Co(III) and Fe(III) complexes of Schiff bases derived from 2,4-dihydroxybenzaldehyde S-allyl-isothiosemicarbazonehydrobromide

Article abstract of DOI:10.1080/00958972.2013.856420

Two new complexes, [Co(L¹)(Py)₃]Cl _0.75Br_0.25 (L¹=4-hydroxy salicylaldehyde S-allyl-isothiosemicarbazonato-N,N′,O) and [Fe(L²)Cl] ·C₂H₅OH (L²=S-allyl-N

Full text of DOI:10.1080/00958972.2013.856420

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Co(III) and Fe(III) complexes of
Schiff bases derived from 2,4-
dihydroxybenzaldehyde S-allyl-
isothiosemicarbazonehydrobromide
Reza Takjooa, Joel T. Magueb, Alireza Akbaric & Mehdi Ahmadic
a Department of Chemistry, School of Sciences, Ferdowsi
University of Mashhad, Mashhad, Iran
b Department of Chemistry, Tulane University, New Orleans, LA,
USA
c Department of Chemistry, Payame Noor University (PNU),
Tehran, Iran
Accepted author version posted online: 18 Oct 2013.Published
online: 26 Nov 2013.
To cite this article: Reza Takjoo, Joel T. Mague, Alireza Akbari & Mehdi Ahmadi (2013)
Co(III) and Fe(III) complexes of Schiff bases derived from 2,4-dihydroxybenzaldehyde S-allyl-
isothiosemicarbazonehydrobromide, Journal of Coordination Chemistry, 66:22, 3915-3925, DOI:
10.1080/00958972.2013.856420
To link to this article: http://dx.doi.org/10.1080/00958972.2013.856420
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Journal of Coordination Chemistry, 2013
Vol. 66, No. 22, 3915–3925, http://dx.doi.org/10.1080/00958972.2013.856420
Co(III) and Fe(III) complexes of Schiff bases derived from
2,4-dihydroxybenzaldehyde
S-allyl-isothiosemicarbazonehydrobromide
REZA TAKJOO*†, JOEL T. MAGUE‡, ALIREZA AKBARI§ and MEHDI AHMADI§
†Department of Chemistry, School of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran
‡Department of Chemistry, Tulane University, New Orleans, LA, USA
§Department of Chemistry, Payame Noor University (PNU), Tehran, Iran
(Received 21 October 2012; accepted 18 September 2013)
Two new complexes, [Co(L1)(Py)3]Cl0.75Br0.25 (L1=4-hydroxy salicylaldehyde S-allyl-isothiosemicarbazo-
nato-N,N',O) and [Fe(L2)Cl]·C2H5OH (L2=S-allyl-N1-(4-hydroxy salicylaldehyde)-N 4-(salicylaldehyde)
isothiosemicarbazide-N,N',O,O'), have been synthesized and characterized by elemental analysis,
FT-IR and UV–vis spectroscopy, and molar conductivity. The solid-state structures of the complexes
were also determined by single crystal X-ray diffraction. The iron(III) and cobalt(III) complexes
adopt distorted square-pyramidal and octahedral geometries, respectively. The strength of the bond-
ing in these complexes was investigated by thermogravimetric studies with both exhibiting stability
with complete decomposition not occurring until ca. 600 °C.
Keywords: Isothiosemicarbazone; Cobalt complex; Iron complex; TGA; Crystal structure
1. Introduction
S-Alkyl-isothiosemicarbazones are an important class of thiosemicarbazone derivatives
since, in spite of different coordination modes with respect to free thiosemicarbazone
ligands, much attention has been paid to their synthesis and biological properties such
as antimicrobial, antifungal, and antibacterial activities [1–7]. The influence of biologi-
cal activity is elevated by the condensation of S-alkyl-isothiosemicarbazides with alde-
hydes and ketones such as 2-hydroxybenzaldehyde derivatives [8] that form tridentate
NNO donor ligands. These NNO donor ligands can act as either a mono-negative tri-
dentate ligand (by OH deprotonation) or a di-negative tridentate ligand (by OH and
NH2 deprotonation) in coordination with metals [9, 10]. The non-equivalent NH2
groups of S-alkyl-isothiosemicarbazides react with salicylaldehyde and related aromatic
aldehydes in the presence of metal ions to form tetradentate N2O2 donor ligands which
can be regarded as Salen analogs [11].
*Corresponding author. Email: r.takjoo@um.ac.ir
© 2013 Taylor & Francis

