Solvatochromic fluorescence behavior of 2-amino-6-hydroxy-4-(3,4- dimethoxyphenyl)-pyrimidine-5-carbonitrile: A sensitive fluorescent probe for detection of pH and water composition in binary aqueous solutions

Article abstract of DOI:10.1016/j.molliq.2013.03.018

A new class of fluorescence sensor for detection of water in organic solvents based on photo-induced electron transfer (PET) of substituted pyrimidine appended with dimethoxyphenyl system has been designed and characterized. The probe 2-amino-6-hydroxy-4-(3,4-dimethoxyphenyl)-pyrimidine-5- carbonitrile AHDPC (I) was synthesized by one step three-component condensation reaction. The solvatochromic fluorescence behavior of AHDPC featuring electron withdrawing CN group, electron donating - OCH₃, NH₂, OH groups and various π-conjugated backbones in varying polar and non-polar solvents has been investigated. The fluorescence of the compound exhibits red shift from its absorption spectra and correlated with solvent polarity. AHDPC exhibited significant spectral shifts in λ_em as a function of water composition in binary aqueous solvent systems. The changes are due to the specific interactions of AHDPC by intramolecular hydrogen bonding with water, photoinduced electron transfer as well as general solvent effect. The observed solvatochromic fluorescence characteristic of AHDPC could used as a new probe for micro-environmental polarity changes as well as a sensitive sensor for the determination of water composition in binary aqueous solutions. This study shows that due to the solvent sensitive emission, pyrimidine derivatives are good candidates to be used as fluorescent probes.

Full text of DOI:10.1016/j.molliq.2013.03.018

MOLLIQ-03815; No of Pages 6
Journal of Molecular Liquids xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Q21
Solvatochromic fluorescence behavior of 2-amino-6-hydroxy-4-
2
3
(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile: A sensitive fluorescent
probe for detection of pH and water composition in binary aqueous solutions
Q14
Vishwas D. Suryawanshi a,b, Anil H. Gore a, Laxman S. Walekar a, Prashant V. Anbhule a,
5
Shivajirao R. Patil a, Govind B. Kolekar a,
⁎
a
6
7
Fluorescence Spectroscopy Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur-416 004, Maharashtra, India
S. M. Dr. Bapuji Salunkhe Mahavidyalaya, Miraj-416 410, Sangli, Maharashtra, India
b
OOF
8
a r t i c l e i n f o
a b s t r a c t
9
10
Article history:
A new class of fluorescence sensor for detection of water in organic solvents based on photo-induced electron 24
transfer (PET) of substituted pyrimidine appended with dimethoxyphenyl system has been designed and 25
characterized. The probe 2-amino-6-hydroxy-4-(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile AHDPC 26
(I) was synthesized by one step three-component condensation reaction. The solvatochromic fluorescence 27
behavior of AHDPC featuring electron withdrawing CN group, electron donating ―OCH3, NH2, OH groups 28
and various π-conjugated backbones in varying polar and non-polar solvents has been investigated. The fluo- 29
rescence of the compound exhibits red shift from its absorption spectra and correlated with solvent polarity. 30
AHDPC exhibited significant spectral shifts in λem as a function of water composition in binary aqueous sol- 31
vent systems. The changes are due to the specific interactions of AHDPC by intramolecular hydrogen bonding 32
with water, photoinduced electron transfer as well as general solvent effect. The observed solvatochromic 33
fluorescence characteristic of AHDPC could used as a new probe for micro-environmental polarity changes 34
as well as a sensitive sensor for the determination of water composition in binary aqueous solutions. This 35
study shows that due to the solvent sensitive emission, pyrimidine derivatives are good candidates to be used 36
11
12
13
14
Received 16 January 2013
Received in revised form 21 March 2013
Accepted 29 March 2013
Available online xxxx
156
17
18
19
20
21
22
23
Keywords:
Fluorescence
Solvatochromism
Pyrimidine
Photophysical
Detection
as fluorescent probes.
