Di-μ-oxidovanadium(V) di-nuclear complexes: Synthesis, X-ray, DFT modeling, Hirshfeld surface analysis and antioxidant activity

Article abstract of DOI:10.1016/j.ica.2019.119276

In this work, two di-μ-oxidovanadium(V) complexes, [(L₁H)VO(μ-O)]₂ (C1) and [(L₂H)VO(μ-O)]₂ (C2), with tridentate Schiff base ligands, [N-(2-hydroxyethylamino)ethyl]-5-methoxysalicylaldimine (L₁H) and

Full text of DOI:10.1016/j.ica.2019.119276

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Research paper
Di-μ-oxidovanadium(V) di-nuclear complexes: Synthesis, X-ray, DFT model-
ing, Hirshfeld surface analysis and Antioxidant activity
Ali Hasnaoui, Ismail Hdoufane, Abderrahim Alahyane, Abdallah Nayad, Driss
Cherqaoui, Mustapha Ait Ali, Larbi El Firdoussi
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S0020-1693(19)30860-6
https://doi.org/10.1016/j.ica.2019.119276
ICA 119276
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10 November 2019
Please cite this article as: A. Hasnaoui, I. Hdoufane, A. Alahyane, A. Nayad, D. Cherqaoui, M. Ait Ali, L. El
Firdoussi, Di-μ-oxidovanadium(V) di-nuclear complexes: Synthesis, X-ray, DFT modeling, Hirshfeld surface
analysis and Antioxidant activity, Inorganica Chimica Acta (2019), doi: https://doi.org/10.1016/j.ica.2019.119276
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Di-μ-oxidovanadium(V) di-nuclear complexes: Synthesis, X-ray, DFT
modeling, Hirshfeld surface analysis and Antioxidant activity
1
2
3
1
Ali Hasnaoui , Ismail Hdoufane , Abderrahim Alahyane , Abdallah Nayad , Driss
Cherqaoui 2, Mustapha Ait Ali 1 and Larbi El Firdoussi 1*
1 Equipe de Chimie de Coordination et de Catalyse, Département de Chimie, Université Cadi Ayyad, Faculté des
Sciences Semlalia, BP 2390, Marrakech, Morocco ;
2 Laboratory of Molecular Chemistry, Department of Chemistry, Faculty of Sciences Semlalia, Cadi Ayyad
University of Marrakech, BP 2390, Morocco;
3 Food Sciences Laboratory, Department of Biology, Faculty of Sciences-Semlalia, Cadi Ayyad University of
Marrakech, P.O. Box 2390, Morocco.
ABSTRACT
In this work, two di-μ-oxidovanadium(V) complexes, [(L1H)VO(μ-O)]2 (C1) and
[(L2H)VO(μ-O)]2 (C2), with tridentate Schiff base ligands, [N-(2-hydroxyethylamino)ethyl]-
5-methoxysalicylaldimine (L1H) and 2-[(2-(2-Hydroxyethylamino) ethylimino)methyl]
phenol (L2H), respectively, were prepared and characterized by various spectroscopic
techniques. The X-ray diffraction of C1 showed six-coordinate vanadium in a distorted
octahedral geometry with the imine, phenolate and amine donors of the ligand and two oxo-
group bonds. Density functional theory (DFT) was carried out using B3LYP level with the 6-
31G basis set in order to predict the molecular structure of C1, delineate its vibrational
wavenumbers and define the theoretical NMR shifts, which were performed with the GIAO
approach. Thereafter, Hirshfeld surface (HS) and 2D fingerprint analysis were used to
investigate the intermolecular contacts in the C1 complex. The DPPH free radical scavenging
assay was used to evaluate the antioxidant activity of both C1 and C2 complexes.
Keywords: Vanadium complexes; X-ray diffraction; DFT; Hirshfeld analysis; Antioxidant
activity.
* Corresponding author: Prof. Larbi El Firdoussi (elfirdoussi@uca.ac.ma)

