4-Amino-3-nitro naphthalimides-structures and spectral properties

Article abstract of DOI:10.1016/j.jphotochem.2012.10.004

4-Aryl(alkyl)amino-3-nitro-1,8-naphthalimides show substituent and solvent dependent absorbances. The substituent steric volume and character strongly influence the charge transfer within the system. Arylamino-substituted derivatives are strongly NH acidi

Full text of DOI:10.1016/j.jphotochem.2012.10.004

Journal of Photochemistry and Photobiology A: Chemistry 250 (2012) 92–98
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4-Amino-3-nitro naphthalimides—Structures and spectral properties
Stanimir Stoyanova,∗, Petar Petrova,∗, Malinka Stoyanovab, Miroslav Dangalova,b, Boris Shivachevc,
Rosica Nikolovac, Ivan Petkova
a Department of Organic Chemistry, Faculty of Chemistry and Pharmacy, Sofia University St. Kliment Ohridsky, 1, James Bourchier Blvd., 1164 Sofia, Bulgaria
b Institute of Organic Chemistry, Bulgarian Academy of Sciences, 9, Acad. G. Bonchev Str., 1113 Sofia, Bulgaria
c Central Laboratory of Mineralogy and Crystallography, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
a r t i c l e i n f o
a b s t r a c t
Article history:
4-Aryl(alkyl)amino-3-nitro-1,8-naphthalimides show substituent and solvent dependent absorbances.
The substituent steric volume and character strongly influence the charge transfer within the system.
Arylamino-substituted derivatives are strongly NH acidic and their spectra are highly sensitive to even a
weak base such as DMF.
Received 15 August 2012
Received in revised form
27 September 2012
Accepted 6 October 2012
Available online 15 October 2012
© 2012 Elsevier B.V. All rights reserved.
Keywords:
1,8-Naphthalimides
Charge transfer
Naked-eye sensors
1. Introduction
2. Materials and methods
The development of photoactive devices for sensing and repor-
ting of chemical species is currently of significant importance
for both chemistry and biology [1]. Chemosensors for detection
and measurement of transition metal ions are being actively
investigated, because these metals are essential trace elements
in biological systems and important elements in environmental
chemistry [2–10]. Fluorescent 1,8-naphthalimide derivatives serve
as dyes for synthetic polymers and textile materials [11], liquid-
crystal additives [12], electrooptically sensitive materials in laser
technology [13], DNA intercalators [14] and fluorescent markers
[15] in medicine and biology. Diamino-1,8-naphthalimide deriva-
tives have been developed as signal molecules for transition metal
ions [16,17]. However important and useful naphthalimides (1H-
benz[de]isoquinoline-1,3(2H)-diones) are, some structure motifs
remain unexplored. Herein we present 4-amino-3-nitro substi-
tuted 1,8-naphthalimides – potential photoactive sensors and
starting compounds for further transformations to fluorescent sen-
sors. The spectroscopic and structural properties are clarified by
means of single crystal X-ray diffraction, UV–vis absorption and
NMR spectroscopy.
2.1. Synthesis
All new synthesized compounds were purified by column
chromatography and characterized on the basis of NMR and micro-
analytical data. NMR spectra were recorded on Bruker Avance II+
600 (1H at 600.1 MHz; 13C at 150.9 MHz) spectrometer, with TMS as
the internal standard; J values are given in Hertz. Flash chromatog-
raphy was performed on Silica Gel 60 (0.040–0.063 nm, Merck).
Elemental analyses were performed by the Microanalytical Service
Laboratory of Faculty of Chemistry, University of Sofia, using Vario
ELIII CHNS(O).
2.2. Electronic spectroscopy
The absorption spectra were recorded on Thermo Spectronic
Unicam UV 500 UV–Visible double-beam spectrophotometer using
1 cm quartz cells. Data processing was performed using the Vision-
Pro software package. Samples were scanned from 190 to 900 nm.
All experiments were carried out at room temperature.
2.3. X-ray crystallographic analysis
Crystals of 3–5 suitable for X-ray analyses were obtained
after re-crystallization of the compounds. Afterwards a crystal
was mounted on a glass capillary and all geometric and inten-
sity data were taken from that crystal. Diffraction data were
∗
Corresponding authors. Tel.: +359 2 8161 329; fax: +359 2 9625 438.
