Comparative analysis of the PET and ICT sensor properties of 1,8-naphthalimides containing aza-15-crown-5 ether moiety

Article abstract of DOI:10.1016/j.dyepig.2013.03.008

Novel 4-amino- and 4-(acetyl)amino-N-aryl-1,8-naphthalimides containing aza-15-crown-5 ether receptor unit in the N-aryl fragment and at C-4 of the naphthalimide residue were designed and prepared. Significant internal charge transfer from electron donati

Full text of DOI:10.1016/j.dyepig.2013.03.008

Accepted Manuscript
Comparative analysis of the PET and ICT sensor properties of 1,8-naphthalimides
containing aza-15-crown-5 ether moiety
Pavel A. Panchenko, Yuri V. Fedorov, Olga A. Fedorova, Gediminas Jonusauskas
PII:
S0143-7208(13)00097-1
10.1016/j.dyepig.2013.03.008
DYPI 3877
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 14 January 2013
Revised Date: 12 March 2013
Accepted Date: 13 March 2013
Please cite this article as: Panchenko PA, Fedorov YV, Fedorova OA, Jonusauskas G, Comparative
analysis of the PET and ICT sensor properties of 1,8-naphthalimides containing aza-15-crown-5 ether
moiety, Dyes and Pigments (2013), doi: 10.1016/j.dyepig.2013.03.008.
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Highlights
1,8-Naphthalimides containing aza-15-crown-5 group at C-4 and N-imide are prepared.
The sensors have been shown to bind Ca2+ ions in MeCN with different affinities.
Ion induced optical changes are strongly dependent on the position of receptor unit.
Results have been rationalised in terms of PET and ICT mechanisms.

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Comparative analysis of the PET and ICT sensor properties of
1,8-naphthalimides containing aza-15-crown-5 ether moiety
Pavel A. Panchenkoa,*, Yuri V. Fedorova, Olga A. Fedorovaa, Gediminas Jonusauskasb
aA. N. Nesmeyanov Institute of Organoelement Compounds of Russian Academy of
Sciences (INEOS RAS), 119991, Vavilova str. 28, Moscow, Russia,
Tel.: +7 499 135 80 98, Fax: +7 499 135 50 85, E-mail: pavel@ineos.ac.ru
bLaboratoire Ondes et Matière d’Aquitaine (LOMA), UMR CNRS 5798,
Bordeaux 1 University, 33405, Cours de la Libération 351, Talence, France
Abstract
Novel 4-amino- and 4-(acetyl)amino-N-aryl-1,8-naphthalimides containing aza-15-
crown-5 ether receptor unit in the N-aryl fragment and at C-4 of the naphthalimide residue were
designed and prepared. Significant internal charge transfer from electron donating amino or
amido group at C-4 of the naphthalene ring to the acceptor carboxyimide moiety as well as
photoinduced electron transfer between N-aryl receptor and the naphthalimide fragment was
revealed by the UV/Vis absorption spectroscopy and considerable fluorescence quenching. The
addition of calcium perchlorate to an acetonitrile solution of naphthalimides with the receptor at
imide nitrogen hindered the photoinduced electron transfer process and accordingly restored the
quenched fluorescence of the free ligands. In the case of the compound in which the aza-15-
crown-5 receptor is located at C-4, the coordination with Ca2+ reduced the internal charge
transfer interaction in the chromophore and caused a significant blue-shift of the absorption and
emission peak. The observed spectral effects were analyzed using PM6 semiempirical
calculations. Formation of complexes was also confirmed by 1H NMR spectroscopy.
Keywords: 1,8-naphthalimide, crown compounds, sensors, photoinduced electron transfer
(PET), internal charge transfer (ICT), optical spectroscopy.
1. Introduction
Detecting cations is of great interest to many scientists, including chemists, biologists,
clinical biochemists and environmentalists. With this regard, the development of fluorescent and
colorimetric chemosensors seems to be advantageous, since the optical spectroscopy has turned
to be one the most effective and reliable analytical methods [1]. Optical sensor devices are
generally multi-component systems comprising a signaling moiety (chromophore) and cation
binding site (usually termed as receptor). The components are chosen so that the complexation

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event triggers the modulation of photophysical characteristics of the chromophore such as the
position of emission / absorption band maxima or the fluorescence intensity. Noteworthy, the
mechanism of binding signal transduction between the sensor components may differ depending
on the sensor design and may involve the photoinduced electron transfer (PET), the internal
charge transfer (ICT), the resonance energy transfer or the formation of excimer / exciplex [2–5].
1,8-Naphthalimides bearing electron donating substituents in the naphthalene moiety are
well-known organic fluorophores showing good photostability, large Stokes shifts and strong
absorption and emission in the UV/Vis region. Such compounds have been used in a large
variety of areas, including coloration of polymers and optical brightening [6–8], laser active
media [9,10], luminescent crack detection [11], electroluminescent materials [12–14], anticancer
agents [15], liquid crystal displays [16,17] and fluorescent markers in biology [18–20]. The
ability of 1,8-naphthalimide derivatives to be very sensitive to their surrounding render them as
solvatochromic probes where the effects of solvent polarity on the electronic emission and
absorption spectra are studied [21,22].
Owing to the unique feature of the naphthalimide chromophore that consists in its
electron-accepting properties, and thus possibility of photoinduced electron / energy transfer
process or excimer / exciplex formation in the excited state, a significant number of
naphthalimides have been developed as fluorescent chemosensors for metal cations and protons.
pH-Dependent fluorescence was found for piperazine substituted 4-aminonaphthalimides, which
were configured as «fluorophore–spacer–receptor» systems playing on the PET ON-OFF
response [23,24]. Wang et al. synthesized a fluorescent naphthalimide based PET-sensor for Zn2+
with di-2-picolylamine as a recognizing group [25]. Typically to ICT-sensors, 4-piperidine-
naphthalimide derivatives containing 2-imino-oxazolidin (thiazolidin) side chain at the imide
moiety exhibited strong fluorescence quenching and some red shift in weakly acidic conditions,
caused by the formation of an intramolecular H-bond [26]. A selective and ratiometric Cu2+
fluorescent probe based on naphthalimide excimer–monomer switching was designed by Xu et
al. [27].
Even though crown ether receptors have been extensively used in the construction of
fluorescent probes, there have been only few examples of naphthalimide chemosensors bearing
crown ether groups as a receptor unit [28–33]. Recently, we studied the cation-dependent
fluorescent properties of benzo-15-crown-5-containg 4-amino- and 4-(acetyl)amino-N-aryl-1,8-
naphthalimides 1c and 2c (Scheme 1) [34]. It was shown that the complex formation with the
alkaline earth metal cations (Mg2+, Ba2+) results in enhancement of emission intensity in the case
of 4-(acetyl)aminonaphthalimide 2c due to inhibition of the PET process, which is originally

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operated in the free ligand. In contrast, 2a demonstrated the lack of fluorescence PET switching
upon the coordination with metal ions.
Herein, we report on the synthesis and investigation of complexation properties of aza-
15-crown-5-substituted naphthalimides 1b, 2b and 3a. Considering the general principles used in
the design of fluorescent probes [2–4], there exist two opportunities for combination of azacrown
ether receptor and naphthalimide chromophore. In the compounds 1b and 2b, the receptor is
attached to the N-aryl moiety. Alternatively, the aza-15-crown-5 may be presented in the
molecule as a substituent at C-4 of the naphthalimide residue in a manner ensuring the
conjugation between the receptor’s amino nitrogen and carbonyl groups of the carboxyimide
functionality, the feature implemented by us in the design of sensor 3a. In such a case cation
detection is possible not only by monitoring of emission intensity but also position of absorption
and fluorescence maxima, which may be of interest for the development of ratiometric probes.
2. Experimental
2.1. Materials and general methods
4-Nitro-1,8-naphthalic anhydride [35,36] 4, 4-bromo-N-phenyl-1,8-naphthalimide 9 [37]
and N-(4-aminophenyl)aza-15-crown-5 ether 7 [38] were prepared by literature procedures. All
other reagents were purchased from commercial sources and were of the highest grade. Solvents
were purified and dried according to standard procedures. Calcium perchlorate was dried in
vacuum (7–8 mm Hg) at 240 °C and kept anhydrous over P2O5 in desiccator (Caution! Calcium
perchlorate may explode when heating. It decomposes at 270 °C [39]). Raney nickel catalyst was
prepared from nickel aluminum alloy (weight percentage of nickel is 50%) according to the
known procedure [40].
Melting points were measured on Melt-temp melting point electrothermal apparatus and
were uncorrected. The reaction course and purity of the final products was followed by TLC on
silica gel (DC-Alufolien Kieselgel 60 F254, Merck). Column chromatography was conducted over
silica gel (Kieselgel 60, particle size 0.063-0.200 mm, Merck) using as an eluent the gradient
solvent mixtures benzene – ethanol and hexane – ethylacetate. FT-IR spectra were recorded on
Magna-IR 750 Nicolet spectrometer and were obtained with potassium bromide pellets.
Elemental analyses were carried out in the Microanalysis Laboratory of the A.N. Nesmeyanov
Institute of Organoelement Compounds.
1
NMR measurements. H and 13C NMR spectra were recorded on an Avance 300,
Avance 400 and Avance 600 spectrometers (Bruker) operating at 300.13, 400.13, 600.22 MHz
1
(for H) and 75.47, 100.61, 150.93 MHz (for 13C) respectively. The measurements were
performed in DMSO-d6, CDCl3 and CD3CN solutions. The chemical shifts (given as δ) were

