Luminescent Zn(NCS)2 and Cd(NCS)2 coordination compounds with pyridine derivatives: Synthesis, structures and physical properties

Article abstract of DOI:10.1016/j.ica.2018.03.002

Reaction of Cd(NCS)₂ and Zn(NCS)₂ with the co-ligands 4-benzylpyridine or 4-benzoylpyridine leads to the formation of eight new compounds, of which one crystallizes in two polymorphic modifications. The co-ligand rich compounds with the composition M(NCS)₂(L)₄ (M = Cd, Zn and L = 4-benzylpyridine or 4-benzoylpyridine) (1) form discrete complexes, in which the metal cations are each coordinated by four co-ligands and two N-bonded anionic ligands within slightly distorted octahedra. In the co-ligand deficient compounds (2) with the composition M(NCS)₂(L)₂ two structure types are observed. The Zn compounds form discrete complexes in which the Zn cations are tetrahedral coordinated (2-Zn), whereas in the Cd compounds (2-Cd) the metal cations are octahedral coordinated and linked into chains by pairs of μ-1,3-bridging thiocyanate anions. Upon heating, compounds 1 loose half of the co-ligands and transform into compounds 2. The coordination mode of the anionic ligands was also investigated by IR and Raman spectroscopy. All compounds show blue-green ligand-based luminescence with emission maxima varying between 21,857 cm^?1 and 18,264 cm^?1.

Full text of DOI:10.1016/j.ica.2018.03.002

Accepted Manuscript
Luminescent Zn(NCS)2 and Cd(NCS)2 Coordination Compounds with Pyridine
Derivatives: Synthesis, Structures and Physical Properties
Tristan Neumann, Inke Jess, Cesar dos Santos Cunha, Huayna Terraschke,
Christian Näther
PII:
S0020-1693(18)30125-7
https://doi.org/10.1016/j.ica.2018.03.002
ICA 18147
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
23 January 2018
28 February 2018
6 March 2018
Please cite this article as: T. Neumann, I. Jess, C. dos Santos Cunha, H. Terraschke, C. Näther, Luminescent
Zn(NCS)2 and Cd(NCS)2 Coordination Compounds with Pyridine Derivatives: Synthesis, Structures and Physical
Properties, Inorganica Chimica Acta (2018), doi: https://doi.org/10.1016/j.ica.2018.03.002
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Luminescent Zn(NCS)2 and Cd(NCS)2 Coordination Compounds with
Pyridine Derivatives: Synthesis, Structures and Physical Properties
Tristan Neumann, Inke Jess, Cesar dos Santos Cunha, Huayna Terraschke and
Christian Näther*
*
Prof. Dr. Christian Näther, Fax: +49-431-8801520, E-Mail: cnaether@ac.uni-kiel.de
Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-
Straße 2, 24118 Kiel, Germany
Keywords: Crystal structures; coordination polymers; zinc thiocyanate; luminescence; IR
and Raman spectroscopy; thermal properties.
Abstract
Reaction of Cd(NCS)2 and Zn(NCS)2 with the co-ligands 4-benzylpyridine or 4-
benzoylpyridine leads to the formation of eight new compounds, of which one crystallizes in
two polymorphic modifications. The co-ligand rich compounds with the composition
M(NCS)2(L)4 (M = Cd, Zn and L = 4-benzylpyridine or 4-benzoylpyridine) (1) form discrete
complexes, in which the metal cations are each coordinated by four co-ligands and two N-
bonded anionic ligands within slightly distorted octahedra. In the co-ligand deficient
compounds (2) with the composition M(NCS)2(L)2 two structure types are observed. The Zn
compounds form discrete complexes in which the Zn cations are tetrahedral coordinated
(2-Zn), whereas in the Cd compounds (2-Cd) the metal cations are octahedral coordinated
and linked into chains by pairs of µ-1,3-bridging thiocyanate anions. Upon heating,
compounds 1 loose half of the co-ligands and transform into compounds 2. The coordination
mode of the anionic ligands was also investigated by IR and Raman spectroscopy. All
compounds show blue-green ligand-based luminescence with emission maxima varying
between 21857 cm-1 and 18264 cm-1.
1

Introduction
The synthesis of new coordination compounds and polymers based on pseudo-halide ligands
like cyanides, azides, thio- or selenocyanates is still an important field in coordination
chemistry.[1-7] Especially transition metal azides have been extensively used in the past, e.g.
for the synthesis of new molecular magnetic materials because they are able to bridge metal
cations in the end-on (µ1,1) or the end-to-end (µ1,3) bonding mode leading to either dominating
ferro- or antiferromagnetic interactions between the metal cations.[1-3, 8-16] Magnetic
exchange can also be mediated by thio- or selenocyanate anions but in contrast to azides, it is
weaker and the µ-1,3-bridging mode is the most prominent, which can mediate both, ferro- or
antiferromagnetic exchange.[4, 17-21] However, for azides and thio- or selenocyanates also
many compounds are known, in which the anionic ligand is only terminally N-bonded to the
metal cation. Whereas for azides and, e.g., 3d metal cations like Mn(II), Fe(II), Co(II) and
Ni(II) an equal number of terminal and bridging compounds are reported. In the case of thio-
and selenocyanates the terminal mode dominates and this might be traced back to the low
chalcophilicity of most of these metal cations.[5]
However, despite the importance of paramagnetic compounds there is an increasing interest in
pseudohalides with d10 metal compounds like Cd(II) or Zn(II) and even Cu(I) because of their
potential luminescence properties and an increasing number of them were recently
reported.[22-35] Concerning their structural properties, most Zn(II) compounds show a
tetrahedral coordination, even if there are also some examples for a trigonal-bipyramidal, a
square pyramidal or an octahedral coordination.[36-38] In contrast, Cd(II) compounds
predominantly show an octahedral coordination, whereas a four or five-fold or a four-fold
coordination is rare.[36, 39-41] More importantly, Zn(II) is less chalcophilic and therefore, in
practically all cases thiocyanate anions are only N-terminally coordinated to the metal cations.
This is completely different for Cd(II), which prefers coordination to sulfur and thus, can
easily form compounds with a bridging coordination. This also includes different
modifications, as shown previously for [Cd(NCS)2(pyridine)2]n, that forms three different
isomers, of which one exists in polymorphic modifications.[42, 43] The structural diversity of
especially Cd(NCS)2 compounds is one reason why we became interested in these
compounds.
In our ongoing project we are interested in the synthesis and magnetic properties of M(NCS)2
(M = Mn(II), Fe(II), Co(II) and Ni(II)) coordination polymers, that additionally contain N-
donor co-ligands, because in most of them cooperative magnetic properties are observed.[44-
2

52] As mentioned above, these metal cations are less chalcophilic and therefore, the desired
compounds with a bridging coordination are often difficult to synthesize in solution. In this
case the desired compounds with a bridging coordination can often be synthesized by thermal
annealing of the discrete complexes with terminal coordinated anionic ligands.[47] This leads
to microcrystalline powders, which cannot be characterized by single crystal X-ray diffraction
(XRPD). Therefore, a chalcophilic metal cation with comparable structural properties to those
of the paramagnetic analogs was needed and we chose Cd(II). In this case the bridging
compound can easily be prepared in solution, crystallized and structurally characterized and in
those cases, where they are isotypic to the paramagnetic counterparts, the structure of the
latter can be determined by Rietveld refinements.[53] In the same way Zn(II) compounds can
be used to retrieve structural information on tetrahedral intermediates than can form, e.g., with
Co(II) and this also justifies our interest in the chemistry of Zn(NCS)2 and Cd(NCS)2
coordination compounds. In this context the question arose whether it would be possible to
differ between the two coordination modes of the anionic ligand or between different
coordination modes of the metal cations or the co-ligand by e.g. luminescence spectroscopy,
which can be helpful if no other structural information is available.[26] It is noted that in most
cases no definite conclusions can be made on the basis of IR and/or Raman data, because the
important vibrations for the terminal or bridging coordination of the anionic ligands
frequently overlaps with those of the neutral co-ligands. However, even if preliminary
investigations reveal differences in the luminescence spectra dependent no definite trend can
be extracted.[54, 55] Therefore, additional investigations might be needed.
In the present work 4-benzylpyridine (BP) and 4-benzoylpyridine (BOP; Scheme 1) were
selected as ligands for which no Cd(NCS)2 and Zn(NCS)2 coordination compounds are
reported in the CCDC. Both ligands differ only by one carbonyl O atom and thus, similar
structures might be expected (Scheme 1). In this context it is noted, that an excess of
monodentate co-ligand usually leads to discrete complexes with the composition
M(NCS)2(co-ligand)4 (M = Mn(II), Fe(II), Co(II), Ni(II), Zn(II) and Cd(II)) in which the
metal centers are octahedrally coordinated. If less co-ligand is used, frequently compounds
with the general formula M(NCS)2(co-ligand)2 are obtained, in which Zn is tetrahedral
coordinated, whereas all other metal cations are usually octahedral coordinated.
3

