Synthesis and Coordination Chemistry of Ligands for Supramolecular Chemistry and Sensing Applications

A series of multidentate N-donor ligands have been synthesised all containing pyridyl
and pyridyl/thiazole units and their coordination behaviour is described.
The ligands are classified into four types; i) terpyridine containing pyridyl/thiazole
ligands (L1-3); ii) pyridyl/thiazole ligands containing a 3,3′-disubstituted bipyridine
core. (L4-8); iii) 2,2′-bipyridine containing a crown ether moiety (L9-11); and iv) a 2,2′-
bipyridine derived ligand containing a urea functional group in the 3,3′-positions
(L12).

Chapter II describes terpyridyl/pyridyl/thiazole ligands: - the synthesis of (L1-3) is
described and the complexes ([Cu(L1)][ClO4]2, [Ni(L2)][ClO4]2, [Co(L2)][ClO4]2,
[Cd3(L3)2][ClO4]6) structurally characterised. Partitioning of the ligands (L1-3) is
dependant on the position of the thiazole ring within the ligand chain. This
partitioning is found to occur at a position adjacent to that of the thiazole ring in all
but the L2 ligand complexes, where it is partitioned preferentially at a position
creating favourable coordination geometry for the metal ion.

Chapter III describes 3,3′-disubstituted pyridyl/thiazole ligands (L4-8): - the novel
potentially hexadentate ligands (L4, 5), the potentially octadentate ligand (L6) and the
potentially tetradentate ligands (L7, 8) have been synthesized and structurally
characterised. All ligands are found to partition at the central pyridine unit due to
unfavourable steric interactions to form a pyridyl/thiazole/pyridyl-binding domain
(L4-6) and the pyridyl/thiazole-binding domain (L7,8). The substituents are found to
dominate the control of the formation of complexes produced ([Zn(L4)][ClO4]2,
[Cd(L5)][ClO4]2, [Cd2(L6)2][ClO4]2, [Cd2(L8)2][ClO4]2).

Chapter IV, Section 1 describes ditopic bipyridine/crown ether ligands: - the synthesis
of (L9-11) is described and the Ru (II) complexes (L9-11) structurally characterised. The
Ru(II) complexes of these 3,3′-disubstituted crown ether species were found to
luminesce. Modulation of the luminescent properties of the ruthenium complex was
investigated with a selection of common cations but resulted in little or no response.

Chapter IV: - Section 2- Ditopic bipyridine/urea ligands: - the novel ligand containing
urea substituent side chains (L12) has been synthesised and a ligand containing both
pyridine and urea substituents has been synthesised and characterised.

A ruthenium complex (X) was synthesised with ligand (L12) and (bipy)2RuCl2, the
resulting structure confirmed via 1H & 13C NMR as well as electrospray mass
spectrometry (ESI-MS). Unfortunately no complexes have been structurally
characterised due to the instability and decomposition of the complex after a short
period of time. The ruthenium complex however was found to luminesce;
ligand/anion recognition studies with complex (X) and a selection of common anions
showed a marked change, a ten fold increase in the luminescence was observed with
the addition of H2PO4
- when in a non-aqueous solvent.