Synthesis and study of novel coumarin derivatives potentially utilizable as memory media

Article abstract of DOI:10.3390/molecules14124838

Novel coumarin derivatives, 2-oxo-2H-chromenecarbaldehyde hydrazones were prepared by reaction of substituted 2-oxo-2H-chromenecarbaldehydes with N-aminoimides in ethanol in the presence of 4-toluenesulfonic acid as catalyst. The photochromic and thermochromic properties of the prepared compounds were investigated.

Full text of DOI:10.3390/molecules14124838

Molecules 2009, 14, 4838-4848; doi:10.3390/molecules14124838
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis and Study of Novel Coumarin Derivatives Potentially
Utilizable as Memory Media
Radoslav Flašík, Henrieta Stankovičová *, Anton Gáplovský and Jana Donovalová
Institute of Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH-2,
SK-842 15 Bratislava, Slovak Republic; E-Mails: rflasik@hotmail.com (R.F.);
gaplovsky@fns.uniba.sk (A.G.); donovalova@fns.uniba.sk (J.D.)
*
Author to whom correspondence should be addressed; E-Mail: stankovh@fns.uniba.sk;
Tel.: +421-2-60296319; Fax: +421-2-60296337.
Received: 22 October 2009; in revised form: 17 November 2009 / Accepted: 23 November 2009 /
Published: 25 November 2009
Abstract: Novel coumarin derivatives, 2-oxo-2H-chromenecarbaldehyde hydrazones were
prepared by reaction of substituted 2-oxo-2H-chromenecarbaldehydes with N-aminoimides
in ethanol in the presence of 4-toluenesulfonic acid as catalyst. The photochromic and
thermochromic properties of the prepared compounds were investigated.
Keywords: chromenes; photochromism; thermochromism
1
. Introduction
Information technology has revolutionized daily life and the continuosly increasing amount of data
to be stored and manipulated has strongly stimulated the search for switching and memory elements as
tiny as a single molecule. Molecular switches can be converted from one state to another by an
external stimulus such as light, temperature, electricity or a chemical reaction. The operation of any
optically controlled device is critically dependent upon the efficiency of light absorption by the input
chromophore, and its ability to undergo electron transfer. Three characteristics make an excellent input
chromophore: a large extinction coefficient, long-lived excited state, and a high fluorescence quantum
yield. Photochromic compounds, where the reversible switching process is based on photochemically
induced interconversions, are particularly attractive. Photochemical switching of mechanical devices
[1], catalysts [2], transport systems [3], sensors [4] and surface properties of materials [5] are only a

Molecules 2009, 14
4839
few applications that can be envisioned. Another important advantage of this type of systems is that
light can be used for writing and processing information and, comparable to glass fiber technology,
this would offer a highly increased speed compared to electronic addressing and switching.
Chromenes, especially 2-oxo-2H-chromenes (coumarins), have been extensively studied due to
their commercial applications in several fields. These compounds have outstanding optical properties,
including an extended spectral range, high quantum yield, superior photostability and good solubility
in common solvents. Typical feature of chromene derivatives is that photophysical and spectroscopic
properties can be readily modified by introduction of substituents in the chromene ring, giving
themselves more flexibility to fit to various applications [6-8]. Coumarin derivatives are widely used
as laser dyes [9], optical brighteners [10] and fluorescence markers [11].
The aim of this work was to synthesize new coumarin derivatives with C=N double bonds, which
can potentially be used as a memory media. E-Z isomerization around C=N double bond can serve as a
process on which a molecular switch is based [12]. The conversion from one isomer to the other can be
initiated by light or temperature [13,14]. Besides E-Z isomerization around the C=N double bond, the
possibility of conformer and tautomer formation should be considered, depending on the structure of
adjacent fragments. Similar systems, 4-oxo-4H-chromene (chromone) derivatives with C=N bonds in
position 3, were already synthesized [12].
2
. Results and Discussion
2
.1. Synthesis of 2-oxo-2H-chromenecarbaldehyde hydrazones
Reaction of substituted 2-oxo-2H-chromenecarbaldehydes 1 or 2 with N-aminoimides 3 afforded 2-
oxo-2H-chromenecarbaldehyde hydrazones 4 or 5, respectively (Scheme 1) under mild conditions.
