Dangling and Hydrolyzed Ligand Arms in [Mn₃] and [Mn₆] Coordination Assemblies: Synthesis, Characterization, and Functional Activity

Abstract

Two flexible, branched, and sterically constrained di- and tripodal side arms around a phenol backbone were utilized in ligands HL1 and HL2 to isolate {Mn} and {Mn} coordination aggregates. 2,6-Bis{(1-hydroxy-2-methylpropan-2-ylimino)methyl}-4-methylphenol (HL1) gave trinuclear complex [Mn(μ-HL1)(μ-OCCH)(CHOH)](ClO)·4CHOH (1), whereas 2,6-bis[{1-hydroxy-2-(hydroxymethyl)butan-2-ylimino}methyl]-4-methylphenol (HL2) provided hexanuclear complex [Mn(μ-HL2)(μ-HL3)(μ-OH)(μ-OCCH)](ClO)·2HO (2). Binding of acetates and coordination of {HL1} provided a linear MnMnMn arrangement in 1. A Mn fused diadamantane-type assembly was obtained in 2 from propionate bridges, coordination of {HL2}, and in situ generated {HL3}. The magnetic characterization of 1 and 2 revealed the properties dominated by intramolecular anti-ferromagnetic exchange interactions, and this was confirmed using density functional theory calculations. Complex 1 exhibited field-induced slow magnetic relaxation at 2 K due to the axial anisotropy of Mn centers. Both the complexes show effective solvent-dependent catechol oxidation toward 3,5-di-tert-butylcatechol in air. The catechol oxidation abilities are comparable from two complexes of different nuclearity and structure.

Mono- and Rare Trinuclear Zn(II) Complexes with Near-Infrared Emissive Ligands: Anion-Responsive Nuclearity Control, Interconversion, Solid-State NIR Emission, and Latent Fingerprint Imaging

“…The ability to control the nuclearity of complexes derived from a series of similar ligands is important in developing metal–organic systems with predesigned properties. However, such nuclearity control is often difficult due to the involvement of multiple variables. − The common approaches employed for nuclearity control in metal complexes include changing the anions, reaction temperatures, reaction conditions, and additives. − Similarly, the development of strategies for the interconversion of metal complexes of different nuclearities is also vital as a synthetic approach. − Still, the predictable nuclearity control and the interconversion of metal complexes of different nuclearities remain challenging tasks to achieve. Further, the situation becomes more complicated if the metal ions do not show any crystal field stabilization energy for a particular geometry .…”

Entrapment of a Pseudo‐Tetrahedral CoII Center by Thioether Sulfur Bound {Co2(μ‐L)} Fragments: Synthesis, Field‐Induced Single‐Ion Magnetism and Catechol Oxidase Mimicking Activity

“…Recently other metal ions like Mn II/III and Ni II have also been used for the synthesiso fs uch functional mimics. [12][13][14] The synergism between the chosen ligand and used metal ions providesastrong influence on the affinity for substrate catechol. Dinuclear and otherc obalt(II/III) complexes were less extensively explored as synthetic mimics for catechol oxidation activity.…”

“…Functional mimetic studies were centered on [Cu 2 ] complexes due to the fact that CO is a Type‐III copper enzyme. Recently other metal ions like Mn II/III and Ni II have also been used for the synthesis of such functional mimics . The synergism between the chosen ligand and used metal ions provides a strong influence on the affinity for substrate catechol.…”

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

“…The reaction between 2-amino-2-methylpropan-1-ol and 2-hydroxy-3-mehoxybenzaldehyde under refluxing conditions using MeOH as the solvent provided a yellow oily mass of H 2 L. Similar Schiff base ligands with an alcohol arm were found to be effective to incorporate 3d and 4f ions side by side, where the imine N donor shows preferential binding of the 3d ion and shows pinning of the lanthanide ion by two adjacent O donors. 45 Such a type of ligand developed on 2-amino-2-methylpropan-1-ol has been used to obtain the homometallic clusters of {Ni 4 and Ni 6 }, 46 {Mn 3 and Mn 4 }, 44 {Mn 6 } 47 from our laboratory. Several other examples of similar Schiff base ligands are known to produce [Cu 4 ] clusters having a cubane, 48 step-cubane 49 or open-cubane 50 topology.…”