Electron spin resonance and optical spectroscopic studies of Co-ZSM-5 with nitric oxide

• Published in: Applied magnetic resonance Vol. 19; no. 1; pp. 21 - 33
• Main Authors: Park, S. K., Kurshev, V., Lee, C. W., Kevan, L.
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01-05-2000
• Subjects: Adsorption; Cobalt; Cobalt compounds; Dehydration; Diamagnetism; Electron paramagnetic resonance; Electron spin; Electrons; Fourier transforms; Infrared spectroscopy; Ion exchange; Nitric oxide; Room temperature; Spectrum analysis; Spin resonance; Ultraviolet reflection; Ultraviolet spectroscopy; Visible spectrum; Zeolites
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/BF03162258

The reaction of nitric oxide with ZSM-5 zeolite ion-exchanged by Co(II) (Co-ZSM-5) has been studied by electron spin resonance (ESR), Fourier transform infrared (FTIR) and diffuse reflectance ultraviolet-visible spectroscopy. When dehydrated Co-ZSM-5 reacts at room temperature with nitric oxide, the ESR spectrum of Co(II) atg = 5.5, which is only observable below 45 K, is greatly reduced and a new59Co hyperfine octet forms at gavg = 2.11. The overall Co(II) ESR intensity decreases by about 50% which suggests formation of some diamagnetic cobalt complex. Mononitrosyl cobalt complexes such as Co(I)-NO+ or less probably Co(III)-(NO)− are suggested as possible precursors of a dintrosyl cobalt complex. The octet indicates hyperfine interaction with59Co and is associated with a cobalt dinitrosyl complex. FTIR bands at 1813 and 1896 cm−1 confirm a dinitrosyl species and a broad band from 1600–1800 cm−1 is tentatively interpreted as a mononitrosyl species. The visible spectrum for dehydrated Co-ZSM-5 shows a tetrahedral Co(II) band from 500–700 nm with three components which disappears after NO adsorption at room temperature. We suggest that Co(0)-(NO)22+ forms after NO adsorption onto Co(II)-ZSM-5 zeolite on the basis of ESR and ultraviolet-visible spectroscopy.