Synthesis, spectral characterization and X-ray crystal structure of Fe(III) and Co(III) complexes with an acyclic Schiff base ligand

Article abstract of DOI:10.1016/j.ica.2013.07.018

Two complexes of composition [Co(HL)2]'ClO₄·CH ₃OH (1) and [Fe₂L₃]·0.38H₂O (2) (H₂L = 2-((2-(2-hydrox-ybenzylamino)ethylamino)methyl)phenol) have been synthesized and their structures have been characterized. The mononuclear cobalt complex 1 shows the metal ion Co(III) in an octahedral environment, being coordinated to two ligand molecules in a N4O2 core, remaining one of the two hydroxyl phenol groups of each ligand not deprotonated and uncoordinated. Instead, complex 2 is dinuclear, and each of the two metal centers is coordinated by one molecule ligand and other ligand molecule acts as bridge between the two metal centers, resulting a distorted N4O2 octahedral environment for each Fe(III) ion. In this case the two hydroxyl phenol groups of the ligand molecules are deprotonated and coordinated. Variable-temperature solid-state magnetic studies have been performed for compound 2.

Full text of DOI:10.1016/j.ica.2013.07.018

Inorganica Chimica Acta 406 (2013) 171–175
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Inorganica Chimica Acta
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Synthesis, spectral characterization and X-ray crystal structure of Fe(III)
and Co(III) complexes with an acyclic Schiff base ligand
a
a
Mouhamadou Moustapha Sow a, Ousmane Diouf a, , Mohamed Gaye , Abdou Salam Sall ,
⇑
Paulo Pérez-Lourido b, , Laura Valencia-Matarranz b, Goretti Castro b, Andrea Caneschi c, Lorenzo Sorace c
⇑
a Department of Chemistry, University Cheikh Anta Diop, Dakar, Senegal
b Departamento de Química Inorgánica, Facultade de Química, Universidad de Vigo, 36310 Vigo, Pontevedra, Spain
c Dipartimento di Chimica ‘‘U. Schiff’’ and INSTM Research Unit, Università di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 9 May 2013
Received in revised form 9 July 2013
Accepted 10 July 2013
Available online 19 July 2013
Two complexes of composition [Co(HL)2]ꢀClO4ꢀCH3OH (1) and [Fe2L3]ꢀ0.38H2O (2) (H2L = 2-((2-(2-hydrox-
ybenzylamino)ethylamino)methyl)phenol) have been synthesized and their structures have been charac-
terized. The mononuclear cobalt complex 1 shows the metal ion Co(III) in an octahedral environment,
being coordinated to two ligand molecules in a N4O2 core, remaining one of the two hydroxyl phenol
groups of each ligand not deprotonated and uncoordinated. Instead, complex 2 is dinuclear, and each
of the two metal centers is coordinated by one molecule ligand and other ligand molecule acts as bridge
between the two metal centers, resulting a distorted N4O2 octahedral environment for each Fe(III) ion. In
this case the two hydroxyl phenol groups of the ligand molecules are deprotonated and coordinated. Var-
iable-temperature solid-state magnetic studies have been performed for compound 2.
Keywords:
Schiff base
Cobalt
Iron
Ó 2013 Elsevier B.V. All rights reserved.
Dinuclear complexes
Antiferromagnetic
1. Introduction
capacity of this acyclic ligand towards the first row transitional me-
tal Co(II) and Fe(II) ion has been investigated producing complexes
Organic molecules containing amine moieties, phenoxo groups
and aliphatic chain are interest compounds useful to study the
bonding of metal ions to synthesize inorganic complexes [1–7]
which have found utility in a wide range of applications [8–11].
Schiff bases issued from salicylaldehyde and diamines have been
largely investigated owing to their capacity to append various sub-
stituents [12–14]. Because of the versatility to adopt various
modes, this chemistry is able to generate stable framework
[15,16]. The combination of versality of the binding modes and
the nature of the metal ion is expected to generate new com-
pounds. In the course of our studies on the chemistry of transition
metal compounds, we have prepared and characterized a number
of chelates containing N and O donor sites.
One of this Schiff base ligand largely used in the chemistry of 3d
transition metal ions is salen (N,N0-diaminoethane-salicylaldii-
mine) [17–20]. Here we report the synthesis of the acyclic ligand
derived from the salicylaldehyde precursor and ethylenediamine
(tetrahydro-salen). We have prepared the acyclic hydrogenated
derivative H2L ligand (Scheme 1), which has a N2O2 receptor cavity
suitably disposed to coordinate metal ions. The complexation
of formulae [Co(HL)2]ꢀClO4ꢀCH3OH (1) and [Fe2L3]ꢀ0.38H2O (2).
