Synthesis, crystal structures and DFT calculations of two new phenol-based ester derivatives

Article abstract of DOI:10.1007/s10870-016-0632-4

Two new phenol-based ester derivatives, namely C₁₃H₉ClO₂ (I) and C₂₀H₁₄O₄ (II) have been synthesized and characterized by NMR spectroscopy, single crystal X-ray diffraction and density functional theory (DFT) geometry optimization and molecular orbital calculations. Compound I crystallizes in the orthorhombic space group Pca2(1),with a = 7.6297 (5) ?, b = 5.5875 (3) ?, c = 26.1624 (12) ?, α = β = γ = 90°, V = 1115.33(11) ?³ and Z = 4. Compound II crystallizes in the triclinic space group P $βar 1$$ 1 ˉ, with a = 5.7970 (4) ?, b = 8.1366 (8) ?, c = 8.8057 (9) ?, α = 83.246 (8)°, β = 72.138 (8)°, γ = 76.696 (8)°, V = 384.22 (6) ?³ and Z = 1. Geometry optimization calculations for each compound is consistent with these observations. A comparison of the dihedral angles between mean planes of the benzene rings in the crystal with the DFT theoretical calculations and weak intermolecular hydrogen bond interactions has been included for each molecule. Electronic transitions have been predicted by DFT Molecular Orbital calculations and compared with experimental absorption spectra.

Full text of DOI:10.1007/s10870-016-0632-4

J Chem Crystallogr
DOI 10.1007/s10870-016-0632-4
ORIGINAL PAPER
Synthesis, Crystal Structures and DFT Calculations of Two New
Phenol-Based Ester Derivatives
Javeed A. Ganaie1 Jubin Kumar1 Ray J. Butcher2 Jerry P. Jasinski3
·
·
·
·
Sushil K. Gupta1
Received: 22 June 2015 / Accepted: 5 January 2016
© Springer Science+Business Media New York 2016
Abstract Two new phenol-based ester derivatives,
namely C13H9ClO2 (I) and C20H14O4 (II) have been syn-
thesized and characterized by NMR spectroscopy, single
crystal X-ray diffraction and density functional theory
(DFT) geometry optimization and molecular orbital cal-
culations. Compound I crystallizes in the orthorhombic
˚
space group Pca2(1),with a = 7.6297 (5) A, b = 5.5875
˚
˚
(3) A, c = 26.1624 (12) A, α = β = γ = 90°, V = 1115.33
3
˚
(11) A and Z = 4. Compound II crystallizes in the triclinic
space group P1, with a = 5.7970 (4) A, b = 8.1366 (8) A,
c = 8.8057 (9) A, α = 83.246 (8)°, β = 72.138 (8)°,
γ = 76.696 (8)°, V = 384.22 (6) A and Z = 1. Geometry
ꢀ
˚
˚
˚
3
˚
optimization calculations for each compound is consistent
with these observations. A comparison of the dihedral
angles between mean planes of the benzene rings in the
crystal with the DFT theoretical calculations and weak
intermolecular hydrogen bond interactions has been
included for each molecule. Electronic transitions have
been predicted by DFT Molecular Orbital calculations and
compared with experimental absorption spectra.
Keywords Phenol-based ester derivatives · Crystal
structure · DFT geometry optimization calculations ·
Frontier molecular orbitals
Introduction
Graphical Abstract Synthesis, crystal structures, DFT
geometry optimization and molecular orbital surface cal-
culations of two new phenol-based ester derivatives of
4-chlorophenyl benzoate, (I): C13H9ClO2 and 1,4-pheny-
lene dibenzoate, (II): C20H14O4.
