Formation of secondary fullerene ozonides in the ozonolysis of C60 solutions and chemiluminescence upon their hydrolysis

The formation of secondary fullerene ozonides (SFOs) in the ozonolysis of C₆₀ solutions in CCl₄ has reliably been determined for the first time; SFOs are accumulated during the whole ozonolysis time as a suspension in CCl₄. Hydrolysis of the SFOs results in chemiluminescence (CL) (I _max = 2.65·10⁸ photon s⁻¹ mL⁻¹), whose spectra contain maxima at 558, 608, and 685 nm. The most probable CL emitters are excited fullerene polyketones. Hydrogen peroxide was identified as a stable hydrolysis product of the SFOs by the color reaction with diphenylcarbazide and CL arisen upon the addition of an aqueous solution of FeSO₄·9H₂O to the hydrolyzate of the SFO. Chemiluminescence upon hydrolysis is a selective test for SFOs and allows one to find them in a complex mixture of the ozonolysis products of C₆₀. The rate constant and activation energy of SFO hydrolysis were determined from the kinetic measurements of CL. For SFO hydrolysis several probable reactions were proposed, including the formation of the CL emitters, and their heat effects were estimated using the PM3/RHF and AM1/RHF semiempirical methods for one-and two-cage model structures of SFOs. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1322–1329, August, 2006.     

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 C₆₀O _n (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.     

Generation of fullerenyl radicals and chemiluminescence in the (C<Subscript>60</Subscript>—R<Subscript>3</Subscript>Al)—O<Subscript>2</Subscript> system

Fullerenyl radicals (FR) RC₆₀ ^· and chemiluminescence (CL) are generated in the presence of O₂ in C₆₀—R₃Al (R = Et, Buⁱ) solutions in toluene (T = 298 K). The FR are formed due to the addition of the R^· radical, which is an intermediate of R₃Al autooxidation, to C₆₀. Mass spectroscopy and HPLC were used to identify Et_nC₆₀H_m (n, m = 1–6), Et_pC₆₀ (p = 2–6), and dimer EtC₆₀C₆₀Et as stable products of FR transformations. As found by ESR, the EtC₆₀ ^· radical (g = 2.0037) is also generated by photolysis of solutions obtained after interaction in the (C₆₀— R₃Al)—O₂ system. In the presence of dioxygen, the FR is not oxidized but yields complexes with O₂, which appear as broadening of the ESR signals. Chemiluminescence arising in the (C₆₀—R₃Al)—O₂ system is much brighter (I _max = 1.86·10⁸ photon s⁻¹ mL⁻¹) than the known background CL (I _max = 6.0·10⁶ photon s⁻¹ mL⁻¹) for the autooxidation of R₃Al and is localized in a longer-wavelength spectral region (λ_max = 617 and 664 nm). This CL is generated as a result of energy transfer from the primary emitter ³CH₃CHO* to the products of FR transformation: R_nC₆₀H_m, R_pC₆₀, and EtC₆₀C₆₀Et. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 205–213, February, 2007.     

Inertness of C<Subscript>60</Subscript> fullerene toward RO<Subscript>2</Subscript><Superscript>·</Superscript> peroxy radicals

The reactivity of fullerene C₆₀ toward peroxy radicals RO₂ ^· was tested by the chemiluminescence method. A comparison of the influence of C₆₀ and known inhibitors on the kinetics of liquid-phase chemiluminescence (CL) during oxidation of a series of hydrocarbons (ethyl-benzene, cyclohexane, n-dodecane, and oleic acid) shows that the fullerene does not react with the RO₂ ^· radicals. A sharp decrease in the CL intensity observed upon C₆₀ addition is caused by the quenching of CL emitters with fullerene but not by inhibition of hydrocarbon oxidation. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1808–1811, August, 2005.     

Self-assembling of fullerene C<Subscript>60</Subscript> into (C<Subscript>60</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> clasters in aromatic solvents

Self-assembling of fullerene C₆₀ into (C₆₀) _n clusters in aromatic solvents was studied. The role of the π-π interactions and dispersion forces in the (C₆₀) _n cluster formation in these media is demonstrated using the data on the solubility of fullerene C₆₀ in these solvents and their ionization potentials and also spectral characteristics of fullerene C₆₀ in the range of 326–340 nm in different solvents.     

