The thermodynamics of copper oxidation and reduction depends on Cu site speciation, and in turn, the zeolite composition and framework Al arrangement, as shown by the DFT-derived phase diagrams reported by Paolucci et al. All Cu ions at 6-MR paired sites are in their Cu(II) states at 723 K (21 kPa O2), while Cu ions at 6-MR isolated Al sites may reside as mixtures of Cu(II) and Cu(I) states at 723 K (21 kPa O2). The Cu speciation also influences observed auto-reduction behavior at 673 K (1 Pa O2 in balance He), as Z2Cu sites remain Cu(II) while ZCuOH sites thermodynamically prefer the Cu(I) state. Elementary steps to complete ZCuOH auto-reduction events likely require two [CuOH] + within close enough proximity to form binuclear Cu-oxo species, which suggests that spatially distant ZCuOH sites will not auto-reduce. This interpretation is consistent with Raman spectra (λex = 532 nm, 18,800 cm -1 ) collected in He at 723 K that do not show discernible features for binuclear Cu-oxo structures, (Figure ; spectrum at 0 ks solely reflects background fluorescence), which if formed presumably have auto-reduced.