Library of Azabenz-Annulated Core-Extended Perylene Derivatives with Diverse Substitution Patterns and Tunable Electronic and Optical Properties

Article abstract of DOI:10.1021/acs.joc.6b01573

Here, we present a collection of different azabenz-annulated perylene derivatives. By developing new synthetic strategies and improving existing protocols, we have expanded the structural diversity of these dye molecules to a multifunctional class of ligating chromophores. The Pictet-Spengler (PS) reaction of 1-amino-perylenes with different aldehydes is used to modify the terminal substitution pattern. PS transformations of 1,6- and/or 1,7-diamino perylenes result in 2-fold annulated nitrogen-containing coronene-type molecules like anti-(ab)₂-PBI 15, syn-(ab)₂-PBI 16, and syn-(ab)₂-PTE 18. In addition, azabenz-annulated perylene bisanhydrides (ab-PBA 6 and syn-(ab)₂-PBA 19) were explored as universal starting materials providing access to any desired imide functionality. Furthermore, a newly developed regioselective nitration procedure for perylene monoimide diesters (PMIDE) enables the synthesis of 1-nitro-PMIDE 10 and thus of azabenz-annulated perylene derivatives with unsymmetric peri-substitution patterns (ab-PMIDE 12 and ab-PMIMA 13). According to our spectroscopic and theoretical investigations, the optical and electrochemical properties of these multifunctional chromophores can easily be modified and adjusted to many desirable applications following the synthetic strategies presented in this work.

Full text of DOI:10.1021/acs.joc.6b01573

Article
pubs.acs.org/joc
Library of Azabenz-Annulated Core-Extended Perylene Derivatives
with Diverse Substitution Patterns and Tunable Electronic and
Optical Properties
Marcus Schulze, Michael Philipp, Waldemar Waigel, David Schmidt, and Frank Wurthner*
̈
Institut fur Organische Chemie and Center for Nanosystems Chemistry, Universitat Wurzburg, Am Hubland, 97074 Wurzburg,
̈
̈
̈
̈
Germany
S
* Supporting Information
ABSTRACT: Here, we present a collection of different azabenz-annulated perylene
derivatives. By developing new synthetic strategies and improving existing protocols,
we have expanded the structural diversity of these dye molecules to a multifunctional
class of ligating chromophores. The Pictet−Spengler (PS) reaction of 1-amino-
perylenes with different aldehydes is used to modify the terminal substitution
pattern. PS transformations of 1,6- and/or 1,7-diamino perylenes result in 2-fold
annulated nitrogen-containing coronene-type molecules like anti-(ab)2-PBI 15, syn-
(ab)2-PBI 16, and syn-(ab)2-PTE 18. In addition, azabenz-annulated perylene
bisanhydrides (ab-PBA 6 and syn-(ab)2-PBA 19) were explored as universal starting
materials providing access to any desired imide functionality. Furthermore, a newly
developed regioselective nitration procedure for perylene monoimide diesters
(PMIDE) enables the synthesis of 1-nitro-PMIDE 10 and thus of azabenz-annulated
perylene derivatives with unsymmetric peri-substitution patterns (ab-PMIDE 12 and
ab-PMIMA 13). According to our spectroscopic and theoretical investigations, the optical and electrochemical properties of these
multifunctional chromophores can easily be modified and adjusted to many desirable applications following the synthetic
strategies presented in this work.
Because of the longitudinally oriented transition dipole
moment of the lowest energetic optical transition (S0−S1), the
peri-positions have the strongest impact on the photophysical
properties of the respective chromophores.5,6 Particularly, the
ester, anhydride, and imide functionalized derivatives of
3,4,9,10-perylene tetracarboxylic acid (abbreviated as PTE
(perylene tetraester)), PBA (perylene bisanhydride), and PBI
(perylene bisimide)), are of fundamental interest for industry
and academia, for example, as industrial organic pigments for
the coloration of textiles and automotives, as fluorophore
materials for biological sensing, organic electronics (e.g.,
organic field effect transistors, OFET), and photovoltaics
(e.g., bulk heterojunction solar cells, BHJ).4,7,8 Among the
perylene derivatives mentioned above, perylene bisimides
combine the most important molecular features like planar-
ity/rigidity, (photo)chemical and thermal stability, solubility,
and structural versatility in a very advantageous way.9
Consequently, the PBI π-system was systematically derivatized
to create even more extended chromophores without
compromising their superior properties. Thus, the peri-
extension of perylene bisimides along its long molecular axis
by insertion of additional naphthalene subunits results in higher
homologue rylenes like terrylene (TBI) and quaterrylene
INTRODUCTION
■
Perylene, one of the most prominent polycyclic aromatic
hydrocarbons, constitutes a unique structural motive for many
organic dye chemists for more than a century.1−3 As a
consequence of its flat and π-conjugated polyaromatic core,
perylene derivatives, in particular the imides and bisimides,
were found to be highly desirable (photo)chemically robust
colorants with optical absorptions that can be tuned from the
near-ultraviolet to the near-infrared spectral region.4 These
diverse optical and electronic properties can be attributed to the
exceptional chemistry of perylene with three sets of different
carbon atoms located at its edges (Figure 1), four peri-
(3,4,9,10), four ortho- (2,5,8,11), and four bay-positions
(1,6,7,12), which can be functionalized selectively.
Received: June 30, 2016
Figure 1. Structure and specific positions of perylene.
© XXXX American Chemical Society
A
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bisimides (QBI) with bathochromically shifted absorption
maxima even in the near-infrared region.10,11
extended system.31 The respective amino-functionalized
perylene precursors can be obtained by well-established
sequences of perylene core nitration (1- or 2-fold) and nitro
group reduction to the amines.32−34 However, for the synthesis
of ab-PBIs 3a−f (Scheme 1) containing up to three
Likewise, the short molecular axis of perylene bisimides can
easily be subjected to structural variations by introduction of
additional substituents at the ortho- and bay-positions.
However, ortho-functionalization has only been accomplished
recently by different research groups using transition metal-
catalyzed procedures to insert aliphatic or aromatic substituents
as well as boronic acid ester functionalities.12−15 These boronic
acid esters provide additional access to a variety of substitution
reactions such as halogenation, cyanation, or Suzuki−Miyaura
cross-coupling for the construction of complex molecular
architectures.16,17 The ortho-modification indeed changes the
optical and electronic properties of perylene bisimides without
any significant impact on the planarity of the PBI π-system.12,15
In contrast, the introduction of bay-substituents at the aromatic
core directly influences the electronic structure of the PBI and
causes contortion of the core. Depending on the size and the
number of bay-substituents, the dihedral distortion strongly
deviates from 0° to 35° like for tetra-brominated PBI-
derivatives leading to (P) and (M) atropo-enantiomers.18 In
general, the bay-positions of perylene bisimides are prone to
undergo chlorination, bromination, nitration, transition metal-
mediated cross-coupling, or Diels−Alder reactions. The
halogenated derivatives are of particular interest because these
compounds can readily be used for nucleophilic substitutions or
cross-coupling reactions.9,19,20 Even core-annulated coronene-
type derivatives as well as their azabenz-annulated analogues
can be prepared starting from suitable bay-substituted PBI
precursors.21−23 These core-extended PBI derivatives are
characterized by increased oscillator strength for the higher
energetic S0−S2 transition because the respective transition
dipole moment is aligned along the short molecular axis of the
parent perylene core and rises with core extension.5,6
Scheme 1. Synthesis of ab-PBIs 3a−f by Pictet−Spengler
Reaction of Amino-PBI 1 with Different Aldehydes 2a−f
The optical, electronic, and structural properties of PBI
derivatives can further be influenced by incorporating them via
the bay-position as ligand systems into metal−organic
complexes.24−28 Only recently, we could demonstrate that
core-extended azabenz-annulated perylene bisimides (abbre-
viated as ab-PBI) efficiently coordinate to ruthenium and
iridium complex fragments.29 The corresponding PBI transition
metal complexes exhibit new and interesting optical properties
like phosphorescence out of the PBI triplet state generated by
spin−orbit coupling, which cannot be observed for the
individual components. Therefore, we became highly interested
in this exceptional class of PBI-based ligand systems and
present now versatile protocols for the synthesis of azabenz-
annulated perylene derivatives with different optical and
electronic properties as well as variable coordination sites for
the potential construction of multinuclear transition metal
complexes.
coordinating pyridyl subunits, we have developed a slightly
modified procedure because the synthetic PS protocol
described in the literature does not work for less reactive
aldehydes.22 Therefore, we (i) shifted the equilibrium of
iminium ion formation toward the product by using dry N,N-
dimethylformamide and adding molecular sieves to remove the
released water; and (ii) after completion of iminium ion
formation (∼30 min), the inert atmosphere was exchanged by
pure oxygen to facilitate the oxidative rearomatization. Thus,
ab-PBIs 3a−f could be obtained in yields of up to 57%, which is
remarkably high for such systems.
