Synthesis, characterization, crystal structure and theoretical approach of (E)-2-[(3-carboxylphenylimino)methylene]phenoxyacetic acid

Article abstract of DOI:10.1016/j.molstruc.2012.10.028

The title compound, (E)-2-[(3-carboxylphenylimino)methyl]phenoxyacetic acid (C₁₆H₁₃NO₅), had been synthesized and characterized by FT-IR, UV-vis spectrum, fluorescence spectrum, elemental analysis, electrochemistry and sin

Full text of DOI:10.1016/j.molstruc.2012.10.028

Journal of Molecular Structure 1032 (2013) 246–253
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization, crystal structure and theoretical approach of
(E)-2-[(3-carboxylphenylimino)methylene]phenoxyacetic acid
c,
Shi-Liang Chen a,b, Zheng Liu a, , Guo-Cheng Han
⇑
⇑
a College of Chemical and Biological Engineering, Guilin University of Technology, Guilin 541004, PR China
b Shaanxi Xianyang Chemical Industrial Co. Ltd., Xianyang 712000, PR China
c School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004, PR China
h i g h l i g h t s
"
"
"
"
"
Aromatic carboxylic acid compound had been synthesized and characterized.
Part of crystal structure of compound shown formation of centrosymmetric R22ð8Þ dimer.
Compound engendered strong fluorescence emission in purple region.
Redox action of compound is very difficult.
DFT calculation results are good agreed with experimental data.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 22 April 2012
Received in revised form 8 October 2012
Accepted 9 October 2012
Available online 17 October 2012
The title compound, (E)-2-[(3-carboxylphenylimino)methyl]phenoxyacetic acid (C16H13NO5), had been
synthesized and characterized by FT-IR, UV–vis spectrum, fluorescence spectrum, elemental analysis,
electrochemistry and single crystal X-ray diffraction techniques. Crystallographic analysis show that
non-covalent CAHꢀ ꢀ ꢀCg and inter-molecular hydrogen bonding interactions assemble the 3D network
structure of the title compound. Moreover, the vibrational frequencies of the title compound in the
ground state had been calculated using the Hartree–Fock (HF) and density functional methods (B3LYP)
with 6-31Gꢁ and 6-31+G(d) basis set, respectively. The results of the calculational optimized molecular
structure, absorption spectra and fluorescence emission are exhibited and compared with the experimen-
tal results of X-ray diffraction, UV–vis spectrum and fluorescence spectrum, respectively. In addition,
frontier molecular orbitals (FMOs), mulliken charges, wiberg bond index and molecular electrostatic
potential (MEP) were executed by the RB3LYP/6-31+G(d) method.
Keywords:
Schiff bases
Crystal structure
Fluorescence property
Electrochemical property
Vibrational assignment
DFT calculations
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
chemistry and biochemistry [10,11]. Numerous reports on metal-
organic frameworks based on Schiff base ligands have been re-
Schiff bases and aromatic carboxyl derivatives had been exten-
sively investigated in the past decades, because they own proper-
ties of strong metals chelateing tendency, plant growth
regulating activity, photochemistry and their vital role in photopo-
lymerization activity [1–7]. Many of these compounds possess bio-
chemical and pharmacological properties, especially their
antimicrobial, anti-tumor and anti-inflammatory activity, which
may afford them potential as therapeutic agents and make them
very useful [8,9]. In addition, they are widely used as ligands in
the field of coordination chemistry as well as in diverse fields of
ported [12,13]. In recent years, density functional theory (DFT)
has been a shooting star in theoretical modelling. The development
of better and better exchange-correlation functional made it possi-
ble to calculate many molecular properties with comparable accu-
racies to traditional correlated abinitio methods [14].
In this study, the crystal structure of (E)-2-[(3-carboxylphenyli-
mino)methyl]-phenoxyacetic acid was determined by single crys-
tal X-ray diffraction technique and characterized by FT-IR,
fluorescence spectrum and UV–vis spectrum. In order to get more
insight on stability and its activity areas, the computational studies
at DFT and HF levels were carried out. The excitation energies were
obtained using DFT calculations starting from optimized geometry.
We hope our work will be helpful for the further studies on their
potential applications.
⇑
Corresponding authors. Tel.: +86 773 5896453 (Z. Liu), tel.: +86 773 2291002
(G.-C. Han).
