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.     

Quantum-chemical study of C<Subscript>n</Subscript>F2<Subscript><Emphasis Type="Italic">n</Emphasis>+2</Subscript> conformers. Structure and IR spectra

Quantum-chemical calculations of the geometrical structure and vibrational spectra of C_nF_2n+2 oligomers (n = 5–8) in the chain and branched conformations are reported. The lengthening of the chain of C_nF_2n+2 does not substantially affect the geometrical parameters of the oligomers. In all cases under study, the most optimal structure of the molecule is a zigzag chain with bond lengths R(C-C) = 1.53 –1.54 and R(C-F) = 1.36 –1.34 ; the chain is rolled into a helix, which makes an angle of 17° with the plane. The IR spectra are sensitive to the structural deficiency of oligomers C_nF_2n+2 associated with the lateral trifluoromethyl groups formed in the chain; the spectra can be used for revealing defects of this type in the structure of polytetrafluoroethylene (PTFE). The possibility of defects associated with the lateral CF₃ groups in the structure of PTFE and its low-temperature modifications is explained based on the calculated total energies of C_nF2 _n+2.Original Russian Text Copyright © 2004 by L. N. Ignatieva, A. Yu. Beloliptsev, S. G. Kozlova, and V. M. BuznikTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 632–643, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

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.     

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.     

Experimental Study of Capacitive RF <Emphasis Type="Italic">c</Emphasis>-C<Subscript>4</Subscript>F<Subscript>8</Subscript> Discharge with Synchrotron Vacuum Ultraviolet Photoionization Mass Spectrometry

Capacitive radio frequency (RF) discharge of c-C₄F₈ (octafluorocyclobutane) has been studied with synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry (PIMS) at 4 Torr and 33.33 kHz. Various free radicals and reactive intermediates have been identified through measurement of photoionization mass spectra and photoionization efficiency (PIE) spectra. CF₂=CF₂ is main product in the plasma, indicating that the dissociation of c-C₄F₈ into CF₂=CF₂ is one of prominent reactions in the present experimental conditions. The observation of large species including C₅F₈, C₅F₁₀ and C₆F₁₀ is presented in our work. Besides, the dependences of the signals of neutral species in the discharge of c-C₄F₈ on RF power are presented in this paper.     

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.     

Subsolidus phase diagram of binary system in the perovskite type layer compounds (<Emphasis Type="Italic">n</Emphasis>-C<Subscript>n</Subscript>H<Subscript>2n+1</Subscript>NH<Subscript>3</Subscript>)<Subscript>2</Subscript>MnCl<Subscript>4</Subscript>

The thermotropic phase transitions in the perovskite type layer compound (n-C₁₀H₂₁NH₃)₂MnCl₄ and (n-C₁₄H₂₉NH₃)₂MnCl₄ were synthesized and, at the same time, a series of their mixtures C₁₀Mn-C₁₄Mn were prepared. The experimental binary phase diagram of C₁₀Mn-C₁₄Mn was established by differential thermal analysis (DTA), IR and X-ray diffraction. In the phase diagram new material (n-C₁₀H₂₁NH₃)(n-C₁₄H₂₉NH₃)MnCl₄ and two eutectoid invariants were observed, two eutectic points temperatures are about 29.8 and 27.9°C. Contrasting other similar system, there are three noticeable solid solution ranges (α, β, γ) at the left and right boundary and middle of the phase diagram.     

Liquid-liquid equilibrium in the-<Emphasis Type="Italic">n</Emphasis>-heptane-<Emphasis Type="Italic">n</Emphasis>-perfluorohexane system

The shape of the liquid-liquid coexistence curve in the C₇H₁₆-C₆F₁₄ system in the molar concentration-temperature coordinates close to the critical solution point was studied by narrow-beam gamma-raying of two-phase samples. The molar volumes of the coexisting liquid phases and critical point coordinates (critical temperature T _c = 316.266 ± 0.03 K and critical concentration x _c = 39.0 ± 0.4 mol % C₆F₁₄) were determined. The critical index β of the coexistence curve was found to be 0.322 ± 0.005. The diameter of the coexistence curve did not obey the classic “rectilinear diameter rule.”     

