Corrole-imide dyads - Synthesis and optical properties

Article abstract of DOI:10.1142/S1088424615500339

Two rarely seen building blocks have been incorporated into light absorbing arrays: corroles and 2,3-naphthalimides. General synthetic strategy consisting in direct condensation of formyl substituted aromatic imides with dipyrranes led to diverse range of

Full text of DOI:10.1142/S1088424615500339

Journal of Porphyrins and Phthalocyanines
J. Porphyrins Phthalocyanines 2015; 19: 479–491
DOI: 10.1142/S1088424615500339
Published at http://www.worldscinet.com/jpp/
Corrole–imide dyads — Synthesis and optical properties
Roman Voloshchuka, Mariusz Tasiora, Adina I. Ciuciub, Lucia Flamigni*b
and Daniel T. Gryko*a◊
a Institute of Organic Chemistry of the Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
b Istituto per la Sintesi Organica e Fotoreattivita’(ISOF), CNR, Via P. Gobetti 101, 40129 Bologna, Italy
Dedicated to Professor Shunichi Fukuzumi on the occasion of his retirement
Received 10 November 2014
Accepted 29 December 2014
ABSTRACT: Two rarely seen building blocks have been incorporated into light absorbing arrays:
corroles and 2,3-naphthalimides. General synthetic strategy consisting in direct condensation of formyl
substituted aromatic imides with dipyrranes led to diverse range of trans-A2B-corroles in acceptable
yields. Spectroscopic properties of all five dyads studied suggest that regardless the imide’s structure,
components are weakly electronically coupled. Positioning 2,3-naphthaimide unit partially above the
corrole core leads to slight alteration of their optical properties. Dyads bearing blue-absorbing imide
components display different behavior depending on their structure. In corrole linked with naphthalenyl-
naphthalene-1,8-carboximide a 100% effective energy transfer reaction from the imide component to
the corrole component occurred. On the contrary, in small, strongly polarized amino-cyano-phthalimide
neither efficient energy-nor electron-transfer could be detected and excitation leads to fluorescence from
both components.
KEYWORDS: corroles, imide, synthesis, fluorescence, dipyrranes.
because an efficient conversion of sunlight into chemical
INTRODUCTION
energy or electricity might solve the rising environmental
The synthesis and photophysical characterization
and energy supply problems. Furthermore, this research
of multichromophoric arrays capable of energy and/
area is providing a deep insight into processes like
or electron transfer have been one of the most exciting
photoinduced electronic energy transfer and electron
and fruitful areas of research in the last few decades
transfer, which are of interest for a wide range of
[1]. The study of model systems mimicking the basic
applications, from material chemistry to biology.
photochemical events in natural photosynthesis, often
The majority of chromophores involved into natural
called “artificial photosynthesis,” together with the
photosynthesis belongs to the porphyrinoid class. Nature
crystallization of natural photosynthetic membrane
has chosen these tetrapyrrolic macrocycles to play such an
complexes, considerably helped to establish the rules that
important role because of their unique structure (aromatic
govern the photoinduced processes observed in Nature
[2]. Recently this basic subject has developed into a
18 p-electron [18]-diazaannulene system), spectroscopic
and redox properties, the ability of charge delocalization
more advanced field which aims at light-driven water
and formation of complexes with many metal cations. It
splitting and carbon-free fuel hydrogen production [3].
is not surprising that the most frequently used building
The interest in artificial photosynthesis is still growing,
blocks for the construction of artificial multichromophoric
arrays are meso- substituted porphyrins [4]. However,
other porphyrinoids like chlorins [5], phthalocyanines
◊ SPP full member in good standing
[6] and subporphyrins [7] have been also used for this
purpose. We recently incorporated another member of
porphyrinoid family — corroles, into light harvesting
*Correspondence to: Daniel T. Gryko, email: daniel.gryko@
icho.edu.pl, tel: +48 22-3433063, fax: +48 22-6326681; Lucia
Flamigni, email: lucia.flamigni@isof.cnr.it
Copyright © 2015 World Scientific Publishing Company

480
R. VOLOSHCHUK ET AL.
arrays [8]. Corroles are one carbon short analogs of
porphyrins with three meso-carbons between the four
pyrrole rings. Because of structural similarity to corrin
(macrocycle found in vitamin B12) they attracted attention
since early 60s of the last century [9], however, lack of
efficient synthetic methodologies strongly hampered
the progress in their chemistry. Nevertheless, recent
discoveries in this area made them readily available [10],
openingthedoorforvariousapplications[11].Theanalysis
of spectroscopic, photophysical and electrochemical
properties of meso-substituted corroles reveals that
they exhibit more intense absorption of red light, larger
Stokes shift, higher fluorescence quantum yields [12]
and lower oxidation potentials [13], when compared to
similarly substituted porphyrins. By taking advantage of
these properties, we were able to achieve ultra-fast and
efficient energy and electron transfer in corrole-fullerene
[8f], corrole-aromatic imide [8b, 8i] and (aromatic)
bisimide dyads and triads [8c, 8e, 8j, 8m]. Fullerenes and
aromatic imides and bisimides are particularly convenient
building blocks for multichromophoric arrays, because
the former dye secures excellent charge separation
lifetimes, whereas the latter is amenable for structural
modifications, thus allowing an easy alteration of the
properties of the resulting model systems. While working
with the corrole-aromatic imide dyads and triads, we
focused our attention on the very rare 2,3-naphthalimides.
This type of chromophore, to the best of our knowledge,
has never been used in the construction of light absorbing
arrays, despite the structural similarity to broadly used
1,8-naphthalimides [8b, 14] and naphthalene-4,5:1,8-
bis(dicarboximides) [15]. Attracted by the interesting
photophysical properties of corrole-imide dyads, we set
ourselves the difficult task of incorporation, for the first
time, of 2,3-naphthalimides and few other less common
aromatic imides into multichromophoric array. In spite
of the development of new methodologies towards the
synthesis of meso-substituted corroles, this could be
a serious synthetic challenge, mostly due to solubility
problems. In this paper we present the results of our
synthetic efforts, the spectroscopic characterization of the
prepared dyads and the basic photophysical properties.
region. We would like one of them to possess large
p-system without strong electron-withdrawing character
and the second one very small but still possessing strong
absorptionbetween400and450nm. Inordertosynthesize
trans-A2B-corrole–imide dyads we decided to utilize the
well-developed [2+1] condensation between dipyrranes
and aldehydes. Given the moderate stability of corroles,
we followed the general strategy starting from the
preparation of an elaborated aldehyde which would then
be used in the corrole forming reaction. Therefore our
strategy was as follows: the synthesis of imide-derived
aldehyde followed by final condensation with dipyrrane.
