Solid-state transformation of [Co(NCS)2(pyridine)4] into [Co(NCS)2(pyridine)2]n: From Curie-Weiss paramagnetism to single chain magnetic behaviour

Article abstract of DOI:10.1039/c0dt00904k

Reaction of Co(NCS)₂ with pyridine (pyr) in aqueous solution at room temperature leads to the formation of the pyridine-rich 1:4 compound of composition [Co(NCS)₂(pyridine)₄] (1) reported recently. On heating, the pyridine-rich 1:4 compound transforms into its corresponding pyridine-deficient 1:2 compound of composition [Co(NCS)₂(pyridine) ₂]_n (2), which decomposes on further heating. In the crystal structure of compound 2 the metal cations are coordinated by four N-atoms of two pyridine ligands and two N-bonded thiocyanato anions, each in mutually trans orientation, and by two S-atoms of two adjacent thiocyanato anions in a slightly distorted octahedral geometry. The thiocyanato anions bridge the metal cations forming one-dimensional polymeric chains. IR spectroscopic investigations on the pyridine-deficient 1:2 compound prepared in thermal decomposition are in accordance with bridging thiocyanato anions. Magnetic measurements of the pyridine-rich 1:4 compound and pyridine-deficient 1:2 compound reveal different behaviour with Curie-Weiss paramagnetism for compound 1 and single chain magnetic behaviour for compound 2, with a Mydosh-parameter φ = 0.12 and an effective energy barrier (-U _eff/k_B) of 62.5 K for the spin relaxation. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/c0dt00904k

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www.rsc.org/dalton | Dalton Transactions
Solid-state transformation of [Co(NCS)2(pyridine)4] into
[Co(NCS)2(pyridine)2]n: from Curie–Weiss paramagnetism to single chain
magnetic behaviour†
Jan Boeckmann and Christian Na¨ther*
Received 23rd July 2010, Accepted 10th September 2010
DOI: 10.1039/c0dt00904k
Reaction of Co(NCS)2 with pyridine (pyr) in aqueous solution at room temperature leads to the
formation of the pyridine-rich 1 : 4 compound of composition [Co(NCS)2(pyridine)4] (1) reported
recently. On heating, the pyridine-rich 1 : 4 compound transforms into its corresponding
pyridine-deficient 1 : 2 compound of composition [Co(NCS)2(pyridine)2]n (2), which decomposes on
further heating. In the crystal structure of compound 2 the metal cations are coordinated by four
N-atoms of two pyridine ligands and two N-bonded thiocyanato anions, each in mutually trans
orientation, and by two S-atoms of two adjacent thiocyanato anions in a slightly distorted octahedral
geometry. The thiocyanato anions bridge the metal cations forming one-dimensional polymeric chains.
IR spectroscopic investigations on the pyridine-deficient 1 : 2 compound prepared in thermal
decomposition are in accordance with bridging thiocyanato anions. Magnetic measurements of the
pyridine-rich 1 : 4 compound and pyridine-deficient 1 : 2 compound reveal different behaviour with
Curie–Weiss paramagnetism for compound 1 and single chain magnetic behaviour for compound 2,
with a Mydosh-parameter j = 0.12 and an effective energy barrier (-Ueff/kB) of 62.5 K for the spin
relaxation.
correlations, the enlightenment of the fundamental physical origin
of the SCMs and their possible auspicious future application
Introduction
as high-density storage materials or molecular electronics,6 the
systematic investigations, rational design and synthesis of such
magnetic chain compounds received increasing importance.7,8
These compounds are in general built up of inorganic MXn
substructures (M = paramagnetic metal; X = e.g. SCN-, CN-,
Recently, the design, synthesis and enlightenment of new co-
ordination polymers, inorganic–organic hybrid compounds or
metal–organic frameworks have gained increasing interest.1 The
combination of pure inorganic coordination compounds and
organic spacer ligands resulted in new functional materials like
energy storage, gasholder, catalyst and photochemical or magnetic
switchable materials.2 In this context, an interesting class of
magnetic systems represents the single molecule magnets (SMMs).