Whereas the functional properties of perylene bisimides are
primarily encoded in the core substituents, the imide subunits
are frequently used to manipulate properties like solubility or
aggregation behavior in organic and aqueous media.9 Usually,
the synthesis of such customized imide substituents, which
might be prone to oxidation, reduction, and/or labile under PS
reaction conditions, is even more elaborate than that of the PBI
itself, and the amount of material is often limited to a few
milligrams. Therefore, we established an alternative synthetic
procedure (Scheme 2) for the preparation of ab-PBIs bearing
RESULTS AND DISCUSSION
■
Monoazabenz-Annulated Perylene Derivatives with
Symmetric peri-Substitution. The key step for the synthesis
of all azabenz-annulated perylene derivatives presented in this
work is the Pictet−Spengler (PS) reaction. Starting from
amino-substituted perylene derivatives and the corresponding
aldehydes, this Mannich-type transformation is initiated by an
iminium ion formation followed by an intramolecular electro-
philic aromatic substitution of the aromatic system by the
iminium ion.30 After annulation of the perylene core, an
oxidative rearomatization takes place to generate the fully π-
B
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such azabenz-annulated perylene derivatives, we developed a
synthetic procedure for the preparation of unsymmetrically
peri-substituted analogues like ab-perylene monoimide diester
(PMIDE) 12. These coordinating chromophores should be
interesting starting materials for the fabrication of photoactive
hybrid materials by attaching them to semiconducting surfaces
like TiO2. Accordingly, the regioselective nitration of
unsymmetric perylene monoimide diester38 (9, Scheme 3)
Scheme 2. Synthetic Protocol for the Preparation of
Azabenz-Annulated Perylene Bisanhydride ab-PBA 6 and Its
Imidization Using the Customized Amine Derivative 7
Scheme 3. Synthesis of Unsymmetric ab-PMIDE 12 and ab-
PMIMA 13 by Regioselective Nitration and PS
Transformation of PMIDE 9
complex functional imide substituents in which the imidization
is the final step of the entire synthetic route. The key
intermediate of this pathway is the azabenz-annulated perylene
bisanhydride (ab-PBA 6), which constitutes a versatile starting
material in this route. However, anhydride formation can be a
tedious procedure starting from perylene bisimides (usually
strong bases like KOH in refluxing alcohols are required) and is
much more efficient from perylene tetraesters (usually organic
acids in refluxing hydrocarbon solvents are utilized).35,36 Thus,
using the modified PS reaction protocol described above, we
converted the literature-known amino-PTE 437 with pyridine-2-
carboxaldehyde 2a into the bright-yellow ab-PTE 5 in 62%
yield. Subsequently, the ester groups of 5 were hydrolyzed
under acidic conditions to yield almost quantitatively the
azabenz-annulated bisanhydride ab-PBA 6. Like many other
perylene bisanhydrides, 6 is nearly insoluble in all common
organic solvents and is therefore difficult to characterize.
using cerium(IV)ammonium nitrate (CAN) and nitric acid as
nitronium ion source yielded 1-nitro-PMIDE 10 in a very good
yield of 86%.39,40 Interestingly, under the applied reaction
conditions (15 min at room temperature), only trace amounts
of 2-fold nitrated byproducts could be detected by mass
spectrometry.
Besides the high yield, an exclusive regioselectivity could be
confirmed for the mononitrated 1-nitro-PMIDE 10 (for the
numbering of the perylene core, see Figure 1) by 1D and 2D
NMR spectroscopy (Figure 2 and Figure S1). It is important to
note that the rotation of the “swallowtail” 12-tricosanyl
(CH(C11H23)2) imide substituent around the C−Nimide bond
is somewhat restricted at room temperature, giving rise to
broad resonances for the protons at the 2 and 5 positions.41
Although this signal broadening usually hampers the inter-
pretation of NMR data, it can in this case be used as a sensitive
probe for the correct assignment of the regioselectivity.
Accordingly, for the 1-nitro-substituted PMIDE isomer, broad
resonances can be detected for the hydrogen atoms at the 2 and
5 positions along with sharp doublets for the protons at the 6,
1
However, H and 13C NMR spectroscopy in D2SO4 clearly
proved the absence of any aliphatic proton with an appropriate
number of aromatic signals for the protons of the perylene core
and the pyridyl functionality.
An exemplary imidization reaction of ab-PBA 6 with an
oligoethylene glycol-functionalized amine 7 was used to
demonstrate the advantages of this synthetic pathway. After
reacting 6 with 2 equiv of 7 in a mixture of molten imidazole
and pyridine, the desired PBI 8 could be isolated in a good yield
of 72%. Starting from commercially available perylene
bisanhydride, this protocol illustrates even more convincingly
its superiority by virtue of a total yield of 27% for compound 8
that drops down to an overall yield of only 2% using the
conventional procedure described in Scheme 1.
1
7, 8, 11, and 12 positions (see H NMR trace in Figure 2),
which exhibit appropriate 3JHH cross-signals. In contrast, for the
corresponding 7-nitro-substituted regioisomer, a sharp singlet
was expected for the hydrogen atom at the 8-position, which is
clearly absent in the proton NMR spectrum. Further evidence
is provided by two-dimensional correlation spectra (1H,13C-
HMBC and 1H,1H-NOESY; see Figure S1) where cross-signals
between H8/H11 and the carbonyl carbon atoms in the 1H,13C-
Monoazabenz-Annulated Perylene Derivatives with
Unsymmetric peri-Substitution. To extend the scope of
C
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substituted azabenz-annulated perylene bisimides and can
additionally be used to anchor such dye molecules onto
semiconducting surfaces.42−44 All of these chromophores were
1
fully characterized by H and 13C NMR spectroscopy, high-
resolution mass spectrometry, and UV/vis spectroscopy, and
their regioselective integrity was substantiated by 2D NMR
spectroscopy.
Bisazabenz-Annulated Perylenes. While the azabenz-
annulated perylene derivatives mentioned so far are capable of
coordinating single transition metal centers, they do not
provide access to multinuclear transition metal complexes with
multiple redox active subunits and more sophisticated photo-
physics.45−48 Therefore, we turned to bisazabenz-annulated
systems, which have rarely been reported in the literature.22
Starting from a 3:2 mixture of 1,7- and 1,6-diamino-substituted
perylene bisimides (Scheme 4, left), anti-(ab)2-PBI 15 and syn-
(ab)2-PBI 1622 are accessible by the PS protocol described
above, and the regioisomers could be separated by column
chromatography. Because of an elaborate purification process,
both molecules were isolated in only moderate yields of 23%
and 14%, respectively, pursuant to the isomeric ratio of the
diamino-substituted precursor. Similarly, the bisazabenz-annu-
lated perylene tetraester syn-(ab)2-PTE 18 was synthesized by
PS transformation of isomerically pure 1,6-diamino-PTE 17 in
37% yield (the corresponding 1,7-isomer could not be prepared
as analytically pure material). After hydrolysis of 18, the
corresponding bisanhydride syn-(ab)2-PBA 19 can be converted
into bisazabenz-annulated perylene bisimides containing any
desirable imide substituents (R) as illustrated by an imidization
reaction using 2,6-diisopropylaniline as an example (Scheme 4,
right).
1
Figure 2. H,1H-COSY spectrum with assigned JHH couplings of 1-
nitro-PMIDE 10 in CD2Cl2 at room temperature (400 MHz). In the
structure of 10 (above), the curved arrows indicate the cross coupling.
HMBC spectrum and between H8/H11 and Hc in the H,1H-
NOESY spectrum confirm the structural assignment.
1
After reduction of the nitro group using tin(II)chloride as
reductant, 1-amino-PMIDE 11 was subjected to a PS
transformation to obtain ab-PMIDE 12 in 61% yield.
Subsequently, the ester functionalities of 12 were hydrolyzed
under acidic conditions to generate the corresponding
anhydride ab-perylene monoimide monoanhydride (PMIMA)
13. Both diester 12 and particularly anhydride 13 are versatile
starting materials for the preparation of unsymmetrically imide-
Although anti-(ab)2-PBI 15 and syn-(ab)2-PBI 16 cannot be
distinguished by high-resolution electron spray mass spectrom-
etry, both isomers exhibit completely different dynamic
behavior in solution as revealed by temperature-dependent
Scheme 4. Synthetic Access to Bisazabenz-Annulated Perylene Derivatives (ab)2-PBI (left) and (ab)2-PTE (right)
D
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NMR spectroscopy in deuterated THF. Whereas syn-(ab)2-PBI
16 is characterized by well-resolved NMR signals even at room
temperature (295 K), only strongly broadened resonances are
observed for anti-(ab)2-PBI 15, presumably due to the
restricted rotation of the peripheral pyridine substituents that
can efficiently be suppressed by protonation of the bipyridine
subunits (see Figures S3 and S4). However, upon decreasing
the temperature to 233 K, all aromatic resonances sharpened
gradually, facilitating an unambiguous structural assignment.
Unequivocal structural evidence for the anti-bisazabenz-
annulation in (ab)2-PBI 15 is provided by X-ray diffraction
experiments performed on single crystals grown from THF
solutions (Figure 3). Apart from the anti-arrangement, (ab)2-
alities) on the optoelectronic properties of monoazabenz-
annulated perylenes. Because the variation of the terminal
substituents does not significantly influence the optical
properties of the individual chromophores, these data were
exclusively summarized in Table S1.
Obviously, upon core extension, a hypsochromic shift of the
S0−S1 transition band, referred to the parent PBI, can be
observed that is less pronounced for the bisazabenz-annulated
PTE 18 and its PBI analogues 15 and 16 (see Figure 4a and
Figure S5 (top)). Simultaneously, the oscillator strengths and
the intensities of the S0−S2 transitions strongly increase with
core extension because the S0−S2 transition dipole moments
are aligned along the laterally elongated molecular axes.
Therefore, the UV/vis absorption spectra of syn-(ab)2-PTE
18, syn-(ab)2-PBI 16, and anti-(ab)2-PBI 15 are not
predominated anymore by the lowest energy S0−S1 transitions
but by higher energy absorption bands with extinction
coefficients of up to ε = 119 × 103 M−1 cm−1. Similar
observations (hypsochromic shift of the absorption maxima and
intensification of the S0−S2 transition) have already been
reported by the groups of Nijegorodov, Adachi, and Mullen for
̈
core-extended perylene derivatives (Nijegorodov, perylene,
1,12-benzoperylene, and coronene; Adachi and Mullen,
̈
perylene bisimide, benzo[g,h,i]-perylene bisimide, and coro-
nene bisimide).5,50,51 However, for the monoazabenz-annulated
compounds ab-PBI 3a, ab-PMIMA 13, ab-PMIDE 12, and ab-
PTE 5, the S0−S1 transitions (longitudinally polarized along the
N−N molecular axes) still exhibit enough oscillator strength,
giving rise to intensive lowest energy absorption bands with
well-resolved vibronic progressions (Figure 4b). Both chromo-
phores 3a and 13 have nearly the same conjugation length and
are therefore characterized by similar absorption spectral
features with a minor spectral shift of only 6 nm that can be
ascribed to slightly different electronic properties (vide infra).
