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In this work, the aqueous speciation of Rh(III) in chloride medium was investigated by UV-vis spectroscopy for ligand to metal ratios R = (Cl&minus, )/(Rh) ranging from 300 to 5000, at fixed Rh concentration (2.4 &times, 10&minus, 3 M). Under the chemical conditions of this work, no time evolution was observed, which allows for the fitting of the UV-vis data by Principal Component Analysis (PCA) and Multi-Curve Resolution (MCR). From this, and by comparison with literature data, the three independent species [RhCl4]&minus, [RhCl5]2&minus, and [RhCl6]3&minus, were identified, their individual absorption spectra derived and their respective contribution to the collected experimental UV-vis spectra calculated. Then, extraction of Rh(III) towards the ionic liquid trihexyltetradecylphosphonium chloride was performed. Comparison with the speciation data gives insight into the extraction mechanism and the extracted species.

A novel tetradentate macrocyclic ligand viz. 1,5,8,13-tetraaza-2,9-dimethyl-4,11-diphenylcyclotetradeca-2,4,9,11-tetraene (L) and its complexes with PdII, PtII, RhIII and IrIII metal ions were synthesized. These complexes were characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, IR and electronic spectral studies. On the basis of molar conductance and elemental analyses the general stoichiometries of the complexes were found to be [M(L)]Cl2 and [M′(L)Cl2]Cl, where M = Pd(II), Pt(II) and M′ = Rh(III), Ir(III). The spectral studies reveal the four coordinated square planar geometry for PdII and PtII complexes and six coordinated octahedral geometry for RhIII and IrIII complexes. In vitro the synthesized ligand and its metal complexes have been screened for bactericidal and fungicidal activities using disc diffusion and food poison technique, respectively, at different concentrations. The organisms used in antibacterial investigation included Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and for antifungal investigation Aspergillus-niger, Aspergillus-glaucus, Fusarium odum. The antimicrobial data reveal that the metal complexes act more as bactericidal and fungicidal agents as compared to the uncomplexed ligand and the metal salts from which they derive.