They show superparamagnetic behaviour below a blocking tem-
perature TB and slow relaxation of the magnetization.3 Single
molecule magnets represent zero-dimensional (0D) compounds,
where the magnetic coupling is mediated through superexchange
interactions. A related class of compounds represents magnetic
one-dimensional (1D) polymeric coordination compounds with
slow relaxation of the magnetization and magnetic hysteretic be-
haviour at low temperatures, called single chain magnets (SCMs).
This behaviour was observed for the first time by Caneschi et al.,4
in a compound that contained 1D cobalt(II)-nitronyl nitroxide
chains, and a theoretical model for the occurrence of SCMs was
first introduced by Glauber, based on Ising spin chains.5 Due to
the promising opportunities for exploration of magneto-structural
-
N3 ) which are further coordinated by monodentate ligands which
separate the chains.8
Recently we have investigated the potential of thermal decom-
position reactions of ligand-rich (ligand-rich = rich in neutral
coligands) precursor compounds for the directed synthesis of
multidimensional coordination polymers. In further investigations
we have successfully expanded this approach for the rational
design of coordination polymers with cooperative magnetic
exchange interactions.9,10 In these precursors the metal centres
are octahedrally coordinated by neutral coligands and small-
sized anions that are only terminal bonded and therefore cannot
be involved in magnetic exchange interactions. On heating, the
neutral coligands are stepwise removed and the anions become
bridging and therefore can mediate magnetic exchange inter-
actions. Within this project we have prepared a large amount
of compounds based on e.g. thiocyanates, selenocyanates or
formates that show ferro- or antiferromagnetism.9,10 Most of
these precursor compounds contain bridging coligands like e.g.
pyrazine, 4,4¢-bipyridine or pyrimidine that directly lead to the
formation of 2D coordination networks. Based on these results it
can be assumed that substitution of such spacers by monodentate
coligands can lead to the formation of chains as ligand-deficient
(ligand-deficient = lacking neutral coligands) intermediates that
can show single chain magnetic behaviour. Suitable candidates
are represented by discrete complexes of composition [MX2L4]
Institut fu¨r Anorganische Chemie Universita¨t zu Kiel, Max-Eyth-Straße
2, 24098, Kiel, Germany. E-mail: cnaether@ac.uni-kiel.de; Fax: +49-431-
8801520; Tel: +49-431-8802092
† Electronic supplementary information (ESI) available: Experimental and
calculated X-ray powder pattern for compound [Co(NCS)2(pyridine)4]
(1), IR-spectra of compounds [Co(NCS)2(pyridine)4] (1) and
[Co(NCS)2(pyridine)2]n (2) and plots of in-phase cM¢ and out-of-
phase cM¢¢ AC magnetic susceptibility as a function of frequency for 2.
CCDC reference number 793741. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt00904k
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in which the metal centres are octahedrally coordinated by two
terminal anions and four terminal coligands. Examples for such
discrete complexes are represented by e.g. the literature known
compounds of composition [M(NCS)2(pyridine)4] (M = Co (1),
Fe, Mn, Ni),11–13 which are easily accessible and therefore are
promising precursor compounds to check our approach. In this
context it is mentioned that the structures of the corresponding
compounds of composition [M(NCS)2(pyridine)2]n (M = Cu,
Co, Ni)13–15 are already described in the literature, so that the
thermal decomposition products can be easily identified. Because
several compounds based on cobalt show single chain magnetic
behaviour,7,8,16,17 we have investigated [Co(NCS)2(pyridine)4] in the
beginning. However, these investigations should also show if the
pyridine-deficient intermediates can be isolated during the solid-
state process or if all pyridine ligands are removed in one step.
Here we report on the results of these investigations.
32.20%]. The DTG curve shows that both events are well separated
(Fig. 1).
