Synthesis, Characterization and Solvatochromic Studies Using the Solvent Polarity Parameter, ENT on 2-Chloro-3-Ethylamino-1,4-Naphthoquinone

Article abstract of DOI:10.1007/s10895-017-2090-6

Quinones are molecules with varied biological activities and electronic properties which are used for important applications [1, 2]. Quinone with a heteroatom substituted, namely 2-chloro-3-ethylamino-1,4-naphthoquinone (N-CAN) was synthesized and characterized by various techniques such as H¹-NMR, C¹³-NMR, Mass spectroscopy and FT-IR spectroscopy. In this study, the solvatochromic effects on the spectral properties of 2-chloro-3-ethylamino-1,4-naphthoquinone have been investigated in different solvents taking into consideration, the solvent parameters like dielectric constant (ε) and refractive index (η) of different solvent polarities. Using Lippert-Mataga, Bakshiev’s, Kawski-Chamma-Viallet and Reichardt equations, the ground state (μ_g) and excited state (μ_e) dipole moments were calculated. The angle between the excited state and ground state dipole moments were also calculated. [Figure not available: see fulltext.].

Full text of DOI:10.1007/s10895-017-2090-6

J Fluoresc
DOI 10.1007/s10895-017-2090-6
ORIGINAL ARTICLE
Synthesis, Characterization and Solvatochromic Studies
Using the Solvent Polarity Parameter, ENT
on 2-Chloro-3-Ethylamino-1,4-Naphthoquinone
Arulappan Durairaj1 & Asir Obadiah1 & Subramanian Ramanathan1
&
Princy Merlin Johnson2 & Antony Paulraj Bella2 & Samuel Vasanthkumar1
Received: 4 January 2017 /Accepted: 4 April 2017
#
Springer Science+Business Media New York 2017
Abstract Quinones are molecules with varied biological ac-
tivities and electronic properties which are used for important
applications [1, 2]. Quinone with a heteroatom substituted,
namely 2-chloro-3-ethylamino-1,4-naphthoquinone (N-
CAN) was synthesized and characterized by various tech-
niques such as H1-NMR, C13-NMR, Mass spectroscopy and
FT-IR spectroscopy. In this study, the solvatochromic effects
on the spectral properties of 2-chloro-3-ethylamino-1,4-
naphthoquinone have been investigated in different solvents
taking into consideration, the solvent parameters like dielec-
tric constant (ε) and refractive index (η) of different solvent
polarities. Using Lippert-Mataga, Bakshiev’s, Kawski-
Chamma-Viallet and Reichardt equations, the ground state
(μg) and excited state (μe) dipole moments were calculated.
The angle between the excited state and ground state dipole
moments were also calculated.
Introduction
Photophysical studies are an important tool to bring out new
technology and develop new organic non-linear optical mate-
rials. Optical absorption and fluorescence spectroscopy tech-
niques reveal the solute–solvent interactions, which can be stud-
ied using the frequency, shape and the intensity of the spectrum.
Spectral shift results are due to the difference in solvent polarity,
specific solute-solvent interactions such as hydrogen bonding,
acid base reactions and charge transfer interactions.
Reorganisation of the solvent molecules around the newly
formed excited solute molecules gives rise to the well-known
stokes shifts. The magnitude of the spectral shifts depends
strongly on the molecule excited and on the nature of the solvent.
