Catalytic and conductivity studies in two dimensional coordination polymers built with a thiazole based ligand

Article abstract of DOI:10.1016/j.poly.2018.04.040

The employment of the commercial available organic ligand 2-mercapto-4-methyl-5-thiazoleacetic acid (H₂L) in Zn and Cd chemistry yields two-dimensional (2D) coordination polymers (CPs) with pseudopolymorphic character. Thermal, catalytic and co

Full text of DOI:10.1016/j.poly.2018.04.040

Accepted Manuscript
Catalytic and Conductivity Studies in Two Dimensional Coordination Polymers
Built with a Thiazole Based Ligand
Prashant Kumar, Smaragda Lymperopoulou, Edward Loukopoulos, Wakana
Matsuda, Nikolaos Kourkoumelis, Shu Seki, George E. Kostakis
PII:
S0277-5387(18)30217-1
https://doi.org/10.1016/j.poly.2018.04.040
POLY 13142
DOI:
Reference:
To appear in:
Polyhedron
Received Date:
Accepted Date:
19 March 2018
30 April 2018
Please cite this article as: P. Kumar, S. Lymperopoulou, E. Loukopoulos, W. Matsuda, N. Kourkoumelis, S. Seki,
G.E. Kostakis, Catalytic and Conductivity Studies in Two Dimensional Coordination Polymers Built with a Thiazole
Based Ligand, Polyhedron (2018), doi: https://doi.org/10.1016/j.poly.2018.04.040
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.

Catalytic and Conductivity Studies in Two Dimensional Coordination Polymers
Built with a Thiazole Based Ligand
a,b
a
a
b
Prashant Kumar,*
Smaragda Lymperopoulou, Edward Loukopoulos, Wakana Matsuda,
c
b
a
Nikolaos Kourkoumelis, Shu Seki,* and George E. Kostakis*
a
Department of Chemistry, School of Life Sciences, University of Sussex, Brighton BN19QJ, UK,
E-mail: G.Kostakis@sussex.ac.uk
b
Department of Molecular Engineering, Graduate School of Engineering, Kyoto University,
Nishikyo-ku, Kyoto 615-8510, Japan
E-mail: seki@moleng.kyoto-u.ac.jp; kumar.prashant.25n@st.kyoto-u.ac.jp
c
Department of Medical Physics, School of Health Sciences, University of Ioannina, 45110
Ioannina, Greece.
Abstract
The employment of the commercial availiable organic ligand 2-mercapto-4-methyl-5-thiazoleacetic
acid (H L) in Zn and Cd chemistry yields two-dimensional (2D) coordation polymers (CPs) with
2
pseudopolymorphic character. Thermal, catalytic and conductivity studies are discussed.
Keywords: Zinc; Cadmium; Coordination Polymers; Catalysis; Conductivity;
Introduction
Organic ligands bearing several donor atoms (i.e. N, O or S) have been a subject of
considerable interest in the field of Chemistry and Material Science during the last few decades. In
coordination chemistry, multidentate ligands coordinate to various metals yielding compounds that
possess intriguing structural motifs and remarkable properties.[1–4] In the field of advanced
materials, the synthetic community shows a preference in the use of five- and six-membered
heteroaromatic systems.[5,6] Several compounds based on thiophene and the azole rings have been
reported, however the presence of N- and S- atoms in the thiazole five-membered ring gives to the
resulting compounds desirable properties.[7] 2-mercapto-4-methyl-5-thiazoleacetic acid (H L,
2
Scheme 1) is a hybrid ligand and has five donor atoms (2S, 2O and 1N) exhibiting high versatility
and coordination flexibility with a variety of metal ions.[8–10] The different donor sites of
heterocyclic thiones can bind with two or more metal ions in order to form metal complexes.[11]
Also, the size of the metal anion plays a significant role in the way the metal coordinates to the
ligand and as a result in the final polymer’s dimensions.[12] H L has a very rich chemistry and can
2
find applications in many different aspects. For example, H L and some of its coordination
2

