ISMSC 2007 - Università degli Studi di Pavia

Sensing with cavitands: Moving from selectivity to specificity
Paolo Betti a , Gionata Battistini b , Luca Prodi b , Enrico Dalcanale a
a Dipartimento di Chimica Organica ed Industriale, Università di Parma, viale G.P. Usberti 17/a,
43100 Parma, Italy
b Dipartimento di Chimica “G. Ciamician”, via F. Selmi n.2, 40126 Bologna, Italy
Quartz-Crystal-Microbalance mass transducers (QCM) are by far the easiest platforms to
translate the chemical recognition proprieties of a receptor in a treatable signal. We have
already designed and tested QCM supramolecular sensors using phosphonate cavitands as
coated molecular receptors. These cavitands present a phosphonate bridging group as
hydrogen bond acceptor having the P=O group oriented alternatively inward (POin) or outward
(POout) with respect to a preorganised cavity, capable of CH-π interactions.[1] The simultaneous
presence of the two interactions which is possible only for the POin isomer, provides an
exceptional rise in selectivity toward short chain alcohols.[2] However, upon increasing the
chain length of the alcohol, the purely dispersive unspecific interactions become dominant with
respect to the specific ones, jeopardizing the selectivity of the sensors.
To overcome this problem and reach the desired specificity we have designed and tested a new
class of phosphonate cavitands incorporating a suitable transduction group (a chromophore),
which can be activated exclusively by the molecular recognition event.
More specifically, by coupling the H-bond acceptor to the chromophore it has been possible to
change the emission spectra of the chromophore upon analyte complexation. This behavior has
been observed both in solution and in a coated solid film.
O
O
O
R
R
O
NH
R
O
P
O
R
O
O
O
Analytes
Emission Spectra
[1] R. Pinalli, M. Suman, E. Dalcanale, Eur. J. Org. Chem., 2004, 451 – 462
[2] L. Pirondini, E. Dalcanale, Chem. Soc. Rev., 2007, 35, in press
PSA 17
The Construction of Coordination Networks Incorporating {M(tpy)2} n+ PSA 18
(tpy =
2,2:6,2-terpyridine) Groups
Jonathon E. Beves, a Edwin C. Constable, a Catherine E. Housecroft, a Cameron J. Kepert b ,
Markus Neuburger, a David J. Price b and Silvia Schaffner a
a Department of Chemistry, University of Basel, Spitalstrasse 51, CH-4056, Basel, Switzerland
b School of Chemistry, University of Sydney, NSW 2006, Australia
Iron(II) and ruthenium(II) complexes of 2,2’:6’,2’’-terpyridine are the focus of extensive interest
in supramolecular chemistry [1]. The inclusion of these groups into extended structures offers
the opportunity to build electrochemical or photophysical properties into addressable molecular
frameworks.
~7 Å
N
N
~18 Å
N
N
N
Ru
N
N N
N
1 2
N
2+
~22 Å
N
N
NH
N
N N
Ru
N N
We are developing [2] coordination polymers containing {M(tpy)2} units. A key building block is
the ligand 4’-(4-pyridyl)-2,2’:6’,2”-terpyridine, which acts as a terdentate ligand with a pendant 4pyridyl
ring. In these structures the {M(tpy)2} moieties act as ‘expanded 4,4'-bipyridines’ in which
the two 4-pyridyl metal-binding domains are separated by metal-containing {M(tpy)2} scaffolds.
Figure 1 ([Ru(tpypy)2]-Ag-)n coordination polymer
[1] E. C. Constable, Chem. Soc. Rev., 2007, 36, 246.
[2] J. E. Beves, E. C. Constable, C. E. Housecroft, C. J. Kepert, D. J. Price, CrystEngComm,
2007, in press.
N
HN N
3
N
2+