(1)
4-Benzylpyridine
4-Benzoylpyridine
Results and discussion
Synthetic investigations
Reaction of different molar ratios of Zn(NCS)2 or Cd(NCS)2 with 4-benzylpyridine or 4-
benzoylpyridine in water, methanol or ethanol lead to the formation of eight crystalline
phases, for which elemental analysis indicates a composition of M(NCS)2(co-ligand)4 (1) or
M(NCS)2(co-ligand)2 (2). It is noted, that compounds 1 can only be prepared pure if an excess
of the co-ligand is used, whereas for the synthesis of compounds 2, in most cases an excess of
the metal salt is needed. If the reaction is performed using the reactants in a ratio given by the
molecular formula, mixtures of compounds 1 and 2 were frequently obtained, which indicates,
that the co-ligand rich (1) and deficient (2) compounds are in equilibria. It is also noted that
for Cd(NCS)2(4-benzylpyridine)4 two crystalline phases were obtained. 1-Cd-BP/I was
obtained from methanol whereas 1-Cd-BP/II has formed in ethanol. For 1-Cd-BP/II single
crystals were obtained, which was not the case for 1-Cd-BP/I. However, it was found that this
additional crystalline phase is isotypic to Ni(NCS)2(4-benzylpyridine)4 reported by
Nassimbeni et al.[56] If the lattice parameters from a Pawley-Fit are used to calculate the
powder pattern, excellent agreement with the experimental pattern is observed (Figure S1 and
S2 in the SI). For all remaining compounds single crystals were obtained and investigated by
single crystal X-ray diffraction (see Tables S1 and S2). Altogether, the following compounds
were obtained:
Zn(NCS)2(4-Benzoylpyridine)4 (1-Zn-BOP)
Zn(NCS)2(4-Benzylpyridine)4 (1-Zn-BP)
Cd(NCS)2(4-Benzoylpyridine)4 (1-Cd-BOP)
Cd(NCS)2(4-Benzylpyridine)4 (1-Cd-BP/I)
Cd(NCS)2(4-Benzylpyridine)4 (1-Cd-BP/II)
Zn(NCS)2(4-Benzoylpyridine)2 (2-Zn-BOP)
Zn(NCS)2(4-Benzylpyridine)2 (2-Zn-BP)
4

Cd(NCS)2(4-Benzoylpyridine)2 (2-Cd-BOP)
Cd(NCS)2(4-Benzylpyridine)2 (2-Cd-BP)
Based on the structural results XRPD patterns were calculated and compared with the
experimental patterns, which proves, that all compounds were obtained as pure phases (Fig.
S3 – S10).
To investigate the thermodynamic stability of 1-Cd-BP/I and 1-Cd-BP/II, a solvent mediated
conversion experiment was performed, in which a mixture of both forms with an excess of
solid was stirred in ethanol for 6 d at room temperature. The obtained residue was
investigated by X-ray powder diffraction (XRPD). Unfortunately, XRPD investigations reveal
that a part of the sample transformed into the 4-benzylpyridine deficient phase 2-Cd-BP,
which seems to be more stable and which might be traced back to the high chalcophilicity of
Cd and therefore, no definite conclusion on the stability can be drawn (Figure S11).
Crystal structures of compounds 1
Compounds 1-Zn-BOP and 1-Cd-BOP are isotypic and crystallize in the monoclinic space
group P21/c with Z = 2 and the metal cations located on centers of inversion (Table S1). The
4-benzylpyridine compounds 1-Zn-BP and 1-Cd-BP/I form also isotypic pairs (space group
Cc) with one crystallographically independent metal cation in a general position (Table S2).
Because these compounds are also isotypic to the corresponding Ni compound, one can
assume that this structure corresponds to the most stable arrangement, which indicate that 1-
Cd-BP/II (space group P-1 with two Cd cations on centers of inversion) might be metastable
(Table S2).
All compounds form discrete complexes in which the metal centers are 6-fold coordinated by
four co-ligands and two trans, N-bonded thiocyanate anions (Figure 1 and Figures S12-S14).
The Zn-N bond lengths in 1-Zn-BOP (2.086(2)-2.245(2) Å and 1-Zn-BP (2.106(2)-2.255(2)
are comparable and correspond to literature values (Table S3 and S5). As expected, the Cd-N
bond lengths are longer (1-Cd-BOP: 2.277(2)- 2.388(2) Å and 1-Cd-BP/II: 2.301(3)-
2.382(3)) and are very similar for both compounds (Table S3 and S7). The bond angles
deviate from ideal values, which shows that the octahedra are slightly distorted (Table S3, S5
and S7). At first glance, the arrangement of the BOP and the BP ligands around the metal
center are quite similar, but significant differences are found in the dihedral angles between
the 6-membered rings, for which the carbonyl group in the BOP ligand might be responsible.
5

In 1-Cd-BOP and in 1-Zn-BOP these angles amount to 55.2° and 56.0°, respectively 54.2°
and 54.6°, whereas in 1-Cd-BP/II and 1-Zn-BP values of 84.1°, 89.9°, 94.3° and 94.2°,
respectively 89.1°, 90.5°, 92.9° and 95.0° are observed, which shows that these rings are
perpendicular to each other. The arrangement of the complexes in the crystals are very
different and there are only some short contacts indicating C-H···N, C-H···O or C-H···S
interactions. However, all these values are below 140°, which shows that these represent very
weak interactions (Table S4, S6 and S8).
Figure 1. View of the coordination sphere of 1-Zn-BP as a representative. ORTEP plots of 1-
Zn-BOP, 1-Cd-BOP, 1-Zn-BP and 1-Cd-BP/II are given in Figure S12-S14.
Crystal structures of compounds 2
The crystal structures of compounds 2 can be divided in two groups. The Zn compounds 2-
Zn-BOP (space group C2/c) and 2-Zn-BP (space group P21) form discrete complexes, in
which the Zn cation is tetrahedral coordinated by two terminal N-bonded thiocyanate anions
and two neutral co-ligands (Table S1 and S2 and Figure 2). In 2-Zn-BOP these complexes are
located on a 2-fold rotation axis, whereas in 2-Zn-BP they occupy a general position (Figure
S15 and S16). The Zn bond lengths in both compounds are very similar and the bonding
angles indicate that the tetrahedra are slightly distorted (Table S9 and S11). As for compounds
1, the conformation of the benzoyl and benzyl ligand is completely different, because in 2-
Zn-BOP the 6-membered rings are perpendicular to each other, which is not the case in 2-Zn-
BP (Figure 2). In the crystal structure of 2-Zn-BOP there are two C-H···S contacts, which are
indicative for hydrogen bonding, which is not the case for 2-Zn-BP (Table S10).
6

