Polyfunctional Sterically Hindered Catechols with Additional Phenolic Group and Their Triphenylantimony(V) Catecholates: Synthesis, Structure, and Redox Properties

New polyfunctional sterically hindered 3,5-di-tert-butylcatechols with an additional phenolic group in the sixth position connected by a bridging sulfur atom—(6-(CH2-S-tBu2Phenol)-3,5-DBCat)H2 (L1), (6-(S-tBu2Phenol)-3,5-DBCat)H2 (L2), and (6-(S-Phenol)-3,5-DBCat)H2 (L3) (3,5-DBCat is dianion 3,5-di-tert-butylcatecolate)—were synthesized and characterized in detail. The exchange reaction between catechols L1 and L3 with triphenylantimony(V) dibromide in the presence of triethylamine leads to the corresponding triphenylantimony(V) catecholates (6-(CH2-S-tBu2Phenol)-3,5-DBCat)SbPh3 (1) and (6-(S-Phenol)-3,5-DBCat)SbPh3 (2). The electrochemical properties of catechols L1–L3 and catecholates 1 and 2 were investigated using cyclic voltammetry. The electrochemical oxidation of L1–L3 at the first stage proceeds with the formation of the corresponding o-benzoquinones. The second process is the oxidation of the phenolic moiety. Complexes 1 and 2 significantly expand their redox capabilities, owing to the fact that they can act as the electron donors due to the catecholate metallocycle capable of sequential oxidations, and as donors of the hydrogen atoms, thus forming a stable phenoxyl radical. The molecular structures of the free ligand L1 and complex 1 in the crystal state were determined by single-crystal X-ray analysis.

Synthesis And Spectroscopic Studies Of New Bis(N-1-hydroxy-2,6-Di-Fe/Tf-Butylphenyl- Salicylideneaminato)Cobalt(Ii) Complexes And Their Oxidation With PbO2

A series of new bis[N-(1-OH-2,6-di-tert-butylphenyl)salicylaldiminato]cobalt(II) complexes possessing one or two HO- and CH3O - substituents on the salicylaldehyde moiety were prepared, and their spectroscopic properties as well as their oxidation with PbO2 were examined. ESR data indicate that oxidation of the complexes produces stable phenoxyl radicals. All phenoxyl radicals have similar g-values and hyperfine coupling constants, which are influenced very little by the substituents and by coordination. The experimental observations indicate that the Co(L·x)2 radicals are ligand-localized and that there is no notable contribution from the metal d-orbitals to the values of the g-factors. Satellite peaks from the 13C nuclei in the aromatic ring were also observed. The ESR spectra of some of the complexes showed partial conversion of primary radicals to secondary paramagnetic species exhibiting interaction with 59Co(I = 7/2) and 14N nuclei