En Route Towards the Control of Luminescent, Optically-Active 3D Architectures

Article abstract of DOI:10.1002/anie.202011368

π-Extended systems are key components for the development of future organic electronic technologies. While conceiving molecules with improved properties is fundamental for the evolution of materials science, keeping control over the 3D arrangement of molecules represents an ever-expanding challenge. Herein, a synthetic protocol to replace carbon atoms of π-systems by dissymmetric phosphorus atoms is reported; in particular, it allowed for conceiving new fused phosphapyrene derivatives with improved properties. The presence of dissymmetric phosphorus atoms precluded the formation of excimers. X-ray diffraction revealed that, meanwhile, strong intermolecular interactions are taking place in the solid state. The phosphapyrenes photoluminesce in the visible region with high quantum yields; importantly, they are CD-active. In addition, the unique non-planar features of phosphorus atoms allowed for the control of the 3D arrangement of molecules, rendering lemniscate-like structures. Based on our discoveries, we envisage the possibility to construct higher-order, chiral 3D architectures from larger phosphorus-containing π-systems.

Full text of DOI:10.1002/anie.202011368

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Accepted Article
Title: En Route Towards the Control of Luminescent, Optically-Active
3D Architectures
Authors: Carlos Romero Nieto, Frank Rominger, and Philip Hindenberg
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10.1002/anie.202011368
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RESEARCH ARTICLE
En Route Towards the Control of Luminescent, Optically-Active
3D Architectures
Philip Hindenberg,[a] Frank Rominger[a] and Carlos Romero-Nieto*[a],[b]
strong impact on the molecular properties. Pyrene derivatives
have focused the attention of researchers for decades because of
their blue photoluminescence with high quantum efficiency;[11]
however, they present two main drawbacks: a) pyrenes emit in
the UV,[12] which is unsuitable for optical applications, and b) they
have a high tendency to form excimers by intermolecular
interactions already at low concentrations, leading to a broad, red-
shifted emission with reduced quantum yield.[12-13] Thus, excimers
are a hurdle task to overcome for luminescent purposes.
Synthetic strategies have been proposed to circumvent excimer
formation in p-extended systems including pyrenes; they mostly
involve the decoration of the main framework with bulky
Abstract: p-Extended systems are key components for the
development of future organic electronic technologies. While
conceiving molecules with improved properties is fundamental for the
evolution of materials science, keeping control over the 3D
arrangement of molecules represents an ever-expanding challenge.
Herein, a synthetic protocol to replace carbon atoms of p-systems by
dissymmetric phosphorus atoms is reported; in particular, it allowed
for conceiving new fused phosphapyrene derivatives with improved
properties. The presence of dissymmetric phosphorus atoms
precluded the formation of excimers. X-ray diffraction revealed that,
meanwhile, strong intermolecular interactions are taking place in the
solid state. The phosphapyrenes photoluminesce in the visible region
with high quantum yields; importantly, they are CD-active. In addition,
the unique non-planar features of phosphorus atoms allowed for the
control of the 3D arrangement of molecules, rendering lemniscate-like
structures. Based on our discoveries, we envisage the possibility to
construct higher-order, chiral 3D architectures from larger
phosphorus-containing p-systems.
functionalizations
to
preclude
the
intermolecular
interactions[11a],[14],[15] However, despite a few exceptions, the
latter strategy leads, among others, to randomly organized
molecules.[14b],[15],[16] Thus, an ideal solution – also applicable to a
variety of p-extended systems – would be to insert (hetero)atomic
components into the main framework that could allow not only for
the modulation of the properties but also for the control of the
molecular arrangement, with the possibility to create well-defined
3D motifs. Notwithstanding, this concept remains underdeveloped.