37
© 2013 Published by Elsevier B.V. 38
42
41
3490
43
1. Introduction
the development of a variety of interesting and practically usable 61
fluorescence probes [16]. Chemical sensors for detection and quanti- 62
fication of water in organic solvents are of a fundamental interest in 63
analytical chemistry and of a great importance in industrial applica- 64
tions. In most of these fluorescent water sensors, however, the fluo- 65
rescence intensity decreases with an increase of water in organic 66
solvents [17–20]. Most distinctively, this new class of pyrimidine de- 67
rivative exhibits good luminescent properties in polar solvents, which 68
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Fluorescence sensors have received a considerable attention for
their potential applications to biochemical and medical analyses and
optoelectronic devises [1–6]. Pyrimidine derivatives were intensively
investigated as electroluminescent materials in the past and as two-
photon absorption organic chromophores [7–9]. The influence of the
pyrimidine additives on the dye sensitized solar cell performance
was also investigated [10]. The effect of solvents on the spectral prop-
erties of molecules, generally referred as solvatochromism, has been
investigated for many years, generating a copious of literature [11].
Recently some marine alkaloids such as dihydropyrimidine-5-
can be used potentially as organic electroluminescent media.
69
In this paper, we focus on the investigation of absorption and 70
fluorescence spectral characteristics of 2-amino-6-hydroxy-4- 71
(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile AHDPC (Scheme 1), 72
carboxylate have beeUn syntNhesizeCd andOused Ras fluoRresceEnt proCbes TED PR
in different solvents. A dual fluorescence emission for AHDPC was ob- 73
[12,13].
In recent years considerable efforts have been given to the design
served in polar solvents. The first is ascribed to intramolecular proton 74
transfer occurring across pre-existing intramolecular hydrogen bond; 75
and the second is the normal fluorescence emission, which changes 76
with the change of solvent polarity [21], with a maximum observed 77
in high-polarity acetonitrile. From these measurements Stoke's shift 78
(Δν) and fluorescence quantum yield (ϕ) were determined. Solvent po- 79
larity and the local environment have profound effects on the emission 80
spectral properties of fluorophore molecules. The effect of solvent po- 81
larity is one origin of the Stoke's shift, which is one of the observations 82
and synthesis of functional molecules that could serves as sensitive
sensors for the analytical detection of chemically and biologically im-
portant species [14,15]. For this purpose, the advantages of fluores-
cence signaling in high selectivity and sensitivity have encouraged
⁎
Corresponding author. Fax: +91 231 2692333.
E-mail address: gbkolekar@yhaoo.co.in (G.B. Kolekar).
0167-7322/$ – see front matter © 2013 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.molliq.2013.03.018
Please cite this article as: V.D. Suryawanshi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2013.03.018

2
V.D. Suryawanshi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
OMe
OMe
OMe
CHO
OMe
+
NH
NaOH
O
+
NC
EtOH, Reflux
H2N
NH2.HCl
CN
OH
O
N
H2N
N
AHDPC (I)
Scheme 1. Synthesis of desired probe, 2-amino-6-hydroxy-4-(3,4-dimethoxyphenyl)-pyrimidine-5-carbonitrile, AHDPC (I).
3. Results and discussion
104
105
t1:1
t1:2
Table 1
Spectral maxima and photophysical parameters of AHDPC (I) in different solvents.
