Synthesis, X-ray crystal structure and DFT study of potential ligands of (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenyl"alk"-2-en-1-one type

Article abstract of DOI:10.1016/j.molstruc.2006.11.006

The main aim of the study was the synthesis and X-ray and spectroscopic investigations of potential ligands of transition metal complexes. A new compound, (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenylpent-2-en-1-one, was obtained and the detailed experimental results are reported. Theoretical investigations based on the Density Functional Theory (DFT) were also performed for the presented compound as well as for its two analogues. Conformational analysis was done to find minima on the potential energy surface (PES). Analysis of the electrostatic potential (ESP) showed regions in the molecules sensitive to external interactions. Furthermore, topological analysis of the electron density (AIM theory) was applied to confirm the existence of an intramolecular H-bond in the molecules studied. The obtained theoretical results are in good agreement with the available experimental data.

Full text of DOI:10.1016/j.molstruc.2006.11.006

Journal of Molecular Structure 839 (2007) 33–40
www.elsevier.com/locate/molstruc
Synthesis, X-ray crystal structure and DFT study of potential ligands
of (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenyl’’alk’’-2-en-1-one type
*
Aneta Jezierska , Lucjan B. Jerzykiewicz, Jerzy Kołodziejczak, Jarosław M. Sobczak
University of Wrocław, Faculty of Chemistry F. Joliot-Curie 14, 50-383 Wrocław, Poland
Received 23 May 2006; received in revised form 26 October 2006; accepted 1 November 2006
Available online 11 December 2006
Abstract
The main aim of the study was the synthesis and X-ray and spectroscopic investigations of potential ligands of transition
metal complexes. A new compound, (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenylpent-2-en-1-one, was obtained and the detailed
experimental results are reported. Theoretical investigations based on the Density Functional Theory (DFT) were also performed
for the presented compound as well as for its two analogues. Conformational analysis was done to find minima on the poten-
tial energy surface (PES). Analysis of the electrostatic potential (ESP) showed regions in the molecules sensitive to external
interactions. Furthermore, topological analysis of the electron density (AIM theory) was applied to confirm the existence of
an intramolecular H-bond in the molecules studied. The obtained theoretical results are in good agreement with the available
experimental data.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Ketoenamine; Crystal structure; DFT; AIM
1. Introduction
tone form (Scheme 1, reaction 1), for which the occurrence
of the iminoenol and aminoenone forms (Scheme 2, reac-
tion 2) is assumed.
Homogenous catalysis reactions are currently very
important tools in the chemical industry and applied chem-
istry. The search for new potential ligands for catalytic com-
plexes is important in developing faster and more efficient
processes. In this paper, we would like to report experimental
and theoretical results concerning the geometrical and
electronic structure description of a new potential ligand of
transition metal complexes, (2Z)-3-[(2-hydroxyphenyl)ami-
no]-1-phenylpent-2-en-1-one (marked as III). Additionally,
the Molecular modeling section contains a discussion of
two previously published compounds, N-(2-hydroxyphe-
nyl)-4-amine-3-pentene-2-one and 3-[(3-hydroxyphenyl)-
However, structural data (i.e. X-ray) show that, inde-
pendently of the type of reacting substances, derivatives
of aminoenones were obtained. For example, starting
from 2,4-pentadione and o-aminophenol, N-(2-hydroxy-
phenyl)-4-amine-3-pentene-2-one (I) is prepared [1,4].
Benzoyloacetone is reacted with o-aminophenol to form
3-[(3-hydroxyphenyl)amine]-1-phenylbut-3-en-1-one (II),
for which the three conformational forms (we will mark
these as IIa, IIb, and IIc, respectively; see [3] for details)
and the ethanol solvate (marked as IId) [2] have been
found. Similarly, the reaction of benzoyloacetone with
2-aminoethanol leads to 3-(hydroxyethyl)amine-1-phenyl-
but-2-en-1-one [5]. In the same way, o-aminophenol reacts
with different benzoyl derivatives, e.g. 1-phenyl-3-methyl-
4-benzoyl-5-pyrazolone [6]. An analogous reaction pro-
ceeds in the case of 5,5-dimethylcyclohexane-1,3-dione
with o-aminophenol [7]. This class of compounds, which
exist as aminoenones, formed complexes with metals, in
amine]-1-phenylbut-3-en-1-one (marked as
I and II,
respectively), with similar structural parameters [1–3].
