Molecular structures and thermochemistry of the derivatives of C<Subscript>24</Subscript> fullerene by attaching a variety of chemical groups

A series of exohedrally functionalized derivatives of the D ₆-symmetrical C₂₄ fullerene, with attached -CH₂OH, -CONH₂, -COOH, and -COH chemical groups, have been investigated by using density-functional theory approach at the UB3LYP/6-31G(d) level. According to the calculated results, the C₂₄(COOH) is the most stable structure, with −73.58 kcal mol⁻¹ value for the functionalization reaction energy and 3.16 eV for the dissociation energy, while C₂₄(CONH₂) displays the largest dipole moment (3.09 D). It was also found that the HOMO-LUMO energy gaps, the vertical ionization potentials (VIP), and vertical electron affinities (VEA) of these functionalized derivatives are similar to those of the more stable C₂₄ fullerene. Moreover, their corresponding HOMO and LUMO orbitals are mainly associated with the surface of the cage. Also, the vibrational frequencies of these derivatives are discussed. It was concluded that it would be possible to produce novel species for bio-medical applications by attaching selected chemical groups.     

Theoretical studies of C60/C70 fullerene derivatives: C60O and C70O

A semiempirical (AM1) calculation on the structures and stabilities of isomers of the fullerene derivatives C₆₀O and C₇₀O is carried out. The ozonolysis reaction mechanism and the thermodynamics of the compounds are studied. The two isomers of C₆₀O (56 bond and 66 bond) formed by an oxygen atom bridging across a C-C bond have an epoxide-like or an annulene-like structure. According to the ozonolysis reaction mechanism and kinetic factor analysis, the possible products of this ozonolysis reaction are C₆₀O with oxygen bridging over the 66 bond (C_2v) as an epoxide-like isomer and that with oxygen bridging over the 56 bond (C_s) as an annulene-like isomer. Further, the sixteen isomers of C₇₀O (both epoxide-like and annulene-like structures) have been studied with respect to the same reaction mechanism. The most possible product in this ozonolysis reaction contains oxygen bridging across in the upper part (66 bond in C₇₀O-2 or C₇₀O-4) as an epoxide-like structure. The other possible product is C₇₀O-8 (annulene-like structure), in which oxygen bridges across an broken equatorial CC bond in C₇₀ (D_5h). The vibrational frequency analysis and the electronic structure of the selected C₆₀O and C₇₀O isomers are generated for experimental characterisation. The experimental results indicate that C₆₀O and C₇₀O may decompose into the odd number fullerenes C₅₉ and C₆₉. We therefore studied the structures of C₅₉ and C₆₉ also.     

Theoretical study of fullerene derivatives: C40H4 and C40X4 cluster molecules

Herein we demonstrate that the C₄₀ cluster molecule is easily formed to T_d symmetry structure and its ground state is ⁵A₂ open shell with four unpaired electrons. These four unpaired electrons are located at the tip points of the T_d symmetry structure. This work also indicates that these four unpaired electrons can easily react with a single valence atom, such as hydrogen or halogen atoms, to form a stable carbon hydrogen cluster molecule, C₄₀H₄, and carbon halogen cluster molecules, C₄₀X₄ (X=F, Cl, Br, I), respectively. The PM3 semiempirical molecular orbital method from Gaussian 94W computer program package was applied very well to these cluster molecules. According to the results in this study, the structures of geometrical optimization, ionization potential, energy gap, heat of formation, atomization energy, vibration frequency, and the remaining data of C₄₀H₄ and C₄₀X₄ cluster molecules. The above-calculated data prove that these unknown cluster molecules are stable and have a stable capacity similar to 1,3,5,7-tetrahaloadamantane molecules. They can be possibly synthesized experimentally in the near future. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 273–284, 1998     