The crystal structures of the Cd compounds are completely different from that of the Zn
compounds. 2-Cd-BOP crystallizes triclinic in the space group P-1 with the Cd cations
located on centers of inversion, whereas 2-Cd-BP crystallizes in the monoclinic space group
P21/n with all atoms in general positions (Table S1 and S2). In both compounds the Cd
cations are octahedral coordinated by two N and two S coordinating thiocyanate anions and
two co-ligands and are linked into chains by pairs of µ-1,3-bridging thiocyanate ligands
(Figure 3).
Figure 2. View of the coordination sphere of 2-Zn-BOP (top) and 2-Zn-BP (bottom).
ORTEP plots of both compounds are given in Figure S15 and S16.
In 2-Cd-BOP, the thiocyanate N respectively S atoms as well as the BOP N atoms are always
in trans-position, which leads to the formation of linear chains (Figure 3: top). This
corresponds to the usual chain geometry observed in many other thiocyanate compounds with
Cd(II), Mn(II), Fe(II), Co(II) or Ni(II). In contrast, in 2-Cd-BP, the thiocyanate S atoms and
the BP N atoms are in cis-position, whereas the thiocyanate N atoms are trans to each other,
which leads to the formation of zig-zag-like chains (Figure 3: bottom). The Cd-N bond
lengths to the thiocyanate anions are very similar in both compounds, whereas the Cd-N bond
lengths to the co-ligand and the Cd-S distances are slightly elongated in 2-Cd-BP, where
these atoms are cis (Table S12 and S14).
In the crystal structure of 2-Cd-BOP, the Npyridine-Npyridine vectors to the BOP ligands
perpendicular to the Cd(NCS)2Cd planes are parallel, which correspond to one of the two
arrangements observed in such thiocyanate structures with linear chains (Figure S19). Along
7

the chain the pyridine planes are nearly parallel to the chain direction (Figure S19). This is
different for the structures of the corresponding compounds with the 3d metal cations, where
these planes are frequently perpendicular to each other, which can be traced back to the
shorter metal to metal separation. In 2-Cd-BP, the chains proceed along the a-axis and the BP
ligands are arranged into columns in this direction (Figure S20).
Figure 3. View of the coordination sphere of 2-Cd-BOP (top) and 2-Cd-BP (bottom).
ORTEP plots of both compounds are given in Figure S17 and S18 in the SI.
Finally, as mentioned in the introduction we are generally interested in the structural
chemistry of Cd(NCS)2 and Zn(NCS)2 coordination compounds to investigate which
differences occur and how these structures are related to that of the paramagnetic compounds
in which we are also interested. In this context it is noted that 1-Cd-BOP and 1-Zn-BOP are
isotypic to, e.g., Co(NCS)2(4-benzoylpyridine)4 reported by Drew et.al.,[57] which for co-
8

ligand rich compounds with an octahedral coordination is frequently the case. However, the
structure of 2-Cd-BOP is different from that of [Co(NCS)2(4-benzoylpyridine)2]n.[46] In both
compounds linear chains are observed, but in the Cd compound all coordinating atoms are in
trans-position, whereas in the Co compound the BOP ligand is trans, whereas the thiocyanate
N and S atoms are in cis-position. Moreover, compounds with 4-benzylpyridine are currently
under investigations and we already have prepared crystalline powders with the composition
[M(NCS)2(4-benzoylpyridine)2]n (M = Mn(II), Co(II) and Ni(II) by thermal decomposition of
the corresponding discrete complexes. First XRPD investigations have shown that the Mn and
the Co compound are isotypic to 2-Cd-BP, which, surprisingly is not the case for the Ni
compound.
IR and Raman spectroscopy
To determine the values of the CN stretching vibrations of the thiocyanate anions and to
check if one can differ between an octahedral and tetrahedral or between a terminal and a
bridging coordination, measurements using IR and Raman spectroscopy were performed. For
the discrete complexes 1 with composition M(NCS)2(L)4 with terminal N-bonded thiocyanate
anions values between 2054 and 2070 cm-1 in the IR and between 2054 and 2084 cm-1 in the
Raman spectra are observed, which are in good agreement with values reported for a similar
coordination (Table 1 and Figures S21 to S25). For 1-Cd-BP/II two values are observed,
which can be traced back to the fact, that the asymmetric unit contains two
crystallographically independent complexes. No general trend is observed between Zn and Cd
and thus, one cannot differ between both cations. If the spectra of compounds 1 are compared
with that of the Zn compounds 2-Zn-BOP and 2-Zn-BP that contain terminal N-bonded
anionic ligands also, it becomes obvious that one cannot differ between an octahedral and a
tetrahedral coordination (Table 1, Figures S25 and S27). In contrast, for the Cd compounds 2-
Cd-BOP and 2-Cd-BP with terminal anionic ligands, the vibrations are shifted to higher
values but the overall difference is small. Therefore, one cannot differ surely between the
different coordination modes of the metal cations and that of the anionic ligands (Figures S26
and S28).
Table 1. Values of the CN-stretching vibration in compounds 1 and 2.
M(NCS)2(L)4 IR / cm-1
Raman / cm-1 M(NCS)2(L)2 IR / cm-1
Raman / cm-1
2070
2063
2073
2074
2063
2096
-
1-Zn-BOP
1-Zn-BP
2-Zn-BOP
2-Zn-BP
2084, 2071
9

2061
2066, 2054 2066, 2058
2056 2075, 2061
2067
2085
2090
1-Cd-BOP
1-Cd-BP/I
1-Cd-BP/II
2-Cd-BOP
2-Cd-BP
2095, 2104 2104
Thermoanalytical investigations
To investigate the thermal properties of compounds 1, measurements using simultaneously
differential thermoanalysis and thermogravimetry were performed. In this context it would be
of interest, if compounds 1 can be transformed into compounds 2 by thermal decomposition,
as frequently observed for such compounds.
Upon heating 1-Cd-BOP or 1-Zn-BOP with 8°C/min only one mass step is observed in the
TG curve, that is accompanied with an endothermic event in the DTA curve (Figure S29 and
S30). The mass loss 83.1 % respectively 82.1 % is larger than that expected for the removal of
all BOP ligands. This indicates, that all ligands are removed and the thiocyanate salt formed
as intermediate decompose in only one step. If the heating rate is lowered to 1°C/min no
better resolved TG curve is observed (Figure S29 and S30). Therefore, there is no indication
that 1-Cd-BOP or 1-Zn-BOP can be transformed into 2-Cd-BOP or 2-Zn-BOP. However, in
the DTA curve of 1-Zn-BOP there is an endothermic event, where the sample mass does not
change, indicating some preliminary transformation (Figure S30). Therefore,
thermomicroscopic measurements were performed, which show a continuous change of the
optical appearance of the sample and no definite melting is observable. Upon cooling, no
changes in the images are observed (Figure S31). To investigate this in more detail DSC
heating and cooling cycles were measured at 10°C/min. Upon heating an endothermic event is
observed that might corresponds to the melting point, but on cooling no crystallization is
observed, indicating the formation of an amorphous solid. Interestingly, with increasing
number of heating runs, there is a preliminary not well resolved signal directly before melting,
but the melting enthalpy remains practically constant, which is in disagreement with the
formation of a, e.g., glassy phase (Figure S32). However, a closer look at the cooling runs
shows very broad exothermic signals, that might correspond to some continuous
crystallization but the integral of these events is always lower than that in the heating runs.
However, in each heating run there is a very broad exothermic signal between 35 and 80°C,
which might correspond to a cold-crystallization of the compound formed by melting (Figure
S32). That this compound tend to recrystallize after melting is also indicated by one additional
DSC measurement performed at 3°C/min, where a sharp exothermic signal is observed at
28°C upon cooling, indicating for crystallization (Figure S33). However, this was observed
10

only once. Finally, the residue obtained after first melting was investigated by XRPD, which
shows that the major phase corresponds to that of the pristine compound that is contaminated
with some smaller amount of 2-Zn-BOP (Figure S34).
In contrast, if 1-Cd-BP/I or 1-Cd-BP/II are heated, clearly two well resolved mass steps are
observed in the TG curve with endothermic events in the DTA curves (Figure 4 and Figure
S35. The experimental mass loss of 39.0 % for 1-Cd-BP/I and of 36.5 % for 1-Cd-BP/II are
in reasonable agreement with that expected for the removal of two BP ligands (Δm = 2x18.7
% = 37.4%), indicating that a compound of composition Cd(NCS)2(BP)2 forms as
intermediate.
Figure 4. DTA, TG and DTG curve for 1-Cd-BP/I at 8 °C/min. The curve for 1-Cd-BP/II
can be found in Figure S35.
To prove this assumption, a second TG run was performed for both compounds and stopped
after the first mass step. If these residues are investigated by XRPD it is proven that 1-Cd-
BP/I and 1-Cd-BP/II have been transformed into 2-Cd-BP (Figure 5). In the second mass
step, the removal of the remaining BP ligands overlaps with the decomposition of Cd(NCS)2
formed as intermediate.
11