In particular, despite the replacement of carbon atoms of pyrenes’
core by other heteroatoms dates from the 1960s,[17] the use of
phosphorus atoms in that context has received little attention. This
is surprising. Phosphorus atoms present unique electronic and
structural features to develop new strategies for tackling the
above-mentioned ongoing challenges of p-extended systems: a)
phosphorus centers may act as electron donors or acceptors,[18]
and b) once embedded into p-systems, they accept up to two out-
of-plane substituents,[19] fragments E1 and E2 (Figure 1a), which
in turn may impact the electronic properties through unique
hyperconjugative effects.[18b],[20] Notably, the E1 and E2
substituents may be alkyl or aryl groups, halogens, transition
metals or main-group elements among others.[18,19]
Modern organic chemistry has led to a rapid evolution of p-
extended systems since they are pivotal for the development of
future technologies. This is due to their capacity to absorb and
(often) emit light, their accessible redox processes and/or their
charge transport properties.[1] In the last years, scientists have
devoted extensive research efforts to tailor the electronic
properties of p-extended systems to particular applications.[1],[2]
Thus, important advances have been made in the bottom up
synthesis of all-carbon architectures including nanoribbons,[3]
acenes,[4] rylenes,[5] helicenes,[6] and truxenes.[7] However,
conceiving molecules with new intriguing features is not sufficient.
Intermolecular interactions ultimately define the magnitude of the
molecular properties; luminescence, electronic and structural
properties of the materials strongly depend on the spatial
disposition of molecules. This has triggered a plethora of
investigations towards the precise organization of molecules by
means of either covalent,[8] non-covalent[9] or coordinative
interactions.[10] Nevertheless, despite the progresses in the field,
the development of strategies for controlling the 3D arrangement
of molecules has become an everlasting scientific challenge.
In that context, pyrenes are a representative example of p-
extended system in which the molecular arrangement has a
With the latter features in mind, we targeted to use the out-of-
plane phosphorus substituents as vector directors to
synergistically control the 3D organization of p-extended
molecules while modulating the optoelectronic properties. In addi-
[a]
[b]
P. Hindenberg, Dr. F. Rominger, Priv.-Doz. Dr. C. Romero-Nieto
Ruprecht-Karls-Universität Heidelberg
Organisch-Chemisches Institut
Im Neuenheimer Feld 270, 69120 Heidelberg (Germany)
E-mail: carlos.romero.nieto@oci.uni-heidelberg.de
Priv.-Doz. Dr. C. Romero-Nieto
Universidad de Castilla-La Mancha
Faculty of Pharmacy
Calle Almansa 14 – Edif. Bioincubadora, 02008, Albacete (Spain)
Supporting information for this article is given via a link at the end of
the document.
Figure 1. a) Representation of the phosphorus out-of-plane substituents E1 and
E2 as potential vector directors for building up well-defined 3D architectures. b)
Designed novel phosphapyrenes 1 and 2.
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tion, utilizing two different out-of-plane substituents E1 and E2
would afford dissymmetric phosphorus centers, which could
potentially provide intrinsic optical activity to the p-systems
(Figure 1a). It is noteworthy that luminescent optically active
molecules are particularly attractive since they are key for the
development of applications such as encrypted transport, anti-
glare displays, optical communication, etc.;[21] they are
consequently receiving increasing attention over the last few
years.
The requirements for the precise organization of molecules are:
a) the p-system must necessarily present more than one
dissymmetric phosphorus atom, and b) the latter should not be
invertible to keep control over the orientation of the p-system.
Importantly, the number of available structures in literature with
such particular characteristics is very limited.[19a, 19e] As a matter
of fact, synthetic methodologies to replace carbon atoms in p-
systems by dissymmetric phosphorus centers are rather scarce.
