Synthesis and photochromic behavior of fluoro 2H-1-benzopyrans containing a carbazole moiety

Article abstract of DOI:10.1080/15421400590947153

The synthesis of new photochromic 2,2-di(4′-fluoro-phenyl)-2H-1- benzopyrans fused to an indole moiety is described. Spectrokinetic data (λmax of colored form, colorability and rate constant of bleaching) obtained by UV-Visible spectroscopy and the struct

Full text of DOI:10.1080/15421400590947153

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Synthesis and Photochromic
Behavior of Fluoro 2H-1-
Benzopyrans Containing a
Carbazole Moiety
M. Manuel Oliveira a , Maria A. Salvador a , Gaston
Vermeersch b , Jérôme Berthet b & Stéphanie
Delbaere b
a Centro de Química – Vila Real , Universidade de
Trás-os-Montes e Alto Douro , Portugal
b Laboratoire de Physique et LARMN, UMR CNRS
8009 , Faculté de Pharmacie, Université de Lille 2 ,
France
Published online: 31 Aug 2006.
To cite this article: M. Manuel Oliveira , Maria A. Salvador , Gaston Vermeersch ,
Jérôme Berthet & Stéphanie Delbaere (2005) Synthesis and Photochromic Behavior of
Fluoro 2H-1-Benzopyrans Containing a Carbazole Moiety, Molecular Crystals and Liquid
Crystals, 431:1, 473-485
To link to this article: http://dx.doi.org/10.1080/15421400590947153
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Mol. Cryst. Liq. Cryst., Vol. 431, pp. 173=[473]–185=[485], 2005
Copyright # Taylor & Francis Inc.
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400590947153
Synthesis and Photochromic Behavior of Fluoro
2H-1-Benzopyrans Containing a Carbazole Moiety
M. Manuel Oliveira
Maria A. Salvador
ꢀ
´
Centro de Quımica – Vila Real, Universidade de Tras-os-Montes
e Alto Douro, Portugal
Gaston Vermeersch
´ ˆ
Jerome Berthet
´
Stephanie Delbaere
´
Laboratoire de Physique et LARMN, UMR CNRS 8009, Faculte de
´
Pharmacie, Universite de Lille 2, France
The synthesis of new photochromic 2,2-di(40-fluoro-phenyl)-2H-1-benzopyrans
fused to an indole moiety is described. Spectrokinetic data (kmax of colored form,
colorability and rate constant of bleaching) obtained by UV-Visible spectroscopy
and the structure of photomerocyanines elucidated by NMR spectroscopy, are
reported.
Keywords: fluoro-benzopyrans; hydroxycarbazole; NMR; photochromism; synthesis;
UV-visible spectroscopy
INTRODUCTION
Among the different classes of photochromic families, benzopyrans
represent an important group, which were first investigated by Becker
and Michl who established their photochromic properties in a rigid
matrix at 77 K [1,2]. The photochromism of benzopyrans involves a
´
The 300 MHz NMR facilities were funded by the Region Nord-Pas de Calais (France),
`
´
the Ministere de l’Education Nationale, de l’Enseignement Superieur et de la Recherche
´
´
´
(MENESR) and the Fonds Europeens de Developpement Regional (FEDER). This work
is supported by Calouste Gulbenkian Foundation and CPU=CRUP in the framework
´
´
‘‘Actions Universitaires Integrees Luso-Franc¸aises’’.
´
Address correspondence to M. Manuel Oliveira, Centro de Quımica – Vila Real,
ꢀ
Universidade de Tras-os-Montes e Alto Douro, P-5000-911 Vila Real, Portugal. E-mail:
moliveir@utad.pt
173=[473]

