Spin Transition and Charge Transfer in Co²⁺/Co³⁺ Complexes of Meridional Ligands Holding Nearby Redox‐active Triarylamine

Titelangaben

Schnaubelt, Linda ; Petzold, Holm ; Speck, J. Matthäus ; Rüffer, Tobias ; Hörner, Gerald ; Lang, Heinrich:
Spin Transition and Charge Transfer in Co²⁺/Co³⁺ Complexes of Meridional Ligands Holding Nearby Redox‐active Triarylamine.
In: Zeitschrift für anorganische und allgemeine Chemie. Bd. 644 (2018) Heft 21 . - S. 1257-1267.
ISSN 1521-3749
DOI: https://doi.org/10.1002/zaac.201800274

Angaben zu Projekten

Abstract

Phenanthroline‐pyridyl bases containing a triarylamine (Tara) 1 –4 and their respective Co2+ ([Co(L )2](ClO4)2, L = 1 –4 ) and Co3+ complexes ([Co(L )2](ClO4)3–n (BF4)n , L = 2 , 3 ) were prepared. The structure of [Co(3 )2](ClO4)2 in the solid state was determined by single‐crystal X‐ray diffractometry. The oxidation processes of [Co(L )2](ClO4)2 (L = 1 –4 ) were investigated by cyclic voltammetry. The first oxidation step in [Co(L )2](ClO4)2 (L = 1 –3 ) is chemically reversible and cobalt‐centered. This process is followed by the irreversible oxidation of the Tara units at higher potentials. In case of [Co(4 )2](ClO4)2 the first oxidation is Tara‐centered and electrochemically reversible. The electronic coupling between the Co3+ ion and Tara in in‐situ prepared [Co(L )2]3+ (L = 2 , 3 ) was investigated by UV/Vis/NIR spectroelectrochemistry. In spectra of in situ prepared [Co(L )2]3+ (L = 2 , 3 ) ligand‐to‐metal charge transfer (LMCT) bands were found between 600–1250 nm, which were assigned to a charge transfer from the Tara to the Co3+ ion. Physical parameters (wavenumber ν̃max, extinction ε max, and full‐width at half‐maximum Δν1/2) of the charge transfer (CT) bands were obtained by deconvolution of the UV/Vis/NIR spectra. In addition analogous Co3+ complexes [Co(L )2]3+ (L = 2 , 3 ) were isolated as the mixed BF4–/ClO4– salts. These compounds exhibit the same CT bands as observed in the in situ oxidation experiments.