Structural, proton-transfer, thermodynamic and nonlinear optical studies of (E)-2-((2-hydroxyphenyl)iminiomethyl)phenolate

Article abstract of DOI:10.1016/j.saa.2012.04.094

Recently, the study of imine-bridged organics is interested in proton-transfer and photo-responsive material fields. Herein, we make a investigation on the structural, thermodynamic and nonlinear optical properties of (E)-2-((2-hydroxyphenyl)iminiomethyl)

Full text of DOI:10.1016/j.saa.2012.04.094

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Structural, proton-transfer, thermodynamic and nonlinear optical studies
of (E)-2-((2-hydroxyphenyl)iminiomethyl)phenolate
a,b,c,
⇑
c
b
b
b
Yuxi Sun
, Yufeng Wang , Zengwei Liu , Changliang Huang , Cheng Yu
a
Research Center of New Energy & Materials, Mianyang Normal University, Mianyang 621000, PR China
School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, PR China
Key Laboratory of Education Ministry for Soft Chemistry and Functional Materials, Nanjing University of Science and Technology, Nanjing 210094, PR China
b
c
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
"
"
"
"
"
"
The title compound (HPIMP) was
synthesized in one step by an amine-
formaldehyde reaction.
The HPIMP molecule adopt trans
configuration about C@N bond with
intramolecular hydrogen bonding.
A proton-transfer characteristic of
HPIMP is proved by experimental
results of X-ray and FT-IR.
The vibrational spectra have been
precisely ascribed to molecular
structure.
The thermodynamic properties have
been obtained by the theoretical
vibrational analysis.
The theoretical first-order
hyperpolarizabilities is 19.9 times
magnitude of urea.
a r t i c l e i n f o
a b s t r a c t
Article history:
Recently, the study of imine-bridged organics is interested in proton-transfer and photo-responsive
material fields. Herein, we make a investigation on the structural, thermodynamic and nonlinear optical
properties of (E)-2-((2-hydroxyphenyl)iminiomethyl)phenolate (HPIMP). The structural varieties of the
studied compound are characterized by the X-ray single crystal diffraction and vibrational spectral tech-
niques, as well as the vibrational spectral bands are precisely ascribed to the studied structure with the
aid of DFT theoretical calculations. The experimental results of the FT-IR and X-ray measurements supply
good proofs to reveal the proton-transfer procedures of HPIMP, and exhibit that the studied compound is
a good proton-transfer model. In addition, the thermodynamic properties are obtained from the theoret-
Received 23 February 2012
Received in revised form 18 April 2012
Accepted 27 April 2012
Available online 7 May 2012
Keywords:
2
-((2-Hydroxyphenyl)iminiomethyl)
phenolate
X-ray
Vibrational spectra
Proton transfer
Nonlinear optical
ical vibrations of the optimized HPIMP. The linear polarizability (
a
0
) and first-order hyperpolarizabilities
3
ꢁ30
5
(
b
0
) respectively present the values of 26.28 Å and 7.41 ꢀ 10
cm /esu predicated theoretically by the
DFT-B3lYP method at 6-31G(d) level, which indicates that the studied compound is a promising nonlin-
ear optical material candidate.
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
Recently, the imine-bridged organics attract extensive attention
because of their potential applications in the fields of optical
communications, optoelectronic materials, optical switching and
⇑
Corresponding author at: Research Center of New Energy & Materials, Mianyang
Normal University, Mianyang 621000, PR China. Tel.: +86 816 2200064; fax: +86
8
16 2200819.
E-mail address: yuxisun@163.com (Y. Sun).
1
386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.04.094

Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
43
ꢁ
1
ꢁ1
ꢁ1
biofunctional compounds [1–7]. As we know that the heterojunc-
tion units are the core structures of a number of natural products
as amine acids, DNA, and bioelectric or photovoltaic materials.
Schiff bases used usually as models have been proved to be a class
of multifunctional active compounds. For example, Hadjoudis et al.
have found that some Schiff base compounds exhibit thermochro-
mism or photochromism properties [8]. Ünver et al. have reported
the structural and NLO properties for some imine-bridged aromatic
compounds [1,7,9]. Our group has been engaged in the study of
imine-bridged antipyrine derivatives and finds most of them pres-
ent good NLO properties in recent years [3–6]. Bondar et al. have
reported the suppression of the back proton-transfer from Aps85
to the retinal Schiff base in bacteriorhodipsin [10]. Filarowski
et al. have reported the intramolecular hydrogen bond and proton
transfer reaction in N-methyl-2-hydroxybenzylidene amine [11].
The imine-bridged organics often present tautomerism in ortho-
hydroxylated Schiff bases as a result of intramolecular proton
transfer between oxygen and nitrogen atoms [12]. Simultaneously,
these molecules can lead to charge transfer by forming pull–push
30 cm min and a spectral width of 2.0 cm on a Bruker IFS
66 V FI-IR spectrometer using KBr pellet technique.
The FT-Raman spectrum was measured on RENISHAM inVia Ra-
man microscope equipped with a counter current detector and a
diode laser (785 nm line of Nd-YAG laser as excitation wavelength)
ꢁ1
in the region of 4000–100 cm
with a spectral resolution of
ꢁ
1
1.0 cm in the backscattering configuration.
