Synthesis, structure, spectral and coordination properties of a crown ether derivative of 1,3-indandione. A new structural evidence for the versatile reactivity of 2-acetyl-1,3-indandione

Article abstract of DOI:10.1016/j.crci.2009.10.010

The current study describes the synthesis of a new 1,3-indandione derivative with conjugated N-phenylaza-15-crown-5 moiety (4). The crystal structure of compound 4 was solved and its optical properties were studied in various solvents and in presence of alkaline and alkaline-earth metal ions. Quantum chemical (DFT) methods were employed to describe the structure and the optical properties of the studied compound and its complexes. The obtained results indicated that the synthesis of compound 4 using acid-catalyzed aldol reaction between 2-acetyl-1,3-indandione and the corresponding aldehyde is accompanied with an unexpected deacetylation step. In this way, the N-phenylaza-15-crown-5 moiety is directly conjugated with the 1,3-indandione fragment, known as a very strong electron acceptor. Therefore, the absorption spectra of 4 are only slightly influenced by complexation with Ba²⁺ and Sr²⁺ ions.

Full text of DOI:10.1016/j.crci.2009.10.010

C. R. Chimie 13 (2010) 1269–1277
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´
Full paper/Memoire
Synthesis, structure, spectral and coordination properties
of a crown ether derivative of 1,3-indandione. A new structural
evidence for the versatile reactivity of 2-acetyl-1,3-indandione
a
b
a
a
Anife Ahmedova a, , Nikola Burdzhiev , Samuele Ciattini , Elena Stanoeva , Mariana Mitewa
*
a Faculty of Chemistry, University of Sofia, 1, J. Bourchier avenue, 1164 Sofia, Bulgaria
b
`
Dipartimento di Chimica, Universita degli Studi di Firenze, Via della Lastruccia 3, 50019, Sesto Fiorentino (FI), Italy
A R T I C L E I N F O
A B S T R A C T
Article history:
The current study describes the synthesis of a new 1,3-indandione derivative with
conjugated N-phenylaza-15-crown-5 moiety (4). The crystal structure of compound 4 was
solved and its optical properties were studied in various solvents and in presence of
alkaline and alkaline-earth metal ions. Quantum chemical (DFT) methods were employed
to describe the structure and the optical properties of the studied compound and its
complexes. The obtained results indicated that the synthesis of compound 4 using acid-
catalyzed aldol reaction between 2-acetyl-1,3-indandione and the corresponding
aldehyde is accompanied with an unexpected deacetylation step. In this way, the N-
phenylaza-15-crown-5 moiety is directly conjugated with the 1,3-indandione fragment,
known as a very strong electron acceptor. Therefore, the absorption spectra of 4 are only
slightly influenced by complexation with Ba2+ and Sr2+ ions.
Received 10 August 2009
Accepted after revision 23 October 2009
Available online 22 January 2010
Keywords:
2-acetyl-1,3-indandione
N-phenylaza-15-crown-5
Crystal structure
DFT
Optical properties
Metal complexes
´
ß 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction
2-acyl-1,3-indandiones has been thoroughly studied, since
they served as useful synthons for the preparation of
Synthesis of compounds that change drastically their
optical properties upon complexation with metal ions is of
practical importance, since they can be used for metal ion
sensing and as optical switches [1]. In this respect, the
photochemical and complexation properties of aza-crown
ethers modified with chromophore groups are of major
practical interest and have been part of our studies in the
last decades [2–6]. On the other hand, the photochemical
properties of 2-substituted 1,3-indandiones are well
known [7–9], as well as their good complexation ability
with the transition metal ions [10–12]. The synthesis of
various 2-substituted-1,3-indandiones has initially been
stimulated by their known anticoagulant and pharmaco-
logical properties [13–15]. Further, the chemistry of
variety of tricyclic heterocycles [16,17].
In the last few decades, the interest in 1,3-indandiones
has moved from pure synthetic chemistry to the field of
material science [18]. As a very strong electron acceptor,
1,3-indandione is
a part in new dipolar molecules
exhibiting interesting optical properties and used as
dopants in novel functional materials [19–21]. A famous
example is N,N-dimethylamino-benzylidene-1,3-indan-
dione (DMABI) and its derivatives, whose photophysical
and non-linear optical properties were extensively studied
[9,20,22–27].
