New thiocyanato iron(II) complex with 3,5-bis(3-pyridyl)-1,2,4-thiadiazole: Synthesis, structure, magnetic and spectral properties

Article abstract of DOI:10.1016/j.ica.2014.01.032

The new iron(II) complex [Fe(NCS)₂(CH₃OH) ₂(bpta)₂] (bpta = 3,5-bis(3-pyridyl)-1,2,4-thiadiazole) has been prepared by refluxing Fe(NCS)₃ or Fe(NCS)₂ with thionicotinamide in methanol solution. It is supposed that the bpta ligand is generated in situ by the oxidative dimerization of thionicotinamide. The complex was characterized by X-ray structural analysis at 150 and 293 K, elemental analysis, spectral and magnetic measurements. The compound crystallizes in the monoclinic P2₁ space group, with unit cell parameters at 293 K: a = 7.869(2), b = 17.056(3), c = 12.637(3) ?, β = 102.88(1). The crystal structure analysis showed that the iron atom has a distorted octahedral environment with FeN₄O₂ chromophore. Iron atom is coordinated by two nitrogen atoms from NCS^- ions, by two oxygen atoms from methanol molecules in the equatorial plane and by two nitrogen atoms of pyridine rings from dpta ligands in axial positions. The crystal lattice forms 2D supramolecular network which is stabilized by a system of hydrogen bonds and π-π stacking interactions. Variable-temperature magnetic susceptibility data in the temperature range 1.8-300 K show that the octahedral iron(II) is high-spin S = 2(⁵T_2g) and as a result effects due to zero-field splitting are anticipated at low temperatures. Structural parameters and infrared spectra of similar complexes are compared and discussed.

Full text of DOI:10.1016/j.ica.2014.01.032

Inorganica Chimica Acta 414 (2014) 33–38
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
New thiocyanato iron(II) complex with 3,5-bis(3-pyridyl)-
1,2,4-thiadiazole: Synthesis, structure, magnetic and
spectral properties
Róbert Uhreck y´ a, , Iveta Ondrejkovi cˇ ová , Darina Lacková , Zuzana Fáberová , Jerzy Mrozi n´ ski ,
⇑
a
a
a
b
b
c
a
Bo z_ ena Kali n´ ska , Zde nˇ ka Pad eˇ lková , Marian Koman
a
Institute of Inorganic Chemistry, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia
Faculty of Chemistry, University of Wrocław, F. Joliot-Curie 14, 50-383 Wrocław, Poland
Department of General and Inorganic Chemistry, University of Pardubice, 532 10 Pardubice, Czech Republic
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 May 2013
Received in revised form 22 January 2014
Accepted 23 January 2014
Available online 31 January 2014
The new iron(II) complex [Fe(NCS) (CH OH) (bpta) ] (bpta = 3,5-bis(3-pyridyl)-1,2,4-thiadiazole) has
2
3
2
2
been prepared by refluxing Fe(NCS)
3
or Fe(NCS)
2
with thionicotinamide in methanol solution. It is
supposed that the bpta ligand is generated in situ by the oxidative dimerization of thionicotinamide.
The complex was characterized by X-ray structural analysis at 150 and 293 K, elemental analysis, spectral
and magnetic measurements. The compound crystallizes in the monoclinic P2
1
space group, with unit cell
parameters at 293 K: a = 7.869(2), b = 17.056(3), c = 12.637(3) Å, b = 102.88(1)°. The crystal structure
Keywords:
Iron(II) complex
Thiocyanate complex
analysis showed that the iron atom has a distorted octahedral environment with FeN
4
O
2
chromophore.
ꢀ
Iron atom is coordinated by two nitrogen atoms from NCS ions, by two oxygen atoms from methanol
molecules in the equatorial plane and by two nitrogen atoms of pyridine rings from dpta ligands in axial
positions. The crystal lattice forms 2D supramolecular network which is stabilized by a system of hydro-
3
,5-Bis(3-pyridyl)-1,2,4-thiadiazole
Crystal structure
Infrared spectra
Magnetic properties
gen bonds and
p–p stacking interactions. Variable-temperature magnetic susceptibility data in the
5
temperature range 1.8–300 K show that the octahedral iron(II) is high-spin S = 2( T2g) and as a result
effects due to zero-field splitting are anticipated at low temperatures. Structural parameters and infrared
spectra of similar complexes are compared and discussed.
