Combined experimental and theoretical approaches to the molecular structure of 4-(1-formylnaphthalen-2-yloxy)phthalonitrile

Article abstract of DOI:10.1016/j.saa.2012.07.005

The novel compound 4-(1-formylnaphthalen-2-yloxy)phthalonitrile, C ₁₉H₁₀N₂O_2, has been synthesized and characterized by IR, UV-vis, NMR and X-ray single-crystal determination. The title compound, is built up from two planar groups (naphthalen and phthalonitrile), with a dihedral angle of 64.10(4)° between them. The crystal structure is stabilized by weak C-H...O hydrogen-bond and π-π interactions. The structural and spectroscopic data of the compound in the ground state have been calculated using density functional theory (DFT) and Hartree-Fock (HF) with the 6-31G(d,p) basis set. The vibrational study was interpreted in terms of potential energy distribution (PED). The observed wave number in FT-IR spectra was analyzed and assigned to different normal modes of the molecule. Using the TD-DFT and TD-HF methods, electronic absorption spectra of the title compound were predicted and good agreement with the TD-DFT method and the experimental determination was found. Isotropic chemical shifts ( ¹³C and ¹H NMR) were calculated using the gauge-invariant atomic orbital (GIAO) method. The HOMO and LUMO analyses were used to elucidate information regarding charge transfer within the molecule.

Full text of DOI:10.1016/j.saa.2012.07.005

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Combined experimental and theoretical approaches to the molecular structure
of 4-(1-formylnaphthalen-2-yloxy)phthalonitrile
a
a
b
c,
c
⇑
_
_
Hidayet Tereci , Iskender Askerog˘lu , Nesuhi Akdemir , Ibrahim Uçar , Orhan Büyükgüngör
a Department of Physics, Faculty of Arts and Sciences, Gaziosmanpaßsa University, Gaziosmanpaßsa Üniversitesi, Taßslıçiftlik Yerleßskesi, 60250 Tokat, Turkey
b Department of Chemistry, Faculty of Arts and Sciences, Amasya University, 05100 Amasya, Turkey
c Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, Kurupelit, TR-55139 Samsun, Turkey
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
"
The crystal structure is stabilized by
weak C–Hꢀ ꢀ ꢀO hydrogen-bond and
p–p interactions.
"
The structural and spectroscopic
data of the compound was
calculated using DFT and HF
methods.
"
"
Electronic absorption spectra of the
title compound were predicted and
good agreement with the TD-DFT
method.
Isotropic chemical shifts (13C and 1H
NMR) were calculated using the
GIAO method.
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 16 July 2012
The novel compound 4-(1-formylnaphthalen-2-yloxy)phthalonitrile, C19H10N2O2, has been synthesized
and characterized by IR, UV–vis, NMR and X-ray single-crystal determination. The title compound, is built
up from two planar groups (naphthalen and phthalonitrile), with a dihedral angle of 64.10(4)° between
Keywords:
Phthalonitrile
X-ray diffraction
FT-IR
them. The crystal structure is stabilized by weak C–Hꢀ ꢀ ꢀO hydrogen-bond and
p–p interactions. The
structural and spectroscopic data of the compound in the ground state have been calculated using density
functional theory (DFT) and Hartree–Fock (HF) with the 6-31G(d,p) basis set. The vibrational study was
interpreted in terms of potential energy distribution (PED). The observed wave number in FT-IR spectra
was analyzed and assigned to different normal modes of the molecule. Using the TD-DFT and TD-HF
methods, electronic absorption spectra of the title compound were predicted and good agreement with
13C and 1H NMR
UV–Vis
DFT
the TD-DFT method and the experimental determination was found. Isotropic chemical shifts (13C and 1
H
NMR) were calculated using the gauge-invariant atomic orbital (GIAO) method. The HOMO and LUMO
analyses were used to elucidate information regarding charge transfer within the molecule.
Ó 2012 Elsevier B.V. All rights reserved.
Introduction
are also used in medicine, as singlet oxygen photosensitisers for
photodynamic therapy (PDT) [2]. Some phthalocyanines have been
Phthalonitriles have been used as starting materials for phthal-
ocyanines [1], which are important components for dyes, pig-
ments, gas sensors, optical limiters and liquid crystals, and which
used by the petroleum industry as catalysts for the oxidation of
sulfur compounds in the gasoline fraction. Applications as photo-
conductors in the xerographic double layers of laser printers and
copy machines, and as active materials in writable disks, are also
known [3]. Vibrational studies of phthalonitriles are of interest in
their own right and they are extremely valuable when performing
vibrational studies of larger composite molecular systems [4].
⇑
Corresponding author. Tel.: +90 3623121919; fax: +90 3624576081.
E-mail address: iucar@omu.edu.tr (I. Uçar).
