Dianion N1,N4-bis(salicylidene)-S-allyl- thiosemicarbazide complexes: Synthesis, structure, spectroscopy and thermal behavior

Article abstract of DOI:10.1016/j.poly.2012.05.004

The products with the general formulas VO(Salits) 1, Mn(Salits)Br 2, Fe(Salits)Cl 3 and UO₂(Salits)(MeOH) 4 (Salits = N¹,N ⁴-bis(salicylidene)-S-allyl-thiosemicarbazide) are prepared by the reaction of salicylaldehyde-S-allyl-thiosemicarbazone (H₂L) and salicylaldehyde with VOSO₄·3H₂O, Mn(CH ₃COO)₂·4H₂O, FeCl₃· 6H₂O and UO₂(CH₃COO)₂·2H ₂O, respectively. Complexes 1-4 were characterized by elemental analysis, spectroscopic (FT-IR and UV-Vis) and TGA techniques. Crystal and molecular structures of the complexes were determined by single crystal X-ray diffraction. The results revealed that the complexes 1, 2 and 3 contain a dideprotonated tetradentate form of Salits coordinated via N₂O ₂ donors along with oxido, bromido or chlorido ligands, respectively, and they have distorted square pyramidal geometries. However, the complex 4 adopts a severely distorted pentagonal bipyramidal geometry consisting of N ₂O₂ coordination of Salits, a methanol ligand and two oxygens of the uranyl moiety. TG analysis showed that complex 3 is more stable than the others.

Full text of DOI:10.1016/j.poly.2012.05.004

Polyhedron 42 (2012) 128–134
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Polyhedron
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Dianion N1,N4-bis(salicylidene)-S-allyl-thiosemicarbazide complexes: Synthesis,
structure, spectroscopy and thermal behavior
Mehdi Ahmadi a, Joel T. Mague b, Alireza Akbari a, Reza Takjoo c,
⇑
a Department of Chemistry, Payame Noor University (PNU), 19395-4697 Tehran, Iran
b Department of Chemistry, Tulane University, New Orleans, LA 70118, USA
c Department of Chemistry, School of Sciences, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
The products with the general formulas VO(Salits) 1, Mn(Salits)Br 2, Fe(Salits)Cl 3 and UO2(Salits)(MeOH) 4
(Salits = N1,N4-bis(salicylidene)-S-allyl-thiosemicarbazide) are prepared by the reaction of salicylalde-
hyde-S-allyl-thiosemicarbazone (H2L) and salicylaldehyde with VOSO4ꢀ3H2O, Mn(CH3COO)2ꢀ4H2O,
FeCl3ꢀ6H2O and UO2(CH3COO)2ꢀ2H2O, respectively. Complexes 1–4 were characterized by elemental
analysis, spectroscopic (FT-IR and UV–Vis) and TGA techniques. Crystal and molecular structures of the
complexes were determined by single crystal X-ray diffraction. The results revealed that the complexes
1, 2 and 3 contain a dideprotonated tetradentate form of Salits coordinated via N2O2 donors along with
oxido, bromido or chlorido ligands, respectively, and they have distorted square pyramidal geometries.
However, the complex 4 adopts a severely distorted pentagonal bipyramidal geometry consisting of
N2O2 coordination of Salits, a methanol ligand and two oxygens of the uranyl moiety. TG analysis showed
that complex 3 is more stable than the others.
Received 28 March 2012
Accepted 5 May 2012
Available online 14 May 2012
Keywords:
Isothiosemicarbazide
N2O2 donor
TGA
Spectroscopy
Crystal structures
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
sulfur atom in the main skeleton may change some of their proper-
ties such as the biological [15], catalytic [16,17] or solubility. Con-
The tetradentate ligands with the N2O2 donor set and their me-
tal complexes are of great importance in chemistry as they provide
synthetic models for the metal-containing sites in metallo-proteins
and metallo-enzymes and extensive catalytic and bioactive appli-
cations. The prototype of this group is Salen. Since the first synthe-
sis of Salen compounds in 1869 [1], many theoretical and empirical
studies on these compounds and their complexes have been done
[2], and a wide range of their properties such as bioactivity [3], cat-
alytic [4,5], phosphorescence and electroluminescence [6] have
been investigated.
In contrast to Salen-like compounds, bis(salicylidene)isothiose-
micarbazides (Scheme 1a) with a similar structure have been less
studied.
These compounds were synthesized and characterized for the
first time in 1971 [7]. Since that time, few studies have been done
on them and only a few crystal structures of their complexes have
been reported, all of which are complexes of the S-methyl and S-
propyl analogues [8–14].
sidering the presence of the N-salicylideneaniline fragment in the
Salitss ligand, one can expect photochromism for these materials
as well [18]. The ‘‘Half-Salits’’ ligands (Scheme 1b) have been stud-
ied extensively; however, very few Salits compounds (Scheme 1a)
have been prepared and no studies of their properties and applica-
tions have been done so far. Therefore, studies on the synthesis,
characterization, structure and properties of the Salits compounds
can be very important in inorganic chemistry and materials science.
In this study, four new complexes, N1,N4-bis(salicylidene)-S-
allyl-isothiosemicarbazidato)oxidovanadium(IV) 1, bromido(N1,
N4-bis(salicylidene)-S-allyl-isothiosemicarbazidato)manganese(III)
2, chlorido(N1,N4-bis(salicylidene)-S-allyl-isothiosemicarbazidato)
iron(III)
3
and methanol(N1,N4-bis(salicylidene)-S-allyl-isothio-
have been synthesized
semicarbazidato)dioxidouranium(VI)
4
and characterized by spectroscopic and TG analysis and their struc-
tures have been determined by X-ray crystallography.
