Novel Schiff-base and Benzamide N,O-Donor Ligands for Development as Fluorionophores and Selective Metal Ion Binders

A new family of Schiff-base ligands using meta-hydroxybenzaldehyde and a variety of di- and triamines as precursors were prepared and fully characterised. These ligands were reacted with various MX2 salts (M = Cu, Ni and Zn and X = perchlorate, acetate and chloride). In every case except one (where a coordination polymer was formed), hydrolysis of the ligand occurred to give the liberated amine and aldehyde. The amine bound to the metal ion to give the appropriate metal-amine complex. In two cases these by-products were characterised by X-ray crystallography. One showed the entrapment of a two-coordinate copper(II)chloride molecule within the lattice, along with the inclusion of a monochloro-bridged dinuclear copper species. A novel class of benzazines were prepared, some of them macromolecular derivatives, using a tetra tert-butylcalix[4]arene difunctionalised at the lower rim as a molecular scaffold. X-ray crystal structures for these calix[4]arene derivatives were obtained in four cases. Zn(II) complexes of this family of compounds were prepared in several cases. Both the ligands and their Zn(II) complexes were examined for fluorescent character. An increase in emission upon complexation of the Zn(II) ion was obtained. A new benzamide derivative was synthesised and characterised by X-ray crystallography. The HCl salt of the ligand was also prepared and its X-ray structure obtained. The free ligand displayed ambidentate character and complexes with the various metal salts mentioned above, were prepared. In the case of its reaction with Cu(II) perchlorate, two complexes, one with an octahedral geometry and the other with a square planar geometry were obtained, both of whom were solved by X-ray crystallography. The above ligand was also bound to the calix[4]arene. Two derivatives were prepared, one with a methyl protecting group on the terminal phenol (X-ray crystal structure solved), the other possessed the free phenol. Both were examined for metal binding traits using Na(I), Ag(I) and Zn(II) salts. Only the deprotected ligand was found to bind metals and was selective for acetate salts. An explanation for its selectivity was given using pKa values