ISMSC 2007 - Università degli Studi di Pavia

Bishydrazide derivatives of isoindoline – the simple anion receptors
selective for carboxylates
Pawe Dydio a,b , Tomasz Zieliski a , Janusz Jurczak a,b
a
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224
Warsaw, Poland
b
Department of Chemistry, Warsaw University, Pasteura 1, 02-093 Warsaw, Poland
Anions are of crucial importance in many essential chemical and biological processes, due to
this fact the development of strong and selective artificial anion receptors is an area of intensive
exploration. [1] Recently scientists’ attention has been focused on neutral ligands which bind
anions by hydrogen bond. Because of directional and distance-dependent character of this
interaction it is possible to construct binding sites adjusted for specific anion. Thus, in order to
achieve high selectivity, researchers investigate hosts that use hydrogen bond donors as
anchoring points (mainly amide, sulphonoamide, urea, hydrazide, hydrazone groups or pyrrole
moiety). [2] Presence of a chromophore in such systems can lead to optical sensors for anions.
1,3-diiminoisoindoline moiety combines both of these attractive features – contains acidic proton
NH and has been used for construction of artificial dyes. Therefore, we decided to examine
simple hydrazide-based receptors built on isoindoline skeleton.
.
N
N N
O
N
O O
N
H
H H
C H 5 11
C H 5 11
Scheme 1
N
N N
N
H
N
H H
O
O
N
N
H
N
H
N
N
H
N
N
O
O
N
N N
N N
H
H
H
N H N
H
1 2 3 4
PSA 47
We prepared bishydrazides (1-4) derived from isoindoline (Scheme1) and examined their anion
binding properties. NMR and UV/Vis titrations revealed that these simple acyclic ligands,
equipped with just three (five for 4) anchoring points, have strong affinity towards anions even in
the very demanding solvent – DMSO. We observed high selectivity of our ligands for
carboxylates over phosphates. Moreover, these compounds signal presence of anions by
switching-on absorption of visible light.
[1] J. L. Sessler, P. A. Gale, W. S. Cho, Anion Receptor Chemistry, The Royal Society of
Chemistry, Cambridge, 2006.
[2] S. O. Kang, R. A. Begum, K. Bowman-James, Angew. Chem. Int. Ed., 2006, 45, 7882-7894;
P. A. Gale, R. Quesada, Coord. Chem. Rev., 2006, 250, 3219-3244.
O
Protonated Macrobicycle Host Containing Pyridine Head-Units for the
Recognition of Anions
David Esteban-Gómez, Carlos Platas-Iglesias, Teresa Rodríguez-Blas and Andrés de Blas.
Universidade da Coruña; Departamento de Química Fundamental, Facultade de Ciencias,
Campus da Zapateira s/n (15071) A Coruña, Spain.
Herein In this work we report two macrobicyclic receptors based on azacrown platforms
containing pyridine head units useful for anion recognition. UV-Vis and 1 H NMR studies indicate
that these receptors can be triprotonated in acetonitrile by addition of CF3COOH. The first two
protonation processes involve the protonation of the nitrogen atoms of the crown moiety, while
the third protonation occurs on the pyridine nitrogen atom. The interaction of the protonated
lateral macrobicycles with different anions have been followed by means of spectrophotometric
titrations in acetonitrile solution. Among the different anions investigated, the highest affinity of
these receptors is observed with chloride. The association constants for the interaction of halide
anions with the protonated forms of the macrobicycles vary in the following order:
F - < Cl - > Br - > I - , with an increase of the binding constants by more than two logarithmic units
from F - to Cl - being observed for L 1 . The association constants also indicate an important
degree of selectivity of these macrobicyclic receptors for Cl - over Br - or I - . On the other hand,
the binding constants data indicate that these receptors present a high sulphate to nitrate
binding selectivity.
ε x 10 -3 M -1 cm -1
25
20
15
10
5
0
N
NH HN
N
N
O n
O O
L 1 : n = 1
L 2 : n = 2
ε x 10 -3 M -1 cm -1
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
CF3COOH NH
N
H
HN
[Bu4N]·A 0 2 4 6 8 10
250 300 350 400 450
wavelength, nm
equiv H +
NH HN
O n
O O
319 nm
ε x 10 -3 M -1 cm -1
25
20
15
10
5
0
3+
ε x 10 -3 M -1 cm -1
5.5
5.0
4.5
4.0
3.5
3.0
wavelength, nm
NH
N
H
A
HN
NH HN
O n
O O
-
0 1 2 3 4
equiv Cl -
300 nm
PSA 48
250 300 350 400
The X-ray crystal structures analysis of the chloride and bromide complexes of L 1
confirms the formation of the desired supramolecular complexes, with the halide anions being
hold within the macrobicyclic cavity by five NH···X hydrogen bonds.
2+