Phenol-based esters are very useful building blocks for the
synthesis of a wide range of acyclic and cyclic compounds
with interesting photo-reduction properties [1–4]. These
compounds have proved to be useful in a variety of bio-
logical applications such as anti-inflammatory [5],
antimalarial [6], anticancer [7], inhibitors of acetyl-
cholinesterase [8] and inhibitors of HIV [9]. The related
esters are an important precursor for Schiff bases which
can be used to prepare transition metal complexes with
varied applications [10–13].The crystal structures of some
related monoester derivatives, viz. phenyl benzoate [14],
dimethylphenyl benzoate [15–17], 2-benzoyl-4-methyl-
phenyl benzoate [18], 2-benzoyl-4-chlorophenyl benzoate
[19] and 2-(4-chlorophenyl)-2-oxoethyl benzoate [20] have
& Sushil K. Gupta
skggwr@gmail.com
1
School of Studies in Chemistry, Jiwaji University,
Gwalior 474 011, India
2
Department of Chemistry, Howard University, 525 College
Street NW, Washington, DC 20059, USA
3
Department of Chemistry, Keene State College, 229 Main
Street, Keene, NH 03435-2001, USA
123

J Chem Crystallogr
been reported. A search of the Cambridge Structural
Database (Version 5.35, updates to November 2013) [21]
revealed the crystal structures of five related diester
derivatives, viz.1-phenyl-3-{4-[4-(4-undecyloxybenzoyloxy)
phenyloxycarbonyl]phenyl}triazene 1-oxide [22], p-pheny-
lenebis(4-octyloxy benzoate) [23, 24], p-phenylene-
4-methoxybenzoate 4-trifluoromethylbenzoate [25] and
1-phenyl-3-(4-(4-(4-octyloxybenzoyloxy)phenyloxycarbonyl)
phenyl)triazene-1-oxide [26], and4-((4-(nonyloxy)benzoyl)
The solid mass was extracted with chloroform and dried
over anhydrous NaHCO3. Colourless crystals of X-ray
quality were obtained by slow evaporation from ethanol
solution. The structure of the product was confirmed by
1
elemental analyses, mass spectrometry, IR, electronic, H
and 13C NMR spectroscopy, and single crystal XRD. The
characteristics of the product are given below.
Yield 60 %. M.P. 351–353 K. Anal. Calc. for C13H9
ClO2 (%): C, 67.11; H, 3.90; Cl, 15.24. Found: C, 67.68; H,
3.85; Cl, 15.14.ESI–MS: m/z = 232.65 (calculated), m/
oxy)phenyl
4-(3-hydroxy-3-phenyl-3λ5-2-triazen-1-yl)
1
benzoate [27]. We have reported earlier the synthesis and crystal
structure of biologically important diketones, 4-methyl-2,6-
dibenzoylphenol (mdbpH) [28] and 4-tert-butyl-2,6-
dibenzoylphenol (bdbpH) [29]. As part of our on-going work
on phenol-based Schiff base chemistry, we herein report the
synthesis, spectra, crystal structures, and DFT studies of
4-chlorophenylbenzoate (I) and 1,4-phenylene dibenzoate
(II). A comparison of theoretical (based on DFT MO calcu-
lations) and experimental electronic spectra is also presented.
z = 232.97 [M+] (found). H NMR (400 MHz, CDCl3):
δ8.18 (d, J = 7.2 Hz, 2H, C9,13H); 7.64 (t, J = 7.2 Hz, 2H,
C11H); 7.50 (t, J = 7.2 Hz, 1H, C10,12H); 7.38 (d,
J = 7.2 Hz, 2H, C3,5H); 7.16 (d, J = 7.2 Hz, 2H, C2,6H).
13C NMR (100 MHz, CDCl3): δ165.1 (COO), 149.6
(C − O/phenolate), 133.9 (C11), 131.4 (C4), 130.4 (C9,
C13), 129.7 (C3, C5), 129.4 (C8), 128.8 (C10, C12), 123.3
(C2, C6). IR (KBr, cm−1): 3448, 1734, 1662, 1487, 1450,
1403, 1263, 1203, 1060, 1020.
Synthesis of 1,4-Phenylene Dibenzoate (II)
Experimental
4-Methoxyphenol (3.75 g, 0.0117 mol) was added to anhy-
drous AlCl3 (20.0 g, 0.150 mol) and dissolved in dry
nitrobenzene (30.0 mL) with stirring for 10 min. In an ice
bath, benzoyl chloride (10.5 g, 0.075 mol) was added over a
period of 1.5 h. The reaction mixture was heated to 80 °C for
8 h (Scheme 1). The solution was brought to ambient tem-
perature and an ice cooled solution of 6 M HCl (40.0 mL) was
slowly added. After overnight the organic layer was separated
and was steam distilled to remove nitrobenzene. The solid
mass was extracted with chloroform and dried over anhydrous
NaHCO3. Colourless crystals of X-ray quality were obtained
by slow evaporation from ethanol solution. The structure of
the product was confirmed by mass spectrometry, IR, elec-
All the chemicals were of reagent grade and were used as
received. Solvents were purified by standard methods [30]
and freshly distilled prior to use.
Physical Measurements
Elemental analyses were carried out on a CARLO ERBA
model DP 200 instrument. Melting points of compound in
capillaries are uncorrected. The electrospray ion mass spectra
(ESIMS) were recorded on a MICROMASS QUATTRO II
triple quadruple mass spectrometer. Infrared spectra were
recorded on a Shimadzu IR prestige-21 FT spectropho-
tometer with KBr pellets (4000–400 cm−1). Electronic
spectra in 10−3 mol L−1 CH3CN/MeOH solution were
obtained on a Perkin-Elmer Lambda 35 UV–Vis spec-
1
tronic, H and 13C NMR spectroscopy, and single crystal
XRD. The characteristics of the product are given below.