Generally, polar solvents give rise to larger shift [3]. The mole-
cules are subjected to change in polarity on excitation and thus
the solvent environment plays an effective role stabilizing or
destabilizing the excited state, which may lead to a bathochromic
(red, called positive solvatochromism) shift or a hypsochromic
(blue, called negative solvatochromism) shift in the fluorescence
emission spectrum of the molecules [4, 5]. Excitation of a mol-
ecule by photon cause the redistribution of charges in the excited
state leading to conformational changes. The dipole moment of
an electronically excited state of a molecule is an important prop-
erty that provides information on the electronic and geometrical
structure of the molecule in short-lived states. Knowledge of the
excited-state dipole moment of electronically excited molecules
is quite useful in designing nonlinear optical materials [6]. The
excited dipole moment is expected to increase or decrease than
the dipole moment of the ground state. The determination of
excited-state dipole moment is derived using various techniques
e.g. electronic polarization of fluorescence [7], electric-dichroism
[8], microwave conductivity [9] and stark splitting [10], but ev-
ery technique has some limitation because they are considered to
be equipment sensitive. Among the techniques available for the
.
Keywords 2-chloro-3-ethylamino-1,4-naphthoquinone
.
Lippert-Mataga, Bakshiev’s Kawski-Chamma-Viallet,
.
Reichardt equations Dipole moments
Electronic supplementary material The online version of this article
(doi:10.1007/s10895-017-2090-6) contains supplementary material,
which is available to authorized users.
* Samuel Vasanthkumar
kumar2359@yahoo.com
1
Department of Chemistry, Karunya University,
Coimbatore, Tamilnadu 641114, India
2
Department of Chemistry, Bishop Heber College,
Trichirapalli, TN 620017, India

J Fluoresc
determination of the excited-state dipole moments, the most pop-
ular one is that, which is based on Lippert–Mataga equation [11,
12], Bakshiev’s equation [13], Kawski-Chamma-Viallet’s equa-
tion calculations [14, 15] and Reichardt equation [16]. In this
methodology, absorption and fluorescence shifts follow bulk sol-
vent polarity, described by dielectric constant (ε) and refractive
index (η).
Several workers have made extensive experimental and
theoretical studies on ground (μg) and excited state (μe) di-
pole moments using different techniques on a variety of or-
ganic fluorescent compounds like coumarins [17], indoles
[18], purines [19], exalite dyes [20], quinazolines [21], acri-
dines and phenazine [22], anthraquinone [23], fluorescein
[24], flavone [25], phthalamide [26], boronic acid [27], and
pyrimidine [28] etc.
ethanol and refluxed. The mixture was heated to gentle
boiling condition and the ethyl amine was added in drops
slowly through the condenser. To this mixture, a small
amount of the base triethylamine was added. The
refluxing was continued for two to four hours, and to
ensure the completion of reaction, it was monitored by
TLC. The hot reaction solution was treated with cold wa-
ter to get a red colour solid. The crude product was sep-
arated by filtration, washed with water to remove excess
base and starting material. The compound was purified
using column chromatography on silica gel (60–120
mesh) using Hexane: Ethylacetate (4:1) eluent system.
Characterization Techniques
The quinone derivatives have a variety of structural and
electronic properties. The electron uptake capacity of a given
moiety can be introduced by directly adding substituent to the
quinone structure. The electron donating and accepting sys-
tem may be useful in the organic non-linear optics, and other
applications. In this present study, the dipole moment of the
quinone compound is evaluated both in the excited singlet
state and ground state. The donor ligand of an amine group
and acceptor ligand of a ketone has a compound influence on
solvents of various polarities. Therefore the electronic absorp-
tion and emission spectra of the N-alkyl amino
naphthoquinone (N-CAN) will be interesting to study. The
(N-CAN) compound was synthesized, characterized and the
dipole moments of the ground state and excited singlet states
evaluated by Lippert-Mataga equation, Bakshiev’s equation,
Kawski-Chamma-Viallet equation and Reichardt correlation
equation. The angle between the excited and ground state
dipole moments is also calculated.
Steady-state absorption spectra at room temperature
(298 K) were recorded by dual beam Jasco V- 550 spec-
trometer. The emission spectra were recorded by using
flurolog-3 photoluminescence and data were analyzed by
the related software. The FT-IR were recorded by IR pres-
1
tige 21 Shimadzu instrument. The H NMR and 13C spec-
tra were recorded with the help of 400 MHz Bruker NMR
spectrometer using CDCl3 as the solvent and chemical shift
values were in internal standard. For Absorption and emis-
sion measurements, samples were taken in 1 cm × 1 cm
Quartz cells. The concentration of solvents used for the
spectroscopy studies was 10−4 mol dm−3 in all cases.
