Colorimetric detection of aliphatic primary amines and a molecular logic gate based on a photochromic phenoxyquinone derivative

Article abstract of DOI:10.1016/j.jphotochem.2012.04.003

A photochromic phenoxyquinone-based, sensor for aliphatic primary amine was developed. An efficient trans-to-ana photoisomerization was occurred when 6-(4′-methoxyphenoxy)-5,12-naphthacenequinone in acetonitrile was irradiated with 365 nm UV light. The photochemically generated ana quinone intermediate was found to undergo nucleophilic substitution reactions by aliphatic primary amines to afford a large bathochromic shift in the absorption spectra, allowing colorimetric detection of the aliphatic primary amines. Neither aromatic nor secondary and tertiary amines were able to promote the bathochromic spectral shift of the phenoxyquinone. Removal of the phenoxy group by a primary amine was confirmed by using ¹H NMR analysis and a preparative scale reaction. In addition, colorimetric detection of the aliphatic primary amine was demonstrated to be feasible with phenoxyquinone-containing PDMS films. Since the large bathochromic shift occurs only in the presence of UV light and aliphatic primary amine, the sensor system functions a molecular AND logic gate.

Full text of DOI:10.1016/j.jphotochem.2012.04.003

Journal of Photochemistry and Photobiology A: Chemistry 238 (2012) 1–6
Contents lists available at SciVerse ScienceDirect
Journal of Photochemistry and Photobiology A:
Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Colorimetric detection of aliphatic primary amines and a molecular logic gate
based on a photochromic phenoxyquinone derivative
In Sung Parka, Eunjoo Heoa, Yoon-Seung Nama, Chan Woo Leeb,∗, Jong-Man Kima,∗
a Department of Chemical Engineering, Hanyang University, Seoul 133-791, Republic of Korea
b Department of Chemistry, Hanyang University, Seoul 133-791, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
A
photochromic phenoxyquinone-based, sensor for aliphatic primary amine was developed.
An efficient trans-to-ana photoisomerization was occurred when 6-(4ꢀ-methoxyphenoxy)-5,12-
naphthacenequinone in acetonitrile was irradiated with 365 nm UV light. The photochemically generated
“ana” quinone intermediate was found to undergo nucleophilic substitution reactions by aliphatic pri-
mary amines to afford a large bathochromic shift in the absorption spectra, allowing colorimetric
detection of the aliphatic primary amines. Neither aromatic nor secondary and tertiary amines were
able to promote the bathochromic spectral shift of the phenoxyquinone. Removal of the phenoxy group
by a primary amine was confirmed by using 1H NMR analysis and a preparative scale reaction. In
addition, colorimetric detection of the aliphatic primary amine was demonstrated to be feasible with
phenoxyquinone-containing PDMS films. Since the large bathochromic shift occurs only in the presence
of UV light and aliphatic primary amine, the sensor system functions a molecular AND logic gate.
© 2012 Elsevier B.V. All rights reserved.
Received 1 February 2012
Received in revised form 26 March 2012
Accepted 4 April 2012
Available online 10 April 2012
Keywords:
Phenoxyquinone
Photochromic sensor
Amine sensor
Logic gate
1. Introduction
Shiraish et al. demonstrated that a photochromic spiropyran could
be utilized to detect cyanide anion in a sensitive and reversible
Photochromic materials experience reversible structural
changes that interconvert two distinctly colored isomeric forms
upon irradiation at specific wavelength [1–4]. Owing to their light
driven molecular switching properties, photochromic compounds
have been incorporated into many interesting systems, includ-
ing molecular switches [5–8], optical memory devices [9–11],
holographic gratings [12,13], logic devices [14–16], and drug
delivery vesicles [17]. Azobenzene, spiropyran, phenoxyquinone,
and bisthienylethene derivatives are representative photochromic
compounds. These molecules undergo various types of struc-
tural isomerization reactions, such as cis-trans isomerization
(azobenzene), ring opening (spiropyran), phenyl group migration
(phenoxyquinone), or ring closure (bisthienylethene), upon UV
irradiation. Moreover, the reverse processes are readily promoted
by irradiation with visible light.
