Synthesis, characterization, DFT and TD-DFT study of novel bis(5,6-diphenyl-1,2,4-triazines)

Article abstract of DOI:10.1016/j.molstruc.2020.129345

Due to the numerous biological as well as pharmacological activities of 1,2,4-triazine derivatives, we reported a synthesis of novel series of bis(5,6-diphenyl-1,2,4-triazines) via alkylation of 5,6-diphenyl-1,2,4-triazine-3(4H)-thione with the appropriate bis(halo) compounds in ethanolic KOH. The chemical structures of these compounds were confirmed by spectroscopic techniques. The absorption and excited-emission spectra of the studied novel series were monitored experimentally in ethanol solvent. The molecular structures of these triazines were optimized using B3LYP/6–31G(d) level of theory. The electronic absorption and emission spectra of the novel compounds, in gas and ethanol solvent, were calculated using time dependent density functional theory (TDDFT) at mPW1PW91/ 6–31 G (d) level. The obtained theoretical results were compared to experimental ones. The results show that, the computational optical properties of the studied novel series are in agreement with experimental results.

Full text of DOI:10.1016/j.molstruc.2020.129345

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Synthesis, Characterization, DFT and TD-DFT study of Novel
bis(5,6-diphenyl-1,2,4-triazines)
Mahmoud A.S. Sakr Data curation; Methodology; Software ,
Adel A. Mohamed Software; Validation ,
Maram T.H. Abou Kana Visualization; Investigation ,
Ahmed H.M. Elwahy Conceptualization; Original draft preparation ,
Samy A. El-Daly , El-Zeiny M. Ebeid Reviewing and Editing
PII:
S0022-2860(20)31663-X
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.129345
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Mahmoud A.S. Sakr Data curation; Methodology; Software ,
Maram T.H. Abou Kana Visualization; Investigation ,
Adel A. Mohamed Software; Validation ,
Ahmed H.M. Elwahy Conceptualization; Original draft preparation ,
Samy A. El-Daly ,
El-Zeiny M. Ebeid Reviewing and Editing , Synthesis, Characterization, DFT and TD-DFT
study of Novel bis(5,6-diphenyl-1,2,4-triazines), Journal of Molecular Structure (2020), doi:
https://doi.org/10.1016/j.molstruc.2020.129345
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Highlights
 Synthesis of novel series of bis(5,6-diphenyl-1,2,4-triazines).
 Confirmation of their chemical structures by spectroscopic techniques.
 Studies of their absorption and excited-emission spectra experimentally in
ethanol solvent.
 Calculation of their electronic absorption and emission spectra in gas and
ethanol solvent using time dependent density functional theory (TDDFT).

Synthesis, Characterization, DFT and TD-DFT study of Novel bis(5,6-
diphenyl-1,2,4-triazines)


Mahmoud A. S. Sakr,a,b Adel A. Mohamed c, Maram T. H. Abou Kanad , Ahmed H.M. Elwahye ,
Samy A. El-Dalyb, El-Zeiny M. Ebeida,b
a Misr University for Science and Technology (MUST), 6th of October City, Egypt
bChemistry Department, Faculty of Science, Tanta University, Tanta, Egyp
cChemistry Department, Faculty of Science, Helwan, University, Cairo, Egypt
dLaser Sciences and Interactions Department, National Institute of Laser-Enhanced Sciences (NILES),
Cairo University, Giza, Egypt
eChemistry Department, Faculty of science, Cairo University, Giza, Egypt
Abstract: Due to the numerous biological as well as pharmacological activities of 1,2,4-triazine
derivatives, we reported a synthesis of novel series of bis(5,6-diphenyl-1,2,4-triazines) via
alkylation of 5,6-diphenyl-1,2,4-triazine-3(4H)-thione with the appropriate bis(halo) compounds
in ethanolic KOH. The chemical structures of these compounds were confirmed by spectroscopic
techniques. The absorption and excited-emission spectra of the studied novel series were
monitored experimentally in ethanol solvent. The molecular structures of these triazines were
optimized using B3LYP/6-31G(d) level of theory. The electronic absorption and emission
spectra of the novel compounds, in gas and ethanol solvent, were calculated using time
dependent density functional theory (TDDFT) at mPW1PW91/ 6-31G (d) level. The obtained
theoretical results were compared to experimental ones. The results show that, the computational
optical properties of the studied novel series are in agreement with experimental results.
Key words: Bis(5,6-diphenyl-1,2,4-triazines); Optical properties; Fluorescence spectra; Density
functional theory (DFT); Time dependent density functional theory (TDDFT).
1. Introduction:
The preparation of novel organic л-conjugated luminophores has been of significant
important over the last few decades, because of their wide applications in a lot of fields such as
optoelectronics, bio-imaging, and optical storage devices [1-4]. Organic compounds having both
electron donating (D) and accepting (A) substituents in a single molecule show great optical and
Corresponding author: Ahmed H. M. Elwahy E-mail: aelwahy@hotmail.com
Corresponding author: Maram T. H. Abou Kana E-mail: mabou202@niles.edu.eg
2