2. Experimental
2.1. Physical measurements
Elemental analyses were carried out using a LECO CHNS-932
instrument. The IR spectra were recorded as KBr discs on a Bruker
IFS-66V spectrophotometer (4000–400 cmꢁ1). The UV–Vis spectra
were run on a Shimadzu UV-2501 PC Recording Spectrophotome-
ter (1000–200 nm). The FAB mass spectra were recorded using a
Micromass Autospec spectrometer using 3-nitrobenzyl alcohol as
the matrix. The 1H and 13C NMR spectra of the Schiff base were re-
corded in DMSO-d6 on a BRUKER 500 MHz spectrometer at room
temperature using TMS as an internal reference. The molar con-
ductance of 10ꢁ3 M solutions of the metal complexes in DMF was
measured at 25 °C using a WTW LF-330 conductivity meter with
a WTW conductivity cell. Magnetic measurements for complex 2
were performed in the temperature range of 2–300 K by using a
Cryogenic S600 SQUID magnetometer in an applied magnetic field
of 1000 Oe. Raw data were corrected for the diamagnetism of the
sample holder, measure in the same temperature and field range,
and the intrinsic contribution of the sample, estimated by Pascal’s
constants.
⇑
Corresponding authors. Tel.: +34 986812607.
E-mail addresses: ousmanediouf37@yahoo.fr (O. Diouf), paulo@uvigo.es (P.
Pérez-Lourido).
0020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.07.018

172
M.M. Sow et al. / Inorganica Chimica Acta 406 (2013) 171–175
red crystals suitable for X-ray study were obtained by slow evapo-
ration to the air of the solution (Yield: 65%, based on Fe). Anal. Calc.
for C48H54.75Fe2N6O6.38: C, 62.0(; H, 6.2; N, 9.08.9. Found: C, 62.1; H,
6.0; N, 8.9%. IR (KBr, cmꢁ1): 3250; 1594; 1566; 1478; 1454; 1282;
1109; 1032; 756; 568; 451. FAB-MS (m/z): 922 [Fe2L3]+, 652 [Fe2L2] +,
598 [FeL2]+.
2.5. X-ray data collection, structure determination, and refinement
Scheme 1.
The details of the X-ray crystal structure solution and refine-
ment are given in Table 1. Measurements were made on a Bruker
SMART CCD Area Detector. All data were corrected for Lorentz and
polarization effects. Empirical absorption correction was applied.
Complex scattering factors were taken from the program package
SHELXTL [22]. The structures were solved by direct methods, which
revealed the position of all non-hydrogen atoms. All the structures
were refined on F2 by a full-matrix least-squares procedure using
anisotropic displacement parameters for all non hydrogen atoms
[23]. All hydrogen atoms were located in their calculated positions
and refined using a riding. Molecular graphics were generated
using ORTEP-3 [24].
2.2. Chemicals and starting materials
Ethylendiamine, salicylaldehyde, sodium tetrahydroborate, per-
chlorate salts and iron metal plate were commercial products
(from Alfa and Aldrich) and were used without further purification.
The solvents used were of reagent grade and were purified by the
usual methods.
Caution: Although no problems were encountered during the
course of this work, attention is drawn to the potentially explosive
nature of the perchlorate salts.
2.3. Synthesis of H2L
3. Results and discussion
Ethylenediamine (3.00 g, 50 mmol) dissolved in 30 mL of etha-
nol was refluxed with an ethanolic solution of salicylaldehyde
(12.20 g, 100 mmol), in the presence of few drops of glacial acetic
acid. The resulting yellow solution was refluxed during 3 h. On
cooling to room temperature a separated yellow precipitate was
formed. It was thoroughly washed with ether and dried over
P4O10. The resulting solid was dissolved at 0 °C in 70 mL of metha-
nol and NaBH4 (1.76 g, 46.4 mmol) was added in small portions.
The white precipitate formed during the reaction was isolated by
filtration. The solid product was washed with several portions of
diethylether and dried in a vacuum dessicator over P4O10. Anal.
