A fluorescence and fluorescence probe study of benzonaphthyridines

Article abstract of DOI:10.1007/s10895-011-0945-9

A series of benzo[b][1,8]naphthyridines has been synthesized by Friedlaender condensation of 2-aminoquinoline-3-carbaldehyde 1 (o-aminoaldehyde) with alicyclic ketones in basic medium. Benzonaphthyridines branched with various side-chains and substituents

Full text of DOI:10.1007/s10895-011-0945-9

J Fluoresc (2012) 22:17–29
DOI 10.1007/s10895-011-0945-9
RAPID COMMUNICATION
A Fluorescence and Fluorescence Probe Study
of Benzonaphthyridines
Deepak Prakash Shelar & Sandeep R. Patil &
Ramhari V. Rote & Madhukar N. Jachak
Received: 20 June 2011 /Accepted: 2 August 2011 /Published online: 16 August 2011
#
Springer Science+Business Media, LLC 2011
Abstract A series of benzo[b][1,8]naphthyridines has
been synthesized by Friedländer condensation of 2-
aminoquinoline-3-carbaldehyde 1 (o-aminoaldehyde) with
alicyclic ketones in basic medium. Benzonaphthyridines
branched with various side-chains and substituents are
prepared with the aim of being investigated as a good
fluorescent material. Electronic absorption and fluorescence
properties of some representative benzonaphthyridines in
organic solvents, water-dioxane, and SDS, CTAB and
Triton-X-100 micelles have been examined. The linear
correlation between solvent polarity and fluorescence
properties is observed. This study may provide new
directions for the development of fluorescence probes as
reporters of microenvironments of organized assemblies.
bonds [3–5]. Optical linear and nonlinear properties of such
push-pull molecules depend on the polarizability of the
electrons localized in π-bonding molecular orbitals [6, 7].
Although the polarizability of a molecule is mainly given by
its chemical structure, in particular by the length of the π-
conjugated spacer and the electronic nature of the donors and
acceptors attached [8–10], it can also be affected by external
factors such as frequency of radiation, state of matter, and
solvent used for preparation of solution. However, a general
description of external factors (solvent) affecting optical and
nonlinear optical properties is more complex.
It is observed that, fluorescence probes such as sensors
and reporters of microenvironments are of much current
interest [11]. The environment-sensitive molecular fluores-
cence probe shows different fluorescence behaviors in
hydrophilic and hydrophobic surroundings. Fluorescence
studies of such probe gives useful information about the
microenvironment of their location. Such fluorescence
probes are widely used for characterizing the microenviron-
ments in biological systems like proteins, lipid bilayers and
nucleic acids, which are known to have structural domains
having differences in physico-chemical properties, acid–
base characters, viscosity, polarity, etc. In general these
probes are very useful for getting information about the
structural features and functional dynamics of complex
structural systems [12–14]. Fluorescence probe technique
represents the most important area of fluorescence spec-
troscopy to study biologically important systems and are
rapidly gaining popularity in the study of biological
microheterogeneous systems due to their non-invasive
nature and the large extent of information gleaned thereby
[15, 16]. Probes that show massive spectral changes on
being tagged to such systems are being designed and
developed and their spectral responses are then exploited to
gain information about the structure and dynamics of the
.
Keywords Benzo[b][1,8]naphthyridines Sodium dodecyl
.
sulfate (SDS) Cetyl trimethyl ammonium bromide
.
(CTAB) Triton-X-100
Introduction
π-Conjugated organic molecules attract much attention due to
their prospective application as efficient materials in organic
electronics and optoelectronics [1, 2]. A typical organic
charge-transfer (CT) chromophore (D-π-A) consists of strong
electron donors D (e.g., NR2 or OR groups), strong electron
acceptors A (e.g., NO2 or CN groups), and a π-conjugated
core featuring (hetero)-aromatic rings and/or double or triple
:
:
:
D. P. Shelar S. R. Patil R. V. Rote M. N. Jachak (*)
Organic Chemistry Research Centre, Department of Chemistry,
K.T.H.M. College,
Gangapur Road,
Nashik 422 002, MS, India
e-mail: mnjachak@hotmail.com

