In this article, we propose molecular implementation of the quantum logic gate originally realized by the linear triple-quantum dot array accommodating two electrons. To reach this goal we propose to employ the mixed-valence triferrocenium complex exhibiting three isomeric forms with different oxidation degrees Fe^III-Fe^II-Fe^III, Fe^III-Fe^III-Fe^II, and Fe^II-Fe^III-Fe^III, which correspond to three instant localizations of the two holes over three iron ions. The long-range interaction between the terminal metal sites is considered in the framework of the Hubbard-like Hamiltonian which accounts for the electron transfer and inter- and intrasite Coulomb repulsion and takes into account differences in the orbital energies of Fe^III and Fe^II ions. The interaction of the electrons with the applied electric field is also included in the Hamiltonian. It is shown that due to long-range superexchange between the two electronic spins the ground state of the triferrocenium complex is always a spin-singlet, and the first excited level is a spin-triplet. The electric field is shown to increase the antiferromagnetic exchange coupling. The efficiency of the electric field control is especially pronounced due to the field-induced transformation of the system from the isomeric form Fe^III-Fe^II-Fe^III to the form Fe^III-Fe^III-Fe^II. Estimations of the efficiency of the electric field control of the exchange coupling and entanglement show that the triferrocenium complex is emerging as a potential candidate to act as a gate in quantum computing.