Ground State and Excited Dipole Moment
Different methods are available for calculating the excited
dipole moment of organic compounds. The solvatochromic
method is a method used for determining the ground state
and excited state dipole moment. The N-CAN compound
ground state and excited state dipole moment were calculated
using Lippert-Mataga equation [11, 12], Bakshiev’s equation
[13] and Kawaski-Chamma-Viallet’s equation [14, 15]. The
three equations are given below.
Experimental
Materials
Lippert-Mataga equation:
The chemicals such as dicholoronaphthoquinone,
triethylamine, ethylamine were purchased from Sigma-
Aldrich, and used without further purification. The solvents
used in the study like Hexane, Acetonitrile (ACN),
Chloroform (CHCl3), Dimethylformamide (DMF), Ethanol,
Methanol, 1,4-Dioxne, Acetone, Dicholoromethane (DCM),
Ethylacetate (EA), Isopropyl alcohol (IPA) were purchased
from sigma Aldrich India (HPLC grade).
va−vf ¼ Z1 F1ðε; ηÞ þ C
Bakshiev’s equation:
ð1Þ
ð2Þ
va−vf ¼ Z2 F2ðε; ηÞ þ C
Kawaski-Chamma-Viallet equation:
va þ vf
¼ −Z3 F3ðε; ηÞ þ C
ð3Þ
Synthesis of N-Alkylamino Compound (N-CAN)
2
The process to be followed for the preparation of the
building block of basic quinone compound is as follows:
Dicholoronaphthoquinone (DCNQ) was dissolved in
In these equations F1(ε, η), F2(ε, η), F3(ε, η) are the
corresponding Lippert’s polarity function, Bakshiev’s
polarity function, Kawaski-Chamma-Viallet polarity

J Fluoresc
function respectively. These polarity functions are
expressed by the following equations
state and excited state dipole moment are also evaluated by
means of the following equations.
1
2
ꢀ
ꢁ
Z2−Z1 hca3
ꢀ
ꢁ
μg ¼
ð7Þ
ε−1
η2−1
2
2Z1
F1ðε; ηÞ ¼
−
ð4Þ
ð5Þ
2ε þ 1 2η2 þ 1
1
2
ꢀ
ꢁ
Z2 þ Z1 hca3
ꢀ
ꢁ
μe ¼
μe ¼
ð8Þ
ð9Þ
ε−1
η2−1 ð2η2 þ 1Þ
2
2Z1
F2ðε; ηÞ ¼
F3ðε; ηÞ ¼
−
2ε þ 1 2η2 þ 1 ðη2 þ 2Þ
ꢀ
ꢁ
Z2 þ Z3
ꢀ
ꢁ
μg ðfor Z3 > Z2Þ
ε−1
η2−1 ð2η2 þ 1Þ
Z3−Z2
−
2ε þ 1 2η2 þ 1 ðη2 þ 2Þ
The Suppan equation [29] gives the Onsager cavity radius
of the molecules. Where ‘M’ denotes molecular weight, ‘δ’
denotes the density of the solute molecule and ‘N’ denotes
Avagadro number. The Suppan equation is given below.
3
2
ðη4−1Þ
2ðη þ 2Þ
þ
ð6Þ
2
2
Where va and vf are the absorption and emission wave-
length in cm−1. The symbols ε and η corresponds to the di-
electric constant and refractive index respectively. The ground
1
3
ꢂ
ꢃ
3M
4πδN
a ¼
ð10Þ
Fig. 1 The absorption spectra of the N-CAN compound with changing solvent polarity

J Fluoresc
Reichardt proposed the microscopic solvent polarity scale EN
to overcome the error in the estimation of Onsager cavity. The
ENT also takes into account the intermolecular solute and solvent,
hydrogen bond donor and acceptor interaction [16, 30–34].
