| Sumario: | 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 species encapsulated in an MFl-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 which originate from 4s- 4p transitions due to the Zn+ species with paramagnetic nature that is formed in MFI. The transformation process (Zn → Zn) was explained by considering the mechanism via the excited triplet state ( P) caused by the intersystem crossing from the excited singlet state ( P) produced through the excitation of the 4s-4p transition of an atomic Zn 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 O molecule having a triplet spin state in the ground state, forming an η type of Zn-O- species. These features clearly indicate the peculiar reactivity of Zn+ in MFI, whereas Zn-(H)MFI hardly reacts with O at room temperature. The bonding nature of [Zn-O-] species was also evidenced by ESR measurements and was also discussed on the basis of the results obtained through DFT calculations.
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