An ab initio fragment orbital theory (AFOT) for molecules: Application to some platinum poly-ynes

The AFOT formalism, which treats a molecule fragment by fragment, has hitherto been restricted to primarily π-electron systems. The method has been successfully applied to calculate the energetics and two-photon absorption properties of several organic molecules. The present work extends the formalism to include organometallic compounds, allowing non-π like valence framework. The extension also allows the use of effective core potentials (ECP). We apply the present modified AFOT formalism to calculate the low-lying excited states of a series of platinum poly-yne oligomers. Comparison with experiment indicates the suitability of the model for such compounds.