SPECTRAL STUDY OF SOME 4-STYRYL-COUMARINE
DERIVATIVES
S. Filote, M. Cotlet, G. Singurel, Tatiana Nicolaescu *,
Catinca Simion*, R. Gradinaru* and Dana Dorohoi
”Al. I. Cuza” University, Faculty of Physics, Bd. Copou 11, 6600 Iasi, Romania
*
”Al. I. Cuza” University, Faculty of Chemistry, Bd. Copou 11, 6600 Iasi,
Romania
The spectrometric study of some 4-styryl-coumarine derivatives is reported. 1H
NMR and IR spectra were used in order to determine the compounds structure.
Some spectral parameters determined from electronic absorption spectra in
solution and diffuse reflectance spectra have been estimated. A chemical quantum
calculation for these compounds was made to estimate electronic transitions and
to compare with those obtained from spectra.
INTRODUCTION
Coumarine derivatives are organic compounds with biological action due to the
functional group or heterocycle introduced in the side chain of benzene in coumarine residue
[1, 2]. Some coumarines derivatives are reported as strongly fluorescent compounds [3] or as
pH sensors [4].
This paper deals with a study of spectral properties of some 4-styryl coumarine
derivatives, in solutios and solid state.
EXPERIMENTAL
4-styryl coumarine (4-SC) derivatives analyzed in this paper are presented in Fig.1 and
Table I.
Table 1. Substituents of the 4-SC derivatives
Compound
Substituent
R1
R2
R3
R4
I
-H
-OH
-OH
-H
II
-H
-OH
-OCH3
-H
III
-H
-OH
-H
-Cl
IV
-CH3
-H
-N(CH3)2
-H
V
-H
-OH
-N(CH3)2
-H
Fig.1. Structural formula
of the analyzed 4-SC
Structural analysis. In order to determine the 4-SC structure both chemical and
spectroscopic analysis were carried out. The 1H NMR spectra were recorded in DMSO, at 80
MHz on a Bruker spectrometer. The IR spectra were recorded in KBr pellets on a SPECORD71 apparatus. The structural elements yield from the spectral features are lised in Table 2 and
3.
4-SC
I
II
III
IV
V
4-SC
I
II
III
IV
V
Table 2. 1H RMN signals (ppm) recorded in DMSO
Chemical shifts  (ppm)
7.3-8.1 (m, 7H aromatic); 7.3 [d, 2H(-CH=CH-)]; 6.65 (s, 1H, H3)
7.2-8.1 (m, 7H aromatic); 7.2 [d, 2H(-CH=CH-)]; 6.65 (s, 1H, H3)
7.3-7.9 (m, 7H aromatic); 6.8 [d, 2H(-CH=CH-)]; 6.6 (s, 1H, H3)
7.3-7.9 (m, 7H aromatic); 7.3 [d, 2H(-CH=CH-)]; 6.65 (s, 1H, H3);
3.2 [s, 6H, N(CH3)2]; 2.4 (s, 3H, CH3)
7.3-7.9 (m, 7H aromatic); 7.1-7.3 [d, 2H(-CH=CH-)]; 6.65 (s, 1H, H3);
3.2 [s, 6H, N(CH3)2]; 2.4 (s, 3H, CH3)
Table 3. IR spectra in KBr pellets
Wavenumbers  (cm-1)
3420 (OH); 1760(C=O); 1620(C=C); 1560, 1480 (aromatic ring); 980(=C-H)
3410 (OH); 1764(C=O); 1620(C=C); 984(=C-H)
3390 (OH); 1760(C=O); 1625(C=C); 980(=C-H)
2995 (C-H aliphatic); 1768(C=O); 1625(C=C); 1375 (CH3); 985(=C-H)
3420 (OH); 2900 (C-H aliphatic); 1760(C=O); 1620(C=C);
1560, 1482 (aromatic ring); 1370 (CH3); 980(=C-H)
Measurements. The following spectra of the analyzed 4-SC were recorded:
-electronic absorption spectra (EAS) in solution, at room temperature (296K), in the
range [45000-14000] cm-1, using a SPECORD UV VIS spectrophotometer with Data
Acquisition Sistem. Solvent used, ethanol (EtOH), from Merck, was spectral grade. The
concentration of the solutions was under 10-4M l-1. At this concentration, the eventually
molecular associations between spectrally active molecules can be neglected.
