Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4 f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling. In this work we explore the limiting case when the role of a radical bridge is played by a single unpaired electron. We synthesize an array of air-stable Ln 2 @C 80 (CH 2 Ph) dimetallofullerenes (Ln 2 = Y 2 , Gd 2 , Tb 2 , Dy 2 , Ho 2 , Er 2 , TbY, TbGd) featuring a covalent lanthanide-lanthanide bond. The lanthanide spins are glued together by very strong exchange interactions between 4 f moments and a single electron residing on the metal–metal bonding orbital. Tb 2 @C 80 (CH 2 Ph) shows a gigantic coercivity of 8.2 Tesla at 5 K and a high 100-s blocking temperature of magnetization of 25.2 K. The Ln-Ln bonding orbital in Ln 2 @C 80 (CH 2 Ph) is redox active, enabling electrochemical tuning of the magnetism.

The synthesis and characterisation of the new endohedral cluster fullerene Sc(3)CH@C(80) is reported. The encapsulation of the first hydrocarbon cluster inside a fullerene was achieved by the arc burning method in a reactive CH(4) atmosphere. The extensive characterisation by mass spectrometry (MS), high- pressure liquid chromatography (HPLC), (45)Sc NMR, electron spin resonance (ESR), UV/Vis-NIR and Raman spectroscopy provided the experimental evidence for the caging of the five-atom Sc(3)CH cluster inside the C(80) cage isomer with icosahedral symmetry. The proposed new structure was confirmed by DFT calculations, which gave a closed shell and large energy gap structure. Thus a pyramidal Sc(3)CH cluster and the I(h)-C(80) cage were shown to be the most stable configuration for Sc(3)CH@C(80) whereas alternative structures give a smaller bonding energy as well as a smaller energy gap.

The combination of NMR spectroscopy and electrochemistry provides an in situ method to measure structural changes of the redox components in an electrochemical reaction by proton NMR experiments. As the use of metal thin film radio frequency (RF) transparent electrodes in NMR spectroelectrochemical studies is limited by layer thickness and electrodes size, we present a new spectroelectrochemical NMR cell design consisting of nearly metal free symmetrically arranged large scale carbon fiber electrodes. Due to the advantages of modern NMR spectroscopy, a cell rotation is not necessary for high resolution measurements. This makes the presented cell for in situ spectroelectrochemical NMR measurements easy to prepare. The cell design is universal for a large variety of NMR spectrometers and frequencies used for detection of different nuclei. The feasibility of this new in situ NMR spectroelectrochemical cell is demonstrated in a detailed study of the electrochemical behavior of p-benzoquinone in different aqueous solutions.

Lanthanide–lanthanide bonds are exceptionally rare, and dimetallofullerenes provide a unique possibility to stabilize and study these unusual bonding patterns. The presence of metal–metal bonds and consequences thereof for the electronic properties of M2@C82 (M = Sc, Er, Lu) are addressed by electrochemistry, electron paramagnetic resonance, SQUID magnetometry and other spectroscopic techniques. A simplified non-chromatographic separation procedure is developed for the isolation of Er2@C82 (Cs(6) and C3v(8) cage isomers) and Sc2@C82 (C3v(8) isomer) from fullerene mixtures. Sulfide clusterfullerenes Er2S@C82 with Cs(6) and C3v(8) fullerene cages are synthesized for the first time. The metal–metal bonding orbital of the spd hybrid character in M2@C82 is shown to be the highest occupied molecular orbital, which undergoes reversible single-electron oxidation with a metal-dependent oxidation potential. Sulfide clusterfullerenes with a fullerene-based HOMO have more positive oxidation potentials. The metal-based oxidation of Sc2@C82-C3v is confirmed by the EPR spectrum of the cation radical [Sc2@C82-C3v]+ generated by chemical oxidation in solution. The spectrum exhibits an exceptionally large a(45Sc) hyperfine coupling constant of 199.2 G, indicating a substantial 4s contribution to the metal–metal bonding orbital. The cationic salt [Er2@C82-C3v]+SbCl6− is prepared, and its magnetization behavior is compared to that of pristine Er2@C82-C3v and Er2S@C82-C3v. The formation of the single-electron Er–Er bond in the cation dramatically changes the coupling between magnetic moments of Er ions.

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