Published on the web May 26, 2012
625
Synthesis and Properties of Novel i- and g-Line Sensitive Photoacid Generators Based
on 9-Fluorenone Derivatives with Aryl-Ethynyl Units
Shintaro Kodama, Haruyuki Okamura, and Masamitsu Shirai*
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University,
1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531
(Received March 22, 2012; CL-120252; E-mail: mshirai@chem.osakafu-u.ac.jp)
Imino sulfonate photoacid generators (PAGs) sensitive to
i- and g-line were synthesized using 9-fluorenone derivatives
Ar1 =
Ar2
=
with aryl-ethynyl units as starting materials. The PAGs
exhibited good thermal stability and photoreactivity at 365
(i-line) and 436 nm (g-line) compared with that of an imino
sulfonate PAG synthesized from unfunctionalized 9-fluorenone.
R
S
O
R
S
O
CF3
O S O
O
N
O
O
O
N
O
N
Ar1
1a (R = CF3)
Ar2
Photoacid generators (PAGs) play an important role in many
fields such as photoinduced acid-catalyzed polymerization
systems (photoinduced curing systems) and photoresists.1 PAGs
sensitive to 365 nm light (i-line) or 436 nm light (g-line) have
been getting much attention recently, because of their applica-
tion to UV curing and chemically amplified photoresists for
i- and g-line lithography.2 However, practical i- and g-line
sensitive PAGs are still limited, and therefore, much effort has
been devoted for the development of new i- and g-line sensitive
PAGs by ourselves and other groups.2a,3 Among i- and g-line
sensitive PAGs, nonionic PAGs have received attention, because
of their better solubility in organic solvents and polymer films
compared with that of ionic PAGs.4 In addition, PAGs with an
ability to generate superstrong acids such as CF3SO3H or
C4F9SO3H have been desirable for the application of highly
photosensitive resists. We reported the synthesis of 9-fluorenyl-
ideneimino trifluoromethanesulfonate (FITf).3q Although FITf
was sensitive to i-line, the molar extinction coefficients (¾) of
FITf at 365 nm was relatively low, and FITf was not thermally
stable. After the investigation of the synthetic methods of the
new PAGs, we successfully found an entry of i- and g-line
sensitive imino sulfonate PAGs 1a, 1b, 2a, and 2b (Figure 1)
obtained using 9-fluorenone derivatives with aryl-ethynyl units
as starting materials.
FITf
2a (R = CF3)
2b (R = C4F9)
1b(R = C4F9)
Figure 1. Structures of PAGs 1a, 1b, 2a, 2b, and FITf.
Ar1
(1.1 equiv)
[PdCl2(PPh3)2] (1 mol%)
PPh3 (8 mol%)
CuI (3 mol%)
O
O
Ar1
OH
Br
Et3N, THF, 60 °C, 19 h
3, 83%
N
NH2OH . HCl (2.7 equiv)
EtOH, H2O, reflux, 19 h
Ar1
4, 90%
Ar1 =
O
O
(1.2 equiv)
F3C S O S CF3
O
O
2,6-lutidine (1.5 equiv)
1a, 45%
1b, 72%
toluene, -30 °C, 1 h
then, 0 °C, 3 h
O
O
4
(1.2 equiv)
Here we report the synthesis of the PAGs 1a, 1b, 2a, and 2b
and the photochemical properties of the PAGs.
F9C4 S O S C4F9
O
O
2,6-lutidine (1.5 equiv)
Synthesis of PAGs 1a and 1b was performed as shown in
Scheme 1. A 9-fluorenone derivative 3 was synthesized by the
Sonogashira coupling reaction of arylacetylene derivatives and
2-bromo-9-fluorenone. Next, an oxime derivative 4 was obtained
by the reaction of 3 with hydroxylamine hydrochloride,
followed by esterification of 4 using trifluoromethanesulfonic
anhydride to afford 1a. Synthesis of 1b was also achieved by
the reaction of 4 with nonafluorobutanesulfonic anhydride. In
addition, PAGs 2a and 2b were obtained by a similar synthetic
procedure as shown in Scheme 2.
Characteristics of the PAGs are shown in Table 1. The
thermal decomposition temperatures of 1a, 1b, 2a, and 2b (158-
187 °C) were higher than that of FITf (135 °C). The PAGs 1a,
1b, 2a, and 2b exhibited high molar absorptivity at 365 nm
(i-line). Especially, the ¾ values at i-line of 2a and 2b were about
sixty times larger than that of FITf. Furthermore, the PAGs 1a,
toluene, -30 °C, 1 h
then, 0 °C, 3 h
Scheme 1. Synthesis of PAGs 1a and 1b.
1b, 2a, and 2b showed a strong absorption at 436 nm (g-line).
Thus, the PAGs 1a, 1b, 2a, and 2b can work not only as i-line
sensitive PAGs but also as g-line sensitive PAGs.
Photolysis of PAGs 1a, 1b, 2a, and 2b was examined in
acetonitrile. The UV spectral changes of 1a and 2a on irradiation
at 365 nm are shown in Figure 2. In the case of 1a, the
absorption band at 290 nm decreased on irradiation. The spectral
change in photolysis of 2a was also observed, and the
absorbance at 310 nm decreased. The photolysis of PAGs 1b
and 2b was also investigated, and similar spectral changes were
Chem. Lett. 2012, 41, 625-627
© 2012 The Chemical Society of Japan