Theoretical investigation on the reactivity and photophysical properties of cobalt(II) and manganese(II) complexes constructed using Schiff base ligands based on ALIE and TDDFT calculations

Article abstract of DOI:10.1016/j.poly.2017.03.049

Herein, we describe the synthesis of two novel Schiff base ligands, 2-[(3-bromo-5-hydroxybenzylidene)-amino]-6-methylpyrimidin-4-ol (1) and 3-bromo-5-[(5-methylthiazol-2-ylimino)methyl]phenol (2), and their Co(II) and Mn(II) complexes (4–6). The molecular

Full text of DOI:10.1016/j.poly.2017.03.049

Accepted Manuscript
Theoretical investigation on the reactivity and photophysical properties of co-
balt(II) and manganese(II) complexes constructed using Schiff base ligands
based on ALIE and TDDFT calculations
Kollur Shiva Prasad, Renjith Raveendran Pillai, Stevan Armaković, Sanja J.
Armaković
PII:
S0277-5387(17)30247-4
DOI:
http://dx.doi.org/10.1016/j.poly.2017.03.049
POLY 12564
Reference:
Polyhedron
To appear in:
Received Date:
Revised Date:
Accepted Date:
5 January 2017
16 March 2017
19 March 2017
Please cite this article as: K.S. Prasad, R.R. Pillai, S. Armaković, S.J. Armaković, Theoretical investigation on the
reactivity and photophysical properties of cobalt(II) and manganese(II) complexes constructed using Schiff base
ligands based on ALIE and TDDFT calculations, Polyhedron (2017), doi: http://dx.doi.org/10.1016/j.poly.
2017.03.049
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Theoretical investigation on the reactivity and photophysical
properties of cobalt(II) and manganese(II) complexes constructed
using Schiff base ligands based on ALIE and TDDFT calculations
Kollur Shiva Prasada*, Renjith Raveendran Pillaib, Stevan Armakovićc, Sanja J. Armakovićd
a
Laboratory of Synthetic and Materials Chemistry, Manipal Centre for Natural Sciences,
Manipal University, Karnataka – 576104, India.
b Department of Physics, TKM College of Arts and Science, Karicode, Kollam, Kerala-69100,
India.
c
University of Novi Sad, Faculty of Sciences, Department of Physics, Trg D. Obradovića 4,
21000 Novi Sad, Serbia
d
University of Novi Sad, Faculty of Sciences, Department of Chemistry, Biochemistry and
Environmental Protection, Trg D. Obradovića 3, 21000 Novi Sad, Serbia
*Corresponding author email: shivachemist@gmail.com (K. Shiva Prasad)
Abstract
Herein, we describe the synthesis of two novel Schiff base ligands, 2-[(3-bromo-5-
hydroxybenzylidene)-amino]-6-methylpyrimidin-4-ol (1) and 3-bromo-5-[(5-methylthiazol-2-
ylimino)methyl]phenol (2), and their Co(II) and Mn(II) complexes (4-6). The molecular
structures of the obtained compounds were confirmed using physical and analytical
characterization techniques. The global stability properties of the ligands and their coordination
complexes have been assessed by analyzing their frontier molecular orbitals, while their
reactivity properties have been assessed by calculating average local ionization energies (ALIE).
In addition, TDDFT calculations have been performed in order to theoretically obtain the UV-
Visible spectra of the title compounds.
Keywords: Schiff base, Metal complexes, Analytical techniques, ALIE, TDDFT calculations.

Introduction
In the last few years, metal-organic frameworks (MOF’s), which are derived from organic
ligands and metal ions, have emerged as important candidates for porous materials with
intriguing new structural topologies and potential applications as functional materials [1-3]. Due
to their varied structural behavior and stability, MOF’s are widely used in catalysis, [4,5],
sensing probes [6], light-emitting materials [7] and drug delivery systems [8]. Apart from their
numerous applications in the field of electronics, they are also a subject of interest in medicinal
chemistry due to their biological and pharmaceutical properties, such as antibacterial,
antiparasitic and antitumor activities [9]. Schiff base-transition metal complexes have continued
to play a role with some interesting reactivity as photoluminescence of light-emitting materials
[10]. In particular, pyrimidine based Schiff base ligands and their metal complexes have attracted
much attention over many years due to their luminescent properties [11]. For instance, rare earth
metal-organic coordination compounds can find wide applications in electroluminescent
materials/devices because of their high fluorescent properties [12].
Push-pull chromophoric systems have been studied using Density Functional Theory (DFT)
methods in recent years [13-15]. Due to the ample advantages of using DFT based computational
methods in understanding functional properties like luminescence and hyperpolarizability at the
molecular level [16-18], these theoretical computations have become very much important tools
to understand the excited state configuration and electronic spectra of medium-sized and large
molecules.
The above facts and observations led us to choose 2-amino-4-hydroxy-6-methylpyrimidine and
5-methylthiazol-2-ylamine based ligands to construct Co(II) and Mn(II) complexes. Our choice

