Theoretical study of the derivative hydrocarbons of biphenylene. I. Electronic spectrum of the biphenylene

Abstract

AbstractsThe electronic spectrum of biphenylene has been studied theoretically. The investigation is based on the semi-empirical LCAO SCF MO method with various degrees of approximations. The results have been analysed with regard to the following two factors: ( a ) The difference in effective electronegativity between the carbon atoms in the four-membered ring and the other carbon atoms in the molecule. ( b ) The inclusion of doubly excited configurations in the description of the n-electronic molecular states. The theory satisfactorily interprets the excitation energies and the nature of the electronic transitions. The predictions are particularly affected by the inclusion of the doubly excited configurations. On the basis of these results, the empirical parameters used are discussed.Une ttude thkorique du spectre tlectronique du biphenylhe est donnee. Cette ttude est baste sur la mtthode semi-empirique LCAO SCF MO avec difftrents niveaux d'approximation. L'effet des deux facteurs suivants sur les rtsultats est analyst: ( a ) La difference d'electrontgativitt effective entre les atomes de carbone dans le cycle tetra-atomique et les autres carbones de la moltcule. ( b ) L'inclusion de configurations doublement excittes dans la description des ttats n-tlectroniques. La thtorie interprete de fason satisfaisante les energies d'excitation et la nature des transitions Clectroniques. L'inclusion des configurations doublement excitkes s'avere un des facteurs essentiels A I'interprttation des donntes expCrimentales. Sur la base de ces rtsultats, on discute les parametres empiriques utilists.