174=[474]
M. M. Oliveira et al.
bond cleavage of the spiro carbon and the oxygen atom of the pyran
ring under UV irradiation. This heterolytic breaking leads through a
zwitterionic intermediate to a cis-cisoid isomer whose rearrangement
gives rise to a set of stereoisomers of the photomerocyanine. Such
structures commonly named open and colored forms, have a distinct
absorption spectrum, generally in the visible range and return to
the initial closed form via thermal or photochemical pathways.
Equilibrium between closed and open forms has found a large var-
iety of applications, mainly in a use as variable-transmission materi-
als. In the course of development of novel applications, research is
turned to the design of systems that are responsive to solar irradiation
at room temperature and exhibit good photochromic properties (high
colorability, low response to visible light and fast thermal bleaching)
associated with high fatigue resistance [3].
The photochromism at room temperature of 2H-1-benzopyran was
observed after structural modifications, such the presence of phenyl
groups at the sp3 C-atom and the heteroaromatic annellation with
five or six-membered rings [4,5,6,7,8]. The 2,2-disubstituted-2H-
naphtho[2,3-b]pyran (annellation 6,7) is photochromic only at very
low temperatures, even when conjugate substituants are present, which
is the result of the loss of aromaticity of both rings in the naphthalene
nucleus present in the open form [1,2]. As reported in a previous
paper, benzopyrans containing a carbazole moiety present significantly
different properties according to the position of annellation [9].
In the present paper, we report the synthesis of 2,2-diphenyl-2H-1-
benzopyrans substituted by fluorine atoms in para position of both
phenyl groups and annellated in position 6–7 to a carbazole moiety,
and their spectrokinetic properties (kmax of colored form, colorability
and rate constant of bleaching) obtained by UV-Visible spectroscopy.
In addition, 1 and 2D NMR spectroscopy has been used to characterize
the structures of open forms after UV irradiation and to investigate
their kinetic behavior.
EXPERIMENTAL
General Remarks
¨
Solvents (Riedel-Haen and Merck) were used without further purifi-
cation. Column chromatography was performed on silica gel Merck
60 (70–230 mesh). IR spectra were recorded on a Perkin-Elmer-
FTIR-1600 spectrophotometer using KBr disks and wavenumbers
are given in cmꢀ1. UV=VIS spectra were recorded on a CARY 50
Varian spectrophotometer. The mass spectra were obtained under

Synthesis and Photochromic Behavior
175=[475]
electronic impact (EI ¼ 70 eV) on AutoSpecE spectrometer. Melting
points (ꢁC), measured in capillary tubes on Bu¨chi 535 apparatus, are
uncorrected. All new compounds were determined to be >95% pure
1
by H NMR spectroscopy.
Spectrokinetic Studies under Flash Photolysis
The flash photolysis experiments were monitored by a Warner and
Swasey rapid spectrometer (acquisition time 1 ms, repetitivity
1.25 ms) [10,11]. Flashes (duration 50 ms) were generated by two xenon
tubes with a quartz envelope. The energy of the flashes was 60 J for
the whole polychromatic emission spectrum. For measurements,
thermostated (25ꢁC) 100 mm cells were used. The light from the
analysis lamp (50 W, quartz-iodide) was filtered using a Schott
GC400 high-pass filter.
Spectrokinetic Studies under Continuous Irradiation
Irradiation experiments were made using a CARY 50 Varian spec-
trometer coupled to a 150 W Ozone free Xenon lamp (6255 Oriel
Instruments). The light from the UV lamp was filtered using a water
filter (61945 Oriel Instruments) and then carried to the spectrophoto-
meter holder at the right angle to the monitoring beam using an
optical fiber system (77654 Oriel Instruments). A light flux of
40 W mꢀ2, measured with a Goldilux Photometer with UV-A probe
was used. A thermostated (10 and 20ꢁC) 10 mm quartz cell, containing
the sample solution (3.5 ml), equipped with magnetic stirring was
used. In a preliminary experiment, the visible absorption spectrum
of the closed form and the kmax of the open form were determined.
In a second experiment the absorbance at photostationary equilib-
rium, Aeq, was measured at kmax and then the decrease in the absor-
bance vs. time was monitored. The rate constants were calculated
using a multi exponential model.
NMR Spectroscopy
1
1
1D (1H, H-1D-roesy, 13C-J-mod and 19F with H decoupling) and 2D
(1H-1H cosy-gp, 1H-1H roesy, 1H-13H HSQC-gp, 1H-13C HMBC-gp)
NMR spectra were acquired using Bruker 300 NMR spectrometer
operating at 300 MHz (1H), 75 MHz (13C) and 282 MHz (19F), equipped
with a BBI probehead fitted with an actively shielded z-gradient coil
for delivering pulsed field gradient (DPX spectrometer) or with a
QNP (1H, 13C, 19F, 31P) probe head (AC spectrometer). UV irradiation

