Synthesis, biological activity, DNA binding and anion sensors, molecular structure and quantum chemical studies of a novel bidentate Schiff base derived from 3,5-bis(triflouromethyl)aniline and salicylaldehyde

Article abstract of DOI:10.1016/j.molstruc.2015.03.047

Synthesis, biological activity, spectroscopic and crystallographic characterization and density functional theory (DFT) studies of the Schiff base 3,5-bis(triflouromethyl)aniline and salicylaldehyde are reported. It crystallizes as a monoclinic space group P2₁/c with a = 7.7814(3) ?, b = 26.8674(9) ?, c = 7.4520(2) ?, V = 1379.98(8), Z = 4, D_c = 1.6038 g cm^-3, and μ = 0.156 mm^-1. The molecular structure obtained from X-ray single-crystal analysis of the investigated compound in the ground state was compared using Hartree-Fock (HF) and density functional theory (DFT) with the functionals B3LYP and B1B95 using the 6-311++G(d,p) basis set. The antimicrobial activities of the compound were investigated for its minimum inhibitory concentration (MIC). The interaction of the Schiff base with calf thymus DNA was investigated using UV-visible spectra. The colorimetric response of the Schiff base receptors in DMSO was investigated before and after the addition of an equivalent amount of each anion to evaluate the anion recognition properties.

Full text of DOI:10.1016/j.molstruc.2015.03.047

Accepted Manuscript
Synthesis, biological activity, DNA binding and anion sensors, molecular struc-
ture and quantum chemical studies of a novel bidentate Schiff base derived from
3
,5-bis(triflouromethyl)aniline and salicylaldehyde
Mustafa Yıldız, Özge Karpuz, Celal Tuğrul Zeyrek, Bahadir Boyacioglu, Hakan
Dal, Neslihan Demir, Nuray Yıldırım, Huseyin Unver
PII:
S0022-2860(15)00282-3
DOI:
http://dx.doi.org/10.1016/j.molstruc.2015.03.047
MOLSTR 21431
Reference:
To appear in:
Journal of Molecular Structure
Received Date:
Revised Date:
Accepted Date:
16 February 2015
23 March 2015
24 March 2015
Please cite this article as: M. Yıldız, Ö. Karpuz, C.T. Zeyrek, B. Boyacioglu, H. Dal, N. Demir, N. Yıldırım, H.
Unver, Synthesis, biological activity, DNA binding and anion sensors, molecular structure and quantum chemical
studies of a novel bidentate Schiff base derived from 3,5-bis(triflouromethyl)aniline and salicylaldehyde, Journal
of Molecular Structure (2015), doi: http://dx.doi.org/10.1016/j.molstruc.2015.03.047
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Synthesis, biological activity, DNA binding and anion sensors, molecular
structure and quantum chemical studies of a novel bidentate Schiff base
derived from 3,5-bis(triflouromethyl)aniline and salicylaldehyde
a,b
a
c
d
e
Mustafa Yıldız *, Özge Karpuz , Celal Tuğrul Zeyrek , Bahadir Boyacioglu , Hakan Dal ,
f
g
h
Neslihan Demir , Nuray Yıldırım , Huseyin Unver *
a
Department of Chemistry, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart
University, TR-17100 Çanakkale, Turkey.
b
Nanoscience and Technology Research and Application Center (NANORAC), Çanakkale
Onsekiz Mart University, Çanakkale, Turkey
c
Ankara Nuclear Research and Training Center, Turkish Atomic Energy Authority, TR-06100
Besevler-Ankara, Turkey
d
Vocational School of Health Services, Ankara University, TR-06290 Kecioren-Ankara,
Turkey
e
Department of Chemistry, Faculty of Science, Anadolu University, TR-26470 Yenibağlar,
Eskişehir, Turkey
f
Department of Biology, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University,
TR-17100 Çanakkale, Turkey.
g
Health Services Vocational School, Çanakkale Onsekiz Mart University, TR-17100
Çanakkale, Turkey
h
Department of Physics, Faculty of Science, Ankara University, TR-06100 Besevler-Ankara,
Turkey
E-mail:myildiz@comu.edu.tr (Mustafa Yildiz)
unverh@ankara.edu.tr (Hüseyin Ünver)
ABSTRACT
Synthesis, biological activity, spectroscopic and crystallographic characterization and
density functional theory (DFT) studies of the Schiff base 3,5-bis(triflouromethyl)aniline and
salicylaldehyde are reported. It crystallizes as a monoclinic space group P2 /c with
1
-3
a=7.7814(3)Å, b= 26.8674(9)Å, c =7.4520(2) Å, V = 1379.98(8), Z = 4, D = 1.6038 g cm ,
c
-1
and µ= 0.156 mm . The molecular structure obtained from X-ray single-crystal analysis of
the investigated compound in the ground state was compared using Hartree-Fock (HF) and
density functional theory (DFT) with the functionals B3LYP and B1B95 using the 6-
3
11++G(d,p) basis set. The antimicrobial activities of the compound were investigated for its
minimum inhibitory concentration (MIC). The interaction of the Schiff base with calf thymus
DNA was investigated using UV-visible spectra. The colorimetric response of the Schiff base

receptors in DMSO was investigated before and after the addition of an equivalent amount of
each anion to evaluate the anion recognition properties.
Keywords: Schiff base; Density functional theory; Antimicrobial activity; Tautomerism; Calf
thymus-DNA; Anion sensors.
1
. Introduction
Schiff bases have been reported for their biological properties, such as antibacterial,
antifungal, antiinflammatory, analgesic, anticonvulsant, antitubercular, anticancer, antioxidant
and antihelmintic activities [1-26]. Schiff base metal complexes have applications in the areas
from material science to biological sciences. They have been widely studied because they
have anticancer and herbicidal applications [20-21]. Schiff base complexes show greater
biological activity than free ligands [3, 6, 22-26]. The DNA binding, cytotoxicity and
apoptosis induction activity were studied for Schiff base copper(II) complexes [27-29]. A
rather commonly used technique regards the development of fluorescent chemosensor
quenching of fluorescence by interaction with anions. The sensors can provide fast and visible
color changes from yellow to red in the presence of strong basic anions. Over the past 10
years, several excellent chemosensors have been reported for recognition and sensing of
anions with high selectivity and sensitivity [30-37]. Tautomerism in Schiff bases with an OH
group in ortho position to the imino group both in solution and in solid state were investigated
using spectroscopy and X-ray crystallography techniques [4-5, 38-44]. Schiff bases with OH
group in ortho position to the imino group are of interest mainly due to the existence of either
…
…
O–H N or O H–N type hydrogen bonds and tautomerism between enol-imine and keto-
amine form. In some instances the hydrogen from the OH group is completely transferred to
the imine nitrogen. In other words, enol-imine ꢀ keto-amine equilibrium shifts

predominantly to the keto-amine side. The keto-amine form is always observed when the
Schiff base is derived from 2-hydroxy-1-naphthaldehyde and aromatic amine. In Schiff bases
derived from salicylaldehyde and aromatic amines, the keto-amine form is not observed in
solution and solid state.
In this study, a novel bidentate Schiff base has been synthesized by the reaction of 3,5-
bis(triflouromethyl)aniline with 2-hydroxy-1-benzaldehyde. The structure of the synthesized
Schiff base was investigated using data obtained from elementary analysis, FT-IR, UV-
1
13
visible, H-NMR and C-NMR techniques. The solid state structure of the Schiff base (E)-2-
(3,5-bis(trifluoromethyl)phenylimino)methyl]phenol(Scheme 1) was also determined
[
crystallographically. The minimal inhibitory concentration (MIC) of the compound was
screened in vitro against bacteria and yeast cultures using broth micro dilution tests [45-48].
DNA binding of the Schiff base was investigated. Also, anion sensing ability of the Schiff
-
-
-
-
-
-
-
base was observed colorimetrically in DMSO for F , Br , I , CN , SCN , ClO , HSO ,
4
4
-
-
-
-
CH COO , H PO , N and OH anions. The molecular structure, atomic charges, molecular
3
2
4
3
electrostatic potential (MEP), nonlinear optical (NLO) effects and thermodynamic properties
of the compound were investigated by DFT. The result of theoretical calculations was
compared with crystallographic data. Additionally, we theoretically investigated the
geometric structure and energy contents of both enol-imine and keto-amine tautomers of the
compound.
2
. Experimental
2
.1. Reagents and techniques
1
13
The H and C NMR spectra were recorded on a Bruker AVANCE- 500 spectrometer
operating at 400 and 101,6 MHz. Infrared absorption spectra were obtained from a Perkin
-1
Elmer BX II spectrometer in KBr discs and were reported in cm units. The UV-VIS spectra
were measured using a SHIMADZU 1800 series spectrometer. Elementary analyses were