Figure 5. Experimental XRPD pattern of the residues obtained after the first mass loss in the
DTA-TG measurement of 1-Cd-BP/I (top), 1-Cd-BP/II (middle) together with the powder
pattern calculated for 2-Cd-BP (bottom).
For 1-Zn-BP the TG curve is poorly resolved at 8°C/min but also at 1°C/min and there are no
indications for the formation of 2-Zn-BP as intermediate. However, as it was observed for 1-
Zn-BOP, an endothermic signal is observed in the DTA curve before the sample mass
decreases, indicating a preliminary transition or melting of the complex. Thermomicroscopic
measurements support melting of this compound (Figure S37) and DSC heating and cooling
measurements indicate a behavior similar to that of 1-Zn-BOP that with increasing cycles the
sample tend to form amorphous residues on cooling, that recrystallize on further heating
(Figure 6).
Figure 6. DSC heating and cooling cycles for 1-Zn-BP at 10 °C/min.
12

The XRPD pattern of the residue is identical to that of the pristine material, except some
additional low intense reflections, that might indicate some decomposition during melting
(Figure S38). Obviously, both compounds tend to form amorphous or semi-crystalline phases
that on further heating crystallize over a wide temperature range.
Luminescence measurements
Compounds 1 and 2 are colourless under ambient light but show luminescence in the blue-
green spectral range when irradiated with UV light (Figure S39 and S40). The colourless
appearance under ambient light is in agreement to the respective reflection spectra of these
samples (Figure S41 and S42), which show a constantly high reflectance for energies lower
than 25000 cm-1 and therefore low absorbance in the visible spectral range. In contrast, for all
samples, the reflectance starts to decrease for energies higher than 25000 cm-1, showing a
strong absorption in the UV spectral range.
Emission and excitation spectra of compounds 1 and 2 as well as of the pure ligands are
presented in Figures S43-S53 and discussed below. Figure 7 shows the emission spectra of
the compounds with 4-benzoylpyridine in comparison to the emission spectrum of the pure
-1
ligand, excited at 25000 cm . The emission spectrum of 1-Cd-BOP ( = 25000 cm-1, Figure
~
ex
7, red curve) consists of a combination of several bands in the blue spectral range with
maxima at e.g. 17094 cm-1, 18747 cm-1, 20312 cm-1, 21857 cm-1 and 23441 cm-1. This
emission spectrum coincides in shape and position to that of 1-Zn-BOP ( = 25000 cm-1,
~
ex
Figure 7, pink curve), confirming the isotypic nature of the crystal structures of 1-M-BOP (M
= Cd, Zn) compounds. As previously discussed in the literature for other Cd(II) and Zn(II)
hybrid organic-inorganic compounds,[58, 59] these do not present radiative electronic
transitions. Hence, the emission of the Cd(II) and Zn(II) complexes originate from the S1→S0
transitions of the aromatic units of the organic ligand.[60] The attribution of the optical
properties of the Cd(II) and Zn(II) complexes to ligand-based luminescence is confirmed by
the similarities in shape and position of the emission spectra of 1-Cd-BOP and 1-Zn-BOP in
comparison to that of the pure 4-Benzoylpyridine ligand ( = 25000 cm-1, Figure 7, black
~
ex
curve).
The emission spectrum of 2-Cd-BOP consists of a broad band with maximum in the green
spectral range at 18264 cm-1, between approximately 13000 cm-1 and 24000 cm-1 with full
-1
width at half maximum (FWHM) of 4716 cm ( = 25000 cm-1, Figure 7, blue curve),
~
ex
13

therefore red-shifted in comparison to the emission spectrum of 1-Cd-BOP. Similarly, the
emission spectrum assigned to 2-Zn-BOP ( = 25000 cm-1, Figure 7, green curve) is also
~
ex
red-shifted in comparison to the emission spectrum of 1-Zn-BOP.
Considering the luminescence measurements of the 4-Benzylpyridine-based structures, the
emission spectra of all 1-M-BP and 2-M-BP (M = Cd, Zn) samples strongly overlap with the
~
emission spectrum of the ligand. In detail, the emission band assigned to 1-Cd-BP/I (
=
ex
25000 cm-1, Figure 8, red curve) presents a maximum at 20383 cm-1 and FWHM of 5824 cm-
1
, while the emission maximum of the band assigned to 1-Cd-BP/II ( = 25000 cm-1, Figure
~
ex
8, violet curve) is located at 20197 cm-1 with a FWHM of 4436 cm-1. Similarly, the emission
spectrum of 2-Cd-BP ( = 25000 cm-1, Figure 8, blue curve) is centered at 20656 cm-1 with a
~
ex
FWHM of 5634 cm-1.
Figure 7. Emission spectra ( = 25000 cm-1) of 1-Cd-BOP (red curve), 2-Cd-BOP (blue
~
ex
curve), 1-Zn-BOP (pink curve), 2-Zn-BOP (green curve) and of the BOP ligand (black
curve).
~
For the Zn(II) 4-benzylpyridine compounds, the emission bands assigned to 1-Zn-BP (
=
ex
-1
25000 cm , Figure 8, pink curve) and 2-Zn-BP ( = 25000 cm-1, Figure 8, green curve) are
~
ex
also overlapped. Within these spectra, the emission band of 1-Zn-BP presents a maximum at
20153 cm-1 and FWHM of 3658 cm-1 while the emission band assigned to 2-Zn-BP is
centered at 20614 cm-1 and FWHM of 5715 cm-1. Therefore, no clear trend of luminescence
properties concerning ligand rich and ligand deficient compounds as well as compounds
containing BP or BOP ligands is observed.
14

Figure 8. Emission spectra ( = 25000 cm-1) of 1-Cd-BP/I (red curve), 1-Cd-BP/II (violet
~
ex
curve), 2-Cd-BP (blue curve), 1-Zn-BP (pink curve), 2-Zn-BP (green curve) and of the BP
ligand (black curve).
The measurements of the emission spectra shown in Figures 7-8 and S43-S53 allowed the
calculation of the colour coordinates of the International Commission internationale de
l’éclairage (CIE) 1931 chromaticity diagram for the 4-benzoylpyridine and 4-benzylpyridine
compounds, listed in Table 2 and displayed in Figure 9.
Table 2. CIE 1931 colour coordinates and respective excitation energies for compounds 1-M-
BOP, 2-M-BOP, 1-M-BP and 2-M-BP (M = Cd, Zn).
Compound
1-Cd-BOP
2-Cd-BOP
1-Zn-BOP
2-Zn-BOP
1-Cd-BP/I
1-Cd-BP/II
2-Cd-BP
Excitation energy
25510 cm-1
25000 cm-1
25974 cm-1
25000 cm-1
25000 cm-1
25000 cm-1
25000 cm-1
25000 cm-1
25000 cm-1
x
y
0.1504
0.3629
0.1591
0.2117
0.2778
0.1959
0.2742
0.1736
0.2292
0.2578
0.4731
0.2187
0.4336
0.3997
0.4249
0.3862
0.4511
0.3863
1-Zn-BP
2-Zn-BP
15

