Inorganic Chemistry
Article
−
1
controls the spatial arrangement of the ferric complex units
(M
= 1819.81 g mol ): C, 60.85% (62.04%); N, 13.01% (13.47%);
w
3
−
H, 4.95% (5.01%). FT-IR (KBr): 3405(s) (OH), 3224(w), 3062(w)
coordinated on [M(CN) ] , because both compounds
6
(
C −H), 2947(w) (C −H), 2876(w) (C −H), 2166(m) (CN),
reported herein with a diamagnetic Co(III) ion adopt a
facial-like coordination contrary to the T-shaped molecule
ar
al
al
2
128(s) (CN), 1617(s) (C −C and CN), 1603(s) (C −C
ar
ar
ar
ar
and CN), 1541(s) (C −C and CN), 1509(w) (C −C and
ar ar ar ar
[
{
{Fe(L2)NC} Cr(CN) ] with a meridional-like alignment of
Fe(L2)} moieties. SA-CASSCF+NEVPT2 calculation with a
3 3
CN).
Synthesis of 2 ([{Fe(L2)NC} Co(CN) ]·CH OH·2H O). K [Co-
CN) ] (77 mg, 0.23 mmol, 3 equiv) was added to 40 cm of a
methanolic solution of mononuclear complex [Fe(L2)Cl] (0.3 g, 0.70
mmol, 3 equiv), and the reaction mixture was refluxed overnight at 70
°C. The resulting solution was filtered off and subjected to slow
crystallization at 5 °C, which allowed formation of dark violet crystals
after a couple of days. Yield: 55 mg (0.037 mmol, 31%). Elemental
Anal. Found (calcd) for C H CoFe N O (M = 1462.92 g mol ):
C, 53.95% (55.01%); N, 13.48% (14.36%); H, 5.05% (5.31%). FT-IR
KBr): 3406 (OH), 2931 (C−H), 2177, 2162, 2156, 2141 (CN),
3
3
3
2
3
large active space of nine electrons in 12 orbitals reproduced
correctly the ground spin state on individual Fe(III) centers
and suggested that the spin state was governed by the delicate
arrangement of the ligand, especially its secondary structure
involving the aromatic rings. One can thus conclude that the
3
(
6
similar delocalization of bonding e orbitals in compounds 2
g
−
1
6
7
77
3
15
9
w
and [{Fe(L2)NC} Cr(CN) ] containing the same pentaden-
3
3
2−
tate ligand L2 possesses an effectively weaker ligand field
(
1
compared to that of L12 stabilizing the permanent HS state in
−
620 (CN).
2
. On the other hand, L12− stabilizes the LS state and
Crystal Structure Determination. Single-crystal X-ray diffrac-
incomplete SCO in the solvated and desolvated forms of 1,
respectively. Indeed, a similar conclusion stating that twisted
ligand conformations displacing the ligand lone pairs from the
metal−ligand vector weaken the ligand field in the complexes
was drawn elsewhere for a specific class of Fe(II) SCO
complexes. In conclusion, one can speculate that SCO in
system 2 is not hindered by the intermolecular strain; rather,
the ligands do not provide a suitable ligand field. On the
contrary, the ligands of system 1 support SCO behavior that
can be further modulated by intermolecular interactions.
tion data of 1 were collected on a STOE IPDS2T diffractometer with
monochromated Mo Kα (0.71073 Å) radiation at low temperatures.
22
23
Using Olex2, the structures were determined with the ShelXS
structure solution program using direct methods and refined with the
2
4
ShelXL refinement package using least-squares minimization.
Refinement was performed with anisotropic temperature factors for
all non-hydrogen atoms (disordered atoms and solvent molecules
were refined isotropically); hydrogen atoms were calculated at
idealized positions. Single-crystal X-ray diffraction data of 2 were
collected using an Oxford diffraction Xcalibur diffractometer with a
Sapphire CCD detector installed in a fine-focus sealed tube (Mo Kα
radiation; λ = 0.71073 Å) and equipped with an Oxford Cryosystems
nitrogen gas-flow apparatus. The structure was determined with the
ShelXs software using direct methods and refined using least-squares
1
9
EXPERIMENTAL SECTION
■
General. All purchased chemicals and solvents were used as
received. Methanol, acetonitrile, and diethyl ether were used as
solvents without further purification. Potassium hexacyanidocobaltate
24
minimization with the ShelXL software incorporated in the Wingx
25
package. For each structure, its space group was checked by the
26
20
ADSYMM procedure of the PLATON software. All non-hydrogen
atoms were refined anisotropically. The hydrogen atoms were placed
into the calculated positions and included in the riding-model
approximation with a Uiso of 1.2Ueq or 1.5Ueq (atom of attachment).