_
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.07.005

570
H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
Computational Chemistry, which is also called Molecular Mod-
1H NMR (CDCl3): d: ppm: 7.16 (d), 7.26–7.95 (m), 8.20 (d), 9.24
(d), 10.73 (s); 13C-NMR (CDCl3): d: ppm: 110.37, 114.63, 115.00,
118.20, 119.20, 121.63, 121.70, 122.04, 125.52, 127.25, 128.66,
130.53, 130.13, 131.72, 135.76, 138.09, 157.23, 161.09, 189.88.
eling, is based on a set of techniques for investigating chemical
problems on a computer. Some of the subjects that are commonly
investigated computationally are the molecular optimization, the
IR, UV and NMR spectra, the EPR parameters, the energies of mol-
ecules and transitions states, chemical reactivity and the physical
properties of substances [5–8]. Density functional theory (DFT) is
a quantum mechanical theory used in physics and chemistry to
investigate the electronic structure of many-body systems, in par-
ticular atoms, molecules, and the condensed phases [9,10]. By
means of DFT, the properties of a many-electron system can be
determined by using functionals, i.e. functions of another function,
which in this case is the spatially dependent electron density. The
development of better exchange–correlation functionals made it
possible to calculate many molecular properties with comparable
accuracies to traditional correlated ab initio methods, with more
favorable computational costs [11].
In our ongoing research, we have recently synthesized some
phthalonitriles derivatives and their structures have been reported
[12]. In this article, we present the synthesis, crystal, molecular,
electronic structures, and spectroscopic characterization of 4-(1-
formylnaphthalen-2-yloxy)phthalonitrile. In order to help to make
further investigate on the properties of the synthesized com-
pounds density functional theory (DFT) and HF calculations were
carried out.
Crystal structure determination and refinement
The diffraction data were collected on a STOE IPDSII image plate
detector using Mo Ka radiation (k = 0.71073 Å, T = 297 K). The tech-
nique used was w–2h scan mode with limits 2.7–27.5°. A summary
of the key crystallographic information is given in Table 1. Data
collection: Stoe X-AREA [15]. Cell refinement: Stoe X-AREA [15].
Data reduction: Stoe X-RED [15]. The structure was solved by di-
rect-methods using SHELXS-97 [16] and anisotropic displacement
parameters were applied to non-hydrogen atoms in a full-matrix
least-squares refinement based on F2 using SHELXL-97 [16]. All
H atoms attached to carbon atoms were positioned geometrically
and refined by a riding model with Uiso 1.2 times that of attached
atoms. Molecular drawings were obtained using DIAMOND 3.0
(demonstrated version) [17].
Computational methods
The crystal structure was used as an initial molecular geometry.
Quantum chemical calculations are performed with GAUSSIAN 03
program packages [18]. The output files are visualized by means
of GAUSSIAN VIEW 03 software [19]. The geometry of neutral form
of title compound was optimized at two levels of theory: density
functional theory (DFT) and Hartree–Fock Theory using the 6-
31G(d,p) [20,21] basis set, respectively. The DFT method employed
is B3LYP, which combines Backe’s three-parameter non-local ex-
change function with the correlation function of Lee et al.
[22,23]. Molecular geometry of the studied structure was fully
optimized by the force gradient method using Berny’s algorithm.
The electronic spectrum of title complex was calculated with
the TDDFT and TDHF method starting from the ground-state geom-
etry optimized in the gas phase. The solvent (ethanol) effect was
stimulated using the polarizable continuum model (PCM). The cal-
culated vibrational frequencies were carried out using the DFT/
B3LYP and HF level of theories. For the structures, the stationary
points found on the molecule potential energy hypersurfaces were
characterized using standard analytical harmonic vibrational anal-
ysis. The absence of the imaginary frequencies, as well as of nega-
tive eigenvalues of the second derivative matrix, confirmed that
the stationary points correspond to minima of the potential energy
hypersurfaces. A detailed interpretation of the vibration spectra of
this compound has been made on the basis of the calculated poten-
tial energy distribution (PED) using the VEDA 4 program.
Experimental and theoretical methods
General method
2-Hydroxy-1-naphthaldehyde was purchased from the Fluka. 4-
Nitrophthalonitrile was synthesized according to the reported pro-
cedure [13]. All other reagents and solvents were of reagent-grade
quality and were obtained from commercial suppliers. All solvents
were dried and purified as described by Perin and Armarego [14].
The solvents were stored over molecular sieves (4 Å). The homoge-
neity of the products was tested by TLC (SiO2 or Al2O3). The IR spec-
tra were recorded in the 4000–400 cmꢁ1 region using KBr pellets
on a Vertex 80 V Bruker FT-IR spectrophotometer. Electronic
absorption spectra were measured on a Unicam UV–VIS spectrom-
eter in the range 900–200 nm. 1H NMR and 13C NMR studies were
made on a Bruker AC-200 FT-NMR spectrometer.