Theoretical study of fullerene derivatives: C28H4 and C28X4 cluster molecules

Based on the basic theory of C₂₈ cluster molecule proven by H. W. Kroto and the research findings of C₂₈'s derivative such as Ti@C₂₈* and Mg@C₂₈, proven by T. Guo, B. I. Dunlap, O. D. Haberlen, and others, we examine the two series fullerene derivatives, C₂₈H₄ and C₂₈X₄ cluster molecules, which are formed by the skeleton of C₂₈ cluster molecule. In this work, we not only prove that C₂₈ cluster molecule belongs to the T_d symmetry structure and its ground state is ⁵A₂ open-shell with four unpaired electrons, but also find that C₂₈ can easily react with single valence electron atoms, like hydrogen atom and halogen atoms, to be formed to stable fullerene derivatives, C₂₈H₄ and C₂₈X₄ cluster molecules (X=F, Cl, Br, I). The PM3 semiempirical molecular orbital method from G94W and Hyperchem program packages were applied very well in these fullerene derivatives. According to the results presented herein, we obtain the structures of geometrical optimization, ionization potential energy gap, heat of formation, atomization energy, and vibration frequency data of the C₂₈H₄ and C₂₈X₄ cluster molecules. The above calculation data confirm that these unknown fullerene derivatives are stable molecules; the stable behavior resembles the 1,3,5,7-tetrahaloadamantane molecules. It is quite possible that they can be synthesized experimentally in the near future. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 187–197, 1998     

Theoretical studies of growth mechanism of small fullerene cage C24 (D6d)+

The ring‐collapse mechanism of C₂₄ (D_6d) has been analyzed using semiempirical AM1 and B3LYP/cc‐pVDZ methods. Based on the ring‐stacking/circumscribing model, two precursors are selected. Transition states and intermediates are located and energetics are computed. Before the stacking begins, the precursor and belt reach a suitable relative orientation accompanied by the release of a large amount of energy. It is observed that the reactions between the precursors and the belts are essentially endoergic in nature, whereas the reactions between the stable intermediates and the final belts are exoergic. The deformation energies (DE) and the bond lengths R of the precursors have been computed. The DE values suggest that there is a chance of the cleavage of the bicyclic precursors as the growth process proceeds toward the cage formation. In contrast, the monocyclic precursor is found to have lower deformation energies than the bicyclic precursor. Analysis of average bond length at different cages shows that a large window is formed and the system appears to follow a cascade‐type bond formation. Comparisons are made to our previous results on C₂₈ growth. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

C36衍生物C36H12和C36X12簇分子的理论研究

采用从虎ＨＦ／ＳＴＯ－３Ｇ方法,对３６及其衍生物Ｃ３６Ｈ１２和Ｃ３６Ｘ１２（Ｘ＝Ｆ,Ｃｌ,Ｂｒ,Ｉ）进行计算研究,讨论了Ｃ３６Ｈ１２和Ｃ３６Ｘ１２簇分子几何结构随卤素Ｘ原子序数变化的规律,分子的稳定性及电荷转移情况,结果表明,Ｃ３６Ｈ１２和Ｃ３６Ｆ１２在所有簇分子中是较为稳定的。     

Theoretical studies of structures and stabilities of a new odd-numbered fullerene dimer: C141

The possible isomers of a newly synthesized C(141) molecule are calculated using MNDO, AM1, PM3, B3LYP/3-21G, and B3LYP/6-31G(d) methods. The geometry optimizations showed that the isomer 8-8 has the lowest total energy in all 64 possible structures of C(141). Unlike those of C(130), C(140), etc., the C(141) 8-8 shows a new structure: two C(70) side cages open [6.6] ring junctions located at the equator (instead of cap) area to create new chemical bonds for the bridge atom. Theoretical measurements of the average length of the long and short axes of C(70) side cages in the C(141) molecule reveal that when two C(70) cages are connected with each other at the equators, their geometric shapes become more spherical compared with the pristine C(70); this leads to a reduction of the molecular polarizability. Analysis of the local and global strain indicates that the global strain of C(70) monomer in the C(141) 8-8 is greatly reduced compared to the pristine C(70). The stable C(70) derivatives that are formed with reacted C-C bonds in the equator area may put new insights into fullerene chemistry, in particular, for C(70) to react with a large molecule. The results are discussed together with the experimental data.     