of pyrimidine and thiazole based ligands as organic frameworks is based on the fact that they
possess interesting photophysical properties, such as visible excitation and emission wavelengths
[19]. The structure elucidation of the compounds was performed by using FT-IR, UV-Vis, NMR
(1H and 13C), MS and thermal analysis techniques.
Experimental
Materials and methods
Guanidine and acetoacetic ester were procured from Aldrich chemicals (USA). The metal salts
and other chemicals were obtained from SD Fine chemicals private limited (India). All the
solvents were obtained from Merck chemical company and were distilled by known procedures
before use. FT-IR spectra of the compounds were obtained on a Perkin-Elmer spectrometer
1
version 10.03.09 by the nujol-mull technique. H and 13C NMR spectra were obtained on a
Bruker Avance 400 MHz NMR spectrometer using TMS as an internal standard. Mass spectra
were recorded on Q-TOF micro mass spectrometer using the electrospray ionization method. The
purification of the compounds was done by column chromatography. Thin layer chromatography
(TLC) was performed on pre-coated silica-gel plates (Merck, India) and spots were visualized by
UV irradiation. The thermal analysis (TGA/DTG) was recorded on TGA-50 and DTA-50
Shimadzu differential thermal analyzers. The thermal studies were done under a nitrogen
atmosphere using 5 mg of the sample at a heating rate of 10 °C/min in the temperature range
from ambient to 600 °C using a platinum cup as the sample holder. Molar conductance was
measured for the above prepared complexes in DMF using an ELICO model CM82T
conductivity bridge.
The Jaguar 9.4 [20] program has been used for the DFT and TDDFT calculations on the ligand
and complex structures. In order to obtain ground state geometries of the investigated molecules

geometrical optimizations of all the structures have been performed with the B3LYP exchange-
correlation functional coupled with the 6-31G(d,p) basis set. The LACVP(d,p) basis set has been
used for sulfur, cobalt and manganese atoms. True ground states have been confirmed by
frequency calculations, which yielded only positive frequencies. UV spectra have been obtained
by TDDFT calculations with the CAM-B3LYP [21] exchange-correlation functional together
with the 6-31+G(d,p) basis set. For TDDFT calculations, the Tamm-Dancoff approximation [22]
has been used and 40 excitations have been taken into account. Also, in the case of TDDFT
calculations, solvent effects of dimethyl sulfoxide (DMSO), acetonitrile (ACN) and ethanol have
been taken into account by Poisson-Boltzmann solver [23,24]. The Jaguar program was used as
implemented in Schrödinger Materials Science Suite 2016-4, whereas the Maestro GUI [25] was
used for the preparation of input files and analysis of the results.
General synthesis
Synthesis of 2-amino-4-hydroxy-6-methylpyrimidine
The above compound was prepared using a previously reported method with minor
modifications [26] as shown in Scheme 1. To a solution of guanidine (2.02 g, 33.84 mM) in
acetone/ethanol mixture (1:2), a solution of acetoacetic ester (4.40 g, 33.86 mM) in
acetone/ethanol was added dropwise and the resulting solution was stirred at room temperature
for 10 h. The solid product obtained was separated by filtration and recrystallized from acetic
acid to obtain colorless crystals.
1
Yield: 1.36 g (52 %). H NMR (400 MHz, CDCl3, ppm), δ: 11.09 (s, 1H, OH), 5.92 (s, 2H,
13
NH2), 5.14 (s, 1H, Ar-H), 2.14 (s, 3H, Ar-CH3). C NMR (100 MHz, CDCl3, ppm) δ: 162.3,
161.1, 155.3, 102.5, 23.9. ESI-MS calc. for C5H7N3O [M+]: 125.06; found 126.07 [M+ + 1].

