Blue-emitting pyrene-based aggregates

Article abstract of DOI:10.1039/c5cc03616j

The supramolecular polymerization of pyrene imidazoles 1 and 2, governed by H-bonding and C-H···π interactions, yields aggregates showing the characteristic bluish emission pattern of pyrene-based monomers.

Full text of DOI:10.1039/c5cc03616j

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: L. Sanchez, J. S.
Valera, J. Calbo, R. Gómez and E. Orti, Chem. Commun., 2015, DOI: 10.1039/C5CC03616J.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/chemcomm

ChemComm
Page 1 of 5Journal Name
Dynamic Article Links ►
View Article Online
DOI: 10.1039/C5CC03616J
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/xxxxxx
ARTICLE TYPE
Blueꢀemitting pyreneꢀbased aggregates
Jorge S. Valera,a‡ Joaquín Calbo,b‡ Rafael Gómez,a Enrique Ortí*b and Luis Sánchez*a
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
The preparation of 1 and 2 was accomplished by the
5
The supramolecular polymerization of pyreneimidazoles 1
and 2, governed by Hꢀbonding and C−H···π interactions,
yields aggregates showing the characteristic blueish emission
pattern of pyreneꢀbased monomers.
methodology reported by Kumar et al.,6 starting from pyrene, 4ꢀ
45 carboxybenzaldehyde and the corresponding amine (Scheme S1,
ESI). Prior to the synthesis of the final derivatives, two tertꢀbutyl
groups were incorporated at positions 2 and 7 of the pyrene
moiety to increase the solubility of the target compounds. The
chemical structure of 1 and 2 was confirmed by NMR, FTꢀIR and
50 HRMS analysis (see the ESI†).
Since its discovery in 1837 by Laurent,1 pyrene has become
10 one of the most studied polycyclic aromatic hydrocarbons due to
its attractive electronic and photophysical properties, and it has
been widely tested as an active component in organic
electronics.2,3 Pyrene is a blueꢀemitting material with limited
applicability in optoelectronic devices due to its strong tendency
15 to form excimers both in solution and in the solid state. The
formation of excimers redꢀshifts the emission of pyrene and
reduces its intensity.2,3 To improve the emissive properties, big
efforts have been devoted to the structural modification of pyrene
to avoid aggregation and to suppress the quenching effect of the
20 πꢀπ interactions. The optimization of the functional unit of pyrene
and the control of its supramolecular organization are essential
requirements to achieve highꢀperformance in organic electronics
devices. Therefore, a challenging task in pyrene chemistry is the
design of derivatives in which supramolecular order and
25 appropriate blueꢀemitting features can coexist.
Herein, we describe the synthesis and the supramolecular
polymerization of the pyreneimidazoles 1 and 2 endowed with
peripheral achiral and chiral alkyl chains, respectively (Fig. 1).
Using a synergistic experimental and theoretical investigation, a
30 detailed insight into the supramolecular polymerization
mechanism is presented, what is unprecedented for pyreneꢀbased
molecules despite the number of reports that refer to the selfꢀ
assembly of pyrene derivatives.4 1 and 2 have been designed with
a variety of supramolecular interaction motifs that guide their
35 selfꢀassembly by Hꢀbonding interactions between amide groups
and imidazole moieties together with a number of CꢀH···π
dispersion interactions. The organized supramolecular structures
are able to immobilize apolar solvents like cyclohexane forming
gels.5 Notably, the aggregates formed by 1 and 2 show the
40 characteristic blueꢀemitting pattern of pyreneꢀbased monomers.
To unravel the supramolecular polymerization mechanism of 1
and
2,
temperatureꢀdependent
UVꢀVis
spectroscopy
measurements were performed in methylcyclohexane (MCH) as
solvent (Fig. S1 and S2, ESI†). The bands observed at around 355
55 and 400 nm in the UVꢀVis spectra of both 1 and 2 experience a
slight bathochromic shift and a broadening when decreasing the
temperature, what is diagnostic of the aggregation process.
