A facile route for the synthesis of new 1D copper(II) coordination polymer as precursors for preparation of nano structures: Crystallography and Hirshfeld surface analysis

Article abstract of DOI:10.1016/j.molstruc.2019.127020

The purpose of the present study was to investigate a simple approach for synthesis of new 1D copper (II) coordination polymer as a precursor for preparation of nano-structures based on crystallography and Hirshfeld surface analysis method. In doing so, A

Full text of DOI:10.1016/j.molstruc.2019.127020

Journal of Molecular Structure 1200 (2020) 127020
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
A facile route for the synthesis of new 1D copper(II) coordination
polymer as precursors for preparation of nano structures:
Crystallography and Hirshfeld surface analysis
,
, **
Nozar Fayaz bakhsh a, Mohammad Jaafar Soltanian Fard a *, Payam Hayati b
,
Ardavan Masoudiasl c, Jan Janczak d
a Department of Chemistry, Faculty of Chemical Science, Firoozabad Branch, Islamic Azad University, P.O. Box 74715-117, Firoozabad, Fars, Iran
b Persian Gulf Science and Technology Park, Nano Gostaran Navabegh Fardaye Dashtestan Company, Borazjan, Iran
c Department of Chemistry, Payame Noor University, Tehran, Iran
d Institute of Low Temperature and Structure Research Polish Academy of Sciences, P.O. Box 1410 Okolna 2 Str., 50-950, Wroclaw, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 July 2019
Received in revised form
19 August 2019
Accepted 2 September 2019
Available online 17 September 2019
The purpose of the present study was to investigate a simple approach for synthesis of new 1D copper (II)
coordination polymer as a precursor for preparation of nano-structures based on crystallography and
Hirshfeld surface analysis method. In doing so, A novel 1D copper(II) coordination polymer compound of
[Cu(tp)(phen)]n (1) (tp ¼ 1,4-benzendicarboxylic acid and phen: 1,10-Phenanthroline) was synthesized
using two different methods, such as branched-tube and sonochemical methods. The X-Ray Diffraction
(XRD) results revealed that with applying both methods, the produced compounds have a same crys-
talline phase. A Single crystal X-ray analysis of produced compound 1 using the branched-tube method
showed that Cu2þ ions are 6-coordinated. The contribution of intermolecular interactions in compound 1
were studied by Hirshfeld Surface Analysis method. The role of sonication power, reaction time, con-
centrations of reactants, temperature on the growth and final morphology of the obtained nano-
structures were studied by the sonochemical method. While, the concentrations of reactants and
reaction time directly affected the final size of nano-structures of compound 1, the sonication power and
temperature showed an inverse impact. Compound 1 was used as a new precursors for preparation of
Cu(II) oxide structures via solid-state thermal decomposition process. The nano-structures of compound
1 were further analyzed by IR spectroscopy, powder X-ray diffraction (PXRD) and Scanning Electron
Microscopy (SEM).
Keywords:
Coordination polymer
Ultrasound irradiation
Hirshfeld surface methods
Morphology
© 2019 Elsevier B.V. All rights reserved.
1. Introduction
Up to now, various approaches have been developed to
assemble CPs such as slow diffusion of the reactants into a poly-
In recent decades, coordination polymers (CPs) have attracted
great attentions among researchers of synthetic chemistry and
materials science fields. Because these compounds possess unique
structures with specific properties and reactivities compared with
mononuclear compounds [1e10]. Among various incorporated
metal ions to fabricate CPs, Cu(I) and Cu(II) have been a main
component in a large number of CP's structures. Copper based CPs
have been applied in a variety of practical applications [11e13].
meric matrix, diffusion from the gas phase, evaporation of the
solvent at ambient or reduced temperatures, precipitation or
recrystallisation from
a mixture of solvents, temperature-
controlled cooling, hydrothermal and sono-chemical methods
[14e20].
Regarding the two important factors - amount of time needed
and the homogeneity in the nucleation to prepare nanomaterials e
sono-chemical method could be considered as an excellent choice
in comparison with other mentioned methods [21]. The basic
mechanism which employed by this method to affect a chemical
reactions is the formation and collapsing bubbles generating
extremely localized hot spots having pressures of about 1000 bar,
temperatures of roughly 5000 K, and heating and cooling rates of
* Corresponding author.