-diffuse reflectance spectra (DRS) in solid pellets with MgO, at room temperature
(296K), using a VSU–2P spectrophotometer adapted for measuring reflection factor. As
standard diffuser was used a MgO pellet.
Precaution on solvent purity, weighting of compounds, preparation of solutions and
pellets were considered.
Calculations. In order to build theoretically the electronic energy levels of the analyzed
molecules and to compare with those experimentally obtained, quantum chemical calculations
were performed using the AM1 (Austin Method) SCF (Self Consistent Field) method [5,6].
Optimization of the molecules geometry was performed before using Molecular Mechanics 2
(MM2) method.
RESULTS AND DISCUSSION
The EAS of the studied 4-SC in EtOH were processed for determining frequencies and
molecular extinction coefficients in the maximum of the bands. The processing was made in
the following maner: the EAS spectra of 4-SC were deconvoluted [7], extracting the
absorption bands S0-S1, S0-S2 and S0-S3. The frequencies in the maximum of these bands were
estimated by deriving the corresponding extracted bands. In Table 4 are shown the
wavenumbers and the molar absorptivities in the absorption spectra of 4-SC.
Table 4. The wavenumbers  (cm-1) and the molar absorptivity (lM-1cm-1) in the absorption
spectra of 4-SC
Transition
I
II
III
 (cm-1) (lM-1cm-1)
 (cm-1) (lM-1cm-1)
 (cm-1) (lM-1cm-1)
S0-S1
19420
762
18870
150
23360
5406
20330
824
21190
300
S0-S2
30400
12390
30490
14830
31150
7040
35090
11490
36230
6176
35210
288
39530
9940
39220
7360
37740
15764
S0-S3
45250
18900
46950
24645
47620
27950
Transition
 (cm-1)
IV
(lM-1cm-1)
S0-S1
S0-S2
S0-S3
30770
34720
39680
46730
7400
3270
1929
7900
V
 (cm-1) (lM-1cm-1)
23810
4960
31060
34480
39370
47850
7100
3180
2100
28100
The DRS recorded in MgO pellets give informations about the compounds in solid
state. The DRS were deconvoluted in the same manner as EAS, obtaining the frequencies in
the maximum of each S0-S1, S0-S2 and S0-S3 bands. On passing from the liquid solutions to
solid state of the compounds I, II, III one can see a hypsochromic shift of the electronic bands.
The wavenumbers in the maximum of the bands from DRS spectra of 4-SC are listed in
Table 5.
Table 5. The wavenumbers  (cm-1) in the maximum of the bands from DRS spectra of 4-SC
Transition
S0-S1
S0-S2
S0-S3
I
19.13
27.95
II
18.08
27.91
III
19.62
27.46
IV
18.65
22.39
30.64
Table 6 contains the wavenumbers in the fluorescence spectra of 4-SC. The first two
compounds have a fluorescent band with vibronic structure. The IV and V compounds,
having -N(CH3)2 substituent, present the smallest values for wavenumbers of the fluorescence
bands. The visible absorption and emission bands have mirror symetry [4].
Table 6. The wavenumbers  (cm-1) in the fluorescence spectra of 4-SC
4-SC
 (cm-1)
I
19380; 17300; 16580
II
19090; 17610; 16610
III
22570
IV
16590
V
16570
The total energy of the ground state, the ground state dipole moment and the wave
numbers of the electronic transitions and the oscillator strenght for molecules considered in
vacuum were estimated through the AM1 method [5,6]. In Table 7 are given the calculated
values for the frequencies and the oscillator strength for the electronic transitions. The total
energies and dipole moments for the ground state are presented in Table 8.