3916
R. Takjoo et al.
In Salen complexes, the central ion is placed into a planar or nearly planar environment
which aids d electron delocalization into the N2O2 moiety, important for catalytic activity
and nonlinear optical properties [12, 13].
In this work, we describe the synthesis of two new Schiff base complexes,
chlorido-(S-allyl-N1-(4-hydroxy salicylaldehyde)-N4-(salicylaldehyde)isothiosemicarbazide-
N,N′,O,O′)-iron(III) ethanol solvate (1) and the tris(pyridine)-(4-hydroxy salicylaldehyde
S-allyl-isothiosemicarbazonato-N,N′,O)-cobalt(III) cation isolated as a mixed chloride/
bromide salt (2), and their characterization by FT-IR and UV–vis spectroscopy, molar
conductivity, TGA, and X-ray structure.
2. Experimental
2.1. Materials and methods
All solvents and metal salts were of analytical reagent grade and were used without
purification. Molar conductivity of the complexes at 10−3 M was measured on a Metrohm
712 Conductometer at room temperature. C, H, and N analyzes were obtained using a
Thermo Finnigan Flash Elemental Analyzer 1112EA instrument. FT-IR spectra were
recorded on a FT-IR 8400-SHIMADZU spectrophotometer, with samples prepared as KBr
pellets (500–4000 cm−1). Electronic absorption spectra of compounds were recorded on a
SHIMADZU model 2550 UV–vis spectrophotometer. TG analyzes were carried out on a
TGA-50 SHIMADZU at a heating rate of 10 °C/min. X-ray single crystal structure
determinations were carried out on a Bruker Smart APEX CCD diffractometer.
2.2. X-Ray crystallography
Suitable crystals of 1 and 2 were mounted on a Cryoloop® with a film of Paratone® oil, and
placed in a cold nitrogen stream on the Bruker-AXS Smart-APEX diffractometer. Full
spheres of data were collected using three sets of 400 frames, each of width 0.5° in ω
collected at φ = 0.00°, 90.00°, and 180.00° and 2 sets of 800 frames, each of width 0.45° in
φ, collected at ω = –30.00 and 210.00° for 1 and three sets of 606 frames (0.3° width in ω)
at φ = 0, 120 and 240° for 2. Analysis of 783 reflections having I/σ(I) > 13 with CELL-NOW
[14] showed the crystal of 1 to belong to the triclinic system and to be twinned by a 180°
rotation about a*. Processing of the raw data and generation of final unit cell parameters was
performed with SAINT [15], while absorption corrections and merging of equivalent reflec-
tions were carried out with TWINABS [16] for 1 and SADABS [17] for 2. The structures were
solved by Patterson methods for 1 and direct methods for 2 (SHELXS) [18] and completed
by full-matrix, least-squares refinement (SHELXL) [18]. The final refinement of 1 employed
the full two-component reflection file and all additional computations were carried out with
the SHELXTL package [19]. Crystallographic details are presented in table 1.
2.3. Preparation of 2,4-dihydroxybenzaldehyde S-allylisothiosemicarbazone
hydrobromide (H2L)
H2L was prepared by following the literature method [20]. Yield: 5.2 g, 85%. m.p.: 190 °C.
Anal. Calcd for C11H13BrN3O5S (331.21 g mol−1): C, 39.77; H, 4.25; N, 12.65. Found: C,