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determined with an accuracy of 0.01 ppm relative to the signals corresponding to the residual
solvents and recalculated to the internal standard (TMS); the spin-spin coupling constants (J)
were measured with an accuracy of 0.1 Hz. The numbering of carbon atoms in the naphthalimide
moiety, N-aryl ring and crown ether fragment of compounds 1b, 2b, 3a, 5 and 6 commonly used
by us for the description of 1H and 13C NMR spectra is shown on Fig. 2, 5 and 8. The assignment
of 1H and 13C signals is based on 2D NMR experiments (HMBC, HSQC, 1H COSY), which were
performed using standard pulse sequences from the Bruker library. 2D NMR spectra are
presented in Supplementary data.
Mass spectrometry. LC-ESI-MS analyses were performed on a Finnigan LCQ
Advantage mass spectrometer equipped with octopole ion-trap mass-analyzer, MS Surveyor
pump, Surveyor auto sampler, Schmidlin-Lab nitrogen generator (Germany) and Finnigan X-
Calibur 1.3 software for data collecting and processing. Acetonitrile (Panreac, HPLC-gradient
grade) was used as the mobile phase. Dilute MeCN solutions of compounds 1b, 2b, 3a and 5
were studied in the presence of 1 eq. of HClO4. The isocratic elution was maintained at a flow
rate of 50 µL ꢀ min–1 without column. The effluent from LC was passed directly into the
electrospray ion source without a split. Positive electrospray ionization was achieved using a
ionization voltage at 3 kV with temperature at 200 °C. Isotope patterns were calculated with
Molecular Weight Calculator, Version 6.37 (Matthew Monroe).
Electron impact (EI) (70 eV) mass spectra were obtained from Finnigan Polaris Q
instrument (ion-trap) in standard conditions.
Optical measurements. The absorption spectra were taken on a Varian-Cary 5G
spectrophotometer. The fluorescence quantum yield measurements were performed using a
Varian-Cary 5G spectrophotometer and
a
FluoroMax-3 spectrofluorimeter. Spectral
measurements were carried out in air-saturated acetonitrile solutions (acetonitrile of
spectrophotometric grade, water content <0.005%, Aldrich) at 20 ± 1 ºC; the concentrations of
studied compounds were of about 0.5–2.0 ꢀ 10–5 M. All measured fluorescence spectra were
corrected for the nonuniformity of detector spectral sensitivity. Coumarin 481 in acetonitrile (ϕfl
= 0.08) [41] was used as reference for the fluorescence quantum yield measurements. The
fluorescence quantum yields were calculated by the equation (1) [42]:
wherein ϕifl and ϕ0fl are the fluorescence quantum yields of the studied solution and the standard
compound, respectively; Di and D0 are the absorptions of the studied solution and the standard,
respectively; Si and S0 are the areas underneath the curves of the fluorescence spectra of the
studied solution and the standard, respectively; and ni and n0 are the refraction indices of the
solvents for the substance under study and the standard compound (ni = n0 = 1.342, acetonitrile).

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Equilibrium constant determination. Complex formation of dyes 1b, 2b and 3a with
Ca2+ in acetonitrile at 20 ± 1 °C was studied by spectrofluorometric (for 1b, 2b and 3a) and
spectrophotometric (for 3a) titration [43,44]. The ratio of dye to Ca2+ was varied by adding
aliquots of a solution of Ca(ClO4)2 of known concentration to a solution of ligands 1b, 2b or 3a
of known concentration. The fluorescence (absorption) spectrum of each solution was recorded,
and the stability constants of the complexes were determined using the SPECFIT/32 program
(Spectrum Software Associates, West Marlborough, MA). The following equilibria were
considered in the fitting (equations (1) and (2), L = 1b, 2b or 3a; M = Ca2+):
In doing so, it was found that the experimental data corresponded to the theoretical ones if only
the equation (2) was taken into account and the formation of the complexes with composition of
2 : 1 was not observed.
The equilibrium constants for protonation of ligands 1b and 2b were not determined by
this method because of high stability (K > 107 M–1) of protonated forms (1b)ꢀH+ and (2b)ꢀH+.
Determination of fluorescence quantum yields of complexes. The fluorescence
quantum yields of complexes (1b)ꢀCa2+ and (2b)ꢀCa2+ were determined using solutions of ligands
1-2b in CH3CN containing an excess of Ca(ClO4)2 in order to obtain 90-95% of ligand bound
with the cation. The required Ca(ClO4)2 excess was calculated from the known stability
constants using the SPECFIT/32 program. The measurements of ϕfl for (1b)ꢀH+ and (2b)ꢀH+ were
done in the presence of 2 eq. HClO4 in ligand solutions, which can be understood from the fact
that the further addition of HClO4 did not result in fluorescence enhancement and complex
formation had already been finished. In the case of complex (3a)ꢀCa2+, the direct quantum yield
determination was impossible because the presence of considerable amount of the free ligand 3a
which appreciably contributes the measured total absorption at λex and integrated emission signal
might not be avoided even at high excess of calcium cation. The quantum yield of (3a)ꢀCa2+
complex was estimated using the known quantum yield of 3a and the ratio of areas underneath
the calculated fluorescence spectra of the individual components 3a and (3a)ꢀCa2+.
X-ray diffraction analysis. Orange crystals of compound 1b were prepared by slow
evaporation of solution of 1b in the mixture of benzene and ethanol (v/v = 1/1) at room
temperature. Crystals of 1b (C28H31N3O6) at 100 K are monoclinic, space group Cc, a =
13.801(2), b = 14.290(2), c = 12.990(2) Å,
dcalc = 1.326 g cm-3, (MoKα) = 0.94 сm–1, F(000) = 1072. Intensities of 7584 reflections were
measured with a Smart APEX2 CCD diffractometer at 100 K ( (MoKα ) = 0.71072 Å, -scans
with 0.3° step, 2 < 58°), and 3356 independent reflections (Rint = 0.0425) were used in further
β
= 98.634(4)°, V = 2532.9(5) Å3, Z = 4, M = 505.56,
µ
λ
ω
θ
refinement. The structure was solved by direct method and refined by the full-matrix least-
squares technique against F2 in the anisotropic-isotropic approximation. Hydrogen atoms of NH2

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group were located from the Fourier synthesis while all others were placed in calculated
positions and refined in the riding model. The refinement converged to wR2 = 0.0950 and GOF =
1.009 for all independent reflections (R1 = 0.0460 was calculated against F for 2595 observed
reflections with I > 2σ(I)). All calculations were performed using SHELX software package
[45]. Crystallographic data for the structure of 1b has been deposited with the Cambridge
Crystallographic Data Centre as supplemental publication CCDC 916216. These data can be
obtained free of charge from The Cambridge Crystallographic Data Centre through
www.ccdc.cam.ac.uk/data_request/cif.
Computational details. Quantum chemical calculations were carried out by the MOPAC
2009 program package using the PM6 semiempirical method [46]. CI calculations were
performed at optimized geometries, which reached gradient variations less than 0.01 kcal/mol.
The solvent effect was included in geometry optimizations following the “COnductorlike
Screening MOdel” (COSMO) implemented in MOPAC 2009. A dielectric constant of ε = 40 and
a refraction index of solvent (n) such that n2 = 2 were used. The CI included eight occupied and
eight unoccupied MOs.
2.2. Synthesis of the compounds
2-(4-(1,4,7,10-Tetraoxa-13-azacyclopentadecan-13-yl)phenyl)-6-amino-1H-
benzo[d,e]isoquinoline-1,3(2H)-dione (1b). Method A. To a solution of compound 5 (242 mg,
0.452 mmol) in 1,4-dioxane (10.3 mL) hydrazine-hydrate (1.8 mL, 100 wt. %) was added at
90 ºC. Raney nickel catalyst prepared from 1.5 g of nickel aluminum alloy was added
portionwise to the reaction mass over a period of 30 min. The resulting mixture was stirred for
1.5 h at 90 ºC (TCL control in a solvent system benzene – ethanol, v/v = 5/1) and then was
filtered hot. The filtrate was evaporated under vacuum. The crude product was purified by
column chromatography on silica gel using the gradient solvent mixture benzene – ethanol and
1
then recrystallized from ethanol. Yield 112 mg (49%). M. p. 282 – 284 ºС. H NMR (600.22
MHz, DMSO-d6, 31 ºС):
δ = 3.51 – 3.60 (m, 16Н; СН2(15), СН2(17), СН2(18), СН2(19),
СН2(20), СН2(21), СН2(22), СН2(24)), 3.67 – 3.72 (m, 4Н; СН2(16), СН2(23)), 6.70 (d, 3J(H,H)
= 8.9, 2Н; Н(11), Н(13)), 6.87 (d, 3J(H,H)= 8.5, 1Н; Н(3)), 7.01 (d, 3J = 8.9, 2Н; Н(10), Н(14)),
3
3
3
7.40 (br s, 2Н; NH2), 7.67 (dd, J(H,H) = 7.3, J(H,H) = 8.6, 1Н; Н(6)), 8.18 (d, J(H,H) = 8.5,
3
3
1Н, Н(2)), 8.41 (d, J(H,H) = 7.3, 1Н; Н(7)), 8.64 (d, J(H,H) = 8.6, 1Н; Н(5)). 13С NMR
(100.61 MHz, DMSO-d6, 27 ºС): = 52.10 (CН2(15), CН2(24)), 67.93 (CН2(16), CН2(23)),
δ
69.12 (CН2(19), CН2(20)), 69.45 (CН2(17), CН2(22)), 70.38 (CН2(21), CН2(18)), 108.05 (C(1)),
108.16 (C(3)), 110.86 (C(11), C(13)), 119.49 (C(4a)), 122.40 (C(8)), 124.00 (C(6)), 124.18
(C(9)), 129.31 (C(5)), 129.56 (C(10), C(14)), 130.08 (C(8a)), 131.07 (C(7)), 133.95 (C(2)),

