Squarylium-Triazine Dyad
FULL PAPER
tiator (a squarylium dye/triazine combination or a triazine-linked squary-
lium dye), a polyfunctional acrylate monomer (pentaerythritol tetraacry-
actants places this compound as a very efficient dissociative
photoinitiator for free radical photopolymerization or as
phototrigger. This concept of visible light absorbing dye
linked to a dissociative electron acceptor open new opportu-
nities for the development of photoradical generators ab-
sorbing in the green–red region of the electromagnetic spec-
trum.
late) and
a
polymeric binder (polymethyl methacrylate MW =
35000 gmolꢀ1) were dissolved in a 16:1:1 (w/w/w) mixture of solvent
(methyl ethyl ketone/1-methoxy-2-propanol/THF), and the solution was
cast on a glass or on a polypropylene film by using a 24 mm RKprint K
Hand Coater. The solvent was evaporated by heating at 908C for 2 min.
The thickness of the film thus prepared was about 4 mm. Films were over-
coated by a polyvinyl alcohol film (MW =2000 gmolꢀ1) to prevent diffu-
sion of atmospheric oxygen.
The photosensitivity of the dyad were measured by Real-Time FTIR and
performed by using a 635 nm laser diode as an irradiation source with
the irradiance intensity at the surface of the sample adjusted to
10 mWcmꢀ2. The kinetics of the polymerization were measured by fol-
lowing the disappearance of the acrylic double bond at 1410 cmꢀ1. The
degree of acrylate double bond conversion (C) was calculated from the
decrease of the area of the IR absorption peak between 1402 and
1418 cmꢀ1 of the sample after exposure using the following Equation (6):
Experimental Section
Triazine-linked squarylium dyes S-n-T: Synthesis of linked compound S-
2-T and S-6-T was performed according to the general procedure[11,25,26]
shown in Scheme 2.
Synthesis of S-2-T:
(trichloromethyl)-1,3,5-triazin-2-yl]benzoate (2.00 g, 3.42 mmol) and 3-hy-
droxy-4[4-(N,N-dibutylanilino)]cyclobut-3-ene-1,2-dione (1.03 g,
A mixture of [2-(N-ethylanilino)ethyl] 4-[4,6-bis-
ACHTUNGTRENNUNG
C ð%Þ ¼ ðA0ꢀAtÞ=A0 ꢂ 100
ð6Þ
3.13 mmol) in dry 2-propanol/triethylorthoformate (20 mL, 5:1, v/v) was
heated at reflux for 5 h under nitrogen, under green light because of the
red sensibility of the product. The reaction was then stopped by addition
of a mixture of cyclohexane/ethyl acetate (60 mL, 5:1, v/v). The solvent
was evaporated, and the residue was purified by using column chroma-
tography (cyclohexane/ethyl acetate=1:1, v/v as eluent), to afford the
product as a green solid (0.703 g, 0.81 mmol, 26%). 1H NMR (CDCl3):
d=0.99 (t, J=7.2 Hz, 6H), 1.20–1.48 (m, 8H), 3.44 (t, J=7.5 Hz, 4H),
3.63 ( q, J=6.9 Hz, 2H), 3.90 (t, J=5.7 Hz, 2H), 4.61 (t, J=5.7 Hz, 2H),
6.72 (d, J=9.0 Hz, 2H), 6.86 (d, J=8.7 Hz, 2H), 8.16 (d, J=7.5 Hz, 2H),
8.37 (d, J=8.7 Hz, 4H), 8.75 ppm (d, J=7.5 Hz, 2H); HRMS: m/z calcd
for C40H40N5O4Cl6: 866.1181 [M+H+]; found: 866.1164.
in which A0 represent the initial peak area before irradiation and At rep-
resent the peak area of the acrylic double bond at time, t.[38]
Acknowledgements
The Cercle Gutenberg, Strasbourg is fully acknowledged for the Chaire
dꢂExcellence provided to K.K.
