Synthesis and characterization of Manganese(III) tetraphenylporphyrinato chloride immobilized on multi-wall carbon nanotubes, and its application as an efficient and reusable catalyst in the biomimetic oxidation of sulfides: A comprehensive experimental and computational study

Article abstract of DOI:10.1016/j.molstruc.2020.128980

In the present study, manganese(III) tetraphenylporphyrinato choloride, was immobilized on multiwall carbon nanotubes by covalent bonding. The structures of [Mn(TPP)Cl]&at;AP-MWC catalyst was confirmed by FT-IR, UV–vis spectroscopic techniques and scanning electron microscopy (SEM). Then, the ability of this novel heterogeneous catalyst was investigated in the oxidation of linear and cyclic sulfides under magnetic stirring conditions. Also, the DFT computational method (B3PW91 method with LanL2DZ basis set) was used for further analysis of this catalyst. Based on this method, the molecular geometries and frequencies of vibrations, chemical shifts, absorbed wavelengths, hyper-conjugative interactions, electron transitions between electron surfaces, positive and negative charges, HOMO and LUMO gap, wavelength (λ), chemical potential (μ), ionization energy (IE), global hardness (η), global softness (S), electrophilicity index (ω) and electronegativity (α) of the most intensity electronic transition for carbon nanotubes and [Mn(TPP)Cl]&at;AP-MWCNT catalyst were calculated. The activity and efficiency of this catalyst were then investigated in the biomimetic oxidation of sulfides. The [Mn(TPP)Cl]&at;AP-MWC heterogeneous catalyst showed the advantages such as high efficiency, good to excellent yield, short reaction times, easy separation and high reusability of the catalyst.

Full text of DOI:10.1016/j.molstruc.2020.128980

Journal Pre-proof
Synthesis and characterization of manganese(III)
tetraphenylporphyrinato chloride immobilized on multi-wall carbon
nanotubes, and its application as an efficient and reusable catalyst in
the biomimetic oxidation of sulfides: A comprehensive experimental
and computational study
Mostafa Khajehzadeh , Majid Moghadam , Pardis Norbakhsh
PII:
S0022-2860(20)31287-4
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.128980
MOLSTR 128980
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Journal of Molecular Structure
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Accepted date:
8 March 2020
21 July 2020
22 July 2020
Please cite this article as: Mostafa Khajehzadeh , Majid Moghadam , Pardis Norbakhsh , Synthesis
and characterization of manganese(III) tetraphenylporphyrinato chloride immobilized on multi-wall car-
bon nanotubes, and its application as an efficient and reusable catalyst in the biomimetic oxidation
of sulfides: A comprehensive experimental and computational study, Journal of Molecular Structure
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Highlights
 Manganese (III) tetraphenyl porphyrin, ([Mn(TPP)Cl]@AP-MWC), was fixed on
multiwall carbon nanotubes by covalent bonding.
 The [Mn(TPP)Cl]@AP-MWC catalyst was characterized by experimental and
theoretical methods such as FT–IR and UV–vis spectroscopic techniques, scanning
electron microscopy (SEM) and natural bond orbital (NBO) analysis.

Synthesis and characterization of manganese(III) tetraphenylporphyrinato
chloride immobilized on multi-wall carbon nanotubes, and its application
as an efficient and reusable catalyst in the biomimetic oxidation of sulfides:
A comprehensive experimental and computational study
Mostafa Khajehzadeh1,*, Majid Moghadamb, Pardis Norbakhshb
aYoung Researchers and Elite Club, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran.
bDepartment of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746–73441, Iran.
Abstract
In the present study, nanganese(III) tetraphenylporphyrinato choloride, was immobilized on
multiwall carbon nanotubes by covalent bonding. The structures of [Mn(TPP)Cl]@AP-MWC
catalyst was confirmed by FT-IR, UV-vis spectroscopic techniques and scanning electron
microscopy (SEM). Then, the ability of this novel heterogeneous catalyst was investigated in
the oxidation of linear and cyclic sulfides under magnetic stirring conditions. Also, the DFT
computational method (B3PW91 method with LanL2DZ basis set) was used for further
analysis of this catalyst. Based on this method, the molecular geometries and frequencies of
vibrations, chemical shifts, absorbed wavelengths, hyper-conjugative interactions, electron
transitions between electron surfaces, positive and negative charges, HOMO and LUMO gap,
wavelength (λ), chemical potential (µ), ionization energy (IE), global hardness (η), global
softness (S), electrophilicity index (ω) and electronegativity (α) of the most intensity
1
Corresponding author: Tel.: +98 – 917 – 7425331; E-mail: Khajehzadeh.chem@yahoo.com (M. Khajehzadeh)