spectral properties because of intramolecular charge transfer (ICT). This phenomenon led to
substantial manuscripts being of potential applications in photoelectronic and nonlinear optical
devices [5], chemical sensing [6], and investigating photochemical and photobiological processes
[7]. The photophysical properties of these compounds exhibited very strong solvent polarity
dependent [8].
Moreover, 1,2,4-triazine is an important core system and many of their derivatives have
gained considerable attention because they are found in numerous natural and synthetic
biologically as well as pharmacologically active compounds [9]. 1,2,4-Triazine derivatives have
been reported to possess a broad spectrum of biological activities including anti-inflammatory
[10] antimicrobial [11, 12], anti-HIV [13], anticancer [14-16], antihaemostatic activity [17],
antiviral [18], antimalarial [19], anticonvulsant [16], neuroprotective[20], antifungal [21],
antiproliferation [22, 23]. Some 1,2,4-triazine derivatives have also used as kinase inhibitors [24,
25], and α-glucosidase inhibitors [26, 27]. Some drugs containing triazine moiety are outlined in
Fig. 1 [28]. The chemistry and biological applications of this class of compounds have been
recently reviewed [29].
Fig. 1 Some drugs containing triazine moiety.
In connection with these findings, we report herein the synthesis of some novel bis(1,2,4-
triazines) via alkylation of 5,6-diphenyl-1,2,4-triazine-3(4H)-thione with the appropriate
bis(halo) compounds and to validate the chemical structural model that best describes their
electronic properties as well as their chemical reactivity parameters. Density functional theory
(DFT) and time dependent density functional theory (TDDFT) were selected to calculate the
3

ground and exited states electronic properties, as well as their electronic spectra which were then
compared with the corresponding experimental results.
1. Experimental:
1.1 General
|Infrared spectra were investigated in potassium bromide disks on a PyeUnicam SP3-300 and
1
Shimadzu FTIR 8101 PC infrared spectrophotometer. The H NMR spectra were determined on
a Varian Mercury VX 300 NMR spectrometer using TMS as an internal standard and DMSO-d6
as a solvent. Mass spectra were recorded on a GCMS-QP1000 EX spectrometer at 70 eV.
Elemental analyses were investigated at the Microanalytical Center of Cairo University, Giza,
Egypt. All required chemicals were purchased from Sigma Aldrich and used without further
purification. The absorption and excited-emission spectra of the novel series of bis(5,6-diphenyl-
1,2,4-triazines) were monitored experimentally in ethanol solvent using spectral ultraviolet
radiation (Shimadzu UV-2450) and a spectrometer (Shimadzu, RF-5301PC).
1.2 Synthesis of compounds 5, 7 and 9:
To a solution of 3 (10 mmol) and KOH (10 mmol) in absolute ethanol (10 ml) the
appropriate dibromo compounds 4, 6 and 8 (5 mmol) was added. The reaction mixture was
heated at reflux for 1 h, allowed to cool to room temperature. The formed crude solid was
filtered off, dried and recrystallized from dimethylformamide (DMF) to give yellow crystals of
5, 7 and 9, respectively.
1,4-Bis((5,6-diphenyl-1,2,4-triazin-3-yl)thio)butane (5)
With the use of the general procedure, compound 3 and 1,4-Dibromobutane 4 gave crude 5
1
(75%); IR: υ max 3049, 2924 (CH), 1597, 1490 (C=C) cm-1, H NMR (DMSO) δ 2.0 (br, 4H,
SCH2CH2), 3.88 (br, 4H, SCH2CH2), 7.32-7.49 (m, 8H, ArHs) ppm. MS: m/z 584 (M+); Anal.
for C38H28N6S2, Calcd. C, 69.83; H, 4.83; N, 14.37; S, 10.97. Found: C, 70.10; H, 4.60; N, 14.50.
1,4-Bis(((5,6-diphenyl-1,2,4-triazin-3-yl)thio)methyl)benzene (7)
With the use of the general procedure, compound 3 and 1,4-bis(bromomethyl)benzene 6 gave
crude 7, which crystallized from DMF as colorless crystals (84%); IR: υ max 3046, 2930 (CH),
4

1536, 1487 (C=C) cm-1, 1H NMR (DMSO) δ 4.59 (s, 4H, SCH2), 7.34-7.48 (m, 24H, ArHs) ppm.
MS: m/z 632 (M+); Anal. for C38H28N6S2, Calcd. C, 72.13; H, 4.46; N, 13.28. Found: C, 72.40;
H, 4.20; N, 13.10.
2,6-Bis(((5,6-diphenyl-1,2,4-triazin-3-yl)thio)methyl)pyridine (9)
With the use of the general procedure, compound 3 and 2,6 bis(bromomethyl)pyridine 8 gave
crude 9, which crystallized from DMF as colorless crystals (85%); IR: υ max 3051, 2938 (CH),
1
1581, 1493 (C=C) cm-1, H NMR (DMSO) δ 4.72 (s, 4H, OCH2), 7.30-7.74 (m, 23 H, ArH,
Pyridine-H) ppm. MS: m/z 633 (M+); Anal. for C37H27N7S2, Calcd. C, 70.12; H, 4.29; N, 15.47.
Found: C, 70.30; H, 3.90, N, 15.20.
1.3 Computational details
The electronic ground and excited states structures of compounds 3, 7, 5 and 9 were
obtained using the density functional theory (DFT) and the time dependent density functional
theory (TDDFT). All calculations were generated with the Gaussian 09 program package [35].
The chemical structure optimizations were carried out at the DFT/6-31G(d) level of theory
without any constrains. According to three possible criteria for Pitch gradient drainage, the
correlation capabilities were corrected for Lee-Yang-Parr Gradient (B3LYP) [30] and all
calculations were generated utilizing the 6-31G (d) basis set.
The electronic absorption and emission spectra of the novel compounds, in gas and ethanol
solvent, were calculated using time dependent density functional theory (TDDFT) at
mPW1PW91/ 6-31G (d) level.
2. Results and discussions:
2.1. Synthesis
The starting compound 5,6-diphenyl-1,2,4-triazine-3(4H)-thione 3 was synthesized in good
yield by heating benzil 1 with thiosemicarbazide 2 in acetic acid at reflux using a previously
reported procedure (Scheme 1) [20].
5