Plotting the variation of the absorbance at 404 nm with the
temperature results in cooling curves with an apparent sigmoidal
60 shape, characteristic of an isodesmic supramolecular
polymerization mechanism (Fig. S1b and S2b, ESI†).7
To obtain a complete set of thermodynamic parameters, the
UVꢀVis cooling curves derived for 1 and 2 were fitted to the
model recently reported by ten Eikelder et al. (EQ model), in
65 which the equilibria between monomers and supramolecular
polymers are considered, together with a modified version of the
van’t Hoff analysis.8 The thermodynamic parameters obtained for
1 and 2 demonstrate that the branched nature of the peripheral
alkyl chain in 2 plays a relevant role, showing significantly
70 different values of the enthalpy of elongation (∆He), the entropy
of elongation (∆S) and the nucleation penalty (∆Hn) (Table 1).
Table 1. Thermodynamic parameters for 1 and 2 (MCH).
1
2
ꢀHe [kJ/mol]
ꢀS [J/Kmol]
ꢀHn [kJ/mol]a
ꢀG [kJ/mol]a
–72±1
ꢀ52±1
–122±3
–7.1±0.2
ꢀ35.88
5.5 × 10–2
2.04 × 106
1.13 × 105
ꢀ58±2
ꢀ11.5±0.2
ꢀ34.73
σ
[ꢀ]b
9.3 × 10–3
1.5 × 106
1.21 × 104
Ke [L/mol]b
Kn [L/mol]b
a The nucleation penalty ꢀHn is negative, which implies that the enthalpy gain
b
is smaller for nucleation compared to elongation. The equilibrium constants
75 for elongation (Ke) and dimerization (Kn), and the cooperativity factor (
Ke) are calculated at 298 K.
σ = Kn /
In contrast, the total free energy (∆G) is very similar in both
pyrene derivatives (~35 kJ/mol). Especially interesting is the
calculated value of the degree of cooperativity
σ, which
80 corresponds to the quotient between the nucleation (Kn) and the
elongation (Ke) binding constant values. Despite the sigmoidal
Fig. 1 Chemical structure of pyreneimidazoles 1 and 2
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 1

ChemComm
Page 2 of 5
View Article Online
DOI: 10.1039/C5CC03616J
shape of the cooling curves,
σ
presents values of 5.5 × 10–2 and
capable to exhibit the aboveꢀmentioned emissive features? To
give an appropriate answer to these questions, a synergistic
experimental and theoretical study was performed. First, FTIR
9.3 × 10–3 for compounds 1 and 2, respectively, which denote a
certain degree of cooperativity in the supramolecular
polymerization of these pyrene derivatives (Table 1).
1
50 and H NMR spectroscopies were used. In the FTIR spectra of 1
5
Interestingly, the selfꢀassembling properties of compounds 1
and 2 are similar and both readily form gels in cyclohexane as
solvent at a concentration of ca. 1 wt%. The organogels exhibit
blue emission upon irradiation at 364 nm (Fig. 2).
and 2, the Amide I and Amide II bands at around 1635 and 1560
cm–1, diagnostic of the formation of Hꢀbonds between the amide,
1
are visible (Fig. S6, ESI†).13 In the concentrationꢀdependent H
NMR experiments, the triplet at
δ ~ 6.3, corresponding to the
The emission properties of 1 and 2 were investigated in CHCl3 55 amide groups, and the resonance corresponding to the imidazole
10 and MCH. The emission spectra in MCH at 1 × 10–5 M,
conditions under which 1 and 2 are aggregated, show the typical
pattern of monomeric pyrene with maxima at 400, 423 and 447
nm (Fig. 2 and Fig. S3, ESI†). In contrast, the emission spectra in
N−H group (δ ~ 13) show a downfield shift with increasing
concentrations that is indicative of the formation of an array of Hꢀ
bonds (Fig. S7, ESI†). On the other hand, the aromatic
resonances, used to envisage the intermolecular interactions
CHCl3, a good solvent that facilitates the solvation of isolated 60 between the aromatic fragments, show an opposite shifting of the
15 molecules, at 1 × 10–5 M feature broad and structureless bands
centred at 448 nm, evidencing the formation of pyrene excimers
(Figure 2 and S3).9,10 Compounds 1 and 2 show a remarkable
fluorescence quantum yield (φf) in the aggregated state (MCH, 1
δ
values upon increasing the concentration. Thus, whilst the
resonance of pyrene at ~ 9 experiences a shielding effect, one of
the anisochronous protons at the para position of the benzamide
moiety ( ~ 8.2) shifts to lower values. A rotatingꢀframe
δ
δ
δ
× 10–5 M) of 0.43. A lower φf value is measured for the excimer 65 Overhauser effect spectroscopy (ROESY) NMR experiment in a
20 formed in CHCl3 (0.38 and 0.22 for 1 and 2, respectively). To the
best of our knowledge, this unusual emissive behaviour has only
been described for a pyrene derivative endowed with a chiral
oligo(glutamic acid) side chain,11 and it was ascribed to a helical
supramolecular organization.
