Mechanism of the Addition Reaction of Alkyl Azides to [60]Fullerene and the Subsequent N₂ Extrusion to Form Monoimino-[60]fullerenes

Abstract

The 1,3-dipolar cycloaddition of methyl azide to C60 and the subsequent nitrogen elimination from the formed triazoline intermediate to yield the aziridine adduct have been studied using semiempirical and density functional methods. The results obtained show that the addition of methyl azide to C60 takes place in the ring junction between two six-membered rings leading to a closed [6,6]-trizoline intermediate with an energy barrier of about 20 kcal mol-1 and an exothermicity of ca. 2 kcal mol-1 at the B3LYP/6-31G**//AM1 level of theory. The subsequent thermal loss of N2 takes place through a stepwise mechanism in which the cleavage of the N-N single bond precedes the breaking of the N-C bond, with a total activation energy of approximately 45 kcal mol-1. The N2 loss occurs simultaneously with the formation of the new N-C bond. During the process, the steric effects of the leaving N2 molecule prevent the addition of the nitrene substituent to the [6,6]-ring junction attacked initially and force the addition to an adjacent [5,6]-ring junction.

Heteroanalogues of PCBM: N‐Bridged Imino‐PCBMs for Organic Field‐Effect Transistors

“…[2,3] From an electronic-structure point of view, the [5,6]-open isomers are appealing since they conserve the 60 p electrons of the parent C 60 . However, they readily transform into the thermodynamically more stable [6,6]-closed isomers by thermal, electrochemical, pH, and photochemical means, [2,3,[14][15][16] thus making their intrinsic properties in electronic applications difficult to assess.Therefore, we directed our attention toward the reaction of azides with C 60 for the following reasons: 1) the possibility of an increased degree of stabilization of the [5,6]-open versus [6,6]-closed isomers [17][18][19] and 2) the potential influence of the nitrogen heteroatom of iminofullerenes on the electronic properties of the fullerene cage, [20] which can possibly tune the device performance. This is important since it enables us to study the electronic device performance whilst comparing two isomeric configurations, that is, hexagon-pentagon (C 60 -like) versus hexagon-hexagon junction (PCBM-like; PCBM = [6,6]-phenyl-C 61 -butyric acid methyl ester), as a function of the perturbation of the fullerene p system.…”

Polyhedral oligomeric silsesquioxane‐bound iminofullerene

“…[38] Incompletely condensed POSS [R 7 Si 7 O 9 (OH) 3 , R = iBu] was reacted with trichloro[(4-chloromethyl)phenyl]trichlorosilane to form the monosubstituted POSS chloride, which was subsequently reacted with sodium azide to form the desired mosubsituted POSS azide. [38] The resultant POSS azide underwent 1,3-dipolar cylcoaddition with C 60 , followed by thermal extrusion of nitrogen, [39] to yield the desired POSS iminofullerene.…”

“…Depending on the mode of addition, one of four isomers can be formed, the open [5,6], closed [5,6], open [6,6] or closed [6,6]. [39] The iminofullerene structure can be quantified through 13 C NMR, as closed [6,6] fullerenes possess two sp 3 type carbons, whilst open [5,6] fullerenes contain only sp 2 type carbons (Fig. 2).…”

Computational Studies of 1,3-Dipolar [3 + 2]-Cycloaddition Reactions of Fullerene-C60 with Nitrones

“…Due to the large size of the systems under study the geometries could not be fully optimized at higher levels of theory [29]. The starting geometries of the molecular systems were constructed using Spartan's graphical model builder and minimized interactively using the SYBYL force field [30]. Geometry optimizations were carried out without symmetry restrictions.…”