176=[476]
M. M. Oliveira et al.
of the samples in the NMR tube were performed in a home-built appar-
atus with a 1000 Watts Xe-Hg lamp, equipped with filter Schott
011FG09 (259 < k < 388 nm with kmax ¼ 330 nm and T ¼ 79%). Dur-
ing irradiation, the sample was kept spinning for homogenization
and the temperature was controlled with a variable temperature unit.
After irradiation had been stopped, the tube was transferred into the
NMR probe, also thermoregulated, of the spectrometer.
RESULTS AND DISCUSSION
Synthesis and NMR Characterization
The 2-hydroxy-9-methylcarbazole (1) was obtained from the commer-
cial 2-hydroxycarbazole by methylation with NaH and CH3I and
demethylation with pyridinium hydrochloride in 34% overall yield.
2-bromo-7-hydroxy-9-methylcarbazole (2) was prepared in 66% over-
all yield by crossed Ullmann reaction from commercially available
compounds followed by treatment with triethylphosphite at 160ꢁC,
N-methylation with NaH and CH3I and demethylation [12]. Among
several methods available to obtain heteroannellated 2,2-diaryl-2H-
chromenes we have considered the most adequate method for basic
phenols like hydroxycarbazoles. The choice of this method led us to
prepare the a,b-unsaturated aldehyde, 3,3-di-(40-fluorophenyl)prop-2-
enal 4, starting from the corresponding benzophenone and passing
through the 1,1-di(40-fluorophenyl)-2-propyn-1-ol 3, (Scheme 1) [13].
The method involves the organotitanium mediated condensation of a
‘‘phenol’’ with an a,b-unsaturated aldehyde, leading to C-alkylation
in ortho-position that through a subsequent electrocyclisation yields
the new benzopyrans CF-1 and CF-2 (Scheme 2) [14]. All the known
compounds (1, 2, 3 and 4) showed melting points and spectral charac-
teristics in accordance with literature values [9,15,16].
SCHEME 1 General synthesis of 3,3-di-(40-fluorophenyl)prop-2-enal, 4.