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146.70 (C(12)), 152.65 (C(4)), 163.51 (C(8b)), 164.35 (C(8c)). FT-IR (КBr), cm–1: 3355, 3415,
3255 (νNH2); 3080, 2865 (νCH), 1680, 1635 (νN–C=O). ESI-MS in MeCN, calculated for [M+H]+,
m/z: 506.23; found: 506.19. Elemental analysis: calculated (%) for C28H31N3O6 (MW 505.56): С
66.53, Н 6.14, N 8.32; found С 66.56, Н 6.10, N 8.27. Method B. To a suspension of 4-
nitronaphthalimide 5 (68 mg, 0.127 mmol) in ethanol (1.0 mL) a solution of SnCl2ꢀ2H2O (100
mg) in concd hydrochloric acid (0.5 mL,
ρ = 1.18 g/mL) was added dropwise and the mixture
was stirred at ambient temperature for 2 h. The reaction mixture was poured into NaOH water
solution (7.0 mL, 5 wt. %). The brown precipitate was filtered off, washed with distilled water,
dried at 60 ºС and then chromatographed on silica gel using gradient benzene – ethanol mixture
as an eluent. Consequently, two fractions were isolated: fraction 1 (10 mg) and fraction 2 (14
mg). Fraction 1 was found to be 3-chloro-4-aminonaphthalimide 6 (the data for the compound 6
1
are listed below), fraction 2 – target product 1b (yield 22%). M. p. 264 – 272 ºС. H NMR
(300.13 MHz, DMSO-d6, 23 ºС):
δ = 3.46 – 3.63 (m, 16Н; СН2(15), СН2(17), СН2(18),
СН2(19), СН2(20), СН2(21), СН2(22), СН2(24)), 3.64 – 3.75 (m, 4Н; СН2(16), СН2(23)), 6.69
3
3
3
(d, J(H,H) = 8.9, 2Н; Н(11), Н(13)), 6.86 (d, J(H,H) = 8.5, 1Н; Н(3)), 7.01 (d, J(H,H) = 8.9,
2Н; Н(10), Н(14)), 7.44 (br s, 2Н; NH2), 7.67 (dd, 1Н, 3J(H,H) = 7.3, 3J(H,H) = 8.6; Н(6)), 8.18
(d, 3J(H,H) = 8.5, 1Н; Н(2)), 8.41 (dd, 4J(H,H) = 0.7, 3J(H,H) = 7.3, 1Н; Н(7)), 8.64 (dd, 4J(H,H)
= 0.7, 3J(H,H) = 8.6, 1Н; Н(5)). EI-MS, m/z (I, %): 506 (19), 505 (59) [M]+, 449 (29), 386 (34),
360 (46), 330 (54), 316 (100), 303 (34), 196 (36), 195 (81).
N-(2-(4-(1,4,7,10-Tetraoxa-13-azacyclopentadecan-13-yl)phenyl)-1,3-dioxo-2,3-
dihydro-1H-benzo[d,e]isoquinolin-6-yl)acetamide (2b). To a suspension of compound 1b (40
mg, 0.079 mmol) in an anhydrous dichloromethane (1.0 mL) acetylchloride (60 ꢁL, 0.844 mmol)
was added. The reaction mass was refluxed and stirred for 3 h to afford a clear solution. After the
completion of the reaction, the mixture was diluted with ethanol (1.0 mL). The solvents were
removed under vacuum and Na2CO3 water solution (5.0 mL, 10 wt. %) was added to the residual
solid to neutralize HCl. Product 2b was extracted with dichloromethane, the extract was washed
with distilled water and evaporated under vacuum. The resulting solid (38 mg) was recrystallized
1
from ethanol to afford 33 mg of pure 2b (yield 76%). M. p. 114 – 117 ºС. H NMR (300.13
MHz, DMSO-d6, 21 ºС):
δ = 2.30 (s, 3Н; СН3), 3.48 – 3.64 (m, 16Н; СН2(15), СН2(17),
СН2(18), СН2(19), СН2(20), СН2(21), СН2(22), СН2(24)), 3.64 – 3.75 (m, 4Н; СН2(16),
3
СН2(23)), 6.71 (d, 2Н, J(H,H) = 8.9; Н(11), Н(13)), 7.09 (d, 3J(H,H) = 8.9, 2Н; Н(10), Н(14)),
3
7.85 – 7.97 (m, 1Н; Н(6)), 8.33 (d, 1Н, J(H,H) = 8.2; Н(3)), 8.47 (d, 1Н, 3J(H,H) = 8.2; Н(2)),
3
3
8.52 (d, J(H,H) = 7.3, 1Н; Н(7)), 8.74 (d, J(H,H) = 8.6, 1Н; Н(5)), 10.44 (br s, 1Н; NHCO).
13С NMR (150.93 MHz, DMSO-d6, 21 ºС):
= 24.09 (CH3), 52.12 (CH2(15), CH2(24)), 67.91
(CH2(16), CH2(23)), 69.12 (CH2(19), CH2(20)), 69.47 (CH2(17), CH2(22)), 70.38 (CH2(18),
δ

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CH2(21)), 110.93 (C(11), C(13)), 118.12 (C(1)), 119.44 (C(3)), 122.96 (C(8)), 123.54 (C(9)),
124.16 (C(4a)), 126.40 (C(6)), 128.71 (C(8a)), 129.23 (C(5)), 129.47 (C(10), C(14)), 130.88
(C(7)), 131.61 (C(2)), 140.26 (C(4)), 146.96 (C(12)), 163.51 (C(8b)), 164.07 (C(8c)), 169.62
(CH3CO). FT-IR (КBr), cm–1: 3350 (νNH); 2920, 2855 (νCH); 1705, 1660 (νN–C=O); 1520 (δNH).
ESI-MS in MeCN, calculated for [M+H]+, m/z: 548.24; found: 548.18. Elemental analysis:
calculated (%) for C30H33N3O7 (MW 547.60): С 65.80, Н 6.07, N 7.67; found С 65.71, Н 6.06, N
7.62.
2-Phenyl-6-(1,4,7,10-tetraoxa-13-azacyclopentadecan-13-yl)-1H-benzo-[d,e]-
isoquinoline-1,3(2H)-dione (3a). A mixture of 4-bromo-N-phenyl-1.8-naphthalimide 9 (422 mg,
1.199 mmol) and aza-15-crown-5 ether (988 mg, 4.511 mmol) was heated to reflux in
methoxylethanol (3 mL) under argon atmosphere for 8 h (TCL control in a solvent system
benzene – ethanol, v/v = 5/1). After removal of methoxylethanol, the solid was purified by silica
gel column chromatography using benzene – ethanol gradient mixture as an eluent. The weight
1
of isolated product 3a was 220 mg (yield 37%). M. p. 149 – 150 ºС. H NMR (300.13 MHz,
DMSO-d6, 21 ºС),
δ = 3.52 – 3.67 (m, 16Н; СН2(15), СН2(17), СН2(18), СН2(19), СН2(20),
СН2(21), СН2(22), СН2(24)), 3.68 – 3.77 (m, 4Н; СН2(16), СН2(23)), 7.30 – 7.38 (m, 2Н; Н(10),
Н(14)), 7.41 – 7.58 (m, 4Н; Н(3), Н(11), Н(12), Н(13)), 7.79 (dd, 3J(H,H) = 7.3, 3J(H,H) = 8.5,
3
1Н; Н(6)), 8.36 (d, 3J(H,H) = 8.2, 1Н; Н(2)), 8.46 (dd, 4J(H,H) = 0.7, J(H,H) = 7.3, 1Н; Н(7)),
8.81 (dd, 4J(H,H) = 0.7, 3J(H,H) = 8.5, 1Н; Н(5)). 13С NMR (100.61 MHz, DMSO-d6, 27 ºС):
δ
= 52.76 (CH2(15), CH2(24)), 68.66 (CH2(16), CH2(23)), 69.85 (2×CH2), 69.97 (2×CH2), 70.42
(2×CH2), 114.93 (C(1)), 116.59 (C(3)), 122.86 (C(8)), 125.42 (C(6)), 126.22 (C(4a)), 128.04
(C(12)), 128.81 (C(11), C(13)), 129.18 (C(10), C(14)), 130.09 (C(8a)), 130.69 (C(7)), 131.67
(C(2) or С(5)), 131.76 (С(5) or С(2)), 136.27 (С(9)), 155.41 (C(4)), 163.28 (C(8b)), 163.91
(C(8c)). ESI-MS in MeCN, calculated for [M+H]+, m/z: 491.22; found: 491.29. EI-MS, m/z (I,
%): 490 (32) [M]+, 357 (34), 341 (37), 316 (49), 315 (91), 314 (100), 313 (66), 301 (59), 299
(52), 288 (47), 208 (34), 196 (34). Elemental analysis: calculated (%) for C28H30N2O6 (MW
490.21): С 68.56, Н 6.16, N 5.71; found С 68.49, Н 6.19, N 5.68.
2-(4-(1,4,7,10-Tetraoxa-13-azacyclopentadecan-13-yl)phenyl)-6-nitro-1H-benzo[d,e]-
isoquinoline-1,3(2H)-dione (5). A solution of a mixture of 4-nitro-1,8-naphthalic anhydride 4
(304 mg, 1.251 mmol) and N-(4-aminophenyl)aza-15-crown-5-ether 7 (554 mg) in 80 % acetic
acid (1.3 mL) was kept at reflux for 1.5 h. The reaction mass was cooled down; the crystals
precipitated upon cooling were filtered off and washed on a filter with distilled water. The
product was dried at 80°С and purified by column chromatography on silica gel using the
mixture of benzene – ethanol (v/v = 50/1) as an eluent. The weight of the obtained product 5
was 401 mg (yield 60 %). M. p. 227 – 229 ºС. 1H NMR spectra (400.13 MHz, DMSO-d6, 50 ºС):