However, the size of the fully π-conjugated system is gradually
reduced from ab-PBI 3a to ab-PMIDE 12 and ab-PTE 5,
resulting in hypsochromically shifted absorption spectra with
lowest energy UV/vis transitions located at 475, 454, and 430
nm, respectively. Thus, a blue-shift of approximately 23 nm per
introduced diester functionality can be ascertained for the S0−
S1 transitions with nearly unaffected higher energetic UV/vis
absorptions. All present perylene derivatives exhibit fluores-
cence emission out of the first excited singlet state with mirror
image like vibronic fine structures and comparatively small
Stokes shifts (see Figure S6). However, azabenz-annulation
causes the fluorescence quantum yield to be quenched by 30−
40% per azabenz-annulation due to decreasing oscillator
strengths of the S1−S0 transitions (vide supra).52 Therefore,
the bright fluorescence of PTE and PBI (quantum yields close
to unity) is reduced to 41−69% for monoazabenz-annulated
chromophores and diminishes to 9−23% for the bisazabenz-
annulated derivatives (see Table 1). Likewise, protonation of
the azabenz-annulated chromophores with trifluoroacetic acid
gradually quenches the emission, as it has exemplarily been
demonstrated for ab-PBI 3a (see Figure S7).
Figure 3. Molecular structure of anti-(ab)2-PBI 15 in the solid state
from top (a) and side views (b, ellipsoids set at 50% probability level;
THF solvent molecules are omitted for clarity).
PBI 15 exhibits a completely flat aromatic core with both
pyridyl substituents oriented out of the π-surface by 25° and
36°, respectively. Moreover, each bipyridine-like subunit is
characterized by transoid oriented nitrogen atoms to minimize
the electronic repulsion between the bipyridyl lone pairs. The
length of the C−C bonds, which connect the pyridine
substituents to the aromatic core (1.49 Å), is comparable
with those of other 2,2′-bipyridine (∼1.49 Å).49 The whole
single crystalline material is composed of well THF-solvated
PBI dimers with less extended π−π-stacking due to the
perpendicular oriented 2,6-diisopropylphenyl imide groups,
which efficiently prevent columnar π−π-stacking arrangements.
Optical and Redox Properties of ab-Perylene Deriv-
atives. The variety of different azabenz-annulated perylene
derivatives accomplished in this work enables a systematic
comparison of their optical and redox properties (see Table 1).
Two distinct effects can thus be studied based on this library of
compounds: (i) the effect of perylene core extension (1- and 2-
fold) along the short molecular axis; and (ii) the influence of
the peri-substituents (imide, anhydride, and ester function-
To experimentally assess the energies of the frontier
molecular orbitals as a function of perylene core extension
and peri-substitution, we determined the reduction potentials of
the individual chromophores by cyclic voltammetry in
dichloromethane using n-Bu4NPF6 as electrolyte and ferrocene
as internal standard (see Table 1). Apparently, upon core
first red
1/2
second red
1/2
annulation, both reduction processes E
and E
become gradually shifted to more negative values. Accordingly,
E
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a
Table 1. Summary of the Optical and Redox Data of Different Azabenz-Annulated Perylene Derivative Series
λabs/nm (ε/103 M−1 cm−1
)
λem/nm
S1−S0
b
b
c
d
ELUMO/eV
EHOMO/eV
first red
second red
compounds
PTE
S0−S1
S0−Sx
ΦF
E
1/2
/V
E
/V
1/2
471 (40.6)
430 (25.7)
445 (1.8)
353 (2.4)
319 (43.4)
336 (119)
370 (5.8)
333 (29.2)
354 (85.0)
355 (83.0)
333 (29.2)
322 (33.4)
318 (32.3)
319 (43.4)
486
440
450
532
484
493
485
484
478
468
440
0.98
0.41
0.09
0.96
0.69
0.23
0.22
0.69
0.50
0.77
0.41
−1.54
−1.60
−1.68
−0.99
−1.06
−1.13
−1.16
−1.06
−1.05
−1.35
−1.60
−1.79
−1.88
−1.98
−1.22
−1.34
−1.43
−1.44
−1.34
−1.31
−1.64
−1.88
−3.26
−3.20
−3.12
−3.91
−3.74
−3.67
−3.64
−3.74
−3.75
−3.45
−3.20
−5.85
−6.06
−5.89
−6.25
−6.33
−6.21
−6.21
−6.33
−6.37
−6.15
−6.06
ab-PTE (5)
syn-(ab)2-PTE (18)
PBI
527 (94.7)
475 (68.4)
485 (20.5)
478 (4.8)
ab-PBI (3a)
anti-(ab)2-PBI (15)
syn-(ab)2-PBI (16)
e
ab-PBI (3a)
475 (68.4)
469 (41.7)
454 (36.9)
430 (25.7)
ab-PMIMA (13)
ab-PMIDE (12)
e
ab-PTE (5)
a
b
c
Measured in dichloromethane at 298 K. Measured with 0.1 M n-Bu4NPF6 and with Fc+/Fc as a reference. Energy of the lowest unoccupied
molecular orbital ELUMO in eV as calculated considering the energy level of Fc+/Fc with respect to the vacuum level by using ELUMO = [−(E
) −
first red
1/2
d
4.8] eV. Energy of the highest occupied molecular orbital EHOMO in eV was calculated by using EHOMO = [ELUMO − Eopt.gap]; Eopt.gap determined at
e
the intersection of the absorption and emission spectra with the latter being normalized with respect to the lowest-energy absorption. For the sake
of clarity, the data are repeated for comparison.
Figure 4. UV/vis absorption spectra (c = 1 × 10−5 M) of the core-extended perylene tetraester series (a) and of the monoazabenz-annulated
perylenes derivative series (b). Cyclic voltammograms (c = 2.5 × 10−4 M, electrolyte: 0.1 M n-Bu4NPF6) of the core-extended perylene tetraester
series (c) and of the monoazabenz-annulated perylene derivative series (d). The electrochemical values were corrected versus ferrocenium/ferrocene
(Fc+/Fc) as an internal standard. All measurements were performed in dichloromethane at room temperature.
azabenz-annulation disfavors reduction to mono- and dianionic
species as it becomes evident by comparing both the PTE
(PTE, ab-PTE 5, syn-(ab)2-PTE 18; see Figure 4c) and the PBI
series (PBI, ab-PBI 3a, anti-(ab)2-PBI 15, syn-(ab)2-PBI 16; see
Figure S5 (bottom)). In contrast, the reduction potentials of
the monoazabenz-annulated systems are highly dependent on
the electron-accepting properties of the respective peri-
substituents. Thus, with an increasing number of coplanar
electron-withdrawing subunits (ab-PTE 5 < ab-PMIDE 12 <
ab-PMIMA 13 ≈ ab-PBI 3a; see Figure 4d), the two reduction
processes are gradually shifted to more positive potentials.
Altogether, an electrochemical window of 690 and 760 mV for
the first and second reduction, respectively, can be covered by
this library of azabenz-annulated perylene derivatives.
Energies of Frontier Molecular Orbitals and DFT
Calculations. Considering the energy level of ferrocenium/
F
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ferrocene (Fc+/Fc) with respect to the vacuum level (−4.8 eV),
perylene monoimide monoanhydride (ab-PMIMA 13) and ab-
perylene monoimide diester (ab-PMIDE 12), which can be
used either for the fabrication of unsymmetrically substituted
ab-perylene bisimides or for anchoring such chromophores on
semiconducting surfaces, and (iv) bisazabenz-annulated de-
rivatives for the preparation of even multinuclear transition
metal complexes. A comprehensive characterization of their
molecular properties by NMR and optical spectroscopy, cyclic
voltammetry, high-resolution mass spectrometry, and single-
crystal structure analysis, in combination with DFT calcu-
lations, revealed that the optical and electronic properties of
these multifunctional chromophores can readily be adjusted to
many desirable applications by ligation on surfaces, for example,
TiO2, or coordination to transition metals.29,42 Accordingly, our
current efforts are directed to implement these promising
ligands as integral components into hybrid materials for the
construction of photoredox catalysts, which will be reported in
due course.
the LUMO levels of the azabenz-annulated perylene derivatives
can readily be estimated using their experimentally determined
first red
1/2
reduction potentials according to ELUMO = −[E
+ 4.8] eV
(see Table 1). The order of the LUMO energies thus obtained
is well reproduced by our DFT calculations on a B3LYP/
def2SVP level of theory (Figure 5, black and gray marks). The
energetic offset of up to 0.5 eV can presumably be ascribed to
solvent effects, which were not implemented in our theoretical
considerations.
EXPERIMENTAL SECTION
■
Materials and Methods. N,N′-Bis(2′,6′-diisopropylphenyl)-1-
amino-perylene-3,4:9,10-tetracarboxylic acid bisimide (1, amino-
PBI),34 a 1,6- and 1,7-isomeric mixture of N,N′-bis(2′,6′-diisopropyl-
phenyl)-diamino-perylene-3,4:9,10-tetracarboxylic acid bisimide (14,
1,7- and 1,6-diamino-PBI),34 1-amino-perylene-3,4,9,10-tetracarboxylic
acid tetrabutyl ester (4, amino-PTE),37 1,6-diamino-perylene-3,4,9,10-
tetracarboxylic acid tetrabutyl ester (17, 1,6-diamino-PTE),37 N-(12′-
tricosanyl)-perylene-3,4-dicarboxylic acid monoimide-9,10-dicarboxylic
acid dioctyl ester (9, PMIDE),38 6-phenyl-pyridine-2-carboxaldehyde
(2c),53 6-pyridin-2′-yl-pyridine-2-carboxaldehyde (2d),54 and
2,5,8,11,15,18,21,24-octaoxapentacosan-13-amine (7)55,56 were syn-
thesized according to literature known procedures. All other starting
materials were purchased from commercial sources and used as
obtained, unless otherwise noted. Dichloromethane and N,N-
dimethylformamide were dried with a commercial solvent purification
system. Column chromatographic separations were performed on
silica gel 60 M (0.04−0.063 mm). For thin-layer chromatography
(TLC) aluminum sheets precoated with silica gel 60 F254 were used.
