Vibrational spectroscopic studies, theoretical aspects, and X-ray analysis of xanthenodiones (1,8-dioxooctahydroxanthenes)

Article abstract of DOI:10.1002/jhet.4214

Compounds containing a pyran moiety fused to two cyclohexen-2-one rings are collectively called xanthenodiones (1,8-dioxooctahydroxanthenes). With the aim of increasing the knowledge about the structures of xanthenodiones, in the present investigation two

Full text of DOI:10.1002/jhet.4214

Received: 4 September 2020
DOI: 10.1002/jhet.4214
Revised: 7 December 2020
Accepted: 18 December 2020
A R T I C L E
Vibrational spectroscopic studies, theoretical aspects,
and X-ray analysis of xanthenodiones
(
1,8-dioxooctahydroxanthenes)
1
1
Milene Lopes da Silva
| Róbson Ricardo Teixeira
|
2
| Luciano de Moura Guimar a~ es3
Fabrício Marques de Oliveira
|
4
Felipe Terra Martins
1
Departamento de Química, Universidade
Abstract
Federal de Viçosa, Viçosa, Brazil
2
Compounds containing a pyran moiety fused to two cyclohexen-2-one rings
are collectively called xanthenodiones (1,8-dioxooctahydroxanthenes). With
the aim of increasing the knowledge about the structures of xanthenodiones,
in the present investigation two xanthenodiones, namely 9-(4-hydroxy-
3-methoxyphenyl)-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2H)-dione (1) and
Instituto Federal de Minas Gerais,
Campus Ouro Branco, Ouro Branco,
Brazil
3
Departamento de Física, Universidade
Federal de Viçosa, Viçosa, Brazil
4
Instituto de Química, Universidade
Federal de Goiás, Campus Samambaia,
Goiânia, Brazil
9-(4-hydroxyphenyl)-3,6-diisopropyl
3,4,5,6,7,9-hexahydro-1H-xanthene-1,8
(2H)-dione (2), were synthesized. Their structures were investigated by
nuclear magnetic resonance, single-crystal X-ray diffraction, infrared (IR),
and Raman spectroscopy techniques along with mass spectrometry. In
addition, a computational study was carried out involving vibrational spec-
troscopy, which allowed us to assign vibrational modes and their shifts as
lattice environment. Even though compound 2 has two stereocenters, it
Correspondence
Róbson Ricardo Teixeira, Departamento
de Química, Universidade Federal de
Viçosa, Av. P. H. Rolfs, S/N, 36.570-900,
Viçosa, Minas Gerais, Brazil.
Email: robsonr.teixeira@ufv.br
crystallized in a centrosymmetric space group (P2 /c) as expected from its
1
achiral synthesis. This compound also crystallized as monohydrate and the
presence of water molecule did not change the conformation of the target
compounds.
1
| INTRODUCTION
These compounds are known to have antip-
[
6]
[7]
[8,9]
roliferative,
fungicidal
leishmanicidal,
activities. Because of the biological proper-
ties presented by xanthenodiones and their applications
antibacterial,
and
[
10]
Heterocycles possibly represent the largest and most
diverse group of compounds in organic chemistry.
They are widespread in nature and natural heterocy-
cles present a broad range of important biological
activities.
chemicals are heterocyclic compounds.
are also an integral part of several dyes, luminophores,
and polymers.
The xanthenodiones (1,8-dioxooctahydroxanthenes)
are a subclass of heterocycles derived from xanthene
characterized by the presence of a pyran moiety fused to
two cyclohexen-2-one rings (Figure 1).
[
1]
[
11,12]
in photodynamic therapy and laser technology,
several synthetic methodologies for their preparation
have been described. In general, the preparation of
xanthenodiones involves a three-reaction sequence,
namely Knoevenagel condensation, Michael addition, and
[
2,3]
A myriad of pharmaceuticals and agro-
[
4,5]
Heterocycles
[13]
dehydration. Despite being a class of compounds that have
been widely studied from the preparation point of view,
investigations on the structural features of xanthenodiones
[
14–24]
are less common.
Within this context and consider-
ing our interest in the chemistry, bioactivities, and
J Heterocyclic Chem. 2021;58:777–792.
wileyonlinelibrary.com/journal/jhet
© 2020 Wiley Periodicals LLC.
777