fashion [18]. The photochemically generated merocyanine (MC)
form of spiropyran was readily reacted with cyanide anion to yield
an adduct. The formation of spiropyran–cyanide adduct resulted
in the colorimetric change of the solution. More recently, they
reported a coumarin–spiropyran conjugate sensor system for the
detection of cyanide anion [19]. Unlike the simple spiropyran
derivative, the fused coumarin–spiropyran system allowed a flu-
orometric detection of cyanide anion. Thus, no fluorescence was
observed with a photochemically generated ring-opened coumarin
fused spiropyran molecule. A strong fluorescence was monitored
when the fused sensor molecule binds with cyanide anion. We also
reported a cyanide-specific chemosensor based on a polythiophene
having spiropyran moieties as pendent groups [20]. The fluores-
cence emission of polythiophene was quenched by fluorescence
resonance energy transfer (FRET) from the polymer backbone to
MC form of the spiropyran when the spiropyran–polythiophene
conjugate was irradiated with UV light. Recovery of the fluores-
cence was observed when the solution was exposed to cyanide
anion, allowing a FRET-based cyanide sensor. Most recently, we
reported a cyanide selective photochromic chemosensor system
based on a phenoxyquinone derivative [21]. We observed that
addition of cyanide anion to a UV irradiated solution of a phenoxy-
naphthacene quinone derivative brought about a significant change
in the absorption spectra that enabled detection of cyanide ion in
Recently, applications of photochromic materials in the
chemosensor area have received great attention [18–21]. That
molecular sensing properties can be triggered by light is a very
intriguing phenomenon since it enables “On-Off” switching of sen-
sory functions to be governed by UV or visible light irradiation.
∗
Corresponding authors. Tel.: +82 2 2220 0522; fax: +82 2 2298 4101.
E-mail addresses: lcw@hanyang.ac.kr (C.W. Lee), jmk@hanyang.ac.kr (J.-M. Kim).
1010-6030/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jphotochem.2012.04.003

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I.S. Park et al. / Journal of Photochemistry and Photobiology A: Chemistry 238 (2012) 1–6
n-butylamine adduct 4 (20 mg, 58%). m.p.: 158–159 ◦C; 1H NMR
(300 MHz, in CDCl3): ı = 8.55 (1H, m), 8.46 (1H, m), 8.14 (1H, m),
7.99 (1H, m), 7.82 (1H, m), 7.73 (2H, m), 7.59 (2H, m), 4.12 (2H,
q, J = 8 Hz), 1.99 (2H, q, J = 8 Hz), 1.63 (2H, m), 1.04 (3H, t, J = 8 Hz);
13C NMR (75 MHz, in CDCl3): ı = 183.8, 177.5, 160.2, 136.1, 135.7,
134.1, 133.4, 133.0, 131.5, 131.2, 130.8, 129.6, 129.4, 128.9, 128.8,
126.7, 120.0, 106.3, 50.2, 33.6, 20.9, 14.4; IR (KBr) ꢀ max (cm−1):
3432, 3303, 3056, 2956, 2927, 2869, 1974, 1945, 1834, 1724 1654,
1583, 1552, 1527, 1425, 1375, 1328, 1247, 1083, 956, 892, 757,
a highly selective and sensitive manner. A carbanion intermediate
was shown to be responsible for the long wavelength absorption
band that is generated by cyanide addition.
The development of reliable detection methods for volatile
aliphatic amines is important in the fields of environmental moni-
toring, food quality control, and chemical device processing. Due
to their relative ease of handling and monitoring, colorimetric
and fluorometric chemosensors have been extensively studied
for the detection of the volatile aliphatic amines [22–29]. How-
ever, no photochromic, colorimetric amine sensors have been
described to date. As part of our continuing interest in the design
of photochromism-based chemosensors [19,20], we have carried
out an investigation that has led to the development of a facile col-
orimetric method for the sensitive detection and differentiation of
aliphatic primary amines from their secondary and tertiary coun-
terparts. In addition, the feasibility of a molecular logic gate with
the photochromic amine sensor system is described.
