Substitution effect on chalcone based materials for corrosion and photocrosslinking applications

Article abstract of DOI:10.1039/c4ra10884a

Three different substituted novel chalcone based materials namely (E)-3-(4-(benzyloxy)phenyl)-1-(4-hydroxyphenyl)prop-2-en-1-one (chalcone I), (E)-1-(4-(benzyloxy)phenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (chalcone II) and (E)-1,3-bis(4-(benzyloxy)phenyl)prop-2-en-1-one (chalcone III) were designed and synthesized by a standard Claisen-Schmidt condensation reaction. The different surface morphologies of these materials were obtained from SEM (Scanning Electron Microscopy) analysis. Single crystal XRD studies of chalcone III indicate a monoclinic system with a space group of P2₁/c. Thermal studies such as TGA, DSC and HOPM revealed good thermal stability, crystallinity and phase changing properties of material III. The HOMO, LUMO and bandgap energies of these three materials were calculated by theoretical (DFT) calculations. The electrochemical analysis involves Tafel plots and cyclic voltammetry studies to demonstrate high corrosion inhibition percentage and oxidation-reduction behaviour of materials I, II and III. Dissimilar photocrosslinking time of all three materials was obtained from micro photo-reactor and UV-visible spectrophotometry. The comparative and structural linearity statement reveals the outline view property of the similar chalcone families. This journal is

Full text of DOI:10.1039/c4ra10884a

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Substitution effect on chalcone based materials for
corrosion and photocrosslinking applications†
Cite this: RSC Adv., 2015, 5, 586
a
b
a
c
*
V. Ramkumar, S. Anandhi, P. Kannan and R. Gopalakrishnan
Three different substituted novel chalcone based materials namely (E)-3-(4-(benzyloxy)phenyl)-1-(4-
hydroxyphenyl)prop-2-en-1-one (chalcone I), (E)-1-(4-(benzyloxy)phenyl)-3-(4-hydroxyphenyl)prop-2-
en-1-one (chalcone II) and (E)-1,3-bis(4-(benzyloxy)phenyl)prop-2-en-1-one (chalcone III) were
designed and synthesized by a standard Claisen–Schmidt condensation reaction. The different surface
morphologies of these materials were obtained from SEM (Scanning Electron Microscopy) analysis.
Single crystal XRD studies of chalcone III indicate a monoclinic system with a space group of P21/c.
Thermal studies such as TGA, DSC and HOPM revealed good thermal stability, crystallinity and phase
changing properties of material III. The HOMO, LUMO and bandgap energies of these three materials
were calculated by theoretical (DFT) calculations. The electrochemical analysis involves Tafel plots and
cyclic voltammetry studies to demonstrate high corrosion inhibition percentage and oxidation–reduction
behaviour of materials I, II and III. Dissimilar photocrosslinking time of all three materials was obtained
from micro photo-reactor and UV-visible spectrophotometry. The comparative and structural linearity
statement reveals the outline view property of the similar chalcone families.
Received 21st September 2014
Accepted 14th November 2014
DOI: 10.1039/c4ra10884a
www.rsc.org/advances
nonlinearity can be enhanced by large delocalized p-electron
systems with strong donor and acceptor groups.13
Introduction
Corrosion is an important task to handle in solving prob-
lems, because the loss of metals is increasing with respect to
corrosive nature.14 Some chalcones act as a good inhibitor for
the corrosion science.15 Substituting suitable compounds into
the metals as coating or painting or some other forms to metal
surface inhibits corrosive nature of the metal.16 The addition of
various compounds make as less oxidative nature to metal
surface and atmospheric oxygen.14 It is inferred from the
previous reports that hydroxyl substituted chalcone compounds
are giving good inhibiting nature.17
On the other hand, among many organic compounds are
reported for their photocrosslinking, chalcone derivatives
exhibits excellent photocrosslinking nature due to the presence
of a,b-unsaturated ketone group.18,19 Since the conjugated
double bonds of enone moiety involves photocrosslinking
changes. In addition, chalcone based materials also useful in
biological eld. The presence of a,b-unsaturated compounds
leads to have variety of medicinal purposes such as antibacte-
rial, anticancer, antimalarial, anti-inammatory, antifungal,
and anti-tumor.20,21
Chalcone based materials play an important role in upcoming
research elds,1–3 since they have the push–pull conjugation
effect and a,b-unsaturated ketone group present in the mate-
rial.4 The special intra charge transfer (ICT) leads to delocal-
ization of electrons within the chalcone molecule.5 The electron
withdrawing and accepting groups in this type of chalcone
molecule leads to a drastic change in behaviour and has been
used in industry for various application.4 The chalcone core
crystals nd a place in optics, communications, liquid crystals
and frequency modulation.6–8 The chalcone nonlinear optical