electronic transition for carbon nanotubes and [Mn(TPP)Cl]@AP-MWCNT catalyst were
calculated. The activity and efficiency of this catalyst were then investigated in the
biomimetic oxidation of sulfides. The [Mn(TPP)Cl]@AP-MWC heterogeneous catalyst
showed the advantages such as high efficiency, good to excellent yield, short reaction times,
easy separation and high reusability of the catalyst.
Keywords: [Mn(TPP)Cl]@AP-MWC; Multiwall carbon nanotubes; UV–vis; FT–IR; FE–
SEM; NBO; FMO; oxidation of sulfides.
1. Introduction
Today, many reactions (chemical or industrial) are performed in the presence of catalysts.
Each catalyst can operate individually and improve the progress of a reaction. However,
some catalysts can also be used in several different reactions. Excellent and useful catalysts
maintain their efficiencies during the reaction. Compared to homogeneous catalysts, their
heterogeneous counterparts are separated from the reaction mixture in an easier way. Features
of a good catalyst are high efficiency, short reaction time, easy separation, low price and fit in
with green chemistry. Intermediate metals play a very important role in the synthesis of
catalysts. One of these metals is manganese, which has been used as a catalyst in many
reactions. For example, a series of Sm modified Mn/TiO2 catalysts were proposed for
selective catalytic reduction of NO with NH3 and their catalytic activity was evaluated at low
temperature [1]. A series of flower-like Cu–Mn–Ce mixed oxides catalysts for soot removal
were prepared via a facile co-precipitation approach followed by calcination [2]. Ag–
Mn/AlTi catalysts were prepared by complexation-impregnation process with citric acid [3].
LaCo1-xMnxO3 perovskites with different substitutions of Co by Mn were investigated as
precursors of catalysts for the CO hydrogenation to produce higher alcohols [4]. Sulfate

radical-based advanced oxidation processes (AOPs) have drawn increasing attention during
the past two decades, and Mn-based materials have been proven to be effective catalysts for
activating peroxymonosulfate (PMS) and peroxydisulfate (PDS) to degrade many
contaminants [5]. A series of Mn/TiO2 catalysts were prepared by ultrasonic spray pyrolysis
(USP) method for selective catalytic reduction (SCR) of NOx from flue gas at low
temperatures [6]. Also, using quantum mechanics, a lot of research has been done to identify
the structure and evaluate the efficiency of the catalysts. Some chemists use computational
methods to reduce the dangers of chemicals. But the best way is to compare computational
methods with experimental ones [7–13].
Herein, we report the synthesis of [Mn(TPP)Cl]@AP-MWC, and the structure has been
confirmed by using UV–vis, FE-SEM and FT–IR spectra, and molecular geometry and
optimized parameters (bond length and bond angles), the electronic dipole moment,
polarizability and first hyper polarizability are computed, and the performance of the
computational method for B3PW91 at LanL2DZ level of theory with experimental methods
was compared. Chemical reactivity of the compound was discussed in view of the global
reactivity descriptors and highest occupied molecular orbital (HOMO) and Lowest
unoccupied molecular orbital (LUMO) energies. Natural charges and Mulliken charges were
determined to investigate the charge distribution on the molecule. These methods predict
relatively accurate molecular structure and vibrational spectra with moderate computational
effort. Also, it shows that the computational data are in close agreement with the
experimental data. And after thorough analysis of this catalyst, it was used in the biomimetic
oxidation of sulfides reaction. The results show that this catalyst performs very well in these
reactions.
2. Experimental

All chemicals were purchased from Merck, Fluka and Aldrich chemical companies. FT–IR
spectra of the [Mn(TPP)Cl]@AP-MWCNT catalyst was recorded in the range of 4000–400
cm–1 (KBr) with a Perkin-Elmer (Q0315) FT‎–‎IR instrument. The UV–vis spectra of the
samples were recorded on a Shimadzu UV–vis 160 spectrophotometer or a JASCO, V-670
spectrophotometer. Scanning electron microscopy (SEM) measurements were performed on a
Philips–XL30 field emission scanning electron microscope. The Mn content of the catalyst
was measured by an inductively coupled plasma optical emission spectrometry (ICP–OES),
using a Varian 730–ES analyzer [14]. The characteristic od MWCNTs are listed in Table 1.
Table 1. The specification of MWCNT-COOH used in this study.
MWCNT- COOH
Outside diameter
20-30 nm
Inside diameter
5-10 nm
Length
30 µm
COOH content
1.5%
Specific Surface Area
>110 m2/g
The meso-tetraphenylporphyrin (H2TPP) and Mn(TPP)Cl were prepared according to the
literature [15, 16].
The UV-vis spectrum of H2TPP (Fig. 1a) shows three absorption maxima at 416.5, 430, and
438 nm while in the UV-vis spectrum of Mn(TPP)Cl (Fig.1b), these bands appear at 477.5,
582.5, and 617.5 nm.
2.1. Immobilization of Mn(TPP)Cl on multi-wall carbon nanotubes, [Mn(TPP)Cl]@AP-
MWCNT
First, MWCNTs-COOH were converted to MWCNTs-COCl by the reaction with SOCl2. In
this manner, multi-walled carbon nanotubes containing carboxylic acid groups, MWCNTs-
COOH, (5 g) were refluxed in 30 ml of thionyl chloride for 3 h. At the end of the reaction, the