Scheme 1: Synthesis of 2-amino-6-methylpyrimidin-4-ol.
Synthesis of the Schiff base ligands
3-Bromo-5-[(5-methylthiazol-2-ylimino)methyl]phenol (1)
A solution of 3-bromo-5-hydroxybenzaldehyde (1.31 g, 6.55 mM) in methanol (10 mL) was
added dropwise with continuous stirring to a solution of the primary amine, 5-methylthiazol-2-
ylamine (0.75 g, 6.57 mM) in methanol (15 mL), over a period of 5 min. The reaction mixture
was refluxed at 60 ᴏC for about 6 h. The completion of the reaction was monitored by TLC. The
product was isolated by pouring the reaction mixture into ice cold water. The precipitate formed
was filtered off and dried to obtain a pale yellow solid. The compound was then purified by
column chromatography using silica gel (230-400 mesh size) with ethyl acetate and petroleum
ether as eluents.
1
Yield: 0.81 g (67 %). H NMR (400 MHz, CDCl3, ppm), δ: 9.88 (s, 1H, OH), 8.69 (s, 1H, -
13
HC=N), 6.93-7.38 (m, 4H, Ar-H), 2.19 (s, 3H, Ar-CH3). C NMR (100 MHz, CDCl3, ppm) δ:
169.9, 161.1, 160.3, 136.3, 135.7, 130.1, 125.1, 124.5, 125.1, 121.4, 112.8, 12.1. ESI-MS calc.
for C11H9N2OSBr [M+]: 295.96; found 296.11 [M+].
Scheme 2: Preparation pathway for 3-bromo-5-[(5-methylthiazol-2-ylimino)methyl]phenol (1).

2-[(3-Bromo-5-hydroxybenzylidene)-amino]-6-methylpyrimidin-4-ol (2)
A solution of 3-bromo-5-hydroxybenzaldehyde (1.20 g, 6.00 mM) in methanol (20 mL) was
added dropwise with continuous stirring to a solution of the primary amine, 2-amino-6-
methylpyrimidin-4-ol (0.75 g, 5.99 mM) in hot methanol (15 mL), over a period of 5 min. The
ᴏ
reaction mixture was refluxed at 60 C for about 6 h. The completion of the reaction was
monitored by TLC. The product was isolated by pouring the reaction mixture into ice cold water.
The precipitate formed was filtered off and dried to obtain a white solid. The compound was then
purified by column chromatography using silica gel (230-400 mesh size) with ethyl acetate and
petroleum ether as eluents.
Yield: 0.78 g (64 %). 1H NMR (400 MHz, CDCl3, ppm), δ: 11.27 (s, 1H, OH), 9.92 (s, 1H, OH),
13
8.72 (s, 1H, -HC=N), 6.34-8.42 (m, 5H, Ar-H). C NMR (100 MHz, CDCl3, ppm) δ: 167.8,
161.3, 160.9, 160.2, 159.8, 138.1, 126.2, 125.1, 122.5, 115.2, 114.8. ESI-MS calc. for
C11H8N3O2Br [M+]: 292.98; found 293.1 [M+].
Scheme 3: Preparation pathway for 2-[(3-bromo-5-hydroxybenzylidene)-amino]-6-
methylpyrimidin-4-ol (2).
Synthesis of the metal complexes
Synthesis of Co(BMTMP)2 and Mn(BMTMP)2 (3 and 5)

