Bipyridinium molecular switch:: Ab-initio electronic structure calculation

Density functional study has been carried out using B3PW91/6-311G(d,p) method for bi-pyridinium molecule connected with poly-methylene chains (upto n = 9), reported experimentally to behave like molecular switch. Fully optimized geometries. electronic structures, HOMO-LUMO gaps, Muliken point charge distribution and orbital orientation have been analyzed to understand the electronic behavior in this molecule. The electronic transport across the molecule has been explained assuming that the incoming electron passes through the lowest unoccupied molecular orbitals. The conduction barrier is determined from the energy levels of HOMO and LUMO energy states. Front the results it is predicted that a bias voltage of 1.66 V is required to transfer one electron from metal electrode to the LUMO energy state, quite good in agreement with the experimentally reported results.