Generally, condensation reaction of b-diketones with
primary amines (see Scheme 1) should lead to an iminoke-
*
Corresponding author. Tel.: +48 71 3757 308; fax: +48 71 3282 348.
E-mail address: anetka@elrond.chem.uni.wroc.pl (A. Jezierska).
0022-2860/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.11.006

34
A. Jezierska et al. / Journal of Molecular Structure 839 (2007) 33–40
R
O
O
O
N
H2N R
[1]
+
R
R
2
1
R
R
1
2
R
R
R
R
R
O
N
OH
N
O
HN
[2]
R
R
2
R
R
1
1
2
1
2
Scheme 1. Synthesis of iminoketones and its tautomeric forms.
O
O
O
CH3
NaOEt
EtCOOEt
+
Δ
CH3
HO
O
O
OH
H
H2N
O
N
EtOH
+
Δ
CH3
CH3
Scheme 2. Scheme of the synthesis reaction pathway of (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenylpent-2-en-1-one (III).
which they can co-ordinate in monodentate or chelate
structures. Examples are compounds of Co, Sn, the lan-
thanides [8], as well as Pd and U [9]. In the presence of
an additional hydroxyl group (in the case of reactions
of b-diketones with o-aminophenol or 2-aminoalcohols),
potentially tridentate monobasic ligands can be formed.
Such examples are titanium complexes with derivatives
of N-(2-hydroxyethyl)-4-amine-3-pentene-2-one [10]. In
order to support the experimental investigations and
develop new models useful for further study, theoretical
investigations were performed. In our case, calculations
based on the Density Functional Theory (DFT) [11] were
carried out to discuss the conformational flexibility of the
molecules studied. The electronic structure description
gives insight into the electrostatic potential distribution
around the studied compounds showing atoms mostly
involved into external interactions. Bader’s analysis, in
this case, was applied to investigate theoretically the pres-
ence of an intramolecular hydrogen bond [12–14].
2.1. Preparation of 1-phenylpentane-1,3-dione
The title compound was obtained from acetophenone
and ethyl propionate prepared according to the procedure
described for benzoylacetone [15]. GC-MS analysis of the
obtained crude oil shows three main peaks: unreacted ace-
tophenone, 1-phenylpentane-1,3-dione (the highest peak),
and 1,5-diphenylpentane-1,3,5-trione. The mixture was dis-
tilled under reduced pressure and pure title compound was
collected (confirmed by GC-MS).
IR (film), cmÀ1: m(O–H) ca. 3000 m,br; m(C–H) 3064 vw,
3031 vw, 2978 w, 2940 w, 2879 sh, 2740 vw; m(O–HÁ Á ÁO)
ca. 2658 vw, br; m(C@O), d(O–H) and m(C@C) 1720 m,
1686 m, 1604 vs, 1574 vs, 1492 m; d(C–H) 1455 s, 1419 m,
1378 m; 1339 w; d(C–OPh) 1270 s; 1180 m; 1155 m; 1085 w;
1068 m; 1043 w; 999 m; 930 w; 823 m; d(C–CPh) 763 s, c(C–
HPh) 714 sh, 695 s; 668 w; 546 w.
1H NMR (CDCl3, at 20 °C): d 0.95 (t, 3H, –CH3), 2.2 (q,
4H, –CH2–Me), 5.92 (s, 1H, @CH–), 7.2 (m, 3H, Ph), 7.6
(m, 2H, Ph).
2. Experimental and computational procedures
2.2. Preparation of (2Z)-3-[(2-hydroxyphenyl)amino]-
1-phenylpent-2-en-1-one (III)
All the reagents and the solvents employed were com-
mercially available and used with no further purification.
Acetophenone (Aldrich), propionic acid (Koch-Light),
and 2-aminophenol (Ferak) were used.