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δ
= 3.49 – 3.62 (m, 16Н; СН2(15), СН2(17), СН2(18), СН2(19), СН2(20), СН2(21), СН2(22),
3
СН2(24)), 3.65 – 3.74 (m, 4Н; СН2(16), СН2(23)), 6.73 (d, J(H,H) = 8.7, 2Н; Н(11), Н(13)),
7.13 (d, 3J(H,H) = 8.7, 1Н; Н(10), Н(14)), 8.08 – 8.17 (m, 1Н; Н(6)), 8.58 (d, 3J(H,H) = 8.2, 1Н;
3
3
3
Н(3)), 8.61 (d, J(H,H) = 8.2, 1Н; Н(2)), 8.63 (d, J(H,H) = 7.3, 1Н; Н(7)), 8.76 (d, J(H,H) =
8.6, 1Н; Н(5)). 13С NMR spectra (75.47 MHz, DMSO-d6, 21 °C):
= 52.12 (CН2(15), CН2(24)),
δ
67.88 (CН2(16), CН2(23)), 69.10 (CН2(19), CН2(20)), 69.48 (CН2(17), CН2(22)), 70.38
(CН2(21), CН2(18)), 110.94 (C(11), C(13)), 122.85 (C(4a)), 122.99 (C(8)), 123.50 (C(9)), 124.28
(C(3)), 127.42 (C(1)), 128.32 (C(8a)), 128.72 (C(5)), 129.33 (C(10), C(14)), 129.57 (C(2)),
130.14 (C(6)), 131.69 (C(7)), 147.15 (C(12)), 149.15 (C(4)), 162.73 (C(8b)), 163.55 (C(8c)). FT-
IR (КBr) / cm-1: 3085, 2865 (νСН); 1715, 1680 (νN–C=O); 1525, 1350 (νNO2). ESI-MS in MeCN,
calculated for [M+H]+, m/z: 536.20; found: 536.13. Elemental analysis: calculated (%) for
C28H29N3O8 (MW 535.55): С 62.80, Н 5.46, N 7.85; found С 63.01, Н 5.49, N 7.81.
2-(4-(1,4,7,10-Tetraoxa-13-azacyclopentadecan-13-yl)phenyl)-6-amino-5-chloro-1H-
benzo[d,e]isoquinoline-1,3(2H)-dione (6). According to the Method B for the reduction of nitro
group in the compound 5 (see above), 10 mg of 4-amino-3-chloronaphthalimide 6 (yield 15%)
was obtained from 68 mg of 5, 100 mg of SnCl2ꢀ2H2O, 0.5 mL of concd HCl and 1.0 mL of
ethanol. M. p. 288 – 291 ºС. 1H NMR (300.13 MHz, DMSO-d6, 23 ºС):
СН2(15), СН2(17), СН2(18), СН2(19), СН2(20), СН2(21), СН2(22), СН2(24)), 3.64 – 3.75 (m,
δ = 3.49 – 3.63 (m, 16Н;
3
3
4Н; СН2(16), СН2(23)), 6.69 (d, J(H,H) = 8.9, 2Н; Н(11), Н(13)), 7.03 (d, J(H,H) = 8.9, 2Н;
3
3
Н(10), Н(14)), 7.55 (br s, 2Н; NH2), 7.76 (dd, 1Н, J(H,H) = 7.3, J(H,H) = 8.6; Н(6)), 8.21 (s,
1Н; Н(2)), 8.44 (dd, 4J(H,H) = 0.7, 3J(H,H) = 7.3, 1Н; Н(7)), 8.78 (dd, 4J(H,H) = 0.7, 3J(H,H) =
8.6, 1Н; Н(5)). 13С NMR (150.93 MHz, DMSO-d6, 25 ºС):
δ = 52.10 (CH2(15), CH2(24)), 67.91
(CH2(16), CH2(23)), 69.12 (CH2(19), CH2(20)), 69.47 (CH2(17), CH2(22)), 70.38 (CH2(18),
CH2(21)), 109.48 (C(1)), 110.89 (C(11), C(13)), 111.71 (C(3)), 120.29 (C(4a)), 122.74 (C(8)),
123.76 (C(9)), 125.40 (C(6)), 128.35 (C(8a)), 129.37 (C(5)), 129.48 (C(10), C(14)), 131.04
(C(7)), 132.65 (C(2)), 146.82 (C(12)), 147.51 (C(4)), 162.85 (C(8b)), 164.03 (C(8c)). EI-MS,
m/z (I, %): 541 (20) [M+2]+, 539 ([M]+) (55), 486 (26), 420 (29), 394 (49), 380 (37), 364 (59),
350 (100), 337 (38), 231 (28), 229 (75). Elemental analysis: calculated (%) for C28H30ClN3O6
(MW 540.01): С 62.28, Н 5.60, N 7.78; found С 62.34, Н 5.65, N 7.74.
3. NMR data for the free dyes and their complexes with Ca2+ in CD3CN.
Compound 1b. СL = 6.8·10–3 M. 1H NMR (300.13 MHz, CD3CN, 21 ºC):
δ = 3.50 – 6.64
(m, 16Н; CH2(15), CH2(24), CH2(17), CH2(22), CH2(18), CH2(21), CH2(19), CH2(20)), 3.69 –
3
3.78 (m, 4Н; CH2(16), CH2(23)), 5.90 (br s, 2Н; NH2), 6.77 (d, J(H,H) = 8.9, 2Н; Н(11),
3
3
Н(13)), 6.93 (d, J(H,H) = 8.3, 1Н; Н(3)), 7.04 (d, J(H,H) = 8.9, 2Н; Н(10), Н(14)), 7.69 (dd,

