Synthesis, FT-IR, NMR and DFT analysis of a new salophen based on diaminophenazine moiety

Article abstract of DOI:10.1016/j.molstruc.2014.01.012

As a rigid diamine, diaminophenazine was prepared by the condensation of 1,2-phenylene diamine and characterized by FT-IR and EI mass spectroscopy. Then, a new salophen was synthesized based on a phenazine moiety, by the condensation of salicylaldehyde and synthesized diamine. The prepared salophen was characterized by FT-IR and ¹H NMR spectroscopy. The geometry of the prepared salophen was examined by density functional theory (DFT) method at B3LYP/6-31G(d) level. Also, due to the structure of salophen, IR and NMR spectra of the more stable isomers were calculated by DFT method using camB3LYP/6-311+G(d) level and compared with the experimental results. Also, root mean square (RMS) errors observed between the experimental and calculated results for the NMR and IR were 0.75 ppm and 94.9 cm^-1.

Full text of DOI:10.1016/j.molstruc.2014.01.012

Journal of Molecular Structure 1062 (2014) 44–47
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, FT-IR, NMR and DFT analysis of a new salophen based
on diaminophenazine moiety
a
a
a
Amir Abdolmaleki a,b, , Hossein Tavakol , Mohammad Reza Molavian , Koorosh Firouz
⇑
a Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran
b Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan 84156-83111, Islamic Republic of Iran
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
ꢀ
ꢀ
A new salophen was synthesized
based on a phenazine moiety.
Geometry of prepared salophen was
examined by DFT method at B3LYP/
631G(d) level.
ꢀ
ꢀ
IR and NMR spectra were calculated
by DFT method using camB3LYP/
6311+G(d) level.
RMS errors for the NMR and IR are
0.75 ppm and 94.9 cm-1 respectively.
a r t i c l e i n f o
a b s t r a c t
Article history:
As a rigid diamine, diaminophenazine was prepared by the condensation of 1,2-phenylene diamine and
characterized by FT-IR and EI mass spectroscopy. Then, a new salophen was synthesized based on a phen-
azine moiety, by the condensation of salicylaldehyde and synthesized diamine. The prepared salophen
was characterized by FT-IR and 1H NMR spectroscopy. The geometry of the prepared salophen was exam-
ined by density functional theory (DFT) method at B3LYP/6-31G(d) level. Also, due to the structure of
salophen, IR and NMR spectra of the more stable isomers were calculated by DFT method using cam-
B3LYP/6-311+G(d) level and compared with the experimental results. Also, root mean square (RMS)
errors observed between the experimental and calculated results for the NMR and IR were 0.75 ppm
Received 7 December 2013
Received in revised form 7 January 2014
Accepted 7 January 2014
Available online 17 January 2014
Keywords:
Diaminophenazine
Salophen
and 94.9 cmꢁ1
.
DFT calculation
Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction
and tunable chelate ligands [3]. One interesting feature of
salen-type ligands is their facile variation of electronic and steric
properties [4]. For example, different substituents can be placed
on the phenol rings that change steric properties of the respective
salen [5]. These compounds and their transition metal complexes,
because of unique properties, are interesting and used in many
fields of chemical research such as biochemistry, luminescence
[6–8], sensor and catalysis [8–12]. These compounds act as an
initiator [13] or homogenous catalyst [14] for many reactions
including: polymerization [15,16], cyclization, ring opening, epox-
idation of alkenes [17], oxidation and other reactions [1,4,18–21].
For example, Coletti et al. reported the synthesis of some salophen
Schiff base ligands are known as ‘‘privileged ligands’’ due to
simple preparation by the condensation of primary amines and
an aldehyde. Salens, as one class of Schiff base ligands, were
prepared by the condensation of salicylaldehyde derivatives and
1,2-diamines [1,2]. Salen-type ligands are known as multipurpose
⇑
Corresponding author at: Department of Chemistry, Isfahan University of
Technology, Isfahan 84156-83111, Islamic Republic of Iran. Tel.: +98 311 3913249.
E-mail
addresses:
abdolmaleki@cc.iut.ac.ir,
abdolmalek@gmail.com
(A. Abdolmaleki).
0022-2860/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2014.01.012