Figure 9. CIE 1931 colour coordinates for 1-Cd-BOP/I (♦),2-Cd-BOP (♦), 1-Zn-BOP (■)
and 2-Zn-BOP (■) (top) as well as for 1-Cd-BP/I (♦),1-Cd-BP/II (♦),2-Cd-BP (♦), 1-Zn-BP
(■) and 2-Zn-BP (■) (bottom), applying the excitation energies listed on Table 2.
Conclusions
In the present work new coordination compounds with the composition M(NCS)2(L)4 (M =
Cd, Zn and L = 4-benzylpyridine or 4-benzoylpyridine) were prepared and structurally
characterized. All co-ligand rich compounds forms discrete octahedral complexes, whereas
the ligand-deficient compounds with Zn forms discrete tetrahedral complexes and that with
cadmium chains with octahedral coordinated metal cations. Interestingly, the chain
compounds with benzylpyridine seems to be isotypic to the corresponding paramagnetic
compounds with Mn(II) and Co(II) which are under investigations and for which still only
crystalline powders were prepared by thermal decomposition. This indicates, that in several
cases the diamagnetic compounds can be used as structural analogs for the paramagnetic
compounds as recently observed. IR and Raman spectroscopic investigations shows, that one
cannot surely differ between compounds with only terminal N-bonded thiocyanate anions and
between that with a µ-1,3-bridging coordination, because the differences are not significant.
However, upon heating the ligand-rich compounds with 4-benzylpyridine, a transformation
into the ligand-deficient occur, which, surprisingly is not observed for the 4-benzoylpyridine
16

compounds. Luminescence measurements show the ligand-based emission of all Cd and Zn
compounds in the blue-green spectral range with no clear trend differentiating between BP
and BOP ligand rich or ligand deficient compounds. However, a clear trend might be
expected for compounds, in which the luminescent ligand will act either as terminal or as
bridging ligand and this will be the subject of further investigations.
Experimental Section
Synthesis
Ba(NCS)2·3H2O, 4-benzylpyridine and 4-benzoylpyridine were purchased from Alfa Aesar,
KSCN, Cd(NO3)2∙4H2O, Cd(SO4)·8/3H2O, Zn(NO3)2∙6H2O and Zn(SO4)·H2O were bought
from Merck. All chemicals were used without further purification. Cd(NCS)2 and Zn(NCS)2
were prepared by the reaction of equimolar amounts of Zn(SO4)·H2O, Cd(SO4)·8/3H2O and
Ba(NCS)2·3H2O in water. The resulting white precipitate of BaSO4 was filtered off and the
filtrates were concentrated to complete dryness resulting in white residues of Cd(NCS)2 and
Zn(NCS)2.
Synthesis of 1-Cd-BOP: Single crystals suitable for single crystal X-ray structure
determination were obtained by the reaction of Cd(NCS)2 (22.8 mg, 0.1 mmol) with 4-
benzoylpyridine (128 mg, 0.8 mmol) in a mixture of 3.0 mL ethanol with 1.0 mL H2O after it
was left in a closed test tube at room temperature for several days. A crystalline powder was
obtained by the reaction of Cd(NCS)2 (114.3 mg, 0.5 mmol) with 4-benzoylpyridine (457.5
µL, 2.5 mmol) in 1.5 mL H2O after 4 days of stirring. Elemental analysis for C50H36CdN6O4S2
(961.4056 g/mol): C 62.47, H 3.77, N 8.74, S 6.67. Found: C 65.28, H 3.98, N 8.54, S 5.23.
IR (ATR): ν = 2061 (s), 1724 (w), 1660 (s), 1593 (m), 1552 (m), 1494 (w), 1446 (m), 1416
(m), 1326 (m), 1277 (s), 1217 (m), 1180 (w), 1152 (m), 1098 (w), 1065 (m), 1011 (w), 935
(m), 873 (w), 845 (m), 791 (m), 748 (m), 727 (m), 698 (s), 663 (m), 642 (s), 573 (m) cm-1
Raman: ν = 2067 cm-1 (Figure S22).
Synthesis of 2-Cd-BOP: Single crystals suitable for single crystal X-ray structure
determination were obtained by the reaction of Cd(NCS)2 (34.3 mg, 0.15 mmol) with 4-
benzoylpyridine (27.5 mg, 0.15 mmol) in 1.5 mL methanol in a closed test tube at room
temperature. For the synthesis of a microcrystalline powder of 2-Cd-BOP Cd(NCS)2 was
prepared in situ from the reaction of Cd(NO3)2∙4H2O (308 mg, 1.0 mmol) with KSCN (194
mg, 2.0 mmol) in 1.5 mL ethanol. The resulting white residue was filtered off after three
hours. 4-benzoylpyridine (91.0 mg, 0.5 mmol) was dissolved in ethanol and was then added
17

dropwise to the filtrate of the former reaction. Elemental analysis for C26H18CdN4O2S2
(594.9865 g/mol): C 52.49, H 3.05, N 9.42, S 10.78. Found: C 52.063, H 2.913, N 9.267, S
10.825. IR (ATR): ν = 2085 (s), 1655 (s), 1596 (m), 1579 (m), 1545 (m), 1491 (w), 1447 (m),
1412 (m), 1317 (m), 1284 (s), 1216 (m), 1177 (w), 1153 (m), 1064 (m), 1025 (w), 1007 (m),
970 (w), 945 (m), 843 (m), 791 (m), 748 (m), 727 (m), 696 (s), 645 (s), 575 (m) cm-1. Raman:
ν: = 2090 (s) cm-1 (Figure S26).
Synthesis of 1-Zn-BOP: Single crystals suitable for single crystal X-ray structure
determination were obtained by the reaction of Zn(NCS)2 (27.2 mg, 0.15 mmol) 4-
benzoylpyridine (109.9 mg, 0.6 mmol) in 1.5 mL methanol after it was left in a closed test
tube for several days. A crystalline powder was obtained by the reaction of Zn(NO3)2∙6H2O
(297 mg, 1.0 mmol) with KSCN (194 mg, 2.0 mmol) in 1.5 mL ethanol. The precipitate was
filtered off and a solution from 4-benzoylpyridine (1.098 g, 6.0 mmol) in ethanol was added
dropwise to the filtrate of the former reaction. The product was filtered off after 6 days.
Elemental analysis for C50H36ZnN6O4S2 (914.3856 g/mol): C 65.68, H 3.97, N 9.19, S 7.01.
Found: C 65.643, H 3.861, N 9.315, S 6.647. IR (ATR): = 2070 (s), 1659 (s), 1595 (w), 1552
(m), 1446 (m), 1412 (m), 1324 (m), 1277 (s), 1216 (m), 1181 (w), 1153 (m), 1100 (w), 1064
(m), 1011 (m), 944 (m), 876 (w), 845 (m), 791 (m), 749 (m), 729 (m), 697 (s), 665 (m), 642
(s), 573 (m) cm-1 (Figure S9). Raman: ν = 2073 cm-1 (Figure S21).
Preparation of single crystals of 4-benzoylpyridine: Single crystal of the commercial available
compound were prepared by stirring 4-benzoylpyridine (366 mg, 2.0 mmol) in 1.5 mL H2O
for 1 d. The residue was filtered off and the filtrate was left to stand in a closed test tube.
After a few days crystals suitable for single crystal X-ray-diffraction formed.
Synthesis of 2-Zn-BOP: Single crystals suitable for single crystal X-ray structure
determination were obtained by the reaction of Zn(NCS)2 (27.2 mg, 0.15 mmol) with 4-
benzoylpyridine (55.0 mg, 0.3 mmol) in 1.5 mL ethanol in a closed test tube at room
temperature after several days. A crystalline powder was obtained by the reaction of
Zn(NO3)2∙6H2O (297 mg, 1.0 mmol) with KSCN (194 mg, 2.0 mmol) in 1.5 mL ethanol. The
precipitate was filtered off and a solution from 4-benzoylpyridine (366 mg, 2.0 mmol) in
ethanol was added dropwise to the filtrate of the former reaction. Elemental analysis for
C26H18N4O2S2 (547.9665 g/mol): C 56.99, H 3.31, N 10.22, S 11.70. Found: C 56.81, H
3.117, N 10.123, S 11.357. IR (ATR): ν = 2074 (s), 1664 (s), 1620 (m), 1592 (m), 1546 (w),
1500 (w), 1487 (w), 1447 (m), 1422 (m), 1318 (m), 1278 (s), 1223 (m), 1181 (w), 1150 (w),
18