Yield 60 %. M.P. 441–443 K. Anal. calc. for C20H14O4
(%): C, 75.46; H, 4.43. Found: C, 75.67; H, 4.58.ESI–MS:
m/z = 318.31 (calculated), m/z = 319.19 [MH+] (found).
1H NMR (400 MHz, CDCl3): δ8.21 (d, J = 7.6 Hz, 2H,
C2,6H); 7.64 (t, J = 7.6 Hz, 2H, C3,5H); 7.52 (t, J = 7.6 Hz,
2H, C9,13H); 7.28(s, 1H).13C NMR (100 MHz, CDCl3):
δ165.4 (COO), 148.4 (C–O/phenolate), 133.8 (C4), 130.2
(C2, C6), 129.2 (C1), 128.6 (C3, C5), 122.7 (C9, C10). IR
(KBr, cm−1): 3170, 1731, 1601, 1261, 1173, 1063.
1
trophotometer. H (400 MHz) and 13C NMR (100 MHz)
measurements were carried out on a Burker DRX-400
spectrometer in CDCl3with chemical shifts relative to SiMe4.
Synthesis of 4-Chlrophenyl Benzoate (I)
4-Chlorophenol (3.75 g, 0.0161 mol) was added to anhy-
drous AlCl3 (20.0 g, 0.150 mol) and dissolved in dry
nitrobenzene (30.0 mL) with stirring for 10 min. In an ice
bath, benzoyl chloride (10.5 g, 0.075 mol) was added over a
period of 1.5 h. The reaction mixture was heated to 80 °C for
8 h (Scheme 1). The solution was brought to ambient tem-
perature and an ice cooled solution of 6 M HCl (40.0 mL)
was slowly added. After overnight the organic layer was
separated and was steam distilled to remove nitrobenzene.
Structure Determination and Refinement
X-ray data for (I) and (II) were collected with an Agilent
Gemini Eos CCD area detector using CrysAlisPro software
˚
[31] and graphite-monochromated Mo-Kα (λ = 0.71073 A)
˚
for (I) and Cu-Kα (λ = 1.54178 A) for (II) at 173(2) K.
123

J Chem Crystallogr
l
C
Cl
O
O
Cl
AlCl3
Nitrobenzene
O
H
O
I
OMe
Cl
O
AlCl3
Nitrobenzene
O
OH
O
O
O
II
Scheme 1 Synthesis scheme for (I) and (II)
Computational Details
The structures were solved by Superflip [32] using charge
flipping and all of the non-hydrogen atoms were refined
anisotropically by full-matrix least-squares on F2 using
SHELXL2014 [33]. All the hydrogen atoms were placed in
their calculated positions and then refined using the riding
Density Functional Theory (DFT) Calculations
A density functional theory (DFT) geometry optimized
molecular orbital calculation (WebMo Pro [36]) with the
GAUSSIAN-03 program package [37] employing the
B3LYP (Becke three parameter Lee–Yang–Parr exchange
correlation functional, which combines the hybrid
exchange functional of Becke [38] with the gradient-cor-
relation functional of Lee, Yang and Parr [39] and the 6-31
G(d) basis set [40] were performed on the title molecules.
No solvent corrections were made with these calculations.
Starting geometries were taken from X-ray refinement data.
The optimized geometry results in the free molecule state
are, therefore, compared to those in the crystalline state. A
comparison of selected bond distances and angles in the
crystals to that from the DFT calculation is given in
˚
model with Atom—H lengths of 0.95A (CH). Isotropic
displacement parameters for these atoms were set to 1.20
(CH) times Ueq of the parent atom. A multi-scan absorption
correction was performed using CrysAlis RED and all
calculations including molecular graphics were performed
using SHELXTL [34]. Crystal and experimental data for
(I and II) are listed in Table 1. Structural diagrams of the
asymmetric unit and crystal packing of (I) and (II) are
shown in Figs. 1, 2, 3 and 4, respectively. Bond lengths and
bond angles are all within expected ranges [35]. Selected
geometric parameters for (I and II) are listed in Table 2.
Weak intermolecular C–H···π interactions are listed in
Table 3.