Co(III) and Fe(III) base complexes
Table 1. Crystal data for 1 and 2.
3917
1
2
Formula
F. W.
C20H21ClFeN3O4S
490.76
C26H26Br0.25Cl0.75CoN6O2S
592.08
T (K)
100(2)
100(2)
λ (Å)
Crystal system
Space group
0.71073
Triclinic
P-1
0.71073
Orthorhombic
P212121
Unit cell (Å, °)
a
b
c
8.2182(15)
11.862(2)
23.346(5)
9.892(7)
14.110(9)
18.985(13)
α
79.914(4)
β
82.089(3)
γ
80.613(3)
2196.7(7)
V (Å3)
2650(3)
Z
4
4
Density (Calcd Mg/m3)
1.484
0.934
1012
1.484
1.215
1218
Abs. coeff. (mm−1
F (000)
)
Size (mm)
θ range (°)
Reflns. total
0.25 × 0.18 × 0.05
2.10 to 28.37
64,238
0.25 × 0.06 × 0.06
1.80 to 27.99
22,923
Indep. reflns. (Rint
Compl., % to (θ°)
Tmax, Tmin
Data/restraints/parameters
GooF on F2
)
19,876 (0.0511)
99.5 (28.00)
0.9548, 0.8000
19,876/0/544
1.069
6204 (0.0507)
99.4 (27.75)
0.9307, 0.7726
6204/0/334
1.040
Final R1, wR2(I > 2σ(I))
R1, wR2 (all data)
Largest diff. peak, hole
0.0602, 0.1605
0.0707, 0.1683
1.937, −0.822 e.Å−3
0.0311, 0.0716
0.0341, 0.0738
0.494, −0.675 e.Å−3
39.56; H, 4.17; N, 12.51%. IR (cm−1): 3250 (ms), 3186 (ms), 3150 (w), 2820–2950 (w),
1650 (w), 1627 (vs), 1581 (vs), 1157 (ms), 1060 (w), 794 (mw). UV–vis (MeOH, λmax nm,
log ε, L mol−1 cm−1): 240 (4.2), 288sh (4.19), 300 (4.23), 330 (4.46).
2.4. Preparation of chloro-(S-allyl-N1-(4-hydroxy salicylaldehyde)-N4-(salicylaldehyde)
isothiosemicarbazide-N,N',O,O')-iron(III) ethanol solvate (1)
Sodium hydroxide (0.08 g, 2 mM) was added to 2,4-dihydroxybenzaldehyde
S-allylisothiosemicarbazone hydrobromide (0.33 g, 1 mM) in 10 mL of ethanol. The
mixture was stirred for 15 min. Salicylaldehyde (0.146 g, 1.2 mM) was then added to
the solution, and the stirring continued for 30 min more followed by the addition of
FeCl3·6H2O (0.27 g, 1 mM) as a solid. The reaction mixture was stirred and heated in
a beaker for 1 h at 50 °C. Crystals suitable for X-ray analysis were obtained by slow
evaporation of the solution over two weeks at room temperature. Yield: 0.32 g, 65%.
m.p.: 213 °C. Anal. Calcd for C20H21ClFeN3O4S: C, 48.95; H, 4.31; N, 8.56. Found:
C, 47.93; H, 4.42; N, 8.48%. IR (cm−1): 3371 (m), 3130 (w), 2970 (w), 2916 (w),
1604 (vs), 1581 (vs), 1535 (vs), 1427 (s), 1365 (m), 1311 (mw), 1283 (vw), 1141
(m), 1041 (w), 987 (w), 918 (w), 840 (w), 802 (w), 763 (m), 685 (m), 610 (mw), 470
(mw). UV–vis [DMF, λmax nm (log ε/M−1 cm−1)]: 294 (4.51), 404 (4.02), 470 (3.95).
Molar conductivity (1.0 × 10−3 M; DMF): 16 Ω−1 cm2 mol−1.