Mass spectrometric determination of the electron affinity of C<Subscript>60</Subscript>(CF<Subscript>3</Subscript>)<Subscript>10</Subscript> and C<Subscript>60</Subscript>(CF<Subscript>3</Subscript>)<Subscript>12</Subscript> molecules

Knudsen cell mass spectrometry was used to study ion-molecular electron exchange reactions between some trifluoromethyl derivatives of C₆₀ fullerene. Electron affinity values were experimentally determined for C₆₀(CF₃)₁₀ and the S ₆ isomer of C₆₀(CF₃)₁₂ and compared with the results of calculations and the data in the literature.     

Synthesis of 3<Emphasis Type="Italic">d</Emphasis>-3<Emphasis Type="Italic">d</Emphasis> heterometallic 4-amino-1,2,4-triazole complex with the structure depending on the reaction time

One-pot reaction containing Zn(NO₃)₂, Cd(NO₃)₂, NH₄SCN, and 4-amino-1,2,4-triazole (Atrz) proceeded by refluxing for different periods and gave different products. When the mixture was refluxed for 1 h, the product was a 1D chain polymer [Cd(Atrz)₂(SCN)₂] _n . However, when the refluxing time was increased to 3 h, a novel 3D 3d-3d heterometallic framework complex [Cd_2.84Zn_2.16(Atrz)₆(SCN)₁₀] · 4H₂O (I) with 6⁶ topology was obtained. The fluorescent property of I in the solid state was discussed.     

Low temperature radiolysis of fullerene C<Subscript>60</Subscript> and its solutions in isopropylbenzene and <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone

Low-temperature (77 K) radiolysis of solid fullerene C₆₀ and its glassy solutions in isopropylbenzene (IPB) and N-vinylpyrrolidone (N-VP) has been investigated with the use of ESR spectroscopy. Radiationchemical yields for the formation of paramagnetic centers (G _PMC, 1/100 eV) have been determined to be ∼0.001 for pure fullerene and 0.3 and 0.7 for its solutions in IPB and N-VP, respectively. The low value of G _PMC for fullerene indicates a high stability of this form of carbon. The increase in G _PMC in solutions as compared to the pure solvents (0.15 for IPB and 0.3 for N-VP) indicates the sensitizing effect of C₆₀.     

Synthesis of 3<Emphasis Type="Italic">d</Emphasis>-3<Emphasis Type="Italic">d</Emphasis> heterometallic 4-amino-1,2,4-triazole complex with the structure depending on the reaction time

One-pot reaction containing Zn(NO₃)₂, Cd(NO₃)₂, NH₄SCN, and 4-amino-1,2,4-triazole (Atrz) was proceeded by refluxing for different periods and gave different products. When the mixture was refluxed for 1 h, the product was a 1D chain polymer [Cd(Atrz)₂(SCN)₂] _n . However, when the refluxing time was increased to 3 h, a novel 3D 3d-3d heterometallic framework complex [Cd_2.84Zn_2.16(Atrz)₆(SCN)₁₀] · 4H₂O (I) with 66 topology was obtained. The photoluminescence property of I in the solid state was discussed..     

Effect of free valence on the characteristics of internal rotation in <Emphasis Type="Italic">n</Emphasis>-alkyl radicals

A study of internal rotation in the radicals n-C _n H_2n+1C^·H₂, (2 ≤ n ≤ 7) was carried out for the case of rotation around the bonds not including the radical center. 21 potential functions of internal rotation V(φ) were calculated. The coefficients in V(φ) were shown to depend only on the immediate environment at the bond of rotation. Characteristics of internal rotation in n-alkyl radicals were compared with related parameters of the corresponding alkane molecules. The generalized function V _av(φ) with the coefficients defined only by the position of the bond of rotation in the hydrocarbon chain and possessing the transposition property were proposed. The functions V _av(φ) were recommended for the simulation of the structure and properties of large molecules containing hydrocarbon fragments. This work continues a systematic study on the characteristics of the internal rotation in the n-alkane molecules and the groups containing free valence in n-alkyl radicals.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

The solubility of fullerenes in <Emphasis Type="Italic">n</Emphasis>-alkanols-1

The isothermal and polythermal solubility of C₆₀ and fullerene mixture (60% C₆₀, 39% C₇₀, and 1% C_76–90) in unbranched saturated alcohols C₁–C₁₁ was studied over the temperature range 20–80°C. The isotherms and polytherms of solubility are presented and characterized.     