In all cases 5-(pentafluorophenyl)dipyrrane was chosen,
since previous studies showed that electron-withdrawing
substituents are necessary to secure reasonable stability
of final corrole [8b].
The shortest approach towards the necessary aldehydes
would be to use aminobenzaldehydes and perform their
direct condensation with the corresponding anhydrides.
Such compounds, however, are generally unstable
and even traces of acids initiate their polymerization.
Therefore some kind of protection of an aldehyde
functionality has to be used.We decided to investigate two
approaches: protection of aldehyde in the form of acetal
and the use of aminobenzyl alcohols as one oxidation
level lower precursors for corresponding aldehydes. The
latter option is justified by the fact that such alcohols are
readily oxidized to corresponding aldehydes by a variety
of methods. Thus, 2,3-naphthalenedicarboxylic acid
anhydride (2) was reacted with 3-aminobenzyl alcohol
in a boiling DMF and, after aqueous workup and flash
chromatography purification, the desired alcohol 3 was
obtained in 70% yield as a readily crystallizing solid. The
solubility of the prepared alcohol in common organic
solvents was rather low, presumably due to p-stacking
and intermolecular hydrogen bond formation, and this
fact complicated the search for appropriate conditions
for oxidation reaction. The brief survey of oxidizing
systems was made and in most cases either conversion
was incomplete or complex mixtures arose. Surprisingly,
oxidation of alcohol 3 with [bis(acetoxy)-iodo]benzene
(BAIB)/TEMPO system [16] in dichloromethane gave
target aldehyde 6 in a yield of 92%, though substrate
was never dissolved and the reaction was performed in
solid-to-solid regime, whereas better solubilizing solvent
(THF) gave the expected product in much lower yield
(17%) (Scheme 1).
RESULTS AND DISCUSSION
Design and synthesis
Some time ago we found that 3-aminobenzaldehyde
polymer reacts readily with 1,8-naphthalenedicarboxylic
acid anhydride, forming the desired imidoaldehyde
in one step [8b]. To our delight, anhydride of
2,3-naphthalenedicarboxylic acid exhibited similar
reactivity against both 3-aminobenzaldehyde polymer
(4) and 4-aminobenzaldehyde polymer (5), thus allowing
straightforward, one step synthesis of aldehydes 6 and 7.
According to our plan, ortho-substituted isomer of
aldehydes 6 and 7 was one of the crucial substrates.
We were curious how spatial arrangement, especially
strained face-to-face orientation of the dyad counterparts
will influence its spectroscopic and photophysical
properties. We required chromophore with elongated
shape and absorption below 400 nm, so its absorption
will not entirely overlap with Soret band of corroles.
Consequently, we have chosen naphthalene-2,3-
carboxyimide as a key structural element. In addition,
we also designed to imides absorbing in violet-blue
Copyright © 2015 World Scientific Publishing Company
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CORROLE–IMIDE DYADS — SYNTHESIS AND OPTICAL PROPERTIES
481
O
O
H2N
O
O
OH
O
O
+
+
H2N
O
O
1
2
2
8
DMF, reflux, 6 h, 70%
AcOH, reflux (33%) or
chloroform, imidazole (43%)
O
O
N
O
N
OH
O
3
O
O
BAIB/TEMPO in THF (17%) or
BAIB/TEMPO in DCM (92%)
9
TFA, 5% H2SO4(aq)
chloroform, 24 h, 96%
,
O
O
N
O
N
CHO
6 = m-isomer
7 = p-isomer
CHO
O
10
2, AcOH,
reflux,
78%
Scheme 2.
H
N
n
Finally, continuing the search towards new small
chromophores with interesting optical properties,
derivatives of 3-amino-4-cyano-5,6-diphenylphthalimide
were synthesized. Corresponding anhydride 19 was
prepared according to published procedure [18]. Simple
derivatives of this anhydride (phthaloyl hydrazide and
N-hydroxy phthalimide) were described in the literature
exclusively from the point of view of their biological
activity (antitumor agents). Their spectroscopic properties
were never studied and N-aryl-substituted imides of such
type were unknown before our work. The combination of
electron-withdrawing and electron-donating groups alters
theelectronicstructureoforganicchromophoredecreasing
the difference between HOMO and LUMO. As a result,
anhydride 19 strongly absorbs violet-blue light. Assuming
that free amino group will not cause complications during
imide formation due to the combined effect of steric
hindrance and its electron-poor character, anhydride 19
was used in further steps without modifications. In order
to synthesize the necessary aldehyde, the mixture of
anhydride 19 and p-aminobenzaldehyde polymer (5) was
refluxed in acetic acid. Aldehyde 20 was obtained with
good yield and acceptable purity without chromatographic
purification (Scheme 4).
OH
4 = m-isomer
5 = p-isomer
Scheme 1.
Therefore we synthesized acetal 9, by the condensation
of 8 with anhydride 2. Among tested reaction conditions,
boiling substrates in chloroform with an excess of
imidazole gave the best results [17]. Subsequent
deprotection of aldehyde function gave desired compound
10 (Scheme 2).
Aldehyde 15, possessing skeleton unknown before,
is particularly interesting, as its p-expanded structure
can be characterized by strong donor–acceptor
character, resulting in significant bathochromic shift
of both absorption and emission maxima. Its synthesis
was achieved in two steps starting from anhydride 11.
Sonogashira coupling with commercially available
naphthalene-based arylacetylene 12, followed by
condensation of newly prepared anhydride 13 with
3-aminobenzaldehyde ethylene acetal (14) in imidazole/
chloroform mixture, and deprotection step gave desired
aldehyde 15 in excellent overall yield (Scheme 3).
With a small library of aromatic aldehydes, precursors
for corrole synthesis, we began a dyads’ synthesis. We
have chosen the reaction conditions optimized for corroles
Copyright © 2015 World Scientific Publishing Company
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482
R. VOLOSHCHUK ET AL.
OMe
Ph
CN
CN
O
+
Br
OH
Ph
+
16
17
morpholine,
DMF, 81%
O
O
O
H
12
11
N
Ph
Ph
Pd(PPh3)2Cl2
CuI, Et3N, 98%
NH2
O
O
O
O
O
O
18
maleic anhydride
DMSO, 70%
MeO
+
NH2
N
OH
13
Ph
14
1. imidazole
Ph
NH2
+
n
2. acetone, p-TsOH,
N
84% (two steps)
H
O
O
O
5
O
N
O
19
MeO
AcOH, 66%
CHO
15
NH2
O
N
O
N
Scheme 3.
