Solvent-assisted synthesis of a shape-persistent chiral polyaza gigantocycle characterized by a very large internal cavity and extraordinarily high amplitude of the ECD exciton couplet

Article abstract of DOI:10.1039/c8cc10184a

A giant, chiral square-shaped octaimine macrocycle has been obtained in a controlled manner from readily available and inexpensive substrates: 9,10-diphenylanthracene-based dialdehyde and trans-1,2-diaminocyclohexane. Reduction of the polyimine led to a c

Full text of DOI:10.1039/c8cc10184a

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Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
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DOI: 10.1039/C8CC10184A
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Solvent-assisted synthesis of shape-persistent chiral polyaza
gigantocycle characterized by a very large internal cavity and
extraordinarily high amplitude of the ECD exciton couplet
Received 00th January 20xx,
Accepted 00th January 20xx
Mikołaj Zgorzelak,*a Jakub Grajewski,a Jacek Gawroński,a and Marcin Kwit*a,b
DOI: 10.1039/x0xx00000x
www.rsc.org/
A giant, chiral square-shaped octaimine macrocycle has been (DACH, 1) and linear 1,4-dialdehyde leads to
obtained in a controlled manner from readily available and symmetrical product with [3+3] stoichiometry and a triangle
inexpensive substrates: 9,10-diphenylanthracene-based structure (trianglimine). It is believed that this particular
a highly
dialdehyde and trans-1,2-diaminocyclohexane. Reduction of the cycloimination reactions proceed smoothly, irrespective to the
polyimine led to chiral octaamine characterized by a very large substitution pattern in the 1,4-dialdehyde skeleton, solvent
internal hydrophobic cavity.
polarity and concentration of the substrates.8,9
While the terephthalaldehyde and 4,4’-diformyldiphenyl
derivatives are the most common substrates, anthracene-based
derivatives have been used very rarely in cycloimination
reactions. Due to a poor solubility in organic solvents,
difficulties in synthesis and in proper characterizations, there
are only two examples of chiral [3+3] triangular polyimine
macrocycles containing anthracene moieties known to date.10
This remains in contrast to a number of macrocyclic structures
built on the basis on 9,10-anthracene and 9,10-
diphenylanthracene units. Being highly fluorescent, the latest
derivatives and their heteroatom analogs are frequently used
for construction of light-emitting materials.11 The characteristic
feature of 9,10-diphenylanthracene is the almost perpendicular
orientation of the anthracene and phenyl units associated with
hindered rotation around CAr-CAr bonds.12
We reasoned that an addition of bulky, hydrophobic tert-
butyl groups to the 9,10-diphenylanthracene skeleton would
make the parent aldehyde and the resulting macrocycle more
soluble in organic solvents. On the other hand, the presence of
bulky groups attached to the anthracene significantly increases
steric strains and may completely prevent macrocyclization.
Thus, we expanded our study into chiral polyimine 9,10-
diphenylanthracene derivatives to demonstrate the influence
of the aldehyde structure and/or reaction conditions on the
structure of the product(s). Meanwhile, we anticipated that the
newly synthesized chiral macrocycles, containing very complex
chromophoric systems, might constitute interesting objects for
the study with the use of the electronic circular dichroism (ECD)
spectroscopy. Interactions between electric dipole transition
moments (EDTMs) polarized within aromatic chromophores
should lead to strong exciton Cotton effects (CEs), allowing the
Shape-persistent macrocycles have become one of the most
important organic compounds useful in many aspects of
chemistry among the macrocyclic structures known so far.