Scheme 1. Synthesis of compounds 4 and 5.
O
O
C H O
p -T s O H
E tO H ,
N
N
+
H 2
N
N
R
R
O
O
O
O
O
O
1
1
a
R = H
4 a p ro d u c t o f 1 a + 3 a
4 b p ro d u c t o f 1 a + 3 b
3
a N -a m in o p h th a lim id e
b R = N M e 2
3 b N -a m in o b e n z [d e ]is o q u in o lin e -1 ,3 -d io n e
4
4
c
d
p ro d u c t o f 1 b + 3 a ,
p ro d u c t o f 1 b + 3 b
O
p -T s O H
+
H 2
N
N
E tO H ,
M e 2
N
M e 2 N
O
O
O
O
O
C H O
N
N
O
3
3
a N -a m in o p h th a lim id e
b N -a m in o b e n z [d e ]is o q u in o lin e -1 ,3 -d io n e
O
5 a p ro d u c t o f 2 + 3 a
5 b p ro d u c t o f 2 + 3 b
2
The reaction of equimolar amounts of aldehyde 1 and imide 3 in alcohol in the presence of 4-
toluenesulfonic acid as catalyst was carried out under reflux. The reaction undergoes quantitatively.

Molecules 2009, 14
4840
Alcohols were found as the most suitable solvents for the synthesis. The isolation of products is very
simple because they precipitate from a refluxing reaction mixture. Hydrazones 4 or 5 are stable
crystalline products and can be easily purified by recrystallization, resp. trituration from alcohol.
2
.2. Photochromism and thermochromism
-Oxo-2H-chromene derivatives, depending on their structure, absorb light in a spectral range
2
which is very suitable and attractive because readily available light sources can be used to store, resp.
delete information. The photochromic (solvatochromic and fluorosolvatochromic) and thermochromic
properties of synthesized compounds 4, 5 were studied using UV-VIS and fluorescence spectroscopy.
All studied compounds absorb light in the range λ = 200-520 nm. Their absorption maxima are
bathochromically shifted (positive solvatochromism) few nanometers with increasing polarity of
solvent (e.g. for 4c λmax-MeOH = 444 nm, λmax-PhMe = 434 nm, Figure 1). This absorption corresponds to
π→π∗ band. Introduction of electron donating substituent into position 7 of the 2-oxo-2H-chromene
fragment induces a large shift of absorption maximum (e.g. for 4c λmax-MeOH = 444 nm, for 4a λmax-MeOH
=
354 nm, Figure 1).
Figure 1. Absorption spectra of 4a in methanol (⎯⎯) and of 4c in methanol (⎯⎯) ,
toluene (⎯⎯).
2,00
1,75
1,50
1,25
1,00
0,75
0,50
0,25
0,00
300
325
350
375
400
425
450
475
500
λ [nm]
Intensity of fluorescence emission of prepared compounds derived from unsubstituted aldehyde 1a
in methanol (Figure 2) is several-fold lower than for compounds derived from 7-N,N-dimethylamino-
-oxo-2H-chromene-3-carbaldehyde (Figure 3). 2-Oxo-2H-chromene-3-carbaldehyde hydrazones emit
2
light with maximum of emission in the range of wavelenghts 420-460 nm. The maximum of the
fluorescence emission is bathochromically shifted with increasing electron donating ability of
substituent bound in position 7 of 2-oxo-2H-chromene fragment as well as with increasing solvent
polarity. This shift confirms that the excited state of these compounds is more polar than their ground
state. The dipole moment of the molecule increases after excitation, particularly of derivatives with
dimethylamino substituent. Structure of molecule influences charge separation. Such “bipolar”
structures (Figure 4) are better stabilized by more polar solvents.

Molecules 2009, 14
Figure 2. Absorption (⎯⎯) and fluorescence emission (λ =360 nm ⎯⎯) spectra of 4a
4841
ex
in methanol.