Preparative size-exclusion chromatography was performed using a
styrene-based material (mesh size, 200−400; molar mass operation
range, up to 2000 g/mol) swollen with dichloromethane/methanol
9:1. NMR spectra were recorded on a 400 MHz NMR spectrometer in
deuterated solvents at 25 °C. Chemical shifts are reported in parts per
million (ppm, δ scale) relative to the signal of the residual
undeuterated solvent. The following abbreviations were used to
describe nuclear spin coupling: s = singlet, d = doublet, t = triplet, sept
= septet, m = multiplet, and b = broad. Melting points were
determined on a commercial polarization microscope and are
uncorrected. MALDI-ToF MS spectra were measured with commer-
cial spectrometers either in the positive or in the negative reflector
mode using trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-
propenylidene]malononitrile (DCTB) as a matrix. In addition, high-
resolution mass spectra (ESI) were recorded on a standard mass
spectrometer with a time-of-flight detector. UV/vis absorption spectra
were measured on a commercial UV/vis spectrophotometer at 20 °C
by using 1 cm quartz cuvettes in dichloromethane as solvent
(spectroscopy grade). Emission spectra were recorded on a
commercial fluorescence spectrophotometer at 20 °C in 1 cm quartz
cuvettes as dichloromethane (spectroscopy grade) solutions, which
had a maximal absorbance of less than 0.05. The quantum yields were
determined using a commercial absolute quantum yield measurement
system. The system is composed of an excitation source that uses a
150 W CW xenon light source, a monochromator (250−700 nm,
fwhm 10 nm), an integrating sphere, and a multichannel spectrometer
capable of simultaneously measuring multiple wavelengths between
300 and 950 nm and counting the number of absorbed and emitted
photons. The reported quantum yields are averaged from values
Figure 5. Schematic representation of the frontier molecular orbital
energies of azabenz-annulated perylene derivatives. The experimentally
determined values are obtained from electrochemical and absorption
properties (see Table 1). The theoretical data are based on DFT
calculations at the B3LYP/Def2SVP level of theory (for details, see the
Supporting Information).
In contrast, the HOMO levels of these chromophores could
not be estimated by following the same approach because the
oxidation potentials of many derivatives are not covered by the
electrochemical window of our experimental setup. However,
on the basis of the assumption that the lowest energetic optical
transition directly reflects the HOMO−LUMO energy gap, the
HOMO energies should in principle be accessible by
subtracting the optical band gap from the respective LUMO
level (EHOMO = ELUMO − Eopt.gap, Table 1 and Figure 5, red
marks). Although the energetic order of these values is in good
agreement with the corresponding ones obtained by DFT
methods (Figure 5, pink marks), there is an obvious deviation
from the directly calculated values (Figure 5, blue marks). This
divergence can be explained by the fact that especially for the
bisazabenz-annulated perylene derivatives, transitions between
other molecular orbitals like HOMO−1 and LUMO+1
contribute to the lowest energetic UV/vis absorption (see
Table S2).
CONCLUSION
■
In summary, we presented here synthetic approaches for the
preparation of different azabenz-annulated perylene derivatives
possessing versatile functionalities. These include (i) poly-
pyridyl core-substituted monoazabenz-annulated compounds as
chelating ligands with different binding modes, (ii) perylene
bisanhydrides like ab-PBA 6 and syn-(ab)2-PBA 19, which serve
as universal starting materials for the construction of azabenz-
annulated perylene bisimides with complex and highly
functionalized imide substituents, (iii) regioisomers of ab-
G
DOI: 10.1021/acs.joc.6b01573
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The Journal of Organic Chemistry
Article
measured at three different excitation wavelengths. Electrochemical
measurements were performed on a commercial instrument with a
standard three-electrode configuration; scan rates from 20 to 1000
mV/s were applied. The experiments were carried out in dry
(distillation over CaH2) and degassed dichloromethane at a
concentration of 2.5 × 10−4 M containing tetra-n-butylammonium
hexafluorophosphate (0.1 M) as electrolyte. Ferrocene (Fc) was added
at the end of each experiment as an internal standard. The potentials
are referred to the ferrocenium/ferrocene couple (Fc+/Fc). All
computational calculations were performed using the Gaussian 09
program package.57 The DFT calculations were carried out with
B3LYP58−60 as functional and def2-SVP61 as basis set. The structures
were geometry optimized, followed by frequency calculations on the
optimized structures, which confirmed the existence of an energy
minimum. Time-dependent (TD)-DFT calculations were carried out
on the optimized structure with the lowest energy of the compounds
using the same functional (B3LYP) and basis set (def2-SVP) as for the
geometry optimization. The data are summarized in Tables S2−S12.
Long alkyl chains were replaced by ethyl groups to simplify and thus
accelerate the calculations.
X-ray Crystal Structure Determination. Single-crystal X-ray
diffraction data for anti-(ab)2-PBI 15 were collected at 100 K on a
commercial diffractometer using multilayered mirror monochromated
Cu Kα radiation. The structures were solved using direct methods,
expanded with Fourier techniques, and refined with a standard
software package.62 All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were included in the structure factor calculation
on geometrically idealized positions. Single crystals of anti-(ab)2-PBI
15 suitable for X-ray structural analysis were grown by slow
evaporation of a concentrated solution of tetrahydrofuran (THF).
The single crystals thus obtained were highly sensitive toward
temperature. Therefore, the crystalline material was directly immersed
(in solution) into a film of perfluorpolyether, which was precooled to
200 K on a copper substrate. Subsequently, the investigated single
crystal was transferred on a Teflon loop to the diffractometer
continuously cooled by evaporated liquid nitrogen. The refinement
showed at least two more disordered THF molecules, which could not
be modeled satisfactorily. Therefore, the SQUEEZE routine of
PLATON was used to remove the electron density. The remaining
structure could be refined nicely.63
In the following, a general structure of azabenz-annulated PBI (ab-
PBI) is depicted with indexing of atom and bond positions applied in
the nomenclature of the compounds.
N,N′-Bis(2′,6′-diisopropylphenyl)-13-(pyridin-2″-yl)-azabenzo-
[pqr]-perylene-3,4:9,10-tetracarboxylic Acid Bisimide (ab-PBI, 3a).
The reaction was performed according to the general Pictet−Spengler
reaction procedure using 0.74 g (1.02 mmol) of amino-PBI 1 and 0.72
g (6.72 mmol) of pyridine-2-carboxaldehyde 2a. The product was
obtained as a yellow solid after column chromatography (SiO2,
EtOAc/hexane 1:2) and recrystallization (EtOAc). The analytical data
are in agreement with those described in the literature.22 Yield: 0.43 g
(0.53 mmol, 52%). Mp > 300 °C. 1H NMR (400 MHz, CD2Cl2): δ =
10.52 (s, 1H), 9.63 (s, 1H), 9.45−9.40 (m, 2H), 9.22−9.18 (m, 2H),
3
4
5
8.96−8.94 (m, 1H), 8.62 (ddd, J = 7.9 Hz, J = 1.2 Hz, J = 0.8 Hz,
3
4
1H), 8.13 (td, J = 7.8 Hz, J = 1.8 Hz, 1H), 7.62−7.55 (m, 3H),
7.44−7.41 (m, 4H), 2.90 (sept, 3J = 6.7 Hz, 4H), 1.24−1.19 (m, 24H).
13C NMR (100 MHz, CD2Cl2): δ = 164.3, 164.20, 164.20, 164.1,
157.90, 157.87, 149.4, 146.54, 146.52, 144.5, 138.0, 135.7, 135.12,
135.09, 133.9, 131.51, 131.47, 131.45, 130.5, 130.4, 130.1, 130.0,
129.1, 127.7, 126.8, 126.3, 124.73, 124.68, 124.6, 124.5, 124.1, 123.9,
123.6, 123.4, 122.8, 122.7, 120.1, 29.7, 29.6, 24.23, 24.20, 24.16. MS
(MALDI-TOF, matrix, DCTB; mode, negative): m/z calcd for
[C54H44N4O4]− 812.3; found 812.0. HRMS (ESI-TOF, positive,
acetonitrile/chloroform): m/z [M + H]+ calcd for [C54H45N4O4]+
813.3441; found 813.3435 (error = 0.2 ppm). UV/vis (CH2Cl2, nm):
λmax (εmax M−1 cm−1) = 475 (68 400), 445 (37 200), 431 (26 900), 334
(29 300). CV (CH2Cl2, 0.1 M TBAPF6, V vs Fc+/Fc): E1/2 = −1.06
(PBI−/0), −1.34 (PBI2−/−).
N,N′-Bis(2′,6′-diisopropylphenyl)-13-(6″-bromopyridin-2″-yl)-
azabenzo[pqr]-perylene-3,4:9,10-tetracarboxylic Acid Bisimide (3b).
The reaction was performed according to the general Pictet−Spengler
reaction procedure using 0.70 g (0.964 mmol) of amino-PBI 1 and 1.0
g (5.36 mmol) of 6-bromo-pyridine-2-carboxaldehyde 2b. The product
was obtained as a yellow solid after column chromatography (SiO2,
EtOAc/hexane 1:2) and recrystallization (MeOH). Yield: 0.49 g (0.55
mmol, 57%). Mp > 300 °C. 1H NMR (400 MHz, CD2Cl2): δ = 10.66
Crystal data for anti-(ab)2-PBI 15 (C60H46N6O4·4C4H8O): Mr =
1203.44, 0.34 × 0.23 × 0.19 mm3, triclinic space group P1, a =
̅
10.9630(5) Å, α = 97.6970(16)°, b = 18.4513(8) Å, β = 97.8872(16)°,
c = 33.0607(14) Å, γ = 100.9697(16)°, V = 6414.6(5) Å3, Z = 4,
ρ(calcd) = 1.246 g cm−3, μ = 0.646 mm−1, F(000) = 2560, GOF(F2) =
1.065, R1 = 0.0809, wR2 = 0.2239 for I > 2σ(I), R1 = 0.0895, wR2 =
0.2313 for all data, 25 241 unique reflections [θ ≤ 72.817°] with a
completeness of 99.6% and 1707 parameters, 208 restraints.
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no. CCDC
1489244. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.ac.uk/data.
request/cif.