A. Abdolmaleki et al. / Journal of Molecular Structure 1062 (2014) 44–47
45
Table 1
and salen oxo vanadium complexes that were used for sulfide oxi-
Stabilization energy of different salophen isomers.
dation; also, Tong et al. reported the synthesis of luminescent host
systems based on binuclear platinum(II) and zinc(II) complexes
based on salophen ligands [7].
Isomer
Method
Energy (kCal/mol)
Main isomer
Tautomer 1
Tautomer 2
camB3LYP/6-311+G(d)
camB3LYP/6-311+G(d)
camB3LYP/6-311+G(d)
0
In recent years, quantum mechanics computation has largely
been developed by the progress of computers. These methods are
used for predicting and confirming structural, thermodynamical,
electronical, and molecular properties such as equilibrium struc-
ture, UV–Vis spectra, charge distribution, FT-IR and NMR spectra.
Among various methods, density functional theory (DFT) is the
most popular method that is widely used for computational works
[22–26]. Salens can adopt several isomers contributing to tautom-
erism. Computational methods can be used for structural studies of
salens.
3.926
6.473
predominant product was selected and examined by computa-
tional IR and NMR.
2.3. Synthesis and characterization of salophen (2)
In this work, a new salophen containing phenazine moiety was
synthesized and characterized by various spectroscopic methods.
Also, DFT method was used to study different probable salophen
structures. Then, the main structure of salophen was confirmed
according to stabilization energy. Computational data were com-
pared to the experimental results, showing a good correlation.
Salophen (2) was synthesized by the condensation of 1 mmol of
2,3-diaminophenazine and 2 mmol of salicylaldehyde. The pre-
pared compound was investigated by FT-IR and 1H NMR spectros-
copy. Fig. 2 shows FT-IR spectrum of compound (2). This spectrum
showed a broad peak at 3433 cmꢁ1 which was assigned to OH
group and a peak at 1630 cmꢁ1 was related to C@N group; also
C@C peak appeared in 1505 cmꢁ1. Computational IR spectrum of
compound (2) was calculated by DFT method using camB3LYP/
6-311+G(d) level and compared with the experimental results in
Table 2. RMS errors between the calculated and experimental
results of IR spectrum were 94.9. So, the computational result con-
firmed the experimental result of FT-IR spectroscopy.
2. Results and discussion
2.1. Synthesis and characterization of 2,3-diaminophenazine (1)
2,3-Diaminophenazine (1) was synthesized by the condensation
of 2 mmol of 1,2-phenylene diamine in the presence of FeCl3 at
room temperature. Fig. 1 shows FT-IR spectra related to com-
pounds (1) and (2). FT-IR spectrum of compound (1) showed two
peaks at 3394 and 3188 cmꢁ1 and a peak at 1633 cmꢁ1 that were
assigned to NH2 and C@N group, respectively. Peaks at 1505 and
1552 cmꢁ1 were assigned to C@C vibrations; also CAN vibration
The synthesized salophen was characterized by 1H NMR spec-
troscopy. Fig. 5 shows 1H NMR spectrum of compound (2). Accord-
ing to this image, protons related to OH group showed 2 different
peaks at 12.90 and 13.56 ppm; also aromatic hydrogens appeared
in the range of 7.09–8.50 ppm. NMR spectrum of compound (2)
was also examined by DFT method at camB3LYP/6-311+G(d) level.
Table 3 shows computational results of salophen (2). Computa-
tional results showed a good correlation with the experimental re-
sult, indicating 2 peaks for OH groups. RMS errors for NMR
spectrum were 0.75 ppm.
appeared at 1240 cmꢁ1
.
Fig. 3 shows E.I. mass spectrum of 2,3-diaminophenazine (1).
According to this image, molecular ion peak appeared in m/
z = 210 due to the rigid structure of compound (1), molecular ion
peak known as the base peak. Also, elemental analysis was mea-
sured and the experimental result showed a good agreement with
the calculated one.
3. Experimental
3.1. Materials
2.2. Geometry and molecular properties
1,2-Phenylene diamine, salicylaldehyde, FeCl3, methanol and
dimethyl sulfoxide (DMSO) were purchased from Merck and
Sigma–Aldrich chemicals Company. DMSO, as the solvent, was
dried over barium oxide and then distillated. Also 1,2-phenylene
diamine was purified by sublimation.
Different isomers related to salophen are depicted in Fig. 4.
Table 1 shows stabilization energy of different salophen isomers.
According to the calculated energy, the main isomer was more
stable than tautomers 1 and 2. So, the main isomer as the
Fig. 1. FT-IR spectra related to; (a) compound (1) and (b) compound (2).
Fig. 2. Calculated IR spectrum of salophen (2).