ACCEPTED MANUSCRIPT
3
3
3
3J(H,H) = 7.3, J(H,H) = 8.3, 1Н; Н(6)), 8.27 (d, J(H,H) = 8.3, 1Н; Н(2)), 8.35 (d, J(H,H) =
8.3, 1Н; Н(7)), 8.49 (d, 3J(H,H) = 7.3, 1Н; Н(5)).
1
Compound 2b. СL = 1.0·10–2 M. H NMR (300.13 MHz, CD3CN, 21 ºC):
δ = 2.30 (s,
3Н; СН3СО), 3.53 – 6.65 (m, 16Н; CH2(15), CH2(24), CH2(17), CH2(22), CH2(18), CH2(21),
3
CH2(19), CH2(20)), 3.70 – 3.78 (m, 4Н; CH2(16), CH2(23)), 6.79 (d, J(H,H) = 8.9, 2Н, Н(11),
3
3
3
Н(13)), 7.08 (d, J(H,H) = 8.9, 2Н; Н(10), Н(14)), 7.83 (dd, J(H,H) = 7.2, J(H,H) = 8.5, 1Н;
3
3
3
Н(6)), 8.31 (d, J(H,H) = 8.2, 1Н; Н(3)), 8.49 (d, J(H,H) = 8.2, 1Н; Н(2)), 8.52 (d, J(H,H) =
8.5, 1Н; Н(7)), 8.55 (d, 3J(H,H) = 7.2, 1Н; Н(5)); 8.88 (br s, 1Н; NHCO).
Compound 3a. СL = 1.0·10–2 M. 1H NMR (300.13 MHz, CD3CN, 21 ºC):
δ = 3.55 – 3.70
(m, 16Н; CH2(15), CH2(24), CH2(17), CH2(22), CH2(18), CH2(21), CH2(19), CH2(20)), 3.71 –
3.80 (m, 4Н; CH2(16), CH2(23)), 7.27 – 7.38 (m, 2Н; Н(10), Н(14)), 7.42 – 7.59 (m, 4Н; Н(3),
3
Н(11), Н(12), Н(13)), 7.74 (dd, 3J(H,H) = 7.2, J(H,H) = 8.6, 1Н; Н(6)), 8.41 (d, 3J(H,H) = 8.3,
1Н; Н(2)), 8.50 (dd, 4J(H,H) = 1.1, 3J(H,H) = 7.2, 1Н; Н(7)), 8.85 (dd, 4J(H,H) = 1.1, 3J(H,H) =
8.6, 1Н; Н(5)).
1
Complex (1b)·Са2+. СL = 1.0·10–2 M. Metal to ligand ratio М : L = 3 : 1. H NMR
(300.13 MHz, CD3CN, 21 ºC):
δ = 3.39 – 3.49 (m, 4Н; CH2(15), CH2(24)), 3.82 – 3.98 (m, 16Н;
CH2(16), CH2(17), CH2(18), CH2(19), CH2(20), CH2(21), CH2(22), CH2(23)), 6.02 (br s, 2Н;
3
3
NH2), 6.94 (d, J(H,H) = 8.3, 1Н; Н(3)), 7.34 (d, J(H,H) = 8.9, 2Н; Н(11), Н(13)), 7.45 (d,
3
3
3J(H,H) = 8.9, 2Н; Н(10), Н(14)), 7.70 (dd, J(H,H) = 7.3, J(H,H) = 8.4, 1Н; Н(6)), 8.28 (d,
3J(H,H) = 8.3, 1Н; Н(2)), 8.39 (dd, 4J(H,H) = 1.0, 3J(H,H) = 8.4, 1Н; Н(7)), 8.50 (dd, 4J(H,H) =
1.0, 3J(H,H) = 7.3, 1Н; Н(5)).
1
Complex (2b)·Са2+. СL = 1.0·10–2 M. Metal to ligand ratio М : L = 3 : 1. H NMR
(300.13 MHz, CD3CN, 21 ºC):
δ = 2.33 (s, 3Н; СН3СО), 3.41 – 3.50 (m, 4Н; CH2(15),
CH2(24)), 3.84 – 3.99 (m, 16Н; CH2(16), CH2(17), CH2(18), CH2(19), CH2(20), CH2(21),
CH2(22), CH2(23)), 7.36 (d, 3J(H,H) = 8.9, 2Н; Н(11), Н(13)), 7.47 (d, 3J(H,H) = 8.9, 2Н; Н(10),
Н(14)), 7.88 (dd, 3J(H,H) = 7.4, 3J(H,H) = 8.4, 1Н; Н(6)), 8.30 (d, 3J(H,H) = 8.1, 1Н; Н(3)), 8.48
– 8.64 (m, 3Н; Н(2), Н(5), Н(7)), 9.06 (br s, 1Н; NHCO).
1
Complex (3a)·Са2+. СL = 1.0·10–2 M. Metal to ligand ratio М : L = 5 : 1. H NMR
(300.13 MHz, CD3CN, 21 ºC):
δ = 3.64 – 3.73 (m, 4Н; CH2(15), CH2(24)), 3.76 – 3.91 (m, 16Н;
CH2(16), CH2(17), CH2(18), CH2(19), CH2(20), CH2(21), CH2(22), CH2(23)), 7.30 – 7.39 (m,
3
2Н; Н(10), Н(14)), 7.45 – 7.60 (m, 4Н; Н(3), Н(11), Н(12), Н(13)), 7.86 (dd, J(H,H) = 7.2,
3
3
3J(H,H) = 8.6, 1Н; Н(6),), 8.51 (d, J(H,H) = 8.2, 1Н; Н(2)), 8.58 (dd, 4J(H,H) = 1.0, J(H,H) =
7.2, 1Н; Н(7)), 8.78 (dd, 4J(H,H) = 1.0, 3J(H,H) = 8.6, 1Н; Н(5)).

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3. Results and Discussion
3.1. Synthesis of crown containing naphthalimides
Compounds 1b and 2b containing crown a ether fragment in the N-aryl moiety were
prepared as shown in Scheme 2. Starting from 4-nitronaphthalic anhydride 4, the intermediate
4-nitro-1,8-napthalimide 5 was afforded by the reaction with N-(4-aminophenyl)aza-15-crown-5
ether 7 in AcOH media. The reduction of nitro group in 5 to yield 1b was performed by the
hydrazine hydrate over Raney nickel catalyst in 1,4-dioxane solution. Unexpectedly, the use of
tin (II) chloride with hydrochloric acid for the reduction didn’t allow us to isolate compound 1b
with high yield unlike the synthesis of 4-aminonaphthalides containing benzo-15-crown-5 ether
groups we have described previously [47]. Moreover, we observed simultaneous introduction of
chlorine atom in ortho-position towards the amino group in this case. At the final step, the
treatment of 1b with acetylchloride under anhydrous conditions resulted in
4-(acetyl)aminonaphthalimide 2b.
Scheme 2 also shows synthesis of azacrown ether derivative 3a. According to the routine
procedure [37], 4-bromonaphthalic anhydride 8 first was refluxed in glacial acetic acid with
aniline. Subsequent nucleophilic substitution of the bromine atom in the isolated N-phenylimide
9 with aza-15-crown-5 ether yielded target aminonaphthalimide 3a.
Amine 7 used in Scheme 2 is a known compound; it was obtained from commercially
available N-(phenyl)diethanolamine and triethylene glycol di(p-toluenesulfonate) in a three-step
synthesis [38]. 4-Amino- and 4-(acetyl)amino-N-phenyl-1,8-naphthalimides 1a and 2a have been
previously synthesized in our laboratory [47].
3.2. Photophysical properties of the compounds
Photophysical characteristics of the compounds 1a, 1b, 2a, 2b and 3a were measured in
acetonitrile solution and the data are presented in Table 1. As an example, Fig. 1 shows
absorption and emission spectra of N-phenylnaphthalimides 1a, 2a and 3a. Similarly to other 4-
amino- and 4-amidonaphthalimide derivatives [48,49], the broad and structureless absorption
band in the long wavelength region arises from the polarization of chromophore naphthalimide
system due to the intramolecular charge transfer (ICT) interaction occurring between the
electron-donating substituents at C(4) and the acceptor carboxyimide fragment. Substitution of
amino hydrogen in 1a, 1b by the acetyl group to produce 2a, 2b causes a blue shift of λmaxabs and
λmaxfl with a concomitant changes in fluorescence quantum yields, which is a result of decreased
donor ability of NHAc group relative to NH2.
The introduction of aza-15-crown-5 ether substituent at C-4 of the naphthalene ring when
going from 1a to 3a is expected to enhance ICT interaction in the molecule because of inductive

ACCEPTED MANUSCRIPT
effect of two alkyl groups. Surprisingly, we observed only slight bathochromic shift (3 nm) in
the absorption spectra (Table 1, Fig. 1). As compared with compound 1a, the fluorescence
maximum of 3a is 22 nm red-shifted with the emission intensity dramatically decreased. This is
very similar to the observations of Saha and Samanta [50] who studied the influence the structure
of the amino group on the photophysical properties of 4-aminonaphthalimide derivatives. The
small red shift in the absorption spectra can be understood if it is assumed that the dialkylamino
group is twisted with respect to the naphthalimide plane in a manner ensuring the partial loss of
steric repulsion between the azacrown ether substituent and the peri hydrogen atoms of
naphthalene residue. Such repulsion disfavors charge separation and reduces the donor properties
of azacrown ether substituent. In fact, the PM6 optimized ground state geometry of the
compound 3a depicted in Fig. S1 (see Supplementary data) confirms this assumption.
The relatively low fluorescence quantum yield of compound 3a with respect to 1a is also
a result of conformational changes at the 4-amino moiety. As it has been proposed by Saha and
Samanta [50], the increase in steric strain in the excited ICT-state of
4-dialkylaminonaphthalimides, more planar in nature in comparison with the ground state,
enhances the nitrogen inversion rate responded for nonradiative deactivation pathway in these
systems.
To predict the cation-induced spectral effects in the case of crown-containing derivatives
1b and 2b we studied the influence of the nature of the N-aryl group on photophysical properties.
N-Phenyl substituted naphthalimides 1a and 2a were used for comparison. The introduction of
electron-donating dialkylamino group in the N-aryl fragment doesn’t virtually change the
position of absorption and emission maxima, whereas the fluorescence quantum yield drops
sharply by more than two orders of magnitude (Table 1). The former observation is consistent
with the X-ray crystallography data of the compound 1b (Fig. 2) showing the dihedral angle
between the naphthalimide moiety and N-aryl group to be close to 90 º. Thus, one can conclude
that the π-electronic interaction between these two fragments is very weak and negligible in the
ground state.
The effect of decrease in emission intensity induced by the presence of azacrown ether
groups in the compounds 1b and 2b can be explained in terms of PET quenching mechanism
commonly used in the design of fluorophore–spacer–receptor signaling systems [2–5]. With this
point of view, fast electron transfer process could be suggested between the electron rich N-aryl
receptor in 1b, 2b molecules and the excited naphthalimide fluorophore, which acts as an
acceptor. Apparently, the N-aryl σ-bond is used as a spacer in this case. According to common
principles in the construction of fluorescent PET sensors [2], such spacer enables the required

