(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl] benzene-1,2-diol: X-ray and DFT calculated structures

Article abstract of DOI:10.3906/kim-0906-33

The crystal structure of (E)-3-[(3-(Trifluoromethyl)phenylimino)-methyl] benzene-1,2-diol was determined using X-ray diffraction and the molecular structure was investigated with density functional theory (DFT). The X-ray study showed that the title compound has a strong intramolecular O-H... N hydrogen bond and 3-dimensional crystal networks are primarily determined by O-H... O intermolecular hydrogen bonds and weak van der Waals interactions. The strong O-H... N bond is evidence of the preference for the phenol-imine tautomeric form in the solid state. Optimized molecular geometry was calculated with DFT at the B3LYP/6-31G(d,p) level. The results from both experiment and theoretical calculations for the title compound are compared with each other in this study. TUBITAK.

Full text of DOI:10.3906/kim-0906-33

Turk J Chem
34 (2010) , 481 – 487.
¨
˙
c
ꢀ TUBITAK
doi:10.3906/kim-0906-33
(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl]
benzene-1,2-diol: X-ray and DFT calculated structures
1
2
Ba¸sak KOS¸AR1,∗, C¸ ig˘dem ALBAYRAK , Mustafa ODABAS¸OGLU and
˘
3
¨
¨
¨
¨
Orhan BUYUKGUNGOR
1Faculty of Education, Sinop University, TR-57100, Sinop-TURKEY
e-mail: bkosar@omu.edu.tr
2Chemistry Program, Pamukkale University, TR-20159, Denizli-TURKEY
3Faculty of Arts & Sciences, Ondokuz Mayıs University,
TR-55139, Samsun-TURKEY
Received 10.06.2009
The crystal structure of (E)-3-[(3-(Trifluoromethyl)phenylimino)-methyl]benzene-1,2-diol was determined
using X-ray diffraction and the molecular structure was investigated with density functional theory (DFT).
The X-ray study showed that the title compound has a strong intramolecular O-H. . . N hydrogen bond
and 3-dimensional crystal networks are primarily determined by O-H.. . O intermolecular hydrogen bonds
and weak van der Waals interactions. The strong O-H.. . N bond is evidence of the preference for the
phenol-imine tautomeric form in the solid state. Optimized molecular geometry was calculated with DFT
at the B3LYP/6-31G(d,p) level. The results from both experiment and theoretical calculations for the title
compound are compared with each other in this study.
Key Words: Schiff bases, phenol-imine, X-ray crystal structure, IR, DFT.
Introduction
Schiff bases (R1 HC=N-R2) are formed by reaction of a primary amine and an aldehyde, they are widely used as
ligands in the field of coordination chemistry, and they play an important role in various fields of chemistry due to
their activities.1o-Hydroxy Schiff bases derived from the reaction of o-hydroxy aldehydes with aniline have been
examined extensively.2−4 Some Schiff bases derived from salicylaldehyde have attracted the interest of chemists
and physicists because they show thermochromism and photochromism in the solid state by H-atom transfer
∗Corresponding author
481

(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl]benzene-1,2-diol: X-ray..., B. KOS¸AR, et al.,
from the hydroxy O atom to the N atom.5 It has been proposed that molecules showing thermochromism are
planar, while those showing photochromism are non-planar.6
Figure 1. Phenol-imine (a) and keto-amine (b) tautomers of o-hydroxy Schiff bases.
In general, o-hydroxy Schiff bases exhibit 2 possible tautomeric forms; the phenol–imine (or benzenoid)
and keto–amine (or quinoid) forms can be seen in Figure 1(a) and (b), respectively. Depending on the
tautomers, 2 types of intra-molecular hydrogen bonds are possible: O-H. . . N in benzenoid and N-H. . . O in
quinoid tautomers. o-Hydroxy Schiff bases have been previously observed in the keto form,7 in the enol form,8
or in enol/keto mixtures.9,10 Related to this phenomenon, we present here the crystal and molecular structures
of the title compound.
Experimental
Synthesis
The compound (E)-3-[(3-(trifluoromethyl)phenylimino)methyl]benzene-1,2-diol
was prepared by reflux of a mixture of a solution containing 2,3-dihydroxybenzaldehyde (0.5 g 3.6 mmol)
in 20 mL of ethanol and a solution containing 2-aminobenzotrifuloride (0.58 g 3.6 mmol) in 20 mL of ethanol.
The reaction mixture was stirred for 1 h under reflux. The crystals of (E)-3-[(3-(trifluoromethyl)phenylimino)
methyl]benzene-1,2-diol suitable for X-ray analysis were obtained from ethanol by slow evaporation (yield 76%;
mp 387-389 K). The IR spectra of the compound were recorded on KBr discs with a Bruker 2000 FT-infrared
spectrometer. IR (cm−1): 1617.8 (C=N str.), 3311.0 (OH str.), 1391.9 (N=C-H bend.), 1144.2 (C-O str.
aromatic), 1324.2 (O-H bend.), 1106.8 (C-F str.), 1507.68-1462.2 (C-C str. aromatic).
Figure 2. The chemical diagram of the title compound.
X-ray diffraction analysis
A suitable sample was selected for the single crystal X-ray study. All diffraction measurements were per-
formed at room temperature (296 K) using graphite monochromated MoKα radiation and an STOE IPDS 2
482