Lastly, our interest was focused on the photochemical
and complexation properties of 2-cinnamoyl-1,3-indan-
diones [28], which are easily obtained by Claisen-
Schmidt condensation between 2-acetyl-1,3-indandione
(2AID) and the corresponding aromatic aldehyde [29]. In
this way, the complexation properties of 2AID are
* Corresponding author.
E-mail address: ahmedova@chem.uni-sofia.bg (A. Ahmedova).
preserved due to the presence of the
b-dicarbonyl
1631-0748/$ – see front matter ß 2009 Acade´mie des sciences. Published by Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.crci.2009.10.010

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A. Ahmedova et al. / C. R. Chimie 13 (2010) 1269–1277
Scheme 1. Condensation between 2AID and p-(N,N-dimethylamino)benzaldehyde and 4-(aza-15-crown-5)benzaldehyde in piperidine.
fragment. Additionally, the absorption band of the
formed 2-cinnamoyl-1,3-indandiones is shifted to the
indandiones [29]. However, the described reaction did not
yield compound 2, but rather the starting compound was
recovered. That is why the condensation reaction between
the 2AID and the 4-(aza-15-crown-5)benzaldehyde was
performed in acetic acid (Scheme 2), similarly to a
procedure, already used by us, for the synthesis of N-
phenylaza-15-crown-5 derivatives of barbituric acid and
its analogues [2]. Unexpectedly, the reaction resulted in
compound 4, instead of compound 2. The structure of
compound 4 was established by NMR and X-ray data and
will be described further on.
visible region of the spectrum, due to the elongated
p-
system, and gives rise to interesting optical properties
[30]. These features motivated our studies in the search
of new optical sensors and/or extracting agents for metal
ions among the 2-cinnamoyl-1,3-indandiones. There are
several reports on analytical applications of various 2-
acyl-1,3-indandiones for optical detection of some
lanthanide ions [31,32] or extraction of transition metal
ions (Fe3+) [33].
In order to prove that the condensation reactions
between the 2AID and p-(N,N-dialkylamino)benzalde-
hydes proceed in different ways depending on the acidity
of the reaction medium, we performed the reactions in
piperidine and in acetic acid (according to Scheme 1 and
Scheme 2, respectively) using p-(N,N-dimethylamino)ben-
zaldehyde as well. When the reaction of 2AID with p-(N,N-
dimethylamino)benzaldehyde was carried out in piperi-
dine, compound 1 was obtained. Further, the reaction of
2AID with p-(N,N-dimethylamino)benzaldehyde was car-
ried out in boiling acetic acid, similarly to the reaction for
preparation of 4. The product obtained was proved to be 3
(DMABI). It should be noted that the isolation yields of the
newly prepared compounds are moderate (ca. 40%).
Compounds 1 and 3 were characterized by elemental
analyses, IR and NMR spectroscopy. The spectroscopic data
(IR and NMR) are in good agreement with the structures,
corresponding to 1 and 3 (DMABI), as depicted in Schemes
1 and 2, respectively. These results clearly show that a
deacetylation step takes place when the condensation
reaction is performed in acetic acid.
2. Results and discussion
2.1. Synthetic schemes
In the current study, we aimed to synthesize a new 2-
cinnamoyl-1,3-indandione derivative conjugated with N-
phenylaza-15-crown-5, compound 2 (Scheme 1), and
investigate its optical and complexation properties. As a
chromophoric system we used 2AID, the structure and
optical properties of which are well known [7,34].
Moreover, the crystal structure, optical and physicochem-
ical properties of the dipolar compounds containing
electron-donor group conjugated to the 2AID, such as 1
and DMABI are also reported [35,36] and show interesting
possibilities for practical application [24,27,37,38]. Exist-
ing in the exocyclic enolic form (depicted in Schemes 1
and 2), the 2AID reacts as a strong vinylogous acid that
may easily participate in condensation reaction. There-
fore, in order to obtain compound 2 (which is the crown
ether analogue of compound 1) we performed the
condensation reaction of 2AID with 4-(aza-15-crown-
5)benzaldehyde in piperidine (Scheme 1), employing the
known procedure for the synthesis of 2-cinnamoyl-1,3-
Based on the results obtained from the described
experiments and the structural data on the isolated
products, we assumed that the condensation of 2AID

A. Ahmedova et al. / C. R. Chimie 13 (2010) 1269–1277
1271
Scheme 2. Reaction products from condensation between 2AID and p-(N,N-dimethylamino)benzaldehyde and 4-(aza-15-crown-5)benzaldehyde in acetic
acid.
with p-(N,N-dialkylamino)benzaldehydes in acetic acid is
accompanied by deacetylation of the obtained intermedi-
ate. The mechanism we suggest is depicted in Scheme 3.