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J Chem Crystallogr
Table 1 Crystal and
experimental data for I and II
I
II
Formula
C
13H9ClO2
C20H14O4
318.31
Formula weight
Crystal colour, habit
Crystal size (mm)
Temperature (K)
232.65
Colourless, prism
0.34 9 0.27 9 0.12
173 (2)
Colourless, plate
0.45 9 0.35 9 0.12
173 (2)
˚
Wavelength (A)
0.71073
1.54178
Crystal system
Orthorhombic
P c a 21, 4
7.6297 (5)
5.5875 (3)
26.1624 (12)
90.0000 (0)
90.0000 (0)
90.0000 (0)
1115.33 (11)
1.386
Triclinic
Space group, Z
P −1, 1
˚
a (A)
5.7970 (4)
8.1366 (8)
8.8057 (9)
83.246 (8)
72.138 (8)
76.696 (8)
384.22 (6)
1.376
˚
b (A)
˚
c (A)
α (°)
β (°)
γ (°)
3
˚
Volume (A )
ρcalc (mg m−3
)
μ (mm−1
)
0.322
0.787
F(000)
480.0
166.0
Θ range for data collection
Index ranges
3.115–25.927
5.28–71.09
h
9 to 9,
−6 to 5
k
−6 to 6,
−9 to 9
l
−22 to 31
6706
−10 to 10
2133
Reflections collected
Independent reflections
Completeness to theta = 25.500°
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I [ 2σ(I)]
R indices (all data)
1735 [R(int) = 0.0258]
99.8 %
1434 [R(int) = 0.0233]
99.4 %
Semi-empirical from equivalents Semi-empirical from equivalents
1.00000 and 0.49504
Full-matrix least-squares on F2
1735/1/145
1.00000 and 0.61555
Full-matrix least-squares on F2
1434/0/110
1.043
1.074
R1 = 0.0314, wR2 = 0.0833
R1 = 0.0323, wR2 = 0.0842
0.182 and −0.164
R1 = 0.0554, wR2 = 0.1532
R1 = 0.0582, wR2 = 0.1570
0.307 and −0.252
−3
˚
Largest diff. peak and hole (eA
)
DFT calculation as well as inclusion of weak intermolec-
ular hydrogen bond interactions has been included in a
discussion of the structural aspects of the title compounds.
All calculations were performed on a Workstation PC
using the default convergence criteria.
Molecular Orbital Calculations
Fig. 1 Molecular structure of C13H9ClO2 (I), with the atom labelling
scheme of the asymmetric unit and 50 % probability displacement
ellipsoids of non-H atoms
Molecular orbital calculations were carried out on the
ground state for (I) using the geometry optimized structure
derived from the DFT, B3LYP exchange correlation
functional with the 6–31 G(d) basis set described earlier.
Theoretical calculations and experimental results are given
in Table 4. Experimentally determined oscillator strengths
Table 2. In addition, a comparison of the angles between
mean planes of the chlorobenzene and benzoyl rings in
(I) and the benzene rings in (II) in the crystals and with the
123

J Chem Crystallogr
Fig. 2 Crystal packing of
C13H9ClO2 (I) viewed along the
b axis
Fig. 3 The partial packing of
the title compound (I), showing
the two weak C–H···π
interactions (see Table 3 for
details)
(f) were determined by use of the equation relating them to
the molar decadic absorption coefficient (ε) (f = 4.32 9 10–9.
the UV–Vis absorption spectra, electronic excitation tran-
sition predications are suggested.
ε
cient measures the intensity of the optical absorption at a
max⋅ Δw ) [41–43]. The molar decadic absorption coeffi-
½
given wavelength. Deconvolution of the spectra to obtain
Results and Discussion
the εmax and Δw values was carried out by the Origin
½
program [44]. Surface plots for the two highest occupied
molecular orbital (HOMO and HOMO-1) and three lowest
unoccupied molecular orbitals (LUMO, LUMO +1 and
LUMO+2) are displayed to provide a visual evidence of
the molecular orbitals involved in the spectroscopic elec-
tronic energy transitions examined. Based on correlation of
the energies of these HOMO–LUMO frontier surfaces to
Structural and Theoretical Study of (I):
4-Chlorophenyl Benzoate
It is interesting to note here that the Friedel–Crafts acylation
with 4-chlorophenol did not yield the expected 2,6-dibenzoyl-
4-chlorophenol. Instead, it forms an ester (I) via O-acylation
of the hydroxyl group of the phenol derivative [45–47].
123

J Chem Crystallogr
Fig. 4 Schematic MO diagram
of I. The energy gap between
the HOMO and LUMO
Δ = 5.20 eV
In I, C13H9ClO2, the compound crystallizes in the
orthorhombic crystal system (Pca2(1) space group)
(Fig. 1). The seven atoms of the chlorophenyl residue are
˚
planar (r. m. s. deviation 0.003 (5) A) with the exception of
˚
the Cl atom which lies 0.132(5) A out of their mean plane
observed in the crystals at 61.81(12)° and 4.15(7)° for (I).