performed on a Vario EL III CHNS elemental analyzer. Melting points were measured with
an Electro Thermal IA 9100 apparatus using a capillary tube. 3,5-Bis(triflouromethyl)aniline,
salicylaldehyde, EtOH, Ethidium bromide (EB), calf thymus DNA (CT-DNA), (Bu) NF,
4
(Bu) NBr, (Bu) NI, (Bu) NCN, (Bu) NSCN, (Bu) NClO , (Bu) NHSO , (Bu) NCH COO,
4 4 4 4 4 4 4 4 4 3
(
Bu) NH PO , (Bu) NN , (Bu) NOH and DMSO were purchased from Aldrich. The Tris–HCl
4
2
4
4
3
4
buffer solution was prepared with triple-distilled water. CT-DNA stock solution was prepared
by diluting DNA to Tris–HCl/NaCl buffer (5 mM Tris–HCl, 50 mM NaCl, pH 7.2), and kept
at 4 °C for no longer than two days.
2
.2. Synthesis of (E)-2-[(3,5-bis(trifluoromethyl)phenylimino)methyl]phenol
-3
3
,5-Bis(triflouromethyl)aniline (0.50 g, 2.18x10 mol) was added to EtOH (100 mL)
-3
solution of salicylaldehyde (0.265 g, 2.18x10 mol) [44]. The mixture was stirred and
refluxed for 1 h. Compound (1) was obtained from the evaporation of EtOH. It was
crystallized from CHCl : n-hexane (3:2) as a yellow crystal, mp 86 °C, 0.57 g (85%) yield.
3
Found: C, 54.05; H,2.72; 4.20. Calc. For C H F NO; C, 54,07; H, 2.70; N, 4.20 %. IR(KBr,
1
5
9 6
-1
cm ); O-H; 3434 m, Ar-H; 3098 w, C=N; 1629 s, C=C; 1616-1602, 1582s, C-N; 1497
1
m, C-O; 1361m. H-NMR (DMSO); δ ppm, 12.25 (s, 1H, Ar-OH); 9.07 (s, 1H, Ar-CH=N-);
13
8
.10-6.97 (m, 7H, Ar-H). C-NMR (DMSO); δ ppm, 119.89 (s, 1C, C-CH=N); 160.23 (s, 1C,
C-OH); 116.73 (s, 1C, CH-C-OH); 132.71 (s, 1C, CH-CH-C-OH); 122.07 (s, 1C, CH-CH-C-
CH=N); 131.48 (s, 1C, CH-C-CH=N); 166.57 (s, 1C, -CH=N); 150.62 (s, 1C, C-N=CH);
1
2
24.24 (s, 2C, CH-C-N=CH); 134.15 (s, 2C, C-CF ); 122.48 (s, 1C, CH-C-CF ); 131.21 (s,
3 3
C, CF3).
.3. Crystallography
Crystallographic data were recorded on a Bruker Kappa APEXII CCD area-detector
2
diffractometer using MoK radiation ( = 0.71073Å) at T = 100 K. Data collection, reduction

and corrections for absorption and crystal decomposition for the compound were achieved by

using X-AREA, X-RED software [49] and the structure was solved by SHELXS-97 and
refined with SHELXL-97 [50-51]. The positions of the H atoms bonded to C atoms were
calculated (C-H distance 0.96 (), and refined using a riding model, but the H1 atom of the O1
was found in a difference electron-density map at the end of the refinement process as a small
positive electron density. All atoms (except hydrogen) were located from a difference Fourier
map and refined anisotropically. The atoms of C(10)F group are disordered over two
3
positions. For F1, F2 and F3 atoms the site occupancy factor is 0.65 and for F1A, F2A, and
F3A atoms the site occupancy factor is 0.35. The details of the X-ray data collection, structure
solution and structure refinements are given in Table S1. The bond distances, bond and
torsion angles are listed in Table S2. The molecular structure with the atom-numbering
Scheme is shown in Fig.1 [52]. Crystallographic data (excluding structure factors) for the
structures reported in this paper has been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication number CCDC 1038662 [53].
2
.4.Screening for antimicrobial activities
Bacillus subtilis ATCC 6633, Saphylococcus aureus ATCC 25923, Escherichia coli
ATCC 25922, Enterococcus faecalis ATCC 29212, Pseudomonas aeruginosa ATCC 254992,
Escherichia coli ATCC 35218, Bacillus cereus NRRL B-3711, Proteus vulgaris ATCC
1
3315, Candida albicans ATCC 60193, and Candida tropicalis ATCC 13803 were used as
microorganisms. Gentamicin, ampicillin and fluconasol were used as controls in this study as
they are well-known broad-spectrum antibiotics that have different mechanisms of activity,
such as interruption of protein synthesis (gentamicin) and inhibition of cell wall synthesis
(ampicillin) [54]. The compounds were dissolved in DMSO (dimethyl sulfoxide) to a final
concentration of 500 g/mL. The concentration of the compounds on different plates was 500
µg/mL, 250 µg/mL, 125 µg/mL, 62.5 µg/mL, 31.25 µg/mL, 15.6 µg/mL, 8 µg/mL, 4 µg/mL,
2
µg/mL, and 1 µg/mL.

2
.5. DNA-Binding experiments
The UV-visible spectra titrations were carried out in Tris–HCl/NaCl buffer at room
temperature to investigate the binding affinity between CT-DNA and the Schiff base. The
UV-VIS absorbance at 260 and 280 nm of CT-DNA solution in Tris buffer give a ratio of
1
.8–1.9, indicating that the DNA was sufficiently free of protein [55]. Tris–HCl/NaCl buffer
−
5
(
3 mL) and the solutions of Schiff base (3 mL, 1.13×10 M) were placed into two cuvettes,
respectively. Then one aliquot (5 μL, 0.01 M) of buffered CT-DNA solution was added to
each cuvette in order to eliminate the absorbance of DNA itself. Before the absorption spectra
were recorded, the Schiff base-DNA solutions were incubated at room temperature for 5 min.
2
.6. Anion Sensors Measurements
Schiff base (0.05 μmol) was dissolved in DMSO (50 mL). Tetrabuthylammonium salts
-
-
-
-
-
-
-
-
-
-
-
(
F , Br , I , CN , SCN , ClO , HSO , CH COO , H PO , N , OH ) (0.05 μmol) were
4 4 3 2 4 3
dissolved in DMSO (50 mL). Each solution of tetrabutylammonium salts was added to the
Schiff base solution (1:1) in the UV tube. After mixing them, UV absorption spectra were
taken at room temperature.
2
.7. NMR Titration
Three NMR tubes of Schiff base dissolved in DMSO-d were prepared and then
6
different equivalents (0.0, 0.5, and 1.0 equiv.) of tetraethylammonium fluoride dissolved in
1
DMSO-d were added to two solution of Schiff base tube. After shaking thoroughly, H NMR
6
spectra were taken at room temperature.
2
.8. Calculation details
The molecular geometry of the compound was taken directly from the X-ray
diffraction experimental result of the geometry optimization. This result was used in the
Gaussian 09W software package and the Gauss-view visualization program [56-57] for DFT
calculations with Becke’s one and three-parameter hybrid exchange functionals (B1 and B3)