46
A. Abdolmaleki et al. / Journal of Molecular Structure 1062 (2014) 44–47
Table 3
Computational results related to 1H NMR spectrum of salophen (2).
H atom
camB3LYP/6-311+g(d) (ppm)
Experimental (ppm)
H1
H1
H2
H2
H3
H3
H4
H4
H5
H5
H6
H6
H7
H7
H8
H8
H9
H9
11.41
10.46
9.15
9.00
8.42
8.33
8.10
8.06
8.06
7.99
7.85
7.73
7.67
7.64
7.07
7.03
7.03
6.98
13.46
12.80
8.60
8.60
8.31
8.31
8.24
8.24
8.19
8.19
7.88
7.88
7.52
7.52
7.13
7.13
7.10
7.10
Fig. 3. Mass spectrum of 2,3-diaminophenazine (1).
designated as singlet (s), doublet (d), triplet (t) and multiplet
(m). UV–Vis absorption spectra were obtained in DMSO (ca.
ꢂ10ꢁ5 mol/L) on a JASCO-570, UV–Vis spectrometer. EI mass spec-
trum was measured by Micromass LCT time-of-flight (TOF) mass
spectrometer in dithranol matrix and elemental analysis was also
performed by Malek-Ashtar University of Technology, Tehran, Iran.
Fig. 4. Different salophen isomers.
Table 2
3.3. Computational study
Calculated and experimental FT-IR spectra.
Functional group
camB3LYP/6-311+G(d) (cmꢁ1
)
Experimental (cmꢁ1
)
DFT calculations with Becke’s three-parameter hybrid exchange
functional (B3) and the correlation functional of Lee, Yang, and Parr
(LYP) were performed on a personal computer using Gaussian 09.
Geometry optimization of E,E isomer and the related tautomers,
without any symmetry restriction, was performed by DFT method
using B3LYP/6-31G(g) level. Then, in order to access energy and the
calculated IR spectra, frequency calculation was performed at cam-
B3LYP/6-311+G(d) level of DFT method. Also, the calculated NMR
spectra were achieved by NMR calculation at the same level of fre-
quency computations. RMS errors were calculated for IR and NMR
spectra using the following expression [27].
OH
3217
1623
1501
1546
1246
1005
3433
1630
1505
1552
1257
956
C@N
C@C
C@C
CAN
CAO
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
X
nðmci alcu
ꢁ
mei xp
Þ
ð1Þ
1
2
RMS ¼
i
n ꢁ 1
3.4. 2,3-Diaminophenazine synthesis (1)
2,3-Diaminophenazine was prepared according to the proce-
dure reported in the literature [28]. 6 mL of 0.08 mol/L aq FeCl3
solution was added into 30 mL of a 0.02 mol/L aqueous 1,2-pheny-
lene diamine solution with fast stirring at ambient temperature. A
quick color change from purple-black to reddish-brown was
observed upon the addition of FeCl3. After 5 h, white precipitate
was formed. The solid was washed many times with deionized
water, and then separated by centrifugation and sublimated to
achieve compound 1 as a white crystal. Yield = 98%; mp > 300 °C.
Fig. 5. 1H NMR spectrum of salophen (2).
FT-IR (KBr, cmꢁ1
) m: 3394 (s), 3313 (s), 3188 (w), 1692 (m), 1633
(m), 1531 (s), 1478 (s), 1383 (m), 1371 (m), 1240 (m), 1149 (m),
891 (w), 834 (m), 772 (m), 750 (m). EI/MS m/z (C12H10N4): M+,
210. Anal. Calc. for C12H10N4 (%): C 68.56, H 4.79, N 26.65; found:
C 68.42, H 4.71, N 26.59.
3.2. Techniques
FT-IR spectra were recorded using a Jasco-680 FT-IR spectro-
photometer (Japan) with KBr pellet. Vibration bands were reported
as wavenumber (cmꢁ1). The band intensities were classified as
weak (w), medium (m), strong (s), broad (br) and shoulder (sh).
1H NMR (500 MHz) spectra were obtained in deuterated dimethyl-
sulfoxide (DMSO-d6) on a Bruker Avance 500 MHz instrument
(Bruker, Rheinstetten, Germany). Chemical shifts are given in the
d scale and in parts per million (ppm). Proton resonances are
3.5. Salophen synthesis (2)
In a 25 mL round-bottom flask, 0.21 g (1 mmol) of 2,3-diamino-
phenazine (1) and 0.244 g (2 mmol) of salicylaldehyde were added
to 10 mL absolute methanol and refluxed with stirring for 24 h.

