Anion dependent formation of linear trinuclear mixed valance cobalt(III/II/III) complexes and mononuclear cobalt(III) complexes of a pyrazole derived ligand – Synthesis, characterization and X-ray structures

Mixed-Valent Trinuclear CoIII-CoII-CoIII Complex with 1,3-Bis(5-chlorosalicylideneamino)-2-propanol

A mixed-valent trinuclear complex with 1,3-bis(5-chlorosalicylideneamino)-2-propanol (H₃clsalpr) was synthesized, and the crystal structure was determined by the single-crystal X-ray diffraction method at 90 K. The molecule is a trinuclear Co^III-Co^II-Co^III complex with octahedral geometries, having a tetradentate chelate of the Schiff-base ligand, bridging acetate, monodentate acetate coordination to each terminal Co³⁺ ion and four bridging phenoxido-oxygen of two Schiff-base ligands, and two bridging acetate-oxygen atoms for the central Co²⁺ ion. The electronic spectral feature is consistent with the mixed valent Co^III-Co^II-Co^III. Variable-temperature magnetic susceptibility data could be analyzed by consideration of the axial distortion of the central Co²⁺ ion with the parameters Δ = –254 cm⁻¹, λ = –58 cm⁻¹, κ = 0.93, tip = 0.00436 cm³ mol⁻¹, θ = –0.469 K, g_z = 6.90, and g_x = 2.64, in accordance with a large anisotropy. The cyclic voltammogram showed an irreversible reduction wave at approximately −1.2 V·vs. Fc/Fc⁺, assignable to the reduction of the terminal Co³⁺ ions.

Robust, highly active, and stable supported Co(ii) nanoparticles on magnetic cellulose nanofiber-functionalized for the multi-component reactions of piperidines and alcohol oxidation

The new recyclable cobalt three-core magnetic catalyst obtained by anchoring a Schiff base ligand sector and cellulose nanofiber slings on MNP (Fe3O4) was prepared and named as MNP@CNF@ATSM-Co(ii). Separately, MNPs and CNF have adsorbent properties of great interest. In this way, this catalyst was designed to synthesize piperidine derivatives under solvent-free conditions and alcohol oxidation reactions in EtOH as the solvent. It should be noted that this catalyst is environmentally safe and does not need an external base. This MNPs@CNF@ATSM-Co(ii) separable catalyst has been evaluated using various characterization techniques such as FT-IR, XRD, FE-SEM, EDX, EDS, ICP, TGA, DLS, HRTEM, and VSM. The catalyst was compatible with a variety of benzyl alcohols, benzaldehydes, and amines derivatives, and gave complimentary coupling products with sufficient interest for all of them. The synergistic performance of Co (trinuclear) in the catalyst was demonstrated and its different homologs such as MNPs, MNPs@CNF, MNPs@CNF@ATS-Co(ii), and MNPs@CNF@ATSM-Co(ii) were separately synthesized and applied to a model reaction, and then their catalytic activity was investigated. Also, the performance of these components for the oxidation reaction of alcohols was evaluated. The advantages of the current protocol include the use of a sustainable and safe low temperature, eco-friendly solvent no additive, and long-term stability and magnetic recyclability of the catalyst for at least five successive runs, thus following green chemistry principles. This protocol is a benign and environment-friendly method for oxidation and heterocycle synthesis. This powerful super-magnetic catalyst can use its three arms to advance the reactions, displaying its power for multi-component reactions and oxidation.

σ-Hole halogen bonding interactions in a mixed valence cobalt(iii/ii) complex and anti-electrostatic hydrogen bonding interaction in a cobalt(iii) complex: a theoretical insight

Supramolecular interactions in the solid state structures of a mixed valence cobalt(ii/iii) complex and a cobalt(iii) complex have been studied using DFT calculations.

A novel 1,3,5-triaminocyclohexane-based tripodal ligand forms a unique tetra(pyrazolate)-bridged tricopper(ii) core: solution equilibrium, structure and catecholase activity

A polydentate tripodal ligand forms a series of tricopper(ii) complexes, that feature unique pyrazolate-bridged linear core. The Cu₃H₋₃L₂ complex is an efficient catecholase mimic with a surprisingly low pH optimum at pH = 5.6.

Preparation and characterization of di-, tri-, and tetranuclear schiff base complexes derived from diamines and 3,4-dihydroxybenzaldehyde

A series of new di-, tri-, and tetranuclear Co(II) and Cu(II) complexes of three new diSchiff base ligands were synthesized by two different methods. The first method involved the synthesis of the three ligands from condensation reaction of 3,4-dihydroxybenzaldehyde (L′H₂) with ethylenediamine (en), o-phenylenediamine (o-PD), or 4,5-dimethyl-1,2-phenylendiamine (DMPD) in a mole ratio of 2 : 1 followed by the reaction of the resulting Schiff bases ligands with Cu(II) or Co(II) ions in the presence of 2,2′-bipyridyl (L) to form the di- and trinuclear metal complexes. The second method involved the condensation of the copper complex LCu(II)L′ (L = 2,2′-bipyridyl, L′ = 4-formylbenzene-1,2-bis(olate)) with en, o-PD, or DMPD in a mole ratio of 2 : 1, respectively, followed by reaction with CuCl₂ or Cu(ClO₄)₂ to form di-, tri-, and tetranuclear copper (II) complexes, respectively. The structures of the ligands and metal complexes were characterized by elemental analyses, NMR, and FTIR spectra. The geometries of metal complexes were suggested according to elemental analysis, electronic spectra, thermal analyses, atomic absorption, and magnetic moments and conductivity measurements.