** Corresponding author.
E-mail addresses: mohammadjaafar_soltanian@yahoo.com, mj.soltanian@iauf.
ac.ir (M.J. Soltanian Fard), payamhayati1362@gmail.com (P. Hayati).
https://doi.org/10.1016/j.molstruc.2019.127020
0022-2860/© 2019 Elsevier B.V. All rights reserved.

2
N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
Table 1
Crystal data and structure refinement for compound 1.
CCDC deposit number
Molecular formula
MW
1922310
20H12CuN2O4
407.86
C
Crystal system
Space group
Z
Monoclinic
C2/c
4
a,b,c,
b
15.3180 (9), 10.0629 (7), 10.3152 (8) (Å) 92.540 (6) (ꢀ)
Volume (Å3)
1588.46 (19)
1.705
1.41
100
Calculated density (Mg/m3)
Absorption coefficient (mmꢁ1
T (K)
)
l
(Å)
0.71073
F (000)
828
Crystal size (mm)
q
0.26 ꢂ 0.22 ꢂ 0.17
range for data collection (ꢀ)
3.1e28.9
Limiting indices
Reflections collected/unique
R (int)
h ¼ ꢁ20 / 20, k ¼ ꢁ13 / 13, l ¼ ꢁ14 / 14
22544, 2108
0.039
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness of fit GOF) on F2
1.000, 0.921
Full-matrix least-squares on F2
2108/0/123
1.00
0.028, 0.060
0.38, ꢁ0.25
R[F2 > 2
s
(F2)], wR(F2)
Largest difference peak/hole (e. Å3)
about 1010 Ks Between the microbubble and the bulk solution.
With applying these conditions-occurring pressure and tempera-
ture gradients and rapid molecular motions the following phe-
nomena took place: the production of excited states, bond
breakage, the formation of free radicals, mechanical shocks and
high shear gradients [22]. The use of high-intensity ultrasound to
enhance the reactivity of metals as a stoichiometric reagent has
become a synthetic technique for many heterogeneous organic and
organometallic reactions [23e28].
Nano scaled CPs such as nanoparticles, nano-cubes, nano-rods,
and nanotubes with finite repeating units offering distinctive
properties which could not be provide by bulk CPs, have been the
main topic of synthetic studies recently [29]. However, CPs in the
form of nanoparticles among other nanosized forms are the most
Table 2
Selected bond lengths (Å) and angles (ꢀ) for 1.
Bond length (Å)
Cu1eN1
Cu1eO1
2.0252 (12)
1.9348 (10)
2.680
2.0252 (12)
1.9348 (10)
2.680
Cu1eO2
Cu1eN1i
Cu1eO1i
Cu1eO2i
Bond angle (ꢀ)
N1eCu1eO1
N1eCu1eO2
N1eCu1eN1i
N1eCu1eO1i
N1eCu1eO2i
O1eCu1eO2
O1eCu1eN1i
O1eCu1e O1i
O1eCu1e O2i
O2eCu1eN1i
O2eCu1e O1i
O2eCu1e O2i
N1idCu1d O1i
N1idCu1d O2i
O1idCu1d O2i
172.99 (5)
125.83
81.52 (7)
91.57 (5)
89.90
54.94
91.57 (5)
95.36 (6)
93.19
89.90
93.19
134.68
172.99 (5)
125.83
54.94
Table 3
The influence of sonication power, reaction time, concentration of reactants and temperature on the size of compound 1 particle.
1
T (ꢀC)a
t (min)b
Concentration (M)
Sonication of power (W)
Frequency (kHz)
SEMc (þ/ꢁ6 nm)
Morphology
1e1
1e2
1e3
1e4
1e5
50
50
50
50
70
60
60
30
60
60
0.1
0.1
0.1
0.5
0.1
0
40
40
40
40
40
252
174
93
153
76
Mainly flake structure (2D)
Mainly flake structure (2D)
Mainly flake structure (2D)
Mainly flake structure (2D)
Mainly flake structure (2D)
60
60
60
60

N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
3
Scheme 1. Synthetic route from initial reagents to copper(II) oxide nanoparticles.