Synthesis
Synthesis of 4-(1-formylnaphthalen-2-yloxy)phthalonitrile
2-Hydroxy-1-naphthaldehyde (0.90 g, 5,23 mmol) and 4-
nitrophthalonitrile (0.82 g, 4.74 mmol) were dissolved in dry
dimethylformamide (60 ml) with stirring under N2. Dry fine-
powdered potassium carbonate (2.00 g, 14.49 mmol) was added
in portions (10 ꢂ 1.5 mmol) every 10 min. The reaction mixture
was stirred for 48 h at room temperature and poured into ice-
water (150 g). The product was filtered off and washed with water
until the filtrate was neutral. Recrystallization from ethanol solu-
tion gave a brown product (yield 0.28 g, 19.86%). Single crystals
(Scheme 1) were obtained from DMF solution of the compound
via slow evaporation at room temperature (m.p. 451–454 K).
Results and discussion
Molecular structure of 4-(1-formylnaphthalen-2-yloxy)phthalonitrile
The crystal structure of (1) is shown in Fig. 1 and selected bond
distances and angles are summarized in Table 2. The compound
(1), crystallizes in the monoclinic space group C2/c with eight mol-
ecules in the unit cell. It contains two ring systems, naphthalen and
O
H
O
H
O
OH
CN
CN
CN
CN
K2CO3
DMF
+
O2N
Scheme 1.

H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
571
Table 1
Table 2
Crystal
yloxy)phthalonitrile.
data
and
structure
refinement
for
4-(1-formylnaphthalen-2-
Selected structural parameters by X-ray and theoretical calculations for compound
(1).
Formula
C19H10N2O2
298.29
297 K
0.71073
Monoclinic
C2/c
Experimental
Calcd.
HF
Formula weight (g)
Temperature (K)
Wavelength (Mo Å)
Crystal system
Space group
Unit cell dimensions
a, b, c (Å)
DFT/B3LYP
0
Bond lengths (ÅA)
N1–C1
N2–C2
C6–C7
O1–C6
C16–C17
O2–C19
C12–C17
1.13891(2)
1.13684(3)
1.37882(3)
1.36783(2)
1.41543(3)
1.19665(3)
1.41814(2)
1.13931
1.13975
1.38257
1.38018
1.42022
1.21407
1.41137
1.14621
1.14699
1.38593
1.37744
1.42201
1.21911
1.41679
27.976(5), 8.350(5), 14.418(5)
b (°)
117.891(5)
2977(2)
8
1.331
0.088
Volume (Å3)
Z
Calculated density (g cmꢁ3
)
Bond angles (°)
C2–C3–C4
N1–C1–C4
O1–C6–C5
O1–C9–C18
C12–C17–C18
N2–C2–C3
O1–C6–C7
C16–C17–C18
l
(mmꢁ1
F(0,0,0)
)
120.819(15)
179.217(19)
123.081(15)
117.495(13)
118.638(16)
178.960(19)
115.543(14)
123.899(14)
120.978
179.374
122.853
118.843
118.849
179.214
116.446
122.956
121.268
179.121
122.866
118.765
118.756
179.024
116.101
123.368
1232.0
Crystal size (mm)
h Ranges (°)
0.4 ꢂ 0.3 ꢂ 0.1
2.7–27.5
ꢁ33 6 h 6 36
ꢁ9 6 k 6 10
ꢁ18 6 l 6 18
25745
_
Index ranges
Reflections collected
_
3404 [R(int) = 0.023]
Independent reflections
Reflection observed (I > 2
Absorption correction
Refinement method
r
)
2355
Integration
naphthalen group (C9ꢁC10ꢁC11ꢁC12/C17ꢁC18; Slippage dis-
tance between the two phenyl rings is 1.129 Å). The centroid to-
centroid and centroid-to-plane distances between the phenyl rings
are 3.791(2) and 3.412(5) Å, respectively. The closest interatomic
distance between these ring planes is [C9ꢀ ꢀ ꢀC10(1/2 ꢁ x,1/2 ꢁ
y,ꢁz)] 3.488(3) Å.
Full-matrix least-squares on F2
Data/restrains/parameters
3404/0/209
0.973
0.037
0.060
0.13 and ꢁ0.13
Goodness-of-fit on F2
Final R indices [Ih2
r
(I)]
R indices (all data)
Largest diff. Peak and hole (e Åꢁ3
)
Optimized structure
phthalonitrile, linked by an O atom, forming non-planar molecular
structure. The phthalonitrile ring exhibits normal geometry and is
planar. The two cyano groups deviate from this plane by 0.009(1)
and 0.008(1) Å at atoms N2 and N1, respectively. The naphthalen
system is also planar, with a maximum deviation of 0.033(3) Å
for atom C17. The phthalonitrile and naphthalen groups make
Ab initio calculations were performed on compound (1) at DFT/
B3LYP/6-31G(d,p) and HF/6-31G(d,p) level of theory. Some opti-
mized geometric parameters of (1) are listed in Table 2. A superpo-
sition of the molecular structure of compounds as established by
quantum mechanical calculations and X-ray study shows an excel-
lent agreement (Fig. 3). Comparing the theoretical data with the
experimental ones indicates that optimized bond lengths and an-
gle values are slightly different with the experimental results. It
should be noted that the geometry of the solid state structure is
subject to intra and intermolecular interactions, such as hydrogen
bonding and van der Waals interactions.
a
dihedral angle of 64.10(4)°. The C„N bond lengths
[N1„C1 = 1.139(2) Å and N2„C2 = 1.137(2) Å] compare well with
values reported in the literature [24,25]. As expected, the N„CAC
angles [N1„C1AC4 = 179.2(2)° and N2„C2AC3 = 178.9(2)°] are
linear.