Based on the experimental mass losses, it can be assumed
that the pyridine-deficient 1 : 2 compound of composition
[Co(NCS)2(pyridine)2]n (2) is formed in the first step. On further
heating, the remaining pyridine ligands are removed to give
Co(NCS)2, which decomposes on further heating. A similar
thermal behaviour is found for several pyridine-type complexes
of transition metal halides.18
In order to verify the nature of the intermediate formed,
additional TG measurements were performed and stopped after
the first TG step. Elemental analysis of the residue obtained
yielded a composition of [Co(NCS)2(pyridine)2]n (see Experi-
mental section). Single crystals of compound 2 were obtained
from solution and the crystal structure was determined (see
below). Additional XRPD investigations on the residue obtained
in thermal decomposition of compound 1 clearly show that its
powder pattern is in perfect agreement with that calculated for 2
from single crystal data (Fig. 2).
Results and discussion
Thermoanalytical investigations
On heating the pyridine-rich 1 : 4 compound [Co(NCS)2-
(pyridine)4] (1) in a thermobalance to 350 ◦C, two mass steps
are observed in the TG curve, which are accompanied with
endothermic events in the DTA curve (Fig. 1). The MS trend scan
curve shows that only the pyridine ligand (m/z = 79) is lost during
these steps (Fig. 1). The experimental mass losses in the first step
of Dmexp.(1st step) = 31.66% and in the second step of Dmexp.(2nd
step) = 31.77% are in good agreement with that calculated for the
loss of two pyridine molecules in each step [Dmcalcd.(-2 pyridine) =
Fig. 2 Experimental XRPD pattern of the residue 2 obtained in the first
TG step in the thermal decomposition reaction of compound 1 and XRPD
pattern calculated from single crystal data for compound 2.
Structural investigations
The crystal structure of [Co(NCS)2(pyridine)2]n has already been
described in the literature and refined in the centrosymmetric mon-
oclinic space group C2/m with two formula units in the unit cell.13
Surprisingly the calculated powder pattern based on this structure
shows significant differences to that of the residue obtained
by thermal decomposition, indicating a different modification.
Interestingly [Cu(NCS)2(pyridine)2]n and [Ni(NCS)2(pyridine)2]n
¯
crystallizes in the centrosymmetric triclinic space group P1with
three formula units in the unit cell.14,15 However, a detailed
structure investigation on compound 2 shows the occurrence of
super structure reflections, leading to a transformation of the
monoclinic unit cell with Z = 2 into the triclinic unit cell with
Z = 3. Thus, compound 2 is isotypic to [Cu(NCS)2(pyridine)2]n
and [Ni(NCS)2(pyridine)2]n. The asymmetric unit consists of two
crystallographically independent metal cations, of which one is
Fig. 1 DTG, TG, DTA and MS trend scan curves of compound
[Co(NCS)2(pyridine)4] (1). Heating rate = 4 ◦C min-1; m/z = 79 (pyridine);
given are the mass changes [%] and the peak temperatures TP [◦C].
11020 | Dalton Trans., 2010, 39, 11019–11026
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◦
˚
Table 1 Selected bond lengths [A] and angles [ ] for the ligand-deficient
located on a centre of inversion, as well as of three thiocyanato
anions and of three pyridine ligands in general positions.
In the crystal structure the metal cations are coordinated by four
N-atoms of two pyridine ligands and two N-bonded thiocyanato
anions, each in mutually trans orientation, and by two S-atoms of
two adjacent thiocyanato anions in a slightly distorted octahedral
geometry (Fig. 3). The thiocyanato anions bridge the metal cations
forming one-dimensional polymeric chains (Fig. 4).
