The activated complex (transition state) is the short-lived, high-energy species formed at the top of the energy barrier during a reaction, in which old bonds are partially broken and new bonds partially formed. It sits at the maximum of the reaction's energy profile and can either go on to products or revert to reactants. Its energy above the reactants is the activation energy.

活化络合物(过渡态)是反应过程中在能垒顶端形成的、寿命极短的高能物种,其中旧键部分断裂、新键部分形成。它位于反应能量曲线的最高点,既可继续转化为产物,也可退回反应物。它高于反应物的能量即为活化能。