The crystal packing is formed by weak intra and intermolecular
hydrogen bonding (CAHꢀ ꢀ ꢀO) interactions (Fig. 2, Table 3). Apart
from these, there is also symmetry-related weak slipping face to
As seen in Table 2, the largest discrepancies between the calcu-
lated and experimental geometrical parameters are observed for
C–H. Large deviation from experimental C–H bond distances may
face
p–p stacking interaction between the two phenyl rings of
Fig. 1. The molecular structure of 4-(1-formylnaphthalen-2-yloxy)phthalonitrile, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 40%
probability level and H atoms are shown as small spheres of arbitrary radii.

572
H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
line shape, the VEDA 4 program and the animation option of
GAUSS VIEW 3.0. The potential energy distribution is also support-
ing the present study. The computed intensities show marked
deviations from the observed values, since computed wavenum-
bers correspond to the isolated molecular state, whereas the ob-
served wavenumbers correspond to the solid state spectra.
The heterocyclic aromatic compounds and its derivatives are
structurally very close to benzene. These compounds shows the
presence of C–H stretching vibration in the region 3100–
3000 cmꢁ1, which is the characteristic region for the ready identi-
fication of C–H stretching vibrations [32]. In this region, the nature
of the substituents does not make any appreciable change [33]. In
this study, first ten vibrations are assigned to C–H stretching,
which correspond to stretching modes of the C–H of ring and alde-
hyde units. All modes are almost pure stretching vibrations 100%
PED terms. The C–H in-plane bending wavenumbers appear in
the range of 1000–1500 cmꢁ1 and C–H out-of-plane bending vibra-
tion in the range of 700–1000 cmꢁ1. The in-plane C–H bending
vibrations were assigned in the range that mentioned above and
according to their PED; they are described as mixed modes, gener-
ally with C–C vibrations. The C–C stretching vibrations show
absorption in the region 1300–700 cmꢁ1 [34]. Accordingly, the
bands observed at 1279 and 1066 and 709 cmꢁ1 in FT-IR spectra
have been assigned to CC stretching vibrations which are well
comparable with the computed values. The theoretically calculated
CCC bending vibration has been found to be consistent with the re-
corded spectral values and is listed in Table 4 with the contribution
of 30–23% PED.
Fig. 2. A view of the packing of 4-(1-formylnaphthalen-2-yloxy)phthalonitrile,
showing hydrogen bonding and p–p interactions as dashed lines.
Table 3
Hydrogen bonding interactions for 4-(1-formylnaphthalen-2-yloxy)phthalonitrile.
D–Hꢀ ꢀ ꢀA
D–H
Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA
D–Hꢀ ꢀ ꢀA
C5–H3ꢀ ꢀ ꢀO2i
C16–H9ꢀ ꢀ ꢀO2
C19–H10ꢀ ꢀ ꢀO1
0.93
0.93
0.93
2.45
2.27
2.31
3.359(3)
2.906(3)
2.708(3)
167
125
105
The sharp band in the region of 2210–2270 cmꢁ1 is easily as-
signed to the characteristic C„N stretching mode [35]. In previ-
ously reported similar studies were assigned the cyano stretching
vibration in the range of 2229–2249 cmꢁ1 for hydroxy-containing
phthalonitrile model compounds [4,36–38]. In this study, the
strong band at 2230 cmꢁ1 in FT-IR spectrum and calculated band
at 2212–2216 cmꢁ1 (DFT), 2276–2281 cmꢁ1 (HF) are assigned to
C„N stretching vibrations which have good correlation with
literature.
Symmetry code: (i) = 1/2 ꢁ x,1/2 + y,1/2 ꢁ z.
arises from the low scattering factors of hydrogen atoms in the X-
ray diffraction. Several authors have been reported that the HF
methods under estimate some bond length and DFT/B3LYP meth-
ods predicts bond lengths which are systematically too long, espe-
cially C–H bond lengths [26–29].
The largest difference between experimental and calculated
DFT bond length is 0.022 Å (C2–C3) for, whereas this difference
for HF method is 0.017 Å (C2–C3), which suggest that the calcula-
tional precision is satisfactory [30]. These theoretical results indi-
cate that the HF method gives geometric parameters, which are
much closer to experimental ones. Similar situation is also ob-
served for calculated bond angles with HF and DFT method.
The C@O/CAO band is reasonably easy to be recognized due to
its high intensity [39]. In this study, the band observed at
1674 cmꢁ1 in FT-IR spectra (mode No.13) has been assigned to
C@O stretching vibration, with the contribution of 45% PED. The
band observed at 990 cmꢁ1 in FT-IR spectrum is assigned to C–O
stretching vibration (mode No. 45), which is in good agreement
with the theoretically calculated values.