E-mail addresses: lisa4.6@163.com (Z. Liu), hangc81@guet.edu.cn (G.-C. Han).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.10.028

S.-L. Chen et al. / Journal of Molecular Structure 1032 (2013) 246–253
247
Table 1
2. Experimental
Crystal data and structure refinement for 1.
2.1. Materials and physical measurements
CCDC reference no.
821265
16H13NO5
299.27
293(2)
0.71073
Triclinic
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
C
The reagents were commercially available and were used with-
out further purification for the synthesis. Carbon, Hydrogen and
Nitrogen were estimated micro-analytically by Vario ELI elemen-
tal instrument. FT-IR spectrum of the title compound was recorded
on a Shimadzu FTIR-8400 spectrometer in KBr disk. Elemental
analyses for carbon, hydrogen and nitrogen were performed by a
Vario ELI elemental instrument. The FT-IR spectra were recorded
in the range of 4000–400 cmꢂ1 using KBr pellets on a Shimadzu
FT-IR-8400 spectrophotometer. UV–vis spectra were recorded in
N,N-dimethylformamide solution using GBC UV–vis spectropho-
tometer. The emission/excitation spectra were measured on a Hit-
achi RF-5301 fluorescence spectrophotometer. The electron
transfer behavior of the complex was examined using cyclic vol-
tammogram on a CHI-860D electrochemical analysis system by a
three-electrode cell at room temperature. A glass carbon (GC)
working (3 mm in diameter), a saturated calomel electrode (SCE)
as reference electrode and a platinum wire electrode as auxiliary
electrode.
P ꢂ 1
Unit cell dimensions
(Å, °)
a = 8.0822(8), b = 9.4699(11), c = 0.3581(15)
a
= 67.1770(10), b = 82.465(2), c = 5.8130(10)
Volume (Å3)
707.85(15)
2
1.404
Z
Density (calculated)
(Mg/m3)
Absorption coefficient
0.106
(mmꢂ1
)
F(000)
312
Crystal form, color
Crystal size (mm)
h range for data
collection (°)
Index ranges
Reflections collected
Independent reflections
Block, yellow
0.31 ꢃ 0.28 ꢃ 0.14
2.39–25.02
ꢂ9 6 h 6 8 , ꢂ10 6 k 6 11, ꢂ12 6 l 6 12
3731
2461 (0.0368)
(Rint
)
Refinement method
Data/restraints/
parameters
Full-matrix least-squares on F2
2461/2/201
2.2. Preparation of the title compound
Goodness-of-fit on F2
1.203
Final R indices [I > 2
R indices (all data)
Weighting scheme
r
(I)] R1 = 0.0814, wR2 = 0.1918
R1 = 0.1262, wR2 = 0.2103
2.2.1. Synthesis of the o-formylphenoxyacetic acid
The o-formylphenoxyacetic acid had been obtained by reaction
of salicylaldehyde and chloroactic acid according to the literature
preparation [15], m.p.: 131–133 °C, which is accordant for litera-
ture values.
Calc. w = 1/[r2ðFo2Þ + (0.047 9P)2 + 1.178 1P]
where P ¼ ðF2o þ 2Fc2Þ=3
0.254 and ꢂ0.238
Largest diff. peak and
hole (e Åꢂ3
)
2.2.2. Synthesis of the title compound
A solution of o-formylphenoxyacetic acid (0.90 g, 5 mmol) in
methanol (20 mL) was added dropwise with stirring at room tem-
perature to a solution of 3-formylbenzoic acid (0.69 g, 5 mmol) in
methanol (15 mL). The mixture was refluxed with stirred for 3 h
at 70 °C until yellowish precipitate was formed. The precipitate
was collected by filtration and washed with ethanol (Scheme 1).
At the same time, the production was desiccated in the loft drier
(yield: 30%, m.p.: 220–222 °C). The single crystal of the complex,
suitable for X-ray diffraction study was cultured from the filtered
reaction solution by a slow evaporation method at room tempera-
ture for 2 weeks.
2.3. X-ray crystal structure determination
good block single crystal suitable with dimensions
A
0.31 ꢃ 0.28 ꢃ 0.14 mm was mounted on goniometer and data col-
lection was performed on a CCD area detector diffractometer by
the
u
and
x scan technique using graphite-monochromatic Mo
Ka radiation (k = 0.71073 Å) at 293(2) K. In the range of
2.39° 6 h 6 25.02°, reflections were 3731 collected including
2461 unique ones (Rint = 0.0368), of which were observed with
I > 2r(I) (1533 observed reflections). The structures were solved
by direct methods with SHELXS-97 [16], and non-hydrogen atoms
were refined anisotropically by full-matrix least-squares on F2
using the SHELXTL-97 [17] program. H atoms on O atoms were lo-
cated in a difference Fourier map and refined freely. H atoms at-
tached to C atoms were refined as riding on their parent C atoms.