The A suitable single crystal was attached to a glass fiber. Data
were collected at 295(2) K on a Bruker AXS SMART APEX area-
detector diffractometer (MoKa radiation, k = 0.71073 Å) with
SMART [16] as a driving software; data integration was performed
by SAINTPlus software [17] with multiscan absorption correction
applied using SADABS [18]. The crystal structure was solved by a
direct method based on difference Fourier and refined by least
2
squares on F with anisotropic displacement parameters for non-
H atoms. All of H atoms attached to C/O were placed in calculated
positions. All the calculations to solve the structure, to refine the
proposed model, and to obtain the derived results were carried
out with the computer programs of SHELXS-97 [19], SHELX-L97
[19] and SHELXTL [20]. Full use of CCDC package was also made
for searching in the CSD database.
structural system due to
p-electron conjugated moieties. Cur-
rently, the -bond structure with electron donor and acceptor
p
groups can increase the asymmetric electronic distribution to per-
form an increased optical nonlinearity [1,13]. Thereby, the imine-
bridged aromatic derivatives are very promising proton-transfer
model compounds and photo-responsive materials. Based on these
considerations, we have previously reported the synthesis,
crystal structure, vibrational spectra and NLO properties of
N-(4-hydroxy-phenyl)-2-hydroxybenzaldehyde-imine [14]. As an
further extension of our work, (E)-2-((2-hydroxyphenyl)iminiom-
ethyl)phenolate (HPIMP) (Scheme 1) was synthesized and charac-
terized in details by a combined experimental and theoretical
investigation. And the structural, spectral, thermodynamic and
nonlinear optical characteristics of the studied compound are
gained. Especially, a significant example for proton-transfer re-
search is present by the results measured by X-ray and spectral
techniques in this work.
Theoretical
In this work, for meeting the requirements of accuracy and
economy, the theoretical method and basis set should be consid-
ered firstly. The density functional theory (DFT) has been proved
to be extremely useful in treating electron relativities, and the ba-
sis set of 6-31G(d) has been used as a very effective and econom-
ical level for many organic molecules[21]. Based on the points,
the density functional Becke3–Lee–Yang–Parr (DFT/B3LYP) meth-
od with standard 6-31G(d) basis set was adopted to compute the
properties of the studied compound in the present work. All the
calculations were performed using Gaussian 03W program pack-
age [22] with the default convergence criteria.
As the first step of our calculation, the initial geometrical config-
uration was generated from its X-ray diffraction (XRD) crystallo-
graphic data, and the optimized geometry corresponding to the
minimum on the potential energy surface was obtained by solving
self-consistent field equation iteratively without any constraints.
The harmonic vibrational frequencies were analytically calculated
by taking the second order derivative of energy using the same le-
vel of theory. Normal coordinate analysis was performed to gain
full description of the molecular motion pertaining to the normal
modes using the GaussView program [23]. Simultaneously, the sta-
tistical thermodynamic functions were theoretically predicted by
the harmonic frequencies of the optimized structure for the stud-
ied compound.
Experimental
Chemical synthesis
All chemicals (reagent grade) were obtained from a commercial
source and used without further purification. The title compound
was synthesized according to the classical condensation of alde-
hyde and ammonia [15], and its reaction path is shown in Scheme
1
as well as the preparation technique was explained in previous
studies cited above. In the end, the brown prism-shaped crystals
were gained at the bottom of the vessel with slow evaporation of
the solvent (yield 85.3%).
The Raman scattering activities (S
program were suitably converted to relative Raman intensities (I
i
) calculated by Gaussian 03W
i
)
using the following relationship derived from the basic theory of
Raman scattering stated in previous Refs. [24,25]:
Physical measurements
4
fð
v
0
ꢁ
v
i
Þ S
i
I
i
¼
h
ꢀ
ꢁi
ð1Þ
FT-IR absorption spectrum was recorded in the range of 4000–
ꢁhcvi
v
i
1 ꢁ exp
ꢁ1
kT
4
00 cm
in an evacuation mode with a scanning speed of
Scheme 1. Synthetic route of HPIMP.

4
4
Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
is the exciting frequency (in cm 1 units),
ꢁ
where
v
0
i
v is the vibra-
tional wavenumber of the ith normal mode, h, c and k are universal
constants, and f is a suitably chosen common scaling factor for all
the peak intensities.
The nonlinear optical (NLO) properties can be obtained by the
previously stated methods [26–37]. In this work, using the x, y, z
components, the total static dipole moment ( ), linear polarizabil-
l
0
ity ( ) and first-order hyperpolarizability (b ) are calculated by
a
0
0
the following equations defined in previous Refs. [26,33–36]:
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
2
2
2
l0
¼
l
þ
l
þ
l
ð2Þ
ð3Þ
x
y
z
a
xx
þ
a
yy
þ
a
zz
a
0
¼
3
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
2
2
2
b0 ¼ ðb þ b þ b Þ þ ðb þ b þ b Þ þ ðb þ b þ b
Þ
xxx
xyy
xzz
yyy
xxy
yzz
zzz
xxz
yyz
ð4Þ
Fig. 1. The displacement ellipsoid plots with atomic numbering for HPIMP.
Results and discussion
Molecule structure
Table 2
Selected bond lengths (Å) and bond angles (°) for HPIMP.
The X-ray diffraction result proves that the molecular structure
and its packing mode of the studied compound are very close to
the previous report [38]. In the present case, the salicylaldimine
also takes tautomeric keto form, and the strong intra- and inter-
molecular NAHꢂ ꢂ ꢂO and OAHꢂ ꢂ ꢂO interactions (Table 1) have effect
on the same conformations of the studied molecules and their
packing structure as the values reported previously [38]. The dis-
placement ellipsoid plots with atomic renumbering are shown in
Fig. 1 in order to state better in this work.
An asymmetric unit of the studied compound is made up of two
crystallographically independent molecules, but the two molecular
structures are nearly close to each other as shown in Table 2. So,
one molecular structure in an asymmetric unit was selected as
the initial geometry for theoretical calculations in this work, and
the atomic numbering of the theoretical molecule is the same as
the first molecule of an asymmetric unit. In order to compare with
experimental data better, the optimized parameters gained at
B3LYP/6-31G level are listed in Table 2.