complexes have been found to possess interesting biological properties.[13,14] H L has been used
2
for the synthesis of a 40-membered macrocycle containing two distannoxane ladders,[15] and a
series of organotin complexes.[16–18] Moreover, H L has been used as co-ligand to yield a
2
coordination compound that acts as photosensitizer and can be used in photodynamic therapy,[19]
for chemosensor synthesis for determination of heavy metal ions[20] and finally as a stabilizing
agent for nanoparticles’ (NPs) synthesis for the very same reason.[13,21–23]
I
From the structural point of view, the reactions of H L along with Au ion results in a
2
-
-
tetranuclear complex, [Au(LH )] [24] and three dimers formulated as [Au(LH ) ]Cl·3H O,
2
4
2
2
2
Na [Au(LH ) ]·6H O and Na [Au(LH ) ]·10.5H O with aurophilic interactions and uncommon
3
2 2
2
3
2 2
2
eclipsed conformation.[25] Moreover, reactions of the ruthenium complexes [RuH(CO)Cl(PPh ) ]
3
3
and [RuCl (PPh ) ] with H2L leads two mononuclear complexes formulated as
2
3 3
[
RuCl(CO)(PPh ) (H L)] and [RuCl(PPh ) (H L)].[12] The reaction of H L with R SnCl yields a
3 2 2 3 3 2 2 3
one dimensional triorganotin carboxylates is formed as R Sn[O CCH (C H NS)S]SnR , (R=Me and
3
2
2
4
3
3
Ph). [16]
Scheme 1. The protonated forms of the organic ligand 2-mercapto-4-methyl-5-thiazoleacetic acid
H L) used in this work.
(
2
Organic ligands containing S-atoms have been less used, in contrast to organic ligands that
bear N or O atoms, in the field of coordination polymers (CPs), despite their large range of
applications such as catalysis, magnetism, gas storage and conductivity.[26] Bearing all these in
mind, in this work we have chosen to incorporate the commercial available ligand H L along with
2
Zn and Cd salts to form coordination polymers. To the best of our knowledge, this is the first
attempt to synthesize CPs with the use of H L as the main ligand. We report herein the synthesis,
2
II
characterization, catalytic and conductivity properties of two compounds formulated as [Zn (HL) ]
2
II
(
1) and [Cd (HL) ] (2).
2
Experimental Section
Materials
Chemicals (reagent grade) were purchased from TCI chemicals and Alfa Aesar. All experiments
were performed under aerobic conditions using materials and solvents as received.
Instrumentation

−
1
IR spectra of the samples were recorded over the range of 4000–600 cm on a Perkin Elmer
Spectrum One FT-IR spectrometer (PerkinElmer, Waltham, MA, USA) fitted with an UATR
polarization accessory (PerkinElmer). TGA analysis was performed on a TA Instruments Q-50
model (TA, Surrey, UK) under nitrogen, at a scan rate of 20 °C/min. NMR spectra were measured
on a Varian VNMRS solution-state spectrometer (Bruker BioSpin, Rheinstetten, Germany) at 500
MHz at 30 °C using residual isotopic solvent (CDCl , δ = 7.24 ppm) as an internal chemical shift
3
H
reference. Chemical shifts are quoted in ppm. Coupling constants (J) are recorded in Hz. ESI-MS
was performed on a VG Autospec Fissions instrument (EI at 70 eV).
X-ray Crystallography. Data for compounds 1 and 2, were collected (ω-scans) at the University of
Sussex using an Agilent Xcalibur Eos Gemini Ultra diffractometer with CCD plate detector under a
flow of nitrogen gas at 173(2) K using Cu Kα radiation (λ = 1.54184 Å). CRYSALIS CCD and
RED software was used respectively for data collection and processing. Reflection intensities were
corrected for absorption by the multi-scan method. All structures were determined using Olex2[27],
solved using SHELXT[28] and refined with SHELXL-2014[29]. All non-H atoms were refined
with anisotropic thermal parameters, and H-atoms were introduced at calculated positions and
allowed to ride on their carrier atoms. In both structures, the H-atom bonded to N on the 5
membered aromatic ring could be located and freely refined, however it was preferred to introduced
at calculated position. Crystal data and structure refinement parameters for both compounds are
given in Table 1. Geometric/crystallographic calculations were performed using PLATON[30],
Olex2[27], and WINGX[31] packages; graphics were prepared with Crystal Maker and
MERCURY[32]. Each of the crystal structures has been deposited at the CCDC 1830208 -
1
830209.
Table 1. Crystal data and structure refinement for 1 and 2.
Compound
1
2
Empirical formula
C H N O S Zn
C H CdN O S
4 4
1
2
12
2
4
4
12 12
2
Formula weight
Temperature/K
441.85
173.0
488.88
173.0
Crystal system
Space group
monoclinic
C2/c
orthorhombic
Pbca
a/Å
b/Å
c/Å
α/°
β/°
γ/°
Volume/Å
Z
15.5598(8)
7.4328(5)
13.7649(8)
90
99.416(6)
90
14.8393(2)
14.9312(2)
15.1186(3)
90
90
90
3
1570.50(16)
3349.82(9)
8
4
3
ρ g/cm
calc
1.869
1.939

