The structural study, Hirshfeld surface analysis, and DFT calculations of ferrocenyl-hydrazine Schiff base: A novel precursor for the selective preparation of Fe2O3 nanoparticles

Article abstract of DOI:10.1016/j.molstruc.2019.06.109

Ferrocenyl-Hydrazine Schiff base (FHS) was synthesized via a reaction between acetylferrocene and 2, 4-dinitrophenylhydrazine at stoichiometric 1:1 M ratio at 70 °C for 4 h. The crystal structure of the Schiff base was determined by single crystal X-ray diffraction (XRD) technique. The compound was crystallized in a tetragonal crystal system with a space group I4₁/a. Also, the physical properties of the product were studied by FT-IR, UV-Vis spectroscopies, and density functional theory (DFT) calculation. In this study, inter-molecular interactions were investigated using Hirshfeld surface analysis. Fe₂O₃ nanopowders (S₁) were synthesized by thermal decomposition synthesis by ferrocenyl 2, 4-dinitrophenylhydrazine (FHS) at 800 °C for 8 h. According to TG data, 800 °C was chosen as the reaction temperature. Crystallite nature and phase purity of the prepared compounds were investigated via PXRD and FT-IR techniques. Structural analyses were performed by the FullProf program employing profile matching with constant scale factors. The results showed that the patterns had a main hexagonal structure with a space groupR3?C. The morphological and structural properties of the obtained materials were examined by FESEM images. The photocatalytic performance of the synthesized nanomaterial was studied under the following photocatalytic conditions: 0.1 mL H₂O₂ and 30 mg catalyst for the removal of methyl orange, rodamin B, alizarin, malachite green (MG), xylenol orange in aqueous solutions under direct visible and UV-Vis light irradiations.

Full text of DOI:10.1016/j.molstruc.2019.06.109

Accepted Manuscript
The structural study, Hirshfeld surface analysis, and DFT calculations of ferrocenyl-
hydrazine Schiff base: A novel precursor for the selective preparation of Fe O
2 3
nanoparticles
Sakineh Parvarinezhad, Mehdi Salehi, Shahin Kademinia, Maciej Kubicki
PII:
S0022-2860(19)30832-4
DOI:
https://doi.org/10.1016/j.molstruc.2019.06.109
MOLSTR 26751
Reference:
To appear in: Journal of Molecular Structure
Received Date: 26 March 2019
Revised Date: 16 June 2019
Accepted Date: 29 June 2019
Please cite this article as: S. Parvarinezhad, M. Salehi, S. Kademinia, M. Kubicki, The structural study,
Hirshfeld surface analysis, and DFT calculations of ferrocenyl-hydrazine Schiff base: A novel precursor
for the selective preparation of Fe O nanoparticles, Journal of Molecular Structure (2019), doi: https://
2 3
doi.org/10.1016/j.molstruc.2019.06.109.
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ACCEPTED MANUSCRIPT
In this research, synthesis, characterization, structural study, Hirshfeld's analyses and DFT
calculations a ferrocenyl-hydrazine Schiff base and preparation Fe2O3 of powders produced by
thermal decomposition synthesis have been investigated.