Vibrational assignments
UV–vis spectrum and electronic properties
Some primary calculated harmonic frequencies are listed in Ta-
ble 4, together with experimentally determined frequencies
(Fig. 4). Calculated vibrational frequencies of (1) at DFT/B3LYP
and HF levels were scaled by 0.96 and 0.89, respectively [31].
According to the theoretical calculations, both the optimized
molecular structures belong to the C1 point group as it does not
display any special symmetry. As a result of this all the normal
modes of both compounds are infrared active. The vibrational
assignments have been done on the basis of relative intensities,
The UV–vis electronic spectra of compound (1) in ethanol solu-
tion were recorded within 200–800 nm range. The theoretical elec-
tronic excitation energies, oscillator strengths and nature of the
first 20 spin-allowed singlet–singlet electronic transitions were
calculated by the TD-DFT/PCM method for the above solvents.
The major contributions of the transitions were designated with
the aid of SWizard program [40]. The experimental and calculated
results of UV–vis spectral data were compared in Table 5. Each
Fig. 3. Atom-by-atom superimposition of the 4-(1-formylnaphthalen-2-yloxy)phthalonitrile calculated (red) over the X-ray structure (black) (for interpretation of the
references to color in this figure legend, the reader is referred to web version of this article).

H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
573
Table 4
Comparison of the observed and calculated vibrational spectra of compound (1).
Experimental
DFT/B3LYP
HF/6-31 G(d,p)
PED (P10%)
Assignments
FT-IR (cmꢁ1
)
Scaled (cmꢁ1
)
Scaled (cmꢁ1
)
3070
3040
2882
2230
1674
1621
1584
1509
1486
1459
1436
1415
1371
1344
1307
1279
1245
1209
1163
1088
1065
989
3141
3120
2937
2216
1621
1604
1584
1504
1479
1456
1431
1403
1368
1360
1305
1280
1274
1227
1166
1083
1057
976
3078
3037
2942
2281
1674
1629
1607
1504
1495
1463
1432
1400
1360
1341
1289
1272
1247
1210
1153
1081
1071
1021
949
t
t
t
t
t
t
t
CHR3 (98)
CHR1 (99)
CHAldehit (100)
CꢃN (85) +
tCC (12)
CO (45)
CO (23) +
{CHR1 + CHR2} (33)
{CHR2 + CHR3} (10)
b(HCCR1) (22) + b(HCCR2) (26) + b(CCCR1) (10)
b(HCCR3) (19) + b(HCCR2) (12) + b(HCCalde) (11) + b(HCCR1) (15)
CCR3 (14) + CCR2 (14) + b(HCCalde) (12)
b(HCO)Ald (66)
CCR2(14) +
CCR2(14) +
CCR1(77)
t{CHR1 + CHR2 + CHR3} (36)
b(HCCR2) (11) +
t
t
t
t
t
t
t
t
t
tCCR3(14) + b(HCCalde) (12)
tCCR3(14)
CCR1(15) + b(HCCR1) (27) + b(HCCR2) (29)
CCR3(15) + b(HCCR3) (27) + b(HCCR1) (29)
CCR1(21) + tCO (21)
b(HCCR3) (17) + b(HCCR2) (11) + b(HCCR1) (13)
t
t
CCR1(10) + b(CCCR1) (10) + b(HCCR1) (20)
{CCR2 + CCR3}(19) + b{(CCCR2) + (CCCR3)} (28)
c
CHR3(23) +
CCR1(11) +
CHR1(72)
b(CCCR3)(31) + b(CCO)(12) + b(CCCR2)(14)
c
CHR2(34)
936
899
863
916
896
855
t
c
tCCR2(12) +
tCO (14)
920
885
836
764
843
759
860
784
c
c
CHR1(78)
CHR3(22) + cCHR2(40)
709
720
720
tCCR1(16) + b(CCCR1)(39)
671
640
666
633
672
640
b(OCC)(11) +
b(OCC)(11)
c
OCCC (15)
602
572
526
509
618
568
525
508
629
566
535
513
c
OCCC (20) +
b(CCO)(14) + b{(CCCR1) + (CCCR2) + (CCCR3)}(12)
{CCCCR1 + CCCCR2 + CCCCR3}(27)
b{(CCCR1 + CCCR2 + CCCR3)}(10) + b(CCC)(13)
CCCCR1(13) + CCCCR2(13) + CCCCR3(21)
cCCCCR1 (12)
c
408
410
416
c
c
c
R1: phthalonitrile ring; R2 and R3: naphthalene rings; t: stretching; b: in-plane bending; c: out-of-plane bending.
Fig. 4. The experimental Infrared spectra of the present 4-(1-formylnaphthalen-2-yloxy)phthalonitrile.
calculated transition is represented by
a
Gaussian function
to the experimental results; therefore these results are not dis-
cussed in this part.
The analysis of the wave function indicates that the electron
absorption corresponds to the transition from the ground to the
2
y ¼ ceꢁbx with the height c equal to the oscillator strength and b
equal to 0.04 nmꢁ2. The predicted absorption wavelengths using
the HF level of theory for title compound are not corresponding

574
H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
Table 5
Calculated electronic transitions for 4-(1-formylnaphthalen-2-yloxy)phthalonitrile with TD-DFT and TD-HF methods.