E-mail addresses: sstoyanov@chem.uni-sofia.bg (S. Stoyanov),
ppetrov@chem.uni-sofia.bg (P. Petrov).
1010-6030/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jphotochem.2012.10.004

S. Stoyanov et al. / Journal of Photochemistry and Photobiology A: Chemistry 250 (2012) 92–98
93
collected at room temperature by ␻-scan technique, on an Agilent
Diffraction SuperNova Dual four-circle diffractometer equipped
with Atlas CCD detector using mirror-monochromatized MoK␣
˚
(ꢀ = 0.7107 A) radiation from micro-focus source. The determina-
tion of cell parameters, data integration, and scaling and absorption
correction were carried out using the CrysAlis Pro program package
[18]. The structures were solved by direct methods [19] and refined
by full-matrix least-square procedures on F2 [19].
Crystals of 3–5 suitable for X-ray structural analysis were
obtained as follows: 3 and 5: after recrystallization and slow evap-
oration of cyclohexane/DCM 4:1 solution at room temperature; 4:
slow evaporation of hexane/Et2O 1:4 (v/v) solution at room tem-
perature.
2.4. General procedure for synthesis of N-aryl substituted
6-amino-7-nitro-benz[de]isoquinoline-1,3(2H)-diones
Fig. 1. Arbitrary numbering given for description of the NMR spectral data of com-
pounds 3–6.
4-Bromo-5-nitro-1,8-naphthalic anhydride was mixed with 4
equivalents of the appropriate primary amine in a closed vessel
and the reaction mixture was heated at the boiling point of the
amine for 24 h. After cooling to room temperature propionic acid
was added and the heating was continued for another 24 h at 140 ◦C.
After evaporation of the volatiles in vacuo the residues are purified
by flash chromatography eluting with cyclohexane:DCM = 3:2.
1H NMR (600.13 MHz, CDCl3): ı 0.90 (t, 3H, 19-H, J = 7.4 Hz), 0.93
(t, 3H, 14-H, J = 7.3 Hz), 1.32–1.39 (m, 2H, 18-H), 1.43–1.49 (m, 2H,
13-H), 1.58–1.63 (m, 2H, 17-H), 1.75–1.80 (m, 2H, 12-H), 3.87–3.93
(m, 2H, 16-H), 4.01–4.07 (m, 2H, 11-H), 7.60–7.64 (m, 1H, 8-H),
8.55–8.61 (m, 2H, 7-H, 9-H), 9.15 (s, 1H, 4-H), 9.86 (br s, 1H, NH);