ACCEPTED MANUSCRIPT
The structural study, Hirshfeld surface analysis, and DFT calculations of
ferrocenyl-hydrazine Schiff base: A novel precursor for the selective
preparation of Fe2O3 nanoparticles
Sakineh Parvarinezhada, Mehdi Salehi a,*, Shahin Kademiniaa, Maciej Kubickib
a,*Corresponding author at: Department of Chemistry, Semnan University, Semnan, Iran
bDepartment of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland
E-mail address: msalehi@semnan.ac.ir
Abstract
Ferrocenyl-Hydrazine Schiff base (FHS) was synthesized via a reaction between acetylferrocene and 2,
4-dinitrophenylhydrazine at stoichiometric 1:1 molar ratio at 70 for 4 h. The crystal structure of the
℃
Schiff base was determined by single crystal X-ray diffraction (XRD) technique. The compound was
crystallized in a tetragonal crystal system with a space group I41/a. Also, the physical properties of the
product were studied by FT-IR, UV-Vis spectroscopies, and density functional theory (DFT) calculation.
In this study, inter-molecular interactions were investigated using Hirshfeld surface analysis. Fe2O3
nanopowders (S1) were synthesized by thermal decomposition synthesis by ferrocenyl 2, 4-
dinitrophenylhydrazine (FHS) at 800
℃ for 8 h. According to TG data, 800 ℃ was chosen as the reaction
temperature. Crystallite nature and phase purity of the prepared compounds were investigated via PXRD
and FT-IR techniques. Structural analyses were performed by the FullProf program employing profile
matching with constant scale factors. The results showed that the patterns had a main hexagonal
ꢁ
structure with a space group ꢀ3ꢂ. The morphological and structural properties of the obtained materials
were examined by FESEM images. The photocatalytic performance of the synthesized nanomaterial was
studied under the following photocatalytic conditions: 0.1 mL H2O2 and 30 mg catalyst for the removal
of methyl orange, rodamin B, alizarin, malachite green (MG), xylene orange in aqueous solutions under
direct visible and UV-Vis light irradiations.
Keywords: Schiff base; Hirshfeld; DFT; Nanoparticles; Fe2O3; photocatalytic performance
1. Introduction
Organometallic Schiff-base ligands have attracted considerable attention during recent years [1-2]. The
ligand in the complex is of great use and importance in terms of electrochemical, fiber optic, liquid,
solid, gas, and homogeneous catalyst, nonlinear optics, materials science, and pharmacology [3-5].
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Several studies have been reported on acetylferrocene with various amines by the Schiff method.
Synthesis of the ligand and the complex with amines has been reported previously for materials such as
thiosemicarbazones [6], pyrazinoyl hydrazine and nicotinoyl hydrazine [7] and 2-aminophenol [8]. The
preparation of single-phase hematite polymorph is still a great challenge [9]. Ferrocene-based
organometallic compounds have become a promising precursor material for preparing iron oxide micro-
nanoparticles [10]. In recent years, nanomaterials, specifically metal oxides, have been the subject of
intense research because of their distinctive properties in modern technologies and sciences [11-12]. Iron
oxide is obtained in various polymorphs including alpha and gamma phases [13]. Its magnetic properties
depend on pressure, particle size, and magnetic field parameters [14]. Fe2O3 is used in photocatalysis
process and acts as a photodiode for the oxidation of water [15] and surface performance [16-18]. Fe2O3
is obtained by a sol-gel reaction followed by reflux process [19], hydrothermal, microwave and pyrolysis
methods [20-23]. By choosing a suitable molecular precursor, crystalline products could be obtained
under desired conditions [12]. Fe2O3 nanoparticles have found wide applications in several processes
such as cosmetics, paints, coating materials, catalysis, pollution treatments, optoelectronics devices,
corrosion protection, and chemotherapy [24-26]. Thermal degradation method can be utilized in Fe-
doped copolymer of anthranilic acid and o-aminophenol (AA-co-OAP) [24], FeCl3-doped Poly o-
aminophenol (POAP), and polymer doped α-Fe2O3 nanoparticles synthesized via thermal decomposition
route [27-28]. The present study is an extension to our previous work [29] on Schiff-base ligand through
condensation of 2, 4-dinitrophenylhydrazine with acetylferrocene (Scheme 1). The structure of this
compound by X-ray was determined for the first time in the present work. Hydrogen bonding and other
inter-molecular interactions were also investigated using the Hirshfeld surface analysis. DFT calculation
as one of the capable theoretical methods to combine experiments and theories is another aspect of this
work. In the present study, Moreover, the synthesis thermal decomposition method of Fe2O3
nanomaterial is investigated using ferrocenyl 2,4-dinitrophenylhydrazine raw material [29]. Then, FT-
IR, FESEM, and XRD analyses are utilized to identify and study the physical properties of the obtained
samples. The photocatalytic performance of the synthesized nanomaterial is investigated for the
degradation of the pollutant methyl orange, rodamin B, alizarin, malachite green (MG) and xylene
orange in aqueous solutions under visible light and UV-Vis light irradiations.
Scheme 1.
2. Experimental section
2.1. Materials and methods
All chemicals were of analytical grade, obtained from commercial sources, and used without further
purification. Diffraction data were collected by the
ω-scan technique at room temperature on Rigaku
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SuperNova four-circle diffractometer with Atlas CCD detector and mirror-monochromatic CuKα
radiation (λ=1.54178 Å). Phase identifications were performed on a powder X-ray diffractometer D5000
(Siemens AG, Munich, Germany) using Cu-Kα radiation. The morphologies of the obtained materials
were examined with a field emission scanning electron microscope (Hitachi FE-SEM model S-4160).
Absorption spectra were recorded on an Analytik Jena Specord 40 (Analytik Jena AG Analytical
Instrumentation, Jena, Germany). The FT-IR spectra of the complex were recorded in 4000-400 cm-1 as
KBr pellets on a SHIMADZU FT-IR instrument. UV-Vis spectra were carried out at room temperature
on UV-1650 PC SHIMADZU spectrophotometer in acetonitrile solutions. The TG data of the complex
were recorded at 100-1000
℃ on STA PT 1600, Linseis (Germany). The Hirshfeld surface analysis was
done using the Crystal Explorer Hirshfeld program, with the ability to read the crystallographic
information file. All calculations were performed by density functional theory (DFT) in the Gaussian 09
program Package.
2.2. Synthesis
2.2.1. Synthesis of the Schiff bases (FHS)
Synthesis of ferrocenyl-hydrazine was performed using Schiff base method. For this purpose, 0.114 g
(0.5 mmol) acetylferrocene (MW = 228.1 gmol−1) was dissolved in 20 mL of ethanol. Then, 0.099 g (0.5
mmol) 2, 4-dinitrophenylhydrazine (Mw = 198.14 gmol−1) was dissolved in 20 mL of ethanol. The
solution was added dropwise to the acetylferrocene solution. The mixture was refluxed for at 70 ºC for 1
h. Then, 2 drops of concentrated sulfuric acid and 0.02 mL of water were added into the mixture and
refluxed further for 3 hours [29]. Afterward, the thin layer chromatography (TLC) tests were performed
to find the reaction end. After 4 hours, a brown precipitate was obtained. After collecting the resulting
sediment, a solubility test was performed on acetonitrile, ethyl acetate, and ethanol solvents. Next, the
crystallization process was performed and the crystals were observed in acetonitrile and ethyl acetate
solvents.
2.2.2 Preparation of Fe2O3 nanoparticles
In thermal decomposition experiment, 1.22 g (3 mmol) of ferrocenyl- hydrazine precipitate (MW =
408.20 gmol−1) was ground in a mortar until a nearly homogeneous powder was obtained. The obtained
powder was added into a 25 mL crucible and treated thermally in one step at 800
℃ for 8 h. The crucible
was then cooled normally in the furnace to the room temperature. The obtained yellowish powder was
collected for further analyses. The synthesis yield was 87% for Fe2O3 (MW= 159.6 gmol-1).
2.2.3 Photocatalytic activity
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The photocatalytic activity of the synthesized Fe2O3 nanomaterials was investigated using five dyes (i.e.,
methyl orange, rodamin B, alizarin, malachite green (MG), and xylene orange) under direct visible and
UV-Vis light irradiation. About 0.03 g of the catalyst was added to 70 mL of the dye solution. The
solution was stirred in a dark room at room temperature. After 10 min, 0.1 mL of H2O2 was added to it.
Next, it was exposed to light and stirred for different times: methyl orange for 130 min, rodamin B for
150 min, alizarin for 100 min, xylene orange for 55 min and malachite Green color for 40 min. After the
completion of the reaction, the catalyst was extracted and the absorption spectrum of the solution was
studied to calculate the final dye concentration.
2.3. Crystal structure determination
The recorded X-ray diffraction data were corrected for Lorentz-polarization as well as for absorption
effects [30]. Precise unit-cell parameters were determined by the least squares fit of 3916 reflections of
the highest intensity, chosen from the whole experiment. The structures were solved with SHELXT-2013
[31] and refined with the full-matrix least-squares procedure on F2 by SHELXL-2013 [31]. All non-
hydrogen atoms were refined anisotropically. NH hydrogen atom was located in the difference Fourier
map and freely refined with isotropic thermal parameters. All other hydrogen atoms were placed in
idealized positions and refined as ‘riding model’ with isotropic displacement parameters set at 1.2 times
Ueq of appropriate carrier atoms. Table 1. Shows the crystallographic data.
Crystallographic data for the structural analysis has been deposited with the Cambridge Crystallographic
Data Centre, Nos. CCDC-1831893. Copies of this information may be obtained free of charge from: The
Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK; e-mail: deposit@ccdc.cam.ac.uk, or www:
www.ccdc.cam.ac.uk.
2.4. Hirshfeld surface (HS) analysis
Hirshfeld surface refers to the amount of space occupied by a crystal molecule and the way the electron-
crystal density is distributed in the molecule. By making the crystalline space separation by the
molecular Hirshfeld surface, an understanding of the accumulation and intermolecular interactions in
molecular crystals will be possible. Also, Hirshfeld’s surface analysis has the ability to read the
crystallographic information file. Crystal Explorer supports the surface of the Hirshfeld molecular
surface of the crystal into areas where the electron distribution of a set of spherical atoms dominates Pro
molecule over the corresponding electron distribution of the Pro crystal [32-33]. In fact, it can be stated
that Hirshfeld is a function of molecular weight and is a collection of electron densities of unique atoms.
ꢄ ꢆ
ꢒꢓ ∈ ꢇ ꢅ ꢔꢅꢉ ꢕꢉꢋꢍꢌꢎꢋꢍ
ꢄ ꢆ
ꢓ ∈ ꢇ ꢅ ꢔꢅꢉ ꢌꢅꢊꢏꢐꢑꢋ
ꢇ ꢈꢅꢉ ꢈꢊꢋꢌꢍꢋꢋꢎꢋꢉꢏꢍ
ꢇ ꢈꢅꢉꢌꢅꢊꢏꢐꢑꢋ
ꢄ ꢆ
ꢃ ꢅ =
ꢄ ꢆ
ꢃ ꢅ =
,
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The Hirshfeld surface defines the various types of intermolecular interactions using the color encoding
of distances from the surface to the closest external and internal atoms to the surface, which are apparent
features of the original curvature of the surface [34]. Hirshfeld’s surface relates to the space around the
molecule. The Hirshfeld surface shape relies on intermolecular interaction in the crystal as well as
molecular atoms. Hirshfeld’s surface creates an outstanding and immediate image of the types of
interactions. The main purpose of this tool is to create a 3D image that defines any point on the surface
of Hirshfeld by the distance from the surface to the closest atom in and out of the surface [35]. Dnorm is
defined as the distance between the closest large atoms that is not highlighted on the surface of the
Hirshfeld.
Dnorm represents a positive and negative sign. When the intermolecular contact is shorter than the sum of
the distances of the van der Waals radius, it is a negative sign. On the other hand, when the
intermolecular contact is greater than the sum of the van der Waals radius, this parameter is a positive
sign. This parameter with red color indicates the short contact that is due to the strong interaction. In
comparison, the white color shows the contact around the van der Waals distance (equal to the sum of
distances in the van der Waals range) that is due to the intermediate interactions. The blue color area
shows the lack of any close contact and poor interactions [36].
2.5. Computational details
The structural and electronic properties of FHS was investigated using the B3LYP hybrid functional
which consists of a combination of exchange functional [37] and HF and B3LYP correlation functional
[38]. A split valance double- basis along with a single polarization function (6-31G) was used for all
ξ
of the atoms. The structure of complexes was fully optimized without any constraint. The frequency
calculations were also carried out on the optimized structures in order to confirm that the optimized
structures are real local minima on the potential energy surfaces. The natural bond orbital (NBO)
analyses [39] were performed using the NBO 3.1 program at the same level of theory and basis set. UV-
Vis spectra and NMR spectral studies all calculations were done using the Gaussian03 program package
[40].
3. Results and discussions
3.1. FT-IR analysis of the (FHS)