Scheme 1: Synthesis of compound 3.
The synthetic utility of 3 as building block for novel bis(5,6-diphenyl-1,2,4-triazines) 5, 7 and 9
was investigated as outlined in Schemes 1 and 2. Thus, reaction of 3 with 1,4-dibromobutane 4
in ethanol containing KOH at refluxing temperature afforded 1,4-bis((5,6-diphenyl-1,2,4-triazin-
3-yl)thio)butane 5 in 75% yield (Scheme 2).
Scheme 2: Synthesis of compound 5.
Using a similar approach, the reaction of 3 with 2,6-bis(bromomethyl)benzene 6 in ethanol
containing KOH at refluxing temperature afforded 1,4-bis(((5,6-diphenyl-1,2,4-triazin-3-
yl)thio)methyl)benzene (7) in 84% yield. Similarly, the 2,6-bis(((5,6-diphenyl-1,2,4-triazin-3-
yl)thio)methyl)pyridine (9) was prepared in 85% yield by the reaction of 3 with 2,6-
bis(bromomethyl)pyridine 8 in ethanol containing KOH at refluxing temperature (Scheme 3).
Scheme 3: Synthesis of compounds 7 and 9.
6

All the isolated compounds were characterized by elemental analyses, as well as their spectral
data which agree with the proposed structures. The structures of bis(5,6-diphenyl-1,2,4-triazines)
1
5, 7 and 9 were confirmed by IR and, H-NMR and mass spectra. Thus, the absence of an
absorption band corresponding to NH or C=S stretching frequencies of the parent 5,6-diphenyl-
1,2,4-triazine-3(4H)-thione 3 in the IR spectrum of 5, 7 and 9 clearly confirmed the formation of
1
bis(5,6-diphenyl-1,2,4-triazine) derivatives. Moreover, the H NMR spectra of compound 5
showed two broad signals at δ 2.0 and δ 3.88 each integrated for four protons attributed to the
1
methylene protons of the butyl spacer. The H NMR spectra of compounds 7 and 9 showed two
singlet signals at δ 4.59 and δ 4.72, respectively, each integrated for four protons characteristic
for the OCH2 protons. All other protons were seen at the expected chemical shifts and integral
values. Mass spectra of compounds 5, 7 and 9 showed intense molecular ion peaks at m/z 584,
632 and 633, respectively, in agreement with their respective molecular formulae.
2.2. DFT calculation
The electronic ground state structures of compounds 3, 7, 5 and 9 were obtained using the
DFT method. The chemical structure optimizations were carried out at the B3LYP /6-31G(d)
level of theory and the results are given in Fig. 2. Compound 3 is not planar where one of the two
phenyl rings rotates out of the trizine plane by 33.44o to avoid the steric hindrance.
The C-C bonds connecting the two phenyl rings and the traizine ring have the lengths 1.483
and 1.484 Å, single bond character. This is confirmed on both of HOMO and LUMO MOs, Fig
3. The HOMO MO is localized one (over the traizine and phenyl rings) while the LUMO is
delocalized over the target molecule. In case of compounds 5, 7 and 9, the nonplanar structure
was also found; the phenyl and pyridyl groups rotate with different angles relative to traizine
rings (Fig. 3 and Table 1). Consequently, the л-interaction between the different sub-systems in
each molecule is small, which will be reflected on their UV-spectra. Both of HOMO and LUOM
MOs are localized on certain sub-systems of the target molecule, as shown in Fig. 3. The
geometrical parameters of the 3, 5, 7 and 9 compounds in gas state are listed in Table 1. The
labeling scheme is shown in Fig. 2. Table 1 showed the difference between the bond lengths or
angles of the triazine moiety in compound 3 and the other studied molecules.
7

Fig. 2 Optimized geom. of compounds 3, 5, 7 and 9.
o
Table 1 Selected optimized geometrical parameters (bond length in Å and dihedral angle in )
computed for 3, 5, 7 and 9 in gas phase using B3LYP/6-31G(d). For labeling, refer to Fig. 2.
parameters
1.336
parameters
1.332
parameters
1.339
parameters
1.356
3
5
7
9
C2-N4
N4-C3
C3-N5
N5-N6
C1-C2
C2-C13
C1-C23
C3-S7
C16-N22
N22-C15
C15-N21
N21-N23
C17-C16
C16-C64
C17-C49
C15-S14
C23-N28
N28-C22
C22-N29
N29-N30
C24-C23
C23-C53
C24-C66
C22-S18
C22-N29
N29-C21
C21-N27
N27-N28
C23-C22
C22-C52
C23-C63
C21-S17
1.332
1.337
1.332
1.339
1.342
1.340
1.347
1.358
1.325
1.328
1.318
1.344
1.426
1.429
1.421
1.424
1.483
1.484
1.484
1.480
1.484
1.485
1.484
1.480
1.772
1.767
1.770
1.816
C12-C13-
C2-N4
C65-C64-
C16-N22
C54-C53-
C23-N28
C53-C52-
N22-N29
33.44
15.04
34.04
14.36
148.55
15.13
35.49
14.31
C13-C2-
C1-C23
C64-C16-
C17-C49
C53-C23-
C24-C66-
C52-C22-
C23-C63
C15-S14-
C12-C7
C18-S13-
C22-S18-
C14-C6
C19-S17-
C21-S17-
C13-C5
C18-S16-
177.56
176.14
176.67
176.68
179.48
179.49
8