3918
R. Takjoo et al.
2.5. Preparation of tris(pyridine)-(4-hydroxy salicylaldehyde S-allylisothiosemicarbazonato-
N,N′,O)-cobalt(III) chloride(0.75) bromide(0.25) (2)
2,4-Dihydroxybenzaldehyde S-allyl-isothiosemicarbazonehydrobromide (0.331 g, 0.1 mM)
was dissolved in a mixture of 10 mL of absolute ethanol and 2 mL of pyridine. This was
stirred for 15 min and the resulting solution was added to a 5 mL ethanolic solution of
CoCl2·6H2O (0.238 g, 0.1 mM). The solution was stirred for 3 h in the beaker at room
temperature, during which time the color gradually turned black green. Crystals suitable for
X-ray analysis were obtained by slow evaporation of the solution over four days in a
refrigerator. Yield: 0.46 g, 76%. m.p.: 195 °C decomposed. Anal. Calcd for C26H26Co-
N6O2SBr0.25Cl0.75: C, 52.72; H, 4.24; N, 14.10. Found: C, 52.78; H, 4.17; N, 13.94%. IR
(cm−1): 3247 (m), 3109 (s), 3016 (s), 1596 (vs), 1550 (s), 1496 (vs), 1442 (vs), 1357 (s),
1211 (vs), 1160 (s), 1126 (m), 1072 (mw), 1018 (mw), 1001 (w), 933 (mw), 848 (w), 763
(m), 694 (s), 640 (w), 586 (w), 532 (w), 470 (w). UV–vis [MeOH, λmax nm (log ε/M−1
cm−1)]: 250 (4.71), 310 (4.22), 376 (4.26), 556 (2.69). Molar conductivity (1.0 × 10−3 M;
DMF): 84 Ω−1 cm2 mol−1.
3. Results and discussion
The two complexes were synthesized in good yields. They have good solubility in DMF
and DMSO, but are insoluble in H2O and CHCl3. C, H, and N analyzes are in good agree-
ment with theoretical values. The molar conductivity of 16 Ω−1 cm2 mol−1 for 1 in DMF
(10−3 M) suggests nonelectrolytic behavior [21] while that of 84 Ω−1 cm2 mol−1 for 2 in
DMF (10−3 M) is consistent with the proposed ionic formulation [22]. The synthetic route
is shown in scheme 1. In the preparation of the iron complex, we used slightly more salicyl-
aldehyde to increase the efficiency.
3.1. Spectral properties
The IR spectrum of 1 lacks bands assignable to the asymmetric and symmetric stretching
modes of the isothioamide NH2 functional group, indicating that the template reaction had
Scheme 1. General synthetic route of complexes.

Co(III) and Fe(III) base complexes
3919
proceeded to completion [23]. The peak at 3371 cm−1 can be assigned to ν(OH) of the
lattice ethanol [24] while the very weak bands at 2970–3130 cm−1 are due to
ν(CH)aromatic + ν(CH2)allyl. The complex shows three strong bands at 1604, 1581, and 1535
cm−1 which are assigned to ν(C=N) and ν(C=C) combination modes [25]. In addition, the
complex exhibits a C–O stretching band at 1141 cm−1 that indicates coordination of the
deprotonated phenolic oxygen [26]. Bands attributed to N–N stretching and aromatic out-
of-plane-bending were found at 1041 and 685 cm−1, respectively. The electronic spectrum
of 1 in DMF shows an intra-ligand n→π* transition of the isothioamide moiety at 294 nm
and LMCT bands for O(p)→M(d) and N(p)→M(d) transitions at 404 and 470 nm, respec-
tively [27]. The tail of the strong LMCT absorption bands may cover the d-d transition
bands [28] as the latter could not be located with confidence.
The FT-IR spectrum of 2 shows a sharp band at 3247 cm−1 due to stretching vibration of
the isothioamide NH group [29]. The asymmetric and symmetric bands of the isothioamide
NH2 group and the ν(OH) band of the phenol were not observed, indicating di-deprotonation
of the ligand and coordination to the metal center [22]. The absorption in the 3109–3016
cm−1 region can be assigned to the mixture of the C–H pyridine and aromatic stretching
vibrations. Four strong bands with the same intensity at 1596, 1505, 1496, and 1442 cm−1
are assigned to the combination of ν(C=N)azomethin + ν(C=N)pyridine + ν(C=C)aromatic [30],
while a very strong band at 1211 cm−1 is assigned to ν(C–O) [31]. The out-of-plane bending
vibration modes for the pyridine and aromatic rings are seen at 640 and 694 cm−1, respec-
tively [32]. The electronic spectrum of 2 in methanol exhibits a band at 250nm attributable
to π→π* transitions of the aromatic ring. The band at 310 nm is assigned to an intra-ligand
n→π* transition of the isothioamide fragment [20]. A broad band centered at 376 nm is
assigned to an LMCT charge transfer transition, while a weak band near 556 nm is attributed
to the 1A1g→1T1g transition for distorted octahedral cobalt(III) [33].
3.2. Thermal studies
Thermo-analytical measurements were performed at 27–1000 °C. The TG curves for 1 and
2 are shown in figure 1 and the proposed mechanisms for thermal decomposition are shown
in scheme 2 with theoretical values displayed in parentheses.
Figure 1. TGA curves of Fe(III) and Co(III) complexes.