(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl]benzene-1,2-diol: X-ray..., B. KOS¸AR, et al.,
diffractometer. Reflections were collected in the rotation mode and cell parameters were determined by using
X-AREA software.11 Absorption correction was achieved by the integration method via X-RED32 software.11
The structure was solved by direct methods using SHELXS-97.12 The refinement was carried out by full-
matrix least-squares method using SHELXL-97 on the positional and anisotropic temperature parameters of
the non-hydrogen atoms, or equivalently corresponding to 221 crystallographic parameters.12 All non-hydrogen
atom parameters were refined anisotropically and all H atoms refined freely with C-H distances in the range
2
˚
˚
0.90(4)-0.98(3) A and Uiso (H) values in the range 0.016(6)-0.057(11) A . The data collection conditions and
parameters of refinement process are listed in Table 1.
Table 1. Crystal data, data collection, and refinement details.
Chemical Formula
C14H10F3NO2
281.23
Formula Weight
Crystal System
Monoclinic
P 21/c
Space group
Z
4
Crystal Color
Orange
˚
a, b, c
16.2181 (8), 4.7632 (2), 18.2882 (10) A
β
121.748 (4)◦
3
˚
V
1201.37 (10) A
Dx
1.555 Mg m−3
˚
Radiation, λ
MoKα, 0.71073 A
μ
0.14 mm−1
T
293 K
Tmin, Tmax
0.927, 0.984
Scanning mode
ω
Scan range
–20 < h < 20, –5 < k < 5, –22 < l < 22
Crystal size
0.65 × 0.37 × 0.11 mm
θmin, θmax
1.5, 26.00◦
Number of measured/independent reflections, Rint
5430/2316, 0.041
Number of reflections with 2σ(I)
1876
221
Number of refined parameters
S
1.07
R[F2 > 2σ(F2)]
wR(F2)
0.059
0.156
˚
0.82, -0.64 e A
−3
Δρmax, Δρmin
Computational procedure
The geometry optimization of the molecule was carried out by using B3LYP hybrid exchange-correlation
functional with 6-31G(d,p) basis set.13,14 The calculation was started from the crystallographically obtained
483

(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl]benzene-1,2-diol: X-ray..., B. KOS¸AR, et al.,
geometry of the molecule listed in Table 2 and carried out using the GAUSSIAN03W package.15 The optimized
molecular geometry, total molecular energy, dipole moment, and Mulliken charges were obtained from the
computational process.
2
Table 2. Fractional atomic coordinates and Ueq (A ) for non-H atoms.
˚
Atom
C1
x
y
z
Ueq/Uiso*
0.25898 (17) 0.2197 (5) 0.25332 (15) 0.0200 (5)
0.35663 (16) 0.1623 (5) 0.28136 (14) 0.0194 (5)
C2
C3
0.37686 (16)
0.30291 (18)
0.20633 (18)
-0.0484
-0.1978
-0.1417
0.23952 (15) 0.0199 (5)
0.17251 (15) 0.0221 (5)
0.14510 (16) 0.0232 (5)
C4
C5
C6
0.18485 (17) 0.0654 (5) 0.18535 (15) 0.0227 (5)
0.23549 (17) 0.4340 (5) 0.29623 (15) 0.0200 (5)
0.28116 (17) 0.7832 (5) 0.40328 (15) 0.0203 (5)
0.18794 (17) 0.8690 (5) 0.37926 (15) 0.0216 (5)
0.17584 (17) 1.0751 (5) 0.42668 (15) 0.0226 (5)
0.25545 (18) 1.1982 (5) 0.49773 (16) 0.0244 (5)
0.34792 (19) 1.1134 (6) 0.52119 (16) 0.0263 (5)
0.36030 (18) 0.9075 (5) 0.47432 (16) 0.0238 (5)
0.07517 (18) 1.1629 (5) 0.39908 (17) 0.0267 (6)
0.30220 (14) 0.5765 (4) 0.35980 (13) 0.0209 (4)
0.43175 (12) 0.3019 (4) 0.34638 (11) 0.0253 (4)
C7
C8
C9
C10
C11
C12
C13
C14
N1
O1
O2
F1
0.47316 (12)
-0.0913
0.26893 (12) 0.0242 (4)
0.07073 (14) 1.3507 (5) 0.44976 (14) 0.0647 (7)
0.03086 (13) 1.2922 (6) 0.32197 (13) 0.0646 (7)
F2
F3
0.01862 (16) 0.9549 (4)
0.3893 (2)
0.0909 (11)
Results and discussion
An ORTEP-3 plot showing the atom-numbering scheme of the title compound is shown in Figure 3.16 It is clear
that the structure reported here adopts a phenol-imine tautomeric form. The bond lengths with this form were
˚
1.288(3) A for the N1=C7 double bond and 1.347(2) for the O1-C2 single bond. These distances are in agree-
˚
ment with those observed in N-(2-methyl-5-chlorophenyl)salicylaldimine (1.281(3), 1.354(3) A)), which is also
a phenol-imine tautomer.17 The same bond distances can be compared with the corresponding distances in 4-[(4-
Methylphenyl)diazenyl]-6-methoxy-2-{[tris(hydroxymethyl)methyl]aminomethylene}cyclohexa-3,5-dien-1(2H)-
one (1.296(5), 1.279(5)), which is a keto-amin tautomer.18
484