In this paper, such compounds are briefly called ‘‘Salits’’. They
have structures similar to that of the Salen-type ligands and are
expected to manifest similar properties although the presence of a
2. Experimental
2.1. Materials and instrumentation
⇑
All chemicals and solvents were of analytical reagent grade and
were used without any further purification.
Corresponding author. Tel./fax: +98 511 8975457.
E-mail address: rezatakjoo@yahoo.com (R. Takjoo).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.05.004

M. Ahmadi et al. / Polyhedron 42 (2012) 128–134
129
S
N
O
R
S
R
S
R
N
C
N
C
HN
C
HC
N
O
CH
HC
N
NH2
HC
N
NH
M
OH
OH
a
b
Scheme 1. (a) The general structure of Salitss and (b) the tautomery in half-Salitss (H2L).
Microanalyses for C, H, N and S were performed on a Thermo
Finnigan Flash Elemental Analyzer 1112EA. Molar conductances
of ca. 10ꢁ3 M solutions of the complexes in methanol were mea-
sured by means of a Metrohm 712 Conductometer. IR spectra were
recorded on a FT-IR 8400-SHIMADZU spectrophotometer with
samples prepared as KBr (400–4000 cmꢁ1) pellets. The electronic
spectra of the compounds were run in methanol solutions on a
SHIMADZU model 2550 UV–Vis spectrophotometer in the range
of 220–900 nm. The TGA diagrams were recorded in a TGA-50 SHI-
MADZU instrument at a heating rate of 10 °C/min in a air atmo-
sphere over the temperature range of 20–850 °C. Diffraction data
were measured using a Bruker Smart APEX CCD diffractometer.
kmax
(
e
max) 246, 334, 436 and 478sh nm (39100, 29900, 9900 and
7450 Mꢁ1 cmꢁ1). IR (KBr, cmꢁ1
)
1603(s), 1574(s), 1527(m),
1506(m), 1427(w), 1373(w), 1288(m), 1203(w), 1141(m),
1119(m), 1026(w), 918(w), 810(w), 764(w), 671(w), 609(w),
501(vw). Anal. Calc. for C18H15BrMnN3O2S (472.24 g molꢁ1): C,
45.78; H, 3.20; N, 8.90; S, 6.79. Found: C, 45.36; H, 3.19; N, 8.76;
S, 6.85%.
2.3.3. Chlorido(N1,N4-bis(salicylidene)-S-allyl-isothiosemicarbazidato)
iron(III) (3)
Plate,
brown.
Mp = 223 °C.
Molar
conductivity
(1 ꢂ 10ꢁ3 mol Lꢁ1; DMF): 27
X
ꢁ1 cm2 molꢁ1. UV–Vis (methanol):
kmax (emax) 238, 278sh, 306, 372, 430 and 608 nm (27650, 22500,
2.2. Preparation of salicylaldehyde S-allyl-isothiosemicarbazone
hydrobromide (H2L)
31000, 12550 and 1250 Mꢁ1 cmꢁ1). IR (KBr, cmꢁ1
) 1606(s),
1574(s), 1527(m), 1506(m), 1427(w), 1373(w), 1296(m),
1142(m), 1026(w), 810(w), 764(w), 671(w), 602(w), 510(vw). Anal.
Calc. for C18H15ClFeN3O2S (428.69 g molꢁ1): C, 50.43; H, 3.53; N,
9.80; S, 7.48. Found: C, 49.65; H, 3.49; N, 9.69; S, 7.34%.
A solution of thiosemicarbazide (0.46 g, 0.50 mmol) in ethanol
(10 ml) was treated with allyl bromide (0.60 ml, 0.55 mmol) and
was refluxed for 1 h. An ethanolic solution (5 ml) of salicylalde-
hyde (0.61 g, 0.50 mmol) was then added and the reflux continued
for extra 2 h. The resulted yellow precipitate was filtered off,
washed with cold ethanol and dried in vacuum over silica gel.
Yellow solid. Yield: 1.365 g (83%). Mp = 185 °C. UV–Vis (metha-
2.3.4. Methanol(N1,N4-bis(salicylidene)-S-(allyl)-
isothiosemicarbazidato)dioxidouranium(VI) (4)
Block, red. Mp = 190 °C. Molar conductivity (1 ꢂ 10ꢁ3 mol Lꢁ1
;
DMF): 4
X (emax) 238sh,
ꢁ1 cm2 molꢁ1. UV–Vis (methanol): kmax
nol): kmax (emax) 228, 292, 302, 332 and 402 nm (27450, 33200,
280, 326, 338 and 446 nm (16200, 15850, 13200, 12500 and
33950, 38300 and 1150 Mꢁ1 cmꢁ1). IR (KBr, cmꢁ1) 3240(w),
3100(w), 1628(s), 1581(w), 1443(m), 1413(w), 1335(m),
1257(m), 1142(m), 933(w), 764(m), 625(m), 544(w), 478(w). Anal.
Calc. for C11H14BrN3OS (316.22 g molꢁ1): C, 41.78; H, 4.46; N,
13.29; S, 10.14. Found: C, 41.86; H, 4.55; N, 13.18; S, 9.98%.
