1-Acetylferroceneoxime-based photoacid generators: Application towards sol-gel transformation and development of photoresponsive polymer for controlled wettability and patterned surfaces

Article abstract of DOI:10.1039/c4tc00203b

A newsworthy class of carboxylate and sulfonate esters of 1-acetylferroceneoxime has been demonstrated as non-ionic photoacid generators (PAGs). PAGs based on 1-acetylferroceneoxime were synthesized in good yields by simple treatment of 1-acetylferroceneoxime with various carboxylic and sulfonyl chlorides. Newly developed PAGs of 1-acetylferroceneoxime showed good absorbance >350 nm. On irradiation using UV light (≥365 nm), carboxylates and sulfonates of 1-acetyl ferroceneoxime in aqueous acetonitrile solvent underwent efficient homolytic cleavage of N-O bond, resulting in the generation of carboxylic and sulphonic acids, respectively, with high chemical and good quantum yields. Further, we demonstrated the application of our newly developed 1-acetylferroceneoxime-based PAGs for gelation of biopolymer alginate on UV irradiation. More interestingly, we synthesized a ferroceneoxime bound photoresponsive polymer, 1-acetylferroceneoxime-polycaprolactone (AFO-PCL), and demonstrated its controlled surface wettability and generation of patterned surfaces.

Full text of DOI:10.1039/c4tc00203b

Journal of
Materials Chemistry C
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PAPER
1-Acetylferroceneoxime-based photoacid
generators: application towards sol–gel
transformation and development of
photoresponsive polymer for controlled wettability
and patterned surfaces†
Cite this: J. Mater. Chem. C, 2014, 2,
622
4
Mohammed Ikbal, Rakesh Banerjee, Shrabani Barman, Sanghamitra Atta,
Dibakar Dhara* and N. D. Pradeep Singh*
A newsworthy class of carboxylate and sulfonate esters of 1-acetylferroceneoxime has been demonstrated
as non-ionic photoacid generators (PAGs). PAGs based on 1-acetylferroceneoxime were synthesized in
good yields by simple treatment of 1-acetylferroceneoxime with various carboxylic and sulfonyl
chlorides. Newly developed PAGs of 1-acetylferroceneoxime showed good absorbance >350 nm. On
irradiation using UV light ($365 nm), carboxylates and sulfonates of 1-acetyl ferroceneoxime in aqueous
acetonitrile solvent underwent efficient homolytic cleavage of N–O bond, resulting in the generation of
carboxylic and sulphonic acids, respectively, with high chemical and good quantum yields. Further, we
demonstrated the application of our newly developed 1-acetylferroceneoxime-based PAGs for gelation
of biopolymer alginate on UV irradiation. More interestingly, we synthesized a ferroceneoxime bound
photoresponsive polymer, 1-acetylferroceneoxime-polycaprolactone (AFO-PCL), and demonstrated its
controlled surface wettability and generation of patterned surfaces.
Received 30th January 2014
Accepted 2nd April 2014
DOI: 10.1039/c4tc00203b
www.rsc.org/MaterialsC
8
chemical modication, and reaction diversity. Though organic
materials have the above advantages, they lack the intrinsic
Introduction
Recently, application of external stimuli, such as light, solvent, properties possessed by inorganic materials such as good
pH, or an electric eld, for tuning surface properties has chemical and mechanical stability, low cost, and outstanding
1
9
captured great attention. In comparison to other external photo/electro-properties. Hence, photoresponsive organic–
stimuli, light offers excellent spatial and temporal control over inorganic hybrid materials exhibiting both inorganic and
2
10
the energy input required for tuning surface properties. Hence, organic properties were developed.
Generally, photo-
several photoresponsive materials were developed and their responsive hybrid materials are bicomponent systems, and they
surface properties such as wetting behavior, adhesion, and are prepared by combining both organic and inorganic building
11
adsorption were demonstrated to be easily tuned by external blocks. The major concern with the bicomponent system is
3
stimulus light.
loading inefficiency of inorganic material on organic compo-
In particular, the design of photoresponsive materials with nent or vice versa. By any means if we can develop photo-
controlled wettability has become as an exciting topic from the responsive compounds containing both inorganic and organic
viewpoint of both fundamental scientic theory and practical nature, then we can eliminate the above loading inefficiency.