[
(
58-59] using Becke’s time-dependent gradient-corrected (B95) [58] and Lee-Yang-Parr
LYP) correlation functionals with the 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d)
and 6-311++G(d,p) basis sets [60-63].
It is well-known that the vibrational wavenumbers obtained by DFT computations are
usually overestimated compared to their experimental counterparts. To overcome
discrepancies between observed and calculated wavenumbers, the scaling factors have been
introduced by using the relationship between the calculated unscaled (ucal) and experimental
(exp) wavenumbers is linear and is described by the following equation:
ꢖ
ꢁꢂꢃꢄ ꢅ ꢆꢇꢈꢉꢈꢊꢋꢁꢌꢍꢎꢏ ꢐ ꢑꢒꢇꢋꢒꢆꢊꢓꢔ ꢕ ꢅ ꢆꢇꢈꢈꢊꢒꢈ
(1)
According to the fitting results of equation (1), the general scale factor value was
found to be 0.97964 for B3LYP/6-311++G(d,p) level. We calibrated the vibrational
wavenumbers by using a scale factor value of 0.97964. The assignments of each vibrational
mode were defined from their potential energy distributions (PED) which were calculated by
using VEDA 4 program based on B3LYP [64]. The visual checks for the vibrational band
assignments were also performed by using Gauss-View molecular visualization program.
To investigate the tautomeric stability, some properties such as total energy, HOMO
and LUMO energies of the compound in gas phase were obtained at B3LYP/6-311++G(d,p)
level. These properties were also examined in five kinds of solvent media (chloroform,
dicholorethane, ethanol, dimethylsulfoxide and water) by using a Polarized Continuum
(PCM) model. To investigate the reactive sites and to identify sites of intra- and
intermolecular interactions of the compound, the molecular electrostatic potential surface was
evaluated by using B3LYP/6-311++G(d,p) method. The total molecular dipole moment (µ),
linear polarizability (α), and the first-order hyperpolarizability (β) was predicted by the
B3LYP method with different base sets, 6-31G(d), 6-31+G(d,p), 6-31++G(d,p), 6-311+G(d)
and 6-311++G(d,p), to investigate the effects of basis sets on the NLO properties.

Finally, the standard thermodynamic functions were obtained from statistical
thermodynamics based on the vibrational frequency analysis at B3LYP/6-311++G(d,p) level
using the Gaussian 09 software package.
3
. Results and discussion
3
.1. Crystallographic study
2
-Hydroxybenzaldehyde Schiff base ligands are of interest mainly due to the existence
…
…
of either O H – N or O – H N type hydrogen bonds and the tautomerism between enol and
keto forms [65-66]. The crystal structure is stabilized by intramolecular and intermolecular
hydrogen bonding of these types of ligands [65-66]. In the compound, hydrogen bonds are
observed between the 2-hydroxy group and the imine nitrogen atom. In some instances, the
hydrogen atom from the phenol group is completely transferred to the imine nitrogen atom or
is just converse. In the Schiff base ligand studied in this paper, the molecule is not planar in
the solid state. A [O1, C1-C7] and B [N1, C8-C15, F1-F6] are inclined at an angle of 29.30
…
(
8)°. In the crystal structure of the compound there is a strong intramolecular O H–N
…
…
hydrogen bond [O1–H1 = 0.804 Å, H1 N1 = 1.942 Å, O1 N1 = 2.608(3) Å]. The sum of the
Van der Waals radius of the O and N atoms (3.07 Å) is significantly longer than the
…
intramolecular O N hydrogen bond length [67]. This intramolecular hydrogen bond can be
compared with N-[2-hydroxy-1-naphthylidene]3,5-bis(trifluoromethyl)aniline 2.558(7) Å
[
44].
In the compound, the C=N group seems to have a strong electron withdrawing
character. Thus, the O1-C1 bond distance of 1.359(5) Å is also consistent with the C-O single
bonding; similarly the C7=N1 distance of 1.290(5) Å is a consistent with the C=N double
bonding. For these bonds, when we compare with our previous work [44], C-O 1.327(8) Å is
longer and C=N 1.308(7) Å is shorter. In addition to spectroscopic studies, the existence of
the enol-imine tautomer was also confirmed by using X-ray diffraction data.

3
.2. Optimized molecular structure
The molecular structure of (E)-2-[(3,5-bis(trifluoromethyl)phenylimino)methyl]phenol
was experimentally determined. Geometric optimization of the compound was performed by
using DFT/B3LYP method with 6-311++G(d,p) basis set (Table S2). The calculated bond
distances, bond angles and torsion angles are compared with the experimental values for the
compound, and are shown in Fig. S2a, b, c. The aniline ring is rotated relatively to the
salicylaldimino part in both the optimized and experimental structures.
The conformational discrepancies between the X-ray structure and optimized
counterparts can be seen from Fig. S2a, S2b, S2c. According to Fig. S2a and S2b, the biggest
difference in bond lengths between the experimental and the optimized values is found for the
C14–F2 bond with the difference being 0.1075 Å, and the biggest difference for the bond
o
angles is found as 5.53 at F2-C14-F3. The discrepancy for the enol form is less than for the
keto form, as seen in Fig. S2a and S2b. The orientation of CF groups is a remarkable
3
discrepancy between these counterparts and the orientation of these groups is defined by
torsion angles C9−C10−C14−F2, C11-C12-C15-F6, C9-C10-C14-F3 and C11-C10-C14-F1
o
o
o
o
with values of 1.1(7) , -80.1(5) , 115.7(5) and 53.1(6) from X-ray, respectively. The
o
differences in the torsion angles between the experimental and calculated values are 59.52
o
o
(
C11-C12-C15-F6) for HF, 18.34 (C9−C10−C14−F2) for the B3LYP and 29.15 (C9-C10-
C14-F3) for B1B95. In the structure of the Schiff base molecule, the most important torsion
angles between the aniline ring with the salicylaldimino-part are [θ1(C8−N1−C7−C6)],
[
[
θ2(C7−N1−C8–C13)] and [θ3(C5−C6−C7−N1)]. From the X-ray structure determination,
θ1(C8−N1−C7−C6)], [θ2(C7−N1−C8–C13)] and [θ3(C5−C6−C7−N1)] values were obtained
o
o
o
as 177.1(3) , -32.7(5) and -178.1(4) , respectively. These angles have been calculated as
o
o
o
o
o
o
1
76.99 , -39.77 and −179.11 for B3LYP/6-311++G(d,p); 178.33 , -46.46 and −178.91 for
o
o
o
HF/6-311++G(d,p); and 177.62 , -38.52 and −179.08 for the B1B95/6-311++G(d,p) level in

the optimized structure in Table S2 and Fig. S2c. As seen from Table S2, most of the
optimized bond lengths are slightly longer than the experimental values. It can be said that the
experimental results belong to the solid phase, whereas the theoretical calculations belong to
the gas-phase. The resulting differences of bond parameters between the calculated and
experimental values depend on the existence of the crystal field along with the inter-molecular
interactions connecting the molecules together in the solid state. The geometric parameters
calculated using the B3LYP/6-311++G(d,p) method are in good agreement with the X-ray
structure.
According to these results, it may be concluded that theHF/DFT(B3LYP-B1B95)
calculations well reproduce the bond distances and the bond angles for the enol-imine form,
while the same calculations are better at predicting the torsion angles for the keto-amine form
of the compound.
In spite of the small differences, calculated geometric parameters represent a good
approximation, and they are the basis for calculating other parameters such as PES scan,
vibrational frequencies, atomic charges, molecular electrostatic potential (MEP), nonlinear
optical (NLO) effects and thermodynamic properties of the compound, as described below.
3
.3. Potential energy surface (PES) scan
To investigate the conformational stability of the compound, the potential energy
surface (PES) scans for the link fragments of the aldehyde ring (ring1) with respect to the
aniline ring (ring2) part in the whole molecule were investigated. For this reason, the torsion
angles T1(C9–C8–N1–C7) and T2(C1–C6–C7-N1) are relevant coordinates for
conformational flexibility of the investigated molecule. The scans were obtained by
minimizing the potential energy using B3LYP/6-311++G(d,p) level of theory in all
o
o
geometrical parameters by varying the torsion angles in steps of 10 in the range of 0-360