The title compound was obtained via condensation of 1-
phenylpentane-1,3-dione (3.2 mL, 0.02 mol) and 2-amino-

A. Jezierska et al. / Journal of Molecular Structure 839 (2007) 33–40
35
phenol (2.19 g, 0.02 mol) in absolute ethanol (20 mL). The
mixture was refluxed for 3 h. Yellow-green crystals were
formed during reflux. The crystals were collected, washed
with alcohol, and dried in vacuum to yield 3.22 g (60.2%)
of the title compound (m.p. = 188.5–189.5 °C).
of charge at www.ccdc.cam.ac.uk/conts/retrieving.html (or
from the Cambridge Crystallographic Data Centre, 12,
Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk). Additionally,
the crystallographic data are also available on request from
the Authors.
Anal. Calcd for C17H17NO2: C, 76.38; H, 6.41; N, 5.24.
Found: C, 76.1; H, 6.7; N, 5.3.
IR (KBr disk), cmÀ1: m(O–H) 3435 w,br; m(C–H) 3089
m,br, 2974 m, 2934 w, 2873 w, 2730 w, 2595 vw;
m(C@O), d (N–H) and m(C@C) 1602 s, 1576 vs, 1540 m,
1516 s; d (C–H) 1458 s, 1378 m, 1334 s, 1281 s; 1249 m;
d (C–OPh) 1226 s; m(C–N) 1178 s; 1102 m; 1071 m; 1052
2.5. Computational methodology
The Density Functional Theory (DFT) proposed by
Hohenberg and Kohn was applied in order to investigate
the geometrical parameters and the electronic structure of
the molecules studied [11,17]. Nonlocal three-parameter
hybrid exchange and correlation functional proposed by
Becke in conjugation with the Lee–Young–Parr correlation
formula (B3LYP) was used during the theoretical investi-
gations [18,19]. The 6-31G(d,p) double-zeta basis set with
polarization functions on both heavy and hydrogen atoms
[20] was applied during the conformational analysis. For
each of the molecules studied, a one-dimensional potential
energy surface (PES) scan was performed by variation of
selected dihedral angles (24 steps with 15° increments and
full geometry optimization during the conformational
search). The conformers corresponding to the minimum
on the PES were obtained and the basis set was further-
more enlarged to 6-311+G(d,p) [21–23]. The obtained
structures were re-optimized and the vibrational frequen-
cies were calculated, confirming that the geometrical
parameters correspond with a minimum, not a saddle
point. In the next step, the electrostatic potential (ESP)
and Kohn-Sham determinant pseudo-wavefunction for
Atoms in Molecules (AIM) [12–24] were calculated using
the triple-zeta 6-311+G(d,p) basis set. Molecular modeling
in silico was performed using the Gaussian03 series of pro-
grams [25]. Topological analysis of the electron density
according to Bader theory was performed using the AIM-
PAC package [26]. Visualization of the obtained results
was achieved with the help of the Molekel [27] and gOpen-
Mol [28] programs.
m; 942 w; 857 w; 827w, 806 w; d(C–CPh) 755 s; c(C–HPh
)
702 m; 688 w; 648 m; 539 w; 503 w; 464 w; 444 w; 417
vw; 402 w.
UV–vis (MeOH) [kmax/nm (e/MÀ1 cmÀ1)]: 352 (15100),
246 (9300), 208 (16900).
1H NMR (CDCl3, at 20 °C): d 0.8 (t, 3H, –CH3), 2.0 (q,
4H, –CH2–), 5.72 (s, 1H, @CH–), 6.8 (m, 1H, HPh), 7.0 (m,
2H, HPh), 7.1 (m, 1H, HPh), 7.4 (m, 4H, HPh and –NH–),
7.8 (m, 2H, HPh), 12.3 (s, 1H, –OH).
13C NMR (CDCl3, at 20 °C): d 10.2 (–CH3); 24.1
(–CH2–); 90.9 ( = CH–); 115.3, 118.7, 123.2, 125.4, 125.7,
126.7, 127.1, 127.4, 129.5, 130.7, 138.5, 150.8 (CPh); 168.9
(„C–NH–); 187.7 (@C@O).