4
applications. Several research groups have developed photo-
Ferrocene, namely cyclopentadienyl iron with the chemical
3
responsive materials with controlled wettability by using formula of Fe(C
everything from inorganic nanomaterials to small organic organometallic building blocks. It is of considerable interest in
molecules and photoactive polymers. In comparison with various areas, like asymmetric catalysis, non-linear optics
inorganic materials, organic materials have many advantages in and electrochemistry due to the quasi-reversible oxidation of
terms of the number of adaptable species, the capability of iron II. In addition, ferrocene photochemical behaviour has also
H ) , is one of the most studied and versatile
5 5 2
5
6
7
12
13
14
15
16
been well studied. Although they are oen photochemically
inert, ferrocene and ferrocenyl derivatives undergo chemical
Department of Chemistry, Indian Institute of Technology Kharagpur,
Kharagpur-721302, India. E-mail: dibakar@chem.iitkgp.ernet.in; ndpradeep@
yahoo.co.in; Fax: +91-3222-282252; Tel: +91-3222-282324
17
modications in the presence of light. They are also used as
18
excited state quenchers or photosensitizers. Moreover, a
ferrocene moiety also provides the capability of chemical
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c4tc00203b
19
modication and reaction diversity. Inspired by the ability of
1
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ferrocenyl derivatives to exhibit both inorganic and organic
In the present study, we have described the synthesis and
properties, we were prompted to design single component characterization of 1-acetylferroceneoxime-based PAGs. We
photoresponsive materials based on a ferrocene moiety. examined the acid generation ability of PAGs by irradiating with
We have recently become interested in imparting photo- UV light above 365 nm and demonstrated the application of the
responsiveness to materials using a photoacid generator (PAG). acid generation ability of PAGs in sol–gel transformation of the
PAGs are commercially available molecules that have been used biopolymer alginate. Further, we constructed the photo-
20
for a long time in the microelectronics industry. Their responsive polymer acetylferroceneoxime-polycaprolactone
distinctive property is that they get photolyzed by UV light to (AFO-PCL) using ring-opening polymerization (ROP). Moreover,
form an acidic moiety. Accordingly, we have constructed pho- we also investigated the photoresponsive behaviour of the above
toresponsive materials by imparting PAGs like 1-hydroxy-2(1H)- synthesized polymer in terms of controlled wettability and
21
22
quinolone
and N-hydroxyanthracene-1,9-dicarboxyimide.
generation of patterned surfaces.
Further, we also demonstrated the switchable wettability
behavior of the above photoresponsive materials with a large
change in contact angle (CA) from hydrophobic to hydrophilic.
Hence, we thought to design for the rst time new PAGs based Results and discussion
on 1-acetylferroceneoxime and use them in the construction of
photoresponsive materials.
Carboxylates and sulfonates of (E)-1-acetylferroceneoxime as
PAGs
Synthesis of PAGs (3a–d and 4a–d). 1-Acetylferroceneoxime
2) was initially prepared by condensation of 1-acetylferrocene
(
(
Table 1 Reaction time and synthetic yield of PAGs (3a–d and 4a–d)
23
1) with hydroxylamine hydrochloride in ethanol at reux
24
condition. Later, treatment of 2 with various acid chlorides
a
PAGs
Acid chloride
Reaction time (h)
Yield (%)
and sulfonyl chlorides in the presence of 2 equiv. triethylamine
ꢀ
3
3
3
3
4
4
4
4
a
b
c
d
a
b
c
CH
2
]CHCOCl
COCl
p-MeC COCl
p-MeOC COCl
CH SO Cl
SO Cl
P(CH ]CH)C
2,4(df)C SO
15
12
12
15
15
18
18
18
82
80
84
85
80
81
80
75
in dry DCM at 0 C for a period of 12–18 h afforded corre-
C
6
H
5
sponding carboxylates (3a–d) and sulfonates (4a–d), with good
yields (75–85%, Table 1) (Scheme 1). All the carboxylates and
6
H
4
6
H
4
1
13
sulfonates were puried and characterized by H, C NMR, IR
and mass spectral analysis.
3
2
C
6
H
5
2
H
4
SO
2
Cl
UV-vis study of PAGs (3a–d and 4a–d). UV-vis absorption of 1
2
6
ꢂ4
d
6
H
3
2
Cl
ꢁ 10 M solution of PAGs (3a–d and 4a–d) (carboxylate and
a
sulfonate esters) was recorded in methanol and their corre-
sponding UV-vis spectra are shown in Fig. 1a and 1b. The
Based on isolated yield.