rotation around the bond. The variations of potential energy change from its equilibrium with
the torsional perturbation are presented in Fig. S3a and S3b.
Potential energy surface (PES) scan for torsion angle T1 showed three minima
o
o
o
o
positions at 70 , 170 and 250 , while T2 shows one minimum position at 170 . Among
these, the deepest minima values correspond to the optimized molecular geometry [T1(C9–
o
o
C8–N1–C7) = 250 and T2(C1–C6–C7–N1) = 170 ] of the compound which is directly taken
from the X-ray diffraction experimental result. The energy of the most stable conformation is
-306.45009680 Hartree.
3
.4.Vibrational spectra
-1
The infrared spectra of the investigated compound were recorded in the 4000–400 cm
region using KBr pellets on a Perkin Elmer BX II spectrometer and are given in Fig. 4. The
vibrational band assignments were performed at B3LYP/6-311++G(d,p) theory level to
compare the experimental (FT-IR) and calculated vibrational frequencies of the compound.
We analyzed the normal vibrational frequencies and compared our calculated results for the
investigated compound with the experimental ones on the basis of potential energy
distributions (PED), given in Table S3. The infrared spectra of the investigated compound
have some characteristic bands for stretching vibrations of the O–H, C–H, C = N, C– O, C–C,
and C–F groups.
3
3
.4.1. Hydroxyl group vibrations
The characteristic region of the O–H group vibration spectrum in the Schiff bases,
-1
which have a free hydroxyl group or non-hydrogen bonded, is 3550–3700 cm [68]. If the
intramolecular hydrogen bonding occurs in six membered ring systems, the O–H stretching
band will be reduced to the 3550–3200 region [69]. In this study, the experimental O–H
-1
stretching vibration was observed at 3434 cm . The O–H stretching vibration was calculated
-1
as 3225 cm for B3LYP/6-311++G(d,p) level with 99% contribution of PED. The

experimentally and theoretically predicted frequency for O–H vibration by B3LYP/6-
11++G(d,p) level shows excellent agreement with the recorded spectrum, as well as the
3
literature data, and is also supported by PED values [70-72]. The strong hydrogen bonding if
present in the Schiff bases composed of the 2-hydroxy-1-napthaldehyde system would reduce
-1
the O–H stretching band shifting to a lower wavenumber 2900 cm [73]. In plane O–H
-1
bending modes are observed at 1533, 1467, and 1381 cm , while the corresponding bands are
-1
calculated at 1573, 1496, and 1448 cm with 14%, 19%, and 41% contribution of PED. The
-1
band observed at 846 cm is assigned as an out of plane bending of the O–H group, and this
-1
band is calculated at 855 and 807 cm for B3LYP with 13% and 23% contribution of PED,
respectively.
3
.4.2. C–H vibrations
The aromatic structure shows the presence of C–H stretching vibrations in the region
-1
3
000 – 3125 cm , which is the characteristic region for the identification of υ(CH) stretching
vibrations. But in this region, the bands are not appreciably affected by the nature of the
substituent [74]. In the FT-IR spectrum of the compound, symmetric C–H stretching
-1
vibrations are observed at 3067 and 3098 cm . The corresponding bands are calculated at
-1
3
135 and 3151/3145 cm with 99% and 99/100% contribution of PED. The observed
-1
asymmetric C–H stretching vibration is 2990 cm , while the calculated values for the
-1
asymmetric C–H stretching vibrations are 3129/3108/3097 cm with 98/36/65% contribution
of PED. Substitution sensitive C–H in-plane bending vibrations lie in the region 1000–1300
-1
-1
cm [71]. In the compound, infrared bands ranging from 1240 and 1133 cm are assigned to
-1
C–H in-plane bending vibrations. These vibrations correspond to 1268 and 1155 cm from
the calculated values. The C–H out-of-plane bending vibrations appear in the range 1000–675
-1
-1
cm [71, 75-76]. The observed vibrations are 950, 900, 858, 846 and 735 cm for the C–H
-1
out-of-plane bending vibrations. The bands at 973, 907/897, 884, 855, and 751 cm are

assigned to the C–H out-of-plane bending vibrations for the investigated compound. As seen
in Table S3, the C–H out-of-plane bending vibrations are assigned as mixed and pure modes,
respectively.
3
.4.3. C=N vibrations
The C=N stretching vibrations were assigned in the region 1500-1600 cm by
Silverstein [77]. In the present study, the C=N bond stretching vibration band is observed at
-1
-1
1
602 experimentally, while it is calculated at 1632/1627 cm with B3LYP/6-311++G(d,p)
level. The PED for this mode is 16 and 31%. The PED for this mode suggests that this is a
-1
mixed mode (Table S3). The band at 1170 cm is designated as C–N stretching vibration, and
-1
this mode is assigned at 1178 cm by B3LYP level. For C=N and C–N stretching vibrations,
the results observed and calculated by B3LYP/6-311++G(d,p) method are in good agreement
with similar Schiff base compounds [70, 73, 78].
3
.4.4. Phenyl ring vibrations
The ring C=C stretching vibrations for the aromatic group generally appear at 1430-
-
1
1
1
1
625 cm [79]. For this compound, the C=C stretching vibrations are observed at 1602, 1582,
-1
561, 1533, and 1400 cm in FT-IR spectrum. These vibrations correspond to 1632/1627,
601, 1573, and 1448 from the calculated values. The bands at 1332, 1319, 1268, and 1235
-1
cm are also assigned to C–C stretching vibrations for the investigated compound. These
vibration modes are highly mixed modes with the range of 11-58% contribution of PED. The
-1
mean difference between the theoretical and experimental frequencies is about 14 cm . It
shows good agreement between theoretical and experimental values of the ring C=C and C–C
stretching vibrations for the aromatic group.
3
.4.5. C–O and C–F vibrations
The C–O stretching vibrations appear in the spectral range 1168-1310 [80]. For the
-1
compound, the phenolic C–OH stretching vibration is observed at 1278 cm and assigned at

-1
1
291 cm with 38% contribution of PED. For C–OH stretching vibration, the result observed
and calculated by B3LYP/6-311++G(d,p) method are in good agreement with similar Schiff
-1
base compounds [70, 73, 78]. The bands at 1120 and 1030 cm in the FT-IR spectrum are
appointed as C–F stretching vibrations and these modes are calculated in the range of 660-
-1
-1
1
230 cm . According to the calculations 1140 and 717 cm are assigned to the symmetric C–
-1
F stretching modes, while the 1132 cm vibration is the asymmetric C–F stretching mode.
3
3
-1
In the predicted spectra, out-of plane F–C–F bending vibration is appointed at 656 cm with
3
1% contributions of PED.
The calculated values of other group vibrations show good agreement with the
experimental results. The other experimental and calculated vibrational values can be seen in
Table S3. To make a comparison with the experimental observations, we present correlation
graphics in Fig. S5a and S5b. The relationships between experimental ( ) and calculated
exp
scaled ( ) wavenumbers is linear and described by the following equation:
cal
ꢖ
ꢁꢂꢃꢄ ꢅ ꢗꢇꢆꢆꢒꢒꢑꢁꢍꢎꢏ ꢐ ꢑꢊꢇꢉꢘꢒꢑꢈ ꢕ ꢅ ꢆꢇꢈꢈꢉꢊ
(2)
As a result, the scaled fundamental vibrationals have good consistency with
experimental results and are found in good agreement with that predicted in the literature.
1
13
3
.5. H NMR and C NMR Spectroscopic studies
1
13
The H-NMR and C-NMR data are given in synthetic procedures for the compound.
1
The H-NMR data for the compound show that the tautomeric equilibrium favours the enol-
imine in DMSO. The -OH and -CH=N- protons are observed at 12.25 and 9.07 ppm singlets
for the compound (Table 4). The phenyl protons of the compound gave multiplets at 8.10-
1
3
6
.97 ppm. According to the C-NMR spectra, the compound has 12 signals, showing that the
structures in solution are symmetrical (Fig. S6).
In nuclear magnetic resonance spectroscopy (NMR) the isotropic chemical shift
analysis allows us to identify relative ionic species and to calculate reliable magnetic