solvent was evaporated using a rotary evaporator. The solid materials obtained are
chlorinated carbon nanotubes.
For the preparation of [Mn(TPP)Cl]@AP-MWCNT, a mixture of chlorinated carbon
nanotubes (2 g), NEt₃ (5 mL) and 4–amino phenol (0.018 mol, 2 g) in DMF (50 mL) was
o
heated at 80 C for 72 h. During the reaction, NEt₃ (3 mL) was added every 8 hours to the
reaction mixture. At the end of the reaction, the final mixture, AP-MWCNT, was filtered,
washed with DMF (20 mL) and acetone (20 mL), and dried in a vacuum oven at 80 °C for 2
h.
Next, for synthesis of [Mn(TPP)Cl]@AP-MWCNT catalyst, a mixture of AP-MWCNT (1 g)
and [Mn(TPP)Cl] (0.2 g) in toluene (50 mL) was refluxed for 72 h. At the end of the reaction,
the final mixture was filtered, washed several times with acetonitrile and dried in a vacuum
oven at 70 °C for 3 h. These processes were monitored by UV–vis, FT–IR, FE–SEM and
confirmed by NBO and HOMO‒LUMO analysis [17].
2.2. Oxidation of sulfides with sodium periodate catalyzed by [Mn(TPP)Cl]@AP-
MWCNT
A mixture of sulfide (1 mmol) and catalyst (0.013 mmol) in CH3CN (5 ml) was prepared.
Then, sodium peridate (2 mmol) in H2O (5 ml) was added to this mixture, and the reaction
mixture was stirred at room temperature. The reaction progress was monitored by GC. At the
end of the reaction, the catalyst was filtered, washed with acetonitrile and acetone and dried.
3. Computational details
A systematic analysis based on B3PW91 (B3 Exchange + PW91 correlation) with LanL2DZ
calculation of the structural, electronic and photophysical properties in the ground electronic
state was performed for carbon nanotubes and [Mn(TPP)Cl]@AP-MWCNT catalyst. All
DFT calculations were performed using Gaussian 09 W program package on personal
computer, and Gauss View 6.0 molecular visualization software was used to draw the initial

structure and to visualize the results [18, 19]. First, the molecular structure of the
[Mn(TPP)Cl]@AP-MWCNT and carbon nanotubes were optimized using DFT–B3PW91
method with the LanL2DZ basis set [20]. The geometrical parameters, vibrational
wavenumbers and other molecular properties like HOMO and LUMO were carried out by the
optimized structure. Information about delocalization of charge, summary of natural
population analysis, natural electronic configuration, (ΔEHOMO–LUMO), λmax and hybridization
of Mn─N, Mn─O, C─O, C─N, C═C and C═O bonds in the synthesized compound were
provided through NBO analysis [21].
4. Results and discussion
The [Mn(TPP)Cl]@AP-MWCNT immobilized on multi-wall carbon nanotubes were
prepared according to the Scheme 1. In this manner, MWCNTs-COOH were chlorinated and
modified with 4-aminiphenol. Finally, the prepared AP-MWCNT was used as a
heterogeneous axial ligand for immobilization of Mn(TPP)Cl.
Scheme 1. Preparation of the [Mn(TPP)Cl]@AP-MWCNT catalyst
The FT-IR spectroscopy was utilized to identify the chemical changes and vibrations in the
important bands. By comparing the bands of different frequencies, it was observed that the

band intensities were due to most of the functional groups present in their molecular
structure. The vibrational bands of carbon nanotubes, MWCNT-AP and [Mn(TPP)Cl]@AP-
MWCNT compounds have been investigated by using experimental and theoretical methods
(Figs. 2 and 3). As can be seen, in the experimental FT-IR spectrum of the MWCNT-AP,
there are five important bands (Fig. 2a) and in the experimental FT-IR spectrum of the
[Mn(TPP)Cl]@AP-MWCNT, there are eleven important bands (Fig. 2b). Also, the
vibrational assignments have been also proposed for some important IR bands with the help
of animated modes, and the FT–IR spectrum of MWCNT-AP and [Mn(TPP)Cl]@AP-
MWCNT synthesis, and which are shown with (υ–stretching band, π–in plane bending, α–out
of plane bending).
IRexp (KBr, cm-1) for MWCNT-AP: υ = 3446 (N─H), 1633 (C═O), 1600 (C═C), π = 1395
(C─Hpyrol), 825 (C─H), 470 (N─H) (Fig. 2a). IRexp (KBr, cm-1) for [Mn(TPP)Cl]@AP-
MWCNT: υ = 3444 (N─H), 2921 (C─Hpyrol), 2852 (C─H), 1634 (C═O), 1595 (C═C), π =
1400 (C─Hpyrol), 1232 (C═N), 1173 (C─H), 799 (C─Hpyrol), 516 (C─H), 449 (N─H) (Fig.
2b).
Figure 3 shows the computational vibrational spectra of the [Mn(TPP)Cl]@AP-MWCNT and
carbon nanotubes.The results showed that the calculated frequencies by the software
Gaussian 09 were great values. Therefore, these frequencies should be multiplied by scaling
factor (0.96) to obtain corrected values which were closer to the experimental values.
For carbon nanotubes, IRcal (cm‒1): υ = 1624, 1590, 1587, 1584, 1571, 1568, 1558, 1555,
1550, 1546, 1514, 1507, 1499, 1494, 1473, 1389, 1380, 1373, 1328 (C═C), π = 818, 812,
805, 801, 796, 791, 787, 765 (C═C), α = 743,729, 713, 707, 694, 688, 680 (C─C).
For [Mn(TPP)Cl]@AP-MWCNT, IRcal (KBr, cm‒1): υ = 3557, 3539, 3481, 3477, 3406, 3381,
3372, 3312 (N─H), 3129, 3112, 3091, 3082 (C─Hpyrol), 1639 (C═O), 1605, 1561 (C═C), π =
1486 (C─Hpyrol), 1475, 1469, 1439, 1431, 1408, 1388, 1273 (N─H), 1232 (C─O), 1179

