On the other side, it is essential to differentiate the charge transfer (QCT) vs. spin-transfer phenomena since the spin density (ρS) is the difference between α and β spin density: ρS=ρα-ρβ. In this sense, the QCT parameter does not differ between α and β electrons, but spin density transfer can occur with QCT = 0 if the spin density location is balanced . In the cases of C2-G, C3-G, and C4-G hybrids, charge transfer/spin density delocalization coincides, analogous to forming a transient corrole radical due to an electron transfer .