ACCEPTED MANUSCRIPT
separation of donor and acceptor units due to their nearly orthogonal disposition in space and
also links them together in a shortest way facilitating effective PET.
A striking evidence for existence of PET quenching pathway is also provided by the PM6
semiempirical calculations of the highest occupied and lowest unoccupied molecular orbitals
(HOMO–LUMO) for the compounds 1a, 2a and 1b, 2b. The calculation results are collected in
Fig. 3 and Table 2. Fig. 3 shows the energy levels of the frontier orbitals of the naphthalimide
fluorophore and local MOs of N-aryl groups (marked with spot) in the crown ether containing
derivatives 1b, 2b. The assignment of local orbitals is based on their images, which are also
depicted on Fig. 3 (see Fig. S2 in Supplementary data for orbital images of other molecules and
complexes presented in Table 2). As it can be seen, both molecules exhibit the HOMO localized
over the benzene ring. The highest occupied MOs of naphthalimide fragments appear to be the
HOMO(-1) in whole molecules 1b, 2b and therefore possess lower energy. Such situation
corresponds to high driving force for PET process occurring between HOMO of N-aryl receptor
and half occupied HOMO(-1) in the excited state. In contrast, the energy level of the N-phenyl
group HOMO in the compounds 1a, 2a is lower relative to 4-amino- or 4-amidonaphthalimide
frontier orbitals (Table 2). Thus, in this case PET is hampered and a high fluorescence quantum
yield value should be anticipated.
3.3. Complex formation studies of naphthalimides 1b, 2b and 3a
Having established the spectral effects induced by the introduction of aza-15-crown-5
fragment in N-phenyl-1,8-naphthalimides 1a, 2a, we examined the ability of crown ether
derivatives 1b, 2b and 3a to change their photophysical properties as a result of Ca2+ binding, the
cation we used for the complexation studies. This cation was chosen because it has high affinity
for aza-15-crown-5 ether in acetonitrile solution [51], which is convenient when studying cation-
induced optical effects.
Typically to fluorescent PET sensors, the addition of calcium perchlorate to the
acetonitrile solutions of ligands 1b, 2b does not lead to significant changes in the positions of
absorption and fluorescence bands but results in pronounced increase in fluorescence intensity
(Table 1). The fluorescence enhancement was assigned to coordination of Ca2+ with crown ether
moiety in 1b, 2b molecules. Such coordination should weaken the electron donor strength of N-
phenylazacrown ether receptor thus decelerating the PET quenching process. This is consistent
with the fact that in complexes (1b)ꢀCa2+ and (2b)ꢀCa2+ the HOMOs of N-aryl groups possess
fl
lower energy relative to the free ligands (Table 2). Nearly identical position of λmaxabs and λmax
for 1b, 2b in comparison with (1b)ꢀCa2+, (2b)ꢀCa2+ is obviously due to efficient separation of N-
arylazacrown ether receptor and naphthalimide chromophore by the N–Ar σ-bond. The

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fluorescence emission spectra of compounds 1b and 2b were recorded in the presence of
graduated amount of Ca(ClO4)2 in acetonitrile solution (see Fig. 4 for 1b and Fig. S3 in
Supplementary data for 2b) and the titration data were applied for the calculation of stability
constants (Table 1).
The NMR analysis clearly confirmed the formation of complexes (Table 3). The addition
of Ca2+ cations causes the downfield shift of the resonance proton signals of N-phenylazacrown
ether part. The positions of the other proton signals stay unchanged. As an example, Fig. 5 shows
cation induced changes in the 1H NMR spectrum of 1b. These results are in good agreement with
the optical data demonstrating only small changes in the position of absorption and emission
bands of ligands 1b and 2b upon the addition of Ca(ClO4)2.
As is evident from Table 1, the fluorescence quantum yield value for complex (1b)ꢀCa2+
is very close to that for N-phenylnaphthalimide 1a. In contrast, (2b)ꢀCa2+ demonstrates
considerable reduction of emission intensity as compared with 2a. To explain this fact we
proposed that in the case of (2b)ꢀCa2+ PET interaction is only partially blocked due to the
relatively low energy level of the highest occupied MO of 4-amidonaphthalimide fluorophore (–
9.50 eV, Table 2) in comparison with 4-aminonaphthalimide fragment (–9.04 eV) in (1b)ꢀCa2+.
Thus, the decrease in energy of the N-aryl localized MO in 1b occurring under complex
formation with Ca2+ is high enough to ensure efficient quenching of PET interaction, whereas in
(2b)ꢀCa2+ PET inhibition is lower because the same changes in the donor ability of N-aryl group
lead to more proximate disposition of HOMO and HOMO(-1) on energy scale (Table 2).
With the aim to confirm our assumption concerning partial inhibition of PET in the
(2b)ꢀCa2+, we measured photophysical characteristics of protonated forms of ligands 1b, 2b
(Table 1). The addition of HClO4 in acetonitrile solutions of 1b, 2b results in formation of highly
fluorescent complexes (1b)ꢀH+ and (2b)ꢀH+ similar in φfl values to 1a, 2a. In these complexes
the lone electron pair of receptor’s anilino nitrogen is fully engaged in coordination with the
cation due to formation of N–H σ-bond, which breaks the conjugation, significantly lowers the
potential energy of N-aryl group and thus completely quenches PET process in both cases. It
should be also noted that in spite of the presence of two amino groups in the compound 1b only
the anilino nitrogen of crown ether is subjected to protonation. This results from the observation
that the position of λmaxabs and λmaxfl remains virtually unchanged upon addition of HClO4.
Unlike the typical PET sensors 1b and 2b, the mechanism for binding signal transduction
in compound 3a is supposed to be completely different. In this case the crown ether receptor’s
nitrogen is part of the π-system of naphthalimide signaling moiety. Thus, the complexation
should give rise to dual response in both absorption and fluorescence emission spectra. Fig. 6
shows the influence of gradually increasing amounts of Ca2+ on the electronic absorption spectra

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of 3a in acetonitrile solution. As it can be seen, the binding of metal ion causes an enhancement
in the absorbance at 352 nm which corresponds to complex (3a)ꢀCa2+ with decreasing the
absorbance of the free ligand 3a centered at 420 nm. Obviously, the blue shift of the long
wavelength band is due to strong interaction of the crown ether nitrogen lone pair with the cation
and reduced displacement of π-electron density from donor to acceptor unit in naphthalimide
chromophore as a result.
The spectrophotometric titration data of 3a were applied for calculation of complex
(3a)ꢀCa2+ stability constant (Table 1) as well as its absorption spectra (marked with dash–dot line
on Fig. 6). Considering the higher intensity at 352 nm of the calculated spectra as compared with
that of the spectra recorded in the presence of 1000 equivalents of Ca2+, one could propose that
ligand 3a is not fully engaged in a calcium complex even at such high excess of metal cation.
Indeed, the constant stability value for (3a)ꢀCa2+ appears to be lower by more than two orders of
magnitude than in the case of (1b)ꢀCa2+ and (2b)ꢀCa2+, which is a consequence of conjugation
between receptor’s nitrogen with electron acceptor carbonyl groups of carboxyimide moiety.
The fluorescence spectra of the compound 3a exhibited pronounced increase in emission
intensity with the fluorescence band maxima blue shifted up to 27 nm in the presence of
ascending amounts of Ca2+ (Fig. 7). Interestingly, the blue shift of the long wavelength
abs
abs
abs
absorption band was considerably higher (∆λmax
=
λmax [3a] – λmax [(3a)·Са2+] = 68 nm).
This result indicates that, following the excitation, the nitrogen lone pair breaks its bond with the
cation (as already reported for other fluoroionophores [33,52,53]), but the cation is not excluded
from the macrocyclic cavity since it is still bonded with the oxygenated part of the crown ether.
Such cation – nitrogen atom decoordination leads to ICT excited state in which the emission
characteristics of naphthalimide chromophore fairly resemble that of the free ligand 3a.
However, the proximity of positively charged metal ion reduces to some extent the electron
donor properties of nitrogen atom due to electrostatic interaction, thereby decreasing the push-
pull character of ICT state. This explains the moderate hypsofluoric shift and enhancement of
emission intensity. The data presented on Fig. 7 were also used for the calculation of complex
stability constant and the obtained lg K value was essentially the same to the value derived from
spectrophotometric titration experiment.
1
Upon addition of Ca(ClO4)2, the changes in H NMR spectrum of compound 3a in
CD3CN were related only to downfield shift of naphthalimide and crown ether proton signals
(Fig. 8), which indicates the receptor’s nitrogen lone pair is engaged in the cation coordination.
Simultaneously, the position of N-phenyl group proton signals remains virtually unchanged.

