Objectives: Theoretical studies as well as experiments have proven that Porphyrinoids can behave as active devices in molecular electronics such as transistors and spin filters.[1–3] Previous studies in our research group shows that porphyrinoids can be divided into two groups according to the topology of induced electronic current, (a) An aromatic versus (b) an antiaromatic porphyrinoid; the preferred current path in the system (a)-type systems is around the edge of the molecule but in systems of type (b) electronic current passes around the central metal atom. Changing the ring structure, as well as the substituents on the ring, influences the current path substantially. This change is the result of changing the energy levels of virtual molecular orbitals. The more the atomic orbitals from the central metal atom contribute to the low-lying MOs, the more electronic current shifts towards the central ring. Consequently, the more the current passes around the inner core of the ring it becomes more affected by the nature of the central metal atom. For example, one expects that the spin state of the central metal influences the spin polarity of the electronic current around the ring. In the present thesis we aim to answer to this question that whether manipulation of the porphyrinoid structure can affect conductivity and spin-filtering properties of the molecule. The non-equilibrium Green’s function (NEGF) computations will be the main tool that will be used during the thesis. [1] J. Zeng, K.-Q. Chen, J. Mater. Chem. C 2013, 1, 4014–4019. [2] W. J. Cho, Y. Cho, S. K. Min, W. Y. Kim, K. S. Kim, J. Am. Chem. Soc. 2011, 133, 9364–9369. [3] J.-F. Cheng, L. Zhou, Z. Wen, Q. Yan, Q. Han, L. Gao, J. Phys. Condens. Matter 2017, 29, 175201.