Perfluoro-1,1′-biphenyl and perfluoronaphthalene and their derivatives as π-acceptors for anions

Article abstract of DOI:10.1039/c4nj01654h

Addition of anions to perfluorinated 1,1′-biphenyl 1 or naphthalene 2 results in a shift of the ¹⁹F NMR signals. However, any specific interaction cannot be assigned to this effect. In order to study the interaction in more detail, the salt derivatives 3 and 4 were prepared and studied by single crystal X-ray diffraction revealing weak anion-π interactions in the solid state.

Full text of DOI:10.1039/c4nj01654h

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Perfluoro-1,1 -biphenyl and perfluoronaphthalene
and their derivatives as p-acceptors for anions†
Cite this: New J. Chem., 2015,
3
9, 746
a
a
bc
b
Hai Yi, Markus Albrecht,* Arto Valkonen and Kari Rissanen
Received (in Montpellier, France)
5th September 2014,
Accepted 3rd November 2014
0
19
Addition of anions to perfluorinated 1,1 -biphenyl 1 or naphthalene 2 results in a shift of the F NMR
signals. However, any specific interaction cannot be assigned to this effect. In order to study the
interaction in more detail, the salt derivatives 3 and 4 were prepared and studied by single crystal X-ray
diffraction revealing weak anion–p interactions in the solid state.
2
DOI: 10.1039/c4nj01654h
www.rsc.org/njc
Introduction
The study of anion–p interactions, an attractive interaction between
anions and electron-deficient arenes, is a very recent research topic
in supramolecular chemistry. Although anion–p interactions are
observed in Nature, they have not been brought to the forefront of
1,2
research earlier than in the 1990s. Recently, investigations on
anion–p interactions have advanced significantly both computation-
3
ally and experimentally. One of the most significant tasks in this
field is the design and synthesis of receptors acting as anion–p hosts.
Anion–p interactions have a major influence on the formation of
4
specific structures in the solid state. In solution the contribution of
Scheme 1 Perfluorinated aromatic receptor compounds (1 and 2) and their
methylene DABCO bromide salts (3 and 4) investigated in the present study.
this interaction together with other attractive forces seems to play a
5
role. In the crystal anion–p interactions are even able to be a driving
6
force for the stabilization of highly reactive species. However, the
anion–p interactions are elusive and difficult to study due to
In this contribution we report an extension to the anion–p
numerous competing other non-covalent interactions (e.g., hydrogen hosts by introducing two new electron-deficient fluorinated
0
and halogen bonds, p–p and C–H–p interactions, etc.).
aromatic motifs: perfluoro-1,1 -biphenyl (PFBP) and perfluoro-
Fluorine is the most electronegative element and as a sub- naphthalene (PFN) (Scheme 1). Solution studies of the parent
stituent in hexafluorobenzene induces a large positive quadrupole compounds (1 and 2) as well as the solid state studies of their
7
moment (Qzz (C
6
F
6
) = +9.50 B). Thus, it is not surprising that methylene DABCO bromide salts (3 and 4) are performed.
electron-deficient fluorinated arenes act as p-acceptors for a
multitude of anions.
Recently, PFBP and PFN are widely used in the areas of
8
materials science, environmental science, crystal engineering,
1
0
Previously, we have systematically studied several anions fuel cells, as well as supramolecular chemistry. However, until
manifesting p interactions when the pentafluorophenyl group now PFBP and PFN have not been systematically used in the
9
11
was utilized as the p-acceptor.
studies of anion–p interactions.
a
Institut f u¨ r Organische Chemie, RWTH Aachen, Landoltweg 1, 52074 Aachen,
Germany. E-mail: markus.albrecht@oc.rwth-aachen.de
b
c
Department of Chemistry, Nanoscience Center, University of Jyv a¨ skyl a¨ ,
Survontie 9, 40014 Jyv a¨ skyl a¨ , Finland. E-mail: kari.t.rissanen@jyu.fi
Department of Chemistry and Biotechnology, Tampere University of Technology,
Korkeakoulunkatu 8, 33720 Tampere, Finland. E-mail: arto.valkonen@tut.fi
Electronic supplementary information (ESI) available: Experimental details,
Results and discussion
Solution studies with perfluoro-1,1 -biphenyl (PFBP, 1) and
0
perfluoronaphthalene (PFN, 2) as anion receptors
19
†
F
The anion binding behaviour of the electron deficient 1 and 2 was
NMR spectra for the titration of 1 or 2 with various tetrabutylammonium salts.
