An Ytterbium-Pyrazine Square [(CHMe)Yb(pyz)] Formed by Reversible Electron Transfer and Concomitant Self-Assembly.

Pyrazine (pyz) has been used extensively in coordination chemistry to manifest electron delocalization in mixed-valent compounds and strongly coupled materials. In the current work, using a Yb precursor, [(CHMe)Yb(THF)] (), a molecular square [(CHMe)Yb(pyz)]·/(CHF) () was synthesized by metal-ligand redox cooperativity. Complex shows evidence of charge transfer from Yb to pyrazine in a range of studies including structural analysis, magnetometry, vibrational spectroscopy, X-ray absorption near-edge structure spectroscopy, and electronic structure calculations.

Strong Magnetic Coupling and Single-Molecule Magnet Behavior in Tetrazinyl Radical-Bridged Metallocenes.

Exchange coupling is essential in defining the magnetic behavior of polymetallic lanthanide-based (Ln) single-molecule magnets (SMMs), where, thanks to the unpaired electron(s), radical ligands show promise as magnetic bridges between the paramagnetic metal centers. Combining high-performance lanthanide metallocene [Cp*₂Ln] (Cp* = pentamethylcyclopentadienyl) units with the 3,6-bis(2-pyrimidyl)-1,2,4,5-tetrazine radical ligand (bmtz) yielded two new radical-bridged dinuclear lanthanide metallocenes, [(Cp*₂Ln)₂(bmtz)](BPh)·Solvent (Ln = Gd (1), Solvent = THF; Dy (2), Solvent = toluene). The strong magnetic exchange coupling of J = -12.

Near-Infrared Magnetic Circularly Polarized Luminescence and Slow Magnetic Relaxation in a Tetrazinyl-Bridged Erbium Metallocene.

The magnetic and magneto-optical properties of a tetrazinyl radical-bridged Er metallocene, [(Cp*Er)(bpytz)][BPh] (; Cp* = pentamethylcyclopentadienyl, bpytz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine), are reported. As confirmed by these studies strong Ln-rad coupling is achieved, with exhibiting slow magnetic relaxation under a 1000 Oe dc field. The optical and magneto-optical profile of is completed by both near-infrared (NIR) luminescence and magnetic circularly polarized luminescence (MCPL), representing the first example of NIR MCPL with Er.

Stabilizing an exotic dianionic tetrazine bridge in a Ln metallocene.

The unique electronic nature of the 1,2,4,5-tetrazine or -tetrazine (tz) ring has sparked tremendous scientific interest over the last few years. Tetrazines have found numerous applications, and their ability to coordinate to metal ions has opened the possibility of exploring their chemistry in both molecular systems and extended networks. The rich redox chemistry of -tetrazines allows them to exchange electrons and switch between their dihydro (Htz), neutral (tz), and radical (tz˙) forms.

Formation of a Decanuclear Organometallic Dysprosium Complex via a Radical-Radical Cross-Coupling Reaction.

Over the years, polynuclear cyclic or torus complexes have attracted increasing interest due to their unique metal topologies and properties. However, the isolation of polynuclear cyclic organometallic complexes is extremely challenging due to their inherent reactivity, which stems from the labile and reactive metal-carbon bonds. In this study, the pyrazine ligand undergoes a radical-radical cross-coupling reaction leading to the formation of a decanuclear [(Cp*)Dy(L1)] ⋅ 12(CH) (1; where L1 = anion of 2-prop-2-enyl-2H-pyrazine; Cp* = pentamethylcyclopentadienyl) complex, where all Dy metal centres are bridged by the anionic L1 ligand.

Probing the magnetic and magneto-optical properties of a radical-bridged Tb single-molecule magnet.

Reaction of the 1,2,4,5-tetrazine (tz˙) radical and {Cp*Tb} has yielded a tetranuclear radical-bridged Tb single-molecule magnet. The strong Ln-radical coupling and the electronic differences of the Tb ions in [(Cp*Tb)(tz˙)]·3CH (1) are probed magnetic, magneto-optical and computational studies.

Molecular Capacitors: Accessible 6- and 8-Electron Redox Chemistry from Dimeric "Ti(I)" and "Ti(0)" Synthons Supported by Imidazolin-2-Iminato Ligands.

Reduction of the diamagnetic Ti(III)/Ti(III) dimer [ClTi(μ-NIm)] () (NIm = [1,3-bis(Dipp)imidazolin-2-iminato], Dipp = CH-2,6-Pr) with 4 and 6 equiv of KC generates the intramolecularly arene-masked, dinuclear titanium compounds [(μ-N-η-Im)Ti] () and {[(EtO)K](μ-N-μ:η-Im)Ti} (), respectively, in modest yields. The compounds have been structurally characterized by X-ray crystallographic analysis, and inspection of the bond metrics within the η-coordinated aryl substituent of the bridging imidazolin-2-iminato ligand shows perturbation of the aromatic system most consistent with two-electron reduction of the ring. As such, and can be assigned respectively as possessing metal centers in formal Ti(III)/Ti(III) and Ti(II)/Ti(II) oxidation states.

Radical-Bridged Ln Metallocene Complexes with Strong Magnetic Coupling and a Large Coercive Field.

Inducing magnetic coupling between 4f elements is an ongoing challenge. To overcome this formidable difficulty, we incorporate highly delocalized tetrazinyl radicals, which strongly couple with f-block metallocenes to form discrete tetranuclear complexes. Synthesis, structure, and magnetic properties of two tetranuclear [(Cp* Ln) (tz ) ]⋅3(C H ) (Cp*=pentamethylcyclopentadienyl; tz=1,2,4,5-tetrazine; Ln=Dy, Gd) complexes are reported.

Probing optical and magnetic properties subtle stereoelectronic effects in mononuclear Dy-complexes.

Tapping into the secondary coordination environment of mononuclear DyIII-complexes leads to drastic changes in luminescence and magnetism. Visualization of effects induced by stereoelectronics on the opto-magnetic properties was achieved through subtle modifications in the ligand framework.

Enhancing Magnetic Communication between Metal Centres: The Role of s-Tetrazine Based Radicals as Ligands.

Although 1,2,4,5-tetrazines or s-tetrazines have been known in the literature for more than a century, their coordination chemistry has become increasingly popular in recent years due to their unique redox activity, multiple binding sites and their various applications. The electron-poor character of the ring and stabilization of the radical anion through all four nitrogen atoms in their metal complexes provide new aspects in molecular magnetism towards the synthesis of new high performing Single Molecule Magnets (SMMs). The scope of this review is to examine the role of s-tetrazine radical ligands in transition metal and lanthanide based SMMs and provide a critical overview of the progress thus far in this field.