To the best of our knowledge, this is the first example
for a 2-acyl-1,3-indandione deacetylation observed in an
acidic medium as a subsequent step of acid-catalyzed
condensation with aldehydes.
2.2. Structure and optical properties
The crystal structure of compound 4 was solved by
means of single-crystal X-ray diffraction. The compound 4
crystallizes in the monoclinic P21/n space group. There are
four molecules in the unit cell. ORTEP view of the crystal
structure of 4 and the way of crystal packing are depicted
Scheme 3. Suggested reaction mechanism of the acid-catalyzed condensation between 2AID and p-(N,N-dialkylamino)benzaldehydes.

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A. Ahmedova et al. / C. R. Chimie 13 (2010) 1269–1277
Fig. 1. ORTEP view of the crystal structure of compound 4 (the ellipsoids represent 50% probability) (a), and view of the crystal packing with selected
distances (b).
in Fig. 1a and b, respectively. List of bond lengths and bond
angles is available as Supplementary Material. The C-N
bonds from the crown ether ring [N1-C17 1.449(4) and N1-
C26 1.455(4) A8] are in character, whereas the N1-C1 bond
ether are compared with the experimental data (see the
Supplementary Material). Two different basis sets were
used for optimization of the non-coordinated crown ether
and for the studied complexes, namely 6-31G** and
LanL2DZ. The former basis set was used for the K+, Na+,
Ca2+ and Mg2+ complexes while the LanL2DZ basis set was
applied for the Ba2+ and Sr2+ complexes. The calculated
data for the crown ether, compound 4, using both basis sets
are in very good agreement with the experimental ones.
The structural changes caused by coordination of alkaline
and alkaline-earth metal ions were also studied by means
of quantum chemical methods. The optimized structure of
the non-coordinated crown ether and those of its com-
plexes with K+, Na+, Mg2+, Sr2+ and Ba2+ are presented in
Fig. 2. As could be seen from the figure, the coordination of
metal ions affects not only the conformations of the crown
ether ring but also its orientation relative to the
indandione fragment. Upon coordination, the crown ether
fragment is rotated about the C1-N1 bond and moves
closer to the hydrogen atoms of the phenyl ring. The
calculated distances between the metal ion and the donor
atoms of the crown ether are given in Table 1. The C4-C7
and C1-N1 bond lengths of those connecting the phenyl
ring with the indandione fragment and with the crown
length [1.363(3) A8] shows that there is moderate
p-
electron conjugation between the phenyl ring and the
crown ether. The same holds for the C4-C7 bond [1.422(3)
˚
A] connecting the phenyl ring with the indandione
fragment. The data also show that the 2-benzylidene-
1,3-indandione fragment in the molecule is planar. The
crown ether fragment is almost perpendicular to the
aromatic rings. One of the C-atoms from the crown ether,
C20, shows a high disorder and is represented by two
possible occupations, shown as C20A and C20B. Two types
of intermolecular interactions are observed – weak
p-p-
stacking interactions between the aromatic fragments of
˚
two adjacent molecules (approx. distance 3.35 A) and
weak C-H...O contacts involving a third molecule.
The crystal structure of compound 4 was used as a
starting geometry in the quantum chemical calculations.
Other conformers were also modeled and optimized but
were found to be energetically less favourable and
therefore were not considered further. The optimized
gas-phase structural parameters of the studied crown

A. Ahmedova et al. / C. R. Chimie 13 (2010) 1269–1277
1273
Fig. 2. B3LYP optimized structures of compound 4 and its K+, Na+, Sr2+, Mg2+ and Ba2+ complexes.
ether moiety, respectively, are also given in order to
estimate the changes in the degree of conjugation between
both fragments as a result of coordination with the metal
ion.
compound 4 (Table 1). These results can be used as a measure
for the loss of conjugation between the electron donor and
acceptor parts in the molecule and correspondingly explains
the observed optical properties.