18
J Fluoresc (2012) 22:17–29
system under study. Probe like ANS [17–21] show polarity
dependant spectral characteristics and are being widely
used as fluorescent labels for studying proteins, vesicles,
micelles, mixed micelles and similar biological or bio-
mimetic micro-heterogeneous systems.
naphthyridine 5(a-b) in 82–85% yield. However, reaction of
1 with dimedone 6(a-b) was unproductive in ethanolic KOH
due to its more enolic character; hence this condensation is
achieved by heating without solvent at 180–185 °C to afford
3,3-dimethyl-3,4-dihydrodibenzo[b,g][1, 8]naphthyridin-1
(2H)-one 7(a-d) in good yield. Analog, cyclocondensation
of 1a or 1b with cetralene 8 in ethanolic KOH under reflux
gave 5-(3,4-dichlorophenyl)-5,6-dihydrobenzo[b]naphtho
[2,1-g][1,8]naphthyridine 9(a-b). All synthesized compounds
are characterized by spectroscopic and analytical methods.
For e.g. IR of 7d shows streching frequency at 1703 cm-1 for
C=O. 1H NMR spectrum of 7d in CDCl3 shows four singlet
at 1.25, 2.39, 2.94 and 4.09 ppm corresponds to protons of
methyl (2 x CH3), methylene (2 x CH2s’) and methoxy
(OCH3) groups respectively. All aromatic protons shows
expected chemical shifts and splitting patterns which
resembles with the structure proposed. The mass spectrum
Recently, we have reported the synthesis of fluorescent
benzo[b][1,8]naphthyridine-3-carbonitrile using 2-
aminoquinoline-3-carabldehyde (o-aminoaldehyde) 1 [22]
and also reported that certain banzonaphthyridines are
capable of solvatochromic fluorescence emission and these
are used as a fluorescence probes for studying the
microenvironment of organised assemblies such as Bovine
serum albumin (BSA) [23]. In this work, various fluores-
cent benzo[b][1,8]naphthyridines are synthesized via
Friedländer condensation of 1 with cyclic ketones in basic
reaction condition. Some representative benzonaphthyri-
dines (3d, 5b and 7d) are investigated for their absorption
and fluorescence properties in homogeneous media of
organic solvents, 1,4-dioxane-water binary mixtures and in
the microheterogeneous media of Sodium dodecyl sulfate
(SDS), Cetyl trimethyl ammonium bromide (CTAB) and
Triton-X-100 micelles. Moreover, semi-empirical calcula-
tions have been performed using MOPAC-2009 to investi-
gate the effect of substituent (i.e. OCH3) on fluorescence
properties of benzonaphthyridines.
of 7d reveals an H+ molecular ion peak m/z at 307. The 13
C
NMR spectrum of this compound in agreement with the
structure proposed (Scheme 1). Synthesized benzonaphthyr-
idines are further utilized for study their photophysical
properties.
Semi-empirical Study of Benzo[b][1,8]naphthyridine
The HOMO and LUMO of a molecule are usually
important characteristics for its chemical reactivity and for
biological activity [24–27]. The fluorophores which are
useful as Organic Light Emitting Diodes (OLEDs) should
fluoresces between 400–700 nm and HOMO/LUMO or
‘electron-hole’ gap is in the range of 2.7–3.0 eV i.e. low
gap [28]. Prompted with these quotations, we perform some
computational calculations like heat of formation, ioniza-
tion potential, HOMO, LUMO energies and electron hole
gap (HOMO-LUMO energy separations) of synthesized
benzonaphthyridines by using MOPAC-2009 (Version
8.331) [29, 30] and are summarized in Table 1. The charge
is more concentrated on ring A as compared to ring B and
C (Fig. 1). The donor chromophore (−OCH3 group) on ring
A plays an important role in increasing the electron density
and lowering electron hole gap. Compounds 3b, 3d, 5b, 7b,
7d and 9b bearing -OCH3 gr. on ring A shows low Gap
values indicating higher overlapping of HOMO or LUMO
orbital’s which shows red shift in its fluorescence maxima
and high quantum yields as compared to others.
Results and Discussion
Reactions of o-aminoaldehydes with cyclic ketones are
especially valuable for the construction of polycondensed
heterocyclic systems. The availability and structural variety
of cyclic ketones provide easy and direct access to a large
number of fused heterocyclic systems for which in many
cases alternate annelation methods are not readily available.
Herein, we extend Friedländer condensation using different
cyclic ketones having reactive methylene group to generate
libraries of new heterocycles. We employed mild reaction
conditions in the Friedländer condensation to permit the
transformation of functional groups from the starting ketone
into the annelated heterocyclic ring. Known 2-aminoquinoline-
3-carbaldehyde (o-aminoaldehyde) 1 has been synthesized by
novel method reported in our previous communication
[22]. The base catalyzed condensation (in ethanolic KOH)
of 1 with cyclopentanone 2a gave the strained heterocycle
2,3-dihydro-1H-benzo[b]cyclopenta[g][1,8]naphthyridine
3(a-b) in 80-84% yield also available via acid catalyzed
condensation (in aq. HCl) of the components although in
much lower yield i.e. 40–45%, hence we performed
further cyclocondensation in basic medium. Therefore,
cyclocondensation of 2-aminoquinoline-3-carbaldehyde 1a or
1b with 2-methylcyclohexanone 4 in ethanolic KOH
furnished into 4-methyl-1,2,3,4-tetrahydrodibenzo[b,g][1,8]
Photophyscial Properties
Solvent-Induced Shifts of Absorption and Fluorescence
A variety of environmental factors affect fluorescence
emission, including interactions between the fluorophore

J Fluoresc (2012) 22:17–29
19
Scheme 1 Synthesis of benzo
[b][1,8]naphthyridines by
Friedländer condensation of o-
aminoaldehyde with alicyclic
ketones
O
(CH2)n
2 (a-b)
R
(CH2)n
EtOH/ KOH,
reflux, 5h
N
N
3 (a-d)
3a; R = H, n = 1
3b; R = OCH3, n = 1
3c; R =H, n = 2
3d; R = OCH3, n = 2
O
R
4
EtOH/ KOH,
reflux, 6h
N
N
O
5 (a-b)
O
R1
R2
5a; R =H
5b; R =OCH3
O
O
R
H
6 (a-b)
R
R1
R2
N
NH2
180-185 °C,
15 mins.
N
N
1 (a-b)
7 (a-d)
1a; R =H
7a; R, R1, R2 = H,
1b; R =OCH3
7b; R=OCH3; R1, R2 = H,
7c; R=H; R1, R2 = CH3,
7d; R=OCH3; R1, R2 = CH3
O
Cl
Cl
Cl
R
8
Cl
EtOH/KOH,
reflux, 3h
N
N
9 (a-b)
9a; R =H
9b; R =OCH3
and surrounding solvent molecules (dictated by solvent
polarity), other dissolved inorganic and organic compounds,
temperature, pH and the local concentration of the
fluorescent species. The effects of these parameters vary
widely from one fluorophore to another, but the absorption
and emission spectra, as well as quantum yields, can be
heavily influenced by environmental variables. In fact, the
high degree of sensitivity in fluorescence is primarily due to
interactions that occur in the local environment during the
excited state lifetime. This research article explores relaxation
effects and associated spectral shifts that occur as a
function of solvent polarity. Thus, in this piece of work,
we mainly give emphasis on to study effect of solvent on
absorption and fluorescence emission, because solvents play
an important role in physical and chemical processes. Solvent
effects are related to the nature and the extent of the solute-
solvent interactions developed in the solvation shell of the
solutes [31]. Organic mixed solvents are widely used as
the mobile phase in liquid chromatography, capillary
electrophoreses and as a reaction medium. Solvent mixtures
have improved physical properties such as solvation power,
density, viscosity and refractive index compared with pure
solvents [32]. When the solute is dissolved in a solvent,
the solvent exerts a definite influence on the solute. This
influence depends on the nature of the solvent. This
influence reflects changes in the absorption and fluores-
cence spectrum [33] and this phenomenon is known as
solvatochromism. Solvatochromism is used to describe the
pounced change in position sometimes in intensity of an
absorption band, accompanying a change in the polarity of
the medium. The preferential solvation phenomenon that
is the selective enrichment of the certain solvent component in
the solvation shell of a given solute is of paramount
importance in the interpretation of many physiochemical

