ISMSC 2007 - Università degli Studi di Pavia

PSA 65
Synthesis of Self-Assembly Systems through Multiple Hydrogen Bonding
Interactions between DNA modified bases for Supramolecular Applications
Elisabetta Greco a , Abil E. Aliev a , Kason Bala b , Peter Golding b and Helen C. Hailes a .
a Department of Chemistry, University College London, 20, Gordon Street, London WC1H 0AJ,
UK; b AWE, Aldermaston, Reading, Berkshire, RG7 4PR, UK. (e.greco@ucl.ac.uk)
Supramolecular hydrogen-bonded polymers have numerous applications in materials chemistry,
including use as reversible polymers that respond to changes in temperature or solvent 1 .The
properties of such materials can be tailored according to the type of hydrogen-bonding array
utilised, or the polymeric units inserted. The design of novel supramolecular materials requires
the synthesis of core modules capable of forming strong hydrogen bonding interaction. Despite
considerable progress in this area, the synthesis of supramolecular polymers based on the selfassembling
DDAA modules has been predominantly restricted to materials incorporating the
ureidopyrimidinone (Upy) unit reported by Meijer et al. 2
We have recently reported the synthesis and characterisation of a novel quadruple
hydrogen-bonding system incorporating a cytosine unit as a DDAA module 3 . The cytosine
module was designed such that it does not undergo tautomeric changes which are observed
with UPys. It formed quadruple hydrogen bonded assemblies both in solution and in the solid
state, and the dimerization constant was estimated to be > 9 10 6 M -1 in C6D6.
One major advantage of the cytosine-based arrays are that bifunctional cytosine motifs
can readily be prepared through incorporation of a group R in addition to the polymeric or
spacer unit. Recent results on the synthesis of cytosine modules possessing alternative R group
will be described, together with the utilisation of different hydroxyl and amine terminated
spacers or telechelic polymers (Figure 1).
R
N
O N N
H
O
N
H
n
N
H
O
O
Polymer
O
O N H
A A D D Polymer or small unit in the middle linked by
a flexible spacer to the Cytosine unit
Figure 1: R = alkyl chain
The synthesis of polymers incorporating single and double urea units will also be reported and
the physical properties of the materials prepared. Our results will highlight that the new cytosine
module can be used successfully for the generation of novel supramolecular polymers.
[1] J.M.Lehn, Supramolecular Chemistry, Science, 1993, 260, 1762-63.
[2] A.T. Ten Cate, H. Kooijman, A.L. Spek, R.P. Sijbesma, E.W. Meijer, J. Am. Chem. Soc.,
2004, 126, 3801-08.
[3] V.G.H. Lafitte, A.E. Aliev, P.N. Horton, M.B. Hursthouse, K. Bala, P. Golding, H.C. Hailes, J.
Am. Chem. Soc., 2006, 128, 6544-45.
n
N
H
O
N
H
N
N R
O
A New Schiff Base Expanded Porphyrin Derived from Carbazole
Jonathan L. Sessler, Dustin E. Gross and Vincent M. Lynch
Department of Chemistry and Biochemistry, 1 University Station, The University of Texas at
Austin, Austin, TX, 78712, USA
Schiff base oligopyrrole macrocycles (so-called ‘expanded porphyrins’) 1 have attracted much
attention for use as ligands for the coordination of various lanthanide, actinide, and transition
metal cations. 2 The resulting complexes have been studied for a variety of applications,
including those associated with drug development. Complementing these ongoing studies is
the recognition that Schiff base expanded porphyrins, especially when protonated, may have a
role to play as easy-to-modify receptors for neutral and anionic substrates. 3 This awareness
has prompted us to focus on the construction of new, rationally designed Schiff base
oligopyrrolic anion receptors. In this context, we have synthesized and characterized through
X-ray diffraction means the new expanded, non-aromatic Schiff base macrocycle 3. As shown
in the scheme below, it was prepared by condensing 1,8-diaminocarbazole 1 with a diformyl
tripyrrane 2 in the presence of an acid catalyst. Macrocycle 3, containing sp 3 -hybridized meso
bridging carbon centers, could be readily oxidized to afford 4. This latter product was found to
bind chloride anions effectively in the solid state. Based on these findings, macrocycle 4 has
been studied as a potential anion receptor and as a possible cation coordinating ligand in
organic media. The results of these investigations will be detailed in this presentation.
R
R' R'
H 2N
O
NH
N
H
1
+
H
N
2
NH 2
O
HN
R
HCl
MeOH
R
R' R'
N
NH
N
H
Cl -
H
N
3 HCl
N +
H
HN
R
air, TEA
acetone
R
R' R'
N
NH
N
H
Cl -
H
N
4 HCl
N +
H
HN
R = CH 2CH 3, CH 2CH 2CH 2OH, CH 2CH 2CH 2OCOCH 3
R' = Cl, alkyl
[1] Callaway, W. B.; Veauthier, J. M.; Sessler, J. L. J. Porphyr. Phthalocy. 2004, 8, 1-25.
[2] Sessler, J. L.; Seidel, D. Angew. Chem., Int. Ed. 2003, 42, 5134-5175.
[3] Sessler, J. L.; Gale, P. A.; Cho, W. S., Anion Receptor Chemistry. Royal Society of
Chemistry: Cambridge, 2006.
PSA 66
R