concentrated solution of 1 (45 × 10–3 M, CDCl3, 298 K) was
therefore conducted to extract more information about the
supramolecular organization of this pyrene derivative.14
25
Fig. 2 a) Emission spectra of 1 in MCH and CHCl3 (298 K, 1 × 10–5 M,
λexc = 334 nm). The inset shows a picture of the cyclohexane gels
obtained from compounds 1 and 2 with illumination at 364 nm.
70 Fig. 3 ROESY NMR spectrum (CDCl3, 300 MHz, 45 × 10–3 M, 293 K)
of 1. The dotted blue, green and black lines highlight intraꢀ,
intermolecular or both throughꢀspace coupling signals, respectively. The
inset shows the chemical structure of 1 depicting the anisochronous
protons by coloured circles.
The presence of the sterogenic center on the side chain of 2
30 was utilized to put in evidence the possible helical organization of
the aggregates formed by 1 and 2 in an attempt to justify the
observed emission properties. Compound 2 shows a weak
dichroic response with a poorly defined bisignated Cotton effect
centered at around 250 nm (Fig. S5a, ESI†). In addition,
35 sergeantsꢀandꢀsoldiers (SaS) experiments were performed by
mixing achiral 1 and chiral 2 to investigate the amplification of
chirality.12 The SaS experiment shows a linear increase of the
dichroic response upon increasing the amount of chiral sergeant 2
(Fig. S5b, ESI†). The dichroic data reveal that compounds 1 and
40 2 do not selfꢀassemble forming helical structures and, therefore,
this supramolecular organization cannot be invoked to justify the
observed emission features.
75
The ROESY experiment clearly shows a number of
intramolecular throughꢀspace coupling signals between the
protons spatially close within the molecule, like for instance both
para protons of the benzamide moiety (see the dotted blue circles
in Fig. 3). In addition, ROESY signals corresponding to
80 intermolecular contacts are also observed (dotted green lines in
Fig. 3). Especially interesting are the contacts observed between
the methylene units of the alkyl side chain and most of the
aromatic protons of the pyrene unit. These contacts suggest an
alternated distribution of the pyrene units in the aggregated state
85 that could justify the observed monomeric emission properties.
Theoretical calculations were performed on compound 1
within the density functional theory (DFT) framework to shed
light on the structural and energetic aspects of the
The extracted experimental data arise two important questions:
1) which are the nonꢀcovalent forces participating in the selfꢀ
45 assembly of the investigated pyreneimidazoles?, and 2) what kind
of supramolecular aggregate is formed upon their selfꢀassembly
2
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 3 of 5
ChemComm
View Article Online
DOI: 10.1039/C5CC03616J
pyreneimidazole system upon aggregation (see the ESI† for
computational details). The isolated molecule shows a planar
strong Hꢀbonds is the recognition driving force, have been
modelled (Fig. 4). Whereas dimers D and E are only stabilized by
minimumꢀenergy structure with an outꢀofꢀplane disposition of the 45 the Hꢀbond interaction between the imidazole or the amide
amide group (Fig. S8, ESI†) that facilitates Hꢀbonding
interactions between neighbouring molecules. To unravel the
possible contribution of the different parts of the molecule in the
operation of nonꢀcovalent forces, the molecular electrostatic
potential (MEP) calculated for 1 (Fig. S9, ESI†) was analysed.