2500 Mꢁ1 cmꢁ1). IR (KBr, cmꢁ1
)
1605(s), 1573(s), 1527(s),
1465(m), 1427(m), 1388(m), 1288(m), 1203(w), 1142(m),
1011(w), 910(w), 756(w), 671(m), 586(w), 440(w). Anal. Calc. for
C
19H19N3O5SU (639.47 g molꢁ1): C, 35.69; H, 2.99; N, 6.57; S,
5.01. Found: C, 35.36; H, 2.93; N, 6.56; S, 4.97%.
2.3. General method for preparation of the complexes
2.4. Crystallography
A mixture of H2L (0.5 mmol), the appropriate metal salt (VO-
The crystals of 1–4 were mounted on a Cryoloop™ with a film of
Paratone™ oil and transferred to the goniometer head attached to
the Bruker-AXS Smart APEX diffractometer where they were
cooled to 100 K with a nitrogen cold-stream. Complete spheres of
data were collected under control of APEX2/BIS [19] following
SO4ꢀ3H2O,
Mn(CH3COO)2ꢀ4H2O,
FeCl3ꢀ6H2O
or
UO2(CH3-
COO)2ꢀ2H2O) (0.5 mmol) and salicylaldehyde (0.6 mmol) in
ethanol (5 ml) was heated at 100 °C for 2 h. The product crystal-
lized after several days at room temperature. (Hint: methanol
was used as a solvent for uranium-complex preparation.)
which ca. 1500–2200 reflections having I/r(I) ꢃ 15 were used to
determine approximate unit cell parameters. From these results,
1 and 4 were found to be single crystals, 2 was triclinic and con-
sisted of one major and 2–3 minor domains (determined with
CELL-NOW) [20] and 3 was a 2-component triclinic crystal with
the two domains rotated 10.6° about the axis (0.65, 0.43, 1.00).
Integration of the raw intensities, application of Lorentz and polar-
ization corrections and global refinement of unit cell parameters
(using 7138–9973 reflections) was performed with SAINT [21] using
1-component control files for 1 and 4, the control file for the major
component of 2 as generated by CELL-NOW and the 2-component
control file for 3 as generated by CELL-NOW. Absorption correc-
tions (GAUSSIAN integration based on indexing of the crystal faces
for 1 and use of equivalent reflections from different regions of re-
ciprocal space for the others) were applied with SADABS [22] for 1, 2
and 4 and with TWINABS [23] for 3. Heavy atom positions were deter-
mined from Patterson functions (SHELXS) [24] and the remainder of
2.3.1. N1,N4-bis(salicylidene)-S-allyl- isothiosemicarbazidato)
oxidovanadium(IV) (1)
Slat, yellow. Mp = 222 °C. Molar conductivity (1 ꢂ 10ꢁ3 mol Lꢁ1
;
DMF): 10
X (emax) 228sh,
ꢁ1 cm2 molꢁ1. UV–Vis (methanol): kmax
314, 340sh, 416 and 650 nm (72550, 31850, 24550, 13500 and
171 Mꢁ1 cmꢁ1). IR (KBr, cmꢁ1
)
1605(s), 1575(s), 1535(s),
1512(m), 1427(m), 1373(m), 1296(m), 1203(w), 1142(mb),
980(s), 918(w), 802(w), 764(m), 602(w), 494(w). Anal. Calc. for
C
18H15N3O3SV (404.34 g molꢁ1): C, 53.47; H, 3.74; N, 10.39; S,
7.93. Found: C, 52.48; H, 3.69; N, 10.25; S, 7.79%.
2.3.2. Bromido(N1,N4-bis(salicylidene)-S-allyl-isothiosemicarbazida-
to)manganese(III)’’ (2)
Tablet,
brown.
Mp
>300 °C.
X
Molar
conductivity
(1 ꢂ 10ꢁ3 mol Lꢁ1; DMF): 110
ꢁ1 cm2 molꢁ1. UV–Vis (methanol):

130
M. Ahmadi et al. / Polyhedron 42 (2012) 128–134
Table 1
Crystal data and structure refinement.
Complex
1
2
3
4
Formula
Formula weight
T (K)
C
18H15N3O3SV
C18H15BrMnN3O2S
472.24
100(2)
C18H15ClFeN3O2S
428.69
100(2)
C19H18N3O5SU
638.45
100(2)
404.33
100(2)
k (Å)
0.71073
0.71073
0.71073
0.71073
monoclinic
C2/c
Crystal system
Space group
Unit cell dimensions
a (Å)
b (Å)
c (Å)
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
7.0279(13)
9.6498(18)
13.257(3)
7.2641(15)
9.755(2)
13.527(3)
7.213(2)
9.701(3)
13.571(5)
40.399(7)
11.389(2)
19.186(4)
a
(°)
72.974(2)
71.905(3)
72.477(3)
b (°)
82.838(2)
80.600(3)
81.568(5)
108.209(2).