20
J Fluoresc (2012) 22:17–29
Table 1 The molecular electronic properties (HOMO-LUMO energy, GAP) of the benzo[b][1,8]naphthyridine 3(a-d), 5(a-b), 7(a-d) and 9(a-b)
Comp.
R
R1
R2
Heat of Formation
(K CAL.)
Ionization
Potential (eV)
HOMO (eV)
LUMO (eV)
Gap (eV)
3a
3b
3c
3d
5a
5b
7a
7b
7c
7d
9a
9b
H
–
–
73.55
41.18
66.08
26.13
61.52
21.56
36.71
−2.87
22.84
−16.71
110.58
70.07
9.021
8.849
8.957
8.486
8.948
8.485
9.269
8.728
9.235
8.699
9.166
8.703
−9.022
−8.849
−8.957
−8.487
−8.949
−8.485
−9.269
−8.728
−9.236
−8.699
−9.167
−8.704
−1.235
−1.219
−1.241
−1.231
−1.232
−1.221
−1.667
−1.671
−1.633
−1.639
−1.476
−1.480
7.787
7.630
7.716
7.256
7.717
7.264
7.602
7.057
7.603
7.060
7.691
7.224
OCH3
H
–
–
–
–
OCH3
H
–
–
–
–
OCH3
H
–
–
–
–
OCH3
H
–
–
CH3
CH3
–
CH3
CH3
–
OCH3
H
OCH3
–
–
GAP=ELUMO-EHOMO
parameters measured in the mixtures [34]. In the study of
preferential solvation, hydrogen bonding plays an important
role and has been widely investigated because it is present in
large variety of chemical, biochemical and pharmacological
events [35].
polar n-hexane to polar DMF. The maximum red shift is
observed for 3d in its fluorescence emission. We observed
linear correlation between solvent polarity and fluorescence
property, as the solvent polarity increases from non-polar
n-hexane to polar aprotic DMF, fluorescence maxima is shift
to the longer wavelength (red shift). The fluorescence
excitation maximum in organic solvents is similar to the
absorption maximum in the same solvents. The excitation
spectrum was found to be independent of emission wave-
length in all the media studied. (Table 2)
The blue-shifted fluorescence emission of these benzo-
naphthyridines in non-polar solvents can be from the
locally excited state, while the longer wavelength emission
can be from an intramolecular charge transfer excited state,
which is more polar and lower in energy than the locally
excited state. The intramolecular charge transfer excited
state can involve conformational relaxation of the single
bonds connecting the donor group to the acceptor group.
Hence, the polar solvents stabilise the excited state,
resulting in red-shifted fluorescence emission.
Undertaking these literature results, herein, we investi-
gate electronic absorption and fluorescence properties of
some representative benzonaphthyridines (3d, 5b and 7d)
in homogeneous media of organic solvents with different
solvent polarity. UV–vis absorption and fluorescence
spectral data of benzonaphthyridines 3d, 5b and 7d in
organic solvents (homogeneous media) of different polarity
are summarized in Table 2 and graphically represented in
Fig. 2. A very moderate solvent polarity effect on the
absorption maximum and almost no effect on the fluores-
cence excitation spectrum, there is a marked influence of
the solvent polarity on the fluorescence emission behavior
of these benzonaphthyridines (Fig. 2). Benzonaphthyridine
3d, 5b and 7d shows a red shift of 27, 22 and 18 nm
respectively, in its fluorescence maxima in going from non-
Fig. 1 3D picture of benzo[b]
[1, 8]naphthyridines 7c and 7d

J Fluoresc (2012) 22:17–29
21
Table 2 UV–vis absorption and
fluorescence spectral data of
benzonaphthyridines 3d, 5b and
7d in homogeneous media of
organic solvents at room
temperature
Comp.
3d
Solvent
lmax (nm)
Stokes’Shift/cm-1
Фf ( 0.002)
abs
emi
exi
n-hexane
dioxane
THF
362
367
366
364
364
369
360
362
362
362
362
368
389
394
396
401
402
407
461
469
474
480
480
488
459
464
470
475
473
481
482
488
490
497
496
500
362
365
366
363
363
365
360
360
365
359
361
367
390
391
399
398
401
410
4917
5068
5836
6342
6342
6096
4239
4446
5105
5877
5637
5583
5894
6475
6969
7648
7584
7227
0.256
0.263
0.297
0.318
0.315
0.345
0.261
0.274
0.291
0.321
0.310
0.378
0.367
0.379
0.385
0.395
0.390
0.403
MeCN
MeOH
DMF
5b
7d
n-hexane
dioxane
THF
MeCN
MeOH
DMF
n-hexane
dioxane
THF
MeCN
MeOH
DMF
Fluorescence Quantum Yields (Фf) and Stokes Shift of 3d,
5b and 7d in Organic Solvents
resulting emission is very weak. In polar solvents, however,
there is reversal of states from Ag*- to Bu*+, which gives
rise to allowed Bu*- → Ag transition responsible for
relatively increased Фf. A relatively higher Фf and large
red-shifted fluorescence of banzonaphthyridines (3d, 5b
and 7d) in aprotic polar solvents further indicate that the
fluorescence originates from highly polarized excited state.
Solvent relaxation effects on fluorescence can result in a
dramatic effect on the size of Stokes’ shift. From Table 2, it
observed that, Stokes’ shift is increased with solvent
polarity.
These benzonaphthyridines show rather strong fluorescent
emission. In general, the solvent polarity and the type of
substituent and its position appear to influence the
fluorescence quantum yields. In non polar solvents like n-
hexane, the fluorescence quantum yields (Фf) are low as
compare to polar protic and polar aprotic solvents. Increase
in Фf with increase in solvent polarity can partly be
attributed to the possible state reversals of the lowest
excited states of the benzonaphthyridines. In nonpolar
Further, UV–vis and fluorescence spectra of compounds
3(a-d), 5(a-b), 7(a-d) and 9(a-b) are taken in DMF as a
solvent. Fluorescence quantum yield of all synthesized
-
solvent, the fluorescent excited state can be of Ag nature.
-
Since Ag * → Ag transition is symmetry forbidden; the
Fig. 2 UV–vis absorption (λabs
max) and fluorescence (λf max)
spectra of 3d in (i) n-hexane, (ii)
dioxane, (iii) THF, (iv) MeCN,
(v) Methanol, (vi) DMF