1. Introduction
Schiff bases constitute an important class of versatile ligands that can bind to metal ions
forming metal complexes [1]. Their corresponding complexes have gained significant interest
among scientists due to the existing range of applications, especially in the field of
electrochemistry and catalysis [2–5]. Furthermore, they exhibit biological proprieties, such as
antibacterial [6,7], anticancer [8,9], antifungal [10] and antioxidant activities [11,12].
The coordination chemistry of oxovanadium (IV), oxovanadium (V), and dioxovanadium
(V) have attracted much attention and has been extensively studied due to its biological and
therapeutic applications [13,14]. These elements are involved in a variety of biochemical
processes including insulin-mimetic drugs [15,16], nitrogen fixation [17], anti-parasitic agents
[18], haloperoxidation [19], and enzyme inhibition [15]. Numerous oxo and dioxovanadium
complexes with Schiff base ligands are described in the literature [20], and their catalytic
activity in oxidation has been investigated [21,22]. Also, many di-μ-oxidovanadium (V)
compounds in a dimer symmetry with a methoxy or oxido group bridge were reported with
NNO , NNS, and NOO donor ligands along with their biological and catalytic activities [23–
32].
Quantum chemical calculations are known to be powerful approaches for the prediction of
molecular structures and electronic properties [33]. They are widely used in the calculation of
various spectroscopic characteristics such as vibrations, absorption, Raman and NMR spectra.
They are also used in the understanding of reactions and the underlying kinetic profile and
chemical mechanisms for organic and inorganic compounds [34] [35]. Several Vanadium
complexes bearing Schiff bases were computed using the density functional theory DFT
approach [36].
In the current work, we aim to extend our previous researches on Schiff base metal
complexes [37] and to contribute to the discovery of effective and potent products with strong
chemical and biological profile. To this end, a new di-oxovanadium (C1) in complex with [N-
(2-hydroxyethylamino)ethyl]-5-methoxysalicylaldimine (L1H) and an already described
complex (C2) [38] were synthesized via one pot reaction. The structures of C1 and C2 were
studied with the DFT method using the B3LYP/6-31G basis set. In addition, their
intermolecular interactions were visualized and quantified using Hirshfeld Surface analysis
and two-dimensional fingerprint plots. Thereafter, the antioxidant activity of C1 and C2 was
tested using a DPPH free radical scavenging assay and compared with BHT and Quercetin
(commercially available antioxidant products).

NH
OH
N
H
O
V
O
O
R
O
O
O
VOSO4
MeOH
N
V
H
O
NH2
OH
R
HN
HO
N
R
C1: R= OCH3
C2: R= H
Scheme 1. Schematic synthesis of C1 and C2 complexes.
2. Experimental
2.1. Material and methods
VOSO4, methanol, 2-((2-aminoethyl)amino)ethanol, 4-methoxysalicylaldehyde, DPPH,
BHT, and Quercetin were purchased from Sigma Aldrich. NMR studies were recorded in
DMSO-d6 using a Bruker Avance 300 spectrometer. Chemical shifts are given in ppm relative
to external TMS and coupling constants (J) are provided in Hz. FT-IR analysis was performed
in KBr on a VERTEX 70.
2.2. Synthesis of oxovanadium complexes
For the complex C1, a mixture of 3-methoxysalicylaldehyde (100 mg, 0.66 mmol) and 2-
((2-aminoethyl)amino)ethanol (68 mg, 0.66 mmol) in 15 mL of methanol was stirred at 70 °C
during 15 min. Then, a solution of (106 mg, 0.66 mmol) VOSO4 in methanol (5mL) was
added dropwise to the mixture. After five hours of stirring, a yellow precipitate was obtained.
The solid was filtered and washed with methanol. Recrystallization in CH3OH/H2O (8/2, v:v)
afforded the C1 product in 58% yield (0.23 g, 0.37 mmol). The same procedure was adopted
to synthesize the C2 complex in the presence of salicylic aldehyde with a 52% yield (0.25 g,
0.43 mmol). The experimental spectra for C1 and C2 are shown in the supporting
information.
C1: (C12H17 N2O5V)2 Color yellow: FT-IR (cm-1, KBr): υ(C=N) 1635, υ(V=O) 915,
1
υ(V-O) 843 (Fig.S1). H NMR (300 MHz, DMSO-d6, ppm): 3.37 (3H, S), 3.47-3.97
(6H, m), 4.83 (H, S), 5.51 (H, S), 6.32(H, m), 6.43 (H, d, J = 3 Hz), 7.44 (H, s), 8.75
13
(H, S). C NMR (75 MHz, DMSO-d6, ppm): 48.35 (CH2), 55.31(CH3), 57.44 (CH2),
58.35 (CH2), 59.86 (CH2), 102.09 (CH), 106.57(CH), 114.34 (C), 135.09 (CH), 165.61
(C), 166.93 (C), 167.55 (CH=N) (Fig.S2).