Result and Discussion
Spectroscopical Analysis
T
The N-CAN compound was synthesised and analysed by
spectroscopical studies. Mp: 124-126 °C, FT-IR (KBr, cm−1):
NH (3271.41 cm−1), C-N (1295.29 cm−1), C = O
ꢂ
ꢃ
2
ꢄ
ꢅ
Δμ
ao
a
va−vf ¼ 11307:6
3ENT þ Constant
ð11Þ
1
(1680.07 cm−1), C-Cl (720.49 cm−1); H NMR (300 MHz,
Δμb
CDCl3): δ 8.00 (m, 2H), δ 7.6 (dd, 2H), δ 6.02 (1H, s), δ 3.9
(2H, q), δ 1.39 (3H, t); 13C (MHz, CDCl3): δ 180.3, 143.9,
134.7, 132.1, 129.5, 125.6, 39.7, 16.13; MS:EI (m/e): 235.21.
Where Δμb= 9D, the change in dipole moment, ao = 6.2 Å
the Onsager cavity radius of Betaine dye respectively. Δμ and
‘a’ are the change in dipole moment and Onsager cavity radius
of the molecule were taken under study.
Generally the dipole moments μg and μe are not parallel to
each other but are having a small angle ϕ between them and
the angle (ϕ) calculated by the equation given below [34]
Electronic Absorption Spectra
The ultraviolet absorption spectra of (N-CAN) in various
solvents ranging from non-polar solvents to polar protic
solvents are presented in Fig. 1. Non-polar solvents like
n-hexane, toluene, borderline aprotic solvents like EA,
DCM, polar aprotic solvents like acetone, ACN and polar
ꢀ
ꢁ
ꢄ
ꢅ
ꢄ
ꢅ
1
Z2
Z3
cosφ ¼
μ2g þ μ2e
−
μ2e−μ2g
ð12Þ
2μeμg
Fig. 2 The emission spectra of the N-CAN compound with varying polarity of solvents

J Fluoresc
Fig. 3 HOMO and LUMO geometry of N-CAN
solvents like methanol, ethanol were used in this study.
The absorption spectra obtained are characterized by one
sharp band for which the maxima was in the range
272 nm to 284 nm. The solvent effect due to polarity
was obtained as a red shift for the absorption in all the
solvents. The detailed study of stokes shift values was
carried out for all polarity changes due to solvent changes.
The results of the study indicate that the spectrum of N-
CAN in all the solvents used is characterized by two elec-
tronic transitions, namely n → π* and π → π*. The pres-
ence of a unique transition in this solvent series may be
explained only by the overlapping of n → π* and π → π*
bands which are very close in energy. As the polarity of
the solvents increases the magnitude of absorbance values
also increase. All these go to indicate that the excited state
is stabilized more when compared to the ground state.
Fluorescence Spectroscopy
The fluorescence spectra for N-CAN in different organic sol-
vents are shown in Fig. 2. Florescence band maxima are large-
ly bathochromic shifted when the solvent polarity increases.
This fact indicates a higher dipole moment in the excited state
than the dipole moment of the ground state. Interestingly by
some molecules have opposite behaviour of the emission
spectra, such as acridine [35], 7-methoxy-4-methyl-
coumarins [36] systems. The band at the lower wavelength
in the spectra, corresponds to the non-aggregated compounds
and a peak at the higher wavelength is caused by the emission
of aggregated and aromatic units. The investigated compound
shows single emission band in most of the solvents. The
shoulder found in the spectra of Acetone, DMF and CAN
indicates the formation of two excited states in these solvents.