Fig. 1 shows the FT-IR spectrum of the FHS compound. As can be seen, the formation of the Schiff base
of the FHS compound is due to the presence of a strong IR band at 1595 cm-1, which attributes to (C=N)
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vibrations of the imine group. The band related to the tensile vibration N-H at 3320 cm-1, and C=C at
1616 cm-1 [41].
Figure 1
3.2. UV-Vis study of (FHS)
UV-Vis spectrum of FHS compound in the ethanol solvent is shown in Fig. 2. The absorption band at
300 nm is indexed to π → π* transition in the ligand (C = N). The band at 230-250 nm corresponds to
π
→ π* charge transition of the aromatic ring. Also, the band at 380 nm refers to n→ π* charge transition
of imine group in the ligand.
Figure 2
3. 3. Description of the crystal structures of (FHS)
The molecular structures of complex (FHS) were determined using the single crystal X-ray diffraction
technique. Fig.3 shows the perspective view of the molecule. Complex (FHS) crystallizes in the
tetragonal space group I41/a. Table 2. Lists the relevant geometrical parameters. The dihedral angles
between the planar fragments of the molecule are relatively small (Table 2). Intermolecular N7-
H7···O21 hydrogen bond (N-H 0.83(3) Å, H···O 2.04(3) Å, N···O 2.638(3) Å, N-H···O 129(3) º)
influences the conformation of the molecule. It might be noted that the involvement in hydrogen bond
results in elongation of N-O bond (cf. Table 2).
Figure 3
3.4. Hirshfeld surface analysis
Fig. 4 shows the Hirshfeld surface analysis data. It is clear that the hydrogen bonding of C-H ... O
marked by the red spots on the Hirshfeld surface are different from other intermolecular interactions. In
other words, strong interactions of hydrogen bonding are among the most significant intermolecular
interactions. The results show that Hirshfeld surface makes a strong covalent bond among them and a
strong interaction of H with di-nitro (on a 6-member ring). So, the distance of C-H...O hydrogen bond is
short. Hydrogen bonding with other intermolecular interactions with distances less than the sum of the
van der Waals radius is highlighted in red color. The intervals resulting from the interactions are listed in
Table 3.
Figure 4
C15-H15…O22 and C19-H19…O41 were generated by the interaction of N-O with 5-membered carbon.
Also, C91-H91C…O21 was created through the interaction of N-O with methyl carbon. C5-H5 ... O42
and C6-H6 ... O41 were been created via the interaction of N-O with C-H of the phenyl ring. An
intermolecular hydrogen bond N7-H7….O21 (d (D
―H) (Å) = 0.834, d (H...A) (Å) =2.035, d (D...A) (Å)
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=2.638, (DHA) (°) =128.67) shows the poor interaction and affects the formation of the molecule and
causes the elongation of the N-O bond. The crystallographic data confirm this conclusion.
The hydrogen bond acceptor regions are marked as flat and red spots and the hydrogen bond donor
regions are flat and green spots (Fig. 5). An examination of the blue characteristic on the surface of the 5-
corners (1) with 5 blue star blades is shown in Fig. 5. As can be noted, there is an overlap and proximity
between two 5-member loops. Besides, the 6 corners (2) with 6 blue blades represent that the
accumulation of 2 loops is 6 members.
Figure 5
The fingerprint chart is a unique color chart that shows the intermolecular interaction as well as the
relative level of each interaction in the crystal. The two-dimensional graph is a summary of the frequency
of the internal and external distance from the surface. Each of the points in this graph contains
information about the adjacent physical environment. The average between de and di at the center of the
triangle is calculated. Based on the frequent participation of points in blue, green, and red colors, with a
low abundance of blue and a moderate abundance of green, the red color is the most abundant color [42].
The 2D fingerprint graph shows the distribution of the contribution and participation of each of the
interactions resulting from the combination of the FHS by the accumulation of crystals.
C…H(7.5%),N…O(0.9%),O…O(0.7%),O…C(4.1%),N…H(2.8%),N…N(0.9%), N…C(4.5%)
,C…C(5.4%) ,H...H(41.3%),O…H(32.1%). Table 4. Presents the information obtained from the 2D
fingerprint graph for the FHS.
The pairs of tentacles shown in number 1 are in the graph of the interaction of O ... H (32.1%). The pairs
of tentacles have been revealed by the hydrogen interaction of C-H ... O. This bond created the greenest
points that should be compared with other interactions (i.e., di + de = 2.4). As shown in Table 4, H ... H
(41.3%) marked by number 2 shows a larger contribution in the crystalline structure than other
interactions. Fig. 6 presents that in the fingerprint graph di + de = 2.6 is obtained by the H ... H
interaction, which forms the low plenty of veins with a moderate abundance.
Figure 6
3.5. Computational Chemistry and Density functional theory (DFT) calculations
Computational chemistry, called molecular modeling, is a collection of techniques for checking chemical
problems using a computer. Molecular reactivity, multipolar moments, interaction energies, charge
distribution in molecules, ionizing energy the electron energy, the reaction formation heat, the activation
energy, the energy and molecular structures (thermosensory stability), the synthetic paths of the
reactions, the mechanism of the reactions, the vibration frequencies, the electron transport, and the
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effects of magnetic displacement are the information obtained by computational studied [43]. Based on
scientific observations, the DFT method has a lower speed than other methods with the same precision.
To calculate the energy of a molecule using a wave function, the electron density is used to maximize the
advantages of a coherent diffraction DFT integrator on a three-dimensional function and to consider the
effects of electron correlation during computation.
3.5.1. Vibrational analysis
Gaussian09 program package with HF and B3LYP method were used for structural and electron study of
hydrogen bond types in FHS compound [40]. Besides, B3LYP and HF methods using CIF as the initial
structure were used to obtain the vibrational frequency from the base set (i.e., 6-31G). Also, structural
parameters were optimized followed by comparing the geometric parameters of the experimental and
computational data related to the bending angle and the torsional angle, and the bond lengths obtained
from the two methods. The data comparison using the B3LYP shows that the bond length is slightly
larger than that of the HF method. As can be seen from Table 5. The results of the bond length of the HF
method and the angles of the B3LYP method are more consistent with experimental data.
Table 6. Presents that the information about the frequency data obtained using the B3LYP method is
predicted better. The experimental bands in the range of 2855-2933 cm−1 are assigned to C-H stretching
vibration modes of CH2 (in the rings). The peaks in the range of 3194-3251cm−1 (HF/6-31G method) and
in the range of 3039-3093cm−1 (B3LYP/6-31G method) are attributed to the stretching vibration modes.
The N-H stretching vibration mode is found at 3320 cm−1. At wavenumbers higher than about 3453 cm−1
(B3LYP/6-31G method) and 3853 cm−1 (HF/6-31G method), the combinations of the vibrations are
observed. The stretching vibration modes of C=C bonds are indexed to the bands at 1811 and 1664 cm−1.
The stretching vibration modes of C=N bonds are indexed to the bands at 1622 and 1866 cm−1. The
stretching vibration modes of NO2 bonds are indexed to the bands at 1529, 1444, 1453, and 1225 cm−1.
3.5.2. UV-Vis spectrum
The UV-Vis spectrum in ethanol solvent shows an absorption band at 380 nm indicating the transitions
of n→π* in C=N. The B3LYP method was used to calculate this structure and obtain the UV-Vis
spectrum from the base set (6-31G) level of theory. Computational results indicate the energy of 3.17 eV
at a wavelength of 390 nm. Frontier molecular orbitals are very important in investigating optical
properties and chemical reactivity of an entity. The calculated HOMO-LUMO energy gaps are 3.17 eV
for FHS. These large energy gaps indicate good stability as well as large chemical hardness. Higher
chemical hardness indicates a lower reactivity of the entity [44-45]. The assignments in FHS are
discussed in detail in the NBO section.
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3.5.3. NMR spectral studies
The experimental and theoretical chemical shifts of 13C-NMR and H-NMR spectra are presented in
Table 7. The 13C-NMR, H-NMR spectrum of the FHS compound, computational data, and experimental
comparison data obtained from the HF/6-31G and B3LYP/6-31G method are presented in Table 6. The
signal at 155.1 ppm is indexed to the deshielded azomethine carbon. The signal at 14.2 ppm is attributed
to the methyl carbon. Signals in 116.8, 123.8, 129.1, 130.1, 137.7, and 144.7 ppm are related to a carbon
phenyl group. Signals at 67.5, 69.6, 71, and 82.3 ppm are related to carbon atoms of the ferrocenyl
moiety. Hydrogen conjunct to nitrogen appears in the range 9.1 ppm, hydrogen phenyl signal appears in
8.3, 8.0, and 7.2 ppm, and hydrogen in the 5-member ring appears in 4.7, 4.4, and 4.2 ppm. The
hydrogen methyl group appears in the area 2.33 ppm [29]. The results of the table indicate that the data
obtained from the HF method is more consistent with experimental data.
3.5.4. NBO analysis
To investigate the structural and electron study, various interactions were FHS-combined with
theoretical calculations and NBO natural bond analysis. The bonding and accepting interactions and the
bonding energy for electron transfer are obtained in kilocalories per mole. Table 8 represents energy
Failure Deploys (kcal.mol-1) for various orbital interactions computed at the surface (B3LYP / 6-31G).
The resonance between the electron pair of nitrogen and oxygen atoms and the orbital π* N-O in the
FHS combinations are well known and have the largest energy values (Lp O (N-O) → π* N (N-O)). The
results show the formation of hydrogen bond and the increase in the negative charge on the oxygen and
nitrogen atom; besides, the amount of resonance of the electron pair of the nitrogen atom and the orbital
of the π* N (N-O) increases, leading to an increase in the electron transfer. Also, the maximum energy
change in the electron transfers is listed in Table 8. A strong covalent bond established between N-O has
the highest amount of energy. The resulting inter-molecular hydrogen bond is weak. The results of the
B3LYP/6-31G method confirm the results of X-ray crystallographic and Hirshfeld surface analysis.
Table 9. Displays the normal charge and Wiberg bond index calculated by natural orbital analysis (NBO)
at level B3LYP/6-31G. The bond order, charge, and Wiberg bond index were studied using natural
orbital bonding in this interaction. The relatively large negative values for oxygen and nitrogen atoms
and relatively small amounts for hydrogen indicate the formation of hydrogen bonding, which absorbs
the positive charge of the hydrogen atom by the negative oxidation density of the hydrogen bond. In this
case, it creates an intermolecular hydrogen bond. The results of normal charge, Wiberg bond index, X-
Ray analysis, and the Hirschfeld analysis confirm the hydrogen bonding formation.
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The molecular orbital of FHS is shown in Fig. 7. The HOMO and LUMO orbital transitions are
distributed on phenyl ring atoms, Cp ring, and C=N, NO2 and Fe atoms with different ratios. In
HOMO
→ LUMO and HOMO-8→ HOMO-4 transitions (15.65% Occupied volume of orbitals), the
orbital distribution is greater on the phenyl ring, C=N, and NO2 atoms while the orbital distribution of
NO2 in ortho position is much higher than NO2 in a para position, which is a small amount on the iron. In
HOMO-6
HOMO-2 transitions, the orbital distribution is greater on the Cp ring and Fe atoms. The distribution is
small on the phenyl ring, C=N, and also at small proportion for NO2 atom. In HOMO-5 LUMO,
HOMO-8
HOMO-3 transition distribution is small on the phenyl ring and C=N; the orbital
distribution is greater on the Cp ring and Fe atom. Also, HOMO-8
HOMO-3 transition, the
HOMO-2 transition, the orbital distribution is on all of
→ HOMO (15.45% occupied volume of orbitals), HOMO-8→ LUMO, and HOMO-8→
→
→
→
distribution is small on the C=N. In HOMO-5
the atoms of the composition.
→
Figure 7
3.6. FT-IR analysis of Fe2O3 nanoparticles
Fig. 8 shows Fe2O3 nanoparticles synthesized at 800 ºC for 8 hours. The Fe2O3 absorption band is in the
ranges of
υ
(Fe-O) 480, 580 cm-1, and
γ
(Fe-O) 1100-1300 cm-1 [46]. From the obtained spectra, the FT-
IR clearly shows the synthesis of Fe2O3.
Figure 8
3.7. TG analysis
Fig. 9 shows thermogravimetry (TG) analysis of the as-synthesis complex as the precursor for the
synthesis of Fe2O3 nanomaterial. The data indicate that there are some weight loss regions when the
material is thermally treated in a temperature range of 100 to 1000
200-211 with 6.8 mg weight loss and at 211-478 with 2.8 mg weight loss. This is because of the
decomposition of the organic fragments of the complex [47]. A weak weight loss region is also
observed at 733-897 with only 0.13 mg weight loss that is due to the transformation of gamma to
alpha crystal phase [48]. According to the TG results, the optimum synthesis temperature can be 800
℃. The main weight loss range is at
℃
℃
℃
℃
where Fe converts to high-crystalline
α
-Fe2O3 [49].
Figure 9
3.8. XRD analysis
10

