Table 1.

Computed reduction potentials of nickel hangman porphyrins

Oxidized species	Sox	Reduced species	Sred	E0/V vs. Fc+/Fc*
HOOC–NiP	0	[HOOC–NiP]–	1/2	−1.37 (–1.37)†
[HOOC–NiP]–	1/2	[HOOC–NiP]2–	1	−1.85
[OOC–NiP]–	0	[OOC–NiP]2–	1/2	−1.40 (–1.43)
[OOC–NiP]2–	1/2	[OOC–NiP]3–	1	−2.01 (–1.99)
[OOC–Ni(H)P]–	1/2	[OOC–Ni(H)P]2–	1	−0.81
[OOC–Ni(H)P]2–	1	[OOC–Ni(H)P]3–‡	3/2	−1.84
2-Ni	0	[2-Ni]–	1/2	−1.34 (–1.39)
[2-Ni]–	1/2	[2-Ni]2–	1	−1.91 (–1.96)
3-Ni	0	[3-Ni]–	1/2	−1.32 (–1.27)
[3-Ni]–	1/2	[3-Ni]2–	1	−1.76 (–1.82)

Calculations were performed with DFT using the B3P86 functional, 6–31+G(d), and 6–31+G(d,p) basis sets, and conductor-like polarizable continuum model (C-PCM) solvation. Geometries were optimized in solution.

^*Experimental midpoint potential (E_1/2) values are given in parentheses.

^†These experimental and computational values are the same by construction because this is the reference reaction used in computation.

^‡This reduced species refers to the formally Ni(I) hydride; the spin density on nickel remains ∼2 (SI Appendix), indicating that the reduction is ligand-based.