Theoretical investigation of functionalized fullerene nano carrier drug delivery of fluoxetine

In recent years, fullerene nanoparticles have received extensive attention due to their unique physical and chemical properties. Properly modified fullerene nanoparticles have excellent biocompatibility and significant anti-tumor activity and anti-depression, which makes them have broad application prospects in the field of cancer anti-depression. The present study used the density functional theory (DFT) calculations to perform a theoretical examination of the interaction of fluoxetine (F) as medicine with the functionalized fullerene O and NO (F–O and F–NO surface in gas phase physiological media. According to DFT calculations, adsorption energies were ?3396.6350645, ?3540.2952907, ?6778.526894, and ?6952.251487 kJ for F/P complexes (fullerene O and NO (F–O and F–NO surface) respectively, proposing the possibility of the adsorption process of F molecule onto the fullerene surface concerning the energetic perspective. Calculations of electronic parameters aimed at determining the molecule's reactivity. Bandgap of F–O and F–NO were 0.03715, 0.04328 respectively, by this value we can recognize the reactivity of complexes.     

Quantum chemical calculations of the molecular structures of hybrid amino acid derivatives of fullerene C60

The stereoselectivity of the formation of hybrid amino acid derivatives of fullerene (AADF) C₆₀ was studied. The energies of the model addition reactions C₆₀ + n C₂H₆ ? Me _n -C₆₀-Me _n (1) and C₆₀ + n EtNC₄H₇Me ? Et _n -C₆₀-(NC₄H₇Me) _n (2) (n = 1–3) were calculated by the DFT method B3LYP/6-31G*. The most stable products of reaction (1) are hexamethylated fullerene derivatives in which five Me groups are arranged in the form of a regular pentagon. Among the AADF obtained by reaction (2), 1,4-disubstituted fullerene isomers are most stable. The molecular structures of such isomers were calculated for six biologically active hybrid AADF; the solvent contact areas of these molecules were evaluated.     

Polyadducts of fullerene C60 with tert-butyl groups

New soluble fullerene derivatives Bu^t _n C₆₀ were synthesized by the reaction of C₆₀M _n (THF) _x (M = Li, Na; n = 4, 6, 8, 10, 12) with tert-butyl bromide ButBr. The thus obtained compounds were characterized by spectroscopic methods (IR and NMR spectroscopy), mass spectrometry (MALDI), elemental analysis, and quantum chemical calculations. HPLC was used for chromatographic separation of the products of the reaction of C₆₀Na _n (THF) _x (n = 4, 6, 8, 12) with Bu^tBr. It was found that Bu^t ₄C₆₀ and Bu_t ⁶C₆₀ decompose on the column. A complex of physicochemical methods of analysis was used for establishing compositions of individual fractions of chromatographic separation of Bu^t ₄C₆₀. The structure of one of the components was determined as 1-tert-butyl-1,2-dihydrofullerene 1,2-Bu^tC₆₀H.     

Convergent synthesis of a polyfunctionalized fullerene by regioselective five-fold addition of a functionalized organocopper reagent to C60

[reaction: see text] A method for one-step preparation of polyfunctionalized fullerene derivatives by regioselective penta-addition of an organocopper reagent is described. A functionalized aryl iodide is first converted to the corresponding Grignard reagent and then to a copper reagent and finally is allowed to react with C(60). The method allows introduction of five functional groups to the C(60) skeleton in a convergent manner. The shuttlecock-like molecules crystallize into a columnar packing structure.     

Highly selective reactions of C60Cl6 with thiols for the synthesis of functionalized [60]fullerene derivatives

Chlorofullerene C(60)Cl(6) undergoes highly selective reactions with thiols forming compounds C(60)[SR](5)H with high yields. These reactions open up straightforward synthetic routes to many functionalized fullerene derivatives, e.g. water-soluble compounds showing interesting biological activities.     