ꢀ
Scheme 1 Synthesis of PAGs (3a–d) and (4a–d). Reagents and conditions: (i) NH
2
OH.HCl, EtOH, reflux, (ii) and (iii) Et
3
N, 0 C-rt, dry DCM, 12–18 h.
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Fig. 1 (a) UV-vis absorption spectra of carboxylate esters (3a–d). (b) UV-vis absorption spectra of sulfonate esters (4a–c).
Table 2 UV-vis absorption data of PAGs (3a–d and 4a–d)
Table 3 Photolysis of PAGs (3d) in various solvents
a
b
UV-vis absorption
Solvent system
% of acid generated
Quantum yield (F
p
)
a
b
PAGs
l
max (nm)
log 3
MeOH
ACNc
80
65
—
—
—
90
80
0.074
0.060
—
—
—
3
3
3
3
4
4
4
4
a
b
c
d
a
b
c
320
325
330
328
327
328
329
329
3.20
3.39
3.57
3.04
3.75
3.64
3.79
3.77
THF
c
CHCl
3
c
Benzene
MeOH–H O (95 : 1)
ACN–H O (95 : 1)
2
2
0.083
0.074
a
b
Photolysis yield based on HPLC. Quantum yield for the generation of
c
p-anisic acid at room temperature (error limit within ꢃ5%). Polymeric
d
products were observed.
a
b
Maximum absorption wavelength. Molar absorption coefficient.
esters of 1-acetylferroceneoxime (3a–d and 4a–d) in MeOH–H
95 : 1) using UV light ($365 nm) as shown in Scheme 2.
We found that all the PAGs generated their corresponding
acids (5a–d and 6a–d) and 1-acetylferrocene (1) in nearly
quantitative yield as tabulated in Table 4. In each case, the
photolysis was stopped when conversion reached at least 90%
2
O
(
absorption maxima and molar absorptivities of the above esters
are summarized in Table 2.
The UV-vis absorption data showed that all the carboxylate
and sulfonate esters exhibited good UV absorption near 350 nm,
indicating that the photolysis can be carried out using UV light
above 350 nm.
(
(
as indicated by HPLC). For all the esters, their photoproducts
carboxylic or sulfonic acid and 1-acetylferrocene) were isolated
1
Solvent effect on the photogeneration of acid by PAG (3d). To
identify the right solvent required for the effective generation of
acids from their corresponding PAGs, we carried out photolysis
and characterized by H NMR spectra and compared with their
corresponding authentic samples. Quantum yields for the
generation of various carboxylic and sulfonic acids were found
to be in the range of 0.097 to 0.051 using valerophenone as an
ꢂ4
of 3d (1.0 ꢁ 10 M) in various solvents including methanol
25
(MeOH), acetonitrile (ACN), tetrahydrofuran (THF), chloroform
actinometer.
(
CHCl ), benzene, MeOH–H O (95 : 1) and ACN–H O (95 : 1) for
3 2 2
As a representative example, we have represented the UV-vis
absorption (Fig. 2) spectra of carboxylate ester 3d at regular
intervals of irradiation time.
7
0 min under UV light ($365 nm) by 125 W medium pressure
solution in 0.1 N
), and the results are tabulated in Table 3. We found
carboxylate (3d) generated p-anisic acid in relatively high
quantum and chemical yield in MeOH–H O (95 : 1) compared
to other solvents used for the study. In other solvents such as
Hg lamp using a suitable lter (1 M CuSO
SO
4
H
2
4
Mechanism for the photogeneration of carboxylic and
sulfonic acids
2
THF, CHCl3 and benzene, polymeric products were also Based on the mechanistic studies as reported by Scaiano and
27
28
observed.
his coworkers and Shirai et al. for the photolysis of oxime
Photolysis of PAGs (3a–d and 4a–d). Based on the above sulfonates and from our solvent investigation, we proposed the
solvent study, we photolysed the carboxylate and sulfonate possible mechanism for the photogeneration of acids. On
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Scheme 2 Photogeneration of acids (5a–d or 6a–d) by PAGs.
