Full Paper
etry (HRMS) analyses were performed on a JEOL JMS-700 mass
spectrometer. Separative HPLC was performed on a JASCO LC-
2
000 Plus Series. Quantum yields were measured with QYM-01
[47]
photoreaction quantum yield evaluation system (l=313 nm).
Absorption and fluorescence spectra in solution were studied with
a JASCO V-670 and JASCO FP-6500 spectrophotometers, respec-
tively. DFT calculations were performed with Gaussian 09 at the
wB97XD/6–31(d) level. Conformational search with the MMFF94s
force field was performed on the CONFLEX program (CONFLEX
Corp.). Thermogravimetric analysis was carried out using a Shimad-
zu DTG-60. SEM images were taken with a Hitachi TM 3030. Fluo-
rescence microscopic measurements were performed with an
Olympus BX-51 optical microscope.
Synthesis
4
3
-(3-Bromobenzo[b]thiophen-2-yl)-2-phenylthiazole
00 mL four-necked flask was charged with 2,3-dibromobenzo[b]-
thiophene (1.9 g, 6.3 mmol), 2-phenyl-4-(4,4,5,5-tetramethyl-1,3,2-
dioxaborolan-2-yl)thiazole (1.8 g, 6.3 mmol), (0.19 g,
.73 mmol), 2mK PO solution (12 mL), and 1,4-dioxane (110 mL).
(6):
A
PPh3
Figure 5. a) SEM image of a photopattern fabricated by a chemically ampli-
fied photoresist system containing PAG-5. b) Fluorescent microscope image
of the film just before the development process.
0
3
4
Then Pd(PPh3)4 (0.548 g, 0.474 mmol) was added to the solution
under N flow and the mixture was stirred at 1008C for 24 h under
2
N atmosphere. The reaction mixture was extracted with ethyl ace-
2
ing the optimization of conditions may reveal the utility of
present PAGs in a chemically amplified photoresist system.
tate. The organic layer was dried with anhydrous MgSO . After the
4
solvent was evaporated, the crude product was purified with silica
gel column chromatography by using a mixture of hexane and
CHCl as an eluent to afford compound 4-(3-bromobenzo[b]thio-
3
1
Conclusions
phen-2-yl)-2-phenylthiazole (1.7 g, 72%) as colorless solid. H NMR
(
8
300 MHz, CDCl , TMS): d=7.47–7.51 (m, 5H), 7.81–7.87 (m, 2H),
.02–8.05 (m, 2H), 8.31 ppm (s, 1H).
3
We have demonstrated two levels of improvement of our
newly based PAG molecular systems, gaining insight into the
structural requirement to improve their photoefficiencies.
4
2
-(3-(2-Methoxy-5-phenylthiophen-3-yl)benzo[b]thiophen-2-yl)-
-phenylthiazole (Pre-PAG-1): Pre-PAG-1 was prepared according
1) Non-aromatic acid sources seem to be required if one would
to the same condition with the synthesis of compound 6 by using
keep high level of photosensitivity in solution. For the same
acid source, compare to our previous compound, replacing
one thiazolyl group by a thienyl one already brought about
2-(2-methoxy-5-phenylthiophen-3-yl)-4,4,5,5-tetramethyl-1,3,2-diox-
aborolane and 6. 0.70 g of Pre-PAG-1 was obtained in 68% yield.
1
H NMR (300 MHz, CDCl , TMS): d=3.84 (s, 3H), 7.13 (s, 2H), 7.35–
3
7
1
.38 (m, 5H), 7.44–7.46 (m, 3H), 7.55–7.60 (m, 3H), 7.87–7.90 (m,
H), 8.00–8.03 ppm (m, 2H).
+
10% of enhancement, pushing the QY value to 0.6 in tolu-
ene. 2) A higher level of improvement could be achieved in
changing the sequence of the heteroaromatic rings while
keeping each of them identical to our previous example. Plac-
ing the benzothiophene as side-aryl group increased the yield
to 0.7 in non-polar solvent. As a proof of principle, we demon-
strated that the most efficient PAG-5 could induce the acid-
catalyzed chemical amplification in a positive-tone resist film.
Furthermore, the photolysis of self-contained PAGs induced
the simultaneous formation of a fluorescent fused aromatic
polycycle, which could also report the formation of acid mole-
cule. Since the terarylene framework is prepared simply by
controlled Pd-catalyzed aryl–aryl cross-coupling reactions,
a combinatorial approach in regard to the type of aromatic
units as well as their connection sequences may lead to further
improvement in the photoacid generation efficiency.
Photoacid generators (PAG-1a–4a): PAG compounds 1a to 4a
were prepared from the identical precursor Pre-PAG-1 by using
the same method according to our previous work.
[30]
1
PAG-1a: Yield: 28 mg, 41%. H NMR (300 MHz, CDCl , TMS): d=
3
2
7
.63 (s, 3H), 7.18 (s, 2H), 7.39–7.45 (m, 8H), 7.58–7.63 (m, 3H),
.89–7.92 (m, 1H), 7.95–7.99 ppm (m, 2H); C NMR (75 MHz, CDCl3,
13
TMS): d=167.77, 149.21, 139.95, 139.37, 138.82, 136.65, 133.40,
133.19, 130.61, 129.34, 129.20, 128.58, 126.84, 125.79, 125.58,
125.20, 123.34, 122.61, 122.27, 115.81, 37.70 ppm; HRMS (ESI) m/z
+
+
calcd for C28
H19NO S
3
Na [M+Na] : 568.01455; found: 568.01514.
4
1
PAG-2a: Yield: 25 mg, 39%. H NMR (300 MHz, CDCl
, TMS): d=
3
1
.99 (s, 3H), 7.10 (s, 1H), 7.19 (s, 1H), 7.36–7.46 (m, 8H), 7.57–7.63
1
3
(
(
m, 3H), 7.89–7.92 (m, 1H), 7.99–8.02 ppm (m, 2H); C NMR
75 MHz, CDCl , TMS): d=167.56, 167.16, 149.64, 147.08, 140.38,
3
1
1
2
5
38.94, 136.82, 133.90, 133.20, 130.35, 129.10, 129.03, 127.79,
26.70, 125.44, 124.99, 124.57, 123.22, 122.36, 121.27, 115.15,
+
+
0.37 ppm; HRMS (ESI) m/z calcd for C H NO S Na [M+Na] :
29
19
2 3
32.04756; found: 532.04576.
Experimental Section
1
PAG-3a: Yield: 30 mg, 39%. H NMR (300 MHz, CDCl , TMS): d=
3
2
.07 (s, 3H), 6.70–6.73 (d, 2H), 6.88 (s, 1H), 7.06 (s, 1H), 7.28–7.48
General
(m, 11H), 7.56–7.59 (m, 2H), 7.78–7.81 (m, 1H), 7.98–8.01 ppm (m,
1
13
All compounds were characterized by H NMR (400 MHz) and
2H); C NMR (75 MHz, CDCl , TMS): d=166.98, 149.25, 146.00,
145.53, 139.72, 139.09, 138.64, 136.06, 133.49, 133.26, 131.07,
130.53, 129.30, 129.20, 128.46, 127.95, 126.82, 126.26, 125.66,
3
1
3
C NMR (75 MHz) spectroscopy on JEOL JNM-ECP400 and JNM-
AL300 spectrometers, respectively. High-resolution mass spectrom-
&
&
Chem. Eur. J. 2016, 22, 1 – 9
6
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