Experimental
Theoretical
Bond length (Å)
N1AC7
N1AC8
O1AC1
O2AC9
C1AC2
C1AC6
C2AC3
C3AC4
C4AC5
C5AC6
C6AC7
C8AC9
C8AC13
C9AC10
C10AC11
C11AC12
C12AC13
1.296 (4)
1.430 (4)
1.304 (4)
1.355 (4)
1.414 (5)
1.420 (5)
1.375 (5)
1.381 (5)
1.357 (5)
1.404 (4)
1.417 (5)
1.389 (5)
1.362 (5)
1.379 (5)
1.360 (5)
1.389 (5)
1.387 (5)
N2AC20
N2AC21
O3AC14
O4AC22
C14AC15
C14AC19
C15AC16
C16AC17
C17AC18
C18AC19
C19AC20
C21AC22
C21AC26
C22AC23
C23AC24
C24AC25
C25AC26
1.299 (5)
1.428 (4)
1.317 (4)
1.355 (4)
1.405 (5)
1.409 (5)
1.369 (5)
1.381 (5)
1.352 (5)
1.408 (5)
1.418 (5)
1.384 (5)
1.383 (5)
1.384 (5)
1.380 (5)
1.373 (5)
1.385 (5)
1.335
1.403
1.260
1.365
1.448
1.473
1.368
1.431
1.367
1.431
1.394
1.412
1.400
1.394
1.396
1.395
1.395
Bond Angles (°)
C7AN1AC8
O1AC1AC2
O1AC1AC6
C2AC1AC6
C3AC2AC1
C2AC3AC4
C5AC4AC3
C4AC5AC6
C5AC6AC7
C5AC6AC1
C7AC6AC1
N1AC7AC6
C13AC8AC9
C13AC8AN1
C9AC8AN1
O2AC9AC10
O2AC9AC8
C10AC9AC8
C11AC10AC9
C10AC11AC12
C13AC12AC11
C8AC13AC12
As seen from Table 2, it can be observed that the experimental
and theoretical geometric parameters are not agree with each
other completely owing to the two facts, viz., the first one is that
a isolated molecule considered in theoretical calculation in gas
phase is contrary to the packing molecules with intermolecular
interactions recorded in condensed phase in experimental mea-
surement [39], the second one is that a theory derived from reality
is generally imperfect with a case. In the studied case, the largest
deviations of bond lengths and bond angles between the optimized
values and experimental ones are of 0.06 Å and 2.2°, respectively.
Despite the optimized parameters are slightly different from the
crystallographical data for the studied compound, the optimized
structure depend upon the method and the basis set used in the
127.4 (3)
122.1 (4)
121.5 (3)
116.3 (4)
121.0 (4)
121.7 (4)
119.1 (4)
121.1 (4)
118.4 (3)
120.7 (3)
120.9 (3)
123.5 (4)
120.6 (3)
122.8 (3)
116.6 (3)
123.4 (3)
117.3 (3)
119.2 (3)
120.5 (4)
120.5 (4)
119.2 (4)
120.1 (4)
C20AN2AC21
O3AC14AC15
O3AC14AC19
C15AC14AC19
C16AC15AC14
C15AC16AC17
C18AC17AC16
C17AC18AC19
C18AC19AC14
C18AC19AC20
C14AC19AC20
N2AC20AC19
C26AC21AC22
C26AC21AN2
C22AC21AN2
O4AC22AC23
O4AC22AC21
C23AC22AC21
C24AC23AC22
C25AC24AC23
C24AC25AC26
C21AC26AC25
126.9 (3)
120.9 (4)
122.1 (3)
117.0 (4)
120.8 (4)
121.5 (4)
119.7 (4)
120.3 (4)
120.6 (4)
118.1 (3)
121.3 (3)
122.6 (4)
120.2 (4)
123.3 (3)
116.5 (3)
122.9 (3)
117.9 (3)
119.3 (4)
120.6 (4)
119.8 (4)
120.2 (4)
119.8 (4)
127.3
122.1
122.1
115.8
121.5
122.0
119.3
121.1
119.7
120.3
120.1
123.3
118.8
124.1
117.1
123.6
116.2
120.2
120.3
119.8
120.1
120.7
Table 1
a
Hydrogen bonding parameters for HPIMP .
Hydrogen bonding
DAH(Å)
Hꢂ ꢂ ꢂA(Å)
Dꢂ ꢂ ꢂA(Å)
DAHꢂ ꢂ ꢂA(°)
N1AH1Nꢂ ꢂ ꢂO1
N2AH2Nꢂ ꢂ ꢂO3
N2AH2Nꢂ ꢂ ꢂO4
0.86 (4)
0.86 (3)
0.86 (3)
0.820
1.84 (4)
1.88 (3)
2.33 (3)
1.770
2.603 (4)
2.601 (5)
2.656 (4)
2.585 (4)
2.580 (4)
148.0 (5)
141.0 (5)
103.0 (5)
170.0
Torsion Angles (°)
C5AC6AC7AN1 ꢁ178.7
4)
C8AN1AC7AC6 ꢁ178.9
4)
C18AC19AC20AN2 178.2 (4) ꢁ179.7
C21AN2AC20AC19 180.0 (4) ꢁ178.2
(
i
O2AH2Oꢂ ꢂ ꢂO3
ii
O4AH4Oꢂ ꢂ ꢂO1
0.820
1.770
168.0
(
a
C7AN1AC8AC9 ꢁ170.7 (4) C20AN2AC21AC22 171.0 (4) ꢁ169.3
Symmetry codes: (i) ꢁx, 1 ꢁ y, 1 ꢁ z; (ii) 1 ꢁ x, 1 ꢁ y, 1 ꢁ z.

Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
45
ꢁ
1
ꢁ1
calculations are accepted as a base to calculate other properties or
to evaluate some characteristics for the studied compound.
band at 1632 cm in FT-IR spectrum and 1627 cm in FT-Raman
is ascribed to a vibration combined with C@N, C1AO1 and CAC
stretching vibrations as well as imine NAH and CAH in-plane
bending, which agrees well with the calculated value at
Vibrational spectral analysis
ꢁ1
1
622 cm
quency (mode No. 51) at 1290 cm
stretching vibration with N1AH in-plane bending mode, which
(mode No. 64). And the theoretically predicted fre-
ꢁ1
The two benzene rings of the studied molecule are not abso-
lutely planar with torsion angle of about 10.4(4)°, and the molecu-
is attributed to the CAN
ꢁ1
lar structure belongs to C
1
point group. The molecule with 27
also matches the experimental value at 1276 cm in FT-IR. All
these results are close to the data reported by Ilic et al. [44].
atoms has 75 normal vibrations. All the fundamental modes with
their mode numbers can be obtained by theoretical calculation.
According to the motion of the individual atoms with the aid of
GaussView 3.0 software [23], the detailed vibrational spectral
assignments have been given in Table 3 with theoretical frequen-
cies scaled by the factor of 0.9614 for B3LYP method [40,41].
The IR and Raman spectra of the studied compound are shown
in Figs. 2 and 3, respectively. The detailed vibrational analysis is
completely given below in the work.
CAO vibrations
ꢁ1
In the studied case, the medium band at 1593 cm in FT-IR and
the strong band at 1597 cm are ascribed to C1AO1 stretching
vibration mixed with imine CAH in-plane bending mode, which
agree with the calculated value at 1565 cm (mode No. 60). And
the theoretically predicted frequency (mode No. 49) at
1258 cm is ascribed to the C9AO2 stretching vibrational mode
mixed with CAH in-plane bending vibrations of the No. 2 ring,
which is also matches the experimental medium-strong band of
ꢁ1
ꢁ1
ꢁ1
CAH vibrations
ꢁ1
ꢁ1
The aromatic CAH stretching vibration shows in the region
1224 cm in FT-IR and the medium band of 1308 cm in FT-Ra-
man. We can find that the CAO vibration has been affected by
neighboring molecular interactions.
ꢁ1
3
100–3000 cm , which is a typical vibration region for character-
ization of the aromatic compounds [42,43]. In the present case, the
ꢁ1
scaled CAH stretching vibrations region at 3095–3045 cm (mode
Nos. 74–66) by B3LYP/6–31G(d) method are in excellent agree-
OAH vibrations
ꢁ1
ment with the FT-IR band observed at 3046 cm . In this region,
the involvement of the substitution has not much impact on the
vibration of the aromatic CAH stretching.
The reported in-plane OAH bending leads to a medium to
ꢁ1
strong band in the region of 1440–1260 cm [43]. In this case,
The OAH in-plane bending vibration is mixed with other vibrations
such as CAH in-plane bending, CAC stretching vibration and CAN
stretching vibration. The calculated frequencies at 1328, 1281,
The aromatic CAH in-plane bending vibration occurs in the
ꢁ1
range of 1290–900 cm and the out-of-plane bending vibration
ꢁ1
ꢁ1
shows in the frequency range of 999–755 cm in the substituted
1215, 1181, 1157, 1147 and 1082 cm (mode Nos. 53, 50, 47–
benzene compounds [42,43]. The CAH in-plane bending vibrations
44, 41) show slightly deviates from the FT-IR bands at 1307,
ꢁ1
ꢁ1
computed at 1281–1019 cm (mode Nos. 50, 47 and 45–39) by
B3LYP/6–31G(d) method are closed to experimental FT-IR wave-
1244, 1161, 1140, 1117, 1026 cm and the FI-Raman peaks at
ꢁ1
1281, 1256, 1167, 1143, 1101 cm . These vibrational modes are
designated to O-H in-plane bending vibrations mixed with C7AH,
or CAH of No. 1 or No. 2 rings. The OAH and NAH stretching modes
exhibit marked differences between experimental and theoretical
spectra, which attract us to reveal them explained in Proton trans-
fer analysis.
ꢁ1
lengths at 1244, 1161, 1026 cm and 1256, 1143, 1101, 1046,
ꢁ1
1
030 cm in FT-Raman spectrum. These vibration modes often
accompany with the CAC, CAO or CAN vibrations. The FT-IR peaks
ꢁ1
ꢁ1
at 854, 808, 765, 726 cm and FT-Raman spectrum at 738 cm
are assigned to CAH out-plane bending vibrations, which also
show good agreements with the theoretically scaled values at
ꢁ
1
9
43–701 cm (mode Nos. 37–33, 31–29, 27, 25–23).
Proton transfer analysis
Ring vibrations
For an isolated phenol, the frequency of OAH stretching vibra-
ꢁ1
The aromatic ring C@C stretching vibrations generally appear in
tion in the gas phase is at about 3650 cm [45,46]. In this work,
ꢁ
1
ꢁ1
the special region of 1650–1450 cm [39]. In the present work,
the ring C@C stretching vibrations are very prominent. In the stud-
ied case, the strong bands observed at 1632, 1613, 1530, 1487,
the theoretical OAH stretching vibration is also at 3605 cm close
to the values reported previously[45,46]. However, the FT-IR spec-
trum shows obvious abnormal spectral bands in the high region,
which indicate the OAH group vibrations are affected by surround-
ings strongly. As a result, it is a different work to assign the hydro-
gen-bonding vibrational bands by the old-fashioned way.