Calc. for C16H20N2O2: C, 70.6); H, 7.4; N, 10.3. Found: C, 70.5; H,
7.4; N, 10.3%. Yield: 95%. M.P. 124–126 °C. FAB-MS (m/z): 273
The synthesis of the acyclic Schiff base H2L was achieved in a
two steps procedure using the direct condensation salicylaldehyde
with ethylenediamine followed by reduction with NaBH4 in meth-
anol with a yield of 95%.
The presence of phenol hydroxyl moiety in the free ligand H2L
were confirmed by the appearance in the IR spectrum of an intense
broad band centered at ca. 3294 cmꢁ1
(m
O–H) and bands with med-
ium intensities at 1577, 1526 and 1461 cmꢁ1
(mCAr@CAr). No band
assignable to mC
@ is present but a vibration of moderately inten-
N
sity at 3277 cmꢁ1, which is ascribed to N–H stretching vibration is
observed. These facts suggest that the reduction of the imines
group of the Schiff base with NaBH4 was successful.
[H2L]+. IR (KBr, cmꢁ1): 3294s (
983s, 870s; 2833s; 1602m, 1577m, 1526m, 1461s, 752s (
1176 m (
C–O). 1H NMR(dmso-d6) d 2.65 (s, 4H, –N–CH2–CH2–N–),
m
O–H); 3277m, 3038m, 1082s,
The mass spectrum of the ligand present an intense peak
respectively at 273 uma corresponding to the molecular ion of
[H2L]+. The NMR spectra of the ligand were recorded in deuterated
dimethylsulfoxide. The 1H NMR spectrum of the compound shows
two signals at d 2.65 and 3.80 ppm representative of –N–CH2–CH2–
N– and Ar–CH2–N– respectively. The broad signal of the –OH of the
phenol group is pointed at 12.25 ppm. The 13C NMR spectrum of
H2L shows a signal at d = 168 ppm which represents the aromatic
Cipso of the OH of the phenol.
m
C@C);
m
3.80 (s, 4H, Ar–CH2–N–), 6.60–7.10 (m, 8H, HAr), 8.35 (s, 2H, HN–),
12.25 (s, (broad), 2H, Ar–OH) ppm. 13C NMR (dmso-d6) d 168, 125,
129, 128, 118, 116 (CAr), 51 (–N–CH2–CH2–N–), 48 (Ar–CH2–N–)
ppm.
2.4. Synthesis of the complexes
The reactions of H4L with perchlorate cobalt salt and with iron
by electrochemical synthesis were investigated.
2.4.1. [Co(HL)2]ꢀClO4ꢀCH3OH (1)
To a methanolic solution (5 mL) of the ligand H2L (2 mmol), was
added a solution of Co(ClO4)2ꢀ6H2O (2 mmol) also in methanol
(5 mL). The solution was stirred at room temperature for 3 h and
filtered off. The resultant brown solution was filtered. Crystals of
[Co(HL)2]ꢀClO4ꢀCH3OH suitable for X-ray diffraction were obtained
after three days by concentration to the air of the solution. (Yield:
75%, based on Co). Anal. Calc. for C33H42CoN4O9Cl: C, 57.1; H, 5.9; N,
8.3(. Found: C, 58.4; H, 6.0; N, 8.4%. IR (KBr, cmꢁ1): 3477, 3280,
3250; 1558; 1485; 1588; 1250; 1121; 1103; 627; 572 ; 465.
In both cases the complexes appear to be air stable after isola-
tion from the solvent and soluble in common organic solvents. The
complexes were characterized by elemental analysis, mass spec-
trometry, IR and UV–Vis spectroscopy, molar conductivity and
magnetic measurements. Crystals of [Co(HL)2]ꢀClO4ꢀCH3OH and
[Fe2L3]ꢀ0.38H2O suitable for X-ray diffraction were obtained by
slow evaporation to the air of the corresponding solutions.