Table 1 Solvatochromic data of N-CAN
À
Á
À
Á
Solvents
λanm
λfnm
vaðcm−1
Þ
vf ðcm−1
Þ
va−vf
va þ vf
ETN
1
2
ðcm−1
Þ
ðcm−1
Þ
Hexane
Toluene
CHCl3
EA
272.07
284.02
276.07
273.80
273.43
275.67
274.80
274.30
275.89
273.39
274.44
390.16
405.46
402.00
394.00
397.68
388.00
388.75
400.00
409.00
402.11
391.94
36755.25
35208.79
36222.70
36523.01
36572.43
36275.26
36349.10
36456.43
36246.33
36577.78
36437.84
25641.03
24663.35
24875.62
25316.46
25145.85
25773.2
11114.22
10545.44
11347.08
11206.55
11432.50
10502.06
10625.62
11456.43
11796.45
11708.97
11500.18
31198.14
29936.07
30549.16
30919.73
30859.14
31024.23
31636.28
30728.22
30348.10
30723.3
0.009
0.099
0.254
0.22
0.46
0.31
0.16
0.35
0.39
0.65
0.76
ACN
DCM
Dioxane
Acetone
DMF
25723.47
25000.00
24449.88
24868.82
24937.66
EtOH
MeOH
30687.75

J Fluoresc
Fig. 4 The studies of variation of Stokes shift vs Various equation. aThe
variation of Stoke’s shift with F1(ε, η) using Lippert-Mataga equation for
N-CAN, b The variation of Stoke’s shift with F2(ε, η) using Bakshiev’s
equation for N-CAN, c The variation of stoke’s shift with F3(ε, η) using
Kawski-Chamma-Viallet equation for N-CAN d The variation of Stoke’s
shift with ENT for N-CAN
The quinone molecule exhibits dual emission in aprotic sol-
vents due to the presence of two close-lying excited states
[37]. An emission band is observed due to the forbidden
n → π* electronic transition which arises due to the interac-
tion of the lone pair of nitrogen atoms with the solvent mole-
cules. The emission band of the N-CAN compound was ob-
served between 350 nm to 460 nm. As the solvent polarity was
measured from Hexane to methanol, the emission maximum
is shifted from shorter wavelength to longer wavelength. The
bathochromic shift from 362 nm to 423 nm, corresponding to
a 61 nm shift confirms a π → π* electronic transitions which
are borne out from the conjugation between the Ketone and
the aromatic ring system. On increasing the solvent polarity
the stoke shift value increase from 11,114.22 cm−1 in hexane
to 11,500 cm−1 in methanol. The magnitude of stokes shifts
indicates the operation of partial intramolecular charge trans-
fer from donor (Carbonyl) to acceptor (Amine). All these data
imply that the molecule is influenced by parameters such as
polarity, hydrogen bond donor-acceptor strength. In the study
of the emission spectra of N-CAN compound, the non-polar
solvents and the borderline aprotic solvents only exhibit a
bathochromic shift. In the case of polar protic solvents and
polar aprotic solvents such as acetone, DMF, IPA, ethanol,
and methanol a hypsochromic shift due to the strong hydrogen
bonding formation between the heteroatom present in the N-
Table 2 Statistical treatment of the correlation of solvent spectral
studies of N-CAN
Compound
N-CANs
Method
Slope
Correlation
Data
Lippert Mataga
Bakshiev’s
3260.80
1286.37
−2701.2
3378.90
0.9000
0.9200
0.8998
0.8009
8
8
7
7
Chamma-Viallet
EN
T

J Fluoresc
Table 3 Ground state and Excited State dipole moments of N-CAN
a
b
c
d
e
f
g
h
ao
μg (D)
μe (D)
μg (D)
μe (D)
μe (D)
μe (D)
μe (D)
μe (D)
Δμj
(Å)
i
μe
μg
N-CAN
4.19
0.51
4.76
1.77
4.78
4.76
6.65
4.77
6.21
2.70
2.73
Debye (D) = 3.33564 х 10−30 cm = 10−18 esu cm
a Theoretical ground state dipole moment using DFT studies (B3LYP level)
b Theoretical excited state dipole moment using DFT studies (B3LYP level)
c The ground state dipole moment calculated using Eq. 10
d The excited dipole moment calculated using Eq. 11
e The excited dipole moment calculated using Eq. 12
f The change of excited dipole moment calculated from Lippert-Mataga expression
g The excited dipole moment calculated from Bakshiev’s expression
h The excited dipole moment calculated from Kawaski-Chamma-Viallet expression
i The ratio of excited state and ground state value
j The change in dipole moment calculated from Reichardt expression
CAN compound was observed. Thus it reveals that the mole-
cule is more stabilized in the excited state in polar solvents
than the ground state implying that the expected excited state
dipole moment should be higher.
