Direct synthesis of radioactive carbon labeled fullerences using nuclear reactions

The¹¹C and¹⁴C labeled fullerenes were produced by charged-particle and neutron irradiation, of C₆₀, C₇₀ and their mixture. It was found that a carbon atom of fullerence can be easily exchanged with a radioactive carbon atom produced by a nuclear reaction. The HPLC method was effective for identification and purification of various labeled fullerene families as chemically stable compounds. The radiochemically interesting aspect of the results is not only the production of¹¹C and¹⁴C labeled fullerenes but also the formation of radioactive higher fullerenes which can be simultaneously produced with high yield and in carrier-free form.     

Synthesis of Fullerene-end Functionalized Poly（methyl methacrylate） via Reverse Atom Transfer Radical Polymerization

The use of the reverse atom transfer radical polymerization （RATRP） to end-functionalize poly（methyl methacrylate） （PMMA） with fullerenes, e.g. C60 and C70 was described in this paper. The Cl-terrninated PMMA was prepared via RATRP with designed molecular weight and narrow molecular weight distributions, and then directly used to react with fullerenes to produce C60（C70） terminated PMMA polymers in the presence of CuBr/Cu/bipy or FeCl2/bipy catalysts. The resultant polymers exhibit good solubility in some common organic solvents, e.g. THF, CHCl3 and toluene, and were well structurally characterized by a variety of physical techniques.     

Thermochemistry of C60 and C70 fullerene solvates

In an effort to improve understanding of dissolution behaviour of fullerenes and their simple chemical derivatives the binary systems of C₆₀, C₇₀ and the piperazine monoadduct of [60] fullerene C₆₀ N₂C₄H₈ with a series of aromatic solvents have been studied by means of DSC. In certain systems solid solvates have been found to be the thermodynamically stable phases relative to saturated solution at room temperature. Identified solid solvates were characterized by their compositions, temperatures and enthalpies of incongruent melting transitions. The regularities in thermodynamic stability of the solvated crystals have been discussed along with dissolution properties of fullerenes and the derivative. Certain correlations have been observed.     

Addition of sulfur radicals to fullerenes

The addition of oxygen‐centered radicals to fullerenes has been intensively studied due to their role in cell protection against against hydrogen peroxide induced oxidative damage. However, the analogous reaction of sulfur‐centered radicals has been largely overlooked. Herein, we investigate the addition of S‐centered radicals to C₅₀, C₆₀, C₇₀, and C₁₀₀ fullerenes by means of DFT calculations. The radicals assayed were: S, SH, SCH₃, SCH₂CH₃, SC₆H₅, SCH₂C₆H₅, and the open‐disulfide SCH₂CH₂CH₂CH₂S. Sulfur, the most reactive species, prefers to be attached to a 66‐bond of C₆₀ with a binding energy (E_bind) of 2.4 eV. For the SR radicals the electronic binding energies to C₆₀ are 0.77, 0.74, 0.58, 0.67, and 0.35 eV for SH, SCH₃, SCH₂CH₃, SCH₂C₆H₅, and SC₆H₅, respectively. The reactivity of C₆₀ toward SR radicals can be increased by lithium doping. For Li@C₆₀, the E_bind is increased by 0.65 eV with respect to C₆₀, but only by 0.33 eV for the exohedral doping. Fullerenes act like free radical sponges. Indeed, the C₆₀‐SR E_bind can be duplicated if two radicals are added in ortho or para positions. The enhanced reactivity because of multiple additions is mostly a local effect, although the addition of one radical makes the whole cage more reactive. Therefore, as observed for hydroxylated fullerenes, they should protect cells from oxidative damage. However, the thiolated fullerenes have one advantage, they can be easily attached to gold nanoparticles. For the addition on pentagon junctions smaller fullerenes like C₅₀ are more reactive than C₆₀. Interestingly, C₇₀ is as reactive as C₆₀, even for the addition on the equatorial belt. For larger fullerenes like C₁₀₀, reactivity decreases for the carbon atoms belonging to hexagon junctions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Supramolecular Porphyrin‐Based Metal–Organic Frameworks with Fullerenes: Crystal Structures and Preferential Intercalation of C70

