The First Fulleropyrrolidine Derivative of Sc₃N@C₈₀:  Pronounced Chemical Shift Differences of the Geminal Protons on the Pyrrolidine Ring

Abstract

The first pyrrolidine adduct on Sc(3)N@C(80) was synthesized and fully characterized. Addition of the N-ethylazomethine ylide occurs regioselectively on a [5,6] double bond on the surface of the icosahedral symmetry Sc(3)N@C(80), exactly in the same position as that described previously for a Diels-Alder adduct of the same compound.(11a,b) This addition pattern results in symmetric pyrrolidine carbons and unsymmetric geminal hydrogens on the pyrrolidine ring, as confirmed by (1)H and (13)C NMR spectroscopy, especially by HMQC. The shielding environment experienced by these geminal hydrogens differs by 1.26 ppm, indicative of pronounced ring current effects on the surface of this endohedral fullerene. This represents the first fully characterized pyrrolidine adduct on an endohedral metallofullerene.

Chemical, Electrochemical, and Structural Properties of Endohedral Metallofullerenes

“…In the same year Echegoyen and co-workers reported another separation method for the I h isomer from the isomeric mixture (D 5h and I h ) of Sc 3 N@C 80 which involved the selective synthesis of N-ethylpyrrolidino-Sc 3 N@C 80 . [53,61] Under certain reaction conditions only the I h isomer reacts, even in the presence of Sc 3 N@C 78 . Once the pyrrolidino adduct is isolated it is heated at reflux with maleic anhydride to recover the pure I h isomer.…”

“…This showed that the pyrrolidine ring was formed regioselectively at a [5,6] bond of the Sc 3 N@C 80 (I h ) isomer. [53] The same year, Echegoyen and co-workers reported the first pyrrolidine adduct of Y 3 N@C 80 (I h , 13 b; Scheme 5), but the cycloaddition occurred at a [6,6] bond for this metallic nitride EMF. [54] Later, Dorn, Gibson, and co-workers reported the functionalization of M 3 N@C 80 (M = Sc, Er) with N-methylglycine and 13 C-formaldehyde, and they observed a similar addition to a [5,6] bond as observed with the Sc 3 N@C 80 (I h ) isomer.…”

“…Finally, Dorn et al reported the pyrrolidine derivative of Sc 3 N@C 80 in a patent application, but with few characterization details. [52] In 2005 Echegoyen and co-workers reported the first pyrrolidine adduct of Sc 3 N@C 80 (I h ) [53] by adding an excess of N-ethylglycine and 13 C-formaldehyde to a solution of a mixture of Sc 3 N@C 80 (D 5h ) and (I h ) in o-DCB. The mixture was heated for 15 minutes at 120 8C, and a monoadduct 13 a (Scheme 5) was isolated by column chromatography and analyzed with the same techniques used by Dorn and coworkers [43] ( 1 H NMR, 13 C NMR, and HMQC experiments).…”

Fullerene derivatives as nano-additives in polymer composites

“…A photoinduced electron-transfer reaction in the Sc 3 N@C 80 -Fc donor-acceptor dyad 138 was reported. 137 N-methyl-2-ferrocenyl [5,6]-Sc 3 N@I h -C 80 -fulleropyrrolidine was prepared by thermal reaction of Sc 3 N@I h -C 80 with sarcosine and ferrocenecarboxaldehyde in a toluene/ o-dichlorobenzene (o-DCB) mixture.…”

Electric field induced effects in Y3N@[C80]6− anionic solid

“…Functionalization of Sc 3 N@C 80 has been accomplished using both a Diels-Alder reaction and an azomethine ylide addition. 16,17 In the case of Diels-Alder reaction, addition products were formed at the 5:6 ring junction of the C 80 cage. On the other hand, azomethine ylide addition to Y 3 N@C 80 produced an adduct at the 6:6 ring junction.…”