Exper. k (nm)
DFT/B3LYP
HF/6 31G(d,p)
k (nm)
Osc. strength
E (eV)
Major contributions
k (nm)
Osc. strength
E (eV)
Major contributions
386
329
260
379
355
331
326
276
253
242
238
0.0092
0.0786
0.0653
0.2830
0.0564
0.2521
0.1044
0.1368
3.27
3.49
3.74
3.80
4.48
4.88
5.11
5.21
H-2 ? L (44%)
H ? L (88%)
H-1 ? L (22%)
–
–
–
–
–
–
–
–
H ? L + 1 (92%)
H-1 ? L (62%)
H ? L + 2 (78%)
H-3 ? L + 1 (43%)
H-2 ? L + 2 (48%)
H-5 ? L (41%)
–
–
H-2 ? L (22%)
H-3 ? L (11%)
H-1 ? L + 2 (39%)
H-5 ? L (25%)
H ? L + 3 (16%)
246
232
0.2921
0.2223
5.03
5.34
H ? L (50%)
H-1 ? L (44%)
H ? L + 1 (33%)
H-1 ? L + 1 (21%)
215
214
0.4337
5.77
H-2 ? L (36%)
H-2 ? L + 1 (24%)
H: HOMO.
L: LUMO.
Fig. 5. Molecular orbital surfaces and energy levels using the DFT/B3LYP method for the, HOMO, HOMOꢁ1, LUMO and LUMO + 1/2 of 4-(1-formylnaphthalen-2-
yloxy)phthalonitrile.
first excited state. It is mainly described by one-electron excitation
from the highest occupied molecular orbital (HOMO) to the lowest
unoccupied molecular orbital (LUMO). The HOMO energy charac-
terizes the ability of electron giving, LUMO characterizes the ability
of electron accepting, and the gap between HOMO and LUMO char-
acterizes the molecular chemical stability [41]. The several con-
tours of occupied and unoccupied MOs (active in the electronic
states) are presented in Fig. 5.
transitions from the HOMO and lower occupied MOs to LUMO
and higher unoccupied MOs. Molecular orbital coefficients analy-
ses based on DFT/B3LYP optimized structure indicate that frontier
molecular orbitals are mainly composed of p atomic orbitals, so
electronic transitions are mainly derived from the n ?
p
⁄ and
p
?
p⁄ transitions. It is clear from Fig. 5 that while the HOMO
and HOMO-2 orbitals are delocalized on the naphthalene and alde-
hyde group, in LUMO and LUMO+1 electron cloud is completely
delocalized on whole compound. The HOMO could be character-
According to the TD–DFT, the predicted electronic spectrum at
bands between the 200–400 nm is assigned to the electronic
ized as a
p-bonding (between a pair of naphthalene ring atoms)

H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
575
Fig. 6. The experimental 1H (a) and 13C (b) NMR spectra of 4-(1-formylnaphthalen-2-yloxy)phthalonitrile in CDCl3 solution.
Table 6
Experimental and theoretical, 1H and 13C isotropic chemical shifts (d) and magnetic isotropic shielding constants (
r) (with respect to TMS) of compound (1) by DFT/B3LYP
method.
Atom
Gaseous
DMSO
Water
CDCl3
d Exp.
d Calcd.
r
Calcd.
d Calcd.
r
Calcd.
d Calcd.
r
Calcd.
d Calcd.
r
Calcd.
