ESR study of light-induced valence tautomerism of a Co mononuclear complex: [Co(phen)(3,5-DTBSQ)(3,5-DTBCat)]

Photo-induced valence tautomerism and polarization switching in mononuclear cobalt complexes with an enantiopure chiral ligand

Light-induced polarization switchable molecular materials have attracted attention for decades owing to their potential remote manipulation and ultrafast responsiveness. Here we report a valence tautomeric (VT) complex with an enantiopure chiral ligand. By a suitable choice of counter anions, a significant improvement in photoconversion has been demonstrated, leading to novel photo-responsive polarization switching materials.

Controlling dynamic magnetic properties of coordination clusters via switchable electronic configuration

Large-sized coordination clusters have emerged as a new class of molecular materials in which many metal atoms and organic ligands are integrated to synergize their properties. As dynamic magnetic materials, such a combination of multiple components functioning as responsive units has many advantages over monometallic systems due to the synergy between constituent components. Understanding the nature of dynamic magnetism at an atomic level is crucial for realizing the desired properties, designing responsive molecular nanomagnets, and ultimately unlocking the full potential of these nanomagnets for practical applications. Therefore, this review article highlights the recent development of large-sized coordination clusters with dynamic magnetic properties. These dynamic properties can be associated with spin transition, electron transfer, and valence fluctuation through their switchable electronic configurations. Subsequently, the article also highlights specialized characterization techniques with different timescales for supporting switching mechanisms, chemistry, and properties. Afterward, we present an overview of coordination clusters (such as cyanide-bridged and non-cyanide assemblies) with dynamic magnetic properties, namely, spin transition and electron transfer in magnetically bistable systems and mixed-valence complexes. In particular, the response mechanisms of coordination clusters are highlighted using representative examples with similar transition principles to gain insights into spin state and mixed-valence chemistry. In conclusion, we present possible solutions to challenges related to dynamic magnetic clusters and potential opportunities for a wide range of intelligent next-generation devices.

Switching metal complexes via intramolecular electron transfer: connections with solvatochromism

Solvent-induced color-changing phenomena exhibited by some metal complexes can illuminate key aspects of their switchable behavior.

Photoswitchable stable charge-distributed states in a new cobalt complex exhibiting photo-induced valence tautomerism

We report the synthesis and magnetic and photomagnetic behaviour of a novel valence tautomeric cobalt complex, [Co(3,5-dbbq)₂(μ-bpym)] (1) (3,5-dbbq = 3,5-di-tert-butyl-1,2-benzoquinone and μ-bpym = 2,2′-bipyrimidine). The synthesis is performed by reacting Co₂(CO)₈ and μ-bpym in the presence of the ligand 3,5-dbbq in a mixed solvent under inert atmosphere. The magnetic behavior clearly shows the presence of electron transfer from the catecholate ligand to the cobalt center, producing valence tautomers of [Co^II(SQ)₂] with a transition temperature (T_1/2) of 215 K. Photomagnetic studies, performed via both SQUID magnetometry and X-band electron paramagnetic resonance, show the clear presence of photoinduced valence tautomerism, at temperatures considerably higher than previous systems. A metastable charge distribution is observed, strengthening previous investigations on the character of mixed valence ligands. Entropy-driven valence tautomeric interconversion is observed, and drives the transition to the most stable charge distribution. The complex has the ability to coordinate and can be used as a photoswitchable building block, with the photomagnetic characterisation evidencing a metastable state lifetime of the photo-induced valence tautomeric process of ca. 2.9 × 10⁴ s below 20 K. The observed yields are higher than ones in similar systems, showing that tiny changes in the molecular structures may have a huge impact.

The synthesis, characterization and catecholase activity of dinuclear cobalt(ii/iii) complexes of an O-donor rich Schiff base ligand

A dinuclear Co^III complex oxidizes 3,5-di-tert-butylcatechol by binding to two molecules of the substrate simultaneously during oxidation along with the formation of H₂O₂.