22
J Fluoresc (2012) 22:17–29
compounds are determined by standard literature procedure
using quinine sulphate as a reference standard [13, 36] and
are given in Tables 2 and 3.
487 nm when dioxane contained 60% water. Similarly, 464,
488 nm fluorescence of 5b and 7d in dioxane shifted,
respectively, to 481 and 524 nm in dioxane containing 60%
water. Thus, fluorescence is highly red-shifted as the water
content in the solvent mixture is increased. This observation
is similar to that of the studies in organic solvents of different
polarity. In organic solvents and dioxane-water systems, as
the polarity (relative permittivity, ε) of the media is
increased, the lf max undergoes a red shift. The maximum
red shift is observed for 7d in its fluorescence emission when
dioxane contained 60% of water. From the Table 4, we
observed that, quantum yields (Фf) tends to decrease as the
% of water is increase in 1,4-dioxane. Maximum decrease in
quantum yield (Фf) is observed for 7d.
Despite numerous efforts to determine effect of solvent
polarity on fluorescence properties of heterocyclic com-
pounds, the solvent properties of the micellar environment
are still poorly understood. Among various physical
methods employed, fluorescence probes have been widely
used because of their simplicity, wide scope, and extreme
sensitivity at very low probe concentration [37]. Comparison
of the spectral data in micelles with those in homogeneous
solvent systems provides information on the micellar
environment. Thus, as compared to the homogeneous media
of organic solvents, the micellar environment does not cause
significant change in the absorption spectra of these
benzonaphthyridines (Table 5). The fluorescence spectrum
of compounds 5b in micelles is significantly red-shifted as
compared to that in non-polar n-hexane. However, the
fluorescence maxima (lf max) in micelles are similar to
those in polar solvents like DMF, MeCN and MeOH. As
compared to in polar solvents, the fluorescence maximum
(lf max) of 5b is blue-shifted in Triton-X-100 micelles
(Table 5 and Fig. 5). In general, as compared to the
fluorescence of benzopanaphthyridines 3d, 5d and 7d in
non-polar n-hexane, in micellar media the fluorescence of
these benzonaphthyridines is red-shifted; the maximum red
shift is observed for 5b. A comparison of the lf max of
benzonaphthyridines 3d, 5b and 7d in polar organic solvent
such as methanol with those in micelles reveals that the
benzonaphthyridines, experience relatively polar environ-
Electronic Spectroscopy of 3d, 5b and 7d in Dioxane-Water
Mixture and in Microheterogeneous Media of Micelles
Solvent polarity dependent fluorescence properties of
substituted benzonaphthyridines prompted us to study the
fluorescence properties of 3d, 5b and 7d in micelles of
SDS, CTAB and Triton-X-100. We have employed these
fluorophores for characterizing the microenvironment of
these micelles. Since the solvatochromic fluorescence
properties of these benzonaphthyridines were to be used
to probe micellar environments, it was necessary to ensure
that the fluorescence emission in surfactant solution is not
due to any specific interaction between the benzonaphthyridine
and water molecules. The inefficiency of solubility of
benzonaphthyridines in water prohibits direct spectroscopic
study in aqueous solution. Therefore, we examined electronic
spectra of 3d, 5b and 7d in dioxane-water mixture. The
absorption and fluorescence spectral data of benzonaph-
thyridines 3d, 5b and 7d in various compositions of 1,4-
dioxane-water are summarized in Table 4. The absorption
and fluorescence emission spectra of compound 3d and 7d
are graphically presented in Figs. 3 and 4 respectively. From
the Table 4, we observed that, in 1,4-dioxane-water mixtures
absorption maximum (labs max) tends to decrease as the
water content is increased. These absorption spectral features
can be due to ground state hydrogen bond interactions and
aggregate formation, particularly in water in which benzo-
naphthyridines are not freely soluble. When the water
content was varied between zero and 60% in dioxane, the
absorption maximum (labs max) shift to the blue by 9, 11
and 15 nm for 3d, 5b and 7d respectively. On the other hand,
as the water content (% water) is increased in 1,4-dioxane,
the excitation maximum (lex max) considerably red-shifted
as compared to its absorption maximum. However, benzo-
naphthyridines 3d, 5b and 7d exhibited red-shifted fluores-
cence in dioxane containing increasing amounts of water.
Thus, 469 nm fluorescence of 3d in dioxane shifted to
Table 3 UV–vis absorption and fluorescence spectral data of 3(a-d), 5(a-b), 7(a-d) and 9(a-b) in DMF as the solvent at room temperature
Comp.
labs max/nm
lf max/nm
ϕF ( 0.002)
Comp.
labs max/nm
lf max/nm
ϕF ( 0.002)
3a
3b
3c
3d
5a
5b
360
365
362
369
365
368
472
481
477
488
472
481
0.294
0.327
0.301
0.345
0.284
0.378
7a
7b
7c
7d
9a
9b
368
373
370
407
398
418
478
498
489
500
472
487
0.311
0.397
0.350
0.403
0.351
0.372

J Fluoresc (2012) 22:17–29
23
Table 4 UV–vis absorption (labs max) and fluorescence (lf max) spectral data of 3d, 5b and 7d in 1,4-dioxane- water mixtures at room
temperature
Comp.
3d
% Water in
1,4-dioxane
labs max/nm
lf max/nm
lex max/nm
Stokes’ Shift/cm-1
Фf ( 0.002)
0
367
365
362
360
359
359
358
362
361
361
358
356
353
351
394
391
387
386
382
380
379
469
475
478
478
483
486
487
464
475
478
478
478
478
481
488
492
510
512
513
515
524
367
370
376
374
373
373
373
359
360
360
354
354
352
351
396
395
393
394
394
392
392
5068
5947
5712
5712
5357
5369
5884
4446
5241
5302
5317
5579
5792
5822
6475
6337
7367
7512
7641
7837
8227
0.263
0.254
0.239
0.239
0.225
0.221
0.218
0.274
0.263
0.254
0.253
0.253
0.255
0.249
0.379
0.363
0.356
0.349
0.341
0.332
0.316
10
20
30
40
50
60
0
5b
10
20
30
40
50
60
0
7d
10
20
30
40
50
60
ment in the micelles. The quantum yield (Фf) of these
benzonaphthyridines (3d, 5b and 7d) is relatively higher in
Triton-X-100 as compared to either SDS or CTAB. The
fluorescence efficiency is lowest in SDS micelles for all three
benzonaphthyridines. Since we already showed that there is
an increase in quantum yield (Фf) with increase in solvent
polarity of the medium, the increase in Фf in micelles is
attributable to the grater polarity of the media. The Stokes’
shift for all three benzonaphthyridines in polar homogeneous
media of organic solvents such as DMF, acetonitrile and
methanol is greater than that in micellar media. Among the
three micelles studied, the smallest Stokes’ shift is observed
in neutral Triton-X-100. Thus, the ionic micelles of SDS and
CTAB affect the fluorescence spectra most. This can be due
to interactions between the micellar charges and the polar
benzonaphthyridine fluorophore. Thus, while benzonaph-
Fig. 3 UV–vis absorption and
fluorescence emission (lf max)
spectra of 3d in different con-
centration of water (i) 0%, (ii)
10%, (iii) 20%, (iv) 30%, (v)
40%, (vi) 50%, (vii) 60%

