| dc.description.abstract | Nature has always inspired supramolecular chemists who,
with the aim to mimic the structural features of the natural
receptors, have designed artificial systems with amazing
functions and properties. Therefore, in the last two
decades, macrocyclic compounds based on naphthalene
or anthracene units have been reported, with the aim of
obtaining new supramolecular hosts embedding deep π-
electron-rich aromatic cavity.a
Prompted by these considerations, during this PhD
project, I focused my efforts on the synthesis of novel
naphthol-based macrocycles. Thus, prismarenesb
(a in
Figure) and the calix[2]naphtha[2]arenec
(b in Figure)
have been obtained and their supramolecular properties
were investigated.
Methoxy-based prism[n]arenes (n = 5 and 6),b were
formed by exploiting thermodynamic intermolecular
templating effects with alkylammonium-guests. b
Differently, the formation of prismarenes bearing longer
alkyl chains,d such as ethyl or propyl groups, was obtained
by a thermodynamic intramolecular self-templating effect
due to the alkyl chains, which drive the macrocyclization
toward the formation of the hexameric derivatives.dc,
Prismarenes were found to be interesting for their
molecular recognition properties: in fact, their π-electron
rich deep cavities can host ammonium guests by
cation···π and +NC−H···π interactions.b,d
We have also investigated a procedure for the synthesis
of per‒hydroxylated prism[n]arenes PrS[n]OH (n = 5 and
6).ed
In details, PrS[5]Me can be efficiently demethylated
by a supramolecularly assisted reaction in the presence of
tetramethylammonium iodide. PrS[n]OH can be
considered as useful synthetic precursors to obtain novel
hosts with intriguing supramolecular properties. In fact,
starting by per‒hydroxylated prism[n]arenes PrS[n]OH (n= 5 and 6), water-soluble prism[n]arenes (n = 5 and 6)
bearing carboxylato anionic groups were obtained.fe
Carboxylato-prism[n]arenes (n = 5 and 6), PrS[5]COONa
and PrS[6]COONa were able to form complexes with
organic ammonium cations Gn+@PrS[n]COO-
(n = 5 and 6)
in water as confirmed by NMR titration experiments. ITC
studies showed that the complexation processes, are
driven by different thermodynamic factors depending on
prismarene size and cation charge.e
Finally, we obtained a new class of phenol−naphthalene
hybrid macrocycles, named calix[2]naphth[2]arenes.cf X-
ray studies show that calix[2]naphth[2]arene adopts a
rare 1,2-alternate conformation (b in Figure). Moreover,
this conformation is also observed when alkali metal
cations are added to the solution of host. [edited by Author] | it_IT |
