The relationship between the manganese(II) zero-field interaction and Mn(II)/Mn(III) redox potential of Mn(4′-X-terpy)₂ complexes

The Mn(II)/Mn(III) redox potentials and Mn(II) zero-field interactions were measured for a series of Mn(II)(4′-X-terpy)₂ complexes as a function of the electron-donating properties of the 4′-substituent. The two properties were found to be linearly related to each other. Density functional calculations demonstrated that the variation of both the redox potential and zero-field interaction depended on the charge on the center nitrogen of the terpy ligand that was modulated by the 4′-substituent. A similar relationship was found for Mn(II) complexes formed with the N,N-bis(2-ethyl-5-methylimidazol-4-ylmethyl)aminopropane ligand, indicating that the relationship between the Mn(II) zero-field interaction and the Mn(II)/Mn(III) redox potential was likely to be general.