ꢁ1
1
463, 1416, 1370 cm in FT-IR and the middle to strong bands
ꢁ1
at 1526, 1513, 1372, 1358 cm in FT-Raman are assigned to the
aromatic C@C stretching vibrations, which are good coherence
ꢁ1
with theoretically calculated data at 1622–1322 cm (mode Nos.
4–61, 59–54, 52). In general, most of these modes are accompa-
nied with the combination of the CAH in-plane bending vibrations.
In order to reveal these vibrations, we need to research on the
atomic positions of hydrogen for the studied compound. As we
know that the experimental hydrogen positions cannot be ob-
tained directly by the X-ray diffraction technique, and hydrogen
atoms are generally placed to their adjacent parent atoms by a
semiempirical theoretical calculation. In the fact, the real atomic
positions can be determined by the Q peaks, viz., Fourier differ-
ences obtained by X-ray diffraction technique. In other word, the
Q peaks can supply the real atomic positions effectively. Based
on the viewpoint, we need to research the adjacent Q positions
of the N and O atoms to find out the real positions of the hydro-
gen-bonding atoms. The Q peak positions presented by X-ray dif-
fraction are shown in Fig. 4.
6
ꢁ1
The bands observed of 573, 549, 525, 478 and 420 cm in FT-IR
spectrum are assigned to CACAC deformation vibrations of the
phenyl rings. The deformation vibrations appear at 631, 582, 544,
ꢁ
1
4
77 and 446 cm in FT-Raman spectrum. The theoretically com-
puted CACAC deformation vibrations have been found to show
good agreement with recorded spectral date region.
CAN vibrations
The identification of CAN vibration is a rather difficult task for
imine compounds, because the CAN vibrational modes often
accompany with the combination of neighboring substructures.
However, the CAN vibrational spectral assignments can be identi-
fied through the animation application of GaussView 3.0 graphical
interface for Gaussian output file. In view of this, a very strong
In the packing structure of the studied compound, the real H
atomic positions should be close to the Q peaks shown in Fig. 4.
According to the Q positions and Hooke’s Law for harmonic oscilla-
tor, we can assign the experimental FT-IR bands related to the

4
6
Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
Table 3
Experimental bands and theoretical frequencies with approximate assignments for HPIMP.
a,b
Mode Nos.
Experimental
IR
Theoretical
Frep.
Approximate assignments
Raman
I
IR
I
Raman
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
3605
3095
3091
3088
3078
3069
3067
3054
3048
3045
2938
1622
1616
1589
1583
1565
1496
1486
1454
1444
1409
1361
1328
1322
1290
1281
1258
1231
1215
1181
1157
1147
1142
1103
1082
1034
1019
964
943
924
903
893
880
842
838
815
802
797
755
738
729
717
701
639
51.2
1.5
4.0
3.7
2.3
1.5
0.8
1.4
0.6
1.5
1.6
0.7
86.5
92.6
18.3
4.5
98.1
20.4
5.0
49.2
4.1
7.9
10.2
2.5
21.8
0.8
t
t
t
t
t
t
t
t
t
t
t
t
O2H
19.0
21.2
23.2
18.1
2.4
CH of R
CH of R
CH of R
CH of R
CH of R
C7H
C3H
C10H
C5H
2
1
2
1
2
3046w
1.7
99.7
346.2
28.8
51.4
256.2
17.2
75.7
14.6
105.7
27.9
68.4
75.1
30.7
53.7
14.5
55.0
4.3
82.3
21.5
29.1
4.1
15.2
181.3
23.9
2.4
26.0
7.1
47.1
3.8
3.2
9.5
0.3
0.0
0.9
6.7
N1H
C@C of R
1632vs
1613m
1627s
1
+
t
t
C7N1 +
C7N1 + bN1H
t
C1O1 + bN1H + bC7H
ttC@C of R
1
+
t
t
t
t
t
t
t
t
t
C@C of R
C@C of R
C1O1 + bN1H
C@C of R
C@C of R
C@C of R
C@C of R
C@C of R
C@C of R
2
2
1593m
1530s
1487m
1463vs
1597s
1526m
1
2
2
1
1
1
+ bCH of R
+ bCH of R
+ bCH of R
+ bCH of R
+ bCH of R
2
2
1
1
1
1513m
1416w
1370w
1307m
1372ms
1358vs
bC7H + bCH of R
1
+ bO2H
+ bCH of R + bO2H + bC7H
C7N1 + bN1H
+ bO2H
C9O2 + bCH of R
bC7H + bN1H + bC5H
bCH of R + bO2H +
bO2H + bN1H + N1C8 + bCH of R
t
t
C@C of R
2
2
1276ms
1244s
1224ms
0.7
bCH of R
2
1308m
1281m
1256ms
1167m
18.6
3.2
24.9
53.9
0.7
5.0
3.9
0.2
t
2
1161w
1140vs
1117w
1
tN1C8
t
2
1
bO2H + bCH of R
bO2H + bCH of R
bCH of R
bCH of R
a
t
t
c
c
c
c
1143s
2
1
1
+
t
CAC of R
1
1026w
904w
1101m
1046m
1030w
2.0
R
2
+ bCH of R
C11C12 + bCH of R
C3C4 + bCH of R
2
+ bO2H
4.7
6.3
6.4
0.0
0.2
0.6
1.7
0.7
3.0
2
1
C7H +
c
N1H
CH of R
CH of R
CH of R
1
2
1
aR
1
854vw
15.7
8.0
0.1
c
c
c
a
c
CH of R
C7H +
CH of R
N1C8 +
2
850s
c
N1H
0.8
1
+
a
R
2
+
tN1C8
808vw
765m
3.6
1.1
1.2
11.7
1.0
1.0
4.1
0.3
R
2
+
t
cCH of R
1
72.8
23.9