Fig. 2. 1D zigzag chain of [Cu(tp)(phen)]n in a direction.
synthesized morphology due to the wide potential applications in
gas storage, conductivity, molecular recognition and separations,
catalysis, chirality, photonics and magnetic materials [30e38].
The purpose of the present study was to discuss a simple
approach for preparation of Cu(II) based 1D CP nanostructures
based on sono-chemical method. Additionally, the CP's structure
was studied by geometrical and Hirshfeld surface analysis method.
Moreover, the impacts of a few influential sonication power
parameter, reaction time, concentration of reactants and temper-
ature on the structural properties were studied.
titanium oscillator (horn) with 12.5-mm diameter. The generator
was operated at 40 kHz with a maximum power output of 600 Wat
room temperature for 1 h.
2.2. Crystallography
A Single crystal X-ray diffraction data was collected on a RIGAKU
XtaLabPro diffractometer equipped with a Mo microfocus sealed
tube generator coupled to a double-bounce confocal Max-Flux®
multilayer optic and a HPAD PILATUS3R 200K detector. A total of
2. Experimental
874 frames in ten
u-scans was recorded in shutter less mode with
oscillations of 0.5ꢀ. CrysAlisPro 1.171.39.43c [39] was employed for
the data collection and processing, with SCALE3 ABSPACK scaling
algorithm implemented for the empirical absorption correction
using spherical harmonics. The structure was solved by intrinsic
phasing methods using SHELXT [40a] and refined by full-matrix
least squares against F2 using SHELXL software [40b]. Non-
hydrogen atoms were refined with anisotropic thermal parame-
ters. Aromatic hydrogen atoms were geometrically fixed and
refined with Uiso set to 1.2Ueq(C) of their parent atom. Molecular
Hirshfeld surfaces (HS) and the associated 2D fingerprint plots (FP)
[41e44] were calculated using Crystal Explorer [45] computer
program with taking X-ray crystallography data as input.
2.1. Materials and characterization instruments
The chemical materials and solvents were purchased from
SigmaeAldrich and Merck companies, respectively and were used
without further purification. A Heraeus Analytical Jena, Multiple EA
3100 CHNO speedy analyzer was utilized for Elemental analyses (C,
H and N). Fourier transform infrared (FT-IR) spectra in the range of
4000-400 cmꢁ1 were recorded on a Bruker Vector 22 FT-IR spec-
trometer using KBr disks. Thermal analyses were carried out under
argon atmosphere with a heating rate of 10 ꢀC/min using a SDT
Q600 V20.9 Build 20 instrument. An electrothermal 9100 devices
was used for determination of Melting points. X-Ray powder
diffraction (XRPD) measurements were done utilizing X'pert
2.3. Synthesis of copper(II) coordination polymer (1) as single
crystal
diffractometer made by Philips with monochromatized Cu ka rays
and simulated XRPD patterns in view of single crystal data were
well prepared utilizing the Mercury software [40c]. The
morphology of synthesized compounds was analyzed using scan-
ning electron microscopy (SEM) (S-4200, Hitachi, Japan). The ul-
Single crystals of [Cu(tp)(phen)]n (1)- suitable for the X-ray
structure determination-were prepared with a slow diffusion in a
branched tube as follow [46]: The main arm of a branched tube was
charged with tp ¼ 1,4-benzendicarboxylic acid (1.0 mmol in H2O/
NaOH), copper(II) nitrate (1.0 mmol in H2O) and phen ¼ 1,10-
Phenanthroline (1.0 mmol in methanol). Then, the tube was
sealed and immersed in an oil bath at 60 ꢀC, while the other arm
was kept at ambient temperature. After 10 days, single crystals
suitable for X-ray analysis were formed in the cooler arm, which
was filtered off, washed with acetone, dried in air.
trasonically synthesis of samples was carried out under
a
multiwave ultrasonic generator (Sonicator_3000, Misonix Inc.,
Farmingdale, NY, USA) equipped with a converter/transducer and
[Cu(tp)(phen)]n (1) (single crystal): yield: 62.47%. m.p ¼ 272 ꢀC.