13C NMR (150.9 MHz, CDCl3): ı 13.91 (1C, CH3), 13.99 (1C, CH3),
20.33 (1C, CH2), 20.43 (1C, CH2), 30.27 (1C, CH2), 33.46 (1C, CH2),
40.11 (1C, CH2), 47.56 (1C, CH2), 117.11 (1C), 122.95 (1C), 123.19
(1C), 124.04 (1C), 126.14 (1C), 126.60 (1C), 127.13 (1C), 127.72 (1C),
134.96 (1C), 137.66 (1C), 164.15 (1C), 164.72 (1C). Anal: Calcd. for
2.4.1. 2-Mesityl-6-(mesitylamino)-5-nitro-1H-benzo
[de]isoquinoline-1,3(2H)-dione (3), yield: 89%
1H NMR (600.13 MHz, CDCl3): ı 2.10 (s, 6H, 18ꢀ-, 22ꢀ-H), 2.17
(s, 6H, 11ꢀ-, 15ꢀ-H), 2.36 (s, 3H, 20ꢀ-H), 2.41 (s, 3H, 13ꢀ-H), 7.04 (s,
2H, 19-, 21-H), 7.06 (s, 2H, 12-, 14-H), 7.35 (dd, 1-H, 8-H, J = 8.7,
7.4 Hz), 7.96 (dd, 1H, 9-H, J = 8.7, 1.0 Hz), 8.64 (dd, 1H, 7-H, J = 7.4,
1.0 Hz), 9.45 (s, 1H, 4-H), 11.34 (s, 1H, NH); 13C NMR (150.9 MHz,
CDCl3): ı 17.83 (2C, C-11ꢀ, -15ꢀ), 18.66 (2C, C-18ꢀ, -22ꢀ), 21.14 (C-20ꢀ),
21.22 (C-13ꢀ), 111.76, 123.33, 123.44, 126.18, 129.42 (2C), 129.52,
130.32 (2C), 130.47, 130.93, 131.59, 132.70, 134.01 (2C, C-18, -
22), 134.38, 135.03 (2C, C-11, -15), 135.06, 138.46, 138.63, 148.27,
161.96, 163.08. Anal: Calcd. for C30H27N3O4: (%) C 73.01; H 5.51; N
8.51. Found: C 73.00; H 5.41; N 8.70.
C20H23N3O4: (%) C 65.03; H 6.28; N 11.37. Found: C 64.92; H 6.20;
N 11.39
2.4.4. 2-tert-Butyl-6-(tert-butylamino)-5-nitro-1H-benzo[de]
isoquinoline-1,3(2H)-dione (6), yield: 0.472 g, 84%
4-Bromo-3-nitro naphthalic anhydride 0.490 g (1,52 mmol) was
mixed with 2.31 ml tert-butylamine (14.4 equivalents) and the
reaction was stirred and refluxed for 4 h. Acetic acid (10 ml) was
then added and the reaction was heated at 120 ◦C for additional
24 h All volatiles were removed in vacuo and the solid residue
was recrystallized from acetic acid-pyridine (2:1 vol) 1H NMR
(600.13 MHz, DMSO-d6): ı 1. 17 (s, 18H, 6CH3), 7.55 (dd, 1H, 8-
H, J = 7.7 Hz), 8.32 (dd, 1H, 9-H, J = 7,4, 1,1 Hz), 8.58 (dd, 1H, 7-H,
J = 7.9, 1.1 Hz), 8.80 (s, 1H, 4-H); 13C NMR (150.9 MHz, DMSO-d6):
27.12 (6C) ı 50.85 (2C), 94.61 (1C), 117.77 (1C), 124.50 (1C), 131.91
(1C), 133.01 (1C) 133.06 (1C), 133.45 (1C), 134.29 (1C), 134.43 (1C),
160.29 (1C), 162.24 (1C), 169.17 (1C). Anal: Calcd. for C20H23N3O4:
(%) C 65.03; H 6.28; N 11.37. Found: C 65.20; H 6.40; N 11.30
2.4.2.
2-(2,6-Diisopropylphenyl)-6-(2,6-diisopropylphenylamino)-5-
nitro-1H-benzo[de]isoquinoline-1,3(2H)-dione (4), yield: 93%
1H NMR (600.13 MHz, CDCl3): ı 1.06 (d, 6H, H-22, J = 6.9), 1.17
(d, 6H, H-13, J = 6.9), 1.21 (d, 6H, H-16, J = 6.8), 1.26 (d, 6H, H-25,
J = 6.8), 2.69–2.76 (m, 2H, 12-H, 15-H), 3.07–3.14 (m, 2H, 21-H,
24-H), 7.32 (dd, 1H, 8-H, J = 8.8, 7.4 Hz), 7.34–7.37 (m, 2H, 26-H),
7.39–7.41 (m, 2H, 17-H), 7.50 (dd, 1H, 18-H, J = 7.8 Hz), 7.55 (dd,
1H, 27-H, J = 7.8 Hz), 7.92 (dd, 1H, 9-H, J = 8.8, 1.0 Hz), 8.65 (dd, 1H,
7-H, J = 7.4, 1.0 Hz), 9.51 (s, 1H, 4-H), 11.73 (br s, 1H, NH); 13C NMR
(150.9 MHz, CDCl3): ı 22.52 (2C, C-22), 23.98 (2C, C-13), 24.05 (2C,
C-16), 24.29 (2C, C-25), 29.12 (2C, C-12, -15), 29.17 (2C, C-21, -24),
111.56 (1C), 122.94 (1C), 123.31 (1C), 124.08 (2C, C-26), 125.11 (2C,
C-17), 125.70 (1C, C-8), 129.09 (1C), 129.62 (C-18), 129.70 (C-27),
130.54 (1C), 130.71 (C-4), 132.65 (C-9), 133.03 (1C), 134.61 (C-7),
134.68 (1C), 144.76 (2C, C-20, -23), 145.57 (2C, C-11, -14), 148.55
3. Results and discussion
The desired compounds were synthesized starting from the
commercial 4-bromo-1,8-naphthalic anhydride by the following
synthetic scheme [20] (Scheme 1).