Thus, to demonstrate the feasibility of our concept, we designed
the novel phosphapyrenes 1 and 2 (Figure 1b). Note that they
contain two fused thiophenes through different patterns to
investigate the influence of the latter rings into the molecular
properties. Both molecules 1 and 2 possess two dissymmetric
phosphorus centers as cornerstones for the construction of the
3D structures. For each out-of-plane E1 and E2 phosphorus
substituents, we chose an oxygen atom and a phenyl ring,
respectively. P-O bonds are strongly polarized and could be
potentially used as vector directors to link the molecular
components by electrostatic non-covalent interactions through
appropriate linkers.
The first bottleneck of our approach was the synthesis of 1 and 2.
To that end, we initially designed synthetic strategies A and B
(Scheme 1); they involve a double cyclization from phosphine
moieties placed either at the peripheral aromatic substituents
(intermediate 5) by electrophilic aromatic substitution (SEAr) or at
the naphthalene core (compound 9) through metal-catalyzed
reaction, respectively.
Strategy A was unsuccessful. Suzuki coupling at the 1,5-positions
of the naphthalene derivative 3 with the corresponding aromatic
rings, led to precursor 4 (see Supporting Information for details).
However, subsequent double cyclization by SEAr, i.e. treatment of
t
4 with BuLi at low temperature followed by the reaction with
dichlorophenylphosphane,[22] did not lead to the targeted
compounds 1 and 2. Further optimizations by modifying the
reaction temperature were fruitless. We then moved to strategy B
(Scheme 1).
Scheme 1. Synthetic routes A, B and C for the preparation of phosphapyrenes 1 and 2. i) BBr3; ii) PhNTf2, Et3N, DMAP. FG = Functional Group. [Catalyst] =
Pd(OAc)2. See Supporting Information for details.
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Figure 2. X-Ray structures of 1-cis, 1-trans and 2-cis, 2-trans. Numbers in red indicate intermolecular distances in angstrom.
Here, the placement of the phosphine moieties at the naphthalene
core (compound 9), requires the preparation of the 1,5-dihalo
intermediate 8. We undertook its synthesis from the 1,5-dihydroxy
derivative 6 (see Supporting Information for details). However, the
1,5-positions turned out to be highly unreactive. Direct
halogenation of the hydroxy groups with Ph3PBr2, POCl3,
POCl3/PCl5, Ph3PCl2 or PhPCl4 were unsuccessful to obtain
molecule 8. The transformation of the hydroxy moieties into good
leaving groups such as SO3H, OTf, SC(O)NMe2 and OC(O)CMe3
ultimately did not allow us to introduce the targeted halogen atoms
into the 1,5-positions, either through nucleophilic aromatic
substitution or by metal-catalyzed reactions. Importantly,
reactions from the model compound naphthalene 1,5-ditriflate
with, for example, Pd2(dba)3 and KBr under the same conditions
utilized for 7 (FG = OTf) afforded the corresponding 1,5-
dibromonaphthalene (see Supporting Information for details).
This supports the deactivation of the 1,5-positions by the
peripheral aromatic substituents; further investigation of this fact
goes beyond the scope of this investigation and will be published
elsewhere.
In views of the impossibility to access compound 9 through
strategy B, we re-designed our approach to incorporate the
phosphorus moieties into the 1,5-positions before the introduction
of the peripheral aromatic substituents (strategy C, Scheme 1).
Thus, we incorporated the diphenylphosphine oxide fragments
t
from 10 by halogen-lithium interchange with BuLi, reaction with
chlorodiphenylphosphane and subsequent oxidation obtaining
derivative 11. The transformation of the methoxy groups of 11 into
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triflates (compound 13) led to the required reactant to introduce
the peripheral aromatic substituents (see Supporting Information
for details). To this end, we chose thiophene moieties; they can
be regioselectively functionalized through a variety of reactions,
from lithiation to metal-catalyzed transformations. Whereas
several attempts via Stille cross-coupling reactions with different
conditions failed, double Suzuki coupling from 13 yielded
compounds 14a-b (Scheme1) (see Supporting Information for
details). The final step, the double cyclization, was critical. Taking
into consideration the versatile reactivity of thiophenes towards C-
H insertions,[23] we started considering reactions based on
palladium-catalyzed P-C bond formations through direct C-H
activation at the thiophene rings. The reaction would necessarily
occur through a seven-membered P-Pd carbocycle (7MP-Pd),[24]
even though the latter 7MP-Pd intermediates can hardly be found
in literature.