ACCEPTED MANUSCRIPT
Fig. 10 represents the PXRD pattern of the synthesized Fe2O3 nanoparticles on scale 2θ = 10-90o. In
addition, structural analysis was performed by the Fullprof to fit the profile with a constant scale factor.
The red lines indicate the experimental while the black lines are the calculated data. The blue lines show
the difference between the experimental and computational data. The results show that this pattern
corresponds to the hexagonal structure and has a hexagonal crystalline structure of Fe2O3 with the space
ꢁ
group ꢀ3ꢂ [50].
Figure 10
Table 10. Represents the crystallite size data obtained from the Scherrer equation using the peak with the
highest intensity (2 = 33.16°) and the cell parameters data obtained from the Rietveld analysis. Also,
θ
Table 10. Shows RF, RBragg, and χ2. The table also shows the cell parameters a and b for the synthesized
Fe2O3 sample. The obtained RF Factor and RBragg Bragg and χ2 parameters are in the desired range.
3.9. FESEM images
Figs. 11 (a-d) show the FESEM images of Fe2O3 nanoparticles synthesized at 800
℃ for 8 h. As can be
seen, the produced particles have a porous morphology. Fig. 12 presents the size measurement of 100
randomly selected particles of Fig. 11d in the scale of 500 nm. Presents the particle size distribution
profile of the synthesized Fe2O3 particles where the maximum particle size distribution is in the range of
70-80 nm. The statistical results show that the particles have a uniform dispersion.
Figure 11
Figure 12
3.10. Photocatalytic activity
The photocatalytic activity of the synthesized Fe2O3 was investigated for the degradation of some dyes
(i.e., methyl orange (λmax= 454 nm), rodamin B (λmax= 520 nm), alizarin (λmax= 258 nm), malachite green
(MG) (λmax= 610 nm), and xylene orange (λmax= 570 nm)) at the presence of H2O2 (30 w/w%) under
visible and/or UV light irradiations. The UV-Vis spectra of the photocatalytic degradation of the as
mentioned pollutant dyes are presented in the supplementary file. To prepare a 40 ppm dye solution, 8
mg of dyes powder was dissolved in 70 mL of deionized water. In a typical photocatalytic experiment, a
certain amount of Fe2O3 was added to 70 mL of the prepared dye aqueous solution and sonicated for 10
min in a dark room to establish an adsorption/desorption equilibrium between dyes molecules and the
surface of the photocatalyst. Afterward, 0.1 mL of H2O2 was added into the mixture followed by further
magnetic stirring under visible and/or UV-Vis light irradiations. After a specified matter of time, the
solution was extracted and the photocatalyst was separated by centrifugation. Finally, the concentration
11