1 : 2 compound
[Co(NCS)2(pyridine)2]n
Co(1)–Co(2)
Co(1)–S(1)
Co(1)–N(2)
Co(1)–N(31)
S(1)–Co(1)–S(1I)
N(2)–Co(1)–S(1)
N(2)–Co(1)–S(1I)
N(2)–Co(1)–N(2I)
N(2)–Co(1)–N(31)
N(2)–Co(1)–N(31I)
N(31)–Co(1)–S(1)
N(31)–Co(1)–S(1I)
N(31)–Co(1)–N(31I)
Co(2)–S(2)
5.6399(14)
2.6199(12)
2.062(4)
2.177(4)
180.0
93.42(10)
86.58(10)
180.0
88.30(16)
91.70(16)
90.81(12)
89.19(12)
180.0
2.6043(13)
2.063(4)
2.062(4)
2.169(4)
2.169(4)
178.17(4)
179.17(13)
88.02(15)
89.67(16)
94.68(11)
87.15(11)
89.57(11)
90.43(11)
177.67(14)
89.98(10)
90.10(10)
Co(2)–N(1)
Co(2)–N(3II)
Co(2)–N(11)
Co(2)–N(21)
S(2)–Co(2)–S(3)
N(3II)–Co(2)–N(1)
N(3II)–Co(2)–N(11)
N(3II)–Co(2)–N(21)
N(3II)–Co(2)–S(3)
N(3II)–Co(2)–S(2)
N(11)–Co(2)–S(2)
N(11)–Co(2)–S(3)
N(11)–Co(2)–N(21)
N(21)–Co(2)–S(2)
N(21)–Co(2)–S(3)
Fig. 3 Crystal structure of [Co(NCS)2(pyridine)2]n (2) with view of the
coordination sphere of the metal cations with labelling and displacement
ellipsoids drawn at the 50% probability level. Symmetry codes: I = -x +
1,-y + 1,-z + 1; II = -x + 2,-y + 2, -z + 2. The disordered pyridine rings
are omitted for clarity.
The different coordination modes of the thiocyanato anions
can also be distinguished by their vibrational spectra.10,12–14,21 For
terminal N-bonded thiocyanato anions the very strong stretching
vibration n(CN) is observed < 2100 cm-1, whereas for bridging
thiocyanato anions n(CN) is found ≥ 2100 cm-1. These results are
in full agreement with IR-spectroscopic investigations, in which for
compound 1 n(CN) is found at 2073 cm-1, whereas for compound
2 n(CN) is observed at 2099 cm-1.
Magnetic investigations
In [Co(NCS)2(pyridine)4] (1) the metal centres are not bridged by
the anions, whereas in [Co(NCS)2(pyridine)2]n (2) the Co atoms
are linked by only 3 atoms of the thiocyanato anions, which
might enable cooperative magnetic phenomena. To investigate the
differences in the magnetic properties of 1 and 2 the temperature
dependence of the magnetic susceptibility was investigated apply-
ing a magnetic field of H = 0.1 T in the temperature range of 300–
2 K. It has to be mentioned that for compound 1 meff has already
been measured at selected temperatures by Hunter et al.24 and
Figgis et al.25 but it was reinvestigated by us for better comparison
of the magnetic behavior of compound 1 and 2.
For the pyridine-rich 1 : 4 compound [Co(NCS)2(pyridine)4] (1)
only Curie–Weiss paramagnetism is found with a Weiss constant
q = -18.4 K (Table 2) (Fig. 5). However, the Weiss constant is
unavoidably overestimated on the negative side for a mononuclear
octahedral Co(II) complex, due to zero-field splitting and similar
magnetic behaviour is found in different mononuclear octahedral
Co(II) complexes.22 The effective magnetic moment meff for com-
pound 1 of 5.30 mB is larger than the spin-only value for a high
spin Co2+ ion (3.87 mB, S = 3/2, g = 2.00) (Table 2). However, it is
Fig. 4 Packing diagram of [Co(NCS)2(pyridine)2]n (2) with view onto the
polymeric chains (aqua = Co, blue = N, yellow = S, grey = C, light-grey =
H).
˚
˚
The Co–N distances ranges from 2.06 A to 2.18 A and the M–S
˚
˚
distances are between 2.60 A and 2.62 A (Table 1). The intra-chain
metal to metal separation through the thiocyanato anions range
˚
˚
between 5.62 A and 5.64 A. The latter vary in the literature from
19
20
˚
˚
4.98 A to 6.17 A.
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Fig. 5 Results of the magnetic measurements by plots of paramagnetic susceptibility and reciprocal paramagnetic susceptibility (left; red solid line = fit
to the Curie–Weiss law) and cMT (right) as a function of temperature for the pyridine-rich 1 : 4 compound [Co(NCS)2(pyridine)4] (1).
