Distance Matters: Biasing Mechanism, Transfer of Asymmetry, and Stereomutation in N-Annulated Perylene Bisimide Supramolecular Polymers

Article abstract of DOI:10.1021/jacs.1c06125

The synthesis of two series of N-annulated perylene bisimides (PBIs), compounds 1 and 2, is reported, and their self-assembling features are thoroughly investigated by a complete set of spectroscopic measurements and theoretical calculations. The study co

Full text of DOI:10.1021/jacs.1c06125

pubs.acs.org/JACS
Article
Distance Matters: Biasing Mechanism, Transfer of Asymmetry, and
Stereomutation in N‑Annulated Perylene Bisimide Supramolecular
Polymers
́
Manuel A. Martínez, Azahara Doncel-Giménez, Jesus Cerdá, Joaquín Calbo, Rafael Rodríguez,
Juan Aragó, Jeanne Crassous, Enrique Ortí,* and Luis Sánchez*
Cite This: J. Am. Chem. Soc. 2021, 143, 13281−13291
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: The synthesis of two series of N-annulated perylene bisimides (PBIs), compounds 1 and 2, is reported, and their self-
assembling features are thoroughly investigated by a complete set of spectroscopic measurements and theoretical calculations. The
study corroborates the enormous influence that the distance between the PBI core and the peripheral groups exerts on the
chiroptical properties and the supramolecular polymerization mechanism. Compounds 1, with the peripheral groups separated from
the central PBI core by two methylenes and an ester group, form J-type supramolecular polymers in a cooperative manner but exhibit
negligible chiroptical properties. The lack of clear helicity, due to the staircase arrangement of the self-assembling units in the
aggregate, justifies these features. In contrast, attaching the peripheral groups directly to the N-annulated PBI core drastically
changes the self-assembling properties of compounds 2, which form H-type aggregates following an isodesmic mechanism. These H-
type aggregates show a strong aggregation-caused quenching (ACQ) effect that leads to nonemissive aggregates. Chiral (S)-2 and
(R)-2 experience an efficient transfer of asymmetry to afford P- and M-type aggregates, respectively, although no amplification of
asymmetry is achieved in majority rules or “sergeants-and-soldiers” experiments. A solvent-controlled stereomutation is observed for
chiral (S)-2 and (R)-2, which form helical supramolecular polymers of different handedness depending on the solvent
(methylcyclohexane or toluene). The stereomutation is accounted for by considering the two possible conformations of the terminal
phenyl groups, eclipsed or staggered, which lead to linear or helical self-assemblies, respectively, with different relative stabilities
depending on the solvent.
govern the supramolecular polymerization of discrete self-
assembling units. The first one, termed isodesmic and
comparable to covalent step polymerization, is characterized
by a single binding equilibrium constant for all of the
supramolecular reactions yielding the final supramolecular
polymer.5 The second one, named cooperative and related to
INTRODUCTION
■
The molecular recognition by complementary triple hydrogen
bonding between diacylaminopyridines and uracil derivatives
reported by Lehn and co-workers paved the way to boost the
discipline of supramolecular polymerization (SP).1 This
seminal work, supported by the discovery of J-type aggregates
made by Scheibe and Jelley2 and the development by Klug and
co-workers of the transmission electron microscopy,3 promp-
ted an extraordinary progress in the field of supramolecular
polymers.4 A key issue in the further development of functional
supramolecular polymers was the establishment of mathemat-
ical models allowing for an accurate description of the SP
process.5 Two main mechanisms have been amply described to
Received: June 14, 2021
Published: August 11, 2021
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291
© 2021 American Chemical Society
13281

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
Figure 1. Chemical structure of the N-annulated PBIs 1 (a) and 2 (b) displaying the formation of staircase-like and helical aggregates, respectively,
and the derived features of the resulting supramolecular polymers.
covalent chain polymerization, features two binding constants
for the extreme regimes of nucleation (Kn) and elongation (Ke).5
In the nucleation regime, very short aggregates are formed,
which, upon overcoming a critical concentration or temper-
ature, elongate to yield the final supramolecular polymer.
However, in a cooperative mechanism with Ke ≫ Kn, the
opposite situation is also possible, producing an anticooperative
mechanism.5 It is worth noting that the investigation of the SP
mechanism requires a thermodynamic control of the process.
In this regard, a number of exciting examples of pathway
complexity, in which a single self-assembling unit is able to
generate different aggregates in a competitive or consecutive
manner, have been reported in the literature during the past
few years.6
An intriguing question concerning the investigation of
supramolecular polymers relies on establishing clear struc-
ture/function relationships that allow predicting and control-
ling the mechanistic pathway. The first examples of cooperative
supramolecular polymers involved (i) the formation of
intermolecular H-bonding arrays, (ii) the subsequent con-
formational changes experienced by the self-assembling units
to form these H-bonding interactions, and (iii) the synergy of
different noncovalent forces (H-bonding, π-stacking, hydro-
phobic interactions, etc.).7 These structural requirements were
adopted as general rules to attain cooperative pathways.
Importantly, George and co-workers demonstrated that
permanent dipole−dipole interactions in the direction of
polymer growth are the driving force for cooperative
mechanisms.8 In this sense, some examples of cooperative
supramolecular polymers that do not involve H-bonding
interactions have been reported.9
(SaS) or majority rules (MR) experiments, is an efficient
strategy to attain helical homopolymers from the coassembly of
different entities.12 Importantly, a cooperative mechanism is
behind most of the examples of transfer and amplification of
asymmetry in supramolecular polymers, with very few
examples being reported for helical supramolecular polymers
formed by following isodesmic or weakly cooperative
processes.13
Herein, we report on the relevant role exerted by the
chemical nature and the flexibility of the bridging units
separating the peripheral side chains and the central aromatic
core constituting the N-annulated perylene bisimide (PBIs)
self-assembling units in the supramolecular polymerization
(SP) of compounds 1 and 2 (Figure 1). While compounds 1
readily form highly luminescent, charge transfer (CT)
mediated J-type aggregates in a cooperative manner,14
compounds 2 self-assemble into H-type aggregates following
an isodesmic mechanism that results in a strong aggregation-
caused quenching (ACQ).15 The J-type aggregates formed
from chiral (S)-1 and (R)-1 exhibit negligible chiroptical
properties, as demonstrated by electronic (ECD) and vibra-
tional (VCD) circular dichroism studies, and a lack of
circularly polarized luminescence (CPL). In contrast, the
intense and bisignated ECD and VCD spectra displayed by the
H-type aggregates formed by (S)-2 and (R)-2 reveal the
formation of helical aggregates with no CPL emission due to
the ACQ effect. In addition, chiral (S)-2 and (R)-2 present a
solvent-dependent stereomutation, which can be rationalized
by considering the formation of two different self-assemblies
(linear vs helical) with opposite stabilities depending on the
solvent conditions. The synergy of experimental evidence and
theoretical calculations has been used to further justify these
findings. Thus, for compounds 1, the complementarity
between the π-stacking of the aromatic PBI cores and the
electrostatic forces between the peripheral benzoate groups
favors the formation of staircase-like aggregates with a
nonhelical long-axis-displaced supramolecular structure, lead-
ing to negligible chiroptical properties for the resulting J-type
aggregates. In contrast, the parallel arrangement of the PBI
units, conditioned by the eclipsed or staggered conformation of
Supramolecular polymers have found significant applications
in different topics. One of these applications relies on the
efficient achievement of supramolecular chirality and, more
specifically, the generation of helical supramolecular struc-
tures.10 Supramolecular chirality is usually obtained by the
efficient transfer of asymmetry from the molecular to the
supramolecular level, starting from self-assembling units
bearing elements of asymmetry (point or/and axial chirality).11
Amplification of asymmetry, by using sergeants-and-soldiers
13282
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
Figure 2. (a) UV−vis spectra of (S)-1 at different temperatures (MCH, cT = 32 μM). Arrows indicate the absorption changes upon decreasing the
temperature from 90 to 10 °C. (b) Plot of the variation of the degree of polymerization (α) of (S)-1 in MCH versus temperature on cooling at 1
°C min−1. Red curves correspond to the fitting to the EQ model. (c) Photoluminescence (PL) spectra of (S)-1 in MCH (λexc = 555 nm) and
CHCl3 (λexc = 495 nm) (cT = 10 μM, 298 K). The inset shows the pictures of the solutions of (S)-1 in MCH and CHCl3 used to register the PL
spectra without (top samples) and with UV lamp illumination (bottom samples). (d) AFM image and (e) height profile along the green line in (d)
of the bundles of fibrillar supramolecular polymers formed by (S)-1 in MCH onto HOPG (spin coating, cT = 10 μM, 298 K).
