Density Functional Theory Study on the Decay of Fullerenyl Radicals RC60•, ROC60•, and ROOC60• (R = tert-Butyl and Cumyl) and Polarizability of the Formed Fullerene Dimers

The Triumph of the Spin Chemistry of Fullerene C60 in the Light of Its Free Radical Copolymerization with Vinyl Monomers

The spin theory of fullerenes is taken as a basis concept to virtually exhibit a peculiar role of C60 fullerene in the free radical polymerization of vinyl monomers. Virtual reaction solutions are filled with the initial ingredients (monomers, free radicals, and C60 fullerene) as well as with the final products of a set of elementary reactions, which occurred in the course of the polymerization. The above objects, converted to the rank of digital twins, are considered simultaneously under the same conditions and at the same level of the theory. In terms of the polymerization passports of the reaction solutions, a complete virtual picture of the processes considered is presented.

Attaching a Dipeptide to Fullerene as an Antioxidant Hybrid against DNA Oxidation

Emerging evidence has revealed that oxidative damages of DNA correlate with the pathogenesis of some diseases, and numerous investigations have also suggested that supplementation of antioxidants is beneficial for keeping health by rectifying in vivo redox status. Here, we construct antioxidative dipeptides with the Ugi four-component reaction (comprising p-aminobenzyl alcohol, benzaldehyde, or vanillin, a series of antioxidative carboxylic acids and isocyanides as reagents) and then attempt to attach the dipeptides to [60]fullerene by the Bingel reaction. However, this endeavor does not lead to the amelioration of the radical-scavenging property because abilities of fullerenyl dipeptides to trap 2,2'-diphenyl-1-picrylhydrazyl and galvinoxyl radicals are still dependent upon the phenolic hydroxyl group in the dipeptide scaffold rather than upon the fullerenyl group. Alternatively, when the obtained fullerenyl dipeptides are evaluated in a peroxyl radical-induced oxidation of DNA, it is found that introducing a fullerene moiety into dipeptide enables antioxidative effect to be enhanced 20-30% because the fullerene moiety facilitates the corresponding dipeptide to intercalate with DNA strands, and thus, to increase the antioxidative efficacy. Our results suggest that connecting an antioxidative skeleton with the hydrophobic fullerene moiety might lead to a series of novel antioxidant hybrids applied for the inhibition of DNA oxidation.

The Influence of the Substitution of Transition Metals on Pristine C20: A DFT Study

The stabilities and reactivities of two transition metal ([Formula: see text], Zn)-doped structures of C[Formula: see text] fullerene have been investigated by density functional theory approach. We have observed a noticeable structural change in pristine C[Formula: see text] due to the substitution of one of its carbon atom by Cu or Zn atom. From our findings, it is found that the energy gap of C[Formula: see text]Cu and C[Formula: see text]Zn increases with respect to pristine C[Formula: see text], thus making the two doped fullerenes more stable than their pristine counterpart. The reactivity parameters such as chemical hardness, chemical potential and electrophilicity index for these structures are also studied. Interestingly, our calculations reveal that both the doped fullerenes obey the maximum hardness principle and minimum electrophilicity principle. Also, from the electronic absorption spectra analysis, it can be inferred that the maximum absorption peak of the two heteroatom-substituted fullerenes C[Formula: see text]Cu and C[Formula: see text]Zn are shifted towards the longer wavelength region as compared to the pure C[Formula: see text] fullerene, which clearly indicates that a red shift is introduced on account of doping.

Regioisomer effects of [70]fullerene mono-adduct acceptors in bulk heterojunction polymer solar cells

Regioisomer separations of [70]fullerene mono-adducts for polymer solar cell (PSC) applications were conducted for the first time.

Despite numerous organic semiconductors being developed during the past decade, C₇₀ derivatives are predominantly used as electron acceptors in efficient polymer solar cells (PSCs). However, as-prepared C₇₀ mono-adducts intrinsically comprise regioisomers that would mask individual device performances depending on the substituent position on C₇₀. Herein, we separate the regioisomers of C₇₀ mono-adducts for PSC applications for the first time. Systematic investigations of the substituent position effect using a novel symmetric C₇₀ mono-adduct ([70]NCMA) and a prevalent, high-performance one ([70]PCBM) reveals that we can control the structures of the blend films with conjugated polymers and thereby improve the PSC performances by regioisomer separation. Our approach demonstrates the significance of exploring the best-matching regioisomer of C₇₀ mono-adducts with high-performance conjugated polymers, which would achieve a remarkable progress in PSC devices.