These compounds may act as supramolecular building blocks
forming various architectures in the solid state and in solution,
scaffolds for artificial receptors and porous solids.1 Generally,
the shape-persistent macrocycles have a regular structure
characterized by alternatively repeated units, which in
principle, should simplify synthesis. However, due to the need
to achieve a high level of substrate pre-organization, controlled
synthesis of shape-persistent macrocycles larger than 50-
membred (gigantocycles), represents still a challenging task.2,3
Based on the Dynamic Covalent Chemistry concept
thermodynamically controlled and reversible formation of the
imine C=N double bonds gives a chance for obtaining cyclic
compounds, if energy gain associated with the formation of
cyclic products disfavors formation of acyclic oligomers.4 Since
our pioneering work, the interest in template-free synthesis and
subsequent applications of chiral polyimine and polyamine
macrocycles is still increasing.5-8 Success of cycloimination
reactions relies primarily on the proper choice of substrates that
should be structurally predisposed to form chiral strain-free
cyclic structures. So far, it has been an axiom to say that the
combination of optically pure trans-1,2-diaminocyclohexane
a. Department of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61 614
Poznań, Poland; e-mail: mikolaj.zgorzelak@amu.edu.pl or
marcin.kwit@amu.edu.pl.
b. Centre for Advanced Technologies, Adam Mickiewicz University, Umultowska 89C,
61 614 Poznań, Poland.
† Electronic Supplementary Information (ESI) available: [enlarged versions of
Scheme 1 and Figures, experimental procedures, calculation details, copies of 1H
and 13C NMR spectra]. See DOI: 10.1039/x0xx00000x
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interpretation of the ECD spectra in terms of exciton chirality can be of particular importance. The macrocycle V4iewisAsrtticalebOlenlinine
rule.9,13
the solid state. However, in solution, 4DuOnI:d1e0.r1g0o39e/sC8sCteCp10-w18i4sAe
decomposition, which is slowed down in the presence of an
excess of triethylamine.
The 1H NMR recorded at specific time intervals for the
macrocycle 4, carried out in dry, pure CDCl3 (Figure 2a,b), gave
an insight into the course of the equilibration process. A
contraction of macrocycle 4 into 3 started immediately upon
dissolution, ran through an open-chain intermediate product
and within 5 hours, the mixture reached equilibrium. The
reaction equilibrium constant has been calculated as 1.1.
At a reduced temperature, we observed broadening of the
Scheme 1. Synthesis of macrocycles [3+3]-3, [4+4]-4 and [4+4]-5 (see ESI for
1
enlarged version).
respective aromatic H NMR signals of imine 4. Unfortunately,
below -40 °C the macrocycle precipitated from chloroform
solution, prevented further study (see ESI). A subsequent
reduction of 4, by simply treatment with sodium borohydride in
methanol-dichloromethane solution, led to chemically stable
octaamine 5. The characteristic for neutral 5, ArCH2N benzyl
protons, appeared as two doublets at δ = 4.14 and 3.90, shifted
downfield upon protonation of the amine by trifluoroacetic acid
(δ = 4.65 and 4.43, Figures 1c,d). The number of diagnostic
The synthesis of a new tert-butyl-substituted dialdehyde 2
was achieved by a three-step sequence of reactions from
inexpensive reagents and without a column chromatography
(sees ESI). The initial attempts to obtain macrocycle from (R,R)-
1 and 2 have failed. In conditions typical of cycloimination
reactions (chloroform, RT, 24 h),8 we did not observe the full
substrate conversion and the mass spectrum indicated the
presence of many different products, mainly open-chain, in the
reaction mixture. However, the reaction carried out in a boiling
toluene and in the presence of catalytic amounts of p-
toluenesulfonic acid, unexpectedly, provided the mixture of
two products. The conversion of substrates was complete and
in no case, did we observe the formation of linear oligomers.
Mass spectrometry indicated that the mixture consisted of
[3+3]-3 and [4+4]-4 macrocycles. The 3:4 ratio was
approximately equimolar as estimated on the basis on
integration of the CHN imine signals appeared at δ = 8.51 and
1
signals, which appeared in H and 13C NMR spectra of 4 and 5,
suggests their high symmetry.
1
8.27 in diagnostic region of the H NMR spectrum (Figure 1a).