materials are expected to be dynamic for optical communica-
tion and opto-electronics because of their applications in high-
speed and high-density data processing.9–11 Second order
nonlinear optical materials were used in optical switching,
frequency conversion and electro-optical applications.12 It has
been generally understood that the second-order molecular
aDepartment of Chemistry, Anna University, Chennai-25, India
bDepartment of Physics, Maamallan Institute of Technology, Sriperumpudhur,
Chennai, 602105, India
The objective of this present investigation is about synthesis
and characterization of three different substituted new chal-
cone based materials (Fig. 1). The physico chemical properties
and theoretical analysis of these three materials were subjected
to different characterization techniques such as TGA, DSC,
HOPM, SEM, cyclic voltammetry and DFT analysis. The rate of
corrosion and the rate of photocrosslinking of these three
cCrystal Research Laboratory, Department of Physics, Anna University, Chennai-25,
India. E-mail: krgkrishnan@annauniv.edu; krgkrishnan@yahoo.com
† Electronic supplementary information (ESI) available: The harvested crystal
image (Fig. S1), FT-IR data of intermediate and nal product of chalcone III is
shown Fig. S2, ORTEP diagram of chalcone I, II, III, Fig. S3, hydrogen bonding
coordinates data of crystal III (Table S1), video clip of isotropic state to cooling
crystalline state is also available. CCDC 909642. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c4ra10884a
586 | RSC Adv., 2015, 5, 586–596
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1
aliphatic, 1670 (C]O), 1100 (C–O). H-NMR (Fig. 2) (500 MHz,
CDCl3) (d/ppm): 5.18 (s, 2H, Ar-CH2); 7.05 (d, 1H, Ar-CH); 7.09
(d, 1H, Ar-CH); 7.36 (m, 1H, Ar-H); 7.42 (m, 1H, Ar-CH); 7.61 (d,
1H, Ar-H); 7.62 (d, 1H, Ar-H); 7.80 (d, 1H, Ar-H); 8.06 (d, 1H,
Ar-H) (Scheme 1).
Crystal growth
Dichloromethane was found to be the suitable solvent for single
crystal growth of material III, whereas acetone was accom-
plished as preferred solvent for crystallization of I and II.4 This
different recrystallization solvent is due to the absence of –OH
group leads to less hydrogen bonding in material III. The fully
saturated solution of material III in the dichloromethane is
stirred at ambient temperature for 1 h. Then the solution was
ltered, slightly warmed and allowed to evaporate very slowly at
room temperature. Aer 5 days, good quality seed crystals were
observed to a dimension of 15 mm ꢂ 12 mm ꢂ 5 mm. The
grown crystals are shown in Fig. S1.†
Fig. 1 The molecular structure of chalcone I, II and III.
materials were evaluated using electrochemical analyser and
micro photo reactor and UV-visible spectrophotometer.
Experiments and characterization
Materials
Measurements
All the chemicals such as benzyl chloride, 4-hydroxy-
benzaldehyde, 4-hydroxyacetophenone, potassium carbonate
(K2CO3), potassium iodide (KI), sodium hydroxide (NaOH),
ethanol, DMF and acetone and other precursors were procured
from Sigma Aldrich (USA).
High-resolution 1H-NMR spectrum of the compound was
recorded on a 500 MHz AVANCE III spectrometer in CDCl3 with
TMS as an internal standard. The Fourier Transform Infrared
(FT-IR) spectra of respective aldehyde, ketone and material III
were recorded between the regions of 600 to 4000 cmꢁ1 using a
Bruker IFS 66V Fourier transform spectrometer and shown in
Fig. S2.† Thermo gravimetric analysis (TGA) was performed on a
Mettler TA3000 thermal analyser under nitrogen atmosphere at
Synthesis of materials
The chalcone I and II were synthesized by adopting Claisen–
Schmidt condensation reaction and chalcone III synthesized by
similar method from the intermediate derivatives of respective
aldehyde and ketone as follows.4 Equimolar quantities (0.01
mol each) of the intermediate product of compound I (4-(ben-
zyloxy)benzaldehyde) and compound II (4-(benzyloxy)aceto-
phenone) were stirred in ethanol (60 mL) for about 30 min.
Aqueous solution of sodium hydroxide (0.02 mol, 5 mL, 10%)
was added very slowly drop wise while stirring. The reaction
mixture was poured into ice cold water (300 mL) and le for 10 h
and obtained yellow colour precipitate. The resulting solid
product was obtained from ltration, dried and further puried
two times using ethanol by repeated recrystallization. Material
III: yield: 85%; mp 147 ꢀC. FT-IR (KBr) (cmꢁ1): 2875 (C–H)
ꢁ1
ꢀ
a heating rate of 5 C min with a sample weight of 3–5 mg.
DSC measurements were performed on a Mettler Toledo STARe
system to scan the synthesized material in unsealed alumina
pan in a dry nitrogen atmosphere with an empty aluminium
pan as a reference. The scans were carried out at a heating rate
of 5 C minꢁ1. Hot stage optical polarized microscopy (HOPM)
ꢀ
studies were made on a Euromax polarizing optical microscope
equipped with a Linkem HFS-91 heating stage and a TP-93
temperature programmer. Small quantity of material was
Fig. 2 1H-NMR spectrum of chalcone III.
Scheme 1 (i) a ¼ EtOH/NaOH and (ii) b ¼ 6 hours per 10 ꢀC.