all optimized geometries are essentially planar. HOMO and
LUMO appear homogeneously distributed over the entire surface
including the phosphorus atoms (Figure 3a and S5). This points
to an efficient electronic delocalization of the frontier molecular
orbitals along the phosphapyrene structures. Even though the
differences are rather small, the HOMO and LUMO energies from
the cis- and trans-derivatives of 1 and 2 vary slightly (Table S3).
This may be attributed to the proximity of the phenyl P-
substituents in the cis-molecules. Compounds 1-cis and 1-trans,
present a LUMO energy at -2.94 eV and HOMO energies at -6.21
and -6.20 eV, respectively (Table S3). In turn, the LUMO energies
of 2-cis and 2-trans are at -2.83 and -2.84 eV, whereas the HOMO
energies are -6.32 and -6.3 eV, respectively. These values are in
stark contrast with the frontier molecular orbital energies of
pristine pyrene; i.e. LUMO and HOMO are -1.83 and -5.65 eV
(Table S3, Figure S7). Thus, the bandgap is remarkably reduced
from 3.82 eV for the parent pyrene to 3.27 and 3.26 eV for 1-cis
and 1-trans, and 3.48 and 3.46 eV for 2-cis and 2-trans. Extending
the conjugation through the fused thiophenes could be the
explanation. However, calculations of the dithiophene-fused
pyrene analogues to 1 and 2 (fused pyrenes 1 and 2, Figures S6)
revealed that, while the LUMO is slightly reduced compared to the
parent pyrene as a result of extending the conjugation from -1.83
to -1.98 eV for the fused pyrene 1, the enrichment of the pyrene
core with further electronic density from the thiophene moieties
increases the HOMO from -5.65 to -5.38 eV (Table S3). As
evidenced in Figure S7, embedding two phosphorus atoms within
the pyrene core appears, therefore, to be responsible for the
pronounced reduction of LUMO and HOMO levels.
To test the cyclization reaction, we first reduced the phosphorus
centers of 14 with HSiCl3 to yield 9a-b. The cyclization reaction
turned out to be intriguing. The use of varying catalytic amounts
of Pd(OAc)2 (from 2 to 10 mol%), with different solvents (toluene
or dimethylformamide) and reaction temperatures up to 130 ºC
did not lead to any ring closure; only the starting materials were
detected in the reaction controls. However, after
a long
optimization process, we found out that the treatment of 9a-b with
3.2 equivalents of Pd(OAc)2 successfully led not only to close both
phosphorus rings through direct C-H activation but also to cleave
one of the phenyl substituents of the phosphorus atom; oxidation
of the phosphorus centers took place during the standard reaction
workup. As a result, we successfully obtained 1 and 2 with two
dissymmetric phosphorus atoms; i.e. with the desired oxygen
atom as vector director to construct 3D architectures. Importantly,
both derivatives were photo- and air-stable; we did not observe
any decomposition over months. Such a stability allowed us to
separate the respective cis- and trans-isomers, i.e. derivatives
with the P-phenyl substituents either at the same or different
planes of the molecule, by column chromatography. It is
noteworthy that the phosphorus atoms did not invert even at
temperatures up to 130 ºC; a characteristic that was already
observed in other phosphorus p-systems.[25]
The structures of the cis- and trans-isomers of compounds 1 and
2 obtained by X-ray diffraction are shown in Figure 2 (see Figures
S1 to S4 for bond distances analyses). Indeed, all molecules
present two dissymmetric phosphorus centers. Their molecular
frameworks are planar, although the phosphorus atoms appear
slightly out-of-plane (Figures S1 to S4). This was already
observed in p-systems with cationic phosphorus centers.[26]
Remarkably, the cis-isomers of 1 and 2 present similar packing in
the solid state; i.e. the position of the sulfur atoms does not
influence the molecular packing. Compounds 1-cis and 2-cis
intercalate with each other with p-p distances of 3.36 and 3.32 Å,
respectively (Figures 2, S1 and S3). Thus, strong
phosphapyrene-phosphapyrene interactions are observed in the
solid state. On the contrary, while 1-trans also presents
intercalated molecules with p-p distances of 3.39 Å, 2-trans
displays slipped p-stacks arranged along one axis and
herringbone pattern between stacks (Figure 2).