(C─N), 1159, 1093 (C─H), α = 954, 940, 856, 840, 820, 813, 721 (C─Hpyrol), 768, 715, 705,
687, 683, 677, 643 (N─H), 628, 619 (C─C), 604 (Mn─N), 556 (N─H), 534 (C─Hpyrol), 506,
468, 456, 446, 444, 426 (N─H), 411 (C─H).
The nanotubes used for this purpose are multi-walled carbon nanotubes with acidic functional
groups. Figure 4 shows the SEM image of the multi-walled carbon nanotube (MWCNT) and
[Mn(TPP)Cl]@AP-MWCNT structure. On the MWCNT SEM image it is clear that it
contains uniform nanotubes (Fig. 4a). In addition, the SEM image of this catalyst shows that
the carbon nanotubes retain their tubular structure (Fig. 4b).
The diffuse reflectance UV-vis spectrum of [Mn(TPP)Cl]@AP-MWCNT compound was
recorded experimentally. Time-dependent density functional theory (TD-DFT) and B3PW91
with LanL2DZ basis set have been used DMF solvent, the electronic spectra are simulated.
The experimental and computed spectra are shown in Fig.5.
The UV–vis experimental spectrum of [Mn(TPP)Cl]@AP-MWCNT (Fig. 5a) showed three
absorption maxima at λmax ∼610 nm, ∼570 and ∼469 nm (Soret band), and the maximum
absorption was at 610 nm.
Fig.5 (b) shows the computational UV–vis absorption spectrum of [Mn(TPP)Cl]@AP-
MWCNT in the 2000–200 nm region, and three absorption peaks were observed. Differences
were also found in UV–vis spectra, concerning bands of intensity of [Mn(TPP)Cl]@AP-
MWCNT. Three important absorption peaks were observed at λmax ∼1079.04 nm, ∼858.83
nm and ∼841.71 nm.
Fig.5 (c) shows the computational UV–vis absorption spectrum of carbon nanotubes in the
900–100 nm region, and three absorption peaks were observed at λmax ∼497.50 nm, ∼452.23
and ∼423.12 nm (Table 2) [22–24].

4.1. Molecular Geometry
The optimized, stable and minimum energy of [Mn(TPP)Cl]@AP-MWCNT is obtained using
Gaussian 09W and Gaussview 6 program packages as shown in Fig. 6. In this image the H
atoms were removed for clarity, and only the final structure of the complex is shown. The Mn
atoms have five bonds with nitrogen and oxygen atoms. In this work, we proceed to compare
the relevant bond lengths and bond angles between (Mn, N, C and O) atoms computed for
[Mn(TPP)Cl]@AP-MWCNT and carbon nanotubes with the corresponding theoretical values
Table 3.
Based on the results, in the carbon nanotubes, the theoretical C16─C9 bond length is 1.555 ,
C16─C17 bond length is 1.521 , C16─C21 bond length is 1.408 . Also, the bond angles were
calculated using the theoretical method. The theoretical C9─C16─C21 bond angle was
calculated 112.659°, the C9─C16─O17 bond angle was calculated 111.973°, the C21─C16─C17
bond angle was calculated 107.178°, the C17─C16─C50 bond angle was calculated 109.668°,
and the C9─C16─C50 bond angle was calculated 107.623°.
Also, in the [Mn(TPP)Cl]@AP-MWCNT complex, the theoretical C1─C2 bond length is
1.401 , C1─C6 bond length is 1.409 , C2─C3 bond length is 1.414 . The C3─O7 bond
length is shorter than the C6─N8 bond because the oxygen electro negativity is greater than
the nitrogen bond and makes the bond shorter. The theoretical Mn11─O7 bond length is
1.892 , N8─C9 bond length is 1.375 , C9─O10 bond length is 1.249 , Mn11─N12 bond
length is 1.849 , Mn11─N12 bond length is 1.898 , Mn11─N14 bond length is 1.921 , and
Mn11─N14 bond length is 1.902 . Also, in the [Mn(TPP)Cl]@AP-MWCNT complex, the
bond angles were calculated using the theoretical method. The theoretical C2─C1─C6 bond
angle was calculated 120.198°, the C2─C3─O7 bond angle was calculated 120.697°, the
C1─C6─N8 bond angle was calculated 121.645°, the O7─Mn11─N12 bond angle was

calculated 86.976°, and the N12─Mn11─N13 bond angle was calculated 88.988°. The bonding
angle between manganese and oxygen is smaller than the bonding angle of manganese with
bromine [25].
4.2. Natural bond orbital (NBO) analysis
The NBO analysis was performed to show the interaction between the donor NBO [Highest
Occupied Molecular Orbital], and acceptor NBO [Lowest Occupied Molecular Orbital] in the
molecule. A most useful aspect of the NBO method is that it gives information about
interactions between donors and acceptors and estimating their stabilization energy by the
theory of 2nd order perturbations.
In the current research, summary of the natural population analysis (core, valence and
Rydberg) and natural electronic configuration of [Mn(TPP)Cl]@AP-MWCNT complex and
carbon nanotubes by B3PW91 method with LanL2DZ basis set were calculated (Tables 4 and
5).
Based on these results, the [Mn(TPP)Cl]@AP-MWCNT has C, H, Mn, N and O atoms,
which have a different electron configuration. The results show that N12, N13, N14 and N15
atoms are complex with Mn. That the natural electron configuration of Mn is:
[core]
. Thus, 17.988 core electrons, 6.554 valence electrons (on
atomic orbitals (AO)), and 0.068 Rydberg electrons (mainly on ) give a total of
. Thus,
atomic orbitals (AO)), and 0.022
Rydberg electrons (on ) give a total of 5.685 electrons. Natural electron configuration of
O7 is: [core] . Thus, 1.999 core electrons, 6.659 valence electrons (on
and atomic orbitals (AO)), and 0.01 Rydberg electrons give a total of 8.674 electrons.
Natural electron configuration of N15 is: [core] . Thus, 1.999 core electrons,
,
3d and
24.611 electrons. Natural electron configuration of C3 is: [core]
1.998 core electrons, 3.664 valence electrons (on and