Table 1. Thermodynamic Parameters of (S)-1, (R)-1, 2, and (S)-2
a
a
b
b
(S)-1
−91.4 0.5
−211
(R)-1
−93.9 0.4
−219
2
(S)-2
−78.9 0.6
−141
d
ΔHe (kJ mol−1
)
−77.0 0.7
−137
−77.0 0.7
1
3.7 × 106
ΔS (J mol−1
)
1
1
2
1
c
d
ΔHn (kJ mol−1
)
−16.2 0.2
1.2 × 10−3
1.9 × 105
2.4 × 102
−16.5 0.2
1.1 × 10−3
2.0 × 105
2.2 × 102
−78.9 0.6
1
5.1 × 106
c
σ
c
Ke (L mol−1
)
c
Kn (L mol−1
)
a
b
c
In MCH. In decalin. The equilibrium constants for elongation (Ke) and dimerization (Kn) and the cooperativity factor σ (=Kn/Ke) were
d
calculated at 298 K. When the isodesmic nature of the supramolecular polymerization of compounds 2 is considered, the values of ΔHe and ΔHn
are equal.
the peripheral trialkoxyphenyl moieties directly attached to the
PBI core in 2, is responsible for the formation of H-type
aggregates that experience a solvent-dependent stereomuta-
tion. The studies presented in this manuscript contribute to
the elaboration of structure/function relationships that are
useful to predict relevant features of supramolecular polymers.
and heating curves.14 In good analogy, chiral (S)-1 and (R)-1
present similar self-assembling features (Figure S2a). Thus, the
monomeric state of these chiral N-annulated PBIs, attained by
heating up diluted solutions of these compounds at 90 °C,
shows two absorption peaks at 485 and 519 nm, ascribable to
the A0−1/A0−0 transitions (Figure 2a).16 This absorption
pattern coincides with that observed by using a “good” solvent
such as chloroform (Figure S2b). Cooling these solutions
provokes the red shift of the absorption bands to 557 and 602
nm, diagnostic of the formation of J-type aggregates (Figure
2a). The depletion of the absorption peaks at 485 and 519 nm
and the increase in the peaks at 557 and 602 nm upon cooling
presents a nonsigmoidal shape characteristic of a cooperative
mechanism. The global fitting of the variation of the degree of
aggregation α versus temperature to the equilibrium (EQ)
model17 (Figure 2b and Figure S3) allows derivation of all the
thermodynamic parameters (nucleation (ΔHn) and elongation
(ΔHe) enthalpies, entropy (ΔS), nucleation (Kn) and
elongation (Ke) binding constants, and the degree of
cooperativity σ) associated with the supramolecular polymer-
ization of these chiral compounds, which are similar to those
derived for achiral 1 (Table 1).14
The formation of J-type aggregates for compounds 1 has also
been confirmed by the intense emission of a MCH solution of
(S)-1 at cT = 10 μM (Figure 2c). The fluorescence spectrum
shows a sharp band centered at 626 nm with a shoulder at 684
nm, which presents a small Stokes shift between the absorption
and the emission maxima of 24 nm, characteristic of J-type
aggregates.18 The photoluminescent quantum yield (Φlum) and
the lifetime (τ) estimated for the aggregated species show
values of 0.716 and 5.7 ns, respectively (Table S1). These
emission features contrast with those observed in CHCl3, in
which a much less intense spectrum, displaying maxima at 543
RESULTS AND DISCUSSION
■
Synthesis and Supramolecular Polymerization Mech-
anism. The synthesis of N-annulated PBIs 1 and 2 was
accomplished by following a procedure similar to that reported
for achiral 1, in which the corresponding chiral 2-aminoethyl
3,4,5-trialkoxybenzoate 9 (for (S)-1 and (R)-1) or 3,4,5-
trialkoxyaniline 14 (for 2, (S)-2, and (R)-2) was reacted with
N-annulated perylene-3,4,9,10-tetracarboxylic dianhydride 5 in
the presence of Zn(AcO)2 and imidazole.14 All of the new
compounds were characterized by common spectroscopic
techniques. A complete description of the synthetic protocols
and the spectroscopic characterization is included in the
Supporting Information.
A detailed investigation of the supramolecular polymer-
ization mechanism of the chiral (S)-1 and (R)-1 was
performed, resting on the previous results on achiral 1.14
The synergy of experimental and theoretical studies on 1
demonstrated the formation of J-type aggregates by the π-
stacking of the aromatic moieties with the pyrrolic rings of the
adjacent monomers pointing to the same direction. These
noncovalent forces are also operative in the self-assembly of
chiral (S)-1 and (R)-1 (Figure S1). Variable-temperature (VT)
UV−vis experiments in methylcyclohexane (MCH) as solvent
proved that the supramolecular polymerization mechanism of
1 occurs in a cooperative manner under thermodynamic
control, since no thermal hysteresis is observed in the cooling
13283
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
and 581 nm, is observed with lower values of Φlum (0.191) and
τ (1.91 ns) (Figure 2c and Table S1). The aggregation of these
N-annulated perylenes is recognizable by the naked eye
through a color change of the solution from orange to deep
red, with a clear change in the fluorescence under illumination
(Figure 2c, inset). The morphology of the aggregates formed
upon the supramolecular polymerization of (S)-1 was
visualized by atomic force microscopy (AFM) imaging
employing highly oriented pyrolytic graphite (HOPG) as the
surface. The AFM images recorded for the samples deposited
onto HOPG show the formation of fibrillar aggregates bundled
in highly uniform strips constituted by fibers with a typical
height of 2.5 nm (Figure 2d,e and Figure S4).
To investigate the geometrical structure of the J-type
aggregates, a conformational theoretical study on a simplified
monomer of 1, bearing flexible ethyl benzoate peripheral
groups and methyl groups on the amine nitrogens, was first
performed at the semiempirical GFN2-xTB level using the
conformer−rotamer ensemble sampling tool (CREST).19
Among all the structural possibilities and despite the higher
stability of conformer I, only conformers II and III shown in
Figure S5 are able to undergo self-assembly. Therefore,
conformers II and III were used to build up the most plausible
supramolecular pentamers, which were fully optimized through
the cost-effective GFN2-xTB method. Pentamers 1A5 and 1B5
in parts a and b of Figure 3, respectively, correspond to the
as evidenced by the 1H NMR spectra shown in Figure S1, and
between the peripheral benzoate groups of vicinal molecules,
with CH···O contacts of 2.40 Å (1A5) and 2.73−2.94 Å (1B5),
and the C=O dipole−dipole electrostatic interactions between
vicinal benzoates. From now on, we will focus on the most
stable 1A5 aggregate, which grows up as a staircase-like
aggregate with a negligible helical long-axis-displaced supra-
molecular structure (Figure S6).