24
J Fluoresc (2012) 22:17–29
Fig. 4 UV–vis absorption and
fluorescence emission (λf max)
spectra of 7d in different
concentration of water (i) 0%,
(ii) 10%, (iii) 20%, (iv) 30%, (v)
40%, (vi) 50%, (vii) 60%
thyridine 5b shows significant micelle-charge dependent
fluorescence peak shifts, 3d and 7d do not show such
marked changes in their fluorescence lf max.
addition to library of fluorescent heterocyclic compounds.
Synthesized benzonaphthyrdines are studied for their photo-
physical properties. The fluorescence property of benzonaph-
thyridines depends upon the nature of substituent present on
ring A. Thus benzonaphthyridines bearing electron-releasing
group i.e. OMe (Compound 3b, 3d, 5b, 7b, 7d and 9b) on
ring D (Fig. 1) fluoresces at longer wavelength as compared
to Compound 3a, 3c, 5a, 7a, 7c and 9a. From empirical
calculations, we reveals that benzonaphthyridines which
shows low electron hole gap values (e.g. 3b, 3d, 5b, 7b,
7d and 9b) have high fluorescence emission as well as have
high quantum yields. While compounds with higher electron
hole gap (e.g. 3a, 3c, 5a, 7a, 7c and 9a) shows low
fluorescence emission and low quantum yield and are in
agreement with theoretical observations. Moreover, certain
benzonaphthyridines (3d, 5b and 7d) are studied for UV–vis
absorption (labs max) and fluorescence emission (lf max) in
homogeneous media of organic solvents, 1,4-dioxane-water
binary mixtures and in micellar environment. From these
studies, we reveal that, these benzonaphthyridines (3d, 5b
and 7d) exhibits solvatochromic fluorescence emission may
be due to a polar, conformationally relaxed, intramolecular
charge transfer excited state. The absorption maximum
Thermal Properties
The organic compounds which are used in OLEDs and
opto-electronic applications should be thermally and chemi-
cally stable [38]. Thermal analysis of synthesized benzo-
naphthyridines, by differential scanning colorimetry (DSC)
and TGA reveal that they are thermally stable compounds up
to 350 °C and high crystallization temperature.
Conclusion
In conclusion, the formation of linear tetracyclic and
pentacyclic benzonaphthyridines from dicyclic o-aminoalde-
hyde 1 represents remarkable efficient heteroannelation
reaction. Friedländer condensations of 1 with heterocyclic
5-membered and 6-membered ring ketones are employed
extensively. All these newly synthesized compounds are
Table 5 UV–vis absorption
Comp.
Media
lmax (nm)
Stokes’Shift/cm-1
Фf ( 0.002)
(labs max) and fluorescence
(lf max) spectral data of benzo-
naphthyridines 3d, 5b and 7d in
microheterogeneous media of
micelles at room temperature
abs
emi
exi
3d
5b
7d
CTAB
372
372
372
376
371
376
404
399
404
477
477
474
475
477
471
494
487
491
369
368
369
372
370
372
398
395
398
5916
5916
5602
4773
5261
4137
6977
5819
5784
0.332
0.227
0.383
0.384
0.302
0.394
0.371
0.244
0.389
SDS
Triton-X-100
CTAB
SDS
Triton-X-100
CTAB
SDS
Triton-X-100

J Fluoresc (2012) 22:17–29
25
Fig. 5 Fluorescence spectra of all three benzonaphthyridines (3d, 5b and 7d) in micelles of (a) CTAB (b) SDS and (c) Triton-X-100
(labs max) of these compounds undergoes a moderate red
shift with increasing solvent polarity; on the other hand
fluorescence maxima (lf max) becomes highly red shifted
with increasing solvent polarity. It is observed that, in 1,4-
dioxane-water mixtures, blue shift in absorption maximum is
observed as the water content is increased and on the other hand
red shifted fluorescence emission is observed for benzonaph-
thyridine 3d, 5b and 7d. However, these benzonaphthyridines
(3d, 5b and 7d) exhibit micellar charge dependent changes
in their fluorescence intensity in the micellar environment.
These fluorescence properties of benzonaphthyridines can be
used to probe the micro-environment of ionic micelles and
related organized assemblies.
disk were measured on a Shimadzu FTIR-408 spectropho-
tometer. 1H NMR and 13C NMR spectra were recorded on a
Varian XL-300 MHz spectrometer using tetramethylsilane
(TMS) as internal standard and solvents were deuterio-
chloroform (CDCl3) and deuterio-dimethylsulphoxide
(DMSO-d6). Chemical shifts were reported in ppm from
internal tetramethylsilane standard and were given in δ-units.
Mass spectrum was recorded on Shimadzu GC-MS QP
2010A mass spectrometer with an ionization potential of
70 eV. Elemental analyses were performed on a Hosli CH-
Analyzer and within 0.3 of the theoretical percentage. The
absorption spectra were measured using a Shimadzu UV-
1601 UV–VIS spectrophotometer. The fluorescence spectra
were recorded on a RF-5301 PC spectrofluorophotometer by
exciting the samples at their absorption maximum (labs. max.).
Compounds for UV and fluorescence measurements were
dissolved in DMF, UV and fluorescence scan were recorded
from 200 to 700 nm. The Фf relative to quinine sulphate in
1.0 x 10-3 mol L-1 H2SO4 (Фf=0.57) was measured at room
temperature by standard literature procedure [39–41]. Both
samples and standard were excited at the same excitation
wavelength and the optical density (OD) of the standard and
the sample was adjusted to be nearly equal. For all electronic
spectroscopic studies (absorption, fluorescence excitation
and emission) 1.0×10-3 mol L-1 solutions of the compounds
were used. All reactions were monitored by thin layer
chromatography, carried out on 0.2 mm silica gel 60 F254
(Merck) plates using UV light (250 and 400 nm) and
Fluorescence light (400 and 600 nm) for detection.
Experimental
General
Surfactants [cetyl trimethyl ammonium bromide (CTAB),
sodium dodecyl sulfate (SDS) and Triton-X-100 for micelle
preparation] and quinine sulphate [for determination of Φf]
were purchased from Hi-Media Laboratories Pvt. Ltd.
Mumbai (India) and Research-Lab Fine Chem Industries,
Mumbai (India) respectively. All other chemicals, reagents
and solvents [such as acetonitrile, dimethylformamide
(DMF), dioxane, ethanol, ethyl acetate, n-hexane, pet-ether
methanol and tetrahydrofuran (THF)] used in spectroscopic
and other studies were obtained from LOBA Chemie. Pvt.
Ltd., Mumbai (India), Spectrochem, Mumbai (India) and E.
Merck (India). Deionized, double distilled water (Millipore)
was used for preparing the micelle solutions. All AR-grade
organic solvents were dried and freshly distilled prior to use.
The UV-grade solvents were used for spectral studies. Melting
points were determined on a Gallenkamp melting point
apparatus, Mod. MFB595 in open capillary tubes and were
uncorrected. Fourier transform infrared (FTIR) spectra in KBr
Synthesis
Synthesis of 2,3-Dihydro-1H-benzo[b]cyclopenta[g][1,8]
naphthyridine (3 a-d) The mixture of 2-aminoquinoline-3-
carbaldehyde (1a-b) (0.001 mol) & cyclopentanone 2a
(0.001 mol) in ethanolic potassium hydroxide solution
(10 mL, 2%) was refluxed for 5 h. Completion of the