3920
R. Takjoo et al.
The TG curve of 1 showed that the thermal decomposition takes place in five steps. The
complex is stable below 87 °C. Gradual decomposition from 87 to 247 °C is related to the
loss of the ethanol molecule by an 8.9% weight loss (9.39%). The second step of weight
loss, 7% (7.22%), occurs at 260 °C, which is attributed to the separation of a Cl atom. The
third stage at 272–360 °C corresponds to a 17.90% (19.96%) weight loss and is attributed
to the loss of the S-allyl group. The remainder of the ligand is subsequently removed in two
stages. From the TG curve, it appears that loss of an N–CH=N–N=C–Ph–(O)OH fragment
takes place in the fourth step from 372 to 450 °C with a mass decrease of 35.4% (36.5%),
while the last stage, with a 18.77% weight loss (19.50%), corresponds to the loss of a
Ph–O fragment at 445–590 °C. The weight of the final product is inconsistent with metal
oxide Fe2O3 from the 18.36% (17.08%) residual weight.
Scheme 2. The proposed mechanisms for thermoanalyses of Fe(III) and Co(III) complexes.

Co(III) and Fe(III) base complexes
3921
Thermo-analysis of 2 showed that it is generally stable up to 167 °C before the onset of
decomposition, which subsequently occurs in three steps. The first step occurs over the
range 167–202 °C and corresponds to the loss of two pyridine ligands and the halide ions
with a mass loss of 31% (29%). The second stage is a slow process from 202–519 °C due
to simultaneous loss of the third pyridine ligand and the S-allyl fragment with a mass loss
of 22% (22%). The sharp stage with a mass loss of 33% (31%) corresponds to the removal
of the NH–C=N–N=C–Ph–(O)(OH) fragment. The final decomposition product is cobalt
oxide as indicated by the residual weight of 15% (13%).
3.3. Crystal structures
Pertinent bond distances and interbond angles for 1 and 2 are presented in tables 2 and 5,
respectively, while perspective views of the complexes are shown in figures 2 and 3, respec-
tively. There are also some hydrogen bonds in complexes 1 and 2 that are shown in table 3
and 6, respectively. From table 2, the corresponding metal–ligand bond distances in the two
independent molecules are substantially the same, while the corresponding angles tend to
differ to a greater extent. This is also evident from table 4, which shows that each of the
three chelate rings formed by the tetradentate ligand are more folded along the line joining
the respective donor atoms in molecule 2 than in molecule 1. Despite this, the distance of
the iron atom from the mean plane of the four donor atoms is the same in both (0.534(1) and
0.536(1) Å). The coordination geometry can thus be described as distorted square-pyramidal
(SPY) with the metal atom displaced from the basal plane towards the apical ligand.
A five-coordinate complex can adapt a trigonal–bipyramidal (TBPY) or SPY geometry.
Addison et al. introduced the parameter τ that is used for determining TBPY or SPY config-
uration. The parameter τ is defined as τ = (β−α)/60 (where β and α are the largest angles in
the metal coordination sphere with β > α). This value for 1 is 0.06, indicating that the com-
plex has a slightly distorted SPY geometry [34].
The Fe–O and Fe–N bond lengths are similar to those reported in the crystal structures of
SPY coordinated Fe(III) complexes with N2O2 donor isothiosemicarbazone derivatives [21].
Coordination of the asymmetric ligand to the iron atom generates three chelate rings, two
six-membered and one five-membered. In the isothioamide fragment, the C–C and C=N
Table 2. Bond distances (Å) and interbond angles (°) for 1.
Molecule 1
Molecule 2
Fe1–O2
Fe1–O1
Fe1–N1
Fe1–N3
Fe1–Cl1
1.898(2)
1.9090(19)
2.068(2)
2.099(2)
2.2532(8)
Fe2–O5
Fe2–O4
Fe2–N4
Fe2–N6
Fe2–Cl2
1.894(2)
1.901(2)
2.059(2)
2.094(2)
2.2440(8)
O2–Fe1–O1
O2–Fe1–N1
O1–Fe1–N1
O2–Fe1–N3
O1–Fe1–N3
N1–Fe1–N3
O2–Fe1–Cl1
O1–Fe1–Cl1
N1–Fe1–Cl1
N3–Fe1–Cl1
95.68(8)
144.47(9)
86.99(9)
86.58(9)
148.77(9)
73.97(9)
107.32(7)
106.85(7)
105.70(7)
102.10(7)
O5–Fe2–O4
O5–Fe2–N4
O4–Fe2–N4
O5–Fe2–N6
O4–Fe2–N6
N4–Fe2–N6
O5–Fe2–Cl2
O4–Fe2–Cl2
N4–Fe2–Cl2
N6–Fe2–Cl2
94.06(8)
146.41(10)
87.39(9)
86.87(9)
147.34(10)
74.68(10)
110.80(7)
110.51(7)
99.93(7)
99.49(7)

