Coordination of Cu+ and Cu2+ ions in ZSM-5 in the vicinity of two framework Al atoms

Citation
D. Nachtigallova et al., Coordination of Cu+ and Cu2+ ions in ZSM-5 in the vicinity of two framework Al atoms, PHYS CHEM P, 3(8), 2001, pp. 1552-1559
Citations number
35
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
ISSN journal
14639076 → ACNP
Volume
3
Issue
8
Year of publication
2001
Pages
1552 - 1559
Database
ISI
SICI code
1463-9076(2001)3:8<1552:COCACI>2.0.ZU;2-K
Abstract
A combined quantum mechanics/interatomic potential function technique has b een used to examine Cu+/Al- sites in the vicinity of H+Al- sites and Cu2+ i n the vicinity of two framework Al atoms under dehydrated conditions. The s ymmetrical coordination of Cu2+ ions to four framework oxygen atoms is the most stable site and Cu2+ is hard to reduce at these sites. In agreement wi th EPR measurements a square-pyramidal coordination of Cu2+ at these sites is suggested. However, this symmetrical coordination is attained only for s pecific positions of the framework aluminium pair. Coordination changes upo n reduction of divalent to monovalent copper ions and upon excitation of Cu + ions in the first triplet excited state are also investigated. The coordi nation of the copper ions does not significantly change during reduction in the dehydrated state. Coordination changes of Cu+ upon excitation in the t riplet state and calculated transition energies for Cu+/Al- sites in the vi cinity of H+Al- sites are identical to those observed for isolated Cu+/Al- sites.