26
J Fluoresc (2012) 22:17–29
reaction was monitored by Thin Layer Chromatography
(TLC). The mixture was then cooled to room temperature;
the separated solid product was collected by suction filtration,
washed with pet-ether, dried and recrystallized from ethanol.
[M+] (72), 220 (42), 132 (29), 110 (33), 44 (77), 32 (68).
Anal. Calcd. for C17H16N2O (264.32): C, 77.27; H, 6.06; N,
10.60% Found: C, 77.29; H, 6.09; N, 10.58%
Synthesis of 4-Methyl-1,2,3,4-tetrahydrodibenzo[b,g][1,8]
naphthyridine (5 a-b) A mixture of 2-aminoquinoline-3-
carbaldehyde (1a-b) (0.001 mol) & 2-methylcyclohexa -none
(4) (0.001 mol) in ethanolic potassium hydroxide solution
(10 mL, 2%) was refluxed for 6 h. Completion of the
reaction was monitored by Thin Layer Chromatography
(TLC). The mixture was then cooled to room temperature;
the separated solid product was collected by suction
filtration, washed with cold-methanol, dried and recrystal-
lized from ethanol.
2,3-Dihydro-1H-benzo[b]cyclopenta[g][1,8]naphthyridine
(3a) Yield: 0.178 g (80%), recrystallized from ethanol to
afford faint yellow solid; M.p. 171-173 °C. IR (KBr):
3012 m, 2968 m, 2912 w, 1610 scm-1. 1H NMR (300 MHz
CDCl3) δ: 1.95 (m, 2H, CH2), 2.49 (t, 2H, J=7.4 Hz, CH2),
3.09 (t, 2H, J=6.8 Hz, CH2), 7.34 (dd, 1H, J=7.9 & 8.3 Hz,
Ar-H), 7.74 (dd, 1H, J=8.3 & 8.4 Hz, Ar-H), 8.09 (d, 1H, J=
7.9 Hz, Ar-H), 8.36 (d, 1H, J=8.4 Hz, Ar-H), 8.78 (s, 1H,
Ar-H), 9.19 (s, 1H, Ar-H). Anal. Calcd. for C15H12N2
(220.27): C, 81.81; H, 5.45; N, 12.72% Found: C, 81.80; H,
5.48; N, 12.70%
4-Methyl-1,2,3,4-tetrahydrodibenzo[b,g][1,8]naphthyridine
(5a) Yield: 0.204 g (82%), recrystallized from ethanol to
afford yellow prism; M.p. 211-213 °C. IR (KBr): 3015 m,
8-Methoxy-2,3-dihydro-1H-benzo[b]cyclopenta[g][1,8]
naphthyridine (3b) Yield: 0.211 g (84%), recrystallized
from ethanol to afford faint yellow needles; M.p. 184-
186 °C. IR (KBr): 3019 m, 2972 m, 2929 m, 1619 s, 1026 s
cm-1.1H NMR (300 MHz DMSO-d6) δ: 1.88 (m, 2H, CH2),
2.37 (t, 2H, J=7.1 Hz, CH2), 3.14 (t, 2H, J=6.9 Hz, CH2),
4.02 (s, 3H, OCH3), 7.43 (d, 1H, J=7.7 Hz, Ar-H), 7.51 (s,
1H, Ar-H), 8.24 (d, 1H, J=7.7 Hz, Ar-H), 9.21 (s, 1H, Ar-H),
9.44 (s, 1H, Ar-H). MS (70 eV) m/z (%): 250 [M+] (83), 206
(37), 125 (19), 77 (22), 44 (85), 32 (47). Anal. Calcd. for
C16H14N2O (250.29): C, 76.80; H, 5.60; N, 11.20% Found:
C, 76.82; H, 5.62; N, 11.22%
1
2968 m, 2912 m, 1618 scm-1. H NMR (300 MHz CDCl3)
δ: 1.52 (d, 3H, J=5.5 Hz, CH3), 1.89 (m, 2H, CH2), 2.04
(m, 2H, CH2), 2.49 (t, 2H, J=7.4 Hz, CH2), 3.26 (m, 1H,
CH), 7.16 (dd, 1H, J=7.9 & 8.3 Hz, Ar-H), 7.77 (dd, 1H,
J=8.3 & 8.5 Hz, Ar-H), 8.14 (d, 1H, J=7.9 Hz, Ar-H),
8.27 (d, 1H, J=8.5 Hz, Ar-H), 8.82 (s, 1H, Ar-H), 9.07
(s, 1H, Ar-H). 13C NMR (75 MHz CDCl3) δ: 19.1, 20.5,
28.7, 29.9, 31.2, 119.9, 126.1, 127.8, 128.5, 129.5, 131.1,
133.9, 135.3, 138.2, 149.5, 158.1, 161.5. Anal. Calcd. for
C17H16N2 (248.32): C, 82.25; H, 6.45; N, 11.29% Found: C,
82.27; H, 6.46; N, 11.30%
1,2,3,4-Tetrahydrodibenzo[b,g][1,8]naphthyridine (3c) Yield:
0.202 g (86%), recrystallized from ethanol to afford yellow
solid; M.p. 206-209 °C. IR (KBr): 2994 m, 2971 m,
9-Methoxy-4-methyl-1,2,3,4-tetrahydrodibenzo[b,g][1,8]
naphthyridine (5b) Yield: 0.239 g (85%), recrystallized
from ethanol to afford yellow solid; M.p. 171-173 °C. IR
1
1
2917 m, 1622 scm-1. H NMR (300 MHz CDCl3) δ: 1.67-
(KBr): 3021 m, 2959 m, 2926 m, 1622 s, 1029 scm-1. H
1.74 (m, 4H, CH2), 2.60 (t, 2H, J=6.8 Hz, CH2), 2.94 (t,
2H, J=6.9 Hz, CH2), 7.27 (dd, 1H, J=8.2 & 8.6 Hz, Ar-H),
7.61 (dd, 1H, J=8.6 & 8.1 Hz, Ar-H), 7.97 (d, 1H, J=
8.2 Hz, Ar-H), 8.31 (d, 1H, J=8.1 Hz, Ar-H), 8.68 (s, 1H,
Ar-H), 9.17 (s, 1H, Ar-H). Anal. Calcd. for C16H14N2
(234.30): C, 82.05; H, 5.98; N, 11.96% Found: C, 82.03; H,
6.00; N, 11.98%
NMR (300 MHz CDCl3) δ: 1.47 (d, 3H, J=5.8 Hz, CH3),
1.84 (m, 2H, CH2), 2.12 (m, 2H, CH2), 2.45 (t, 2H, J=
6.7 Hz, CH2), 3.12 (m, 1H, CH), 3.98 (s, 3H, OCH3), 7.33
(d, 1H, J=8.3 Hz, Ar-H), 7.44 (s, 1H, Ar-H), 7.97 (d, 1H, J=
8.3 Hz, Ar-H), 9.32 (s, 1H, Ar-H), 9.49 (s, 1H, Ar-H). MS
(70 eV) m/z (%): 278 [M+] (100), 263 (92), 249 (47), 206
(22), 131 (12), 109 (22). Anal. Calcd. for C18H18N2O
(278.35): C, 77.69; H, 6.47; N, 10.07% Found: C, 77.70; H,
6.48; N, 10.09%
9-Methoxy-1,2,3,4-tetrahydrodibenzo[b,g][1,8]naphthyridine
(3d) Yield: 0.231 g (87%), recrystallized from ethanol to
afford yellow needles; M.p. 231–234 °C. IR (KBr):
3006 m, 2968 m, 1618 s, 1011 scm-1.1H NMR (300 MHz
CDCl3) δ: 1.55-1.68 (m, 4H, CH2), 2.74 (t, 2H, J=7.1 Hz,
CH2), 3.01 (t, 2H, J=6.5 Hz, CH2), 4.02 (s, 3H, OCH3),
7.38 (d, 1H, J=8.8 Hz, Ar-H), 7.58 (s, 1H, Ar-H), 8.17
(d, 1H, J=8.8 Hz, Ar-H), 9.02 (s, 1H, Ar-H), 9.31 (s, 1H,
Ar-H). 13C NMR (75 MHz CDCl3) δ: 21.9, 22.2, 32.5,
34.7, 58.1, 112.9, 123.4, 125.1, 129.1, 131.2, 133.5, 135.1,
137.8, 144.7, 156.2, 157.9, 159.9. MS (70 eV) m/z (%): 264
Synthesis of 3,4-Dihydrodibenzo[b,g][1,8]naphthyridin-1
(2H)-one (7 a-d) A mixture of 1a-b (0.001 mol) and
dimedone (6a-b) (0.001 mol) was heated at 180–185 °C for
15 mins. The molten mass on cooling was stirred in methanol
(10 mL) for 15 mins. The separated solid was collected by
suction filtration and recrystallized from ethanol.
3,4-Dihydrodibenzo[b,g][1,8]naphthyridin-1(2H)-one (7a)
Yield: 0.199 g (80%), recrystallized from ethanol to afford