-1
μ/mm
7.340
15.291
F(000)
Crystal size/mm
Radiation
896.0
1936.0
3
0.12 × 0.1 × 0.04
CuKα (λ = 1.54184)
13.04 to 142.89
0.14 × 0.1 × 0.06
CuKα (λ = 1.54184)
10.24 to 143.118
2
Θ range for data collection/°
-
18 ≤ h ≤ 19, -8 ≤ k ≤ 8, -16 ≤ l ≤ -13 ≤ h ≤ 18, -18 ≤ k ≤ 17, -18 ≤ l ≤
Index ranges
1
5
18
Reflections collected
2365
17294
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F
1473 [Rint = 0.0623, Rsigma = 0.1002]
3237 [Rint = 0.0423, Rsigma = 0.0227]
1473/0/106
3237/0/210
1.053
2
1.058
Final R indexes [I>=2σ (I)]
Final R indexes [all data]
Largest diff. peak/hole / e Å
R = 0.0658, wR = 0.1555 R = 0.0366, wR = 0.0956
1 2 1 2
R = 0.0863, wR = 0.1826 R = 0.0375, wR = 0.0967
1
2
1
2
-3
1.18/-0.84
0.70/-1.17
Flash photolysis-time-resolved microwave conductivity (FP-TRMC) measurements.
The charge carrier transporting property in the synthesised 2D CPs was measured by a FP-TRMC
technique at room temperature under air. Film samples on a quartz plate were prepared using
CP/poly(methylmethacrylate) and dried under vacuum at room temperature. The charge carriers
were generated in the prepared film upon direct photoexcitation of CPs by laser pulses of third
harmonic generation ( = 355 nm) from a Nd:YAG laser which corresponds to Spectra Physics
model INDI-HG with a pulse duration of 5–8 ns. The photon density of a 355 nm pulse was 9.1 x
1
5
1
0 photons per pulse. The microwave frequency and power were set at ~ 9.1 GHz and 3mW,
respectively and The TRMC signal from a diode were recorded by a Tektronix model TDS3032B
digital oscilloscope. The complete experimental procedure is mentioned by Seki et. al.[33]
Synthetic procedures
Synthesis of (1)
Zn(NO ) .6H O (29 mg, 0.1 mmol) was dissolved in 1 ml H O and 1 ml DMF and added to a
3
2
2
2
solution of H L (38 mg, 0.2 mmol), (1 ml EtOH and 1 ml DMF). The resulting solution was stirred
2
for 10 min and it was placed in a 25 ml glass vial. This was heated at 90 °C for 24 h and then cooled
slowly at room temperature. After cooling at room temperature, colorless crystals were obtained in
6
5% yield (based on Zn). The crystals were filtered, washed with H O, EtOH and Et O, and dried in
2 2
−
1
air. Selected IR peaks for (cm ): 3456 (w), 3017 (m), 2971 (m), 2946 (m), 1739 (s), 1433 (m),
366 (s), 1229 (s), 1217 (s), 1206 (s), 1112 (w), 1092 (w), 1062 (w), 903 (m), 788 (w), 770 (w), 718
w), 699 (w). Elemental analysis for C H N O S Zn: calcd. C 32.62, H 2.74, N 6.34, S 29.03
1
(
1
2
12
2
4 4
found C 32.33, H 2.38, N 6.25, S 28.39.
Synthesis of (2)

Compound (2) was synthesized in an analogous manner to (1) by altering Zn(NO ) .6H O with
3
2
2
Cd(NO ) .4H O. After cooling at room temperature, yellowish crystals were obtained in 69% yield
3
2
2
−
1
(
based on Cd). Selected IR peaks (cm ): 3453 (w), 3017 (w), 2971 (m), 2945 (w), 1739 (s), 1658
m), 1554 (s), 1418 (s), 1366 (s), 1229 (s), 1217 (s), 1207 (s), 1105 (w), 1060 (m), 1033 (w), 909
w), 787 (w), 714 (w), 691 (w). Elemental analysis for C H CdN O S : calcd. C 29.48, H 2.47, N
(
(
1
2
12
2
4 4
5
.73, S 26.23 found C 29.25, H 2.52, N 5.67, S 25.45.
Result and Discussion
Crystallographic description
Compound 1 crystallizes in the monoclinic C2/c space group. X-Ray determination of the
crystal structure reveals the formation of a neutral two-dimensional (2D) CP (Figure 1, left). The
asymmetric unit of 1 consists of a zinc atom on a two-fold rotation axis and one single deprotonated
-
ligand (HL ). The ligand coordinates to two Zn centres; via one oxygen atom of the carboxylate
group and the mercapto S atom (Coordination mode A, Scheme 2). Interestingly, the ligand adopts
form B (Scheme 1), however according to the crystallographic data, the two C – S bond lengths are
almost equivalent (1.709(6) and 1.716(7)Å) indicating delocalization. The Zn centre adopts a
distorted tetrahedral geometry and is coordinated to two O atoms and two S atoms. A detailed list of
the bond lengths and angles in 1 is given in Tables S1-2. The compound is a layered structure
extending to two dimensions parallel to the a0b plane. The stability of this architecture is further
supported by the formation of several intermolecular interactions; a) a strong intramolecular N-
H···O bond between atoms from two different ligands (see Table S5), b) a short intermolecular
S···S interaction (see Table S7) and c) weak π-π interactions from adjacent layers (see Table S6).
Compound 2 crystallizes in the orthorhombic Pbca space group. X-Ray determination of the
crystal structure reveals the formation of a neutral two-dimensional (2D) CP (Figure 1, right). The
-
asymmetric unit of 2 consists of one Cd centre and two single deprotonated ligands (HL ). Each
ligand coordinates to two Cd centres; via two oxygen atoms of the carboxylate group (chelated) and
the mercapto S atom. The ligand adopts form B (Scheme 1), however according to the
crystallographic data, the two C – S bond lengths are almost equivalent (1.705(3) and 1.710(3)Å for
S1/S2 and 1.704(3) and 1.718(3)Å for S3/S4) indicating delocalization. Interestingly, despite that
the two organic ligands adopt the same coordination mode (B, Scheme 2) in the first case the Cd
centres is situated above the plane of the 5-memebered ring, where in the second case is placed
below the plane. This structural difference has a significant impact in the topological analysis (see
below). The Cd centre is coordinated to four O atoms and two S atoms and adopts a pseudo-
tetrahedral geometry, if we consider that the two O-atoms of the chelated carboxylate occupy one
corner of the tetrahedron. Selected bond lengths and distances for both compounds are given in
Tables S3-4. In regards to its architecture, 2 presents a layered structure extending to two