2,5
2,0
1,5
1,0
0,5
0,0
300
350
400
450
500
550
600
λ [nm]
Figure 3. Fluorescence emission spectra of 4c in toluene (λ = 490 nm ⎯⎯) and of 4d in
ex
toluene (λex= 430 nm ⎯⎯) and in methanol ((λex= 430 nm ⎯⎯).
40
30
20
10
0
425
450
475
500
525
550
575
600
625
650
675
λ [nm]
Figure 4. Bipolar structures.
R'
R'
N
O
O
N
O
O
Irradiation of studied derivatives at λ ≅ 310 nm in methanol or toluene at room temperature induces
hypsochromic shift of absorption maximum as well as decrease of intensity of long-wave absorption
band. This change of long-wave band was assigned to E-Z isomerization around C=N bond (Figure 5).

Molecules 2009, 14
4842
Figure 5. Absorption spectra of 4c in methanol (E-isomer ⎯⎯, Z-isomer ⋅⋅⋅⋅⋅⋅.) and in
toluene (E-isomer ⎯⎯, Z-isomer ⋅⋅⋅⋅⋅⋅.).
1,75
1,50
1,25
1,00
0,75
0,50
0,25
0,00
325
350
375
400
425
450
475
500
525
λ [nm]
Isomerization around the C=N bond is a reversible process. Retro-Z-E isomerization occurs
photochemically with visible light or thermally in polar solvents (Figure 6). Thermal back
isomerization takes place in non-polar solvents (Figure 7).
Figure 6. Absorption spectra of 4a in methanol (dissolution of 4a (⎯⎯), heating of
solution to the boiling point of solvent (⎯⎯), irradiation with visible light (halogen lamp,
t=30 s, ⎯⎯), irradiation with UV light (310 nm, t=15s, ⎯⎯), repeated heating of solution
to the boiling point of solvent (⎯⎯), repeated irradiation with UV light (310 nm, t=15s,
⎯
⎯).
2
1
1
1
1
0
,00
,75
,50
,25
,00
,75
3
00
325
350
375
λ [nm]

Molecules 2009, 14
Figure 7. Absorption spectra of 4a in toluene (dissolution of 4a (⎯⎯), heating of solution
4843
to the boiling point of solvent (⎯⎯), irradiation with UV light (310 nm, t=15s, ⎯⎯),
repeated heating of solution to the boiling point of solvent (⎯⎯).
0
0
0
0
,75
,50
,25
,00
3
00
325
350
375
400
425
λ [nm]
When the compounds are dissolved, an increase of absorbance of the long-wave band is observed
after standing a few minutes at room temperature. This change is probably due to reaching equilibrium
between isomers, eventually conformers. This equilibrium is reached faster in polar than in non-polar
media. Heating of solutions also causes fast reaching of equilibria between geometrical isomers.
Irradiation of samples with UV-light induces hypsochromic shift of absorption maximum (the less
stable isomer is formed in solution). Irradiation of this mixture with visible light causes bathochromic
shift of absorption maximum. This process was repeated several times. The evidence for photochromic
and thermochromic behaviour of studied compounds is, for examples of compound 4d, also decrease
of intensity of long-wave band (at λ = 450 nm) simultaneously with increase of intensity of absorption
band at λ= 330 nm at irradiation of sample with UV-light followed by heating (Figure 8).
Figure 8. Absorption spectra of 4d in methanol (sample irradiated after heating (⎯⎯),
sample heated after irradiation (⎯⎯)).
1
0
0
0
0
,00
,75
,50
,25
,00
3
00
325
350
375
400
425
450
475
λ [nm]

Molecules 2009, 14
4844
3
. Experimental
3
.1. General
1
13
Melting points (uncorrected) were measured on a Kofler hot stage. The H-NMR and C-NMR
spectra were recorded at 300 MHz and at 75 MHz, respectively, on a Varian Gemini 200 spectrometer
in CDCl or DMSO-d with tetramethylsilane as internal standard. Elemental analyses were performed
3
6
on a Carlo Erba Strumentacione 1106 apparatus. Chemicals and solvents were purchased from the
major chemical suppliers as highest purity grade. All solvents were dried by standard methods and
distilled prior to use. Reactions with moisture-sensitive chemicals were performed under argon in an
oven-dried flask. N-Aminobenz[de]isoquinoline-1,3-dione (3b) [15] and 2-oxo-2H-chromene-3-
carbaldehyde (1) [16] were prepared according to literature procedures. For column chromatography
Merck silica gel 60, 230-400 mesh was used with the indicated eluents.