The obtained distances between the metal ion and the
donor atoms from the crown ether are compared with the
sum of the covalent radii of the corresponding atoms, as
available in Cambridge Structural Database (CSD). It is only
The optical properties of compound 4 are characterized
with a very strong absorbance in the visible region of the
spectrum,
lmax = 480 nm in acetonitrile. A bathochromic
shift of 14 nm is observed in DMSO, while in cyclohexane
the absorption maximum is shifted to 466 nm. The
compound shows weak fluorescence with a Stokes shift
of 62 nm. The emission band is a mirror image of the
absorption spectrum. In order to study the effect of metal
˚
the Mg-O distances that are in the range of Æ 0.4 A
tolerance for establishing a bonding connection. On the
other hand, however, the largest elongation of the C4-C7 and
N1-C1 bonds is obtained for the Ba2+ and Sr2+ complexes of

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A. Ahmedova et al. / C. R. Chimie 13 (2010) 1269–1277
Table 1
Calculated (B3LYP) bond lengths and distances in the crown ether complexes. The calculated (B3LYP/6-31G**) C1-N1 and C4-C7 distances in the compound
˚
4 are 1.379 and 1.436 A, respectively.
˚
Distance [A]
Na - complex
(6-31G**)
K - complex
(6-31G**)
Mg - complex
(6-31G**)
Ca - complex
(6-31G**)
Sr - complex
(LanL2DZ)
Ba - complex
(LanL2DZ)
M-O3
M-O4
M-O6
M-O7
M-N1
C1-N1
C4-C7
2.229
2.367
2.321
2.295
2.515
1.455
1.459
2.675
2.696
2.720
2.688
2.930
1.452
1.458
2.144
2.174
2.147
2.116
2.236
1.471
1.462
2.364
2.353
2.371
2.368
2.494
1.467
1.462
2.517
2.520
2.503
2.524
2.676
1.478
1.468
2.701
2.709
2.676
2.716
2.885
1.476
1.468
ions on the optical properties of compound 4, spectra in
presence of K+, Na+, Mg2+, Sr2+ and Ba2+ ions were recorded.
The observed changes are very subtle and are better
pronounced only in presence of the Sr2+ and Ba2+ ions, as
can be seen in Fig. 3. Although the good complexation
ability of N-phenylaza-15-crown-5 moiety with the
divalent ions is well known, in the studied case it does
not lead to drastic change in the absorbance spectra of
compound 4. One possible explanation can be that the
crown ether moiety is directly bound to a very strong
electron acceptor, which is the 1,3-indandione fragment.
Therefore, the involvement of the N-atom’s lone pair in
coordination with the metal ion only slightly affects the
electron density distribution in the molecule. The calcu-
lated vertical excitation energies of the crown ether 4 and
its complexes predict correctly the expected hypsochromic
shift upon coordination, but the corresponding transitions
in the complexes are with very weak oscillator strength. An
additional factor to remark on is the stability of the formed
complexes. As has been previously reported on other N-
phenylaza-15-crown-5 derivates, their complexes with
alkaline-earth metal ions have low stability constants and
the observed absorption spectra are, in some cases, with
low intensity [5,6]. In order to estimate the stabilization
energy of the metal complexes of compound 4, the EST for
each of them was calculated with the appropriate basis set.
The results for EST, defined as ECOMPL-ECROWN-EION, are
listed in Table 2 together with the HOMO and LUMO
energies, being additional measure of the complex
stability. The higher the absolute value of the calculated
D
D
energy differences,
DEST, the higher is the expected
stability of the complex. Moreover, single-point calcula-
tions were performed on the optimized structure of the
complexes after removing the metal ion. The resulting
energies are compared with the optimized structure of the
free crown ether. In this way, it is possible to estimate the
role of the metal ion coordination in the energy increase
due only to the conformational changes,
DECONF. These
data, along with the structural parameters, are used to
explain the obtained stability of the complexes, except for
the known ion radius and cavity size matching. For
example, the largest obtained stability of the Mg-
complexes, which contradicts to the known trends, is
apparently due to the strongest metal-oxygen bonds
obtained in this case. The energy contribution of the
structural changes in the ligand, caused by the coordina-
Fig. 3. Absorption spectra of compound 4 in acetonitrile; C = 2 Â 10-5 M, and in presence of Mg2+, Sr2+ and Ba2+ (perchlorates, C = 10-3 M).

