Policabornitrile: a semiemperical ab initio and de density functional study of molecular stability

Abstract

2 p. : il., tabThe theoretical literature data with respectt o the electronic properties of this compound is quite scarce and makes use of the planar alltransStructure as the most stable for the calculations In this work semiempirical (AM1 and PM3), ab initio (at the Hartree-Fock level)and density functional theory (using the correlation functional of Vosko, Wilk and Nussair) were used to anaIyse the conformationalstability of the all-trans and all-cis dimers, t rimers and tetramers of polycarbonitrile.The semiempirical and ab initio calculations at theHartree-Fock level showed in general that the all-trans structure with respect to other conformers is the most unstable s tructure. TheInclusion of electronic correlation energy through t he MP2 calculations or the VWN functional method suggest that the trans structure isthe most stable. The relative energies calculated at the correlated level presented diferences around 2 kcal/mol among the differentconformers . While the all-cis compounds presented a planar structure for any of the three methods the all-trans polymer showed a strongdeviation of planarity with a set of local minima in its energy surface.These results suggestth that further calculations on the electronic properties of this polymer can be significantly different of those actually available in the literature