3
.2. General procedure for the preparation of 7-N,N-dimethylamino-2-oxo-2H-chromenecarbadehydes
1
b and 2
Step 1- 4-N,N-dimethylamino-2-hydroxybenzaldehyde: A solution of 3-N,N-dimethylaminophenol (21
g, 0.15 mol) in dry DMF (25 mL) was added dropwise to a Vilsmeier Haack adduct prepared from
POCl (16.5 mL, 0.18 mol) and dry DMF (34 mL, 0.44 mol) at room temperature. The reaction
3
mixture was stirred at room temperature for 15 minutes, at 37 °C for 15 minutes and at 85-90 °C for
3
0 minutes. After cooling, the reaction mixture was poured into crushed ice, the solution was
neutralized with Na
2
CO
3
, the precipitate was filtered off, washed with water and dried. Mp 80.5-81 °C;
): δ 3.08 (6H, s, CH ), 6.09 (1H, d, J = 2.1 Hz, H-3), 6.29 (1H, dd, J = 9,
1
1
2
7.7 g, 70%; H-NMR (CDCl
3
3
.1 Hz, H-5), 7.29 (1H, d, J = 9 Hz, H-6), 9.53 (1H, s, CHO), 11.6 (1H, s, OH).
Step 2- 7-N,N-dimethylamino-2-oxo-2H-chromene: A mixture of 4-N,N-dimethylamino-2-hydroxy-
benzaldehyde (10 g, 60.5 mmol) and ethyl (triphenylphosphoranylidene)acetate (24.3 g, 69.8 mmol)
was heated at 180 °C under argon for 1 hour. Method A [17]: after cooling, the crude product was
purified by column chromatography on silica gel with hexane/ethyl acetate (2:1). Mp 163-165 °C;
1
6
1.7 g, 77%. Method B: after cooling, the crude product was crystallized from ethanol. Yield 6.93 g ,
1
1%; H-NMR (CDCl ): δ 3.06 (6H, s, CH ), 6.07 (1H, d, J = 9.3 Hz, H-3), 6.5 (1H, d, J = 2.4 Hz,
3
3
H-8), 6.59 (1H, dd, J = 8.7, 2.4 Hz, H-6), 7.27 (1H, d, J = 8.7 Hz, H-5), 7.57 (1H, d, J = 9.3 Hz, H-4).
Step 3- 7-N,N-dimethylamino-2-oxo-2H-chromene-3-carbadehyde (1b): Method A: A solution of 7-
N,N-dimethylamino-2-oxo-2H-chromene (1.5 g, 7.93 mmol) in dry DMF (40 mL) was added dropwise
3
to a Vilsmeier Haack adduct prepared from POCl (3.7 mL, 40.3 mmol) and dry DMF (8 mL, 0.1 mol)
at room temperature. The reaction mixture was stirred at 50 °C for 3 hours. After cooling, the reaction
mixture was stirred at room temperature overnight, poured into crushed ice, the precipitate was filtered
1
off, washed with water and dried. Mp 204-205 °C; 0.95 g, 55%; H-NMR (CDCl ): δ 3.12 (6H, s,
3
CH
.28 (1H, s, H-4), 10.14 (1H, s, CHO). Method B: A solution of 7-N,N-dimethylamino-2-oxo-2H-
chromene (1.8 g, 9.51 mmol) in dry DMF (70 mL) was added dropwise to a Vilsmeier Haack adduct
3
), 6.49 (1H, d, J = 2.4 Hz, H-8), 6.66 (1H, dd, J = 8.7, 2.4 Hz, H-6), 7.44 (1H, d, J = 8.7 Hz, H-5),
8

Molecules 2009, 14
4845
prepared from POCl (1.74 mL, 18.95 mmol) and dry DMF (1.46 mL, 18.95 mmol) at room
3
