Molecular geometry: Bonded versus nonbonded interactions

Abstract

Proposes simplified computational models to facilitate a comparison between the relative roles of bonded and nonbonded interactions in directed valence.

Contributions to the Chemistry of Boron, LXXV The Crystal and Molecular Structure of a Tetraazadiborine: 3,6-Bis(dimethylamino)-1,2,4,5-tetramethyl-1,2,4,5,3,6-tetraazadiborine

“…Compared with the N-N bond in the planar trans-CHO-NH-NH-CHO (1.39 Ä), the NN linkage in 1 e is rather long inspite of the sp 2 hybridisation, and this suggests considerable repulsion by n,n-interaction. The same phenomenon is also found for the nonplanar bicyclic system 6 18 . A good indication for this interaction is provided by the C( 1) N( 1) N(2) C(2) dihedral angle of 72°.…”

Electronic structures of solids from a simple viewpoint: some structures derived from the cesium chloride arrangement

“…5 drops to lower energy and the HOMO-LUMO gap gets smaller, commensurate with a larger energy stabilization when viewed in perturbation-theory terms. Similar arguments have also been used to rationalize the bond angles in AX 2 and AX 3 molecules as the electronegativity of X increases (Bartell, 1968). Systems with the largest distortion away from the linear or trigonal-planar geometries are those where X has the highest electronegativity.…”

“…Of particular interest to us is the mixing of HOMO and LUMO of the parent structure as the result of a perturbation (distortion of the molecule). Often described under the umbrella of the second-order Jahn-Teller approach (Hoffmann, 1971;Bartell, 1968;Pearson, 1969Pearson, , 1970 we need to find that distortion coordinate which effectively mixes HOMO and LUMO, leads to a dramatic stabilization of the former (if the HOMO-LUMO energy gap is small) and perhaps of the whole system on distortion. Because of the symmetry species of HOMO and LUMO for SF 4 at the tetrahedral structure a distortion of symmetry t 2 is predicted as in (2) and the HOMO-LUMO gap in the distorted structure is larger than that in the parent.…”

Structural–electronic relationships in rutile

“…(4) expands the electronic energy, E0(q), for the electronic ground state l0 > as a function of some distortion coordinate q, using the familiar language of perturbation theory (Bartell, 1968). The stability of some (usually high symmetry) structure is tested, initially in first order and then in second order if two pathways are of equal energy in first order or if Eo0)(q) =0.…”