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placed between two thin glass cover slips, heated and cooled at used as working electrode and a platinum foil was used as a
the rate of 5 ꢀC minꢁ1. The phase change on heating of crystal counter electrode and Ag/AgCl electrode was used as reference
was observed and photographs taken on a Canon EOS 1000D electrode.23 Reference electrode was calibrated aer each
camera.
measurement using ferrocene (Fc).
Photocrosslinking studies
Single crystal X-ray diffraction
The UV-visible spectrophotometer SHIMADZU UV-1650PC and
microwave photo reactor (Heber micro photo reactor) were used
to analyse the photocrosslinking of all the three materials.
Typical procedure was adopted for photo-isomerization process
as follows: chalcone materials were subjected to UV-irradiation
starting from a 125 W pressure mercury lamp (365 nm) kept at a
distance of 10 cm from a sample at various intervals of time
followed by UV absorption measured on the spectrophotometer
respectively.24 This procedure was repeated until reduction in
absorption was completed.
The obtained structural conguration of materials I, II and III
were been as (E) conguration has conrmed from single crystal
XRD diffraction (ORTEP Diagram) as shown in Fig. S4.† Inten-
sity data for crystal III was collected at room temperature for a
crystal dimension of 0.35 ꢂ 0.25 ꢂ 0.2 mm3 using a Bruker AXS
Kappa APEX II single crystal CCD diffractometer equipped with
˚
graphite-monochromated MoKa radiation (l ¼ 0.71073 A). The
unit cell parameters were determined from 36 reections
measured along the three different crystallographic zones by
the method of difference vectors. The data collection, reduction
and absorption correction were performed by APEX2, SAINT-
plus and SADABS program.4
Results and discussion
Single crystal X-ray diffraction
The structure was solved by direct method and non-
hydrogen atoms subjected to anisotropic renement by full-
matrix least squares on F2 using SHELXL-97 program.4 The
positions of all the hydrogen atoms were identied from
different electron density map and constrained to ride on the
corresponding non-hydrogen atoms. The hydrogen atom bound
to carbon atoms were constrained to a distance of C–H ¼ 0.93–
The crystalline structure and physical properties of materials I
and II were reported in the previous work4 and the new material
III crystal structure and properties were analysed and reported
in the present investigation.† Single crystal XRD data of mate-
rial III exhibit the liberal packing of the system. Since there is a
weak hydrogen bonding in this material, the packing lies to
form a layer like structure. Fig. 3 demonstrates that various
packing alignment of crystal III. Table 1 provide the crystal data
for III. The material III crystallizes in centrosymmetric mono-
clinic crystal system with space group of P21/c.
˚
0.97 A and Uiso(H) ¼ 1.2Ueq(C) and 1.5Ueq(C). The hydrogen atom
associated with oxygen atom was allowed to ride on the parent
˚
atom with a distance of 0.82 A and Uiso(H) ¼ 1.5Ueq(C)
.
Electrochemical analysis
Preparation of mild steel specimens and electrolytes
Morphology
CH electrochemical analyser model 604B was used to record
Tafel polarization curve. The mild steel having compositions of
C ¼ 0.22%, Mn ¼ 0.22%, Zn ¼ 0.22% and Fe ¼ 99.34% were
procured and used for further analysis. A conventional three-
electrode system was used for this analysis.22 Mild steel spec-
imen of an exposed area of 1 cm2 was used as a working elec-
trode. Pt and SCE were used as auxiliary and reference
electrodes, respectively. The working electrode was polished
with a series of emery papers from 400 to 1200 grade and
washed thoroughly with double distilled water, degreased with
acetone and then air dried. The concentration range of inhibi-
tors employed was varied from 10 to 100 ppm and the electrolyte
used was 100 mL per experiment. The solutions were prepared
by dilution of analytical grade 37% HCl with double distilled
water in the absence and presence of inhibitors. The potentio-
dynamic polarization curves were recorded by changing elec-
trode potential versus the open-circuit potential (OCP) with a
scan rate of 20 mV minꢁ1. The linear Tafel segments of the
anodic (ba) and cathodic (bc) curves were extrapolated to the
corrosion potential to obtain corrosion current densities (Icorr).
Cyclic voltammetry measurements were performed on a CHI
600D electrochemical analyser at room temperature with three
electrode cell in a solution of Bu4NClO4 (0.1 M) in dichloro-
The morphology of the crystal III can be simulated from powder
X-ray diffraction pattern using WinXMorph (Version 1.0,
Release 4, Build 6) soware and is shown in Fig. 4. The gener-
ated morphology view of the crystal was found to be similar,
indicating block morphology. The grown crystal and derived
structure of the crystal are the same shape.
Fig. 3 (a) ORTEP diagram. (b) Packing alignment along b axis. (c)
methane at a scanning rate of 100 mV sꢁ1. GC electrode was Different packing alignment of crystal III.