Anal. Calc. for C20H12CuN2O4: C, 58.90%; H, 2.97%; N, 6.87%; Found:
C, 59.21%; H, 2.64%; N, 17.98%. IR (cmꢁ1): 3417(w), 3050(w),
1634(w), 1584(m), 1482(w), 1383(s), 1279(m), 1145(m), 1107(m),
1012 (m), 849(m), 777(w), 719 (s), 646(w), 430(w).
Fig. 1. A fragment of the crystal structure of [Cu(tp)(phen)]n. The Hydrogen atoms are
omitted for clarity. (Symmetry transformations used to generate equivalent atoms: (i)
-xþ1, -yþ1, -zþ1; (ii) -xþ1, -yþ2, -zþ1.
Fig. 3. Six chains surrounding the central one.

4
N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
3. Results and discussion
3.1. Description of the structure of [Cu(tp)(phen)]n
Coordination environment is shown in Fig. 1. The bond lengths
and bond angles covering the primary coordination sphere are
shown in Table 2.
The asymmetric unit of compound 1 is composed of one Cu
atom, one half terephthalic acid (tp), and one half 1,10-
phenanthroline (phen). The investigation of crystal structure
shows the formation of infinite 1D zigzag chain (Fig. 2) constructed
from {Cu(phen)} nodes and tp2ꢁ linkers. In this polymeric structure,
each copper atom is hexa-coordinated with a distorted octahedral
geometry, giving a CuN2O4 chromophore: two nitrogen atoms from
the phenanthroline ligand, and four oxygen atoms from two
chelating carboxylate groups arising from two tp2ꢁ linkers. In this
distorted octahedral geometry, the basal plane includes four atoms
of N1, N1i, O1, and O1i, while two apical positions are occupied by
O2 and O2i atoms. The deviation of nitrogen and oxygen atoms
from the basal CuN2O2 plane is slight: 0.021 Å for N1 and N1i and
0.019 Å for O1 and O1i. The two apical oxygen atoms (O2 and O2i)
lie above and below the basal CuN2O2 plane at 2.180 Å. The
investigation of bond angles of the CuN2O4 chromophore indicate
the angles of N1eCu1eO1 and N1'dCu1dO1’ equal to 172.99(5)ꢀ
for the trans atoms system of the basal plane and an angle of
O2eCu1eO2’ ¼ 134.68ꢀ for the JahneTeller apical positions. Also,
the basal and basal-apical bond angles are ranging from 81.52(7)ꢀ
to 95.36(6)ꢀ and 54.94ꢀe125.83ꢀ, respectively, showing the devia-
tion from the ideal value of 90ꢀ. The bite angle for five-membered
Fig. 4. Simplification representation of coordination networks in 1.
Fig. 5. A fragment of the framework in 1.
2.4. Sono-chemical synthesis of Cu(II) coordination polymer
The sono-chemical preparation of nano-structure samples of
[Cu(tp)(phen)]n (1) was followed using a general procedure: a high-
density ultrasonic probe placed into the solution of copper(II) ni-
trate salt. Then, 1,4-benzendicarboxylic acid and 1,10-
Phenanthroline in intended solvent were added as dropwise. The
reaction mixture was kept under the ultrasonic irradiation for a
certain time period. After that the reaction product was centri-
fuged, filtered, dried and placed under vacuum. The effect of
different parameters on morphology and size of thesynthesized
coordination polymer was investigated by carrying out the above
experiment with the change of reaction time, reagents concentra-
tion, solvent type and reaction temperature. The details of these
experiments are summarized in Table 3.
chelate
ring
arising
from
phenanthroline
ligand
(N1eCu1eN1i ¼ 81.52(7)ꢀ) is in compliance with the mixed ligand
Cu(II) complex containing phenanthroline and carboxylate ligands
[47,48]. The order of the bond lengths around copper centre follows
as: CueObasal < CueNbasal < CueOapical, which is also observable in
six-coordinated Cu complex containing CuN2O4 chromophore
[48e50]. Although the CueOapical bonds seems to be long (2.680 Å),
but the larger values have been also reported in some Cu(II) com-
plexes with similar structure (2.723 Å and 2.729 Å in
[Cu(phen)(C6H5CO2ꢁ)2] and 2.724 Å in [Cu(C2H2BrO2)2(C12H8N2)]
[51,52]. The specific lengthening of two axial CueO distances than
[Cu(tp)(phen)]n (1) (Nanostructure): m.p ¼ 244 ꢀC. Anal. Calc.