3.1. Absorption spectra
(1C), 162.57 (C-3), 163.69 (C-1). Anal: Calcd. for C36H39N3O4: (%) C
74.84; H 6.80; N 7.27. Found: C 75.01; H 6.99; N 7.30.
The UV–vis absorption properties of the systems were studied
in various solvents of different polarity. Three notable character-
istics distinguish these naphthalimides: (i) presence of two major
absorption maxima for all compounds; (ii) sensitivity to the media
polarity and basicity; (iii) dependence of spectral properties from
the 4-NH(R)-substituent volume (Fig. 1).
Representative spectra of the investigated compounds in ace-
tonitrile are shown in Fig. 2. The longest wavelength absorption of
the systems is characterized by a broad band with main maximum
2.4.3. 2-Butyl-6-(butylamino)-5-nitro-1H-benzo
[de]isoquinoline-1,3(2H)-dione (5), yield: 1.84 g, 80%
2 g (6.21 mmol) 4-bromo-3-nitro naphthalic anhydride was
mixed with 3.7 ml n-butylamine (6 equivalents) in 100 ml of
ethanol. The reaction mixture was stirred at 75 ◦C for 6 h, the
volatiles were removed in vacuo and the solid residue purified by
flash chromatography eluting with ethylacetate–cyclohexane 4:1.

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S. Stoyanov et al. / Journal of Photochemistry and Photobiology A: Chemistry 250 (2012) 92–98
Scheme 1. Synthesis of 3–6. Reagents and conditions: (a) HNO3/H2SO4; (b) RNH2 3: R = 2,4,6-trimethylphenyl; 4: R = 2,6-diisopropylphenyl; 5: R = n-Bu; 6: R = t-Bu.
Fig. 4. Peri effect illustration.
of 10000 M−1 cm−1) [22]; neither 4-unsubstituted naphthalimides
[23] nor naphthylamines [24] exhibit this band.
Another type of electronic transitions typical for these systems
are ␲–␲* in the aromatic ring, usually around 340 nm for unsub-
stituted naphthalimides [25]. It is expected that both substituent
types in the present series (electron donating in position four and
electron withdrawing in position three) will have hyperchromic
effect and cause bathochromic shift of the maximum.
Fig. 2. Absorption spectra of compounds 3–6 in acetonitrile, c = 1 × 10−5 mol l−1
.
appearing between 380 and 410 nm and well pronounced shoul-
der around 440–450 nm. A clear exception is compound 6, which
exhibits main maximum in the visible region (around 430 nm) with
a clear sign of asymmetry on the short wavelength edge. In order
to perform more detailed analysis of the spectroscopic data we
have applied a model for obtaining the absorption spectrum by the
superposition of Gaussian-type functions.
On this basis, neglecting the fine structure typical for the
␲–␲* transition, we applied deconvolution procedure using two
Gaussian-type functions (Fig. 3) with initial center positions 440
(CT-band, denoted with a) and 380 nm (red-shifted ␲–␲* transi-
tions, denoted with b), respectively. The results obtained for the
wavelength and molar absorptivity of the maxima are summarized
in Table 1.
Their exact number is difficult to be determined, especially
when the vibronic transitions have to be considered, but in first
approximation one can estimate the number and position of the
main absorption maxima from general considerations about the
chromophore structure and electronic effects of the substituents.
As it known from the numerous studies on 4-amino naph-
thalimides, they possess a broad structureless absorption band
around 450 nm, which is usually assigned to an intramolecular
charge transfer (ICT) between the electron-donating amino group
and the accepting carbonyl moiety [21]. Typical characteristics of
this band, which gives evidence of its CT nature, are: the absorp-
tion is fairly broad and intense (molar absorptivities in the range
As can be seen from Table 1 and Fig. 3, compounds 3–5 possess
similar properties in non-polar solvents such as TCM (CCl4), with
predominant influence of the band b (ratio a/b about 0.45), while
the deconvoluted spectrum of compound 6 gives two maxima with
similar intensity (a/b ∼ 1), explaining the different shape of the
recorded spectrum. It is known from the literature that monoalky-
lamino substituents in position 4 cause hyper- and bathochromic
shift of the CT-absorption band as compared to the non-alkylated
amino derivatives [26]. Further alkylation to dialkylamino group
shifts the maximum back to shorter wavelengths and weaker
intensity. This is due to the so called peri effect–steric interactions
between one of the alkyl groups and the hydrogen at the 5-position
Fig. 3. Representative deconvoluted spectra of 3 and 6 in selected solvents.