Ó 2014 Elsevier B.V. All rights reserved.
1
. Introduction
Thiadiazoles constitute an important class of five membered
Recently we reviewed the structural data of 83 metal complexes
with bis(n-pyridyl)-thiadiazoles (n = 2, 3 or 4) and analyzed their
coordination modes [12]. Thiadiazoles act as mono- to tetra-den-
tate ligands without involving the sulfur atom. The ligands have
four potential donor sites, viz. two N atoms of the pyridine rings
and two N atoms of the thiadiazole ring. The most numerous group
form complexes with 2,5-bis(n-pyridyl)-1,3,4-thiadiazoles (81
examples). There are 50 examples of 4-pyridyl, 26 examples of 2-
pyridyl and 5 with 3-pyridyl derivatives. There are only four iron
complexes with 2,5-bis(2-pyridyl)-1,3,4-thiadiazole (L) of the com-
nitrogen-sulfur heterocycles exhibiting a large variety of biological
activities [1,2]. Moreover, the derivatives of thiadiazoles and
their metal complexes have attracted increasing attention because
of their potential applications in pharmaceutical, agricultural,
industrial, coordination and polymer chemistry [3–11].
Thiadiazoles with two substituted pyridyl groups, i.e. bis(n-pyr-
idyl)-thiadiazoles (n = 2, 3 or 4) occur in different isomeric forms
such as 4,5-bis(n-pyridyl)-1,2,3-thiadiazoles, 3,5-bis(n-pyridyl)-
2 2 4 3
position [Fe(L) (X) ] (X = NCS, NCSe, B(CN) , NCBH ) [4,5]. The
1
,2,4-thiadiazoles, 2,5-bis(n-pyridyl)-1,3,4-thiadiazoles and 3,4-
bidentate thiadiazole ligands L are coordinated to the Fe(II) atom
forming five membered chelate rings. There are known also two
complexes with 3,4-bis(2-pyridyl)-1,2,5-thiadiazole [6]. According
to our best knowledge, complexes with 4,5-bis(n-pyridyl)-1,2,3-
thiadiazoles and 3,5-bis(n-pyridyl)-1,2,4-thiadiazoles have not
yet been characterized by X-ray structural analysis [12].
bis(n-pyridyl)-1,2,5-thiadiazoles. In the literature there is much
information on the 1,3,4-thiadiazole derivatives and their
coordination compounds.
This paper is a continuation of our previously reported studies
on iron complexes with pyridine derivatives [13–16]. During
⇑
Corresponding author. Tel.: +421 2593 25 184; fax: +421 2524 93 198.
E-mail address: robert.uhrecky@stuba.sk (R. Uhreck y´ ).
http://dx.doi.org/10.1016/j.ica.2014.01.032
020-1693/Ó 2014 Elsevier B.V. All rights reserved.
0

3
4
R. Uhreck y´ et al. / Inorganica Chimica Acta 414 (2014) 33–38
attempts to prepare iron(III) complexes with thionicotinamide,
there was observed reduction of Fe(III) to Fe(II) and formation of
the title complex. Herein, we report the syntheses, crystal and
molecular structure, magnetic and spectral properties of the
17.68; Fe, 7.79%; found (method B): C, 46.20; H, 3.37; N, 19.22;
S, 17.74; Fe, 7.79%.
The title compound has been also obtained from the reaction
mixtures containing a (2–6): 1 M mix of thionicotinamide and
Fe(II) complex, [Fe(NCS)
-bis(3-pyridyl)-1,2,4-thiadiazole. The compound has been
prepared by the reaction of FeCl O and KSCN with thionicoti-
ꢁ6H
namide in methanol and also when was used FeCl O instead
ꢁ4H
of FeCl O. This complex represents the first example of metal
ꢁ6H
complex with the 1,2,4-thiadiazole ligand.
2
(CH
3
OH)
2
(bpta)
2
]
where bpta is 3,
3
Fe(NCS) in methanol.