c
(°)
80.277(3)
844.6(3)
76.065(3)
880.2(3)
77.517(3)
880.8(5)
V (Å3)
8386(3)
Z
2
2
2
16
2.023
7.877
4816
Dcalc (Mg/m3)
1.590
0.735
414
1.782
3.157
472
1.616
1.144
438
Absorption coefficient (mmꢁ1
F(000)
)
Crystal size (mm)
h range for data collection (°)
Index ranges
0.27 ꢂ 0.07 ꢂ 0.04
2.23–29.03
ꢁ9 ꢅ h ꢅ 9, ꢁ11 ꢅ k ꢅ 12,
ꢁ17 ꢅ l ꢅ 17
14661
4209 [Rint = 0.0436]
semi-empirical from
equivalents
0.9705 and 0.7519
0.12 ꢂ 0.08 ꢂ 0.05
2.24–29.05
ꢁ9 ꢅ h ꢅ 9, ꢁ13 ꢅ k ꢅ 13,
ꢁ18 ꢅ l ꢅ 18
15516
4411 [Rint = 0.0317]
semi-empirical from
equivalents
0.8581 and 0.6933
0.22 ꢂ 0.10 ꢂ 0.02
1.58–28.34
ꢁ9 ꢅ h ꢅ 9, ꢁ11 ꢅ k ꢅ 12,
ꢁ18 ꢅ l ꢅ 18
14884
3930 [Rint = 0.0353]
semi-empirical from
equivalents
0.9775 and 0.7844
0.22 ꢂ 0.18 ꢂ 0.12
1.87–28.34
ꢁ53 ꢅ h ꢅ 53, ꢁ15 ꢅ k ꢅ 15,
ꢁ25 ꢅ l ꢅ 25
71144
10271 [Rint = 0.0652]
numerical
Reflections collected
Independent reflections
Absorption correction
Maximum and minimum
transmission
0.4466 and 0.2434
Data/restraints/parameters
4209/7/254
1.071
4411/3/244
1.064
3930/8/254
1.056
10271/138/511
1.022
Goodness-of-fit (GOF) on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0439, wR2 = 0.1025
R1 = 0.0547, wR2 = 0.1081
0.433 and ꢁ0.621
R1 = 0.0322, wR2 = 0.0809
R1 = 0.0377, wR2 = 0.0833
0.926 and ꢁ0.532
R1 = 0.0583, wR2 = 0.1513
R1 = 0.0695, wR2 = 0.1588
1.256 and ꢁ1.156
R1 = 0.0349, wR2 = 0.0756
R1 = 0.0485, wR2 = 0.0809
1.940 and ꢁ1.680
Largest diff. peak and hole
(e Åꢁ3
)
the structures developed by the repeated cycles of full-matrix,
least-squares refinement followed by the calculation of a differ-
ence Fourier synthesis (SHELXL) [24]. In the case of 4, there are two
crystallographically independent molecules in the asymmetric unit
while for the others the asymmetric unit consists of a single mol-
ecule. In all four complexes, the bis(Schiff base) ligand is disor-
dered end-to-end in the ratios 68:32 (1), 57:43 (2), 56:44 (3) and
75:25 (4, each independent molecule). Because the ligand, with
the exception of the {N@C–S–CH2–CH@CH2} portion, is symmetri-
cal, there is no significant effect of the disorder on the extremities
but there are two separate locations of the S-allyl side-chain. This
disorder was modeled by refining two locations of the full {N@C–
S–CH2–CH@CH2} portion with restraints to make both components
of the disorder have approximately the same geometry and have
the sum of the occupancies of the two components be 1.0. All H-
atoms were included as riding contributions in idealized positions
with isotropic displacement parameters. For 3, trial refinements
with the full 2-component reflection file and with the 1-compo-
nent file for the major component extracted from the full data
set with TWINABS showed that the latter refinement was superior.
Calculations not noted above were performed with SHELXTL [25].
The crystal data and structural refinement parameters for com-
plexes are listed in Table 1.
The complexes 1 and 2 are the first examples of the family of
vanadium and manganese ‘‘Salits’’ complexes with the square
pyramidal structure for which the structures have been deter-
mined by X-ray crystallography (for Salits complexes as a whole,
2 is the second complex of manganese to be structurally character-
ized) so far.
All the complexes are soluble in common organic solvents such
as DMF, DMSO, chloroform, alcohols and are insoluble in water.
The molar conductance values show that 1, 3 and 4 behave essen-
tially as non-electrolytes in methanol, while 2 is a 1:1 electrolyte
which can be explained by the following reaction. Such a phenom-
enon has been reported previously [26].
½MnðSalitsÞBrꢄ þ MeOH ! ½MnðSalitsÞMeOHꢄþ þ Brꢁ
3.1. IR
The IR spectra of the complexes exhibit several prominent
bands in the 500–4000 cmꢁ1 region. Because the preparation of
the ligand and complexes is done in one step, we cannot make a
comparison between the IR spectra of the complexes and the cor-
responding ligand although the IR data for the H2L precursor can
provide a starting point for the interpretation of the spectra of
the complexes.
3. Results and discussion
The infrared absorptions at 3240 and 3100 cmꢁ1, which are
attributed to the OH and NH2 functional groups and are seen in sal-
icylaldehyde and H2L, are absent in the spectra of the complexes.
The complexes 1–4 were prepared via a straightforward tem-
plate method which involves the direct reactions of H2L, salicylal-
dehyde and the appropriate metal salt in a 1:1:1 M ratio in ethanol
or methanol as solvent. All the obtained structures were predict-
able except for that of 2 where the bromide ion of H2L became
coordinated to Mn, resulting in a metal oxidation number of +3.
The deletion of
C@N bonds demonstrate the condensation reaction of aldehyde
and thioamide in the presence of metal ion. Using the (C@N)
absorption band in H2L as a guide, we assign the two strong bands
at 1606–1603 and 1575–1573 cmꢁ1 to
(C@N) [27,28]. In addition,
v(OH) and v(NH2) peaks and the formation of
v
v

M. Ahmadi et al. / Polyhedron 42 (2012) 128–134
131
the medium intensity absorptions in the 1296–1288 cmꢁ1 region
were assigned to the v(Ar–O) vibration mode [18,29] and the in-
tense band in the region 1535–1527 cmꢁ1 is assigned to the C@C
vibration [30]. The 1427 cmꢁ1 band is assigned to the NCS stretch-
ing vibration [31], while the (U@O)asy and V@O frequencies appear
at 910 and 980 cmꢁ1, respectively [32,33].
