Four iodide anionic water clusters of I-(H2O)(1-4) in two supramolecular complexes of [Fe(phen)(3)][I-2(H2O)(3)] (1) and [Zn(phen)(3)][I-2(H2O)(4.5)] (2) have been determined by single-crystal X-ray diffraction analysis. The diffuse reflectance spectra for the solid iodide anionic water clusters of I-(H2O)(1-4) were investigated, and their absorption bands were demonstrated by denisty functional theory calculation. The electrochemical reaction of I-(H2O)(1-4) -> I center dot + e(-)(H2O)(1-4) with the oxidation potential of E-p = 0.61 eV was first found and reported in two aqueous solutions (1 mmol.dm(-3)) of 1 and 2.