2.3. Physical measurements
IR spectra were measured using an Impact 400 (Nicolet)
FT-IR spectrophotometer. UV–vis electronic spectra were
obtained using Hewlett Packard Model 8452A Diode
Array spectrophotometers. 1H and 13C NMR spectra were
recorded on a Bruker 300 spectrometer. A Hewlett Packard
5890 II series gas chromatograph coupled with a Hewlett
Packard Model 5971A mass selective detector was used
for the GC/MS analyses. Elemental analyses were per-
formed in the Microanalytical Laboratory of the Faculty
of Chemistry, University of Wrocław. Melting points were
obtained on a Boe¨tius apparatus and are uncorrected.
2.4. Determination and refinement of the structure
3. Results and discussion
Preliminary examination and intensity data were deter-
mined on a Kuma KM4CCD j-axis diffractometer
with graphite-monochromated MoKa radiation (k =
3.1. Synthesis and X-ray crystal structure discussion
The Claisen condensation reaction between acetophe-
none and ethyl propionate followed by distillation under
low pressure gave 1-phenylpentane-1,3-dione. Treatment
of this compound with one equivalent of o-aminophenol
in refluxing ethanol for 3 h produced (2Z)-3-[(2-hydroxy-
phenyl)amino]-1-phenylpent-2-en-1-one (III) (Scheme 2).
Both of the prepared compounds were studied using
˚
0.71073 A). For all data, Lorentz and polarization correc-
tions were applied. The structures were solved by direct
methods and refined by the full-matrix least-squares
method on all F2 data using the SHELXTL 5.0 package
[16]. Carbon-bonded hydrogen atoms were included in
the calculated positions and refined in the riding mode
using SHELXTL default parameters. Other hydrogen
atoms were located in a difference map and refined freely.
Full crystallographic details of the structures reported in
this paper have been deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication
no. CCDC 290376. Copies of the data can be obtained free
1
NMR, IR, and UV–vis spectroscopic methods. In the H
NMR spectrum of a CDCl3 solution of 1-phenylpentane-
1,3-dione, the signal of the methine proton at 5.92 ppm
points at a predominance of the enol form. Similarly, the
1H NMR spectrum of (2Z)-3-[(2-hydroxyphenyl)amino]-
1-phenylpent-2-en-1-one (III) shows the signals of the

36
A. Jezierska et al. / Journal of Molecular Structure 839 (2007) 33–40
˚
methine proton at 5.72 ppm and of the N–H proton at ca.
7.4 ppm, pointing at the existence of the aminoenone form.
For these compounds, inter- and intramolecular hydrogen
bonds were observed in solid state and in IR spectrum
(broad absorption in the range of 3300–2600 cmÀ1).
Besides the spectroscopic investigations, the crystal
structure was also determined using X-ray crystallography.
A single crystal of (2Z)-3-[(2-hydroxyphenyl)amino]-1-phe-
nylpent-2-en-1-one (III) suitable for X-ray structure analy-
sis was obtained (Fig. 1).
C11 of the ethyl group is 3.945(3) A. The proton donor
group N8–H21 forms an intramolecular hydrogen bond
with oxygen atom O14, with a bond length of 2.633(2) A
˚
and a valence angle of 144(2)° (Table 2).
An intermolecular H-bond, O7–H22Á Á ÁO14, of length
˚
2.653(3) A and valence angle 172(2)° is also observed.
Because of this hydrogen bond, zig-zag chains are formed.
The presence of the H-bond appears as an important prop-
erty of the molecule, stabilizing its conformation in the
crystal; as shown in the Molecular modeling part, this is
also visible in the model obtained for the molecule
discussed.
Crystal data and structure refinement details for (III) are
presented in Table 1.