3.2. UV–Vis absorption spectra of complexes
All the absorption spectra of the complexes in diluted methanol
solutions are listed in the experimental section. In the high-energy
region, below 300 nm, two absorption bands were detected which
are related to
tronic spectra of complexes show two intense bands which are
attributable to
p⁄ and n ? p⁄ transitions of the azomethine
p ?
p⁄ transitions of the phenyl rings [34]. The elec-
p
?
chromophore below 400 nm [28,35], while phenoxide-to-metal
ion charge-transfer transitions appear in the region 416–478 nm.
Complexes 1 and 3 show d–d transitions at 650 and 608 nm,
respectively, but the d–d transitions were not observed for the oth-
ers because they are covered by charge-transfer and intraligand
transition bands.
Fig. 1. Perspective view of 1. Displacement ellipsoids are drawn at the 50%
probability level and H-atoms are shown as spheres of arbitrary radius.
3.3. Thermogravimetric analysis
Thermogravimetric analysis (TGA) has been done to investigate
the physical behavior of the complexes and their thermograms are
presented in Supplementary material.
In complex 1 the TGA curve shows an initial 9.87% (Calc.
10.16%) weight loss, which is in a good agreement with the re-
moval of an allyl group, followed by the second loss in the 315–
427 °C range in which the sulfur atom of the ligand is separated
and results in 8.48% (Calc. 8.82%) decrease in weight. Eventually,
the remainder is decomposed to stable VO2 residue with a concom-
itant 76.59% (Calc. 76.57) weight loss relative to the initial
material.
Complex 2 decomposes in three endothermic steps which can
be seen on the DTA curve (20–244, 481–637 and 709–787 °C). In
the first step, it loses 8.90% (Calc. 8.77%) of its weight with the re-
moval of an allyl group. In the two other steps the bromide is elim-
inated at 481–637 °C with a weight loss of 18.61% (Calc. 18.55%).
Major mass losses occur at 709–787 °C attributed to decomposi-
tion to Mn2O3 with a weight loss of 81.25% (Calc. 83.28%) relative
to complex 2.
Fig. 2. Perspective view of 2. Displacement ellipsoids are drawn at the 50%
probability level and H-atoms are shown as spheres of arbitrary radius.
For the Fe complex, the TGA curve shows that the thermal
decomposition of the complex occurs within the temperature
ranges of 243–277 and 427–530 °C. The first step of gradual ther-
mal changes on the DTG curve is attributed to the removal of allyl
sulfide with a weight loss of 17.27% (Calc. 17.06%). The last DTG
peak, having a maximum at 488.8 °C, demonstrates a large weight
loss of about 61.33% (Calc. 61.9%) and it is due to rapid thermal
decomposition of the remainder to Fe3O4.
The TG/DTG curves of compound 4 indicates four thermal
decomposition steps at 171–215, 315–350, 470–542 and 646–
702 °C, respectively. The TG/DTG curves of compound 4 reveal a
prominent stability up to its melting point at 191 °C. At this point,
171–215 °C, the methanol molecules, and therefore, a 5% (Calc.
5.02%) reduction in its weight can be seen. In the second step, over
the 315–350 °C range (maximum 341 °C), the elimination of –
CH@N–C–S-allyl takes place which is revealed by a 18.68% (Calc.
18.49%) weight loss. The –O–Ph–CH@N–N– fragment is rapidly re-
moved in the third step, which is consistent with a 27.47% (Calc.
26.93%) decrease in weight at 470–542 °C. The last TGA peak, with
its maximum at 686 °C is attributable to the presence of U3O8 res-
idue [36].
Fig. 3. Perspective view of 3. Displacement ellipsoids are drawn at the 50%
probability level and H-atoms are shown as spheres of arbitrary radius.

132
M. Ahmadi et al. / Polyhedron 42 (2012) 128–134
Table 3
Bond lengths (Å) and angles (°) for 4.
