ABSTRACTThe exchange of the extra-framework Na⁺ ions in Engelhard titanosilicate (ETS-10) with Ag⁺ and Ru³⁺ has been investigated theoretically by means of density functional theory (DFT) and experimentally, with the aim of elucidating its effects on the structural, electronic and vibrational properties of the Ti-O-Ti quantum wire. A comparison of theoretical findings and experimental Raman data in the region of Ti-O-Ti stretching reveals that the introduction of the Ag⁺ ions preserves the integrity of the wire to a large extent while Ru³⁺ ions cause large-scale distortions along with some loss in crystallinity.