CHO
Ph
Ph
bearing electron-withdrawing substituents, which were
elaboratedinourgroup[10j].Thereactionswereperformed
in dichloromethane as a solvent with TFA concentration of
ca. 13 mM. After bilane (the linear tetrapyrrolic corrole
precursor) formation, the oxidation step was performed
with DDQ. Under these conditions we were able to obtain
five corrole-aromatic imide dyads, usually in moderate
yield (14–18%). Only corrole 26 was formed in lower
yield (6%, Table 1). Among possible unfavorable factors,
free amino group of aldehyde was considered to be a site
which is capable to bind acidic catalyst and hence reduce
its active concentration in the reaction mixture. Having this
in mind, reaction was repeated with doubled concentration
of TFA (ca. 27 mM) but, unfortunately, it did not improve
outcome of the experiment.
20
Scheme 4.
with their imides and corrole models, 28, 29, 13 and 30
respectively. Corrole 30 has been previously extensively
investigated by our groups [12a] and often used as
model for corrole containing multi-component systems
[8a, 8c, 8e].
Dyads 22, 23, 24. The absorption spectra of dyads
22–24 are reported in Fig. 1 overlaid to those of the
corresponding models. These dyads differ for the linking
position (ortho, meta, para) of the imide to the corrole
and one of the aims of our study was to detect differences
in their spectroscopic and photophysical properties.
Naphthalene-imide 28 displays a structured absorption
band with maxima at 358 and 341 nm with a molar
absorption coefficient <3,000 M-1.cm-1, whereas corrole
30 has an intense Soret band at 419 nm (e = 120,000 M-1.
cm-1) and weaker Q-bands at 523, 562, 617 and 640 nm
(e < 20,000 M-1.cm-1). As can be seen from Fig. 1,
the spectra of the meta and para dyads 22 and 23 are
Finally, imides 28 and 29 and corrole 30 were prepared
and used for photophysical studies as model compounds
lacking additional chromophore (Scheme 5). All prepared
corroles were sufficiently stable both in solid state and in
solution, thus allowing their spectroscopic characterization.
Spectroscopic characterization of prepared dyads
The five corrole-based dyads have been studied in
toluene (TOL) solutions at room temperature along
Copyright © 2015 World Scientific Publishing Company
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CORROLE–IMIDE DYADS — SYNTHESIS AND OPTICAL PROPERTIES
483
Table 1. Synthesis of corrole–aromatic imide dyads
Aldehyde Corrole
R
Yield, %
16
6
22
23
24
25
26
7
14
17
18
6
10
15
20
perfectly superimposable to the plain superposition of the
component models 28 and 30 (Figs 1a and 1b). They in
fact display additivity both in the UV, where the imide 28
bands position and intensity are well-reproduced and at
lower energies, where the Soret and Q-bands of corrole
30 are perfectly overlapped. This is an indication of a
poor electronic coupling of the component units in the
dyads. On the contrary the ortho isomer 24 displays poor
additivity (Fig. 1c) which can be noticed predominantly
in the region of corrole absorbance, in the intensity of
the 419 nm Soret band and in the lowest energy Q-band
at 640 nm, which is missing in the dyad. However, also
in the UV region where the imide bands are discernible,
the total absorbance is lower than expected on the basis
of a plain additivity. The behavior of the ortho dyad 24 is
ascribed to a perturbation induced by the positioning of
aromatic system over the corrole ring.
photoinduced processes were affected by the substitution
type. The imide model 28 displays a broad emission
spectrum with maximum at 501 nm and a weak
luminescence yield with Ffl = 0.011 and corrole 30
shows a more intense luminescence with Ffl = 0.14 after
excitation on the respective bands (Table 2).
The dyads, after excitation in the imide band at 358 nm
displayed a luminescence which was essentially that of
corrole (Fig. 2). The luminescence of the imide moiety
is almost completely quenched (<ꢀ97%) whereas the
corrole band appears sensitized by a value of ca. 20% in
the isomers 22 and 23. On the contrary, the emission of
the corrole unit in the ortho isomer 24 has an intensity
identical to that of corrole. This indicates that in the
decoupled dyads 22 and 23 a complete energy transfer
from the imide moiety to the corrole occurs, in fact
20% is also the amount of photons absorbed by the
donor imide at the excitation wavelength, see absorption
spectra. For dyad 24, characterized as discussed above
The luminescence properties of dyads 22–24 were
examined in detail in order to ascertain whether the
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484
R. VOLOSHCHUK ET AL.
O
O
+
H2N
O
27
2
AcOH, reflux, 87%
O
N
O
28
N
N
Ph
Ph
27, AcOH,
reflux, 54%
Ph
NH2
Ph
NH2
O
O
N
O
O
O
19
29
NH
N
C6F5
C6F5
NHHN
30
Scheme 5.
by some electronic interaction because of the geometric
arrangement, the sensitization is not clearly detected.
However, an excitation spectrum registered at 660 nm,
where only corrole moiety emits, indicate the presence of
the bands of the imide (Fig. 3), showing that also in this
case energy transfer occurs.
Excitation of the corrole unit in the dyads leads to an
emission identical to that of the model in dyads 22 and
23, whereas in the ortho derivative 24 there is a quenching
of the order of 20% (data not shown). Time resolved
experiments after 355 nm excitation shows that in all
dyads the lifetime of the model imide measured at 500 nm,
1.6 ns in the model, is reduced to 55 5 ps, identical
within experimental uncertainty, whereas the lifetime of
corrole moiety measured at 660 nm is identical to that of
the models for all dyads, 3.85 0.5 ns. These data allow
to calculate a rate of energy transfer from the imide to the
corrole moiety of the order of 1.8 × 1010 s-1 for all dyads.
Such a high rate is not surprising given the strong overlap
Fig. 1. Absorption spectra of dyads 22, 23 and 24 in TOL
overlaid with those of the models 28 and 30
between the emission of donor 28 and the absorption of
acceptor 30, a critical parameter for the occurrence of
energy transfer. The “strange” behavior of the ortho dyad
24, which appears to have a lower emission yield from
the corrole unit than the model and the other dyads might
be ascribable to the electronic perturbation brought about
by the close packing of the two chromophores which are
expected to alter the radiative parameters. However we
cannot completely exclude the hypothesis that a through
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CORROLE–IMIDE DYADS — SYNTHESIS AND OPTICAL PROPERTIES
485
Therefore, from the present data there is no clear
evidence that the different types of substitution either
ortho, meta or para, affect the nature or the rate of the
photoinduced processes. It can however be noticed that
in the ortho isomer 24 the proximity of the electronic
clouds of the two moieties due to the positioning of the
imide over the tetrapyrrolic ring, induces an electronic
interaction leading to a variation in spectroscopic
parameters.