C1-C5
C11-C3
C10-C1
The graphical presentation of the HOMO-1, HOMO, LUMO, LUMO+1 orbitals, energy
gap between HOMO and LUMO (Eg1) and between HOMO-1 and LUMO+1 (Eg2) for 3, 7, 5 and
9 compounds in gas at B3LYB/6-31G(d) level of theory is shown in Fig. 3. It is worth noting that
these MOs are mainly localized over certain part of the molecule (traizine and phenyl groups)
and not extended over the entire molecule. In addition, the calculated energy values of HOMO,
HOMO-1, HOMO-2, LUMO, LUMO+1 and LUMO+2, energy gap between HOMO and LUMO
(Eg1) and energy gap between HOMO-1, LUMO+1 (Eg2) and energy gap between HOMO-2 and
LUMO+2(Eg3) of the studied compounds are listed in Table 2. The calculated Eg1 of the studied
novel compounds increases in the following order 5 < 9 < 7 < 3 which means that compound 5
has the highest reactivity and compound 3 has lowest reactivity.
Fig. 3 Graphical presentation of the highest occupied (HOMO), lowest unoccupied molecular
(LUMO) orbitals, HOMO-1, LUMO+1 energy gap between HOMO and LUMO (Eg1) and
energy gap between HOMO-1 and LUMO+1 (Eg2) for 3, 7, 5 and 9 compounds in gas at
B3LYB/6-31G(d) level of theory.
9

Table 2 Energy values of HOMO, HOMO-1, HOMO-2, LUMO, LUMO+1 and LUMO+2,
energy gap between HOMO and LUMO (Eg1) and energy gap between HOMO-1, LUMO+1
(Eg2) and energy gap between HOMO-2 and LUMO+2(Eg3) for 3, 7, 5 and 9 compounds in gas at
B3LYB/6-31G(d) level of theory.
EHOMO ELUMO Eg1
(eV) (eV) (eV) 1 (eV)
-6.281 -2.113 4.168 -6.469 -1.564
-5.776 -2.247 3.528 -6.106 -1.992
-6.027 -2.062 3.965 -6.186 -2.160
-6.183 -2.262 3.921 -6.045 -2.012
EHOMO- ELUMO+1 Eg2
(eV)
EHOMO- ELUMO+2 Eg3
Compounds
(eV) 2 (eV)
(eV)
4.905 -6.920 -0.430
4.114 -6.286 -1.478
4.026 -6.249 -1.626
4.033 -6.300 -1.467
(eV)
6.490
4.808
4.623
4.833
3
5
7
9
According to Kobmann theorem the I.P, the ability to lose electron, equal to - EHOMO
therefore, the order of I.P values of this series is 5<7<9<3. On the other hand, ELUMO is related to
the electron affinity (E.A), of the compound using the relation E.A = ELUMO. Table 3 shows that
order of E.A values of this series is 7 <3 <5< 9; i.e compound 9 has the highest tendency to
accept electrons. The energy gap between frontier molecular orbitals (HOMO and LUMO) is
used as a powerful indicator of chemical reactivity, kinetic stability and biological activity of
molecular systems. The energy gap (Eg) is given by the difference [ELUMO - EHOMO]. The
calculated Eg of the studied 1,2,4-triazine compounds increases in the following order 5
< 9 < 7 < 3 i.e. 5 has higher reactivity. The lowering of Eg value of 5, 9 and 7 compared to that
of 3 indicates less stability, a significant effect of intramolecular charge transfer (ICT),
consequently the absorption spectra is red shifted. Another important calculated parameters,
using ELUMO and EHOMO values, are the chemical potential (µ), electronegativity (ꭕ) and the
chemical hardness (η). These parameter are calculated as follows
[31],
ꭕ
[31]
[31] and chemical softness (s=1/ . Generally,
when the molecules having a high dipole moment, it has a high asymmetry in the distribution of
electronic charge hence, and can be more reactive sensitive to change its electronic molecular
structure and its electronic characteristics under an external electric field. As shown in Table 3,
the dipole moment (ρ) of the compounds 7 and 9 are higher than that of 3 and 5. Consequently,
these compounds are more reactive. The lower chemical potential value, μ, of compared 9
compared to the other three 1,2,4-triazines (3, 7 and 5) (see Table 3), indicates the tendency of
the electrons to escape from compound 9 is lower than that of the others (3, 7 and 5) [31]. Hence,
the molecule 9 is considered harder, most stable and least reactive compared to the others [32].
10

Also, compound 9 has a high ꭕ value than other compounds (3, 7 and 9) (Table 3), thus the
molecule 9 is the one that is able to attract the electrons from other compounds. In another side,
compound 3 has a high η value in comparison with other three 1,2,4-triazine molecules (7, 5 and
9), this indicates that compound 3 is very difficult to liberate the electrons, while the other 1,2,4-
triazine molecules (7, 5 and 9) are good candidates to give electrons to another acceptor
molecule (see Table 3).
The excited state life times (τ) of the molecule sensitizers were calculated via utilizing the
following formula: (τ = 1.499/f E2) [33], where E is the excitation energy of the different
electronic states (cm-1) and f is the oscillator strength of the electronic state. The calculated τ
values for the four 1,2,4-triazine compounds (3, 7, 5 and 9) are listed in Table 3. Consequently,
long radiative lifetimes facilitate the electron transfer via the photoexcited electron, from LUMO
of electron-donor to LUMO of electron-acceptor, hence lead to high light-emitting efficiency.
Table 3 Calculated EHOMO, ELUMO, energy gap (Eg), dipole moment (ρ) and other quantum
chemical parameters as electronegativity (χ), chemical potential (μ), chemical hardness (η) and
excited state life time (τ) values of the studied compounds obtained by B3LYP/6-31G(d) level.
ρ
τ
EHOMO
(eV)
ELUMO
(eV)
Eg
μ
η
χ
Compounds
f
(eV)
(eV)
(eV) (eV)
(D)
(ns)
0.2400 -6.281
-2.113
4.168
-4.197 2.084 4.197 3.470 5.526
3
0.0057 -6.027
0.0028 -5.776
0.0057 -6.183
-2.062
-2.247
-2.262
3.965
3.528
3.921
-4.044 1.982 4.044 9.940 0.025
-4.011 1.764 4.011 4.780 0.066
-4.222 1.960 4.222 8.880 0.026
7
5
9
2.3. Electronic absorption and emission spectra
The electronic absorption spectra of the studied compounds were measured experimentally
using ethanol as a solvent; the results are given in Fig 4A. The electronic absorption spectrum of
3 in ethanol consists of mainly one peak appearing at 400 nm in the range between 300-600 nm.
It is assigned as π-π* transition as indicated by its extinction coefficient, 5280 Lmol-1cm-1. Also,
Fig. 4A shows that the electronic absorption spectra of 7, 5 and 9 measured in ethanol solvent
11