Direct Mass Spectrometric Study of the Ionic Species Content of a C<Subscript>2</Subscript>HCl<Subscript>3</Subscript>/He/O<Subscript>2</Subscript> Microwave Discharge Plasma

Direct on-line studies of a C₂HCl₃/He/O₂ microwave discharge plasma made possible the evolution and detection of many unfamiliar ionic species. Numerous ionic chlorocarbons, chlorohydrocarbons, oxygenated chlorohydrocarbons, oxygenated hydrocarbon radicals, and simple hydrocarbon species were identified mass spectrometrically as by-products: C _m Cl _n (m = 1–4, 6, 8; n = 1–8), C _m H _n Cl _x (m = 1–4, 6, 7, 10; n, x = 1–6), C _m H _n Cl _x O _y (m = 1–5, 12; n = 1–7; x = 1, 2, 4, 6; y = 1–3), C _n H_2n−1O (n = 2, 3), C _m H _n (m = 2, 4, 6, 8; n = 2, 4), and so on. The studies clearly showed the presence of various unfamiliar positive ionic O-containing species such as C₂ClO₂, CCl₃CO, C₂H₂Cl₄O₂, and C₄H₂Cl₆O₃. It is apparent that positive-ion reactions play a significant role in producing many ionic species in the chemistry of C₂HCl₃ plasmas.     

Nonlinear optical properties of solutions of heavy fullerenes in the near-ultraviolet region

Nonlinear optical properties (particularly optical limiting) are determined for solutions of heavy fullerenes C₇₆ + C₇₈ + C₈₄ + C₉₀ + …, in the near-ultraviolet region (λ ≈ 280 ± 7 nm). It is shown that no optical limiting is observed in solutions of light fullerenes (C₆₀ and C₇₀), but found in solutions of water-soluble fullerenol-d (a mixture of oxypolyalcohols of fullerene C₆₀-C₆₀(OH) _n1O _n2, with their sodium salts) based on light fullerenes.     

Circular dichroism of optically active organometallic derivatives of fullerenes C<Subscript>60</Subscript> and C<Subscript>70</Subscript>

Palladium and platinum complexes of fulleienes C₆₀ and C₇₀ containing the axially chiral ligand (—)-BITIANP (BITIANP is 2,2’-bis(diphenylphosphino)-3,3’-bi(benzo[b]thiophene)) and pynolidino[60]fullerene bearing a planar chiral organometallic π-complex substituent in the heteiocyclic ring were studied by circular dichroism (CD) spectroscopy.     

Chemiluminescence in the reaction of LnI<Subscript>2</Subscript> (Ln = Dy,Nd) with water

Chemiluminescence (CL) upon the reaction of crystalline LnI₂ (Ln = Dy, Nd) with water was found. The CL emitters are the Ln³⁺* electron-excited ions (Dy³⁺*, λ_max = 470, 570 nm; Nd³⁺*, λ = 700–1200 nm) generated by the electron transfer from the Ln^II ions to the H₂O molecules. The identified reaction products are H₂, dissolved LnI₃, and insoluble LnI(OH)₂ (49–51% and 48–50% yield for DyI₂ and NdI₂, respectively). The treatment of NdI₂ with an H₂O solution in THF gives the NdI₂OH(thf)₂·3H₂O complex and hydrogen. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1890–1893, October, 2007.     

The solubility of C<Subscript>60</Subscript>Br<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 6, 8, 24) in organic solvents

The polythermal (over the temperature range 20–80°C) solubility of fullerene bromo derivatives C₆₀Brn (n = 6, 8, 24) in several solvents (o-xylene, o-dichlorobenzene, n-decanol-1, and enanthic acid) was studied. The corresponding solubility polytherms are given.     

Red and green chemiluminescence of Na, Mg, and lanthanide triphenylmethyl derivatives during oxidation by dioxygen and cerium(IV)

Chemiluminescence (CL) of triphenylmethyl organometallics (TPM), Ph₃CNa, Ph₃CMgCl, and Ph₃CLnCl₂ (Ln=Cd, Eu, and Dy), in THF and toluene during oxidation by O₂ and the (NH₄)₂Ce(NO₃)₆ complex was found. The first CL is caused by the luminescence of two emitters: (Ph₃C)^*, emitting in the green spectral region (λ_max=524, 550 nm), and an unstable product of substitution of the hydrogen atom in the phenyl ring of the Ph₃C radical, emitting in the red region (λ_max=580±20 nm). The emitter of the second CL, Ph₃C^.*, is generated in the elementary electron transfer from the Ph₃C⁻ anion to Ce^IV, reducing the latter to Ce^III. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1102–1105, June, 1999.     

