An assessment of semiempirical (MNDO, AM1 and PM3) methods to model buckybowls

2002 ◽  
Vol 579 (1-3) ◽  
pp. 63-72 ◽  
Author(s):  
T.C Dinadayalane ◽  
G Narahari Sastry
Keyword(s):  
Semiempirical Mndo

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

1995 ◽  
Vol 60 (4) ◽  
pp. 527-536 ◽  
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.

Borinine (Borabenzene): Its Structure and Vibrational Spectrum. A Quantumchemical Study

1987 ◽  
Vol 42 (4) ◽  
pp. 352-360 ◽  
Author(s):  
Gerhard Raabe ◽  
Wolfgang Schleker ◽  
Eberhard Heyne ◽  
Jörg Fleischhauer
Keyword(s):  
Electronic Structure ◽  
Vibrational Spectrum ◽  
Ab Initio ◽  
Vibrational Spectra ◽  
Photoelectron Spectrum ◽  
High Reactivity ◽  
Basis Sets ◽  
Rare Gas ◽  
Ab Initio Theory ◽  
Semiempirical Mndo

Recently we reported the results of some semiempirical and ab initio studies in which we compared the electronic structure of the hitherto unknown borinine with those of benzene and pyridine. The results of our calculations led us to the conclusion that the elusive nature of borabenzene is caused by its high reactivity, which might at least in part be due to the pronounced σ acceptor properties of a low-lying σ* molecular orbital.We now present the results of further ab initio and semiempirical (MNDO) investigations in which we performed full geometry optimizations for the molecule using two different basis sets (STO-3G, 4-31G) and also calculated the vibrational spectra of the 10B and 11B isotopomeric borabenzene molecules at the 4-31 G level of ab initio theory and with the semiempirical MNDO method.The calculated vibrational spectrum might be helpful to the experimentalist in identifying the molecule, for example trapped in a rare gas matrix among the side products.The calculated orbital energies can be useful in identifying the molecule by means of its photoelectron spectrum.

On the Structure of Lead(II) Complexes in Aqueous Solutions. III. Hexanuclear Clusters

2002 ◽  
Vol 67 (2) ◽  
pp. 219-227 ◽  
Author(s):  
Martin Breza ◽  
Alena Manová
Keyword(s):  
Quantum Chemistry ◽  
Aqueous Solutions ◽  
Electronic Structures ◽  
Mndo Method ◽  
Experimental Techniques ◽  
Hexanuclear Clusters ◽  
Semiempirical Mndo

Optimum geometries based on experimental structures and corresponding electronic structures of [Pb6(μ3-OH)8]4+ and [Pb6O(μ3-OH)6]4+ clusters as well as of their hydrated [Pb6(μ3-OH)8(H2O)6]4+ and [Pb6O(μ3-OH)6(H2O)6]4+ analogues are investigated using the semiempirical MNDO method of quantum chemistry. Direct Pb-Pb and O-O bonds are vanishing in the systems under study. Small differences in interatomic Pb-Pb and Pb-O distances between these clusters indicate that they cannot be distinguished by recent experimental techniques in solution. Both the mentioned structures are stable and might coexist in solution.

Structural isomers and tautomerism of chlorophyll a in the ground state studied by semiempirical MNDO-d method

2004 ◽  
Vol 681 (1-3) ◽  
pp. 213-224 ◽  
Author(s):  
M Nsangou ◽  
A Ben Fredj ◽  
N Jaı̈dane ◽  
M.G Kwato Njock ◽  
Z Ben Lakhdar
Keyword(s):  
Chlorophyll A ◽  
Ground State ◽  
Structural Isomers ◽  
Semiempirical Mndo

Triaziridines. Part V. A semiempirical MNDO study of nitrogen inversion and amide rotation in Formyltriaziridines

1986 ◽  
Vol 69 (6) ◽  
pp. 1461-1468 ◽  
Author(s):  
Jos� Kaneti ◽  
Lienhard Hoesch ◽  
Andr� S. Dreiding
Keyword(s):  
Nitrogen Inversion ◽  
Amide Rotation ◽  
Semiempirical Mndo

Cyclisation of alkoxy radicals. A semiempirical MNDO-PM3 study

1994 ◽  
pp. 877 ◽  
Author(s):  
Ivan O. Jurani? ◽  
Mihailo Lj. Mihailovi? ◽  
Milan M. Dabovi?
Keyword(s):  
Alkoxy Radicals ◽  
Semiempirical Mndo

Semiempirical MNDO/H calculations of opiates

1990 ◽  
Vol 207 (1-2) ◽  
pp. 1-14 ◽  
Author(s):  
Amiram Goldblum ◽  
Omar Deeb ◽  
Gilda H. Loew
Keyword(s):  
Semiempirical Mndo

Molecular electronic structure of subphthalocyanine macrocycles

2000 ◽  
Vol 04 (06) ◽  
pp. 611-620 ◽  
Author(s):  
V. R. FERRO ◽  
L. A. POVEDA ◽  
R. H. GONZÁLEZ-JONTE ◽  
J. M. GARCIA DE LA VEGA ◽  
T. TORRES ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Central Region ◽  
Quantum Chemical ◽  
Theoretical Calculations ◽  
Molecular Electronic ◽  
X Ray ◽  
Compositional Changes ◽  
Molecular Electronic Structure ◽  
Semiempirical Mndo

Quantum chemical calculations at semiempirical (MNDO methods) and ab initio (6-31G and STO-3G basis ses) levels have been performed on boron(III) subphthalocyanines 1-10. Theoretical calculations predict a cone-shaped structure for these compounds independently of the kind of peripheral substitution and even of compositional changes in the central region of the macrocycle (for example, substitution of the boron atom by two hydrogens). The theoretical calculations are in excellent agreement with previous X-ray determinations.

Dehydrochlorination of Poly(vinyl chloride) in Isotactic Systems

1993 ◽  
Vol 58 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Jaroslav Burda ◽  
Rudolf Lukáš
Keyword(s):  
Molecular Weight ◽  
Point Of View ◽  
Low Molecular Weight ◽  
Ionic Mechanism ◽  
Polyene Chain ◽  
Subsequent Growth ◽  
Reaction Conditions ◽  
Poly Vinyl Chloride ◽  
Semiempirical Mndo ◽  
Thermodynamic Factors

The dehydrochlorination of isotactic, low-molecular-weight models of PVC, dimers to pentamers, was studied using the semiempirical MNDO method. The results obtained lead to the conclusion that the thermal dehydrochlorination of PVC can occur through either a radical or an ionic mechanism, depending on the reaction conditions. The arising conjugated polyene structures do not grow by the generally accepted "zip" mechanism, but rather through the "alternating growth" mechanism. A comparison was also made to the reactivity of isotactic and syndiotactic sequences from the point of view of kinetic and thermodynamic factors. It follows from the computations that the splitting off of the first HCl molecule is easier in the isotactic sequence, but that subsequent growth of the polyene chain occurs more readily in syndiotactic systems.

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