The syntheses and characterization of two new porphyrin‐based metal–organic frameworks (P‐MOFs), through the complexation of 5,10,15,20‐tetra‐4‐pyridyl‐21 H,23 H‐porphine (H₂TPyP) and copper(II) acetate (CuAcO) in the presence of the fullerenes C₆₀ or C₇₀ are reported. Complex 1 was synthesized in conjunction with C₆₀, and this reaction produced a two‐dimensional (2D) porous structure with the composition CuAcO‐CuTPyP?m‐dichlorobenzene (m‐DCB), in which C₆₀ molecules were not intercalated. Complex 2 was synthesized in the presence of C₇₀, generating a three‐dimensional (3D) porous structure, in which C₇₀ was intercalated, with the composition CuAcO‐CuTPyP?C₇₀?m‐DCB?CHCl₃. The structures of these materials were determined by X‐ray diffraction to identify the supramolecular interactions that lead to 2D and 3D crystal packing motifs. When a combination of C₆₀ and C₇₀ was employed, C₇₀ was found to be preferentially intercalated between the porphyrins.     

Tandem mass spectrometry of aminated fullerene derivatives

The products of the reaction between fullerenes (C₆₀/C₇₀) and dimethylamine were investigated by fast atom bombardment (FAB) mass spectrometry and tandem mass spectrometry (MS/MS). The FAB mass spectrum shows peaks corresponding to the addition of up to eight dimethylamine species, exclusively to C₇₀. MS/MS reveals an unusual fragmentation pattern. The mass spectrum of the reaction products, together with a number of tandem mass spectra, are shown.     

The hydrogenolysis of C60 and C70

Temperature-programmed reaction (TPR) of C₆₀ and C₇₀ with H₂ was carried out on nickel in order to investigate the thermal stability of the fullerenes in the catalytic hydrogenation. The TPR profiles showed two methanation peaks and the corresponding weight decrease above 420°C, indicating the hydrogenolysis to CH₄. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis of Octadecahydroxylated C70

Synthesis of novel hydrophilic [70]fullerenols was described. The reaction involved an oleum-induced oxidative sulfation of the C₇₀ molecules with a product yield of 86%. The rate of fullerene sulfation was accelerated either moderately or greatly by the addition of P₂O₅ or SeO₂, respectively. Hydrolysis of the resulting polycyclosulfated C₇₀ in H₂O at 80°C afforded [70]fullerenols in a yield of more than 72%. The negative ion MALDI-TOF mass spectrum of [70]fullerenols showed a well-defined pattern of ion fragmentations with a nearly constant, consecutive weight increase in 17 mass units from the mass of C₇₀. Detection of a molecular ion at m/z 1146 was indicative for the composition of [70]fullerenols as octadecahydroxyfullerenes, containing 18 hydroxy addends per C₇₀ cage. That correlates the structure of their polycyclosulfated precursors to nonacyclosulfated [70]fullerenes, C₇₀(SO₄)₉.     

Transient Absorption Spectral characterization of Electron Transfer between Fullerenes（C60／C70）and N,N,N’，N’—Tetra（p—methylphenyl）—4,4’—diamino—1,1’—diphenyl Sulphide（TPDAS）

In search of new systems with a photoexcited redox pair which exhibits a strong and stable photoinduced absorption band to understand the photophyscial and photochemical properties of electron transfer between fullernes (C60/C70) and organic donor[N,N,N’，N’-tetra(p-methylphenyl)-4,4’-diamino-1,1’-diphenyl sulphide(TPDAS)],we studied characteristic absorption spectra in the near-IR region obtained from 532nm nanosecond laser flash photolysis of a mixture of the fullerenes (C60/C70) and TPDAS in polar solvents.When fullerenes (C60/C70)were photoexcithed,the rise of the radical anion of fullerenes (C60/C70)with the rapid decay of their excited triplet states were observed in benzonitrile.It can be deduced that the electron transfer reaction does take place from TPDAS to excithed triplet state of rullerens(C60/C70).The rate consants(ket)and quantum yiekls(φet) of this process have been also evaluated.     

