Chemosensors designed around a calix[4]arene scaffold, possessing distal isoxazole nuclei as potential recognition sites in conjugation with fluorogenic reporting moieties, have been synthesised and their molecular structures determined by single crystal X-ray analysis. PIC (pyrene-isoxazole-calix[4]arene) and AIC (anthracene-isoxazole-calix[4]arene) are found to be selective and sensitive for the recognition of copper(II) ions over a range of divalent metal ions in a spectrofluorometric study in acetonitrile. Following exposure to copper(II) ions the fluorescence emission intensity of the host was dramatically quenched, in contrast there were no significant shifts to the UV–vis spectra. 1H NMR spectroscopic studies could not provide unambiguous evidence for the mode of ion recognition. Hybrid Density Functional Theory (DFT) calculations for the PIC-copper(II) complex suggests that the metal ion adopts tetrahedral geometry in an acetonitrile solution, while a distorted square pyramidal coordination is also possible in the absence of solvent molecules. Both of these binding conformations cause the disruption of the pyrene–pyrene stacking, consistent with the observed fluorescence quenching.

The synthesis of several diorganotin(IV) dicarboxylate compounds, including acetates and nicotinates as well as diorganotin(IV) dichloride complexes of the ligands phen, dione and dppz were undertaken. Several difficulties in either the syntheses or complexation reactions with the organic ligands were encountered. The diorganotin(IV) dichloride complexes of the ligands (R2SnCl2·L where R=Me, n-Bu or Ph and L=phen, dione or dppz) were tested against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The dibutyltin(IV) derivatives exhibited the broadest range of activity in comparison to the dimethyltin(IV) or diphenyltin(IV) derivatives. The addition of the nicotinate group did not promote activity against any of the bacteria. Furthermore, only in the case of Ph2SnCl2·dione was there improved activity compared to the organic ligand itself.