New dinuclear cobalt (ΙΙ, ΙΙΙ) and tetranuclear manganese (ΙΙΙ) complexes assembled by a polydentate Schiff-base ligand: synthesis, structure and magnetic properties

Synthesis and Structural Features of New Schiff Base Complexes of Mononuclear MnIV, Dinuclear CoIICoIII, and Tetranuclear CuII

“…No intervalence transition at lower energy was observed, thus suggesting that the valences are also localized [Co (1) III ; Co(2) II ] when 2 is dissolved in CH 3 CN solution. [12] In the case of tetranuclear Cu II complex 3 was observed a typical UV/Vis spectrum of a copper(II) complex. The lower energy absorptions can be assigned to d-d transitions at 621 nm (log ε = 3.01) and are typical of Cu II complexes in a highly distorted octahedral environment, in agreement with the X-ray structure of complex 3, which reveals that the central copper atoms are in the oxidation state 2+.…”

“…The first anodic peak observed at E pa = +1.03 V can be assigned to the one-electron oxidation of the mixed-valence Co II Co III complex to the corresponding Co III Co III species, in which the Co 2 N 2 O 4 moiety is coordinated by a dichelated ligand containing N-imine and O-phenolate donor atoms (Co 2 L). [12] The second oxidation process observed at E pa = +1.30 V can be assigned to the ligand oxidation Schiff base type.…”

“…An analogue mixed valence complex of cobalt was already reported by Ke, Xie and co-workers. [12] The tetramer [Cu(LH 2 )(H 2 O)] 4 (3) crystallizes in the tetragonal space group I4 1 /a and the equivalent atoms can be generated from the asymmetric unit by the symmetry transformations (Ј) -y+7/4, x-1/4, -z+7/4, (ЈЈ) y+1/4, -x+7/4, -z+7/4 99.58 (13) and (ЈЈЈ) -x+4/2, -y+3/2, z (see Figure 3 and Figure 4). The copper(II) ions achieve a distorted tetrahedral configuration, without metal-metal interaction.…”

“…These Schiff base ligands allow the formation of both monomers [11] and polynuclear transition metal complexes. [7,12] Specifically 2-hydroxy Schiff base ligands are of interest, mainly due to the existence of O-H···N and N-H···O hydrogen bonds as models for the study of keto-enol tautomerism. [13][14][15] Structurally, Schiff bases derived from salicylaldehyde gen-molecules of the ligand with one manganese(IV) ion.…”

“…[18] Many groups are involved in the utilization of the multisite Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (as abbreviation LH 4 ), [19] to prepare 4f clusters, 3d-4f mixed metal compounds, and a small number of first row polynuclear transition metal complexes. [20][21][22][23][24] With the aim to provide new complexes obtained from LH 4 …”