The Synthesis and Coordination Chemistry of Quinoline- and Naphthalene-Based Ligands

Abstract

This thesis details the synthesis and characterisation of several multidentate ligands that contain the aromatic moieties quinoline, naphthalene and pyrene, and their associated transition metal complexes. Chapter One presents an introduction to multidentate ligands containing both pyridine and quinoline units. The synthesis and characterisation of each ligand is described in Chapter Two. This includes the synthesis of nine new 2-quinolylbased ligands including tri- and tetradentate ligands, and a discussion on these ligands is presented in Chapter Three. In addition, four new multidentate tripodal ligands that contain a 2-methyl-1H-naphtho[2,3-d]imidazole moiety and one pyrene-based bidentate ligand are described in Chapter Six. All the new ligands synthesised have been reacted with transition metal ions and their corresponding complexes have been analysed using a number of techniques. The new complexes [Pd(58)Cl]Cl.xH2O, [Cu(55)NCCH3](ClO4)2, [Zn(55)NCCH3](ClO4)2, [(Mn(55))2O2](ClO4)2.2CH3CN and [(62)Co(OH)3Co(62)](ClO4)3.CH3CN, which contain the new quinoline-containing ligands have been prepared and structurally characterised. The synthesis of each complex is presented in Chapter Two and the structural characterisation is expanded on in Chapter Four. The crystal structure for the complex [Pd(58)Cl]Cl.xH2O showed the species to be mononuclear exhibiting a square planar geometry in which three of the nitrogen donor atoms of the ligand and one chloridoligand are coordinated to the metal ion. The fourth nitrogen donor atom of the ligand belongs to a quinoline group, and this remains uncoordinated. This Pd(II) complex is the first example of a structurally characterised metal complex that contains a 2-quinolylethyl-containing ligand. The complexes [Cu(55)NCCH3](ClO4)2 and [Zn(55)NCCH3](ClO4)2 are isomorphous and are shown to be mononuclear, each exhibiting distorted square-based pyramid geometries about the metal centres (τ5 = 0.256 and τ5 = 0.160, respectively). The crystal structures of the complexes [(Mn(55))2O2](ClO4)2.2CH3CN and [(62)Co(OH)3Co(62)](ClO4)3.CH3CN reveal dimer species in which the two metal centres are bridged by either two oxido or three hydroxido ligands, respectively. For those compounds in which crystal structures were not obtained, alternative solution state characterisation methods were employed including mass spectrometry and visible spectroscopy (Job’s method). The data obtained from these experiments showed all the ligands to form mononuclear 1:1 complexes in solution. A discussion of these results is presented in Chapter Five and Six. Chapter Seven presents the work conducted as part of a separate side project that investigated 6-amino-2,3-naphthalimide derivatives. This work describes the synthesis and characterisation of a series of 6-amino-2,3-naphthalimide derivatives. This included the synthesis of the 2,3-naphthalimide moiety in which several derivatives were formed with varying imide functional groups. These compounds have been cross-coupled with a variety of small amine groups to achieve amination at the 6-position on the naphthalimide ring. Preliminary photophysical studies of three compounds has been conducted.