778
da SILVA ET AL.
and are uncorrected. Analytical thin layer chromatogra-
phy analysis was carried out on TLC plates recovered
with 60GF254 silica gel. The NMR and mass spectra as
well as CIF data of compounds 1 and 2 are avaialable in
the supplementary information.
O
R5
O
O
R3
R4
R1
O
R2
Xanthene
Xanthenodione
FIGURE 1 Structure of xanthene and general structure of
1
2
3
4
5
2.2 | Preparation of compounds
xanthenodiones. R , R , R , R , and R are different groups.
5
Typically, R is an aryl group
2
3
.2.1 | Synthesis of 9-(4-hydroxy-
-methoxyphenyl)-3,4,5,6,7,9-hexahydro-1H-
[16,25,26]
structural features of xanthenodiones,
we herein
xanthene-1,8(2H)-dione (1)
describe the synthesis and characterization of two
hydroxylated xanthenodiones. Their full characteriza-
tion was achieved using nuclear magnetic resonance
In a typical procedure, a round-bottomed flask (25 ml)
was charged with cyclohexan-1,3-dione (231 mg,
2.00 mmol), 4-hydroxy-3-methoxybenzaldehyde (155 mg,
1.00 mmol), and ZrOCl ꢀ 8H O (12.0 mg, 2 mol%).
(
NMR), single-crystal, X-ray diffraction, infrared (IR),
and Raman spectroscopy techniques along with mass
spectrometry. In addition, a computational study was
carried out involving vibrational spectroscopy, which
allowed a comparison with the experimental data.
2
2
ꢁ
The mixture was stirred at 85 C and the progress of
the reaction was monitored by TLC analysis. After
completion of the reaction, the mixture was cooled
down to room temperature. Thereafter, it was added
to the flask 50 ml of dichloromethane and the mixture
was kept under stirring for about 30 min. Then, the
catalyst, which is insoluble in dichloromethane, was
separated by filtration. After that, 50 ml of ethanol
was added and the system was kept upon stand for
crystallization. This procedure afforded compound
1 as a beige solid in 94% yield (320 mg, 0.940 mmol).
Crystals suitable for X-ray diffraction studies were
obtained from the abovementioned crystallization
procedure. The obtained crystals were thoroughly
washed with cold ethanol and dried. Structure of 1 is
supported by the following data.
2
2
| EXPERIMENTAL
.1 | Generalities
All reagents were purchased from commercial sources
Sigma Aldrich-St. Louis, MO, US and Vetec, Rio de
(
Janeiro, Brazil) and were employed as received. Solvents
were purchased from Vetec (Rio de Janeiro, Brazil) and
1
13
were used as received. The H and C NMR spectrum
were recorded on a Varian Mercury 300 instrument
(
Varian, Palo Alto, CA, USA) at 300 MHz and 75 MHz,
1
ꢁ
respectively, using deuterated chloroform as solvent. H-
NMR data are presented as follows: chemical shift (δ) in
ppm, number of hydrogen atoms, multiplicity, J values
in Hertz (Hz). Multiplicities are shown as the following
abbreviations: s (singlet), d (doublet), dd (double of dou-
blets), t (triplet), m (multiplet). Infrared (IR) spectra
were obtained using Varian 660-IR equipped with Gladi-
ATR (Varian, Palo Alto, CA, USA). The Raman mea-
surements were performed with microRaman InVia
Renishaw spectrometer (Wotton-under-Edge, Glouces-
tershire, United Kingdom) with ×50 objective. The
Mp 237–238 C. IR (ATR): 3504–3100, 2953, 2889,
−
1
1663, 1641, 1619, 1467, 1273, 1203, 1170, 1120 cm
.
1
H NMR (300 MHz, CDCl ) δ: 1.92–2.07 (4 H, m),
3
2.24–2.43 (4H, m), 2.48–2.67 (4 H, m), 3.87 (3 H, s),
4.72 (1 H, s), 5.82 (1 H, s), 6.54 (1 H, dd, J = 8.1 Hz,
J = 2.0 Hz), 6.72 (1 H, d, J = 8.1 Hz), 7.04 (1 H, d,
1
3
J = 2.0 Hz). C NMR (75 MHz, CDCl ) δ: 20.3, 27.1,
3
31.0, 37.0, 55.9, 112.4, 114.0, 117.0, 119.8, 136.6, 144.1,
145.9, 163.8, 196.8. MS, m/z (%): 340 (100), 323 (52),
309 (62), 217 (96), 55 (31).
7
85 nm diode laser line was employed as the excitation
source and the laser power intensity on the sample was
kept up below 5 mW. Mass spectra were recorded on a
SHIMADZU GCMS-QP5050A) instrument (Shimadzu
Scientific Instruments, Kyoto, Japan) under electron
impact (70 eV) conditions. The mass was acquired in
positive mode scanning from 50 to 1000 Da. Melting
points were determined using an MQAPF-302 melting
point apparatus (Microquimica, Santa Catarina, Brazil)
2.2.2 | Synthesis of 9-(4-hydroxyphenyl)-
3,6-diisopropyl-3,4,5,6,7,9-hexahydro-1H-
xanthene-1,8(2H)-dione (2)
A similar procedure to that described for the prepara-
tion of 1 was used to synthesize compound 2. The
structure of xanthenodione 2 is supported by the
following data.

da SILVA ET AL.
779
ꢁ
Mp 176–177 C. IR (ATR): 3620–3001, 2959, 2873,
TABLE 1 Crystal data and refinement statistics for compounds
−
1
1
1
671, 1645, 1612, 1463,1375, 1181 cm . H NMR
elucidated in this study
(
1
300 MHz, CDCl ) δ: 0.94–0.89 (12 H, t, J = 6.6 Hz),
3
1
2
.80–1.96 (2 H, m), 2.00–2.12 (2 H, m), 2.26–2.67 (6 H,
Structural formula
C
20
H
20
O
5
30 4
(C25H O )
m), 4.69 (1 H, s), 6.55–6.60 (2 H, m), 7.04–7.10 (2 H, m).
(
H
2
O)
412.51
Orthorhombic Monoclinic
1
3
C NMR (75 MHz, CDCl ) δ: 19.4. 19.5, 19.6, 30.8, 31.0,
3
Fw (g/mol)
Cryst syst
Space group
Z/Z'
340.36
3
1
1.8, 38.7, 197.7, 40.1, 41.0, 41.4, 115.3, 116.4, 116.7,
16.8, 129.3, 135.6, 135.8, 154.8, 163.9, 164.4, 164.5, 197.7.
MS, m/z (%): 394 (88), 377 (52), 351 (15), 301 (100),
96 (22), 41 (19).
Pna2
1
P2
1
/c
2
4/1
4/1
T (K)
296(2)
296(2)
Unit cell dimensions
a (Å)
2
.3 | X-ray diffraction analysis
18.5688(16)
10.3325(9)
8.7446(7)
90
13.092(3)
15.524(4)
12.030(3)
90
b (Å)
Block-shaped single crystals of compounds 1 and 2 were
mounted on a κ-goniostat of a Bruker-AXS Kappa Duo
diffractometer and then exposed to X-ray beam (Mo Kα,
λ = 0.71073 Å) at room temperature. X-Ray diffraction
intensity data were measured on an APEX II CCD detec-
tor. Crystallographic softwares were used as follows:
APEX2 (data collection strategy setup with φ and ω scans
and κ offsets), SAINT
ing of raw data), SHELXS-97
Direct Methods), SHELXL-97
full-matrix least squares method on F2) and MER-
c (Å)
ꢁ
α ( )
ꢁ
β ( )
90
109.624(7)
90
ꢁ
γ ( )
90
3
V (Å )
1677.8(2)
1.347
2302.9(9)
1.190
[27]
Calculated density
(indexing, integration, and scal-
3
(
Mg/m )
[28]
(structure solving using
(structure refinement by
[28]
Absorp. coefficient μ
0.097
0.082
−
1
(
mm )
[29]
θ range for data collection
2.19–25.37
1.65–25.53
CURY.
(structure analysis and graphical representa-
ꢁ
(
)
tions). All non-hydrogen atoms of asymmetric units were
directly attributed from the electronic density Fourier
synthesis. Free anisotropic and fixed isotropic atomic dis-
placement parameters were set for non-hydrogen and
Index ranges
h
−20 to 22
−12 to 8
−10 to 9
4508
−14 to 15
−18 to 14
−9 to 14
11,200
4233
k
hydrogen atoms, respectively (U (H) = 1.2U (C) or
iso
iso
l
1
.5Uiso (Cmethyl or O). All hydrogens were placed at con-
Data collected
Unique reflections
Observed reflections
Observed reflections
Symmetry factor (Rint
strained sites according to previous stereochemical
knowledge of bond lengths and angles and they were not
refined freely, but their coordinates oscillate as those of
the bonded carbon and oxygen atoms so that bond
lengths and angles did not change. Data collect descrip-
tors and refinement statistics for compounds 1 and 2 are
presented in Table 1.
2489
2489
4233
2270
1983
)
0.0221
98.7
0.0925
98.3
ꢁ
Completeness to θ = 25
(%)
F (000)
720
888
Parameters refined
227
298
2
.4 | Computational details
2
Goodness-of-fit on F
1.139
0.0383
1.108
0.1058
Final R1 factor for I > 2σ
I)
The geometries of the xanthenodiones 1 and 2 were first
designed in the SPARTAN 10 software.
former distribution routine of SPARTAN and the semi-
empirical PM6 method,
species was carried out to identify the most stable con-
formers in each case. The outputs obtained with the
SPARTAN 10 program were used to generate inputs for
the calculations with the Gaussian 09 program. . The
lower energy conformer was then fully optimized in a gas
phase using the Becke three parameter hybrid functional
(
0
[30]
Using the con-
wR2 factor for all data
0.1357
0.3721
[31]
Largest diff. Peak/hole
0.253/−0.244
0.632/−0.267
a conformational analysis of
3
(
e/Å )
CCDC deposit number
1,509,388
1,509,389
0
[32]
combined with the Lee, Yang, and Parr correlation func-
[
33]
tional (B3LYP)
set.
in conjunction with 6–31+G(d,p) basis
[
34]
Based on optimized geometries, IR and Raman

