Synthesis and characterization of two self-assembled [Cu6Gd3] and [Cu5Dy2] complexes exhibiting the magnetocaloric effect, slow relaxation of magnetization, and anticancer activity

Two new paths for coordination driven self-assembly reactions under the binding support of 2-((1-hydroxy-2-methylpropan-2-ylimino)methyl)-6-methoxyphenol (H₂L) have been discovered from the reactions of Cu(ClO₄)₂·6H₂O, NEt₃ and GdCl₃/DyCl₃·6H₂O in MeOH/CHCl₃ (2 : 1) medium. A similar synthetic protocol is useful to provide two different types of self-aggregated molecular clusters [Cu₆Gd₃(L)₃(HL)₃(μ₃-Cl)₃(μ₃-OH)₆(OH)₂]ClO₄·4H₂O (1) and [Cu₅Dy₂(L)₂(HL)₂(μ-Cl)₂(μ₃-OH)₄(ClO₄)₂(H₂O)₆](ClO₄)₂·2NHEt₃Cl·21H₂O (2). The adopted reaction procedure established the importance of the HO^- and Cl^- ions in the mineral-like growth of the complexes, derived from solvents and metal ion salts. In the case of complex 1, one Gd^III center has been trapped at the central position of the core upheld by six μ₃-OH and three μ₃-Cl groups, whereas for complex 2 one Cu^II center was trapped using four μ₃-hydroxo and two μ-chlorido groups. The magnetothermal behavior of 1 has been examined for a magnetocaloric effect of -ΔS_m = 11.3 J kg^-1 K^-1 at 2 K for ΔH = 7 T, whereas the magnetic susceptibility measurements of 2 showed slow magnetic relaxation with U_eff = 15.8 K and τ₀ = 9.8 × 10^-7 s in zero external dc field. Cancer cell growth inhibition studies proved the potential of both the complexes with interestingly high activity for the Cu₆Gd₃ complex against human lung cancer cells. Both complexes 1 and 2 also exhibited DNA and human serum albumin (HSA) binding abilities in relation to the involved binding sites and thermodynamics.

Structure, DFT studies and evaluation of catechol oxidase (CO) mimic activity of mononuclear Co(II) complexes derived from aminoalcohols: an experimental and theoretical approach

The impetus to modeling of enzyme mimics comes from their potential to provide insight to the alternate mechanistic pathways of the native enzymes. The present study demonstrates the syntheses and characterization of two different cobalt(II) complexes, [Co(pdm)(Phen)Cl]Cl·H₂O (1) and [Co(pmmH)₂(SCN)₂] (2) with the aminoalcohol ligands such as pyridine-2,6-dimethanol (pdmH₂) or 2-pyridinemonomethanol (pmmH) and their assessment as catechol oxidase (CO) enzyme mimic. Single Crystal X-ray diffraction and powder X-ray diffraction data suggest the octahedral environment around the Co(II) ion and the complexes form extensive 1D or 2D propagating network as a result of non-covalent interactions (O···H and C-H···π). TD-DFT calculations were used to explain the spectral bands obtained during the UV-Vis absorption studies and it is ascertained that the transitions were mainly of the intra-ligand charge transfer (ILCT) type. The catecholase biomimetic catalytic activity of the synthesized complexes has been investigated in detail and the kinetics is also performed. The results obtained show that both the complexes catalyze the aerobic oxidation of catechol to the corresponding o-quinone. The K_cat value for 1 is 106.99 h^‒1 and for 2 is 90.32 h^‒1 in methanol. It may be mentioned here that 1 and 2 are effective catalysts, with the order of activity being 1 > 2. The order of enzymatic activity is well justified by CV and DFT studies.Communicated by Ramaswamy H. Sarma.

Solvent-induced structural transformation from heptanuclear to decanuclear [Co–Ln] coordination clusters: trapping of unique counteranion and understanding of aggregation pathways

The MeCN solvent-induced transformations of heptanuclear LnIII3CoII2CoIII2⁺ cationic aggregates, associated with literature unknown Ln(iii)-pivalate-based counter anions, to decanuclear LnIII3CoII3/2CoIII4/5 clusters have been investigated.

In situ transformation of a tridentate to a tetradentate unsymmetric Schiff base ligand via deaminative coupling in Ni(ii) complexes: crystal structures, magnetic properties and catecholase activity study

An N₂O donor reduced Schiff base in presence of Ni(ClO₄)₂·6H₂O and SCN⁻ transforms into N₂O₂ donor ligand via deaminative coupling. Metal complexes 1 and 3 exhibit catecholase like activity and antiferromagnetic coupling between the Ni(ii) ions.

Exploring solvent dependent catecholase activity in transition metal complexes: an experimental and theoretical approach

Four coordination compounds are designed with pyridinemethanol ligands, characterized with spectral, magnetic and X-ray analyses, and assessed for catecholase activity in various solvents.

The catalytic activities and magnetic behaviours of rare μ3-chlorido and μ1,1,1-azido bridged defective dicubane tetranuclear Mn(ii) complexes

A μ₃-chlorido and a μ_1,1,1-azido bridged defective dicubane tetranuclear Mn(ii) complexes of polynucleating Mannich base ligand show significant catalytic oxidase activities and are antiferromagnetically coupled which is rationalized by DFT calculations.

The first alternating MnII–MnIII 1D chain: structure, magnetic properties and catalytic oxidase activities

A one-dimensional mixed-valence Mn^II/Mn^III chain has been synthesized using N-salicylidene-l-alanine and 2,2′-bipyridine. The complex shows moderate catecholase and phenoxazinone synthase-like activity.

Syntheses and characterization of monobasic tridentate Cu(ii) Schiff-base complexes for efficient oxidation of 3,5-di-tert-butylcatechol and oxidative bromination of organic substrates

Enhanced bifunctional catalytic activities are shown by monobasic tridentate Cu(ii) Schiff-base complexes.

Importance of C–H⋯π interactions in stabilizing the syn/anti arrangement of pendant alkoxy side arms in two manganese(iv) Schiff base complexes: exploration of catechol oxidase and phenoxazinone synthase like activities

Two manganese(iv) complexes have been prepared and characterized. Both complexes exhibit catechol oxidase and phenoxazinone synthase like activities.

Competitive coordination aggregation for V-shaped [Co3] and disc-like [Co7] complexes: synthesis, magnetic properties and catechol oxidase activity

The synthetic procedures, magnetic properties and catecholase-like activity of a V-shaped [CoII3L₄] and planar disc-like [CoII7L₆] complexes have been discussed.

Nickel(ii) and copper(ii) complexes constructed with N2S2 hybrid benzamidine–thiosemicarbazone ligand: synthesis, X-ray crystal structure, DFT, kinetico-catalytic and in vitro biological applications

We report nickel(ii) and copper(ii) complexes containing the benzamidine–thiosemicarbazone ligand together with DFT, enzyme kinetics and in vitro biological applications such as DNA/BSA affinities and anticancer properties.