Figure 3. a) HOMO and LUMO distribution of 1 and 2. b) Absorption and
emission spectra of 1 and 2 from DCM solutions. c) 3D emission mapping of
compound 1-cis.
Initial investigations on the electronic properties of the
phosphapyrenes came from DFT calculations at the B3LYP/6-
311+G(d) level of theory. In agreement with the X-ray structures,
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The energetic differences between 1 and 2 were corroborated by
electrochemical measurements (Table S5 and Figures S8 and
S9). In line with the theoretical calculations, the behavior of
isomers cis and trans of compound 1 and 2 differed. All
derivatives present an irreversible oxidation process; they
maximize at 1.37 and 1.38 V for the 1-cis and 1-trans, and 1.26
and 1.36 V for 2-cis and 2-trans, respectively. The reduction
processes are notably different. Compound 1-cis shows a
reversible reduction at -0.86 V[27] and a quasi-reversible reduction
at -1.3 V. On the other hand, 1-trans presents two irreversible
reductions at -0.88 V and at -1.24 V (Figure S8). In turn, 2-cis
shows two quasi-reversible reductions at -0.98 and -1.45 V, and
2-trans two irreversible ones at -0.95 and -1.43 V. The differences
between isomers agree with distinct electronic reorganizations
after the redox processes. All in all, it is worth highlighting that the
presence of two phosphorus atoms converts the pyrene moieties
into excellent electron acceptors reducing the reduction potential
from -2.04 V for parent pyrenes[28] to c.a. -0.87 V and -0.97 for 1
and 2, respectively.
Steady-state spectroscopy revealed a peculiar scenario. Typical
absorption spectrum of genuine pyrene features three absorption
bands in the UV; i.e. 308, 320 and 336 nm.[29] Following a
comparable pattern, although red shifted, 1-cis and 1-trans exhibit
maxima at 385, 405 and 428 nm with an additional high-energy
band at 266 nm, whereas the absorption spectra of 2-cis and 2-
trans maximize at 366, 385 and 406 nm (Figure S11 and Table
S6). Estimations from TD-DFT calculations at the B3LYP/6-
311+G(d) level of theory assign a pure HOMO-LUMO transition
for the lowest energetic bands; their corresponding theoretical
lmax fit quite well with the experimental values (Table S4 and
Figure S10). The more energetic bands involve a combination of
electronic transitions from different molecular orbitals (Table S4).
Note that the latter combinations differ within the cis and trans
derivatives. The theoretical lmax of the more energetic absorption
bands are however underestimated due to, presumably, the
intrinsic limitation of the utilized theoretical base function.
The concentration-dependent emission of pyrenes has been well
documented.[12-13] Already at low concentrations, they tend to form
excimers by intermolecular interactions; i.e. the emission spectra
of pyrenes feature a broad and red-shifted band with low quantum
yield. [12-13] Along those lines, we investigated the absorption and
emission spectra of the phosphapyrenes at high concentrations.
Importantly, we did not observe any changes in neither the
absorption nor emission spectra at concentration as high as 10-4
M.[32] In other words, the formation of excimers was prevented by
the introduction of phosphorus centers into the pyrenes’ core.