Synthesis and Photochromic Behavior
177=[477]
SCHEME 2 General synthesis of [indole]benzopyrans CF-1 and CF-2.
Benzopyran CF-1. White solid. Yield 30%. Mp 234.2–234.5. IR:
2956, 2927, 1629, 1600, 1504, 1230, 833, 746. UV=Vis (closed form):
1
285 (48560), 302 (27120), 341 (7840), 358 (12660). H NMR (300 MHz,
3
toluene-d8): d 2.9 (s, 3H, CH3), 5.75 (d, J3-4 ¼ 9.8 Hz, 1H, H-3), 6.60
(d, 1H, H-4), 6.70 (s, 1H, H-11), 6.84 (dd, 3J3 -2 ¼ 9.0 Hz, 3J3 -F ¼ 8.6 Hz,
0
0
0
4H, H-30 ¼ H-300), 6.94 (dd, 3J9-8 ¼ 8.0 Hz, 4J9-7 ¼ 0.9 Hz, 1H, H-9), 7.21
3
3
4
(ddd, J7-8 ¼ 8.3 Hz, J7-6 ¼ 7.7 Hz, 1H, H-7), 7.31 (ddd, J8-6 ¼ 1.3 Hz,
4
1H, H-8), 7.38 (dd, J2 -F ¼ 5.3 Hz, 4H, H-20 ¼ H-200), 7.50 (s, 1H,
0
H-5), 7.90 (dd, 1H, H-6). 13C NMR (75 MHz, toluene-d8): d 28.0
(CH3), 82.3 (Cq, C-2), 96.8 (CH, C-11), 108.8 (CH, C-9), 114.6 (Cq,
2
C-4a), 115.3 (CH, d, J3 -F ¼ 21.7 Hz, C30 ¼ C300), 118.9 (CH, C-5),
0
119.7 (CH, C-7), 120.0 (CH, C-6), 123.4 (Cq, C-6a), 124.8 (Cq, C-5a),
125.1 (CH, C-8), 125.6 (CH, C-4), 126.4 (CH, C-3), 129.6 (CH, d,
3
J2 -F ¼ 8.3 Hz, C20 ¼ C200), 141.0 (Cq, C-10 ¼ C-100), 141.3 (Cq, C-9a),
0
1
0
142.2 (Cq, C-10a), 152.0 (Cq, C-1a), 162.5 (Cq, d, J4 -F ¼ 258 Hz,
C-40 ¼ C-400). 19F NMR (282 MHz, toluene-d8): d-113.92 ppm. MS: m=z
(%): 423 (Mþ , 100), 328 (54), 313 (6), 211 (8), 201 (5). Exact mass for
C28H19F2NO: 423.1435. Found: 423.1454.
Benzopyran CF-2. White solid. Yield 30%. Mp 259.7-260. IR: 2958,
2927, 2857, 1727, 1629, 1596, 1506, 1232, 838, 809. UV=Vis (closed
form): 303 (27760), 310 (26400), 343 (8690), 360 (12220). 1H NMR
3
(300 MHz, toluene-d8): d 2.7 (s, 3H, CH3), 5.71 (d, J3-4 ¼ 9.7 Hz, 1H,
3
0
0
H-3), 6.53 (d, 1H, H-4), 6.57 (s, 1H, H-11), 6.79 (dd, J3 -2 ¼ 8.9 Hz,
3
4
J3 -F ¼ 8.7 Hz, 4H, H-30 ¼ H-300), 7.12 (d, J9-7 ¼ 1.8 Hz, 1H, H-9),
0
3
4
7.26 (dd, J7-6 ¼ 8.1 Hz, 1H, H-7), 7.31 (dd, J2 -F ¼ 5.4 Hz, 4H, H-20
¼ H-200), 7.32 (s, 1H, H-5), 7.48 (d, 1H, H-6). 13C NMR (75 MHz, tolu-
ene-d8): d 27.9 (CH3), 82.3 (Cq, C-2), 96.7 (CH, C-11), 111.7 (CH, C-9),
0
115.0 (CH, d, 2J3 -F ¼ 21.7 Hz, C30 ¼ C300), 115.1 (Cq, C-4a), 117.1 (Cq,
0
C-5a), 118.4 (CH, C-5), 120.5 (CH, C-6), 122.1 (Cq, C-6a), 122.4 (CH,
C-7), 124.9 (CH, C-4), 125.1 (Cq, C-8), 126.5 (CH, C-3), 129.2 (CH, d,
3
J2 -F ¼ 8.3 Hz, C20 ¼ C200), 141.1 (Cq, C-10 ¼ C-100), 142.0 (Cq, C-9a),
0