C2: (C11H15N2O4V)2 Color yellow: FT-IR (cm-1, KBr): υ(C=N) 1640, υ(V=O) 927, υ(V-O)
829. 1H NMR (300 MHz, DMSO-d6, ppm): 3371-4.02 (6H, m), 4.58 (2H, S), 6.77 (H, d, J=3
Hz), 6.83 (H, d, J=3 Hz), 7.43 (H, d, J =3 Hz), 7.55 (H, d, J =3 Hz), 8.88 (H, S). 13C NMR (75
MHz, DMSO-d6, ppm): 48.08 (CH2), 57.36 (CH2), 57.78 (CH2), 58.32 (CH2), 116.98 (CH),
119.45 (CH), 120.41 (C), 133.95 (CH), 135.46 (CH), 164.58 (C), 168.13 (CH=N) (Fig.S3).
2.3. X-ray crystallography
A crystal of complex C1 was mounted on a Stoe Image Plate Diffraction system equipped
with a φ circle goniometer, using Mo-Kα graphite monochromated radiation (λ = 0.71073 Å)
with φ range 0-200º. The structure was solved by direct methods using the program
SHELXS-2014, while the refinement and all further calculations were carried out using
SHELXL-2014 [39]. The H-atoms were included in calculated positions and treated as riding
atoms using the SHELX default parameters, while the non-H atoms were refined
anisotropically, using a weighted full-matrix least-square on F2. In C1, a methoxy group is
disordered over two positions, with occupancies of 0.7 and 0.3, respectively. Crystallographic
details are summarized in Table 1 and Figure 1, is drawn with ORTEP [40].
Table 1. Crystallographic and structure refinement parameters for complex C1.
Chemical formula
Formula weight
Crystal system
Space group
Crystal color & shape
Crystal size
a (Å)
C24H34N4O10V2
640.43
monoclinic
P 21/c (no. 14)
yellow block
0.22 x 0.21 x 0.18
10.8559(12)
9.5098(9)
13.7023(15)
103.863(9)
1373.4(3)
2
b (Å)
c (Å)
 (o)
V (Å3)
Z
T (K)
293(2)
1.549
0.743
1.93    29.23
3715
Dc (g.cm-3)
 (mm-1)
Scan range (o)
Unique reflections
Reflections used [I2(I)]
Rint
2460
0.0529
Final R indices [I2(I)]*
R indices (all data)
Goodness-of-fit
Max, Min /e (Å-3)
0.0378, wR2 0.0747
0.0743, wR2 0.0826
0.903
0.277, -0.279

