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

Abstract

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