R. G. Bulgakov

Ozone addition to C60 and C70 fullerenes: A DFT study

Three modes of synchronous ozone addition ([6.6]-, [5.6]-, and 1,4-addition) to C(60) fullerene and three modes of ozone addition to C(70) (ab-, cc-, and de-addition) have been studied using density functional theory calculations. Comparison of activation enthalpies shows that in the case of C(60), [6.6]-addition of ozone is the most favorable energetically and occurs without a barrier. In the case of the C(70) fullerene, additions to ab- and cc-bonds are the most favorable. The initial step of interaction between a C(60)/C(70) and O(3) is the formation of a molecular complex, which then converts into a primary ozonide. The calculated rate constant of the [6.6]-addition to the C(60) fullerene according to the proposed scheme is 3.90 x 10(6)L mol(-1)s(-1), which corresponds well to the experimental value.

Polarizability exaltation of endofullerenes X@Cn (n = 20, 24, 28, 36, 50, and 60; X is a noble gas atom)

AbstractzThe polarizability exaltation in molecules of endohedral complexes of C20, C24, C28, C36, C50, and C60 fullerenes with He, Ne, Ar, and Kr noble gas atoms has been revealed and studied by the density functional theory method. It has been found that the sign of the Δα polarizability exaltation depends on the number of atoms in a fullerene molecule.

Quantum Chemical Modeling of Ozone Addition to C60 Fullerene

1,2‐, 2,3‐ and 1,4‐addition of ozone to C60 have been studied. Comparison of enthalpies and activation barriers obtained with PBE/3z method for each route shows that 1,2‐addition is the most favorable energetically and runs without activation barrier. The initial step of interaction C60 with O3 is the molecular complex forming, which then converts to primary ozonide C60O3. The advantage of 1,2‐addition is caused with peculiarities of orbital structure of reactants and insignificant deformation of C60 cage.

Reactivity of Fullerene Derivatives C60O and C60F18 (C 3v ) in Terms of Local Curvature and Polarizability

Theoretical approaches based on the indices of local curvature and polarizability have been used for estimation of reactivity of C60 derivatives – C60O and C60F18 – in the model reaction of O addition. The first of this species as shown by indices has to produce all possible C60O2 isomers; the second, C60F18, has to generate C60F18O adducts with functionalized 6.6 bonds being characterized high curvature and polarizability indices.

New property of the fullerenes: the anomalously effective quenching of electronically excited states owing to energy transfer to the C70 and C60 molecules

The quenching of the electronically excited states of various energy donors—Tb3+; 9,10-anthracene dibromide; and adamantanone—by C70 fullerene has been detected and analyzed. The quenching is characterized by anomalously high biomolecular quenching rate constants, which are obtained from the Stern-Volmer dependences of the energy-donor photoluminescence intensity on the concentration of the C70 molecules. It has been shown that the high efficiency of quenching by the C70 fullerene as compared to the C60 fullerene is due to the higher polarizability of the C70 molecule and large overlap integrals of the energy-donor photoluminescence spectra with the absorption spectrum of the C70 fullerene.

Oxidation of fullerenes with ozone

Heterophase and liquid-phase oxidation reactions of fullerene with ozone and the data on chemiluminescence generated in these reactions were considered and classified for the first time.

Water-soluble polyketones and esters as the main stable products of ozonolysis of fullerene C60 solutions

Stable ozonolysis products of C60 solutions in CCl4, toluene, and hexane were studied by elemental analysis, HPLC, and UV and IR spectroscopy. Polyketones and esters were established for the first time to be the main stable products, whose content increased during the whole ozonolysis time (1 h). Epoxides C60On (n = 1—6) are accumulated within 1—3 min, and after 5 min of ozonolysis their concentration decreases to zero. Fullerene C60 disappears from the reaction solution due to its conversion to oxides and mechanical capturing of C60 by these oxides to form a precipitate. The oxidation of C60 is completed in the solid phase by the formation of the C60O16 oxide in which 9.68 O atoms fall on fullerene polyketones, 6 O atoms are attributed to esters, and 0.32 O atoms fall per epoxides. The optimum medium for preparation of the C60 oxides is CCl4 rather than traditional toluene, which reacts with ozone in the side reaction to form products containing active oxygen. The C60 cage is raptured during ozonolysis because of the C=C bond cleavage to form two C=O groups at the ends of the open hexagon. Ozonolysis of C60 solutions in CCl4 is efficient for synthesis of water-soluble fullerene oxides due to the high yield and solubility of polyketones and esters in water.

Dehydration of LnCl3·6H2O (Ln=Tb, Nd, Dy) in the reaction with i-Bu3Al, Et3Al, Et2AlCl, EtAlCl2 and formation of the complexes LnCl3·3(BuO)3PO

Abstract The dehydration of toluene insoluble salts TbCl 3 ·6H 2 O ( 1 ), DyCl 3 ·6H 2 O ( 2 ) and NdCl 3 ·6H 2 O ( 3 ) in their reaction with organoaluminum compounds (R n AlX 3− n ): i -Bu 3 Al, Et 3 Al, Et 2 AlCl, EtAlCl 2 and the influence of (BuO) 3 PO (TBP) on the process were studied. In the reaction of R n AlX 3− n with the water of crystallization of salts 1 – 3 , aluminoxanes and the following gases are formed: i -BuH for i -Bu 3 Al, EtH for Et 3 Al, EtH and HCl for Et 2 AlCl and EtAlCl 2 as a result of the attack on the AlC or AlCl bond independent of the presence of TBP. In the absence of TBP the salts 1 – 3 are dehydrated by R n AlX 3− n to give insoluble products LnCl 3 ·0.5H 2 O·0.5(R 2 Al) 2 O, where R is alkyl for i -Bu 3 Al and Et 3 Al, or R is alkyl and Cl for Et 2 AlCl. The reaction of R n AlX 3− n with 1 – 3 in the mixture of toluene–TBP at the ratio TBP/Ln≥12:1 results in the complete removal of water from LnCl 3 ·6H 2 O and leads to the formation of homogeneous solutions, containing aluminoxanes and LnCl 3 ·3TBP complexes. Homogeneous solutions, obtained after interaction in the system NdCl 3 ·6H 2 O+TBP+PhMe+R 3 Al were then activated with either i -Bu 3 Al or ( i -Bu 2 Al) 2 O and used as catalysts for polymerization of butadiene. All the catalysts were highly active for polymerization of butadiene, and produced a low-molecular polybutadiene.

Polarizability of C70 Fullerene Derivatives C70X8 and C70X10

The mean polarizabilities and their anisotropies for C70 derivalives C70X8 and C70X10 (X = H, Me, Ph, Cl, Br, OO t Bu) have been calculated. The deviation from additive scheme, that is, depression of polarizability, has been found for all studied C70X8 and C70X10 molecules. The deviation increases as the number of added X groups increases. The correction to additive polarizability taking into account this phenomenon is considered and can be used in the design of modern fullerene-containing materials.

Polarizability of fullerene [2+2]-dimers: a DFT study

Currently, the exaltation of polarizability of (C60)2 dimers has been predicted with DFT-methods (D. Sh. Sabirov, RSC Adv., 2013, 3(42), 19430). It consists of an increase in the polarizability when two C60 molecules are united, forming a [2+2]-dimer. In the present work, we point attention to the bicage structures of the other fullerenes, which are promising compounds for nano-applications. We have performed the first density-functional theory study on the polarizability of fullerene [2+2]-dimers (Cn)2 (n = 20, 24, 30, 36, 50, and 70) and shown that the exaltation of polarizability is typical for all the members of the fullerenes family.