Redox Ladder of Ni3 Complexes with Closed-Shell, Mono-, and Diradical Triphenylene Units: Molecular Models for Conductive 2D MOFs

We report the isolation and characterization of a series of trinickel complexes with 2,3,6,7,10,11-hexaoxytriphenylene (HOTP), [(Me(3)TPANi)(3)(HOTP)](BF4)(n) (Me(3)TPA=N,N,N-tris[(6-methyl-2-pyridyl)methyl]amine) (n=2, 3, 4 for complexes 1, 2, 3). These complexes comprise a redox ladder whereby the HOTP core displays increasingly quinoidal character as its formal oxidation state changes from -4, to -3, and -2 in 1, 2, and 3, respectively. No formal oxidation state changes occur on Ni, allowing the isolation of singlet diradical, monoradical, and closed-shell configurations for HOTP in 1, 2, and 3, respectively, with a concomitant decrease in the spin coupling strength upon oxidation. Because the three complexes can be considered models of the smallest building blocks of 2D conductive metal-organic frameworks such as Ni9HOTP4, these results serve as possible inspiration for the construction of extended materials with targeted electric and magnetic properties.

Automated summary

The study of these trinickel complexes suggests they can serve as models for the construction of extended materials with targeted electromagnetic properties, and the redox ladder in the complexes also exhibits certain characteristics.