Thermal ellipsoid diagrams for solved structures of 3 and 4. CCDC 1014200 and
investigated in CDCl
various anions as their tetrabutylammonium (TBA) salts (TBAꢀCl,
TBAꢀBr, TBAꢀF, TBAꢀI, TBAꢀNO and TBAꢀBF ). As representative
3
by room temperature NMR-titrations with
1
014201. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c4nj01654h
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case of the BF addition rules out the formation of a Meisenheimer
type complex. Due to the electron deficient nature of the aromatic
ring systems, interaction with the anion by anion–p interactions
is feasible. However, the results obtained do not allow any final
quantitative or even qualitative interpretation of the nature of
the interaction in solution.
Crystal structures of the bromide salts 3 and 4
In order to get some insight into the anion–p interactions of PFBP
or PFN units in the solid state, the bromide salt derivatives 3 or 4
were prepared (Scheme 2). The cationic DABCO methylene unit
was chosen as a substituent according to our earlier systematic
12
studies with related pentafluorophenyl derivatives.
Bromides 3 or 4 were synthesized from the parent com-
pounds 1 and 2 as shown in Scheme 1. In both cases a similar
reaction protocol was followed. Initially the perfluoroaromatic
cores were methylated twice (for 1) or once (for 2), respectively,
to obtain the methyl derivatives 5 and 7. Bromination of the
latter utilizing NBS in tetrachloromethane afforded the corre-
sponding bromomethyl derivatives 6 and 8. Addition of DABCO
resulted in the formation of the bromide salts 3 and 4 by
nucleophilic substitution reaction.
The bromides 3 and 4 crystallize well and allow the determina-
tion of their single crystal X-ray structures. The dicationic PFBP
2
derivative 3 was crystallized by diffusing Et O into the methanol
solution of 3. The salt crystallizes in the chiral space group C2 with
only a half molecule in the asymmetric unit. The perfluorobiphenyl
system has a torsional angle between the planes of the two phenyl
Fig. 1 19F NMR spectra for the titration experiment of PFBP (1) with TBA units of 49.4(13)1 (Fig. 2).
bromide (top) and tetrafluoroborate (bottom).
The two DABCO-methylene substituents of 3 are anti-orientated
with respect to the biphenyl unit. The bromides are slightly
disordered (92 : 8) over two positions and related by symmetry
1
9
examples, the F NMR spectra for the titrations of PFBP (1)
with TBA bromide (top) and tetrafluoroborate (bottom) are
shown in Fig. 1. Similar spectra are observed in all titrations
for both 1 and 2 (see ESI†).
Addition of a small amount of the respective salt does not
1
9
lead to significant shift differences in the F NMR spectra of
the perfluorinated compounds. Addition of six equivalents or
more reveals some significant high field shifting of the fluoride
signals. However, this cannot be correlated with some specific
binding between the aromatics and the salts; a more or less
linear relation between salt addition and peak shifting is found.
Nevertheless, there are two remarkable features when comparing
the two sets of spectra shown in Fig. 1 which are worth mentioning.
1. Addition of the spherical easily polarizable bromide anion
results in a more pronounced shifting of the aromatic fluorine
resonances compared to the shifting detected upon addition of
the ‘‘less coordinating’’ tetrafluoroborate anion.
2. The fluoride resonance of the tetrafluoroborate anion is also
dependent on the ratio between the electron deficient aromatic and
the anion. Upon addition of salt (reducing the amount of PFBP vs.
