Synthesis of an unexpected [Zn2]2+ species utilizing an MFI-type zeolite as a nano-reaction pot and its manipulation with light and heat

Abstract

Compared with mercury, the existence of [Zn₂]²⁺ species is rare. We succeeded in preparing a stable [Zn₂]²⁺ species by utilizing an MFI-type zeolite as a nano-reaction pot, which was confirmed using XAFS spectroscopy: the bands at R = 2.35 Å due to the Zn⁺–Zn⁺ scattering and at 9660.7 eV due to the 1s–σ* (the anti-bonding orbital comprised of the 4s–4s orbital) transition of the [Zn₂]²⁺ species. This species also gives the characteristic band around 42 000 cm⁻¹ due to its σ–σ* transition. Furthermore, UV-irradiation corresponding to the σ–σ* transition causes the bond dissociation, forming two unprecedented Zn⁺ ions, and detached Zn⁺ ions were recombined through heat-treatment at 573 K: [Zn⁺–Zn⁺] ⇄ 2Zn⁺. These processes were reproduced by applying the DFT calculation method to the assumed triplet, σ(α)–σ*(α), structure formed on the M7-S2 site with the specific Al array in the MFI-type zeolite. Research into the specific field using zeolites to synthesize “ultra-state ions” is very promising.