the excited state values are more sensitive than the ground state
values. The dipole moment excited state value of Lippert-
Mataga (6.65 D), Kawski-Chamma-Viallet (6.21 D) is higher
than the value derived from the Bakshiev’s method (4.77 D).
The different dipole moment values clearly explain that the N-
CAN compound has more charge transfer in the emitting state.
The radius of the N-CAN was calculated using the Suppan
Eq. (10). The dipolemoments are assumed to be parallel and
the ground state and excited state values are calculated using
Eqs. (7) and (8). The angle between ground and excited dipole
moments was calculated from Eq. (12). From Table 3, it is
observed that the value of excited state dipole moment is more
than the ground state dipole moment. Therefore we conclude
that the excited state is more polar than the ground state.
Assuming that excited state dipole moment is almost parallel
with the ground state. The angle between ground state dipole
moment (1.77 D) and excited state dipole moment (4.78 D)
were calculated and the value was found to be 0.98°, which
supports that the dipole moments are nearly parallel. N-CAN
compound has higher values of dipole moment due to the in-
termolecular hydrogen bond formation ability.
Experimental and Theoretical Calculations of Dipole
Moments
Figure 3, the ground state geometry of the compound is fully
optimized at the semi empirical AM1 level and refined at
B3LYP level using a standard 6–31 (g) basis set on all atoms
with the Gaussian 09 suite of the program. The N-CAN spec-
troscopic properties were investigated by solvatochromic be-
haviour using relevant solvent polarity scales of Lippert-
Mataga correlation, Bakshiev’s correlation and Kawski-
Chamma-Viallet correlation methods. The stokes shift values
are given in Table 1. The stokes shift value can be plotted
against polarity functions F1(ε, η), F2(ε, η), F3(ε, η) and ENT .
The stokes shift value plotted against F1(ε, η), F2(ε, η) are given
in Fig. 4a, b. The average values of stokes shift are plotted
against F3(ε, η) and ENT given in Fig. 4c, d. The stokes shift
range was plotted against polarity function of the various sol-
vents. The different solvents polarity function values of
Lippert-Mataga, Bakshiev’s, Kawaki-Chamma-Viallet are giv-
en in ESM (Electronic supplementary material). The linear pro-
gression was done and the data was fit to a straight line and the
corresponding values of the slopes are given in Table 2. In most
of the cases the correlation co-efficient are higher than 0.90 and
it indicates a good linearity for Z1, Z2, Z3 with selected number
of stokes shift data points. Generally, the deviation from line-
arity may be due to specific solute-solvent interactions. The
dipole moment of N-CAN in the ground state and excited state
changes due to electron densities. The invariance of absorption
spectra and emission spectra with solvent polarity suggests that
Conclusion
We have studied the photophysical properties of a quinone
derivative. The study of solvent effects on the absorption
and fluorescence spectra can be contributed to elucidate the
internal structure of the organic compound and to estimate the
electro-optical molecular parameters such as dipole moments
or polarizabilities of the compound. In absorption spectra, we
observed a red shift upon increasing the solvent polarity,
which indicates the occurrence of a π → π* transition in the
molecule. In the emission spectra, we observed both
bathochromic shift and hypsochromic effect on increasing

J Fluoresc
18. Sharma N, Sapan K, Rastogi RC (2007) Solvatochromic study of
excited state dipole moments of some biologically active indoles
and tryptamines. Spectrochim Acta Part A 66:171–176
19. Aaron JJ, Gaye MD, Parkanyi C, Cho NS, Szentpaly LV (1987)
Experimental and theoretical dipole moments of purines in their
ground and lowest excited singlet states. J Mol Struct 156:119–135
20. Inamdar SR, Nadaf YF, Mulimani BG (2004) Ground and excited
state dipole moments of some exalite UV laser dyes from
solvatochromic method using solvent polarity parameters. J Mol
Struct (THEOCHEM) 678:177–181
the solvent polarity. The experimental excited state dipole
moment of N-CAN was estimated using Lippert-Mataga,
Bakshiev’s, Kawski-Chamma-Viallet and Reichardt correla-
tion methods. The quinone derivative has a higher dipole mo-
ment in the excited state when compared to the ground state
dipole moment, which indicates that the excited state dipole
moment is more polar than the ground state dipole moment.