dimensions parallel to the b0c plane. As in the case of 1, strong intramolecular N-H···O bonds
further stabilize the framework. Weak π-π interactions between adjacent layers and short
intermolecular S···S distances are also present. As in 1, the adjacent layers in 2 stack following the
ABAB pattern along the c axis. The parameters for all these interactions may be found in Tables
S1-S10. The topological analysis[34] of the 2D net found in 1 results in the most common sql
network, whereas the net found in 2 corresponds to a honeycomb (hcb) structure. Therefore,
compounds 1 and 2, despite possessing the same molecular formula, they exhibit different topology
and thus can be considered as pseudopolymorphs polymers.[35–37]
-
Scheme 2. The coordination modes of ligand HL , found in compounds 1 (left) and 2 (right).
Figure 1. (left) The 2D framework of 1 along the a0b plane. (right) The 2D framework of 2 along
the b0c plane. Certain H atoms of the structures have been omitted for clarity. Colour code: Zn
(grey), Cd (light purple), C (black), H (light pink), N (light blue), O (red), S (yellow).
Figure 2. The networks found in 1 (left) and 2 (right).

TGA and PXRD studies.
Both compounds were subjected to thermal analysis in order to study their thermal stability (Figure
S1). The results show that both compounds are stable up to 300-320°C because of the absence of
water molecules in their structures. Decomposition starts after this point and is completed at
approximately 600°C, indicating the full collapse of the coordination framework. The final residues
of these 2D compounds are ZnO for compound (1), (observed: 17.96%, calc: 18.42%) and CdO for
compound (2), (observed: 27.37%, calc: 26.26%). The homogeneity of a bulk crystalline sample
from 1 and 2 was confirmed by powder X-ray diffraction. The PXRD patterns of both compounds
(Figure 3) were coincide with the simulated PXRD pattern, indicating that the framework is not
sensitive upon exposure to air. To assess possible differences between the crystal structure and the
powder form of the compounds, Rietveld refinement was performed to the respective powder
diffraction patterns. Pseudo-Voigt and FCJ profile functions[38] were used for the fitting
approximation of the peak shapes. The background curve was modeled iteratively using polynomial
approximation. The U, V and W instrument parameters were also refined, followed structural
parameters (coordinates and thermal displacement). The results obtained by Rietveld fit are in good
agreement with those obtained by single crystal x-ray data. Specifically, the dimensions of the unit
cell for the Zn compound (C2/c) were calculated to a=15.572(2), b=7.443(1), c=13.936(2),
b=99.198(6) while for the Cd compound (Pbca) were calculated to a=14.726(3), b=14.905(3),
c=15.102(2). Similarly, minimal differences were observed for the atomic positions. The successful
refinement is depicted in Figure 3 where the resulted Rietveld fit along with the corresponding
figures of merit, profile residual, Rp, and weighted profile residual, wRp, are shown.
Figure 3. Rietveld refinement to experimental X-ray diffraction pattern for (a) Zn compound (left)
Cd compound (right). The vertical ticks indicate the calculated positions of the Bragg peaks.