ꢀ
salt) a low field shift of the BF
4
resonance is observed.
Based on the described results we conclude that upon
addition of the tetrabutylammonium salts, an interaction is
taking place with the perfluoroaryl derivative. Shifting in the Scheme 2 Preparation of 3 and 4.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015
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Crystal structure analyses of the salt derivatives 3 and 4 clearly
indicate four positive interactions between bromide ions and
the electron deficient aromatics. Due to the symmetry of the
4
aromatic parts, a Z -type orientation of the bromide towards
the rings is observed in both cases. The present work has some
relevance in the search for anion receptors utilizing anion–p
interactions as one attractive energy contribution to selectively
Fig. 2 The structure of the bisbromide salt 3 as observed in the crystal (C: bind negatively charged species. It shows that this concept is not
black, H: grey, Br: brown, F: yellow-green, N: blue).
restricted to singular aromatic systems (e.g. pentafluorophenyl)
but can be found for a broad variety of electron deficient
rings. In addition our work might give further evidence for
possible interaction modes of fluorinated derivatives, e.g. in
1
3
medicinal chemistry.
Acknowledgements
We are grateful for the financial support from the China Scholar-
ship Council. This work was also supported by the Academy
of Finland (K. R.: project no. 122350, 140718, 265328, and
Fig. 3 Side view and top view of the structure of 4 in the crystal (C: black,
H: grey, Br: brown, F: yellow-green, N: blue, O: red).
2
63256), the University of Jyv ¨a skyl ¨a and the Tampere University
of Technology. Valuable discussions with Dr Michael Giese are
gratefully acknowledged.
(two-fold axis perpendicular to b). They are located close to the
corresponding cationic parts interacting weakly with a-hydrogens
of the DABCO unit (Brꢀ ꢀ ꢀH = 2.85, 2.88 Å, distances from the
Notes and references
2% component Br). Due to the torsion of the biphenyl units,
9
the bromide anions are not located on top of the centre of the
aromatic units, but in contrast to the related pentafluorophenyl
1
T. D. Hamilton and L. R. MacGillivray, in Self-Assembly
in Biochemistry in Encyclopedia of Supramolecular Chemistry,
ed. J. L. Atwood and J. W. Steed, Dekker, New York, 2004,
p. 1257.
(a) H.-J. Schneider, F. Werner and T. Blatter, J. Phys. Org.
Chem., 1993, 6, 590; (b) D. Qui n˜ onero, C. Garau, C. Rotger,
A. Frontera, P. Ballester, A. Costa and P. M. Dey `a , Angew.
Chem., Int. Ed., 2002, 41, 3389; (c) P. de Hoog, P. Gamez,
I. Mutikainen, U. Turpeinen and J. Reedijk, Angew. Chem.,
Int. Ed., 2004, 43, 5815.
1
2
derivative, are situated at the rim of the perfluorobenzene
ring with distances of 3.624(7), 3.640(7), 3.899(7) and 3.917(6) Å
to close CF carbon atoms. This indicates an attractive anion–p
2
4
interaction resulting in a Z -type interaction of the anion
towards the tetrafluorophenyl unit. In addition weak inter-
molecular Brꢀ ꢀ ꢀH interactions (2.75–2.91 Å) with neighbouring
DABCO moieties take place.
Crystals of the PFN-derivative 4 were obtained from methanol
by slow evaporation (space group Pbca) as methanol solvate. The
bromide ion has several weak contacts with DABCO units of
adjacent cations and the cocrystallized methanol molecule is also
hydrogen bonded to it (HꢀꢀꢀBr = 2.39(2) Å; OꢀꢀꢀBr = 3.228(4) Å,
3
4
(a) P. Ballester, Struct. Bonding, 2008, 129, 127; (b) B. L. Schottel,
H. T. Chifotides and K. R. Dunbar, Chem. Soc. Rev., 2008, 37, 68;
(c) B. P. Hay and V. S. Bryantsev, Chem. Commun., 2008, 2417;