Dyads 25 and 26. The absorption spectra of the dyads
and the related models 13, 29 and 30 are reported in
Fig. 4. Due to the low amount of compound available,
the molar absorption coefficients might be affected by
some uncertainty. Imide 13 displays a structured band
with maxima at 403 and 417 nm (e ca. 27,000 M-1.cm-1)
and 29 displays a broad absorption band around 415 nm,
with an e = 10,000 M-1.cm-1, in agreement with similar
compounds [19]. The dyad spectra appear to be the
simple superposition of the component units within
experimental errors, indicating that the level of electronic
interaction between the components is weak.
Table 2. Luminescence parameters of dyads 22–24 and
pertinent models in TOL at room temperature
lemmax, nma
Ffbl
Ffcl
t, ns
1.6
28
30
22
23
24
501
0.011
656, 716
660, 716
661, 717
661, 715
0.14d
0.14
0.14
0.11
3.8d
<0.0001, 0.16
<0.0001, 0.17
0.0003, 0.14
0.054; 3.8
0.060; 3.9
0.050; 3.9
a Data from corrected spectra. bLuminescence quantum yield,
c
excitation in the imide band (350 nm). Luminescence quantum
yield, excitation in the corrole band (560 nm). dData from Ref. 12a.
The photophysics of these dyads was examined with
a lower detail in comparison to the former ones. The
Fig. 2. Fluorescence spectra in TOL of dyads 22, 23 and 24 and
models after excitation at 358 nm (optically matched solutions
with A = 0.09)
Fig. 3. Arbitrarily scaled absorption and excitation spectra of 24
in TOL. The excitation spectrum has been recorded at 660 nm
space electron transfer can occur with low efficiency in
such a close packing of donor (30) and acceptor (28) both
via LUMO–LUMO (when corrole is excited) than via
HOMO–HOMO (when the imide is excited) mechanisms.
Fig. 4. Absorption spectra of dyads 25 and 26 in TOL overlaid
with those of the models 13, 29 and 30
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486
R. VOLOSHCHUK ET AL.
Fig. 6. Fluorescence spectra in TOL of dyad 26 and models
after excitation at 350 nm (optically matched solutions with A =
0.07). The luminescence intensity of 26 is multiplied by 10 only
in the 400–600 nm range
Fig. 5. Fluorescence spectra in TOL of dyad 25 and models
after excitation at 350 nm (optically matched solutions with
A = 0.07)
emission spectra of dyad 25 and of optically matched
models 13 and 30 after excitation at 350 nm are reported
in Fig. 5. The fluorescence of reference 13 maximizes
at 478 nm and is quite high compared to the other imide
components (luminescence quantum yield close to 1),
but not unusual for this type of structures [19]. The
luminescence of the imide is totally quenched in the dyad
whereas the luminescence of the corrole unit is sensitized
by a factor of 2. By taking into account that at 350 nm
the imide component absorbs ca. 50% of the incident
photons (see Fig. 4a), the observed phenomena can be
interpreted by a 100% effective energy transfer reaction
from the imide component to the corrole component.
Selective excitation of the dyad on the corrole band at
560 nm leads to a luminescence identical to that of the
model corrole (data not shown).
Figure 6 illustrates the luminescence spectra of 26 and
model components. The imide 29 displays a very weak
luminescence, with lmax at 495 nm, similar to the one of
the previously seen model 28. Excitation of 26 at 350
nm leads to a luminescence from the imide units reduced
to about 80% of that of the model 29, accompanied
by a 20 nm hypsochromic shift. No sensitization or
quenching was noticed in the luminescence of the
corrole moiety with respect to 30 upon excitation at the
same wavelength. A selective excitation at 560 nm where
only the corrole absorbs, led to a luminescence decrease
of this unit in the dyad to ca. 80% compared to the model
(data not shown). The results are not so clear-cut as the
former one. The photoinduced processes, which might
be a combination of energy and electron transfer are
however rather inefficient, leaving the luminescence of
both components almost unaffected. A more detailed
examination involving time resolved absorption
techniques would be necessary in order to elucidate the
detailed mechanism.
EXPERIMENTAL
General
All commercially available compounds were used
without additional purification, unless otherwise noted.
Organic solvents were purified according to generally
accepted literature methods [20]. Reactions involving
air and/or moisture sensitive reagents were performed
under inert atmosphere (argon). Reactions progress was
controlled by thin layer chromatography (TLC), performed
on commercially available aluminum plates covered with
silica gel or neutral aluminum oxide (60 F254, Merck).
All Rf values are referred to SiO2. For the purification
by the means of column chromatography silica gel 60
(Merck) was used. Dry column vacuum chromatography
was performed on MN-Silica gel P/UV254 for preparative
chromatography. Size exclusion column (SEC) was filled
with BioRad Bio-Beads SX-1 and eluted with either THF
or toluene. Melting points were measured on Automatic
Melting Point Apparatus (EZ-Melt, Stanford Research
Systems) and are presented without correction. Structure
and purity of synthesized compounds was confirmed using
1H, 13C NMR, MS and elemental analysis (all values are
given as percentages). NMR spectra were obtained on
Varian Mercury 400 MHz, Bruker DRX500 MHz, Varian
VNMRS 500 MHz or 600 MHz. Reported chemical shifts
(d, ppm) were determined relative to TMS as the internal
reference. Mass spectra were obtained onAMD-604 (AMD
Intectra GmbH), Mariner (Perseptive Biosystems, Inc.),
4000 Q-TRAP (Applied Biosystems) or GCT Premier
(Waters). Some compounds were synthesized following
literature procedures: 8 [21], 14 [22], 19 [18], 30 [10j].
Compounds 1, 2, 4, 5, 11, 12, 16, 17, 27 were commercially
available and used without further purification.
Copyright © 2015 World Scientific Publishing Company
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CORROLE–IMIDE DYADS — SYNTHESIS AND OPTICAL PROPERTIES
487
Synthesis
overnight. Orange color disappeared (reaction mixture
becomes yellow). The precipitate, formed after cooling
Preparation of 2-(3-(hydroxymethyl)phenyl)-
to rt, was filtered off, washed with AcOH and dried under
vacuum (2.38 g, 79%). Rf 0.3 (DCM). 1H NMR (500 MHz,
DMSO-d6, TMS): d, ppm 7.79 (2H, d, J = 8.4 Hz, C6H4),
7.82 (2H, m, naphth.), 8.10 (2H, d, J = 8.4 Hz, C6H4), 8.33
(2H, m, naphth.), 8.67 (2H, s, naphth.), 10.09 (1H, s, CHO).
13C NMR (125 MHz, DMSO-d6, TMS): d, ppm 125.5,
127.7, 128.0, 130.0, 130.4, 130.8, 135.6, 135.7, 137.8,
166.7, 192.9. Anal. calcd. for C19H11NO3: C, 75.74; H,
3.68; N, 4.65; found C, 75.68; H, 3.68; N, 4.63. HRMS-EI:
m/z [M]·+ calcd. for C19H11NO3, 301.0739; found 301.0729.