Crystal data and refinement parameters are listed in Table 1 and
selected bond length, angles and torsion angles are reported in
Table 2.
Anal. Calcd. for C16H13NO5: C 64.21, H 4.38, N 4.68%. Found: C
64.25, H 4.41, N 4.63%.
O
H2
O
C
C
OH
H2N
+
i
CHO
2.4. Computational methods
O
The starting atomic coordinates were taken from the final X-ray
refinement cycle. The geometry optimizations were performed at
the RB3LYP/6-31+G(d) and RHF/6-31Gꢁ levels with the Gaussian
03 W program package [18,19]. The vibrational analysis has been
performed to convince that all normal mode frequencies are real
and non-negative and the calculated structures are stable. The
Mulliken charge analysis, Frontier molecular orbitals (FMOs),
molecular electrostatic potential (MEP) [20] were performed at
the RB3LYP/6-31+G(d) levels, respectively. For the calculations of
the wiberg bond index, the same levels of theory RB3LYP/
HO
O
H2
C
C
O
OH
O
OH
C
H
N
Scheme 1. The reaction process of the title compound 1. (i): CH3OH reflux 3 h.

248
S.-L. Chen et al. / Journal of Molecular Structure 1032 (2013) 246–253
6-31+G(d) and RHF/6-31Gꢁ, were used. The experimental and the-
oretical results are presented in Tables 2 and 4. No constraints to
bonds, angles or dihedral angles were applied in the calculations
and all atoms were free to optimize.
Table 2
The experimental and optimized bond lengths (Å) , angles (°) and torsion angles (°) for
compound.
Bond lengths
Experimental Calculated
RB3LYP/6-
31+G(d)
RHF/6-
31Gꢁ
3. Results and discussion
N(1)AC(8)
N(1)AC(4)
O(1)AC(1)
O(2)AC(1)
O(3)AC(10)
O(3)AC(16)
O(4)AC(15)
O(5)AC(15)
C(1)AC(2)
C(2)AC(3)
1.289(6)
1.426(6)
1.246(5)
1.287(5)
1.374(5)
1.421(5)
1.328(5)
1.186(5)
1.488(7)
1.391(6)
1.2843
1.4063
1.2173
1.3602
1.3700
1.4066
1.357
1.2055
1.4868
1.4018
1.2577
1.407
1.1907
1.3303
1.3523
1.385
1.3299
1.181
3.1. Crystal structure
The X-ray structural determination at 293(2) K of the title com-
pound, confirms the assignment of its structure from spectroscopic
data. The molecular structure of the title compound is shown in
Fig. 1, in which displacement ellipsoids are drawn at the 30% prob-
ability level and the formation of centrosymmetric R dimer of the
title compound is shown in Fig. 2, the perspective view of the crys-
tal packing is shown in Fig. S1. Selected bonds lengths, angles and
torsion angles are listed in Table 2. Table 3 presents bond lengths
and angles of the hydrogen bonds. All of the bond lengths and bond
angles in phenyl rings are in the normal range. The distances (CAX,
X = O, C, N) are closer than these the reported works [21–24].
Although in one molecule, the two phenyl rings are not coplanar
with the dihedral angle of 29.5°, which are imposed from the in-
tra-molecular biggish repulsion. In the crystal lattice, there are
two potentially intermolecular interactions (OAHꢀ ꢀ ꢀY, Y = O, N),
details of which are given in Table 3 and Fig. 2. The intermolecular
complementary O2AH2ꢀ ꢀ ꢀO1 hydrogen bonds form centrosym-
metric dimmers, and generating R22ð8Þ supra-molecular synthon
[25] (Fig. 2). O2A atom in the molecule at (x, y, z) and O2B atom
in the molecule at (2 ꢂ x, 1 ꢂ y, 2 ꢂ z) act as donors to O1B atom
in the molecule at (2 ꢂ x, 1 ꢂ y, 2 ꢂ z) and O1A atoms in the mol-
ecule at (x, y, z), respectively. The distance of Cꢀ ꢀ ꢀO is changed from
3.18 to 3.42 Å and the C–Hꢀ ꢀ ꢀO angle is changed from 118° to 144°
(Table 3, Fig. 2 and Fig. S1). It is very closer than expected for
charge assisted C ꢂ Hꢀ ꢀ ꢀCg (edge to face) intermolecular interac-
tions (Table 3 and Fig. S1) [24]. The compound was further formed
a 3-D network through intermolecular interactions (Fig. S1).