ACCEPTED MANUSCRIPT
of the dye was calculated using UV-vis spectrophotometry. The photodegradation yield (%) of dyes was
calculated via the following formula:
A0-At
ꢖ
ꢗ × 100
A0
Where A0 and At represent the initial absorbance of dyes and the absorbance at time t, respectively.
The results of photocatalytic activity under visible light UV-Vis light irradiations are presented in Fig.
13. The data indicate that the obtained nanomaterial considerably removes dye contaminants in aqueous
solution. Under UV-Vis light irradiation, the degradation yield for malachite green was 54% while under
visible light it was 81%. The degradation yields of the other pollutant dyes are shown in Figure 13.
Figure 13
4. Conclusion
This study was conducted to synthesize and purify FHS composition. The synthesis of Schiff’s base
(FHS) was investigated from acetylferrocene concentration with 2, 4-dinitrophenylhydrazine. Using this
analysis, the present study revealed that the successful synthesis of the ligand. In addition to preparing
the FHS composition, it was attempted to study the structural and spectral parameters of the prepared
composition with different attitudes. The Hirshfeld surface analysis was applied to analyze the
intermolecular interaction in the C18H16FeN4O4 composition. The hydrogen bond through the red spots
on the Hirshfeld surface was distinguished from other distinct intermolecular interactions and by
comparing the length of the bonds in the combination. Also, with using the fingerprint chart, H…H,
H…O showed the most contribution. Followed by investigating and comparing the angle of bond and
analysis of the hydrogen bond strength by natural orbital analysis (NBO) and classification of the
13
stretching vibration frequency C=N, NO2, CH2, C=C, N-H in the infrared spectrum, we examined C-
NMR, H-NMR and UV-Vis using computational chemistry. The results of X-ray Crystallography and
Hirshfeld analysis and the computational chemistry confirmed the strong covalent bond of NO2 and the
intermolecular hydrogen bond N-H…O. Furthermore, synthesis of Fe2O3 nanoparticles was studied. TG
data showed that the optimum reaction temperature was 800
℃. So, the synthesis procedure was
performed using a thermal decomposition rout at 800 for 8 h. The photocatalytic activity results of
℃
Fe2O3 nanoparticles under visible and UV-Vis lights irradiations showed that the photocatalyst
performance is different under different light sources.
5. Acknowledgments
We thank Semnan University for supporting this study.
6. References
12

