Proton transfer in HnRhI3 + n: Conductivity and 1H NMR studies

Proton transfer in the solid HI-enriched rhodium iodide (H0.81RhI3.81) at 150–400 K was studied using conductivity measurements and 1H NMR. The compound displays rather high proton conductivity (10− 4 S/cm at 360 K) associated with the activation energy for proton migration of ≈ 0.32 eV which is very close to the activation energy reported earlier for solid iodine doped with HI. From quantum-chemical calculations it was supposed that the interaction between HI molecules and I− ions results in symmetrical or quasi-symmetrical H-bonded complexes [HI2]−, and the conductivity mechanism is apparently a two-stage proton transfer: proton displacement along the hydrogen bond followed by HI reorientation.