ISMSC 2007 - Università degli Studi di Pavia

Functional [2×2] Grids
Xiao-Yu Cao a , Jack Harrowfield a , Jean-Marie Lehn a , Augustin Madalan a , Jonathan R.
Nitschke a,b
a Institut de Science et d'Ingénierie Supramoléculaires, 8, allée Gaspard Monge, 67083
Strasbourg, France
b Department of Organic Chemistry, University of Geneva, 30 quai Ernest-Ansermet, 1211
Genève 4, Switzerland
PSA 25
Generation of well-defined supramolecular architectures from metal-directed self-assembly of
complexes of multidentate ligands has emerged as a highly promising pathway to nanometresized
functional materials during the last decade. Grid-type metallosupramolecular entities are
of particular interest as they form well-defined arrays of metal ions that exhibit novel optical,
electronic and magnetic properties. The extensively studied [2×2] grids possess similar fourfoldsymmetric
structural features to those of the versatile scaffolds of calix-[4]arenes and
porphyrins, but are distinguished by the ease of ringing changes such as the nature of their
substituents, the bound metal ions and size of the ligands.
Here, we report the modification of two types of bis-hydrazone ligands by the introduction of
functional residues. Complex formation with metal ions [Fe(II), Co(II), Ni (II), Cu(II), Zn(II) etc.]
gives [2×2] grids with two distinct modes of decoration. "Axial" decoration provides "bisquartet"
receptor arrays on each side of the grid. "Lateral" decoration provides multivalent assemblies
with eight branches surrounding the grids. The ultimate goal of this work is to produce grids with
appropriate functionality to act as multivalent receptors for biomolecules, that is, to provide what
may be termed “nanosized biochips”.
[1] Nitschke, J. R.; Lehn, J.-M. Proc.Natl. Acad. Sci. U. S. A. 2003, 100, 11970-11974.
[2] Ruben, M.; Rojo, J.; Romero-Salguero, F. J.; Uppadine, L. H.; Lehn, J.-M. Angew. Chem.-Int.
Ed. 2004, 43, 3644-3662.
[3] Tielmann, P.; Marchal, A.; Lehn, J.-M. Tetrahedron Lett. 2005, 46, 6349-6353.
[4] Barboiu, M.; Ruben, M.; Blasen, G.; Kyritsakas, N.; Chacko, E.; Dutta, M.; Radekovich, O.;
Lenton, K.; Brook, D. J. R.; Lehn, J.-M. Eur. J. Inorg. Chem. 2006, 784-792.
[5] Cao, X.-Y.; Kyritsakas-Gruber, N.; Harrowfield, J.; Madalan, A.; Nitschke, J.; Ramirez, J.;
Rissanen, K.; Russo, L.; Stadler, A.-M.; Vaughan, G.; Lehn, J.-M. Eur. J. Inorg. Chem. In press.
PSA 26
Binding studies of a protonated dioxatetraazamacrocycle with anionic
guests
Sílvia Carvalho a , Rita Delgado a,b , Michael M. G. Drew c , Vânia Calisto d and Vítor Félix d
a Instituto de Tecnologia Química e Biológica, UNL, Apartado 127, 2781-901 Oeiras, Portugal;
b Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; C School of
Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK d Departamento de
Química, CICECO, Universidade de Aveiro, 3810-193 Aveiro, Portugal
Email: silviac@itqb.unl.pt
The interest in the recognition process of anionic species (guests) and different synthetic hosts
arises mainly from the importance of anions in the environment, the medicine and in industry.
The recognition is achieved by formation of non-covalent bonds between a rigid and preorganized
host architecture and the guest sites [1,2].
In the present work, the association ability of H4[26]pbz2N4O2 4+ [3] for
N
O
N
[26]pbz2N4O2
N
O
N
phthalate (ph 2- ), isophthalate (iph 2- ), terephthalate (tph 2- ),
benzenetricarboxylate (btc 3- ), citrate (cit 3- ), cyclohexanetricarboxylate
(cta 3- ) and malonate (mal 2- ) was evaluated by potentiometric and NMR
spectroscopic measurements.
The binding constants of the
(Hn[26]pbz2N4O2) n+ with the various anions
were determined in aqueous solution at
298.2 K and 0.10 M KCl. The strongest
associations were observed for the iph 2- and
btc 3- anions.
1 H NMR titrations in D2O allowed to understand the type of
interactions involved in the host-guest association process.
The single crystal structures of H4[26]pbz2N4O2 4+ with ph 2- and
tph 2- anions showed that both guests are inserted between two
macrocyclic units forming supramolecular associations as illustrated for tph 2- in the figure above.
The molecular recognition processes between the receptor and selected carboxylate anions
(ph 2- , iph 2- and btc 3- ), as well as halides (F - , Cl - , Br - and I - ), were also investigated by molecular
dynamics simulations carried out in water solution. The obtained structural and theoretical
energetic data will be presented and compared with the experimental results.
[1] V. Amendola, M. Bonizzoni, D. Esteban-Gómez, L. Fabbrizzi, M. Licchelli, F. Sancenón, A.
Taglietti, Coord. Chem. Rev., 250, 1451, 2006.
[2] S. Carvalho, R. Delgado, N. Fonseca, V. Félix, New J. Chem., 30, 247, 2006.
[3] S. Carvalho, R. Delgado, M. G. B. Drew, V. Félix, Dalton Trans., in press
The authors acknowledge the financial support from Fundação para a Ciência e Tecnologia (FCT) and
POCI, with coparticipation of the European Community fund FEDER (Project n. POCI/QUI/56569/2004).
Sílvia Carvalho also acknowledges the PhD grant from FCT (SFRH/BD/13793/2003).