178=[478]
M. M. Oliveira et al.
1
0
142.6 (Cq, C-10a), 152.0 (Cq, C-1a), 162.2 (Cq, d, J4 -F ¼ 258 Hz,
C-40 ¼ C-400). 19F NMR (282 MHz, toluene-d8): d-113.71 ppm. MS:
m=z (%) 503 (100, 81Br), 501 (98, 79Br), 422 (9), 406 (75), 393 (6),
327 (7), 250 (5), 201 (9), 163 (5), 75 (6). Exact mass for C28H18BrF2NO:
501.0540. Found: 501.0550.
Studies by UV-Visible Spectroscopy
The new fluorobenzopyrans CF-1 and CF-2 exhibit photochromic
behavior at room temperature in toluene solutions. The relevant para-
meters (activation wavelengths of closed forms, maxima wavelengths
of the colored forms, colorability and thermal bleaching rate) were
evaluated under flash photolysis and continuous irradiation. Both
methods are extensively used although the information obtained
by the two methods can be very distinct since the time scales of
observation and the light flux applied are completely different. The
data are summarized in Table 1 together with the corresponding
[indole]benzopyrans without fluorine atoms (Ref 1–2,10-dihydro-10-
methyl-2,2-diphenylpyrano[2,3-b]carbazole and Ref 2–8-bromo-2,
10-dihydro-10-methyl-2,2-diphenylpyrano[2,3-b]carbazole), and the
reference compounds Ref 3–3,3-di(40-fluorophenyl)-3H-naphtho[2,
1-b]pyran, Ref 4–3,3-diphenyl-3H-naphtho[2,1-b]pyran.
Continuous Irradiation
From a general point of view, all the closed forms have absorption
bands in the near UV. For benzopyrans CF-1 and CF-2 when
compared with Ref 1 and Ref 2 the introduction of the fluorine atom
TABLE 1 Maximal Wavelengths of the Colored Forms (k1, k2), Colorability
(A0, Aeq), Fading Rates (k1 and k2) of the Described 2H-1-benzopyrans and
Five Reference Compounds in Toluene Solutions under Flash Photolysis
(2.5 ꢂ 10ꢀ5 M–Ref 1 to Ref 4 and 8.33 ꢂ 10ꢀ6ꢁM – CF-1 and CF-2, at 25ꢁC)
and Continuous Irradiation (1 ꢂ 10ꢀ4 M at 20 C)
Flash photolysis
Compound A0 k1 (nm) k1 (sꢀ1 k2 (sꢀ1
Continuous irradiation
Aeq k1 (nm) k2 (nm) k1 (sꢀ1
)
)
)
k2 (sꢀ1
)
CF-1
CF-2
Ref 1 [9] 2.5
Ref 2 [9] 5.5
Ref 3 [17]
Ref 4 [18] 0.84 432 0.09
2.8
3.5
461 0.32 (68) 0.03 (32) 0.48 451
461 0.44 (81) 0.03 (19) 0.32 450
444 0.19 (48) 0.02 (52) 0.72 444
454 0.20 (81) 0.02 (19) 0.51 454
699 0.03 (100)
688 0.05 (100)
–
–
–
–
–
–
0.02 (100)
0.03 (96) 0.001 (4)
0.08 0.0002
0.06 (80) 0.0003 (20)
–
–
–
–
–
0.20 430
0.21 432