(CDCl3)
H3
H14
H7
H1
H6
H8
H2
H5
H9
H10
C3
C10
C1
C2
C4
C5
C18
C7
C16
C14
C13
C12
C15
C17
C8
6.07
6.07
6.69
6.69
6.78
6.97
6.97
6.97
9.33
11.08
99.67
101.72
102.51
102.70
105.60
106.23
107.32
107.42
111.25
112.58
112.79
115.88
115.94
116.63
120.35
122.13
144.67
145.30
181.18
25.81
25.79
25.20
25.16
25.10
24.95
24.90
24.87
22.55
20.79
82.78
80.74
79.95
79.76
76.86
76.23
75.14
75.04
71.21
69.88
69.67
66.58
66.52
65.83
62.11
60.33
37.79
37.16
1.27
6.48
6.60
7.05
7.25
7.25
7.25
7.50
7.59
9.10
11.00
97.96
103.22
104.50
105.19
105.78
107.35
107.35
110.17
110.51
111.44
114.11
116.10
116.10
116.10
122.60
125.42
146.65
146.65
183.88
25.40
6.55
6.61
7.05
7.24
7.24
7.24
7.49
7.60
9.09
11.00
97.88
103.38
104.51
105.33
105.91
107.34
107.65
110.10
110.44
111.37
114.13
116.07
116.07
116.07
122.50
125.43
146.79
146.87
184.06
25.32
6.34
6.42
6.95
7.09
7.09
7.18
7.34
7.42
9.18
11.01
98.41
102.59
104.37
104.85
104.94
106.78
107.37
109.46
111.27
111.45
113.60
116.07
116.16
116.30
121.99
124.43
145.96
146.28
183.02
25.53
7.13
7.17
7.26
7.31
7.32
7.33
7.36
7.41
9.24
10.73
110.37
111.63
115.00
118.20
119.20
121.63
121.70
122.04
125.52
127.25
128.66
130.13
130.53
131.72
135.76
138.09
157.23
161.09
189.88
25.27
24.83
24.64
24.63
24.62
24.38
24.28
22.78
20.88
84.49
79.24
77.96
77.27
76.68
75.14
75.09
72.29
71.95
71.02
68.34
66.38
66.35
66.34
59.87
57.03
35.82
35.81
ꢁ1.42
25.26
24.83
24.65
24.63
24.62
24.38
24.27
22.78
20.88
84.58
79.07
77.95
77.12
76.55
75.12
74.81
72.36
72.02
71.08
68.33
66.41
66.40
66.35
59.96
57.03
35.67
35.59
ꢁ1.59
25.45
24.92
24.79
24.78
24.69
24.53
24.46
22.70
20.86
84.05
79.87
78.09
77.61
77.52
75.67
75.09
73.00
71.19
71.01
68.86
66.39
66.30
66.16
60.47
58.04
36.50
36.18
ꢁ0.55
C11
C9
C11
C19

576
H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
Table 7
Selected interactions between ‘‘filled’’ (donors) Lewis-type NBOs and ‘‘empty’’ (acceptor) non-Lewis NBOs.
a
b
Donor Lewis Type NBOs
Occupancy
Acceptor non Lewis NBOs
E
(2)(kJmolꢁ1
)
E(j)–E(i) (kJmolꢁ1
)
r
p
p
p
(O2–C19)
(C18–C17)
(C7–C8)
1.99
1.69
1.66
1.63
p⁄(C18–C17)
p⁄(O2–C19)
p⁄(C5–C6)
p⁄(C7–C8)
26.16
89.32
93.38
71.73
971.41
708.88
708.88
761.41
(C5–C6)
Selected occupancy of NBOs and hybrids calculated for title compound
Donor Lewis Type NBOs
Occupancy
Hybrid
AO(%)c
Acceptor non Lewis NBOs
r
p
r
r
r
p
(C18–C17)
(C18–C17)
(C11––C12)
(C7–C8)
1.97
sp1.96(C18)
sp1.55(C17)
sp1.0(C18)
sp99.9(C17)
sp1.76(C11)
sp1.79(C12)
sp1.82(C7)
sp1.82(C8)
sp1.61(C5)
sp1.92(C6)
sp1.0(C5)
s(33.81%)p(66.19%)
s(39.27%)p(60.70%)
s(0.01%)p(99.99%)
s(0.03%)p(99.97%)
s(36.23%)p(63.77%)
s(35.78%)p(64.22%)
s(35.49%)p(64.53%)
s(35.47%)p(64.53%)
s(38.25%)p(61.75%)
s(34.28%)p(65.72%)
s(0.01%)p(99.99%)
s(0.01%)p(99.99%)
r⁄(C18–C17)
1.69
1.97
1.97
1.97
1.63
p⁄(C18–C17)
r⁄(C11–C12)
r⁄(C7–C8)
r⁄(C5–C6)
p⁄(C5–C6)
(C5–C6)
(C5–C6)
sp1.0(C6)
a
b
c
Second order interaction energy (stabilization energy).
Energy difference between donor and acceptor i and j NBO orbitals.
Percentage contribution of atomic orbitals in NBO hybrid.
and nonbonding molecular orbital (aldehyde oxygen atom). Final-
ly, the LUMO and LUMO 1/2 exhibit a -antibonding character be-
tween some pair of phthalonitrile and naphthalene groups.
natural charge [ꢁ0.25] on the N1 atom. The largest negative
charges are located on the oxygen atoms O1 (ꢁ0.51 e) and O2
(ꢁ0.52 e) for title compound.
p
Hyperconjugation is the interaction of the electrons in a sigma
bond with an adjacent empty (or partially filled) non-bonding p-
13C and 1H NMR calculations
orbital or antibonding
p orbital or filled p orbital, to give an ex-
In order to provide an unambiguous assignment of 13C and 1H
NMR spectra of compound (1) (Fig. 6), we undertook a series of
NMR calculations using GIAO approximation, and the results of
these calculations are shown in Table 6. The default PCM model
provided by GAUSSAIN03 was also tested in order to describe the
influence exerted by solvent on the NMR spectra of the given com-
pound. The isotropic shielding values were used to calculate the
tended molecular orbital that increases the stability of the system
when these orbitals are properly oriented. Second order perturba-
tion theory allows making conclusions about the strength the
hyperconjugative interaction energy. The larger the second order
interaction energy (E2) value, the more intensive is the interaction
between electron donors and electron acceptors, i.e., the more
donating tendency from electron donors to electron acceptors
and the greater the extent of conjugation of the whole system.