The X-ray structure showed that the dihedral angles
between the N8–C9@C12–C13@O14 plane and the ben-
zene and substituted benzene rings are 28.40(8)° and
67.35(9)°, respectively. For a similar compound, i.e. 3-[(3-
hydroxyphenyl)amine]-1-phenylbut-3-en-1-one (II), for
which the three conformational forms and the ethanol sol-
vate were found (IIa–d), the same dihedral angles are
17.99(7)° and 41.52(8)° for IIa, 14.36(9)° and 57.05(8)°
for IIb, 27.60(9)° and 84.64(3)° for IIc [3], and 21.96(13)°
and 46.68(13)° for IId (ethanol adduct) [2]. This is a proof
of the flexibility of the investigated molecular skeleton,
which will also be evident in the calculated rotational pro-
files. Because of the steric repulsion between the monosub-
stituted phenyl ring and ethyl group, the rotation of the
ring is hindered. The distance between the O7 atom and
3.2. Computational study
The structures of the compounds discussed, with the
atom numbering scheme used during the computational
investigations, are presented in Fig. 2.
The conformational analysis of the studied molecules
was performed based on the DFT and at the B3LYP/6-
31G(d,p) level. During the conformational study, special
attention was focused on the phenyl and phenolic ring rota-
tions in all of the studied compounds (I, II, and III). For
compound III the rotation of the ethyl group was also tak-
en into account as an important feature for discussing the
steric effects in the molecule. Additionally, the values
obtained for the electron density and its Laplacian at the
Fig. 1. The molecular structure of (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenylpent-2-en-1-one with atom numbering scheme (III).

A. Jezierska et al. / Journal of Molecular Structure 839 (2007) 33–40
37
Table 1
Crystal data and structure refinement details for (2Z)-3-[(2-hydroxyphe-
nyl)amino]-1-phenylpent-2-en-1-one (III)
Compound
(2Z)-3-[(2-Hydroxyphenyl)amino]-1-
phenylpent-2-en-1-one
Formula
M
C17H17NO2
267.32
T (K)
100(2)
Crystal system
Space group
a (A)
Monoclinic
P 21
˚
8.524(3)
9.866(3)
8.796(3)
102.89(3)
721.1(4)
2
˚
b (A)
˚
c (A)
b (°)
3
˚
U (A )
Z
Dc(g cmÀ3
)
1.231
0.081
l (mmÀ1
)
hmin À hmax (°)
3.01 to 27.49
5751
1729
Reflections measured
Unique reflections
Rint
0.0276
Observed reflections [I > 2r(I)]
Parameters
1501[I > 2r(I)]
189
R1 (observed reflections)
wR2 (all reflections)
S
0.0332
0.0732
1.066
0.188; À0.146
À3
˚
Dqmax; Dqmin (e.A
)
bond critical point (BCP) between proton and acceptor
based on AIM theory supported our study, proving theo-
retically the presence of an intramolecular hydrogen bond
according to the criteria of Koch and Popelier [14]. The
electrostatic potential surface (ESP) analysis gave insight
into the electronic structure of these three compounds,
showing places potentially involved in complex formation.
The variation of the dihedral angle (C2–C1–N8–C9) and
the OH group position of N-(2-hydroxyphenyl)-4-amino-3-
penten-2-one (I) was analyzed and the obtained results are
presented in Fig. 3.
Fig. 2. The structures of the theoretically investigated compounds with
atom numbering scheme. (A) N-(2-Hydroxyphenyl)-4-amino-3-penten-2-
one (I). (B) 1-Phenyl-3-(2-hydroxyphenylamino)-2-buten-1-one (II). (C)
(2Z)-3-[(2-Hydroxyphenyl)amino]-1-phenylpent-2-en-1-one (III).
Two symmetry-related minima were found for 60° and
150° with a small barrier between them (1 kcal/mol). A
much higher barrier (6 kcal/mol) is present when the OH
group of the phenolic ring passes closely to the methyl
group. Both conformers are almost identical with respect
to energy, although lower energy was obtained for the
60° structure (the –OH group of the phenolic ring is in
syn position with respect to the methyl group). The small
rotational barrier enables an easy exchange between these
two conformers. This is important because of their different
coordination abilities (discussed below).
The theoretical results confirming the presence of the
intramolecular hydrogen bond are presented in Table 3.