From the infrared spectra of the complexes, information regard-
ing the possible bonding modes of the ligand was obtained. The
Km = 57 cm2
X
ꢁ1 molꢁ1 in DMF. UV–Vis (solid state, nm): 315,
band assignable to (mO–H) disappears in the spectrum of the Fe(III)
415; 622. FAB-MS (m/z): 601 [Co(HL)2]+, 330 [Co(HL)]+.
complex suggesting the total deprotonation of the phenol groups
of the ligand upon complexation. This band remains in the spec-
trum of the cobalt complex with a moderate blue shift. The bands
in the region 3280–3270 cmꢁ1, attributed to the symmetrical
stretching mode mN–H in the spectra of the ligands, shift to 3260–
3245 cmꢁ1 in those of the complexes, as a consequence of the coor-
dination of the nitrogen atom of the amino group, as observed in
the literature [25]. Bands in the 575–525 cmꢁ1 region are assigned
2.4.2. [Fe2L3].0.38H2O (2)
This complex was prepared by electrochemical oxidation at
10 mA during 1 h of an iron metal electrode in a solution of H2L
(0.15 g, 0.56 mmol) in 50 ml of CH3CN containing 10 mg of tetrabu-
thylammonium perchlorate as electrolyte [21]. The loss of 7.8 mg
of the anode resulted. The red solution was filtered. After few days

M.M. Sow et al. / Inorganica Chimica Acta 406 (2013) 171–175
173
ꢀCH3OH lies in the range observed for 1:1 electrolytes (0–70 cm2
Table 1
X
ꢁ1 molꢁ1) [31].
Crystal data and structure refinement for [Co(HL)2]ꢀClO4ꢀCH3OH (1) and [Fe2L3]-
ꢀ0.38H2O (2).
(1)
(2)
3.1. Crystal structure of [Co(HL)2]ꢀClO4ꢀCH3OH (1)
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell dimensions
a (Å)
C
66H84Cl2Co2N8O18
C48H54.75Fe2N6O6.38
929.43
293(2)
0.71073
orthorhombic,
Pbcn
1466.17
293(2)
0.71073
triclinic
The structure is analogous to that previously reported for the
corresponding nitrate complex [Co(HL)2]ꢀNO3ꢀH2O [32]. The crystal
structure of one cation [Co(HL)2]+ is illustrated in Fig. 1 together
with the atomic numbering scheme adopted and selected bond
lengths and angles. The compound crystallizes in the centrosym-
ꢀ
P1
9.572(2)
11.243(3)
17.185(4)
93.162(4)
104.347(4)
109.419(4)
1670.6(6)
1
17.8831(14)
25.948(2)
19.9771(15)
90
90
90
9269.9(12)
8
1.332
b (Å)
c (Å)
ꢀ
metric space group P1. The asymmetric unity contains two half
similar Co(III) mononuclear complexes, as the Co(III) ion is located
on an inversion center. Each cobalt ion is bounded by two symmet-
rically related monoanionic ligand molecules where each ligand
molecule coordinates the Co(III) ion through the secondary amine
nitrogen atoms and one deprotonated phenol group, remaining the
other phenol group protonated and uncoordinated. Each cobalt
center has a slightly distorted N4O2 octahedral geometry.
The Co–N distances are similar for both molecules, varying from
1.968(2) to 2.006(2) Å, whilst the Co–O bond lengths are 1.906 (2)
[for Co(1)–O(1)] and 1.900 (2) Å [for Co(2)–O(3)]. These distances
are similar to the corresponding nitrate complex [32], and longer
to that corresponded to the octahedral Co(III) complex with the
same ligand but with the amine groups substituted by methylpyr-
idyl pendant-arms [ Co–O, 1.879 and 1.886 Å, Co–O 1.975, 1.978 Å]
[33]. The ranges of equatorial angles [84.45(10)–94.55(10)°] reflect
slightly distortion of the N4O2 environment from ideal octahedral
geometry. The perchlorate ion interacts with the secondary amine
group N(1)–H(1): N(1)–Hꢀ ꢀ ꢀO3P_$1 3.362(5) Å, 138(1)°; $1 ꢁx, ꢁy,
ꢁz.
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (Mg/m3)
1.457
0.654
Absorption coefficient
0.681
(mmꢁ1
)
F(000)
Crystal size (mm)
h (°)
Limiting indices
768
3902
0.50 ꢂ 0.47 ꢂ 0.12
1.94–25.10
ꢁ11 6 h 6 11,
ꢁ13 6 k 6 13,
ꢁ20 6 l 6 20
12821
0.52 ꢂ 0.49 ꢂ 0.32
1.38–25.02
ꢁ20 6 h 6 21,
ꢁ30 6 k 6 30,
ꢁ23 6 l 6 12
47681
Reflections collected
Completeness to theta % 99.0 (25.10)
(°)
Absorption correction
Maximum and
minimum
transmission
Data/restraints/
parameters
99.9 (25.02)
empirical
0.9256 and 0.7356
empirical
0.8115 and 0.7184
5905/0/436
1.044
8183/0/573
1.071
Goodness-of-fit (GOF)
on F2
Final R indices [I >
R indices (all data)
r(I)]
R1 = 0.0464,
wR2 = 0.1271
R1 = 0.0620,
R1 = 0.0541,
wR2 = 0.1528
R1 = 0.1211,
wR2 = 0.1425
0.859 and ꢁ0.450
wR2 = 0.2217
0.900 and ꢁ0.592
Largest difference in
peak and hole (e Aꢁ3
)
to m mM–N vibrations [26].
