where 𝐸 𝑜𝑥 6𝑀𝑃 is the oxidation potential of 6MP determined using equation (1), 𝐸 𝑟𝑒𝑑 𝑂 2 is the reduction potential of ground state O2, 𝐸 𝑇 6𝑀𝑃 is the adiabatic energy of the lowest-energy triplet state of 6MP, and C is the Coulombic interaction term experienced by the ion pair following the electron transfer process. The latter term represents a small contribution to the overall energy change for neutral species in polar solvents and has approximated to be 0.06 eV in acetonitrile. The reduction potential of ground state O2 has been reported to be -51.7 kJ/mol. Femtosecond Broadband Transient Absorption Spectroscopy. Transient absorption spectroscopy with femtosecond time resolution was used to study the ultrafast excited-state dynamics of Aza and 6MP. The procedure used is detailed elsewhere. Briefly, a Ti-Sapphire amplifier laser system (Libra-He, Coherent, Inc.) generates 4.0 W, 100 fs pulses at 800 nm and a repetition rate of 1 kHz. The fundamental laser beam was split into two distinct beams using a beam splitter. One of the beams was used to pump an optical parametric amplifier (OPA, TOPAS, Quantronix/Light Conversion), of which the output was tuned to the excitation wavelengths of 350 nm, 334 nm, or 316 nm and attenuated to 1 J at the sample using a neutral density optical filter. The other fraction of the fundamental beam from the Libra-He was used to pump a constantly translating CaF2 crystal of 2 mm thickness to generate the white light continuum (WLC) to be used as the probe beam (320-710 nm). A Helios spectrometer (Ultrafast Systems, LLC.) was used, with a mechanical delay stage of a maximum of 3 ns for the probe pulse. This probe pulse was split into two fractions before reaching the sample. One fraction goes through the sample (2 mm path length) while the other fraction is used as reference, to account for changes in the WLC throughout the course of the experiment. The reference signal is generated via a chopper wheel, which blocks every other pump pulse. This provides an alternating sequence of spectra with and without sample excitation, thus allowing for the collection of A transient absorption data. Detection is achieved by placing two complementary metal-oxide-semiconductor (CMOS) detectors, one for the probe fraction that goes through the sample beam and one for the probe reference beam.