The advantage of our synthetic protocol lies in the possibility to
introduce phosphorus atoms with two different out-of-plane
substituents (i.e. chiral centers) into p-extended systems. Thus,
the presence of such phosphorus centers within the
phosphapyrene frameworks motivated us to investigate their
interaction with polarized light by circular dichroism spectroscopy
(CD). Indeed, the inclusion of dissymmetric phosphorus atoms
induced an optical response into typically non-active pyrenes.
From dichloromethane solutions, the trans isomers from both 1
and 2 showed a negative Cotton effect (Figure 4, S14 and S15).
Both CD spectra fit quite well with their respective absorption
features. The ellipticity of 1-trans minimizes at 266, 385, 405 and
428 nm, whereas 2-trans presents minima at 366, 385 and 406
nm. Thus, the insertion of phosphorus atoms into pyrenes’ core
led to defined molecular packings, modulating the optoelectronic
properties, avoiding excimer formations and inducing optical
activity.
In stark contrast with the parent pyrenes, the phosphapyrenes
photoluminesce in the visible region of the electromagnetic
spectrum (Figures 3 and S11 to S13); i.e. the phosphorus atoms
in combination with their two out-of-plane substituents lead to
modulating the optical properties of the p-core. Diluted
dichloromethane solutions of pristine pyrene present an emission
spectrum in the UV that is characterized by three main vibrational
peaks at 375, 385 and 397 nm.[30] In contrast, the emission
features of 1 and 2 mirror-image the absorption spectra with
prominent bands in the blue region of the visible spectrum; i.e. 1-
cis and 1-trans display maxima at 446, 468 and 502 nm and
derivatives 2-cis and 2-trans at 419, 443 and 469 nm (Figures 3b
and S11 to S13). All derivatives were photostable. This allowed
us to map the 3D emission of 1 and 2 (Figures 3c, S12, S13); it is
highly relevant to identify the excitation wavelength that leads to
the most intense photoluminescence. In turn, the emission color
coordinates are x = 0.145; y = 0.136 for 1 and x = 0.153; y = 0.053
for 2. The fluorescence quantum yields (F) are comparable to the
monomeric pristine pyrene (0.32);[31] i.e. F = 0.24 and 0.34 for 1-
cis and trans and F = 0.2 and 0.24 for 2-cis and trans, respectively
(Table S6).
Figure 4. Absorption (up) and CD spectra of 1-trans and 2-trans from DCM
solutions
Once we corroborated the impact of inserting phosphorus atoms
into the pyrenes’ core, we investigated the possibility to use the
out-of-plane oxygen atoms as vector directors to construct 3D
architectures by non-covalent interactions. Molecular rings are
suitable motifs to verify the directionality of the phosphorus
centers. Thus, we designed a proof-of-principle model structure
(Figure 5); it consists of two 1-cis molecules – whose oxygen
atoms are at the same plane of the main framework – linked by
halogen bonds through the 1,4-diiodotetrafluorobezene (DITFB)
(Figure 5). The interaction of such rings along one edge could
potentially lead to tubular structures.
The assembly of the molecular rings turned to strongly depend on
the employed solvent. Indeed, the use of EtOH and DCM as
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Figure 5. (Top left) Representation of the Targeted Model designed from the 1-cis derivatives and the diiodotetrafluorobezene (DITFB). (Top right) X-ray of the
Experimental Model A. (Bottom) Representation and X-ray structure of the Experimental Model B.
solvents successfully led to the formation of the experimental
model A (Figure 5); i.e. molecular rings, although tilted, with PO···I
distances between 2.86 and 3.63 Å.