The obtained electron density and its Laplacian at the
hydrogen bond critical point (BCP) have quite large values
Table 2
˚
Experimental and theoretical hydrogen bond parameters for (2Z)-3-[(2-hydroxy-phenyl)amino]-1-phenylpent-2-en-1-one (III) (A and °)
D–HÁ Á ÁA
Experimental intra- and intermolecular hydrogen bond parameters
d(D–H)
d(HÁ Á ÁA)
d(DÁ Á ÁA)
<(DHA)
N(8)–H(21)Á Á ÁO(14)
0.90(2)
0.92(3)
1.86(2)
1.74(3)
2.633(2)
2.653(2)
144(2)
172(2)
O(7)–H(22)Á Á ÁO(14)#1
Theoretical intramolecular hydrogen bond parameters (DFT, B3LYP/6-31G(d,p), and B3LYP/6-311+G(d,p), respectively)
N(8)–H(21)Á Á ÁO(14)
1.0327
1.0296
1.7418
1.7712
2.6181
2.6307
139.97
138.31
Symmetry transformations used to generate equivalent atoms: #1 À x, y + 1/2, 1 À z.

38
A. Jezierska et al. / Journal of Molecular Structure 839 (2007) 33–40
Fig. 3. Results of the one-dimensional relaxed B3LYP/6-31G(d,p) conformational search of the studied compounds. The conformational search consisted
of 24 steps (geometry optimization) with 15° increases in the indicated dihedral angle at each step. N-(2-Hydroxyphenyl)-4-amino-3-penten-2-one (I). The
variation of the C2–C1–N8–C9 dihedral angle (top). 1-Phenyl-3-(2-hydroxyphenylamino)-2-buten-1-one (II). The variation of the dihedral angle C2–C1–
N8–C9 (middle left) and C15–C14–C12–O13 (middle right). (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenylpent-2-en-1-one (III). The variation of the dihedral
angle H22–O7–C2–C3 (bottom left) and C11–C10–C9–C12 (bottom right).
typical for compounds with this kind of rather short hydro-
gen bond according to the criteria proposed by Koch and
Popelier [14].
Electrostatic potential (ESP) maps (see Fig. 4) were
obtained for both conformers in order to show the differ-
ence in their complexation ability.
The structure, with the OH and methyl groups in anti
position, is clearly a bi- or tridentate ligand because of
the large region of negative ESP caused by favorable
arrangement of the O7, N8, and O13 atoms. Because of
the rotational freedom and small energy difference between
these two conformers, the mode of coordination described
above should be generally preferred in the metal complexes
of (I). The presence of the hydrogen bond in the ligand
Table 3
Electron density and its Laplacian at the bond critical point (BCP)
between proton and acceptor of the intramolecular hydrogen bond based
on B3LYP/6-311+G(d,p)
BCP parameters
(I)
0.04044
+0.13204
(II)
0.04116
+0.13507
(III)
0.04202
+0.13683
q [e=a30]
$2q [e=a50]

A. Jezierska et al. / Journal of Molecular Structure 839 (2007) 33–40
39
variations in the phenol, phenolic ring, and OH group posi-
tions were taken into account during the study. The
obtained results are presented in Fig. 3. The most stable
conformer has the same atomic arrangement as the X-ray
structure reported in the literature [3]. The phenolic ring
rotation energy profile shows three minima (at ca. À160°,
À90°, and +120°, respectively), but one of the rotation bar-
riers is 10 kcal/mol, which suggests a strong steric repulsion
between the OH and methyl groups. The phenyl ring has
two preferred conformations, which are in fact symmetrical
and equivalent (À30° and +150°). The presence of the
hydrogen bond (between atoms N8–H20Á Á ÁO13) was con-
firmed theoretically as shown in Table 3. The ESP distribu-
tion (see Fig. 4) indicates that (II) is also likely to act as a
tridentate ligand. The concentration of the negative ESP is
visible between atoms containing lone electron pairs. The
carbonyl group and OH group from the phenolic ring have
a significant contribution and the negative ESP is localized
between these two groups.
