Spin-philicity and spin-donicity as auxiliary concepts to quantify spin-catalysis phenomena

For molecular systems Susceptible to undergo a change of their spin state as a result of a chemical reaction with a given reactant, the spin-polarized density functional theory is used to define the concepts of spin-philicity (omega(S)(+)) and spin-donicity (omega(S)(-)) as global reactivity indexes. They are defined as the maximum energy change when a molecular system acquires or donates a spin number DeltaN(S) to increase (omega(S)(+)) or decrease (omega(S)(-)) its spin multiplicity. The spin transformation of chemically reactive species induced by the interaction of these molecules with external spin carriers-a phenomenon known as spin catalysis-is discussed on the basis of an absolute scale for omega(S)(+) and omega(S)(-). As an illustration of the method, a selection of paramagnetic and diamagnetic molecules, commonly used as spin catalyst. is classified within this scale and the hierarchy obtained is compared with the available experimental information.