Table 4 Photolysis data of the carboxylate and sulfonate esters of (E)-
1
-acetylferroceneoxime (3a–d and 4a–d)
Photogeneration of acids
Time of
photolysis (min)
Quantum
yield (F )
p
a
b
c
PAGs
Yield (A–OH)
3
3
3
3
4
4
4
4
a
b
c
d
a
b
c
100
85
80
70
80
60
70
75
80
80
85
90
85
90
82
80
0.051
0.060
0.068
0.083
0.068
0.097
0.075
0.071
d
a
b
1
c
Photolysis time. Photolysis yield based on H NMR. Quantum yield
for the generation of various acids at room temperature (error limit Scheme 3 Mechanism for the photogeneration of acids.
within ꢃ5%). The literature reported quantum yields for
26
naphthalimide photoacid generators is ꢄ0.18–0.20.
atom from the solvent to produce the corresponding carboxylic
or sulfonic acid (5a–d or 6a–d) and 1-acetylferrocene (1).
Aer successful demonstration of carboxylate and sulfonate
esters of 1-acetylferroceneoxime as PAGs, we focused our
attention on the application of the PAGs.
Application of PAGs based on 1-acetylferroceneoxime towards
sol–gel transformation and development of photoresponsive
polymer surfaces for controlled wettability
Application of PAGs based on 1-acetylferroceneoxime for
sol–gel transition. To investigate the ability of our newly
developed PAGs in sol–gel transition, we carried out photogel-
ling of well-known biopolymer alginate as described by
29
Raghavan et al. We prepared a sample of 2 wt% sodium algi-
nate, 30 mM solubilized PAG in minimum amount of DMSO
(
4a), and 15 mM dispersed CaCO particles. Using sonication,
3
ꢂ4
Fig. 2 UV-vis of 3d (1.0 ꢁ 10 M) at regular intervals of irradiation these particles were homogeneously dispersed in the polymer
2
time in MeOH–H O.
solution. We did not observe any type of aggregation or settling
of the particles over a period of several hours aer sonication.
As shown in Fig. 3, the initial mixture is a low-viscosity sol. Aer
exposure to UV light for 30 min, the PAG gets photolyzed,
generating sulphonic acid. The generated sulphonic acid reacts
excitation, both the carboxylates and sulfonates of 1-ace-
tylferroceneoxime (3a–d and 4a–d) undergo homolytic N–O
bond cleavage from the singlet excited state to generate an
iminyl and acyloxy or sulfonyl radical pair (Scheme 3). The
above generated radical pair in aqueous polar protic solvent
escapes from the cage and subsequently abstracts a hydrogen
2
+
with the insoluble CaCO particles to produce free Ca ions,
3
which cross-link the alginate chains into a gel network. The
resulting alginate gel was found to be good enough to hold its
weight in the inverted vial (Fig. 3).
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Fig. 3 Schematic and visual depiction of UV-induced alginate pho-
togelation. Sodium alginate (2 wt%) is combined with 15 mM of CaCO
3
particles (insoluble) and 30 mM of a photoacid generator (PAG) (a)
before photolysis (b) after photolysis.
Fig. 4 GPC data of copolymer AFO-PCL (8).
Development of photoresponsive polymer surfaces using PAG
based on 1-acetylferroceneoxime for controlled wettability
(
E)-1-Acetylferroceneoxime based polymer 1-acetylferroce-
neoxime-polycaprolactone (AFO-PCL)] as photoacid generators
for carboxylic acid. The copolymer AFO-PCL (8) was synthesized
by the reaction of (E)-1-acetylferroceneoxime (2) with x-capro-
lactone (7) in presence of Sn(Oct)2 as catalyst using ring-
30
opening polymerization (ROP) technique
Scheme 4.
as shown in
Scheme 5 Photogeneration of acid from polymer film.