5.3
74.3
38.9
4.7
0.4
5.5
11.4
3.2
1.5
0.7
1.6
6.6
2.9
4.1
5.0
3.1
107.1
5.7
CH of R
2
772s
aR
2
c
t
c
c
m
a
a
a
m
a
m
a
a
CH of R
C1C6
CH of R
CH of R
1
+
m
R
1
2
743m
726w
738w
2
1
0.2
R
R
R
R
2
+
+
+
+
cCH of R
573w
549m
631w
582m
2.1
3.3
0.5
0.2
0.5
1
1
1
a
a
a
R
R
R
2
2
2
573
564
553
534
522
496
476
442
434
407
356
331
303
251
216
205
R
2
R
1
+
a
C8C9O2
C1O1
R + gC1O1
2
R
2
R
2
a
gC7H
525vw
478m
544w
477m
446w
342s
1.9
1.9
10.8
0.4
3.2
1.6
2.1
0.6
24.0
1.6
2.5
28.7
9.6
38.1
32.4
R
1
R
R
2
1
+
+
+
+
g
a
m
m
m
R
1
R
1
m
420w
g
g
g
g
g
q
q
q
q
C9O2 +
N1H +
O2H
O2H
C9O2
C5C6C7
295vw
242w
0.3
3.7
0.7
1.6
1.4
0.3
0.4
Skeleton
214m
182vw
145vw
Skeleton
Skeleton
Skeleton
180
131
68
xSkeleton

Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
47
Table 3 (continued)
Mode Nos.
Experimental
IR
Theoretical
Frep.
Approximate assignments
Raman
I
IR
I
Raman
2
1
54
32
1.2
0.9
46.7
369.2
x
Skeleton
sSkeleton
a
Mode numbers are extracted from the output result of the B3LYP calculation;
B3LYP scaled wavenumbers (cm ). The calculated IR intensities (IIR) are in k mmol ; the calculated Raman scattering intensities (IRaman) are in arbitrary units by Eq. (1);
b
ꢁ1
ꢁ1
s, strong; vs. very strong; m, medium; ms, medium strong; w, weak; vw, very weak; b, broad; R, ring (R
of-plane bending; , puckering; , wagging; , stretching, , torsion, , nodding.
1
: C1ꢃC6, R : C8ꢃC13); a, angle bending; b, in-plane bending; c, out-
2
m
x
t
s
g
Fig. 2. The IR spectra of HPIMP: (a) recorded (b) simulated.
Fig. 3. The Raman of HPIMP: (a) recorded (b) simulated.

4
8
Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
Table 4
The thermodynamic properties at different temperatures for HPIMP.
H
p;m
H
m
H
m
Temperature (K)
C
(J/mol/K)
S
(J/mol/K)
DH
(kJ/mol)
100.0
200.0
298.1
400.0
500.0
600.0
700.0
800.0
89.97
329.36
412.33
489.75
568.25
642.06
711.59
776.57
837.17
6.13
18.50
37.77
65.15
98.33
136.54
178.74
224.16
159.45
233.08
302.69
358.86
403.55
439.22
468.16
Based on the detailed investigation on the hydrogen-bonding
spectral bands and X-ray Q peaks of the N and O atoms, we can fur-
ther draw a mechanism of the intramolecular and intermolecular
proton transfer procedures for the studied compound (Scheme
Fig. 4. The Q positions related to hydrogen-bonding interaction in packing HPIMP.
2). Accompany with resonance, the intramolecular proton ex-
change effect leads to the keto-enol conversion between the phe-
nolate and phenol configurations, while the intermolecular
proton transfer effect brings out the positive and negative
molecules.
The three abnormal spectral bands observed in high region are
ascribed to the strong intramolecular and intermolecular effects,
ꢁ
1
hydrogen-bonding atoms. The broad band at 2856, 2699 cm are
respectively ascribed to the stretching vibration of the phenolic hy-
ꢁ
1
droxyl and imine groups. While the broad band at 2575 cm is
designated to the mixed O1AH and O4AH stretching mode owing
to the intermolecular hydrogen bonding interaction.
Scheme 2. Intramolecular and intermolecular proton transfer procedures of HPIMPa. a Dash lines indicate hydrogen bonding.

Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
49
Table 5
The calculated electric dipole moments (Debye), static polarizability components (a.u.), first hyperpolarizability components (a.u.) of HPIMP.
l
x
l
y
l
z
a
xx
a
yy
a
zz
b
xxx
b
xxy
b
xyy
b
yyy
b
xxz
b
yyz
b
xzz
b
yzz
b
zzz
ꢁ
1.43
ꢁ0.77
ꢁ0.15
322.33
159.26
50.96
649.76
ꢁ431.53
22.92
ꢁ91.45
ꢁ25.64
9.25
2.73
ꢁ5.38
ꢁ0.92
which supply a clear experimental proof for the proton transfer
mechanism. Based on the breakthrough, the variable structures
of the studied molecule can be obtained by the interpretation on
the proton transfer procedure.
We can find that the strong hydrogen bonds have great effect on
the stretching modes of the hydrogen-bonding-related atoms. The
IR and X-ray techniques provide an excellent approach for us to
study the strong interactions. The vibrational spectral characteris-
tics in high region and X-ray Q peaks supply important experimen-
tal evidences to research on the proton-transfer interaction in
medicine, life, material fields. The proton transfer analysis in this
work provides a good demonstration to study long-range proton
transfer processes.
