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Spin Transition and Charge Transfer in Co 2+ /Co 3+ Complexes of Meridional Ligands Holding Nearby Redox‐active Triarylamine
Author(s) -
Schnaubelt Linda,
Petzold Holm,
Speck J. Matthäus,
Rüffer Tobias,
Hörner Gerald,
Lang Heinrich
Publication year - 2018
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201800274
Subject(s) - chemistry , redox , cyclic voltammetry , crystallography , cobalt , electrochemistry , ion , transition metal , analytical chemistry (journal) , inorganic chemistry , electrode , catalysis , chromatography , biochemistry , organic chemistry
Phenanthroline‐pyridyl bases containing a triarylamine (Tara) 1 – 4 and their respective Co 2+ ([Co( L ) 2 ](ClO 4 ) 2 , L = 1 – 4 ) and Co 3+ complexes ([Co( L ) 2 ](ClO 4 ) 3– n (BF 4 ) n , L = 2 , 3 ) were prepared. The structure of [Co( 3 ) 2 ](ClO 4 ) 2 in the solid state was determined by single‐crystal X‐ray diffractometry. The oxidation processes of [Co( L ) 2 ](ClO 4 ) 2 ( L = 1 – 4 ) were investigated by cyclic voltammetry. The first oxidation step in [Co( L ) 2 ](ClO 4 ) 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 ](ClO 4 ) 2 the first oxidation is Tara‐centered and electrochemically reversible. The electronic coupling between the Co 3+ 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 Co 3+ ion. Physical parameters (wavenumber ν̃ max , extinction ε max , and full‐width at half‐maximum Δν 1/2 ) of the charge transfer (CT) bands were obtained by deconvolution of the UV/Vis/NIR spectra. In addition analogous Co 3+ complexes [Co( L ) 2 ] 3+ ( L = 2 , 3 ) were isolated as the mixed BF 4 – /ClO 4 – salts. These compounds exhibit the same CT bands as observed in the in situ oxidation experiments.