1341207-28-0Relevant articles and documents
Phenolate and phenoxyl radical complexes of Cu(ii) and Co(iii), bearing a new redox active N,O-phenol-pyrazole ligand
Zats, Galina M.,Arora, Himanshu,Lavi, Ronit,Yufit, Dmitry,Benisvy, Laurent
, p. 10889 - 10896 (2011/11/29)
The synthesis and characterisation of the new N,O-phenol-pyrazole pro-ligand, pzLH, comprising a pyrazole covalently linked to an o,p-di-tert-butyl-substituted phenol, are herein reported. In CH 2Cl2 at room temperature, the cyclic voltammogram (CV) of pzLH exhibits a quasi-reversible one-electron oxidation process (at E1/2 = 0.66 V vs. Fc+/Fc) attributed to the formation of the phenoxyl radical cation [pzLH]+. pzLH reacts with MII(BF4)2 (M = Cu, Co) in a 2:1 ratio to afford the bis-CupzL2 (1) and tris-Co pzL3 (2) complexes respectively. The X-ray structure of 1 reveals a Cu(ii) ion in a square-planar trans-CuII-N 2O2 coordination environment whereas that of 2 consists of a Co(iii) ion with an octahedral mer-N3O3 coordination sphere; formed by the chelation of two (in 1) or three (in 2) N,O-bidentate phenolate ligands respectively. Both structures are preserved in CH 2Cl2 solution, as revealed by their NMR (for 2) and EPR (for 1) data. The CVs of 1 and 2 consist of two (at E1/2: 0.43 and 0.58 V vs. Fc+/Fc) and three (E1/2 = 0.12, 0.54 and 0.89 V vs. Fc+/Fc) reversible one-electron oxidation processes, respectively. The one-electron electrochemical oxidation of 1 and 2 produces the oxidised species, 1+ and 2+, which are stable for several hours at room temperature under inert atmosphere in CH2Cl 2. The UV/vis and EPR data obtained for 1+ and 2 + are unambiguously consistent with the latter being formulated as Cu(ii)- and Co(iii)-phenoxyl radical complexes, as [CuII( pzL)(pzL)]+ and [CoIII( pzL)(pzL)2]+ respectively.