Synthesis of a conjugate of (<Emphasis Type="Italic">R</Emphasis>)-2,2-dichloro- <Emphasis Type="Italic">N</Emphasis>-(1-phenylethyl)acetamide with fullerene C<Subscript>60</Subscript>

The Bingel–Hirsch reaction of (R)-2,2-dichloro-N-(1-phenylethyl)acetamide with fullerene C₆₀ gave the corresponding methanofullerene, and its electrochemical and physical properties were studied. The electron-acceptor characteristics of the new compound were found to be similar to those of the known methanofullerene [60]PCBM.     

The thermodynamic properties of fullerene hydrides C<Subscript>60</Subscript>H<Subscript>2<Emphasis Type="Italic">n</Emphasis></Subscript>

The equilibrium geometric parameters and normal vibration frequencies of the C₆₀H₂, C₆₀H₁₈, and C₆₀H₆₀ molecules were determined using density functional theory at the B3LYP/6-31G* level. The results were used to calculate the thermodynamic properties of the substances in the ideal gas state. The heat capacity of crystalline hydrofullerenes was modeled and the enthalpies of their sublimation estimated. The thermodynamic parameters of the hydrogenation of fullerene C₆₀ were analyzed.     

Supramolecular systems based on alkylated <Emphasis Type="Italic">p</Emphasis>-sulfonatocalix[<Emphasis Type="Italic">n</Emphasis>]arenes: aggregation and catalytic and biological activity

Aggregation, catalytic activity, and the influence of alkylated p-sulfonatocalix[n]arenes (SCA; n = 4, 6, 8) on the energy exchange in cells of wheat roots were studied. In water SCA are surfactants, and their efficiency changes with an increase in the number of aromatic rings (n) and the length of hydrocarbon substituents (R) in the molecule. In the range of critical micelle concentration, SCA form micelles with an effective hydrodynamic diameter of ∼200 nm. The catalytic activity of micellar solutions of SCA (n = 4, 8; R = C₁₂H₂₅) in hydrolysis of ethyl 4-nitrophenyl chloromethylphosphonate (ENCP) decreases with an increase in n, whereas the binding constant of ENCP increases. The modifying effect of SCA on the membranes and the energy exchange in cells of wheat roots was revealed: the membranotropic activity of SCA increases with an increase in the hydrophobicity of substituents R and the macrocycle size.     

Size effect of fullerene cages and encaged clusters in M<Subscript>3</Subscript>N@C<Subscript>2<Emphasis Type="Italic">n</Emphasis></Subscript>

Based on the calculated findings that the sizes of encaged clusters determine the structures and the stability of C₈₀-based trimetallic nitride fullerenes (TNFs), more extensive density functional theory calculations were performed on M₃N@C₆₈, M₃N@C₇₈ and M₃N@C₈₀ (M=Sc, Y and La). The calculated results demonstrated that the structures and stability undergo a transition with the increasing of the sizes of the cages and clusters. Sc₃N is planar inside the three considered cages, Y₃N is slightly pyramidal inside C₆₈-6140 and C₇₈-5 and planar inside I_h C₈₀-7, however, La₃N is pyramidal inside all the three cages. Those cages with pyramidal clusters inside deformed considerably, compared with their parent cages. In these cases, the bonding of metallic atoms toward the cages does not play an important role, and the encaged cluster tends to be located inside the cages with the largest M-M and M-C distances so that the strain energy can be released mostly. These calculations revealed the size effect of fullerene cages and encaged clusters, and can explain the position priority of M3N inside fullerene cages and the differences in yield of M₃N@C_2n . Supported by the Southwest University, China (Grant No. SWNUB2005002)