properties which provide accurate predictions of molecular geometries [50-53]. The optimized
molecular geometry of the compound was obtained by using the B3PLYP method with 6-
3
11++G(d,p) basis set in gas phase and DMSO solvent with the IEFPCM solvent model.
Then, the proton and carbon-13 NMR chemical shifts were calculated at the same level by
1
13
using the GIAO method. The calculated and experimental H- and C-NMR chemical shift
values for the Schiff base molecule are listed in Table 4. As seen from Table 4, the hydrogen
atoms in the hydroxyl and imine groups have resonance in the range 12.33-8.95 ppm [81].
The H(-O) and H7 atoms in hydroxyl and imine groups of the molecule produced a resonance
signal at 12.25 and 9.07 ppm. The calculated values for these hydrogen atoms are 12.26/8.61
ppm (in the gas phase) and 12.33/8.84 ppm (in DMSO), respectively. The protons in phenol
groups give rise to a signal in the interval 4-7.5 ppm, depending on concentration, solvent and
temperature [81]. But the phenolic proton under intra-intermolecular hydrogen bonding
interaction gives a resonance signal between 10–12 ppm [81]. The observed resonance signals
between 6.97–8.10 ppm correspond to chemical shifts of the protons in the aromatic rings.
The calculated chemical shifts for aromatic protons are calculated (in the gas phase/DMSO)
as 6.95/7.90 and 7.14/7.96 ppm, respectively.
The carbon-13 NMR chemical shift values in aromatic rings and carbon atoms which
are bonded to electronegative F, O and N atoms are observed at the interval 116.73–166.57
ppm. The chemical shifts of the C2 and C7 carbon atoms which are bonded to O and N atoms
in hydroxyl and imine groups are observed at 160.23 and 166.57 ppm, respectively. Similarly,
the chemical shifts of the C8, and C14/C15 atoms which are bonded to one N and F atom are
observed at 150.62 and 131.21/ ppm. The calculated values for the C2, C7, C8 and C14/C15
atoms are (in gas phase/DMSO) 170.71/169.48, 169.64/172.07, 158.00/158.16, and
1
33.19/133.58, 133.24/133.69 ppm, respectively. For aromatic carbons, the experimental and

calculated 13C NMR chemical shifts are between 166.57–116.73 ppm and 169.64–
22.31/172.07–121.14 ppm (in gas phase/DMSO), respectively.
1
3
.6. UV-Visible and HOMO–LUMO analysis
The UV-VIS spectrum of the compound was studied in DMSO (Fig. S7). The Schiff
bases show absorption in the range greater than 400 nm in polar and nonpolar solvents. It
should be pointed out that the new band belongs to the keto-amine form of the Schiff base
with -OH group in ortho position to the imino group in polar and nonpolar solvents in both
acidic and basic media [38-39]. The band was not observed at greater than 400 nm in DMSO
for the compound. The enol-imine form is dominant in DMSO for the compound. The
experimental UV-vis spectrum of the compound shows only two broad bands at 279 nm and
3
42 nm, which are assigned to the π–π* and n–π* transition of C=C and C=N. The computed
UV–Vis was processed using the TD-DFT method on the B3LYP and 6-311G(d,p) basis set
in Gaussian 09W software package [56]. The main results of experimental and TD-DFT
calculated absorptions are summarized in Table S5. In DMSO solvent, the experimental
spectrum presents two maximum absorption bands between 279 and 342 nm, whereas the TD-
DFT results predict these bands around 290 and 345 nm. Experimentally, the long-wavelength
maximum shifts towards high energy when the solvent polarity is increased, in agreement
with previous reports [73, 78]. Comparing the experimental and the TD-DFT results shown in
Table S5, a reasonable concordance between the wavelengths is observed. In addition, the UV
absorption band at 346 nm of the compound results from an electronic transition from HOMO
to LUMO localized mainly on the aromatic ring π-π* transition of the C=C from experimental
results.
There are the other two absorption bands located at 306 and 290 nm, arising from
HOMO-1 LUMO and HOMO LUMO+1 transitions which were estimated as π-π* and n–π*
transition of the C=C and C=N transitions as seen in Table S5 and Fig. S8. Because the band

was not observed at greater than 400 nm in DMSO for the compound, in the keto form the
HOMO-LUMO transition has not been observed at higher wavelengths because the energy of
HOMO in keto structure is higher than that in enol structure and the energy of LUMO in the
keto structure is lower than that in enol structure. The most important orbitals in a molecule
are the frontier molecular orbitals, called HOMO and LUMO. These orbitals determine the
way the molecule interacts with other species. The frontier orbital gap helps characterize the
chemical reactivity and kinetic stability of the molecule. A molecule with a small frontier
orbital gap is more polarizable and is generally associated with a high chemical reactivity,
low kinetic stability and is also termed a soft molecule [82]. The energy gap between HOMO
and LUMO is a critical parameter to determine molecular electrical transport properties. By
using HOMO and LUMO energy values for a molecule, chemical hardness–softness,
electronegativity and electrophilicity index can be calculated as follows:
ꢚ
ꢙ ꢅ ꢛꢜ ꢐ ꢝꢞ
(3)
ꢖ
In equation (3) I is the vertical ionization energy and A stands for the vertical electron
affinity. According to the Koopman theorem [83], the ionization energy and electron affinity
can be equalized through HOMO and LUMO orbital energies:
ꢟꢝ ꢅ ꢐꢠꢡꢢꢣꢢ
ꢜꢤ ꢅ ꢐꢠꢥꢦꢣꢢ
(4)
(5)
According to the equation (4), the hardness corresponds to the gap between the
HOMO and LUMO orbitals. Hence, the larger the HOMO-LUMO energy gap, the harder
molecule.
ꢚ
ꢙ ꢅ ꢛꢠ
ꢐ ꢠꢡꢢꢣꢢ
ꢞ
(6)
ꢥꢦꢣꢢ
ꢖ
For enol and keto forms of the compound, the chemical hardness (ꢙ) was calculated
with the B3LYP/6-311++G(d,p) base set. The results are given in Table S6. The energy
separation between the HOMO and LUMO is 4.039 eV for the enol form and 3.179 eV for the

keto form. This large HOMO–LUMO gap for the enol form suggests high excitation energies
for many of the excited states, a good stability and high chemical hardness for the compound.
Indeed, as seen from Table S6 the chemical hardness of the enol form (ꢙꢂꢧꢨꢏ= 2.0195 eV) is
greater than the keto one (ꢙꢩꢂꢪꢨ= 1.5894 eV), which once again indicates that the enol form of
the molecule is more stable than its keto form in the gas phase, respectively.
3
.7. Atomic charge distributions, energy and dipole moment behavior in the gas and the
solution phases
The Mulliken atomic charges for the excluded H atoms of the compound have been
calculated at B3LYP and B1B95/6-311++G(d,p) level using the Self-Consistent Isodensity
Polarized Continuum Model (SCI-PCM) in the gas phase (Fig. S9). In order to investigate the
solvent effect, five kinds of solvent were selected (= 4.9, chloroform; = 10.36,
dichloroethane; = 24.55, ethanol; = 46.7, dimethylsulfoxide and = 78.39 water) and the
atomic charge distributions of the compound were also calculated using density functional
theory (DFT) with the functional B3LYP 6-311++G(d,p) basis set. The calculated values for
atomic charges of the compound in the gas phase and solution phase are listed in Table S7.
According to the calculated Mulliken atomic charges, the imine N1 atom has a positive
atomic charge and hydroxyl O1 atom has a large negative atomic charge in the gas phase.
…
This behavior may be the result of the N1–H O1 hydrogen bond. On the other hand, as
shown in Table S7, the negative atomic charge values of the O atom in solution phase become
more negative while the positive atomic charge of N1 decreases with the increase in the
polarity of the solvent.
The total energies and dipole moments of the compound were also calculated with
B3LYP/6-311++G(d,p) level for five solvents in order to evaluate the difference in total
energy and dipole moment behavior of the compound in solvent media. The results are given