1.4876
1.3903
Bond angles
C(8)AN(1)AC(4)
C(10)AO(3)AC(16)
O(1)AC(1)AO(2)
C(7)AC(2)AC(3)
C(3)AC(4)AN(1)
C(5)AC(4)AN(1)
N(1)AC(8)AC(9)
O(3)AC(10)AC(11)
O(3)AC(10)AC(9)
O(5)AC(15)AO(4)
O(5)AC(15)AC(16)
O(4)AC(15)AC(16)
O(3)AC(16)AC(15)
117.8(4)
119.7769
119.1282
121.6108
120.3467
123.1786
117.7953
121.6591
123.6839
115.8212
123.8978
126.872
119.9002
120.6502
121.7831
120.5085
123.346
117.6059
121.4163
123.6189
115.9049
123.8079
126.6267
109.5652
108.199
117.2(3)
122.7(5)
120.1(5)
122.4(4)
118.5(4)
124.3(4)
123.7(4)
116.2(4)
125.8(5)
126.3(4)
107.9(4)
109.4(4)
109.2301
108.2571
Torsion angles
O(1)AC(1)AC(2)AC(7)
O(2)AC(1)AC(2)AC(7)
C(2)AC(3)AC(4)AN(1)
C(8)AN(1)AC(4)AC(3)
C(8)AN(1)AC(4)AC(5)
C(4)AN(1)AC(8)AC(9)
C(10)AO(3)AC(16)AC(15)
O(4)AC(15)AC(16)AO(3)
ꢂ2.3(7)
177.5(5)
ꢂ178.7(4)
ꢂ43.3(7)
139.6(5)
177.3(4)
168.6(4)
176.2(4)
ꢂ2.096
177.9291
ꢂ178.3811
ꢂ40.3866
142.7538
176.8407
179.8806
179.4352
1.8127
178.1643
ꢂ178.9631
41.9592
140.706
178.66
179.7091
179.3484
Fig. 1. The molecular structure of the title compound 1.

S.-L. Chen et al. / Journal of Molecular Structure 1032 (2013) 246–253
249
Fig. 2. Part of the crystal structure of the title molecule, showing the formation of centrosymmetric R22ð8Þ dimer. Part atoms were omitted, the hydrogen bonds are indicated
by dotted lines.
Table 3
Hydrogen bonding of 1 (Å, °).
Table 4
Comparison of experimental and theoretically predicted IR frequencies.
DAHꢀ ꢀ ꢀA
d(DAH) d(Hꢀ ꢀ ꢀA)
<DHA
174
d(Dꢀ ꢀ ꢀA)
Symmetry
codes
Assignment
Experimental
frequency
Calculated frequency
O2AH2ꢀ ꢀ ꢀO1(i)
0.86
1.77
2.63
(i): 2 ꢂ x,
1 ꢂ y,
RB3LYP/6-
31+G(d)
RHF/6-
31Gꢁ
2 ꢂ z
OAH str.
3431
3079
2918
1760
3206
3066
3026
1789
3267
3087
3036
1789
O4AH4ꢀ ꢀ ꢀN1(ii)
C3AH3ꢀ ꢀ ꢀO4(iii)
0.86
0.93
1.92
2.62
160
144
2.75
3.41
(ii): x,
CAH asym-str.
CAH sym. str.
C@O str. + OAH
rock.
y + 1, z
(iii): 1 ꢂ x,
2 ꢂ y,
1 ꢂ z
C@O str.
C@N str.
CAC str.
C@C str.
CAH bend.
CAH rock.
OAH rock. + CAC
str.
1678
1605
1582
1542
1487
1431
1380
1689
1629
1627
1534
1494
1423
1376
1672
1624
1587
1548
1521
1441
1375
C5AH5ꢀ ꢀ ꢀO5(iv)
C7AH7ꢀ ꢀ ꢀO5(v)
0.93
0.93
2.89
2.55
118
125
3.42
3.18
(iv): x,
ꢂ1 + y, z
(v): 1 ꢂ x,
1 ꢂ y,
2 ꢂ z
C14AH14ꢀ ꢀ ꢀO4(iv)
0.93
2.42
2.80
141
122
3.19
3.41
C16AH16Bꢀ ꢀ ꢀO5(iii) 0.97
OAH rock.