The heating of the suspension of 3 and 4 in p-xylene at boiling
point (140 °C) led to a transparent, deep-yellow colored
solution, which has become turbid and yellow-green-colored
after cooling to temperature below 100 °C. At this point, the
complete conversion of the smaller 66-membered macrocycle
3 into its larger 88-membered counterpart 4 was observed (see
Figure 1b). High boiling point of the solvent is not a sufficient
condition and none of the other organic solvents caused
expansion of the macro ring. It is worth noting that macrocycle
4 can be obtained as the main product if the condensation
reactions are carried out immediately in p-xylene. The
remaining xylene isomers as well as other aromatic solvents in
the above reaction conditions always lead to a mixture of
products (see ESI).
The square-shaped macrocycle 4 is isolated as the complex
with two molecules of p-xylene. The solvent can be partially
removed from the solid material by prolonged drying under
very high vacuum and at elevated temperature. p-Xylene
functions as a template to facilitate preorganization of the sub-
units which form the macrocycle. This type of solvent-assisted
transformation has never been reported for chiral polyimines.
Although the detailed explanation of such phenomenon is not
known at the moment, minimizing the dipole moment in the
tetrameric structure together with CH···π and π···π stacking
interactions between the solvent and the macrocycle formed
Figure 1. Diagnostic parts of 1H NMR spectra of: a) crude mixture of 3 and 4
[CDCl3]; b) pure 4×2(p-xylene) [CDCl3]; c) octaamine 5 [CDCl3] and d) protonated
octaamine 5×8H+ [CD3OD+TFA]. Asterisks indicate trace solvent peaks.
1
The shape of H NMR spectrum of 5×8H+ has changed upon
increasing the temperature of measurement (Figure 2c). The
higher temperatures increased conformational freedom of the
aromatic linkers and allowed anthracenes to rotate around CAr-
CAr’ carbon bonds. Phenyl rotation barrier in 9-
phenylanthracene, estimated by Nikitin and co-workers, is ca.
21 kcal mol-1.12 However, the macrocyle 5×8H+ represents much
more complex system due to a double substitution of each
anthracene and possibility of gearing of anthracene fragments.
The difficulty in obtaining suitable crystals prevents the use of
X-ray diffraction for structure elucidations. Hence, the use of
experimental ECD measurements supported by theoretical
calculations of structure and spectra at the DFT15 level seems to
be the method of choice for structural studies of these
macrocycles. The calculated low-energy structures of 3, 4, 5 and
5×8H+ are shown in Figure 3. As expected, the characteristic
feature for all macrocycles under study is a non-planar
orientation of anthracene and phenylene units associated with
hindered rotation around aryl-aryl single bonds. Therefore, at
normal conditions the aromatic linker can only rotate around
2 | J. Name., 2012, 00, 1-3
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the CAr-CHN single bonds. The triangular imine 3 is characterized with this band is characterized by much lower magnitude (A =
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by highly congested structure, in which tert-butyl groups are 267) and by inverted sign. ProtonatioDnOoI:f105.10d39id/C8nCoCt10a1l8t4eAr
situated at close proximity. Expansion of the macrocyclic ring significantly the observed absorption bands and CEs, confirming
might release the sterical overcrowding at the expense of the by this way similar structure of 5 and 5×8H+ species. The
loss of the linear structure of the linkers. The calculated low- macrocycle 4 contains very complex chromophoric systems,
energy structure of 4 can be very roughly treated as the each of them is made of three sub-units. Due to the almost
equivalent of cyclobutane – two apexes are above and the perpendicular orientation of phenylene and anthracene rings in
remaining two are positioned below the mean macrocycle linkers, there is no possibility for electron delocalization within
plane. Similarly, the tert-butyl substituted anthracene moieties the chromophore. The aromatic linker in 4 consists of an
are alternatively positioned below and above the mean anthracene chromophore flanked by two ArCH=N (imine)
macrocycle plane. In two facing linkers, the phenylene rings chromophores each of which gives an individual contribution to
remain perpendicular to the anthracene plane, whereas in the the overall ECD spectrum.
remaining two, are distorted from perpendicularity. The
aromatic linkers close the cavity and do not allow inclusion
inside the macrocycle.