698; HRMS m/z 329.1419 (calcd C22H19NO2, 329.1416).
2.3.3. Synthesis of 6-hydroxynaphthacenequinone (7)
Method (photochemical): solution
methoxyphenoxy)-5,12-naphthacenequinone (1)
A
A
of
6-(4ꢀ-
(40 mg,
0.105 mmol) in acetonitrile (105 mL) was irradiated with 365 nm
UV light (1 mW/cm2) for 24 h. Diethylamine (0.21 mL, 2.10 mmol)
was added to the mixture and stirred for 4 h at room temperature.
Evaporation of the solvent and unreacted diethylamine gave a
residue which was washed with acetone/THF (1:1) solution to yield
the hydroxyquinone 7 (18 mg, 52%). m.p.: 254–256 ◦C; 1H NMR
(300 MHz, in CDCl3): ı = 8.54 (1H, d, J = 8 Hz), 8.40 (2H, m), 8.33
(1H, s), 8.01 (1H, d, J = 8 Hz), 7.83 (2H, m), 7.74 (2H, qd, J = 2.8 Hz).
Method B (chemical): A mixture of homophthalic anhydride
(1.85 mmol) and NaH (60% in mineral oil, 1.94 mmol) in anhy-
drous THF (25 mL) was stirred at 0 ◦C for 3 min. A solution of
1,4-naphthoquinone (1.85 mmol) in anhydrous THF (5 mL) was
added to the mixture. The mixture was stirred at 0 ◦C for 20 min
and stirred for 11 h at ambient temperature. The reaction mix-
ture was quenched with saturated aqueous NH4Cl (20 mL) and
then extracted with 1 M HCl solution and methylene chloride.
The organic layer was washed with saturated aqueous NaCl, dried
(MgSO4), and concentrated under reduced pressure. The residue
was washed with acetone to give the hydroxyquinone 7 (299 mg,
59%) [32].
2. Experimental
2.1. Apparatus
1H NMR and 13C NMR spectra were recorded on a Varian Unityl-
nova (300 MHz) spectrometer, using CDCl3 as solvent. Melting
points were determined on an IA9100X1 (Thermo Scientific Barn-
stead Electrothermal). IR spectra were recorded on a MAGNa-IR
E.S.P (Thermo Fisher Scientific, Inc). UV–vis spectra were examined
on an Agilent 8453 spectrophotometer.
2.2. Materials
Primary, secondary and tertiary amines investigated in this
study were purchased from Sigma–Aldrich. SYLGARD® 184 sili-
con elastomer base and SYLGARD® 184 silicon elastomer curing
agent were purchased from DOW CORNING. 6-Chloro-5,12-
naphthacenequinone was prepared according to the reported
method [29].
2.4. PDMS film sensor
2.4.1. Preparation
2.3. Synthesis
A solution of phenoxyquinone 1 (10 mg) in chloroform (1 mL)
was mixed with SYLGARD® 184 slicone elastomer base (20 g)
and stirred vigorously until well mixed. SYLGARD® 184 curing
agent (2 g) was added to the PDMS mixture. Bubbles in the
PDMS mixture was removed by a vacuum chamber for 1 h. The
degassed PDMS mixture was slowly poured into a square Petri dish
(12.5 cm × 12.5 cm). The PDMS mixture was cured at room temper-
ature for 2 days to give the phenoxyquinone embedded PDMS film
(film thickness is 950 ␮m).