3922
R. Takjoo et al.
Table 3. Hydrogen bonds for 1 (Å and °).
D–H···A
d(D–H)
d(H···A)
d(D···A)
∠(DHA)
O8–H8O···O4i
O7–H7O···O1
O6–H6O···O7
O3–H3O···O8ii
0.95
0.88
0.92
0.88
1.92
1.93
1.70
1.75
2.831(3)
2.745(3)
2.613(3)
2.622(3)
159
154
169
170
i
Note: Symmetry transformations used to generate equivalent atoms: x, y + 1, z; iix, y–1, z.
Table 4. Chelate ring folding (°) for 1.
Molecule 1
10.5(2)
Molecule 2
Fold along
line
O1–N1
O4–N4
N1–N3
N4–N6
O2–N3
O5–N6
16.2(2)
17.4(2)
26.4(2)
14.2(2)
20.0(1)
bond distances have classical single and double bond characters, indicating π-delocalization
of electron density over this moiety.
In the X-ray sample, the Co(III) complex cation in 2 was isolated as a mixed chloride/
bromide salt in a 3/1 ratio. From table 5, the coordination geometry is that of a modestly
Figure 2. Perspective view of molecule 1 of 1. Displacement ellipsoids are drawn at the 50% probability level
and hydrogens are drawn as spheres of arbitrary radius.

Co(III) and Fe(III) base complexes
3923
Figure 3. Perspective view of the cation of 2. Displacement ellipsoids are drawn at the 50% probability level and
hydrogens are drawn as spheres of arbitrary radius.
distorted octahedron, with the largest deviations from the ideal resulting from the con-
straints of the Schiff base ligand. That ligand is nearly planar but with a slight twist from
end to end.
The dibasic tridentate ligand coordinated to the metal center via the isothioamide nitro-
gen, azomethine nitrogen, and phenolic oxygen atoms. Remaining sites of the octahedral
geometry are occupied with three pyridine molecules. N1 and N3 atoms are in cis position
Table 5. Bond distances (Å) and interbond angles (°) for 2.
Co1–N3
Co1–O1
Co1–N1
1.882(2)
1.8882(18)
1.907(2)
Co1–N5
Co1–N6
Co1–N4
1.959(2)
1.975(2)
1.990(2)
N3–Co1–O1
N3–Co1–N1
O1–Co1–N1
N3–Co1–N5
O1–Co1–N5
N1–Co1–N5
N3–Co1–N6
O1–Co1–N6
94.96(9)
82.13(9)
175.67(8)
174.85(8)
88.34(9)
94.80(9)
91.59(9)
87.69(8)
N1–Co1–N6
N5–Co1–N6
N3–Co1–N4
O1–Co1–N4
N1–Co1–N4
N5–Co1–N4
N6–Co1–N4
N1–Co1–N6
89.18(8)
92.50(8)
88.70(9)
89.98(8)
93.15(8)
87.34(9)
177.67(8)
89.18(8)

