A new family of the supramolecular antiferromagnetically exchange-coupled dimer of single-molecules magnets,[Mn4]2, really behave as a quantum mechanical coupled system and can be used for quantum computation [Tiron et al (2003) Phys. Rev. Lett. 91 227203]. We study the time evolution of [Mn4]2 dimer interacting with an injected electron by solving the time-dependent Schrodinger equations. We find that the variations of [Mn4]2 dimer magnetization and the electron spin crucially depend on the exchange interaction strength. Time evolution of the entanglement between the injected electron and supramolecular dimer [Mn4]2 is evaluated. It is observed that entanglement oscillates in time and is closely related to the spin variation of injected electron. From these characteristics the technique for the reversing and read-out of supramolecular dimer [Mn4]2 spin states is suggested.