Complexes 3 and 5 were synthesized by adding a 2 molar equivalent methanolic solution of 1
(0.29 g, 0.10 mM) to a 1 molar equivalent solution of Co(CH3COO)2.4H2O (0.12 g, 0.49 mM) or
Mn(CH3COO)2.4H2O (0.12 g, 0.50 mM) in methanol separately. The color change was observed
upon mixing the ligand with the metal(II) salt. The above reaction mixture was then refluxed at
ᴏ
65 C for 12 h. The solid obtained was filtered off and washed with diethyl ether and then with
cold ethanol. The product was dried in a vacuum and used for further analysis.
Co(BMTMP)2 - Yield: 56 %. Anal. Calcd. for C26H22Br2N4O6SCo (%): C-40.68, H-2.86, N-7.30;
found, C-40.28, H-2.76, N-7.11. FT-IR (nujol, cm-1): 2973 (Ar-CH), 1613 (-N=CH), 1391 (Ar-
N), 1477 (CH), 1083 (Ar-Br). ESI-MS: Exact mass-766.87 [M+], found-766.90 [M+].
Mn(BMTMP)2 - Yield: 51 %. Anal. Calcd. for C26H22Br2N4O6SMn (%): C-40.89, H-2.88, N-
7.34; found, C-42.31, H-3.52, N-10.59. FT-IR (nujol, cm-1): 2975 (Ar-CH), 1618 (-N=CH), 1386
(Ar-N), 1473 (CH), 1088 (Ar-Br). ESI-MS: Exact mass-762.87 [M+], found-762.9 [M+].
Synthesis of Co(BHAMP)2 and Mn(BHAMP)2 (4 and 6)
Complexes 4 and 6 were synthesized in a similar manner to complexes 3 and 5, as mentioned
above. In this case, a 2 molar equivalent methanolic solution of 2 (0.30 g, 0.97 mM) was used
instead of compound 1.
Co(BHAMP)2 - Yield: 43 %. Anal. Calcd. for C28H24Br2N6O8Co (%): C-42.58, H-3.42, N-10.64;
found, C-42.31, H-3.39, N-10.59. FT-IR (nujol, cm-1): 3459 (Ar-OH), 2987 (Ar-CH), 1609 (-
N=CH), 1383 (Ar-N), 1485 (CH), 1090 (Ar-Br). ESI-MS: Exact mass-760.91 [M+], found-761.1
[M+].
Mn(BHAMP)2 - Yield: 48 %. Anal. Calcd. for C28H24Br2N6O8Mn (%): C-42.80, H-3.57, N-
10.70; found, C-42.71, H-3.52, N-10.62. FT-IR (nujol, cm-1): 3456 (Ar-OH), 2982 (Ar-CH),

1597 (-N=CH), 1388 (Ar-N), 1485 (CH), 1088 (Ar-Br). ESI-MS: Exact mass-756.94 [M+],
found-757.0 [M+].
Scheme 4: Synthetic routes for the metal complexes 3-6 using the Schiff base ligands 1 and 2.
Results and discussion
Two Schiff base ligands, BMTMP (1) and BHAMP (2), and their metal complexes (3-6) were
prepared and their structures have been confirmed by studying their physical and spectral
properties. The synthetic routes for the ligands and their complexes are depicted in Schemes 2, 3

and 4. The metal complexes discussed herein were dissolved in DMF and the molar
conductivities of their 10−3 M solutions at room temperature were measured to establish the
charge of the metal complexes. The lower molar conductance values (15.3-18.0 Ω-1 cm2 mol-1)
indicates that all the metal complexes have a non-electrolytic nature due to the fact that there are
no counter ions in the proposed structures of the Schiff base metal complexes.
The main IR spectral bands of metal complexes are discussed in the synthesis section. Fig. S1
depicts the IR spectra of ligands and complexes 3 and 4. The phenolic OH band in the ligands
were observed between 3270 and 3458 cm-1, which are significantly changed or disappear in the
IR spectra of their metal complexes, confirming the participation of this group in metal
coordination. Due to the involvement of the azomethine nitrogen atom in coordination, a drift in
the IR band of this group is observed in the complexes in comparison with their ligands.
The 1H NMR of signals observed due to different protons in the ligands experience smaller shifts
after metallation into their respective complexes. The aldehydic proton at δ 8.69 and 8.72 ppm in
1 and 2, respectively is shifted to a downfield resonance in the metal complexes, confirming its
participation in complex formation. The disappearance of the phenolic proton signal in the metal
complexes reveal its involvement in coordination. This was also further supported by 13C NMR
studies. The molecular mass of all the prepared compounds were confirmed by recording their
mass spectra (ESI-MS) and the mass values are given in the synthesis section (Fig. S3-S8).
The thermal analyses (TGA and DTG) of the metal complexes were monitored from an ambient
temperature to 600 °C, at a heating rate of 10 °C/min and under a nitrogen atmosphere. The
TG/DTG curves of complex 3 are shown in Fig. S2. The DTG curve of complex 3 reveals the
melting of the complex as the temperature rises. This was further supported by the TG curves,
which clearly indicates the degradation of the complex into two steps. The first degradation step