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Table 1 Single crystal XRD data of chalcone crystal III
Identication code
Crystal III
C29H24O3
Empirical formula
Formula weight
420.48
Temperature
Wavelength
296(2) K
0.71073 A
˚
Crystal system, space group
Unit cell dimensions
Monoclinic, P21/c
ꢀ
˚
a ¼ 22.855(3) A, a ¼ 90
ꢀ
˚
b ¼ 5.7603(5) A, b ¼ 109.164(3)
ꢀ
˚
c ¼ 17.5590(18) A, g ¼ 90
3
˚
Volume
2183.6(4) A
Z, calculated density
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Limiting indices
Reections collected/unique
Completeness to theta ¼ 21.11
Absorption correction
Max. and min. transmission
Renement method
Data/restraints/parameters
Goodness-of-t on F^2
Final R indices [I > 2sigma(I)]
R Indices (all data)
4, 1.279 Mg mꢁ3
0.082 mmꢁ1
888
0.35 ꢂ 0.30 ꢂ 0.25 mm3
2.32 to 21.11ꢀ
ꢁ23 # h # 23, ꢁ5 # k # 5, ꢁ17 # l # 17
12 760/2360 [R(int) ¼ 0.0410]
99.7%
Semi-empirical from equivalents
0.9799 and 0.9020
Full-matrix least-squares on F^2
2360/0/290
1.095
R1 ¼ 0.0461, wR2 ¼ 0.1038
R1 ¼ 0.0609, wR2 ¼ 0.1105
0.0014(4)
Extinction coefficient
Largest diff. peak and hole
0.330 and ꢁ0.119 e Aꢁ3
where, Hv ¼ hardness number, P ¼ applied load, d ¼ indenta-
tion size.
The experiment is repeated 3 times and error bar is plotted
between the applied load and hardness number. Hardness plot
infers that crystal withstands only lower loads indicating the
mechanical stability of the grown chalcone crystal.
Thermal properties of the material
The thermal stability of material III was studied by TGA anal-
ysis. The result was shown in Fig. 6 and proved that the crystal is
stable up to 345 ꢀC and decomposes at 800 ꢀC. The char yield of
Fig. 4 Virtual morphology of chalcone III.
Hardness
Hardness test discloses the mechanical behaviour of the
materials.4 Hardness is the resistance offered by a material for
the applied load. The micro hardness test was performed using
MATZUKA Vickers micro hardness tester attached with dia-
mond pyramidal indenter and microscope. Fig. 5 exhibits the
hardness behaviour of crystal III. At very low load, hardness is
high,25 on increasing the applied load, hardness decreases the
phenomenon is termed as indentation size effect.26 while
increasing load the hardness value decreases owing to reverse
indentation size effect. Meyer's index reveals that the above said
chalcone crystal belongs to the so material category. Hardness
is calculated using the following eqn (1).4
À
Á
1:8544P
d2
Hv ¼
kg mmꢁ2
(1)
Fig. 5 Hardness plot of chalcone crystal III.
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Fig. 6 TGA curve of chalcone III.
material was observed at 7.64%. The DSC curve (Fig. 7) displays
a sharp exothermic peak at 147 ꢀC which implies that material
III has a sharp melting point at 147 ꢀC. This sharp peak
enumerates the evidence that the compound exhibit high
crystalline nature. The cooling curve of the endothermic peak
displays that the compound has a tendency to crystalize while
cooling at 120 ꢀC.
Hot stage optical polarized microscope (HOPM) deals about
thermal properties and phase changes of crystalline to isotropic
and isotropic to crystalline state of material III.4 In particular,
physical change on heating and accurate melting point of the
materials could be obtained from HOPM analysis. Fig. 8 illus-
trates the HOPM analysis result of material III. It reveals that
crystal III has a sharp melting point (crystalline to isotropic) at
147 ꢀC and cooling crystallization (isotropic to crystalline) of the
chalcone occurs at 120 ꢀC while cooling the rst cooling reveals
a needle like image indicating that the material has highly
crystalline nature. Further second heating and cooling shows
Fig. 8 HOPM heating and cooling cycle images of material III at
various temperatures, crystalline to isotropic (30 ꢀC to 147 ꢀC),
isotropic to crystalline (147 ꢀC to 50 ꢀC). Further heating on crystalline
to isotropic (50 ꢀC to 147 ꢀC), cooling on isotropic to crystalline (147 ꢀC
to 30 ꢀC).
the same melting and cooling point which match with the rst
one (Video has been attached†).
The sharp edge and needle like images exhibit that material
III has highly crystalline in nature. The cooling phase and the
room temperature images also imply the good crystalline nature
of the material III. The image evinces the smooth morphology of
material III. The obtained HOPM on heating and cooling
temperature exactly matches with the DSC heating and cooling
curves.
SEM analysis of chalcone materials
The surface morphological analysis of synthesised crude
product of materials I, II and III were examined by Hitachi S
3000H Scanning Electron Microscope (SEM). The SEM analysis
is an essential tool to identify the surface morphology of syn-
thesised materials. The synthesised chalcone materials (I, II
and III) depicts various morphologies (Fig. 9).