Preparation of 2-[2-(5,5-dimethyl-[1,3]dioxan-2-
yl)-phenyl]benzo[f]isoindole-1,3-dione (9). Method A.
Themixtureof2,3-naphthalenedicarboxylicanhydride(2,
420 mg, 2.12 mmol) and 2-aminobenzaldehyde acetal 8
(482mg,2.33mmol)inAcOH(5mL)wasstirredat110°C
overnight. After cooling to rt and solvent evaporation, the
residue was dissolved in DCM, washed with NaHCO3
aq, dried over Na2SO4 and chromatographed (AcOEt/
hexanes 1:3) giving 273 mg (33%) of acetal 9. Method B.
2,3-naphthalenedicarboxylic anhydride (2, 990 mg,
5 mmol), acetal 8 (1.55 g, 7.5 mmol) and imidazole
(6.8 g, 0.1 mol) were loaded into 100 mL round-bottom
flask and chloroform (40 mL) was added. The mixture
was stirred at gentle reflux for 2 h and then cooled to rt.
The solvent was removed on rotary evaporator and the
residue was taken up in small amount of absolute ethanol.
The resulting suspension was sonicated for 15 min
and then filtered. Filter cake was washed with cold
ethanol and air-dried. Column chromatography (DCM/
hexanes 3:1) afforded 838 mg (43%) of 9 as a colorless
benzo-[f]isoindole-1,3-dione (3). The solution of 2,3-
naphthalenedicarboxylic acid anhydride (2, 1.98 g,
10 mmol) and 3-aminobenzyl alcohol (1, 1.23 g, 10
mmol) in DMF (50 mL) was heated under reflux for 6 h.
After cooling the reaction mixture to ambient temperature
water (50 mL) was added. The precipitate was filtered off,
washed with small amount of EtOH and chromatographed
(SiO2, CH2Cl2 + 2%MeOH) affording 3 (2.11 g, 70%) as
1
colorless crystals. mp 214–215°C. H NMR (500 MHz,
DMSO-d6, TMS): d, ppm 4.59 (2H, d, J = 5.8 Hz, CH2),
5.35 (1H, t, J = 5.8 Hz, OH), 7.36 (1H, d, J = 8.0 Hz, C6H4),
7.42 (1H, d, J = 8.0 Hz, C6H4), 7.45 (1H, s, C6H4), 7.51
(1H, t, J = 8.0 Hz, C6H4), 7.81 (2H, m, naphth), 8.30 (2H,
m, naphth), 8.60 (2H, s, naphth). 13C NMR (125 MHz,
DMSO-d6, TMS): d, ppm 62.9, 125.2, 125.7, 126.1,
126.6, 127.8, 129.0, 129.8, 130.7, 132.4, 135.6, 144.0,
167.2. Anal. calcd. for C19H13NO3: C, 75.24; H, 4.32; N,
4.62; found C, 75.23; H, 4.45; N, 4.54. HRMS-EI: m/z
[M]·+ calcd. for C19H13NO3, 303.0895; found 303.0900.
Preparation of 3-(1,3-dioxo-1,3-dihydrobenzo[f]
isoindol-2-yl)benzaldehyde (6). Method A. Alcohol 3
(660 mg, 2.18 mmol) was suspended in the solution of
TEMPO(34mg, 10%mol)inDCM(5mL). Subsequently,
BAIB (772 mg, 2.4 mmol) was added and the reaction
mixture was stirred until the alcohol was fully consumed
(nearly 3 h). The reaction mixture was diluted with
DCM to dissolve solid product, washed with saturated
Na2S2O3 aq and extracted with DCM (3 × 10 mL).
The combined organic extracts were washed with
NaHCO3 and brine, dried over Na2SO4 and concentrated
under reduced pressure. Flash column chromatography
(silica, DCM/hexanes 4:1) afforded title compound as
a colorless crystalline solid (610 mg, 92%). Method B.
2,3-naphthalenedicarboxylic acid anhydride (2, 991 mg,
5 mmol) and 3-aminobenzaldehyde polymer (4, 605 mg,
5 mmol) were suspended in acetic acid (12 mL) and
stirred at reflux overnight. The precipitate, formed after
cooling to rt, was filtered off, washed with AcOH and
dried under vacuum (1.18 g, 78%). Rf 0.4 (DCM). mp
1
solid. Rf 0.5 (DCM/hexanes 3:1). H NMR (500 MHz,
CDCl3, TMS): d, ppm 0.61 (3H, s, CH3), 1.10 (3H, s,
CH3), 3.39 (2H, d, J = 10.9 Hz, CH2), 3.55 (2H, d, J =
11.1 Hz, CH2), 5.42 (1H, s, CH), 7.29 (1H, m, C6H4),
7.51 (2H, m, C6H4), 7.74 (2H, m, naphth.), 7.85 (1H,
m, C6H4), 8.11 (2H, m, naphth.), 8.47 (2H, s, naphth.).
13C NMR (125 MHz, CDCl3, TMS): d, ppm 21.7, 23.0,
30.1, 77.6, 99.0, 125.2, 127.7, 127.9, 129.3, 129.4, 129.5,
129.6, 129.7, 130.3, 135.6, 136.2, 167.2. Anal. calcd. for
C24H21NO4: C, 74.40; H, 5.46; N, 3.62; found C, 74.13; H,
5.36; N, 3.58. HRMS-EI: m/z [M]·+ calcd. for C24H21NO4,
387.1471; found 387.1478.
1
281°C (decomposed). H NMR (600 MHz, DMSO-d6,
TMS): d, ppm 7.78–7.85 (3H, m, C6H4 + naphth), 7.87
(1H, m, C6H4), 8.02 (1H, m, C6H4), 8.07 (1H, m, C6H4),
8.33 (2H, m, naphth), 8.67 (2H, s, naphth), 10.10 (1H, s,
CHO). 13C NMR (150 MHz, DMSO-d6, TMS): d, ppm
124.9, 127.3, 127.3, 129.3, 129.7, 130.2, 132.9, 133.0,
135.1, 136.7, 166.4, 192.5. Anal. calcd. for C19H11NO3:
C, 75.74; H, 3.68; N, 4.65; found C, 75.63; H, 3.71;
N, 4.58. HRMS-EI: m/z [M]·+ calcd. for C19H11NO3,
301.0739; found 301.0724.