M–O and those at 470–435 cmꢁ1 region to
Furthermore, the IR spectrum of [Co(HL)2]ꢀClO4ꢀCH3OH shows
broad absorptions in the region 3600–3400 cmꢁ1 characteristic of
crystallization methanol and the free phenol function of the ligand
[27]. Also, information regarding the possible bonding modes of
the perchlorate group was obtained. Thus, strong, broad absorption
band, which is characteristic of
1103 cmꢁ1 was pointed, and
4ClO4 was present as a sharp shoulder
at 627 cmꢁ1. No band assignable to
1ClO4 was observed, suggest-
m3 of ionic perchlorate at about
m
m
ing a minimal distortion from tetrahedral symmetry of the uncoor-
dinated perchlorate moiety [28]. The electronic spectrum of the
ligand exhibits intense absorption bands in the high energy range
260–325 nm which are identified as phenyl rings
tions [29]. Complexation of the ligand results in a slight blue shift
of the
p⁄ transition of the phenyl rings. The electronic spec-
p ?
p⁄ transi-
p
?
trum of the Co(III) complex shows two bands near 400 and
625 nm, as expected for diamagnetic low spin d6 octahedral com-
plexes. The first band is attributable to the 1T1g 1A1g and the sec-
ond to 1T2g 1A1g transitions [30]. The FAB mass spectra show the
molecular peaks [Co(HL)2]+ and [Fe2L3]+, as well as other peaks
attributed to the molecular fragment of the parent peak from the
loss of different groups of the complexes. Molar conductivity was
measured for freshly prepared solutions in DMF and after standing
for two weeks. The conductivities increased very slightly with time
in dmf for this complex. The conductance value of [Co(HL)2]ꢀ(ClO4)-
Fig. 1. Crystal structure of one cation complex [Co(HL)2]+ (1). Selected bond lengths
(Å) and angles (°): Co(1)–O(1) 1.906(2), Co(1)–N(1) 1.968(2), Co(1)–N(2) 1.993(2),
O(1)–Co(1)–N(2) 85.44(10), O(1)–Co(1)–N(1)#1 85.71 (10). Symmetry transforma-
tions used to generate equivalent atoms: #1 ꢁx + 1, ꢁy, ꢁz.

174
M.M. Sow et al. / Inorganica Chimica Acta 406 (2013) 171–175
Fig. 2. Crystal structure of the dinuclear complex [Fe2L3] (2), showing partially the atom numbering scheme and selected bond lengths (Å) and angles (°):Fe(1)–O(1) 1.931(4),
Fe(1)-O(2) 1.917(4), Fe(1)–O(3) 1.943(4), Fe(1)–N(1) 2.229(4), Fe(1)–N(2) 2.185(4), Fe(1)–N(3) 2.221(4), Fe(2)–O(4) 1.959(4), Fe(2)–O(5) 1.895(4), Fe(2)–O(6) 1.928(4), Fe(2)–
N(4) 2.196(4), Fe(2)–N(5) 2.194(5), Fe(2)–N(6) 2.250(5), O(2)–Fe(1)–N(1) 165.46(16), O(1)–Fe(1)–O(3) 164.29(16), O(2)–Fe(1)–O(1) 98.06(16), N(3)–Fe(1)–N(1) 100.51(15),
N(2)–Fe(1)–N(3) 176.55(17), O(2)–Fe(1)–O(3) 97.06(17), O(6)–Fe(2)–O(4) 165.03(19), O(5)–Fe(2)–N(6) 165.49(17), N(4)–Fe(2)–N(6) 100.81(17), O(5)–Fe(2)–O(4) 96.62(18),
N(5)–Fe(2)–N(4) 178.31(19), O(4)–Fe(2)–N(4) 88.60(17).