Synthesis of S-6-T: S-6-T was synthesized by following the above proce-
dure using [6-(N-ethylanilino)hexyl] 4-[4,6-bis(trichloromethyl)-1,3,5-tri-
ACHTUNGTRENNUNG
azin-2-yl]benzoate as a starting material. Yield: 25%; 1H NMR (CDCl3):
[1] X. Wang, S. Werner, T. Weiss, K. Liefeith, C. Hoffmann, RSC Adv.
d=0.99 (t, J=7.3 Hz, 6H), 1.31–1.90 (m, 19H), 3.43 (t, J=7.7 Hz, 6H),
3.52 ( q, J=7.1 Hz, 2H), 4.39 (t, 6.9 Hz, 2H), 6.69 (d, J=2.7 Hz, 2H),
6.73 (d, J=2.7 Hz, 2H), 8.24 (d, J=8.7 Hz, 2H), 8.34 (d, J=0.7 Hz, 2H),
8.37 (d, J=0.7 Hz, 2H), 8.77 ppm (d, J=8.7 Hz, 2H); HRMS: m/z calcd
for C44H48Cl6N5O4: 922.1808 [M+H+]; found: 922.1807.
[4] K. Dietliker, in A Compilation of Photoinitiators Commercially
Available for UV Today, SITA Technology Limited, 2002.
[6] C. G. Bochet, J. Chem. Soc. Perkin Trans. 1 2002, 125–142.
Methods: Absorbance spectra of solutions were recorded on a Cary 4000
UV-Visible Spectrophotometer (Varian) and absorbance spectra of films
were recorded on Agilent 8453E spectroscopy system (Agilent Technolo-
gies). HRMS were performed on Agilent Technologies Mass Spectrome-
ter Detector 6510 (MSD; Q-TOF, LC/Mass) in positive Electro Spray
Ionization (ESI) source mode. Monomer polymerization was monitored
by RT-FTIR spectroscopy using a Vertex 70 FTIR spectrometer (Bruker
Optik).[37]
ˇ
[7] P. Klꢃn, T. Solomek, C. G. Bochet, A. Blanc, R. Givens, M. Rubina,
[8] J. P. Fouassier, X. Allonas, J. Lalevꢄe, C. Dietlin, in Photochemistry
and Photophysics of Polymer Materials (Ed.: N. S. Allen), Wiley,
Hoboken, 2010, pp. 351–419.
[10] S. Yagi, H. Nakazumi, in Functional Dyes (Ed.: S.-H. Kim), Elsevier,
Amsterdam, 2006, p.215.
[12] S. Yagi, Y. Hyodo, S. Matsumoto, N. Takahashi, H. Kono, H. Naka-
A FluoroMax-4 (Horiba, Jobin–Yvon) spectrofluorometer coupled with a
TCSPC accessory was used to measure steady-state fluorescence spectra
and fluorescence decays. A 607 nm NanoLEDs (duration 1.7 ns) was
used as pulsed excitation source leading to a time resolution, after decon-
volution, of around 200 ps.
Femtosecond time-resolved transient absorption experiments were per-
formed by using Excipro pump-probe apparatus (CDP corp). Femtosec-
ond laser excitation wavelength was adjusted to 610 nm by mean of col-
linear 800 nm pumped CDP2017 (CDP corp) optical parametric amplifi-
er. The 100 fs laser pulses (800 nm) were provided by a Spectra-Physics
Tsunami Ti:Sa oscillator coupled to a Spitfire pro Spectra-physics regen-
erative amplifier. The resulting pump-probe cross-correlation of the
setup was found to be about 200 fs.
[13] C. Prabhakar, K. Bhanuprakash, V. J. Rao, M. Balamuralikrishna,
[16] N. A. Davidenko, Y. P. Get’manchuk, E. V. Mokrinskaya, L. N. Gu-
menyuk, V. A. Pavlov, N. G. Chuprina, N. N. Kuranda, S. V. Khutor-
nyi, A. A. Ishchenko, N. A. Derevenko, A. V. Kulinich, V. V. Kur-
[17] H. Yong, W. Zhou, G. Liu, L. M. Zhen, E. Wang, J. Photopolym.
Sci. Technol. 2000, 13, 253.
UV-grade acetonitrile was purchased from Fluka and UV-grade ethyl
acetate, dichloromethane, chloroform were purchased from Aldrich. An-
other solvents and chemicals were of reagent grade quality and used
without further purification. Pentaerythritol tetraacrylate (PETTA,
SR295) was supplied by Sartomer and used as received.
Films for the measurement of photophysical behavior and photopolyme-
rization were typically prepared in the following manner. The photoini-
[19] S. Noppakundilograt, N. Miyagawa, S. Takahara, T. Yamaoka, J.
Chem. Eur. J. 2013, 19, 12853 – 12858
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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