5
3
2
2.3. Single-crystal X-ray diffraction measurements
2
2
3
2
Intensity data for [Fe(NCS)
method were obtained using Oxford Cryostream low-
temperature device on a Nonius Kappa CCD diffractometer with
graphite-monochromated Mo radiation (k = 0.71073 Å) at
50 K. Absorption correction was applied using the program SADABS
18]. Data reductions were performed with EvalCCD [19]. Intensity
data for the same compound at 293 K were collected using a
Siemens P4 diffractometer with graphite monochromated Mo K
2 3 2 2
(CH OH) (bpta) ] prepared by
A
2
. Experimental
.1. Materials and general methods
All the chemicals and solvents were purchased commercially
K
a
1
[
2
a
and used without further purification. Elemental analysis (C, H, N
and S) was carried out by means of a Flash EA 1112 analyzer.
The contain of Fe was determined spectrophotometrically with
radiation [20]. The diffraction intensities were corrected for
Lorentz and polarization effects with XSCANS [21]. Absorption cor-
rection was applied using the program XEMP [21]. The structures
were solved by direct methods using the program SIR-2011 [22]
and refined by the full-matrix least-squares method on all F data
using the program SHELXL-2013 [23]. Geometrical analysis was per-
formed using SHELXL-2013. The structures were drawn by ORTEP-3
1
,10-phenanthroline. The presence of gaseous sulfane released
during the reaction was proven with Pb(NO . The infrared spec-
3 2
)
2
ꢀ1
trum (4000–100 cm ) was measured by solid-state KBr technique
and recorded on Nicolet 5700 FTIR spectrophotometer.
EPR spectra were recorded at room temperature and 77 K on a
Bruker Elexsys E 500 spectrometer operating at the X-band
equipped with an NMR teslameter (ER 036TM) and frequency
counter (E 41 FC).Variable-temperature magnetic measurements
of polycrystalline sample were carried out with a Quantum Design
SQUID magnetometer (MPMSXL-5-type) at a magnetic field of
[
24] and Mercury [25] software. The single crystal suite WINGX
was used as integrated system for all crystallographic programs
and software for preparing the material for publication [26].
All non-hydrogen atoms of the title compound were refined
anisotropically as independent atoms. Hydrogen atoms were
calculated into idealized positions. Crystal data and conditions of
data collection and refinement are reported in Table 1, bonds
lengths and bonds angles are reported in Table 2 and hydrogen
bonds parameters are reported in Table 3.
0
.5 T over the temperature range 1.8–300 K. Corrections are based
on subtracting the sample-holder signal and contribution Dia
corrections for iron(II) compound estimated from Pascal
v
ꢀ6
3
ꢀ1
constants [17] and equal ꢀ394 ꢂ 10 cm mol . The effective
Discrete positional disorder of the thiadiazole ring [C10A, C11A,
N5A, N6A, S3A] and [C10B, C11B, N5B, N6B, S3B] is observed in the
title compound with site occupancy factor of 0.760(6) and
magnetic moment was calculated from the equation leff
¼
1=2
2
:83ðvMTÞ ðB:M:Þ. Magnetization versus magnetic field measure-
ments were carried out at 2 K in the magnetic field range 0–5 T.
0
.240(6) for (1), and 0.603(5) and 0.397(5) for (2). The sulfur atom
of thiocyanate group [N1, C1, S1A] and [N1, C1, S1B] is localized in
two positions with site occupancy factor of 0.83(2) and 0.17(2) for
2.2. Synthesis of the complex
(
1), and 0.74(1) and 0.26(1) for (2). Results of measurements
at 293 K showed that carbon atom of methanol molecule
C3A, C3B] is also localized in two positions with site occupancy
The title compound was prepared by two similar ways differing
by using starting iron compound. Firstly was used FeCl
method A) and in the second case was used FeCl O (method
ꢁ4H
B).
3 2
ꢁ6H O
[
(
2
2
factor of 0.18(7) and 0.82(7), respectively. All disordered groups
were restrained using SADI and EADP commands of SHELXL-2013
program.