3.2. Crystal structure of [Fe2L3]ꢀ0.38H2O (2)
The structure of the neutral dinuclear iron complex [Fe2L3] to-
gether with selected bond lengths and angles is illustrated in
Fig. 2. The compound crystallizes in the centrosymmetric space
group Pbcn. The crystal structure shows a dinuclear complex with
two Fe(III) ions joined by one ligand molecule acting as bridge be-
tween the iron ions through the phenolate and amine donor
groups. Each metal ion is hexacoordinated in a N3O3 core formed
by two cis-phenolate oxygen atoms and two cis-secondary nitrogen
atoms from one ligand molecule, whilst the coordination environ-
ment is completed by one amine and one phenolate group from the
bridging ligand. The geometry around each iron metal can be de-
scribed as distorted octahedral. The best equatorial plane of the
polyhedra around the Fe(III) ions is constituted by three atoms
(ONO) from the four chelating Schiff base molecule and one oxygen
atom from the bridging ligand molecule which links the two [FeL]
units, (rms 0.1818 for Fe1 and rms 0.1779 for Fe2) with the metal
ion 0.078(2) and 0.080(2) Å out of this plane, for Fe(1) and Fe(2),
respectively. The axial positions are occupied by the nitrogen atom
from the four chelating Schiff base molecule and one nitrogen atom
from the bridging ligand molecule, N2–Fe1–N3, 176.55 (17)° and
N4–Fe2–N5, 178.31 (19)°.
The bond distances at Fe1 and Fe2 sites are similar. The average
bond distances, Fe–O, 1.93 Å and Fe–N, 2.21 Å, are comparable
with those found for similar dinuclear octahedral iron(III) com-
plexes [2,34], especially that with the same ligand incorporating
a metoxy group in the phenolate rings [Fe2L3]ꢀCH2Cl2ꢀ0.5H2O
[L = N,N-ethylenedi(3-methoxysalicylideneimine)] prepared by
Costes et al. [35], but with a Feꢀ ꢀ ꢀFe distance (6.372 Å) longer that
in our case 5.655 Å.
Fig. 3. Experimental (full squares) and best fit
vT ) vs. T data
(emu K mol–1
(continuous line) for the dinuclear Fe(III) complex). Thermal evolution of the
vT
(emu K molꢁ1) for [Fe2L3]ꢀ0.38H2O (2).
3.3. Magnetic properties of complex 2
The magnetic susceptibility of the crystalline compound was
measured in the temperature range of 2–300 K under a 1000 Oe
applied magnetic field. Temperature dependence of the
for the dinuclear [Fe2L3]ꢀ0.38H2O complex is shown on Fig. 3 where
is the molar magnetic susceptibility per 2 Fe and T is the absolute
temperature. The value of
T is 8.68 emu K molꢁ1 at 300 K and is a
vT plots
v
v
little smaller than the expected spin-only value of 8.75 emu K
molꢁ1 for two independent high spin Fe(III) (S = 5/2, g = 2.00)
[36] and at 2 K the
v
T is 4.43 emu K molꢁ1. Upon cooling from
Some intramolecular hydrogen bond interactions between
amine and phenolate groups are present in the net. [N(3)–
H(3A)ꢀ ꢀ ꢀO(6) 3.018(6) 143(1)°; N(4)–H(4A)ꢀ ꢀ ꢀO(1) 2.967(5) Å,
146(1)°].
300 to 6 K, the T values steadily decrease. Below 6 K, the vT
v
values rapidly decrease with further cooling, suggesting that an
antiferromagnetic interaction between the two iron(III). Owing to
the large distance (5.655 Å) and the long path between the two

M.M. Sow et al. / Inorganica Chimica Acta 406 (2013) 171–175
175
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357 (2004) 2143.
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ˆ
ˆ ˆ
isotropic spin Hamiltonian H = ꢁJS1.S2 where the two Fe(III) centers
ˆ
ˆ
are identified by S1 and S2. A satisfactory fit shown was obtained
with g = 1.996 0.002; J = 0.290 0.004 cmꢁ1. The curve profile is
characteristic of two high spin Fe(III) centers coupled by weak
antiferromagnetic interaction, which may originate due to dipolar
coupling between the metal centers linked by a spacer –NH–CH2–
CH2–NH– containing aliphatic chain leading the dinuclear complex
acting as two mononuclear species (Feꢀ ꢀ ꢀFe distance in the dimer is
5.655 Å). These data are consistent with findings in literature.