Thermodynamic properties
On the basis of vibrational frequencies gained at B3LYP/6-
3
1G(d) level and statistical thermodynamic parameters: heat
H
H
H
capacities (C ), entropies (S ) and enthalpies (
D
H ) can be ob-
p;m
m
m
tained from the theoretical frequencies scaled by 0.9614. And the
values of the thermodynamic functions at different temperatures
are listed in Table 4.
As is an evidence from Table 5, all the values of heat capacities
H
p;m
H
m
H
m
(C
), entropies (S ) and enthalpies (
D
H ) increase with tempera-
ture ranging from 100.0 to 800.0 K due to the enhancement of the
molecular vibration with the increasing temperature. The correla-
tive equations between the thermodynamic properties and tem-
peratures were fitted by quadratic formulas, and the
corresponding correlation coefficients are all beyond 0.999. The
correlation graphics shows in Fig. 5 and the corresponding fitting
equations are as follows:
H
p;m
¼ ꢁ3:8694 þ 0:9324T ꢁ 4:2625 ꢀ 10ꢁ4
2
C
T
ð5Þ
ð6Þ
ð7Þ
H
m
¼ 241:4318 þ 0:8911T ꢁ 1:8184 ꢀ 10ꢁ4
2
S
T
Fig. 5. The correlation graphics of thermodynamic functions via temperatures for
HPIMP.
H
m
¼ ꢁ4:8039 þ 0:0657T þ 2:7828 ꢀ 10ꢁ4
2
D
H
T
All the thermodynamic data provide helpful information to fur-
ther study on the title compound in the thermodynamic field.
That is to say, the compound probably is also a good candidate of
NLO materials.
NLO behavior
It is an important and inexpensive way to evaluate the NLO
properties of materials by theoretical calculations. To understand
the microscopic NLO mechanism of the title compound, we have
applied Gaussian 03W program [22] to calculate electric dipole
moment components, static polarizability components and first
hyperpolarizability components. All the calculated results were
Conclusions
Determinations have been made in this present work for the
molecular structure and spectral assignments of (E)-2-((2-
hydroxyphenyl)iminiomethyl)phenolate from single crystal XRD,
FT-IR and FT-Raman spectra with the aid of the theoretical calcula-
tions at B3LYP/6-31G(d) level. The experimental and theoretical re-
sults support well each other. Three abnormal spectral bands can
be explained by the X-ray diffraction Q peak positions of adjacent
N and O atoms, and the bands and Q peaks also supply good exper-
imental evidences to reveal the proton transfer procedures for the
studied compound. In addition, the thermodynamic and NLO prop-
erties for the compound have been given by theoretical calcula-
tions. The theoretical higher hyperpolarizability values imply that
the title compound might become a kind of good NLO material.
listed in Table 5. And the dipole polarizability
l
0
, the average linear
can be
polarizability and the first-order hyperpolarizability b
a
0
0
calculated by the formula (2)–(4). The corresponding values of
l
0,
a
0
and b
respectively. The
0
are 1.63 Debye, 26.28 Å3 and 7.41 ꢀ 10 cm /esu,
ꢁ30
5
0 0
a and b value of the investigated compound
3
are all higher than those of urea
(
a
0
= 3.83 Å ,
b
0
= 3.73 ꢀ
ꢁ31
5
1
0
cm /esu). Especially, the first-order hyperpolarizability value
of the investigated compound is 19.9 times more than that of urea,
which is also larger than several reported values [3,34,37,47,48].

5
0
Y. Sun et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 42–50
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Acknowledgments
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, 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 03W, Version 6.0., Gaussian, Inc. Wallingford CT, 2004.
23] R. Dennington II, T. Keith, J. Millam, K. Eppinnett, W. Lee Hovell, R. Gilliland,
GaussView, Version 3.09., Semichem, Inc. Shawnee Mission, KS, 2003.
24] V. Krishnakumar, G. Keresztury, T. Sundius, R. Ramasamy, J. Mol. Struct. 702
(2004) 9–21.
This work was supported by Natural Science Foundations of
China (No. 21073092 & 21103092), Sichuan Education Department
Fund (No. 12ZA080), Scientific Research Foundation for Excellent
Plan of Binzhou University (BZXYQNLG200704) and Excellent Plan
Foundation of NUST (2008). We also thank Qufu Normal University
for Technical Assistance.
[
[
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2012.04.094.
[
[
[
25] P.L. Polavarapu, J. Phys. Chem. 94 (1990) 8106–8112.
26] R. Zhang, B. Du, G. Sun, Y. Sun, Spectrochim. Acta A 75 (2010) 1115–1124.
27] A. Karakas, A. Elmali, H. Ünver, I. Svoboda, Spectrochim. Acta A 61 (2005)
2979–2987.
28] P.S. Liyanage, R.M. de Silva, K.M.N. de Silva, J. Mol. Struct.: THEOCHEM 639
(2003) 195–201.
[29] P.J. Mendes, J.P.P. Ramalho, A.J.E. Candeias, M.P. Robalo, M.H. Garcia, J. Mol.
Struct.: THEOCHEM 729 (2005) 109–113.
[30] I.C. de Silva, R.M. de Silva, K.M. Nalin De Silva, J Mol Struc: THEOCHEM 728
(2005) 141–145.
[31] J.O. Morley, J. Am. Chem. Soc. 110 (1988) 7660–7663.
[32] H. Li, K. Han, X. Shen, Z. Lu, Z. Huang, W. Zhang, Z. Zhang, L. Bai, J. Mol. Struct.:
THEOCHEM 767 (2006) 113–118.
