Heptanuclear Mixed-Valence Co₄^IIICo₃^II Molecular Wheel─A Molecular Analogue of Layered Double Hydroxides with Single-Molecule Magnet Behavior and Electrocatalytic Activity for Hydrogen Evolution Reactions.

ABSTRACT: We present a bifunctional heptanuclear cobalt(II)/cobalt(III) molecular complex formulated as [Co₇(μ₃-OH)₄(H₂L¹)₂(HL²)₂](NO₃)₆·6H₂O (1) (where H₅L¹ is 2,2'-(((1E,1'E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(azanylylidene))bis(propane-1,3-diol)) and H₂L² is 2-amino-1,3-propanediol). Compound 1 has been characterized by single-crystal X-ray diffraction analysis along with other spectral and magnetic measurements. Structural analysis indicates that 1 contains a mixed-valence Co₇ cluster where a central Co(II) ion is connected to six different Co centers (four Co^III and two Co^II ions) by four μ₃-OH groups, giving rise to a planar heptanuclear cluster that resembles a molecular fragment of a layered double hydroxide (LDH). Two triply deprotonated (H₂L¹)^3- ligands form the outer side of the cluster while two singly deprotonated (HL²)^- ligands are located at the top and bottom of the central heptanuclear core. Variable temperature magnetic measurements indicate the presence of weak ferromagnetic Co^II···Co^II interactions (J = 3.53(6) cm^-1) within the linear trinuclear Co^II cluster. AC susceptibility measurements show that 1 is a field-induced single-molecule magnet (SMM) with τ₀ = 8.2(7) × 10^-7 s and U_eff = 11.3(4) K. The electrocatalytic hydrogen evolution reaction (HER) activity of 1 in homogeneous phase shows an overpotential of 455 mV, with a Faradaic efficiency of 81% and a TOF of 8.97 × 10⁴ μmol H₂ h^-1 mol^-1.

SUBMITTER: Biswas B 

PROVIDER: S-EPMC11005049 | biostudies-literature | 2024 Apr

REPOSITORIES: biostudies-literature