The MEP surface shows that the largest potential energy points
10 are concentrated in the amide and the imidazole groups. Negative
potential energies of –55.7 and –54.6 kcal/mol are calculated in
the oxygen and nitrogen vicinity, respectively, whereas positive
groups, respectively, dimer F forms two Hꢀbonds between the
amide and the imidazole groups together with an extended
CH···π stabilization due to the interaction between the aliphatic
chains and the pyreneimidazole cores.
Table 2 summarizes the interaction energy (Eint) and the main
intermolecular forces governing the selfꢀassembly of dimers A−F
calculated at the B97D3/6ꢀ31G** level. A topological analysis of
the electron density was also carried out by means of the
NCIPLOT software to obtain the nonꢀcovalent interaction (NCI)
5
50
potentials of +101.2 and +121.0 kcal/mol are located in the N−H 55 surfaces, which provide additional information on the origin of
region of the amide and imidazole, respectively. Strong
15 electrostatic interactions are then expected between monomers by
means of Hꢀbonding interactions involving the amide and
imidazole units, as well as weak πꢀπ and/or CꢀH···π dispersion
interactions between the aromatic units and the aliphatic chains.
A number of dimers, as the minimal supramolecular unit, can
20 be modelled for 1 owing to the large variety of supramolecular
interaction motifs present in the monomer: (i) the πꢀextended
aromatic structure, (ii) the polar amide and imidazole groups and
(iii) the nonpolar long aliphatic chain. In a first approach, two
monomers may accommodate either in a parallel or antiparallel
25 disposition by the πꢀstacking of the pyreneimidazole cores with
themselves or with the benzamide group, respectively (dimers A
and B in Fig. 4). In dimer A, an amide–amide N−H···O bond is
formed due to the rotation of ~30º of the upper monomer around
the perpendicular axis. This structure would grow up in a helical
30 column upon selfꢀassembly, but this possibility has been
discarded by CD measurements. Similar to A, dimer C is
arranged in a parallel mode but with the amide groups pointing in
opposite directions and forming a nonꢀlinear Hꢀbond (Fig. 4). A
weak Hꢀbonding N−H···N interaction between the imidazole
35 rings is also present in antiparallel dimer B.
the supramolecular aggregation (Fig. S10 and S11, ESI†).
Table 2 Interaction energy (Eint), number of Hꢀbond contacts
(nHB), distance of the closest Hꢀbond contact (dHB) and dominant
dispersion interactions (πꢀπ, CH···π and CH···CH) that
60 characterize dimers A−F.
Eint (kcal/mol)
–54.6
nHB
1
dHB (Å)
1.918
2.064
2.051
1.826
1.822
1.839
πꢀπ
ꢀ
ꢀ
ꢀ
−
CH···π CH···CH
A
B
C
D
E
F
−
−
ꢀ
−
−
−
−
−
–51.0
1
–53.7
1
−
–32.0
1
ꢀ
−
–7.7
2
−
–61.7
2
−
ꢀ
Dimers A, B and C are computed very close in energy owing
to the similar number and nature of the interactions stabilizing the
aggregate. Dimers B and C (Eint of –51.0 and –53.7 kcal/mol,
respectively) display the typical green surface indicative of
65 dispersion interactions along the πꢀπ skeleton between monomers
(Fig. S10, ESI†). Stabilizing CH···CH interactions between the
aliphatic chains are additionally found for A, which is calculated
slightly more stable (Eint = –54.6 kcal/mol) than B and C. In these
three dimers, weak Hꢀbonds are formed as indicated by the
70 closest NH···N/O contacts in the range of 1.92–2.06 Å (Table 2).