[33] A.D. Tillekaratne, R.M. de Silva, K.M.N. de Silva, J. Mol. Struct.: THEOCHEM 638
(2003) 169–176.
References
[
[
[
[
1] H. Ünver, A. Karakas, A. Elmali, J. Mol. Struct. 702 (2004) 49–54.
2] A. Karakas, H. Ünver, Spectrochim. Acta A 75 (2010) 1492–1496.
3] Y. Sun, Q. Hao, W. Wei, Z. Yu, L. Lu, X. Wang, Y. Wang, J. Mol. Struct.:
THEOCHEM 904 (2009) 74–82.
[
[
4] Y. Sun, Q. Hao, Z. Yu, W. Wei, L. Lu, X. Wang, Mol. Phys. 107 (2009) 223–235.
5] Y. Sun, Q. Hao, W. Wei, Z. Yu, L. Lu, X. Wang, Y. Wang, J. Mol. Struct. 929 (2009)
1
0–21.
[6] Y. Sun, W. Wei, Q. Hao, L. Lu, X. Wang, Spectrochim. Acta A 73 (2009) 772–781.
[7] H. Ünver, A. Karaka ßs , A. Elmali, T.N. Durlu, J. Mol. Struct. 737 (2005) 131–137.
[8] E. Hadjoudis, M. Vittorakis, I. Moustakali-Mavridis, Tetrahedron 43 (1987)
1
345–1360.
[34] D. Sajan, H. Joe, V.S. Jayakumar, J. Zaleski, J. Mol. Struct. 785 (2006) 43–53.
[35] H. Alyar, Z. Kantarci, M. Bahat, E. Kasap, J. Mol. Struct 2007 (2007) 516–520.
[36] N. Sundaraganesan, J. Karpagam, S. Sebastian, J.P. Cornard, Spectrochim. Acta A
73 (2009) 11–19.
[37] K.S. Thanthiriwatte, K.M. Nalin de Silva, J. Mol. Struct.: THEOCHEM 617 (2002)
169–175.
[
9] H. Ünver, T. Nuri Durlu, J. Mol. Struct. 655 (2003) 369–374.
[
[
10] A.N. Bondar, S. Suhai, S. Fischer, J.C. Smith, M. Elstner, J. Struct. Biol. 157 (2007)
54–469.
11] A. Filarowski, A. Koll, A. Karpfen, P. Wolschann, Chem. Phys. 297 (2004) 323–
32.
4
3
[
[
[
12] H. Tanak, A.A. A g˘ ar, O. Büyükgüngör, Spectrochim. Acta A 87 (2012) 15–24.
13] R.R.B.N.K. Sethuraman, Spectrochim. Acta A 66 (2007) 707–711.
14] Y. Wang, Z. Yu, Y. Sun, Y. Wang, L. Lu, Spectrochim. Acta A 79 (2011) 1475–
[38] A.K. Mukherjee, R.L. De, I. Banerjee, C. Samanta, N.P. Nayak, Acta Crystallogr.
Sect. C 55 (1999) 407–410.
[39] M. Karabacak, E. Sß ahin, M. Çınar, I. Erol, M. Kurt, J. Mol. Struct. 886 (2008) 148–
1
482.
157.
[
[
[
[
[
[
15] J.J. Li, Pomeranz–Fritsch reaction, Springer, Berlin Heidelberg, New York, 2006.
pp. 472–474.
16] J.L. Chambers, K.L. Smith, M.R. Pressprich, Z. Jin, SMART, Bruker Advanced X-
ray Solutions, Version 5.628., Bruker AXS Inc. Madison, WI, 2002.
17] SAINTPlus, Data Reduction and Correction Program, Version 6.22., Bruker AXS
Inc. Madison, WI, 2001.
18] G.M. Sheldrick, SADABS, Program for Empirical Absorption Correction of Area
Dectector Data, University of Gottingen, Germany, 1996.
19] G.M. Sheldrick, SHELXS-97 and SHELXL-97; Programs for Structure Resolution
and for Structure Refinement, University of Gottingen, Germany, 1997.
20] G.M. Sheldrick, SHELXTL, Structure Determination Software Suite, Version
[40] A.P. Scott, L. Radom, J. Phys. Chem. 100 (1996) 16502–16513.
[41] I.M. Alecu, J. Zheng, Y. Zhao, D.G. Truhlar, J. Chem. Theory Compu. 6 (2010)
2872–2887.
[42] J. Swaminathan, M. Ramalingam, V. Sethuraman, N. Sundaraganesan, S.
Sebastian, Spectrochim. Acta A 73 (2009) 593–600.
[43] L. Guru Prasad, V. Krishnakumar, R. Nagalakshmi, Physica B 405 (2010) 1652–
1657.
[44] M. Ilic, E. Koglin, A. Pohlmeier, H.D. Narres, M.J. Schwuger, Langmuir 16 (2000)
8946–8951.
[45] D. Michalska, D.C. Bienko, A.J. Abkowicz-Bienko, Z. Latajka, J. Phys. Chem. 100
(1996) 17786–17790.
6
.10., Bruker AXS Inc. Madison, WI, 2000.
[46] G.V. Hartland, B.F. Henson, V.A. Venturo, P.M. Felker, J. Phys. Chem. 96 (1992)
1164–1173.
[47] C. Ravikumar, I.H. Joe, V.S. Jayakumar, Chem. Phys. Lett. 460 (2008) 552–558.
[48] F.F. Jian, P. Zhao, L. Zhang, J. Zheng, J. Fluo. Chem. 127 (2006) 63–67.
[
[
21] H. Arslan, O. Algul, T. Onkol, Spectrochim. Acta A 70 (2008) 606–614.
22] 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,