CAO str.
Ring (phenyl)
breath
1225
1070
919
1221
1094
926
1227
1091
924
DAHꢀ ꢀ ꢀA
d(DAH) d(Hꢀ ꢀ ꢀCg) <DHCg d(Dꢀ ꢀ ꢀCg) Symmetry
codes
C16AH16Aꢀ ꢀ ꢀCg(vi) 0.97
2.92
128
3.59
Cg: C9/
C10/C11/
C12/C13/
C14 ring,
(vi): ꢂx,
2 ꢂ y,
OCO bend
757
776
764
1 ꢂ z
3.3. Fluorescence spectrum
Photoluminescent measurements of the title compound were
carried out in N,N-dimethyl formamide solution with concentra-
tion of 5.0 ꢃ 10ꢂ5 M at room temperature. The compound DFT cal-
culations were started from optimized geometry using the B3LYP/
6-31+G(d) level of theory and were performed for gas phase to cal-
culate excitation energies. The photoluminescent spectrum of the
title compound is depicted in Fig. 3. It can be seen that the intense
purple fluorescence emission at 409 nm from HOMO to LUMO
(kex = 344 nm) and a moderate intensity luminescence with emis-
sion maximum at 409 nm (kex = 275 nm) and may be attributable
3.2. UV–vis spectrum
The UV–vis spectra of the compound were measured in
N,N-dimethyl formamide solution with concentration of 1.0 ꢃ
10ꢂ4 M (1 M = 1 mol Lꢂ1). The computation of UV–vis was pro-
cessed using the density functional theory (DFT) method at the
B3LYP and 6-31+G(d) basis set in Gaussian 03 W software pack-
age. The sharp and strong high-energy absorption bands at
321 nm are assigned as n–pꢁ transition from HOMOꢂ1 ? LUMO
of the C@N group [26].
to
344 nm rise from HOMOꢂ1 to LUMO transitions. The emission in
p–
p⁄ transitions [27]. The value of excitation energy at

250
S.-L. Chen et al. / Journal of Molecular Structure 1032 (2013) 246–253
Fig. 3. The fluorescence of compound.
Fig. 5. Correlation graphics of calculated and experimental frequencies of the title
compound.
Fig. 4. Cyclic voltammogram of 1.0 ꢃ 10ꢂ4 M compound 1.
on the molecules in the solid state. In solid state, the existence of
the crystal field along with the intermolecular interactions have
connected the molecules together, which result in the differences
of bond parameters between the calculated and experimental val-
ues [28]. However, in general, the predicted bond lengths, angles
and torsion angles are still in agreement with the values based
upon the X-ray crystal structure data, which indicates that calcu-
lated geometric parameters were reasonable highly and they are
the bases for calculating other parameters, such as Mulliken charge
analysis, Wiberg bond index analysis and frontier molecular orbi-
tals (FMOs), molecular electrostatic potential (MEP), as we de-
scribed below.
the ultraviolet region indicates that compound appears to be good
candidate for promising purple-light emitting material.
3.4. Electrochemistry
Fig. 4 depicts the cyclic voltammogram of the title compound in
N,N-dimethyl formamide solution containing of 0.1 M tetrabutyl-
ammonium bromide at scan rate 0.03 V sꢂ1
. The oxidation-
reduction peaks vest in the conductive medium redox reaction.
The anodic peak and cathodic peak of the title compound are not
mutativer more feckly than the blank, indicates that the electro-
chemical behavior of the title compound on the glass carbon
electrode is very stable, and which oxidation–reduction reaction
is difficult. This is consistent with the frontier molecular orbitals
analysis results.
3.6. Vibrational frequency
Some primary experimental IR data and calculated frequencies
are listed in Table 4. The descriptions concerning the assignment
[24] have also been indicated in the Table 4. To make comparison
with experiment, we present correlation graphics in Fig. 5 based on
the calculations. As we can see from correlation graphic in Fig. 5,
experimental fundamentals are agreement with the scaled funda-
mentals. As a result, the predicted harmonic vibration frequencies
and the experimental data are very similar to each other. In a word,
the scaled frequencies of the DFT and HF calculations are close to
the corresponding FT-IR vibration data and on the whole the
RB3LYP/6-31+G(d) and RHF/6-31Gꢁ levels can predict the vibra-
tional frequencies for the system studied here.