1101 (w), 1064 (m), 1033 (w), 963 (w), 942 (m), 869 (w), 838 (m), 792 (m), 747 (m), 733
(m), 699 (s), 649 (s), 578 (m) cm-1 Raman: v = 2096 cm-1 (Figure S25).
.
Synthesis of 1-Cd-BP/I: A crystalline powder was obtained by the reaction of Cd(NCS)2
(57.0 mg, 0.25 mmol) with 4-benzylpyridine (80.0 µL, 0.5 mmol) in 1.5 mL methanol after 4
days of stirring. Elemental analysis for C50H44CdN6S2 (905.4716 g/mol): C 66.32, H 4.90, N
9.28, S 7.08. Found: C 63.742, H 4.641, N 9.31, S 7.491. IR (ATR): ν = 2096 (m), 2054 (s),
1979 (m), 1610 (m), 1599 (w), 1558 (w), 1494 (m), 1450 (m), 1420 (s), 1222 (m), 1182 (w),
1151 (w), 1065 (m), 1014 (s), 941 (w), 958 (m), 909 (w), 858 (m), 836 (m), 794 (m), 750 (m),
733 (s), 697 (s), 617 (s), 560 (s) cm-1. Raman: ν = 3053 (s), 2991 (w), 2909 (m), 2844 (w),
2141 (w), 2066 (s), 2058 (s), 1609 (m), 1582 (w), 1561 (w), 1435 (w), 1200 (m), 1154 (w),
1031 (m), 1017 (m), 1002 (s), 840 (w), 796(w), 741 (w), 667 (w), 618 (w), 561 (w) cm-1
(Figure S24).
Synthesis of 1-Cd-BP/II: Single crystals suitable for single crystal X-ray structure
determination were obtained by the reaction of Cd(NCS)2 (20 mg, 0.09 mmol) with 4-
benzylpyridine (47.9 µL, 0.3 mmol) in 2.5 mL ethanol at 120°C. A crystalline powder was
obtained by the reaction of Cd(NO3)2·4H2O (308 mg, 1.0 mmol) with KSCN (194 mg, 2.0
mmol) in 1.5 mL ethanol after the precipitate was filtered off and 4-benzylpyridine (800.0 µL,
5.0 mmol) was added dropwise to the filtrate of the former reaction. Elemental analysis for
C50H44CdN6S2 (905.4716 g/mol): C 66.32, H 4.90, N 9.28, S 7.08 Found: C 65.756, H 4.957,
N 9.329, S 6.721. IR (ATR): ν = 2054 (s), 1610 (m), 1559 (w), 1494 (m), 1450 (w), 1420 (m),
1222 (w), 1064 (w), 1015 (m), 944 (w), 910 (w), 859 (m), 836 (m), 795 (m), 733 (s), 703 (s),
616 (s), 560 (m). Raman: ν = 2075 (s), 2061 (s) cm-1 (Figure S24).
Synthesis of 2-Cd-BP: Single crystals suitable for single crystal X-ray structure determination
were obtained from the reaction of Cd(NCS)2 (68.0 mg, 0.3 mmol) with 4-benzylpyridine
(23.9 µL, 0.15 mmol) in 1.0 mL H2O at room temperature. The precipitate was filtered off
and the filtrate was allowed to stand. After a few days suitable crystals were obtained. For the
synthesis of a microcrystalline powder of 2-Cd-BP Cd(NO3)2∙4H2O (308 mg, 1.0 mmol) was
mixed with KSCN (194 mg, 2.0 mmol) in 1.5 mL ethanol. The precipitate was filtered off and
4-benzylpyridine (160.0 µL, 1.0 mmol) was added dropwise to the filtrate of the former
reaction. Elemental analysis for C26H22CdN4S2 (567.0195 g/mol): C 55.08, H 3.91, N 9.88, S
11.31. Found: C 53.437, H 3.767, N 9.77, S 11.384. IR (ATR): ν = 2095 (s), 1610 (m), 1556
(w), 1494 (m), 1450 (w), 1422 (m), 1223 (w), 1069 (w), 1016 (m), 935 (w), 912 (w), 856 (m),
19

833 (m), 792 (m), 747 (m), 730 (s), 700 (m), 616 (s), 560 (m). Raman: ν: = 2104 cm-1 (Figure
S28).
Synthesis of 1-Zn-BP: Single crystals suitable for single crystal X-ray structure determination
were obtained by the reaction of Zn(NCS)2 (45.0 mg, 0.25 mmol) with 4-benzylpyridine (400
µL, 2.5 mmol) in 1.5 mL EtOH in a sealed test tube at 110°C after three days. For the
synthesis of a microcrystalline powder Zn(NCS)2 (90.5 mg, 0.5 mmol) was reacted with 4-
benzylypridine (1600 µL, 10.0 mmol) in 1.5 mL H2O at room temperature. Elemental analysis
for C50H44N6S2Zn (858.4516 g/mol): C 69.96, H 5.17, N 9.79, S 7.47. Found: C 70.884, H
5.353, N 9.72, S 6.466. IR (ATR): ν = 2063 (s), 1600 (m), 1558 (m), 1494 (m), 1450 (m),
1417 (s), 1222 (m), 1179 (w), 1152 (w), 1064 (m), 1014 (m), 910 (w), 859 (m), 838 (m), 797
(m), 731 (s), 696 (s), 615 (s), 559 (s) cm-1. Raman: v = 2084 (s), 2071 (s) cm-1 (Figure S23).
Synthesis of 2-Zn-BP: Single crystals suitable for single crystal X-ray structure determination
were obtained by the reaction of Zn(NCS)2 (45.0 mg, 0.25 mmol) with 4-benzylpyridine (40
µL, 0.25 mmol) in 1.5 mL H2O in a sealed test tube at 110°C after three days. A crystalline
powder was obtained by the reaction of Zn(NCS)2 (90.8 mg, 0.5 mmol) with 4-benzylypridine
(80.0L µL, 0.5 mmol) in 1.5 mL dest. H2O after stirring the reaction mixture for 4 days.
Elemental analysis for C26H22N4S2Zn (519.9995 g/mol): C 60.06, H 4.26, N 10.77, S 12.33.
Found: C 59.34, H 4.23, N 10.77, S 11.95. IR (ATR): νmax = 2063 (s), 1616 (m), 1600 (m),
1560 (m), 1494 (m), 1453 (m), 1432 (m), 1419 (m), 1223 (m), 1068 (m), 1032 (m), 1014 (m),
861 (m), 836 (m), 795 (m), 753 (m), 733 (s), 702 (s), 615 (s), 561 (m) cm-1. (Figure S27).
Single crystal structure determinations
Data collection for 1-Zn-BOP, 2-Zn-BOP and 1-Cd-BOP/II were performed with a STOE
IPDS-1 and for 1-Cd-BOP, 1-Cd-BP/II, 2-Cd-BP and 1-Zn-BP with a STOE IPDS-2 using
Mo-K radiation. Numerical absorption corrections were performed with X-Red and X-
Shape, which are part of the program package X-Area.[61] Structure solution was done with
SHELXS-97[62] and structure refinement was performed with SHELXL-2014.[63] All non
hydrogen atoms were refined anisotropic. The H atoms were positioned with idealized
geometry and refined isotropic with Uiso(H) = 1.2 Ueq(C) using a riding model. The crystal of
2-Zn-BOP is non-merohedral twinned and therefore, a twin refinement using data in HKLF-5
format was performed leading to a BASF parameter of 0.081(3). Therefore, symmetry
equivalents were merged before generating the data in HKLF-5 format and an absorption
correction cannot be performed. The crystal of 1-Zn-BP is pseudo-merohedral twinned with a
2-fold rotation axis as the twin-element. Therefore, a twin refinement was performed leading
20