3.1. Absorption and emission characteristics in different solvents
t1:3
Solvent
Δf
λ
abs/nm
λ
em/nm
Δν=cm−1
ϕ
t1:4
t1:5
t1:6
t1:7
t1:8
t1:9
1,4-Dioxane
Ethyl acetate
Acetone
Ethanol
Acetonitrile
Methanol
0.0211
0.1995
0.2847
0.2974
0.3054
0.3087
347
356
348
350
359
346
428
442
430
436
456
442
5454.0
5566.5
6008.3
6064.4
6116.0
6277.3
0.0073
0.0185
0.0272
0.0105
0.0893
0.0143
The specific solvent–fluorophore interactions can often be identi- 106
fied by examining absorption and emission spectra in a variety of sol- 107
vents. The absorption and fluorescence emission spectra of AHDPC, 108
(1 × 10−5 M) were measured in polar and non-polar solvents of dif- 109
ferent polarity at room temperature. Typical spectroscopic data such 110
as absorption and emission maxima, Stokes shifts and fluorescence 111
quantum yield are presented in Table 1. The absorption peak of 112
compound in different solvents of varying polarity shows shift from 113
(λab = 345 nm) in 1,4-dioxane to (λab = 359 nm) in acetonitrile. The 114
highly intense long-wavelength absorption band of AHDPC undergoes 115
red shift with increasing solvent polarity (Fig. 1). These features indicate 116
the allowed π → π* transition and large dipole moment in the excited 117
83
84
85
86
in fluorescence. The observed solvatochromic fluorescence characteris-
tic of AHDPC could be used as a new probe for micro-environmental po-
larity changes as well as a sensitive sensor for the determination of
water composition in binary aqueous solutions.
87
88
2. Experimental
a
450
400
2.1. Materials and methods
Methanol
350
89
90
91
92
93
94
95
96
97
98
99
All chemicals and solvents used for synthesis and spectroscopic
measurements were of analytical reagent grade and used without fur-
ther purification. The melting point of the product was determined in
open capillary tubes. The UV–visible absorption spectra were measured
on a Shimadzu UV-3600 UV-VIS NIR Spectrophotometer and Fluores-
cence emission spectra on PC based Spectrofluorophotometer (JASCO
Japan FP-750) respectively. Excitation and emission slit width was fixed
to 10 nm. All pH values were measured by a digital pH-meter with mag-
netic stirrer (Equip-Tronics EQ-614 A). The stock solution (1 × 10−5 M)
was prepared by dissolving the pure solid in different solvents and fluo-
rescence emission spectra were monitored at λex = 370 nm between
Ethanol
300
Ethyl Acetate
Acetonitrile
250
Acetone
200
1,4-dioxane
150
100
50
0
380
420
460
500
540
Wavelength (nm)
100 200 and 600 nm. The desired compound, pyrimidine derivative, was syn-
101 thesized by one step, three-component condensation reaction of aromat-
102 ic aldehyde, ethyl cyano acetate and guanidine hydrochloride in alkaline
103 medium in accordance with the literature method [22].
b
220
200
100
0
1.00
Ethyl acetate
Acetone
Methanol
0.80
Acetonitrile
0.60
0.40
0.20
0.00
Ethanol
1,4-Dioxane
380 400
500
600
Wavelength (nm)
Fig. 2. a. Fluorescence spectra of AHDPC (C = 1.0 × 10−5 M) in varying solvents
(λex = 370 nm): 1,4-dioxane, ethyl acetate, ethanol, acetone, methanol, acetonitrile.
b. Normalized fluorescence spectra of AHDPC (C = 1.0 × 10−5 M) in varying solvents
from left to right (λex = 370 nm): 1,4-dioxane, ethyl acetate, ethanol, acetone, meth-
anol, acetonitrile (for interpretation of the references to color in this figure legend, the
reader is referred to the web version of the article).
250
300
350
400
450
Wavelength (nm)
Fig. 1. UV–visible absorption spectra of AHDPC (C = 1.0 × 10−5 M) in various solvents:
1, 4-dioxane, ethyl acetate, ethanol, acetone, methanol, acetonitrile.