temperature. The reaction mixture was stirred at 50 °C for 4 hours. After cooling, the reaction mixture
was stirred at room temperature overnight, poured into crushed ice, the precipitate was filtered off,
washed with water and dried. Yield 0.86 g of 1b, 42%. The water from filtrate was partially
evaporated, the concentrated filtrate was left to stand, after few days crystals of 7-N,N-dimethylamino-
2
-oxo-2H-chromene-8-carbadehyde (2) were formed. The aldehyde 2 was filtered off and dried. Mp
1
2
23-225 °C; 0.6 g, 29%; H-NMR (CDCl ): δ 3.04 (6H, s, CH ), 6.18 (1H, d, J = 9.4 Hz, H-3), 6.85
3
3
(
1H, d, J = 8.9 Hz, H-6), 7.41 (1H, d, J = 8.9 Hz, H-5), 7.59 (1H, d, J = 9.4 Hz, H-4), 10.62 (1H, s,
1
3
CHO); C-NMR (CDCl
32.46 (C-5), 143.64 (C-4), 154.51 (C-4b), 159.61 (C-7), 160.33 (C-2), 186.07 (CHO); Anal. Calcd.
for C H NO (217.2): C, 66.36; H, 5.1; N, 6.47. Found: C, 66.51; H, 4.94; N 6.45.
3
3
): δ 44.21 (CH ), 108.89 (C-6), 110.09 (C-4a), 110.92 (C-3), 112.54 (C-8),
1
1
2
11
2
3
.3. General procedure for the preparation of 2-oxo-2H-chromene-3-carbadehyde hydrazones 4
Aldehyde 1 was dissolved in 10 mL of hot absolute ethanol. N-Aminoimide 3 was added to the
solution and after its dissolution a crystal of 4-toluenesulfonic acid was added to the reaction mixture.
The mixture was refluxed for 15 minutes. After cooling, the precipitate was filtered off, washed with
ethanol, dried and recrystallized from ethanol.
3
-[(N-phthalimidoyl)iminomethyl]-2-oxo-2H-chromene (4a): Obtained from 1a (50 mg, 0.29 mmol)
1
and 3a (47 mg, 0.29 mmol); Mp 265-267 °C; 67 mg, 73%; H-NMR (CDCl
3
): δ 7.33-7.43 (2H, m, Ar-
): δ 116.21,
18.65, 120.59, 123.51, 124.95, 129.86, 130.15, 133.42, 134.99, 139.95, 150.75, 153.79, 159.53,
64.39; UV (methanol) λmax 353 nm; Anal. Calcd. for C18 (318.3): C, 67.93; H, 3.17; N, 8.80.
1
3
H), 7.56-7.8 (6H, m, Ar-H), 8.33 (1H, s, H-4), 8.79 (1H, s, CH=); C-NMR (DMSO-d
6
1
1
10 2 4
H N O
Found: C, 67.73; H, 3.16; N 8.82.
3
-[N-(1,3-dioxobenz[de]isoquinolinyl)iminomethyl]-2-oxo-2H-chromene (4b): Obtained from 1a (82
1
mg, 0.47 mmol) and 3b (100 mg, 0.47 mmol); Mp 309 °C; 92 mg, 53%; H-NMR (CDCl
3
): δ 7.34-
7
.42 (2H, m, Ar-H), 7.63-7. 68 (2H, m, Ar-H), 7.74-7.78 (2H, t, J= 7.8 Hz, Ar-H), 8.27-8.30 (2H, d, J
1
3
=
8.2 Hz, Ar-H), 8.67-8.70 (2H, d, J = 7.2 Hz, Ar-H), 8.87 (1H s, H-4), 8.91 (1H, s, CH=); C-NMR
): δ 117.18, 118.87, 125.36, 127.26, 127.35, 130, 131.77, 131.89, 132.24, 133.99, 134.69,
34.76, 134.78, 142.63, 142.65, 164.82, 172.31; UV (methanol) λmax 351 nm; Anal. Calcd. for
(368.1): C, 71.74; H, 3.28; N, 7.61. Found: C, 71.52; H, 3.29; N 7.59.