The material I establishes ash like uniform morphology
similar to the reported literature.27,28 The micrographs of
material II exhibits a sphere like morphology and entire surface
of molecules were found to be uniform spheres, though the
materials I and II have the similar chemical frame work in
molecule the morphology gets differed from each other. It may
be due to the presence of carbonyl group (acceptor) occupying
different position (Fig. 1). In material I, the donor group –OH is
very close to the acceptor group (carbonyl) and also the ICT of
material I is faster than II. Hence material II attracts other
Fig. 7 DSC traces of chalcone III.
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Fig. 10 HOMO and LUMO energy diagram of chalcone I, II and III.
different molecular structure, the overall bandgap is found to be
similar for materials I and III, material II shows little higher
value. This is attributed to the existence of similar electron
clouds present in materials I and III unlike material II. The intra
charge transfer of these materials is free of electron motion to
the entire molecule. A small variation in the bandgap may be
ascribed to the change in the position of functional group
present in molecules.
Fig. 9 SEM images of chalcone material I, II and III shown as, (a & b), (c
& d) and (e & f) respectively.
Electrochemical analysis
Corrosion and its application
molecules slowly, thus exhibiting less agglomeration with
sphere like morphology. On the other hand, material III has a
at layer like morphology owing to the weak hydrogen bonding
in the material.29 Because of the absence –OH groups, it leads to
a less hydrogen bonding in the material prominent to the weak
interaction between the molecules resulting in a layered like
morphology.
The corrosion inhibition efficiency of all the three chalcone was
studied by potentiodynamic polarization technique. The anodic
and cathodic polarization curves (Fig. 11) were obtained in the
absence and presence of inhibitors in I, II and III. The corrosion
potential (Ecorr), corrosion current density (Icorr), corrosion rate
and inhibition efficiency percentage (I.E%) were observed by
Tafel plot by extrapolating the anodic and cathodic lines and are
listed in Table 2. The following formula (2) is used to nd out
the corrosion efficiency (I.E%) of the materials.31
Computational study: DFT calculation
HOMO–LUMO energy gap
Corrosion inhibition efficiency
The difference between the highest occupied molecular orbital
(HOMO) and lowest unoccupied molecular orbital (LUMO) of a
neutral system is the easiest way used to calculate excitation
energy at its ground state.30 The HOMO–LUMO energy gap was
computed at B3LYP/6-31G (d,p) level basis set using DFT
Ic0orr
ꢁ
Icorr
I:E% ¼
ꢂ 100
(2)
Icorr
calculation (Gaussian 09). Fig. 10 indicates the HOMO and where, I.E% ¼ inhibition efficiency percentage, Ic0 orr ¼ corrosion
LUMO energy levels of all the three materials.
current density in the absence of inhibitor, Icorr ¼ corrosion
The results of the HOMO energy levels of chalcone I, II, and current density in the presence of inhibitor.
III are ꢁ5.76, ꢁ5.79 and ꢁ5.74 eV. The calculated LUMO energy
The corrosion efficiency was calculated by using the above
levels are ꢁ1.80, ꢁ1.81 and ꢁ1.78 eV. The calculated bandgap eqn (2). The (Ecorr), (Icorr) values and corrosion rate differ much
energy for chalcone I, II and III is as follows 3.96, 3.98 and 3.96 in the presence and absence of the inhibitor. For the prepared
eV. The similar HOMO–LUMO energy gap was obtained for samples, the corrosion rate is 20.99 and in the presence of the
materials I and II attributable to similar electron clouds, but inhibitor the corrosion rate decreases with respect to concen-
there is small increase in energy gap was obtained in material II, tration of inhibitor materials I, II and III.
this may be due to the less electronic cloud conguration of the
material II.
I.E% of the all three materials is as follows: material I evi-
denced 85.18% for 10 ppm, 94.14% for 50 ppm and 95.38 for
Surprisingly, it is inferred that both I and III have the same 100 ppm, whereas material II exhibited 86.80% for 10 ppm,
binding energy value. Though all the three materials have 95.04% for 50 ppm and 96.33 for 100 ppm, on the other hand,
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Table 2 Corrosion parameters of chalcone I, II and III
Ecorr
Icorr
Corrosion rate Inhibition
(mm per year) efficiency (%)
(mV vs. SCE) (mA cmꢁ2
)
Chalcone-I
Blank
10 ppm
50 ppm
ꢁ407.61
ꢁ413.21
ꢁ404.27
1080
20.99
3.11
1.23
—
267.69
106.05
83.39
85.18
94.14
95.38
100 ppm ꢁ409.38
0.969
Chalcone-II
Blank
10 ppm
50 ppm
100 ppm ꢁ417.46
ꢁ407.61
ꢁ448.61
ꢁ420.38
1080
20.99
2.77
1.04
0.77
—
238.03
89.10
66.69
86.80
95.04
96.33
Chalcone-III
Blank
10 ppm
50 ppm
100 ppm ꢁ424.84
ꢁ407.61
ꢁ430.79
ꢁ404.89
1080
20.99
3.54
1.05
0.46
—
304.81
90.23
40.10
83.13
94.99
97.81
The maximum efficiencies for 100 ppm obtained from all the
three materials are given in Table 2. Among the three
compounds, the material III demonstrates higher inhibition
efficiency in 100 ppm. This reveals that the benzyl group has the
more inhibition efficiency than –OH group.