Please cite this article as: V.D. Suryawanshi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2013.03.018

V.D. Suryawanshi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
3
6400
a
y = 2371.5x + 5371
2 = 0.9609
3.0
2.5
2.0
1.5
1.0
0.5
0.0
6200
6000
5800
5600
5400
5200
R
pH = control
pH = 2.0
pH = 3.0
pH = 4.0
pH = 6.0
pH = 7.0
pH = 8.0
pH = 9.0
pH = 10
pH = 12
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
200
250
300
350
400
450
Polarity parameter
Wavelength (nm)
Fig. 4. A plot of Stoke's shifts vs. polarity parameter (for interpretation of the references
to color in this figure legend, the reader is referred to the web version of the article).
b
280
240
200
160
120
80
dramatically decreased. As shown in Fig. 3b, the fluorescence emis- 132
sion intensity was maximum in alkaline medium and decreases in 133
acidic medium; these results demonstrate that the AHDPC has a 134
non-fluorescent (PET inactive) cationic structure (I+) in acidic solu- 135
pH = control
pH = 2.0
pH = 7.0
pH = 12
tions and a fluorescent (PET active) anionic structure (I−) in alka- 136
OOF
line solutions, as shown in Scheme 2.
137
This new class of pyrimidine derivative displays very favorable 138
fluorescence profile. The solvent dependent spectral shifts were also 139
analyzed in terms of the simplified Lippert–Mataga equation [25–27], 140
which describes the Stokes shift in terms of the change in dipole mo- 141
ment of the fluorophore upon excitation and the dependence of the en- 142
ergy of the dipole on the dielectric constant and refractive index of the 143
40
0
380
420
460
500
540
580
Wavelength (nm)
solvent, as given by:
144
Fig. 3. a. pH dependence of absorption spectra of AHDPC in aqueous solutions. b. Selected
pH (control, 2, 7 and 12) dependence of fluorescence spectra (λex = 370 nm) of AHDPC
in aqueous solutions (for interpretation of the references to color in this figure legend, the
reader is referred to the web version of the article).
ꢀ
ꢁ
2
μs−μg
hca2
Δν ¼ νabs−νem
ε−1
¼
Δf þ Const:
ð1Þ
ð2Þ
1456
118 state is higher than in ground state because of internal charge transfer. As
119 this compound has a heterocyclic nitrogen atom, transitions involving
120 the non-bonding nitrogen electrons have similar properties to those of
η2−1
Δf ¼
−
2η2 þ 1
2ε þ 1
⁎
121 π → π transitions [23,24], as the n orbital generally overlaps the π or-
122 bital of adjacent carbon atom. The fluorescence emission occurs in region
123 428–460 nm which exhibits gradual shift from blue (λem = 428 nm) in
124 1,4-dioxane to red in acetonitrile (λem = 460 nm) (Fig. 2). This behavior
125 indicates efficient charge transfer in excited state which is stabilized in
126 polar solvents.
where Δν is the Stokes shift in cm−1, which increases with increas- 1478
ing the solvent polarity pointing to stronger stabilization of the 149
excited state in polar solvent, h = 6.6262 × 10−34 J is Planck's con- 150
stant, c = 2.99 × 108 ms−1 is the velocity of light and α = Onsager 151
cavity radius, ε and η are the dielectric constant and refractive index 152
of the solvent, respectively. The plot of Stokes shift ðΔνÞ versus solvent 153
polarity (Δf) in various solvents was shown in Fig. 4. This shows 154
the good correlation coefficient in excited state and also the dielec- 155
tric solute–solvent interactions are responsible for the observed 156
127
To make sure that AHDPC is photoinduced electron transfer active,
128 the absorption spectra of AHDPC (I) were measured in aqueous solutions
129 of different pH values (Fig. 3a). In the pH range from 3 to 7 (in the acidic
130 and neutral regions), a strong absorption was observed. With increasing
131 pH value from 8 to 12 (in the alkaline region), the absorption intensity
solvatochromic shift for the present molecule.
157
UNCORRECTED PR
Scheme 2. Ionic structures of AHDPC in acidic and alkaline solutions.