2
2 2
2 2 1/2
2
* Structures were refined on F0 : wR2 = [Σ[w(F02 - Fc ) ] / Σw(F0 ) ] , where w-1 = [Σ(F0 ) + (aP)2
2
2
+ bP] and P = [max(F0 , 0) + 2Fc ]/3.
CCDC-1917114 (C1) contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or
from the Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ,
UK; fax: (internat.) +44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
2.4. DFT modeling
All quantum chemical calculations were performed using the Gaussian 09 program
package [41]. The selected molecular geometry and vibrational wavenumbers of C1 were
optimized at the B3LYP level using the 6-31G basis set [42] which was assigned to all atoms
[43]. Furthermore, to ensure that the optimized geometry is the most stable conformation,
vibrational frequency calculations were used, and the calculated results showed no negative
frequencies. The NMR chemical shifts have been calculated using the Gauge Including
Atomic Orbital (GIAO) method with B3LYP/6-31++G(d,p) [43,44].
2.5. Antioxidant activity
The antioxidant activity was investigated by the α,α-diphenyl-β-picrylhydrazyl (DPPH)
assay. The free radical scavenging activity was evaluated using a method already described
[45], with slight modifications. 0.1 mL of various concentrations of C1, C2, butylated
hydroxytoluene (BHT), and Quercetin were added to 0.9 mL of a methanolic solution of
DPPH (60 µM). The reaction mixture was well shaken and kept at room temperature in the
dark for 30 min. The absorbance of the mixture was recorded at 517 nm. The DPPH radical
inhibition was calculated as follows:
DPPH radical scavenging % = [(OD control – OD sample)/OD control] × 100
Where OD control is the absorbance of blank and OD sample is the absorbance of the
samples. The IC50 value is the inhibition concentration of the test sample that decreases 50 %
of initial radical. It was calculated from the response curves of scavenging activity against the
concentrations of the samples.
3. Results and discussion
3.1. Crystal structure analysis
The crystal structure of the C1 complex is depicted in Figure 1. The structure crystallizes
in monoclinic system with a space group P21/c, a = 10.8559(12) Å, b = 9.5098(9) Å, c =

13.7023(15) Å, β = 103.863(9)°, V = 1373.4(3) Å3 and Z = 2. The reported C2 structure also
crystallizes in monoclinic system but with a space group P21/n and a smaller volume of V =
1189(1) Å3 due to the absence of a radical in the salicylaldehyde part [38]. Figure 1 shows
that the symmetric dimer molecule has a slight octahedral distortion with a center of
symmetry formed by a bridge of two oxygen atoms (O5-V1 and O5’-V1’) with a distance of
1.6730 (2) Å. This distance was found to be 1.678 (2) Å in similar di-nuclear complex having
a 3-ethoxy substituent in salicylaldehyde part [46], which is very close to our results. The six
coordinated central vanadium (V) of each monomer is completed with the NNO donor and the
V1N1 and V1N2 bonds with 2.1610(3) Å and 2.1630(3) Å, respectively. Moreover, the angles
formed by O1-V1-O5 and O5-V1-O4 are 99.13(11)° and 107.19(14)°, respectively. They
correlate with those found in reference [46] which were 98.86(10)° and 107.58(12)°.
Similarly, bond lengths and angles described in other di-nuclear vanadium complex structures
[47–49] were found in accordance with the titled complex.
Fig.1. Molecular structure of C1 at 50% probability level ellipsoids, with only one orientation
of the disordered terminal methoxy group being presented (i = 1-x, -y, -z).
3.2. Computational investigations and DFT calculations
The geometry of the complex C1 was obtained in a singlet ground state by DFT at
B3LYP/6-31G. Some significant bond lengths and bond angles of the optimized geometry of
C1 along with their corresponding X-ray data are given in Table 2.