780
da SILVA ET AL.
1
spectrum calculations were performed by using Density
spectrometry. In the H NMR spectra, the hydrogen atom
of the pyran ring was observed at 4.68 and 4.72 ppm. In
Functional Theory (DFT) at the B3LYP/6–311++G(d,p)
[35]
13
level of theory.
the C, the signals for the carbonyl groups were observed
around 196 ppm.
3
3
| RESULTS AND DISCUSSION
.1 | Synthesis of compounds 1 and 2
3
.2 | Crystal structures
Crystal structures of compounds 1 and 2 are shown with
their 30% probability ellipsoids and arbitrary labeling
scheme in Figure 2. Labeling of the rings is also shown in
The compounds 1 and 2 were synthesized using solvent
free reactions catalyzed by ZrOCl ꢀ8H O (Scheme 1), as
2
2
[
16,25,26,36]
previously described.
The formation of these
this figure. Even though compound 2 has two
compounds involved Knoevenagel condensation reac-
tion between aromatic aldehydes and two β-diketones,
followed by Michael addition, and finally dehydration.
The reaction yield obtained for compound 1 was 94%
after 20 min of reaction. In contrast, it took a longer reac-
tion time (80 min) to obtain a 58% yield for compound 2.
This can possibly be associated with the steric hindrance
caused by the presence of the isopropyl substituent in the
β-diketone.
stereocenters, it has crystallized in a centrosymmetric
space group (P2 /c) as expected from its achiral synthesis.
1
In the chosen asymmetric unit, chiral carbons labeled as
C8 and C11 have S and R configurations, but the other
enantiomer is also present in the unit cell. The asymmet-
ric unit of both compounds is composed by just one
xanthenodione molecule. One water molecule is also pre-
sent in the asymmetric unit of 2. The isopropyl group
attached at C11 is disordered over two sets of 50% occu-
pancy sites.
In the two compounds reported here, both rings A
and C adopt a half-chair conformation with C8 and C11
carbons away from the least-squares (l.s.) planes calcu-
lated through the other five coplanar atoms. The distance
of these carbons from l.s. planes is −0.619(3) and 0.659
(3) Å in compound 1 and 0.476(6) and 0.406(8) Å in com-
pound 2, respectively (the root-mean-square deviation
The structures of the compounds were confirmed
1
13
using NMR ( H and C), single-crystal X-ray diffractom-
etry, vibrational spectroscopy (IR and Raman), and mass
OH
OH
R1
R1
O
O
O
[RMSD]
of
the
five
C9-C4-C5-C6-C7
and
CHO
C10-C3-C2-C13-C12 l.s. fitted atoms are 0.0454 and
0.0515 Å in compound 1 and 0.0632 and 0.0207 Å in com-
pound 2). Taking these ring mean planes reference, it is
possible to see that the carbons C8 and C11 at the back of
both half-chairs are oriented toward the same side of the
C1 substituent in compound 2, while in compound 1 C8
R2
R2
R
R2
R3
2
ZrOCl2 8H2O, solvent free,
3
3
O
R
O
8
5 o
C
1): R1 = OCH3, R2 = R3 = H
2): R1 = H, R2 = H, R3 = isopropyl
(
(
SCHEME 1 Synthesis of xanthenodiones 1 and 2
FIGURE 2 30% ellipsoid
representation of the non-hydrogen
atoms in the asymmetric unit of
compounds 1 (a) and 2 (b). In (b), the
labeling of carbons of xanthenodione
and phenyl moieties were not shown for
clarity, but they are exactly the same
ones as shown in (a). The bonds of on
isopropyl group in 50% occupancy site
sets were drawn as dashed double lines
in (b) [Colour figure can be viewed at
wileyonlinelibrary.com]

da SILVA ET AL.
781
ꢁ
is on the opposite side of that lying C11 and the substitu-
ent at C1.
torsion is 9.9[4] ). Concerning the ring B conformation, it
is almost planar, in which C1 carbon is the most deviated
atom (0.165(3) and 0.132(4) Å in compounds 1 and 2)
from the l.s. mean plane encompassing through the other
five ring atom (C2-C3-O1-C4-C5 RMSD of 0.0621 and
0.0652 Å).
Another slight difference among the compounds
herein investigated, which is also responsible for the con-
formational distinction between rings A and C, is the
rotation on the axis of the bond connecting
xanthenodione to its substituent at C1. The plane of this
substituent is slightly pointed toward the ring A in both
compounds. The dihedral angle among the atoms O1, C1,
C14, and C19 describes well this conformational feature.
Crystal packing of compound 1 is featured by the for-
mation of zigzag chains running parallel to [001]
(Figure 3). These chains are primarily stabilized by classi-
cal hydrogen bonds involving the hydroxyl group as
donor and the carbonyl oxygen O3 as acceptor. Accessory
non-classical hydrogen bonds formed with the C10-H …
O2 atoms and C11-H …π (ring D) contributes to the
assembly of the one-dimensional chains in 1. In the
supramolecular architecture of 2, water acts as molecular
glue among three xanthenodione molecules (Figure a).
Water is a hydrogen bonding acceptor from hydroxyl
group of one molecule and simultaneously is donor to O2
ꢁ
ꢁ
It measures 8.9(3) and 8.5(5) in 1 and 2, respectively,
ꢁ
deviating a few from 0 (which would mean the mean
ax
plane of the substituted phenyl ring plane at C1 coincid-
ing with the transverse plane of the xanthenodione skele-
ton). Still, concerning the rotation around C1-C14, an
anti conformation with methoxy group not lying on the
xanthenodione mean plane is noticed in 1. Methoxy
group is also coplanar to phenyl ring D (C15-C16-O4-C20
eq
FIGURE 3 The one-dimensional
chain of compound 1 running parallel to
[
001] is stabilized by classical and non-
classical hydrogen bonds (white dashed
lines) [Colour figure can be viewed at
wileyonlinelibrary.com]
FIGURE 4 (a) Water acts as a glue among three molecules of compound 2, while (b) additional CH…π contacts aid their crystal packing
whose acceptors are (a) oxygen atoms or (b) π-system of ring D. In this picture and in the next, cg(D) denotes the centroid calculated
through ring D carbon atoms and only hydrogen atoms involved in the shown contacts were not hidden for clarity. Also, the shown
measurements refer to the hydrogen…acceptor (i. e., oxygen in (a) or cg(D) in (b)) distance and the hydrogen bonding angle [Colour figure
can be viewed at wileyonlinelibrary.com]