2
.2.1. Method A
Solid thionicotinamide (0.276 g, 2.0 mmol) was added into a
solution of Fe(NCS)3, under stirring, which was prepared from
KSCN (0.145 g, 1.5 mmol) and FeCl O (0.135 g, 0.5 mmol) in
3
. Results and discussion
3
ꢁ6H
2
methanol (50 ml). The reaction mixture was refluxed for 2 h. Then
the mixture was chilled and the insoluble KCl formed during the
reaction was filtered off. The dark-red filtrate was allowed to stand
at room temperature. After a few days, well-formed orange crystals
of the title compound, suitable for X-ray analysis, were obtained.
Yield: 0.614 g; 85.6 %.
3
.1. Synthesis
The title iron(II) complex has been prepared by two ways; by a
reaction of thionicotinamide with of Fe(NCS)
Fe(NCS) (method B) in methanol. It is believed that the bpta ligand
is generated in situ by the oxidative dimerization of thionicotina-
mide (Scheme 1) and then is coordinated to Fe(II). In the first case
3
(method A) or
2
2
.2.2. Method B
(method A) during the reaction iron(III) atom is reduced to iron(II).
ꢀ
Solid thionicotinamide (0.276 g, 2.0 mmol) was added to a
We suppose that there can be oxidized NCS anion to (SCN)
2
[27].
solution of Fe(NCS)2, under stirring, which was prepared from
KSCN (0.097 g, 1.0 mmol) and FeCl O (0.100 g, 0.5 mmol) in
methanol (50 ml). The reaction mixture was refluxed for 2 h. Then
the mixture was chilled and the insoluble KCl was filtered off. The
orange filtrate was allowed to stand at room temperature. Orange
crystals were obtained by similar way as by method A.
The quantity of (SCN)
tion would have been too small to observe. Also, any (SCN)
duced would have undergone hydrolysis [27]. Simultaneously
can also take place oxidation of methanol to methanal [28].
2
that would have been produced in the reac-
pro-
2
ꢁ4H
2
2
2
Formed gaseous H S was detected by smell and by a reaction with
Pb(NO , too. Oxidative dimerization of thioamides (including
3 2
)
Anal. Calc. for C28
7.90; Fe, 7.79. Found (method A): C, 46.07; H, 3.27; N, 19.17; S,
H
24
N
10
O
2
S
4
Fe: C, 46.93; H, 3.35; N, 19.54; S,
thionicotinamide) is one of methods for preparation of 3,5-disub-
stituted 1,2,4-thiadiazoles [10,29,30].
1

R. Uhreck y´ et al. / Inorganica Chimica Acta 414 (2014) 33–38
35
Table 1
The crystal data, X-ray measurements and structure determination summary for
Fe(NCS) (CH OH) (bpta) ] at 150 and 293 K.
Table 3
2 3 2 2
Selected hydrogen-bond parameters for [Fe(NCS) (CH OH) (bpta) ].
[
2
3
2
2
D–H ꢁꢁꢁA
50 K
D–H (Å)
Hꢁ ꢁ ꢁA (Å)
Dꢁ ꢁ ꢁA (Å)
D–Hꢁ ꢁ ꢁA (°)
1
50 K
293 K
1
i
i
Chemical formula
Formula weight
Crystal color, habit
C
28
H
24
N
10
O
2
S
4
Fe
O1S–H1Sꢁ ꢁ ꢁN10
0.84
0.84
1.90
1.91
2.731 (7)
2.721 (6)
170
162
ii
716.66
dark orange, needle
O2S–H2Sꢁ ꢁ ꢁN7
2
93 K
Crystal system, space group monoclinic, P2
1
O1S–H1Sꢁ ꢁ ꢁN10
0.82
0.82
1.95
1.94
2.759 (7)
2.751 (7)
171
170
a (Å)
b (Å)
c (Å)
b (°)
7.749(2)
16.780(3)
12.534(3)
102.36(3)
1592.0(6)
2
7.869(2)
17.056(3)
12.637(3)
102.88(1)
1653.4(6)
2
ii
O2S–H2Sꢁ ꢁ ꢁN7
Symmetry code(s): (i) x + 1, y, z + 1; (ii) x ꢀ 1, y, z ꢀ 1.