The comparison of calculated total energies led to the
conclusion that the smaller one, 3, is more energetically
preferable than its larger counterpart 4 is. The energy cost
associated with ring expansion is around 16 kcal mol-1.
Therefore, the octaimine 4 is a rather metastable compound
that persists in the solid state.
In addition to the increase in chemical stability, reduction of
the imine bonds changes the macrocycle structure. Due to the
possibility of the configuration inversion at the nitrogen atoms
and unhindered rotation around (CAr)CH2-N bonds, the linkers
may adopt conformation in which the bulky elements are far
away from each other. On the other hand, the formation of
Figure 2. a) Traces of 1H NMR spectra [CDCl3] measured for 4 at certain time
intervals. b) Contraction of 4 measured as the increase of the mole fraction of 3
(χ(3)). C) Variable temperature 1H NMR spectra of 5×8H+ [DMSO-d6 + TFA].
NH···N hydrogen bonding is recognized as a key factor that
stabilize structure of trianglamines.16 From the two stable low-
energy structures of 5, found by calculations, the C4-
symmetrical one is characterized by the presence of four
intramolecular NH···N hydrogen bonds, which forces the bowl-
shaped conformation (see Figure S2, ESI). However, the
repulsion between tert-butyl groups raises the energy of the
molecule by 13 kcal mol-1, as computational conformational
analysis indicates, therefore, excluding this conformer from
considerations. On the other hand, the lowest energy
conformer of 5 and 5×8H+ are both characterized by the high D4
symmetry and similar structure. In both 5 and 5×8H+, the
anthracene units are perpendicular, whereas phenylene groups
are positioned, alternatively, above and below the mean
macrocycle plane. Such conformation of aromatic linkers opens
the hydrophobic internal cavity of the macrocycle. The distance
between the middle points of anthracene units is 21.36 Å that
corresponds to radius of a circle inscribed in a square of 10.68
Å. So far, macrocycle 5 represents the first DACH-based and
shape-persistent chiral polyamine, characterized by such a large
internal cavity. The ECD spectrum of octaimine 4 (Figure 4a) is
dominated by the strong exciton negative couplet of amplitude
A = -1380 that appeared at around 270 nm and corresponding
to the UV absorption maximum of ε = 480000. Such a high-
intense exciton couplet has never been reported for chiral
polyimine compounds. Reduction of imine bonds and related
change in structure and electron properties of the
chromophore, significantly affected the ECD and UV spectra of
5. Although the most intense UV absorption band still appears
at around 270 nm (ε = 383100), the exciton couplet associated
Figure 3. Low-energy structures of a) imine 3; b) imine 4; c) amine 5 and d)
octaprotonated amine 5×8H+ calculated at the B3LYP/6-311G(d,p) level.
Using model compound 6 and Coulomb-attenuating method
(see ESI for details),15 the polarizations of the main electronic
transitions responsible for exciton couplets have been
determined. The calculated lowest-energy π-π* (HOMO-LUMO)
electronic transition is polarized along the main axis of the
molecule. Due to the long distance between the electric dipole
transition moments, these interactions are not resulted in
strong exciton-type CEs in experimental spectrum of 4. The
transitions no 2 and 4 involve ArCH=N orbitals. The EDTM’s
associate with these transitions is distorted from the main axis
of 6. The transition no 3, involving anthracene orbitals, is
characterized by the highest oscillator strength and polarized
along the long axis of anthracene (Figures 4c). However, the
generated exciton couplets are dependent on spatial
orientations of chromophores in 4 and they are alternately
positive and negative. Therefore, the imine-imine interactions
are mainly responsible for observed experimentally in ECD
spectrum of 4 strong negative couplet. The interactions
between the adjacent imine and anthracene chromophores are
less important (see Table S1, ESI).