To exclude the possibility of contamination by an amorphous phase in this sample, SEM
observation was performed (Figure S2). The SEM images of the compound 1 and 2 display the
presence of homogeneous plate like morphologies.
Catalysis
Some of us have previously used a series of tetranuclear Zn Ln coordination clusters as effective
2
2
Lewis acid catalysts in Friedel-Crafts alkylation of indole with trans-β-nitrostyrene.[39] This
reaction is poorly promoted by Zn(OTf) salt. In this work, given the polymeric nature of both
2
compounds we examined their catalytic activity against the given alkylation reaction, aiming to
develop an excellent heterogeneous as well re-usable methodology. Compound 2 does not promote
the organic transformation in EtOH, however the reaction proceeds in 100% yield at room
temperature after 24 h in ethanol (entry 1, Table 1) when 1 was used in 1.0% loading . Then we
examined the catalytic activity of compound 1 in different solvents. The use of different solvents
such as THF, water, dichloromethane, chloroform, and DMF (Table 2), give poor or moderate
(toluene, entry 5, Table 2) yields. This difference may be attributed to the diffusion limitations of
the reactants to reach the active Lewis acid sites or strong binding of solvent (DMF) with the active
sites.
a
Table 2. Scope of the FC alkylation of Indoles with various trans-β-nitrostyrene catalysed by 1
b
Entry
I
II
III
IV
V
VI
VII
Solvent
Ethanol
DMF
THF
water
toluene
DCM
CHCl3
Temperature
Yield (%)
r.t
r.t
r.t
r.t
r.t
r.t
r.t
100
10
16
5
76
20
26
a
Reaction conditions: indole (0.2 mmol) with trans-β-nitrostyrene (0.2 mmol) in 3 mL of EtOH
b
and 1.0 mol % of compound 1. Isolated yield by column chromatography.
Having determined the optimal conditions, we extended the scope of the reaction to other
substituted nitrostyrenes as well N-methyl-indole (Table 3). The reaction proceeds in excellent
yields for unsubstituted indole and N-methylindole (100%) (Table 3). Then, we explored the
influence of the substitution in the para position of the aromatic ring in nitrostyrenes (Table 3,
entries 4a-4f). It was found that the p-fluoro (F) substitution yields the corresponding product in

high yield (100%); however, the use of the p-bromo (Br) derivative significantly lowers the yield of
the final product. The use of heteroaromatic nitroalkene (Table 3, 4c) yields the expected product in
excellent yield (100 %).
Table 3. FC alkylation of Indoles with various substituted trans-β-nitrostyrene catalyzed by
a
compound 1.
a
Reaction conditions; indole (0.50 mmol); substituted trans--nitrostyrene (0.50 mmol);
EtOH 5.0 mL; room temperature; 24 h. 1.0% Loading of compound 1.
After catalysis, compound 1 was isolated by filtration, and it was analysed by PXRD. The PXRD
pattern (Fig S3-4) showed that the structural integrity was preserved, however minor structural
changes could be identified. The use of the recycled catalyst yielded the corresponding product in
st
nd
rd
1
00 % (1 cycle), 92 % (2 cycle) and 86 % (3 cycle), respectively, therefore it is highly
anticipated that the morphology of the catalyst changes upon further use (Figure S4).

Charge-carrier transporting properties
The conductivity of as-synthesized 1 and 2 (Zn and Cd) were determined by flash-photolysis time-
resolved microwave conductivity (FP-TRMC) measurement. This technique examines the charge
carrier transport properties on the multinanometer length scale that is much smaller than the size of
an individual grain or crystallite, and is therefore indicative of the intrinsic charge mobility of a
given material.[40] FP-TRMC experiments were performed at room temperature on films made
from 1 and 2 bound with poly(methylmethacryrate) as a electronically inactive matrix for the FP-
TRMC measurement. The films were placed into a resonant microwave cavity and excited at 355
nm laser light with 5–8 ns pulse duration. The FP-TRMC profiles for as-synthesized CPs 1 and 2
and a similar film made from organic linker H L, both shown in Figure 5, show maximum values of
2
-5
2
-5
2
ϕΣμ of 3.9 × 10 cm /V·s 1, and 2.6 × 10 cm /V·s 2 respectively, and a long carrier life time where
ϕ represent the photocarrier generation yield and Σμ is the sum of the generated charge carrier
mobilities for both electrons and holes. The photo-conductivity kinetic traces decayed principally
triple exponential manner; the values are summarized in Table 4. The values in the brackets
represent the relative ratio of the decay components. All of the kinetic traces exhibit pseudo-first
4
-1
order ones with long enough lifetimes as represented by k of 4.2 -5.0 × 10 s ( ~ 20 - 24 s),
3
suggesting that the signals were observed as the transient conductivity of free charge carriers after
geminate charge recombination processes.
0.0001
(a)
(b)
(c)
-
5
1
x 10

-
6
1
x 10
0
2
4
6
8
10
0
2
4
6
8
10
0
2
4
6
8
10
Time (s)
Time (s)
Time (s)
Figure 5 . Conductivity transients observed by FP-TRMC of H L (black trace, a), Zn - CP 1 (green
2
15
trace, b) and Cd – CP 2 (blue trace, c) after laser pulse excitation at 355 nm with 9.1 × 10 photons
-2
-1
cm pulse
Table 4. Kinetics of the Photoconductivity Decay
-
1
-1
-1
Compound
k (s )
k (s )
k (s )
1
2
3
6
a
4
4
1
2
H L
2
1.8 × 10 (0.45)
1.8 × 10 (0.45)
1.6 × 10 (0.52)
9.5 × 10 (0.2)
5.0 × 10 (0.35)
5.0 × 10 (0.15)
4.2 × 10 (0.05)
6
4
4
7.0 × 10 (0.4)
6
4
4
7.0 × 10 (0.43)