3
V (Å )
Z
D
calc (g cm 3
ꢀ
)
1.495
1.440
S
N
Radiation type
Mo K
0.78
a
Mo K
0.75
0.52 ꢂ 0.31 ꢂ 0.26
a
ꢀ
1
l
(mm
)
N
NH2
+
H2S
2
Crystal size (mm)
Diffractometer
Absorption correction
0.47 ꢂ 0.28 ꢂ 0.23
N
Bruker-Nonius KappaCCD Siemens P4
N
S
multi-scan, SADABS
0.710, 0.841
1.03
0.060
0.051, 0.078
6013
W-scan, XEMP
0.696, 0.829
1.02
0.068
0.049, 0.114
3657
N
Tmin, Tmax
S
Scheme 1. Formation of bpta by oxidative dimerization of thionicotinamide.
R
R
int
[F2 > 2
r
(F )], wR
2
(F )
2
1
2
No. of reflections
No. of parameters
No. of restraints
n(II) atom is six coordinated by two nitrogen atoms from two thio-
cyanate anions and two oxygen atoms from methanol molecules in
the equatorial plane, and two nitrogen atoms of pyridine rings
from two bpta ligands in the axial positions. The data indicate that
all the Fe–N and Fe–O distances are in the range 2.089(6)–
429
21
432
23
D
i
max
,
D
i
min (e Åꢀ3)
0.32, ꢀ0.30
0.26, ꢀ0.32
CCDC No.
889109
889110
2
.273(5) Å, typical for high-spin iron(II) compounds. However,
Fe–N(bpta) distances are longer than the Fe–N(NCS) and Fe–O(CH3-
OH) distances where Fe–N(NCS) = 2.095(5) and 2.089(6) Å for (1);
Table 2
Selected geometric parameters (Å, °) for [Fe(NCS)
2
(CH
3
OH)
2
(bpta)
2
].
Fe–N(NCS) = 2.105(6) and 2.110(6) Å for (2); (Fe–O(CH
OH) = 2.124(5) and 2.117(5) Å for (1); Fe–O(CH OH) = 2.166(5)
3
1
50 K
293 K
3
Bonds
Fe1–N1
and 2.122(5) Å for (2); (Fe–N(bpta) = 2.226(6) and 2.242(5) Å for
(1); Fe–N(bpta) = 2.273(5) and 2.257(6) Å for (2). These bond
2.095 (5)
2.105 (6)
Fe1–N2
Fe1–N3
Fe1–N4
Fe1–O1S
Fe1–O2S
2.089 (6)
2.226 (6)
2.242 (5)
2.124 (5)
2.117 (5)
2.110 (6)
2.273 (5)
2.257 (6)
2.166 (5)
2.122 (5)
distances are comparable with those reported for [Fe(4-acpy)
2
2
2
(
(
H
2
O)
bipy)(CH
(H
2
(NCS)
OH)
O)
2
]
(4-acpy = 4-acetylpyridine)
[31],
{[Fe(NCS)
0
3
2
]ꢁbipy}
n
(bipy = 4,4 -bipyridine) [32] and [Fe(NCS)
(3-bpo)
2
2
2
] (3-bpo = 2,5-di-3-pyridyl-1,3,4-oxadiazole) [33].
The thiocyanate anions, bpta and methanol molecules are coordi-
nated to iron(II) in a monodentate terminal mode in mutually
trans-position. The undisordered thiocyanate anions [N2, C2, S2]
are almost linear with the angles of 178.5(6)° for (1) and
Angles
N1–Fe1–N2
N1–Fe1–N3
N1–Fe1–N4
N1–Fe1–O1S
N1–Fe1–O2S
N2–Fe1–N3
N2–Fe1–N4
N2–Fe1–O1S
N2–Fe1–O2S
N3–Fe1–N4
N3–Fe1–O1S
N3–Fe1–O2S
N4–Fe1–O1S
N4–Fe1–O2S
O1S–Fe1–O2S
N1–C1–S1(A);(B)
N2–C2–S2
178.7 (3)
89.7 (2)
90.0 (2)
90.9 (2)
88.7 (2)
90.4 (2)
89.9 (2)
87.8 (2)
92.5 (2)
178.7 (2)
87.8 (2)
90.5 (2)
91.0 (2)
90.8 (2)
178.2 (2)
178.5 (3)
89.4 (2)
89.9 (2)
90.8 (2)
89.2 (2)
89.9 (2)
90.7 (2)
87.9 (2)
92.1 (2)
178.6 (2)
87.4 (2)
91.0 (2)
91.4 (2)
90.2 (2)
178.4 (2)
172.5 (8); 158 (1)
178.9 (6)
1
78.9(6)° for (2). Disordered thiocyanate anions are deviated from
the linear alignment with values of angles in the range from
160(1)° to 173.9(7)° at 150 K and 158(1)° to 172.5(8)° at 293 K.