782
da SILVA ET AL.
and O3 carbonyl oxygens of other two neighboring mole-
cules. Weak non-classical CH…π (ring D) hydrogen bonds
take also place in the crystal packing of 2, which explain
the observed isopropyl conformation. In one of its two
sides, the π-system of rind D is a bifurcated acceptor
from C7-Hax methylene and C21-H21c methyl groups,
while on the other side it is an acceptor from either the
C25'-H25c methyl group or the C24-H24E one
(Figure 4b). These two methyl groups belong to different
isopropyl occupancy site sets with eclipsed and anti con-
formations around C11-C23/C23', respectively, while
isopropyl group bearing the C21-H21c methyl moiety
has a gauche conformation. It is important mention that
the H24E…Cg(D) distance, where Cg(D) refers to the
FIGURE 5 Experimental and theoretical IR and Raman spectra of compounds 1 and 2 [Colour figure can be viewed at
wileyonlinelibrary.com]
FIGURE 6 Computational structure
drawing for compounds 1 (a) and 2 (b)
Colour figure can be viewed at
wileyonlinelibrary.com]
[

da SILVA ET AL.
783
TABLE 2 The experimental and calculated wavenumbers (cm− ) along with IR and Raman relative intensities of compound 1
1
ꢀ
ν
calculated
IR
Raman
ꢀν experimental
ꢀν experimental
cm−
1
)
intensity (%) activity (%)
Raman (cm−1
)
IR (cm−1
3311
—
)
Assignments
(
3
3
3
3
3
2
638
111
092
067
040
998
31
0.5
2
18
8
3317
—
ν
ν
ν
ν
ν
s
s
s
s
s
40
O H (O23 H )
C H of aromatic ring (C25
C H of aromatic ring (C24
C H of aromatic ring (C26
H
H
H
5
2
6
)
)
)
21
4
—
—
3
3054
3031
2993
3068
—
6
26
10
C H of CH
3
(C42
44
H )
4
2997
ν C H of CH
2
out of phase (C18
H
34
;
C
14 28
H )
2
998
2
28
—
—
2 34
ν C H of CH in phase (C18 H ;
C
14 28
H )
2
986
982
7
9
7
—
—
—
—
ν
as C H of CH
3
(C42
H
43; C42
H
45
)
2
21
ν C H of CH out of phase (C15
2
H
31
;
;
C
19 37
H )
2
976
967
0.3
0
5
2
—
—
2944
s 7 27
ν C H of CH (C H )
2
—
ν C H of CH
C
2
2
2
out of phase (C16
H
32
20 38
H )
2
2
967
937
9
7
45
8
2950
2968
ν C H of CH
C
in phase (C16
H
32
;
20 38
H )
—
—
ν C H of CH
out of phase CH
2
(
C
15
H30; C19
H
36
)
2
920
912
13
1
24
4
2925
2911
ν
s
C H of CH
3
(C42
H
45
43; C42 H )
2
—
—
ν C H of CH
2
out of phase (C14
H
29
;
;
C
18 35
H )
2
2
2
912
907
906
4
28
100
5
—
2882
2873
2844
ν C H of CH
C
2
2
2
in phase (C14
in phase (C16
H
H
29
;
;
18 35
H )
11
0
2908
2888
ν C H of CH
C
33
20 39
H )
ν C H of CH
out of phase (C16 H
33
C
20 39
H )
1674
1670
1649
1601
1597
1590
1496
1457
100
1
10
4
1674
1662
1644
—
1678
1667
1645
1602
—
ν C O in phase (C13
ν C O out of phase (C13
ν C C in phase (C 12; C
ν C C out of phase (C
O
2
; C17
22
O )
O
2
22
; C17 O )
40
21
6
37
3
8
C
9 11
C )
8
C
; C
; C
12; C
9
C
11
)
8
1597
1584
1499
1466
ν
ν
ν
as C C C (C
as C C C (C
1
1
C
C
5
6
C
3
2
4
4
C
C
2
C
C
6
)
)
9
13
1
—
C
3
5
61
15
1506
1456
s
C C C (C
2
C
4
C
3
; C
5
C
1
C
6
)
1
γ H C H of CH
3
antisymmetric
43 42 45
(H C H )
1450
1450
1442
1436
3
1
2
2
2
0
2
0
1452
—
—
2
δ C H of CH out of phase
(
H
30
C
15
H31; H36
C
19
H
37
)
—
δ C H of CH
2
in phase (H30
C
15 31
H ;
36 19 37
H C H )
1452
—
1456
—
γ H C H of CH
3
antisymmetric
44 42 45
(H C H )
γ H C H of CH
3
43
symmetric (C42 H ;
C
42 44
H44; C42 H )
(
Continues)