a
The values in the brackets represent the relative ratio of the decay components
Focusing onto the contribution from the photo-generated free charge carriers as ()max
×
(k3 ratio), 1 marked 3-hold higher value than that in 2. Most importantly, the S···S intermolecular
distance observed in 1 and 2 increases from 3.303(2) Å in 1 to 3.6878(11) Å in 2 (Table S7-S10).
2
+
This difference may be attributed to the different ionic radii of Cd (109 pm) when compared with
2
+
Zn (88 ppm), and thus 1 that exhibits the shortest S···S distance shows higher conductivity. This
explanation suggests that shortening the length of the intermolecular S···S contacts, even higher
charge mobility can be obtained, therefore our future studies will be focusing towards this direction.
Conclusions
The first examples of 2D CPs built from 2-mercapto-4-methyl-5-thiazoleacetic acid and Zn
and Cd metal centres are reported. The new compounds show interesting structural features
(pseudopolymorphism). Compound 1 was found to act as an efficient Lewis acid catalyst towards
the Friedel-Crafts alkylation of nitrostyrene-indole. Along with catalysis, we have shown the use of
the thiazole based ligand yields stable, non-sensitive upon exposure to air, CPs that exhibit
moderate conductivity determined by FP-TRMC.
Acknowledgments
P. K. and S. S. are thankful to the Japan Society for the Promotion of Science (JSPS, P16342 for a
fellowship, 26102011, and 15K21721). S. L. acknowledges support from the program LLP Erasmus
Placements. G.E.K. thanks the EPSRC (UK) for funding (grant number EP/M023834/1).
Appendix A. Supplementary data
CCDC 1830208 – 1830209 contains the supplementary crystallographic data for 1 and 2. These
data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from
the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1
223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
References
[
[
1] P. Abbasi, K. Quinn, D.I. Alexandropoulos, M. Damjanović, W. Wernsdorfer, A. Escuer, J.
Mayans, M. Pilkington, T.C. Stamatatos, Transition Metal Single-Molecule Magnets: A
{
Mn31} Nanosized Cluster with a Large Energy Barrier of ∼60 K and Magnetic Hysteresis
at ∼5 K, J. Am. Chem. Soc. 139 (2017) 15644–15647. doi:10.1021/jacs.7b10130.
2] G. Maayan, N. Gluz, G. Christou, A bioinspired soluble manganese cluster as a water

oxidation electrocatalyst with low overpotential, Nat. Catal. 1 (2018) 48–54.
doi:10.1038/s41929-017-0004-2.
[
[
3] A. Baniodeh, N. Magnani, Y. Lan, G. Buth, C.E. Anson, J. Richter, M. Affronte, J. Schnack,
A.K. Powell, High spin cycles: topping the spin record for a single molecule verging on
quantum criticality, Npj Quantum Mater. 3 (2018) 10. doi:10.1038/s41535-018-0082-7.
4] R.L. Siegelman, T.M. McDonald, M.I. Gonzalez, J.D. Martell, P.J. Milner, J.A. Mason, A.H.
Berger, A.S. Bhown, J.R. Long, Controlling Cooperative CO2 Adsorption in Diamine-
Appended Mg2(dobpdc) Metal-Organic Frameworks, J. Am. Chem. Soc. 139 (2017) 10526–
1
0538. doi:10.1021/jacs.7b05858.
[
[
5] F. Shibahara, E. Yamaguchi, T. Murai, Direct arylation of simple azoles catalyzed by 1,10-
phenanthroline containing palladium complexes: An investigation of C4 arylation of azoles
and the synthesis of triarylated azoles by sequential arylation, J. Org. Chem. 76 (2011) 2680–
2
693. doi:10.1021/jo200067y.
6] A. Mori, A. Sugie, Palladium-catalyzed CH arylation and dehydrogenative homocoupling of
heteroaromatic compounds and application to the design of advanced organic materials, Bull.
Chem. Soc. Jpn. 81 (2008) 548–561. doi:10.1246/bcsj.81.548.
[
[
7] B. Ustamehmetoğlu, Synthesis and Characterization of Thiophene and Thiazole Containing
Polymers, Electrochim. Acta. 122 (2014) 130–140. doi:10.1016/j.electacta.2013.12.130.
8] S. Chandra, L.K. Gupta, Sangeetika, Spectroscopic, cyclic voltammetric and biological
studies of transition metal complexes with mixed nitrogen-sulphur (NS) donor macrocyclic
ligand derived from thiosemicarbazide, Spectrochim. Acta - Part A Mol. Biomol. Spectrosc.
6
2 (2005) 453–460. doi:10.1016/j.saa.2005.01.015.
[
[
9] S.H. and M.C.R. de A. and P.G.J. J. Vicente, M. Chicote, Synthesis and Structural
Characterization of Gold (I) and Silver (I) Complexes of the Multidonor Ligand 2-
(Phenacylthio)pyridine Crystal Structures of {py{SCH2C(O)Ph}-2}], Eur. J. Inorg. Chem.
(1998) 511–516.
10] L.M. Brines, J. Shearer, J.K. Fender, D. Schweitzer, S.C. Shoner, D. Barnhart, W. Kaminsky,
S. Lovell, J.A. Kovacs, Periodic Trends within a Series of Five-Coordinate Thiolate-Ligated
[
M II ( S Me2 N 4 ( tren ))] + ( M ) Mn , Fe , Co , Ni , Cu , Zn ) Complexes , Including a
Rare Example of a Stable Cu II − Thiolate, Inorg. Chem. 46 (2007) 9267–9277.
11] H. Tannai, K. Tsuge, Y. Sasaki, O. Hatozaki, N. Oyama, Monodentate and bridging
coordination of 2,5-dimercapto-1,3,4-thiadiazolate to a (2,2′:6′,2″-terpyridine)platinum(II)
center, Dalt. Trans. (2003) 2353–2358.
[
[
12] P. Kumar, M. Yadav, A.K. Singh, D.S. Pandey, Synthesis and characterization of some novel
ruthenium(II) complexes containing thiolate ligands, J. Organomet. Chem. 695 (2010) 994–