Cyclic voltammetry studies
The cyclic voltammetry analysis reveals the oxidation and
reduction properties of the materials. The Fig. 12 displays the
oxidation and reduction behaviour of all the three chalcone
materials. It is found that all the materials indicate different
oxidation states with peaks at the various places 0.85 (eV) for I,
1.05 and 1.09 eV for material II and III respectively. There is no
reduction peaks for materials I and III. But there is a redox peak
for II at around ꢁ0.92 eV, owing to the intra charge transfer
which differs from each other with respect to functional group
present in the materials. In compound I, the ketone group is
very close to functional group of phenolic –OH. Thus, it retains
less number of free electrons and the oxidation occurs at 0.85
eV. In compound II, the free electron is more with respect to
extended conjugation of ketone group to the function phenolic
–OH group which easily moves away from anodic to cathodic
side.
In the case of material III the oxidation peak is shied to
1.09 eV, attributed to more free electrons and there is no
phenolic –OH group. Thus, the peak just shis towards the
anodic position. Here the noticeable point is that there is no
reduction peaks for materials I and III but in material II there is
a redox peak at ꢁ0.92 eV which displays the ow of electron and
ICT take the role on it. In material I the phenolic –OH electron
donor group is very close to the electron acceptor C]O carbonyl
group. The ICT electron transfer occurs just opposite to the
electron ow from the electron donor and acceptor group, once
the applied potential consumes both the places. But in the case
of II, the electron donor, acceptor group and ICT takes place in
Fig. 11 Tafel plots of inhibitors I, II and III.
material III affords 83.13% for 10 ppm, 94.99 for 50 ppm and
97.81 for 100 ppm.
Further increase of inhibitor concentration, there is no
signicant increase in the I.E%. Therefore, the concentration of
100 ppm was considered as optimum one for all three materials.
The entire Tafel polarization curve moves towards the cathodic
side. Thus all the three materials act as cathodic inhibitors.32
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Photocrosslinking studies
The photo-dimerization of the chalcone materials I, II and III
were studied experimentally by 1H-NMR, FT-IR, UV-visible
spectrophotometer and microwave photo reactor.33,34 All the
three materials indicate photocrosslinking nature with various
time intervals. The crosslinking occurs because of the forma-
tion of s bond from p bond in an organic molecule.33 In
previous report the chalcone enone group (pCH]CH) were
retained at 2p + 2p cyclo addition and the formation of s-trans
to s-cis isomerization occurs,34 but this materials exhibits photo-
dimerization of the corresponding chalcones which was further
1
conrmed by H-NMR and in situ FT-IR analysis.17,35,36 At the
end of the crosslinking, materials display fully disappeared p
bond and fully formed s bond.33
The photocrosslinking of the materials I, II and III were
shown in Fig. 13–15 with various time intervals. The electron
donor, acceptor group and ICT lead to a drastic change in
photocrosslinking of the molecule.34 The process occurs here
once the molecule gets the energy in the form of UV-light and
get excited from the ground state. When all the molecules form
s bond from the p bond it gets saturated and further there is no
change in the molecule and it is not reversible. The photo-
crosslinking formation means s bond formation mainly
depends on the donor, acceptor and intra-charge transfer of the
materials.24 The order of the intra-charge transfer in the mate-
rials are as follows I > II > III. The saturation timing of all three
materials is 1100, 290 and 33 seconds.
1
The H-NMR spectra of before then aer photocrosslinking
of compounds I, II and III were shown in Fig. 17–19. From the
1H-NMR spectra, the appearance of peak at 4.2 ppm is due to
the formation of cyclobutane ring and the peak disappearance
at around 7.4 ppm is due to the deformation of enone (pC]C)
of the corresponding compounds. The peak variations between
before and aer photo-crosslinking of other protons are may be
due to different in the aer photo-crosslinking the proton
environment. The spectra clearly indicates that all three mate-
rials undergone photocrosslinking. The in situ photocrosslinkig
Fig. 12 Cyclic voltammograms of compounds I, II and III.
the same side. It may be the reason for the reduction peak at
ꢁ0.92 eV. On the other hand, material III has no reduction peak
due to the absence of electron donor group and also the electron
ow once oxidizes the lack of electron donor and it may not be
reduced easily.
Fig. 13 UV-vis spectra on photocrosslinking of material I upon UV-
irradiation at 365 nm with various time intervals.
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Fig. 14 UV-vis spectra on photocrosslinking of material II upon UV-
irradiation at 365 nm with various time intervals.
Fig. 17 1H-NMR spectra on before (i) and after (ii) UV-irradiation of
compound I.
results it could understand that the photo-dimerization time of
the chalcone compounds may alter with respect to functional
group present in a molecule.
In the material I the donor –OH group is attached to the
acceptor group with bridged phenyl group. This phenolic group
tends to compromise the applied energy in the form of photon.