corresponds to the loss of the organic ligand in the 220 to 400 °C temperature range. The second
step involves the degradation of the leftover organic fragment between 400 to 450 °C, leaving
behind residual metal oxide as the end product.
Frontier molecular orbitals
In order to assess the stability of the investigated molecules in this work we refer to the analysis
of their frontier molecular orbitals. The frontier molecular orbitals (FMO), namely the highest
occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), are
the two most important molecular orbitals, principally determining the global stability and
reactivity properties of molecules. The spatial distribution of the investigated FMOs of the
ligands are presented in Fig. 1, while their energies together with the HOMO-LUMO gaps and
dipole moments are provided in Table 1.
Table 1: Energies of the FMOs, HOMO-LUMO gap and dipole moments of the ligands.
HOMO
[eV]
LUMO
[eV]
HOMO-LUMO gap Dipole moment
Compound
[eV]
3.62
3.93
[D]
-5.96
-6.20
-2.34
-2.27
3.74
3.99
1
2
The results presented in Fig. 1 show that the FMOs are delocalized over the whole ligand
molecules, indicating relatively high stability. The relatively high stability of ligands is also
confirmed by the values of the HOMO-LUMO gaps, which are very similar and take values of
3.62 and 3.93 eV, for 1 and 2 respectively. The relatively high values of the dipole moments,
3.74 and 3.99 D for 1 and 2 respectively, indicate significant charge separation within the
molecules and possibly significant reactivity based on electrostatic interactions.

The FMOs of the complex molecules are visualized in Fig. 2, while Table 2 contains information
on the energies of the FMOs and HOMO-LUMO gaps, together with the dipole moments. From
the aspect of global reactivity, the results presented in Table 2 indicate that complex structure 3
is the least stable one, with a HOMO-LUMO gap of only 0.51 eV. Indeed, an inspection of the
spatial distribution of the FMOs in the case of complex 3 indicates that the HOMO and LUMO
are close to each other. A similar situation can be seen in the case of the next least stable
molecule, denoted with number 5, with a corresponding HOMO-LUMO gap of 1.17 eV. It is
important to note that both least stable complex molecules are based on ligand 1. From the aspect
of the HOMO-LUMO gap, the most stable molecule is the one denoted with number 6, followed
by complex molecule 4. Both 4 and 6 are based on ligand 2. The highest dipole moment has been
calculated in the case of complex molecule 4, indicating that this molecule could have significant
reactive properties based on electrostatic interactions, which is later confirmed by its ALIE
surfaces.
Table 2: Energies of the FMOs, HOMO-LUMO gap and dipole moments of the complexes.
HOMO
[eV]
LUMO
[eV]
HOMO-LUMO gap Dipole moments
Compound
[eV]
0.51
2.52
1.17
3.21
[D]
3.05
-5.42
-5.91
-4.12
-5.83
-4.91
-3.40
-2.94
-2.62
3
4
5
6
8.05
2.60
3.59
ALIE surfaces
In order to be able to investigate reactive properties of molecules, Sjoberg and coworkers have
introduced ALIE as a quantum-molecular descriptor [27,28]. ALIE denotes the energy necessary
for the removal of an electron from a molecule. Thus, areas where this descriptor has the lowest

values are the ones that are very sensitive towards the electrophilic attack. In general, ALIE is
defined as the sum of the orbital energies weighted by the orbital densities according to the
following equation:
ꢀ
ρ
(
r
)
εi
i
I
(r
)
=
ꢀ .
(1)
∑
ρ
(
r
)
i
ꢀ
ρi
(
r
)
εi
,
where
denotesthe electronic density of the i-th molecular orbital at the point
r
ꢀ
ρ
(
r
)
denotes the orbital energy, while
denotes the total electronic density function [29,30]. In
this work ALIE was visualized by mapping of its values to the electron density surface.
Representative ALIE surfaces of ligands are presented in Fig. 3, while representative ALIE
surfaces of the complex molecules are presented in Fig. 4.
The ALIE surface of the ligands reveals that the most important molecule site that is prone to
electrophilic attack is in the vicinity of the bromine atom. This molecule site is characterized by
the lowest ALIE value of ~196 kcal/mol. According to the distribution of the red color, the areas
concerning ligand 1 in the vicinities of the sulfur and nitrogen atoms could also be of importance
for electrophilic attack, while concerning ligand 2, the nitrogen atoms are also characterized by
the presence of red color. While the minimal ALIE values of ligands 1 and 2 are very similar,
their maximal ALIE values are very different, namely they differ by more than 35 kcal/mol. The
highest ALIE values in both cases are located in the vicinity of the hydrogen atoms belonging to
the OH groups, with ligand 1 being the one with the much higher maximal ALIE value.
The ALIE surface of the complex molecules clearly indicates that the most sensitive towards
electrophilic attack is complex molecule 4. It has been already shown that this molecule has the
highest value dipole moment, therefore being the one with the greatest potential for electrostatic