Fig. 6 Results of the magnetic measurements for compound [Co(NCS)2(pyridine)2]n (2) by plots of paramagnetic susceptibility as a function of
temperature (A), zero-field-cooled (ZFC, at H = 0.1 T) and field-cooled (FC, at H = 0.1 T) paramagnetic susceptibility as a function of temperature (B),
cMT as function of temperature (C), and hysteresis loop at 2 K in the range of 0.3 T.
well documented that for cobalt g-values strongly deviating from
2.00 yield greater effective magnetic moments.23
For the pyridine-deficient 1 : 2 compound [Co(NCS)2-
(pyridine)2]n (2) the cM vs. T curve clearly shows weak ferromag-
netic behaviour (Fig. 6A). Fitting the magnetic data according to
the Curie–Weiss law cM = C/(T - q) yielding a negative Weiss
positive Weiss constant can be expected. In the temperature range
of 300–50 K the cMT values decrease upon cooling indicating
antiferromagnetic interactions, and below 50 K the curve passes
a sharp maximum at T = 3.8 K suggesting a transition to
the ferromagnetic state (Fig. 6C). Further hints of the presence
of ferromagnetic behaviour are provided by the magnetization
saturation experiments performed at T = 2 K up to 0.3 T,
(Fig. 6D).
constant of q = -2.73 K and an effective magnetic moment meff
=
5.65 mB for compound 2 (Table 2). However, it must be kept in
mind that besides the ferromagnetic interactions also zero-field
splitting is involved and therefore, without the latter effects a
Surprisingly, alternating current (AC) susceptibility measure-
ments (Fig. 7A and B) showed that both the cM¢ and cM¢¢ (in-phase
11022 | Dalton Trans., 2010, 39, 11019–11026
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Table 2 Results of the fit of the magnetic susceptibility data with the
Curie–Weiss law
Table 3 Frequency dependence of the maximum AC susceptibility
temperature
[Co(NCS)2(pyridine)4]
[Co(NCS)2(pyridine)2]n
f [Hz]
T (cM¢) [K]
T (cM¢¢) [K]
C/cm3 K mol-1
q/K
meff (exp)/mB
meff (calc)23/mB
Ordering state/K
Fit/K
3.51
-18.4
5.30
3.87
—
3.98
-2.7
5.65
3.87
TB = 3.8
35–300
10
50
250
500
1000
2500
3.60
3.75
4.00
4.10
4.20
4.25
2.74
2.96
3.19
3.31
3.44
3.62
48–300
and out-of-phase) curves exhibit broad and frequency-dependent
peak maxima in the range between 2 K and 6 K. This is a typical
behaviour for single chain magnets and a similar AC behaviour
has been found in other magnetic Co chain compounds.7,8,16,17 The
shift of the frequency dependent maxima (Table 3) is measured
by the Mydosh-parameter j = (DTP/TP)/D(logf ) = 0.12, which
is close to the value for a superparamagnet (0.1 < j < 0.3) and
two orders larger than that for a canonical spin glass.8,16,26 Thus, a
frustrated spin glass system can be excluded.
In the case of a single chain magnet, a thermally activated
Orbach process can be assumed and the magnetization relax-
ation times (t) are obtained from the relationship wt = 1 at the
maxima of the cM¢¢ vs. T curves. Fitting the experimental data
according to the Arrhenius law t = t0 ¥ exp[-Ueff/kBT]; where t is
the relaxation time, Ueff is the effective anisotropy energy barrier,
kB is the Boltzmann constant, and T is the temperature, yields
an effective energy barrier for -Ueff/kB of 62.5 K and t0 = 2.02 ¥
10-12 s (Fig. 7C).
