One-electron oxidized nickel(II) complexes of bis and tetra(salicylidene) phenylenediamine Schiff bases: from monoradical to interacting Ni(III) ions.
The Ni(II) complexes of the mono and di-nucleating Schiff base ligands H2LOMe (bis(3,5-di-tert-butylsalicylidene)-4,5-dimethoxy-o-phenylenediamine), H2LNO2 (bis(3,5-di-tert-butylsalicylidene)-4,5-dinitro-o-phenylenediamine) and H4Lbis (tetrakis(3,5-dimethoxy-o-phenylenediamine)-1,2,4,5-benzenetetraamine) were synthesized and characterized. H2LOMe and H2LNO2 differ from one another by the substituents of the phenylene spacer, electron-donating methoxy or electron-withdrawing nitro groups, resp. X-ray crystal structure anal. shows that the Ni(II) ion(s) resides within a square planar geometry in each complex. Cyclic voltammetry curves reveal that the electrochem. communication is strongly influenced by the substituent and the solvent. The 1-electron oxidized species [Ni(LOMe)]+ in CH2Cl2 is a phenoxyl radical with partial delocalization of the spin d. on a metal orbital (contribution of 6.8{%}), whereas [Ni(LNO2)]+ disproportionates once it is generated. A shift of electronic hole is obsd. in the presence of pyridine: both [Ni(LOMe)]+ and the 1-electron oxidn. product of [Ni(LNO2)] are converted into mononuclear octahedral Ni(III) complexes involving two axially bound pyridines. In the dinickel(II) complex of H4Lbis, [Ni2(Lbis)], the phenylene spacer mediates an electronic communication between the two metallic sites. Single oxidn. of [Ni2(Lbis)] affords the delocalized phenoxyl radical [Ni2(Lbis)]+, whose EPR signature is close to that of [Ni(LOMe)]+. Double oxidn. affords the bis-{\{}NiII-delocalized radical{\}} species [Ni2(Lbis)]2+. Each radical is located at a distinct metallic site and a weak but appreciable magnetic interaction exists between the paramagnetic centers. In the presence of pyridine, a complex involving two ferromagnetically coupled Ni(III) ions was obtained. The magnetic coupling was estd. to 3.7 cm-1, while the zero field splitting parameters are |D| = 0.012 cm-1 and E = 0. They are weak, in agreement with the large intermetallic distance (7.7 {\AA}) obsd. in the neutral precursor [Ni2(Lbis)]. [on SciFinder(R)]
Références
- Titre
- One-electron oxidized nickel(II) complexes of bis and tetra(salicylidene) phenylenediamine Schiff bases: from monoradical to interacting Ni(III) ions.
- Type de publication
- Article de revue
- Année de publication
- 2009
- Auteurs
- Rotthaus, Olaf, Jarjayes Olivier, Philouze Christian, Perez del Valle Carlos, and Thomas Fabrice
- Revue
- Dalt. Trans.
- Pagination
- 1792–1800
- ISSN
- 1477-9226
- Mots-clés
- crystal structure nickel salicylidenephenylenediamine salicylidenebenzenetetraamine complex electronic structure nickel salicylidenephenylenediamine salicylidenebenzenetetraamine complex electrooxidn nickel salicylidenephenylenediamine salicylidenebenzenetetraamine complex ESR nickel salicylidenephenylenediamine salicylidenebenzenetetraamine complex nickel salicylidenephenylenediamine salicylidenebenzenetetraamine complex prepn structure salicylidenebenzenetetraamine prepn complexation nickel salicylidenephenylenediamine prepn complexation nickel
- DOI
- 10.1039/b811702k
Soumis le 12 avril 2018