784
da SILVA ET AL.
TABLE 2 (Continued)
ꢀ
ν
calculated
IR
Raman
ꢀν experimental
Raman (cm−1
ꢀν experimental
cm−
1
)
intensity (%) activity (%)
)
IR (cm−1
)
Assignments
δ C H of CH
(
1428
1427
1418
1413
1412
1332
1332
1313
1310
4
8
1
1
3
3
0
0
1
1
1433
1431
2
in phase (H32
C
16
H
33
;
;
H
38
C
20
H
39
)
0
—
1424
1416
—
δ C H of CH
2
out of phase
32 16 20 39
(H C H33; H38 C H )
8
1421
—
s 1 5 3
ν C C C and C C (C C C and
C
2 5
C )
2
2 14 29
δ C H of CH in phase (H28 C H
H
34
C
18
H
35
)
1
—
—
δ C H of CH
2
out of phase
(
H
28
C
14
H
29; H34
C
18
H
35
)
1
—
—
ω C H of CH
2
in phase (H30
C
15 31
H ;
H
36
C
19
H
37
)
4
1333
—
—
ω C H of CH
2
out of phase
(
H
30
C
15
H
31; H36
C
19
H
H
37
37
)
)
15
0
1319
1311
2
τ C H of CH out of phase
30 15 19
(H C H31; H36 C
1309
2 15 31
τ C H of CH in phase (H30 C H ;
H
36
C
19
H )
37
1305
1290
1259
1240
1229
3
1
1
7
1
1
—
—
ω C H (C
ω C H (H28
C O (C
γ C H in plan (C
7
C
27
)
3
1274
1248
1232
1227
1273
1253
—
14 18 35
C H29; H34 C H )
69
2
ν
s
4
O
23; C
3
O
41
)
6
H
26
)
1
—
16 33
τ C H out of phase (H32 C H ;
38 20 39
H C H )
1
218
208
33
13
0
0
1221
1203
1223
1206
ν
s
C C O (C
3 4 23
C O )
1
τ C H in phase (H32
C
16 33
H ;
38 20 39
H C H )
1
1
1
185
180
177
25
35
0
2
1
3
1196
1174
1172
1198
—
γ C H in plan (C
as C O C (C
2 24
C )
ν
9
O
10
8
C )
1173
τ H C (H30
C
15
H31; H36
C
19
19
H
37) in
phase
1
164
155
8
4
1
1165
1151
—
—
γ C H in plan (C
τ H C (H30
out of phase
C O C (C
C C (C
5 25
H )
1
84
C
15
H31; H36
C
H )
37
1154
1130
1117
4
1
1
1
—
1154
1132
1123
ν
ν
s
s
8 10 9
O C )
12
0.4
1129
1118
1 7
C )
τ C H of CH
2
(H28
C
14 29
H ;
H
H
32
C
C
16
20
H
33; H34
C
18
H
35
;
;
38
H39) in phase
1
108
33
1
—
—
τ C H of CH
2
(H28
C
14
H
29
;
H
H
32
C
C
16
20
H33; H34
C
18
H
35
38
H39) out of phase
1106
1099
1039
6
7
3
0
0
0
1101
1081
1039
—
γ C H in plan (C
C C C (C11
γ C C C out of phase (C14
2
H
24; C H )
5 25
—
ν
s
7 12
C C )
1048
15 16
C C ;
C
18 19 20
C C )

da SILVA ET AL.
785
TABLE 2 (Continued)
ꢀ
ν
calculated
IR
Raman
ꢀν experimental
Raman (cm−1
ꢀν experimental
cm−
1
)
intensity (%) activity (%)
)
IR (cm−1
)
Assignments
(
1
036
1
1
—
—
15 16
γ C C C in phase (C14 C C ;
C
18 19 20
C C )
1
023
018
14
0.5
1
1030
1012
—
ν
ν
s
C O (O41
42
C )
1
0.4
1016
15 16
as C C C in phase (C14 C C ;
C
18 19 20
C C )
981
933
909
889
2
1
0
1
0
958
931
906
—
959
934
909
—
ν
s
C C in phase (C13
C
14; C17
18
C )
17
3
ν C C out of phase (C13
C
18
14; C17 C )
ν
ν
s
1 7
C C (C C )
1
as C C C out of phase (C14
15 16
C C ;
C
18 19 20
C C )
882
875
845
843
4
0
1
2
1
1
2
0
—
—
ν
ν
s
s
15 16
C C C out of phase (C14 C C ;
C
18 19 20
C C )
870
849
—
873
852
—
C C C in phase (C14
C
15 16
C ;
C
18 19 20
C C )
ρ C H in phase (H32
C
16
H ;
33
38 20 39
H C H )
ρ C H out of phase (H32
16 33
C H ;
38 20
H C H39) and ω C H out of
plane (C
5 25
H )
8
38
96
3
4
0.2
0
807
795
826
798
(CH , n = 3 in-phase rocking mode
2 n
)
7
ω C H out of plan (C
2 5
H24; C H25) in
phase
7
7
77
14
4
1
8
1
746
728
761
720
Ring breathing motion (aromatic ring)
ω C H out of plan (C
5 6
H25; C H26) in
phase
710
671
621
618
593
543
7
1
3
9
0
2
0.5
1
693
677
626
609
591
556
692
680
629
614
—
ν
s
C C C (C11
Ring breathing motion
δ C Ο C (C
7 12
C C )
0.3
0
8
Ο
10
C
9
)
Ring breathing motion
Ring breathing motion
2
0
550
ρ C = C C (C11 = C
9
C
20
;
C
12 = C
8
C
16
)
5
38
15
4
3
1
0
533
524
536
524
ρ C Ο (C
4
Ο
23
)
5
Ring breathing motion in phase (tricyclic
ring)
5
06
1
1
506
509
Ring breathing motion out of phase
(
tricyclic ring)
497
480
457
450
448
428
419
1
0.4
1
499
481
—
500
479
464
454
—
Ring breathing motion
0.4
0
Ring breathing motion
1
Ring breathing motion (tricyclic ring)
2
0
451
—
γ C = C C (C
Ring breathing motion
γ H Ο (H40
Ring breathing motion
1 5 3 4 2 6
= C C ; C = C C )
1
0
25
1
0
437
—
439
—
23
Ο )
0.3