5.685 valence electrons (on
and
atomic orbitals (AO)), and 0.01 Rydberg electrons
give a total of 7.698 electrons (Table 4).
Also, the structure of carbon nanotubes is made up of carbon atoms, which have a different
electron configuration (Table 5). Based on the results of this table, the natural electron
configuration of C16 is: [core]
electrons (on and atomic orbitals (AO)), and 0.01 Rydberg electrons (mainly on
total of 6.201 electrons. Natural electron configuration of C18 is:
.Thus, 1.999 core electrons, 4.200 valence electrons (on and
. Thus, 1.999 core electrons, 4.186 valence
)
give
a
[core]
atomic orbitals (AO)), and 0.01 Rydberg electrons (on ) give a total of 6.214 electrons.
Natural electron configuration of C19 is: [core] . Thus, 1.999 core electrons,
atomic orbitals (AO)), and 0.01 Rydberg electrons give
4.181 valence electrons (on
a total of 6.195 electrons.
and
Also, the type of hybridization and occupancies of [Mn(TPP)Cl]@AP-MWCNT were
calculated between Mn─N, Mn─O, C─O, C─C, C─N and C═O bonds (Table 6). For
example, the σ (C1─C2) bond is formed from a
35.89 % and 64.11% AO) and hybrid on C2 (which is a mixture of 38.62 % and
61.31% AO), including the square of polarization co-efficient (50.33% C1 and 49.67 % C2).
hybrid on C1 (which is a mixture of
The σ (O7─Mn11) bond is formed from a
hybrid on O7 (which is a mixture of 13.48 %
and 86.52 % AO) and
hybrid on Mn (which is a mixture of 5.80 % , 15.12
%
and 79.08 % AO), including the square of polarization co-efficient (79.61 % O and
20.39 % Mn). The σ (Mn11─N12) bond is formed from a
a mixture of 14.96 % , 19.91% and 65.13 % AO) and
hybrid on Mn (which is
hybrid in N (which is a
mixture of 32.32 % and 67.68 % AO), including the square of polarization co-efficient

(27.97 % Mn and 72.03 % N). The results show that the bond between d orbital Mn with O
and N are well formed [26].
NBO analysis is an efficient method for finding the properties of electronic structure, electron
donor and acceptor orbitals, stability, hybridization, delocalization of electron density,
bonding details and inter and intra-molecular interaction. Normally the second-order
perturbation theory followed [27]. The mathematical relation of stabilization energy E(2)
related to the delocalization value of i, j is obtained by:
E2 = ∆Eij =
Where qi is the occupancy status of donor orbital, Ei and Ej are the energy of donor and
acceptor orbitals and F(i, j) is the Fock, Kohn-sham matrix elements of delocalization.
NBO analysis has been performed on for [Mn(TPP)Cl]@AP-MWCNT by B3PW91 method
with LanL2DZ basis set. The results are presented in Table 7. The results show that, the
highest stabilization energy is from
(4) Mn to (Mn─N15) with a value of 256.37
kcal.mol‒1. The most important interactions of energy in the studied were the electron
coupling LP (2) O7 →
(3) Mn, (E2 = 19.18 kcal.mol‒1), and LP (1) N8 → (C9─O10), (E2
(Mn─N12), (E2 = 46.04 kcal.mol‒1), and
= 27.32 kcal.mol‒1), and
(3) Mn →
(O7─Mn) →
(3) Mn, (E2 = 56.01 kcal.mol‒1), and
(Mn─N12) →
(4) Mn, (E2 =
23.08 kcal.mol‒1), and (Mn─N12) → (Mn─N15), (E2 = 117.67 kcal.mol‒1).
Also, NBO analysis has been performed for carbon nanotubes by B3PW91 method with
LanL2DZ basis set. The results are presented in Table 8. The results show that, the highest
stabilization energy is from (C18─C23) → (C33─C38) with a value of 19.50 kcal.mol‒1.
The most important interactions of energy in the studied were the electron coupling
(C20─C24) →
(C29─C44) with a value of 19.48 kcal.mol‒1, and
(C26─C41)
→
(C31─C35), (E2 = 19.03 kcal.mol‒1), and
(C29─C44) → (C20─C24), (E2 = 19.19

kcal.mol‒1), and
(C30─C39) → (C29─C45), (E2 = 19.29 kcal.mol‒1), and
(C33─C37)
→
(C19─C23), (E2 = 19.07 kcal.mol‒1), and
(C25─C40) → (C30─C39), (E2 = 18.17
kcal.mol‒1). The results show that the electron transfer between the atoms is well performed.
4.3. Frontier molecular orbital (FMO) analysis
In the theory of chemistry, energies and allocations of the frontier molecular orbitals are very
imperative descriptors. Frontier molecular orbital analysis helps in demonstrating the
chemical reactivity, active sites, and kinetic stability of the molecule. The energy difference
between these orbitals involved in bonding plays an important role as an analytical parameter
in the resolution and investigation of molecular transport properties. The electronic properties
of these catalysts were calculated using B3PW91 method with LanL2DZ basis set. In the
current research, the energy gap between the orbital surfaces is also illustrated in Figure 7.
Table 9 shows the calculations related to HOMO and LUMO gap, chemical potential,
ionization energy, global hardness, global softness, electrophilicity index and electro
negativity for carbon nanotubes and [Mn(TPP)Cl]@AP-MWCNT by B3PW91/LanL2DZ in
the presence of DMF solvent.
Based on the results, determined energy values of HOMO and LUMO level in the presence of
DMF solvent are E (HOMO) = –0.1903 eV and E (LUMO) = –0.0839 eV, and ∆E value is
found to be 0.1064 eV for carbon nanotubes.
Based on the results in Table 9, determined energy values of HOMO and LUMO level in the
presence of DMF solvent are E (HOMO) = –0.2162 eV and E (LUMO) = –0.1408 eV, and
∆E value is found to be 0.0753 eV for [Mn(TPP)Cl]@AP-MWCNT.
Also, the chemical potential (µ) of the molecule in the presence of this solvent was
determined. Ionization potential (IE) and electron affinity (EA), we have obtained in the
presence of DMF solvent, EA = – E(LUMO) = 0.0839 eV and IE = – E(HOMO) = 0.1903 eV
for carbon nanotubes. Also, ionization potential (IE) and electron affinity (EA), we have