2.3.1. Synthesis of
6-(4ꢀ-methoxyphenoxy)-5,12-naphthacenequinone (1)
The
naphthacenequinone (1) was prepared according to the
reported general method [30]. mixture of 6-chloro-5,12-
known
compound,
6-(4ꢀ-methoxyphenoxy)-5,12-
A
naphthacenequinone (150 mg, 0.51 mmol), 4-methoxyphenol
(76 mg, 0.62 mmol) and potassium carbonate (92 mg, 0.67 mmol)
in dry DMF (10 mL) was heated at 110 ◦C for 12 h. The mixture was
poured into acidic water (500 mL). The precipitate was collected,
washed with water and dried. Recrystallization from ethyl acetate
led to pure phenoxyquinone 1. Yield: 90 mg (46%). m.p.: 201 ◦C;
1H NMR (300 MHz, CDCl3): ı = 8.86 (1H, s), 8.37–8.13 (4H, m),
7.80–7.63 (4H, m), 6.82 (4H, s), 3.75 (3H, s); 13C NMR (75 MHz, in
CDCl3): ı = 182.9, 181.1, 154.5, 153.4, 152.9, 136.0, 135.4, 134.3,
133.6, 133.5, 131.9, 130.7, 130.3, 130.1, 129.8, 127.6, 127.0, 126.9,
125.0, 121.0, 115.5, 114.8, 55.6.
2.4.2. Sensor test
Liquid amine (2 mL) was placed in a 4 mL glass vial and the vial
was cap-sealed. After generating saturated amine vapor by heating
the vial at the boiling point of respective amines, the vial was open
and a phenoxyquinone embedded PDMS film, which was irradiated
with 365 nm UV light (1 mW/cm2) for 10 min, was placed on the top
of the vial for 2 min and the color change of the film was monitored.
2.3.2. Synthesis of 6-(butylamino)tetracene-5,11-dione (4)
3. Results and discussion
A
solution
of
6-(4ꢀ-methoxyphenoxy)-5,12-
naphthacenequinone (1) (40 mg, 0.105 mmol) in acetonitrile
(105 mL) was irradiated with 365 nm UV light (1 mW/cm2) for
24 h. n-Butylamine (0.21 mL, 2.10 mmol) was added to the solution
and the resulting solution was stirred for 2 h at room temperature.
Evaporation of the solvent and unreacted n-butylamine gave a
reddish residue. The residue was subjected to a silica gel column
chromatography (ethylacetate/hexane (v/v, 2:1)) to afford the
In order to explore the feasibility of colorimetric aliphatic
primary amine sensor, a photochromic 6-(4ꢀ-methoxyphenoxy)-
5,12-naphthacenequinone (1) displayed in Scheme 1 was prepared
according to the literature method [30]. The phenoxyquinone 1 is
expected to undergo a trans-ana isomerization reaction that gener-
ates “ana”-quinone 2 (Scheme 1) [30]. The “ana”-quinone forms of
phenoxyquinones are known to undergo nucleophilic substitution

I.S. Park et al. / Journal of Photochemistry and Photobiology A: Chemistry 238 (2012) 1–6
3
OMe
OMe
R
H
3
N
O
O
O
O
O
O
O
UV
Vis
R-NH2
O
1 (trans)
2 (ana)
Scheme 1. Photoinduced isomerization of 6-(4ꢀ-methoxyphenoxy)-5,12-naphthacenequinone (1) and formation of an amine–quinone adduct 3.
reactions with primary amines to generate amine-quinone adducts
3 [31]. In the context of colorimetric sensing, the substitution pro-
cess is interesting since it should result in a bathochromic shift in
the absorption spectrum owing to hydrogen bonding between the
hydrogen on the amine group and the adjacent carbonyl group in
adduct 3. In addition, the presence of the electron donating amine
group in 3 facilitates formation of a charge transfer excited state
that results in a red shift of the absorption maximum. As a conse-
quence of these phenomena, the photochemically generated “ana”
quinone 2 can serve as a colorimetric chemosensor for primary
amines.
In order to investigate the above proposal, an acetonitrile solu-
tion (25 ␮M) containing the phenoxyquinone 1 was irradiated for
30 min using a handheld laboratory 365 nm UV light lamp. For-
mation of the “ana” quinone form 2 was confirmed by observing
characteristic UV–vis absorption peaks in the 400–500 nm region
(Fig. 1).