2.91 Å. It is worth noting that the phosphapyrenes interact at the
center of the ring through p-p interactions of 3.66 Å from the P-
phenyl substituents, forming a lemniscate-like shape (Figure 5,
Experimental Model B, top view). Finally, despite the latter
lemniscate-like structures did not arrange into the targeted tubular
architectures, they organized in the 3D space as well-defined
porous architecture through additional intermolecular interactions
(Figure 5, Experimental Model B, front view). Thus, the
phosphorus centers of the phosphapyrenes may indeed be
utilized to control the 3D arrangement through soft halogen bond
interactions. As subsequent step, we envisage the possibility to
utilize the phosphorus atoms as cornerstone to conceive
catenanes but based on covalent bonds. The predicted structure
by theoretical calculations is shown in Figure 6; the synthesis is
currently engaged in our laboratories.
Intermolecular distances of 3.47 Å between molecular planes
(Figure 5) pointed that p-p interactions in the solid state are
responsible for such a tilted model. However, the molecular rings
did not lead to tubular structures; instead, the latter rings were
piling in one axis (see Figure S16). Further investigations with
different solvent mixtures revealed that the 3D assembly of the
phosphapyrenes could be rearranged into larger and more
complex molecular rings by using a mixture of CHCl3 and pentane
(Experimental Model B, Figure 5).
In summary, we describe a strategy to keep control over the 3D
arrangement of molecules while providing exciting new properties
to p-systems. In particular, we report a synthetic protocol to
replace carbon atoms of p-architectures by dissymmetric
phosphorus atoms; it allowed to prepare novel, fused
phosphapyrene derivatives. The inclusion of dissymmetric
phosphorus atoms into pyrenes’ core led to the control of the
intermolecular interactions avoiding the formation of excimers in
solution while maintaining pyrene-pyrene interactions in the solid
state. Supported by DFT calculations, the HOMO-LUMO energy
gap was reduced compared to pristine pyrenes. As a result, the
phosphapyrenes photoluminesce in the visible region of the
electromagnetic spectrum with comparable QYs to that of pristine
pyrenes. Inserting dissymmetric phosphorus centers into the
pyrene’ cores induced optical activity. In addition, the presence of
the phosphorus atoms converted pyrenes into improved building
blocks with the possibility to keep control over their 3D
Figure 6. Optimized catenane structure based on molecule 1-cis, built up by
quaternization of the phosphorus centers.
Thus, the molecular ring expanded to twelve components bonded
by halogen bonds with shorter PO···I distances between 2.87 and
arrangement. In fact, as
a proof-of-concept towards more
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Thanikachalam, S. Panimozhi, J. Photochem. Photobiol., A: Chemistry
2017, 346, 296-310.
complex architectures, we constructed well-defined molecular
rings of different sizes by non-covalent interactions that organized
into porous 3D frameworks. Based on our synthetic strategy and
discoveries, we envisage the investigation of superior 3D
architectures from larger phosphorus-containing p-systems.
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Acknowledgements
C.R.-N. and P.H. thank the Organisch-Chemisches Institut of the
University of Heidelberg and the UCLM for the support. P.H.
thanks the Hanns-Seidel-Stiftung for a fellowship. Financial
support from projects RO4899/4-1, SBPLY/17/180501/000518
and RTI2018-101865-A-I00 is gratefully acknowledged.
Keywords: Main group chemistry • phosphorus heterocycles •
organophosphorus materials • optical properties • 3D molecular
arrangement
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This article is protected by copyright. All rights reserved.

10.1002/anie.202011368
Angewandte Chemie International Edition
RESEARCH ARTICLE
Entry for the Table of Contents
P to 3D. A synthetic method to
Philip Hindenberg, Frank Rominger,
Carlos Romero-Nieto*
replace carbon atoms of p-extended
systems by dissymmetric phosphorus
centers was developed. It allowed to
conceive optically-active, luminescent
phosphapyrenes whose dissymmetric
phosphorus atoms could be employed
as cornerstone to keep control over
the 3D arrangement of molecules.
Page No. – Page No.
En Route Towards the Control of
Luminescent, Optically-Active 3D
Architectures
This article is protected by copyright. All rights reserved.