for C20H12CuN2O4: C, 58.90%; H, 2.97%; N, 6.87%; Found: C, 58.51%;
H, 3.23%; N, 18.11%. IR (cmꢁ1): 3415(w), 3067(w), 1634(w), 1581(m),
1478(w), 1387(s), 1291(m), 1153(m), 1107(m), 1019(m), 864(m),
791(w), 721 (s), 649(w), 437(w).
those in the basal CuO2N2 plane represents
a significant
JahneTeller distortion.
2.5. Synthesis of copper(II) oxide nanoparticles
The crystal lattice of 1D zigzag mercury(II) coordination poly-
mer are further expanded by intermolecular interactions such as
The preparation of copper(II) oxide nanoparticles was per-
formed via thermal decomposition of nanostructured copper(II)
coordination polymer. For this purpose, appropriate amount of
copper(II) compound was placed into a porcelain crucible and then
heated up to 400 ꢀC in a furnace under air atmosphere for 2 h. The
product of thermolysis was washed with a little amount of ethanol
solvent to remove any impurity, and then the product was dried at
80 OC. The characterization of final product was carried out using
SEM, XRD and FT-IR methods. The synthetic route from initial re-
agents to copper(II) oxide nanoparticles is presented in Scheme 1
(see Table 1).
CeH/O and CeH$$$p
. The interaction of O2 and O2i atoms
(hydrogen bond acceptor) from carboxylate groups with C5 and C5i
atoms (hydrogen bond donor) from pyridine rings of phenanthro-
line ligand creates the intra-chain CeH/O interactions on two side
of each polymeric chain with the geometric parameters of
H/O ¼ 2.463 Å, C/O ¼ 3.150(2) Å, and CeH/O angle ¼ 129.16ꢀ.
Also, the intra-chain CeH$$$p interactions form between H7 aro-
matic hydrogen from pyridine ring of phenanthroline ligand of one
polymeric chain with phenyl cycle of dicarboxylates ligand from an
adjacent polymeric chain. The geometric parameters of this
Fig. 6. The Hirshfeld surfaces of compound 1 mapped over dnorm (right) and shape index (left).

N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
5
Fig. 7. 2D fingerprint plots of [Cu(tp)(phen)]n.
interaction are H$$$Cg distance ¼ 2.880
Е
and CeH$$$Cg
index (ꢁ1.0 to 1.0 Å) have been shown in Fig. 6.
angle ¼ 154.33ꢀ (Cg: the centroid of phenyl cycle of dicarboxylate
ligand). It should be noted, that each chain in the network is sur-
rounded by six other ones, producing hexagonal shape of growth
for the network (Fig. 3). Simplification of the chain to the under-
lying net reveals in Fig. 4 which is abundant for 1D coordination
polymers. Also a fragment of the network in 1 was shown in Fig. 5.
The most prominent red spots on the dnorm surface of copper(II)
coordination polymer are due to carbon-carbon bonds. In addition
to, two distinct red spots around copper atom are attributed to
Cu/N and Cu/O interactions. Also, the two pale red spots
observed around the atoms of O2 and H5 is due to the participation
of this two atoms in the formation of CeH/O intermolecular in-
teractions. The C/H/H/C close contacts appears as very pale red
spots or the white areas. These contacts which attributed to
3.2. Hirshfeld surfaces analysis
CeH$$$
p
interactions are visible as hollow orange areas (
p$$$H)
The Hirshfeld surface analyses of copper(II) coordination poly-
mer have been carried out on its asymmetric unit. The views of the
Hirshfeld surface mapped over dnorm (ꢁ1.196 to 1.160 Å) and shape
and bulging blue areas (H$$$
The two-dimensional fingerprint plots of the sum of the con-
tacts contributing tothe Hirshfeld surface have been shown in Fig. 7,
p
) on the shape index surface (Fig. 6).