Characterization of the copolymer AFO-PCL (8)
The photolysis of the polymer was monitored by IR spectral
The molecular weight and polydispersity of the polymer (8) were study at different time interval (see ESI, Fig. S1†).We noticed the
ꢂ1
recorded by gel permeation chromatography (GPC). GPC (Fig. 4) peak at 1780 cm (n]CO) due to carbonyl group decreased on
was carried out at ambient temperature using a Viscotek-GPC irradiation, indicated the photodecomposition of the polymer.
system equipped with two GMH HR-H nonpolar organic On the other hand, the generation of 9 was conrmed by acid-
31
columns in series. Tetrahydrofuran was used as an eluent at a catalyzed polysiloxane formation technique. FT-IR spectra
ꢂ1

ow rate of 1 mL min . Polystyrene standards in the M
n
range (Fig. S2†) showed changes of irradiated lm before and aer
of 955–3 715 000 was used for calibrations.
treatment with methyltriethoxysilane (MTEOS). The appearance
3
of new peaks at 780 (Si–CH ), 900 (Si–OH), 1000–1200 (Si–O–Si)
and 3200–3500 (Si–OH) on irradiation of lm showed the
formation of silanol, obtained on hydrolysation of MTEOS
under humid conditions by newly generated acid.
Photogeneration of acid by copolymer AFO-PCL (8)
To investigate the polymer (8) as PAG, it was spin coated onto a
glass slide. The polymer lm was then baked at 90 C for a few
ꢀ
min in a hot oven. Irradiation of the polymer thin lms at $365
nm by the use of 125 W medium pressure Hg lamp at room
temperature resulted in homolytic cleavage of N–O bond,
leading to the generation of acid (Scheme 5).
Investigation of surface photoreactions
32
To investigate the photoresponsive surface property of our
synthesized polymer, we prepared thin polymeric surfaces on
the glass wafer and measured the water contact angle (CA). The
ꢀ
surface showed a water-contact angle of CA z 145 before UV
irradiation, indicating that the surface is hydrophobic in nature
(
Fig. 5).
33
The roughness and trapped air are responsible factors of
the polymer for the observed hydrophobicity (Fig. 6a), but the
surface loses its hydrophobicity and becomes hydrophilic in
nature upon direct UV light irradiation ($365 nm; Fig. 6b). Aer
irradiation, water droplets spread out on the surface, resulting
in a contact angle of z35 . On photolysis the polymer decom-
2
poses and generates polar –CO H.
Scheme 4 Synthesis of copolymer (E)-1-acetylferroceneoxime-pol-
ꢀ
ycaprolactone (AFO-PCL) (8). Reagents and conditions: dry tolune,
ꢀ
Sn(Oct)
2
, 100 C, 16 h.
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good quantum yields. More interestingly, we also synthesized a
ferroceneoxime-based photoresponsive polymer, namely, 1-
acetylferroceneoxime-polycaprolactone
(AFO-PCL),
and
demonstrated its surface wettability. Finally, we used our pho-
toresponsive polymer for the development of patterns on a glass
surface.
Experimental section
Chemicals and starting materials
Fig. 5 (a) Side view (b) and upper view of water droplet on the poly-
meric material before photolysis.
All starting materials, reagents, and solvents were obtained
from commercial sources and used without further purication
unless otherwise stated. All anhydrous reactions were per-
formed under a dry nitrogen atmosphere.
Methods and techniques
1
H NMR (200 MHz) spectra were recorded on a BRUKER-AC 200
MHz spectrometer. Chemical shis are reported in ppm from
tetramethylsilane with the solvent resonance as the internal
standard (deuterochloroform: 7.26 ppm). Data are reported as
follows: chemical shis, multiplicity (s ¼ singlet, d ¼ doublet, t
¼
triplet, q ¼ quartet, dd ¼ doublet of doublet, m ¼ multiplet),
Fig. 6 Water drop on (a) a hydrophobic surface before UV irradiation
and (b) a hydrophilic surface on UV irradiation.
13
coupling constant (Hz). C NMR (50 MHz) spectra were recor-
ded on a BRUKER-AC 200 MHz spectrometer with complete
proton decoupling. Chemical shis are reported in ppm from
tetramethylsilane with the solvent resonance as the internal
standard (deuterochloroform: 77.0 ppm). Chromatographic
purication was done with 60–120 mesh silica gels (Merck). For
reaction monitoring, precoated silica gel 60 F254 TLC sheets
(Merck) were used. UV-vis absorption spectra were recorded on
a Shimadzu UV-2450 UV/vis spectrophotometer. FT-IR spectra
were recorded on a Perkin Elmer RXI spectrometer. High-reso-
lution mass spectra (HRMS) were recorded using an LCT micro
mass spectrometer. HPLC was performed using Shimadzu
Prominence (LC 20 AT) liquid chromatography on a C18 column
Fig. 7 Photolithographic structuring methods using masked irradia-
tion and polymeric material.
