Spectroscopic evidence for the tetraamminecopper(II) complex in a Y-type zeolite

Abstract

Publication costs assisted by the National Science Foundation (USA) and the National Fonds voor Wetenschappeli)k Onderzook (Belgium) The changes in the epr and ir spectra of copper(Il)-ammine complexes in a Y-type zeolite have been studied as a function of the amount of ammonia adsorbed. The intensity of the epr spectrum increased linearly until the ratio of the number of ammonia molecules to the number of cupric ions was 4:1, at which point the addition of excess ammonia failed to change the spectrum. The same behavior was noted in the ir spectrum for the symmetric deformation band of ammonia coordinated to cupric ions. Adsorption of deuterated ammonia on a low-exchanged sample produced an epr spectrum which revealed the superhyperfine splitting of four equivalent nitrogen nuclei in the parallel as well as the perpendicular region of the spectrum. These data provide additional evidence that the [Cu(NH3)4]2+ complex is formed within the zeolite structure. This complex may be detected in the presence of excess ammonia and oxygen at temperatures up to 180°. The change in the epr spectrum of a moderately exchanged sample upon adsorption of ammonia indicates that the copper ions move out of the small cavities, and most of the complexes are formed in the large cavities of the zeolite.

Electron Spin Resonance and Electron Spin Echo Modulation Studies of Cu(II)-Exchanged Silicoaluminophosphate Type 18 Molecular Sieve

“…The [Cu(NH 3 ) 4 ] 2+ complex in Cu−SAPO-18 is quite stable and even exists after 48 h evacuation at room temperature. This behavior of the Cu−ammonia complex is very similar to that found in Y zeolite …”

“…This behavior of the Cuammonia complex is very similar to that found in Y zeolite. 18 For methanol adsorption the ESEM data show that two molecules of methanol are coordinated to Cu(II) (Figure 15). The results for both CD 3 OH and CH 3 OD are consistent and indicate a dipole orientation of the methanols.…”

Catalytic Reduction of NO with NH3 over Cu(II)NaY

“…For one and the same sample, ESR spectra of Cu(II) ions were repeatedly measured after use at various temperatures (Figure 2). Signals 1 and 2 can be ascribed to the square planar tetraammine complex of Cu(II) ion (Flentge et al, 1975), while 3 and 4 agree with the spectra for partially dehydrated Cu(II) exchanged zeolite. In spectrum 5, the decreased Cu(II) concentration has caused the hyperfine splitting to appear (Vansant and Lunsford, 1972).…”

ESR study of copper-ammonia complexes in solution adsorbed on silica gels. 1. Wide-pore silica gels

“…Electron spin resonance (ESR) has been used in the past for the study of the coordination and bonding of copper(II) complexes with nitrogenous ligands adsorbed on silica gels and on other porous supports. [1][2][3][4][5][6][7][8][9][10][11] The major aim of those works was to give further information on the behavior of metal ions bonded on surface sites for its implications in catalytic processes. Thus, almost all reported results were obtained from dried or vacuum-heated samples.…”