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1
2
W. Zhang and J. S. Moore, Angew. Chem. Int. Ed., 2006, 45,
View Article Online
4416 and references therein.
DOI: 10.1039/C8CC10184A
a) V. Martí-Centelles, M. D. Pandey, M. I. Burguete and S. V.
Luis, Chem. Rev., 2015, 115, 8736; b) L. A. Wessjohann, D. G.
Rivera and O. E. Vercillo, Chem. Rev., 2009, 109, 796; c) Y. Jin,
C. Yu, R. J. Denman and W. Zhang, Chem. Soc. Rev., 2013, 42,
6634.
3
4
a) V. Prautzsch, S. Ibach and F. Vögtle, J. Inclusion Phen., 1999,
33, 427; b) M. R. Shah, S. Duda, B. Müller, A. Godt and A.
Malik, J. Am. Chem. Soc., 2003, 125, 5408.
a) S. J. Rowan, S. J. Cantrill, G. R. L. Cousins, J. K. M. Sanders
and J. F. Stoddart, Angew. Chem. Int. Ed., 2002, 41, 898; b) P.
T. Corbett, J. Leclaire, L. Vial, K. R. West, J.-L. Wietor, J. K. M.
Sanders and S. Otto, Chem. Rev., 2006, 106, 3652.
J. Gawroński, H. Kołbon, M. Kwit and A. Katrusiak, J. Org.
Chem., 2000, 65, 5768.
a) M. E. Belowich and J. F. Stoddart, Chem. Soc. Rev., 2012, 41,
2003; b) N. E. Borisova, M. D. Reshetova and Y. A. Ustynyuk,
Chem. Rev., 2007, 107, 46; c) S. Srimurugan, P. Suresh, B. Babu
and H. N. Pati, Mini-Rev. Org. Chem., 2008, 5, 228.
J. Gawroński, M. Kwit and U. Rychlewska, in Comprehensive
Supramolecular Chemistry II, (Eds.: J. L. Atwood, G. W. Gokel,
L. J. Barbour) Oxford: Elsevier, 2017, vol. 3, pp. 267–291, and
references therein.
5
6
Figure 4. a) Experimental (solid lines) of 4 (black line) and 5 (red line) and
calculated at the ZINDO level (dashed black line) ECD spectrum of 4. Due to the
low intensity, the ECD spectrum of 5 was multiplied by the factor of 5.
Wavelengths were not corrected. b) Estimated polarizations and c) orbitals
involved in the main electronic transitions calculated for model compound 6.
The results of the empirical analysis remain in agreement
with the experiment. The empirical analysis was supported by
semi-quantitative calculations of ECD spectra of interacting
chromophoric fragments.17 The contribution from all imine-
imine interactions is almost 5 times as large as that from
anthracene-anthracene interactions (see ESI for details).
Furthermore, these empirical and semi-quantitative analyses
were confirmed by the calculations of ECD spectrum of 4. Even
for a relatively low level of theory, the compatibility of
experimental and theoretical data remains in good agreement
(Figure 3a). The same theoretical analysis carried out for 5
provided results that are in agreement with experimental ECD
data, therefore confirming postulated structure of 5 (see ESI).
We have presented here synthesis and structural studies on
chiral gigantocycles, characterized by the unusual square-
shape. The synthesis of this type of compounds is in
contradiction with the generally accepted view on the [3+3]
selectivity of the condensation reaction between (R,R)-1 and
linear aldehydes. The solvent controlled synthesis of such large
systems gives a chance for their later use. The reduced
macrocycle 5 and its protonated counterpart represent
polyimine-derived rings of the highest value of internal cavity
known so far. Preliminary experiments indicated these
macrocycles as good precursors of new materials. Although, the
initial attempts to obtain porous material from 4 were
unsuccessful and the estimated value of the Brunauer-Emmett-
Teller surface area (SABET) was below 5 m2 g-1, the open
structure of 5 significantly increased measured SABET value up
to 149 m2 g-1. Due to the mismatch of the host and guest
molecules, 5 cannot act as a receptor for C60 or C70 fullerenes. A
very rough estimation indicates that only fullerenes with a size
between C96 and C240 give a chance for effective binding to the
host molecule. Further studies are in progress in our laboratory.