Theoretical studies of isomers of C3H2 using a multiconfigurational approach

 The C₃H₂ isomers are important molecules in interstellar space. An understanding of their electronic structure can contribute significantly to the interpretation of interstellar spectra. In a theoretical study of the C₃H₂ isomers a multiconfigurational treatment is of interest because many of the isomers are carbenes or diradicals. We present such an investigation of all possible C₃H₂ isomers. The most important features of their electronic and vibrational spectra are calculated. Earlier theoretical studies are reviewed and it is shown that the present study yields the same order of stability for the singlet and triplet states as most previous studies. Received: 25 January 2000 / Accepted: 26 April 2000 / Published online: 18 August 2000     

QSAR studies of phenylhydrazine-substituted tetronic acid derivatives based on the 1H NMR and 13C NMR chemical shifts

The quantitative structure–activity relationship models of 40 phenylhydrazine-substituted tetronic acid derivatives were established between the ¹H nuclear magnetic resonance (NMR) and ¹³C NMR chemical shifts and the antifungal activity against Fusarium graminearum, Botrytis cinerea, Rhizoctonia cerealis, and Colletotrichum capsici. The models were validated by R, R², R_A², variance inflation factor, F, and P values testing and residual analysis. It was concluded from the models that the ¹³C NMR chemical shifts of C8, C10, C7, and the ¹H NMR chemical shifts of Ha contributed positively to the activity against Fusarium graminearum, Botrytis cinerea, Colletotrichum capsici, and Rhizoctonia cerealis, respectively. The models indicated that decreasing the election cloud density of specific nucleuses in compounds, for example, by the substituting of electron withdrawing groups, would improve the antifungal activity. These models demonstrated the practical application meaning of chemical shifts in the quantitative structure–activity relationship study. Furthermore, a practical guide was provided for further structural optimization of the antifungal phenylhydrazine-substituted tetronic acid derivatives based on the ¹H NMR and ¹³C NMR chemical shifts.     

Photocurrent increase by doping a liquid crystal host with a functionalized fullerene

Doping a photoconductive mesogenic material with a small amount of functionalized fullerene significantly increases the photocurrent. LESR studies show the appearance of a long-lived charge-separated state under light illumination, with a negative charge on the fullerene moiety. This confirms that in the system studied the fullerene unit acts as an electron trap. In the lamellar structure of the liquid crystalline phase the fullerene units and mesogenic cores are separated, which ensures better space separation between negative and positive charges. As a result the charge recombination is slowed and the photocurrent is amplified.     

Self-organization of poly(methyl methacrylate) and polystyrene macromolecules functionalized by fullerene C60

Poly(methyl methacrylate) and polystyrene functionalized by fullerene C₆₀ tend to form micellar structures comprising a fullerene cluster as a core and a macromolecular shell. Films prepared from PMMA-C₆₀ and PS-C₆₀ micellar solutions are polymer matrices with fullerene-containing globular structures uniformly distributed in the polymer bulk.     

Geometry and stability of fullerene cages: C24 to C70

The electronic structures and geometries of all even carbon fullerenes were investigated theoretically using density functional theory (DFT) at the B3LYP/6‐31G* level. Based on geometries, energies, and aromaticities, the potential relationship between geometry factors and stability has been investigated systematically. The extra stability of C₆₀ has been confirmed by the shorter average bond length, smaller angle strain, widest energy gap, larger binding energy, and dissociation energy. Furthermore, C₃₂ and C₅₀ are predicted to have higher aromaticity due to larger negative nucleus independent chemical shift (NICS) values, whereas C₆₀ displays a weak aromaticity. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Continuous symmetry of C60 fullerene and its derivatives

Conventionally, the I(h) symmetry of fullerene C(60) is accepted, which is supported by numerous calculations. However, this conclusion results from the consideration of the molecule electron system, of its odd electrons in particular, in a closed-shell approximation without taking the electron spin into account. Passing to the open-shell approximation has led to both the energy and the symmetry lowering up to C(i). Seemingly contradicting to a high-symmetry pattern of experimental recording, particularly concerning the molecule electronic spectra, the finding is considered in this Article from the continuous symmetry viewpoint. Exploiting continuous symmetry measure and continuous symmetry level approaches, it was shown that formal C(i) symmetry of the molecule is by 99.99% I(h). A similar continuous symmetry analysis of the fullerene monoderivatives gives a reasonable explanation of a large variety of their optical spectra patterns within the framework of the same C(1) formal symmetry exhibiting a strong stability of the C(60) skeleton. TOC color pictures present chemical portrait of C(60) in terms of atomic chemical susceptibility (Sheka, E. Fullerenes: Nanochemistry, Nanomagnetism, Nanomedicine, Nanophotonics; CRC Press: Taylor and Francis Group, Boca Raton, 2011).