U(1)–O(1)
U(1)–O(2)
U(1)–O(3)
U(1)–O(4)
U(1)–O(5)
U(1)–N(3)
U(1)–N(1)
1.775(4)
1.776(4)
2.238(4)
2.299(3)
2.395(4)
2.560(4)
2.566(4)
U(2)–O(6)
U(2)–O(7)
U(2)–O(8)
U(2)–O(9)
U(2)–O(10)
U(2)–N(4)
U(2)–N(6)
1.774(4)
1.776(4)
2.230(4)
2.296(4)
2.403(3)
2.555(5)
2.574(4)
O(1)–U(1)–O(2)
O(1)–U(1)–O(3)
O(2)–U(1)–O(3)
O(1)–U(1)–O(4)
O(2)–U(1)–O(4)
O(3)–U(1)–O(4)
O(1)–U(1)–O(5)
O(2)–U(1)–O(5)
O(3)–U(1)–O(5)
O(4)–U(1)–O(5)
O(1)–U(1)–N(3)
O(2)–U(1)–N(3)
O(3)–U(1)–N(3)
O(4)–U(1)–N(3)
O(5)–U(1)–N(3)
O(1)–U(1)–N(1)
O(2)–U(1)–N(1)
O(3)–U(1)–N(1)
O(4)–U(1)–N(1)
O(5)–U(1)–N(1)
N(3)–U(1)–N(1)
177.58(16)
91.50(15)
88.82(16)
85.84(15)
93.07(15)
160.99(13)
88.13(15)
89.56(15)
81.24(13)
79.85(13)
99.85(15)
81.78(15)
128.88(14)
70.05(13)
148.06(13)
83.10(15)
99.26(15)
70.41(14)
127.70(13)
150.01(14)
61.94(14)
O(6)–U(2)–O(7)
O(6)–U(2)–O(8)
O(7)–U(2)–O(8)
O(6)–U(2)–O(9)
O(7)–U(2)–O(9)
O(8)–U(2)–O(9)
O(6)–U(2)–O(10)
O(7)–U(2)–O(10)
O(8)–U(2)–O(10)
O(9)–U(2)–O(10)
O(6)–U(2)–N(4)
O(7)–U(2)–N(4)
O(8)–U(2)–N(4)
O(9)–U(2)–N(4)
O(10)–U(2)–N(4)
O(6)–U(2)–N(6)
O(7)–U(2)–N(6)
O(8)–U(2)–N(6)
O(9)–U(2)–N(6)
O(10)–U(2)–N(6)
N(4)–U(2)–N(6)
178.89(17)
88.70(18)
90.62(16)
94.94(17)
85.40(16)
159.83(14)
89.43(15)
89.60(15)
80.52(13)
79.69(13)
98.25(17)
82.34(16)
70.68(15)
128.04(15)
149.90(15)
82.81(16)
98.30(15)
130.20(15)
69.97(15)
147.79(15)
62.30(17)
Fig. 4. Perspective view of molecule 1 for 4. Displacement ellipsoids are drawn at
the 50% probability level and H-atoms are shown as spheres of arbitrary radius.
3.4. X-ray crystal structures
formed and have co-crystallized since the N@C–S-allyl portion is
disordered over two sites in varying amounts in all three com-
plexes. In the case of 4 two co-crystallized isomers must still be
present from the observed positional disorder in the S-allyl group.
Similar results have previously been seen with related complexes
[8,14]. Only the major isomer is shown in Figs. 1–4. The structures
of 1–3 are all very similar with the coordination sphere being a
slightly distorted square pyramid having the tetradentate ligand
in the basal plane. The ligand geometries vary relatively little
among 1–3 as well among several close analogues (Table 4). The
principal distortions of the coordination sphere from ideal square
Perspective views of complexes 1–4 are presented in Figs. 1–4,
respectively, while relevant bond distances and interbond angles
for 1–3 are listed in Table 2 and those for 4 are given in Table 3. Pri-
marily because of the S-allyl side-chain, the ligand is unsymmetri-
cal overall, but since the backbone structure and particularly the
four donor atoms are essentially symmetrical, there is no preferred
orientation of the ligand with respect to the metal as the template
reaction forms it. Consequently, with the presence of the fifth li-
gand in the final complex in 1–3 to provide a ‘‘top/bottom’’ (or
‘‘left/right’’) reference point, two isomers are possible (Scheme
2). It appears from the X-ray results that both isomers have been
Table 2
Bond lengths (Å) and angles (°) for 1–3.
1
2
3
V(1)–O(3)
V(1)–O(2)
V(1)–N(3)
V(1)–N(1)
V(1)–O(1)
C(1)–O(2)
C(1)–C(6)
C(6)–C(7)
C(7)–N(1)
N(1)–C(8)
C(8)–N(2)
N(2)–N(3)
N(3)–C(9)
C(9)–C(10)
C(10)–C(15)
1.9265(16)
1.9404(16)
2.0519(19)
2.0625(19)
1.5968(18)
1.315(3)
1.427(3)
1.419(3)
1.305(3)
1.459(5)
1.290(4)
1.371(5)
1.310(3)
Mn(1)–O(2)
Mn(1)–O(1)
Mn(1)–N(3)
Mn(1)–N(1)
Mn(1)–Br(1)
C(1)–O(1)
C(1)–C(6)
1.8690(16)
1.8773(16)
1.9735(19)
1.9810(19)
2.5324(6)
1.321(3)
1.427(3)
1.419(3)
1.314(3)
1.467(8)
1.280(6)
1.357(7)
1.301(3)
1.435(3)
1.424(3)
Fe(1)–O(2)
Fe(1)–O(1)
Fe(1)–N(3)