To the photoirradiated solution was added various amines
while monitoring the spectral changes. As shown by the spec-
tra displayed in Fig. 2A, addition of primary aliphatic amines,
such as n-propylamine, n-butylamine, n-hexylamine, and n-
decylamine, to the UV irradiated phenoxyquinone 1 results in
large bathochromic shifts of the absorption maximum. Importantly,
secondary amines, such as piperidine and diethylamine do not
induce the bathochromic shift. As expected, almost no changes
in the absorption spectra are observed in the presence of tertiary
amines. Interestingly, the aromatic primary amine aniline does
not induce the red shift of the photochemically generated “ana”
quinone form 2. Thus, the spectral changes in quinone 2 are both
specific for aliphatic primary amines and significantly large to be
readily observed. It should be noted that a solution containing unir-
radiated phenoxyquinone 1 does not undergo any spectral changes
when amines (primary, secondary and tertiary amines) are added
(Fig. 2B). This observation demonstrates that the observed spectral
change promoted by primary amines originates from a reaction of
the “ana”-quinone form 2.
The next phase of the current investigation focused in more
detail on the colorimetric transition of the photoirradiated quinone
1 by the model primary amine n-butylamine. In Fig. 3A are shown
UV–vis absorption spectra of a 365 nm UV irradiated solution of the
phenoxyquinone 1 (25 ␮M) in the presence of various concentra-
tions of n-butylamine.
As expected, absorption at 523 nm appears and increases as
the concentration of n-butylamine increases. The presence of an
observed isosbestic point at 492 nm indicates that the amine-
quinone reaction produces a single product without the existence
Ctrl
aniline
A
0.3
triethylamine
tributylamine
piperidine
0.2
diethylamine
n-propylamine
n-butylamine
n-hexylamine
n-decylamine
0.1
0.0
400
500
600
Wavelength (nm)
B
0.2
0.1
0.0
Ctrl
n-propylamine
0.3
n-butylamine
n-hexylamine
n-decylamine
aniline
e
piperidine
0.2
diethylamine
triethylamine
tributylamine
d
c
0.1
b
a
300
400
500
600
0.0
300
400
500
Wavelength (nm)
Wavelength (nm)
Fig. 2. UV–vis absorption spectra of irradiated (A) and unirradiated (B) acetonitrile
solutions (25 ␮M) of the phenoxyquinone 1 in the presence of various amines (20
molar equiv. to 1). The spectra were recorded 5 min (A) and 30 min (B) after addition
of the amine.
Fig. 1. UV–vis absorption spectra of an acetonitrile solution containing 25 ␮M of
the phenoxyquinone 1 upon irradiation with 365 nm UV light (1 mW/cm2) for 0 (a),
6 (b), 12 (c), 18 (d), and 30 (e) min.

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I.S. Park et al. / Journal of Photochemistry and Photobiology A: Chemistry 238 (2012) 1–6
Fig. 4. 1H NMR (300 MHz) spectra of a CDCl3 solution containing 2 mM of phe-
noxyquinone 1 before (A), after 365 nm UV irradiation for 4 h (B), after addition of
2 equiv. of n-butylamine to the UV irradiated solution (C). 1H NMR spectra of inde-
pendently prepared n-butylamine adduct 4 (D) and commercial 4-methoxyphenol
(E).
Fig. 3. (A) UV–vis absorption spectra of a 365 nm UV-irradiated (30 min, 1 mW/cm2)
acetonitrile solution (25 ␮M) of the phenoxyquinone 1 in the presence of 0 (a), 5
(b), 10 (c), 15 (d), 20 (e), and 25 (f) ␮M of n-butylamine. The inset shows vials
containing photochemically generated “ana” quinone 2 in the absence and presence
of n-butylamine. (B) Plot of absorbance at 523 nm as a function of n-butylamine
concentration. The inset contains a plot of the absorption ratio vs. n-butylamine
concentration in the lower micromolar range.
of intermediates. Based on the plots of absorbance at 523 nm as a
function of butylamine concentration shown in Fig. 3B, the detec-
tion limit of butylamine was determined to be 1.2 ␮M. Since the
saturation of product formation was observed at a much higher
concentration of butylamine (125 ␮M) than the quinone used
(25 ␮M), a possible equilibrium between the initially formed prod-
uct and butylamine may exist.