Table 2 . Selected X-ray and calculated bond distances (Å) and angles (°) for C1
Experimental X-ray
Calculated
Bonds
V1-V2
O1-V1
V1-O4
V1-O5
C1-O1
C3-O2
N1-V1
N2-V1
3.119 (7)
1.907 (14)
1.619 (15)
1.669 (13)
1.331 (2)
1.362 (3)
2.159 (16)
2.162 (17)
1.284 (3)
1.411 (3)
3.169
1.928
1.621
1.680
1.347
1.383
2.159
2.196
1.299
1.426
C7-N1
C1-C6
Angles
V1-O1-C1
C3-O2-C12
O5-V1-O1
O4-V1-O5
N2-C10-C11
132.07 (13)
117.90 (17)
99.13 (6)
107.19 (8)
115.16 (19)
130.24
119.16
99.33
108.77
114.36
3.3.
IR Spectral study
The IR spectra of C1 was computed at the B3LYP/6-31G level of theory in the region
between 400 and 4000 cm-1. The calculated data was compared with the observed values and
the results are listed in Table 3. The experimental FT-IR spectrum is shown in Figure S.1.
Table 3. Vibrational frequency assignments of C1 with experimental and calculated DFT
methods.
Assignments
υ(C-Hsp3)
υ(C=N)
Experimental
Calculated
2940
1635
915
2938
1684
905
υ(V=O)
The C=N stretch observed at 1635 cm-1 is in accordance with results from previous report
[50] and it was found to be in good agreement with the computed value at 1684 cm-1. The
absorption band experimentally observed at 915 cm-1 and calculated at 905 cm-1 is associated
with the V=O vibration [51].
3.4. NMR spectra calculations

1H and 13C NMR chemical shifts of C1 complex were carried out at the B3LYP/6-
31G++(d,p) using GIAO approach in solvent phase. The calculations were performed in
DMSO-d6 solvent by using C-PCM formalism, and the selected shifts were compared with the
experimental values as illustrated in Table 4. The curves between the predicted and the
experimental data are shown in Figure 3. The correlation coefficients R2 of 99.05% and
1
98.51% for the selected H and 13C NMR chemical shifts, respectively, show that
experimental NMR data are consistent with the computed values from the optimized structure
of C1.
Table 4. Selected experimental and theoretical 1H and 13C NMR shifts (ppm) of C1.
1H NMR chemical shifts (ppm)
13C NMR chemical shifts (ppm)
Experimental
(DMSO)
Calculated
DFT/B3LYP (ppm)
Experimental
(DMSO)
Calculated
DFT/B3LYP (ppm)
Atoms
Atoms
H2
H2N
H4
7.44
-
7.08
4.60
4.84
6.19
6.77
4.08
2.34
C1
C2
C3
C5
C6
C7
C8
167.55
106.57
166.93
135.09
102.09
165.61
48.35
166.55
104.31
168.75
132.43
100.53
157.52
50.60
4.83
6.32
6.43
3.97
2.33
H5
H7
H8
H10
Fig. 3. Correlation curves between the predicted and experimental 1H NMR (left) and 13C
NMR (right) chemical shifts for C1.

3.5. Orbital analysis and HOMO-LUMO gap
The highest occupied molecular orbital (HUMO) associated with electron-donating
potential and the lowest unoccupied molecular orbital related to electron affinity [52] are
important in the quantum chemistry [53]. The difference between these two parameters
(HUMO-LUMO gap) can reveal the chemical reactivity of molecules. Contour plots of the
HOMO and LUMO orbitals for C1 and C2 are shown in Figure 4 and Figure S4, respectively.
The energy gap between HOMO and LUMO molecular orbitals of C1 and C2 was found to
be 4.02 and 4.13 eV, respectively, with ligand to metal charge transfer (LMCT).
Fig .4. Isodensity plots of HOMO and LUMO and their energies obtained at B3LYP/6-31G
level for C1.
3.6. Hirshfeld surface and EPS analyses
The Hirshfeld surface (HS) [54], which is the space occupied by a single molecule in a
crystal motif in order to divide the crystal electron density into molecular fragments, was
computed using the Crystal Explorer 17.5 program [55]. HS, combined with the two-
dimensional calculation of fingerprint plots, allow identification of the close contacts of each
atom calculated by the normalized contact distance dnorm with the nearest nucleus internal (di)