Oxygen desorption from polycrystalline palladium: Thermal desorption of O<Subscript>2</Subscript> from a chemisorbed layer of O<Subscript>ads</Subscript> in the course of the decomposition of PdO surface oxide and in the release of oxygen from the bulk of palladium

The desorption of oxygen from polycrystalline palladium (Pd(poly)) was studied using temperature-programmed desorption (TPD) at 500–1300 K and the amounts of oxygen absorbed by palladium (n) from 0.05 to 50 monolayers. It was found that the desorption of O₂ from Pd(poly), which occurred from a chemisorbed oxygen layer (O_ads), in the release of oxygen from a near-surface metal layer in the course of the decomposition of PdO surface oxide, and in the release of oxygen from the bulk of palladium (O_abs), was governed by repulsive interactions between O_ads atoms and the formation and decomposition of O_ads-Pd*-O_abs structures (Pd* is a surface palladium atom). At θ ≤ 0.5, the repulsive interactions between O_ads atoms (ɛ_aa = 10 kJ/mol) resulted in the desorption of O₂ from Pd(poly) at 650–950 K. At 0.5 ≤ n ≤ 1.0, the release of inserted oxygen from a near-surface palladium layer occurred during TPD in the course of the migration of O_abs atoms to the surface and the formation-decomposition of O_ads-Pd*-O_abs structures. As a result, the desorption of O₂ occurred in accordance with a first-order reaction with a thermal desorption (TD) peak at T _max ∼ 700 K. At 1.0 ≤ n ≤ 2.0, the decomposition of PdO surface oxide occurred at a constant surface cover-age with oxygen during TPD in the course of the formation-decomposition of O_ads-Pd*-O_abs structures. Because of this, the desorption of O₂ occurred in accordance with a zero-order reaction at low temperatures with a TD peak at T _max ∼ 675 K. At 1.0 ≤ n ≤ 50, oxygen atoms diffused from deep palladium layers in the course of TPD and arrived at the surface at high temperatures. As a result, O₂ was desorbed with a high-temperature TD peak at T > 750 K.     

Effect of the medium on the reactivity of fullerene N60 with respect to the peroxide radicals RO2 ·. Chemiluminescence in the C60—AIBN—O2—C2H5Ph—PhH system

Chemiluminescence (CL), HLPC, and volumetry were used to demonstrate that fullerene N₆₀ exerts no inhibiting effect on the liquid-phase chain oxidation of hydrocarbons. Peroxide radicals RO₂ · do not add to N₆₀ in hydrocarbons with active C—H bond, because the reaction is suppressed by the competing addition of RO₂ · to the hydrocarbon. The addition of RO₂ · radicals to N₆₀ does occur in benzene (a solvent with strong C—H bonds) in the presence of low concentrations of the hydrocarbon oxidized. Fullerene N₆₀ is found to exhibit a new type of liquid_phase CL, which is presumably generated upon thermal decomposition of fullerene peroxides formed by adding peroxy radicals to fullerene in the C₆₀—AIBN—O₂—C₂H₅Ph—PhH system. The CL spectrum exhibits long-wavelength maxima at 645 and 685 nm. The supposed CL emitters are keto derivatives of fullerene N₆₀.     

Dimerization and Coordination Properties of Zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine in Relation to DABCO in <Emphasis Type="Italic">o</Emphasis>-Xylene and Chloroform

For the first time the interactions between zinc(II)tetra-4-alkoxybenzoyloxiphthalocyanine (Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc) and 1,4-diazabicyclo[2.2.2]octane (DABCO) in o-xylene and chloroform have been studied by calorimetric titration and NMR and electron absorption spectroscopic methods. It has been found that in o-xylene at concentrations of Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc higher than 6×10⁻⁴ mol⋅L⁻¹ π–π dimers species are formed (λ _max= 685 nm). Additions of DABCO to the solution up to mole ratio 1 : 8 (Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc : DABCO) lead to a shift of the aggregation equilibrium towards monomer species due to formation of monoligand axial complexes. Further increasing the DABCO concentration results in formation of Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc—DABCO—Zn(4—O—CO—C₆H₄—OC₁₁H₂₃)Pc sandwich dimers (λ _max= 675 nm).     

Theoretical Study of the Structures,Properties and Spectroscopies on Fullerene Hydrides C<Subscript>26</Subscript>H<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 2, 4, 6, 8)

The structures, stability patterns of C₂₆H _n (n = 2) formed from the initial D _3h C₂₆ fullerene were investigated by use of second-order-Moller–Plesset perturbation theory. The study of the stability patterns of hydrogenation reaction on C₂₆ cage revealed that type (β) carbons were the active site and the analyses of π-orbital axis vector indicated that the reactivity of C₂₆ was the result of the high strain and the hydrogenation reaction on C₂₆ cage was highly exothermic. The calculated ¹³C NMR spectra of C₂₆H _n (n = 2) predicted that the two sp ³ hybridization carbons in C₂₆H _n (n = 2) obviously moved to high field compare with that in D _3h C₂₆. Hence, the C₂₆H₂ should be obtained and detected experimentally. Similarly, the structures and reaction energies of C₂₆H _n (n = 4, 6, 8) were further studied at HF/6-31G*, B3LPY/6-31G* and MP2/6-31G* level. The results suggested the hydrogenation products of C₂₆, C₂₆H _n (n = 4, 6, 8), were more stable than the C₂₆ cage.     

