Firstly this study we reported about the quantum transport in three benzene molecule junction with two sulphur (S) atoms placed between two Au (111)leads, using the ab initio approach implemented in the SIESTA package. The electronic transport through molecular devices very much depend on subtle details of the molecular configuration between the leads. In this paper we studied the evolution of electronic and transport properties of a molecular junction with Fe and then with S, presented with the same parameters; such as the distance between the leads. We consider the transport through a molecule placed between the leads, with the two sulphur atoms bound to the leads, which is preferable in this respect more than the Iron atoms. Secondly in this paper we studied the phenomenon of conductance quantization happens in a same molecule trapped between the leads used as a semiconductor, to achieve this it will be necessary to measure the control and understand electron transport through molecules attached to electrodes and following specific parameters.