Many examples are found in which antiferromagnetic exchange
interactions between transition metal ions seems to be condi-
tioned by the aliphatic spacer length which controls the flexibility
of the chain [37,38]. Examples for iron compounds with weakly
antiferromagnetic coupling due to length of spacer, hydrogen
[16] P.J. Toscano, K.A. Belsky, T.C. Hsieh, T. Nicholson, J. Zubieta, Polyhedron 10
(1991) 977.
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[18] C.J. Whiteoak, G. Salassa, W.A. Arjan, Chem. Soc. Rev. 41 (2012) 622 (and
references therein).
bonding or p–p stacking interactions in high spin Fe(III) complexes
are recorded in the literature [39,40].
4. Conclusion
[19] L. Canali, D.C. Sherrington, Chem. Soc. Rev. 28 (1999) 245 (and references
therein).
Phenoxo complexes of Co(III) and Fe(III) with the acyclic Schiff
base ligand, 2-((2-(2-hydroxybenzylamino)ethylamino)methyl)
phenol) (H2L) have been prepared. For the two complexes the li-
gand molecules adopt a tri- or tetra- dentate chelating mode. In
the mononuclear complex containing cobalt center, each Co(III)
ion is coordinated by two ligands in tridentate mode with one unco-
ordinated perchlorate ions as counter ion. In the dinuclear iron(III)
complex, the ligands adopts a tetradentate mode of coordination.
Each iron center is coordinated by one ligand and the two [FeL]
units are bridged by another ligand molecule. Very few examples
of this behavior of the ligand for Fe(III) complexes have been re-
ported in the literature. The magnetic data of [Fe2L3]ꢀ0.38H2O and
the large separation Feꢀ ꢀ ꢀFe of 5.655 Å are indicate of a weak anti-
ferromagnetic coupling between the two iron(III).
[20] N.S. Venkataramanan, G. Kuppuraj, S. Rajagopal, Coord. Chem. Rev. 249 (2005)
1249 (and references therein).
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University of Gottingen, Gottingen, Germany, 1997.
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Part A 104 (2013) 300.
[26] K. Nakamoto, Infrared and Raman Spectra of Inorganic Coordination
Compounds, Wiley, New York, 1986. p. 232.
[27] W.T. Carnall, S. Siegel, J.R. Ferrano, B. Tani, E. Gebert, Inorg. Chem. 12 (1973)
560.
[28] R.L. de Lima, L.R. de Souza Teixeira, T.M.G. Carneiro, H. Beraldo, J. Braz. Chem.
Soc. 10 (1999) 184.
[29] A.A. Khandar, B. Shaabani, F. Belaj, A. Bakhtiari, Polyhedron 25 (2006) 1893.
[30] M. Das, S. Chattopadhyay, Polyhedron 50 (2013) 443.
[31] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[32] M.M. Sow, O. Diouf, I.E. Thiam, M. Gaye, P. Retailleau, Acta Crystallogr., Sect. E
68 (2012) m121.
Appendix A. Supplementary material
[33] F. Thomas, H. Arora, C. Philouze, O. Jarjayes, Inorg. Chim. Acta 363 (2010) 3122.
[34] C.J. Whiteoak, Inorg. Chem. 49 (2010) 11106.
[35] J.-P. Costes, F. Dahan, F. Dumestre, J.-P. Tuchagues, Polyhedron 29 (2010) 787.
[36] T. Fujinami, K. Nishi, R. Kitashima, K. Murakami, N. Matsumoto, S. Iijima, K.
Toriumi, Inorg. Chim. Acta 376 (2011) 136.
[37] U. Casellato, P. Guerriero, S. Tamburini, P.A. Vigato, C. Benelli, Inorg. Chim. Acta
207 (1993) 39.
[38] J. Sanmartín, M.R. Bermejo, A.M. García-Deibe, O.R. Nascimento, A.J. Costa-
Filho, Inorg. Chim. Acta 318 (2001) 135.
Crystallographic data have been deposited as CCDC 938351 and
938352 for [Co(HL)2]ꢀClO4ꢀCH3OH (1) and [Fe2L3]ꢀ0.38H2O (2),
respectively. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre. 12 Union Road, Cambridge CB21EZ,
UK; fax: (+44) 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
ˇ
´
ˇ
[39] I. Nemec, R. Boca, M. Gembicky, L. Dlhán, R. Herchel, F. Renz, Inorg. Chim. Acta
362 (2009) 4754.
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