The –OH group donates the electrons to the acceptor and delay
the excitation of the enone molecule. As a result there is a need
of more energy to reach the saturation point in the similar
manner, material II has a decreased saturation time when
compared to I.24 The reason may be the chalcone II donor group
is attached with the phenyl ring is already involving the ICT. The
directly attached donor to the ICT does not give more energy
because already occurs delocalization. The donating electrons
are decreased from I resulting in less saturation time compared
to chalcone III. In the case of chalcone III there is no –OH
(donor) group in it, the ow of electrons will be in free motion,
Fig. 15 UV-vis spectra on photocrosslinking of material III upon UV-
irradiation at 365 nm with various time intervals.
process was also obtained from FT-IR spectrophotometer as a
function of UV-exposure time and shown in Fig. 20. There are
signicant changes in spectra upon the various UV-irradiation
times.33 The stretching vibration mode of pC]C (1645
cmꢁ1) decreases while exposing the increase in irradiation time.
Simultaneously there are some other spectral changes may be
due to the formation of cyclobutane ring. From the above
Fig. 16 Structural change upon the UV-irradiation of compounds I, II Fig. 18 1H-NMR spectra on before (i) and after (ii) UV-irradiation of
and III.
compound II.
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Fig. 21 Possible ICT of compounds I, II and III.
efficiency than the reference material: urea. Due to the cen-
trosymmetry nature the materials II and III have no much SHG
response.4 The position of strong donor acceptor substitution
takes a giant role in SHG output. In this molecule there is a
carbonyl group (C]O) as an acceptor and a hydroxyl group –OH
as a donor for I, II and for III benzyl ether as a weak donor.36 In
material I, –OH is close to the acceptor group results in electron
delocalization, leads to enhanced SHG efficiency. In case of
material II contributing charge transfer direction is being from
the carbonyl (C]O) group to the hydroxyl (–OH) group.38
Material I is more polar than material II. In case of material III,
the absence of hydroxyl group leads to less polarity nature next
to the II and I. The order of polarity of the materials are given as
below I > II > III. The shi in the enone position of the material
I, II and III takes a main role in changing the property of the
molecule. The ICT of the materials are exposed in Fig. 21. Intra-
charge transfer and electron donor acceptor groups present in
the compound leads to the change of photocrosslinking timing
in different intervals of time.
Fig. 19 1H-NMR spectra on before (i) and after (ii) UV-irradiation of
compound III.
within the molecule and it's saturation timing still decreases to
33 seconds. Fig. 16 implies that the general schematic structural
changes of chalcone molecule under UV-irradiation
photocrosslinking.
Structural nonlinearity relationship and comparative
statement
Comparative statement is an important tool to assign similar
and dissimilar property of respective group of molecules.37 The
similarity leads to derive various possible compounds and
dissimilar statement concludes the change in the molecular
pattern in altering the property of molecule.4 Here, the non
centrosymmetric material I shows 1.9 times higher SHG
Conclusions
The three different novel chalcone materials have been
synthesized and characterized. The surface morphology of these
materials was visualized through SEM analysis. Theoretical
mode involves HOMO–LUMO calculation of the material from
the DFT calculations. The similarity in bandgap energy of the
materials was evaluated by theoretical calculation. The thermal
properties of material III was studied through the HOPM, DSC
and TGA analyses. The application studies of these three newly
synthesized chalcones were analysed through the corrosion
inhibition and photocrosslinking studies. The comparative
statement deals about the substitution effect of the chalcone
materials. Thus the present investigation helps to study the
properties about different combinations of chalcone and its
derivatives for different applications.
Acknowledgements
The authors gratefully acknowledge the University Grants
Commission, New Delhi, and Government of India for the
nancial support. Instrumentation facility provided under FIST-
DST and DRS-UGC to Department of Chemistry, Anna Univer-
sity are sincerely acknowledged. The authors acknowledge Dr
Rajamony Jagan, SAIF, Indian Institute of Technology, Chennai
Fig. 20 In situ FT-IR spectra of materials I, II and III as a function of UV-
irradiation time.
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for the help in X-ray data collection and structure solving. Help 16 J. Xu, D. Lai, Z. H. Xie, P. Munro and Z.-T. Jiang, J. Mater.
rendered by Dr Hubert Joe towards theoretical calculation is
greatly acknowledged.
Chem., 2012, 22, 2596.
17 R. Baskar, D. Kesavan, M. Gopiraman and K. Subramanian,
RSC Adv., 2013, 3, 17039.
18 R. Balaji and S. Nanjundan, React. Funct. Polym., 2001, 49,
77.
Notes and references
1 S. Vazquez-Rodriguez, R. Figueroa-Guinez, M. Joao Matos,
L. Santana, E. Uriarte, M. Lapier, J. Diego Maya and
C. Olea-Azar, Med. Chem. Commun., 2013, 4, 993.
2 H. J. Ravindra, A. John Kiran, S. M. Dharmaprakash,
N. Satheesh Rai, K. Chandrasekharan, B. Kalluraya and
F. Rotermund, J. Cryst. Growth, 2008, 310, 4169.
3 E. D. D. Silva, G. Krishna Podagatlapalli, S. Venugopal Rao,
D. Narayana Rao and S. M. Dharmaprakash, Cryst. Growth
Des., 2011, 11, 5362.
