A new manganese complex, [Mn(Pc)(CN)]2O, was prepared by an electrocrystallization method. This material is a single-component molecular conductor that displays semiconducting behavior with room temperature conductivity of 4.5 × 10(-3) S cm(-1). Furthermore, we observed negative magnetoresistance at room temperature due to interaction between conduction π electrons and localized d spins. X-ray structural analysis and IR absorption spectroscopy indicated structural disorder. The magnetic susceptibility measurements suggested the unequal spin states of two manganese atoms owing to this structural disorder.