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Cu-Dinitrosyl Species in Zeolites: A Density Functional Molecular Cluster Study R. Ramprasad, K. C. Hass, W. F. Schneider,*, and J. B. Adams
 

Summary: Cu-Dinitrosyl Species in Zeolites: A Density Functional Molecular Cluster Study
R. Ramprasad, K. C. Hass, W. F. Schneider,*, and J. B. Adamsž
Department of Materials Science and Engineering, UniVersity of Illinois, Urbana, Illinois 61801, Ford
Research Laboratory, MD 3083/SRL, Dearborn, Michigan 48121-2053, and Department of Chemical,
Biological and Materials Engineering, Arizona State UniVersity, Tempe, Arizona 85287
ReceiVed: August 30, 1996; In Final Form: March 31, 1997X
A small cluster model proposed earlier to examine bound Cu ions and their interaction with CO and NO in
zeolites [Schneider, W. F.; Hass, K. C.; Ramprasad, R.; Adams, J. B. J. Phys. Chem. 1996, 100, 6032] is
used to study Cu-bound dinitrosyl complexes. The possibility of a single-step, symmetric, concerted reaction
occurring between the two nitrosyl ligands to form either a N-N bond or free N2 and O2 is addressed. Density
functional theory is used to predict molecular and electronic structures and binding energies. N-down dinitrosyl
binding to Cu0, Cu+, and Cu2+ can be represented as [Cu(I)-(NO)2
-], [Cu(I)-(NO)2], and [Cu(I)-(NO)2
+],
respectively, with the dinitrosyl moiety closely resembling the free NO dimer, and having a long N-N bond
(2.8 ┼). Dinitrosyl species bound to Cu through the O display two distinct binding modes, one resembling
the N-down dinitrosyl binding, again with a long N-N bond (2.0 ┼), and the other similar to hyponitrite
binding to a metal atom, displaying a short N-N bond (1.2 ┼). The single-step, symmetric, concerted
decomposition reaction of NO in the vicinity of Cu ion sites in zeolites is forbidden by orbital symmetry and
is anticipated to have a comparable or higher activation barrier than the same reaction in the gas phase.

  

Source: Adams, James B - Department of Chemical and Materials Engineering, Arizona State University

 

Collections: Materials Science