Preparation of 2-(1,3-dioxo-1,3-dihydro-benzo[f]
isoindol-2-yl)-benzaldehyde (10). TFA (8 mL) and
5% H2SO4 were added to acetal 9 (1 mmol) dissolved
in 20 mL of chloroform and the reaction mixture was
stirred for 24 h at rt. The reaction mixture was diluted
with water (50 mL) and allowed to stir for the next
30 min. The mixture was extracted with chloroform (3 ×
10 mL), washed with 2 M NaHCO3, dried over MgSO4 and
concentrated. Residuewasrecrystallizedfromchloroform
Preparation of 4-(1,3-dioxo-1,3-dihydrobenzo[f]-
isoindol-2-yl)benzaldehyde (7). 2,3-Naphthalenedicar-
boxylic acid anhydride (2, 1.98 g, 10 mmol) and
4-aminobenzaldehyde polymer (5, 1.21 g, 10 mmol) were
suspended in acetic acid (25 mL) and stirred at reflux
1
to give crystalline product (96%). H NMR (500 MHz,
DMSO-d6, TMS): d, ppm 7.67 (1H, d, J = 7.8 Hz,
C6H4), 7.76 (1H, t, J = 7.5 Hz, C6H4), 7.83 (2H, m,
naphth.), 7.89 (1H, m, C6H4), 8.08 (1H, m, C6H4), 8.33
Copyright © 2015 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2015; 19: 487–491

488
R. VOLOSHCHUK ET AL.
(2H, m, naphth.), 8.67 (2H, s, naphth.), 10.04 (1H, s,
CHO). 13C NMR (125 MHz, DMSO-d6, TMS): d, ppm
125.6, 128.0, 130.0, 130.1, 130.7, 130.8, 131.5, 132.5,
132.7, 135.2, 135.7, 167.4, 191.7. HRMS-EI: m/z [M]·+
calcd. for C19H11NO3, 301.0739; found 301.0743.
128.2, 128.9, 129.1, 129.4, 129.7, 130.2, 130.3, 131.6,
133.4, 135.1, 135.8, 136.6, 146.6, 154.4, 165.0, 167.1,
191.1. Anal. calcd. for C28H17N3O3: C, 75.84; H, 3.86; N,
9.48; found C, 75.94; H, 3.88; N, 9.44. HRMS-EI: m/z
[M]·+ calcd. for C28H17N3O3, 443.1270; found 443.1257.
Preparation of corrole dyad 22. Aldehyde 6 (0.6 g,
2 mmol) and 5-(pentafluorophenyl)dipyrrane (21, 1.25 g,
4 mmol) were suspended in 30 mL of DCM and 330 mL
of preprepared TFA solution (from now on this solution
will be referred as “TFA stock solution,” 10 mL of TFA
in 100 mL of DCM) was added. The reaction course was
controlled by TLC and after 30 min, the reaction was
quenched by triethylamine addition (60 mL). The reaction
mixture was diluted to 200 mL with DCM and poured
into solution of DDQ (1.18 g, 5.2 mmol) in 300 mL of
DCM stirred vigorously. After 2 h, the reaction mixture
was slightly concentrated and passed through 2 cm
silica pad. Product-containing fractions (contaminated
by dipyrrin) were combined and solvent was removed
under reduced pressure. Residue was washed with small
amount of methanol, suspended in boiling cyclohexane
and after cooling, crystals were filtered off and dried
under vacuum giving 288 mg of corrole 22 (16%). Rf 0.4
(DCM/hexanes 3:2). UV-vis (DCM): lmax, nm (e × 10-3)
613 (13.5), 563 (13.5), 422 (127.7). 1H NMR (500 MHz,
THF-d8, TMS): d, ppm (-4)–(-1.5) (3H, br s, NH), 7.72
(2H, m, naphth.), 7.90–7.97 (2H, m, C6H4), 8.19 (2H,
m, naphth.), 8.25 (1H, m, C6H4), 8.47 (1H, m, C6H4),
8.55 (2H, s, naphth.), 8.59 (2H, br s, b-H), 8.84 (2H,
br s, b-H), 8.87 (2H, d, J = 4.5 Hz, b-H), 9.09 (2H, d,
J = 3.7 Hz, b-H). HRMS-ESI: m/z [M + H]+ calcd. for
C49H22N5O2F10, 902.1608; found 902.1646.
Preparation of corrole dyad 23. Aldehyde 7 (0.6 g,
2 mmol) and 5-(pentafluorophenyl)dipyrrane (21, 1.25 g,
4 mmol) were suspended in 30 mL of DCM and 330 mL of
TFA stock solution (see above) was added. The reaction
course was controlled by TLC and after 30 min, the
reaction was quenched by triethylamine addition (60 mL).
The reaction mixture was diluted to 200 mL and poured
into solution of DDQ (1.18 g, 5.2 mmol) in 300 mL
DCM stirred vigorously. After 2 h, the reaction mixture
was slightly concentrated and passed through 2 cm silica
pad. Product-containing fractions were combined and
solvent was removed under reduced pressure. Residue
was washed with small amount of methanol, suspended
in boiling cyclohexane and after cooling, crystals were
filtered off and dried under vacuum giving 244 mg of
corrole 23 (14%). Rf 0.33 (DCM/hexanes 2:1). UV-vis
(DCM): lmax, nm (e × 10-3) 615 (12.4), 564 (11.3), 419
(118.3). 1H NMR (500 MHz, THF-d8, TMS): d, ppm (-4)–
(-1.5) (3H, br s, NH), 7.78 (2H, m, naphth.), 8.02 (2H, m,
C6H4), 8.25 (2H, m, naphth.), 8.35 (2H, m, C6H4), 8.63
(4H, m, naphth.+b-H), 8.74 (2H, br s, b-H), 8.82 (2H, br
s, b-H), 9.10 (2H, br s, b-H). HRMS-ESI: m/z [M + H]+
calcd. for C49H22N5O2F10, 902.1608; found 902.1618.
Preparation of corrole dyad 24. The mixture
of aldehyde 10 (311 mg, 1.03 mmol) and
Preparation of 4-(6-methoxynaphthalen-2-ylethyn-
yl)-1,8-naphthalenedicarboxylic anhydride (13). A
100 mL round-bottom flask containing a magnetic stirbar
was charged with 4-bromo-1,8-naphthalic anhydride
(11, 830 mg, 3 mmol), triphenylphosphine (16 mg,
0.06 mmol), copper(I) iodide (5.7 mg, 0.03 mmol),
bis(triphenylphosphine)palladium dichloride (2.1 mg,
3 mmol), and 15 mL of triethylamine. 2-Ethynyl-6-
methoxynaphthalene (12, 656 mg, 3.6 mmol) was
added to the flask with 30 mL of toluene. A condenser
containing a nitrogen inlet was placed attached, and
the reaction mixture was heated to reflux for 14 h. The
reaction mixture was cooled and filtered. The filtercake
was washed with toluene and dried at 80°C under
vacuum. At this point the yield of a crude product, yellow
amorphous solid contaminated with small amount of
starting anhydride, was 1.11 g (98%) and it was used in
the next step without any further purification. HRMS-EI:
m/z [M]·+ calcd. for C25H14O4, 378.0892; found 378.0900.
