ISMSC 2007 - Università degli Studi di Pavia

Aryl calix[4]pyrroles. Scaffolds to obtain evidences of anion- interaction.
Guzman Gil-Ramirez, ‡ Mª Angeles Sarmentero ‡ , and Pablo Ballester. §
‡ Institute of Chemical Research of Catalonia (ICIQ), Avda. Països Catalans 16, 43007
Tarragona, Spain. § ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
Supramolecular chemistry of host – guest complexes for cations or neutral species has
received much attention in the last two decades. Nevertheless, the chemistry of anion -
interactions is much less developed. In fact, this term was coined only five years ago by
Frontera and Deyà [1]. Theoretical investigations have been reported on the interaction of
halides with electron deficient -systems, like fluorobenzene, fluoro-s-triazine [2] and s-tetrazine
[3] derivates. All the calculations indicate clearly a favourable non covalent interaction between
the halide and the system. Few experimental evidences, however, have been reported in
support to the theoretical calculations and most of them are based on solid state structures.
Although calix[4]pyrroles were discovered more than a century ago [4], it was not until
1996 when Sessler [5] re-discovered them as receptors capable of interacting with anion and
neutral substrates. Calix[4]pyrroles present four NH groups that can act simultaneously and in a
convergent manner, generating an interaction centre suitable for electron rich neutral molecules
or anions. In particular, isomer of meso- tetraaryl substituted calix[4]pyrroles adopts a
cone conformation with a deep cavity. The presence and chemical modification of the aryl rings
alters the electronic properties of the cavity and modifies its binding affinity towards the anion.
This presentation will describe the synthesis of several calix[4]pyrrole receptors
containing deep aromatic cavities. The complexation process of these receptors with several
anions have been probed using 1 H and 19 F NMR ,as well as, ITC techniques. Furthermore, we
have obtained several crystal structures of the anionic complexes which are in complete
agreement with the results obtained in solutions. The electronic richness of the aromatic cavity
influences the association constants, following a clear trend that can only be explained through
the establishment of favourable anion- interactions.
CN
R R
N
H
R=
NH HN
H
N
1 2 3 4
R
R
Figure 1 –Left – Minimized structure of the complex formed by a calyx[4]pyrrole with a
deep aromatic cavity and clhoride. CPK representation with chloride anion in green. Right –
Molecular structure of of the receptors used in this study.
[1] Quinonero, D.; Garau, C.; Rotger, C.; Frontera, A.; Ballester, P.; Costa, A.; Deya, P. M.,
Angew. Chem., Int. Ed. 2002, 41, (18), 3389-3392.
[2] Mascal, M.; Armstrong, A.; Bartberger, M. D., J. Am. Chem. Soc. 2002, 124, (22), 6274-
6276.
[3] Garau, C.; Quinonero, D.; Frontera, A.; Costa, A.; Ballester, P.; Deya, P. M., Chem. Phys.
Lett. 2003, 370, (1,2), 7-13.
[4] Baeyer, A., Ber. Dtsch. Chem. Ges. 1886, 19, 2184.
[5] Gale, P. A.; Sessler, J. L.; Kral, V.; Lynch, V., J. Am. Chem. Soc. 1996, 118, (21), 5140-
5141.
NO 2
PSA 59
NH 2
PSA 60
Hexa-Phosphorylated Triphenylenes (HPT) for aromatics and carbohydrates
recognition
Cécile GIVELET a ; Brigitte BIBAL a
c.givelet@ism.u-bordeaux1.fr
a University of Bordeaux 1, Institut des Sciences Moléculaires, UMR CNRS 5255
351 cours de la Libération, 33405 Talence, France.
CH- and - interactions are widespread in Nature. 1 They play a crucial role in numerous
biological processes such as the helical structuration of DNA, proteins folding, cellular
recognition, and enzyme-substrate recognition.
A better knowledge of these interactions would bring a major breakthrough in the field of
molecular detection, transport and separation of aromatic and aliphatic compounds.
Our concept is based on hexasubstituted -extended architectures which are able to interact
with biological targets (catecholamine, sugars) or water pollutants (Alachlor,
pentachlorophenol).
-extended platform
(HPT)
GUEST
CH- or - interactions
( )
We designed and efficiently synthesised, a new class of molecular receptors: the Hexa-
Phosphorylated Triphenylenes (HPT) 1a-d.
R
O P R
O
O
O P R
R
R
P
O
O
R
R
O
P
R
O
HPT 1a-d
O
O
P
R
R
O
R
P
O
R
1a : R = Ph
1b : R = C 6H 4 -p-OMe
1c : R = C 6H 4 -p-OH
1d : R = C 6H 4 -p-O(CH 2CH 2) 3OMe
We studied 1a-d in different media using NMR (2D, 1D), UV-Visible Absorption and
Fluorescence Emission spectroscopies. For instance receptor 1c shows high affinity for
Dopamine (Ka H2O/MeOH: 96/4 = 3,56x10 +4 M -1 ) and D-Glucose (Ka H2O/MeOH: 96/4 = 2x10 +4 M -1 ).
Selectivity and nature of the interactions are questioned.
[1] Hunter, C. A.; Lawson, K. R.; Perkins, J. Urch, J. C. J. Chem. Soc. Perkin Trans. 2,
2001,651-669. Hunter, C. A. Sanders, K. M. J. Am. Chem. Soc. 1990, 112, 14, 5525-5534.