(d) A. Frontera, P. Gamez, M. Mascal, T. J. Mooibroek and
1
731). One of the cationic units interacts by means of CHꢀꢀꢀBr
J. Reedijk, Angew. Chem., Int. Ed., 2011, 50, 9564.
See for example: (a) A. Frontera, D. Quinonero, A. Costa,
P. Ballester and P. M. Dey `a , New J. Chem., 2007, 31, 556;
hydrogen bonds (2.79 and 3.06 Å) with the anion while additional
attractive interactions occur by means of anion–p interactions.
Again the anion is not located on top of the perfluoronaphthyl
ring but is located close to the a and b carbon atom of the ring
(b) S. Demeshko, S. Dechert and F. Meyer, J. Am. Chem. Soc.,
2
004, 126, 4508; (c) C. S. Campos-Fern ´a ndez, B. L. Schottel,
4
system bearing the DABCO methylene unit (Z -type; Br–C =
H. T. Chifotides, J. K. Bera, J. Bacsa, J. M. Koomen, D. H. Russell
and K. R. Dunbar, J. Am. Chem. Soc., 2005, 127, 12909; (d) B. L.
Schottel, H. T. Chifotides, M. Shatruk, A. Chouai, J. Bacsa,
L. M. P ´e rez and K. R. Dunbar, J. Am. Chem. Soc., 2006,
3
.571(5), 3.638(4), 3.870(4) and 3.738(5) Å) (Fig. 3).
Conclusions
128, 5895; (e) S. Furkawa, T. Okubo, S. Masaoka, D. Tanaka,
Herein, we demonstrated that electron deficient fluorinated
H. Chang and S. Kitagawa, Angew. Chem., Int. Ed., 2005, 44, 2700;
( f ) P. U. Maheswari, B. Modec, A. Pevec, B. Kozlevcar,
C. Massera, P. Gamez and J. Reedijk, Inorg. Chem., 2006,
45, 6637; (g) H. Casellas, C. Massera, F. Buda, P. Gamez and
J. Reedijk, New J. Chem., 2006, 30, 1561; (h) A. Galstyan,
P. J. S. Miguel and B. Lippert, Chem. – Eur. J., 2010, 16, 5577.
biphenyl or naphthyl units can act as p-acceptors for anions.
1
9
Solution studies show significant F NMR shifts upon addition
of tetrabutylammonium salts with various anions to the parent
compounds PFBP 1 or PFN 2. The underlying interactions
are not specific but might be due to anion–p interactions.
748 | New J. Chem., 2015, 39, 746--749
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E.g. (a) M. Giese, M. Albrecht, T. Krappitz, M. Peters,
M. Albrecht, C. Banwarth, G. Raabe, A. Valkonen and
K. Rissanen, Chem. Commun., 2011, 47, 8542; (d) M. Giese,
M. Albrecht, G. Ivanova, A. Valkonen and K. Rissanen,
Supramol. Chem., 2012, 24, 48; (e) M. Giese, M. Albrecht,
A. Valkonen and K. Rissanen, Chem. Sci., 2015, DOI:
10.1039/C4SC02762K.
V. Gossen, G. Raabe, A. Valkonen and K. Rissanen, Chem.
Commun., 2012, 9983; (b) Z. Sun, M. Albrecht, M. Giese, F. Pan
and K. Rissanen, Synlett, 2014, 2075; (c) A. Bretschneider,
D. M. Andrada, S. Dechert, S. Meyer, R. A. Mata and
F. Meyer, Chem. – Eur. J., 2013, 19, 16988.
6
M. M u¨ ller, M. Albrecht, V. Gossen, T. Peters, A. Hoffmann, 10 (a) A. J. Ilott, S. Palucha, A. S. Batsanov, M. R. Wilson and
G. Raabe, A. Valkonen and K. Rissanen, Chem. – Eur. J.,
010, 16, 12446.