786
da SILVA ET AL.
centroid calculated through the six phenyl carbons, is
the shortest one among all H…Cg distances found in 2.
This suggests that the strength of this interaction can
overcome an energetically unfavorable isopropyl anti
conformation, as the two found isopropyl conformations
have equal populations.
strong intermolecular hydrogen bonding in the crystal
structure of 1 and 2 as opposed to the absence of them in
the gas phase. As previously described, compound 2 crys-
tallized as a monohydrate. The O H stretch bands of
water and the hydroxyl group present in the structure of
2 are superimposed as determined by computational
study (result not shown).
In the following discussion of other vibrational
modes, the described expected values were based on
reference.
3.3 | Vibrational analysis
[
37]
Structures of compounds 1 and 2 were also investigated
by IR and Raman spectroscopy techniques. Figure 5
shows the resulting spectra of these analyses.
3.3.2 | C H vibrations
A well-known fact is that IR and Raman are comple-
mentary spectroscopy techniques. The FT-IR spectros-
copy measures the change in dipole moment in the
molecule being sensitive to vibrations of heteronuclear
functional groups and polar bonds such as, for example,
O H and C O. On the other hand, Raman spectroscopy
depends on the change in polarizability of the molecule
and it is also sensitive to groups containing homonuclear
bonds such as C C. In addition, the frequencies of these
molecular vibrations depend on the masses of the atoms,
their geometric arrangement, and the strength of their
chemical bonds. In this way, it is possible to extract
important information about the studied molecules. The
accuracy of predicted geometric and electronic properties is
a function of the quality of the optimized molecular struc-
ture. The calculated geometry structures of xanthenodiones
In the vibrational spectra of compounds 1 and 2, vibra-
tions of the C H stretching in the range of
−1
2981–2884 cm are observed. The vibrations involving
CH, CH2, and CH3 are expected in the range
−1
3000–2840 cm which are in agreement with experimen-
tal measurement. In addition, in the case of compound
2 it is possible to detect the presence of the isopropyl
group through two angular deformation bands of CH
3
−1
occurring around 1380 and 1365 cm . As can be seen in
−1
Table 3, the first band appears at 1387 cm in the IR and
1375 cm− in the Raman, while the second at 1355 cm
1
−1
in both vibrational techniques. Confirmation of the pres-
ence of the isopropyl group in the molecule can be made
by observing the skeletal vibration bands at
−
1
−1
1175–1165 cm , 1150–1130 cm (usually appears as a
−1
1
and 2 are presented in Figure 6. The vibrational analysis
doublet), and 840–790 cm . However, in the case of this
compound, only one band at 1333 cm− in the IR spec-
trum was observed. The stretching vibrations of the C H
bond of aromatic compounds result in medium intensity
absorptions between 3100–3000 cm in both vibrational
spectroscopies. The C H bonds also absorb in this
region, which may cause confusion in the interpretation
of the spectrum. However, in the case of compounds
1
confirmed the stability of the adopted geometry. The exper-
imental IR and Raman data are mostly well reproduced by
the B3LYP/6–31+G(d,p) (Figure 6) and as such, predicted
properties based on this geometry are closest to the experi-
mental values (Tables 2 and 3). It should be mentioned that
the IR and Raman assignments were based on data avail-
−
1
[37]
able in reference.
1
and 2 this is not a problem since the present double is
tetrasubstituted. For the compounds studied, the
stretching frequencies of C H are in the range of
3.3.1 | Hydroxyl vibration
−1
3020–3068 cm .
The characteristic vibrations involving the O H group
are the stretching and bending vibrations in the plane or
out of plane. Among them, the most important is the
O H stretch band, which in the gas phase occurs around
3.3.3 | Carbonyl groups vibration
−
1
3
600 cm , while in the liquid or solid phase the band is
The carbonyl groups present IR and Raman bands in the
−
1
[37]
−1
observed in the 3500–2500 cm range.
This band
region of 1700–1550 cm . The frequencies in both tech-
occurs with great intensity in infrared. Similarly, in this
work, an intense band was observed in the IR spectrum
at 3317 and 3301 cm for compounds 1 and 2, respec-
niques tend to be the same, but the intensities are different.
In general, the C O bands are very intense in the IR spec-
trum, while in the Raman they are generally weak. In the
case of compounds 1 and 2, the intensity of the bands
corresponding to the C O bonds are high in both vibra-
tional spectra (Figure 5). This can be justified by the
−
1
tively (Figure 5). Comparing this with the calculated
−
1
−1
results, a deviation of 321 cm for 1 and 389 cm for
is observed, which can be ascribed to the presence of
2

da SILVA ET AL.
787
TABLE 3 The experimental and calculated wavenumbers (cm− ) along with IR and Raman relative intensities of compound 2
1
ꢀ
ν
calcuated
IR
Raman
ꢀν experimental
Raman (cm−1
ꢀν experimental
cm−
1
)
intensity (%) activity (%)
)
IR (cm−1
)
Assignments
59
ν O H (O23 H )
(
3
3
3
3
3
3
3
690
093
091
059
052
024
008
17
0
37
33
4
3301
—
—
—
ν
ν
ν
ν
ν
ν
s
s
s
s
s
C H of aromatic ring (C
5
2
6
H
H
H
24
57
25
)
)
)
2
—
—
C H of aromatic ring (C
C H of aromatic ring (C
2
7
—
3066
3053
—
6
27
17
8
3054
3020
—
C—H of aromatic ring (C
C H of CH
3 58
H )
3
2 27
(C14 H )
6
—
as C H of CH
3
(C39
H
40; C39
H
H
H
41
;
;
C
39 42
H )
3
001
999
8
7
12
13
—
—
—
—
ν
as C H of CH
3
3
(H44
(C45
C
43 46
H )
2
νas C H of CH
H
50; C45
51
C
45 52
H )
2
2
993
992
7
7
13
26
—
—
—
—
ν
ν
ν
ν
as C H of CH
3
(C53
H
(C18
55; C53
56) and
νas C H of CH
2
H
32) in phase
2990
2989
2986
12
5
25
9
—
—
—
—
—
—
as C H of CH
3
(H40
C
39
H
H
H
42) and
56) and
55) and
44 43
(H C H45) in phase
as C H of CH
(H C H )
50 49 51
3
(H55
C
53
2
9
3
as C H of CH (H54
C
53
50 49 51
(H C H )
2
2
985
981
4
1
10
4
—
—
—
—
ν C H of CH
2
(C16
as C H of CH (C43
46) and (C49
C H of CH (C20
C H of CH (C
C H of CH
29
H )
ν
3
H
H
44; C43
50; C49
H
H
45
;
C
43
H
51
)
;
2977
2972
2930
4
13
8
—
—
ν
s
ν
s
ν
s
2
34
H )
0.4
17
2959
2933
2969
2943
7 26
H )
4
3
(C43
46) and (C39
H44; C43
H
45
;
C
C
43
39
H
H
H
40; C39
H
41
42
)
2
2
930
922
10
8
100
3
ν
s
s
C H of CH
3
(C45
H
H
50; C45
51
H ;
C
45 52
H )
—
—
—
ν
C H of CH
CH
of phase
C H of CH
CH
phase
2
(C18
31) and ν
s
C H of
3
(C53
H
54; C53
H
55; C53
H
56) out
2
920
1
18
2919
ν
s
2
(C18
H31) and ν
s
C H of
3
(C53
H
54; C53 H55; C53 H56) in
2
919
918
3
6
19
4
—
—
—
—
ν C H of CH
in phase
3
(C39
(C39
(C20
45
H42) and (C43 H )
2
ν
s
s
C H of CH
out of phase
C H of CH
3
45
H42) and (C43 H )
2
2
2
916
916
909
2
4
2
9
—
—
ν
2
H
33
36
28; C16
)
95
12
2871
—
2881
—
ν C H of CH (C35
H
)
ν C H of CH
2
(C14
H
H30) out of
phase
2
904
902
5
4
27
18
2821
2868
ν C H of CH (C37
ν C H of CH (C15
H
38
47
)
)
2
—
—
H
(
Continues)