(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl]benzene-1,2-diol: X-ray..., B. KOS¸AR, et al.,
Figure 3. An ORTEP-3 view of the title compound with the atomic numbering scheme. The dashed line shows the
intramolecular hydrogen bond. Displacement ellipsoids are shown at the 30% probability level.
In a phenol-imine tautomeric form, both rings of the title compound must be aromatic. In order to
make another verification for the phenol-imine form and investigate the aromaticity of rings, HOMA (harmonic
oscillator model of aromaticity) indices were calculated.19,20 The HOMA index is equal to 1 for aromatic
systems and 0 for non-aromatics. The indices are 0.970 and 0.940 for the fluoro-attached ring and the other
one, respectively. The dihedral angle between 2 aromatic rings of the molecule is 4.43(2)◦ . Against this
background we can conclude that the compound is almost planar and displays thermochromic features.
The title compound displays a strong intramolecular hydrogen bond between atoms O1 and N1 as a
common feature of o-hydroxysalicylidene systems.21,22 The crystal structure is stabilized by weak van der
Waals interactions and O-H. . . O bonds in a 3-dimensional network. Geometrical parameters of the intra- and
intermolecular H-bonds are listed in Table 3.
◦
˚
Table 3. Hydrogen bonding geometry (A, ).
D-H. . . A
D-H
H. . . A
D. . . A
∠D-H. . . A
153 (4)
O1—H10. . . N1 0.83 (4) 1.83 (4)
2.594 (3)
O2—H11. . . O2i 0.87 (4) 1.89 (4) 2.7466 (16)
167 (3)
Symmetry code: (i) -x + 1, y -1/2, -z + 1/2.
In the DFT/B3LYP calculations, the total energy of optimized geometry and dipole moment of molecule
were –1044.25 a.u. and 2.6857 debye, respectively. According to the calculated results for Mulliken atomic
charge analysis, atoms N1, O1, and O2 have larger negative charges relative to other atoms as expected. The
charges were calculated as –0.597, –0.557, and –0.544 e, respectively.
485

(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl]benzene-1,2-diol: X-ray..., B. KOS¸AR, et al.,
Figure 4. A packing diagram of the title compound. Dashed lines indicate the O-H. . . O intermolecular hydrogen bonds.
For clarity, only H atoms involved in hydrogen bonding are included.
◦
◦
˚
Table 4. Selected bond lengths (A), angles ( ), and torsion angles ( ) respectively.
X-Ray
DFT/B3LYP
˚
Bond lengths (A)
C8-N1
N1-C7
1.416 (3)
1.288 (3)
1.455 (3)
1.347 (3)
1.406
1.290
1.447
1.337
C7-C1
C2-O1
Bond angles (◦)
C8-N1-C7
122.5 (2)
121.5 (2)
121.2
122.5
N1-C7-C1
Torsion angles (◦)
C13-C8-N1-C7
C8-N1-C7-C1
N1-C7-C1-C6
175.8 (2)
179.1 (2)
178.9 (2)
146.4
177.3
179.5
Comparative results obtained from the X-ray crystallographic and computational studies of bond dis-
tances, angles, and torsion angles are presented in Table 4. It is well known that the DFT and similar calculations
underestimate interactions like inter- and intramolecular hydrogen bonds and handle molecules in the gaseous
phase (in vacuo). For that reason some differences were observed between the X-ray experimental study and
DFT/B3LYP calculation results of bond distance, angle, and torsion angle values.
486

(E)-3-[(3-(Trifluoromethyl)phenylimino)methyl]benzene-1,2-diol: X-ray..., B. KOS¸AR, et al.,
Supplementary data
CCDC 727236 contains the supplementary crystallographic data for this paper. These data can be obtained free
of charge via www.ccdc.cam.ac.uk/data request/cif, by emailing data request@ccdc.cam.ac.uk, or by contacting
The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Acknowledgments
The authors wish to thank the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of
the STOE IPDS 2 diffractometer (purchased under grant F.279 of the University Research Fund).
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