The conformational flexibility of (2Z)-3-[(2-hydroxyphe-
nyl)amino]-1-phenylpent-2-en-1-one (III) was studied by
analysis of the phenol and phenolic rings and OH and ethyl
group positions. The most stable conformer has an atomic
arrangement similar to the structure obtained by X-ray dif-
fraction (compare Figs. 1 and 2; the geometry shown in
Fig. 2 was obtained at the B3LYP/6-311+G(d,p) level).
The structural parameters obtained from the computation-
al study are in good agreement with the experimental data.
The only significant difference is the relative arrangement
of the ethyl group and the phenolic ring, which was found
to be very flexible in the conformational analysis. In Fig. 3
are presented one-dimensional energy profiles obtained by
variation of the dihedral angles containing the OH group
from the phenolic ring and the ethyl group, respectively,
in the molecule studied. The conformer with the lowest
energy was taken as a structure in the minimum on the
PES and investigated further. The observed discrepancies
between experimental and theoretical results, especially in
some flexible torsion angles, are caused by gas-phase mod-
eling which neglects the environmental (steric, electrostatic,
and H-bond) influence of the neighboring molecules. It is
significant to note that the obtained models are in good
agreement with the available experimental data. The pres-
ence of an intramolecular hydrogen bond was confirmed
experimentally and theoretically (see Tables 2 and 3,
respectively). The obtained theoretically distances between
the atoms involved in the hydrogen bond and the value of
the valence angle are in quite good agreement with the
experimental data. The analysis of electron density and
its Laplacian at the hydrogen bond critical point have quite
large values, which proves the presence of the bond ana-
lyzed based on criteria proposed for such a type of bonding
[14]. The electrostatic potential shows that the atoms with
lone electron pairs are in neighboring positions with respect
to each other (see Fig. 4), so the negative ESP is cumulated
and the compound could also act as a potentially tridentate
ligand.
Fig. 4. The electrostatic potential (ESP) for the analyzed compounds (I,
II, and III, respectively). Dark gray marks regions of decrease À0.05 a.u.
and light gray of increase 0.6 a.u. (A) The electrostatic potential (ESP) for
a conformer with a minimum at 60° (above) and at 150° (below) for N-(2-
Hydroxyphenyl)-4-amino-3-penten-2-one (I). (B) 1-Phenyl-3-(2-hydroxy-
phenylamino)-2-buten-1-one (II). (C) (2Z)-3-[(2-Hydroxyphenyl)amino]-
1-phenylpent-2-en-1-one (III).
structure additionally stabilizes both conformations; more-
over, it facilitates proton removal from the nitrogen atom,
which finally leads to tridentate dibasic ligands.
The conformational analysis of 1-phenyl-3-(2-hydroxy-
phenylamino)-2-buten-1-one (II) was also performed as a
first step of the theoretical study of the compound. The

40
A. Jezierska et al. / Journal of Molecular Structure 839 (2007) 33–40
[4] M. Kabak, A. Elmali, Y. Elerman, J. Mol. Struct. 470 (1998) 295.
The theoretical electronic structure analysis showed that
[5] Y.-Ch. Shi, Acta Cryst. E61 (2005) o2005.
the molecules studied have very similar properties and
should form complexes with similar catalytic properties.
The results obtained theoretically describing the geometri-
cal and electronic structure parameters are useful for fur-
ther experimental study. They highlight the bonding
possibilities during complex formation.
[6] J.L. Wang, S.M. Zhang, F.M. Miao, Acta Cryst. E58 (2002) o1365.
[7] H.N. De Armas, N.M. Blaton, O.M. Peeters, C.J. De Ranter, M.S.
Navarro, Y.V. Reyes, E.O. Rodriguez, E.S. Solano, Acta Cryst. C55
(1999) 1029.
[8] A.D. Garnovskii, A.L. Nivorozhkin, V.I. Minkin, Coord. Chem.
Rev. 126 (1993) 1.
[9] F.A. El-Saied, Inorg. Chim. Acta 165 (1989) 147.
[10] S. Doherty, R.J. Errington, N. Housley, J. Ridland, W. Clegg, R.J.
Elsegood, Organometallics 18 (1999) 1018.