obtained in the presence of DMF solvent, EA = – E(LUMO) = 0.1408 eV and IE = –
E(HOMO) = 0.2162 eV for [Mn(TPP)Cl]@AP-MWCNT.
Electro negativity (α) is defined by α = (I + A) and chemical potential (μ) is a negative of
electro negativity μ = – (I + A). In the presence of DMF solvent, the estimated values of α
and μ are 0.1371 eV and –0.1371 eV are the corresponding values for carbon nanotubes.
Also, the estimated values of α and μ are 0.1785 eV and –0.1785 eV are the corresponding
values for [Mn(TPP)Cl]@AP-MWCNT catalyst.
The chemical hardness (η) is defined by η = (I – A) and chemical softness (S) which is the
inverse of S =
(ղ) are 0.0532 eV and 9.3984 eV in the presence of DMF solvent for
carbon nanotubes. Also, the estimated values of η and S are 0.0376 eV and 13.2766 eV are
the corresponding values for the [Mn(TPP)Cl]@AP-MWCNT catalyst.
The electrophilicity index of the compound [Mn(TPP)Cl]@AP-MWCNT is found to be the
electrophilicity index defines as ω = is found to be 0.4232 eV and 0.4771 eV. The results
of the calculations show that the softer the molecule is, the higher its polarity and the higher
its chemical activity [28‒31].
4.4. Nonlinear optical properties (NLO)
In the NLO study, the selection of functional has a major part in obtaining reliable NLO
properties. Therefore the calculation of αtotal, βtotal, Δα and μ values are essential for
understanding the effect of electronic structure on second-order NLO property. The first
order hyperpolarizability (βtotal), linear polarizability (α), total dipole moment (
) and
(Δα) for the compound [Mn(TPP)Cl]@AP-MWCNT and carbon nanotubes were calculated
using a B3PW91 method with LanL2DZ basis set and the following formula [32].
βx = βxxx + βxyy + βxzz

βy = βyyy + βxxy + βyzz
βz = βzzz + βxxz + βyyz
=
μ =
=
Δα =
The results in (Table 10) showed that for carbon nanotubes in the presence of DMF solvent,
the most
were calculated by using a B3PW91 method with LanL2DZ basis set equal to
2.3458 Debye. Also, the most
calculated.
, Δα = 51.7139 and βtotal = 99.2985 were
Based on the results, in the [Mn(TPP)Cl]@AP-MWCNT complex, the most
calculated by using a B3PW91 method with LanL2DZ basis set equal to 9.3981 Debye. Also,
the most , Δα = 36.8589 and βtotal = 700.6320 were calculated.
were
4.5. Mulliken and natural atomic charges
The total atomic charges of the [Mn(TPP)Cl]@AP-MWCNT complex and carbon nanotubes
were obtained by Mulliken and natural atomic charges with a B3PW91 method and
LanL2DZ basis set were listed in Tables 11. As can be seen, in the carbon nanotubes,
Mulliken and natural atomic charges show that the C16, C17, C18, C19, C20, C21, C22, C23 and
C27 atoms have negative charges. Also, in the [Mn(TPP)Cl]@AP-MWCNT complex,
Mulliken and natural atomic charges show that the C1, C2, C4, C5, O7 and N8 atoms have
negative charges. The Mn atom has a positive charge and N13 and N14 atoms have a negative
charge [33].

4.6. Catalytic experiment
4.6.1. Oxidation of organic sulfides catalyzed by [Mn(TPP)Cl]@AP-MWCNT under
magnetic stirring conditions
The catalytic activity of [Mn(TPP)Cl]@AP-MWCNT was studied in the oxidation of
sulfides. To optimize the reaction conditions, the diphenyl sulfide was chosen as a model
substrate and the effect of important parameters such as solvent type and catalyst amount
were investigated (Table 12). First, the effect of the catalyst on the reaction yield was
investigated, and 0.013 mmol (200 mg) of [Mn(TPP)Cl]@AP-MWCNT was found to be the
best choice (Table 9, entry 4). Also, the effect of oxidant and solvents on the reaction was
also investigated, and the CH3CN/ H2O mixture was selected as the best solvent (entry 4),
and NaIO4 was also chosen as the best oxidant (entry 4). Note that in the absence of catalyst
and oxidant, the amount of product was negligible.
4.6.2. Oxidation of sulfides and diphenyl sulfide by NaIO4 catalyzed by
[Mn(TPP)Cl]@AP-MWCNT under magnetic stirring conditions
After finding the optimum conditions in the oxidation of diphenyl sulfide, we decided to use
this catalyst in the oxidation of different sulfides (Table 13). The results show that under
optimized conditions, diapropyl and diallyl sulfides were completely converted to their
corresponding sulfones. While, diaryl sulfides, methylphenyl sulfide, and arylbenzyl sulfides
were converted to their corresponding sulfoxides and sulfones. Note that in these cases, the
major product is sulfoxide and sulfone is produce in lower amounts. The benefits of this
catalytic system include high catalyst activity and an easy separation of the catalyst from the
product.
4.6.3. Catalyst recycling and reuse
The possibility of recycling and reusing the [Mn(TPP)Cl]@AP-MWCNT catalyst was
examined in the oxidation of diphenyl sulfide with NaIO4 under the optimized conditions