Technology for manufacture of pure fullerenes C60, C70 and a concentrate of higher fullerenes

An integrated technology for manufacture of fullerenes was developed. It includes the following stages: synthesis of a fullerene black, extraction of a mixture of fullerenes from the black, preliminary separation of the mixture into concentrates enriched in C₆₀ and C₇₀ fullerenes, and production of C₆₀ and C₇₀ fullerenes of purity exceeding 99.5 and 98.0 wt %, respectively, from the concentrates.     

Synthesis,characterization, DNA binding and cleavage properties of a ternary copper(II) Schiff base complex

A ternary coordination complex 2Cu(C₁₄H₈NO₃Cl)(C₁₂H₈N₂)·3CH₃OH of a Schiff base (C₁₄H₈NO₃Cl: 4-chloroanthranilic acid–salicylaldehyde) was synthesized from 4-chloroanthranilic acid, salicylaldehyde, copper acetate and 1,10-phenanthroline and characterized by physicochemical and spectroscopic methods. X-ray crystallography shows that the copper atom is five coordinated by the imine nitrogen, two nitrogen atoms from 1,10-phenanthroline, the hydroxyl oxygen and the carboxylate oxygen atom. The interaction of the complex with calf-thymus DNA was investigated by UV absorption spectroscopy, fluorescence emission spectroscopy and viscosity. In addition, the cleavage reaction with pBR322 supercoiled plasmid DNA was investigated. The complex binds to DNA and also exhibits significant DNA cleavage activity.     

Photoinduced Electron Transfer between N,N, Nr,N' ‐Tetra‐(p‐methylphenyl)‐4, 4‐diamino‐1, 1'‐diphenyl Ether (TPDAE) and Fullerenes (C60/C70) by Laser Flash Photolysis

The photoinduced electron‐transfer reaction of N, N, N', N'‐tetra‐(p‐methylphenyl)‐4,4'‐diamino‐1,1'‐diphenyl ether (TPDAE) and fullerenes (C₆₀/C₇₀) by nanosecond laser flash photolysis occurred in benzonitrile. Transient absorption spectral measurements were carried out during 532 nm laser flash photolysis of a mixture of the fullerenes (C₆₀/C₇₀) and TPDAE. The electron transfer from the TPDAE to excited triplet state of the fullerenes (C₆₀/C₇₀) quantum yields and rate constants of electron transfer from TPDAE to excited triplet state of fullerenes (C₆₀/C₇₀) in benzonitrile have been evaluated by observing the transient absorption bands in the near‐IR region where the excited triplet state, radical anion of fullerenes (C₆₀/C₇₀) and radical cations of TPDAE are expected to appear.     

Supramolecular Interaction of Fullerenes with a Curved π‐Surface of a Monomeric Quadruply Ring‐Fused Porphyrin

Molecular binding of fullerenes, C₆₀ and C₇₀, with the Zn^II complex of a monomeric ring‐fused porphyrin derivative ( 2 ‐py) as a host molecule, which has a concave π‐conjugated surface, has been confirmed spectroscopically. The structures of associated complexes composed of fullerenes and 2 ‐py were explicitly established by X‐ray diffraction analysis. The fullerenes in the 2:1 complexes, which consist of two 2 ‐py molecules and one fullerene molecule, are fully covered by the concave surfaces of the two 2 ‐py molecules in the crystal structure. In contrast, in the crystal structure of the 1:1 complex consisting of one 2 ‐py molecule and one C₆₀ molecule, the C₆₀ molecule formed a π–π stacked pair with a C₆₀ molecule in the neighboring complex using a partial surface, which was uncovered by the 2 ‐py molecule. Additionally, the molecular size of fullerene adopted significantly affects the ¹H NMR spectral changes and the redox properties of 2 ‐py upon the molecular binding.     