Comment on "Fullerene-based materials for solar cell applications: design of novel acceptors for efficient polymer solar cells--a DFT study" by A. Mohajeri and A. Omidvar, Phys. Chem. Chem. Phys., 2015, 17, 22367

Though a linear correlation has been recently reported between mean polarizabilities of the fullerene derivatives and open-circuit voltages of organic solar cells based on them, we demonstrate that there is no general dependence between these two values and some related quantities (anisotropy of polarizability and LUMO levels).

Reply to the 'Comment on "Fullerene-based materials for solar cell applications: design of novel acceptors for efficient polymer solar cells--a DFT study"' by D. S. Sabirov, A. O. Terentyev and I. S. Shepelevich, Phys. Chem. Chem. Phys., 2016, DOI

It is possible to predict the photovoltaic performance of fullerene derivatives based on their electronic/magnetic properties.

A mechanistic study of manganese(iii) acetate-mediated phosphonyl group additions to [60]- and [70]-fullerenes: the oxidative-ion-transfer mechanism vs. free radical addition

The phosphonylation of fullerenes with HP(O)(OAlk)₂ and Mn(OAc)₃·2H₂O occurs via the oxidative-ion-transfer mechanism involving the intermediate Mn(OAc)₂P(O)(OAlk)₂ rather than by the free radical process.

Activation energies and information entropies of helium penetration through fullerene walls. Insights into the formation of endofullerenes nX@C60/70 (n = 1 and 2) from the information entropy approach

In the present study, we calculate the activation barriers and information entropies of helium penetration into the C₆₀ and C₇₀ fullerenes resulting in the singly and doubly filled endofullerenes He_n@C_60/70 (n = 1 and 2).

Counting the Isomers and Estimation of Anisotropy of Polarizability of the Selected C60 and C70 Bisadducts Promising for Organic Solar Cells

Currently, bisadducts of C60 and C70 fullerenes are widely studied as electron-acceptor materials for organic solar cells. These compounds are usually used as mixtures of the positional isomers. However, as recently shown, the separate use of the purified isomers with lowest anisotropies of polarizability may enhance solar cell output parameters. To predict the structures of the compounds appropriate for this purpose, we calculated anisotropies of polarizability of four classes of fullerene bisadducts, namely, bis-[60]PCBM, [60]OQMF, bis-[70]PCBM, and [70]OQMF (18, 16, 41, and 42 positional isomers, respectively). As found, the anisotropies quadratically correlate with the interaddend distances in fullerene bisadducts, whereas there are no obvious correlations between the structures and lowest unoccupied molecular orbital levels, traditionally used for assessing the efficiency of candidates for organic solar cell electron acceptors. According to our calculations, bisadducts bis-[60]PCBM-ee-1, [60]OQMF-cis-3.2, [60]OQMF-trans-4.2, cc(1.1)cc(2'.1)-bis-[70]PCBM, and cc1cc(2'.1)-[70]OQMF have the lowest anisotropies of polarizability. These compounds have a primary interest for synthesis, purification, and further separate testing in solar cells. The structures of these adducts have a common feature, which we describe with the "not so close and not so far" rule: the distances between the addends in the most isotropic fullerene bisaddicts should be medium among the possible values. These are ee, ef, cis-3, and trans-4 positions in the case of the C60 bisadducts and cc bonds placed on the different poles and the same hemisphere of the C70 skeleton.

Information Entropy of Fullerenes

The reasons for the formation of the highly symmetric C60 molecule under nonequilibrium conditions are widely discussed as it dominates over numerous similar fullerene structures. In such conditions, evolution of structure rather than energy defines the processes. We have first studied the diversity of fullerenes in terms of information entropy. Sorting 2079 structures from An Atlas of Fullerenes [ Fowler , P. W. ; Manolopoulos , D. E. An Atlas of Fullerenes ; Oxford : Clarendon , 1995 . ], we have found that the information entropies of only 14 fullerenes (<1% of the studied structures) lie between the values of C60 and C70, the two most abundant fullerenes. Interestingly, buckminsterfullerene is the only fullerene with zero information entropy, i.e., an exclusive compound among the other members of the fullerene family. Such an efficient sorting demonstrates possible relevance of information entropy to chemical processes. For this reason, we have introduced an algorithm for calculating changes in information entropy at chemical transformations. The preliminary calculations of changes in information entropy at the selected fullerene reactions show good agreement with thermochemical data.

Polarizability as a landmark property for fullerene chemistry and materials science

The review summarizes data on dipole polarizability of fullerenes and their derivatives, covering the most widespread classes of fullerene-containing molecules (fullerenes, fullerene exohedral derivatives, fullerene dimers, endofullerenes, fullerene ions, and derivatives with ionic bonds).