3
(s, 1H), 9.69 (s, 1H), 9.53−9.49 (m, 2H), 9.28 (d, J = 8.1 Hz, 1H),
9.24 (d, 3J = 8.1 Hz, 1H), 8.69 (dd, 3J = 7.7 Hz, 4J = 0.8 Hz, 1H), 8.04
(t, 3J = 7.8 Hz, 1H), 7.83 (dd, 3J = 7.9 Hz, 4J = 0.8 Hz, 1H), 7.64−7.59
(m, 2H), 7.48−7.45 (m, 4H), 2.98−2.90 (m, 4H), 1.27−1.13 (m,
24H). 13C NMR (100 MHz, CD2Cl2): δ = 163.9, 163.8, 163.74,
163.69, 158.0, 155.2, 146.13, 146.11, 144.0, 140.9, 140.0, 135.3, 134.7,
134.0, 133.6, 131.2, 131.1, 131.0, 130.2, 130.1, 129.7, 129.6, 128.8,
128.7, 127.4, 126.0, 125.1, 124.4, 124.20, 124.18, 124.1, 124.0, 123.5,
123.2, 123.1, 122.4, 122.3, 120.0, 29.3, 23.81, 23.78, 23.76. MS
(MALDI-TOF, matrix, DCTB; mode, negative): m/z calcd for
[C54H43BrN4O4]− 890.25; found 890.19. HRMS (ESI-TOF, positive,
methanol/chloroform): m/z [M + H]+ calcd for [C54H44BrN4O4]+
891.2540; found 891.2540 (error = 0.1 ppm). UV/vis (CH2Cl2, nm):
λmax (εmax M−1 cm−1) = 473 (66 200), 443 (36 300), 432 (27 500), 407
(14 100), 337 (30 400).
General Procedure of the Pictet−Spengler Reaction for
Azabenz-Annulation. The mono- or diamino-perylene derivative (1
equiv), the respective aromatic aldehyde (4−20 equiv), and activated
molecular sieve (3 Å) were placed in a Schlenk flask. Afterward, dry
dimethylformamide (10 mL per 100 mg of amino-perylene derivative)
and trifluoroacetic acid (10 equiv) were added under inert conditions,
and the reaction mixture was stirred at 110 °C for 30 min under
nitrogen atmosphere. Subsequently, the inert atmosphere was replaced
by pure oxygen, and the reaction mixture was stirred under this
oxidative environment at 110 °C until a full conversion of amino-
perylene (monitored by TLC). The mixture was quenched by addition
of water and neutralized with 15% sodium hydroxide solution. After
extraction with dichloromethane, the organic layer was washed twice
with brine and twice with water. The crude product was further
purified by column chromatography and recrystallization.
N,N′-Bis(2′,6′-diisopropylphenyl)-13-(6″-phenyl-pyridin-2″-yl)-
azabenzo[pqr]-perylene-3,4:9,10-tetracarboxylic Acid Bisimide (3c).
The reaction was performed according to the general Pictet−Spengler
reaction procedure using 0.29 g (0.40 mmol) of amino-PBI 1 and 0.48
g (2.62 mmol) of 6-phenyl-pyridine-2-carboxaldehyde 2c. The product
was obtained as a yellow solid after column chromatography (SiO2,
EtOAc/hexane 1:2) and recrystallization (EtOAc). Yield: 134 mg
(0.15 mmol, 38%). Mp > 300 °C. 1H NMR (400 MHz, CD2Cl2): δ =
3
10.90 (s, 1H), 9.59 (s, 1H), 9.39−9.37 (m, 2H), 9.16 (d, J = 8.3 Hz,
1H), 9.08 (d, 3J = 8.1 Hz, 1H), 8.59 (dd, 3J = 7.8 Hz, 4J = 0.9 Hz, 1H),
H
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The Journal of Organic Chemistry
Article
8.22−8.20 (m, 2H), 8.11 (t, 3J = 7.9 Hz, 1H), 7.97 (dd, 3J = 7.9 Hz, 4J
(400 MHz, CD2Cl2): δ = 9.80 (s, 1H), 9.76 (s, 1H), 9.59−9.57 (m,
3
3
3
= 0.8 Hz, 1H), 7.49 (t, J = 7.9 Hz, 2H), 7.42−7.33 (m, 7H), 2.83
2H), 9.32 (d, J = 8.3 Hz, 1H), 9.27 (d, J = 8.1 Hz, 1H), 8.77 (m,
3
(sep, J = 6.8 Hz, 4H), 1.17−1.12 (m, 24H). 13C NMR (100 MHz,
1H), 8.72 (ddd, 3J = 4.8 Hz, 4J = 1.8 Hz, 5J = 0.9 Hz, 1H), 8.36 (ddd,
3
3J = 7.9 Hz, 4J = 1.8 and 1.1 Hz, 1H), 8.18 (ddd, J = 7.6 Hz, 4J = 1.8
CD2Cl2): δ = 164.1, 163.93, 163.86, 163.8, 157.2, 157.1, 157.0, 146.2,
146.1, 144.1, 138.9, 138.5, 135.5, 135.2, 134.8, 133.5, 131.2, 131.12,
131.07, 130.3, 130.0, 129.7, 129.6, 129.3, 128.9, 128.8, 127.3, 127.2,
125.9, 124.7, 124.4, 124.2, 123.8, 123.7, 123.5, 123.0, 122.4, 122.3,
121.0, 119.9, 29.29, 29.26, 23.9, 23.82, 23.77, 23.7. MS (MALDI-TOF,
matrix, DCTB; mode, positive): m/z calcd for [C60H48N4O4]+ 888.37;
found 887.96. HRMS (ESI-TOF, positive, acetonitrile/chloroform):
m/z [M + H]+ calcd for [C60H49N4O4]+ 889.3748; found 889.3751
(error = 0.3 ppm). UV/vis (CH2Cl2, nm): λmax (εmax M−1 cm−1) = 478
(61 700), 448 (34 100), 433 (29 400), 338 (33 900). CV (CH2Cl2, 0.1
M TBAPF6, V vs Fc+/Fc): E1/2 = −1.08 (PBI−/0), −1.36 (PBI2−/−).
N,N′-Bis(2′,6′-diisopropylphenyl)-13-(2″,2‴-bipyridin-6″-yl)-
azabenzo[pqr]-perylene-3,4:9,10-tetracarboxylic Acid Bisimide (3d).
The reaction was performed according to the general Pictet−Spengler
reaction procedure using 40 mg (0.07 mmol) of amino-PBI 1 and 92
mg (0.50 mmol) of 6-pyridin-2′-yl-pyridine-2-carboxaldehyde 2d. The
product was obtained as a yellow solid after column chromatography
(SiO2, 99:1 CH2Cl2/MeOH) and precipitation (CH2Cl2 in n-hexane).
and 1.2 Hz, 1H), 7.97 (ddd, 3J = 8.0 Hz, 4J = 1.2 Hz, 5J = 0.8 Hz, 1H),
7.90 (t, 3J = 7.6 Hz, 1H), 7.84 (td, 3J = 7.6 Hz, 4J = 1.8 Hz, 1H), 7.63−
7.57 (m, 2H), 7.47−7.42 (m, 4H), 7.32 (ddd, 3J = 7.5 and 4.8 Hz, 4J =
1.1 Hz, 1H), 2.97−2.85 (m, 4H), 1.25−1.19 (m, 24H). 13C NMR (100
MHz, CD2Cl2): δ = 164.0, 163.84, 163.79, 163.7, 161.4, 156.4, 149.8,
146.1, 146.0, 144.7, 140.2, 139.0, 136.9, 135.6, 135.1, 133.6, 133.2,
131.3, 131.2, 131.1, 131.0, 130.0, 129.9, 129.7, 129.6, 129.3, 128.9,
128.1, 127.3, 126.0, 124.5, 124.19, 124.16, 123.83, 123.76, 123.6,
123.1, 122.6, 122.3, 122.2, 120.6, 119.4, 29.24, 29.20, 23.8. MS
(MALDI-TOF, matrix, DCTB; mode, negative): m/z calcd for
[C60H48N4O4]− 888.37; found 888.31. HRMS (ESI-TOF, positive,
acetonitrile/chloroform): m/z [M + H]+ calcd for [C60H49N4O4]+
889.3748; found 889.3758 (error = 1.1 ppm). UV/vis (CH2Cl2, nm):
λmax (εmax M−1 cm−1) = 477 (60 400), 447 (33 300), 429 (27 300), 406
(13 300), 328 (29 000), 283 (36 000).
13-(Pyridin-2″-yl)-azabenzo[pqr]-perylene-3,4,9,10-tetracarbox-
ylic Acid Tetrabutyl Ester (ab-PTE, 5). The reaction was performed
according to the general Pictet−Spengler reaction procedure using 1.3
g (1.95 mmol) of amino-PTE 437 and 2.5 g (23.4 mmol) of pyridine-2-
carboxaldehyde 2a. The product was obtained as a bright yellow solid
after column chromatography (SiO2, 99:1 → 97:3 CH2Cl2/EtOAc)
and recrystallization (1:1 n-hexane/CH2Cl2). Yield: 911 mg (1.21
mmol, 62%). Mp 128−131 °C. 1H NMR (400 MHz, CDCl3): δ = 9.55
(s, 1H), 9.12 (d, 3J = 8.3 Hz, 2H), 8.99 (s, 1H), 8.88 (ddd, 3J = 4.9 Hz,
1
Yield: 16 mg (18 μmol, 26%). Mp > 300 °C. H NMR (400 MHz,
CD2Cl2): δ = 10.98 (s, 1H), 9.62 (s, 1H), 9.42−9.40 (m, 2H), 9.18 (d,
3J = 8.2 Hz, 1H), 9.11 (d, 3J = 8.2 Hz, 1H), 8.74 (dd, 3J = 7.8 Hz, 4J =
1.0 Hz, 1H), 8.66−8.62 (m, 3H), 8.18 (t, 3J = 7.9 Hz, 1H), 7.68 (td, 3J
4
= 7.6 Hz, J = 2.0 Hz, 1H), 7.52−7.47 (m, 2H), 7.36−7.34 (m, 4H),
7.26 (ddd, 3J = 7.5 and 4.7 Hz, 4J = 1.1 Hz, 1H), 2.83 (sep, 3J = 6.9 Hz,
4H), 1.15−1.12 (m, 24H). 13C NMR (100 MHz, CD2Cl2): δ = 164.3,
164.1, 164.0, 163.9, 156.9, 156.8, 155.9, 155.7, 149.4, 146.3, 146.2,
144.3, 138.8, 137.3, 135.7, 135.4, 135.0, 133.7, 131.3, 131.2, 130.5,
130.2, 129.82, 129.78, 129.0, 127.5, 126.4, 126.0, 124.5, 124.4, 124.2,
124.0, 123.8, 123.7, 123.5, 123.2, 122.6, 122.4, 121.8, 121.4, 120.1,
29.42, 29.40, 24.1, 24.0, 23.9, 23.8. MS (MALDI-TOF, matrix, DCTB;
mode, positive): m/z calcd for [C59H47N5O4]+ 889.36; found 889.29.