Please cite this article as: V.D. Suryawanshi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2013.03.018

4
V.D. Suryawanshi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
a
158
The fluorescence quantum yield (ϕ) was measured relative to quinine
159 sulfate 0.1 M H2SO4 as reference (ϕ = 0.58) with correction made for
160 different refractive indices of the solvents [28,29], according to the follow-
161 ing equation:
300
250
200
150
100
50
40 % H2O
50 % H2O
20 % H2O
10 % H2O
5.0 % H2O
2.0 % H2O
0.0 % H2O
ϕ
F
std:FAstd:η2
std:Aη2std:
ϕ ¼
ð3Þ
1623 where F and Fstd = peak areas of sample and standard solutions, respec-
164 tively; A and Astd = absorbance at excitation wavelength of sample and
165 standard, respectively; η and ηstd refractive index of sample and standard
166 solutions, respectively; ϕ and ϕstd = quantum yield of sample and
167 standard solutions respectively. The fluorescence quantum yield of the
168 compound shows slight variation with the change in solvent polarity in-
169 dicating the negative and positive solvatokinetic effect. For negative
170 solvatokinetic effect, quantum yield increases with a suitable enhance-
171 ment of intramolecular charge transfer (ICT) which involves nπ electron
172 configuration while reduction in quantum yield by strong ICT is called
173 positive solvatokinetic effect. Spectral maxima and photophysical pa-
174 rameters of AHDPC (I) in different solvents are shown in Table 1.
0
380
420
460
500
540
Wavelength (nm)
b
300
250
200
150
100
50
40 % H2O
50 % H2O
60 % H2O
70 % H2O
90 % H2O
175 3.2. Role of addition of water in absorption and fluorescence emission
176
The effect of water on fluorescence emission was further investigated
177 by using a solvent water mixture. The detection of water in ethanol was
178 attempted by measuring the absorption and fluorescence spectra of
179 AHDPC. As shown in Fig. 5, the absorption spectra of AHDPC undergo
180 only small changes in intensity and shape by increasing water content
181 in ethanol, but with higher content of water 90% (v/v), the absorption in-
182 tensity is decreased drastically. On the other hand, the corresponding
183 fluorescence spectra exhibit significant changes in intensity with water
184 content (Fig. 6). When the water content lies between 0 and 40% (v/v),
185 the fluorescence intensity is increased dramatically in ethanol solution.
186 The fluorescence intensity increased with the water content, reaching a
187 maximum at 40% H2O, then decreased as the water content increased
188 further. This means that developed method was applicable only up to
189 40% water content in ethanol. That is a typical of specific solvent effect
190 and possibly due to the formation of strong hydrogen bonding between
191 water and the amino group of or nitrogen of heterocyclic moieties of
192 compound AHDPC. The changes in the fluorescence peak intensity are
193 plotted in Fig. 7 against water composition in ethanol. This observation
194 of sensitive spectral shifts as a function of water composition suggests
195 that the shift in λem can be applied for the detection of water contents
196 in many aqueous organic systems. The significant spectral changes
197 with a small variation in the composition of solvent mixture usually indi-
198 cate specific solvent effects [28]. The mechanism of the fluorescence
199 quenching of (I) is believed to be due to the specific interaction of (I)
200 with water molecules, particularly, with the hydroxyl group oxygen
201 and nitrogen atoms of the heterocycles of the compound (I). The fluores-
202 cence emission features of the AHDPC are assumed to be due to the
0
380
420
460
500
540
Wavelength (nm)
Fig. 6. a. Fluorescence spectra of AHDPC (C = 1.0 × 10−5 M) as a function of water
composition in aqueous ethanol solution containing water (0.0, 2, 5, 10, 20, 40, 50%)
(v/v). b. Fluorescence spectra of AHDPC (C = 1.0 × 10−5 M) as a function of water
composition in aqueous ethanol solution containing water (40, 50, 60, 70, 90%) (v/v)
(for interpretation of the references to color in this figure legend, the reader is referred
to the web version of the article).
formation of intermolecular hydrogen bonds between AHDPC and the 203
water molecules [21]. Through hydrogen bonding the AHDPC molecule 204
can be successively solvated forming mono- and polyhydrate species 205
(Scheme 3). This is a proposed mechanism indicating solvation effect 206
and there is no theoretical support on this mechanism of H-bonding be- 207
tween AHDPC and water molecules.