1
001. doi:10.1016/j.jorganchem.2009.12.006.
[
[
[
[
13] P. Kannan, S.A. John, Highly sensitive determination of hydroxylamine using fused gold
nanoparticles immobilized on sol-gel film modified gold electrode, Anal. Chim. Acta. 663
(2010) 158–164. doi:10.1016/j.aca.2010.01.045.
14] P. Kannan, S.A. John, Highly sensitive electrochemical determination of nitric oxide using
fused spherical gold nanoparticles modified ITO electrode, Electrochim. Acta. 55 (2010)
3
497–3503. doi:10.1016/j.electacta.2010.01.084.
15] C. Ma, J. Sun, A novel self-assembling synthesis and crystal structure of 40-membered
macrocyclic complex containing eight-tin., Dalt. Trans. (2004) 1785–1786.
doi:10.1039/B405247A.
16] C. Ma, J. Sun, L. Qiu, J. Cui, The synthesis and characterization of triorganotin carboxylates
of 2-Mercapto-4-methyl-5-thiazoleacetic acid: X-ray crystal structures of polymeric
Me3Sn[O2CCH2(C4H 3NS)S]SnMe3 and Ph3Sn[O2CCH 2(C4H3NS)S]SnPh3, J. Inorg.
Organomet. Polym. 15 (2005) 341–347. doi:10.1007/s10904-005-7875-4.
[
17] R. Zhang, J. Sun, C. Ma, Synthesis and crystal structure of macrocyclic di-n-butyltin(IV)
complex
Bu2Sn(O2CCH2C4H3NS)SS(C4H3NSCH2CO2)Sn n-Bu2]O}2, Inorganica Chim. Acta.
57 (2004) 4322–4326. doi:10.1016/j.ica.2004.06.026.
with
2-mercapto-4-methyl-5-thiazoleacetic
acid,
{[n-
3
[
[
[
18] R.F. Zhang, J.F. Sun, C.L. Ma, J.H. Zhang, Synthesis, Characterization and Crystal
Structures of Diorganotin(IV) Complexes with 2-Mercapto-4-methyl-5-thiazoleacetic Acid,
Pol. J. Chem. 80 (2006) 367–376.
19] S. Moeno, E. Antunes, S. Khene, C. Litwinski, T. Nyokong, The effect of substituents on the
photoinduced energy transfer between CdTe quantum dots and mercapto substituted zinc
phthalocyanine derivatives., Dalt. Trans. 39 (2010) 3460–3471. doi:10.1039/b926535j.
20] A.A.A. Hamid, C.P. Tripp, A.E. Bruce, M.R.M. Bruce, Application of structural analogs of
dimercaptosuccinic acid-functionalized silica nanoparticles (DMSA- silica ) to adsorption of
mercury, cadmium, and lead, Res. Chem. Intermed. 37 (2011) 791–810. doi:10.1007/s11164-
0
11-0317-8.
[
[
[
21] N. Vasimalai, S.A. John, Off-on and on-off chemosensors for ultratrace mercury(II) and
copper(II) using functionalized thiazole and cadmium sulfide nanoparticles fluorophores,
Sensors Actuators, B Chem. 190 (2014) 800–808. doi:10.1016/j.snb.2013.09.028.
22] P. Kannan, S.A. John, Synthesis, Characterization and Electrocatalytic Activity of Fused
Gold
doi:10.1166/jnn.2011.3561.
23] Y. Su, Y. Lin, Y. Fu, F. Qian, X. Yang, M.M.F. Choi, Synthesis and Characterization of
Nanoparticles,
J.
Nanosci.
Nanotechnol.
11
(2011)
2142–2150.