These values are in very good agreement with previously
reported values for single chain magnet (SCM) and single molecule
magnet (SMM) systems.8,27 To further support the SCM behaviour
the isothermal frequency dependence of cM¢ and cM¢¢ at 3.5 K
was analysed in order to investigate the distribution of the
relaxation times. For a single chain magnet a narrow distribution
is expected. The cM¢ vs. n and the cM¢¢ vs. n plot (see Fig. S4 in
the ESI†) show that the cM¢ values are decreasing with increasing
frequency and the cM¢¢ values are increasing, reaching a maximum
around 650 Hz and decrease again with increasing frequency. The
Cole–Cole plot of cM¢¢ vs. cM¢ can be fitted to a general Debye
model (eqn (1))28 in the 50–10000 Hz range (Fig. 7D), leading
Fig. 7 Temperature dependence of in-phase cM¢ (A) and out-of-phase cM¢¢ (B) AC magnetic susceptibility (Hac = 10 Oe; 10/50/250/500/1000/2500 Hz),
Arrhenius-plot of relaxation rate as a function of reciprocal temperature for compound 2 (C), and cM¢¢ as a function of cM¢ at 3.5 K, known as a Cole–Cole
plot (D).
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Table 4 Selected crystal data and details on the structure determination
from single-crystal data for compound 2
to a maximum in the Cole–Cole plot at an resonance frequency
of 650 Hz and an a value of 0.09 indicating a relative narrow
distribution of the relaxation time. Please note: 0 < a < 1; a = 0
indicates an infinitely narrow distribution of t; a = 1 indicates a
wide distribution of t.
Formula
C12H10CoN4S2
333.29
MW/g mol-1
Crystal system
Space group
Triclinic
¯
P1
˚
a/A
8.5816(13)
8.6752(12)
15.520(2)
92.700(17)
96.254(17)
114.754
1037.5(3)
170
1/ 2
2
⎡
⎢
⎢
⎢
⎢
⎤
⎥
⎥
⎥
⎥
⎡
⎢
⎢
⎢
⎢
⎢
⎤
⎥
˚
b/A
2
2
˚
⎡
⎤
⎥
⎥
⎡
⎤
⎥
⎥
c/A
c0 −cS
c0 −cS
2
c0 +cS
2
′′
′
⎥
′
⎢
⎢
a/◦
b/◦
g /◦
c (c )=−
−
− c −
⎡
⎤ ⎢
⎥
⎦
⎤⎥
⎥⎥
⎥⎥
⎢
p
⎢⎣
⎣
⎦ ⎥
⎥
⎢
⎥
⎢
⎥
2tan (1−a)
⎢
⎢
⎣
2
⎣
⎦
⎦
⎢
⎦
⎥
⎦
⎣
3
˚
V/A
T/K
Z
(1)
3
calc/g cm-3
1.600
1.532
25.00
7776
Eqn (1) shows a fit to the general Debye model with isothermal
(c0) and adiabatic (cS) susceptibilities. Note that in the relevant
part of the diagram eqn (1) represents a circular arc of size (1 -
a)p cutting the c¢ axis at c¢ = cS and c¢ = c0.28
D
m/mm-1
max/deg
q
Measured reflns.
Unique reflns.
Reflns. [F0 > 4s(F0)]
Parameter
3632
2173
310
Rint
0.0707
0.0552
0.1652
1.027
Experimental section
a
R1 [F0 > 4s(F0)]
b
wR2 [all data]
GOF
Drmax, Drmin/e A
Synthesis
-3
˚
0.722, -0.784
Co(NCS)2·H2O was obtained from Alfa Aesar, KNCS was
obtained from Sigma–Aldrich, and pyridine was obtained from
Riedel-de Hae¨n. Solvents were used without further purification.
Crystalline powders of compounds 1 and 2 were prepared by
stirring the reactants in appropriate solvents at room temperature.
The residues were filtered off and washed with ethanol and diethyl
ether and dried in air. The purity of all compounds was checked
by X-ray powder diffraction and elemental analysis.
ꢀ
ꢀ
ꢀ
ꢀ
1
2
a R1 = ꢀF0| - |Fcꢀ/ |F0|. b wR2 = [ [w(F0 - Fc2)2]/ [w(F0 ) ]] .