and external (de) distances to the surface [56]. Additionally, the electrostatic potential surface
(EPS) was defined at the B3LYP/6-311+G(d) level of theory.
HS analysis and EPS (Fig.5) provide 3D presentations of intermolecular interactions
between different contacts of each atom. A red spot over the HS indicates the interaction that
involved hydrogen bonding, whereas in the EPS map, the negative electrostatic potential
appears in the red area (hydrogen acceptors), and the positive electrostatic potential (hydrogen
donor) appears in blue.
C1
C2
Fig. 5. HS mapping surface (left) and EPS (right) for C1 and C2.
Therefore, the inter-contacts over the HS are shown using 2D-fingerprint scatter plots
(Fig. 6). In these scatter plots, de corresponds to the closest external contacts (i.e., external
distance) from a given point of the HS, and di to the closest internal distance. Three colors are
revealed in the map; blue for some occurrence, white if no occurrence, and green for frequent

occurrence [54]. The major intermolecular contacts including reciprocal interactions are
H···H, O···H, and C···H contacts with 47.8 %, 30.2 %, and 16.6 %, respectively for C1 and
the corresponding ones for C2 are 47.1 %, 26.7 % and 18 %, respectively. The O···H contacts
are represented by two spikes in the left region (donor) and a spike in the right region
(acceptor) of the 2D-fingerprint plots. These inter-contacts are significantly medium and
important in the molecular packing of the studied complexes.
C1
C2
Fig. 6. 2D-Fingerprint plots of the major inter-contacts in C1 and C2.
3.7. Antioxidant activity
Several methods (FRAP, ABTS, H2O2, FIC, DPPH, etc.) have been developed to assess
the antioxidant activity of different organic compounds [57]. Some of these methods estimate
the capacity of the bioactive compounds to scavenge specific radicals, chelate ions, or inhibit
peroxidation of lipids [58].
In the present study, the DPPH assay was used to estimate the antioxidant activity of C1
and C2 complexes using BHT and quercetin as antioxidant standards. It shows that H-atom
transfer is involved in the radical scavenging process. Therefore, the antioxidant compounds
donate the hydrogen to a DPPH radical and convert it into DPPH-H. As shown in Table 5, the
complex C1 which possesses one hydroxyl group in the ortho position exhibited the strongest
scavenging activity of DPPH with an IC50 value of 1.446 mg/mL. This was followed by the
complex C2 with a value of IC50 equal to 1.572 mg/mL. According to these results, C1 and

C2 complexes are less active than BHT and quercetin. Although, the antioxidant standards are
the most potent scavengers of the free radical DPPH●, this does not prevent the studied
compounds from being active and having a considerable antiradical capacity. The efficiency
of the ortho and para compounds is in part due to the regeneration of another compound [59]
or the stabilization of the aryloxyl radical by hydrogen bonding [60]. Moreover, it has been
reported that the ortho-methoxy substitution also stabilizes the aryloxyl radical by electron
donation [61] and therefore increases the antioxidant and the antiradical efficiencies. The
bond dissociation energies of the O–H bonds are also important criteria in evaluating the
antioxidant activity, because the weaker the OH bond the easier will be the reaction of free
radical inactivation [62,63].
Table 5. Antioxidant activity of C1 and C2 complexes.
Entry
Compounds
C1
DPPH assay (mg/mL)
1.446 ± 0.012
1
2
3
4
C2
1.572 ± 0.011
BHT
0.060 ± 0.001
Quercetin
0.040 ± 0.001
Values are presented as means ± standard deviation (SD) of three replications
4. Conclusion
In this report, the vanadium (V) di-nuclear complex C1 was synthesized from a Schiff
base (L1H) tridentate bearing NNO donors and VOSO4. The single crystal X-ray diffraction
confirmed the presence of a bridge formed by an oxo group in the dimer structure. The
1
complex has been fully characterized by FT-IR, H, and 13C NMR. The prediction of the
structural parameters and vibrational frequencies using DFT method are in accordance with
the experimental results. The comparison between C1 and C2 complexes has indicated that
both structures crystallized in a monoclinic system. Moreover, it has been found that the
intermolecular interactions over the Hirshfeld surface showed that the major interactions in
both structures are slightly the same. DPPH free radical scavenging was used as a simple,
rapid, and cheap method to determine the antioxidant activity, and the results have clearly
shown that the radical scavenging activity of C1 and C2 is much higher than BHT and
quercetin.