The dihedral angle between the mean planes of the two
benzene rings became 45.63° compared with that of the
single crystal value, 57.72(14)°, clearly suggesting that
these are not coplanar. The presence of ester group in the
two benzene rings plays a significant role in C–H···π
intermolecular interactions and crystal packing.
in (I). The nine atoms of benzoate ring are also perfectly
˚
planar (r. m. s. deviation 0.001(3) A) with the ester O atom
˚
showing the greatest deviation (0.060(3) A) from their
mean plane. The mean plane of the central ester group
makes dihedral angles of61.81 (12) and 4.15 (7)°, respec-
tively with the chlorophenyl and benzoyl rings while the
two aromatic rings form a dihedral angle of 57.72 (14)°.No
classical hydrogen bonds were observed (Fig. 2). Mole-
cules in the crystal are stabilized by weak intermolecular
C–H···π interactions (Fig. 3; Table 3).
Electronic Absorption Spectra and DFT Molecular Orbital
Calculations
Theoretical DFT molecular orbital calculationsusing the
B3LYP/6-31-G(d) basis set for (I) show three absorptions,
which are consistent with the experimental data (Table 4).
The predicted bands at 238, 203 and 198 nm exhibit some
blue shifts compared to the experimental data. For (I), the
bands in the UV region 270–232 nmare assigned to car-
bonyl n → π*and π → π* transitions while the other band at
202 nmis assigned toaromatic π → π* transitions.Calcu-
lated molecular orbital energies (eV) for the surfaces of the
frontier molecular orbitals of (I) are shown in Fig. 4. For
(I), the HOMOis mainly located on the central phenyl ring
andchlorine.The LUMOis mainly distributed on phenyl
ring and carbonyl oxygen. In LUMO + 1 and LUMO + 2,
electronic clouds are mainly distributed on phenyl rings
containing chloro and carbonyl substituents, respectively.
Optimised Geometry
DFT calculations were performed on (I) using the B3LYP/
6-31G(d) level basis set. Starting geometries were taken
from X-ray refinement data. After the DFT geometry
optimization calculation in (I), the bond lengths and bond
angles remained relatively the same throughout the struc-
ture (Table 2). The dihedral angles between the mean plane
of the central ester group and peripheral benzene rings
became 44.42° and 1.24°, slightly twisted from that
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J Chem Crystallogr
˚
Table 2 Selected crystal and DFT* bond lengths (A), bond angles (°), and torsion angles for I and II
(I) C13H9ClO2
Cl(1)–C(4)
1.736 (3)
1.360 (4)
1.379 (4)
1.388 (4)
1.387 (4)
1.486 (4)
1.392 (4)
1.384 (4)
1.386 (4)
1.758*
1.373*
1.394*
1.395*
1.394*
1.487*
1.403*
1.398*
1.394*
O(1)–C(7)
O(2)–C(1)
C(1)–C(2)
C(3)–C(4)
C(5)–C(6)
C(8)–C(9)
C(9)–C(10)
C(11)–C(12)
1.919 (4)
1.395 (3)
1.385 (4)
1.378 (4)
1.385 (4)
1.391 (4)
1.379 (4)
1.385 (4)
1.211*
1.392*
1.396*
1.395*
1.394*
1.401*
1.392*
1.397*
O(2)–C(7)
C(1)–C(6)
C(2)–C(3)
C(4)–C(5)
C(7)–C(8)
C(8)–C(13)
C(10)–C(11)
C(12)–C(13)
(II) C20H14O4
O(1)–C(7)
1.2005 (19)
1.4034 (18)
1.394 (2)
1.382 (2)
1.386 (2)
1.382 (2)
1.394 (2)
1.211*
1.395*
1.402*
1.394*
1.397*
1.394*
1.393*
O(2)–C(7)
C(1)–C(6)
C(1)–C(7)
C(3)–C(4)
C(5)–C(6)
C(8)–C(9)
C(10)–C(8)
1.3601 (19)
1.390 (2)
1.486 (2)
1.389 (2)