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Table 1. Crystal data, data collection and structure refinement.
Compound
Formula
FHS
C18H16FeN4O4
408.20
Formula weight
Crystal system
Space group
a(Å)
tetragonal
I41/a
25.7522(5)
25.7522(5)
10.3978(3)
90
b(Å)
c(Å)
α(°)
90
β(º)
γ(°)
90
V(Å3)
6895.6(3)
16
Z
Dx(g cm-3)
1.573
F(000)
3360
µ(mm-1)
7.318
2Θ range (0)
Reflections:
collected
unique (Rint)
with I>2σ(I)
R(F) [I>2σ(I)]
wR(F2) [I>2σ(I)]
R(F) [all data]
wR(F2) [all data]
75.5
9907
3506 (0.036)
2779
0.042
0.108
0.056
0.119
max/min ∆ρ (e Å-3)
0.27/−0.24

ACCEPTED MANUSCRIPT
Table 2. Selected geometrical parameters (Å, º) with s.u.’s in parentheses. A, B, C and D are the
mean planes of planar fragments: phenyl (A), C-N-N=C-C chain (B) and cpA (C) and cpB (D).
Fe1-C10
Fe1-C12
Fe1-C14
Fe1-C16
Fe1-C18
C1-N7
2.048(2)
2.050(3)
2.043(3)
2.048(3)
2.037(3)
1.361(3)
1.217(3)
1.222(4)
117.5(2)
Fe1-C11
Fe1-C13
Fe1-C15
Fe1-C17
Fe1-C19
N2-O21
N4-O41
2.040(3)
2.045(3)
2.048(3)
2.042(3)
2.040(3)
1.238(3)
1.223(3)
N2-O22
N4-O42
C1-N7-N8
N7-N8-C9
A/B
118.1(2)
13.82(9)
11.95(5)
A/(NO2)
2.5(2); 4.63(12)
6.66(7)
B/C
C/D
A/C
Table 3. Hydrogen bond to be prominent in the FHS.
D―H...A
d(D―H) (Å)
d(H...A) (Å)
d(D...A) (Å)
3.502
Label
(DHA) (°)
145.49
C19-H19...…O41
C6-H6…..…O41
0.929
2.697
Red spot
Red spot
0.931
2.613
3.408
143.71
C5-H5…..…O42
C91-H91C....O21
C15-H15…..O22
0.931
0.931
0.959
2.595
2.695
2.502
3.329
3.277
3.559
136.10
121.31
158.92
Red spot
Red spot
Red spot
Table 4. Represents the information obtained from the 2D fingerprint chart for the FHS.
Interactions
Percentage of participation
di
de
di+de
O…H
32.1%
1.0-2.6
1.0-2.8
2.4
H…H
41.3%
1.1-2.3
1.3-2.7
2.6