The self-assembled model 1A5 was used to further shed light
on the cooperative SP mechanism experimentally observed for
compounds 1. Thus, the binding energy per interacting pair
(ΔEbind,−‑1), computed at the GFN2-xTB level for 1A5-based
oligomers in n-hexane as solvent and as a function of the
oligomer size n, displays a rapid decay from the dimer (−76.2
kJ mol−1) to the decamer (−91.5 kJ mol−1) (Figure S7). After
n = 10, the decrease in ΔEbind,n−1 is attenuated, and ΔEbind,n−1
converges to a value of ca. −94 kJ/mol when n = ∞. This
trend in ΔEbind,n−1 confirms a nucleation−elongation SP
mechanism, where the initial fast decay is associated with the
nucleation and the attenuated part is related to the elongation
process in which the addition of extra molecules has no
significant effect on the stabilization energy of the aggregate.
The presence of different noncovalent interactions stabilizing
the self-assembly (especially π-stacking interactions along with
oriented CO dipole−dipole forces) may explain the
cooperativity of the supramolecular growth mechanism in 1.
The optical properties of 1 were studied by means of time-
dependent density functional theory (TD-DFT) calculations
along with a vibronic excitonic model, similar to that proposed
by Spano and co-workers, to deal with the optical properties in
the aggregated state (see the Supporting Information for full
details).20 Experimentally, the UV−vis spectrum of the
molecularly dissolved state of 1 shows two strong bands at
485 and 519 nm (Figure 2a). These bands are attributed to the
vibrational structure (A0−1/A0−0 vibronic transitions) associ-
ated with the lowest-lying S0 → S1 electronic excitation
according to the simulated absorption spectrum (including
vibrational resolution) calculated for a core model of 1 in its
monomeric form (Figure S8). The theoretical spectrum
predicts two strong bands at 460 and 500 nm, in good
agreement with the experimental spectrum, and confirms that
the absorption features of 1 mainly result from the N-
annulated PBI core. The absorption spectrum of the aggregate
was theoretically calculated by using an excitonic model
including not only local excitations (Frenkel-type states) but
also charge-transfer (CT) states. The latter have been
demonstrated to be relevant for the optical properties of
PBI-based self-assemblies.21,22 Figure S8 shows the simulated
absorption spectrum for an ideal 1A10 aggregate. The spectrum
exhibits two well-separated absorption bands (peaking at ca.
430 and 600 nm) accompanied by their corresponding
vibrational structure. These spectral features are characteristic
of a CT-mediated J-type aggregate and explain the broad and
vibrationally resolved experimental band observed in the 400−
650 nm range (Figure 2a).20,21
Figure 3. Minimum-energy structures (with their relative energies
indicated) calculated at the GFN2-xTB level for the most stable
pentamers 1A5 (a) and 1B5 (b) in the self-assembly of 1.
most stable aggregates found and show a π-stacking of the
aromatic PBI cores with an anti disposition of the peripheral
benzoate groups. The lowest-energy aggregate 1A5 grows up
with a shift of approximately 2.90 Å along the long axis of the
central N-annulated PBI, and an intermolecular distance of
3.20 Å between adjacent monomers. This aggregate can be
initially considered as a typical J-type self-assembly. In contrast,
aggregate 1B5, which is calculated 23.4 kJ mol−1 higher in
energy compared to 1A5 (GFN2-xTB level in gas phase), self-
assembles with a rotational angle (θ) of 35.0°, a growing axis
shifted approximately 2.90 Å with respect to the center of the
PBI core, and an intermolecular core-to-core distance of 3.25
Å. The stabilizing noncovalent interactions present in both
structures are the π-stacking of the central aromatic moieties,
The situation changes drastically in compounds 2, in which
the peripheral trialkoxyphenyl units are directly attached to the
N-annulated PBI core (Figure 1a). Similarly to compounds 1,
1
concentration-dependent H NMR spectra of 2 display the
downfield shift of the three sets of aromatic resonances upon
decreasing the concentration with a minor shift of the aliphatic
protons, indicating the π-stacking of the aromatic units (Figure
S9). To unveil the arrangement of the monomeric units of
13284
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
Figure 4. (a) UV−vis spectra of 2 at different temperatures (decalin, cT = 10 μM). (b) Plot of the variation of the absorbance measured at 519 nm
versus cooling at 1 °C min−1. Red curves correspond to the fitting to the EQ model. (c) PL spectra of (S)-2 in MCH, toluene, and CHCl3 (λexc
=
380 nm, 298 K). The inset shows pictures of the solutions of (S)-2 in MCH, Tol, and CHCl3 used to register the PL spectra without (top samples)
and with illumination (bottom samples). (d) AFM image and (e) height profile along the green line in (d) of the supramolecular polymers formed
by (R)-2 in MCH onto HOPG (spin coating; cT = 10 μM, 298 K).
compounds 2 in forming the corresponding supramolecular
polymers and the mechanism governing their SP, VT-UV−vis
experiments were first performed in MCH as solvent. Unlike
compounds 1, the absorption pattern of achiral 2 in MCH (cT
= 10 μM, 20 °C) shows a broad band centered at 494 nm with
shoulders at 463 and 537 nm, apparently characteristic of H-
type aggregates (Figure S10a).18 Heating this solution to 90 °C
changes the absorption profile, and bands at 517 and 485 nm,
ascribable to the monomeric state of the N-annulated PBI core,
are observed. However, the intensity ratio between these two
bands does not correspond to that recorded in “good” solvents
such as CHCl3 and toluene (Tol), in which the fully
molecularly dissolved state is achieved (Figure S10b). In fact,
plotting the variation of the absorption at 517 nm versus
temperature results in an incomplete cooling curve that
resembles a sigmoidal shape, thus indicating an isodesmic
mechanism (Figure S10c).4 This incomplete disassembly of
the supramolecular polymers of 2 in MCH is also observed by
decreasing cT to 5 μM (Figure S11) or for the chiral congener
(S)-2 (Figure S12a).
aggregates is also confirmed by the strong ACQ effect observed
in the fluorescence spectra (Figure 4c). In good analogy to
compounds 1, N-annulated PBIs 2 show an emission spectrum
in CHCl3 featuring two bands at 586 and 630 nm with a Stokes
shift of 53 nm (Figure 4c). In contrast, the emission spectrum
of the supramolecular polymers of 2 in MCH shows an
unstructured, broad band of very low intensity centered at 662
nm and a large Stokes shift (∼160 nm) (Figure 4c).
The morphology of the H-type aggregates formed from
achiral 2 was visualized by AFM. The AFM images of 2 show
the formation of 2D nanosheets with diameters of a few
micrometers and uniform heights of ∼1.6 nm. On top of these
2D nanosheets, the presence of high micellar aggregates with
∼450 nm thickness and ∼8.5 nm height is also observed
(Figure 4d,e and Figure S14).
To justify the sharp differences found in the supramolecular
polymerization of compounds 2 in comparison to compounds
1, the monomeric and aggregated states of 2 were theoretically
investigated at the GFN2-xTB level.19 As was previously done
for compounds 1, the peripheral alkoxy chains present in the
chemical structure of 2 were removed to reduce the
computational cost. Due to the more rigid structure of 2,
only two possible conformers, differing in the eclipsed (2A) or
staggered (2B) disposition of the peripheral benzene rings with
respect to the long PBI axis, are possible and they were
computed to be practically isoenergetic (Figure 5a). Similarly
to 1, the supramolecular pentamers 2A5 and 2B5 were modeled
and were fully optimized at the GFN2-xTB level (Figure 5b).
