoveizi, M. Roushani, S. Massahi, M. Hadian
S. Ogata, M. Hasegawa, H. Nojiri, M. Damjanović, and K. Salehi, J. Mol. Struct., 2019, 1176, 207.
W. Wernsdorfer, T. Uruga, T. Ina, B. K. Breedlove and 44 M. Llunell, D. Casanova, J. Cirera, P. Alemany and
M. Yamashita, Chem. – Eur. J., 2018, 24, 9285.
21 T. Kanetomo, T. Kihara, A. Miyake, A. Matsuo,
S. Alvarez, SHAPE Program, version 2.1, Universitat de
Barcelona, 2013.
M. Tokunaga, K. Kindo, H. Nojiri and T. Ishida, Inorg. 45 G. Xiao, B. Yan, R. Ma, W. J. Jin, X. Q. Lü, L. Q. Ding,
Chem., 2017, 56, 3310.
C. Zeng, L. L. Chen and F. Bao, Polym. Chem., 2011, 2, 659.
This journal is © The Royal Society of Chemistry 2019
Dalton Trans.

View Article Online
Paper
Dalton Transactions
46 W.-J. Jin, L.-Q. Ding, Z. Chu, L.-L. Chen, X.-Q. Lü, 58 R. Boča, C. Rajnák, J. Titiš and D. Valigura, Inorg. Chem.,
X.-Y. Zheng, J.-R. Song and D.-D. Fan, J. Mol. Catal. A:
Chem., 2011, 337, 25.
47 P. Chen, H. Chen, P. Yan, Y. Wang and G. Li,
CrystEngComm, 2011, 13, 6237.
2017, 56, 1478.
59 J. Titiš, C. Rajnák, D. Valigura and R. Boča, Dalton Trans.,
2018, 47, 7879.
60 R. Boča, C. Rajnák, J. Moncoľ, J. Titiš and D. Valigura,
Inorg. Chem., 2018, 57, 14314.
48 X. Yang, D. Lam, C. Chan, J. M. Stanley, R. A. Jones,
B. J. Holliday and W.-K. Wong, Dalton Trans., 2011, 40, 61 C. Rajnák, J. Titiš, J. Moncoľ, R. Mičová and R. Boča, Inorg.
9795. Chem., 2019, 58, 991.
49 Y. Wang, Q. Zhang, P.-F. Yan, G.-F. Hou and H.-F. Li, 62 F. Yang, Q. Zhou, G. Zeng, G. Li, L. Gao, Z. Shi and S. Feng,
Acta Crystallogr., Sect. E: Struct. Rep. Online, 2012, 68,
m589.
50 L. Xu, Q. Zhang, G. Hou, P. Chen, G. Li, D. M. Pajerowski
and C. L. Dennis, Polyhedron, 2013, 52, 91.
Dalton Trans., 2014, 43, 1238.
63 J. Long, D. M. Lyubov, T. V. Mahrova, A. V. Cherkasov,
G. K. Fukin, Y. Guari, J. Larionova and A. A. Trifonov,
Dalton Trans., 2018, 47, 5153.
51 J.-W. Yang, Y.-M. Tian, J. Tao, P. Chen, H.-F. Li, 64 G. M. Sheldrick, Acta Crystallogr., Sect. C: Struct. Chem.,
Y.-Q. Zhang, P.-F. Yan and W.-B. Sun, Inorg. Chem., 2018,
57, 8065.
52 S. A. Güngör and M. Kose, J. Mol. Struct., 2017, 1150, 274.
2015, 71, 3.
65 G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Adv., 2015,
71, 3.
53 T. Gao, P.-F. Yan, G.-M. Li, J.-W. Zhang, W.-B. Sun, M. Suda 66 M. Nardelli, J. Appl. Crystallogr., 1999, 32, 563.
and Y. Einaga, Solid State Sci., 2010, 12, 597.
54 S. Hazra, J. Titiš, D. Valigura, R. Boča and S. Mohanta,
Dalton Trans., 2016, 45, 7510.
55 C. R. Groom, I. J. Bruno, M. P. Lightfoot and S. C. Ward,
Acta Crystallogr., Sect. B: Struct. Sci., Cryst. Eng. Mater.,
2016, 72, 171.
67 K. Brandenburg and H. Putz, Diamond: Crystal Impact,
GbR, Postfach 1251, D-53002 Bonn, Germany, 2008.
68 (a) F. Neese, Wiley Interdiscip. Rev.: Comput. Mol. Sci., 2012,
2, 73; (b) F. Neese, ORCA – An Ab Initio, Density Functional
and Semi-empirical Program Package, Version 4.1.2.
69 M. Reiher and A. Wolf, J. Chem. Phys., 2004, 121, 2037.
56 W. Wong, X. Yang, R. A. Jones, J. H. Rivers, V. Lynch, 70 (a) D. Aravena, F. Neese and D. A. Pantazis, J. Chem. Theory
W.-K. Lo, D. Xiao, M. M. Oye and A. L. Holmes, Inorg.
Chem., 2006, 45, 4340.
Comput., 2016, 12, 1148; (b) G. L. Stoychev, A. A. Auer and
F. Neese, J. Chem. Theory Comput., 2017, 13, 554.
57 A. Vráblová, J. Černák, C. Rajnák, Ľ. Dlháň, M. Tomás, 71 M. Atanasov, D. Aravena, E. Suturina, E. Bill, D. Maganas
L. R. Falvello and R. Boča, Dalton Trans., 2018, 47, 15523. and F. Neese, Coord. Chem. Rev., 2015, 177, 289.
Dalton Trans.
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