A. Ahmedova et al. / C. R. Chimie 13 (2010) 1269–1277
1275
Table 2
Stabilization energies of the optimized complexes calculated as
to coordination of metal ion (the same basis set is used for the corresponding species, as indicated in parenthesis).
D
EST = ECOMPL-ECROWN-EION together with the conformational energy differences
D
ECONF due
Compound (basis set)
DEST [kcal/mol]
EHOMO [a.u.]
ELUMO [a.u.]
DECONF [kcal/mol]
K_crown (6-31G**)
Na_crown (6-31G**)
Mg_crown (6-31G**)
Ca_crown (6-31G**)
Ba_crown (LanL2DZ)
Sr_crown (LanL2DZ)
À51.185
À80.500
À0.312
À0.310
À0.392
À0.396
À0.395
À0.396
À0.168
À0.167
À0.263
À0.262
À0.263
À0.267
16.037
18.693
33.718
26.385
36.123
37.575
À304.002
À211.576
À149.533
À182.418
tion, plays a little role in the overall stability of the
complex, as can be seen from Table 2.
on a JASCO V-570 - UV/Vis/NIR spectrophotometer. The
emission spectrum was recorded on a Varian - Cary Eclipse
fluorescence spectrophotometer. The NMR measurements
were carried out in CDCl3 using a Bruker DRX-250
spectrometer operating at 250.13 MHz for 1=- and
62.90 MHz - for the 13E-nuclei. The chemical shifts are
related to TMS, used as internal reference. 13C-NMR shifts
assignment was facilitated by DEPT experiment distin-
guishing the quaternary carbons from the rest.
All solvents used were Uvasol grade. Acetonitrile was
distilled over P2O5 before use. The complexation with
metal ions was performed in dry acetonitrile using dried
perchlorates: NaClO4, KClO4, Ba(ClO4)2, Sr(ClO4)2,
Mg(ClO4)2. The absorption spectra of the complexes were
measured in 1:100 ligand-to-metal ratio.
3. Conclusions
The crystal structure of the newly synthesized crown
ether derivative of 2-benzylidene-1,3-indandione (com-
pound 4) was determined by means of single-crystal X-ray
diffraction. The compound
4 was obtained by aldol
condensation of 2AID with the corresponding aromatic
aldehyde in acetic acid. The structure of the obtained
product indicates that the condensation reaction is
accompanied by a deacetylation step. Analogous result
was obtained from the condensation of 2AID with p-(N,N-
dimethylamino)benzaldehyde in acetic acid yielding
compound 3 (DMABI), whose structure was confirmed
by the IR and NMR data. When the condensation reaction
was performed in piperidine, p-(N,N-dimethylamino)-
cinnamoyl-1,3-indandione (1) was obtained. All additional
synthetic and spectroscopic experiments suggest that the
aldol condensation between 2AID and aromatic aldehydes
was followed by unprecedented deacetylation when
performed in acetic acid.
4.2. Synthesis and characterization
4.2.1. 2-(4 -Dimethylamino-cinnamoyl) -2H-indane-1,3-
dione (1)
Compound 1 was obtained according to a known
procedure [29], yield 60%, m.p. 214-2150E. IR (nujol):
n
3400-3500 (n?H), 1700 (
n
C=O), 1635 (nC=O
, nC=C) 1630(nC=O,
n
C=C). 1H NMR (CDCl3):
d = 3.06 (6H, s, 2xCH3), 6.68 (2H, d,
The structure of compound 4 and its complexes with
alkali and alkaline-earth metal ions were optimized in
search of explanation for the observed optical properties.
According to the DFT calculations, the divalent metal ions
form more stable complexes. In the experimental absorp-
tion spectra of Sr2+ and Ba2+ complexes hypsochromic
shifts of the absorption maxima were observed. They are,
however, of very low intensity, as predicted by the TD-DFT
calculations of the vertical excitation energies of the
Ph, J = 8.9 Hz), 7.59 (2H, d, Ph, J = 8.9 Hz), 7.63-7.91 (6H, m,
2xCH, 4Ph), 11.7 (s, 1H, OH) ppm. 13C NMR (CDCl3):
d
= 40.10 (2C, 2xCH3), 106.38 (1C), 111.71 (2C), 111.79
(2C), 121.76 (1C), 122.12 (1C), 122.58 (1C),131.51 (1C),
133.48 (1C), 134.28 (1C), 138.71 (1C), 140.79 (1C), 146.36
(1C), 152.50 (1C), 174.28 (1C), 188.99 (1C, CO), 197.36 (1C,
CO) ppm. Anal. Calcd for C20H17NO3 (319.12): C 75.22%, H
5.37%, N 4.39%; found C 75.11%, H 5.30%, N 4.68%.
studied compounds.
