D. Sh. Sabirov

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.

Catalytic cycloaddition of diazoalkanes to fullerene C60

Cycloaddition to fullerene C60 of monosubstituted diazomethanes generated in situ by oxidation of aldehyde hydrazones in the presence of Pd(acac)2-2 PPh3-4 Et3Al as catalytic system resulted in selective formation of homofullerenes in which the alkyl substituent is located above the plane of the five-membered ring in C60. Under analogous conditions, unsymmetrical disubstituted diazomethanes generated from the corresponding ketone hydrazones gave rise to mixtures of stereoisomeric 5,6-open adducts.

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.

Chemiluminescence in the ozonation of C60 aqueous dispersions

Two types of chemiluminescence (CL) arising upon ozonation of crystalline, amorphous, and molecular aqueous dispersions of C60 prepared in different ways were discovered and studied. The weak long-wavelength CL-1 (λmax > 650 nm) is due to thermocatalytic decomposition of ozone on the surface of fullerene micro- and nanoparticles. The bright short-wavelength CL-2 (λmax = 570 nm) is caused by generation of electronically excited states of the products of C60 oxidation with ozone. CL-1 appears upon ozonation of aqueous dispersions of C60 consisting of surface-hydrated crystalline micro- and nanoparticles by low concentrations of ozone. CL-2 is exhibited upon ozonation of nano-sized C60 aqueous dispersions and colloid solutions, which contain C60 molecules surrounded by a strong aqueous shell and their associates, by higher concentrations of ozone. Owing to shielding by the hydration shell, C60 fullerene in aqueous dispersions is much less reactive towards ozone and forms oxidation products of different composition as compared with C60 in organic solvents.

Decomposition of sodium hypochlorite in an aqueous solution in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) nitroxyl radical as a catalyst

Nitroxyl radical TEMPO is found to catalyze the decomposition of sodium hypochlorite in an aqueous-alkali medium. The mechanism of NaOCl decomposition to form ClO· radical is proposed which involves protonated TEMPO, oxoammonium salt TEMPO+, and hydroxyl radical.

Reduction at low temperature of isomentholactone with diisobutylaluminum hydride in CH2Cl2

We formerly reported on the synthesis of О-isobutyl-derivative of mentholactol 2S,7S-1 by the treatment at low temperature (–70°С) of (–)mentholactone 7S-2 with two-fold excess of diisobutylaluminum hydride in dichloromethane solution [1]. The spectral characteristics of the prevailing amomer 7R-1 [larger spin-spin coupling constant (9.51 Hz) of the acetal proton (4.37 ppm, d.d), and also the more downfield shift of С atom (105.66 ppm)] indicate the equatorial orientation of the О-isobutyl group. Presumably in the oxepane ring of compound 2S,7R-1 the methyl group at the atom С is located in the equatorial position since in the С NMR spectrum its chemical shift (26.88 ppm) is close to the shift of the СН3 group of (–)-mentholactone 7S-2 (23.92 ppm) [1], where all substituents in the ring have the equatorial orientation. Considering the above the forming acetal center has the S-configuration. Consequently the dominant anomer 1 possesses 2S,7R-configuration.