Carbenes play a prominent role as ligands for transition metal catalysts. This is mainly due to their strong s- donor properties and the robustness of the corresponding complexes. These two features result from the presence of the electropositive carbon center and the strength of the carbon-metal bond. Therefore, other types of carbon-based L ligands are highly desirable. This manuscript describes the design and synthesis of a variety of new carbenes belonging to the family of mesoionic carbenes. It will be shown that the stability of mesoionic carbenes depends on the nature of the heteroatoms of their aromatic system. We will also demonstrate that simple alkynes can be used as mesoionic carbene ligand equivalents of various ring sizes towards various transition metals. Moreover, the use of one simple unsaturated compound for the activation of small molecules and the cleavage of enthalpically strong bonds will be discussed

Coordination of Cm(iii) with a chiral decadentate ligand N,N,N,N-tetrakis[(6-carboxypyridin-2-yl)methyl]-1,2-diaminocyclohexane (tpadac) generated complexes with strong luminescence allowing for the unprecedented measurement of well-resolved Cm(iii) circularly polarized luminescence spectra. Quantitative resolution of the electronic structure of the [Cm(tpadac)][K] complexes was achieved at room temperature, highlighting the strength of the combination of luminescence and circularly polarized luminescence spectroscopies to unravel the fundamental electronic structure of Cm(iii). These results are a clear demonstration that these spectroscopies are powerful yet simple tools for the fundamental understanding of electronic structure, which opens the door to future investigations of other Cm(iii) complexes in geometries relevant to nuclear applications, and even other 5f-elements.