21. Aaron JJ, Times A, Gaye MD, Parkanyi C, Boniface C, Bieze TW
(1991) Effects of solvent on the electronic absorption and fluores-
cence spectra of quinazolines, and determination of their ground
and excited singlet-state dipole moments. Spectrochim Acta A 47:
419–424
Acknowledgements The authors thank the Management and the au-
thorities of Karunya University, Coimbatore, for their kind support, con-
stant encouragement.
22. Aaron JJ, Maafi M, Párkányi C, Boniface C (1995) Quantitative
treatment of the solvent effects on the electronic absorption and
fluorescence spectra of acridines and phenazines. The ground and
first excited singlet-state dipole moments. Spectrochim Acta A 51:
603–615
23. Sasirekha V, Umadevi M, Ramakrishnan V (2008) Solvatochromic
study of 1,2-dihydroxyanthraquinone in neat and binary solvent
mixtures. Spectrochim Acta A 69:148–155
24. Acemioglu B, Arık M, Efeoglu H, Onganer Y (2001) Solvent effect
on the ground and excited state dipole moments of fluorescein. J
Mol Struct (THEOCHEM) 548:165–171
25. Kumar S, Jain SK, Rastogi RC (2001) An experimental and theo-
retical study of excited-state dipole moments of some flavones
using an efficient solvatochromic method based on the solvent po-
larity parameter, ENT. Spectrochim Acta A 57:291–298
26. Lyman R et al (1974) Dipole moments of some 3-and 4-substituted
phthalimides and phthalic anhydrides. Influence of steric and reso-
nance effects. J Organomet Chem 39(11):1527–1531
Reference
1. O’Malley PJ (2001) Electronic structure studies of Quinones and
Semiquinones: accurate calculation of spin densities and electron para-
magnetic resonance parameters. Antioxid Redox Signal 3(5):825–838
2. Ma W, Long YT (2014) Quinone/hydroquinone-functionalized
biointerfaces for biological applications from the macro- to nano-
scale. Chem Soc Rev 43(1):30–41
3. John OM, Vincent JD, Pugh D (1987) Non-linear optical properties
of organic molecules. Part 2. Effect of conjugation length and mo-
lecular volume on the calculated hyperpolarisabilities of
polyphenyls and polyenes. J Chem Soc Perkin Trans 2:1351–1355
4. Lakowicz JR (2006) Principles of fluorescence spectroscopy, third
edn. KLuwer Academic/ Plenum Press, New York
5. Ooshika Y (1954) Absorption spectra of dyes in solution. J Phys
Soc Jpn 9:594–602
6. Mataga N (1963) Solvent effects on the absorption and fluorescence
spectra of naphthylamines and isomeric aminobenzoic acids. Bull
Chem Soc Jpn 36:654–659
27. Geethanjali HS, Nagaraja D, Melavanki RM (2015) Estimation of
dipole moments and quantum yield of 5-chloro-2-methoxyphenyl
Boronic acid in different solvents environment. J Fluoresc 25(3):
745–753
7. Czekella J (1960) Electrical fluorescence polarization: the determina-
tion of dipole moments of excited molecule from the polarization
degree of fluorescence in strong electric field, Z. Elektrochem 64:1221