The situation is different for dimers D, E and F. Dimer E is
stabilized by two Hꢀbonding interactions between the two amides
in a cis disposition. The occurrence of dimer E is however very
unlikely because of: (i) the high barrier (15 kcal/mol) that has to
75 be overcome to convert a trans amide into a cis amide (Fig. S12,
ESI †), and (ii) the small interaction energy (–7.7 kcal/mol)
resulting from the lower stability of the cis conformation and the
additional steric interactions that it introduces. The cross shape of
dimer D enables a strong Hꢀbond interaction between the
80 imidazole groups (N···H−N distance of 1.83 Å) and incorporates
C−H···π interactions between the tertꢀbutyl groups of one
monomer and the aromatic pyrene core of the other (Fig. S10,
ESI†). Nonetheless, the Eint computed for this dimer (–32.0
kcal/mol) cannot compete with the stabilization obtained for the
85 πꢀπ patterned dimers A−C. Finally, dimer F combines Hꢀbonding
interactions between the imidazole and amide groups and CꢀH···π
stabilizing interactions between the alkyl chains and the pyrene
cores (Fig. 4 and Fig. S10, ESI†). The additive effect of these
interactions leads to the highest stability (Eint = –61.7 kcal/mol)
90 among all the computed dimers. The structure of dimer F allows
to identify all the ROESY signals observed experimentally and,
in particular, the short contacts between the alkyl chains and the
pyrene cores (Fig. S13, ESI†). In addition, the absence of πꢀπ
interactions between the pyrene cores in dimer F explains the
Fig. 4 Minimumꢀenergy geometries calculated for the different dimers
postulated for 1 at the B97D3/6ꢀ31G** level of theory.
Besides the πꢀπ recognition motif that gives rise to structures
40 A−C, the polar imizadole and amide groups constitute high
potential energy regions for the supramolecular stabilization of
the dimers. Thereby, dimers D−F, in which the formation of
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 3

ChemComm
Page 4 of 5
View Article Online
DOI: 10.1039/C5CC03616J
emission properties similar to the monomer. Dimer F is therefore
(PROMETEO/2012/053)
and
Comunidad
de
Madrid
proposed as the most plausible associate for compounds 1 and 2.
To rationalize how dimer F can grow up from such nonplanar,
distorted disposition of the monomers, the tetramer shown in Fig
5 was built up through an imidazole−amide−imidazole Hꢀbond
sequence. The minimumꢀenergy geometry computed at the
B97D3/6ꢀ31G** level for the tetramer clearly reveals that the Hꢀ
bonding motifs are preserved along the different monomeric
pairs. The average NH(amide)−N(imizadole) contact is computed
10 at 2.18 Å, whereas the CO(amide)−HN(imizadole) interaction is
calculated at 1.82 Å. The total interaction energy in the tetramer
reaches –182.1 kcal/mol, which corresponds with an Eint = –60.7
kcal/mol per monomer pair. This value is very close to the Eint
computed for dimer F (–61.7 kcal/mol), suggesting that: (i) the
15 oligomer can easily grow keeping the strong Hꢀbond pattern and
the stabilizing CꢀH···π forces, and (ii) the degree of cooperativity
in the supramolecular polimerization should be very small.
(NanoBIOSOMA, S2013/MITꢀ2807) is acknowledged. JC thanks
the MECD for a doctoral FPU grant.
5
45 Notes and references
aDepartamento de Química Orgánica, Facultad de Ciencias Químicas,
Universidad Complutense de Madrid, 28040 Madrid (Spain); E-mail:
lusamar@quim.ucm.es
bInstituto de Ciencia Molecular, Universidad de Valencia, 46980 Paterna
50 (Spain); E-mail: enrique.orti@uv.es
† Electronic Supplementary Information (ESI) available: Figures S1ꢀS12,
theoretical computational details and experimental section. See
DOI: 10.1039/b000000x/
‡ These authors contributed equally
55
60
65
70
75
80
1
2
A. Laurent, Ann. Chim. Phys. 1837, 66, 136.
C. Wang, H. Dong, W. Hu, Y. Liu and D. Zhu, Chem Rev. 2012, 112,
2208.
3
4
T. M. FigueiraꢀDuarte and K. Müllen, Chem. Rev. 2011, 111, 7260.
(a) N. Tchebotareva, X. M. Yin, M. D. Watson, P. Samori, J. P. Rabe
and K. Müllen, J. Am. Chem. Soc. 2003, 125, 9734; (b) D.
Venkataraman, S.; Lee, J. S. Zhang and J. S.; Moore, Nature 1994,
371, 591.
5
6
7
(a) A. Ajayaghosh, V. K. Praveen and C. Vijayakumar, Chem. Soc.