to a BASF parameter of 0.463(3). The absolute structure was determined and is in agreement
with the selected setting (Flack x parameter = 0.048(37) by classical fit to all intensities and
0.010(19) from 2005 selected quotients (Parsons' method). It is noted that Rint is 0.086 for
orthorhombic symmetry but In all possible orthorhombic space groups (Cmc21, Cmcm and
Ama2) the structure cannot be refined. Searching for higher symmetry space groups point to
C2/c, which is only valid for 84% of the structure. In this space group the structure can be
solved and refined but strong disorder and very poor reliability factors are observed.
Therefore, space group Cc was selected. Finally, the very low |EE-1| value of 0.771 not only
indicating a non-centrosymmetric structure but also point to twinning. In the crystal structure
of the pure BOP ligand no strong anomalous scattering atoms are present and therefore, the
absolute structure cannot be determined (Flack x-parameter 0.3(8)). Selected crystal data and
results of the structure refinements are given in Tables S1 and S2.
CCDC-1817293 (1-Zn-BOP), CCDC-1817294 (1-Zn-BP), CCDC-1817295 (1-Cd-BOP),
CCDC-1817296 (1-Cd-BP/II), CCDC-1817297 (2-Zn-BOP), CCDC-1817298 (2-Zn-BP),
CCDC-1817299 (2-Cd-BOP) and CCDC-1817300 (2-Cd-BP) contain the supplementary
crystallographic data for this paper. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.
XRPD investigations
The XRPD measurements were performed using a Stoe Transmission Powder Diffraction
System (STADI P) with CuK1 radiation ( = 1.540598 Å) equipped with a MYTHEN 1K
detector (Dectris Ltd.) and a Ge(111) Johann monochromator.
Thermoanalytic measurements
For DTA/TG measurements a STA1600 from Linseis was used. All measurements were
performed with Al2O3 crucibles. For the DSC measurements a DSC 1 Star System with
STARe Excellence Software from Mettler-Toledo AG was used.
All measurements were performed in a dynamic nitrogen atmosphere. The instruments were
calibrated using standard references materials.
IR and Raman spectroscopy
All IR spectra were recorded using an ATI Mattson Genesis Series FTIR Spectrometer,
control software: WINFIRST, from ATI Mattson (Midland, On, Canada).
The Raman-spectra were recorded with an „ISF66/FRA106 Fourier transform Raman-
21

spectrometer“ of Bruker AXS GmbH, Germany with an Nd/YAG laser with λex = 1064 nm.
Luminescence spectroscopy
Luminescence spectra have been measured with a HORIBA Jobin Yvon GmbH
(Unterhaching, Germany) spectrometer (Fluorolog3) at room temperature, equipped with an
iHR-320-FA Triple Grating spectrograph, R928P Photomultiplier and a 450 W xenon lamp.
The photographs of the samples under near UV light have been taken selecting the 400 nm
wavelength of the Xe lamp with aid of the spectrometer monochromator. For avoiding the
detection of the excitation light by the camera, a long pass 420 nm filter was placed before the
lenses. Photographs taken under irradiation at 270 nm did not require long pass filters.
Reflection and absorption spectra were recorded at room temperature with a Varian Techtron
Pty UV/Vis/NIR two-channel Cary 5000 spectrometer. For the absorption spectra of the
ligands, 4-Benzoylpyridine and 4-Benzylpyridine have been solved in chloroform.
Acknowledgements
This project was supported by the Deutsche Forschungsgemeinschaft (Project No. NA 720/5-
2 and TE 1147/1-1) and by the State of Schleswig-Holstein. We thank Wolfgang Bensch for
access to his experimental facilities.
References
[1] A. Escuer, J. Esteban, S.P. Perlepes, T.C. Stamatatos, Coord. Chem. Rev., 275 (2014) 87-
129.
[2] Y.-F. Zeng, X. Hu, F.-C. Liu, X.-H. Bu, Chem. Soc. Rev., 38 (2009) 469-480.
[3] R. Vicente, B. Bitschnau, A. Egger, B. Sodin, F.A. Mautner, Dalton Trans., (2009) 5120-
5126.
[4] J. Palion-Gazda, B. Machura, F. Lloret, M. Julve, Cryst. Growth Des., 15 (2015) 2380-
2388.
[5] C. Näther, S. Wöhlert, J. Boeckmann, M. Wriedt, I. Jeß, Z. Anorg. Allg. Chem., 639
(2013) 2696-2714.
[6] S. Chorazy, J.J. Stanek, J. Kobylarczyk, S.I. Ohkoshi, B. Sieklucka, R. Podgajny, Dalton
Trans., 46 (2017) 8027-8036.
[7] B. Nowicka, M. Reczynski, M. Rams, W. Nitek, M. Koziel, B. Sieklucka,
CrystEngComm, 17 (2015) 3526-3532.
[8] X.-B. Li, G.-M. Zhuang, X. Wang, K. Wang, E.-Q. Gao, Chem. Commun., 49 (2013)
1814-1816.
[9] Y.-Q. Wang, H.-T. Liu, Y. Qi, E.-Q. Gao, Dalton Trans., 43 (2014) 11819-11825.
22