Nonroutine aspects of the structural refinement are as follows. In 1,
the measured crystals exhibited poor diffraction power. This, together
with the relatively large unit cell of 1, affected collection of large-angle
diffractions and resulted in lower completeness of the data. The
aliphatic part of the ligand in one of the {Fe(L1)NC} fragments is
disordered over two positions. While it was possible to model disorder
for the more rigid ethyl part, it was not possible to establish it for the
longer propyl part. The measured crystals suffered from partial solvent
loss, which resulted in lower occupation parameters (0.5), which were
used to reasonably model co-crystallized methanol molecules. The
acetonitrile molecules were also affected; however, it was possible to
model them using SADI/EADP constraints and restraints. In 2, the
electron density corresponding to heavily disordered superimposed
molecules of water and methanol was left unmodeled, because it was
not possible to establish a reasonable model. Attempts to use the
K [Co(CN) ] was prepared as previously described. Elemental
3
6
analysis of carbon, hydrogen, and nitrogen was carried out by an
automated analyzer (Vario, Micro Cube). IR spectra were measured
by the ATR technique or in KBr pellets in the range of 4000−400
−
1
cm (Magna FTIR 750, Nicolet). TG-DTA analysis was performed
−
1
in a He flow at a heating rate of 2.5 K min in a Netzsch STA 409 C
analyzer.
Synthesis of Complexes. Mononuclear Complexes [Fe(L1)Cl]
and [Fe(L2)Cl]. The synthesis of mononuclear complexes [Fe(L1)Cl]
and [Fe(L2)Cl] was adapted according to a previously reported
8,21
3
procedure.
A methanol solution (20 cm ) of the corresponding
carbaldehyde (2 equiv of salicylaldehyde for [Fe(L1)Cl]; 2 equiv of 2-
hydroxynaphthaldehyde for [Fe(L2)Cl]) was combined with aliphatic
triamine (1 equiv of N-(2-aminoethyl)-1,3-propanediamine for
[
Fe(L1)Cl]; 1 equiv of bis(3-aminopropyl)amine for [Fe(L2)Cl])
3
dissolved in 10 cm of CH OH, and the reaction mixture was stirred
at 40 °C for 30 min. Then, 1 equiv of FeCl ·6H O in 10 cm of
CH OH was added to the in situ-prepared Schiff base (H L1 or
3
3
3
2
3
2
H L2), which afforded formation of the desired mononuclear
2
1
27
complex. The mixture was stirred at 60 °C to evaporate / of the
SQUEEZE procedure to remove this electron density resulted in an
3
volume and cooled to −10 °C, and a dark polycrystalline powder was
R much lower than that reported for the structure presented herein,
1
separated by filtration under vacuum, washed with several portions of
but the goodness of fit fell below 0.8. Therefore, we decided not to
use “squeezed” data.
cold CH OH and diethyl ether, and dried. Elemental Anal.
3
[
Fe(L1)Cl] found (calcd) for C H ClFeN O (428.71 g/mol): C,
5.88% (56.03%); H, 5.22% (5.41%); N, 9.72% (9.80%). [Fe(L2)Cl]
Magnetic Measurements. Magnetic investigations were per-
formed by using a SQUID magnetometer (MPMS-XL7, Quantum
Design) in the RSO mode of detection. In all cases, the temperature
dependence of the magnetic moment was recorded at 0.1 T as an
external magnetic field and the temperature sweeping rate was 1 K/
min. Desolvation of compounds 1 and 2 was performed in situ within
the magnetic measurement setup. After the first heating, three
continuous cooling/heating cycles were applied until the last two
measurements were identical. Thereby, the sample was maintained in
the MPMS magnetometer at 380 K for 20 min before every cooling/
heating cycle. The gelatin-made capsules were used as sample holders,
and their small diamagnetic contribution made a negligible
contribution to the overall magnetization, which was dominated by
2
0
23
3
2
5
found (calcd) for C H ClFeN O (514.80 g/mol): C, 62.87%
2
7
25
3
2
(
62.99%); H, 4.80% (4.89%); N, 8.01% (8.16%).
Synthesis of 1 ([{Fe(L1)NC} Co(CN) ]·2CH OH·2.5CH CN). [Fe-
3
3
3
3
3
(
L1)Cl] (0.3 g, 0.7 mmol, 3 equiv) was dissolved in 120 cm of
acetonitrile and methanol (1:1) and combined with solid potassium
hexacyanocobaltate K [Co(CN) ] (64 mg, 0.19 mmol, 3 equiv). The
3
6
reaction mixture was refluxed for 24 h at 70 °C, cooled to room
temperature, and filtered, and the volume of the solvents was reduced
under vacuum by half. Small dark green crystals were collected after
slow crystallization at 5 °C for 2 weeks. Yield: 90 mg (0.048 mmol,
2
5%). Elemental Anal. Found (calcd) for C H CoFe N17.50O8
94 90.50 3
H
Inorg. Chem. XXXX, XXX, XXX−XXX
?alitro?, Ivan
