Synthesis and Coordination Studies of Novel Heteroaryl Tetrazoles

This thesis describes the synthesis, characterisation and coordination studies of an array of heteroaryl 5-substituted tetrazole ligands. A family of 5-substituted pyridyl tetrazole ligands with various functionalities tethered to the tetrazole moiety were prepared and fully characterised. These ligands were reacted with various MX2 salts (M = Cu, Ni, Co, Zn; X = chloride, thiocyanate). A number of the resulting discrete metal complexes were analysed by X-ray crystallography and their potential application as anti-cancer therapeutics are discussed. Carboxylate functionalised pyridyl tetrazole ligands were also synthesised and characterised. These ligands were examined for their potential to form coordination polymers. These investigations have been successful and have led to a series of coordination polymers and discrete clusters, some of which were examined by X-ray crystallography. Diamagnetic materials were subjected to solid state fluorescence studies and exhibited (in all but one case) increased emission when compared to the free parent ligands. EPR spectroscopic studies were also performed on Cu(II) materials. We proceeded to develop these ligands into dicarboxylate systems in order to achieve higher dimensional coordination polymers. This work yielded a plethora of novel 1-D coordination polymers and dinuclear clusters with Cu(II), Ni(II), Co(II), Mn(II) and Zn(II) as the metal ions. Interesting manifestations were observed in these investigations, including the selective hydrolysis of an alkyl ester over an aromatic ester; selective coordination of aromatic carboxylates to hard metal cations; and the presence of coordinatively vacant carboxylate sites which open exciting avenues in the field of postsynthetic modifications. X-ray crystallography was performed on ten products. EPR spectroscopy was performed on Cu(II) materials and the solid state emission spectrum of one Zn(II) complex displayed increased emission compared to its free ligand. Continuing the theme of coordination polymers, we investigated the ability of carboxylate functionalised bis-tetrazole ligands to form coordination polymers with Cu(II). Two categories of bis-tetrazole systems were synthesised and examined: flexible linked and rigidly linked tetrazoles. Investigations of pyrazine linked tetrazoles that were functionalised with carboxylate groups led to two 2-D coordination polymers, one of which contains water clusters and thus presents future opportunities for removal or substitution of these molecules for guest uptake and future applications.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

National University of Ireland Maynooth

Year dc:date.issued

2014

Author dc:creator

• Sheridan, Ursula

Language dc:language

en