Table 7. The frequencies and the oscillator strength for the electronic transitions
I
II
III
Transition Oscillator Transition Oscillator Transition Oscillator
Energy
Strength
Energy
Strength
Energy
Strength
(1/cm)
(1/cm)
(1/cm)
1
27781.8
0.7783
26653.8
0.7321
28192.0
0.7273
2
32149.3
0.3987
32158.9
0.4116
31951.1
0.3630
3
37869.5
0.1729
35087.6
0.2399
42050.8
0.4232
4
38708.7
0.1219
37755.9
0.2306
42517.7
0.6191
5
42533.4
0.3541
41810.8
0.3111
43490.4
0.1344
6
42712.8
0.2695
42574.0
0.2777
43895.5
0.1546
7
43524.5
0.4410
43156.0
0.1284
48638.8
0.1091
8
45617.0
0.1214
45104.8
0.1075
50092.7
0.1140
9
51071.9
0.3409
46067.1
0.2029
52069.2
0.3413
10
51470.6
0.3240
52914.3
0.1214
4-SC.
4-SC
1
2
3
4
5
6
7
8
9
Transition
Energy
(1/cm)
25086.7
33437.1
43375.8
44636.1
45131.5
48636.0
52924.5
55156.7
IV
Oscillator
Strength
0.3345
0.7325
0.5094
0.7396
0.2552
0.1947
0.2535
0.1127
V
Transition Oscillator
Energy
Strength
(1/cm)
25564.3
0.3129
33463.8
0.7704
34226.4
0.3038
43251.3
0.1253
44469.9
0.4748
45375.3
0.3803
47209.9
0.1077
53694.7
0.4489
56515.4
0.1003
Table 8. The energies and dipole moments for the ground state
Total energy
Ground state dipole moment
(kcal/mol)
(Debyes)
I
-83433.0960172
4.099
II
-86795.1805889
8.139
III
-84338.3175319
5.798
IV
-84395.8684528
4.956
V
-88290.7250287
6.043
4-SC
Using the wave number values measured in the electronic absorption spectra and those
computed by AMI method, a diagram of the electronic levels was performed, neglecting the
shift of the fundamental level by passing from the gaseous state to the solution. From this
diagram (Fig.2) it results that the first three compounds, 4-SC I-III, have similar computed
and recorded spectra. They have visible bands in the ethanol solutions, while the computed
spectra do not present visible bands. The last two compounds also have similar computed and
recorded spectra. The compounds 4-Sc IV and V have a visible computed band, but do not
have visible bands in the ethanol solutions.
Fig.2. Diagram of the electronic absorption bands recorded in EtOH solutions (exp.) and
estimated by AM1 (calc.)
In ethanol solutions, the electronic bands of the first three compounds 4-SC I,II and III
shift hypsochromically, while for the last two compounds IV and V bathochromic shifts are
registered. This fact shows that for I, II and III, the intermolecular interactions in ethanol are
smaller in the ground compared with the excited state of the 4-SC compounds. In the case of
the compounds IV and V , the spectral shift suggests that the intermolecular interactions in the
ground state are higher than those in the excited state of these compounds.
Analyzing the values of spectral parameters of 4-SC derivatives in function of Ri
substituents nature, one can observe that the R1 and R2 substituents do not decisively
influence EAS. The R3 and R4 substituents induce major modifications in electronic spectra.
The replacement of H with an electronegative atom (Cl) determines changes in the electronic
charge distribution on the benzene ring to which R4 is bounded.
The substitution in the R3 position of -N(CH3)2 group leads to a bathochromic shift of
the electronic bands and to a decrease of the recorded band number, compared with the
compounds I-III.
CONCLUSIONS
1.
2.
3.
4.
5.
4-SC are spectrally active compounds with mirror symetry of the electronic spectra.
4-SC participate in condensed medium to dipolar interactions.
A visible band forbidden in the case of isolated molecules becomes permitted in
condensed state of the 4-SC I-III.
The substituent Cl in R4 position induces major changes in visible EAS.
The substituent -N(CH3)2 in R3 position determines an decrease of the numbers of
recorded electronic absorption bands in ethanol compared with the corresponding spectra
of I-III.
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