Activation of Isocyanates and Carbon Dioxide by a Monomeric Aluminium Hydrazide as an Active Lewis Pair

The monomeric aluminium hydrazide H₁₀C₅N? N(AltBu₂)? Ad ( 4 ; Ad=adamantyl, NC₅H₁₀=piperidinyl) was obtained in high yield by hydroalumination of the corresponding hydrazone derivative 1 . Compound 4 has a strained AlN₂ heterocycle formed by a donor–acceptor bond between the β‐nitrogen atom of the hydrazide group and the aluminium atom. Opening of this bond resulted in the formation of an active Lewis pair that was able to cooperatively activate carbon dioxide or isocyanates. Insertion of the heterocumulenes into the Al? N bond selectively afforded a carbamate and two urea derivatives in high yield. In the first step, phenyl isocyanate gave the adduct 6 , which has the oxygen atom coordinated to the aluminium atom and its central carbon atom bound to the nitrogen atom of the piperidine moiety. Adduct 6 represents a reasonable intermediate state for these activation processes. The applicability of hydroaluminated compounds, such as 4 , in organic synthesis was demonstrated by the reaction with an imidoyl chloride, which gave the corresponding amidrazone derivative 9 .     

Approach to High Open‐Circuit Voltage in Organic Solar Cells Utilizing a Structural Change of the Oxazolino‐C70 Derivative

Reactions of 2,5‐Bn₂C₇₀ (Bn=CH₂Ph) with hydroxide and ArCN (Ar=Ph, m‐ClPh) followed by quenching with I₂ and BnBr afforded dibenzylated and tetrabenzylated oxazolino[70]fullerenes, respectively. The latter has a novel structural configuration, in which the addends are positioned from the polar to the transequatorial region. A key structural feature of this compound is that the oxygen atom of the oxazoline ring is bound to the equatorial belt region of C₇₀, giving structural change in its reduced state. This enables stabilization of the reduced state, suppressing charge recombination dynamics in organic solar cells to give a high open‐circuit voltage (0.85, 0.93, and 1.11 V in devices using P3HT, PTB7, and DPP(TBFu)₂, respectively).     

Reductive Hydrogenation of Cs‐C70(CF3)8 and C1‐C70(CF3)10

CF₃‐derivatized fullerenes prove once again to be promising scaffolds for regioselective fullerene functionalization: now with the smallest possible addends—hydrogen atoms. Hydrogenation of C_s‐C₇₀(CF₃)₈ and C₁‐C₇₀(CF₃)₁₀ by means of reduction with Zn/Cu couple in the presence of water proceeds regioselectively, yielding only one major isomer of C₇₀(CF₃)₈H₂ and only two for C₇₀(CF₃)₁₀H₂, whose addition patterns are combined in the only abundant isomer of C₇₀(CF₃)₁₀H₄. The observed selectivity is governed by the electronic structure of trifluoromethylated substrates. Interestingly, we discovered that Clar's theory can be utilized to predict the regiochemistry of functionalization, and we look forward to testing it on forthcoming cases of derivatization of pre‐functionalized fullerene building blocks.     