in Table S8. According to the results, the obtained total energy of the compound decreases
with the increasing polarity of the solvent. We can conclude that the stability of the compound
increases with increasing polarity of the solvent. The energy differences between the gas
phase and solvent media and dipole moments are shown in Fig. S10. As can be seen from
Table S8, the dipole moments in the various solvents which are calculated using the SCI-
PCM method increase with increasing solvent polarity. Optimization calculations at
B3LYP/6-311++G(d,p) level were also performed for both the enol and keto forms of
compound to investigate the tautomeric stability. In the gas phase, the total energy of the
enol-imine form is lower than the keto-amine form.
3
.8. Molecular electrostatic potential surface
To investigate reactive sites for electrophilic and nucleophilic attack, the regions of
the MEP for the compound were investigated by DFT calculation using the optimized
geometry of the B3LYP/6-311++G(d,p). As shown in Fig. S11, red and yellow colours
indicate the negative regions of the MEP are related to electrophilic reactivity, while blue
colours indicate positive regions related to nucleophilic reactivity. As can be seen from Fig.
S11, the compound has one possible site for electrophilic attack. The oxygen atom O1 of the
hydroxy group has a negative region. The maximum negative molecular electrostatic potential
value is 0.025 a.u. for the main region of the O1 atom. The C7–H7, C9–H9, C11–H11, and
C13–H13, bonds indicate a possible site for nucleophilic attack with a maximum value of
0
.050 a.u. and around these bonds are maximum positive regions. According to these
calculated results, the region of MEP shows that the negative potential sites are on
electronegative atoms while the positive potential sites are around the hydrogen atoms. The
determining of MEP region is best suited to identify sites for intra- and intermolecular
interactions. According to the MEP surface of the compound, the weak negative region is

associated with O1 atom and also the weak positive region is around the nearby H1 atom. It
…
can be indicative of an intramolecular (N1–H1 O1) hydrogen bonding in the compound.
3
.9. Nonlinear optical (NLO) effects
To investigate the nonlinear optical properties of molecules is very important because
of the key functions of frequency shifting, optical modulation, optical switching, optical logic
and optical memory for emerging technologies in areas such as telecommunications, signal
processing and optical interconnections [84]. Thanthiriwatte and Nalin de Silva have
explained in detail previously how to calculate the total dipole moment (μ ), linear
tot
polarizability (α ), and the first-order hyperpolarizability (β ) from the Gaussian output file
ij
ijk
[
85].
The total molecular dipole moment (µ), linear polarizability (α), and the first-order
hyperpolarizability (β) were calculated by the B3LYP method with each of the 6-31G(d), 6-
1+G(d,p), 6-31++G(d,p), 6-311+G(d) and 6-311++G(d,p) basis sets to investigate the effect
of basis sets on the NLO properties. The calculated values of µ , α and β are listed in
3
tot
tot
tot
Table S8. From Table S8, it can be seen that the calculated values of the µ , α and β
tot
tot
tot
slightly depend on the size of basis sets. The values of the µ , α and β obtained with the
tot
tot
tot
6
-31G(d) basis set are smaller than those obtained with the large size basis sets. It was found
that the results calculated for the basis sets from 6-31+G(d) to 6-311++G(d,p) have minor
differences.
It can be seen from Table S8 that the calculated values of β for the compound are
tot
-30
5
greater than urea (the β of urea is 0.373x10 cm /esu obtained by using B3LYP/6-31G(d)
tot
basis set). When it is compared with similar Schiff base compounds in the literature, the
calculated values of βtot for the compound are larger than that of (E)-N-{2-[2-
-30
5
hydroxybenzylidene)amino]-phenyl}benzenesulfonamide (β =7.98x10 cm /esu) [75], and
tot
-30
5
2
-[2,4-dimethylphenyl)iminomethyl]-3,5-dimethoxyphenol] (β =8.256x10 cm /esu) [76],
tot

-30
calculated with B3LYP/6-311++G(d,p) method. The calculated value of βtot =8.55x10
5
-30
5
cm /esu in the gas phase, which is greater than that of urea (β =0.592x10 cm /esu obtained
tot
by using B3LYP/6-311++G(d,p) method). Especially, the first-hyperpolarizability value of
the investigated compound is about 14 times more than that of urea at the same level
B3LYP/6-311++G(d,p) base set.
3
.10. Thermodynamic Properties
The heat capacity (ꢫꢭ ), entropy (ꢮ ) and enthalpy (ꢯ ) are the standard thermodynamic
ꢭ
ꢭ
ꢄꢔꢬ
ꢬ
ꢬ
functions and were performed using the DFT/B3LYP method with 6-311++G(d,p). The
results obtained from the vibrational analysis are shown in Table S9. The heat capacities,
entropies and enthalpies were obtained by increasing temperature from 200 K to 450 K. As a
result, the increase in temperature increases heat capacities, entropies and enthalpies due to
increasing intensities of molecular vibration. The correlations between the thermodynamic
properties ꢫꢭ , entropy ꢮ and enthalpy ꢯ and temperatures T are described and shown in
ꢭ
ꢭ
ꢄꢔꢬ
ꢬ
ꢬ
Fig. S12, according to the data in Table S9. The correlation equations between these
thermodynamic properties and temperature T are as follows:
ꢭ
ꢅ ꢐꢗꢇꢋꢒꢘꢓ ꢰ ꢆꢇꢑꢓꢈꢗꢱ ꢐ ꢆꢇꢆꢆꢆꢗꢱꢖ
2
ꢫ
ꢄꢔꢬ
(R =0.9999)
(7)
(8)
(9)
ꢭ
ꢖ
2
ꢮ ꢅ ꢉꢗꢇꢓꢗꢉ ꢰ ꢆꢇꢑꢈꢗꢋꢱ ꢐ ꢆꢇꢆꢆꢆꢆꢉꢱ
(R =1)
ꢬ
ꢭ
ꢖ
2
ꢯ ꢅ ꢐꢆꢇꢘꢒꢗꢋ ꢰ ꢆꢇꢆꢗꢋꢱ ꢰ ꢆꢇꢆꢆꢆꢗꢱ
(R =1)
ꢬ
The values of ꢫꢭ , ꢮ and ꢯ can easily be obtained at any temperature using these
ꢭ
ꢭ
ꢄꢔꢬ
ꢬ
ꢬ
relationships and these results will be helpful for further studies of the compound.
3
.11. Minimum Inhibitory Concentration (MIC)
MIC was evaluated by broth micro dilution test. A loop full of bacteria was inoculated
-1
in 100 mL of nutrient broth at 37 °C for 20 h in a test-tube shaker at 150 rev min . The test
compounds were prepared by dissolving in a mini-mal volume of DMSO and were serially
diluted in Muel-ler-Hinton broth at concentrations in the range of 1-500 g/mL. The 24-h

bacterial cultures were then transferred into 10 mL of the Muller-Hinton broth (control and
test compounds) and incubated at 37 °C for 24 h. The growth of bacteria was determined by
measuring the turbidity after 24 h. Thus, the MIC was generally read as the smallest
concentration of the drug in the series that prevents the development of visible growth of the
test organism. The data reported in Table 10 are the average data from three experiments.
The antimicrobial activity spectrum of the Schiff base varied greatly. It can be
observed from Table 10 that the antimicrobial results of Schiff base have a high antifungal
effect on C. albicans ATCC 60193 and C. tropicalis ATCC 13803, while the compound has a
low effect on bacteria. Likewise, the compound has stronger antibacterial effect against S.
aureus ATCC 25923, E. faecalis ATCC 29212, E. coli ATCC 35218, P. aeruginosa ATCC
2
2
54992 and P. vulgaris ATCC 13315 compared to B. subtilis ATCC 6633 and E. coli ATCC
5922. This compound differs significantly in its activity against tested microorganisms. This
difference may be attributed to the fact that the cell wall in Gram-positive bacteria are of a
single layer, whereas the Gram-negative cell wall is a multilayered structure, and the yeast
cell wall is quite complex. Some C. albicans species have shown resistance to antifungal
drugs [86].
3
.12. DNA-Schiff base interaction studies
The potential binding ability of the Schiff base to CT-DNA was characterized by UV
spectroscopy. The absorption spectra of Schiff base in the absence and presence of CT-DNA
at different concentrations are given in Fig. 13. The absorption peaks at 278 nm and 310 nm
are attributed to intraligand π–π* transition. With the concentration of CT-DNA increased,
hyperchromism of 86.9%-133.5% and higher wavelength of 1-19 nm are observed at 278 nm,
while hypochromism of 1.0%–46.0% and red shift of 1 nm are observed at 310 nm. In
addition, the maximum absorption shifted to red indicates a decrease in energy between the
HOMO and LUMO. This explains the interaction of DNA with a Schiff base [87]. Once the