In both aggregates, the pyrrolic units of the central PBI cores
are arranged in the most favorable parallel distribution along
the stacking axis, as demonstrated previously.14 The helical
aggregate 2B5, which stems from monomers 2B with the
peripheral aromatic groups in a staggered disposition, was
calculated to be more stable by a small energy difference of
18.61 kJ mol−1. 2B5 grows with a rotational angle (θ) of 35.8°
along a stacking axis that is shifted ca. 2.90 Å with respect to
the center of the perylene scaffold. Adjacent molecules in 2B5
are separated by an intermolecular distance of 3.20 Å between
the aromatic cores and are arranged with the pyrrole moieties
pointing out of the stack. In contrast, aggregate 2A5, built up
from monomers 2A displaying an eclipsed conformation of the
phenyl groups, grows in a slipped manner with a shift of 2.43 Å
along the short PBI axis and an intermolecular distance of 3.35
Å between consecutive aromatic cores. In both structures,
stabilizing noncovalent intermolecular interactions due to the
π-stacking of both the central PBI cores and the peripheral
phenyl groups and to the CH(phenyl)···O interactions
(distances of 2.02 Å in 2A5 and 2.25−2.48 Å in 2B5) are
To achieve a complete disassembly of the aggregates of N-
annulated PBIs 2 that allows us to elucidate the SP mechanism
and to infer the corresponding thermodynamic parameters, we
used decalin as the solvent due to its higher boiling point in
comparison to MCH. The UV−vis spectrum of the aggregated
species of 2 in decalin presents an absorption profile identical
with that registered in MCH (Figure 4a). However, on heating
to 100 °C, it is possible to achieve a complete disassembly, as
indicated by the relative intensity of the characteristic A0−1
/
A0−0 vibronic transitions (Figure 4a). In good analogy with
compounds 1, no thermal hysteresis is observed in the cooling
and heating curves, which indicates that the supramolecular
polymerization of 2 takes place under thermodynamic control
(Figure S12b). Plotting the variation of the absorbance at 519
nm versus temperature results in sigmoidal curves that, upon
global fitting to the one-component EQ model, yields the
thermodynamic parameters associated with the isodesmic
formation of the H-type aggregates (Figure 4b, Figure S13,
and Table 1). It is worth noting that, despite the lower values
of ΔHe for compounds 2 in comparison to those derived for
compounds 1 and the similar entropies for both 1 and 2, the
binding constants for these H-type aggregates are one order of
magnitude higher than those calculated for the J-type
aggregates formed by compounds 1 (Table 1). This difference
in the stability of the aggregates is justified by the nucleation
penalty present in the cooperative formation of the head-to-tail
supramolecular polymers of 1. The face-to-face arrangement of
the self-assembling units of compounds 2 in the H-type
13285
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
maxima at 260 and 591 nm and the anisotropy factor g ≈ 1 ×
10−4 (Figure 6a). The negligible chiroptical response observed
Figure 6. Amplification-of-asymmetry experiments performed with N-
annulated PBIs 1. (a) ECD spectra for MR experiments. (b) Changes
in ECD intensity at 602 nm as a function of the ee upon adding (R)-1
to a solution of (S)-1. (c) Selected ECD spectra registered for the SaS
experiments performed by mixing 1 and (R)-1. (d) Changes in the
ECD intensity at 602 nm upon increasing the molar fraction (X) of
the chiral sergeant (R)-1. The red line in (d) corresponds to a
Gaussian fit to guide the eye. Experimental conditions: MCH, cT = 50
μM, 20 °C.
Figure 5. Minimum-energy structures (with their relative energies
indicated) calculated at the GFN2-xTB level for the most stable
monomers 2A and 2B (a) and for pentamers 2A5 (b) and 2B5 (c) in
the self-assembly of 2.
present (Figure 5b). Pentamers 2A5 and 2B5 can both be
initially considered as H-type aggregates.
To get further insight into the spectroscopic features
displayed by compounds 2, TD-DFT theoretical calculations
and the excitonic model mentioned above were used to
compute the UV−vis spectra. Figure S15 displays the
simulated absorption spectra for ideal 2A10 and 2B10 decamers.
A broad vibrationally resolved absorption band is obtained for
both aggregates, although with different spectral profiles. The
pattern predicted for 2B10 is especially in good accord with
that experimentally registered in decalin for the supramolecular
polymers formed from compounds 2 (Figure 4a) and confirms
the H-type nature of this aggregate. It is important to note that,
as discussed below, 2B supramolecular oligomers are more
stable than 2A oligomers in apolar solvents.
Chiroptical Features: Transfer and Amplification of
Asymmetry.23 The decoration of compounds (S)-1, (R)-1,
(S)-2, and (R)-2 with chiral side chains, together with the
studies on the supramolecular polymerization of these N-
annulated PBIs discussed above, allows performing a detailed
investigation on the transfer and amplification of asymmetry
resulting from these self-assembling units.
The cooperative supramolecular polymerization found for
compounds 1 was expected to yield an efficient transfer of
asymmetry from the molecular to the supramolecular level.
Previous examples of J-type aggregates have been reported to
give rise to helical aggregates, as demonstrated by the
corresponding ECD spectra.24 To our surprise, the ECD
spectra of the J-type aggregates formed by (S)-1 and (R)-1 in
MCH display a very weak and noisy dichroic response with
for compounds 1 is in agreement with the nonhelical long-axis-
displaced supramolecular structure theoretically predicted for
the aggregates derived from 1 (Figure 3a). The lack of dichroic
response is also corroborated by the noisy VCD spectra
recorded for (S)-1 and (R)-1, which contrasts with the well-
defined FTIR spectra of these N-annulated PBIs in solution,
where the bands corresponding to the imide and ester
carbonyls (1714 and 1692 cm−1) and to the aryl alkyl ethers
(1218 and 1118 cm−1) are clearly visible (Figure S16). In
addition, and despite the strong emission of the supra-
molecular polymers formed by these chiral N-annulated PBIs
(Figure 2c), no CPL signal is observed (Figure S17a).
We also evaluated the ability of chiral N-annulated PBIs 1 to
undergo amplification of asymmetry by developing majority
rules (MR) and sergeants-and-soldiers (SaS) experiments.11a,12
In the MR experiments, unequal amounts of the two
enantiomers (S)-1 and (R)-1, with the total concentration
kept constant, are mixed together. In this case, the ECD
spectra registered at different (S)-1/(R)-1 ratios show the
same weak and noisy profile as that registered for pristine
enantiomers (Figure 6a). In addition, plotting the variation of
the poor dichroic response at 602 nm versus the enantiomeric
excess (ee) results in a linear trend, which indicates either the
negligible ability of these compounds to coassemble into
homochiral aggregates or the inability of detecting this
phenomenon due to the poor dichroic response (Figure 6b).
The lack of a clear dichroic (ECD, VCD, CPL) response for
the supramolecular polymers formed by (S)-1 and (R)-1,
13286
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
despite the cooperative character of their supramolecular
polymerization, is accounted for by the staircaselike
aggregation mode (Figures 1a and 3a and Figure S6) that
yields a nonhelical supramolecular structure.
corroborated by the corresponding VCD spectra that display a
mirror-like vibrational pattern (Figure 7b). VCD spectroscopy
has indeed been recognized as a suitable chiroptical tool to
characterize helical supramolecular polymers.28 This mirror-
like vibrational pattern is observed for those bands at 1700,
1665, and 1600 cm−1, ascribable to the conjugated aromatic
units, and at 1233 and 1111 cm−1, corresponding to the
stretching of the alkoxy groups (Figure 7b and Figure S19). On
the other hand, the strong ACQ effect observed in the
corresponding fluorescence measurements (Figure 4c) results
in null CPL emission from the aggregates formed by (S)-2 and
(R)-2 (Figure S17b).
The SaS experiments, performed by mixing the achiral
soldier 1 and the chiral sergeant (R)-1, produce an abnormal
effect by which the sign of the dichroic signal detected for
relatively low molar fractions (X) of (R)-1 is reversed with
respect to that recorded for the pristine chiral seargent (Figure
6c,d). The weak dichroic response attained in the ECD spectra
could suggest that this effect is an artifact. However, an
analogous effect but of opposite sign is observed for the SaS
experiments carried out by mixing 1 and (S)-1 (Figure S18).