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4. Conclusions
In this work the synthesis and detailed investigation of optical characteristics and
complexation ability of naphthalimide derivatives bearing aza-15-crown-5 ether receptor in the
N-aryl moiety and as a C(4)-substituent of naphthalene ring were done. It was shown that the
presence of crown ether group in the N-aryl moiety of ligands 1b, 2b leads to dramatic decrease
of emission intensity with respect to N-phenylnaphthalimides 1a, 2a due to efficient electron
transfer between naphthalimide chromophore and receptor unit. Upon the addition of Ca2+ the
lone pair of electrons of the crown ether receptor’s nitrogen atom is engaged in cation binding;
abs
this suppresses PET process and causes fluorescence enhancement occurring at constant λmax
and λmaxfl values. In the case of compound 3a receptor’s nitrogen atom is a part of naphthalimide
chromophore system, which is a structural feature of the ICT chemosensor. In contrast to PET
sensors 1b, 2b, the coordination of Ca2+ with 3a reduces ICT interaction and causes significant
hypsochromic and hypsofluoric shift. It was also shown that the various positions of the
azacrown ether fragment in naphthalimide residue result not only in substantial difference in
optical responses but also influence dramatically the affinity of the aza-15-crown-5 ether
receptor for calcium cations. Noteworthy, the response of the compound 3a is useful both in
absorption and emission spectroscopy. The strong wavelength shifts observed in the presence of
Ca2+ make this system suitable for dual wavelength analysis in self-calibrating measurements.
The presented results have shown that compounds 1b, 2b and 3a can be of interest for the
development of fluorescent and colorimetric chemosensors for different kinds of cationic
analysis. Due to versatile structural modification on the crown ether moiety, selective probes
based on aza-15-crown-5-containing 4-amino- and 4-amidonaphthalimides for various metal
cations can be prepared. Related research is being carried out in our laboratory.
Acknowledgements
The work was supported by RFBR program № 12-03-00778, program of Russian
Ministry of Education and Science № 8533 and CNRS-RAS exchange programs. Gediminas
Jonusauskas thanks also the Région Aquitaine for financial support. Prof. Konstantin A.
Lyssenko is gratefully acknowledged for X-ray diffraction data.
Appendix A. Supplementary data
Supplementary data associated with this article can be found in the online version at doi

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References
[1]
Winefordner JD. Trace analysis: spectroscopic methods for elements. New York: John
Wiley & Sons; 1976.
[2]
Bissell RA, de Silva AP, Gunaratne HQN, Lynch PLM, Maguire GEM, McCoy CP,
Sandanayake KRAS. Fluorescent PET (Photoinduced Electron Transfer) Sensors. Top.
Curr. Chem. 1993;168:223–64.
[3]
[4]
[5]
[6]
[7]
Valeur B. Molecular Fluorescence. Principles and Applications. Weinheim: Wiley-VCH;
2006.
Callan J-F, de Silva AP, Magri DC. Luminescent sensors and switches in the early 21st
century. Tetrahedron 2005;61:8551–88.
Formica M, Fusi V, Giorgi L, Micheloni M. New fluorescent chemosensors for metal
ions in solution. Coord. Chem. Rev. 2012;256:170–92.
Grabchev I, Konstantinova T. Synthesis of some Polymerisable 1,8-Naphthalimide
Derivatives for use as Fluorescent Brighteners. Dyes Pigm. 1997;33:197–203.
Grabchev I, Betcheva R. Copolymerization and photostabilization of methylmethacrylate
with 1,8-naphthalimide fluorescent brighteners. J. Photochem. Photobiol.
2001;142:73–8.
A
[8]
[9]
Patrick LGF, Whiting A. Synthesis and application of some polycondensable fluorescent
dyes. Dyes Pigm. 2002;52:137–43.
Martin E, Weigand R, Pardo A. Solvent dependence of the inhibition of intramolecular
charge-transfer in N-substituted 1,8-naphthalimide derivatives as dye lasers. J. Luminesc.
1996;68:157–64.
[10] Patrick LGF, Whiting A. Synthesis of some polymerisable fluorescent dyes. Dyes Pigm.
2002;55:123–32.
[11] May B, Poteau X, Yuan D, Brown RG. A study of a highly efficient resonance energy
transfer between 7-N,N-diethylamino-4-methylcoumarin and 9-butyl-4-butylamino-1,8-
naphthalimide. Dyes Pigm. 1999;42:79–84.
[12] Zhu W, Hu M, Yao R, Tian H. A novel family of twisted molecular luminescent
materials containing carbazole unit for single-layer organic electroluminescent devices, J.
Photochem. Photobiol. A 2003;154:169–77.
[13] Tu G, Zhou Q, Cheng Y, Geng Y, Wang L, Ma D, Jing X, Wang F. Synthesis and
properties of polyfluorenes containing 1,8-naphthalimide moieties for white. Synth. Met.
2005;152:233–36.
[14] Coya C, Blanco R, Juárez R, Gómez R, Martínez R, de Andrés A, Álvarez ÁL, Zaldo C,
Ramos MM, de la Peña A, Seoane C, Segura JL. Synthesis and tunable emission of novel

ACCEPTED MANUSCRIPT
polyfluorene co-polymers with 1,8-naphthalimide pendant groups and application in a
single layer–single component white emitting device. Eur. Polym. J. 2010;46:1778–89.
[15] Li Z, Yang Q, Qian X. Novel thiazonaphthalimides as efficient antitumor and DNA
photocleaving agents: Effects of intercalation, side chains, and substituent groups.
Bioorg. Med. Chem. 2005;13:4864–70.
[16] Grabchev I, Moneva I. Synthesis and Properties of Vinylic Copolymers with Fluorescent
Moieties as Optical Brighteners for Liquid Crystals. J. Appl. Polym. Sci. 1999;74:151–7.
[17] Zhang Y, Zhu W, Wang W, Tian H, Su J, Wang W. Synthesis and nonlinear optical
properties of rod-like luminescent materials containing Schiff-base and naphthalimide
units. J. Mater. Chem. 2002;12:1294–300.
[18] Stewart WW. Synthesis of 3,6-Disulfonated 4-Aminonaphthalimides. J. Am. Chem. Soc.
1981;103:7615–20.
[19] Sawa M, Hsu T-L, Itoh T, Sugiyama M, Hanson SR, Vogt PK, Wong C-H.
Glycoproteomic probes for fluorescent imaging of fucosylated glycans in vivo. Proc.
Natl. Acad. Sci. U. S. A. 2006;103:12371–6.
[20] Lin H-H, Chan Y-C, Chen J-W, Chang C-C. Aggregation-induced emission enhancement
characteristics of naphthalimide derivatives and their applications in cell imaging. J.
Mater. Chem. 2011;21:3170–7.
[21] Li Z, Yang Q, Chang R, Ma G, Chen M, Zhang W. N-Heteroaryl-1,8-naphthalimide
fluorescent sensor for water: Molecular design, synthesis and properties. Dyes Pigm.
2011;88:307–14.
[22] Magalhães JL, Pereira RV, Triboni ER, Filho PB, Gehlen MH, Nart FC. Solvent effect on
the photophysical properties of 4-phenoxy-N-methyl-1,8-naphthalimide. J. Photochem.
Photobiol. A 2006;183:165–70.
[23] Gan J, Chen K, Chang C-P, Tian H. Luminescent properties and photo-induced electron
transfer of naphthalimides with piperazine substituent. Dyes Pigm. 2003;57:21–8.
[24] Li Z-Z, Niu C-G, Zeng G-M, Liu Y-G, Gao P-F, Huang G-H, Mao Y-A. A novel
fluorescence ratiometric pH sensor based on covalently immobilized piperazinyl-1,8-
napthalimide and benzothioxanthene. Sens. Actuators B 2006;114:308–15.
[25] Wang J, Xiao Y, Zhang Z, Qian X, Yang Y, Xu Q. A pH-resistant Zn(II) sensor derived
from 4-aminonaphthalimide: design, synthesis and intracellular applications. J. Mater.
Chem. 2005;15:2836–39.
[26] Cui D, Qian X, Liu F, Zhang R. Novel Fluorescent pH Sensors Based on Intramolecular
Hydrogen Bonding Ability of Naphthalimide. Org. Lett. 2004;6:2757–60.