In order to gain more information about the nature of the inter-
action between n-butylamine and photogenerated “ana”-quinone
2, 1H NMR spectroscopic analysis was carried out (Fig. 4). The four
protons on the phenoxy ring of quinone 1 appear as a singlet at
6.82 ppm due to the presence of similarly electron donating para
substituents (Fig. 4A). This singlet, however, is transformed to an AB
quartet upon 365 nm UV irradiation of the solution (Fig. 4B). In addi-
tion, a downfield shift of the aromatic phenyl proton resonances
occurs upon irradiation, indicating that the electron withdrawing
quinone moiety is produced. Comparison of the aromatic phenoxy
protons before and after UV irradiation suggests that the “trans”
and “ana” quinone forms exist as a 1:1.3 mixture after 365 nm
UV irradiation. Addition of n-butylamine to this solution results
in the complete disappearance of the “ana” quinone form and
simultaneous appearance of new resonances at 6.76 ppm which are
associated with 4-methoxyphenol (Fig. 4C and E). Thus, the results
of the 1H NMR analysis demonstrate clearly that 4-methoxyphenol
Fig. 5. UV–vis absorption spectra of a 365 nm UV-irradiated acetonitrile solution
(25 ␮M) of phenoxyquinone 1 in the presence of n-butylamine (solid) and n-
butylamine adduct 4 isolated from a preparative scale reaction (dash).
is liberated from the “ana” quinone form 2 when n-butylamine is
added. To demonstrate that the displacement reaction promoted by
n-butylamine does indeed take place, the n-butylamine adduct 4
(Scheme 2) was generated by using a preparative scale reaction and
analyzed using 1H NMR spectroscopy (Fig. 4D). Comparison of the
spectra shown in Fig. 4C and D indicates that n-butylamine adduct
4 formation is indeed responsible for the UV–vis and 1H NMR spec-
troscopic changes observed in the experiments described above
(Fig. 5).
Interestingly, addition of secondary amines, such as diethy-
lamine and piperidine, to solutions of the photoirradiated quinone
1 results in hypsochromic shifts of the absorption maximum
(Fig. 2A). We initially thought that amine–quinone adducts (e.g.
5, Scheme 2), were being produced in these processes. However,
the results of preparative scale reactions show that the only prod-
uct generated in these processes is 6-hydroxynaphthacenequinone
7 (Scheme 2). It is believed that the initially formed secondary
amine adducts (e.g. 5) are highly unstable in that they undergo
rapid hydrolysis by adventitious water present in the solution to
produce the stable hydroxyquinone 7 via intermediate 6.

I.S. Park et al. / Journal of Photochemistry and Photobiology A: Chemistry 238 (2012) 1–6
5
Scheme 2. Reaction pathways to the generation of the amine adduct 4 and the hydroxyquinone 7.
0.3
b
c,d,e,f,g,h
a
0.2
0.1
0.0
400
500
600
Fig. 6. 1H NMR (300 MHz) spectra of a CDCl3 solution containing 2 mM of phe-
noxyquinone 1 after addition of 2 equiv. of diethylamine to the UV irradiated
solution (A). 1H NMR spectra of 6-hydroxynaphthacenequinone 7 isolated from a
photochemical reaction (B) and from an independent chemical synthesis (C).
Wavelength (nm)
Fig. 7. UV–vis absorption spectra of a phenoxyquinone 1 solution (CH3CN, 25 ␮M)
before (a) and after (b) 365 nm UV irradiation for 30 min. UV–vis spectra (c–h) of a
UV irradiated quinone solution in the presence of various molar ratios of butylamine
and diethylamine (250:0 (c), 250:50 (d), 250:100 (e), 250:150 (f), 250:200 (g), and
250:250 (h) ␮M).