1.388 (2)
1.382 (2)
1.382 (2)
1.371*
1.402*
1.489*
1.397*
1.392*
1.394*
1.394*
O(2)–C(8)
C(1)–C(2)
C(2)–C(3)
C(4)–C(5)
C(8)–C(10)
C(9)–C(10)
(I) C13H9ClO2
C(7)–O(2)–C(1)
C(6)–C(1)–O(2)
C(1)–C(2)–C(3)
C(3)–C(4)–C(5)
C(5)–C(4)–CI(1)
C(1)–C(6)–C(5)
O(1)–C(7)–C(8)
C(9)–C(8)–C(13)
C(13)–C(8)–C(7)
C(9)–C(10)–C(11)
C(11)–C(12)–C(13)
(II) C20H14O4
C(7)–O(2)–C(8)
C(6)–C(1)–C(7)
C(3)–C(2)–C(1)
C(5)–C(4)–C(3)
C(5)–C(6)–C(1)
O(1)–C(7)–C(1)
C(10)–C(8)–C(9)
C(9)–C(8)–O(2)
(I) C13H9ClO2
C(7)–O(2)–C(1)–C(6)
C(6)–C(1)–C(2)–C(3)
C(6)–C(1)–C(2)–C(3)
C(2)–C(3)–C(4)–C(1)
CI(1)–C(4)–C(5)–C(6)
O(2)–C(1)–C(6)–C(5)
C(7)–O(2)–C(7)–O(1)
O(1)–C(7)–C(8)–C(9)
O(1)–C(7)–C(8)–C(13)
117.5 (2)
116.8 (2)
119.0 (3)
121.9 (3)
118.9 (2)
119.4 (3)
125.6 (3)
120.2 (3)
122.7 (2)
120.1 (3)
120.7 (3)
123.73*
115.92*
119.20*
121.01*
119.53*
119.92*
124.89*
119.85*
120.70*
119.95*
120.13*
C(2)–C(1)–C(6)
C(2)–C(1)–O(2)
C(4)–C(3)–C(2)
C(4)–C(3)–CI(1)
C(6)–C(5)–C(4)
O(1)–C(7)–O(2)
O(2)–C(7)–C(8)
C(9)–C(8)–C(7)
C(10)–C(9)–C(8)
C(10)–C(11)–C(12)
C(12)–C(13)–C(8)
121.7 (3)
121.4 (3)
119.1 (3)
119.1 (2)
118.8 (3)
122.7 (3)
111.6 (2)
117.1 (2)
120.1 (3)
119.9 (3)
119.1 (3)
120.90*
123.05*
119.80*
119.47*
119.18*
123.73*
111.38*
117.45*
120.12*
120.10*
119.84*
118.08 (11)
117.09 (14)
119.63 (14)
120.14 (14)
120.18 (15)
124.99 (14)
122.16 (14)
116.77 (13)
120.92*
117.45*
119.87*
120.07*
120.05*
124.81*
120.96*
116.07*
C(6)–C(1)–C(2)
C(2)–C(1)–C(7)
C(2)–C(3)–C(4)
C(4)–C(5)–C(6)
O(1)–C(7)–O(2)
O(2)–C(7)–C(1)
C(10)–C(8)–O(2)
C(8)–C(9)–C(10)
119.96 (14)
122.91 (14)
120.36 (14)
119.71 (14)
123.27 (14)
111.72 (12)
120.98 (13)
119.09 (14)
119.85*
122.69*
120.14*
120.02*
123.88*
111.31*
122.85*
118.89*
119.5 (3)
−0.7 (4)
0.1 (4)
137.39*
−0.27*
0.20*
C(7)–O( )–C(1) C(2)
O(2)–C(1)–C(2) C(3)
C(2)–C(3)–C(4) C(5)
C(3)–C(4)–C(5)C(6)
C(2)–C(1)–C(6)–C(5)
C(4)–C(5)–C(6)–C(1)
C(1)–O(2)–C(7)–C(8)
O(2)–O(7)–C(8)–C(9)
O(2)–C(7)–C(8)–C(13)
−63.6 (3)
−177.5 (2)
0.7 (4)
−46.66*
−176.02*
0.03*
−178.9 (2)
178.7 (2)
177.5 (2)
0.3 (4)
179.93*
179.90*
176.16*
−0.02*
−1.14*
178.76*
−0.9 (4)
0.6 (4)
−0.20*
0.10*
0.2 (4)
0.13*
−177.9 (2)
−176.7 (2)
3.1 (4)
−179.96*
178.79*
−1.30*
5.2 (5)
−175.0 (3)
123

J Chem Crystallogr
Table 2 continued
C(13)–C(8)–C(9)–C(10)
C(8)–C(9)–C(10)–C(11)
C(10)–C(11)–C(12)–C(13)
C(9)–C(8)–C(13)–C(12)
(II) C20H14O4
−0.4 (4)
0.3 (4)
0.0 (4)
0.2 (4)
0.03*
C(7)–C(8)–C(9)–C(10)
C(9)–C(10)–C(11)–C(12)
C(11)–C(12)–C(13)–C(8)
C(7)–C(8)–C(13)–C(12)
179.5 (2)
−0.1 (4)
179.94*
0.08*
−0.08*
−0.02*
0.03*
−0.1 (4)
−0.03*
179.88*
−179.6 (3)
C(6)–C(1)–C(2)–C(3)
C(1)–C(2)–C(3)–C(4)
C(3)–C(4)–C(5)–C(6)
C(2)–C(1)–C(6)–C(5)
C(8)–O(2)–C(7)–O(1)
C(6)–C(1)–C(7)–O(1)
C(6)–C(1)–C(7)–O(2)
C(7)–O(2)–C(8)–C(10)#1
C(10)#1–C(8)–C(9)–C(10)
C(8)–C(9)–C(10)–C(8)#1
̶
̶
0.4 (2)
0.4 (2)
0.2 (3)
0.06*
C(7)–C(1)–C(2)–C(3)
C(2)–C(3)–C(4)–C(5)
C(4)–C(5)–C(6)–C(1)
C(7)–C(1)–C(6)–C(5)
C(8)–O(2)–C(7)–C(1)
C(2)–C(1)–C(7)–O(1)
C(2)–C(1)–C(7)–O(2)
C(7)–O(2)–C(8)–C(9)
O(2)–C(8)–C(9)–C(10)
177.27 (3)
0.7 (2)
170.96*
−0.04*
0.01*
0.07*
̶
−0.00*
0.02*
−0.6 (3)
0.9 (2)
−176.88 (13)
−176.02 (11)
−173.09 (15)
5.5 (2)
180.00*
179.60*
−178.98*
1.14*
2.6 (2)
−0.28*
1.03*
4.6 (2)
−176.83 (12)
−63.51 (19)
0.1 (3)
178.95*
−48.77*
−0.23*
0.23*
119.95 (15)*
