Water-Soluble Derivatives of Octanuclear Iron-Oxo-Pyrazolato Complexes; An Experimental and Computational Study

Two water-soluble iron-pyrazolato complexes, [Fe₈], have been prepared by the introduction of twelve hydroxyalkyl groups to the periphery of the approximately spherical octanuclear molecule and they are contrasted with their two organosoluble chloroalkyl analogues. All four new complexes, 1 - 4, have been characterized in solution by ¹H-NMR and electrospray ionization mass spectroscopy. The one-electron reduction product of the water-soluble 3, [Fe₈]^-, has been structurally characterized by single crystal diffraction methods. In aqueous media, the four terminal Fe-Cl bonds of [Fe₈] are partially hydrolysed and the resulting chloro/aqua/hydroxo species form supramolecular nanoscale aggregates, as determined by dynamic light scattering and electron microscopy. Preliminary computational studies by density functional theory methods have been employed in order to model the H-bonding interactions controlling the competing solvation and aggregation processes.