The Electronic Structures of A2Y4 Molecules

1963 ◽  
Vol 16 (5) ◽  
pp. 737 ◽  
Author(s):  
RD Brown ◽  
RD Harcourt
Keyword(s):  
Molecular Orbital ◽  
Electronic Structures ◽  
Lone Pair ◽  
Orbital Method ◽  
Molecular Orbital Theory ◽  
Bond Properties ◽  
Orbital Theory ◽  
The Core ◽  
Valence Electrons ◽  
Charge Rule

A study of the electronic structures of A2Y4 molecules containing 34, 36, and 38 valence electrons has been made. An approximate VESCF, molecular- orbital method was used, attention being concentrated mainly on the delocalization of σ-electrons which are classically regarded as lone-pairs on the Y atoms. The results provide explanations of the main features of many of the observed AA- and AY-bond lengths and YAY-bond angles of N2O4, C2O42-, B2F4, B2Cl4, C2F4, C2Cl4, S2O42-, and N2F4. Other A2Y4 systems which have either not been fully characterized or not yet reported are also considered. The extent of lone-pair delocalization is shown to be governed by a parameter aσ, related to the coulomb and resonance parameters of H�ckel molecular-orbital theory. General trends in the value of aσ can be predicted from values of the core charges of A and Y towards the o-electrons concerned. A more detailed "adjacent charge" rule emerges. It differs from the classical rule in that for A2Y4 systems, adjacent negative formal charges on the A atoms should not very greatly affect the AA-bond properties. Difficulties were encountered in consistently interpreting the properties of some A2F4 and A2Cl4 compounds. These deserve further attention.

Molecular orbital theory of the electronic structures of one-dimensional molecular crystals

1979 ◽  
Vol 54 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Akira Imamura ◽  
Kazuyoshi Tanaka ◽  
Tokio Yamabe ◽  
Kenichi Fukui
Keyword(s):  
Molecular Orbital ◽  
Electronic Structures ◽  
Molecular Crystals ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
One Dimensional

Molecular association in liquids I. Molecular association due to lone-pair electrons

1951 ◽  
Vol 205 (1081) ◽  
pp. 155-162 ◽  
Keyword(s):  
Molecular Orbital ◽  
Liquid State ◽  
Lone Pair ◽  
Molecular Association ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
General Survey ◽  
Quantitative Theory ◽  
Lone Pair Electrons ◽  
The Way

This paper aims at giving a general survey of the part played by lone-pair electrons in the range of phenomena commonly classified under the heading of molecular association, with particular emphasis on the liquid state. The position of lone-pair electrons on a molecule and the factors determining their availability for forming intermolecular links are discussed in terms of molecular orbital theory. This is followed by an examination of the way in which these association forces influence the structure of large aggregates of molecules as in liquids. The lines along which a quantitative theory of associated liquids may be developed are indicated.

The molecular orbital theory of chemical valency VIII. A method of calculating ionization potentials

1951 ◽  
Vol 205 (1083) ◽  
pp. 541-552 ◽  
Keyword(s):  
Molecular Orbital ◽  
Empirical Method ◽  
Ionization Potentials ◽  
Orbital Method ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Atomic Orbitals ◽  
Usual Form ◽  
Semi Empirical ◽  
Good Agreement

An analysis of the ‘linear combination of atomic orbitals’ approximation using the accurate molecular orbital equations shows that it does not lead to equations of the form usually assumed in the semi-empirical molecular orbital method. A new semi-empirical method is proposed, therefore, in terms of equivalent orbitals. The equations obtained, which do have the usual form, are applicable to a large class of molecules and do not involve the approximations that were thought necessary. In this method the ionization potentials are calculated by treating certain integrals as semi-empirical parameters. The value of these parameters is discussed in terms of the localization of equivalent orbitals and some approximate rules are suggested. As an illustration the ionization potentials of the paraffin series are considered and good agreement between the observed and calculated values is found.

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