2
2 2
Single-crystal structure analysis
Data measurement was performed with an imaging plate diffrac-
tion system (IPDS-1) with Mo-Ka-radiation from STOE &
CIE. The structure solution was done with direct methods using
SHELXS-97 and structure refinements were performed against F2
using SHELXL-97.29 All non-hydrogen atoms were refined with
anisotropic displacement parameters. All hydrogen atoms were
positioned with idealized geometry and were refined with fixed
isotropic displacement parameters [Ueq(H) = -1.2Ueq(C)] using
Synthesis of [tetrakis(pyridine-jN)-bis(thiocyanato-jN)-
cobalt(II)] (1)
Co(NCS)2·H2O (193.1 mg, 1.00 mmol) and pyridine (632.8 mg,
8.00 mmol) reacted in water (2.00 mL) to give 1 (228.6 mg, 47%)
as a pink crystalline solid (Found: C, 54.0; H, 4.1; N, 17.3; S, 13.4.
Calc. for C22H20CoN6S2: C, 53.8; H, 4.1; N, 17.1; S, 13.1%). IR
˚
a riding model with dC–H = 0.95 A for aromatic H atoms. In 2
the pyridine ligands are disordered and were refined using a split
model. Details of the structure determinations are given in Table 4.
n
max/cm-1 2073 s, 1599 s, 1572 w, 1486 m, 1442 s, 1355 w, 1212 m,
X-Ray powder diffraction (XRPD)
1147 w, 1069 m, 1038 m, 1006 m, 801 w, 766 m, 756 m, 712 s, 700 s,
625 m, 482 w, 431 w, 422 w.
XRPD experiments were performed using a PANalytical X¢Pert
Pro MPD Reflection Powder Diffraction System with Cu-Ka-
radiation (l = 154.0598 pm) equipped with a PIXcel semicon-
ductor detector from PANalytical.
Synthesis of catena-poly[bis(pyridine-jN)-
bis(thiocyanato-jN,jS)-cobalt(II)] (2)
This compound was isolated in the first heating step (see the
Thermoanalytic investigations section in the Results and discus-
sion) of compound 1. It can also be prepared by the reaction
of Co(NCS)2·H2O (579.3 mg, 3.00 mmol) and pyridine (79.1 mg,
1.00 mmol) in water (2.00 mL) to give 2 (158.8 mg, 48%) as a purple
crystalline solid (Found: C, 43.2; H, 2.9; N, 16.5; S, 19.4. Calc. for
C12H10CoN4S2: C, 43.2; H, 3.0; N, 16.8; S, 19.3%). Single crystals
suitable for X-ray structure determination were prepared by the
reaction of Co(NCS)2·H2O (0.50 mmol, 96.60 mg) with pyridine
(0.25 mmol, 20.20 mL) in 1.00 mL ethanol at RT in a closed 3 mL
snap cap vial. After 1 day, purple well-shaped single crystals were
obtained in a mixture with unknown phases. IR nmax/cm-1 2099 s,
1601 m, 1487 w, 1442 m, 1216 w, 1071 w, 1040 w, 1010 w, 755 w,
696 m, 629 w, 475 w, 426 w.
Differential thermal analysis, thermogravimetry, and mass
spectroscopy (DTA-TG-MS)
The DTA-TG measurements were performed in a nitrogen at-
mosphere (purity: 5.0) in Al2O3 crucibles using a STA-409CD
instrument from Netzsch. The DTA-TG-MS measurements were
performed with the same instrument, which is connected to a
quadrupole mass spectrometer from Balzers via Skimmer coupling
from Netzsch. The MS measurements were performed in trend
scan mode in Al2O3 crucibles in a dynamic nitrogen atmosphere
(purity: 5.0) using heating rates of 4 ◦C min-1. All measurements
were performed with a flow rate of 75 mL min-1 and were corrected
for buoyancy and current effects. The instrument was calibrated
using standard reference materials.
11024 | Dalton Trans., 2010, 39, 11019–11026
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Elemental analysis
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Acknowledgements
We gratefully acknowledge financial support by the DFG (project
number NA 720/3-1) and the State of Schleswig–Holstein. We
thank Professor Dr Wolfgang Bensch and Professor Dr Paul
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©