Synthesis and Photochromic Behavior
179=[479]
led to a bathochromic shift and an extension of the visible range on the
spectra of open forms. The observed thermal fading rates for CF-1 and
CF-2 fit well with a monoexponential model and are faster than the
ones observed for the corresponding benzopyrans Ref 1 and Ref 2.
This indicates that the open forms of compounds with fluorine atoms
on the para position of the phenyl substituants are less thermally
stable than the reference compounds. As expected lower values of
colorability were also observed.
Flash Photolysis
Some determinations were also performed by the flash photolysis tech-
nique and in that case the bleaching kinetics fit well with a biexponen-
tial model. This indicates that there is a significant difference in the
relative quantities of photoisomers in the mixture obtained after
irradiation in both methods. For compound CF-1, the amplitude of
the first kinetic was improved (48 to 68%) and for both new com-
pounds the first kinetic phase was faster when compared with refer-
ence compounds without fluorine atoms. For compound CF-1, CF-2,
Ref 1 and Ref 2 the second kinetic phase observed by this method
can be correlated with the one obtained by continuous irradiation indi-
cating a similar nature of the photoisomers in the mixture responsible
for them.
As a group, the 2H-1-benzopyrans are less photochromic and less
responsive to solar irradiation than the corresponding naphthopyrans
due to their UV absorption at lower wavelengths. However compounds
CF-1 and CF-2 exhibit a stronger photocolouration efficiency (2.8 and
3.5 at 8.33 ꢂ 10ꢀ6 M) than the corresponding benzopyrans Ref 1 and
Ref 2 (2.5 and 5.5 at 2.5 ꢂ 10ꢀ5 M) and even stronger than the refer-
ence naphthopyran (Ref 4). It is noteworthy that this faster bleaching
kinetic is not accompanied by a loss in the colorability, such a result
can be interesting for some applications.
Photocoloration of CF-1 Monitored by NMR Spectroscopy
A sample of CF-1 has been irradiated at 203 K with UV light at
1
cumulative periods. Between each UV irradiation, 19F and H NMR
spectra have been acquired to monitor the photocoloration process.
Figure 1 illustrates the course of reaction. After 30 seconds of
irradiation, two 19F signals with equal intensities have been detected
at ꢀ109.7 and ꢀ110.80 ppm and increased with the time of irradi-
ation, while the signal of CF-1 decreased. After about 2 minutes,
1
two other new signals appeared at ꢀ109.7 and ꢀ109.96. In the H
NMR spectra recorded, the same phenomenon is observed with the

180=[480]
M. M. Oliveira et al.
FIGURE 1 19F NMR spectra recorded during UV irradiation at 203 K.
rapid formation of two doublet and two singlet signals at 6.00, 6.03,
6.34 and 9.60 ppm, with a concentration increase. A new doublet then
appeared at 8.40 ppm after 2–3 minutes of irradiation. After
irradiation had been stopped, all the new resonances followed a ther-
mal decay and the initial NMR peaks were retrieved thus, indicating
that they correspond to open photomerocyanines.
Due to symmetry of phenyl groups, only two transoid isomers of the
photomerocyanine are expected, the TC (Transoid-Cis) and the TT
(Transoid-Trans) (Scheme 3).
As two pairs of fluorine resonances are detected, they are straight-
forwardly assigned to both transoid photomerocyanines. In these open
structures, phenyl groups are no longer equivalent due to the hybridi-
zation sp2 of carbon C-2. To assign the exact isomery of each photopro-
duct, 2D NMR experiments have been performed.
Structural Identification of Open Photomerocyanines
1H-1H Cosy experiment of CF-1 after irradiation (Fig. 2) underlines
scalar correlations between the doublet signal at 9.6 ppm and a doub-
let in the overlapping part at 6.90 ppm (3J ¼ 12.1 Hz), and between

Synthesis and Photochromic Behavior
181=[481]
SCHEME 3 Photochromic equilibrium.
two signals at 6.00 and 6.89 ppm. 1H-1H Roesy experiment (Fig. 3)
makes it possible to differentiate the two singlet resonances at 6.03
and 6.34 ppm. Indeed, only the first present a dipolar effect with the
N-methyl group, thus being assigned to proton H-11. The other, deduc-
ing to correspond to proton H-5, shows effectively spatial proximity
with proton at 6.90 ppm, (H-4) and proton at 7.2 ppm (H-6). The pre-
vious cited doublet at 9.6 ppm is assigned to proton H-3, deshielded
=
due to the effect of C O, and a dipolar effect is measured with a doub-
let-doublet signal at 7.0 ppm, belonging to proton H-200. All these con-
firmations are in agreement with a Transoid-Cis structure (TC). The
second detected photoproduct, which has less intense resonances, is
deduced to be the Transoid-Trans isomer (TT). A scalar correlation
is observed between two doublet signals (3J ¼ 11.8 Hz) at 8.4 and
7.1 ppm. Such multiplicity and coupling constant value allow for
associating them to the protons H-4 and H-3, respectively.
Photomerocyanine TC-1. 1H NMR (300 MHz, toluene-d8): d 2.05
(3H, CH3), 6.0 (1H, H-9), 6.03 (1H, H-11), 6.34 (1H, H-5), 6.64 (2H,
H-30), 6.65 (2H, H-20), 6.78 (2H, H-300), 6.89 (1H, H-8), 6.90 (1H, H-
3
4), 7.00 (2H, H-200), 7.06 (1H, H-7), 7.2 (1H, H-6), 9.6 (1H, J3-4
¼
12.1 Hz, H-3). 13C NMR (75 MHz, toluene-d8): d 27.0 (CH3), 99.0