Fe(1)–N(1)
Fe(1)–Cl(1)
C(1)–O(1)
C(1)–C(6)
C(6)–C(7)
C(7)–N(1)
N(1)–C(8)
C(8)–N(2)
N(2)–N(3)
N(3)–C(9)
N(3)–C(9)
C(10)–C(15)
1.886(3)
1.889(3)
2.091(3)
2.106(3)
2.2482(11)
1.312(4)
1.429(5)
1.428(5)
1.305(5)
1.473(12)
1.274(10)
1.354(9)
1.298(5)
1.429(5)
1.430(5)
C(6)–C(7)
C(7)–N(1)
N(1)–C(8)
C(8)–N(2)
N(2)–N(3)
N(3)–C(9)
C(9)–C(10)
C(10)–C(15)
1.420(3)
1.432(3)
O(3)–V(1)–O(2)
O(3)–V(1)–N(3)
O(2)–V(1)–N(3)
O(3)–V(1)–N(1)
O(2)–V(1)–N(1)
N(3)–V(1)–N(1)
O(1)–V(1)–O(3)
O(1)–V(1)–O(2)
O(1)–V(1)–N(3)
O(1)–V(1)–N(1)
89.83(7)
86.95(7)
145.70(8)
141.52(8)
87.10(7)
74.80(8)
109.76(8)
109.20(9)
104.00(9)
107.43(8)
O(2)–Mn(1)–O(1)
O(2)–Mn(1)–N(3)
O(1)–Mn(1)–N(3)
O(2)–Mn(1)–N(1)
O(1)–Mn(1)–N(1)
N(3)–Mn(1)–N(1)
O(2)–Mn(1)–Br(1)
O(1)–Mn(1)–Br(1)
N(3)–Mn(1)–Br(1)
N(1)–Mn(1)–Br(1)
92.82(7)
91.30(7)
160.57(8)
161.08(8)
91.65(8)
78.73(8)
101.27(6)
101.16(6)
96.53(6)
95.97(6)
O(2)–Fe(1)–O(1)
O(2)–Fe(1)–N(3)
O(1)–Fe(1)–N(3)
O(2)–Fe(1)–N(1)
O(1)–Fe(1)–N(1)
N(3)–Fe(1)–N(1)
O(2)–Fe(1)–Cl(1)
O(1)–Fe(1)–Cl(1)
N(3)–Fe(1)–Cl(1)
N(1)–Fe(1)–Cl(1)
96.78(11)
86.60(11)
148.53(12)
145.33(12)
86.61(11)
73.79(12)
107.43(9)
107.34(9)
101.33(9)
104.33(8)

M. Ahmadi et al. / Polyhedron 42 (2012) 128–134
133
S
N
O
R
R
S
N
O
N
C
C
N
HC
N
O
L
CH
L
N
O
CH
CH
M
M
a
b
Scheme 2. The two co-crystallized isomers of 1–3.
Table 4
Comparison of Chelated ligand geometries (Å).a
a
b
c
d
e
f
g
h
i
j
k
l
m
1
1.9404(16)
1.8690(16)
1.867(5)
1.889(3)
1.894(4)
1.905(4)
1.903(4)
2.238(4)
2.230(4)
2.278(4)e
2.263(3)f
1.315(3)
1.321(3)
1.318b
1.312(4)
1.31(1)
1.308(7)
1.316(7)
1.344(4)
1.335(5)
1.322(7)
1.297(6)
1.419(3)
1.419(3)
1.426b
1.428(5)
1.41(1)
1.416(9)
1.409(9)
1.447(6)
1.430(7)
1.431(9)
1.438(8)
1.305(3)
1.314(3)
1.315b
1.305(5)
1.31(1)
1.299(8)
1.300(8)
1.302(7)
1.301(8)
1.312(8)
1.287(7)
2.0625(19)
1.9737(19)
1.995(7)
2.106(3)
2.101(4)
2.106(5)
2.103(5)
2.566(4)
2.555(5)
2.575(5)
2.596(4)
1.459(5)
1.400(3)
1.392b
1.473(12) 1.27(1)
1.40(1)
1.386(7)
1.394(7)
1.410(12)
1.499(9)
1.395(8)
1.415(7)
1.290(4)
1.315(4)
1.329b
1.371(5)
1.403(3)
1.403b
1.354(9)
1.40(1)
1.393(7)
1.407(7)
1.402(9)
1.338(8)
1.427(8)
1.403(6)
1.310(3)
1.300(3)
1.308b
1.298(5)
1.30(1)
1.301(8)
1.317(8)
1.297(7)
1.302(8)
1.292(8)
1.294(6)
1.420(3)
1.435(3)
1.428b
1.429(5)
1.43(1)
1.408(9)
1.429(9)
1.461(6)
1.436(8)
1.434(9)
1.429(8)
1.314(3)
1.320(3)
1.327b
1.311(4)
1.34(1)
1.319(7)
1.317(7)
1.344(4)
1.345(5)
1.305(7)
1.337(5)
1.9265(16)
1.8773(16)
1.893(6)
1.886(3)
1.875(4)
1.922(4)
1.919(4)
2.299(3)
2.296(4)
2.251(4)
2.274(3)
2.0519(18)
1.9806(19)
1.983(7)
2.091(3)
2.084(5)
2.101(5)
2.097(5)
2.560(4)
2.574(4)
2.548(5)
2.549(4)
2
b
c
20
3
30
1.30(1)
1.314(8)
1.300(8)
1.28(1)
1.26(1)
1.277(9)
1272(7)
d
300
4
40
a
b
c
d
e
f
See Fig. 5 for key to column headings.
CCDC entry FEBCEU (Ref. [12]), M = MnCl(MeOH), R = Me, su’s on light atom distances = 0.012.
CCDC entry BOZCEY (Ref. [8]), M = FeCl, R = Me.
CCDC entry CAWCIM (Ref. [9]), M = OFe(L4), R = Me.
CCDC entry EKEWUN (Ref. [13]), M = UO2(n-nonylOH), R = n-Pr, triclinic form.
CCDC entry EKEXAU (Ref. [13]), M = UO2(n-nonylOH), R = n-Pr, monoclinic form.
Table 5
Conformational angles (°) for 1–3.a
Fold of
ring
1along
Oaꢀ ꢀ ꢀNa
Fold of
ring
2along
Naꢀ ꢀ ꢀNb
Fold of
ring
3along
Obꢀ ꢀ ꢀNb
Angle between
mean planes of
phenyl rings
Distance of
metal from
N2O2 plane
(Å)
1
12.83(5)
11.3(4)
<1
12.4(1)
17.8
17.5(2)
10.1(2)
6.3
15.5(5)
14.7
19.3(1)
9.47(9)
<1
18.0(2)
18.7
18.7(1)
5.0(1)
10.7
12.9(2)
4.0
0.606(1)
0.297(1)
0.15
0.524(2)
0.53
2
b
c
20
3
30
d
300
15.8
17.2
24.7
9.9
0.61
Fig. 5. Schematic of 1–3 as a key to the quantities in Tables 4 and 5.
