Effect of substituent groups on the electronic properties of a molecular device: An ab initio theoretical study

Investigation of the geometric and electronic structures of substituted molecular wires was carried out to explore the effect of functional groups on the electronic properties of molecular devices. The wires computed in the present study consist of three units of benzene rings connected by acetylene functional groups, where two H atoms in the middle ring are substituted by electron withdrawing (-NO ₂, -CN) and electron donating groups (-NH ₂ and -CH ₃O). Both ab initio Hartree-Fock and hybrid density functional methods were used in this study. The electronic transport properties of these molecules were analyzed from the shape of the frontier orbitals and their respective energies. The results demonstrate the important role of the acceptor groups, which primarily control the electronic transport in such molecules.