3.5. Geometry optimization
The optimized parameters of the title compound (bond lengths
and angles, and dihedral angles) by RB3LYP/6-31+G(d) and RHF/
6-31Gꢁ methods are listed in Table 2 and compared with the exper-
imental crystal structure for the title compound.
Most of the optimized bond lengths, bond angles and torsion
angles are slightly longer than the experimental values, because
the theoretical calculations are based on the isolated molecules
in the gaseous phase, while the experimental results are based

S.-L. Chen et al. / Journal of Molecular Structure 1032 (2013) 246–253
251
HOMO (-0.22964 a.u.)
HOMO-1 (-0.25066 a.u.)
LUMO (-0.07516 a.u.)
LUMO+1 (-0.05632 a.u.)
Fig. 6. Molecular orbital surfaces and energy levels of 1.
3.7. Frontier molecular orbitals
the title compound. EHOMO is often associated with the electron
donating ability of the molecule. High values of EHOMO are likely
to indicate a tendency of the molecule to donate electrons to
appropriate acceptor molecules with low-energy, empty molecular
orbital. Therefore, the energy of the lowest unoccupied molecular
orbital (ELUMO) indicates the ability of accepting electrons to mole-
cule [30]. The eigenvalues of LUMO and HOMO and their energy
The frontier molecular orbitals play an important role in the
electric and optical properties, as well as in UV–vis spectra, fluores-
cence spectrum and chemical reactions [29]. Fig. 6 shows the dis-
tributions and energy levels of the HOMOꢂ1, HOMO, LUMO and
LUMO+1 1orbitals computed at the RB3LYP/6-31+G(d) level for
Fig. 7. The Mulliken charge population of 1.

252
S.-L. Chen et al. / Journal of Molecular Structure 1032 (2013) 246–253
Table 5
3.8. Mulliken charge analysis
Selected calculate wiberg of the title compound.
Mulliken charge is related to the electronic density and is a very
Wiberg
Bond indexes
useful descriptor in understanding sites for electrophilic attack and
nucleophilic reactions as well as hydrogen bonding interactions
[34–36]. Electric charges in the molecule are obviously responsible
for electrostatic interactions. The local electron densities or
charges are important in many chemical reactions and for phys-
ico-chemical properties of compounds [37]. In order to predict
reactive sites for electrophilic attack for the title compound, Mul-
liken charge was calculated at the RB3LYP/6-31G+(d) level and
shown in Fig. 7. As easily can be seen in Fig. 7, the O atoms and
N atoms take on major negative net charges, so the net charges
of the carboxyl O atoms are more negative than that of the N
atoms, showing the carboxyl are mainly active region. When com-
pounds fall across metal, carboxyl will first provide electronic to
metal atoms form the stable chemical bonds.
RB3LYP/6-31+G(d)
RHF/6-31Gꢁ
WC8N1
WC4N1
WC8C9
WC1C2
WC2C3
WC3C4
WC4C5
WC5C8
WC7C8
WC2C7
WC1O1
WC1O2
WC10O3
WC16O3
1.7629
1.0992
1.0908
1.0197
1.3859
1.3688
1.3528
1.4475
1.4361
1.3698
1.7214
1.0354
0.9982
0.9137
1.8127
1.0434
1.0462
1.0005
1.3858
1.3956
1.3724
1.4480
1.4302
1.3902
1.6886
0.9954
0.9576
0.8963
3.9. Wiberg bond index analysis
Wiberg bond index analysis has been used to evaluate the type
of bands in title compound. Selected wiberg bond index for com-
pound are listed in Table 5. The values of bond order of C4AN1,
C10AO3, C16AO3 and C8AC9 are obviously close 1.0000, respec-
tively, showing these bonds are one-touch. In phenyl ring, the
CAC bonds are typical the conjugate structure. However, the band
C1AO1 and C8AN1 are double-bonds attributed to the bond order
of C1AO1 and C8AN1 are larger than 1.5000, which is consistent
with the conclusion that the shorter the bond length, the larger
the bond order leading to the stronger the bond. Simultaneously,
this result is consistent with the results of the crystallographic data
of compound.