J Fluoresc (2012) 22:17–29
27
faint yellow solid; M.p. 239-241 °C. IR (KBr): 3071 m,
C19H18N2O2 (306.36): C, 74.50; H, 5.88; N, 9.15%
Found: C, 74.52; H, 5.90; N, 9.14%
1
2977 m, 2931 w, 1705 s, 1604 scm-1. H NMR (300 MHz
CDCl3) δ: 1.88 (m, 2H, CH2), 2.56 (t, 2H, J=6.5 Hz, CH2),
2.94 (t, 2H, J=6.7 Hz, CH2), 7.21 (dd, 1H, J=8.2 & 8.6 Hz,
Ar-H), 7.55 (dd, 1H, J=8.6 & 8.1 Hz, Ar-H), 8.11 (d, 1H, J=
8.2 Hz, Ar-H), 8.47 (d, 1H, J=8.1 Hz, Ar-H), 8.68 (s, 1H,
Ar-H), 9.19 (s, 1H, Ar-H). Anal. Calcd. for C16H12N2O
(248.28): C, 77.41; H, 4.83; N, 11.29% Found: C, 77.40; H,
4.80; N, 11.31%
Synthesis of 5-(3,4-Dichlorophenyl)-5,6-dihydrobenzo[b]
naphtho[2,1-g][1,8]naphthyridine (9 a-b) The mixture of
2-aminoquinoline-3-carbaldehyde (1a-b) (0.001 mol) &
cetraline (8) (0.001 mol) in ethanolic potassium hydroxide
solution (10 mL, 2%) was refluxed for 3 h. Completion of the
reaction was monitored by Thin Layer Chromatography
(TLC). The mixture was then cooled to room temperature;
the separated solid product was collected by suction filtration,
washed with pet-ether, dried and recrystallized from ethanol.
9-Methoxy-3,4-dihydrodibenzo[b,g][1,8]naphthyridin-1
(2H)-one (7b) Yield: 0.227 g (81%), recrystallized from
ethanol to afford yellow needles; M.p. 184–186 °C. IR
(KBr): 3009 m, 2970 m, 2918 m, 1698 s, 1615 s, 1019 s
cm-1.1H NMR (300 MHz CDCl3) δ: 1.94 (m, 2H, CH2),
2.47 (t, 2H, J=7.2 Hz, CH2), 2.83 (t, 2H, J=6.6 Hz, CH2),
4.05 (s, 3H, OCH3), 7.37 (d, 1H, J=9.0 Hz, Ar-H), 7.55
(s, 1H, Ar-H), 8.20 (d, 1H, J=9.0 Hz, Ar-H), 9.27 (s, 1H,
Ar-H), 9.38 (s, 1H, Ar-H). 13C NMR (75 MHz CDCl3) δ:
21.8, 31.7, 39.7, 58.3, 113.2, 123.3, 124.9, 128.9, 130.5,
134.5, 136.5, 137.2, 144.7, 156.7, 158.1, 166.5, 197.2. MS
(70 eV) m/z (%): 279 [M+H]+ (100), 236 (22), 202 (48),
174 (37), 131 (38), 77 (57), 51(49). Anal. Calcd. for
C17H14N2O2 (278.30): C, 73.38; H, 5.03; N, 10.07% Found:
C, 73.40; H, 5.05; N, 10.08%
5-(3,4-Dichlorophenyl)-5,6-dihydrobenzo[b]naphtho[2,1-g]
[1,8]naphthyridine (9a) Yield: 0.358 g (84%), recrystal-
lized from ethanol to afford yellow solid; M.p. 284-286 °C.
IR (KBr): 2991 m, 2959 m, 1620 scm-1. 1H NMR
(300 MHz DMSO-d6) δ: 3.84 (d, 2H, J =5.8 Hz, CH2),
5.09 (t, 1H, J=5.8 Hz, CH2), 6.89-7.09 (m, 4H, Ar-H), 7.15
(dd, 1H, J=8.6 & 3.2 Hz, Ar-H), 7.24 (d, 1H, J=3.2 Hz,
Ar-H), 7.39 (dd, 1H, J=8.0 & 8.5 Hz, Ar-H), 7.49 (d, 1H,
J=8.6 Hz, Ar-H), 7.70 (dd, 1H, J=8.5 & 8.1 Hz, Ar-H),
8.14 (d, 1H, J=8.0 Hz, Ar-H), 8.44 (d, 1H, J=8.1 Hz, Ar-H),
8.81 (s, 1H, Ar-H), 9.08 (s, 1H, Ar-H). 13C NMR (75 MHz
DMSO-d6) δ: 38.3, 43.5, 120.2, 121.9, 122.5, 123.1, 124.9,
125.1, 125.8, 127.2, 128.1, 128.7, 129.2, 129.8, 131.4, 132.9,
133.9, 135.6, 136.4, 137.1, 137.9, 141.4, 144.9, 148.3, 159.3,
162.7. Anal. Calcd. for C26H16Cl2N2 (427.33): C, 73.23; H,
3.75; N, 6.57% Found: C, 73.20; H, 3.74; N, 6.55%
3,3-Dimethyl-3,4-dihydrodibenzo[b,g][1,8]naphthyridin-1