(4.5 mm ꢁ 250 mm) with a UV/vis detector. Photolysis of all the
ester was carried out using 125 W medium pressure mercury
lamp supplied by SAIC (India).
Development of photopattern on the polymeric surface AFO-
PCL
General procedure for the synthesis of carboxylates of (E)-1-
acetylferrocene oxime
Finally, we created patterned lms using our photoresponsive
polymer AFO-PCL.
The patterning procedure is illustrated schematically in
Fig. 7. The polymer (AFO-PCL copolymer) layer was smeared on
the glass wafer (Fig. 7a). Aer exposing the polymer surface to
UV light ($365 nm) through a homemade photomask or stencil
To the dry DCM solution of 1-acetylferroceneoxime (0.15 g, 0.61
mmol), acid chloride (0.73 mmol) and Et
3
N (0.20 mL, 1.22
ꢀ
mmol) were slowly added at 0 C. The reaction mixture was
stirred for 12–15 h at room temperature. Aer the completion of
the reaction (as indicated by TLC), it was quenched by ice cold
water and diluted with DCM. The organic layer was separated
(Fig. 7b), the patterned was created (Fig. 7c).
and dried over Na
vacuum to yield crude carboxylate.
E)-1-[(Acryloxyimino)ethyl] ferrocene (3a). The dark red
crude product on purication by column chromatography (5%
2 4
SO , and the solvent was removed under
(
Conclusion
We have introduced for the rst time carboxylates and sulfo- ethyl acetate/hexane) resulted in the title compound 3a (0.18 g,
nates of 1-acetylferroceneoxime as nonionic photoacid genera- 82%) as a gummy solid; TLC R (20% ethyl acetate/hexane) 0.40;
f
ꢂ1
1
tors (PAGs). Irradiation of carboxylates and sulfonates of 1- FTIR (neat) ymax (cm ): 1743, 1654; H NMR (CDCl , 200 MHz)
3
acetylferroceneoxime in aqueous methanol at $365 nm results d: 2.33 (s, 3H), 4.24 (s, 5H), 4.44–4.45 (m, 2H), 4.74–4.75 (m, 2H),
in generation of corresponding carboxylic and sulfonic acids in 5.97 (d, 1H, J ¼ 10.4 Hz), 6.25–6.38 (m, 1H), 6.60 (d, 1H, J ¼ 10.4
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1
3
Hz); C NMR (CDCl
(
3
, 50 MHz) d: 14.8, 67.6 (2C) 69.5 (5C), 69.7
(E)-1-[(Benzenesulfonoxyimino)ethyl] ferrocene (4b). The
+
2C), 78.6, 126.7, 131.4, 163.6, 164.9 HRMS (ES ) calcd for dark brown crude solid sulfonate on purication by column
+
C H FeNO [M + H] 298.0525, found 298.0538.
chromatography (50% ethyl acetate/hexane) gave title
1
5
16
2
(
E)-1-[(Benzoyloxyimino)ethyl] ferrocene (3b). The crude compound 4b (0.19 g, 81%) as a deep brown colour gummy
ꢀ
carboxylate was puried by column chromatography (5% ethyl solid, mp: 120–125 C; TLC R (25% ethyl acetate/hexane) 0.45;
acetate/hexane) to yield the title compound 3b (0.17 g, 80%) as a FTIR (KBr) ymax (cm ): 1292, 1546; H NMR (CDCl , 400 MHz)
brown solid, mp: 59–62 C; TLC R
.45; FTIR (KBr) ymax (cm ): 1742, 1610; H NMR (CDCl
f
ꢂ1
1
3
ꢀ
f
(30% ethyl acetate/hexane) d: 2.75 (m, 3H), 4.25 (m, 5H), 4.63–4.64 (m, 2H), 4.83–4.84 (m,
ꢂ1
1
13
0
3
, 200 2H), 7.53–7.63 (m, 3H), 8.02–8.05 (m, 2H); C NMR (CDCl , 100
3
MHz) d: 2.38 (s, 3H), 4.21 (m, 5H), 4.41 (m, 2H), 4.74 (m, 2H), MHz) d: 21.9, 70.2 (2C), 70.5 (5C), 73.8 (2C), 80.6, 126.9 (2C),
1
3
+
7
.44–7.59 (m, 3H), 8.12 (d, 2H, J ¼ 7.0 Hz); C NMR (CDCl , 100 128.9 (2C), 132.5, 142.1, 185.5; HRMS (ES ) calcd for C H Fe-
3
18 18
+
MHz) d: 15.0, 67.7 (2C), 69.5 (5C), 70.6 (2C), 78.5, 128.4 (2C), NO S [M + H] 384.0351, found 384.0365.