C. Garau, A. Frontera, D. Qui n˜ onero, P. Ballester, A. Costa
and P. M. Dey `a , ChemPhysChem, 2003, 4, 1344.
For selected examples of pentafluorophenyl derivatives as
anion-acceptors see: (a) R. J. G ¨o tz, A. Robertazzi,
I. Mutikainen, U. Turpeinen, P. Gamez and J. Reedijk, Chem.
Commun., 2008, 3384; (b) P. S. Lakshminarayanan,
I. Ravikumar, E. Suresh and P. Ghosh, Inorg. Chem., 2007,
P. Hodgkinson, J. Am. Chem. Soc., 2010, 132, 5179;
(b) M. J. Molski, M. A. Khanfar, H. Shorafa and K. Seppelt,
Eur. J. Org. Chem., 2013, 3131; (c) K. Kasai and M. Fujita,
Chem. – Eur. J., 2007, 13, 3089; (d) J. C. Collings, K. P. Roscoe,
R. Ll. Thomas, A. S. Batsanov, L. M. Stimson, J. A. K. Howard
and T. B. Marder, New J. Chem., 2001, 25, 1410; (e) D. W. Shin,
S. Y. Lee, C. H. Lee, K. Lee, C. H. Park, J. E. McGrath,
M. Zhang, R. B. Moore, M. D. Lingwood, L. A. Madsen,
Y. T. Kim, I. Hwang and Y. M. Lee, Macromolecules, 2013,
46, 7797; ( f ) Y. Chen, C. H. Lee, J. R. Rowlett and
2
7
8
4
6, 4769; (c) I. Ravikumar, P. S. Lakshminarayanan,
M. Arunachalam, E. Suresh and P. Ghosh, Dalton Trans.,
009, 4160; (d) O. B. Berryman, F. Hof, M. J. Hynes and
¨
J. E. McGrath, Polymer, 2012, 53, 3143; (g) T. Oberg and
2
M. S. Iqbal, Chemosphere, 2012, 87, 975; (h) A. Voege,
V. A. Deimede and J. K. Kallitsis, J. Polym. Sci., Part A: Polym.
Chem., 2012, 50, 207; (i) J. Kerres, F. Schoenberger,
A. Chromik, T. Haering, Q. Li, J. O. Jensen, C. Pan, P. Noye
and N. J. Bjerrum, Fuel Cells, 2008, 8, 175.
D. W. Johnson, Chem. Commun., 2006, 506; (e) H. Maeda,
Y. Ishikawa, T. Matsuda, A. Osuka and H. Furuta, J. Am.
Chem. Soc., 2003, 125, 11822; ( f ) H. Schneider,
K. M. Vogelhuber, F. Schinle and J. M. Weber, J. Am. Chem.
Soc., 2007, 129, 13022; (g) L. Adrienssens, G. Gil-Ramirez, 11 I. Alkorta, I. Rozas and J. Elguero, J. Am. Chem. Soc., 2002,
A. Frontera, D. Quinonero, E. C. Escudero-Adan and
P. Ballester, J. Am. Chem. Soc., 2014, 136, 3208.
(a) M. Albrecht, C. Wessel, M. de Groot, K. Rissanen and
124, 8593.
12 M. Albrecht, M. M u¨ ller, O. Mergel, K. Rissanen and
A. Valkonen, Chem. – Eur. J., 2010, 16, 5062.
9
A. L u¨ chow, J. Am. Chem. Soc., 2008, 130, 4600; 13 J. Wang, M. Sanchez-Rosello, J. Luis Acena, C. del Pozo,
(
b) M. Albrecht, M. M u¨ ller, O. Mergel, A. Valkonen and
A. E. Sorochinsky, S. Fustero, V. A. Soloshonok and H. Liu,
K. Rissanen, Chem. – Eur. J., 2010, 16, 5062; (c) M. Giese,
Chem. Rev., 2014, 114, 2432.
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