In the title complex the uncoordinated nitrogen atoms of pyridine
rings from bpta ligands and hydrogen atoms from the methanol
molecules are joined through O1S–H1Sꢁ ꢁ ꢁN10 and O2S–H2Sꢁ ꢁ ꢁN7
hydrogen bonds [length d(Dꢁ ꢁ ꢁA) and angle <(D–Hꢁ ꢁ ꢁA) vary from
2
2
.721(6) to 2.731(7) Å and 162–170° for (1), and 2.751(7) to
.759(7) Å and 170–171° for (2)] into 1D polymeric chain
(
Fig. 2A, Table 3). Moreover, the thiadiazole rings of the bpta li-
gands [N5, N6, C10, C11, S3; N8, N9, C22, C23, S4] are involved
in the face-to-face aromatic stacking interactions with the cen-
troid to centroid distance of 3.489 Å (Fig. 2B) for (1) and 3.579 Å for
2). Furthermore, these 1D chains are stacked parallel to form a 2D
173.9 (7); 160 (1)
178.5 (6)
p-p
(
Formation of the title complex from Fe(NCS)
B) can be described by following equation:
2
and tnia (method
sheet through the inter-chain aromatic interaction between the
thiadiazole rings. Therefore, in the complex the hydrogen bonds
FeðNCSÞ þ 4 tnia þ 2CH
3
OH ! ½FeðNCSÞ ðCH
3
OHÞ ðbptaÞ ꢃ
and
p–p stacking interactions play an influential role in expanding
2
2
2
2
the mononuclear units to 2D supramolecular network (Fig. 2C).
2
þ 2H S
3.3. Magnetic properties
3.2. Structure description
The magnetic properties of the title complex prepared by meth-
The complex [Fe(NCS)
monoclinic system with space group P2
of the neutral mononuclear complex is displayed in Fig. 1. The iro-
2
(CH
3
OH)
2
(bpta)
2
] crystallizes in the
od A were determined over the temperature range 1.8–300 K. Plots
ꢀ
1
1
. The molecular structure
of magnetic susceptibility of
Fig. 3.
v
M
and the
v
M
versus T are given in

3
6
R. Uhreck y´ et al. / Inorganica Chimica Acta 414 (2014) 33–38
2 3 2 2
Fig. 1. ORTEP structure of the [Fe(NCS) (CH OH) (bpta) ], at 150 K showing 50% probability ellipsoids. Hydrogen atoms are omitted for clarity.
Fig. 2. (A) A view of the 1D chains of [Fe(NCS)
Schematic representation of stacking interactions (green lines) in [Fe(NCS)
Fe(NCS) (CH OH) (bpta) ] showing 2D supramolecular network. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of
this article.)
2
(CH
3
OH)
2
(bpta)
2
] formed by N–Hꢁ ꢁ ꢁO hydrogen bonds (blue lines). Irrelevant hydrogen atoms are omitted for clarity. (B)
p–p
2
(CH OH) (bpta) ]. Hydrogen atoms are omitted for clarity. (C) Packing diagram along b axis in
3
2
2
[
2
3
2
2
The variation of the magnetization (M) versus magnetic field (H)
at temperature 2 K indicates a linear variation up to M = 0.7 T and
then relations agree with Brillouin function up to M = 2.72 B.M. at
M
complex.The decrease of the value of v T in the lowest tempera-
ture range is caused by occurrence of zero-field splitting parameter
D and weak antiferromagnetic coupling between Fe(II) centers.