We have previously described a similar effect for self-
assembling units able to form intramolecular hydrogen-bonded
metastable monomers that retard the corresponding supra-
molecular polymerization.25 However, this is not the case,
since N-annulated PBIs 1 cannot form H-bonded metastable
monomers and their supramolecular polymerization is under
thermodynamic control. A similar abnormal SaS effect has
been described for covalent polymers and justified by
considering the different energy preferences exhibited by the
situation in which a chiral sergeant is adjacent to another chiral
sergeant or to an achiral soldier. This energy difference
conditions the sign of the dichroic response.26
In contrast to 1, the transfer of asymmetry from the
molecular to the supramolecular level in N-annulated PBIs
(S)-2 and (R)-2 yields a rich dichroic pattern, with an intense
bisignated Cotton effect with maxima at 490 and 547 nm and
zero crossing points at 508, 344, 278, and 261 nm and with the
anisotropy factor g ≈ 3 × 10−3 (Figure 7a). This bisignated
Cotton effect implies the formation of P- and M-type helical
aggregates for (S)-2 and (R)-2, respectively.27 The formation
of helical aggregates from (S)-2 and (R)-2 is in agreement with
the helical structure predicted theoretically (Figure 5c) and is
Taking into account the efficient transfer of asymmetry
experienced by (S)-2 and (R)-2, we checked the ability of
these N-annulated PBIs to amplify asymmetry by developing
MR experiments. A linear increase in the dichroic response is
observed upon plotting the variation of the ECD signal versus
the ee, diagnostic of the lack of amplification of asymmetry
(Figure S20). Similar findings were inferred from the
corresponding SaS experiments performed by mixing 2 and
(S)-2, for which a linear increase of the dichroic response upon
increasing the amount of the chiral sergeant was observed
(Figure S21). These studies reveal the ability of N-PBIs 2,
which form supramolecular polymers governed by an
isodesmic mechanism, to undergo an efficient transfer of
asymmetry but a negligible amplification of asymmetry.
Finally, the influence of the solvent on the chiroptical
features of the reported N-annulated PBIs was evaluated. The
solvent−solute interactions are crucial in tuning the solubility,
reactivity, and structure of organic compounds and are at the
forefront of the research on supramolecular polymers, since the
solvent can efficiently bias the assembly/disassembly process.29
Some reports describe that the chirality embedded in solvent
molecules exerts a pivotal role in controlling the helical
outcome resulting from the supramolecular polymerization of
achiral or chiral self-assembling units.30 However, there are
scarce examples in the literature of solvent-controlled stereo-
mutation in supramolecular polymers formed under thermody-
namic control and directed by molecular design.31 In our case,
we envision that the two conformers of the monomeric species
of 2, which are isoenergetic (Figure 5a), could originate helical
or linear (with a small net helicity) aggregates of opposite
handedness depending on the solvent conditions. To
investigate this potential stereomutation, we first recomputed
the stability of the optimized pentamers 2A5 and 2B5 by
including n-hexane (as a representative solvent that emulates
the MCH nature) or toluene as solvent. Frequency calculations
were additionally carried out to estimate the free energy of the
aggregation process. The self-assembly free energies per
interacting pair (ΔGsboinlvd,n−1) in n-hexane and toluene are
gathered in Table 2. In n-hexane, the relative stability
calculated in the gas phase is preserved, and the helical 2B5
aggregate is more stable than the linear 2A5 aggregate by 8.30
Table 2. Self-Assembly Free Energy (ΔGsboinlvd,n−1, in kJ mol−1)
Estimated for the Two Most Stable Aggregates of 2 in n-
Hexane and Toluene Solution at the GFN2-xTB/GBSA
Level
Figure 7. (a) ECD spectra of (S)-2 and (R)-2 in MCH (cT = 10 μM,
20 °C). (b) VCD spectra of (S)-2 and (R)-2 in MCH (cT = 0.02−
0.03 M, 20 °C). (c) ECD spectra of (S)-2 and (R)-2 in Tol at 20 °C.
(d) ECD spectra of (S)-2 and (R)-2 in MCH and Tol (cT = 500 μM,
20 °C).
n−hexane
bind,n−1
toluene
aggregate
ΔG
ΔG
bind,n−1
2A5
2B5
−19.63
−27.93
−24.94
−24.35
13287
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
kJ mol−1. In contrast, the stability is reversed in Tol and the
linear aggregate is slightly more stable by 0.59 kJ mol−1. The
relative stability of the aggregates of compound 2 therefore
depends on the solvent nature and, when the most stable
the experiment (Figure 7c,d). In contrast, in n-hexane
(modeling MCH), the most stable aggregate is predicted to
be 2B5, which corresponds to a well-defined helical arrange-
ment with a rotational dihedral angle θ of 35° and thus shows
an intense dichroic pattern (Figure S25) similar to that found
experimentally for (S)-2 and (R)-2 in MCH (Figure 7c,d).
aggregate in each solvent is considered, ΔGn‑hexane
bind,n−1 is calculated
toluene
bind,n−1
to be more negative than ΔG
by ∼3.0 kJ mol−1. These
results thus point to a higher tendency of compounds 2 to self-
assemble in MCH than in Tol, in good accord with the
experimental evidence.
CONCLUSIONS
■
The synthesis of two series of N-annulated PBIs endowed with
peripheral trialkoxyphenyl groups directly attached to the
imide nitrogens of the PBI core (2) or linked by a propionate
spacer (1) is reported. A complete set of spectroscopic
measurements and theoretical calculations demonstrate the
huge influence that the distance and conformational flexibility
of the peripheral groups exert on the optical and chiroptical
properties and on the supramolecular polymerization mecha-
nism of the resulting self-assembly. Compounds 1 present a
cooperative supramolecular polymerization that yields highly
emissive J-type aggregates with negligible chiroptical (ECD,
VCD, and CPL) response for the chiral congeners (S)-1 and
(R)-1. The staircase-like aggregation mode calculated for the
supramolecular polymers formed from 1 and the dipole−
dipole interactions between adjacent CO groups along the
stack justify these features. In contrast, bringing the peripheral
side groups closer to the N-annulated PBI core drastically
changes the self-assembling features of compounds 2. In this
case, the supramolecular polymerization is governed by an
isodesmic mechanism that gives rise to H-type aggregates
exhibiting a strong ACQ effect which, therefore, show low
emissive properties. Chiral (S)-2 and (R)-2 experience an
efficient transfer of asymmetry to afford P- and M-type
aggregates, respectively, but no amplification of asymmetry is
achieved by performing MR and SaS experiments. Finally, a
solvent-controlled stereomutation has been demonstrated for
chiral (S)-2 and (R)-2, which form supramolecular polymers
with different structures depending on the solvent utilized
(MCH or Tol). This stereomutation has been accounted for
by considering the two possible conformations of the
peripheral side chains in compounds 2, eclipsed or staggered.
These conformations lead to linear or helical self-assemblies,
respectively, of opposite stability depending on the solvent
conditions. The synergy between the experimental evidence
and the theoretical calculations presented herein contribute to
elaborate structure/function relationships useful in predicting
relevant features of supramolecular polymers.
The supramolecular mechanism of the self-assembling
process of N-annulated PBIs 2 was furthermore investigated
by performing interaction energy calculations for regular
oligomers of increasing size (from n = 1 to n = 50 monomers)
at the GFN2-xTB level in the presence of the solvent.