19 P. Wen, Z. Zhong, L. Li, A. Zhang, X.-D. Li and M.-H. Lee, J.
Mater. Chem., 2012, 22, 22242.
20 B. P. Bandgar and S. S. Gawande, Bioorg. Med. Chem., 2010,
18, 2060.
21 Z. Nowakowska, Eur. J. Med. Chem., 2007, 42, 125.
22 M. Gopiraman, C. Sathya, S. Vivekananthan, D. Kesavan and
N. Sulochana, J. Mater. Eng. Perform., 2012, 21, 240.
23 N. Sivasankaran and K. Palaninathan, Polym. Degrad. Stab.,
2013, 98, 1852.
4 V.
Ramkumar,
S.
Anandhi,
P.
Kannan
and
24 S. Balamurugan, S. Nithyanandan, C. Selvarasu, G. Y. Yeap
and P. Kannan, Polymer, 2012, 53, 4104.
R. Gopalakrishnan, CrystEngComm, 2013, 15, 2438.
5 P. Poornesh, S. Shettigar, G. Umesh, K. B. Manjunatha,
K. Prakash Kamath, B. K. Sarojini and B. Narayana, Opt.
Mater., 2009, 31, 854.
25 K. Y. Li and D. F. Xue, Chin. Sci. Bull., 2009, 54, 131.
26 K. Sangwal, Mater. Chem. Phys., 2000, 63, 145.
27 V.
Meenatchi,
K.
Muthu,
M.
Rajasekar
and
6 M.-A. Tehfe, F. Dumur, P. Xiao, M. Delgove, B. Graff,
J.-P. Fouassier, D. Gigmes and J. Lalevee, Polym. Chem.,
2014, 5, 382.
7 R. Balaji, D. Grande and S. Nanjundan, React. Funct. Polym.,
2003, 56, 45.
8 H. J. Ravindra, W. T. A. Harrison, M. R. Suresh Kumar and
S. M. Dharmaprakash, J. Cryst. Growth, 2009, 311, 310.
9 H. R. Manjunath, P. C. RajeshKumar, S. Naveen,
V. Ravindrachary, M. A. Sridhar, J. Shashidhara Prasad and
P. Karegoudar, J. Cryst. Growth, 2011, 327, 161.
10 A. N. Prabhu, A. Jayaram, K. Subrahmanya Bhat and
V. Upadhyaya, J. Mol. Struct., 2013, 1031, 79.
S. P. Meenakshisundaram, Phys. B, 2013, 419, 95.
28 A. M. Asiri and S. A. Khan, Mater. Lett., 2011, 65, 1749.
29 K. J. Jarag, D. V. Pinjari, A. B. Pandit and G. S. Shankarling,
Ultrason. Sonochem., 2011, 18, 617.
30 S. Nithyanandan and P. Kannan, Polym. Degrad. Stab., 2013,
98, 2224.
31 P. Sakunthala, S. S. Vivekananthan, M. Gopiraman,
N. Sulochana and A. R. Vincent, J. Surfactants Deterg., 2013,
16, 251.
32 X. Li, S. Deng and H. Fu, Corros. Sci., 2011, 53, 3704.
33 D. H. Choi, S. J. Oh, H. B. Cha and J. Y. Lee, Eur. Polym. J.,
2001, 37, 1951.
11 P. S. Patil, M. S. Bannur, D. B. Badigannavar and
S. M. Dharmaprakash, Opt. Laser Technol., 2014, 55, 37.
12 P. S. Patil and S. M. Dharmaprakash, J. Cryst. Growth, 2007,
305, 218.
34 D.-M. Shin, D.-M. Song, K.-H. Jung and Ji-H. Moon, J.
Photosci., 2001, 8, 9.
35 R. Nagwanshi, M. Bakhru and S. Jain, medicinal chemistry
research, 2012, 21, 1587.
13 P. S. Patil, S. M. Dharmaprakash, K. Ramakrishna,
H.-K. Fun, R. Sai Santosh Kumar and D. Narayana Rao, J.
Cryst. Growth, 2007, 303, 520.
14 T.-I. Yang, C.-W. Peng, Y. Li Lin, C.-J. Weng, G. Edgington,
A. Mylonakis, T.-C. Huang, C.-H. Hsu, J.-M. Yeh and
Y. Wei, J. Mater. Chem., 2012, 22, 15845.
36 K.-S. Choi, H.-W. Kim, Y.-B. Kim and J.-D. Kim, Liq. Cryst.,
2010, 31, 639.
37 H. P. Avila, E. de Fatima Albino Smania, F. D. Monache and
A. S. Junior, Bioorg. Med. Chem., 2008, 16, 9790.
38 B. Zhao, W. Q. Lu, Z. H. Zhou and Y. Wub, J. Mater. Chem.,
2000, 10, 1513.
15 M. Bouklah, B. Hammouti, A. Aouniti, M. Benkaddour and
A. Bouyanzer, Appl. Surf. Sci., 2006, 252, 6236.
596 | RSC Adv., 2015, 5, 586–596
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