DNA interacts with the Schiff base, π-π* transition energy decreases, and the absorption shifts
to red. Hypochromism, hyperchromism and bathochromism in UV absorption spectra,
probably due to stacking interaction between an aromatic ring and the base pairs of DNA,
suggest the Schiff base can interact with CT-DNA [27, 88, 89]. The extent of the
hypochromism and hyperchromism are commonly consistent with the strength of intercalative
and electrostatic interaction [27, 88, 89]. Surprisingly, the compound has both intercalative
and electrostatic binding. Possible mechanisms are shown in Scheme 2 and 3. The Schiff base
enters between the two amino acid molecules of the DNA in the intercalative binding
(Scheme 2). In the electrostatic binding (Scheme 3), DNA breaks protons from the more
acidic Schiff base. As a result, the negative charge distribution is changed in the DNA chain.
Therefore, this leads to disruption of the DNA molecule.
3
.13. Colorimetric anion-sensing
The binding ability of the sensor compound was firstly studied using UV–Vis spectral
titrations in DMSO. Figure 14 shows spectral changes of the Schiff base in the absence and
presence of hydroxy, fluoride, cyanide and acetate ions in DMSO solution. Upon the addition
-
-
-
-
of 3 equiv of each anion, only OH , F , CN and AcO induced distinct spectral changes while
the other anions did not induce any spectral changes (Fig. 14). As a result, the solution color
-
-
of the compound changed from colorless to purple only with CN and to orange with F and
-
-
AcO , and to yellow with OH with a fast response time, indicating that the receptor Schiff
-
-
-
-
base ligand can serve as a “naked-eye” indicator for F , CN , AcO and OH in DMSO (Fig.
1
5).
The free Schiff base ligand shows absorption in the range less than 400 nm in DMSO.
-
-
-
-
The presence of OH , F , CN and AcO resulted in absorbance bands greater than 400 nm
decreasing gradually and new absorbance bands appeared at 435, 416, 416 and 422 nm,
respectively. The excited-state intramolecular proton transfer [29-37] between hydroxy (-OH)

and nitrogen atom of imine (-C=N-) groups was inhibited and as a result, the emission band
greater than 400 nm resulting from excited-state intramolecular proton transfer disappeared,
inducing colorimetric changes to the compound. The high selectivity of the compound for
hydroxy and fluoride may be due to the nucleophilicity of hydroxy and fluoride in DMSO.
-
-
The order of selectivity or the binding affinity of anions for the Schiff base ligand is OH >F
-
-
-
-
-
-
-
-
-
>
CN >AcO >>H PO ~Br ~I ~SCN ~ClO ~HSO ~N . The more acidic hydroxyl proton
2 4 4 4 3
-
-
-
would deprotonate upon exposure to more basic OH , F and AcO ions and therefore, the
intramolecular proton transfer occurs to the keto-amine form [90] (Scheme 4). In contrast,
-
-
-
cyanide has much weaker hydrogen bonding ability in comparison with OH , F and AcO
with stronger nucleophilicity toward the imine group, which results in the addition reaction of
-
CN to the carbon atom of an electron deficient imine group and, subsequently, fast proton
transfer of the phenol hydrogen to the neighboring nitrogen anion through an intramolecular
hydrogen bond [91] (Scheme 5). The formation of the keto-amine form of the compound
leads to higher wavelength absorption. The presence of other anions tested without similar
-
-
-
-
-
-
-
-
-
-
-
basicity as OH , F , CN and AcO , such as Br , I , SCN , ClO , HSO , H PO and N , do not
4
4
2
4
3
exhibit similar absorption.
1
3
.14. H-NMR spectral titrations
1
H NMR titrations were carried out in DMSO-d (Fig. 16a, 16b, 16c). As can seen be
6
in Fig. 16a, the free compound showed one peak at 12.25 ppm, which could be ascribed to -
OH proton. When fluoride ions are mixed (0.5 equv.), the -OH peak intensity decreases
(Fig.16b). When fluoride ions were introduced (1.0 equv.), the signal at 12.25 ppm
disappeared (Fig.16c), indicating the -OH moiety of the compound acted as anion binding site
and exhibited deprotonation upon interacting with strong basic anions. Therefore, the
significant higher wavelength shifts in absorption and color changes resulted from

1
deprotonation of the anion binding sites [92]. Likewise, the H NMR titrations of the
-
compound with F also support the results obtained from the UV-Vis titrations.
4
. Conclusions
E)-2-[(3,5-bis(trifluoromethyl)phenylimino)methyl]phenol
(
(C H F NO)
was
1
5
7 6
synthesized and characterized by spectroscopic method and X-ray single crystal diffraction. In
addition, density functional modelling studies of the Schiff base ligand were reported in this
study. Theoretical calculations were employed to determine the molecular structure,
spectroscopic values, HOMOs, LUMOs levels of the compound. The theoretical calculations
were found to be in good agreement with the experimental data. However, the DFT method
seems to be more convenient than the HF method to calculate the bond angles and geometry
of the investigated compound. In the compound, the X-ray single crystallographic study,
NMR, FT-IR and DFT calculations revealed that the compound exists in the enol-imine form,
…
which is mainly stabilized by the intramolecular O–H N interactions. In addition to
investigating the tautomeric stability of the compound, as seen from the calculations, the total
energy of the enol form is lower than the keto-amine form which also reveals that the enol-
imine tautomer is favored over the keto-amine tautomer. The total molecular energies
obtained by the PCM method decrease with increasing polarity of the solvent and the stability
of the compound increases in going from the gas phase to the solution phase. The MEP map
shows that the negative potential sites are on electronegative atoms while positive potential
sites are around the hydrogen atoms. These sites give intra and intermolecular interactions. In
the compound, the weak negative region associated with N1 atom and also the weak positive
…
region of the nearby H1 atom are indicative of intramolecular (O1–H1 N1) hydrogen
bonding. According to the calculated Mulliken atomic charges, the imine N1 atom has a large
positive atomic charge and the hydroxyl O1 atom has a large negative atomic charge in the
…
gas phase. This behavior may be the result of the N1 – H O1 hydrogen bond. On the other

hand, the negative atomic charge values of the O atoms in the solution phase become more
negative while the positive atomic charge of N1 decreases with the increase in the polarity of
the solvent. The ab initio B3LYP calculations allow a more accurate prediction of the NLO
activity for the compound. Our computational results yield that βtot for the compound is
greater than that of urea. The calculated values of β of the investigated compound are also
tot
compared with the similar Schiff base compounds in the literature. So, the investigated
compound is a good candidate as second-order NLO material. The thermodynamic properties,
ꢭ
ꢭ
ꢭ
of ꢫ , ꢮ , ꢯ and temperatures T were also obtained. The results show that the standard
ꢄꢔꢬ
ꢬ
ꢬ
thermodynamic functions increase at any temperature from 200 to 450 K, because the
intensity of the molecular vibrations increase with increasing temperature.
The compound could act as real-time colorimetric sensor for anions. However, in this
study, the compound was active against both types of bacteria and as well as active against
yeasts, which may indicate broad-spectrum properties. DNA was affected in two ways by the
compound. Electrostatic interaction was found to be very strong according to intercalative
interaction.
We hope that the synthesis, crystallographic and spectroscopic characterization, DNA
binding, anion sensing and DFT studies of the Schiff base (E)-2-[(3,5-
bis(trifluoromethyl)phenylimino)methyl]phenol (C H F NO) will be helpful for the design
15
7 6
and synthesis of new materials.
Acknowledgements
Çanakkale Onsekiz Mart University Grants Commission
for a research grant (Project No. : FDK-2015-307).
Appendix A. Supplementary material