(CDCl
3
1
22 12 2 4
C H N O
7
-(N,N-dimethylamino)-3-[(N-phthalimidoyl)iminomethyl]-2-oxo-2H-chromene (4c): Obtained from
1
1
b (50 mg, 0.23 mmol) and 3a (37.3 mg, 0.23 mmol); Mp 326-328 °C; 45 mg, 54%; H-NMR
(
CDCl
3
): δ 3.11 (6H, s, CH
3
), 6.64-6.65 (1H, d, J = 2.3 Hz, H-8), 6.83 (1H, dd, J = 8.7, 2.3 Hz, H-6),
1
3
7
.75 (1H, d, J = 8.7 Hz, H-5), 7.90-7.95 (4H, m, Ar-H), 8.59 (1H, s, H-4), 9.24 (1H, s, CH=); C-
NMR (DMSO-d ): δ 40.76 (CH ), 96.87 (C-8), 108.13 (C-6), 110.2 (C-4a), 111.48 (C-3), 123.29
6
3
(
C
phth-3,6), 129.95 (C-5), 131.26 (Cphth-1,2), 134.77 (Cphth-4,5), 140.80 (C-4), 150.15 (C-7), 153.55 (C-
b), 156.78 (CH=), 160.44 (C-2), 164.45 (C=O); UV (methanol) λmax 434 nm; Anal. Calcd. for
(368.3): C, 66.48; H, 4.18; N, 11.63. Found: C, 66.28; H, 4.17; N 11.60.
4
20 15 3 4
C H N O

Molecules 2009, 14
4846
7
-(N,N-dimethylamino)-3-[N-(1,3-dioxobenz[de]isoquinolinyl)iminomethyl]-2-oxo-2H-chromene (4d):
1
Obtained from 1b (100 mg, 0.46 mmol) and 3b (98 mg, 0.46 mmol); Mp 320-323 °C; 80 mg, 42%; H-
NMR (CDCl ): δ 3.14 (6H, s, CH ), 6.52 (1H, d, J = 2.4 Hz, H-8), 6.67 (1H, dd, J = 9.8, 2.4 Hz, H-6),
.44 (1H, d, J = 9.8 Hz, H-5), 7.79 (2H, dt, J = 8.4, 7.2, 0.9 Hz, Ar-H), 8.26 (2H, dd, J = 8.4, 0.9 Hz,
3
3
7
1
3
Ar-H), 8.67 (2H, dd, J = 7.2, 0.9 Hz, Ar-H), 8.76 (1H s, H-4), 8.78 (1H, s, CH=); C-NMR (CDCl ): δ
3
4
1
0.52, 97.75, 97.86, 110.22, 110.49, 127.26, 131.27, 131.77, 132.01, 132.42, 134.49, 134.71, 143.16,
45.78, 161.45, 166.41, 166.43, 172.81; UV (methanol) λmax 438 nm; Anal. Calcd. for C H N O
24
17
3
4
(411.4): C, 70.07; H, 4.17; N, 10.21. Found: C, 69.85; H, 4.16; N 10.20.
3
.4. General procedure for the preparation of 2-oxo-2H-chromene-8-carbadehyde hydrazones 5
Aldehyde 2 was dissolved in hot absolute ethanol (10 mL). N-Aminoimide 3 was added to the
solution and after its dissolution a crystal of 4-toluenesulfonic acid was added to the reaction mixture.
The mixture was refluxed for 15 minutes. After cooling, the solvent was partially evaporated, the
precipitate was filtered off, washed with ethanol, dried and recrystallized from ethanol.