These interactions can be identified by finding the increase in elec-
tron density (ED) in anti-bonding orbital that weakens the respec-
isotropic chemical shifts (d) with respect to tetramethylsilane
(TMS), (dXiso
¼
r
ꢁ
rXiso). Comparison between experimental and
TMS
iso
theoretical NMR chemical shifts provides practical information
on the chemical structure and conformation of compounds. It is
clear from Table 6 that the agreement with experimental data is
good, even the trends in relative values are well reproduced. The
largest differentiation for the chloroform solution in 13C chemical
shifts is observed for C14, amounting to about 16 ppm. The differ-
entiation found in 1H, on the other hand, is only of a few tenths of
ppm. Signals for protons were observed at 7.13–10.73 ppm. Since
H atom is the smallest of all atoms and mostly localized on the
periphery of molecules, their chemical shifts would be more sus-
ceptible to intermolecular interactions in the aqueous solutions
as compared to that for other heavier atoms.
tive bonds. The NBO analysis results show that the
participates as donor and the p⁄(C18–C17) antibond as acceptor
(O2–C19) ? p⁄(C18–C17)], and the charge transfer energy value
is 971.4 kJ/mol. This interaction weakens the C18–C17 bond with
r(O2–C19)
[r
elongation of its bond length (1.446 Å). The
r(O2–C19) is formed
from sp1.68 hybrid on O2 (which is mixture of 37.32% s, 62.68% p
atomic orbitals) and sp2.27 on C19 (30.61% s, 69.39% p). Further-
more, the increasing p characters on carbons C18 and C17 bond
orbitals result in lengthening of the
r(C18–C17) bond than the
other C–C bond lengths in the studied compound (Table 7). De-
creased occupancy of the localized p(C18–C17) orbital in the Lewis
structure, and increased occupancy of p⁄(C18–C17) of the non-Le-
wis orbital and their subsequent impact on the molecular stability
and geometry are also related with the pure p character of the two
Natural bond orbital analysis
carbons C18 and C17 of the p(C18–C17) bond orbital as shown in
The natural bond orbital (NBO) calculation of compound (1) was
performed using NBO 3.1 program implemented in the GAUSS-
IAN03 package at the DFT/B3LYP/6-31G(d,p) level. The NBO analy-
sis can be used to investigate the charge transfer or estimate
delocalization of electron density between occupied Lewis-type
orbitals and formally unoccupied non-Lewis NBOs, which corre-
sponds to a stabilizing donor–acceptor interaction [42]. According
to the NBO results, the electronic configuration of N1 atom in com-
pound is [core] 2S1.612p3.64, 1.99 core electrons, 5.24 valence elec-
trons (on 2s, 2p atomic orbitals) and 0.007 Rydberg electrons. This
gives the total of 7.25, which is consistent with the calculated
Table 7. The intramolecular hyperconjugative interaction of the
p
electrons occurs from C7–C8 to p⁄(C5–C6) (93.4 kJ/mol) leads to
strong stabilization of the phthalonitrile moiety.
Finally, the NBO analysis clearly explains the evidence of the
formation of weak H-bonded interaction between the LP(O) and
r⁄(O–H) antibonding orbitals. The stabilization energies E(2) associ-
ated with hyperconjugative interaction LP1(O2) ?
equal to 70.22 kJ/mol, which quantify the extend of intermolecular
r
⁄(C5–H3), is
hydrogen bonding. Notwithstanding the energetic contribution for
LP1(O2) ?
r
⁄(C16–H9) (6.93 kJ/mol) and LP1(O1) ? ⁄(C19–H10)
r

H. Tereci et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 96 (2012) 569–577
577
Cie,
(2.17 kJ/mol) of hyperconjugative interaction is weak, these E(2)
values are chemically significant and can be used as a measure of
the intramolecular delocalization.
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The 4-(1-formylnaphthalen-2-yloxy)phthalonitrile (1) was syn-
thesized and characterized by IR, UV–vis, 1H-13C NMR and X-ray
single-crystal diffraction techniques. Crystal structure of title com-
pound from the X-ray diffraction was found to be slightly different
from its optimized counterparts. According to the computed re-
sults the phthalonitrile group is significantly twisted with respect
to naphthalene group. The vibrational FT-IR spectra of compound
were recorded and assigned with the aid of the experimental and
computed vibrational wavenumbers and their PED. Potential en-
ergy distributions (PED) suggest that several normal modes are
coupled in varying degrees. Therefore, the assignments made at
higher level of theory with higher basis set with only reasonable
deviations from the experimental values seem to be correct. The
electronic absorption spectra calculations indicate that TD-HF
method is not suitable to be used to study whereas TD-DFT method
can predict the electronic spectra approximately. Molecular orbital
coefficients analyses have shown that electronic spectra are assign
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p⁄ and
p
?
p⁄. The magnetic properties of the title com-
pound were observed and calculated. The chemical shifts were
compared with experimental data, showing a very good agreement
both for 13C and 1H. NBO results also suggest that there is a weak
hydrogen bonding possibilities for title compound.
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