[10] X.-M. Zhang, Y.-Q. Wang, K. Wang, E.-Q. Gao, C.-M. Liu, Chem. Commun., 47 (2011)
1815-1817.
[11] W.W. Sun, C.Y. Tian, X.H. Jing, Y.Q. Wang, E.Q. Gao, Chem. Commun., (2009) 4741-
4743.
[12] M.A.M. Abu-Youssef, A. Escuer, F.A. Mautner, L. Ohrstrom, Dalton Trans., (2008)
3553-3558.
[13] S. Naiya, S. Biswas, M.G.B. Drew, C.J. Gómez-García, A. Ghosh, Inorg. Chem., 51
(2012) 5332-5341.
[14] P.P. Chakrabarty, S. Saha, D. Schollmeyer, A.K. Boudalis, A.D. Jana, D. Luneau, J.
Coord. Chem., 66 (2012) 9-17.
[15] J.L. Guillet, I. Bhowmick, M.P. Shores, C.J.A. Daley, M. Gembicky, J.A. Golen, A.L.
Rheingold, L.H. Doerrer, Inorg. Chem., 55 (2016) 8099-8109.
[16] B.W. Dockum, G.A. Eisman, E.H. Witten, W.M. Reiff, Inorg. Chem., 22 (1983) 150-
156.
[17] R. González, A. Acosta, R. Chiozzone, C. Kremer, D. Armentano, G. De Munno, M.
Julve, F. Lloret, J. Faus, Inorg. Chem., 51 (2012) 5737-5747.
[18] E. Shurdha, C.E. Moore, A.L. Rheingold, S.H. Lapidus, P.W. Stephens, A.M. Arif, J.S.
Miller, Inorg. Chem., 52 (2013) 10583-10594.
[19] E. Shurdha, S.H. Lapidus, P.W. Stephens, C.E. Moore, A.L. Rheingold, J.S. Miller,
Inorg. Chem., 51 (2012) 9655-9665.
[20] J. Boeckmann, C. Näther, Polyhedron, 31 (2012) 587-595.
[21] B. Machura, A. Świtlicka, I. Nawrot, J. Mroziński, R. Kruszynski, Polyhedron, 30 (2011)
832-840.
[22] F.A. Mautner, C. Berger, R.C. Fischer, S.S. Massoud, Inorg. Chim. Acta, 439 (2016) 69-
76.
[23] F.A. Mautner, C. Berger, R.C. Fischer, S.S. Massoud, Polyhedron, 111 (2016) 86-93.
[24] F.A. Mautner, C. Berger, R.C. Fischer, S.S. Massoud, Inorg. Chim. Acta, 448 (2016) 34-
41.
[25] F.A. Mautner, M. Scherzer, C. Berger, R.C. Fischer, S.S. Massoud, Inorg. Chim. Acta,
425 (2015) 46-51.
[26] S. Suckert, H. Terraschke, H. Reinsch, C. Näther, Inorg. Chim. Acta, 461 (2017) 290-
297.
[27] I. Nawrot, B. Machura, R. Kruszynski, CrystEngComm, 17 (2015) 830-845.
[28] I. Nawrot, B. Machura, R. Kruszynski, CrystEngComm, 18 (2016) 2650-2663.
[29] K.M. Miller, S.M. McCullough, E.A. Lepekhina, I.J. Thibau, R.D. Pike, X. Li, J.P.
Killarney, H.H. Patterson, Inorg. Chem., 50 (2011) 7239-7249.
[30] D.-B. Dang, X.-F. Hu, Y. Bai, Z.-Y. Qi, F. Yang, Inorg. Chim. Acta, 377 (2011) 20-25.
[31] I. Nawrot, B. Machura, R. Kruszynski, J. Lumin., 156 (2014) 240-254.
[32] M. Maiti, S. Thakurta, D. Sadhukhan, G. Pilet, G.M. Rosair, A. Nonat, L.J.
Charbonnière, S. Mitra, Polyhedron, 65 (2013) 6-15.
[33] A.M. Maroń, J.G. Małecki, Polyhedron, 85 (2015) 549-559.
[34] K.M. Miller, S.M. McCullough, E.A. Lepekhina, I.J. Thibau, R.D. Pike, X. Li, J.P.
Killarney, H.H. Patterson, Inorg. Chem., 52 (2013) 3401-3401.
[35] J. Palion-Gazda, I. Gryca, A. Maroń, B. Machura, R. Kruszynski, Polyhedron, 135
(2017) 109-120.
[36] F.A. Afkhami, A.A. Khandar, G. Mahmoudi, W. Maniukiewicz, J. Lipkowski, J.M.
White, R. Waterman, S. García-Granda, E. Zangrando, A. Bauzá, A. Frontera,
CrystEngComm, 18 (2016) 4587-4596.
[37] P. Chakraborty, S. Purkait, S. Mondal, A. Bauzá, A. Frontera, C. Massera, D. Das,
CrystEngComm, 17 (2015) 4680-4690.
23

[38] S. Saha, C. Sen, S. Roy, D. Mallick, E. López-Torres, C. Sinha, Polyhedron, 97 (2015)
240-247.
[39] B. Guo, X. Zhang, J.H. Yu, J.Q. Xu, Dalton Trans, 44 (2015) 11470-11481.
[40] H.L. Jia, M.J. Jia, G.H. Li, Y.N. Wang, J.H. Yu, J.Q. Xu, Dalton Trans, 42 (2013) 6429-
6439.
[41] X.-Y. Wang, S.-Q. Liu, C.-Y. Zhang, G. Song, F.-Y. Bai, Y.-H. Xing, Z. Shi,
Polyhedron, 47 (2012) 151-164.
[42] S. Wöhlert, J. Boeckmann, I. Jess, C. Näther, CrystEngComm, 14 (2012) 5412-5420.
[43] T. , I. Jess, C. Näther, Z. Anorg. Allg. Chem., 641 (2015) 622-626.
[44] J. Werner, M. Rams, Z. Tomkowicz, T. Runčevski, R.E. Dinnebier, S. Suckert, C.
Näther, Inorg. Chem., 54 (2015) 2893-2901.
[45] M. Rams, M. Böhme, V. Kataev, Y. Krupskaya, B. Büchner, W. Plass, T. Neumann, Z.
Tomkowicz, C. Näther, Phys. Chem. Chem. Phys., 19 (2017) 24534-24544.
[46] M. Rams, Z. Tomkowicz, M. Böhme, W. Plass, S. Suckert, J. Werner, I. Jess, C. Näther,
Phys. Chem. Chem. Phys., 19 (2017) 3232-3243.
[47] S. Suckert, M. Rams, L.S. Germann, D.M. Cegiełka, R.E. Dinnebier, C. Näther, Cryst.
Growth Des., 17 (2017) 3997-4005.
[48] S. Suckert, M. Rams, M.M. Rams, C. Näther, Inorg. Chem., 56 (2017) 8007–8017.
[49] S. Wöhlert, T. Fic, Z. Tomkowicz, S.G. Ebbinghaus, M. Rams, W. Haase, C. Näther,
Inorg. Chem., 52 (2013) 12947-12957.
[50] S. Wöhlert, Z. Tomkowicz, M. Rams, S.G. Ebbinghaus, L. Fink, M.U. Schmidt, C.
Näther, Inorg. Chem., 53 (2014) 8298–8310.
[51] S. Wöhlert, M. Wriedt, T. Fic, Z. Tomkowicz, W. Haase, C. Näther, Inorg. Chem., 52
(2013) 1061-1068.
[52] S. Wöhlert, U. Ruschewitz, C. Näther, Cryst. Growth Des., 12 (2012) 2715-2718.
[53] S. Wöhlert, L. Peters, C. Näther, Dalton Trans., 42 (2013) 10746-10758.
[54] T. Neumann, C. dos Santos Cunha, H. Terraschke, L.S. Germann, R.E. Dinnebier, I. Jess,
C. Näther, Z. Anorg. Allg. Chem., 643 (2017) 1497-1507.
[55] T. Neumann, L.S. Germann, I. Moudrakovski, R.E. Dinnebier, C. Dos Santos Cunha, H.
Terraschke, C. Näther, Z. Anorg. Allg. Chem., 643, (2017) 1904-1912.
[56] L.R. Nassimbeni, M.L. Niven, M.W. Taylor, Acta Cryst., B46 (1990) 354-361.
[57] M.G.B. Drew, N.I. Gray, M.F. Cabral, J.d.O. Cabral, Acta Crystallogr. C, 41 (1985)
1434-1437.
[58] W.W. Lestari, H.C. Streit, P. Lonnecke, C. Wickleder, E. Hey-Hawkins, Dalton Trans.,
43 (2014) 8188-8195.
[59] W.W. Lestari, P. Lonnecke, M.B. Sarosi, H.C. Streit, M. Adlung, C. Wickleder, M.
Handke, W.-D. Einicke, R. Glaser, E. Hey-Hawkins, CrystEngComm, 15 (2013) 3874-3884.
[60] W.W. Lestari, P. Lönnecke, H.C. Streit, M. Handke, C. Wickleder, E. Hey-Hawkins,
Eur. J. Inorg. Chem., 2014 (2014) 1775-1782.
[61] in, STOE & CIE GmbH, Darmstadt (Germany), 2008.
[62] G.M. Sheldrick, Acta Cryst., A64 (2008) 112-122.
[63] G.M. Sheldrick, Acta Crystallogr. , C71 (2015) 3-8.
24

Highlights
 New coordination compounds with Cd and Zn thiocyanate and 4-(Boc-
amino)pyridine were prepared.
 Depending on the metal cations and the amount of co-ligands, discrete
complexes or coordination polymers were obtained.
 Zn(NCS)2 forms discrete complexes with octahedral or tetrahedral
coordination, whereas Cd(NCS)2 forms octahedral discrete complexes or 1D
chain compounds.
 The thermal transformation between co-ligand rich and deficient compounds
was studied.
 All compounds were investigated for their spectroscopic properties, including
luminescence measurements.
25

26