Work

PhenTAA: A Redox-Active N4-Macrocyclic Ligand Featuring Donor and Acceptor Moieties

Year: 2024

Type: article

Abstract: High Resolution Image Download MS PowerPoint Slide Here, we present the development and characterization of the novel PhenTAA macrocycle as well as a series of [Ni(R 2 PhenTAA)] n complexes featuring two sites for ligand-centered redox-activity. These differ in the substituent R (R = H, Me, or Ph) and overall charge of the complex n (n = −2, −1, 0, +1, or +2). Electrochemical and spectroscopic techniques (CV, UV/vis–SEC, X-band EPR) reveal that all redox events of the [Ni(R 2 PhenTAA)] complexes are ligand-based, with accessible ligand charges of −2, −1, 0, +1, and +2. The o -phenylenediamide (OPD) group functions as the electron donor, while the imine moieties act as electron acceptors. The flanking o -aminobenzaldimine groups delocalize spin density in both the oxidized and reduced ligand states. The reduced complexes have different stabilities depending on the substituent R. For R = H, dimerization occurs upon reduction, whereas for R = Me/Ph, the reduced imine groups are stabilized. This also gives electrochemical access to a [Ni(R 2 PhenTAA)] 2– species. DFT and TD–DFT calculations corroborate these findings and further illustrate the unique donor–acceptor properties of the respective OPD and imine moieties. The novel [Ni(R 2 PhenTAA)] complexes exhibit up to five different ligand-based oxidation states and are electrochemically stable in a range from −2.4 to +1.8 V for the Me/Ph complexes (vs Fc/Fc + ).

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.3c03708