Synthesis of endohedral metallofullerene glycoconjugates by carbene addition.

Endohedral metallofullerene glycoconjugates were synthesized under mild conditions by carbene addition using appropriate glycosylidene-derived diazirine with La(2)@I(h)-C(80). NMR spectroscopic studies revealed that the glycoconjugate consists of two diastereomers of [6,6]-open mono-adducts. The electronic properties were characterized using Vis/NIR absorption spectroscopy and electrochemical measurements. This study demonstrates that glycosylidene carbene is useful to incorporate carbohydrate moieties onto endohedral metallofullerene surfaces.

Formation of N-heterocyclic, donor-stabilized borenium ions.

Cationic and zwitterionic boryl bromide species and a borenium-boryl bromide cation have been synthesised which represent new N-donor stabilised cationic boron compounds with ß-diketiminate ligands. The unexpected borenium-boryl bromide results from a head-to-tail dimerisation of the corresponding zwitterionic boryl bromide accompanied by proton migration. The electronic nature of these new species was studied by DFT calculations.

Two regioisomers of endohedral pyrrolidinodimetallofullerenes M2@I(h)-C80(CH2)2NTrt (M = La, Ce; Trt = trityl): control of metal atom positions by addition positions.

The two regioisomers of endohedral pyrrolidinodimetallofullerenes M(2)@I(h)-C(80)(CH(2))(2)NTrt (M = La, Ce; Trt = trityl) were synthesized, isolated, and characterized. X-ray crystallographic analyses of [6,6]-La(2)@I(h)-C(80)(CH(2))(2)NTrt and [6,6]-Ce(2)@I(h)-C(80)(CH(2))(2)NTrt revealed that the encapsulated metal atoms are located at the slantwise positions on the mirror plane that parallels the pyrrolidine ring. Paramagnetic NMR analyses of [6,6]- and [5,6]-Ce(2)@I(h)-C(80)(CH(2))(2)NTrt were also carried out to clarify the metal positions. As for the [6,6]-adduct, the metal positions obtained by paramagnetic NMR analysis agree well with the X-ray structure. In contrast, paramagnetic NMR analysis of the [5,6]-adduct showed that the two Ce atoms are collinear with the pyrrolidine ring. We also compared the observed paramagnetic effects of the pyrrolidinodimetallofullerenes with those of other cerium-encapsulating fullerene derivatives such as bis-silylated Ce(2)@I(h)-C(80) and a carbene adduct of Ce(2)@I(h)-C(80). We found that the metal positions can be explained by the electrostatic potential maps of the corresponding [6,6]- and [5,6]-adducts of [I(h)-C(80)(CH(2))(2)NTrt](6-). These findings clearly show that metal positions inside fullerene cages can be controlled by means of the addition positions of the addends. In addition, the radical anions of the pyrrolidinodimetallofullerenes were prepared by bulk controlled-potential electrolysis and characterized by X-band EPR spectral study.