3.10. Molecular electrostatic potential
Molecular electrostatic potential (MEP) is related to the elec-
tronic density and is a very useful descriptor in understanding sites
for electrophilic attack and nucleophilic reactions as well as hydro-
gen bonding interactions [24]. To predict reactive sites for electro-
philic attack for the title compound, MEP was calculated at the
RB3LYP/6-31+G(d) optimized geometry. The negative (red)1 re-
gions of MEP were related to electrophilic reactivity and the positive
(blue) ones to nucleophilic reactivity shown in Fig. 8. As easily can be
seen in Fig. 8, this molecule has four possible sites for electrophilic
attack. The negative regions are mainly over the O1, O2, O5 and
N1 atoms. For the title compound, negative regions were calculated:
the MEP value around O1 is more negative than that of O2, O5 and
N1 atoms. When compounds molecular meet metal atoms, carboxyl
oxygen atoms (O1) provide electric charges more easily to the metal
atoms unfilled and full electronic track the formation of coordination
bonds key. This is consistent with the frontier molecular orbitals
analysis results.
Fig. 8. Molecular electrostatic potential map calculated at RB3LYP/6-31G+(d) level.
gap reflect the coordination ability with the metal of the molecule.
The calculated self-consistent field (SCF) energy of compound is
ꢂ1048.45344801 a.u. and he value of the energy separation be-
tween the HOMO and LUMO is 0.15448 a.u. Contrast to literature
[31–33], compound molecules with smaller
DE and higher EHOMO,
showed that compounds with metal happen more easily into key
reaction. In addition, the eigenvalues of LUMO and HOMO and
their energy gap reflect the biological activity of the molecule.
The decrease in the HOMO and LUMO energy gap explains the
eventual charge transfer interaction taking place within the mole-
cule which is responsible for the bioactivity of the molecule.
4. Conclusion
As can be seen from Fig. 6, the HOMO corresponds to the
tal of the intra-annular double bond; while LUMO+1 corresponds
to the -antibonding type orbital. It is apparent that for both of
these there is some degree of overlap. The HOMO is located
on the two benzene rings and C@N group. The LUMO is located
on the benzene rings of o-formylphenoxyacetic acid and C@N
group. The value of the energy separation between the HOMO
and LUMO is 0.15448 a.u. and this energy gap indicates that the
oxidation-reduction of title compound is stable, which was con-
formed with results of electrochemistry analysis.
p-orbi-
In this study, a detailed analysis of the title compound was
performed according to its crystal structure, theoretical and
experimental FT-IR, fluorescence, and UV–vis absorption. Crystal-
lographic analysis reveals that the non-covalent CAHꢀ ꢀ ꢀCg inter-
molecular interactions and intermolecular hydrogen bonding
interactions form 3D net in the title compound. The geometric
parameters of the title compound obtained using the RB3LYP/
p
p–p
1
For interpretation of color in Fig. 8, the reader is referred to the web version of
this article.

S.-L. Chen et al. / Journal of Molecular Structure 1032 (2013) 246–253
253
6-31+G(d) and HF/6-31Gꢁ methods match well with the X-ray dif-
fraction data. Considering DFT calculations, it can be said that the
experimentally observed excitation energy at 344 nm correspond
to HOMOꢂ1 ? LUMO transitions, and fluorescence emission at
409 nm from HOMO to LUMO transitions. Experimental electronic
absorption bands at 321 nm are assigned as n–pꢁ transition from
HOMOꢂ1?LUMO of the C@N group. Correspondingly, the wiberg
bond index was performed, the calculation results are good agreed
with experimental data. Molecular electrostatic potential (MEP),
where the negative potential located on O1, O2, O5 and N1 atoms
highlights its behavior as a strong proton acceptor regions. The
lowering of the HOMO–LUMO energy gap value has substantial
influence on the intramolecular charge transfer, coordination abil-
ity and bioactivity of the molecule. Furthermore, the electrochem-
ical studies reveal that redox reaction of the title compound is very
difficult in N, N-dimethyl formamide solution.
[10] Ç. Albayrak, B. Kosßar, S. Demir, M. Odabasoglu, O. Buyukgungor, J. Mol. Struct.
963 (2010) 211.
[11] Ç. Albayrak, R. Frank, J. Mol. Struct. 984 (2010) 214.
[12] M.N. Xanthopoulou, S.K. Hadjikakou, N. Hadjiladis, Eur. J. Med. Chem. 43
(2008) 327.
[13] W. Rehman, A. Badshah, M.K. Baloch, Eur. J. Med. Chem. 43 (2008) 2380.
[14] F.D. Proft, P. Geerlings, Chem. Rev. 101 (2001) 1451.