Fig. 8. FT-IR spectra of crystal structure 1 (up) and nanostructure of 1 (down).

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N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
3.3. FT-IR spectroscopy
The FT-IR spectra data of terephthalic acid and copper coordi-
nation polymer provide information about the coordination mode
of ligand to metal. In the FT-IR spectrum of terephthalic acid, the
strong absorption peak around 1620 cmꢁ1 is attributed to the C]
O(Ar-COOH) stretch frequency. The absence of this peak in the
spectrum of complex and appearance of the characteristic bands of
the carboxylate anions at 1584 cmꢁ1 nasym(COOꢁ)) and 1383 cmꢁ1
(
(
nsym(COOꢁ)) indicates complete deprotonation of the terephthalic
acid (Fig. 8). The bonding mode of carboxylate anion to metal is
characterized by the differences ( ) between the asymmetric
stretch (nasym(COOꢁ)) and symmetric stretch (nsym(COOꢁ)) vibra-
D
tions and its comparison with the
D value of free ionic carboxylic
groups [53]. The asymmetric stretch (nasym(COOꢁ)) and symmetric
stretch (nsym(COOꢁ)) vibrations of disodium terephthalate are
observed at 1567 cmꢁ1 and 1394 cmꢁ1, respectively with the sep-
nasym(COOꢁ) - nsym(COOꢁ)] ¼ 173 cmꢁ1. The calculated
Fig. 9. Thermal behavior of compound 1.
aration Dn
[
Dn value for copper coordination polymer (201 cmꢁ1) is in the
range expected for carboxylate groups that act as unsymmetrical
bidentate ligands [54].
representing in normal mode. Complementary regions are visible
in the fingerprint plots where one molecule act as donor (de > di)
and the other as an acceptor (de < di). The highest share of the total
Hirshfeld surface is related to C/H/H/C close contacts with 30.8%.
The characteristics of these interactions are the appearance as
wings on the fingerprint plot. The wing of the top left (donor) area
represents the H/C contacts with the share of 12.8%, whereas the
wing of the bottom right (acceptor) corresponds to C/H contacts
with the share of 18.0%. The second portion of the total surface
belong to O/H/H/O interactions with 22.8%, representing as two
partly wide spike on the fingerprint plot with the shortest close-
contact distance of di þ de z 2.4 Å.
3.4. Thermal analysis of copper(II) coordination polymer
The thermogravimetric analysis (TGA) has been used for
investing the thermal stability of copper coordination polymer in
the temperature range of 25e600 ꢀC with the heating rates of 10 ꢀC.
minꢁ1 under a static argon atmosphere. The TG/DTG curves (Fig. 9)
show that copper coordination polymer undergoes only one ther-
mal decomposition step in the examined temperature range. This
process is accompanied by a mass reduction 79.42% that was
attributed to loss of all organic parts of compound and a small
H/H close contacts comprise 15.4% of the total surface,
appearing as mostly blue area on dnorm surface. the much sharp
spike on the fingerprint plot with the shortest close-contact dis-
tance of di þ de z 1.4 Å is due to C/C interactions, comprising 13.1%
of the total surface. The interactions related to copper atom
involving Cu/H/H/Cu, Cu/O and Cu/N cover 2.9%, 3.3% and 1.9%
of the Hirshfeld surface areas. The share of other interactions
related to oxygen and nitrogen atoms is 2.8%, 1.4% and 4.5% for
C/N/N/C, O/O and N/H/H/N close contacts, respectively.
amount of copper metal. The maximum peak temperature (Tmax
)
for this process is observed at 275.22 ꢀC. The final remaining weight
(about 20%) corresponds to much of the copper metal (4/5 Cu).
3.5. Characterization of nano-structured copper nitrate complex
The characterization of ultrasonically prepared copper(II) coor-
dination polymer was performed via the techniques of powder X-
ray diffraction (PXRD) and Scanning electron microscopy (SEM).
Fig. 10 represents the computer simulated and experimental PXRD
patterns of copper(II) coordination polymer. Based on this figure, all
major peaks of experimental pattern matche well with that of
Fig. 10. PXRD patterns corresponding to the simulation of compound 1 (blue color)
and the nanostructure systems (pink color).