have the same features. The corresponding λmax and extinction coefficients are (350 nm and
10360 Lmol-1cm-1), (350 nm and 9890 Lmol-1cm-1) and (350 nm, 11190 Lmol-1cm-1),
respectively, i.e these bands are blue shifted relative to 3 transition and also assigned as π-π*
transitions. This means that less π-conjugation exists over the substituted molecules. On the other
hand, the electronic emission spectra of the studied systems were also recorded in ethanol and
presented in Fig. 4B. The experimental maximum emission wavelength of the 3 molecule is 446
nm while the experimental maximum emission wavelength of 5, 7 and 9 is 400 nm as shown in
Fig. 4B.
Fig.4 Experimental absorption (A) and emission (B) spectra of compounds 3, 5, 7 and 9 in
ethanol (1×10-4M).
To understand the above experimental results, the electronic absorption and emission
spectra of the studied systems were calculated in gas and ethanol phases using TDDFT method.
To find out the best functional and basis set for calculating electronic absorption spectra of the
studied systems, many functionals, B3LYP [30], CAM-B3LYP [34], M06-2X [35], ωB97X-D
[36], mPW1PW91 [37, 38], were tested for 7 using 6-31G(d) basis set. The results shown in Fig.
5 indicate that mPW1PW91 gives the nearest results to the experimental data of compound 7,
Table 4. The funstionals CAM-B3LYP, M06-2X, ωB97X-D, underestimates the experimental
results while B3LYP overestimates it. The effect of using different basis sets indicates that
calculated electronic absorption spectrum of molecule 7 is accurate without diffuse functions.
Therefore, involvement of diffuse functions is not essential in obtaining acceptable results.
12

Hence, the mPW1PW91 functional with the 6-31(d) basis set is used to calculate the optical
properties of the all studied molecules.
Fig. 5 Calculated absorption spectra of a model compounds 7 obtained with the use of different
functionals, B3LYP, CAMB3LYP, M06-2X, ωB97X-D and mPW1PW91 and experimental
absorption spectrum of the 7. Vertical lines in each panel correspond to calculated absorptivity.
The 6-31G(d) basis set was applied.
Table 4: Calculated maximum absorption wavelength (Calc. λabs. (nm)) of a model compound 7
obtained with the use of different functionals, B3LYP, CAMB3LYP, M06-2X, ωB97X-D and
mPW1PW91 and experimental absorption wavelength (Exp. λabs. (nm)). The 6-31G(d) basis set
was applied.
Molecular compounds Dependence of the DFT functionals Calc. λabs. (nm) Exp. λabs. (nm)
B3LYP
CAMB3LYP
M06-2X
mPW1PW91
ωB97X-D
363
306
303
349
305
7
350
The calculated electronic absorption and emission spectra of the 3, 7, 5 and 9 molecules, in
gas and ethanol, are generated via utilizing mPW1PW91/ 6-31G (d) level as shown in (Figs. 6)
and the corresponding parameters are given in Table 5. The calculated electronic absorption
spectrum of 3 in gas phase appears as three transitions at 390, 332 and 382 nm while in ethanol
at 379, 337 and 291 nm, Table 5, due to the variation of the stabilization of ground and excited
13

states in polar solvent. The first one corresponding to the experimental peak at 400 nm (f =
0.005) predominately arises from transition of MO68 -> 70. On the other hand, second band (f =
0.110) arises from transition of MO69 -> 70 and the third one f = 0.1210. On substitution of 3,
the calculated electronic absorption spectra of the 7, 5 and 9 molecules in both phases recorded
via utilizing the same level are given Fig 6 and Table 5. The three calculated transitions for 5
appear at 416nm (f = 0.007), 348 nm (f = 0.048) and 335 nm (f = 0.001) in gas. The second one
corresponds to the experimental one (350 nm) and arises from the transition MO153 ->155 and it
does not affect by solvent. The same findings were also found for both 7 and 9 but with red shift
for the experimentally calculated one.
The calculated maximum emission wavelength of molecule 3 is 365 nm, while the
experimental maximum emission wavelength is 446 nm in ethanol as shown in Fig. 6A. The
calculated maximum emission wavelength of 7, 9 and 5 are 415, 410 and 430 nm, respectively,
in ethanol whereas the experimental wavelengths are 400 nm as shown in Fig. 6B, 6C and 6D.
14

Fig. 6 Calculated electronic absorption (Calc. Abs.) and emission spectra (Calc. Ems.) of
compounds 3 (A), 5 (B), 7 (C) and 9 (D) obtained and the experimental absorption (Exp. Abs.)
and emission spectra (Exp. Ems.) of the 3 (A), 5 (B), 7 (C) and 9 (D). Vertical lines in each panel
correspond to calculated absorptivity. The mPW1PW91 functional was applied with 6-31G
(d) basis set.
15