208
4. Conclusions
209
In summary a new class of fluorescence sensor for detection of 210
water in organic solvents based on photo-induced electron transfer 211
of substituted pyrimidine appended with dimethoxyphenyl system 212
has been designed and characterized. Due to the solvent sensitivity 213
350
300
250
200
150
100
50
2.4
0 % H2O
2 % H2O
5 % H2O
10 % H2O
20 % H2O
40 % H2O
50 % H2O
60 % H2O
70 % H2O
90 % H2O
2.0
1.6
1.2
0.8
0.4
0.0
200
250
300
350
400
450
0
0
10 20 30 40 50 60 70 80 90 100
Concentration of water, % (v/v)
Wavelength (nm)
Fig. 5. Absorption spectra of AHDPC (C = 1.0 × 10−5 M) in ethanol containing water
(0.0–90%) (v/v) (for interpretation of the references to color in this figure legend, the
reader is referred to the web version of the article).
Fig. 7. A plot of fluorescence peak intensity as a function of water content (%) in
ethanol.
Please cite this article as: V.D. Suryawanshi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2013.03.018

V.D. Suryawanshi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
5
OOF
Scheme 3. Solvation of AHDPC forming mono- and polyhydrate species (IV–VI).
[4] A.P. de Silva, S.A. de Silva, Journal of the Chemical Society, Chemical Communications 236
(1986) 1709–1710. 237
[5] A.P. de Silva, H.Q.N. Gunaratne, T. Gunnlaugsson, A.J.M.A.P. de Silva, H.Q.N. Gunaratne, 238
T. Gunnlaugsson, A.J.M. Huxley, C.P. McCoy, J.T. Rademacher, T.E. Rice, Chemical 239
214 of their emission, polysubstituted pyrimidine derivative bearing elec-
215 tron donating groups and appended moiety can be used as fluores-
216 cent probes. The observation of sensitive spectral shifts as a function
217 of water composition suggests that the shift in λem can be applied
218 for the detection of water contents in many aqueous organic systems.
219 The sensitive solvatochromic fluorescence behavior can also be used
220 for the assessment of polarity characteristics in a variety of micro-
221 environments in chemical and biological systems. The pyrimidine de-
222 rivatives are promising candidates for organic electroluminescent media
223 because of their good luminescent properties in blue region; also some of
224 them show good anti-bacterial activity against Gram-positive bacteria.
225 The work is in progress and the derivatives are screened as fluorescence
226 chemosensors in due course.
Reviews 97 (1997) 1515–1566.
240
[6] (a) A.P. de Silva, T.P. Vance, M.E.S. West, G.D. Wright, Organic & Biomolecular 241
Chemistry 6 (2008) 2468–2481;
(b) A.P. de Silva, T.S. Moody, G.D. Wright, Analyst 134 (2009) 2385–2393.
242
243
[7] A. Kraft, A.C. Grimsdale, A.B. Holmes, Angewandte Chemie, International Edition 244
37 (1998) 402–428. 245
[8] L. Pascal, J.J. Van den Eynde, Y. Van Haverbeke, P. Dubois, A. Michel, U. Rant, E. 246
Zojer, G. Leising, L.O. Van Dorn, N.E. Gruhn, J. Cornil, J.L. Brédas, The Journal of 247
Physical Chemistry. B 106 (2002) 6442–6450.
[9] B. Liu, X.L. Hu, J. Liu, Y.D. Zhao, Z.L. Huang, Tetrahedron Letters 48 (2007) 249
5958–5962. 250
[10] H. Kusama, H. Arakawa, Journal of Photochemistry and Photobiology A 160 (2003) 251
171–179. 252
[11] C. Reichardt, Solvents and Solvent Effects in Organic Chemistry, 2nd edn VCH, 253
248
UNCORRECTED PR
New York, 1999. 431.