S. Stoyanov et al. / Journal of Photochemistry and Photobiology A: Chemistry 250 (2012) 92–98
95
Table 1
Absorption maxima of compounds 3–6 in solvents with different polarities.
Comp.
ꢀmax, nm (ε, M−1 cm−1
)
Solvent
CCl4
CH2Cl2
MeOH
CH3CN
DMF
DMSO
3
4
5
6
442 (10,800)
387 (23,500)
441 (8940)
386 (21,700)
441 (4140)
387 (11,600)
–
449 (8567)
393 (25,367)
447 (5350)
392 (14,700)
450 (3280)
393 (9860)
387 (5350)
339 (13,200)
444 (6730)
397 (15,700)
443 (6110)
395 (16,100)
442 (3610)
395 (9750)
426 (6320)
399 (12,200)
444 (6420)
393 (14,800)
445 (6110)
392 (16,500)
448 (3980)
393 (10,500)
437 (8950)
409 (9610)
509 (10,600)
425 (8960)
507 (13,200)
430 (10,900)
396 (10,500)
449 (3890)
440 (1790)
412 (1850)
445 (7850)
399 (12,700)
445 (6340)
398 (14,200)
439 (4590)
395 (8320)
442 (10,600)
415 (13,000)
(Fig. 4). It is believed that the hydrogen in the monoalkylamino sub-
stituents is aligned toward the peri hydrogen while the alkyl group
points away, thus minimizing the steric hindrance.
different polarity give different stable geometries of the ground
state, therefore the observed effect is not solvatochromism.
Compound 6 is the exception that confirmed the rule – 6 does
not fit into the pattern set by 3–5. Its absorption maxima are
insensitive to the media polarity and show “reversed” a/b ratio.
This observation can easily be explained if the N-substituent steric
volume is taken into consideration – the tert-Butyl group is too
large, thus the peri effect is strong enough to overcome the stabi-
lization via H-bonding, leading to solvent-independent absorption
band shape, similar to the one observed for monoalkylated 4-amino
derivatives without nitro group.
Another noteworthy result was obtained from the absorption
of compounds 3 and 4 in DMF (Fig. 6). These two solutions were
red colored – a marked difference from the common pale-yellow
color in all other solvents. This phenomenon can be attributed to
deprotonation of the amino moiety at C-4 position and formation
of negatively charged naphthalimide rings. The increased electron
density at the nitrogen shifts the longest wavelength absorption
maximum bathochromically with ca. 80 nm.
In the compounds studied by us (3–6) the nitro group presence
at position 3 clearly has an impact on the rotation around C4
N
bond, due to both steric repulsion and formation of hydrogen bond.
This leads to an unusual alignment in the amino group and stabi-
lization of other possible conformers. The H-bond formation cannot
be neglected, since the increased N H acidity (see below) deter-
mines a stronger N H· · ·O bond which effectively influences the
conformer ratio toward the chelate six-membered cycle (see X-
ray results). Obviously the peri effect and the formation of H-bond
act in opposite directions, leading to a specific geometry of com-
promise. On the other hand, absorption spectra and especially the
intensities of CT-bands are very sensitive to the degree of conjuga-
tion between the nitrogen lone electron pair and the naphthalimide
aromatic system [27]. Indeed, we observed that the stronger the H-
bond is, the weaker the CT band gets – the a/b ratios are smaller in
less-polar solvents (Table 1 and Fig. 3). The use of polar solvents like
DMSO which effectively interferes in the H-bond formation leads
to increase of the relative intensity of CT-bands in compounds 3–5.