176.60 (12)
−135.29
−176.25*
−0.1 (2)
Symmetry codes #1: −x, −y + 2, −z + 1
˚
Table 3 Weak intermolecular interactions for(I) and (II) (A and °)
Table 4 Experimental and calculated energy of molecular orbitals of
(I) and associated transitions
C–H···Cg
C–H H···Cg C···Cg
C –H ···Cg
Experimental
Calculated
(I) C13H9ClO2
λmax (nm/eV)
f*
λmax (nm/eV)
MO contributions
C5–H5A···Cg1#1
C9–H9A···Cg2#2
C12–H12A···Cg2#3
(II) C20H14O4
0.95 2.88
0.95 2.82
0.95 2.87
3.492 (3)
123
131
133
3.514 (3)
3.581 (3)
270/4.59
270/4.59
232/5.34
232/5.34
202/6.14
202/6.14
0.006
0.006
0.041
0.041
0.065
0.065
238.3/5.20
213.1/5.82
203.2/6.10
184.6/6.72
197.9/6.26
180.2/6.88
HOMO → LUMO
HOMO-1 → LUMO
HOMO → LUMO + 1
HOMO-1 → LUMO + 1
HOMO → LUMO + 2
HOMO-1 → LUMO + 2
C(9)–H(9A)···O(1)#4
C(3)–H(3A)···Cg2#5
C(3)–H(3A)···Cg2#6
0.95 2.48
0.95 2.81
0.95 2.81
3.3964 (19) 161
3.5175 (18) 132
3.5175 (18) 132
3.4756 (18) 133
C(10)–H(10A)···Cg1#7 0.95 2.76
f*, f = 4.32 9 10−9.ɛmax. Δɷ1/2. Frontier molecular orbitals from
output in B3LYP/6-31G (d) calculation
Cg1, Cg2 are the centroids of the C1–C6, C8– C13 rings for (I) and
C1–C6, C8–C10, C8A–C10A rings for (II), respectively
Symmetry codes #1: ½ + x, 2 − y, z; #2: ½ + x, 1 − y, z; #3: −½ + x,
2 − y, z; #4: x − 1, y, z; #5: x, −1 + y, z; #6: −x, 1 − y, 1 − z; #7: 1 − x,
1 − y, 1 − z
diester (II) via O-acylation of the hydroxyl and methoxy
groups of phenol derivative [45–47].
In II, C20H14O4, the compound crystallizes in the tri-
ꢀ
clinic crystal system (P1 space group) (Fig. 5). The
The HOMO and HOMO-1 are very similar but on opposite
sides of the molecule as are LUMO and LUMO + 1. It is
evident that electron transitions among frontier molecular
orbitals are corrsponding to the transitions of n → π*and
π → π* transitions.
molecule is located on crystallographic inversion centre
with half molecules in the asymmetric unit. In (II), a ter-
minal ring is coplanar with the attached ester linkage, with
the dihedral angle of 5.94(8)°. The central phenyl ring
makes a dihedral angle of 60.31(9)° with the ester linkage
while the two aromatic rings form a dihedral angle of 55.29
(8)°. Both ester linkages are in anti conformation.The
packing of the molecule is stabilized through weak C–H
···O hydrogen bonding interactions, forming an R22ð14Þ [48,
49] ring motifs (Table 4, Fig. 6). There are three weak C–
H···π interactions found in the crystal structure (Fig. 7),
involving (C1–C6) and (C8–C10, C8A–C10A) rings and
one π–π stacking interaction (Fig. 8) [50], with a centroid–
Structural and Theoretical Study of (II): 1,4-
Phenylene Dibenzoate
To our surprise, the Friedel–Crafts acylation with
4-methoxyphenol did not yield the expected 2,6-dibenzoyl-
4-methoxyphenol. Instead, it leads to the formation of
123

J Chem Crystallogr
Fig. 5 Molecular structure of
C20H14O4 (II), with the atom
labelling scheme of the
asymmetric unit and 50 %
probability displacement
ellipsoids of non-H atoms
Fig. 6 Crystal packing of
C20H14O4 (II) viewed along the
c axis. Dashed lines indicate
C–H···O intermolecular
interactions
˚
Electronic Absorption Spectra and DFT Molecular
Orbital Calculations
centroid distance of 3.9590 (10) A (symmetry code: 1 − x,
1 − y, −z).