5
5
T (Fig. 4).
High-spin octahedral Fe(II) (S = 2) posses a
T2g ground state and
The value of effective magnetic moment at room temperature is
as a result due to zero-field splitting are anticipated at low temper-
equal to 5.38 B.M. and it is higher than the predicted value 4.90
B.M. for S = 2 as usually observed for high-spin iron(II) complexes.
atures [34]. The parameter D was determined by fitting Eq. (1)
2
(using the Hamiltonian, H ¼ DS þ gbHS) to the magnetic data
z
The value of
M
v T product is stable up to 50 K and its lowering is
[35,36]:
observed at the lowest temperatures. The more evident decrease in
3
ꢀ1
2
ꢀD=T
ꢀ4D=T
2g2k
ꢀD=T
ꢀ4D=T
its value, reaching
M
v T = 2.37 cm mol K and
l
eff = 4.36 B.M. at
6g ðe
þ 4e
þ 2e
Þ
B
Tð18 ꢀ 14e
ꢀ 4e
Þ
2
l
¼
þ
ð1Þ
ꢀ
D=T
ꢀ4D=T
ꢀD=T
ꢀ4D=T
1
.8 K.
1 þ 2e
Dð1 þ 2e
þ 2e
Þ
The values of the Curie and Weiss constants determinated from
ꢀ
1
the relation
v
M
= f(T) over the temperature range 1.8–300 K are
where D = zero field splitting parameter (ZFS), g = spectroscopic
splitting factor and k = Boltzmann’s constant.
3
ꢀ1
equal to C = 3.66 cm mol
K
and
H
= ꢀ0.98 K for iron(II)

R. Uhreck y´ et al. / Inorganica Chimica Acta 414 (2014) 33–38
37
1
1
1
0
0
0
0
0
,4
,2
,0
,8
,6
,4
,2
,0
T = 293 K
= 9.757 GHz
8
0
g1
ν
g
2
g
4
60
g
3
4
2
0
0
0
T = 77 K
= 9.591 GHz
ν
g
1
g
4
0
50
100
150
T(K)
200
250
300
g
2
g
3
Mꢀ
1
Fig. 3. Experimental magnetic data plotted as
v
M
(s) and
v
(d) vs. T for the title
0
1000
2000
3000
4000
5000
complex [Fe(NCS)
2
3
(CH OH)
2
(bpta)
2
]. Solid line concern theoretical relation
ꢀ
1
H (G)
v
M
= f(T).
Fig. 5. EPR spectra of [Fe(NCS) (CH OH) (bpta) ] at solid state.
2
3 2 2
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi,sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
4
3
2
1
0
X
n
1
À
Á
X
n
1
exp
i
calc
i
2
R ¼
À
Á
v
ꢀ
v
À
Á
exp
2
i¼1
i¼1
exp
i
v
i
v
The g values in excess of 2.0 are expected for Fe(II) ion as a re-
5
3
sult of the T2g electronic state and the value of D is well within the
range expected for six-coordinate high-spin Fe(II) complexes.
2
T = 2K
1
0
3
.4. EPR and IR spectra
0
1
2
3
4
5
EPR spectra of the iron complex were taken at room and liquid
nitrogen temperatures indicated few weak lines (Table 4 and
Fig. 5).
H (Tesla)
0
50
100
150
200
250
300
The infrared spectrum for the title compound shows typical
bands for N-bonded thiocyanate complexes [14,38]. It is evident
T(K)
ꢀ1
from two peaks at 2053(s) and 816(m) cm which are allotted to
Fig. 4. Experimental magnetic data plotted as
Fe(NCS) (CH OH) (bpta) ]. Solid line concerns the best fit parameters. The inset
showing variation of the magnetization M vs. the magnetic field H for investigated
complex (d) and continuous line corresponds to Brillouin function for an isolated
S = 2 with g = 2.0.