Acknowledgements
The authors would like to thank Professor Bruno Therrien at Institute of Chemistry,
University of Neuchâtel for performing the X-ray diffraction characterization of the sample.
Declaration of Interest
The authors declare that there are no conflicts of interest.
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Highlights
 Synthesis of new di-μ-oxidovanadium(V) complexes [(LH)VO(μ-O)2VO(LH)].
1
13
 The complexes were characterized by H, C NMR, FT-IR and confirmed by
single-crystal X-ray diffraction.
 Computational studies using density functional theory (DFT) method were
computed.
 Hirshfeldsurfaces analysis were applied to observethe intermolecular
interactions in the [(LH)VO(μ-O)2VO(LH)].
 Antioxydant activity of the titled products were investigated.
Marrakech, October 07th 2019
InorganicaChimica Acta
Subject: REVISION OF OUR MANUSCRIPT FOR PUBLICATION

Manuscript Title: "Di-μ-oxidovanadium(V) di-nuclear complexes: Synthesis, X-ray,
DFT modeling, Hirshfeld surface analysis and Antioxidant activity"
Ali Hasnaoui 1, Ismail Hdoufane 2, Abderrahim Alahyane 3, Abdallah Nayad 1, Driss
Cherqaoui 2, Mustapha Ait Ali 1 and Larbi El Firdoussi 1*
Manuscript ID: ICA_2019_777
Declaration of Interest
The authors declare that there are no conflicts of interest.
Di-μ-oxidovanadium(V) di-nuclear complexes: Synthesis, X-ray, DFT
modeling, Hirshfeld surface analysis and Antioxidant activity
Ali
DrissCherqaoui2, Mustapha Ait Ali1and Larbi El Firdoussi1*
Hasnaoui1,
Ismail
Hdoufane2,
AbderrahimAlahyane3,
AbdallahNayad1,
1Equipe de Chimie de Coordination et de Catalyse, Département de Chimie, Université Cadi Ayyad, Faculté des
Sciences Semlalia, BP 2390, Marrakech, Morocco ;
2 Laboratory of Molecular Chemistry, Department of Chemistry, Faculty of SciencesSemlalia, Cadi Ayyad
University of Marrakech, BP 2390, Morocco;
3 Food Sciences Laboratory, Department of Biology, Faculty of Sciences-Semlalia, Cadi Ayyad University of
Marrakech, P.O. Box 2390, Morocco.
* Corresponding author.
ABSTRACT
In this work, two di-μ-oxidovanadium(V) complexes, [(L1H)VO(μ-O)]2 (C1) and
[(L2H)VO(μ-O)]2 (C2), with tridentate Schiff base ligands, [N-(2-hydroxyethylamino)ethyl]-
5-methoxysalicylaldimine (L1H) and 2-[(2-(2-Hydroxyethylamino) ethylimino)methyl]
phenol (L2H), respectively, were prepared and characterized by various spectroscopic
techniques. The X-ray diffraction of C1 showed six-coordinate vanadium in a distorted
octahedral geometry with the imine, phenolate and amine donors of the ligand and two oxo-
group bonds. Density functional theory (DFT) was carried out using B3LYP level with the 6-
31G basis set in order to predict the molecular structure of C1, delineate its vibrational
wavenumbers and define the theoretical NMR shifts, which were performed with the GIAO
approach. Thereafter, Hirshfeld surface (HS) and 2D fingerprint analysis were used to
investigate the intermolecular contacts in the C1 complex. The DPPH free radical scavenging
assay was used to evaluate the antioxidant activity of both C1 and C2 complexes.