scholarly journals Effects of Through-Bond Electron Donor-Acceptor Interaction on the Nitrogen Inversion Potential in Piperidine Derivatives. A Quantum-Chemical Study

1995 ◽  
Vol 60 (1) ◽  
pp. 32-40 ◽  
Author(s):  
A. M. Brouwer ◽  
Bert Krijnen
Keyword(s):  
Electron Donor ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Acceptor Interaction ◽  
Nitrogen Inversion ◽  
Donor Acceptor

Quantum chemical study of physical characteristics of Co- and Ni-faujasites

1982 ◽  
Vol 47 (5) ◽  
pp. 1282-1289 ◽  
Author(s):  
Stanislav Beran
Keyword(s):  
Electron Donor ◽  
Quantum Chemical Study ◽  
Chemical Characterization ◽  
Chemical Study ◽  
Hydroxyl Groups ◽  
Strong Electron ◽  
Charge Densities ◽  
Physico Chemical ◽  
Donor Acceptor ◽  
Trivalent Cations

The CNDO/2 method was used for a physico-chemical characterization of faujasite zeolites, modelled by T6O6(OH)12 clusters containing Ni+, Ni2+, Ni(OH)+, Co2+, Co3+, Co(OH)+ cations localized in the SII and SI' cationic positions. It is shown that the cations are bound preferentially to the oxygen atoms of the zeolite skeleton by a strong electron donor-acceptor bond. As the consequence of the bond formation, the electron charge is significantly shifted from a skeleton to the cation. The charge densities calculated on the cations (Ni+ ~ 0.3, Ni2+ ~ 0.35, Co2+ ~ 0.4, Co3+ ~ 1.1 respectively) show that with uni- and bivalent cations the positive charge is in main part compensated by donation of electrons from the skeleton, while with trivalent cations the compensation is only partial. The Ni+ cation possesses significant electron donor properties whereas the Co3+ cation has a strong electron acceptor character. For both cations bivalency appears to be the most stable valent state. Both studied cations show great affinity to hydratation, however, their corresponding hydroxyl adducts - the Ni(OH)+ and Co(OH)+ cations exhibit substantially less acid properties, compared with the hydroxyl groups of the skeleton.

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