Theoretical DFT molecular orbital calculationsusing the
B3LYP/6-31-G(d) basis set for (II) show three absorptions,
which are consistent with the experimental data (Table 5).
The predicted bands at 237, 234 and 198 nm exhibit some
blue shifts compared to the experimental data. For (II), the
bands in the UV region 342–285 nm are assigned to car-
bonyl n → π*and π → π* transitions while the other band at
280 nmis assigned to aromatic π → π* transitions. Calcu-
lated molecular orbital energies (eV) for the surfaces of the
frontier molecular orbitals of (II) are shown in Fig. 9. For
(II), the HOMO is mainly located on the central phenyl
ring.The LUMOis mainly distributed on both ester carbons
and peripheral benzene rings. In LUMO + 2, electronic
clouds are mainly distributed on central phenyl rings. The
HOMO and HOMO-1 are very similar but on opposite
sides of the molecule as are LUMO and LUMO + 1. It is
evident that electron transitions among frontier molecular
orbitals are corrsponding to n → π*and π → π* transitions.
Optimised Geometry
DFT calculations were performed on (II) using the B3LYP/
6-31G(d) level basis set. Starting geometries were taken
from X-ray refinement data. After the DFT geometry
optimization calculation on (II), the bond lengths and bond
angles remained relatively the same throughout the struc-
ture (Table 2). The dihedral angles between the mean plane
of the central ester group and peripheral benzene rings
became 46.29° and 1.12°, slightly twisted from that
observed in the crystals at 60.31(12)° and 5.94(7)° for (II).
The dihedral angle between the mean planes of the two
adjacent benzene rings became 47.34° compared with that
of the single crystal value, 55.29(8)°, clearly suggesting
that these are not coplanar. The presence of diester groups
in the central benzene rings plays a significant role in C–
H···O, C–H···π and π–π intermolecular interactions and
crystal packing.
123

J Chem Crystallogr
Fig. 7 The partial packing of the compound (II), showing the weak
intermolecular C–H···π interactions (see Table 3 for details)
Fig. 8 Part of the crystal structure of the compound (II), showing the
formation of π–π stacking interactions. Symmetry codes: 1 − x, 1 − y, −z
Summary and Conclusions
The crystal and molecular structure of two phenol-based
ester derivatives have been determined using spectroscopy
and single crystal X-ray diffraction studies. Theoretical
calculations contribute to the analysis of the structures.
Correlation between calculated molecular orbital energies
for the surfaces of the frontier molecular orbitals to the
electronic transitions from the electronic spectra has been
determined and are in good agreement. Bond distances and
angles are in normal ranges. No classical hydrogen bonding
has been observed in (I). Weak intermolecular C–H ···π
interactions are present. However, in (II), weak C–H ···O
interactions are observed leading to the formation of
R22ð14Þ ring motifs in addition to C–H ···π and π···π inter-
actions involving benzene rings which contribute to crystal
Table 5 Experimental and calculated energy of molecular orbitals of
(II) and associated transitions
Experimental
max (nm/eV)
Calculated
max (nm/eV)
λ
f*
λ
MO contributions
342/2.05
342/2.05
285/3.7
285/3.7
280/4.0
280/4.0
0.035
0.035
0.063
0.063
0.069
0.069
237.2/5.22
218.0/5.68
234.8/5.27
216.0/5.73
198.7/6.23
185.1/6.89
HOMO → LUMO
HOMO-1 → LUMO
HOMO → LUMO + 1
HOMO-1 → LUMO + 1
HOMO → LUMO + 2
HOMO-1 → LUMO + 2
f*, f = 4.32 9 10−9.ɛmax. Δω1/2 frontier molecular orbitals from output
in B3LYP/6-31 g (d) calculation
123

J Chem Crystallogr
Fig. 9 Schematic MO diagram
of II. The energy gap between
the HOMO and LUMO
Δ = 5.23 eV
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CCDC 1407715-1407716 contain supplementary crystal-
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free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif, or by
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