Theoretical calculations on 2A5-type aggregates in toluene
reveal that the binding energy per interacting pair (ΔEbind,n−1
)
barely changes with the oligomer size (Figure S22), which is a
clear indication of an isodesmic supramolecular polymerization
mechanism. Similar results are obtained for 2B5-type oligomers
in n-hexane (Figure S22), with even a small ΔEbind,n−1 increase
of ∼5 kJ mol−1 from n = 2 to n = 5 in this case. The absence of
cooperativity predicted in the supramolecular growth of 2
stems from the nature of the noncovalent interactions
stabilizing the self-assembly (mainly π−stacking interactions),
with no directional electrostatic forces such as H-bonding or
dipole−dipole interactions.32
Taking into account the previous report on the stereo-
mutation experienced by a comparable PBI33 and the results of
the theoretical calculations, we experimentally checked the
possibility of (S)-2 and (R)-2 of achieving a solvent-controlled
stereomutation by registering the ECD spectra in Tol as
solvent. Using concentrations as low as those utilized in MCH
(Figure 7a), no ECD response was observed. However, when
the concentration was increased to cT = 100 μM, it was
possible to register a weak but noticeable ECD spectrum
(Figure 7c), showing patterns opposite to those recorded in
MCH (Figure 7a). It is worth noting that the UV−vis
spectrum recorded at cT = 100 μM reveals a degree of
aggregation that increases upon increasing the concentration
up to 500 μM, as the higher intensity observed in the dichroic
response demonstrates (Figure 7c and Figure S23). At cT =
500 μM, the dichroic pattern of N-annulated PBIs 2 in Tol is
opposite to that registered in MCH (Figure 7d) and the
sample is completely aggregated, as supported by the
quenching of the fluorescence emission (Figure 4c).
The influence of the type of aggregation on the circular
dichroism properties of N-annulated PBIs was also analyzed by
means of TD-DFT calculations. To unveil the effect of the
rotational dihedral angle (θ) along the growth axis, the
theoretical ECD spectrum was calculated for a dimer of the N-
annulated PBI core, in which the angle θ ranges from 0 to 10°
(Figure S24). Theoretical calculations indicate that a
significant dichroic signal is obtained even at small dihedral
angles (>2°). This suggests that not only helical aggregates
with a large θ value but also linear stacking aggregates with a
small net θ value, promoted by the point chirality element
embedded in the peripheral groups, may afford a dichroic
signal. The different dichroic reponses observed for chiral 2 in
MCH and Tol can thus be explained by the different
aggregation modes of 2 in these two solvents. In toluene,
theoretical calculations predict that the most stable aggregate
2A5 is an almost regular linear H-type self-assembly and gives
rise to a small dichroic signal (Figure S25) in agreement with
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/jacs.1c06125.
■
sı
Full experimental details and characterization, additional
spectroscopic measurements, and theoretical calcula-
tions, including Figures S1−S25 (PDF)
AUTHOR INFORMATION
Corresponding Authors
■
Enrique Ortí − Instituto de Ciencia Molecular (ICMol),
Universidad de Valencia, 46980 Paterna, Spain;
orcid.org/0000-0001-9544-8286; Email: enrique.orti@
uv.es
Luis Sánchez − Departamento de Química Orgánica, Facultad
de Ciencias Químicas, Universidad Complutense de Madrid,
13288
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
̈
̈
(2) (a) Scheibe, G. Uber die veranderlichkeit der absorptionss-
28040 Madrid, Spain; orcid.org/0000-0001-7867-8522;
Email: lusamar@quim.ucm.es
̈
pektren in losungen und dienebenvalenzen als ihre ursache. Angew.
Chem. 1937, 50, 212−219. (b) Jelley, E. E. Spectral absorption and
fluorescence of dyes in the molecular state. Nature 1936, 138, 1009−
1010.
(3) Klug, A. The tobacco mosaic virus particle: structure and
assembly. Philos. Trans. R. Soc., B 1999, 354, 531−535.
(4) (a) Brunsveld, L.; Folmer, B. J. B.; Meijer, E. W.; Sijbesma, R. P.
Supramolecular polymers. Chem. Rev. 2001, 101, 4071−4098.
(b) Wehner, M.; Wurthner, F. Supramolecular polymerization
̈
through kinetic pathway control and living chain growth. Nat. Rev.
2020, 4, 38−53.
Authors
Manuel A. Martínez − Departamento de Química Orgánica,
Facultad de Ciencias Químicas, Universidad Complutense de
Madrid, 28040 Madrid, Spain
Azahara Doncel-Giménez − Instituto de Ciencia Molecular
(ICMol), Universidad de Valencia, 46980 Paterna, Spain
́
Jesus Cerdá − Instituto de Ciencia Molecular (ICMol),
Universidad de Valencia, 46980 Paterna, Spain
Joaquín Calbo − Instituto de Ciencia Molecular (ICMol),
Universidad de Valencia, 46980 Paterna, Spain;
orcid.org/0000-0003-4729-0757
(5) (a) De Greef, T. F. A.; Smulders, M. M. J.; Wolffs, M.;
Schenning, A. P. H. J.; Sijbesma, R. P.; Meijer, E. W. Supramolecular
polymerization. Chem. Rev. 2009, 109, 5687−5754. (b) ten Eikelder,
H. M. M.; Markvoort, A. J. Mass-Balance Models for Scrutinizing
Supramolecular (Co)polymerizations in Thermodynamic Equili-
brium. Acc. Chem. Res. 2019, 52, 3465−3474. (c) Gershberg, J.;
Rafael Rodríguez − Univ Rennes, CNRS, ISCR (Institut des
Sciences Chimiques de Rennes), F-35000 Rennes, France;
orcid.org/0000-0002-8588-7776
Juan Aragó − Instituto de Ciencia Molecular (ICMol),
Universidad de Valencia, 46980 Paterna, Spain;
orcid.org/0000-0002-0415-9946
Jeanne Crassous − Univ Rennes, CNRS, ISCR (Institut des
Sciences Chimiques de Rennes), F-35000 Rennes, France;
orcid.org/0000-0002-4037-6067
Fennel, F.; Rehm, T. H.; Lochbrunner, S.; Wurthner, F. Anti-
̈
cooperative supramolecular polymerization: a new K2−K model
applied to the self-assembly of perylene bisimide dye proceeding via
well-defined hydrogen-bonded dimers. Chem. Sci. 2016, 7, 1729−
1737.
(6) Matern, J.; Dorca, Y.; Sánchez, L.; Fernández, G. Revising
Complex Supramolecular Polymerization under Kinetic and Thermo-
dynamic Control. Angew. Chem., Int. Ed. 2019, 58, 16730−16740.
(7) (a) Smulders, M. M. J.; Schenning, A. P. H. J.; Meijer, E. W.
Tuning the extent of chiral amplification by tempera-ture in a
dynamic supramolecular polymer. J. Am. Chem. Soc. 2008, 130, 606−
611. (b) García, F.; Viruela, P. M.; Matesanz, E.; Ortí, E.; Sánchez, L.
Cooperative supramolecular polymerization and amplification of
chirality in C3-symmetrical OPE-based trisamides. Chem. - Eur. J.
2011, 17, 7755−7759. (c) García, F.; Sánchez, L. Structural rules for
the chiral supramolecular organization of ope-based discotics:
induction of helicity and amplification of chirality. J. Am. Chem. Soc.
2012, 134, 734−742. (d) García, F.; Korevaar, P. A.; Verlee, A.;
Meijer, E. W.; Palmans, A. R. A.; Sánchez, L. The influence of π-
conjugated moieties on the thermodynamics of cooperatively self-
assembling tricarboxamides. Chem. Commun. 2013, 49, 8674−8676.
Complete contact information is available at:
https://pubs.acs.org/10.1021/jacs.1c06125
Author Contributions
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
Dedicated to Prof. Nazario Martín on the occasion of his 65th
anniversary. Financial support by the MICINN of Spain
(PID2020-113512GB-I00, PGC2018-099568-B-I00, and Uni-
dad de Excelencia María de Maeztu CEX2019-000919-M), the
Generalitat Valenciana (PROMETEO/2020/077 and SEJI/
2018/035), the Comunidad de Madrid (NanoBIOCARGO,
P2018/NMT-4389), and European Feder funds (PGC2018-
099568-B-I00) is acknowledged. M.A.M. and J.A. are indebted
to the MICINN for their predoctoral and Ramón-y-Cajal
(RyC-2017-23500) fellowships. J.C. and A.D.-G. acknowledge
the Generalitat Valenciana for their I+d+i postdoctoral
(APOSTD/2017/081) and predoctoral fellowships. R.R.
thanks the Xunta de Galicia for a Postdoctoral Fellowship.