Water-Soluble Monolayer-Protected Gold Nanoparticles, Adv. Mater. Res. 415–417 (2011)
17–620. doi:10.4028/www.scientific.net/AMR.415-417.617.
24] B. Tzeng, W. Liu, J. Liao, G. Lee, S. Peng, Self-Assembly of Gold ( I ) Compounds with
004, Cryst. Growth Des. 4 (2004) 573–577.
6
[
[
2
25] M. Hapka, M. Dranka, K. Orłowska, G. Chałasinski, M.M. Szczesniak, J. Zachara,
Noncovalent interactions determine the conformation of aurophilic salts with 2-Mercapto-4-
methyl-5-thiazoleacetic acid ligands †, Dalt. Trans. 44 (2015) 13641–13650.
doi:10.1039/b000000x.
[
[
26] E.J. Mensforth, M.R. Hill, S.R. Batten, Coordination polymers of sulphur-donor ligands,
Inorg Chim Acta. 403 (2013) 9–24. doi:10.1016/j.ica.2013.02.019.
27] O. V Dolomanov, A.J. Blake, N.R. Champness, M. Schröder, OLEX: New software for
visualization and analysis of extended crystal structures, J. Appl. Crystallogr. 36 (2003)
1
283–1284.
[
[
[
[
[
28] G.M. Sheldrick, SHELXT – Integrated space-group and crystal-structure determination, Acta
Crystallogr. Sect. A Found. Adv. 71 (2015) 3–8. doi:10.1107/S2053273314026370.
29] G.M. Sheldrick, A short history of SHELX, Acta Crystallogr. Sect. A. 64 (2008) 112–122.
doi:10.1107/s0108767307043930.
30] A.L. Spek, Single-crystal structure validation with the program PLATON, J. Appl.
Crystallogr. 36 (2003) 7–13. doi:10.1107/S0021889802022112.
31] L.J. Farrugia, suite for small-molecule single-crystal crystallography, J. Appl. Crystallogr. 32
(1999) 837–838. doi:10.1107/S0021889899006020.
32] C.F. Macrae, P.R. Edgington, P. McCabe, E. Pidcock, G.P. Shields, R. Taylor, M. Towler, J.
Van De Streek, Mercury: Visualization and analysis of crystal structures, J. Appl.
Crystallogr. 39 (2006) 453–457. doi:10.1107/S002188980600731X.
[
33] F.C. Grozema, L.D.A. Siebbeles, J.M. Warman, S. Seki, S. Tagawa, U. Scherf, Hole
conduction along molecular wires: α-bonded silicon versus π-bond-conjugated carbon, Adv.
Mater.
14
(2002)
228–231.
doi:10.1002/1521-4095(20020205)14:3<228::AID-
ADMA228>3.0.CO;2-3.
[
[
[
34] V.A. Blatov, A.P. Shevchenko, D.M. Proserpio, Applied Topological Analysis of Crystal
Structures with the Program Package ToposPro, Cryst. Growth Des. 14 (2014) 3576–3586.
doi:10.1021/cg500498k.
35] V.N. Dokorou, A.K. Powell, G.E. Kostakis, Two pseudopolymorphs derived from alkaline
earth metals and the pseudopeptidic ligand trimesoyl-tris-glycine, Polyhedron. 52 (2013)
5
38–544. doi:10.1016/j.poly.2012.08.032.
36] C.N. Morrison, A.K. Powell, G.E. Kostakis, Influence of Metal Ion on Structural Motif in

Coordination Polymers of the Pseudopeptidic Ligand Terephthaloyl-bis-beta-alaninate,
Cryst. Growth Des. 11 (2011) 3653–3662. doi:10.1021/cg2007028.
[
37] H.H. Monfared, A.-C.C. Chamayou, S. Khajeh, C. Janiak, Can a small amount of crystal
solvent be overlooked or have no structural effect? Isomorphous non-stoichiometric hydrates
(pseudo-polymorphs): the case of salicylaldehyde thiosemicarbazone, CrystEngComm. 12
(2010) 3526–3530. doi:10.1039/c0ce00041h.
[
[
[
38] L.W. Finger, D.E. Cox, A.P. Jephcoat, IUCr, A correction for powder diffraction peak
asymmetry due to axial divergence, J. Appl. Crystallogr. 27 (1994) 892–900.
doi:10.1107/S0021889894004218.
39] P. Kumar, S. Lymperopoulou, K. Griffiths, S.I. Sampani, G.E. Kostakis, Highly efficient
tetranuclear ZnII2LnIII2 catalysts for the Friedel – Crafts alkylation of indoles and
nitrostyrenes, Catalysts. 6 (2016) 140.
40] A. Saeki, Y. Koizumi, T. Aida, S. Seki, Comprehensive approach to intrinsic charge carrier
mobility in conjugated organic molecules, macromolecules, and supramolecular
architectures, Acc. Chem. Res. 45 (2012) 1193–1202. doi:10.1021/ar200283b.

Graphical Abstract
Graphical Abstract
The employment of the commercial availiable organic ligand 2-mercapto-4-methyl-5-thiazoleacetic
acid (H L) in Zn and Cd chemistry yields two-dimensional (2D) coordation polymers (CPs) with
2
pseudopolymorphic character. Thermal, catalytic and conductivity studies are discussed.
Keywords: Zinc, Cadmium, Coordination Polymers, Catalysis, Conductivity