M
v T (s) vs. T for the title complex
ꢀ1
[
2
3
2
2
m
(C–N) and
uted to the stretch
bands of bpta (
m(C–S) vibrations. The peak at 478(w) cm is attrib-
m
(NCS). The spectrum shows also characteristic
ꢀ1
m
max/cm : 1595(s), 1590(sh), 1477(m), 1400(s),
1
339(s), 1302(m), 1035(s) and 729(s)) which are very close to the
published data for free bpta [29]. The presence of methanol mole-
cules in the complex can be indicated by bands at 1102(w) and
ꢀ
1
ꢀ1
ꢀ1
ꢀ1
1
047(m) cm
(CH )), 1453(m) and 1410(m) cm (d
infrared area are important stretches; (Fe–N) (N is from pyridine
ring) exhibits peak at 255 cm and stretch (Fe–N) (N is from
(
m
(C–O)), 2775(w) cm
(
m
d
(O–H)), 3040(m) cm
Table 4
(m
a
3
(CH )) [38]. In the far
3
EPR data at solid state of [Fe(NCS)
2 3 2 2
(CH OH) (bpta) ].
m
ꢀ1
Temperature (K) Factors g
m
ꢀ
1
2
7
93
7
g
g
1
= 4.50
= 4.20
g
g
2
2
= 3.32
= 3.26
g
g
3
3
= 2.78
= 3.11
g
g
4
4
= 2.06
= 2.11
NCS group) exhibits sharp peak at 295 cm . Band assigned to
(Fe–O) is observed at 410 cm [14,16].
ꢀ1
1
m
4
. Conclusion
The magnetic data was fitted with a molecular field correction
Eq. (2) [37]:
We have successfully prepared first metal complex with
,5-bis(3-pyridyl)-1,2,4-thiadiazole ligand by two ways. It is inter-
esting that the thiadiazole ligand is formed in situ by the oxidative
dimerization of thionicotinamide. The X-ray structural analysis
3
v
corr
M
M
v
¼
0
ð2Þ
2zJ
1
ꢀ Ng
ꢁ vM
2l
2
B
shows that the system of N–Hꢁ ꢁ ꢁO hydrogen bonds and
p–p
where
v
M
is molar magnetic susceptibility of Fe(II) center, N = Avo-
= Bohr magneton, zJ’ = intermolecular exchange
parameter and z is the number of nearest neighbor Fe(II) centers.
stacking interactions stabilized crystal lattice to 2D supramolecu-
lar network. Measurements at two different temperatures showed
small changes in the lattice parameters. Variable-temperature
magnetic susceptibility data in the temperature range 1.8–300 K
gadro’s number,
l
B
ꢀ
1
ꢀ1
The best fit parameters are D = 3.19 cm , zJ’ = ꢀ0.04 cm and
5
g = 2.47, as indicated by the solid curve in Fig. 4. The agreement
show that the octahedral iron(II) is high-spin S = 2 ( T2g) and as a
ꢀ4
factor R is equal R = 3.47 ꢂ 10
.
result effects due to zero-field splitting are anticipated at low
temperatures. The molecular structure is in good agreement with
the observed infrared spectra.
The criterion used in determination of the best fit was based on
minimalization of the sum squares of the deviation:

3
8
R. Uhreck y´ et al. / Inorganica Chimica Acta 414 (2014) 33–38
[
[
13] A. Fargašová, I. Ondrejkovi cˇ ová, Z. Kramarová, Z. Fáberová, Bioresour. Technol.
01 (2010) 6410.
14] I. Ondrejkovi cˇ ová, S. Galková, J. Mrozi n´ ski, J. Kłak, T. Lis, Z. Olejnik, Inorg. Chim.
Acknowledgements
1
This work was supported by the Slovak Grant Agency (VEGA 1/
Acta 361 (2008) 2483.
ˇová, M. Wrzecion, M. Nahorska, J. Mrozi n´ ski, Polish J. Chem. 83
0
056/13 and APVV-0014-11) and by the National Science Centre
[15] I. Ondrejkovic
2009) 1547.
(
(
Poland) under grant No 2011/01/B/ST5/01624.
[
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Appendix A. Supplementary material
18] G.M. Sheldrick, SADABS, Bruker AXS Inc., Madison, Wisconsin, USA, 2003.
CCDC 889109–889110 contain the crystallographic data for title
complex at two different temperatures. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.ica.2014.01.032.
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