We speculated that a quinoid radical derived from the catechol moiety at the B ring of PiceH4 was formed after the second PT (Equation ( )) for its chemical reversibility. Conversely, the bielectronic CV behavior was not observed in the presence of RsvH3 (Figure (b)) owing to the ET scavenging HO2 • and subsequent degradation of the generated radical. Interestingly, spins are primarily distributed in the B ring (H a -H c ) and throughout the molecule of PiceH2 •-, as shown in the ESR results. In the CVs shown in Figure , a reversible redox couple (pc6/pa6) derived from the product appeared, indicating that the product was a quinoid radical (PiceH2 •-) derived from the catechol moiety of the B ring and suggesting that the reaction site of PCET was influenced by the structural differences between PiceH4 and RsvH3. In addition, the aH values obtained from the ESR spectrum were assigned to the hydrogen on another phenolic ring (A ring, H f -H h ) and the linked ethylene bridge (stilbene double bond, H d and H e ), clarifying that the coplanar stilbene moiety contributes to PCET at the catechol moiety. A similar role of the stilbene moiety in contributing the PCET reaction is expected to occur in the RsvH3 molecule, although it was suggested that its product radical, generated via PCET, decomposes upon a subsequent reaction (the ESR spectrum was undetectable).