[12] B. Gangadasu, S. Palaniappan, V.J. Rao, Synlett 7 (2004) 1285–1287.
254
255
227 Acknowledgements
[13] J.S. Yadav, B.V. Subba Reddy, P. Sridhar, J.S.S. Reddy, K. Nagaiah, N. Lingaiah, P.S. 256
Saiprasad, European Journal of Organic Chemistry 3 (2004) 552–557. 257
[14] J.P. Desvergne, A.W. Czarnik, Chemosensors of Ion and Molecule Recognition, 258
Kluwer, Dordrecht, 1997. 259
[15] A.W. Czarnik, Fluorescent Chemosensors for Ion and Molecule Recognition, 260
American Chemical Society, Washington, DC, 1993. 261
[16] R.P. Haugland, Handbook of Fluorescent Probe and Research Products, 8th edn 262
Molecular Probes, Eugene, 2001. , (See http://www.probes.com/handbook). 263
[17] H. Mishra, V. Misra, M.S. Mehata, T.C. Pant, H.B. Tripathi, Journal of Physical 264
Chemistry A 108 (2004) 2346–2352. 265
228
229 from UGC, New Delhi UGC, XIth plan (FIP), and thanks to DST and UGC
230 for providing funds to department under FIST and SAP program.
The author (V.D.S.) gratefully acknowledges receiving a fellowship
231 References
232
233
234
235
[1] K. Köller, Applications of Fluorescence Technology 1 (1989) 1.
[2] A.W. Gzarnik, ACS Symposium Series No. 538, American Chemical Society, Washington,
DC, 1992.
[18] Q. Chang, Z. Murtaza, J.R. Lakowicz, G. Rao, Analytica Chimica Acta 35 (1997) 97–104. 266
[19] S.J. Glenn, B.M. Gullum, R.B. Nair, D.A. Nivens, C.J. Murphy, S.M. Angel, Analytica 267
Chimica Acta 448 (2001) 1–8.
268
[3] A.W. Czarnik, Accounts of Chemical Research 27 (1994) 302–308.
Please cite this article as: V.D. Suryawanshi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2013.03.018

6
V.D. Suryawanshi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
269
270
271
272
273
274
275
276
277
278
289
[20] C.G. Niu, P.Z. Qin, G.M. Zeng, X.Q. Gui, A.L. Guan, Analytical and Bioanalytical
Chemistry 387 (2007) 1067–1074.
[21] W. Liu, Y. Wang, W. Jin, G. Shen, R. Yu, Analytica Chimica Acta 383 (1999)
[25] E.Z. Lippert, Electrochemistry 61 (1957) 962.
[26] N. Mataga, T. Kubota, Molecular Interactions and Electronic Spectra, Marcel Dekker, 280
New York, 1970. 371. 281
[27] F. Ito, T. Nagai, Y. Ono, K. Yamaguchi, H. Furuta, T. Nagamnra, Chemical Physics 282
Letters 435 (2007) 283–288. 283
[28] J.R. Lakowicz, Principles of Fluorescence Spectroscopy, 3rd edn Plenum Press, 284
New York, 2006. 285
[29] S.N. Lad, U.S. Mote, S.L. Bhattar, P.V. Anbhule, S.R. Patil, G.B. Kolekar, Bulletin of 286
279
299–307.
[22] M.B. Deshmukh, S.M. Salunkhe, D.R. Patil, P.V. Anbhule, European Journal of Medicinal
Chemistry 44 (2009) 2651–2654.
[23] B. Valeur, Molecular Fluorescence Principles and Applications, Wiley-VCH, Weinheim,
2002.
[24] E.L. Wehry, in: G.G. Guilbault (Ed.), Practical Fluorescence, Marcel Dekker, New
York, 1990.
the Chemical Society of Ethiopia 23 (2009) 231–238.
287
288
Please cite this article as: V.D. Suryawanshi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2013.03.018