788
da SILVA ET AL.
TABLE 3 (Continued)
ꢀ
ν
calcuated
IR
Raman
ꢀν experimental
ꢀν experimental
cm−
1
)
intensity (%) activity (%)
Raman (cm−1
)
IR (cm−1
2898
1674
—
)
Assignments
(
2
1
1
1
1
1
1
1
1
894
676
671
652
604
600
581
492
470
2
13
10
5
2895
1675
1666
1656
1609
1592
—
48
ν C H of CH (C19 H )
78
15
35
19
16
4
ν C O (C17
ν C O (C13
O
22
21
)
)
O
37
3
1652
1615
1599
—
ν C C (C
ν C C (C
8
8
C
C
12; C
12; C
9
9
C
11) in phase
C
11) out of phase
14
3
ν
ν
ν
as C C C (C
as C C C (C
C C C (C
1
5
C
5
1
C
C
3
6
; C
; C
4
2
C
C
2
4
C
C
6
)
)
C
3
25
1
0.4
0.9
1507
—
—
s
5
C
1
C
6
; C
antisymmetric
46) in
2
C
4
C
3
)
1471
γ H C H of CH
3
(
H
40
C
39
H
41; H44
C
43
H
phase
1
1
1
1
1
1
460
459
456
451
439
438
3
0.2
2
1465
—
1465
—
γ H C H of CH
3
antisymmetric
51 49 53
(H C H52; H55 C H56) in
phase
2
γ H C H of CH antisymmetric
(H C H51; H54 C H56) in
50 49 53
phase
3
1
3
—
—
γ H C H of CH antisymmetric
(H C H42; H44 C H45) in
40 39 43
phase
3
1
0.5
3
1447
—
1447
—
γ H C H of CH antisymmetric
(H C H41; H44 C H46) out of
40 39 43
phase
3
0.4
1
γ H C H of CH antisymmetric
(H C H52; H54 C H55) out of
50 49 53
phase
3
1
—
—
γ H C H of CH antisymmetric
(H C H42; H45 C H46) out of
40 39 43
3
phase
1432
1428
1421
1417
1415
1379
1
2
—
1433
1428
—
ω C H (H33
ω C H (H29
C
20
16
H
H
34
30
)
3
2
1428
—
C
)
4
0.0
2
2 6 3 5
ν C C (C C ; C C )
0.5
2
—
—
τ C H (H31
τ C H (H27
γ C H of CH
C
C
18
14
H
H
32
28
)
4
—
1416
1375
)
3
0.0
1387
3
symmetric (C49
H
50
;
C
C
49
53
H
H
51; C49
55; C53
H
H
52) and (C53
56) in phase
H
54
;
1
379
360
2
0.2
—
—
γ C H of CH
3
(C39
H
H
40; C39
H
H
41
;
C
C
39
43
H
H
42) and (C43
46) in phase
44; C43
45
;
1
3
0.3
—
1369
1355
—
1363
1355
—
48
γ C H (C19 H )
—
—
1
γ C H of CH
3
symmetric (C49
H
H
50
;
;
C
C
49
53
H
H
51; C49
55; C53
H52) and (C53
54
1
358
0.0
H56) out of phase
1
359
3
0.0
—
—
γ C H of CH
3
symmetric (C39
42) and (C43
46) out of phase
H
H
40
;
Cγ39
H
41; C39
H
44
;
C
43
H
45; C43 H
1347
1343
1339
10
0.3
12
2
—
—
—
1
1345
—
1342
—
γ C H (C15
γ C H (C19
H
H
47; C35
48; C37
H
H
36
38
)
)
0.6

da SILVA ET AL.
789
TABLE 3 (Continued)
ꢀ
ν
calcuated
IR
Raman
ꢀν experimental
ꢀν experimental
cm−
1
)
intensity (%) activity (%)
Raman (cm−1
)
IR (cm−1
1331
—
)
Assignments
(
1
1
1
1
330
327
326
318
22
12
2
1
—
—
0.9
0.7
0.4
—
Aromatic ring bending deformation
—
—
ω C H (C15
47
H )
6
1322
1322
2 3 58
γ C H in plan (C H57; C H ;
C
5 6 25
H24; C H )
1307
1299
1272
1265
1240
1236
1230
1215
1207
1175
1167
1156
5
0
—
—
Ring breathing motion (tricyclic ring)
ω C H (C
2
1
—
1300
1270
—
3
H
38
48
36
23
26
14
47
20
)
0.7
2
4
—
ω C H (C19
γ C H (C35
H
)
1
1265
1247
—
H
)
22
9
5
—
ν
s
C O (C
4
O
)
0.9
1
1233
1228
1212
1209
1176
—
γ C H (C
7
H
)
0.8
7
1225
1217
—
ω C H (H27
γ C H (C15
τ C H (H33
C
28
C )
1
H
C
)
3
0.6
4
34
H )
4
1178
1169
—
ν
s
C C (C
1 7
C )
100
4
3
νas C O C (C C C )
8 10 9
2
1160
2 3 58
γ C H in plan (C H57; C H ;
C
5
H24; C
6
H
25
)
1147
1142
1133
1127
1116
1103
1091
1087
7
1
—
1151
1141
—
ν
s
C O C (C
8
O
10
9
C )
40
11
5
3
—
γ O H (H59
τ C H (H27
O
23
)
1
1133
—
C
14
H
28; H29
19 20
32; H33
12
12
C
C
16
H
30
34
)
)
0.4
1
1128
1117
1105
—
ν
s
C C C (C18
C
C
)
36
14
3
—
τ C H (H31
C
18
H
20
H
0.5
0.5
0.4
1101
—
ν
s
C C C (C11
as C C C (C11
C
7
C
)
ν
C
7
C
)
2
—
—
γ C H in plan (C
2
H27; C
3
H
58
;
C
5 6 25
H24; C H )
1
1
1
9
9
9
9
8
079
031
020
80
0.5
3
1
1080
1033
1013
976
—
1060
1033
1011
981
963
959
—
ν
ν
ν
as C C C (C49
as C C C (C18
as C C C (C14
C
C
C
37
C
C
C
53
20
16
)
)
)
0,4
0.7
1
19
15
1
1
Ring breathing motion (tricyclic ring)
Ring breathing motion (tricyclic ring)
Ring breathing motion (tricyclic ring)
Ring breathing motion (tricyclic ring)
62
4
1
58
4
0.8
0.7
0.3
—
46
8
949
860
69
1
867
ν
s
C C C (C18
30; H27
31; H33
19
C C20) and ρ C H
(
H
29
C
16
H
C
14
H
28
)
8
50
0.8
1
—
859
ρ C H (H30
C
18
H
C
20
34
H ;
C
19 40
H )
836
830
809
801
724
3
6
835
—
841
828
—
Αromatic ring bending deformation
4
0.9
2
ν
s
ν
s
ν
s
ν
s
C C C (C49
C C C (C19
C C C (C14
C C C (C15
C
C
C
C
37
37
15
35
C
C
C
C
39
49
16
39
)
)
)
)
4
—
2
1
801
730
805
—
0.3
2
(
Continues)