7
-(N,N-dimethylamino)-8-[(N-phthalimidoyl)iminomethyl]-2-oxo-2H-chromene (5a): Obtained from 2
1
(
50 mg, 0.23 mmol) and 3a (37.3 mg, 0.23 mmol); Mp 193-195 °C; 56 mg, 67%; H-NMR (CDCl
3
): δ
3
.03 (6H, s, CH
3
), 6.19 (1H, d, J = 9.4 Hz, H-3), 6.91 (1H, d, J = 8.8 Hz, H-6), 7.38 (1H, d, J = 8.8 Hz,
), 7.9-7.95 (2H, m, Arphth-H ), 9.61
), 107.18 (C-8), 110.19 (C-6), 110.61 (C-4a),
13.27 (C-3), 123.26 (Cphth-3,6), 130.03 (C-5), 130.67 (Cphth-1,2), 134.72 (Cphth-4,5), 144.51 (C-4),
54.48 (C-4b), 154.73 (C-7), 156.39 (CH=), 159.73 (C-2), 164.44 (C=O); UV (methanol) λmax 371 nm;
(368.3): C, 66.48; H, 4.18; N, 11.63. Found: C, 66,51; H, 4.17; N 11.63.
H-5), 7.60 (1H, d, J = 9.4 Hz, H-4), 7.77-7.82 (2H, m, Arphth-H
β
α
1
3
(
1H, s, CH=); C-NMR (DMSO-d
6
): δ 43.95 (CH
3
1
1
15 3 4
Anal. Calcd. for C20H N O
7
-(N,N-dimethylamino)-8-[N-(1,3-dioxobenz[de]isoquinolinyl)iminomethyl]-2-oxo-2H-chromene (5b):
1
Obtained from 2 (100 mg, 0.46 mmol) and 3b (98 mg, 0.46 mmol); Mp 283-285 °C; 105 mg, 55%; H-
NMR (CDCl ): δ 3.17 (6H, s, CH ), 6.17 (1H, d, J = 9.4 Hz, H-3), 6.94 (1H, d, J = 8.9 Hz, H-6), 7.42
1H, d, J = 8.9 Hz, H-5), 7.62 (1H, d, J = 9.4 Hz, H-4), 7.78-7.82 (2H, m, Ar-H), 8.24-8.29 (2H, m,
3
3
(
1
3
Ar-H), 8.64-8.66 (2H, m, Ar-H), 9.2 (1H, s, CH=); C-NMR (CDCl
3
): δ 44.71, 111.12, 111.25,
12.71, 113.38, 127.25, 131.09, 131.76, 131.86, 132.65, 134.48, 134.70, 143.81, 143.9, 161.17,
61.45, 167.01, 186.25; UV (methanol) λmax 339 nm; Anal. Calcd. for C24 (411.4): C, 70.07;
1
1
17 3 4
H N O
H, 4.17; N, 10.21. Found: C, 69.99; H, 4.15; N 10.21.
3
.5. Photochromism and thermochromism
UV-VIS spectra were recorded on Hewlett-Packard ‘Diode Array 8254’ spectrometer. Fluorescence
spectra were taken in metanol on a Hitachi F2000 spectrometer (S , S = 10 nm). All measurements
1
2
were performed in a 1-cm thick absorption cell, resp. fluorescence cell, at room temperature.
Photolysis experiments were performed in a quartz spectrophotometric cell using the filtered
irradiation (λ ≅ 310 nm) from an UVP, Inc. Chromato VUE transilluminator, Model TM-15 or using
unfiltered light from an Osram halogen lamp (150 W) in degassed methanol or toluene under nitrogen
at room temperature.

Molecules 2009, 14
. Conclusions
-Oxo-2H-chromenecarbaldehydes 1 or 2 react with N-aminoimides 3 to give 2-oxo-2H-
4847
4
2
chromenecarbaldehyde hydrazones 4 or 5 under mild conditions. It was found that E-Z isomerisation
around the C=N bond takes place with ultraviolet light. This isomerization is a reversibile process. The
back-Z-E isomerization occurs photochemically with the visible light in polar and in non-polar
solvents and thermally only in non-polar solvents.
Acknowledgements
This work was supported by grants from the Slovak Grant Agency for Science (VEGA 1/0639/08),
the Slovak Research and Development Agency (APVV-0128-07).
References and Notes
1
2
.
.
Sauvage, J.P. A light-driven linear motor at the molecular level. Science 2001, 291, 2105–2106.