In order to prove the hydroxyquinone 7 was the sole product
from the secondary amine-photogenerated quinine reaction, 1H
NMR spectroscopic analysis was conducted. As displayed in Fig. 6A,
addition of 2 equiv. of diethylamine to the photochemically gener-
ated ana quinone 2 resulted in the formation of hydroxyquinone 7.
The presence of the hydroxyquinone 7 was confirmed by isolation
from the reaction mixture (Fig. 6B) and by independent chemical
synthesis (Fig. 6C) (see Section 2 for details) [32].
Stimulated by the interesting feature of the sensor material 1,
we took a further step to test the selectivity of the quinone 1 as
a colorimetric chemosensor for primary amine in the presence of
secondary amine. Thus, the response of the photochemically gener-
ated “ana” quinone 1 to butylamine was evaluated in the presence
of various concentrations of diethylamine. As displayed in Fig. 7,
nearly the same final absorbance at 523 nm was observed (Fig. 7,
c–h), indicating that no remarkable interference of the secondary
amine was monitored.
The ability to selectively colorimetric detect primary aliphatic
amines and not their secondary and tertiary counterparts is not
limited to the solution phase. In Fig. 8 are shown PDMS films con-
taining phenoxyquinone 1 after exposure to saturated vapors of
various amines. As expected, the unirradiated PDMS films do not
undergo color changes when any amine is present (Fig. 8A). In
addition, irradiation using 365 nm UV light of a phenoxyquinone
1 containing film for 10 min leads to generation of a yellow
color (Fig. 8B, ctrl), which is indicative of the occurrence of the
Fig. 8. Photographs of unirradiated (A) and 365 nm UV irradiated (B) PDMS films
containing phenoxyquinone 1 after exposure to saturated vapors of n-butylamine,
diethylamine and triethylamine for 2 min.
photoisomerization reaction. Exposure of the yellow film produced
in this way to n-butylamine vapor induces a color change to pale
purple (Fig. 8B), showing that the amine adduct was generated.
Since the generation of absorbance at 523 nm is only possible
when the quinone 1 is converted to ana form 2 by UV irradiation
and the quinone 2 reacts with primary amine, construction of a

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I.S. Park et al. / Journal of Photochemistry and Photobiology A: Chemistry 238 (2012) 1–6
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Input 1
(365 nm UV)
Input 2
(n-butylamine)
Output
(abs at 523 nm)
0
1
0
1
0
0
1
1
0
0
0
1
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table (Table 1), no output signal (absorbance at 523 nm) is gener-
ated when input 1 (365 nm UV irradiation) and input 2 (primary
aliphatic amine) are absent. In addition, the output signal is not
monitored when only one input signal is present. Thus, the output
signal is observed only when the two input signals are present, thus
allowing a molecular AND logic gate.
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In summary, the study described above has led to the devel-
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chemosensor for the detection of aliphatic primary amines. Nucle-
ophilic displacement of the phenoxy group in the photochemically
generated “ana” quinone form 2 by an aliphatic primary amine
promotes a large bathochromic shift of the absorption maximum
that enables colorimetric detection of the aliphatic primary amines.
Removal of the phenoxy group by a primary amine was confirmed
by using 1H NMR analysis and a preparative scale reaction. In
addition, colorimetric detection of the aliphatic primary amine
was demonstrated to be feasible with phenoxyquinone-containing
PDMS films. Finally, we proved that the photochromic sensor sys-
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input signals (UV light and aliphatic primary amine). Although
numerous colorimetric chemosensors have been reported, those
based on photochromism probe molecules are rare. Thus, the strat-
egy described above should serve as an important addition to the
chemosensor area.
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The authors gratefully thank National Research Foundation of
Korea for financial support through Basic Science Research Program
(20110018602), Center for Next Generation Dye-sensitized Solar
cells (20110001057), and International Research & Development
Program (K20901000006-09E0100-00610). I. S. Park is a recipient
of Seoul City Scholarship.
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