Fig. 5 shows the recorded spectra of compound 3 in different
solvents. The observed main absorption maximum bathochromic
shift with increasing the solvent polarity can be seen as a classical
example of positive solvatochromism, due to better solvation of
the more polar excited state in solvents like DMSO. Our model for
explanation of the spectroscopic data takes into consideration not
only the shift but also the change in the shape of band. This leads
us to the conclusion that stronger conformational effects, rather
than dipole–dipole interactions, influence the spectra. Solvents of
Similar behavior was observed previously (on 4-amino substi-
tuted naphthalimides without nitro groups), but only after addition
of strong bases NaOH [28] or (C4H9)4NF [29]. The process has also
been found to be reversible – upon reprotonation with hydrochlo-
ric acid the color changes back from red to yellow. From this point
of view, the ability of compounds 3 and 4 to form stable anions in
DMF is unprecedented. Two major factors determine the enhanced
N
H acidity of these dyes: (i) the presence of aromatic ring as
a substituent to the nitrogen; (ii) the presence of the electron
accepting nitro group which further stabilizes the N H acid’s con-
jugated base. Furthermore, the amino nitrogen atom is not basic at
Fig. 5. Normalized absorption spectra of 3 in solvents of different polarity – a/b ratio
dependency on the media.
Fig. 6. Normalized absorption spectra of studied compounds in DMF – sensitivity
of 3 and 4.

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S. Stoyanov et al. / Journal of Photochemistry and Photobiology A: Chemistry 250 (2012) 92–98
Fig. 7. ORTEP view of compound 3 with the atomic numbering scheme; ellipsoids are drawn at 50% probability.
Fig. 8. ORTEP view of compound 4 with the atomic numbering scheme; ellipsoids are drawn at 50% probability.
Fig. 9. ORTEP view of compound 5 with the atomic numbering scheme; ellipsoids are drawn at 50% probability.

S. Stoyanov et al. / Journal of Photochemistry and Photobiology A: Chemistry 250 (2012) 92–98
97
all – in our hands the spectra of compounds 3 and 4 in MeOH could
not be influenced even by adding hypermolar amounts of sulfuric
acid.
3.2. X-ray crystallography
Crystal structure determination of compounds 3–5.
The solid-state structure of 3 was determined using X-ray
crystallography. Compound 3 crystallizes in the centrosymmetric
triclinic group P-1 (SG 2) with one molecule per asymmetric unit
(see ESI – Table 1). An ORTEP view of the molecule of 3 is shown in
Fig. 7 and selected bond distances and bond angles are given (see
ESI – Table 2).
Fig. 10. Overlay of the molecules of 3 (light green), 4 (dark blue) and 5 (light colored)
Compound 4 crystallizes in the centrosymmetric group P21/c
(SG 14) with one molecule per asymmetric unit (see ESI –
Table 1). The ORTEP plot with the atomic numbering system
of 4 is shown in Fig. 8 and selected bond distances and bond
angles are listed (see ESI – Table 2). The bond distance and
angles of the benzoisoquinoline and the two diisopropylbenzene
moieties are comparable to those observed in other structures
[29a,30–34]. The benzoisoquinoline ring is almost planar with
rms of 0.0267. The oxygens of the nitro group (N14/O15/O16) are
slightly out of the plane of the benzoisoquinoline ring thus the
angle between the two mean planes is nitro/benzoisoquinoline is
10.5(3)◦.
The two substituents, diisopropylbenzene and 2,6-
diisopropylaniline are positioned out of the plane of the
benzoisoquinoline; the angle between the mean planes of
the benzoisoquinoline and aromatic rings is 86.2(4)◦ and 74.8(4)◦
for C30/C31/C32/C33/C34/35 and C18/C19/C20/C21/C22/C23,
respectively.
showing the structural deviations.
that the major structural variation concerns the torsion angle
C8–C13–N17–C18, −2.8(4)◦, −23.5(4)◦ and 27.8(5)◦, respectively.
4. Conclusions
Exploring substitution patterns on naphthalimides continues
to reveal their rich spectral properties and provides opportunities
for new applications of this class of compounds. The combina-
tion of nitro and amino groups on a naphthalimide was never
thoroughly studied before and shows that 4-arylamino-3-nitro-
1,8-naphthalimides are promising naked eye sensory systems
which properties can be fine tuned by changing the steric and
electronic properties of N-4.
Acknowledgements
A strong intramolecular hydrogen bond, N17–H17· · ·O16 (D· · ·A
˚
distance of 2.587(4) A) is responsible for the stabilization of the
Financial support from the National Science Fund of Bulgaria
(Projects DCVP 02/2-2009 UNION – S.S. and I.P.; ID 09/0105 – M.S.,
P.P., M.D.; DRNF 02/1 – B.S. and R.N.) and from University of Sofia
is greatly appreciated.
molecules of 4. The presence of four “bulky” isopropyl groups pre-
vents the formation of additional hydrogen bonds.
