Synthesis and properties of N-methyl[60]fullereno[c]pyrrolidines containing cyclopentadienyl(carbonyl)metal fragments

Abstract

In new N methyl[60]fullereno[c]pyrrolidine derivatives, the organometallic substituents in position 2 of the pyrrolidine ring are tricarbonyl(cyclopentadienyl)rhenium, α bicymantrenyl, and β bicymantrenyl (also the optically active (+) enantiomer of the latter). The electrochemi cal and spectroscopic (NMR) properties of the compounds obtained were studied.Fullerenes are known to be strong acceptors capable of taking up to six electrons in solution. Their electrophysical properties can be changed by modifying the C 60 molecule. A possible way of modification is [2+3] cycloaddition of azomethine ylides leading to pyrrolidinofullerenes. This method involves generation of azomethinylides via decar boxylation of immonium salts prepared by condensation of α amino acids with aldehydes. This method is com monly referred to as Prato´s reaction. 1,2In the chemistry of fullerenes, one of the problems associated with their promising use in electronic devices is the synthesis of more electron withdrawing derivatives than C 60 itself. At the same time, it is interesting to obtain derivatives in which the rate of intramolecular electron phototransfer depends on the ratio of the electron dona ting and electron withdrawing properties of their frag ments. A combination of fullerene and organometallic fragments in a molecule allows "fine adjustment" of the degree of intramolecular transfer of the electron density and, consequently, of its electrophysical and optical prop erties. However, only few fullerenopyrrolidines containing organometallic substituents in position 2 of the heterocy cle have been documented. Until recently, such substitu ents included only ferrocenyl fragments. 3, 4 We have re cently studied new [60]fullereno[c]pyrrolidine derivatives containing other organometallic substituents, viz., cyman trenyl, (E) 2 cymantrenylvinyl, 5 (tetramethylcyclobuta dienyl)cobalt(cyclopentadienyl), and (pentamethyl)ruthe nocenyl. 6 To extend the range of N methyl 2 cyclopentadie nyltricarbonyl[60]fullereno[c]pyrrolidines, here we used Prato´s reaction between C 60 , N methylglycine (sar cosine), and appropriate aldehydes 1a-d as a route to new derivatives 2a-d containing substituents with stronger electron withdrawing properties than those of ferrocene (Scheme 1). The chiroptical properties of compounds 1d and 2d will be described elsewhere.

Circular dichroism of optically active organometallic derivatives of fullerenes C60 and C70

“…15 CD measurements. The CD spectra were recorded on a SKD 2 automatic recording spectrophotometer (the collaborative design of the V. A. Engelhardt Institute of Molecular Biology of the Russian Academy of Sciences and the Institute for Spectroscopy of the Russian Academy of Sciences).…”