Quantum chemistry PM3 calculations of sixteen mEGF molecules

Geometry and energy parameters of the individual dissociation intermediate steps of CH4 molecule, parameters of the barrier to linearity and singlet-triplet separation of the CH2 molecule have been calculated by means of the UMP method in the minimum basis set augmented with the bond functions. The results agree well with experimental data except for the geometry of CH2(1A1) and relatively high energy values of CH(2II) and CH2(1A1) where the existence of two UHF solutions indicates a necessity of description of the electronic correlation by more exact methods of quantum chemistry.

Download Full-text

On the Structure of Lead(II) Complexes in Aqueous Solutions. I. Trinuclear Clusters

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19950527 ◽

1995 ◽

Vol 60 (4) ◽

pp. 527-536 ◽

Cited By ~ 10

Author(s):

Martin Breza ◽

Alena Manová

Keyword(s):

Quantum Chemistry ◽

Aqueous Solutions ◽

Electronic Structures ◽

Mndo Method ◽

Model Systems ◽

Trinuclear Clusters ◽

The Stability ◽

Semiempirical Mndo

Using semiempirical MNDO method of quantum chemistry the optimal geometries and corresponding electronic structures of [Pb3(OH)n]6-n model systems as well as of their hydrated [Pb3(OH)n(H2O)8-n]6-n analogues (n = 4, 5) are investigated. The most stable trinuclear lead(II) complexes present in aqueous solutions correspond to cyclo-(μ3-OH)(μ2-OH)3Pb32+, Pb(μ-OH)2Pb(μ-OH)2Pb2+, cyclo-(μ3-OH)2(μ2-OH)3Pb3+, Pb(OH)(μ-OH)2Pb(μ-OH)Pb(OH)+ and Pb(OH)(μ-OH)2Pb(μ-OH)2Pb+ systems. The key role of OH bridges (by vanishing direct Pb-Pb bonds) on the stability of individual isomers is discussed.

Download Full-text

Sterically Crowded Heterocycles. VII. Reduction of Some (Z)-1,3-Diphenyl-3-(2-phenylimidazo[1,2-a]pyridin-3-yl)prop-2-en-1-ones as Their Axial Chirality Probe

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19961018 ◽

1996 ◽

Vol 61 (7) ◽

pp. 1018-1026 ◽

Cited By ~ 4

Author(s):

Richard Kubík ◽

Stanislav Böhm ◽

Josef Kuthan

Keyword(s):

Hydroxy Derivative ◽

Borohydride Reduction ◽

Axial Chirality ◽

Pm3 Calculations

Borohydride reduction of titled ketones 1a-1g gave diastereoisomeric mixtures of (Z)-1,3-diphenyl-3-(2-phenylimidazo[1,2-a]pyridin-3-yl)prop-2-en-1-ols 2a-2g and 3a-3g in which the former ones prevailed. Only individual racemic products were obtained after borohydride reduction of (E)-1,3-diphenyl-3-(2-phenylimidazo[1,2-a]pyridin-3-yl)-prop-2-en-1-one 4 to corresponding 1-hydroxy derivative 5 and by conversion of (Z)-1-oxo derivative 1a to 1,3-diphenyl-3-(2-phenylimidazo[1,2-a]pyridin-3-yl)propan-1-one (6) with sodium hydrogenselenide. Diastereoselectivity of the borohydride reduction is discussed using the PM3 calculations of the molecules 1a, 2a, 2b, 3a, 3b, 4, 5, and 6.

Download Full-text