Würthner, F.; Rebek, J., Jr. Light-switchable catalysis in synthetic receptors. Angew. Chem. Int.
Ed. Engl. 1995, 34, 446–448.
3
.
Willner, I.; Marx, S.; Eichen, Y. Photoswitchable association of an azobenzene-bipyridinium diad
to eosin: photostimulated On-Off guest binding. Angew. Chem. Int. Ed. Engl. 1992, 31,
1
243–1244.
Willner, I. Photoswitchable biomaterials: En route to optobioelectronic systems. Acc. Chem. Res.
997, 30, 347–356.
4
5
.
1
.
Lahav, M., Ranjit, K.T., Katz, E., Willner, I. A β-amino-cyclodextrin monolayer-modified Au
electrode: A command surface for the amperometric and microgravimetric transduction of optical
signals recorded by a photoisomerizable bipyridinium-azobenzene diad. J. Chem. Soc. Chem.
Commun. 1997, 259–260.
6
7
.
.
Novak, I.; Kovač, B. UV photoelectron spectroscopy of coumarins. Electron Spectrosc. Relat.
Phenom. 2000, 113, 9–13.
Gao, F.; Li, H.R.; Zang, Y.Y. Influence of the molecular structure and medium on the absorption
and emission character of ketocoumarin derivatives and probability of as fluorescence probes
Dyes Pigments 2000, 47, 231–238.
8
9
.
.
Raju, B.B.; Eliasson, B. Excited state properties of pre-twisted 7-diethylamino coumarinyl
benzopyrano pyridine: an experimental and AMI study. J. Photochem. Photobiol. A Chem. 1998,
1
16, 135–142.
Reynolds, G.A.; Drexhage, K.H. New coumarin dyes with rigidized structure for flashlamp-
pumped dye lasers. Optics. Commun. 1975, 13, 222–225.
1
1
0. Zollinger, H. Color Chemistry, 3rd ed.; VHCA: Zürich, Switzerland, 2003.
1. Bissell, E.R.; Mitchell, A.R.; Smith, R.E. Synthesis and chemistry of 7-amino-4-
(
trifluoromethyl)coumarin and its amino acid and peptide derivatives. J. Org. Chem. 1980, 45,
283–2287.
2

Molecules 2009, 14
4848
1
2. Gáplovský, A.; Donovalová, J.; Lácová, M.; Mračnová, R.; El-Shaaer, H.M. The photochemical
behaviour of 6-X-4H-3(bicyclo[2.2.1]-5-heptene-2,3-dicarboximidoiminomethyl)-4-chromones.
Photochromism and thermochromism. J. Photochem. Photobiol. A Chem. 2000, 136, 61–65.
3. Görner, H.; Fisher, E. Reversible photochemistry of 4-nitro-substituted diphenylazomethines. J.
Photochem. Photobiol. A Chem. 1991, 57, 235–246.
1
1
1
4. Kessler, H. Nachweis gehinderter Rotationen und Inversionen durch NMR-Spektroskopie. Angew.
Chem. 1970, 82, 237–253.
5. Carpino, L.A.; Göweke, S. Alkaline degradation of 1,1-disubstituted sulfonhydrazides. Synthesis
of a pair of cyclic, benzylic hydrazines derived from acenaphthene and acenaphthylene. J. Org.
Chem. 1964, 29, 2824–2830.
1
1
6 Ito, K.; Nakajima, K. Selenium dioxide oxidation of alkylcoumarins and related methyl-
substituted heteroaromatics. J. Heterocycl. Chem. 1988, 25, 511–515.
7. Takechi, H.; Kamada, S.; Machida, M. 3-[4-(Bromomethyl)phenyl]-7-(diethylamino)-2H-1-
benzopyran-2-one (MPAC-Br): A highly sensitive fluorescent derivatization reagent for
carboxylic acids in high-performance liquid chromatography. Chem. Pharm. Bull. 1996, 44,
7
93–799.
Sample Availability: Not available.
2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
©
This article is an open-access article distributed under the terms and conditions of the Creative
Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).