Rev., 2008, 37, 109; (c) J. W. Steed, Chem. Soc. Rev., 2010, 46, 3686.
D. Kumar, K. R. J. Thomas, C.ꢀC. Lin and J.ꢀH. Jou, Chem.
Asian J. 2013, 8, 2111.
T. F. A. De Greef, M. M. J. Smulders, M. Wolffs, A. P. H. J.
Schenning, R. P. Sijbesma and E. W. Meijer, Chem. Rev. 2009, 109,
5687.
8
9
H. M. M. ten Eikelder, A. J. Markvoort, T. F. A. de Greef and P. A. J.
Hilbers, J. Phys. Chem. B 2012, 116, 5291.
F. M. Winnik, Chem. Rev. 1993, 93 , 587.
10 The emision corresponding to the pyrene monomer is only reached in
CHCl3 by using highly diluted (7 × 10–9 M), deoxygenated solutions
(Fig. S4, ESI†).
11 Y. Kamikawa and T. Kato, Langmuir, 2007, 23, 274.
12 (a) M. M. J. Smulders, A. P. H. J. Schenning and E. W. Meijer, J.
Am. Chem. Soc., 2008, 130, 606; (b) F. García, P. A. Korevaar, A.
Verlee, E. W. Meijer, A. R. A. Palmans and L. Sánchez, Chem.
Commun. 2013, 49, 8674.
13 (a) Y. Matsunaga, N. Miyajima, Y. Nakayasu, S. Sakai and M.
Yonenaga, Bull. Chem. Soc. Jpn. 1988, 61, 207; (b) F. García, P. M.
Viruela, E. Matesanz, E. Ortí and L. Sánchez, Chem. Eur. J. 2011,
17, 7755.
85 14 Prior to this ROESY experiment, the aggregation of 1 was assessed
by diffusionꢀordered spectroscopy (DOSY) NMR, which reveals a
larger value of the diffusion coefficient when compared to a more
diluted solution (Fig. S6b, ESI†). A. Wong, R. Ida, L. Spindler and
G. Wu, J. Am. Chem. Soc. 2005, 127, 6990.
Fig. 5. Top (a) and side (b) views of the B97D3/6ꢀ31G**ꢀoptimized
20 geometry calculated for the tetramer of 1. Dotted lines emphasise the Hꢀ
bonding array established between the imidazole and amide units. Only
hydrogen atoms involved in Hꢀbonding interactions are shown.
In summary, we have synthesised pyreneimidazoles 1 and 2
that prevents the formation of excimers upon aggregation. The
25 number and type of nonꢀcovalent interactions operating in the
aggregation of these pyrene derivatives results in an amazing
scenario of possibilities for 1 and 2 to selfꢀassemble. Both
experimental and theoretical studies demonstrate that the
formation of the aggregates is mainly governed by the Hꢀbonding
30 interaction between the amide functionality and the imidazole
moiety, together with a number of CꢀH···π interactions. The
absence of πꢀπ interactions between the pyrene cores determines
that the aggregate preserves the blueꢀemitting properties of the
monomer. The results presented herein demonstrate the complex
35 pathway followed by 1 and 2 to finally yield blueꢀemitting
supramolecular aggregates and contribute to shed light into the
relationship between functionality and supramolecular
polymerization.
Financial support by the MINECO of Spain (CTQ2011ꢀ22581
40 and CTQ2012ꢀ31914), European Feder funds (CTQ2012ꢀ31914),
UCM (UCMꢀSCHꢀPR34/07ꢀ15826), Generalitat Valenciana
4
|
Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 5 of 5
ChemComm
View Article Online
DOI: 10.1039/C5CC03616J
Blueꢀemitting pyreneꢀbased aggregates
J. S. Valera,a J. Calbo,b R. Gómez, E. Ortí,b* and L.
a
5
Sáncheza*
The selfꢀassembling features and gel formation of two pyreneimidazoles is
presented. The supramolecular aggregation of these synthesised molecules
results in an unusual blueꢀmonomeric emission, which is rationalized by a
10 combined experimental and theoretical investigation.
15
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 5