7
8
9
M. Kwit, J. Grajewski, P. Skowronek, M. Zgorzelak and J.
Gawroński, Chem. Rec., DOI: 10.1002/tcr.201800052.
N. Prusinowska, M. Bardziński, A. Janiak, P. Skowronek and M.
Kwit, Chem. Asian J., 2018, 13, 2691.
10 a) M. Kwit, P. Skowronek, H. Kołbon and J. Gawroński,
Chirality, 2005, 17, S93; b) N. Kuhnert, C. Patel and F. Jami,
Tetrahedron Lett., 2005, 46, 7575.
11 see for example: a) R. Yamakado, S. Matsuoka, M. Suzuki, D.
Takeuchi, H. Masu, I. Azumaya and K. Takagi, RSC Adv., 2014,
4, 6752; b) S. S. Babu, M. J. Hollamby, J. Aimi, H. Ozawa, A.
Saeki, S. Seki, K. Kobayashi, K. Hagiwara, M. Yoshizawa, H.
Mӧhwald and T. Nakanishi, Nat. Commun., 2013, 4, 1969; c)
Y. Fujiwara, R. Ozawa, D. Onuma, K. Suzuki, K. Yoza and K.
Kobayashi, J. Org. Chem., 2013, 78, 2206; d) K. Hagiwara, Y.
Sei, M. Akita and M. Yoshizawa, Chem. Commun., 2012, 48,
7678; e) J.-L. Liu, Z.-L. Tang, J.-Q. Zhang, Y.-Q. Chai, Y. Zhuo
and R. Yuan, Anal. Chem. 2018, 90, 5298; f) K. Yazaki, L. Catti
and M. Yoshizawa, Chem. Commun., 2018, 54, 3195.
12 K. Nikitin, H. Müller-Bunz, Y. Ortin, J. Muldoon and M. J.
McGlinchey, Org. Lett., 2011, 13, 256.
13 N. Harada, K. Nakanishi and N. Berova, in Comprehensive
Chiroptical Spectroscopy (Eds N. Berova, P. L. Polavarapu, K.
Nakanishi, R. W. Woody) Hoboken: Wiley, 2012.
14 Previously, the solvent effects in multicomponent cage
syntheses have been studied, see for example: a) S. Mecozzi
and J. Rebek, Chem. Eur. J., 1998, 4, 1016; b) S. Lahiri, J. L.
Thompson and J. S. Moore, J. Am. Chem. Soc., 2000, 122,
11315; c) X. Liu and R. Warmuth, J. Am. Chem. Soc., 2006, 128,
14120.
15 Gaussian 09, Revision D.01, Gaussian, Inc., Wallingford CT,
2009. All calculations were performed at Poznan
Supercomputing and Networking Centre.
16 J. Gawronski, K. Gawronska, J. Grajewski, M. Kwit, A. Plutecka
and U. Rychlewska, Chem. Eur. J. 2006, 12, 1807.
17 This procedure has been successfully used by us for
interpretation of complex ECD spectra of multichromophoric
systems, see for example: a) M. Kwit, J. Gawronski, D. R. Boyd,
N. D. Sharma and M. Kaik, Org. Biomol. Chem., 2010, 8, 5635;
b) N. Prusinowska, W. Bendzińska-Berus, J. Szymkowiak, B.
Warżajtis, J. Gajewy, M. Jelecki, U. Rychlewska and M. Kwit,
RSC Adv., 2015, 5, 83448.
Conflicts of interest
There are no conflicts to declare.
Notes and references
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