Unique dependence on the nature of metal salt and reaction conditions for coordination assembly reactions of varying architecture and nuclearity have been identified in V-shaped [Co3L4] and planar disc-like [Co7L6] compounds: [CoL2(μ-L)2(μ-OH2)2(CF3CO2)2] (1) and [Co(μ-L)6(μ-OMe)6]Cl2 (2) (HL = 2-{(3-ethoxypropylimino)methyl}-6-methoxyphenol). At room temperature varying reaction conditions, cobalt-ligand ratios and use of different bases allowed unique types of coordination self-assembly. The synthetic marvel lies in the nature of aggregation with respect to the two unrelated cores in 1 and 2. Complex 1 assumes a V-shaped arrangement bound to L(-), water and a trifluoroacetate anion, while 2 grows around a central Co(II) ion surrounded by a {Co} hexagon bound to methoxide and L(-). Magnetic measurements revealed that the intermetallic interactions are antiferromagnetic in nature in the case of complex 1 and ferromagnetic in the case of 2 involving high spin cobalt(ii) ions with stabilization of the high-spin ground state in the latter case. In MeCN solutions complexes 1 and 2 showed catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBCH2) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) in air. The kinetic study in MeCN revealed that with respect to the catalytic turnover number (kcat) 2 is more effective than 1 for oxidation of 3,5-DTBCH2.

Ligand backbone alteration leads to different mechanisms for catecholase activity and order of interaction with DNA molecules.

The synthesis, structural characterization, and magnetic behavior of a new family of binuclear CoII–LnIII complexes of formula [LnIIICoIIL2(NO3)3]·H2O (Ln = La, 1; Gd, 2; Tb, 3; Dy, 4; Ho, 5; HL = 3-methoxy-N-(2-(methylsulfanyl)­phenyl)­salicylaldimine) have been reported. The chosen ligand system HL has adjacent soft ONS and hard OO binding pockets ideal for selective coordination of CoII and 4f metal ions. All the complexes 1–5 exhibit a CoII center in a highly distorted octahedral geometry with the LnIII centers in bicapped square-antiprism geometry. The unique distortion about the CoII center is introduced by the coordination of 4f metal ions in the hard OO coordination site. The distortion is further supported by the presence of −SMe groups giving an S donor atom which owing to its larger size can support large bond distances and angles. The geometry around the CoII centers is intermediate between meridional and facial geometric isomers. The magnetic properties of these complexes have been investigated by a “full model” approach using CONDON with the experimental magnetochemical analysis revealing ferromagnetic Co–Ln coupling in compounds 2–5. Ab initio calculations on the X-ray crystal structures of 1–5 paint a semiquatitative picture about the contribution of the individual anisotropic centers toward the overall magnetic properties of the compounds. Theoretical analysis predicts 1 and 2 as weak single-ion magnet (SIM) and single-molecule magnet (SMM) respectively with CoII being solely responsible for the complex anisotropy. In 2, J CoGd plays a crucial role in preserving the anisotropy contribution of Co by channelizing relaxation via a higher excited exchange doublet. Because of the inefficiency of J CoTb, J CoDy, and J CoHo in quenching single-ion Ln fragment transverse anisotropy and preserving CoII high axial anisotropy (favoring rhombicity), 3–5 lack SMM behavior.

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Solvent induced structural reorganization, trapping of hitherto unknown DyIII–pivalate counter anion and different AC susceptibility behavior in three new CoII/III–DyIII aggregates has been discussed.

Two new families of cobalt(II/III)‒lanthanide(III) coordination aggregates have been reported: Tetranuclear [LnIII2CoIII2L2(N‒BuDEA)2(O2CCMe3)4(H2O)2]•(MeOH)n•(H2O)m (Ln = Gd, 1; Tb, 2; Dy, 3; n=2, m=10 for 1 and 2; n=6, m=2 for 3)...

Heterometallic bridging potential of the anion of 1-(2-hydroxy-3-methoxybenzylidene) semicarbazide (HL) to CoII and four 4f ions have been examined during 4f ion coordination driven cleavage of [Co2(µ-OH2)(O2CCMe3)4(HO2CCMe3)4] (Co2-Piv) and scrambling...

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.