A plausible explanation of the
4.2.2. 2-(4-(Dimethylamino)benzylidene)-2H-indene-1,3-
dione, DMABI (3)
observed very small effect of the metal ion coordination
on the optical properties of compound 4 is probably the
direct conjugation of the N-phenylaza-15-crown-5 moiety
with a very strong electron acceptor, such as the 1,3-
indandione. Additional consequence of this structural
feature of compound 4 is the low stability of the obtained
complexes.
A solution of 2AID (0.188 g, 1 mmol) in acetic acid
(4 mL) was mixed with solution of 4-(dimethylamino)-
benzaldehyde (0.149 g, 1 mmol) in acetic acid (4 mL).
Additional acetic acid (2 mL) was added and the reaction
mixture was refluxed for 5 h. After the completion of the
reaction (TLC), the solvent was removed under reduced
pressure. The resulting oil was dissolved in dichloro-
methane (30 mL) and washed with 10% Na2CO3 (10 mL).
Organic layer was washed with water and dried (Na2SO4).
The solvent was evaporated under reduced pressure and
the resulting oil was recrystallized from ethyl acetate thus
yielding 0.085 g (31%), m.p. 208-210 8C. IR (CHCl3):
4. Experimental section
4.1. General
The IR spectra were recorded on a Perkin-Elmer FTIR-
1600 spectrometer (KBr tablets, and/or nujol mulls).
Elemental analyses were performed on a Vario EU III
instrument. The UV-Vis absorption spectra were recorded
n
d
= 1700
= 3.16 (6H, s, 2xCH3), 6.75 (2H, d, Ph, J = 9.2 Hz), 7.71-
7.76 (2H, m, Ph), 7.80 (1H, s, CH), 7.91-7.96 (2H, m, Ph),
(nC=O), 1655 (nC=O) .
cm-1 1H NMR (CDCl3):

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A. Ahmedova et al. / C. R. Chimie 13 (2010) 1269–1277
8.55 (2H, d, Ph, J = 8.5 Hz) ppm. 13C NMR (CDCl3):
d = 40.11
Table 3
Crystal data and structure refinement for compound 4.
(2C, 2xCH3), 111.40 (2C), 122.49 (2C), 134.13 (2C), 134.41
(2C), 138.02 (1C), 139.87 (1C), 142.23 (1C), 147.55 (2C),
153.96 (1C), 190.03 (1C, CO), 191.82 (1C, CO) ppm. Anal.
Calcd for C18H15NO2 (277.32): C 77.96%, H 5.45%, N 5.05%;
found C 77.33%, H 5.68%, N 5.12%.
Compound 4
Empirical formula
Molecular weight
Temperature
C26H29NO6
451.52
293(2) K
˚
Radiation source/wavelength (
Diffractometer
l
)
MoKa (l=0.71073 A).