Table 5 Calculated electronic absorption parameters for compounds 3, 5, 7 and 9. The
mPW1PW91 functional was applied with 6-31G (d) basis set.
Compound
Solvent
Excited state Electronic
transition
ΔE (eV)
f
Coefficient
Exp.
λabs.
(nm)
Gas
1
2
5
68 -> 70
68 -> 71
68 -> 71
69 -> 70
66 -> 70
67 -> 70
69 -> 71
64 -> 70
68 -> 70
68 -> 71
69 -> 70
66 -> 70
67 -> 70
69 -> 71
151 ->155
151 ->157
151 ->155
151 ->157
153 ->155
150 ->156
150 ->164
152 ->154
152 ->156
151 ->154
151 ->155
153 ->154
153 ->155
151 ->156
162 ->166
163 ->167
162 ->169
163 ->168
164 ->167
165 ->166
162 ->169
163 ->168
164 ->167
165 ->166
161 ->167
162 ->166
163 ->167
164 ->167
165 ->166
162 ->169
163 ->168
162 ->167
3.1808 (390 nm) 0.005
3.7305 (332 nm) 0.110
0.936
0.036
0.048
0.918
400
350
350
3
4.3883(282 nm) 0.1210 0.190
0.540
0.220
0.0002
0.9230
0.0233
Ethanol
1
3.272(379 nm)
0.005
2
5
3.673(337 nm)
4.265(291 nm)
0.1259 0.959
0.1925 0.231
0.392
0.343
Gas
1
3
2.976(416 nm)
3.563(348 nm)
0.0063 0.930
0.053
0.0476 0.027
0.041
5
0.891
6
3.699(335 nm)
0.0018 0.806
0.021
0.061
0.075
Ethanol
Gas
1
3
3.124(397 nm)
3.564(348 nm)
0.007
0.088
0.079
0.877
0.068
0.884
0.078
0.870
5
1
3.833(323 nm)
2.973(417 nm)
0.0025 0.462
0.460
7
3
5
1
3.557(348 nm)
3.638(341 nm)
3.123 (397 nm)
0.0187 0.021
0.021
0.422
0.468
0.0014 0.408
0.421
0.027
0.030
Ethanol
0.002
0.022
0.474
0.449
0.461
0.499
0.428
0.419
0.460
3
5
1
3.564 (348 nm)
3.828(324 nm)
2.968(418 nm)
0.049
0.001
0.001
Gas
350
9
16

163 ->166
164 ->167
165 ->166
162 ->168
162 ->169
163 ->168
163 ->169
162 ->167
163 ->166
164 ->167
165 ->166
162 ->168
162 ->169
163 ->168
163 ->169
0.465
0.0024 0.447
0.484
0.0004 0.331
0.126
3
5
3.475(357 nm)
3.684(336 nm)
0.138
0.276
Ethanol
1
3
5
3.105(399 nm)
3.480(356 nm)
3.865(320 nm)
0.001
0.011
0.001
0.466
0.460
0.468
0.495
0.384
0.041
0.052
0.361
Conclusion: with the appropriate bis(bromo) compounds in ethanolic KOH.
We synthesized a novel series of bis(5,6-diphenyl-1,2,4-triazines) by alkylation of 5,6-diphenyl-
1,2,4-triazine-3(4H)-thione with the appropriate bis(bromo) compound in ethanolic KOH. The
chemical structures of these compounds were confirmed using spectroscopic data as well as
elemental analyses. The mPW1PW91 functional with the 6-31G (d) basis set is used to calculate
the ground state and optical properties of the novel triazine molecules 3, 5, 7 and 9. The
optimized chemical structures of the studied compounds were found to be not planar where one
of the two phenyl rings rotates out of the trizine plane to avoid the steric hindrance. The л-
interaction between the different sub-systems in each molecule is small, which reflected on their
UV-spectra. Utilizing HOMO and LUMO energy values for triazine molecules, the IP, EA, the
energy gap (Eg), chemical potential (µ), electronegativity (χ), chemical hardness (η), dipole
moment (ρ) and excited state life time (τ) parameters were successfully investigated and
compared. The measured electronic absorption spectrum of 3 in ethanol consists of one π-π*
transition at 400 nm while the corresponding λmax of 7, 5 and 9 is blue shifted relative to that of 3
due to less π-conjugation over the substituted molecules (350 nm). This means that less π-
conjugation exists over the substituted molecule. The calculated electronic absorption spectrum
of 3 in gas phase appears as three transitions at 390, 332 and 382 nm while in ethanol at 379, 337
and 291 nm, due to the variation of the stabilization of ground and excited states in polar solvent.
The maximum emission wavelength of 3 is 446 nm while that of 5, 7 and 9 is 400 nm.
17

