For the first time, actinide endohedral metallofullerenes (EMFs) with non-isolated-pentagon-rule (non-IPR) carbon cages, U@C80, Th@C80, and U@C76, have been successfully synthesized and fully characterized by mass spectrometry, single crystal X-ray diffractometry, UV–vis–NIR and Raman spectroscopy, and cyclic voltammetry. Crystallographic analysis revealed that the U@C80 and Th@C80 share the same non-IPR cage of C 1(28324)-C80, and U@C76 was assigned to non-IPR U@C 1(17418)-C76. All of these cages are chiral and have never been reported before. Further structural analyses show that enantiomers of C 1(17418)-C76 and C 1(28324)-C80 share a significant continuous portion of the cage and are topologically connected by only two C2 insertions. DFT calculations show that the stabilization of these unique non-IPR fullerenes originates from a four-electron transfer, a significant degree of covalency, and the resulting strong host–guest interactions between the actinide ions and the fullerene cages. Moreover, because the actinide ion displays high mobility within the fullerene, both the symmetry of the carbon cage and the possibility of forming chiral fullerenes play important roles to determine the isomer abundances at temperatures of fullerene formation. This study provides what is probably one of the most complete examples in which carbon cage selection occurs through thermodynamic control at high temperatures, so the selected cages do not necessarily coincide with the most stable ones at room temperature. This work also demonstrated that the metal–cage interactions in actinide EMFs show remarkable differences from those previously known for lanthanide EMFs. These unique interactions not only could stabilize new carbon cage structures, but more importantly, they lead to a new family of metallofullerenes for which the cage selection pattern is different to that observed so far for nonactinide EMFs. For this new family, the simple ionic A q+@C2n q– model makes predictions less reliable, and in general, unambiguously discerning the isolated structures requires the combination of accurate computational and experimental data.

First X-ray structures and metal oxidation state dependence on cage isomerism for U-EMFs.

Amination of 2,2″-dibromo-p-terphenyl with 2,6-diisopropylaniline, through Pd mediated cross coupling, yields the p-terphenyl bis­(aniline) ligand H2LAr. Deprotonation of H2LAr with excess KH generates the dianion [K­(DME)2]2LAr as a dark red solid. Treatment of [K­(DME)2]2LAr with UI3(dioxane)1.5 produces the mononuclear U­(III) complex LArU­(I)­(DME) (1). Subsequent addition of the nucleophilic metal anion [CpFe­(CO)2]− (Fp–) gives the bimetallic U­(III) compound LArU­(Fp) (2) in modest yield which features a rare instance of an unsupported U–M bond. Inspection of the metrical parameters of the solid-state structures of 1·DME and 2·0.5DME from X-ray crystallographic analyses show a seemingly η6-interaction between the uranium and the terphenyl ligand (1: U1–Ccentroid = 2.56 Å; 2: U1–Ccentroid = 2.45 Å), spatially imposed as a consequence of the anilide N-donor atom coordination. Furthermore, the U–Fe bond length in 2 (U1–Fe1 = 2.9462(3) Å) is consistent with a metal–metal single bond. Notably, electronic structure analyses by CASPT2 calculations instead suggest that electrostatic, and not covalent, interactions dominate between the U–arene systems in 1 and 2 and between the U–Fe bond in the latter.

Two-electron reduction of the Ti compound ( guan)(Im N)Ti(OTf) (3) gives the arene-masked complex ( guan)(η -Im N)Ti (1) in excellent yield. Upon standing in solution, 1 converts to a Ti metallacycle (4) through dehydrogenation of a pendant isopropyl group. Spectroscopic evidence shows this transformation initially proceeds via the oxidative addition of a C(sp )-H bond and can be reversed upon exposure of 4 to H . Interestingly, treatment of 1 with cyclohexene gives cyclohexane and 4 via a titanium-mediated transfer hydrogenation reaction, a process that can be extended to catalytically hydrogenate other unsaturated hydrocarbons under mild conditions. These results, rare for the early-metals, suggest 1 possesses chemical characteristics reminiscent of noble, late-metals.

New 8-NR2-BODIPYs, R2 = H(i)Pr (3a), H(i)Bu (3b), and Et2 (4), are reported. Restricted rotation about the C8-N bond in such molecules has been observed for the first time (3a and 3b) and evaluated using VT NMR. The fluorophores 3a and 3b are blue emitters, and the efficiency of the emission is closely related to the polarity of the solvent, e.g., hexane > toluene > DCM > THF > MeOH > H2O, an effect also noted by emission variation in alcohol solvents H(CH2)nOH, n = 1-6. In mixed-solvent systems, addition of 10-15% of the more polar solvent results in transformation of the emission properties to those of the bulk polar solvent. Compound 4 has zero emission in all solvents. The crystal structures of 3a, 3b, and 4 are reported, along with that of the parent 8-NH2-BODIPY (2). Compounds 2, 3a, and 3b exhibit trigonal planar N atoms which are coplanar with the BODIPY core; 4 exhibits a very significant distortion that breaks the planarity of the extended BODIPY π system due to the steric impact of the two ethyl groups, an observation that explains the lack of emission for 4.