3924
R. Takjoo et al.
Table 6. Hydrogen bonds for 2 (Å and °).
D–H···A
d(D–H)
d(H···A)
d(D···A)
∠(DHA)
O2–H1···Cl1
0.84
0.88
2.25
2.59
3.075(2)
3.452(3)
165
168
N1–H1 N···Cl1i
i
Note: Symmetry transformations used to generate equivalent atoms: –x + 2, y + 1/2, –z + 1/2.
with respect to each other, confirming the ligand coordinates to the cobalt in the E form
[30].
The observed Co–N1 (1.907(2) Å), Co–N3 (1.882(2) Å), and Co–O1 (1.888(2) Å)
distances agree well with previously reported values [35]. The average Co–N (nitrogen of
pyridine molecules) distance (1.974(6) Å) is similar to the reported values [35]. The bond
distances in isothioamide fragment show that π electron delocalization exists in the
deprotonated coordinated organic ligand.
The angle between two chelate rings is 4.41°, showing the ligand coordinates to the
metal in a concave form. The pyridine molecules are bent off the N1–N3–O1–N5 plane by
37.25–89.84°. The bond angles around the central ion are from 87.3(8) to 94.8(8)°. The bite
angles O1–Co1–N1 and N3–Co1–N5 are 175.67(8)° and 174.85(8)°, respectively, matching
the values from the literature for other Co(III) complexes of isothiosemicabazone [36].
4. Conclusion
Treatment of Co(II) chloride in a mixture of ethanol and pyridine with S-allyl-isothiosemic-
arbazone hydrobromide (H2L·HBr) gave [Co(L1)(Py)3]·Cl0.75Br0.25, where L1=4-hydroxy
salicylaldehyde S-allyl-isothiosemicarbazonato-N,N′,O) as a N2O donor ligand. Likewise,
the template reaction of 2,4-dihydroxybenzaldehyde S-allyl-isothiosemicarbazone
hydrobromide with salicylaldehyde in the presence of iron(III) chloride and NaOH yielded
[Fe(L2)Cl]·C2H5OH, where L2=S-allyl-N1-(4-hydroxy salicylaldehyde)-N 4-(salicylaldehyde)
isothiosemicarbazide-N,N′,O,O′) as a N2O2 donor ligand. The complexes were characterized
by elemental analysis, IR and UV–vis spectra, and X-ray crystal structure determinations.
In [Fe(L)Cl]·C2H5OH, Fe(III) had a SPY configuration with the N2O2 donor in the basal
positions and the apical position occupied by the chloride. Co(III) in [Co(L)
(Py)3]·Cl0.75Br0.25 is approximately octahedral with the Schiff base tridentate coordinating
via azomethine nitrogen, deprotonated thioamide nitrogen, and the deprotonated phenoxy;
three pyridines occupy the remaining positions. Thermal stabilities of the cobalt(III) and
iron(III) complexes were also studied and discussed. The TG curves displayed three and
five steps of thermal decomposition for the Co(III) and Fe(III) complexes, respectively.
Supplementary material
CCDC 890227-890228 contain the supplementary crystallographic data for 1 and 2. These
data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or

Co(III) and Fe(III) base complexes
3925
from the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge CB2 1EZ,
UK; Fax: (+44) 1223-336-033; or E-mail: deposit@ccdc.cam.ac.uk.
Acknowledgments
The authors thank the Tulane University Chemistry Department for support of the Tulane
Crystallography Laboratory. R. T. and A. A. thank Ferdowsi University of Mashhad and Payame
Noor University (PNU) for financial assistance.
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