29.3, 129.4 (2C), 133.0, 163.6, 165.2; HRMS (ES ) calcd for
C H18FeNO [M + H] 348.0681, found 348.0691.
19 2
3
+
1
(E)-1-[(p-Styrenesulfonoyloxyimino)ethyl] ferrocene (4c). The
crude product was puried by column chromatography (2%
+
(
E)-1-[4-(Methyl-benzoyloxyimino)ethyl] ferrocene (3c). The ethyl acetate/hexane) to yield the title compound 4c (0.81 g,
crude product was puried by column chromatography (5% 80%) as a gummy solid; TLC R (20% ethyl acetate/hexane) 0.45;
f
ꢂ1
1
ethyl acetate/hexane) to yield the title compound 3c (0.19 g, FTIR (KBr) ymax (cm ): 1298, 1517; H NMR (CDCl , 200 MHz)
3
ꢀ
8
4%) as a red solid, mp: 85–88 C; TLC R
f
(30% ethyl acetate/ d: 2.73 (s, 3H), 4.21 (m, 5H), 4.61–4.63 (m, 2H), 4.80–4.82 (m,
ꢂ1
1
hexane) 0.45; FTIR (KBr) ymax (cm ): 1743, 1654; H NMR 2H), 5.42 (d, 1H, J ¼ 10.8 Hz), 5.89 (d, 1H, J ¼ 17.6 Hz), 6.70–6.84
1
3
(
4
CDCl , 200 MHz) d: 2.40 (s, 3H), 2.44 (s, 3H), 4.23 (m, 5H), 4.43– (m, 1H), 7.55 (d, 2H, J ¼ 8.4 Hz), 7.96 (d, 2H, J ¼ 8.4 Hz);
C
3
.44 (m, 2H), 4.74–4.75 (m, 2H), 7.27–7.31 (m, 2H), 8.01 (d, 2H, J NMR (CDCl , 50 MHz) d: 21.7, 69.5 (2C), 70.3 (5C), 73.6 (2C),
3
1
3
¼
3
8.2 Hz); C NMR (CDCl , 50 MHz) d: 15.0, 22.6, 67.7 (2C), 69.4 78.6, 116.9, 126.3 (2C), 127.1 (2C), 135.5, 140.9, 145.4, 181.0;
5C), 70.6 (2C), 78.7, 126.5, 129.1 (2C), 129.5 (2C), 143.8, 163.6, HRMS (ES ) calcd for C H FeNO S [M + H] , 410.0508 found
+
+
(
2
0
20
3
+
+
1
65.8; HRMS (ES ) calcd for C20
H
20FeNO
2
[M + H] 362.0838, 410.0515.
(E)-1-[(2,4-Diuorobenzenesulfonoxyimino)ethyl] ferrocene
E)-1-[4-(Methoxy-benzoyloxyimino)ethyl] ferrocene (3d). The (4d). The dark brown crude product on purication by column
found 362.0846.
(
orange solid compound 3d (0.19 g, 85%) was obtained on chromatography (5% ethyl acetate/hexane) resulted the title
purication of the crude product by column chromatography compound 4d (0.20 g, 78%) as a brown solid; TLC R (25% ethyl
f
ꢀ
ꢀ
ꢂ1
(
4% ethyl acetate/hexane); mp: 104–106 C; TLC R (20% ethyl acetate/hexane) 0.40; mp: 135–140 C; FTIR (KBr) y
max
(cm ):
f
ꢂ1
1
1
acetate/hexane) 0.45; FTIR (KBr) ymax (cm ): 1743, 1610; H 1298, 1517; H NMR (CDCl , 400 MHz) d: 2.77 (s, 3H), 4.26 (m,
3
3
NMR (CDCl , 400 MHz) d: 2.38 (s, 3H), 3.88 (s, 3H), 4.21 (m, 5H), 5H), 4.64–4.65 (m, 2H), 4.82–4.83 (m, 2H), 6.95–7.01 (m, 2H),
1
3
4
.42 (m, 2H), 4.74 (m, 2H), 6.96 (d, 2H, J ¼ 8.8 Hz), 8.07 (d, 2H, J 8.00–8.06 (m, 1H); C NMR (CDCl , 100 MHz) d: 22.1, 69.5 (2C),
3
1
3
¼
8.8 Hz); C NMR (CDCl
3
, 100 MHz) d: 14.9, 55.4, 67.0 (2C), 70.4 (5C), 73.9 (2C), 111.3, 118.7, 124.3, 130.7, 147.0, 164.4,
9.4 (5C), 70.5 (2C), 78.8, 113.7 (2C), 121.6, 131.5 (2C), 163.4, 166.9, 186.0; HRMS (ES ) calcd for C H F FeNO S [M + H]
+
+
6
1
3
1
8
16
2
3
+
+
63.5, 164.8; HRMS (ES ) calcd for C H FeNO [M + H]
420.0163, found 420.0172.