Fig. 11. XRD patterns of CuO which is prepared by calcination of 1 at 400 ꢀC.

N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
7
simulated pattern with slight differences in 2q values, indicating
their reasonable crystalline phase purity. The observation of some
slightly broadened lines in experimental PXRD than those simu-
lated patterns indicates that the particles are of nanometer di-
mensions. The average size of particles was estimated from
k
l
Scherrer's equation (D ¼
, Where D is the average grain size, K
b
q
is Blank's constant (0.891)C,os
l is the X-ray wavelength (0.15405 nm),
q
and b are the diffraction angle and full-width at half maximum of
an observed peak, respectively). The average size of particles of
Cu(II) coordination polymer according to XRD data was found to be
around 27 nm.
The investigation of the morphology of ultrasound-assisted
prepared samples was carried out using Scanning Electron Micro-
scopy (SEM). These samples were synthesized with the change of
reaction time, reagents concentration, solvent type and reaction
temperature (Table 2).
3.6. Characterization of copper oxide nanoparticles
Fig. 13. SEM image of CuO which is prepared by calcination of 1 in 400 ꢀC.
The direct thermolysis of nanostructured copper coordination
polymer at 400 ꢀC under air atmosphere resulted in the formation
of copper oxide nanoparticles. The characterization of the final
product of calcination was carried out by X-ray powder diffraction
(XRD) and FT-IR spectroscopy.
Also, observable bands in the range of 3400e3500 cmꢁ1 are
assigned to the vibrations of the absorbed water molecules. This
spectral pattern is in agreement with the reported pattern in the
literature [55,56].
3.6.1. XRD analyses of CuO nanoparticles
Fig. 11 visualizes the XRD pattern of compound obtained from
calcination of copper coordination polymer, confirming the for-
mation of copper oxide phase. In this pattern, Bragg's reflections
3.6.3. FE-SEM images of copper oxide nanoparticles
The SEM images of CuO nanoparticles (Fig. 13) shows agglom-
erated and uniform particles with diameters of nano-dimension.
located at about 2q values of 32.55, 35.55, 38.75, 46.15, 48.85, 53.45,
58.30, 61.55, 66.25, 68.00, 72.45, and 75.10ꢀ are attributed to the
crystal planes of (110), (002), (200), (112), (202), (020), (202), (113),
(022), (220), (311) and (222), respectively, indicating the formation
of single-phase CuO with monoclinic structure, standard JCPDS no.
48-1548, space group C2/c and Z ¼ 4. In this XRD pattern, No
characteristic peaks related to any impurity were observed, con-
firming the high purity of prepared sample.
3.7. Sonochemical synthesis
The reaction between copper(II) nitrate, tp and phen provided a
crystalline material with general formula of [Cu(tp)(phen)]n (1). In
this method, sound waves propagates through a liquid at wave-
lengths that is significantly longer than that of the bond lengths
between atoms in the molecule. Therefore, the sound waves cannot
affect vibrational energy of the bond and, therefore, cannot directly
increase the internal energy of a molecule. Instead, sono-chemistry
arises from acoustic cavitation: the formation, growth, and implo-
sive collapse of bubbles in a liquid. The collapse of these bubbles is
3.6.2. FT-IR spectrum of CuO nanoparticles
FT-IR spectrum of calcination product of copper coordination
polymer is depicted in Fig. 12. In this spectrum, strong peak
observed at 531 cmꢁ1 can be attributed to the vibrations of CueO.
Fig. 12. IR spectra of CuO which is prepared by calcination of 1 at 400 ꢀC.