(Table 14). After the reaction was completed, the mixture was diluted with CH3CN (5 mL),
the catalyst was separated by filtration and washed with CH3CN (15 mL) and acetone,
○
successively, and dried at 70 C. This catalyst could be reused for five consecutive cycles
without a significant decrease in its catalytic activity.
Furthermore, the filtrates after each run were used for measuring the amount of Mn by ICP–
OES analysis. The results showed that only small amount of Mn was found in the two first
runs (1.4% for the first round and 0.4% for the second round). This low Mn loss is due to the
very strong bonding it has with nitrogen and oxygen.
5. Conclusion
In the present study, Manganese (III) tetraphenyl porphyrin, ([Mn(TPP)Cl]@AP-MWC),
was designed and synthesized on multiwall carbon nanotubes by covalent bonding. And FT–
IR, UV–vis, scanning electron microscopy (SEM) analysis and B3PW91 method with the
LanL2DZ level of theory were used to identify the structure of this complex. Based on this
method, the molecular geometries and frequencies of vibrations, chemical shifts, absorbed
wavelengths, hyper-conjugative interactions, electron transitions between electron surfaces,
positive and negative charges, HOMO and LUMO gap, wavelength (λ), chemical potential,
ionization energy, global hardness, global softness, electrophilicity index and electro
negativity of the most intensity electronic transition for [Mn(TPP)Cl]@AP-MWCNT catalyst
and carbon nanotubes were calculated. The results of the experimental method are compared
with the theory. The activity and efficiency of this catalyst were then investigated in the
biomimetic oxidation of sulfides. The results show that this catalyst has a high efficiency, low
time and low cost, which can perform the oxidation reaction of sulfides very well.
Acknowledgement

The authors are grateful to the Young Researchers and Elite Club of Islamic Azad University
of Gachsaran to support this work.
Author Contributions Section
Thank you for your consideration of these comments as you finalize revisions to the Common Rule.
Mostafa Khajehzadeh (corresponding author)
Mostafa Khajezadeh as the lead author and performer of laboratory and computational work.
Young Researchers and Elite Club, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran.
Professor Majid Moghaddam (Supervisor)
Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746–73441, Iran.
Pardis Norbakhsh as a collaborator in laboratory work.
Department of Chemistry, Catalysis Division, University of Isfahan, Isfahan 81746–73441, Iran.
Declaration of Competing Interest
☒ The authors declare that they have no known competing financial interests or personal
relationships that could have appeared to influence the work reported in this paper.

References
[1] L. Liu, K. Xu, S. Su, L. He, M. Qing, H. Chi, T. Liu, S. Hu, Y. Wang, J. Xiang., Appli.
Catal. A, General. 592 (2020) 117413. DOI: 10.1016/j.apcata.2020.117413.
[2] S. Ali, X. Wu, Z. Zuhra, Y. Ma, Y. Abbas, B. Jin, R. Ran, D. Weng., Appl. Surf. Science.
512 (2020) 145602. DOI: 10.1016/j.apsusc.2020.145602.
[3] C.Li-jun, L. Zhao, Y. Shan-liang, H. Xin, Z. Biao, J. Yi., J. Fuel. Chem. Technol. 47(11)
(2019) 1379–1385. DOI: 10.1016/S1872-5813(19)30056-8.
[4] S. Gao, N. Liu, J. Liu, W. Chen, X. Liang, Y. Yuan., Fuel. 261 (2020) 116415. DOI:
10.1016/j.fuel.2019.116415.
[5] J. Huang, H. Zhang., Environment International. 133 (2019) 105141. DOI:
10.1016/j.envint.2019.105141.
[6] B. Jianga, B. Lin, Z. Li, S. Zhao, Z. Chen., Coll. Surf. A. 586 (2020) 124210. DOI:
10.1016/j.colsurfa.2019.124210.
[7] S. Samiee, P. Hossienpour., Inorg. Chim. Acta. 494 (2019) 13–20. DOI:
10.1016/j.ica.2019.05.006.