19.6
18.3
18.7
7.3
0.61
a
b
c
See Fig. 5 for key to column headings.
CCDC entry FEBCEU (Ref. [12]), M = MnCl(MeOH), R = Me.
CCDC entry BOZCEY (Ref. [8]), M = FeCl, R = Me.
pyramidal geometry are the small N1–M–N3 (M = V, Mn, Fe) angle
resulted from geometric constraints of the ligand backbone and the
displacement of the metal from the basal plane towards the axial
ligand. The three chelate rings are not coplanar with the metal
but each of the rings is folded about a line joining its two donor
atoms as depicted by the dashed lines in Fig. 5. These fold angles
in 1–3 together with the angles between the mean planes of the
phenyl rings and the displacement of the metal from the basal
plane are presented in Table 5 with corresponding data for several
related complexes. In the 5-coordinate complexes, there is a rough
correlation between both the extent of displacement of the metal
from the N2O2 plane and the folding of the chelate rings and the
length of the bond to the axial ligand with the displacement in
the order X = O > Cl > Br. Addition of a sixth ligand to the metal
substantially reduces the displacement and folding distortions as
the bonding to the metal in the axial directions becomes more
equalized (e.g. chlorido(methanol)(S-methyl-N1,N4-bis(salicylid-
ene)isothiosemicarbazidato)manganese(III) [12] (Table 5) and
thiocyanato(pyridine)(S-methyl-N1,N4-bis(salicylidene)isothiosemi-
carbazidato)iron(III) [11] (no distortion)).
d
CCDC entry CAWCIM (Ref. [9]), M = OFe(L4), R = Me (su’s unavailable for these
values).
There are two independent molecules of 4 in the asymmetric
unit and these primarily differ in the orientation of the allyl group
with respect to the ligand backbone. As is evident from Fig. 4, the
uranium is 7-coordinate but the geometry of the coordination
sphere departs markedly from the expected pentagonal bipyramid.
If we take the plane defined by U1, O5, N1 and N3 as the ‘‘equa-
torial’’ plane, the axis of the nearly linear O1–U1–O2 unitis mark-
edly inclined to it as depicted in Fig. 6. Thus the dihedral angle
between the mean planes defined by U1, O5, N1 and N3 and by
U1, O3, O4 and O5 is 19.4(2)° and the corresponding angle in mol-
ecule 2 is 18.3(2)°. The phenolic portions of the ligand adopt a pro-
peller-like conformation with dihedral angles of 35.8(2)° and
37.6(3)°, respectively, for molecules 1 and 2. Similar distortions
are seen in uranyl complexes of the S-methyl analogue of the li-

134
M. Ahmadi et al. / Polyhedron 42 (2012) 128–134
Fig. 6. View of 4 with the U1, O5, N1, N3 plane horizontal and showing the twist of the coordination about uranium.
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gand employed here as well as ones with the S-propyl side chain
plus two chlorine substituents on one of the aromatic rings. These
range from large (20.8°) to small (6.5°) dihedral angles between
the phenyl rings [13,37]. The distortions are likely, in part, to
accommodate larger radius of uranium as compared with the first
row transition elements and the resulting longer metal–donor
atom distances in 4 without putting significant strain on the back-
bone of the ligand. Molecule 1 (containing U1) forms pair-wise H-
bonds with molecule 2 (containing U2) at x, y ꢁ 1, z (H5Oꢀ ꢀ ꢀO9 (at
x, y ꢁ 1, z) = 1.71 Å, O5–H5Oꢀ ꢀ ꢀO9 = 162°; O4ꢀ ꢀ ꢀH10O (at x, y ꢁ 1,
z) = 1.77 Å, O4ꢀ ꢀ ꢀH10O–O10 = 150° while molecule 2 forms the cor-
responding H-bonds with molecule 1 at x, y + 1, z.
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4. Conclusion
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In this study, we presented the synthesis and characterization
of four new complexes of the novel ligand N1,N4-bis(salicylid-
ene)-S-allyl-thiosemicarbazone (Salits). The spectral and X-ray
studies show that this ligand behaves as a dinegative tetradentate
N2O2 chelate in the presence of metal ions. In 1–3, a fifth coordina-
tion site is occupied by oxygen, bromide and chloride atoms,
respectively. This results in a distorted square pyramidal geometry.
For complex 4, in addition to Salits, two oxygen atoms and a
methanol molecule were coordinated to uranium(VI), giving rise
to a considerably distorted pentagonal bipyramid geometry. The
TG analyses of 1–4 show that they are decomposed at above ca.
190 °C, and finally give a metal oxide residue.
Ülküseven, Dalton Trans. 39 (2010) 10228.
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´
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Acknowledgements
We would like to thank the Tulane University Chemistry
Department for support of the Tulane Crystallography Laboratory;
and the Ferdowsi University of Mashhad and Payame Noor Univer-
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Appendix A. Supplementary data
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CCDC 832353–832356 contain the supplementary crystallo-
graphic data for 1–4. 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, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.poly.2012.05.004. TGA and derivative of TGA curves of
complexes are given as Supplementary publication.
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