A. Abdolmaleki et al. / Journal of Molecular Structure 1062 (2014) 44–47
47
Scheme 1. Synthesis of salophen.
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anol to give a light brown precipitate of salophen (2). Purity of salo-
phen (2) was assigned by TLC. Yeild = 77%; FT-IR KBr (cmꢁ1
) m: 3433
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(br), 3301 (m), 3043 (w), 1630 (m), 1530 (w), 1487 (w), 1429 (w),
1384 (m), 1257 (w), 1010 (s), 750 (w), 555 (m), 466 (m); 1H NMR
(500 MHz, DMSO-d6): d = 13.56 (br, 1H, OH), 12.90 (br, 1H, OH),
8.50 (s, 2H, CH@N), 8.31 (s, 2H, Aromatic H), 8.24 (s, 2H, Aromatic
H) 8.17 (s, 2H, Aromatic H), 7.88 (s, 2H, Aromatic H), 7.52 (t, 2H,
Aromatic H), 7.13 (m, 2H, Aromatic H) ppm, 7.10 (m, 2H, Aromatic
H) ppm; UV–Vis (DMSO): k = 273, 406, 521 nm (see Scheme 1).
4. Conclusion
Here, for the first time, a rigid diamine was synthesized and
characterized by FT-IR and E.I. mass spectroscopy. Then a new
salophen was prepared by the condensation of the prepared dia-
mine and salicylaldehyde. The synthesized salophen was charac-
terized by FT-IR and 1H NMR spectroscopy. Also DFT calculations
were performed for geometry optimization and structural analysis
of the prepared salophen. Computational studies confirmed and
showed a good correlation with the experimental result.
Acknowledgements
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We gratefully acknowledge the partial financial support from the
Research Affairs Division Isfahan University of Technology (IUT),
Isfahan. Further partial financial support of Iran Nanotechnology
Initiative Council (INIC), National Elite Foundation (NEF) and
Center of Excellency in Sensors and Green Chemistry (IUT) is also
gratefully acknowledged.
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