HRMS (ESI-TOF, positive, acetonitrile/chloroform): m/z [M + H]+
calcd for [C59H48N5O4]+ 890.3701; found 890.3710 (error = 1.0
ppm). UV/vis (CH2Cl2, nm): λmax (εmax M−1 cm−1) = 477 (56 400),
447 (31 200), 432 (26 100), 408 (13 300), 337 (30 500).
3
3
4J = 1.7 Hz, 5J = 0.8 Hz, 1H), 8.58 (d, J = 8.2 Hz, 1H), 8.50 (d, J =
8.1 Hz, 1H), 8.33 (ddd, 3J = 7.8 Hz, 4J = 1.2 Hz, 5J = 0.8 Hz, 1H), 8.00
(td, 3J = 7.7 Hz, 4J = 1.8 Hz, 1H), 7.49 (ddd, 3J = 7.6 and 4.8 Hz, 4J =
1.2 Hz, 1H), 4.41−4.30 (m, 8H), 1.83−1.68 (m, 8H), 1.54−1.39 (m,
8H), 0.98−0.90 (m, 12H). 13C NMR (100 MHz, CDCl3): δ = 168.7,
168.5, 168.42, 168.36, 157.7, 156.0, 149.1, 143.2, 137.4, 133.5, 133.1,
133.0, 132.0, 131.3, 130.91, 130.88, 130.1, 129.6, 129.5, 127.7, 126.13,
126.11, 125.6, 125.3, 123.8, 122.6, 122.3, 121.2, 118.8, 65.8, 65.73,
65.69, 65.5, 30.74, 30.66, 30.64, 30.61, 19.33, 19.31, 19.30, 19.28, 13.8.
MS (MALDI-TOF, matrix, DCTB; mode, positive): m/z calcd for
[C46H46N2O8]+ 754.33; found 754.34. HRMS (ESI-TOF, positive,
acetonitrile/chloroform): m/z [M + H]+ calcd for [C46H47N2O8]+
755.3327; found 755.3336 (error = 1.2 ppm). UV/vis (CH2Cl2, nm):
λmax (εmax M−1 cm−1) = 430 (25 700), 407 (24 000), 394 (24 100), 319
(43 400). CV (CH2Cl2, 0.1 M TBAPF6, V vs Fc+/Fc): E1/2 = −1.60
(PBI−/0), −1.88 (PBI2−/−).
N,N′-Bis(2′,6′-diisopropylphenyl)-13-phenyl-azabenzo[pqr]-pery-
lene-3,4:9,10-tetracarboxylic Acid Bisimide (3e). The reaction was
performed according to the general Pictet−Spengler reaction
procedure using 523 mg (0.69 mmol) of amino-PBI 1 and 1.48 g
(13.9 mmol) of benzaldehyde 2e. The product was obtained as a
yellow solid after column chromatography (SiO2, 99:1 CH2Cl2/
MeOH) and recrystallization (MeOH). The analytical data are in
agreement with those described in the literature.22 Yield: 0.21 g (0.26
13-(Pyridin-2″-yl)-azabenzo[pqr]-perylene-3,4:9,10-tetracarbox-
ylic Acid Bisanhydride (ab-PBA, 6). Ab-PTE 5 (679 mg, 0.899 mmol)
was dissolved in 79 mL of glacial acid and 1.7 mL of concentrated
sulfuric acid. The reaction mixture was heated to 130 °C, and after 5 h
reaction time a suspension was obtained. Subsequently, 100 mL of
water was added to the reaction mixture, and the brown precipitate
was separated by filtration and washed successively with acetone,
methanol, and dichloromethane. High vacuum drying at 60 °C
afforded an ocher-colored solid. Yield: 368 mg (0.74 mmol, 83%). Mp
1
mmol, 38%). Mp > 300 °C. H NMR (400 MHz, CD2Cl2): δ = 9.68
3
(s, 1H), 9.67 (s, 1H), 9.52−9.48 (m, 2H), 9.26 (d, J = 8.2 Hz, 1H),
3
9.23 (d, J = 8.2 Hz, 1H), 8.08−8.06 (m, 2H), 7.79−7.69 (m, 3H),
7.60−7.54 (m, 2H), 7.44−7.39 (m, 4H), 2.95−2.82 (m, 4H), 1.23−
1.17 (m, 24H). 13C NMR (100 MHz, CD2Cl2): δ = 164.4, 164.20,
164.15, 164.0, 162.0, 146.54, 146.46, 145.0, 139.0, 135.9, 135.4, 133.9,
133.5, 131.7, 131.5, 131.4, 131.3, 130.3, 130.22, 130.18, 130.1, 130.0,
129.33, 129.29, 127.6, 126.4, 124.8, 124.6, 124.5, 124.4, 124.2, 124.1,
124.0, 123.6, 122.7, 122.6, 119.7, 29.7, 29.6, 24.19, 24.17, 24.16, 24.1.
MS (MALDI-TOF, matrix, DCTB; mode, positive): m/z calcd for
[C55H45N3O4]+ 811.34; found 810.95. HRMS (ESI-TOF, positive,
acetonitrile/chloroform): m/z [M + H]+ calcd for [C55H46N3O4]+
812.3488; found 812.3483 (error = 0.8 ppm). UV/vis (CH2Cl2, nm):
λmax (εmax M−1 cm−1) = 477 (59 500), 447 (33 000), 428 (26 100), 405
(13 200), 327 (26 400), 296 (27 600). CV (CH2Cl2, 0.1 M TBAPF6, V
vs Fc+/Fc): E1/2 = −1.04 (PBI−/0), −1.35 (PBI2−/−).
1
> 300 °C. H NMR (400 MHz, D2SO4): δ = 10.68−10.62 (m, 2H),
3
3
10.50 (s, 1H), 10.30 (d, J = 8.3 Hz, 1H), 10.25 (d, J = 8.2 Hz, 1H),
10.20 (s, 1H), 10.00 (bd, 3J = 5.6 Hz, 1H), 9.88 (bt, 3J = 8.2 Hz, 1H),
9.55 (bd, 3J = 7.7 Hz, 1H), 9.40−9.36 (m, 1H). 13C NMR (100 MHz,
D2SO4): δ = 163.0, 162.9, 162.3, 162.0, 151.3, 146.5, 144.8, 138.7,
138.6, 138.4, 136.7, 136.3, 135.3, 135.2, 134.3, 133.0, 132.9, 132.3,
131.0, 129.8, 129.5, 128.1, 126.6, 123.9, 123.7, 122.9, 122.5, 120.4,
119.4.
N,N′-Bis(2′,5′,8′,11′,15′,18′,21′,24′-octaoxapentacosan-13′-yl)-
13-(pyridin-2″-yl)-azabenzo[pqr]-perylene-3,4:9,10-tetracarboxylic
Acid Bisimide (ab-PBIOEG, 8). The ab-PBA 6 (50 mg, 0.101 mmol),
2,5,8,11,15,18,21,24-octaoxapentacosan-13-amine (7, 105 mg, 0.275
mmol), imidazole (500 mg), and pyridine (50 μL) were placed in a
reaction flask under inert conditions. Afterward, the reaction mixture
was heated to 120 °C, and the brownish suspension turned slowly into
a green solution. After 3 h, the warm reaction mixture (∼50 °C) was
quenched by the addition of 2 mL of 2 N hydrochloric acid and 5 mL
N,N′-Bis(2′,6′-diisopropylphenyl)-13-(3″-(pyridin-2‴-yl)-phenyl)-
azabenzo[pqr]-perylene-3,4:9,10-tetracarboxylic Acid Bisimide (3f).
The reaction was performed according to the general Pictet−Spengler
reaction procedure using 594 mg (0.82 mmol) of amino-PBI 1 and
630 mg (3.44 mmol) of 3-pyridin-2′-yl-benzaldehyde 2f. The product
was obtained as a yellow solid after column chromatography (SiO2,
95:5 CH2Cl2/EtOAc) and recrystallization (2:2:1 n-hexane/EtOAc/
1
CHCl3). Yield: 155 mg (0.17 mmol, 21%). Mp > 300 °C. H NMR
I
DOI: 10.1021/acs.joc.6b01573
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
Article
of dichloromethane. The organic phase was separated and washed
twice with 5 mL of water. The crude product was purified by column
chromatography (SiO2, 99:1 CH2Cl2/methanol) to yield an orange
[C63H90N2O6]− 970.68; found 970.68. HRMS (ESI-TOF, positive,
acetonitrile/chloroform): m/z [M + H]+ calcd for [C63H91N2O6]+
971.6877; found 971.6872 (error = 0.5 ppm). UV/vis (CH2Cl2, nm):
λmax (εmax M−1 cm−1) = 535 (8200), 410 (3300), 276 (9300).
N-(12′-Tricosanyl)-13-(pyridin-2″-yl)-azabenzo[pqr]-perylene-
3,4-dicarboxylic Acid Monoimide-9,10-dicarboxylic Acid Dioctyl
Ester (ab-PMIDE, 12). The reaction was performed according to the
general Pictet−Spengler reaction procedure using 580 mg (0.60
mmol) of 1-amino-PMIDE 11 and 0.77 g (7.23 mmol) of pyridine-2-
carboxaldehyde 2a. The product was obtained as a yellow-orange solid
after column chromatography (SiO2, gradual CH2Cl2 → 9:1 CH2Cl2/
1
solid. Yield: 89 mg (0.073 mmol, 72%). Mp 261−263 °C. H NMR
(400 MHz, CDCl3): δ = 10.16 (bs, 1H), 9.33 (bs, 1H), 9.11−9.08 (m,
2H), 8.99−8.91 (m, 3H), 8.45 (ddd, 3J = 7.8 Hz, 4J = 1.2 Hz, 5J = 0.8
3
4
3
Hz, 1H), 8.07 (td, J = 7.7 Hz, J = 1.7 Hz, 1H), 7.54 (ddd, J = 7.8
and 4.8 Hz, 4J = 1.1 Hz, 1H), 5.80−5.72 (m, 2H), 4.24−4.19 (m, 4H),
3.99−3.97 (m, 4H), 3.76−3.50 (m, 25H), 3.48−3.45 (m, 15H), 3.40−
3.37 (m, 8H), 3.23 (s, 6H), 3.22 (s, 6H). 13C NMR (100 MHz,
CDCl3): δ = 164.09, 164.05, 164.0, 163.8, 157.12, 157.08, 149.3, 143.7,
137.6, 134.0, 132.7, 129.3, 128.0, 126.6, 126.2, 124.2, 123.9, 123.5,
122.7, 122.4, 122.0, 119.0, 71.8, 70.54, 70.52, 70.49, 70.44, 70.43,
70.40, 69.4, 59.0, 52.5. MS (MALDI-TOF, matrix, DCTB; mode,
negative): m/z calcd for [C64H80N4O20]− 1224.54; found 1224.48.