Compounds
3 and 4 possess identical benzoisoquinoline
core and similar substituents 1,3,5-triisopropylbenzene and 1,3-
diisopropylbenzene, respectively. Thus it is not strange if the
major structural features of 3 and 4 are comparable: similar bond
lengths and angles (see ESI – Table 2), almost planar aromatic
rings (rms of 0.132, 0.026 and 0.021 for the benzoisoquinoline,
C27/C28/C29/C30/C31/C32 and C18/C19/C20/C21/C22/C23 of the
respective mean), an angle between the mean planes of the
benzoisoquinoline and respective aromatic rings of 82.2(5)◦ and
63.6(5)◦ and finally an intramolecular N17-H17· · ·O16 (D· · ·A dis-
Appendix A. Supplementary data
Supplementary data associated with this article can be found,
in the online version, at http://dx.doi.org/10.1016/j.jphotochem.
2012.10.004.
References
˚
tance of 2.598(3) A) hydrogen bonding interaction.
[1] (a) J. Liu, A.P. de Silva, Inorganica Chimica Acta 381 (2012) 243–246;
(b) V. Amendola, L. Fabbrizzi, M. Licchelli, C. Mangano, P. Pallavicini, L. Parodi,
A. Poggi, Coordination Chemistry Reviews (1999) 190–192;
(c) A.P. de Silva, H.Q.N. Gunaratne, T. Gunnlaugsson, A.J.M. Huxley, C.P. McCoy,
J.T. Rademacher, T.E. Rice, Chemical Reviews 97 (1997) 1515–1566;
(d) S. Mizukami, T. Nagano, Y. Urano, A. Odani, K. Kikuchi, Journal of the Amer-
ican Chemical Society 124 (2002) 3920–3925;
Compound 5 crystallizes in the centrosymmetric group C2/c (SG
15) with one molecule per asymmetric unit (see ESI – Table 1). An
ORTEP view of the molecule of 5 is shown in Fig. 9 and selected
bond distances and bond angles are given (see ESI – Table 2) In the
case of 5 the identical benzoisoquinoline core to the one present in
compounds 3 and 4 is conserved.
(e) H. He, M.A. Mortellaro, M.J.P. Leiner, R.J. Fraatz, J.K. Tusa, Journal of the
American Chemical Society 125 (2003) 1468–1469.
On the other hand, instead of the diisopropylbenzene and
trimethylbenzene substituents here we have two butanamine sub-
stituents (N17–C18–C19–C20–C21 and N2–C22–C23–C24–C25).
One could say that the three compounds (3–5) preserve a sim-
ilar conformation and thus similar bond lengths and angles. As
in 3 and 4 the core of 5 is almost planar (rms of 0.092), the two
substituents are out of the mean plane of the “core” and a strong
intramolecular hydrogen bond, N17-H17· · ·O16 (D· · ·A distance of
[2] (a) D. Staneva, P. Bosch, I. Grabchev, Journal of Molecular Structure 1015 (2012)
1–5;
(b) H.-J. Kim, D. Moon, M.S. Lah, J.-I. Hong, Angewandte Chemie International
Edition 41 (2002) 3174–3177.
[3] (a) J. Ren, Z. Wu, Y. Zhou, Y. Li, Z. Xu, Dyes and Pigments 91 (2011) 442–445;
(b) K.M. Hendrickson, J.P. Geue, O. Wyness, S.F. Lincoln, A.D. Ward, Journal of
the American Chemical Society 125 (2003) 3889–3895.
[4] Y. Zheng, J. Orbulescu, X. Ji, F.M. Andreopoulos, S.M. Pham, R.M. Leblanc, Journal
of the American Chemical Society 125 (2003) 2680–2686.
[5] J. Zheng, R.M. Dickson, Journal of the American Chemical Society 124 (2002)
13982–13983.
[6] M. Beltramello, M. Gatos, F. Mancin, P. Tecilla, U. Tonellato, Tetrahedron Letters
42 (2001) 9143–9146.
˚
2.614(4) A) is responsible for the stabilization of the molecules
of 5.
[7] S. Bhattacharya, M. Thomas, Tetrahedron Letters 41 (2000) 10313–10317.
[8] G. Klein, D. Kaufmann, S. Schürch, J.-L. Reymond, Chemical Communications
(2001) 561–562.