8
N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
an almost adiabatic process, thereby, results in the massive build-
up of energy inside the bubble and extremely high temperatures
and pressures in a microscopic region of the sonicated liquid. The
high temperatures and pressures result in the chemical excitation
of any matter inside of, or in the immediate surroundings of the
bubble as it rapidly imploded. Thus, this technique is quick, green
with maximum yield, basic safety, energy savings, and uses normal
conditions, prevent waste production, improves mass transfer
compared to other technique such as layering, autoclave and
diffusion [57,58].
are formed, following diffusion control growths of them occurred
and flake morphologies were formed {Fig. 14 b and c}. On the other
hand, it is interesting that compound 1 is a 1D coordination poly-
mer in the solid-state (Fig. 2) and formation of 2 and 3D particles by
sonochemical process may be as a result of 1D coordination poly-
mer chains self-assembly (Fig. 14e). Flakes morphology (2D) was
converted to small cubes morphology (3D) when compound 1 was
exposed to 1-5 setting (Fig. 14 and Table 3).
The shape and size of 1 prepared by the ultrasound method
were evaluated by scanning electron microscopy (SEM). SEM im-
ages of 1 prepared by ultrasonic generator 60W with initial re-
agents concentrations of [Cu2þ] ¼ [tp] ¼ [phen] ¼ 0.1 mol Lꢁ1 in
Fig.14 showed mixed-morphology (mainly flake 2D morphologies).
The results showed that as the power of ultrasonic irradiation
increased, the particles sizes decreased (Fig. 14 a, b) and demon-
strated that optimum time was 30 min to achieve nano particles
(Fig. 14 b, c). It was found that with the increase in the concentra-
tion of reactants, the particle sizes was also increased whereas a
converse effect was observed after increasing temperature of re-
agents (Fig. 14 b, e). According to Table 3 and Fig. 14, the best setting
in obtaining a less agglomerated 2D nanostructures of 1 was the
power of ultrasonic irradiation, reaction time, concentration of
reactants and temperature of 60 W, 60 min, 0.5 M and (Table 3 (1-
5); Fig. 14e). The other suitable setting as well was the power of
ultrasonic irradiation, reaction time, concentration of reactants and
temperature of 60W, 30 min, 0.5 M and 50 ꢀC, respectively (Table 3
(1-3); Fig. 14c).
4. Conclusion
A novel Cu(II) coordination polymer compound, [Cu(tp)(phen)]n
(1), was synthesized utilizing a thermal gradient approach and
sono-chemical irradiation. Space group was determined to be
monoclinic space group (C2/c) by single crystal X-ray diffraction.
The crystal packing of compound 1 was studied using Hirshfeld
surface analysis. The effects of ultrasound power, reaction time,
concentration of reactants and temperature on the shape of
[Cu(tp)(phen)]n (1), was investigated and various morphology
{flake (2D) like} of nanostructures of compound [Cu(tp)(phen)]n (1)
were obtained. The results indicated that higher temperature and
ultrasound power led to decrease in particle size with an optimum
time of 30 min. Finally, the best setting for the producing smaller
particles was found to be as follows: the power of ultrasonic irra-
diation of 60 W, reaction time 60 min, concentration of reactants of
0.1 M and temperature of 70 ꢀC.
As the interactions between molecules are one of the most
important factors that greatly influences particles morphology. The
formation of 1 could be postulated as the result of the strong C/H
intermolecular forces (Hirshfeld surface analysis and Fig. 11) among
2D networks (Fig. 2), on a-axis, leading to a formation of nano-
structures growing more on this direction, a-axis, promoting the
flake structures. Otherwise, with reducing this strong C/H inter-
molecular interaction, on a-axis, the growing of nanostructures
could be the same order on y, z and a-axis leading to the formation
of the small 3D on higher temperature (Table 3). Thus, the nuclei
Supplementary data
Crystallographic data for the structure reported in this paper
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication No. CCDC- 1922310. 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: þ44) 1223-
336-033; or e-mail: deposit@ccdc.
Fig. 14. SEM image of nano particle 1, (a) without sonochemical reaction, (b) by sonochemical reaction with sonochemical of temperature 50C, time of 60 min, concentration of
reactants 0.1 M and power of 60 W, (c) with time of reaction change to 30 min,(d) with concentration of reactants change to 0.5 M,(e) with temperature change to 70 ꢀC.

N. Fayaz bakhsh et al. / Journal of Molecular Structure 1200 (2020) 127020
9
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Acknowledgement
This work were supported by Islamic Azad University, Fir-
oozabad Branch and Persian Gulf Science and Technology Park.
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