Supplementary data associated with this article can be found, in the online version, at
http://dx.doi.org/
References
[
1] K. Mounika, B. Anupama, J. Pragathi, C. Gyanakumari, J. Sci. Res. 3 (2010) 513-
24.
5
[
[
[
2] P. Venkatesh, Asian J. Pharma. Health Sci. 1 (2011) 8-11.
3] M. Yıldız, B. Dülger, S.Y. Koyuncu, B.M. Yapıcı, J. Ind. Chem. Soc. 81(2004) 7-12.
4] H. Ünver, M. Yıldız, B. Dülger, Ö. Özgen, E. Kendi, T.N. Durlu, J. Mol. Struct. 737
(2005) 159-164.
[
5] M. Yıldız, H. Ünver, B. Dülger, D. Erdener, N. Ocak, A. Erdönmez, T.N. Durlu, J.
Mol. Struct. 738 (2005) 253-260.
[
[
[
[
6] M. Yıldız, B. Dülger, A. Çınar, J. Ind. Chem. Soc. 82 (2005) 414-420.
7] M. Yıldız, A. Kiraz, B. Dülger, J. Serb. Chem. 72, 3 (2007) 215-224.
8] A. Kiraz, M. Yıldız, B. Dülger, Asian J. Chem. 21, 6 (2009) 4495-4507.
9]
S.M. Sondhi, N. Singh, A. Kumar, O. Lozach, L. Meijer, Bioorg. Med. Chem.
4,11 (2006) 3758-3765.
1
[
[
10] A. Budakoti, M. Abid, A. Azam, Eur. J. Med. Chem. 41(2006) 63-70.
11] A. Pandey, D. Dewangan, S. Verma, A. Mishra, R. D. Dubey, Int. J. Chem. Tech.
Res. 3 (2011) 178-184.
[
12] C. Chandramouli, M.R. Shivanand, T.B. Nayanbhai, B. Bheemachari, R.H. Udupi, J.
Chem. Pharm. Res. 4, 2 (2012) 1151-1159.
[
[
13] R.P. Chinnasamy, R. Sundararajan, S. Govindaraj, J. Advan. Pharm. Techno. Res. 1,
3
(2010) 342-347.
14] A.K. Chaubey, S.N. Pandeya, Int. J. Phar.Tech. Research. 4 (4) 590 (2012)

[
15]
T. Aboul-Fadl, F.A. Mohammed, E.A. Hassan, Arch. Phar. Res. 26, 10 (2003) 778-
84.
7
[
[
16] R. Miri, N. Razzaghi-asl, M.K. Mohammadi, J. Mol. Model. 19, 2 (2013) 727-735.
17] S.M.M. Ali, M.A.K. Azad, M. Jesmin, S. Ahsan, M.M. Rahman, J.A. Khanam, M.N.
Islam, S.M.S. Shahriar, Asian Pacif. J. Trop. Biomed. 2, 6 (2012) 438-442.
18] D. Wei, N. Li, G. Lu, K. Yao, Sci. China B. 49, 3 (2006) 225-229.
19] P.G. Avaji, C.H.V. Kumar, S.A. Patil, K.N. Shivananda, C. Nagaraju, Eur. J. Med.
Chem. 44, 9 (2009) 3552-3559.
[
[
[
[
[
[
20] P.G. Cozzi, Chem. Soc. Rev. (2004) 410-421.
21] S. Chandra, J. Sangeetika, J. Indian Chem. Soc. 81, (2004) 203-206.
22] Z.H. Chohan, M. Praveen, A. Ghaffar, Met. Based Drugs. 4, 5 (1997) 267-272.
23] Z.H. Chohan, M. Arif, Z. Shafiq, M. Yaqub, C.T. Supuran, J. Enzyme Inhib. Med.
Chem. 21 (2006) 95-103.
[
[
[
[
24] Y.P. Wang, Y.N. Xiao, C.X. Zhang, R.M. Wang, J. Macromol. Sci. Part A, 38
(2001) 1099-1104.
25] M.M. Ali, M. Jesmin, M.K. Sarker, M.S. Salahuddin, M.R. Habib, J.A. Khanam, Int.
J. Biol. Chem. Sci. 2 (2008) 292-298.
26] B.S. Molla, B.S. Rao, K. Shridhara, P.M. Akberali, Farmacology. 55 (2000) 338-
3
44.
27]
X. Qiao, Z.Y. Ma, C.Z. Xie, F. Xue, Y.W. Zhang, J.Y. Xu, Z.Y. Qiang, J.S. Lou,
G.J. Chen, S.P. Yan, J. Inorg. Biochem. 105 (2011) 728-737.
[
[
28] P. de Hoog, M.J. Louwerse, P. Gamez, M. Pitié, E.J. Baerends, B. Meunier, J.
Reedijk, Eur. J. Inorg. Chem. (2008) 612-619.
29] S. Roy, P.U. Maheswari, M. Lutz, A.L. Spek, H. Dulk, S. Barends, G.P. van Wezel,

F.Hartl, J. Reedijk, Dalton Trans. (2009) 10846-10860.
[
[
30] S. Dalapati, S. Jana, N. Guchhait, Spect. Acta Part A: Mol. Biomol. Spect.129 (2014)
4
99-508.
31] K.S. Saravana, B. Shilpa, K.S. Suban, S.K.A. Kumar, J. Fluorine Chem. 164 (2014)
1-57.
5
[
[
[
[
[
32] D. Sharma, S.K. Ashok Kumar, S.K. Sahoo, Tetrahedron Lett. 55, 4 (2014) 927-930.
33] X. Huang, Y. He, Z. Chen, C. Hu, Chin. J. Chem. 27 (2009) 1526-1530.
34] R. Arabahmadia, S. Amania, Supramol. Chem. 26 (2014) 321-328.
35] Y. Li, H. Lin, Z. Cai, H. Lin, Mini-Rev. In Organic Chem. 8 (2011) 25-30.
36] Y.M. Hijji, B. Bararea, A.P. Kennedy, R. Butcherb, Sensors and Actuators B. 136
(
2009) 297-302.
37] S. Devaraj, D. Saravanakumar, M. Kandaswamy, Tetrahedron Lett. 48, 17 (2007)
077-3081.
[
3
[
[
38] M. Yıldız, Z. Kılıç, T. Hökelek, J. Mol. Struct. 441(1998) 1-10.
39] H. Nazır, M. Yıldız, H. Yılmaz, M.N. Tahir, D. Ülkü, J. Mol. Struct. 524 (2000) 241-
2
50.
40] M. Yıldız, H. Ünver, D. Erdener, A. Kiraz, N.O. İskeleli, J. Mol. Struct. 919 (2009)
27-234.
[
2
[
[
41] H. Ünver , M. Yıldız, Spect. Lett. 43 (2010) 114-121.
42] H. Ünver, M. Yıldız, H. Özay, T.N. Durlu, Spectrochim. Acta Part A. 74 (2009)
1
095-1099.
[
[
43] H. Özay, M. Yıldız, H. Ünver, N.O. İskeleli, Synt. React. Inorg., Met-Org., and
Nano-Met.Chem. 42, 6 (2012) 872-877.
44] H. Ünver, M. Yıldız, A. Kiraz, N. Ocak, A. Erdönmez, B. Dülger, T.N. Durlu, J.
Chem. Crystallogr. 36, 3 (2006) 229-237.