Basing on ab initio methods and nonequilibrium Green's function(NEGF) theory, we have investigated the electronic transport properties of 4-4′-dimercaptodibenzene molecular which have been functionalized with different side groups. Numerical results show that the same side group on different site does not strongly affect the resonances responsible for current flow through the molecular. But different side groups on the same site will have a stronger effect on the energetics of the molecular device than on the orbitals responsible for current transport. So functionalization has a significant effect on the interactions within the molecular, and the molecular with NO2 side group exhibit local minima associated with twisted conformations of the molecular device which can induce the molecular memory effect.