2
0
20
3
78.0787, found 378.0793.
Photogeneration of carboxylate acids and quantum yield
measurement
General procedure for the synthesis of sulfonates of (E)-1-
acetylferrocene oxime
A 0.039 mmol sample of carboxylate (3a–d) was dissolved in
MeOH–H O (95 : 1) and individually irradiated by 125 W
2
To the mixture of sulfonyl chloride (0.74 mmol) and 1-ace- medium pressure Hg lamp using pyrex lter. The photoreaction
tylferroceneoxime (0.150 g, 0.61 mmol) in dry DCM, Et
3
N (0.43 was monitored by HPLC using methanol as mobile phase, at a
ꢀ
ꢂ1
mL, 3.09 mmol) was added dropwise at 0 C. The reaction ow rate of 1 mL min (detection: UV 254 nm) at regular
mixture was then stirred overnight at room temperature. Aer intervals of time. Peak areas were determined by HPLC, which
the completion of the reaction (as indicated by TLC), it was indicated an increase in the acid concentration with time.
quenched by ice cold water and diluted with DCM. The organic Based on HPLC data for each compound, we plotted the loga-
layer was separated and dried over Na SO , and the solvent was rithm of concentration of acid [ln C] versus irradiation time (t).
2
4
removed under vacuum to yield crude sulfonate.
We observed a linear correlation for the formation of the acids,
(
E)-1-[(Methanesulfonoxyimino)ethyl] ferrocene (4a). The which suggested a rst order reaction and the corresponding
crude product was puried by column chromatography (5% rate constant was calculated. Further, the quantum yield for the
ethyl acetate/hexane) to yield the title compound 4a (0.16 g, photolysis of compound 3a–e was calculated using eqn (1):
ꢀ
À
Á
8
0%) as a deep red solid, mp: 62–65 C; TLC R
f
(20% ethyl
À
Á
kp
ꢂ1
1
PAG
acetate/hexane) 0.50; FTIR (KBr) ymax (cm ): 1295, 1568; H
NMR (CDCl , 100 MHz) d: 2.69 (s, 3H), 3.13 (s, 3H), 4.25 (m, 5H),
.62 (m, 2H), 4.81 (m, 2H); C NMR (CDCl , 100 MHz) d: 22.0, where F is the photolysis quantum yield, K is the photolysis
3.2, 69.9 (2C), 70.5 (5C), 73.6 (2C), 80.4, 185.0; HRMS (ES ) rate constant, I
fp
¼
(1)
PAG
I
0
ðFPAG
Þ
3
1
3
4
4
3
p
p
+
0
is the incident photon ux and F is the fraction
of light absorbed. The quantum yield for the photogeneration of
+
calcd for C13
H
16FeNO
3
S [M + H] 322.0195, found 322.0199.
4628 | J. Mater. Chem. C, 2014, 2, 4622–4630
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Paper
Journal of Materials Chemistry C
carboxylic acids was analyzed by employing valerophenone as
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2
2017; (b) F. P. Nicoletta, D. Cupelli, P. Formoso, G. D. Filpo,
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ꢀ
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Samples were prepared by combining the CaCO particles with
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4 2 4
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We thank DST (SERB) for nancial support and DST-FIST for
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(India), S. Atta to UGC (India), and S. Barman is thankful to IIT
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4630 | J. Mater. Chem. C, 2014, 2, 4622–4630
This journal is © The Royal Society of Chemistry 2014