182=[482]
M. M. Oliveira et al.
FIGURE 2 2D-Cosy of CF-1 after UV irradiation.
(CH, C-11), 108.5 (CH, C-6), 115.8–115.9 (CH, C-30, C-30), 121.0 (CH,
C-8), 121.9 (CH, C-9), 124.5 (Cq, C-6a), 126.0 (CH, C-7), 127.5 (Cq, C-
4a), 128.0 (CH, C-5), 128.5 (CH, C-3), 131.8 (CH, C-200), 132.0 (Cq, C-
5a), 133.7 (CH, C20), 135.0 (Cq, C-2), 138.1–132.2 (Cq, C-10-C-100),
146.8 (Cq, C-9a), 149.5 (CH, C-4), 154.5 (Cq, C-10a), 162.0 (Cq, C-40-
C-400), 184.5 (Cq, C1-a).

Synthesis and Photochromic Behavior
183=[483]
FIGURE 3 2D-Roesy of CF-1 after UV irradiation.
Photomerocyanine TC-2. 1H NMR (300 MHz, toluene-d8): d 1.8 (3H,
CH3), 5.86 (1H, H-11), 6.16 (1H, H-5), 6.33 (1H, H-9), 6.61 (2H, H-20),
6.62 (2H, H-30), 6.67 (1H, H-6), 6.76 (2H, H-300), 6.92 (1H, H-7), 6.95
3
(1H, H-4), 7.06 (2H, H-200), 9.48 (1H, J3-4 ¼ 12.1 Hz, H-3). 13C NMR
(75 MHz, toluene-d8): d 26.5 (CH3), 99.0 (CH, C-11), 112.0 (CH, C-9),
115.5 (CH, C-30, C-300), 122.0 (CH, C-6), 123.5 (CH, C-7), 128.0 (CH,

184=[484]
M. M. Oliveira et al.
C-5), 128.5 (CH, C-3), 131.5 (CH, C-200), 133.5 (CH, C20), 150.0 (CH,
C-4), 162.0 (Cq, C-40-C-400), 184.2 (Cq, C1-a).
Photomerocyanine TT-2. 1H NMR (300 MHz, toluene-d8): d 1.78
(3H, CH3), 5.77 (1H, H-11), 6.29 (1H, H-9), 6.77 (1H, H-6), 6.79
(2H, H-200), 6.81 (2 þ 1H, H-20 þ H-7), 7.08 (1H, H-3), 7.39 (1H, H-5),
3
8.40 (1H, J4-3 ¼ 12.6 Hz, H-4). 13C NMR (75 MHz, toluene-d8): d
26.5 (CH3), 99.0 (CH, C-11), 112.0 (CH, C-9), 118.8 (CH, C-5), 122.0
(CH, C-6), 123.5 (CH, C-7), 129.7 (CH, C-3), 131.5 (CH, C-200), 133.5
(CH, C20), 144.0 (CH, C-4).
Thermal Evolution of Open Photomerocyanines
1H and 19F NMR spectra of CF-1 were recorded at regular time-
intervals after UV irradiation at low temperature (218, 223 and
228 K). By integrating characteristic resonances in CF-1, TC-1 and
TT-1, the time-evolution curves have been plotted. The TC-1 isomer
follows monoexponential decay to return to the initial closed form
(Fig. 4), while TT-1, which is in a very low concentration, presents
no significant variation during the experiment. From Arrhenius equa-
tion, activation energy of the thermal ring-closure of TC-1 into CF-1
FIGURE 4 Thermal evolution of TC-1.