Octafluorocyclohexa derivatives of [60]fullerene: C<Subscript>60</Subscript>(C<Subscript>4</Subscript>F<Subscript>8</Subscript>)<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 2, 3, 4, and 6)

Fluorocyclohexa adducts C₆₀(C₄F₈) _n were synthesized by high-temperature reaction of fullerene C₆₀ with 1,2-C₂F₄I₂ or 1,4-C₄F₈I₂ in sealed tubes. Their separation by HPLC allowed us to determine molecular structure (X-ray diffraction) of four new compounds C₆(C₄F₈) _n (n = 2, 3, 4, and 6). Structures of isomers C₆₀(C₄F₈) _n were discussed in terms of a concept of consecutive addition of C₄F₈ groups to the fullerene cage.     

Solubility of bromofullerenes C<Subscript>60</Subscript>Br<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 6, 8, 24) in aqueous-ethanolic mixtures at 25°C

Solubility of fullerene bromoderivatives C₆₀Br _n (n = 6, 8, 24) in aqueous-ethanolic mixtures at 25°C were studied. The corresponding solubility isotherms are presented.     

Structure and photochromic and magnetic properties of 1-isopropyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-2<Emphasis Type="Italic">H</Emphasis>-pyrano[3,2-<Emphasis Type="Italic">b</Emphasis>]pyridinium] tris(oxalato)chromate(III)

Single crystals of 1-isopropyl-3,3,5′,6′-tetramethylspiro[indoline-2,2′-2H-pyrano[3,2-b]-pyridinium] tris(oxalato)chromate(III) (Sp)₃Cr(C₂O₄)₃ were prepared for the first time. The molecular and crystal structure of this salt was studied by X-ray diffraction. The crystal structure of the salt consists of the structural units [3(Sp)⁺…Cr(C₂O₄)₃ ³⁻], in which the charged pyranopyridinium moieties of the photochromic cations (Sp)+ are directed toward the oxalate groups, whereas the indoline moieties are directed into the cavities between the structural units. This structure appeared to be favorable for photochromic transformations in the crystals. Under UV irradiation of the (Sp)₃Cr(C₂O₄)₃ salt, the thermally stable closed form of spiropyran (λ_max = 370 nm) is transformed into the open form (λ_max = 574 and 603 nm). The reverse cyclization proceeds slowly in the dark (k = 1.0(2)·10⁻⁵ s⁻¹ and rapidly under visible light irradiation. The spectroscopic and photochromic properties of the oxalatochromate (Sp)₃Cr(C₂O₄)₃ are similar to those of the iodide SpI. The magnetic properties of (Sp)₃Cr(C₂O₄)₃ were studied before and after UV irradiation.     

Non-isothermal kinetics of the thermal decomposition of sodium oxalate Na<Subscript>2</Subscript>C<Subscript>2</Subscript>O<Subscript>4</Subscript>

The thermal transformation of Na₂C₂O₄ was studied in N₂ atmosphere using thermo gravimetric (TG) analysis and differential thermal analysis (DTA). Na₂C₂O₄ and its decomposed product were characterized using a scanning electron microscope (SEM) and the X-ray diffraction technique (XRD). The non-isothermal kinetic of the decomposition was studied by the mean of Ozawa and Kissinger–Akahira–Sunose (KAS) methods. The activation energies (E _α) of Na₂C₂O₄ decomposition were found to be consistent. Decreasing E _α at increased decomposition temperature indicated the multi-step nature of the process. The possible conversion function estimated through the Liqing–Donghua method was ‘cylindrical symmetry (R₂ or F_1/2)’ of the phase boundary mechanism. Thermodynamic functions (ΔH*, ΔG* and ΔS*), calculated by the Activated complex theory and kinetic parameters, indicated that the decomposition step is a high energy pathway and revealed a very hard mechanism.     

Oligomers of C<Subscript>20</Subscript>H<Subscript>8</Subscript> polyhedral molecule: a computer simulation

DFT-PBE/DZ calculations of oligomers of C₂₀H₈ polyhedral molecule (derivative of C₂₀ fullerene) were carried out. From the results obtained it follows that quasi-one-dimensional, quasi-two-dimensional, and three-dimensional polymers with compositions [C₂₀H₈]_n can exist. The geometric parameters of the repeating units of these polymers were estimated.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1813–1817, September, 2004.