(e) Rödle, A.; Ritschel, B.; Muck-Lichtenfeld, C.; Stepanenko, V.;
̈
Fernández, G. Influence of Ester versus Amide Linkers on the
Supramolecular Polymerization Mechanisms of Planar BODIPY Dyes.
Chem. - Eur. J. 2016, 22, 15772−15777.
(8) Kulkarni, C.; Balasubramanian, S.; George, S. J. What Molecular
Features Govern the Mechanism of Supramolecular Polymerization?
ChemPhysChem 2013, 14, 661−673.
(9) (a) Kulkarni, C.; Bejagam, K. K.; Senanayak, S. P.; Narayan, K.
S.; Balasubramanian, S.; George, S. J. Dipole-Moment-Driven
Cooperative Supramolecular Polymerization. J. Am. Chem. Soc.
2015, 137, 3924−3932. (b) Sarkar, A.; Sasmal, R.; Empereurmot,
C.; Bochicchio, D.; Kompella, S. V. K.; Sharma, K.; Dhiman, S.;
Sundaram, B.; Agasti, S. S.; Pavan, G. M.; George, S. J. Self-Sorted,
Random, and Block Supramolecular Copolymers via Sequence
Controlled, Multicomponent Self-Assembly. J. Am. Chem. Soc. 2020,
142, 7606−7617.
ABBREVIATIONS
■
PBI, perylene bisimide; ACQ, aggregation-caused quenching;
SaS, sergeants and soldiers; MR, majority rules; SP, supra-
molecular polymerization; CT, charge transfer; ECD,
electronic circular dichroism; VCD, vibrational circular
dichroism; MCH, methylcyclohexane; AFM, atomic force
microscopy; HOPG, highly oriented pyrolytic graphite; EQ,
equilibrium; GBSA, generalized Born and surface area
continuum solvation model.
(10) Huang, S.; Yu, H.; Li, Q. Supramolecular Chirality Transfer
toward Chiral Aggregation: Asymmetric Hierarchical Self-Assembly.
Adv. Sci. 2021, 8 (1−20), 2002132.
(11) (a) Palmans, A. R. A.; Meijer, E. W. Amplification of chirality in
dynamic supramolecular aggregates. Angew. Chem., Int. Ed. 2007, 46,
8948−8968. (b) Dorca, Y.; Greciano, E. E.; Valera, J. S.; Gómez, R.;
Sánchez, L. Hierarchy of Asymmetry in Chiral Supramolecular
Polymers: Toward Functional, Helical Supramolecular Structures.
Chem. - Eur. J. 2019, 25, 5848−5864. (c) Valera, J. S.; Gómez, R.;
Sánchez, L. Supramolecular polymerization of [5]helicenes. Con-
sequences of self-assembly on configurational stability. Org. Lett.
2018, 20, 2020−2023. (d) Buendía, J.; Greciano, E. E.; Sánchez, L.
Influence of axial and point chirality in the chiral self-assembly of twin
N-annulated perylenecarboxamides. J. Org. Chem. 2015, 80, 12444−
REFERENCES
■
(1) Fouquey, C.; Lehn, J. M.; Levelut, A.-M. Molecular recognition
directed self-assembly of supramolecular liquid crystalline polymers
from complementary chiral components. Adv. Mater. 1990, 2, 254−
257.
13289
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
1245. (e) Aparicio, F.; Nieto-Ortega, B.; Nájera, F.; Ramírez, F. J.;
López Navarrete, J. T.; Casado, J.; Sánchez, L. Inversion of
supramolecular helicity in oligo-p-phenylene-based supramolecular
polymers: influence of molecular atropisomerism. Angew. Chem., Int.
Ed. 2014, 53, 1373−1377. (f) Xie, Z.; Stepanenko, V.; Radacki, K.;
(24) (a) Ghosh, S.; Li, X.-Q.; Stepanenko, V.; Wu
̈
rthner, F. Control
of H- and J-Type p Stacking by Peripheral Alkyl Chains and Self-
Sorting Phenomena in Perylene Bisimide Homo- and Heteroag-
gregates. Chem. - Eur. J. 2008, 14, 11343−11357. (b) Huber, V.;
Sengupta, S.; Wu
̈
rthner. Structure−Property Relationships for Self-
Wu
̈
rthner, F. Chiral J-aggregates of atropo-enantiomeric perylene
Assembled Zinc Chlorin Light-Harvesting Dye Aggregates. Chem. -
Eur. J. 2008, 14, 7791−7807. (c) Ribó, J. M.; Crusats, J.; Sagués, F.;
Claret, J.; Rubires, R. Chiral Sign Induction by Vortices During the
Formation of Mesophases in Stirred Solutions. Science 2001, 292,
2063−2066.
bisimides and their self-sorting behavior. Chem. - Eur. J. 2012, 18,
7060−7070.
(12) (a) Smulders, M. M. J.; Filot, I. A. W.; Leenders, J. M. A.; van
der Schoot, P.; Palmans, A. R. A.; Schenning, A. P. H. J.; Meijer, E. W.
Tuning the extent of chiral amplification by temperature in a dynamic
supramolecular polymer. J. Am. Chem. Soc. 2010, 132, 611−619.
(b) Smulders, M. M. J.; Stals, P. J. M.; Mes, T.; Paffen, T. F. E.;
Schenning, A. P. H. J.; Palmans, A. R. A.; Meijer, E. W. Probing the
limits of the majority-rules principle in a dynamic supramolecular
polymer. J. Am. Chem. Soc. 2010, 132, 620−626. (c) Greciano, E. E.;
Calbo, J.; Buendía, J.; Cerdá, J.; Aragó, J.; Ortí, E.; Sánchez, L.
Decoding the Consequences of Increasing the Size of Self-
Assembling Tricarboxamides on Chiral Amplification. J. Am. Chem.
Soc. 2019, 141, 7463−7472. (d) Dorca, Y.; Sánchez-Naya, R.; Cerdá,
J.; Calbo, J.; Aragó, J.; Gómez, R.; Ortí, E.; Sánchez, L. Impact of
Molecular Size and Shape on the Supramolecular Co-Assembly of
Chiral Tricarboxamides: A Comparative Study. Chem. - Eur. J. 2020,
26, 14700−14707.
(25) (a) Valera, J. S.; Gómez, R.; Sánchez, L. Kinetic Traps to
Activate Stereomutation in Supramolecular Polymers. Angew. Chem.,
Int. Ed. 2019, 58, 510−514. (b) Dorca, Y.; Naranjo, C.; Ghosh, G.;
Gómez, R.; Fernández, G.; Sánchez, L. Unconventional Chiral
Amplification in Luminescent Supramolecular Polymers Based on
Trisbiphenylaminetricarboxamides. Org. Materials 2020, 02, 041−
046.
(26) (a) Sato, T.; Terao, K.; Teramoto, A.; Fujiki, M. On the
Composition-Driven Helical Screw-Sense Inversion of Chiral-Achiral
Random Copolymers. Macromolecules 2002, 35, 5355−5357.
(b) Nagata, Y.; Nishikawa, T.; Suginome, M. Solvent Effect on the
Sergeants-and-Soldiers Effect Leading to Bidirectional Induction of
Single-Handed Helical Sense of Poly(quinoxaline-2,3-diyl)s Copoly-
mers in Aromatic Solvents. ACS Macro Lett. 2016, 5, 519−522.
