Theoretical Study On The Reaction Mechanism Of Synthesizing Trisazafulleroids [C₆₀(NCH₃)₃] With Methyl Azide And C₆₀(NCH₃)₂

This project focuses on the theoretical study of the reaction mechanism of methyl azide(CH₃N₃)with azafulleroid[C₆₀(NCH₃)₂]to yield trisazafulleroids [C₆₀(NCH₃)₃]by using quantum chemistry methods.The geometry structures and the energy results of the stationary points along the reaction process have also been investigated.In the first place,There are three possible isomers for the bis-adduct derived from the reaction of C₆₀(NCH₃)₂ with methyl azide.One most stable product which has been made in the laboratory and CH₃N₃ was selected and full geometry optimizations without symmetry constraints were carried out with AM1 semi-empirical method firstly.In order to improve the accuracy of the energy results,single-point energies for the reactants were further evaluated by B3LYP method at the AM1-optimized geometries employing 6-31G^**basis set (B3LYP/6-31G^**//AM1).Comparisons about geometries and the energy results of the reactants were also made.In the second place,the charge distributions of the two reagents were calculated(B3LYP/6-31G^**//AM1).Two most possible attacking sites were selected and the reaction mechanism of the two reaction paths were studied. Through our calculation,we found that the reaction mechanisms of the two reactions were very similar.Both of the reaction processes can be divided into two stages.The first stage is the 1,3-dipolar cycloaddition(1,3-DC)reaction of methyl azide CH₃N₃ with C₆₀(NCH₃)₂ giving rise to a triazoline intermediate. For this stage,both of the two reactions are endothermic,and their energy barriers are 113.9 kJ/mol and 94.5 kJ/mol,separately.The second stage is the N₂ elimination via two steps.The first step is the breaking of a N-N single bond, which is endothermic with the energy barriers of 185.8 kJ/mol and 144.4 kJ/mol, separately,for the two reactions.And the second one undergoes the liberation of a N₂ molecule which is exothermic with the energy barriers of 205.5 kJ/mol and 189.9 kJ/mol,separately.Two triazafulleroid isomers would be produced through the reaction paths.In addition,in terms of the two reactions,the rate-controlling step appears at the N₂ extrusion process based on the energy calculation evaluated by B3LYP method at the AM1-optimized geometries employing 6-31G^**basis set (B3LYP/6-31G^**//AM1).The results from comparing their corresponding energy barriers of the rate-controlling steps,the interaction energies and the apparent activation energies indicate that the reaction which gives rise to a less stable product is the predominant reaction.However the other reaction may also occur because of the stable product,the small difference between the two energy barriers of the rate-controlling steps and the large amount of released caloric of the rate-controlling steps.The energy barriers of the rate-controlling steps as well as the apparent activation energies of these reactions are all larger than those of the mono-addition reaction of methyl azide to C₆₀.Thus,reactions of methyl azide to C₆₀will lead to mixtures that contain the monoadduct,the isomers of the bisadducts,and the two isomers of the triadducts,with the monoadduct being the major product.