Preparation of aldehyde 15. The mixture anhydride
13 (756 mg, 2 mmol), 3-aminobenzaldehyde ethylene
acetal (14, 396 mg, 2.4 mmol) and imidazole (6.8 g,
0.1 mol) in chloroform (40 mL) was stirred at gentle
reflux for 12 h and then cooled to rt. The solvent was
removed on rotary evaporator and the residue was taken
up in small amount of absolute ethanol. The resulting
suspension was sonicated for 10 min, filtered, washed
with cold ethanol and dried under vacuum. NMR analysis
revealed the mixture of aldehyde and acetal and the
sample was fully deprotected by stirring it with excess
of acetone in the presence of p-TsOH (35 mmol/L). The
product was purified by gravity column chromatography
(DCM/acetone 98:2), furnishing aldehyde 15 as a bright
yellow solid (811 mg, 84%). mp 222–3°C. Anal. calcd.
for C34H23NO5: C, 77.70; H, 4.41; N, 2.68; found C,
77.85; H, 4.34; N, 2.66. HRMS-EI: m/z [M]·+ calcd. for
C34H23NO5, 525.1576; found 525.1564.
Preparation of 4-amino-1,3-dioxo-6,7-diphenyl-2-
p-formylphenyl-2,3-dihydro-1H-isoindole-5-
carbonitrile (20). Anhydride 19 (1.8 g, 5.3 mmol) and
p-aminobenzaldehyde polymer (5, 770 mg 6.36 mmol)
were suspended in AcOH (14 mL) and the reaction
mixture was stirred at reflux overnight. Orange color of
aminobenzaldehyde disappeared and reaction was cooled
to rt. Yellow solid was filtered off, washed with small
amount of AcOH and dried under vacuum, giving 1.54 g
(66%) of aldehyde 20. Rf 0.4 (DCM). 1H NMR (400 MHz,
CDCl3, TMS): d, ppm 6.20 (2H, br s, NH2), 7.00–7.05
(2H, m, Ph), 7.09–7.14 (2H, m, Ph), 7.17–7.24 (3H, m,
Ph), 7.24–7.31 (3H, m, Ph), 7.65 (2H, m, C6H4), 7.97
(2H, m, C6H4), 10.03 (1H, s, CHO). 13C NMR (100 MHz,
CDCl3, TMS): d, ppm 104.0, 110.4, 114.9, 126.3, 127.7,
Copyright © 2015 World Scientific Publishing Company
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CORROLE–IMIDE DYADS — SYNTHESIS AND OPTICAL PROPERTIES
489
5-(pentafluorophenyl)dipyrrane (21, 645 mg, 2.06 mmol)
amount of toluene) was added. After 2 h of stirring at
rt, the reaction mixture was passed through silica pad,
and then chromatographed (DCM/hexanes 1:1). The
product was contaminated with additional fluorescent
compounds which were successfully removed by the
chromatography on SEC (eluted with toluene). Product-
containing fractions were collected and evaporated. After
crystallization, corrole 26 was obtained as dark fine
powder (211 mg, 6%). Rf 0.4 (DCM/hexanes 1:1). UV-vis
(toluene): lmax, nm (e × 10-3) 429 (153), 563 (15.2), 613
in 15 mL of DCM was treated with 170 mL of TFA stock
solution (see above). After 20 min, the reaction was
quenched with 30 mL of triethylamine, diluted with DCM
to 130 mL and DDQ (608 mg, 2.68 mmol) dissolved in
a minimal amount of toluene was added. After 2 h of
stirring, the reaction mixture was passed through silica
pad, evaporated with Celite and chromatographed (DCM/
hexanes 1:4 → 1:1). Product-containing fractions were
collected and evaporated. Crystallization from DCM
afforded 157 mg (17%) of corrole 24 as a crystalline
1
(11.6), 645 (6.9). H NMR (500 MHz, THF-d8): d, ppm
solid. Rf 0.4 (DCM/hexanes 3:2). UV-vis (THF): lmax
,
(-4)–(-1.5) (3H, br s, NH), 6.90 (2H, br s, NH2), 7.02–
7.36 (10H, m, Ph), 7.93 (2H, d, J = 8 Hz, C6H4), 8.33
(2H, d, J = 8 Hz, C6H4), 8.63 (2H, br s, b-H), 8.71 (2H, m,
b-H), 8.83 (2H, br s, b-H), 9.14 (2H, br s, b-H). HRMS-
ESI: m/z [M + H]+ calcd. for C58H28F10N7O2, 1044.2139;
found 1044.2171.
nm (e × 10-3) 296 (22.9), 419 (11.7), 561 (19.4), 611
1
(11.0). H NMR (500 MHz, CDCl3, TMS): d, ppm 7.27
(m, naphth.), 7.48 (2H, m, naphth.), 7.61 (2H, s, naphth.),
7.82 (1H, m, C6H4), 7.89 (1H, m, C6H4), 7.97 (1H, m,
C6H4), 8.25 (1H, m, C6H4), 8.42 (2H, br s, b-H), 8.66
(2H, d, J = 5.9 Hz, b-H), 8.81 (2H, d, J = 6.0 Hz, b-H),
8.91 (2H, br s, b-H). HRMS-ESI: m/z [M + H]+ calcd. for
C49H22N5O2F10, 902.1608; found 902.1579.
Preparation of 2-(p-tolyl)-benzo[f]isoindole-1,3-
dione (28). Anhydride 2 (396 mg, 2 mmol) and p-toluidine
(27, 214 mg, 2 mmol) were heated under reflux in 10 mL
of AcOH overnight. After cooling, the resulting precipitate
was filtered off and washed with AcOH and EtOH,
Preparation of corrole dyad 25. To the
mixture of aldehyde 15 (770 mg, 1.6 mmol) and
5-(pentafluorophenyl)dipyrrane (21, 1 g, 3.2 mmol)
in 24 mL of DCM, 260 μL of TFA stock solution (see
above) was added while stirring. The reaction was very
slow and it was left to stirr overnight, then quenched with
45 μL of triethylamine. After dilution with DCM to 300
mL, DDQ (944 mg, 4.16 mmol), dissolved in a minimal
amount of toluene, was added and the reaction mixture
was stirred for 2 h. Subsequently, the reaction mixture
was passed through silica pad, evaporated with Celite
and chromatographed (DCM/hexanes 3:1). There were
additional spots with similar polarity and the sample was
submitted to SEC purification (eluted withTHF). Product-
containing fractions were collected and evaporated.