4. Conclusions
[11] P. Hohenberg, W. Kohn, Phys. Rev. 136 (1964) B864.
[12] R.F.W. Bader, Atoms in Molecules, A Quantum Theory, Clarendon
Press, Oxford, 1990.
[13] P.L.A. Popelier, Atoms in Molecules – An Introduction, Pearson
Education, Harlow, 2000.
[14] U. Koch, P.L.A. Popelier, J. Phys. Chem. 99 (1995) 9747.
[15] A.I. Vogel, A Text-Book of Practical Organic Chemistry Including
Qualitative Organic Analysis, third ed., Polish translation, WNT,
Warszawa, 1964, p. 881.
[16] G.M. Sheldrick, SHELXTL, Version 5.10 Bruker AXS, Inc., Mad-
ison, WI, 1997.
We have been successful in synthesizing the potential
ligands of (2Z)-3-[(2-hydroxyphenyl)amino]-1-phenyl’’
alk’’-2-en-1-one type. The details of synthesis, spectroscopic
data, and crystal structure of (2Z)-3-[(2-hydroxyphenyl)-
amino]-1-phenylpent-2-en-1-one (III) are presented. Addi-
tionally, quantum-chemical investigations based on the
DFT method were performed for the molecule discussed
(III) and its two analogues (I and II) in order to study the
physico-chemical nature of these compounds, especially
conformational flexibility and the electrostatic potential sur-
face. The experimentally obtained results are in good agree-
ment with theory and the models proposed are useful for our
future studies. The work is still in progress and as a next step
we would like to investigate the synthesis and structure of
metal complexes and their catalytic activity.
[17] W. Kohn, L.J. Sham, Phys. Rev. 140 (1965) A1133.
[18] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[19] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[20] R. Ditchfield, W.J. Hehre, J.A. Pople, J. Chem. Phys. 54 (1971) 724.
[21] A.D. McLean, G.S. Chandler, J. Chem. Phys. 72 (1980) 5639.
[22] R. Krishnan, J.S. Binkley, R. Seeger, J.A. Pople, J. Chem. Phys. 72
(1980) 650.
[23] J.M. Frisch, J.A. Pople, J.S. Binkley, J. Chem. Phys. 80 (1984) 3265.
[24] R.F.W. Bader, P.M. Beddall, J. Chem. Phys. 56 (1972) 3320.
[25] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C.
Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B.
Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X.
Li, J.E. Knox, H.P. Hratchian, J.B. Cross, V. Bakken, C. Adamo, J.
Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R.
Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A.
Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich,
A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck,
K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S.
Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-
Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill,
B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople,
Gaussian 03, Revision C.02, Gaussian, Inc., Wallingford CT, 2004.
[26] R.F.W. Bader, AIMPAC, Suite of Programs For The Theory of
Atoms in Molecules, McMaster University, Hamilton, Ontario,
Canada, 1991.
Acknowledgments
The Authors (A.J. and J.K.) thank Professor Aleksan-
der Koll and Dr. Jarosław Panek for fruitful discussion.
Grateful acknowledgements to the Wrocław Center for
Networking and Supercomputing (WCSS) and the Aca-
´
demic Computer Center CYFRONET-KRAKOW (Grant
KBN/SGI/UWrocl/078/2001) for providing computer time
and facilities. We thank Ms A. Stencel for assistance with
the synthesis of some organic compounds and Mr. Marek
Hojniak (GC-MS Laboratory, Faculty of Chemistry) for
chromatographic analysis.
References
[1] Z.-F. Chen, S.-T. Li, X.-J. Wang, R.-X. Hu, H. Liang, K.-B. Yu,
Chin. J. Org. Chem. 19 (1999) 513.
[27] S. Portmann, H.P. Lu¨thi, MOLEKEL: CHIMIA 54 (2000) 766.
[28] L. Laaksonen, J. Mol. Graph. 10 (1992) 33.
[2] Y.-Ch. Shi, Acta Cryst. E61 (2005) o1130.
[3] T. Głowiak, J.M. Sobczak, J. Crystal. Spectrosc. Res. 22 (1992) 673.