Specifically, we were interested in understanding why the less oxidizing α-chloroamide (1a, Ep/2 = -1.65 V vs. SCE) is reduced preferentially to the nitroalkane (2a, Ep/2 = -0.89 V vs. SCE). We hypothesized that an enzyme templated charge-transfer (CT) complex controlled the electron transfer events. To probe this possibility, the cofactor FMN in CsER was entirely reduced to FMNhq with sodium dithionite, which revealed negligible absorption around 500 nm (Fig. ).