[8] A.V. Kulinich, A.A. Ishchenko. Comput. Theo. Chim. 1154 (2019) 50–56. DOI:
10.1016/j.comptc.2019.03.018.
[9] B. Amul, S. Muthu, M. Raja, S. Sevvanthi., J. Mol. Struct. 1195 (2019) 747–761. DOI:
10.1016/j.molstruc.2019.06.047
[10] M. Promkatkaew, S. Suramitr, T. Karpkird, M. Ehara, S. Hannongbua., J. Lumin. 222
(2020) 117121. DOI: 10.1016/j.jlumin.2020.117121.
[11] Y. Liu, Y. Zhao, Q. Ren, Z. Zhou, H. Chai, C. Zhao., J. Mol. Struct. 1208 (2020)
127869. DOI: 10.1016/j.molstruc.2020.127869.
[12] C.L. Malonga Matanou, B.R.M. Boungou, M. N'dollo, M.D.N. Ngavouka, P.S.
Moussounda, A.T. Raji, B.M.P. Mabiala., J. Physic. Chem. Sol. 138 (2020) 109162. DOI:
10.1016/j.jpcs.2019.109162.
[13] M. Szafran, A. Komasa, M. Anioła, A. Katrusiak, Z.D. Szafran, Vibration. Spectrosc. 84
(2016) 92–100. DOI: 10.1016/j.vibspec.2016.03.003.
[14] M. Khajehzadeh, M. Moghadam., J. Organomet. Chem. 863 (2018) 60–69. DOI:
10.1016/j.jorganchem.2018.03.030.
[15] A. D. Adler, F. R. Long, J. D. Finarelli, J. Goldmacher, J. Assour, L. Korsakoff, J. Org.
Chem. 32 (1967) 476. DOI: 10.1021/jo01288a053
[16] A. D. Adler, F. R. Long, F. Kampas, J. Kim, J. Inorg. Nucl. Chem. 32 (1970) 2443. DOI:
10.1016/0022-1902(70)80535-8.
[17] M. Khajehzadeh, M. Moghadam, S. Jamehbozorgi, J. Inorg. Chim. Acta. 485 (2019)
173–189. DOI: 10.1016/j.ica.2018.09.042.
[18] M. J. Frisch, G. W. Trucks, et al., Gaussian, Inc., Wallingford CT, 2009.
[19] R.I. Dennington, T. Keith, J. Millam, GaussView, Version 5.0.8, Semichem. Inc,
Shawnee Mission, KS, 2008.

[20] M. Khajehzadeh, M. Moghadam, Spectrochim. Acta Part A. Mol. Biomol. Spect. 180
(2017) 51–66. DOI: 10.1016/j.saa.2017.02.055.
[21] M. Khajehzadeh, N. Sadeghi, J. Mol. Liq., 249 (2018) 281–293. DOI:
10.1016/j.molliq.2017.10.142.
[22] M. Khajehzadeh, N. Sadeghi, J. Mol. Liq., 256 (2018) 238–246. DOI:
10.1016/j.molliq.2018.01.099.
[23] N.N. Chipanina, L.P. Oznobikhina, T.N. Aksamentova, A.R. Romanov, A.Y. Rulev,
Tetrahedron 70 (2014) 1207–1213. Doi: 10.1016/j.tet.2013.12.061.
[24] M. Khajehzadeh, M. Moghadam, S. Rahmaniasl., J. Mol. Struct. 1204 (2020) 127526.
DOI: 10.1016/j.molstruc.2019.127526.
[25] K. Ghosh, S. Roy, A. Ghosh, A. Banerjee, A. Bauzá, A. Frontera, S. Chattopadhyay,
Polyhedron 112 (2016) 6–17. DOI: 10.1016/j.poly.2016.02.035.
[26] S.M. Shohayeb, R.G. Mohamed, H. Moustafa, S.M. El-Medani, J. Mol. Struct. 1119
(2016) 442–450. DOI: 10.1016/j.molstruc.2016.05.009.
[27] K. Subashini, R. Govindarajan, R. Surendran, K. Mukund, S. Periandy, J. Mole. Struct.
1125 (2016) 576–591. DOI: 10.1016/j.molstruc.2016.07.017.
[28] G. Ramachandran, S. Muthu, S. Renuga, Spectrochim. Acta Part A. Mol. Biomol.
Spectrosc. 107 (2013) 386–398. DOI: 10.1016/j.saa.2013.01.026.
[29] P. Govindasamy, S. Gunasekaran, G.R. Ramkumaar, Spectrochim. Acta Part A. Mol.
Biomol. Spectrosc. 130 (2014) 621–633. DOI: 10.1016/j.saa.2014.03.065.
[30] B.S. Maksim, S.A. Ebtehal, et al., J. Mol. Struct. 1115 (2016) 258–266. DOI:
10.1016/j.molstruc.2016.02.092.
[31] M. Khajehzadeh, M. Rajabi, S. Rahmaniasl., J. Mol. Struct. 1175 (2019) 139–151. DOI:
10.1016/j.molstruc.2018.07.084.

[32] E.N. Kande, R. Karimian, V. Goodarzi, E. Ghazizadeh., Appli. Surf. Science. 510 (2020)
145490. DOI: 10.1016/j.apsusc.2020.145490.
[33] C.A. Téllez, A.C. Costajr, M.A. Mondragón, G.B. Ferreira, O. Versiane, J.L. Rangel, G.
M. Lima, A.A. Martin., Spectrochim. Acta Part A. Mol. Biomol. Spectrosc. 169 (2016) 95–
107. DOI: 10.1016/j.saa.2016.06.018.
Fig. 1. UV–‎vis spectrum of: (a) H2TPP, (b) Mn(TPP)Cl.

Fig. 2. FT–IR spectrum of: (a) MWCNT-AP, (b) [Mn(TPP)Cl]@AP-MWCNT.
Carbon nanotubes
[Mn(TPP)Cl]@AP-MWCNT complex

Fig. 3. Calculated FT–IR spectrum of carbon nanotubes and [Mn(TPP)Cl]@AP-MWCNT complex by
B3PW91 method with LanL2DZ basis set.

Fig. 4. SEM image of: (a) MWCNT, (b) [Mn(TPP)Cl]@AP-MWCNT.

Fig. 5. Experimental and calculated UV–vis spectrum for [Mn(TPP)Cl]@AP-MWCNT and carbon
nanotubes.
Fig. 6. Molecular structure of the [Mn(TPP)Cl]@AP-MWCNT with atom numbering scheme.