8. Czekella J (1961) Two electro-optical methods to determine dipole
moments of excited molecules. Chimica 15:26
9. Hass MP, Warman JM (1982) Photon induced molecular change
separation studied by nanosecond time-resolved microwave con-
ductivity. Chem Phys 73:35
28. Almeida KJ et al (2001) A Monte Carlo–quantum mechanical study
of the solvatochromism of pyrimidine in water and in carbon tetra-
chloride. Phys Chem Chem Phys 3:1583–1587
29. Suppan P (1983) Excited-state dipole moments from absorption/
fluorescence solvatochromic ratios. Chem Phys Lett 94:272
30. Reichardt C, Welton T (2011) Solvents and solvent effects in or-
ganic chemistry, 4th edn. Wiley-VCH Verlag GmbH & Co. KGaA,
Weinheim
31. Reichardt C (1992) Solvatochromism, thermochromism,
piezochromism, halochromism, and chiro-solvatochromism of
pyridinium N-phenoxide betaine dyes. Chem Soc Rev 21:147–153
32. Ravi M, Samanta A, Radhakrishnan TP (1994) Excited state dipole
moments from an efficient analysis of solvatochromic stokes shift
data. J Phys Chem 98(37):9133–9136
33. Ravi M, Samanta A, Radhakrishnan TP (1995) Excited-state dipole
moments of some hydroxycoumarin dyes using an efficient
solvatochromic method based on the solvent polarity parameter,
ETN. J Chem Soc Faraday Trans 91:2739–2742
34. Rabek JF, Scott GW (1989) Photochemistry and photophysics.
CRC Press, Boca Raton
35. Kellmann A (1977) Intersystem crossing and internal conversion
quantum yields of acridine in polar and nonpolar solvents. J Phys
Chem 81:1195–1198
10. Lombardi JR (1998) Solvatochromic shifts: a reconsideration. J Phy
Chem A 102:2817
11. Liptay W, Lim EC (1961) Excited states, vol.1, academic Press,
New York, 1974. J Czekella Zeitschrift fur Chimica 15:26–29
12. Mataga N, Kaifu Y, Koizumi M (1956) Solvent effects upon fluo-
rescence spectra and the dipolemoment of the excited molecule.
Bull Chem Soc Jpn 29:465–470
13. Bakshiev’s NG (1964) Universal intermolecular interactions and
their effect on the position of the electronic spectra of molecules
in two-component solutions. Opt Spektrosk 16:821
14. Bilot L, Kawski A (1962) To theory of the influence of solvents on
the electron spectra of molecules. Zeitschrift für Naturforschung A
17:621–627
15. Chamma A, Viallet P (1970) Determination of the dipole moment
of a molecule in an excited singlet state: application to indole,
benzimidazole and the indazole. Acad Sci Paris Ser 270 C:1901
16. Reichardt C (1994) Solvatochromic dyes as solvent polarity indica-
tors. Chem Rev 94:2319
36. Uchiyama S, Takehira K, Yoshihara T, Tobita S, Ohwada T (2006)
Environment- sensitive fluorophore emitting in protic environ-
ments. Org Lett 8:5869–5872
37. Haidekker MA, Theodorakis EA (2016) Ratiometric
mechanosensitive fluorescent dyes: design and applications. J
Mater Chem C 4:2707–2718
17. Giri R (1992) M.M. Bajaj, estimation of excited state dipole mo-
ment of substituted coumarins. Curr Sci 62:522–525