Comparative spectroscopic and reactivity studies of Sc3-xYxN@C80 (x=0-3)

A series of endohedral fullerenes Sc3-xYxN@C-80 (x = 0-3) with variable encaged moieties and the same C-80 cage were synthesized, isolated, and spectroscopically characterized by the laser desorption time-of-flight mass spectrometry (LD-TOF-MS), differential pulse voltammetry (DPV), Fourier transform infrared (FTIR), visible-near-infrared (vis-NIR) absorption spectrometry, and so forth. It was revealed that Sc3-xYxN@C-80 (x = 0-3) have a similar electronic structure, (Sc3-xYxN)(6+)@(C-80)(6-). However, because of the relatively larger van der Waals radius of yttrium to that of scandium which induces the size increase of Sc3-xYxN from x = 0 to x = 3, the frontier orbitals of this series of endohedral fullerenes dramatically change. For example, Sc2YN@C-80 shows similar electronic property with its left neighbor Sc3N@C-80 but is quite different with its right neighbor ScY2N@C-80. The cycloaddition reactions of N-enthylazomethine ylide with Sc3-xYxN@C-80 (x = 0-3) were carried out, and the regioselectivity of endohedral fullerenes shows the same trend of variation to that of their electronic properties along with the size of endohedral moiety increasing. It was found that Sc3N@C-80 and Sc2YN@C-80 produce only the [5,6]-pyrrolidine regioisomers, and a critical change in fullerene regioselectivity occurs from ScY2N@C-80 where the [6,6]-pyrrolidine regioisomer appears as a minor regioisomer and finally becomes the major regioisomer in the case of Y3N@C-80.