Xcalibur3 4-circles
Diffractometer
Monoclinic,
4.2.3. 2-(4-(1,4,10,13-Tetraoxa-7-azacyclopentadecan-7-
yl)benzylidene)-2H-indene-1,3-dione (4)
Crystal system,
Space Group
A solution of 2AID (0.188 g, 1 mmol) in acetic acid (4 mL)
was mixed with solution of 4-(1,4,10,13-tetraoxa-7-
azacyclopentadecan-7-yl)benzaldehyde (0.323 g, 1 mmol)
in acetic acid (4 mL). Additional acetic acid (2 mL) was
added and the reaction mixture was refluxed for 5 h. After
the completion of the reaction (TLC), the solvent was
removed under reduced pressure. The resulting oil was
dissolved in dichloromethane (30 mL) and washed with 10%
Na2CO3 (10 mL). Organic layer was washed with water and
dried (Na2SO4). The solvent was evaporated under reduced
pressure. The resulting oil was purified by column
chromatography (light petroleum-ethyl acetate-acetic ac-
id = 1:1:0.01) and recrystallized from ethyl acetate thus
P 21/n
˚
Unit cell dimensions
a = 12.3150(10) A
˚
b = 12.4090(8) A
˚
c = 16.4390(14) A
a=90.008
b= 111.841(10)8
g= 90.008
Volume
Z
2331.83
4
Crystal size
0.2 mm  0.3 mm  0.4 mm
3.928 to 28.988
7632/4558
Full-matrix least-squares on F2
4558/0/297
Theta range for data collection
Reflections collected/unique
Refinement method
Data/restraints/parameters
GooF on F2
0.859
Final R indices [I > 2sigma(I)]
R indices (all data)
R1 = 0.0624, wR2 = 0.1705
R1 = 0.1393, wR2 = 0.1959
yielding 0.106 g (23%), m.p. 191-193 8C. IR (CHCl3):
C=O), 1665 ( C=O), 1120 (
COC) cm-1. 1H NMR (CDCl3):
= 3.62-3.64 (4H, br.s, OCH2), 3.65-3.69 (8H, br.s, OCH2),
n = 1710
(n
n
d
d
3.72 (1H, t, OCH2, J = 6.2 Hz), 3.81 (1H, t, NCH2, J = 6.2 Hz),
6.75 (2H, d, Ph, J = 9.2 Hz), 7.70-7.50 (2H, m, Ph), 7.77 (1H, s,
CH), 7.89-7.95 (2H, m, Ph), 8.51 (2H, d, Ph, J = 8.3 Hz) ppm.
4.4. Quantum chemical calculations
The quantum chemical calculations were performed
with full geometry optimization without any symmetry
restrictions. All calculations were performed with the
Gaussian 03 program package [40]. Geometries of the
studied compounds were optimized using the DFT
method with the hybrid B3LYP functional [41,42]. For
the calculations the 6-31G(d,p) basis set was used, while
in case of Ca2+, Sr2+ and Ba2+ complexes the LanL2DZ basis
set, which includes Dunning-Huzinaga full double zeta
(DZ) basis functions for the first row and Los Alamos
effective core potentials (ECP) for heavy elements, was
employed. Vibrational frequencies were computed at the
same level of theory in order to confirm that local energy
minima were attained. Vertical excitation energies were
computed with the time dependent DFT (TD-DFT)
employing the same functional and basis sets as for
optimization.
13C NMR (CDCl3):
d = 53.03 (2C, NCH2), 68.08 (2C, OCH2),
69.92 (2C, OCH2), 70.27 (2C, OCH2), 71.21 (2C, OCH2), 111.55
(2C, Ph), 122.08 (1C, Ph), 122.44 (2C, Ph), 123.04 (1C, Ph),
134.08 (1C, CH), 134.35 (1C, Ph), 138.00 (2C, Ph), 139.80 (1C,
Ph), 142.15 (1C, Ph), 147.24 (1C, Ph), 152.20 (1C, Ph), 189.92
(1C, CO), 191.71 (1C, CO) ppm. Anal. Calcd for C26H29NO6
(451.51): C 69.16%, H 6.47%, N 3.10%; found C 68.67%, H
6.25%, N 3.00%.
4.3. Crystal structure determination
Single crystals @f compound 4 were obtained by
recrystallization from ethyl acetate. The data were
collected at 293(2) K on a Xcalibur3 4-circles diffractome-
ter using a graphite monochromator, MoKa radiation. A
reference frame was monitored every 50 frames to control
the stability of the crystal and the system revealed no
intensity decay. The data set was corrected for Lorentz,
polarisation effects, and absorption correction was made
by multi-scan method using the CrysAlis Software
package.
Acknowledgements
This work has been supported by the Bulgarian National
Science Fund, Contract MYX-1502/05.
The structure was solved using direct method with
SIR97 software and the refinement was carried out using
the SHELXL-97 software package [39]. All non-hydrogen
atoms were located from the initial solution or from
subsequent electron density difference maps during
the initial course of the refinement. After locating the
non-hydrogen atoms the models were refined against F2,
first using isotropic and finally anisotropic thermal
displacement parameters. The hydrogen atoms were
treated with the riding coordinate method. Details about
the crystal structure and its refinement are given in
Table 3.
Appendix A. Supplementary material
Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/j.crci.
2009.10.010.
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