ISMSC 2007 - Università degli Studi di Pavia

Multi-chromophoric assemblies obtained via metallo-porphyrins and
bisimide dyes coordination
Elisabetta Iengo a , Gregory J. E. Davidson a , G. Dan Pantos a , Jeremy K. M. Sanders a
a
University of Cambridge, Department of Chemistry, Lensfield Road, Cambridge CB2 1EW,
UK. (email: ei212@cam.ac.uk)
The selective affinity of different metallo-porphyrins towards nitrogen or oxygen has been
exploited for the efficient construction of stable multi-chromophoric assemblies. In particular,
Al(III)-porphyrins can axially bind one -COOH or one -OH moiety, whereas Ru(II)(CO)porphyrins
can bind one pyridyl group [1-3]. Therefore, a very flexible strategy can be used to
assemble units with different functionalities. A variety of building blocks, including bisimide dyes
bearing appended pyridyl and/or carboxylic functionalities, as well as Al(III)(OH)-monopyridyl or
tetrapyridyl porphyrins and Ru(II)(CO)-tetraphenyl porphyrins have been prepared. These units
have been successfully combined to produce a variety of multi-component systems with
increasing complexity (some examples are reported in the figure below). All the adducts have
been fully characterized in solution and are very stable (at least up to 10 -5 M). For some of them
the X-ray crystal structure has been obtained. Such systems gathers together different types of
chromophores, and are currently object of photophysical studies.
N N
Al
N N
O
O
N
O
O
O
N
O
O
N
O
[1] J. K. M. Sanders, N. Bampos, Z. Clyde-Watson, S.L. Darling, J.C. Hawley, H-J. Kim, C. C.
Mak and S. J. Webb in The Porphyrin Handbook; K. M. Kadish, K. M. Smith and R. Guilard
Eds.; Academic Press New York, 2000, 3, 1-48.
[2] P. P. Kumar and B. G. Maiya New J. Chem. 2003, 27, 619-625.
[3] G. J. E. Davidson, L. H. Tong, P. R. Raithby and J. K. M. Sanders Chem. Commun. 2006,
29, 3087-3089.
O
N
O
O
O
Al N
PSA 79
Ru CO
PSA 80
Enantiodiscrimination of Carboxylic acid Anions by Abiotic Guanidinium
Receptors
Vinod D. Jadhav and Franz P. Schmidtchen
Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, 85747,
Garching, Germany. e-mail: vinod.jadhav@ch.tum.de
Chiral differentiation of carboxylic acid anions has gained importance due to its presence in
biologically related processes. Towards this goal chiral bicyclic guanidinium anchor groups (cf.
1-3) gained particular prominence recently. The chiral macrocyclic guanidinium host 1 was
shown to effectively differentiate the antipodal tartrate and aspartate anions 1 compared to its
iso-structural open chain analogue 2. The macrocyclic host 1 also forms complexes of higher
stoichiometry with carboxylic anions, thus indicating its structural adaptability. This originates
from its flexibility and the possibility of self-satisfying intramolecular interactions. The great
variety of options for guest binding modes weakens and almost annihilates the chiral recognition
capacity.
N
NO2
O
O
N
H
NH
N
H
N
H N
H
HN
+ +
NH
H
N
H
N
H
N
HN
H
N
O
O
NO 2
1
N
In an effort to emphasize the uniqueness of the binding mode host 3 was constructed. The
design is based on accessibility restrictions of the guanidinium anchor sites formed by rigid
annellation of congested benzimidazole heterocycles. The synthetic strategy started from an
achiral guanidinium building block which after annelation was separated into diastereomeric and
enantiomeric anion hosts. We report on the preparation and preliminary host-guest binding
properties of these novel anion receptors.
N
S
N
N
H
N
R 3
N
H
S
N
(1) Jadhav, V. D.; Schmidtchen, F. P. Org. Lett. 2006, 8, 2329-2332.
N
R
N
NH
NH
O
NH
NH
O
2
N
H
H
N
NO 2
NO 2
X-ray structure of 3-S-mandelate (R=H)