ACCEPTED MANUSCRIPT
[27] Xu Z, Yoon J, Spring DR. A selective and ratiometric Cu2+ fluorescent probe based on
naphthalimide excimer–monomer switching. Chem. Commun. 2010;46:2563–65.
[28] He H, Mortellaro MA, Leiner MJP, Young ST, Fraatz RJ, Tusa JK. A Fluorescent
Chemosensor for Sodium Based on Photoinduced Electron Transfer. Anal. Chem. 75
(2003) 549–55.
[29] Nandhikonda P, Begaye MP, Heagy MD. Highly water-soluble, OFF–ON, dual
fluorescent probes for sodium and potassium ions. Tetrahedron Lett. 2009;50:2459–61.
[30] Chen T, Zhu W, Xu Y, Zhang S, Zhang X, Qian X. A thioether-rich crown-based highly
selective fluorescent sensor for Hg2+ and Ag+ in aqueous solution. Dalton Trans.
2010;39:1316–20.
[31] Bricks JL, Kovalchuk A, Trieflinger C, Nofz M, Büschel M, Tolmachev AI, Daub J,
Rurack K. On the Development of Sensor Molecules that Display FeIII-amplified
Fluorescence. J. Am. Chem. Soc. 2005;127:13522–29.
[32] Rurack K, Resch-Genger U, Bricks JL, Spieles M. Cation-triggered ‘switching on’ of the
red/near infra-red (NIR) fluorescence of rigid fluorophore–spacer–receptor ionophores.
Chem. Commun. 2000;2103–04.
[33] Cosnard F, Wintgens V. A New Fluoroionophore Derived from 4-Amino-N-Methyl-1,8-
Naphthalimide. Tetrahedron Lett. 1998;39:2751–54.
[34] Panchenko PA, Fedorov YV, Perevalov VP, Jonusauskas G, Fedorova OA. Cation-
Dependent Fluorescent Properties of Naphthalimide Derivatives with N-Benzocrown
Ether Fragment. J. Phys. Chem. A 2010;114:4118–22.
[35] Okazaki M, Tanaka T, Taniguchi S. Synthesis of 5-nitroacenaphthene. Chem. Abstr.
1957;51:8050 [J. Soc. Organ. Synth. Chem., Jpn. 1956;14(5):344–6].
[36] Okazaki M, Suhara Y, Fujiyama M. Synthesis of 4-dinitronaphthalic acid. Chem. Abstr.
1957;51:8050 [J. Soc. Organ. Synth. Chem., Jpn. 1956;14(6):394–8].
[37] Nakaya K-, Funabiki K, Muramatsu H, Shibata K, Matsui M. N-Aryl-1,8-naphthalimides
as highly sensitive fluorescent labeling reagents for carnitine. Dyes Pigm. 1999;43:235–9.
[38] Sergeeva AN, Panchenko PA, Fedorov YV, Fedorova OA. Synthesis and Sensor
Propeties of Crown-Containing Derivatives of 4-(1,5-Diphenyl-ꢂ2-Pyrazolin-3-yl)-1,8-
Naphthalimide. Protec. Met. Phys. Chem. Surf. 2012;48(5):524–33.
[39] Perry DL. Handbook of Inorganic Compounds. Boca Raton: CRC Press, 2011.
[40] Vogel AI. Vogel’s textbook of practical organic chemistry. Furniss BS, Hannaford AJ,
Smith PWG, Tatchell AR, editors. New York: John Wiley & Sons; 1989.

ACCEPTED MANUSCRIPT
[41] Nad S, Kumbhakar M, Pal H. Photophysical Properties of Coumarin-152 and Coumarin-
481 Dyes: Unusual Behavior in Nonpolar and in Higher Polarity Solvents. J. Phys. Chem.
A 2003;107:4808–16.
[42] Renschler CL, Harrah LA. Determination of quantum yields of fluorescence by
optimizing the fluorescence intensity. Anal. Chem. 1983;55:798–800.
[43] Connors KA. Binding constants: the measurement of molecular complex stability. New
York: John Wiley & Sons; 1987.
[44] Beck MT, Nagypál I. Chemistry of complex equilibria. New York: John Wiley & Sons;
1990.
[45] Sheldrick GM. A short history of SHELX. Acta Cryst. A 2008;64:112–22.
[46] Stewart JJP. Optimization of parameters for semiempirical methods V: Modification of
NDDO approximations and application to 70 elements. J. Mol. Model. 2007;13:1173–
213.
[47] Panchenko PA, Fedorov YV, Fedorova OA, Perevalov VP, Jonusauskas G. Synthesis and
spectral properties of 4-amino- and 4-acetylamino-N-arylnaphthalimides containing
electron-donating groups in the N-aryl substituent. Russ. Chem. Bull. 2009;58(6):1233–
40.
[48] B.M. Krasovitskii, B.M. Bolotin, Organic luminescent materials, Wiley-VCH, New
York, 1988.
[49] Alexiou MS, Tychopoulos V, Ghorbnian S, Tyman JHP, Brown RG, Brittain PI. The
UV-Visible Absorption and Fluorescence of some Substituted 1,8-Naphthalimide and
Naphthalic Anhydrides. J. Chem. Soc. Perkin Trans. 2 1990;837–42.
[50] Saha S, Samanta A. Influence of the Structure of the Amino Group and Polarity of the
Medium on the Photophysical Behavior of 4-Amino-1,8-naphthalimide Derivatives. J.
Phys. Chem. A 2002;106:4763–71.
[51] Fedorova OA, Strokach YP, Gromov SP, Koshkin AV, Valova TM, Alfimov MV,
Feofanov AV, Alaverdian IS, Lokshin VA, Samat A, Guglielmetti R, Girling RB, Moore
JN, Hester RE. Effect of metal cations on the photochromic properties of
spironaphthoxazines conjugated with aza-15(18)-crown-5(6) ethers. New J. Chem.
2002;26:1137–45.
[52] Mathevet R, Jonusauskas G, Rullière C, Létard J-F, Lapouyade R. Picosecond Transient
Absorption as Monitor of the Stepwise Cation-Macrocycle Decoordination in the Excited
Singlet State of 4-(N-Monoaza-15-crow-5)-4'-cyanostilbene. J. Phys. Chem.
1995;99:15709–13.

ACCEPTED MANUSCRIPT
[53] Létard J-F, Lapouyade R, Rettig W. Synthesis and photophysical study of 4-(N-monoaza-
15-crown-5) stilbenes forming TICT states and their complexation with cations. Pure
Appl. Chem. 1993;65:1705–12.

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Schemes
Scheme 1.
Scheme 2.

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Figures
30
1.0
3'
25
20
15
10
0.8
1
3
1'
0.6
0.4
0.2
0.0
2'
2
λ
ε
5
0
300
400
500
600
700
Wavelength / nm
Figure 1.
Figure 2.

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Е / eV
MO 2b
MO 1b
-5.0
LUMO
(
)
LUMO
-5.75 eV
-5.32 эВ
(
)
-6.0
-7.5
-8.0
-8.5
-9.0
-9.5
HOMO
-7.97 eV
HOMO
-8.02 eV
-
e
-
e
HOMO(-1)
-8.85 eV
(
)
(
)
-9.32 eV
HOMO(-1)
Figure 3.
Imax / a.u.
1.0
0.8
0.6
0.4
0.2
0
0.8
0.4
0
[Ca2+
]
0
30
60
Eq. Ca2+
90
450
500
550
600
650
700
750
800
Wavelength / nm
Figure 4.

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Figure 5.
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.25
Amax
0.20
0.15
0.10
0
500
1000
Eq. Са2+
[Са2+]
3a
(3a) Ca2+
250
300
350
400
450
500
550
Wavelength / nm
Figure 6.

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I
max / a.u.
3
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
2
1
0
[Ca2+]
0
500
1000
Eq. Ca2+
400
450
500
550
600
650
700
750
Wavelength / nm
Figure 7.
CH2(15,17-22,24)
H(3)
H(11ꢀ13)
22
17
21
23
O
2
7
3
6
24
O
N
O
O
20
19
H(2)
1
4
13 14
H(10,14)
N
9
H(5)
15
12
O
H(6)
5
O
H(7)
16
18
10
11
8
CH2(16,23)
3a
a
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
ppm
H(3)
H(11ꢀ13)
CH2(16-23)
H(7)
H(2)
H(10,14)
H(6)
H(5)
CH2(15,24)
b
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
ppm
Figure 8.

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Figure and scheme captions
Fig. 1. Steady-state absorption (1, 2, 3) and normalized emission (1', 2', 3') spectra of the
compounds 1a (1, 1'), 2a (2, 2') and 3a (3, 3') in acetonitrile (C ~ 10-5 M).
Fig. 2. X-Ray crystallography data for the compound 1b. C(8b)–N(2)–C(9)–C(10) Dihedral
angle value is 84.3 º.
Fig. 3. Energy levels of frontier MOs of 1b and 2b molecules. N-Aryl group local orbitals are
marked with spot. Orbitals in brackets correspond to the excited state of naphthalimide
fluorophore. Vertical arrows describe lowest energy electronic transition (ICT transition) in
naphthalimide fluorophore.
Fig. 4. The changes in the fluorescence spectrum of 1b in the presence of graduated amount of
Ca(ClO4)2 in MeCN solution. СL = 5.0·10-6 M, λex = 420 nm. The inserts show the fluorescence
intensity at λ
max (Imax) versus equivalents of Ca2+.
1
Fig. 5. H NMR spectra (300.13 MHz) of compound 1b in the presence (b) and absence (a) of
Ca(ClO4)2 in CD3CN solution at 21 ºC. а) СL = 6.8·10–3 M; b) СL = 1.0·10–2 M, L : M = 1 : 3.
The proton signals of the benzene ring and crown ether moiety are marked with red color.
Fig. 6. The changes in absorption spectra of compound 3a in the presence of graduated amount
of Ca(ClO4)2 in MeCN. СL = 2.0·10–5 M. The insert shows absorption at 420 nm (Amax) versus
equivalents of Ca2+.
Fig. 7. The changes in emission spectra of compound 3a in the presence of graduated amount of
Ca(ClO4)2 in MeCN. СL = 5.0·10–6 M, λex = 355 nm. The insert shows fluorescence intensity at
λ
max (Imax) versus equivalents of Ca2+.
1
Fig. 8. H NMR spectra (300.13 MHz) of compound 3a in the presence (b) and absence (a) of
Ca(ClO4)2 in CD3CN solution at 21 ºC. а) СL = 1.0·10–2 M; b) СL = 1.0·10–2 M, L : M = 1 : 5.
The proton signals of the naphthalimide moiety and crown ether fragment are marked with red
color.
Scheme 1. Chemical structure of the compounds 1a–c, 2a–c and 3a
Scheme 2. Synthesis of the compounds 1b, 2b and 3a