ISMSC 2007 - Università degli Studi di Pavia

PSB 37
New Anthracene-based cyclophane: complexation of organic cations and
formation of Diels-Alder adducts.
Bernardo Masci a , Sara Pasquale a
a Dipartimento di Chimica, Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185
Roma, Italy
Cyclophane 1 and analogues have been found to strongly bind quaternary ammonium ions and
alkylviologen cations. Complex formation has been investigated through both 1 H NMR and UVvis
techniques in CDCl3 or CDCl3- CD3CN solution, moreover the crystal structure has been
obtained of the pseudo-rotaxane complex 2, featuring a propylviologen axle. Work is in progress
to introduce bulky end groups as stoppers to obtain the analogous locked systems. The
presence of the two anthracene units has been exploited to obtain Diels Alder adducts in which
the shape of the cavity is strongly modified. For instance, both mono- and diadduct formation
has been observed in the presence or fullerene C60, the anthracene units undergoing reaction in
9,10-positions. A more extensive investigation has been carried out in the presence of
tetracyanoethylene that gives a fast reversible reaction at room temperature. In the latter case a
quantitative analysis of the formation of monoadduct 3 and diadduct 4 has been performed,
such high values as 3·10 6 L·mol -1 being observed in CDCl3-CD3CN 1:1. The above Diels-Alder
equilibrium is strongly affected by added alkylviologen guests, that selectively bind 1 rather than
the adducts.
t-Bu
O
OR
O
O
RO
1
t-Bu
O
NC
NC
NC
NC
O
t-Bu
t-Bu
O
O
OR
OR
RO
O
NC O
NC
RO
O
NC
O
t-Bu
NC
23
34
2
CN
CN
CN
CN
O
t-Bu
Lariat-type polyamide receptors for anion binding
Marcin Pawlak a , Adam Sobczuk a , Jarosaw Kalisiak 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, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
Anion receptors represent quite new field of supramolecular chemistry 1 . Their design and
synthesis is more demanding task comparing to receptors for cations, due to larger size, variety
of shapes and lower charge density of anions. One of the ways to solve these problems is a
design of the tweezer-like receptors which are flexible enough to adjust their structure to the
guests of various sizes and shapes. A large number of anions receptors were reported so far,
and most of them has positively charged group as binding sites (i.e. ammonium, pyrydinium
groups or metal ions). As neutral binding sites hydrogen-bond donors (i.e. amide, thioamides,
ureas, pyrroles) are employed.
An interesting application of anion receptors is a preparation of optical sensors, especially those
able to give visible response in the presence of anions 2 .
Simple and efficient way of synthesis of macrocyclic, lariat-type polyamide receptors will be
presented. Structures of studied compounds are presented on Fig.1. Various groups were
incorporated to these structures (both in intraanular arm and into the macrocyclic ring) in order
to investigate their influence on anion binding properties. The magnitude of receptor–anion
interactions were evaluated by 1 H NMR titrations in DMSO, using three typical anions – Cl - ,
PhCOO - , and H2PO4 - in tetrabutylammonium salts form. Moreover, crystal structures of both the
receptors and their complexes with anions were obtained.
Nitro group introduced into the intraannular arm, besides amplification of binding strength, also
acts as a strong chromophore. Due to this fact compounds bearing nitro group reveal a
colorimetric response in the presence of anions, changing from colorless to different hues of
yellow.
O
N
O
O H
N X
H
O H
N
O
N
H
H
N
O
Y
O
1. X = Ph, C6H4 p-NO2, CH3
Y = CH, N
Fig.1. General structures of compounds studied in this work: 1. receptors with amide
intraannular arm, 2. receptors with O-benzyl intraannular arm.
[1] F.P. Schmidtchen, M. Berger, Chem. Rev., 1997, 97, 1609-1646
[2] K. Choi, A. D. Hamilton, Coord. Chem. Rev., 2003, 240, 101-110
O
O
O
O
O
N
H
X
H
N
N
H
O
N
H
N
O
2. X = Ph, C6F5, C6H4 p-NO2
PSB 38