Self-Assembled metallomacrocycles that function as sensors and molecular devices

This thesis describes the synthesis of macrocyclic trinuclear ruthenium(II) “bowls”
that incorporated 9-methyladenine, 9-benzyl-9H-purin-6-amine, 9-ethyladenine and
9-(4-methoxybenzyl)-9H-purin-6-amine as ligands with good yields and high
purities. Their binding to a variety of anion guests was investigated through nuclear
magnetic resonance as well as electrochemical studies. These macrocycles possess
extremely interesting binding affinity:1H-NMR investigations revealed selectivity in
the macrocycles-host binding, particularly with medium sized halide anions, namely
chloride and bromide, being most strongly bound. Generally, electrochemistry-based
titrations showed good agreement with the NMR host-guest titrations results, with
potential shifts being dependent on binding affinities -although there are some
specific differences in the results with fluoride and iodide. In the case of nuclear
magnetic resonance we found that the fluoride ion is too small in size to be suitable
for the macrocycle cavity to bind strongly, whilst in the case of electrochemistry
titrations larges shifts are seen after addition of fluoride due to the high charge
density of this ion.
It was found that more complex oxo-anions also bound to the host and affected the
RuII based oxidations. However, in general, the binding affinities for these more
complex anions were lower than the highest values for halide guests. Again
electrochemical potential shifts generally correlated with binding affinity. Studies
also revealed that the electrochemical response to addition of anion guest was
complex, as the guest induced shifts of the three RuII oxidations of the bowls were
not always the same.