Conflict of Interest
The authors declare that they have no conflict of interest.
References
[1] A.C. Grimsdale, K. Leok Chan, R.E. Martin, P.G. Jokisz, A.B. Holmes, Synthesis of light-emitting
conjugated polymers for applications in electroluminescent devices, Chem. rev. 109 (2009) 897-1091.
*2+ D. Braga, G. Horowitz, High‐performance organic field‐effect transistors, Adv. mater. 21 (2009) 1473-
1486.
[3] R.J. Radford, W. Chyan, S.J. Lippard, Peptide-based targeting of fluorescent zinc sensors to the
plasma membrane of live cells, Chem. Sci. 4 (2013) 3080-3084.
*4+ A. Facchetti, π-Conjugated polymers for organic electronics and photovoltaic cell applications, Chem.
Mater. 23 (2011) 733-758.
[5] A.C. Arias, J.D. MacKenzie, I. McCulloch, J. Rivnay, A. Salleo, Materials and applications for large area
electronics: solution-based approaches, Chem. rev. 110 (2010) 3-24.
[6] H. Singh, J. Sindhu, J.M. Khurana, Determination of dipole moment, solvatochromic studies and
application as turn off fluorescence chemosensor of new 3-(4-(dimethylamino) phenyl)-1-(5-methyl-1-
(naphthalen-1-yl)-1H-1, 2, 3-triazol-4-yl) prop-2-en-1-one, Sens. Actuators B: Chem. 192 (2014) 536-542.
[7] Z.R. Grabowski, K. Rotkiewicz, W. Rettig, Structural changes accompanying intramolecular electron
transfer: focus on twisted intramolecular charge-transfer states and structures, Chem. rev. 103 (2003)
3899-4032.
[8] A.M. Asiri, K.A. Alamry, M. Pannipara, A.G. Al-Sehemi, S.A. El-Daly, Spectroscopic investigation,
photophysical parameters and DFT calculations of 4, 4′-(1E, 1′ E)-2, 2′-(pyrazine-2, 5-diyl) bis (ethene-2,
1-diyl) bis (N, N-dimethylaniline)(PENDA) in different solvents, Spectrochim. Acta A: Mol. and Biomol.
Spectrosc. 149 (2015) 722-730.
[9] S. Cascioferro, B. Parrino, V. Spanò, A. Carbone, A. Montalbano, P. Barraja, P. Diana, G. Cirrincione,
An overview on the recent developments of 1, 2, 4-triazine derivatives as anticancer compounds, Eur. J.
Med. Chem. 142 (2017) 328-375.
[10] H. Irannejad, A. Kebriaieezadeh, A. Zarghi, F. Montazer-Sadegh, A. Shafiee, A. Assadieskandar, M.
Amini, Synthesis, docking simulation, biological evaluations and 3D-QSAR study of 5-Aryl-6-(4-
methylsulfonyl)-3-(metylthio)-1, 2, 4-triazine as selective cyclooxygenase-2 inhibitors, Bioorg. Med.
Chem. 22 (2014) 865-873.
[11] M.D. Wittman, J.M. Carboni, Z. Yang, F.Y. Lee, M. Antman, R. Attar, P. Balimane, C. Chang, C. Chen,
L. Discenza, Discovery of a 2, 4-disubstituted pyrrolo [1, 2-f][1, 2, 4] triazine inhibitor (BMS-754807) of
insulin-like growth factor receptor (IGF-1R) kinase in clinical development, J. Med. Chem. 52 (2009)
7360-7363.
[12] T.E.-S. Ali, Synthesis of some novel pyrazolo [3, 4-b] pyridine and pyrazolo [3, 4-d] pyrimidine
derivatives bearing 5, 6-diphenyl-1, 2, 4-triazine moiety as potential antimicrobial agents, Eur. J. Med.
Chem. 44 (2009) 4385-4392.
[13] E. La Kim, J.L. Li, J. Hong, C.-O. Lee, D.-K. Kim, W.D. Yoon, E. Kim, Y. Liu, J.H. Jung, Corrigendum to
“Cytotoxic cytochalasins from the endozoic fungus Phoma sp. of the giant jellyfish Nemopilema
nomurai”*Bioorg. Med. Chem. Lett. 22 (2012) 3126–3129], Bioorg. Med. Chem. Lett. 17 (2012) 5752.
*14+ T. Gucký, I. Fryšová, J. Slouka, M. Hajdúch, P. Džubák, Cyclocondensation reaction of heterocyclic
carbonyl compounds, Part XIII: Synthesis and cytotoxic activity of some 3, 7-diaryl-5-(3, 4, 5-
trimethoxyphenyl) pyrazolo [4, 3-e][1, 2, 4] triazines, Eur. J. Med. Chem. 44 (2009) 891-900.
[15] G. Wang, Z. Peng, J. Wang, X. Li, J. Li, Synthesis, in vitro evaluation and molecular docking studies of
novel triazine-triazole derivatives as potential α-glucosidase inhibitors, Eur. J. Med. Chem. 125 (2017)
423-429.
18