ACCEPTED MANUSCRIPT
Table 5. The most important geometric parameter including the bond length (A°), the bonded
angles and the torsion angles (°) calculated in the base set 6-31G.
Parameter
Length bond
C=N
X-ray
HF/6-31G
B3LYP/6-31G
1.284
0.834
1.384
1.277
0.993
1.377
1.309
1.020
1.383
H-N
N-N
N-O(Ortho)
1.238,1.217
1.241,1.223
1.263,1.287
N-O(Para)
C-N
1.222,1.223
1.361
1.227, 1.228
1.345
1.266,1.268
1.362
Angels
H-N-N
122.01
119.50
123.37
C= N-N
N-O(Ortho)
N-O(Para)
118.08
28.47
121.88
102.51
112.83
105.82
117.24
28.79
123.87
Table 6. The most important vibrational frequency of experimental and computational data and
vibrational modes using the B3LYP and HF method, in the base set (6-31 G).
Experimental
calculated
HF/6-31G
3853
Calculated
B3LYP/6-31G
3453
Tentative assignment
3320
2933
υ (N-H)
υas(CH2)
υs (CH2)
υ (C=C)
υ (C=N)
υ (NO2)
3251
3194
3093
3039
2855
1616
1811
1644
1595
1866
1622
1510,1340
1529,1444
1453,1225

