The two common ionic forms of iron have quite different character with respect to polarizability. The Fe(III) is considered a harder Pearson acid than Fe(II). The octasubstituted C-methyl-calix[4]resorcinarene (1) with its carboxylate arms and aromatic rings can form both "hard" and "soft" ion binding sites, respectively. In this work the interactions of Fe(III) and Fe(II) ions with 1 were investigated by photoluminescence (PL) and quantum-chemical methods. The results suggest that Fe(II) ions form complexes with 1 favorably through cation-pi interactions, while the complexation of Fe(III) ions is mainly based on the chelate formation with the carboxylate moieties of the resorcinarene molecule. This observation makes 1 and its analogues promising candidates to be used in chemical sensors as special redox-sensitive host molecules.