HRMS (ESI-TOF, positive, methanol/chloroform): m/z [M + H]+
calcd for [C64H81N4O20]+ 1225.5439; found 1225.5450 (error = 0.9
ppm). UV/vis (CH2Cl2, nm): λmax (εmax M−1 cm−1) = 473 (60 300),
444 (32 900), 430 (24 100), 405 (12 200), 333 (26 200), 307
(28 300).
1
MeOH). Yield: 388 mg (0.37 mmol, 61%). Mp < 30 °C. H NMR
(400 MHz, CD2Cl2): δ = 9.52 (s, 1H), 8.91−8.84 (m, 1H), 8.82 (ddd,
3J = 4.8 Hz, 4J = 1.8 Hz, 5J = 0.9 Hz, 1H), 8.49 (ddd, 3J = 7.8 Hz, 4J =
5
1.2 Hz, J = 0.8 Hz, 1H), 8.47−8.39 (m, 1H), 8.39−8.29 (m, 2H),
8.21−8.13 (m, 1H), 8.06 (td, 3J = 7.8 Hz, 4J = 1.8 Hz, 1H), 7.50 (ddd,
4
3J = 7.8 Hz, 4.8 Hz, J = 1.2 Hz, 1H), 5.17 (bs, 1H), 4.39−4.28 (m,
4H), 2.25 (bs, 2H), 1.93 (bs, 2H), 1.88−1.76 (m, 4H), 1.53−1.42 (m,
3
4H), 1.42−1.02 (m, 52H), 0.86−0.77 (m, 6H), 0.76 (t, J = 6.7 Hz,
6H). 13C NMR (100 MHz, CD2Cl2): δ = 168.1, 167.9, 164.6, 164.3,
163.6, 163.1, 157.5, 155.2, 148.6, 142.5, 137.2, 134.3, 133.6, 132.1,
131.1, 130.4, 129.1, 128.4, 127.4, 127.1, 126.4, 125.7, 125.2, 124.6,
123.8, 122.3, 122.1, 122.0, 121.5, 121.2, 121.1, 118.3, 66.1, 65.9, 54.7,
32.6, 32.4, 31.9, 29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 28.8, 28.7, 27.2, 26.2,
26.1, 22.7, 22.6, 13.9, 13.8. MS (MALDI-TOF, matrix, DCTB; mode,
positive): m/z calcd for [C69H91N3O6]+ 1057.69; found 1057.67.
HRMS (ESI-TOF, positive, acetonitrile/chloroform): m/z [M + H]+
calcd for [C69H92N3O6]+ 1058.6981; found 1058.6979 (error = 0.2
ppm). UV/vis (CH2Cl2, nm): λmax (εmax M−1 cm−1) = 454 (36 900),
427 (22 900), 413 (22 600), 392 (11 800), 317 (29 800). CV (CH2Cl2,
0.1 M TBAPF6, V vs Fc+/Fc): E1/2 = −1.35 (PBI−/0), −1.64 (PBI2−/−).
N-(12′-Tricosanyl)-13-(pyridin-2″-yl)-azabenzo[pqr]-perylene-
3,4-dicarboxylic Acid Monoimide-9,10-dicarboxylic Acid Mono-
anhydride (ab-PMIMA, 13). The ab-PMIDE 12 (298 mg, 282
μmol) was dissolved in 25 mL of glacial acid and 0.6 mL of
concentrated sulfuric acid and heated to 130 °C. After 5 h of reaction
time, an orange suspension was formed, and the completion of the
reaction was monitored by TLC (SiO2, 99:1 CH2Cl2/MeOH).
Subsequently, 200 mL of water was added to the reaction mixture.
The orange precipitate was separated by filtration and washed pH
neutral with water. The solid was redissolved in a 9:1 dichloro-
methane/methanol mixture and directly used for size exclusion
chromatography (Bio-Beads S-X3, 9:1 CH2Cl2/MeOH) to isolate
the product as an orange solid. Yield: 157 mg (0.19 mmol, 68%). Mp
N-(12′-Tricosanyl)-1-nitro-perylene-3,4-dicarboxylic Acid Mono-
imide-9,10- dicarboxylic Acid Dioctyl Ester (1-Nitro-PMIDE, 10).
PMIDE 938 (99 mg, 104 μmol) and cerium(IV) ammonium nitrate
(88 mg, 160 μmol) were dissolved in 12 mL of dry dichloromethane
under inert conditions. Afterward, fuming nitric acid (0.15 mL, 3.60
mmol) was added to the orange solution, and an immediate color
change to dark red occurred. The completion of the conversion was
monitored by TLC (SiO2, 1:1 CH2Cl2/n-hexane). After 15 min, the
reaction was quenched by the addition of 2 N NaOH aqueous solution
to adjust the pH to ∼7. The pH neutral reaction mixture was extracted
twice with 100 mL each of dichloromethane. The crude product was
purified by column chromatography (SiO2, CH2Cl2/n-hexane: 1:1.2 →
1:1) to obtain a dark red solid. Yield: 90 mg (0.09 mmol, 86%). Mp <
30 °C. 1H NMR (400 MHz, CD2Cl2): δ = 8.53 (bs, 2H), 8.35 (d, 3J =
8.3 Hz, 1H), 8.30 (d, 3J = 8.1 Hz, 1H), 7.97 (d, 3J = 8.0 Hz, 1H), 7.85
3
3
(d, J = 8.0 Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H), 5.10−5.02 (m, 1H),
4.24−4.19 (m, 4H), 2.17−2.09 (m, 2H), 1.79−1.65 (m, 6H), 1.38−
1.11 (m, 56H), 0.84−0.72 (m, 12H). 13C NMR (100 MHz, CD2Cl2):
δ = 167.9, 167.7, 147.4, 133.7, 132.7, 131.1, 130.5, 130.1, 129.5, 129.3,
128.8, 128.0, 127.6, 127.3, 126.1, 123.9, 66.2, 66.1, 55.0, 32.3, 32.0,
29.8, 29.7, 29.6, 29.5, 29.4, 29.3, 28.7, 27.0, 26.1, 22.8, 14.01, 14.00.
MS (MALDI-TOF, matrix, DCTB; mode, negative): m/z calcd for
[C63H88N2O8]− 1000.65; found 1000.64. HRMS (ESI-TOF, positive,
acetonitrile/chloroform): m/z [M + H]+ calcd for [C63H89N2O8]+
1001.6619; found 1001.6613 (error = 0.6 ppm). UV/vis (CH2Cl2,
nm): λmax (εmax M−1 cm−1) = 503 (27 200), 361 (6600), 266 (21 300).
N-(12′-Tricosanyl)-1-amino-perylene-3,4-dicarboxylic Acid
Monoimide-9,10-dicarboxylic Acid Dioctyl Ester (1-Amino-PMIDE,
11). 1-Nitro-PMIDE 10 (90 mg, 90 μmol) and tin(II) chloride
dihydrate (260 mg, 1.15 mmol) were suspended in 8 mL of
tetrahydrofuran. After the reaction mixture was purged with nitrogen
for 40 min, the solution was heated to reflux under inert conditions.
The completion of the conversion was monitored by TLC (SiO2,
100:1 CH2Cl2/MeOH). After 1 h reaction time, the solvent was
removed under reduced pressure, and the violet solid was dissolved in
dichloromethane. The organic solution was washed three times with
100 mL each of water and twice with 50 mL each of sodium hydrogen
carbonate solution. The crude product was purified by column
chromatography (SiO2, 100:1 CH2Cl2/MeOH) to yield a violet solid.
1
< 30 °C. H NMR (400 MHz, CD2Cl2): δ = 9.62 (s, 1H), 8.76−8.74
(m, 2H), 8.59 (bs, 1H), 8.42 (d, 3J = 8.3 Hz, 1H), 8.27−8.21 (m, 2H),
8.18 (ddd, 3J = 7.8 Hz, 4J = 1.2 Hz, 5J = 0.7 Hz, 1H), 7.96 (td, 3J = 7.7
Hz, 4J = 1.8 Hz, 1H), 7.50 (ddd, 3J = 7.6 and 4.8 Hz, 4J = 1.1 Hz, 1H),
5.22−5.14 (m, 1H), 2.28−2.26 (m, 2H), 2.00−1.95 (m, 2H), 1.41−
1.14 (m, 36H), 0.74 (t, 3J = 6.9 Hz, 6H). 13C NMR (100 MHz,
CD2Cl2): δ = 163.7, 162.7, 159.0, 158.9, 156.0, 154.9, 148.9, 143.2,
137.6, 135.6, 133.8, 133.6, 133.1, 131.1, 130.2, 129.4, 128.8, 128.2,
127.8, 126.7, 126.0, 125.4, 124.6, 124.0, 123.7, 123.3, 122.6, 121.4,
120.6, 119.9, 118.1, 116.74, 116.70, 55.2, 32.4, 31.9, 29.8, 29.73, 29.70,
29.4, 27.2, 22.7, 13.9. MS (MALDI-TOF, matrix, DCTB; mode,
negative): m/z calcd for [C53H57N3O5]+ 815.43; found 815.38. HRMS
(ESI-TOF, positive, acetonitrile/chloroform): m/z [M + H]+ calcd for
[C53H58N3O5]+ 816.4371; found 816.4336 (error = 4.2 ppm). UV/vis
(CH2Cl2, nm): λmax (εmax M−1 cm−1) = 469 (41 700), 472 (24 500),
1
Yield: 31 mg (32 μmol, 36%). Mp < 30 °C. H NMR (400 MHz,
323 (25 800). CV (CH2Cl2, 0.1 M TBAPF6, V vs Fc+/Fc): E1/2
−1.05 (PBI−/0), −1.31 (PBI2−/−).