based interactions. In the case of 4, the lowest ALIE value is ~125 kcal/mol and is located in the
vicinity of the carbon atom C22 of the ligand 2 (according to the numbering scheme provided in
Fig. 5). The lowest ALIE value in the case of 4 is much lower than the minimal ALIE values of
the remaining complex molecules, by almost 70 kcal/mol. On the other hand, the highest ALIE
values of 4, 5 and 6 are relatively similar and much higher than the maximal ALIE value of 3,
the value of which is ~331 kcal/mol.
Photophysical properties
The theoretically obtained spectra of the ligands and complex molecules have been presented in
Fig. 6. The results depicted in Fig. 6 indicate that ligand 2 has a slightly larger absorption
comparing to ligand 1. Both of the ligand molecules have two distinct absorption peaks. In
DMSO, one absorption peak is located at 200 nm for both ligands. The second absorption peak
in the case of 1 is located at around 340 nm, while the second absorption peak of 2 is located at
around 300 nm. It can be also seen that absorption peaks are little bit sharper in the case of 1. In
the case of the ligands in ACN and ethanol solvents the maximal values of the absorption peaks
significantly increase, while their locations and ratios remain practically intact, as it can be seen
in Fig. 7.
Among the complex molecules investigated, according to the results presented in Fig. 6, it can be
seen that in DMSO solvent complex 5 has the highest absorption peak, which is located at a
wavelength of around 320 nm. The remaining complexes have relatively similar absorption
properties, according to the height of the absorption peaks, which are all located in the area
between 300 and 450 nm, except complex 6, which has two low absorption peaks located at
around 600 and 710 nm. Concerning the complexes, the only significant change that occurred
with the change of solvent happened in the case of complex 6. While the influence of ACN

(comparing to DMSO) on the absorption peak location and height was practically insignificant,
using ethanol as a solvent resulted in the absence of the two small peaks located at wavelengths
around 625 and 725 nm. The height of the absorption peak of 6, located at a wavelength of
around 350 nm in the cases of DMSO and ACN solvents, decreased in ethanol solvent more than
two fold, while the absorption peak shifted towards a wavelength of 375 nm.
Conclusions
In summary, we have prepared two Schiff base ligands and their Co(II) and Mn(II) complexes.
The molecular structures of the compounds were deduced with the help physical and analytical
techniques. Analysis of the energies and distribution of the frontier molecular orbitals indicated
that the least stable complex is 3. The highest dipole moment has been calculated in the case of
complex 4, designating it to be sensitive towards reactions based on electrostatics. ALIE values
also recognized that complex 4 is prone to undergo electrophilic attacks to the highest extent of
all the investigated structures in this work. Concerning the ligand molecules, the ALIE surfaces
designated that the most sensitive areas towards electrophilic attack are in the vicinity of the
bromine atoms. In DMSO solvent, the ligands 1 and 2 have significantly lower absorption peaks
comparing to ACN and ethanol. On the other hand, ACN and ethanol solvents significantly
influenced only complex 6, removing its two low absorption peaks and shifting the highest
absorption peak towards a significantly higher wavelength.
Disclosure statement
The authors declare no conflict of interest.
Acknowledgments

KSP gratefully thanks Dr. Mohini Gupta, Director, Manipal Centre for Natural Sciences,
Manipal University for funding in the form of a start-up grant. The authors extend special thanks
to the support received from Schrödinger Inc. Part of this study was conducted within the
projects supported by the Ministry of Education, Science and Technological Development of
Serbia, grant numbers OI 171039 and TR 34019.
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Graphical Abstract (pictogram)

Graphical Abstract (synopsis)
Co(II) and Mn(II) complexes synthesized using Schiff base ligands were studied for their
reactivity and photophysical properties by computational methods, such as TDDFT and ALIE
investigations. The theoretical studies designated that the ligands are most sensitive towards
electrophilic attack in the vicinity of the bromine atoms.