Theoretical Investigation of Mono and Multiply Oxygenated C70 Fullerenes

We have applied DFT calculations to investigate atomic arrangements of fullerene oxides, C₇₀O _n with n = 1, 5, 15, 20, and 25. The oxidation reaction energies are generally exothermic. In the case of C₇₀O, the most stable configuration is the one in which the oxygen atom is chemisorbed on the C–C bond at the equatorial belt of fullerene with oxidoannulene like structure. In highly oxygenated fullerenes, the addition of oxygen atoms on the [6, 6] bonds near the pole area of the C₇₀ leads to lower values of reaction energies. Among these, C₇₀O₂₀ with three oxygen atoms adsorbed on a benzenoid ring yields the most energetically favorable configuration. Different positions of the oxygen atoms on the surface of the mono oxygenated fullerenes lead to significant differences in their ¹⁷O NQR parameters. Meanwhile, the ¹⁷O NQR parameters of the highly oxygenated fullerenes divide their oxygen nuclei into a few groups. For example, the electric field gradient tensor for oxygen atoms chemisorbed on the [6, 5] bonds with larger η values becomes considerably asymmetric in comparison to those chemisorbed on the [6, 6] bonds. These are also reflected in the calculated natural charges of oxygen atoms.     

Relationship between reduction potentials and electron affinities of fullerenes and their derivatives

A linear relationship was found between the first reduction potentials (E°_red) and electron affinities (EA) for fullerenes C₆₀ and C₇₀, their hydro- and fluoro-derivatives, and aromatic hydrocarbons: E°_red = –3.04 + 0.81·EA. This equation was used to estimate the unknown values of EA = 2.45 eV for C₆₀H₂, 2.47 eV for C₇₀H₂, –0.15 eV for C₇₀H_36—38, –0.41 eV for C₇₀H_44—46, and E°_red = –1.74—–1.91 V (vs. Fc^0/+) for C₆₀H₁₈.     

Electrochemical behavior of fullerene C60 and substituted fullerenes immobilized on an electrode surface

The effect of substituents with different donor capabilities, which are inserted into a molecule of fullerene C₆₀, on the kinetics and thermodynamics of redox conversions of fullerenes that are immobilized on an electrode, is studied for the first time. To this end, redox conversions that occur with rubbed-on films of fullerene and fulleropyrrolidines are studied using cyclic voltammetry in 0.5 M KCl/H₂O and a 0.1 M (C₄H₉)₄NBF₄/AN solution in acetonitrile. A hypothesis that the kinetics of redox conversions occurring with films of individual fullerenes is defined largely by changes in the structure of initial films in the process of their cathodic doping is used. The effect of the substituents is explained in the framework of this hypothesis by a transition from a dense crystalline structure of nonsubstituted fullerene C₆₀ to an amorphous structure of substituted fullerenes. It is demonstrated that the formal potentials corresponding to redox conversions of fullerenes in a solid cationic lipid matrix are defined by the energy of interaction of anions, which are products of reduction of fullerenes, with cations of the matrix. As a result of this interaction, the formal potentials of the process of cathodic doping shift to less negative values. It is established that the insertion of a donor substituent and increase in its donor capability amplify the energy of interaction of the fullerene anions with the lipid cations.     

2,4,6-Triphenylphenyltellurium(IV) triiodide - supramolecular self-assembling in organotellurium triiodides

2,4,6-Triphenylphenyltellurium(IV) triiodide, (2,4,6-Ph₃C₆H₂)TeI₃, can be obtained by the reaction of the corresponding ditelluride {(2,4,6-Ph₃C₆H₂)Te}₂ with iodine under an atmosphere of dry nitrogen in toluene. The apparent bisphenoidal coordination sphere of the central tellurium atom is extended by the presence of intermolecular Te?I and I?I secondary bonds which form chains along the crystallographic a axis. Weak intramolecular interactions with one of the phenyl rings of the (2,4,6-Ph₃C₆H₅) unit completes the pseudo-octahedral coordination geometry around each tellurium atom. A comparison of the structure of (2,4,6-Ph₃C₆H₂)TeI₃ with the bonding situations in other organotellurium(IV) triiodides suggests a strong dependence of the formation of supramolecular assemblies on the nature of the organic substituents.