[15] D.W. Emmons, Organic Synthesis, John Wiley and Sons Inc., New York, 1966.
vol. 46.
[16] G.M. Sheldrick, Acta Cryst. A 46 (1990) 467.
[17] G.M. Sheldrick, SHELXL-97™ Program for Crystal Structure Refinement,
University of Göttingen, Germany, 1997.
[18] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[19] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y.
Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S.
Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L.
Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M.
Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J.A.
Pople, Gaussian 03, Revision E.01, Gaussian, Inc., Wallingford CT, 2004.
[20] J.S. Murray, T. Brinck, M.E. Grice, P. Politzer, J. Mol. Struct.: Theochem 256
(1992) 29.
[21] F.H. Allen, O. Kennard, D.G. Watson, L. Brammer, A.G. Orpen, R. Taylor, J. Chem.
Soc. Perkin Trans. 2 (1987) S1.
[22] J. Casanovas, A.M. Namba, S. León, G.L.B. Aquino, J. Org. Chem. 66 (2001) 3775.
[23] J.P. Jasinski, R.J. Butcher, M.T. Swamy, B. Narayana, B.K. Sarojini, H.S.
Yathirajan, J. Chem. Crystallogr. 40 (2010) 25.
[24] S. Demir, M. Dincer, E. Korkusuz, Í. Yıldırım, J. Mol. Struct. 980 (2010) 1.
[25] A. Ghosh, A. Sarkar, P. Mitra, et al., J. Mol. Struct. 980 (2010) 7.
[26] R. Gup, B. Kırkan, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 64 (2006)
809.
[27] S. Naskar, S. Naskar, R.J. Butcher, S.K. Chattopadhyay, Inorg. Chim. Acta 363
(2010) 404.
Acknowledgements
This work was supported by the Key Laboratory of Environmen-
tal Engineering, Protection and Assessment of Guangxi, the
National Water Pollution Control and Management of China (No.
2008ZX07317-02) and Guangxi Natural Science Foundation (No.
2012GXNSFAA053034).
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.molstruc.2012.
10.028.
[28] H. Tanak, Y. Köysal, Y. Ünver, M. Yavuz, Sß. Ißsık, K. Sancak, Struct. Chem. 20
(2009) 409.
References
[29] I. Fleming, Frontier Orbitals and Organic Chemical Reactions, Wiley, London,
1976.
[1] V. Alexander, Chem. Rev. 95 (1995) 273.
[2] M.A. Affan, B.A. Fasihuddin, Y.Z. Liew, S.W. Foo, J. Ismail, J. Sci. Res. 1 (2009)
306.
[30] F. Kandemirli, S. Sagdinc, Corros. Sci. 49 (2007) 2118.
[31] J. Fang, J. Li, J. Mol. Struct.: Theochem 593 (2002) 179.
[32] H. Luo, Y.C. Guan, K.N. Han, Corrosion 54 (1998) 721.
[33] M. Behpour, S.M. Ghoreishi, N. Mohammadi, N. Soltani, M. Salavati-Niasari,
Corros. Sci. 52 (2010) 4046.
[34] N.A. Ogorodnikova, J. Mol. Struct.: Theochem 894 (2009) 41.
[35] F.J. Luque, J.M. López, M. Orozco, Theor. Chem. Acc. 103 (2000) 343.
[36] N. Okulik, A.H. Jubert, Internet Electron. J. Mol. Des. 4 (2005) 17.
[37] G. Gece, Corros. Sci. 50 (2008) 2981.
[3] R. Dinda, P. Sengupta, S. Ghash, T.C.W. Mak, Inorg. Chem. 41 (2002) 1684.
[4] A. Sreekanth, U.L. Kala, C.R. Nayar, M.R.P. Kurup, Polyhedron 23 (2004) 41.
[5] N. Tezer, N. Karakus, J. Mol. Model. 15 (2009) 223.
[6] P.B. Sreeja, M.R.P. Kurup, A. Kishore, C. Jasmin, Polyhedron 23 (2004) 575.
[7] W.P. Jia, J.G. Yang, F. Li, F.Y. Pan, J. Inorg. Chem. 24 (2008) 627.
[8] J.G. Yang, F.Y. Pan, W.P. Jia, F. Li, J. Inorg. Chem. 25 (2009) 2207.
[9] X.Q. Shen, Z.J. Li, H.Y. Zhang, Y.F. Zhou, K. Liu, Q.A. Wu, E. Wang, Thermochim.
Acta 428 (2005) 77.