Synthesis and Photochromic Behavior
185=[485]
has been deduced to be equal to 65 kJ.molꢀ1. This value is in complete
agreement with those generally reported.
CONCLUSION
UV-Visible spectroscopy and NMR measurements have pointed out
the formation of the two transoid isomers of photomerocyanines, TC
and TT. The spectrokinetic parameters and the structural assignment
have been obtained, indicating that these two spectroscopies are comp-
lementary: UV owing to its high sensitivity and time-resolution,
and NMR owing to its structural identification, and the possibility of
following the evolution of each form separately.
REFERENCES
[1] Becker, R. S. & Michl, J. (1966). J. Am. Chem. Soc., 88, 5931.
[2] Van Gemert, B. (1999). Organic Photochromic and Thermodynamic Compounds.
J. C. Crano, R. J. Guglielmetti (Eds.), Volume 1, Chapter 3, p. 111, Plenum Press:
New York.
[3] Crano, J. C., Flood, T., Knowles, D., Kumar, A., & Van Gemert, B. (1996). Pure
Appl. Chem., 68, 1395.
[4] Becker, R. S. (1971). US Patent 3–567–605.
[5] Van Gemert, B. & Bergomi, B. (1991). US Patent 5–066–818.
[6] Van Gemert, B., Bergomi, B., & Knowles, D. (1994). Mol. Cryst. Liq. Cryst., 246, 67.
[7] Kumar, A. (1997). Mol. Cryst. Liq. Cryst., 297, 139.
[8] Kumar, A., Van Gemert, B., & Knowles, D. (2000). Mol. Cryst. Liq. Cryst., 344, 217.
[9] Oliveira, M. M., Carvalho, L., Moustrou, C., Samat, A., Guglielmetti, R., & Oliveira-
Campos, A. M. F. (2001). Helv. Chim. Acta., 84, 1163.
[10] Meyer, J. J., Levoir, P., & Dubest, R. (1995). Analyst, 120, 447.
[11] Pottier, E., Dubest, R., Guglielmetti, R., Tardieu, P., Kellmann, A., Tfibel, F.,
Levoir, P., & Aubard, J. (1990). Helv. Chim. Acta, 70, 303.
[12] Patrick, D., Boykin, D. W., Wilson, W. D., Tanious, F. A., Spychala, J., Bender, B. C.,
Hall, J. E., Dykstra, C. C., Ohemeng, K. A., Tidwell, R. R. (1997). Eur. J. Med.
Chem., 32, 781.
[13] Gabbutt, C. D., Heron, B. Mark, Instone, A., Thomas, D. A., Partington, S. M.,
Hursthouse, M. B., & Gelbrich, T. (2003). Eur. J. Org. Chem., 1220.
[14] Sartori, G., Casiraghi, G., Bolzoni, L., & Casnati, G. (1979). J. Org. Chem., 44, 803.
[15] Oliveira-Campos, A. M. F., Oliveira, M. M., Carvalho, L., Moustrou, C., Samat, A.,
Guglielmetti, R., & Seita, J. (1999). Colour Science 98 Proceedings, vol.1, ‘‘Dye and
Pigment Chem.’’, Leeds, 26.
[16] Arnall-Culliford, J. C., Teral, Y., Sgarabotto, P., Campredon, M. & Giusti, G. (2003).
J. Photochem. & Photobiol. A: Chem., 159, 7.
´
´
´
[17] Teral, Y. (2001). PhD Thesis, Universite de la Mediterranee, Marseille Luminy,
France.
[18] Pozzo, J.-L., Lokshin, V., Samat, A., Guglielmetti, R., Dubest, R., & Aubard, J.
(1998). J. Photochem. & Photobiol. A: Chem., 114, 185.