=
CDCl3): δ = 8.61 (d, 3J = 8.1 Hz, 1H), 8.34−8.25 (m, 1H), 8.21 (d, 3J
= 8.3 Hz, 1H), 8.14 (d, 3J = 8.3 Hz, 1H), 8.08−8.01 (m, 1H), 7.99 (d,
N,N′-Bis(2′,6′-diisopropylphenyl)-anti-13,14-di((pyridin-2″-yl)-
azabenzo[pqr])-perylene-3,4:9,10-tetracarboxylic Acid Bisimide
(anti-(ab)2-PBI, 15) and N,N′-Bis(2′,6′-diisopropylphenyl)-syn-
13,14-di((pyridin-2″-yl)-azabenzo[pqr])-perylene-3,4:9,10-tetracar-
boxylic Acid Bisimide (syn-(ab)2-PBI, 16). The reaction was
performed according to the general Pictet−Spengler reaction
procedure using 1.36 g (1.84 mmol) of a 1,7- and 1,6-diamino-PBI
isomer mixture 14 (3:2) and 1.86 g (17.3 mmol) of pyridine-2-
carboxaldehyde 2a. The crude product was first purified by column
3
3J = 8.3 Hz, 1H), 7.96 (d, J = 7,9 Hz, 1H), 7.19 (s, 2H), 5.09 (bs,
1H), 4.29−4.22 (m, 4H), 2.24−2.10 (m, 2H), 1.83−1.67 (m, 6H),
3
3
1.44−1.05 (m, 56H), 0.81 (t, J = 6.1 Hz, 6H), 0.77 (t, J = 6.7 Hz,
6H). 13C NMR (100 MHz, CDCl3): δ = 168.6, 168.5, 144.6, 133.7,
133.6, 132.9, 130.39, 130.37, 130.2, 130.0, 129.5, 129.2, 129.0, 128.8,
128.1, 123.7, 122.8, 122.4, 120.8, 65.8, 65.7, 54.6, 32.4, 31.9, 31.8,
29.64, 29.61, 29.59, 29.3, 29.2, 28.6, 27.0, 26.1, 22.7, 14.13, 14.12. MS
(MALDI-TOF, matrix, DCTB; mode, negative): m/z calcd for
J
DOI: 10.1021/acs.joc.6b01573
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The Journal of Organic Chemistry
Article
chromatography (SiO2, CH2Cl2/MeOH, 99:1) to obtain 638 mg
(0.697 mmol, 38%) of the isomeric mixture (anti-(ab)2-PBI) and syn-
(ab)2-PBI). After multiple column chromatography (SiO2, dry packed,
3:1:3 CH2Cl2/EtOAc/n-hexane), 382 mg (0.417 mmol, 23%) of the
orange anti-(ab)2-PBI 15 and 236 mg (0.258 mmol, 14%) of the
yellow syn-(ab)2-PBI 16 were isolated (isomer ratio ∼3:2). The
analytical data of syn-(ab)2-PBI match those reported in the
literature.22 Single crystals suitable for X-ray diffraction were grown
by slow evaporation of a saturated solution of anti-(ab)2-PBI 15 in
THF at room temperature. anti-(ab)2-PBI 15: Mp > 300 °C. 1H NMR
(400 MHz, d8-THF, 233 K): δ = 10.57 (s, 2H), 9.78 (s, 2H), 8.99 (d,
3J = 7.6 Hz, 2H), 8.43 (d, 3J = 4.4 Hz, 2H), 8.40 (td, 3J = 7.4 Hz, 4J =
PTE 18 (95 mg, 0.111 mmol) was dissolved in 10 mL of glacial acid
and 0.2 mL of concentrated sulfuric acid. The reaction mixture was
heated to 130 °C, and after 17 h reaction time a suspension was
formed. Subsequently, 200 mL of water was added to the cooled
reaction mixture, and the brown precipitate was separated by filtration
and washed successively with water, acetone, methanol, and
dichloromethane. High vacuum drying at 60 °C afforded the product
as an ocher-colored solid. Yield: 64 mg (0.11 mmol, 97%). Mp > 300
1
°C. H NMR (400 MHz, D2SO4): δ = 11.51 (s, 2H), 11.41 (s, 2H),
10.28 (bd, 3J = 5.8 Hz, 2H), 10.14 (bt, 3J = 8.1 Hz, 2H), 9.91 (bd, 3J =
7.7 Hz, 2H), 9.40−9.36 (m, 2H). 13C NMR (100 MHz, D2SO4): δ =
160.3, 160.2, 151.7, 150.8, 147.3, 140.0, 138.0, 136.2, 135.4, 133.9,
133.8, 133.7, 132.1, 129.6, 128.5, 127.1, 124.3, 121.3, 119.1, 119.0.
3
4
1.0 Hz, 2H), 7.77 (ddd, J = 7.5 and 4.8 Hz, J = 0.8 Hz, 2H), 7.72
(dd, 3J = 8.2 Hz, 4J = 1.0 Hz, 2H), 7.64 (t, 3J = 8.2 Hz, 2H), 7.44 (dd,
3J = 7.9 Hz, 4J = 1.0 Hz, 2H), 4.20 (sep, 3J = 6.2 Hz, 2H), 2.66 (sep, 3J
= 6.6 Hz, 2H), 2.00−1.94 (m, 12H), 1.04 (d, 3J = 6.7 Hz, 6H), 0.99 (d,
3J = 6.7 Hz, 6H). 13C NMR (100 MHz, d8-THF, 233 K): δ = 164.2,
163.9, 158.4, 158.3, 149.3, 147.8, 146.2, 142.0, 138.7, 133.7, 133.2,
132.2, 130.2, 128.2, 126.2, 125.5, 125.2, 125.1, 124.7, 124.6, 123.3,
122.4, 118.2, 117.3, 30.6, 29.9, 26.2, 25.7, 24.5, 24.0. MS (MALDI-
TOF, matrix, DCTB; mode, negative): m/z calcd for [C60H46N6O4]−
914.36; found 914.31. HRMS (ESI-TOF, positive, acetonitrile/
chloroform 1:1): m/z [M + H]+ calcd for [C60H47N6O4]+ 915.3653;
found 915.3650 (error = 0.3 ppm). UV/vis (CH2Cl2, nm): λmax (εmax
M−1 cm−1) = 485 (20 500), 455 (11 000), 414 (46 600), 393 (25 800),
355 (85 400), 338 (64 100). CV (CH2Cl2, 0.1 M TBAPF6, V vs Fc+/
Fc): E1/2 = +1.91 (PBI+/0, irrev), −1.13 (PBI−/0), −1.43 (PBI2−/−).
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.joc.6b01573.
Figures S1−S7, Tables S1 and S2 mentioned in the text,
1H, 13C NMR, MALDI, and HR-ESI-TOF mass spectra
of all compounds (Figures S6−S69), as well as
computational data (Cartesian coordinates, total ener-
gies, and frontier molecular orbital plots) (PDF)
X-ray data for compound 15 (CIF)
1
syn-(ab)2-PBI 16: Mp > 300 °C. H NMR (400 MHz, CDCl3): δ =
11.13 (s, 2H), 10.29 (s, 2H), 9.01 (ddd, 3J = 4.8 Hz, 4J = 1.7 Hz, 5J =
0.9 Hz, 2H), 8.73 (ddd, 3J = 7.8 Hz, 4J = 1.2 Hz, 5J = 0.8 Hz, 2H), 8.15
(td, 3J = 7.7 Hz, 4J = 1.8 Hz, 2H), 7.61 (ddd, 3J = 7.7 and 4.8 Hz, 4J =
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: wuerthner@chemie.uni-wuerzburg.de.
3
1.1 Hz, 2H), 7.54−7.47 (m, 2H), 7.40−7.34 (m, 4H), 2.95 (sep, J =
3
3
Notes
6.7 Hz, 2H), 2.86 (sep, J = 6.9 Hz, 2H), 1.20 (d, J = 6.9 Hz, 12H),
1.16 (d, 3J = 6.9 Hz, 12H). 13C NMR (100 MHz, CDCl3): δ = 164.2,
164.1, 158.9, 157.5, 149.4, 145.80, 145.76, 143.5, 138.0, 134.8, 132.8,
130.74, 130.68, 130.0, 129.8, 128.8, 127.7, 126.4, 125.4, 124.7, 124.4,
124.2, 123.7, 123.0, 122.5, 120.6, 119.6, 118.6, 29.5, 29.4, 24.2, 24.1.
MS (MALDI-TOF, matrix, DCTB; mode, negative): m/z calcd for
[C60H46N6O4]− 914.36; found 914.32. HRMS (ESI-TOF, positive,
acetonitrile/chloroform 1:1): m/z [M + H]+ calcd for [C60H47N6O4]+
915.3653; found 915.3656 (error = 0.3 ppm). UV/vis (CH2Cl2, nm):
λmax (εmax M−1 cm−1) = 478 (4800), 448 (6800), 429 (42 100), 405
(25 600), 356 (82 900). CV (CH2Cl2, 0.1 M TBAPF6, V vs Fc+/Fc):
E1/2 = +1.87 (PBI+/0, irrev), −1.16 (PBI−/0), −1.44 (PBI2−/−).
syn-13,14-Di((pyridin-2″-yl)-azabenzo[pqr])-perylene-3,4,9,10-
tetracarboxylic Acid Tetrabutyl Ester (syn-(ab)2-PTE, 18). The
reaction was performed according to the general Pictet−Spengler
reaction procedure using 0.29 g (0.43 mmol) of 1,6-diamino-PTE 17
and 0.91 g (8.5 mmol) of pyridine-2-carboxaldehyde 2a. The product
was obtained as a bright-yellow solid after column chromatography
(SiO2, 99:1 CH2Cl2/MeOH) and recrystallization (n-hexane/
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Bavarian Research Program
“Solar Technologies Go Hybrid”. M.S. thanks the Fonds der
́
Chemischen Industrie for a Kekule fellowship. We thank David
Bialas for his support in theoretical calculations.
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