[16] P. Ahuja, N. Siddiqui, Anticonvulsant evaluation of clubbed indole-1, 2, 4-triazine derivatives: A
synthetic approach, Eur. J. Med. Chem. 80 (2014) 509-522.
[17] R.R. Kamble, B.S. Sudha, Synthesis, spectral characterization and antihaemostatic activity of 1, 2, 4-
triazoles incorporating 1, 2, 4-triazine rings, Journal of Chemical Sciences 118 (2006) 191-194.
[18] V. Rusinov, I. Egorov, O. Chupakhin, E. Belanov, N. Bormotov, O. Serova, Synthesis and antiviral
activity of 1, 2, 4-triazine derivatives, Pharm. Chem. J. 45 (2012) 655-659.
[19] K. Ban, S. Duffy, Y. Khakham, V.M. Avery, A. Hughes, O. Montagnat, K. Katneni, E. Ryan, J.B. Baell, 3-
Alkylthio-1, 2, 4-triazine dimers with potent antimalarial activity, Bioorg. Med. Chem. Lett. 20 (2010)
6024-6029.
[20] H. Irannejad, M. Amini, F. Khodagholi, N. Ansari, S.K. Tusi, M. Sharifzadeh, A. Shafiee, Synthesis and
in vitro evaluation of novel 1, 2, 4-triazine derivatives as neuroprotective agents, Bioorg. Med. Chem. 18
(2010) 4224-4230.
[21] J.N. Sangshetti, D.B. Shinde, One pot synthesis and SAR of some novel 3-substituted 5, 6-diphenyl-1,
2, 4-triazines as antifungal agents, Bioorg. Med. Chem. Lett. 20 (2010) 742-745.
*22+ K. Sztanke, J. Rzymowska, M. Niemczyk, I. Dybała, A.E. Kozioł, Novel derivatives of methyl and ethyl
2-(4-oxo-8-aryl-2H-3, 4, 6, 7-tetrahydroimidazo [2, 1-c][1, 2, 4] triazin-3-yl) acetates from biologically
active 1-aryl-2-hydrazinoimidazolines: Synthesis, crystal structure and antiproliferative activity, Eur. J.
Med. Chem. 41 (2006) 1373-1384.
[23] F. Krauth, H.-M. Dahse, H.-H. Rüttinger, P. Frohberg, Synthesis and characterization of novel 1, 2, 4-
triazine derivatives with antiproliferative activity, Bioorg. Med. Chem. 18 (2010) 1816-1821.
[24] G.R. Ott, G.J. Wells, T.V. Thieu, M.R. Quail, J.G. Lisko, E.F. Mesaros, D.E. Gingrich, A.K. Ghose, W.
Wan, L. Lu, 2, 7-Disubstituted-pyrrolo [2, 1-f][1, 2, 4] triazines: new variant of an old template and
application to the discovery of anaplastic lymphoma kinase (ALK) inhibitors with in vivo antitumor
activity, J. Med. chem. 54 (2011) 6328-6341.
[25] M. Khoshneviszadeh, M.H. Ghahremani, A. Foroumadi, R. Miri, O. Firuzi, A. Madadkar-Sobhani, N.
Edraki, M. Parsa, A. Shafiee, Design, synthesis and biological evaluation of novel anti-cytokine 1, 2, 4-
triazine derivatives, Bioorg. Med. Chem. 21 (2013) 6708-6717.
[26] H. Wang, Z. Zhao, J. Zhou, Y. Guo, G. Wang, H. Hao, X. Xu, Corrigendum to" A novel intestinal-
restricted FXR agonist"[Bioorg Med Chem Lett 27 (2017) 3386-3390], Bioorg. Med. Chem. Lett. 27 (2017)
5353.
[27] G. Wang, Z. Peng, Z. Gong, Y. Li, Synthesis, biological evaluation, and docking studies of novel 5, 6-
diaryl-1, 2, 4-triazine thiazole derivatives as a new class of α-glucosidase inhibitors, Bioorg. Chem. 78
(2018) 195-200.
[28] R. Kumar, T. Sirohi, H. Singh, R. Yadav, R. Roy, A. Chaudhary, S. Pandeya, 1, 2, 4-triazine analogs as
novel class of therapeutic agents, Mini-Rev. Med. Chem. 14 (2014) 168-207.
[29] W.S. Hamama, G.G. El-Bana, S. Shaaban, O. Habib, H.H. Zoorob, Advances in the domain of 4-
amino-3-mercapto-1, 2, 4-triazine-5-ones, RSC Adv. 6 (2016) 24010-24049.
*30+ A.D. Becke, Becke’s three parameter hybrid method using the LYP correlation functional, J. Chem.
Phys 98 (1993) 5648-5652.
[31] M. Bourass, A.T. Benjelloun, M. Benzakour, M. Mcharfi, M. Hamidi, S.M. Bouzzine, M. Bouachrine,
DFT and TD-DFT calculation of new thienopyrazine-based small molecules for organic solar cells, Chem.
Cent. J. 10 (2016) 67.
[32] S.A. El-Daly, K.A. Alamry, Spectroscopic Investigation and Photophysics of a D-π-A-π-D Type Styryl
Pyrazine Derivative, J. fluoresc. 26 (2016) 163-176.
[33] K. Chaitanya, X.-H. Ju, B.M. Heron, Theoretical study on the light harvesting efficiency of zinc
porphyrin sensitizers for DSSCs, RSC Adv. 4 (2014) 26621-26634.
[34] T. Yanai, D.P. Tew, N.C. Handy, A new hybrid exchange–correlation functional using the Coulomb-
attenuating method (CAM-B3LYP), Chem. Phys. Lett. 393 (2004) 51-57.
19

[35] Y. Zhao, D.G. Truhlar, The M06 suite of density functionals for main group thermochemistry,
thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new
functionals and systematic testing of four M06-class functionals and 12 other functionals, Theor. Chem.
Acc. 120 (2008) 215-241.
[36] J.-D. Chai, M. Head-Gordon, Long-range corrected hybrid density functionals with damped atom–
atom dispersion corrections, Phys. Chem. Chem. Phys. 10 (2008) 6615-6620.
[37] Y. Zhao, O. Tishchenko, D.G. Truhlar, How well can density functional methods describe hydrogen
bonds to π acceptors?, J. Phys. Chem. B 109 (2005) 19046-19051.
[38] K. Park, H.-J. Son, J.-I. Choe, mPW1PW91 study for conformational isomers of methylene bridge-
monosubstituted tetramethoxycalix [4] arenes, J. Ind. Eng. Chem. 20 (2014) 3276-3282.
20

CRediT author statement
Mahmoud A. S. Sakr,
Adel A. Mohamed,
Data curation, Methodology, Software
Software, Validation
Maram T. H. Abou Kana,
Ahmed H.M. Elwahy,
Samy A. El-Daly,
Visualization, Investigation
Conceptualization, Original draft preparation
Supervision
El-Zeiny M. Ebeid,
Reviewing and Editing
Declaration of interests
☒ 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.
☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests:
21

Graphical Abstract
22