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Table 7. H-NMR and 13C-NMR combinations FHS and comparison of experimental and computational
data using B3LYP and HF.
Experimental
Calculated
HF/6-31G
Calculated
B3LYP/6-31G
Assignment
13C-NMR
151.0(ppm)
141.0(ppm)
C of C=N
C of Ph
155.10(S)
144.7,137.7,116.8,130.1,129.1,12 146.5,132.0,129.0,123.6,123.2,105.8(ppm)
3.8(S)
127.0,126.8,120.0,114.0,108.0,10
2.0(ppm)
82.3,71.0,69.6,67.5 (S)
125.3,121.0,120.6,119.7,119.2,
69.8,58.5,57.5,57.4,56.3,55.7,54.
7,54.2,53.6, (ppm)
C of Cp
118.0,116.0,112.8,111.0,110.4 (ppm)
14.8(S)
7.5(ppm)
8.9(ppm)
3.0(ppm)
C of CH3
H of N-H
H-NMR
10.5(ppm)
9.1(S)
8.3,8.0,7.2(S)
4.7,4.4,4.2(S)
10.2,8.6,7.4(ppm)
8.6,7.6,7.2(ppm)
H of Ph
H of Cp
8.2,7.28,7.25,7.20,7.18,7.12,6.8,
6.6,6.1(ppm)
3.7,3.02,3.00,2.9,2.8,
2.1,2.54,2.50,2.4(ppm)
1.7,1.5,1.3(ppm)
2.33(S)
1.13,0.93,0.37(ppm)
H of CH3

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Table 8. Energy Failure Deploys kcal.mol-1 for various orbital interactions computed at the surface
(B3LYP / 6-31G).
Orbital interactions
Lp O(N-O)para π*N-CPh
E2(Kcal/mol)
10.23, 13.68
F
∆ꢀ
1.99, 1.68
0.166, 0.127
→
14.40, 14.03
1.70,1.69
0.131, 0.128
Lp O(N-O)ortho
Lp O(N-O)para
Lp O(N-O)ortho
Lp O(N-O)ortho
→
→
→
→
π*N-CPh
151.08, 21.03
191.9,20.44
19.97
1.69 ,0.80
1.87,1.76
1.99
0.218,0.135
0.265,0.138
0.166
π*N(N-O)
π*N(N-O)
π*N(N-H)
Lp N(N-N) → δ* CPh
125.23
0.13
0.134
11.59
1.63
0.134
Lp N(N-N)
Lp N(N-N)
→
→
π*C(C=N)
π*N(N=C)
24.43
0.28
0.077
55.79,51.56, 40.62
47.00
0.16, 0.14,0.16
0.15
0.105,0.093, 0.095
0.092
Lp CPh
Lp Ccp
Lp Ccp
→
→
→
π*CPh
π*N(C=N)
π*Ccp
54.12,51.98,50.20
105.6
0.15,0.15, 0.16
1.84
0.089,0.087, 0.088
0.289
Lp CCP → δ* Fe
Lp Fe * Ccp
Lp* Fe *Ccp
Lp Fe → δ Ccp
44.12,42.14,22.97,20.18
21.31,20.79
110.85
0.32,0.45,0.8,0.8
1.79,1.2
0.03
0.155,0.156,0.064,0.05
0.121,0.104
0.059
→
π
→
π
Table 9. Normal charge, Wiberg bond index due to natural orbital analysis (NBO) calculated at
level B3LYP/6-31G.
Compound / Graph set
Qi
Wiberg
O(N-O)
-0.345,-0.291,-0.296,-0.278
0.897,0.951,0.942,0.938
N(C=N)
N(N-H)
H(N-H)
-0.234
-0.668
0.281
1.675
0.890
0.890
Table 10. Cell parameters are the results of the Reitveld analysis for Fe2O3.
Sample
S1
a=b(Å)
c (Å)
RBragg
RF
χ2
D (nm)
5.0344
13.744
1.95
1.86
1.92
61

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List of Tables
Table 1. Crystal data, data collection and structure refinement……………………………………………………4
Table 2. Selected geometrical parameters (Å, º) with s.u.’s in parentheses. A, B, C and D are the
mean planes of planar fragments: phenyl (A), C-N-N=C-C chain (B) and cpA (C) and cpB……..6
Table 3. Hydrogen bond to be prominent in the FHS. ……………………………………………………………………..6
Table 4. Represents the information obtained from the 2D fingerprint chart for the FHS…………..7
Table 5. The most important geometric parameter including the bond length (A°), the bonded
angles and the torsion angles (°) calculated in the base set 6-31G……………………………………………….8
Table 6. The most important vibrational frequency of experimental and computational data and
vibrational modes using the B3LYP and HF method, in the base set (6-31 G)……………………………..8
Table 7. H-NMR and 13C-NMR combinations FHS and comparison of experimental and
computational data using B3LYP and HF. …………………………………………………………………………………….….8
Table 8. Energy Failure Deploys kcal.mol-1 for various orbital interactions computed at the
surface (B3LYP / 6-31G). …………………………………………………………………………………………………………………..9
Table 9. Normal charge, Wiberg bond index due to natural orbital analysis (NBO) calculated at
level B3LYP/6-31G……………………………………………………………………………………………………………………………9
Table 10. Cell parameters are the results of the Reitveld analysis for Fe2O3………………………………10

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Scheme 1. Synthetic route for the preparation of FHS

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.Shows the FT-IR spectrum of the FHS.
Figure 1
.Shows the UV-Vis spectrum of FHS with a concentration of 10-4mol/L in the ethanol
solvent.
Figure 2

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Figure3. Perspective view of the FHS; ellipsoids are drawn at the 50% probability level,
hydrogen atoms are shown as spheres of arbitrary radii. Intermolecular hydrogen bond is shown
as a dashed blue line.
Figure 4. Hirshfeld surfaces corresponding generated from an atomic spherically averaged
electron density. The color code on the Hirshfeld surfaces represents the geometrical function
dnorm for of FHS.

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Figure 5. The color code on the Hirshfeld surfaces represents the geometrical function created
with de of FHS.
Figure 6. Corresponding 2D fingerprint plots generated from an atomic spherically averaged
electron density using the program Crysnumbers are determined.