For the first time, the paramagnetic Zn+ species was prepared successfully by the excitation with ultraviolet light in the region ascribed to the absorption band resulting from the 4s-4p transition of an atomic Zn 0 species encapsulated in an MFI-type zeolite. The formed species gives a specific electron spin resonance band at g = 1.998 and also peculiar absorption bands around 38,000 and 32,500 cm-1 which originate from 4s-4p transitions due to the Zn+ species with paramagnetic nature that is formed in MFI. The transformation process (Zn0 → Zn +) was explained by considering the mechanism via the excited triplet state (3P) caused by the intersystem crossing from the excited singlet state (1P) produced through the excitation of the 4s-4p transition of an atomic Zn0 species grafted in MFI by UV light. The transformation process was well reproduced with the aid of a density functional theory calculation. The thus-formed Zn+ species which has the doublet spin state exhibits characteristic reaction nature at room temperature for an O2 molecule having a triplet spin state in the ground state, forming an η1 type of Zn2+-O2- species. These features clearly indicate the peculiar reactivity of Zn+ in MFI, whereas Zn0-(H+)2MFI hardly reacts with O2 at room temperature. The bonding nature of [Zn2+-O 2-] species was also evidenced by ESR measurements and was also discussed on the basis of the results obtained through DFT calculations.
ASJC Scopus subject areas
- Colloid and Surface Chemistry