(27) (a) Harada, N.; Nakanishi, K. Optical rotatory power of the
benzoate group. J. Am. Chem. Soc. 1968, 90, 7351−7352. (b) Harada,
N.; Chen, S.-M. L.; Nakanishi, K. Quantitative definition of exciton
chirality and the distant effect in the exciton chirality method. J. Am.
Chem. Soc. 1975, 97, 5345−5352. (c) Swathi, K.; Sissa, C.; Painelli,
A.; Thomas, K. G. Supramolecular chirality: a caveat in assigning the
handedness of chiral aggregates. Chem. Commun. 2020, 56, 8281−
8284.
(28) (a) Greciano, E. E.; Rodríguez, R.; Maeda, K.; Sánchez, L.
Disclosing chirality in consecutive supramolecular polymerizations:
chiral induction by light in N-annulated perylenetetracarboxamides.
Chem. Commun. 2020, 56, 2244−2247. (b) Nieto-Ortega, B.; García,
F.; Longhi, G.; Castiglioni, E.; Calbo, J.; Abbate, S.; López Navarrete,
J. T.; Ramírez, F. J.; Ortí; Sánchez, L.; Casado, J. On the handedness
of helical aggregates of C3-tricarboxamides: a multichiroptical
characterization. Chem. Commun. 2015, 51, 9781−9784. (c) Smulders,
M. M. J.; Buffeteau, T.; Cavagnat, D.; Wolffs, M.; Schenning, A. P. H.
J.; Meijer, E. W. C3-Symmetrical Self-Assembled Structures
Investigated by Vibrational Circular Dichroism. Chirality 2008, 20,
1016−1022. (d) Brizard, A.; Berthier, D.; Aimé, C.; Buffeteau, T.;
Cavagnat, D.; Ducasse, L.; Huc, I.; Oda, R. Molecular and
supramolecular chirality in gemini-tartrate amphiphiles studied by
electronic and vibrational circular dichroisms. Chirality 2009, 21,
E153−E162.
(13) (a) Buendía, J.; García, F.; Yélamos, B.; Sánchez, L. Transfer
and amplification of chirality in Phe-based C3-symmetric non-ionic
amphiphiles. Chem. Commun. 2016, 52, 8830−8833. (b) Kulkarni, C.;
Korevaar, P. A.; Bejagam, K. K.; Palmans, A. R. A.; Meijer, E. W.;
George, S. J. Solvent Clathrate Driven Dynamic Stereomutation of a
Supramolecular Polymer with Molecular Pockets. J. Am. Chem. Soc.
2017, 139, 13867−13875.
(14) Greciano, E. E.; Calbo, J.; Ortí, E.; Sánchez, L. N-Annulated
Perylene Bisimides to Bias the Differentiation of Metastable
Supramolecular Assemblies into J- and H-Aggregates. Angew. Chem.,
Int. Ed. 2020, 59, 17517−17524.
(15) Mei, J.; Leung, N. L. C.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B.
Z. Aggregation-Induced Emission: Together We Shine, United We
Soar! Chem. Rev. 2015, 115, 11718−11940.
(16) Wurthner, F.; Saha-Möller, C. R.; Fimmel, B.; Ogi, S.;
̈
Leowanawat, P.; Schmidt, D. Perylene Bisimide Dye Assemblies as
Archetype Functional Supramolecular Materials. Chem. Rev. 2016,
116, 962−1052.
(17) ten Eikelder, H. M. M.; Markvoort, A. J.; de Greef, T. F. A.;
Hilbers, P. A. J. An equilibrium model for chiral amplification in
supramolecular polymers. J. Phys. Chem. B 2012, 116, 5291−5301.
(18) Wurthner, F.; Kaiser, T. E.; Saha-Möller, C. R. J-Aggregates:
̈
From Serendipitous Discovery to Supramolecular Engineering of
Functional Dye Materials. Angew. Chem., Int. Ed. 2011, 50, 3376−
3410.
(29) Mabesoone, M. F. J.; Palmans, A. R. A.; Meijer, E. W. Solute−
Solvent Interactions in Modern Physical Organic Chemistry:
Supramolecular Polymers as a Muse. J. Am. Chem. Soc. 2020, 142,
19781−19798.
(19) Bannwarth, C.; Ehlert, S.; Grimme, S. GFN2-xTBAn
Accurate and Broadly Parametrized Self-Consistent Tight-Binding
Quantum Chemical Method with Multipole Electrostatics and
Density-Dependent Dispersion Contributions. J. Chem. Theory
Comput. 2019, 15, 1652−1671.
(20) Hestand, N. J.; Spano, F. C. Expanded Theory of H- and J-
Molecular Aggregates: The Effects of Vibronic Coupling and
Intermolecular Charge Transfer. Chem. Rev. 2018, 118, 7069−7163.
(21) Hestand, N. J.; Spano, F. C. Interference between Coulombic
and CT-mediated couplings in molecular aggregates: H- to J-
aggregate transformation in perylene-based π-stacks. J. Chem. Phys.
2015, 143, 244707.
́
́
(30) (a) Slęczkowski, M. L.; Mabesoone, M. F. J.; Slęczkowski, P.;
Palmans, A. R. A.; Meijer, E. W. Competition between chiral solvents
and chiral monomers in the helical bias of supramolecular polymers.
Nat. Chem. 2021, 13, 200−209. (b) George, S. J.; Tomovic, Z.;
Schenning, A. P. H. J.; Meijer, E. W. Insight into the chiral induction
in supramolecular stacks through preferential chiral solvation. Chem.
Commun. 2011, 47, 3451−3453. (c) Isare, B.; Linares, M.; Zargarian,
L.; Fermandjian, S.; Miura, M.; Motohashi, S.; Vanthuyne, N.;
Lazzaroni, R.; Bouteiller, L. Chirality in Dynamic Supramolecular
Nanotubes Induced by a Chiral Solvent. Chem. - Eur. J. 2010, 16,
173−177. (d) Palmans, A. R. A.; Vekemans, J. A. J. M.; Havinga, E. E.;
Meijer, E. W. Sergeants-and-Soldiers Principle in Chiral Columnar
Stacks of Disc-Shaped Molecules with C3 Symmetry. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 2648−2651.
(22) Hong, Y.; Kim, J.; Kim, W.; Kaufmann, C.; Kim, H.; Wurthner,
̈
F.; Kim, D. Efficient Multiexciton State Generation in Charge-
Transfer-Coupled Perylene Bisimide Dimers via Structural Control. J.
Am. Chem. Soc. 2020, 142, 7845−7857.
(23) Palmans, A. R. A.; Meijer, E. W.; Denmark, S. E.
Stereochemical language in supramolecular polymer chemistry: How
we can do better. J. Polym. Sci. 2021, 59, 1171−1174.
(31) Kulkarni, C.; Korevaar, P. A.; Bejagam, K. K.; Palmans, A. R. A.;
Meijer, E. W.; George, S. J. Solvent Clathrate Driven Dynamic
13290
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291

Journal of the American Chemical Society
pubs.acs.org/JACS
Article
Stereomutation of a Supramolecular Polymer with Molecular Pockets.
J. Am. Chem. Soc. 2017, 139, 13867−13875.
(32) Palmans, A. R. A.; Meijer, E. W. Amplification of chirality in
dynamic supramolecular aggregates. Angew. Chem., Int. Ed. 2007, 46,
8948−8968.
(33) Dehm, V.; Chen, Z.; Baumeister, U.; Prins, P.; Siebbeles, L. D.
A.; Wurthner, F. Helical Growth of Semiconducting Columnar Dye
̈
Assemblies Based on Chiral Perylene Bisimides. Org. Lett. 2007, 9,
1085−1088.
13291
https://doi.org/10.1021/jacs.1c06125
J. Am. Chem. Soc. 2021, 143, 13281−13291