790
da SILVA ET AL.
TABLE 3 (Continued)
ꢀ
ν
calcuated
IR
Raman
ꢀν experimental
Raman (cm−1
ꢀν experimental
cm−
1
)
intensity (%) activity (%)
)
IR (cm−1
)
Assignments
18 32
ρ C H (H31 C H )
(
6
6
6
6
5
55
42
27
11
94
2
1
655
—
656
1
0.4
1
638
Ring breathing motion (tricyclic ring)
0.8
4
632
611
588
—
Αromatic ring bending deformation
0.3
1
608/614
591
14 28
ρ C H (H27 C H )
0.7
γ C C out of plan (C
phase
8
8
C
C
12; C
12; C
9
9
C
C
11) in
5
62
1
0.6
555
556/568
γ C C out of plan (C
11) out
of phase
527
522
512
6
2
3
0.3
0.3
0.2
—
—
Ring breathing motion
Ring breathing motion
522
506
—
511
γ C H out of plane (C
5
6 25
H24; C H ;
C
2 3 58
H57; C H )
4
4
94
70
2
1
0
2
484
490
475
Ring breathing motion
Ring breathing motion (tricyclic ring)
—
presence of a conjugated system with the carbonyl
group. Concerning the stretching frequencies, car-
spectrum of compound 2, only the bands at 1507 and
1592 cm− were observed, while in the Raman spectra
1
−
1
bonyl of doubly conjugated ketones appear in the
just the frequency at 1599 cm was noticed. In all
cases, the frequency value found is within the expected
1
1
680–1640 cm− region. As can be seen in Tables 2
[
37]
and 3 the experimental frequencies of compounds
and 2 are in complete agreement with that deter-
mined by the spectroscopic techniques.
range.
1
3.3.5 | Vinyl ethers and aromatic ethers
vibrations
3.3.4 | C C vibrations of alkene and
aromatic ring
The characteristic band that occurs in IR and Raman spectra
for compounds containing ether functionality is related to
The C C stretching band happens around 1650 cm−1 in
both vibrational spectra. However, in the Raman spec-
troscopy, this band is important, as it has a very strong
intensity due to the high polarizability character of
C C. This can be verified in the Raman experimental
spectrum in Figure 5. In addition, the experimental
stretching frequencies observed for compounds 1 and
the C O C system. For compound 1, ν C O C band was
as
−1
observed in the Raman spectrum at 1154 cm and in the IR
−1
this was noticed at 1174 cm . For compound 2, these same
−1
bands were observed at 1151 and 1169 cm . These results
are in accordance with the expected range of frequency for
−1
stretching the C O C bond which is 1270–1060 cm .
Regarding compound 1, in addition to the presence of
the vinyl ether functionality, there is a methoxy group
attached to the aromatic ring. Stretching bands in the range
−
1
2
were in the range 1602–1656 cm , which are in
agreement with expected frequencies (Tables 2 and 3).
The C C bond stretching vibrations of aromatic com-
pounds are typically observed in the region of
−
1
−1
of 1310–1210 cm (aryl O) and 1050–1010 cm (O CH3)
are expected for this group. The experimental frequencies
observed were 1248 cm for IR and 1253 cm for Raman
−
1
−1
−1
1
625–1440 cm . In general, up to four bands can be
−
1
observed in the following regions: 1625–1590 cm ,
related to the aryl O stretch. In terms of O CH , the
3
−
1
−1
−1
1
590–1575 cm , and 1465–1430 cm . However in
observed frequency was 1030 cm in the IR spectra.
some compounds, the absence of one or more of these
bands may occur. In the case of the experimental IR
spectrum of compound 1, for example, three C C bond-
ing stretching frequencies were observed, being 1466,
4 | CONCLUSIONS
−
1
1
499, and 1597 cm . By contrast, in the Raman spectra
In summary, the zirconium catalyzed condensation
between β-diketones and appropriated aldehydes
−
1
of 1 only one band was observed at 1506 cm . In the IR

da SILVA ET AL.
791
afforded two hydroxylated xanthenodiones, the struc-
tures of which were confirmed by NMR spectroscopy
and X-ray diffraction analyses. The computational
study involving vibrational spectroscopy (IR and
Raman) showed a good agreement between experi-
mental and theoretical calculations. The information
described herein can be useful in future investiga-
tions regarding structural and biological aspects of
xanthenodiones.
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ACKNOWLEDGEMENT
We are grateful to FAPEMIG, CNPq, and CAPES.
DATA AVAILABILITY STATEMENT
The data that supports the findings of this study are avail-
able in the supplementary material of this article.
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ORCID
Milene Lopes da Silva https://orcid.org/0000-0001-
5
824-599X
Róbson Ricardo Teixeira https://orcid.org/0000-0003-
181-1108
Fabrício Marques de Oliveira https://orcid.org/0000-
002-6379-3840
Luciano de Moura Guimar a~ es https://orcid.org/0000-
003-3989-4139
Felipe Terra Martins https://orcid.org/0000-0001-9004-
927
3
0
[22] G. Purushothaman, V. Thiruvenkatam, Acta Cryst. Struct. C
018, C74, 830.
2
[
[
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0
K. Fun, Acta Cryst. E 2010, E66, o1538.
24] H. Detert, L. Kluge, D. Schollmeyer, IUCrData 2020, 5,
x202018.
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A. L. Horta, A. A. S. Mendonça, A. C. A. Carneiro, D. M. S. de
Souza, R. D. Novaes, R. R. Teixeira, A. Talvani, J. Glob, Anti-
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