Crystallization from DCM afforded 320 mg (18%) of
corrole 25 as a crystalline solid. Rf 0.4 (DCM/hexanes
3:1). UV-vis (toluene): lmax, nm (e × 10-3) 431 (157),
1
affording 499 mg (87%) of 28 as off-white powder. H
NMR (500 MHz, CDCl3, TMS): d, ppm 2.42 (3H, s, CH3),
7.33, 7.37 (4H, AA′BB′, J = 8.3 Hz), 7.71–7.74 (2H, m,
C10H6), 8.07–8.11 (2H, m, C10H6), 8.44 (2H, s, C10H6). 13C
NMR (125 MHz, CDCl3, TMS): d, ppm 21.2, 125.2, 126.5,
127.5, 129.2, 129.3, 129.8, 130.3, 135.7, 138.3, 167.2.
Anal. calcd. for C19H13NO2: C, 79.43; H, 4.56; N, 4.88;
found C, 79.42; H, 4.55; N, 4.81. HRMS-ESI: m/z [M +
H]+ calcd. for C19H14NO2, 288.1025; found 288.1028.
Preparation of 4-amino-1,3-dioxo-6,7-diphenyl-2-
p-tolyl-2,3-dihydro-1H-isoindole-5-carbonitrile (29).
Anhydride 19 (511 mg, 1.5 mmol) and p-toluidine (27,
193 mg, 1.8 mmol) were heated under reflux in 5 mL
of AcOH overnight. After cooling, solvent was
evaporated off, the residue was dissolved in chloroform,
washed with NaHCO3, water and brine. The organic
layer was separated and dried over MgSO4. Flash
column chromatography (DCM/hexanes 1:3 → 2:1) and
crystallization (chloroform/hexanes) afforded 350 mg
(54%) of 29 as yellow crystals. Rf 0.3 (DCM/hexanes
1
561 (17.1), 614 (12.2), 647 (7.9). H NMR (400 MHz,
CDCl3, TMS): d, ppm (-4)–(-1.5) (3H, br s, NH), 3.95
(3H, s, OCH3), 7.15 (1H, m, C10H6), 7.20 (1H, m, C10H6),
7.67 (1H, m, C10H6), 7.76 (3H, m, C6H4+C10H6), 7.89–8.00
(2H, m, C6H4+naphth.), 8.04 (1H, d, J = 7.6 Hz, naphth.),
8.13 (1H, s, C10H6), 8.22 (1H, m, C6H4), 8.30 (1H, m,
C6H4), 8.57 (2H, br s, b-H), 8.70 (1H, d, J = 7.6 Hz,
naphth.), 8.78 (4H, m, naphth.+b-H), 8.97 (2H, d, J =
4.4 Hz, b-H), 9.11 (2H, d, J = 4.4 Hz, b-H). HRMS-ESI:
m/z [M + H]+ calcd. for C62H31F10N5O3, 1082.2111; found
1082.2142.
Preparation of corrole dyad 26. Aldehyde 20 (1.54 g,
3.47 mmol) and 5-(pentafluorophenyl)dipyrrane (21,
2.17 g, 6.95 mmol) were dissolved in 50 mL of DCM and
0.57 mL ofTFA stock solution (see above) was added.The
reaction mixture was stirred at rt for 20 min and then the
reaction was quenched by the addition of triethylamine
(0.1 mL). The reaction mixture was diluted with DCM to
450 mL and DDQ (2.05 g, 9 mmol; dissolved in minimal
1
1:2). H NMR (500 MHz, CDCl3, TMS): d, ppm 2.37
(3H, s, CH3), 6.14 (2H, br s, NH2), 7.01 (2H, m, C6H4),
7.03 (2H, m, C6H4), 7.11 (3H, m, Ph), 7.15 (7H, m,
Ph). 13C NMR (125 MHz, CDCl3, TMS): d, ppm 21.2,
103.7, 111.0, 115.1, 126.3, 127.6, 127.7, 128.2, 128.5,
128.8, 129.4, 129.5, 129.6, 130.4, 132.0, 133.6, 136.1,
138.2, 146.4, 153.9, 165.7, 167.8; Anal. calcd. for
C28H19N3O2: C, 78.31; H, 4.46; N, 9.78; found C, 78.37;
H, 4.44; N, 9.83. HRMS-ESI: m/z [M + Na]+ calcd. for
C28H19N3O2Na, 452.1370; found 452.1392.
Spectroscopy and photophysics
Spectroscopic grade toluene (C. Erba) was used
without further purification. The absorption spectra
Copyright © 2015 World Scientific Publishing Company
J. Porphyrins Phthalocyanines 2015; 19: 489–491

490
R. VOLOSHCHUK ET AL.
were recorded by a Perkin-Elmer Lambda 950 UV-vis
spectrophotometer and the emission spectra corrected
for the photomultiplier response were detected by an
Edinburgh FLSP920 fluorimeter equipped with a R928P
Hamamatsu photomultiplier with a spectral coverage
from 200 nm to ca. 820 nm. Fluorescence quantum
yields, when reported, were calculated from the corrected
luminescence spectra against a reference with the
following Equation 1:
European Science Foundation (ESF-EUROCORES-
EuroSolarFuels-10-FP-006). A.I.C acknowledges the
European Community’s Seventh Framework Programme
(TOPBIO project-grant agreement no. 264362) for an
ESR grant.
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The reference used for 28 emission quantum yield was
air-equilibrated quinine sulphate in 1N H2SO4 with ffl =
0.546 [23], whereas the reported value of 0.14 for 30 was
used as reference to calculate the emission quantum yield
of the corrole units [12a].
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The comparison of three different methodologies
leading to various small aromatic imides bearing formyl
groups has proven that both reaction with commercially
available polymers of aminobenzaldehydes and
utilization of aminobenzyl alcohols are the best strategies
in terms of overall efficiency. We proved that regardless
the orientation of naphthalene-2,3-imide moiety vs.
corrole ring the interaction between these chromophores
is small. Still placing it above the corrole ring induces
small changes in photophysical behavior. We also have
shown that while altering the size and electron density
in blue-absorbing aromatic imides one can manipulate
the behavior of bichromophoric systems. While large,
slightly polarized imides tend to lead to energy transfer,
small and strongly polarized derivatives of phthalimide
induced more complex behavior.
Acknowledgements
This research has been financially supported by
the Polish National Science Center (844/N-ESF-
EuroSolarFuels/10/2011/0) and the Italian National
Research Council (CNR) in the framework of the
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J. Porphyrins Phthalocyanines 2015; 19: 491–491