[9] P. Ghosh, P.K. Bharadwaj, J. Roy, S. Ghosh, Journal of the American Chemical
Society 119 (1997) 11903–11909.
The comparable geometrical features of the three compounds,
the presence of stiff benzoisoquinoline fragment and the “similar”
positioning of the substituents clearly show the relative struc-
tural rigidity (Fig. 10). The overlay of the molecules of 3–5 shows

98
S. Stoyanov et al. / Journal of Photochemistry and Photobiology A: Chemistry 250 (2012) 92–98
[10] K. Rurack, M. Kollmannsberger, U. Resch-Genger, J. Daub, Journal of the Amer-
ican Chemical Society 122 (2000) 968–969.
[23] A. Samanta, G. Saroja, Journal of Photochemistry and Photobiology A: Chemistry
84 (1994) 19–26.
[11] I. Grabtchev, T. Philipova, P. Meallier, S. Guittonneau, Dyes and Pigments 31
(1996) 31–34.
[24] K. Hirayama, Handbook of Ultraviolet and Visible Absorption Spectra of Organic
Compounds, Plenum Press, New York, 1967.
[12] I. Grabchev, I. Moneva, V. Bojinov, S. Guittonneau, Journal of Materials Chem-
istry 10 (2000) 1291–1296.
[25] A. Pardo, J.M.L. Poyato, E. Martin, Journal of Photochemistry 36 (1987)
323–329.
[13] A.V. Kukhto, É. É Kolesnik, M.I. Tobi, I.K. Grabchev, Journal of Applied Spec-
troscopy 67 (2000) 939–942.
[14] W. Yao, X. Qian, Q. Hu, Tetrahedron Letters 41 (2000) 7711–7715.
[15] J.E. Rogers, S.J. Weiss, L.A. Kelly, Journal of the American Chemical Society 122
(2000) 427–436.
[26] S. Saha, A. Samanta, Journal of Physical Chemistry A 106 (2002) 4763–4771.
[27] H. Shaki, K. Gharanjig, S. Rouhani, A. Khosravi, Journal of Photochemistry and
Photobiology A: Chemistry 216 (1) (2010) 44–50.
[28] D. Staneva, I. Grabchev, J.-P. Soumillion, V. Bojinov, Journal of Photochemistry
and Photobiology A: Chemistry 189 (2007) 192–197.
[16] B. Ramachandram, G. Saroja, B. Sankaran, A. Samanta, Journal of Physical Chem-
istry B 104 (2000) 11824–11832.
[29] (a) T. Gunnlaugsson, P. Kruger, P. Jensen, F. Pfeffer, G. Hussey, Tetrahedron
Letters 44 (2003) 8909–8913;
[17] B. Ramachandram, B. Sankaran, R. Karmakar, S. Saha, A. Samanta, Tetrahedron
56 (2000) 7041–7044.
[18] Agilent, CrysAlis PRO, Agilent Technologies Ltd., Yarnton, England, 2010.
[19] G.M. Sheldrick, Acta Crystallographica. Section A: Foundations of Crystallogra-
phy 64 (2008) 112–122.
[20] A.M. Kadhim, A.T. Peters, Journal of the Society of Dyers and Colourists (1974)
153–157.
[21] M.S. Alexiou, V. Tychopoulos, S. Ghorbanian, J.H.P. Tyman, R.G. Brown, P.I. Brit-
tain, Journal of Chemical Society, Perkin Transactions 2 (5) (1990) 837–842.
[22] I. Grabchev, Dyes and Pigments 38 (4) (1998) 219–226.
(b) B. Liu, H. Tian, Journal of Materials Chemistry 15 (2005) 2681–2686.
[30] S. Banthia, A. Samanta, Chemistry Letters 34 (2005) 722–723.
[31] S. Banthia, A. Paul, Acta Crystallographica. Section E, Structure Reports Online
61 (2005) o3474–o3475.
[32] G.R. Bardajee, M.A. Winnik, A.J. Lough, Acta Crystallographica. Section E, Struc-
ture Reports Online 62 (2006) o1615–o1617.
[33] S. Banthia, A. Samanta, Crystal Growth and Design 6 (2006) 360–362.
[34] Y. Zhang, G.-M. Han, Q. Wu, H.-S. Wang, Acta Crystallographica. Section E,
Structure Reports Online 63 (2007) o4336.