(2H)-one (7c) Yield: 0.229 g (82%), recrystallized from
ethanol to afford faint green solid; M.p. 201–203 °C. IR
1
(KBr): 3033 m, 2960 m, 2914 m, 1696 s, 1626 scm-1. H
NMR (300 MHz CDCl3) δ: 1.19 (s, 6H, CH3), 2.44 (s, 2H,
CH2), 2.89 (s, 2H, CH2), 7.39 (dd, 1H, J=7.9 & 8.5 Hz,
Ar-H), 7.70 (dd, 1H, J=8.5 & 8.1 Hz, Ar-H), 8.09 (d, 1H,
J=7.9 Hz, Ar-H), 8.30 (d, 1H, J=8.1 Hz, Ar-H), 8.71 (s, 1H,
Ar-H), 9.10 (s, 1H, Ar-H). MS (70 eV) m/z (%): 277
[M+H]+ (100), 248 (22), 201 (28), 183 (27), 152 (22), 77
(52), 51 (41), 31 (63). Anal. Calcd. for C18H16N2O (276.33):
C, 78.26; H, 5.79; N, 10.14% Found: C, 78.29; H, 5.80; N,
10.15%
5-(3,4-Dichlorophenyl)-10-methoxy-5,6-dihydrobenzo[b]
naphtho[2,1-g][1,8]naphthyridine (9b) Yield: 0.391 g
(85%), recrystallized from ethanol to afford yellow solid;
M.p. 291-293 °C. IR (KBr): 3011 m, 2975 m, 2934 m,
1609 s, 1029 scm-1. 1H NMR (300 MHz DMSO-d6) δ: 3.77
(d, 2H, J=5.9 Hz, CH2), 4.04 (s, 3H, OCH3), 4.88 (t, 1H,
J=5.9 Hz, CH2), 6.94-7.13 (m, 4H, Ar-H), 7.19 (dd, 1H, J=
8.5 and 2.9 Hz, Ar-H), 7.29 (d, 1H, J=2.9 Hz, Ar-H), 7.37
(d, 1H, J=8.5 Hz, Ar-H), 7.47 (d, 1H, J=8.9 Hz, Ar-H), 7.62
(s, 1H, Ar-H), 8.24 (d, 1H, J=8.9 Hz, Ar-H), 9.21 (s, 1H,
Ar-H), 9.31 (s, 1H, Ar-H). MS (70 eV) m/z (%): 456 [M+]
(86), 458 [M+2] (59), 460 [M+4] (9), 441 (29), 268 (31),
171 (47), 193 (40), 44 (84), 32 (49). Anal. Calcd. for
C27H18Cl2N2O (457.35): C, 71.05; H, 3.94; N, 6.14%
Found: C, 71.07; H, 3.91; N, 6.16%
9-Methoxy-3,3-dimethyl-3,4-dihydrodibenzo[b,g][1,8]
naphthyridin-1(2H)-one (7d) Yield: 0.256 g (83%), recrys-
tallized from ethanol to afford green needles; M.p. 229-
231 °C. IR (KBr): 3018 m, 2966 m, 2913 m, 1703 s,
1604 s, 1010 scm-1.1H NMR (300 MHz CDCl3) δ: 1.25
(s, 6H, CH3), 2.39 (s, 2H, CH2), 2.94 (s, 2H, CH2), 4.09
(s, 3H, OCH3), 7.36 (d, 1H, J=8.8 Hz, Ar-H), 7.51 (s, 1H,
Ar-H), 8.24 (d, 1H, J=8.8 Hz, Ar-H), 9.28 (s, 1H, Ar-H),
9.46 (s, 1H, Ar-H). 13C NMR (75 MHz CDCl3) δ: 23.4,
25.7, 30.6, 44.8, 50.7, 58.7, 113.4, 123.8, 125.3, 131.2,
132.7, 134.1, 136.9, 138.3, 144.1, 156.6, 158.7, 166.2,
197.7. MS (70 eV) m/z (%): 307 [M+H]+ (100), 278 (29),
250 (22), 179 (18), 55 (12), 41 (26). Anal. Calcd. for
Acknowledgements The authors would like to thank Council of
Scientific and Industrial Research (CSIR), New Delhi, India, for
financial support for this research project. Authors also thank to
Professor D. D. Dhavale, Department of Chemistry, University of
Pune, India, for his valuable cooperation for the measurement of 1H
NMR, 13C NMR, Mass and Elemental analysis. Authors acknowledge
their thanks to Dr. V. B. Gaikwad, Principal, K. R. T. Arts, B. H.
Commerce and A. M. Science College, Nashik-02, MS, India, for the
valuable co-operation in measurement of IR, UV and Fluorescence.

28
J Fluoresc (2012) 22:17–29
intramolecular charge-transfer states and structures. Chem Rev
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