Solubility fullerenes

Bezmelnitsin V N, Eletskii A V and Stepanov E V 1994 Cluster origin of fullerene solubility J. Phys. Chem. 98 6665-7... 

Previously (Cataldo and Braun, 2007), it has been noted the interesting correlation between C60 fullerene solubility and the unsaturation level of the fatty acids present in the vegetable oils and measured by the iodine number , an analytical test, which determines the number of double bonds present in the oil by the addition of iodine (Martinenghi, 1963). This correlation is confirmed for C also with the new measurements and is extendable also to C, . The correla-tion is shown in Fig. 13.1 and suggests that the solubility S expressed in milligrams per litre (mg/1) is linked to the iodine number of the oil (NI) according to the following equations ... 

At first glance the relationship between fullerene solubility and fatty acids unsaturation may appear as a surprise. However, it should be noticed that the unsaturation level of vegetable oils correlates also with their refractive index (Martinenghi, 1963). Thus, following the approach of Sivaraman et al. (1994), it is possible to show the change in solubility as function of the polarizability parameter of the solvent defined as ... 

Fig. 14.1 A plot of experimental versus calculated (with equation (14.3)) values of fullerene solubility for the training set...

Theoretical calculation potentialities have been examined in few chapters, giving new instruments to predict fullerene solubility in different solvents, such as fatty acid esters. Visualization approaches necessary to study unusual compounds such as CNT are herein presented. Despite the structural novelty of CNT, its resemblance to cellular structures is highlighted, launching or confirming the hypothesis of using CNTs as communication devices between cells. 

The organic modification of the fullerene, carried out according to many and diverse synthetic strategies, also accomplished the important task of increasing fullerene solubility and processability, since its derivatives are much more soluble than the pristine species in polar solvents or in aqueous media. 

When considering findings on Q)0 fullerene solubility in more detail, we have found that the rule "the similar dissolves in the similar" is not often obeyed. This is illustrated by the data given in Table 1. 

TABLE 1. Dipole moments of solvents and C6o fullerene solubility... 

As the table indicates, C6o fullerene solubility is practically the same in nonpolar benzene and polar pyridine. Like benzene, pyridine has a pronounced "aromatic" nature, i.e. electron distribution in a pyridine molecule is identical to that in benzene. However pyridine has a reasonable dipole moment as opposed to benzene. 

Experimental results given in Table 1 are only a small part of the available data. They suggest that C6o fullerene solubility in different classes of organic compounds is a complicated process. 

Analysis of the data on C6o fullerene solubility in methyl derivatives of benzene has revealed that this magnitude depends not only on the number of CH3-groups, but also on their position in the benzene core. Fig. 2-6 show the structural formulae for methyl derivatives of benzene, the positions of methyl groups and the magnitudes of C6o solubility [1],... 

Summing the presented data, one can write the following series (3) of methyl derivatives of benzene in which C60 fullerene solubility increases (Fig. 6) ... 

In further discussion of C60 fullerene solubility in benzene derivatives we will compare its magnitude with quantitative distribution of nitro isomers which form in the reactions of electrophilic substitution of the benzene derivative considered. 

TABLE 2. Isomer ratio (%) in the nitration of alkyl-benzenes and Q)0 fullerene solubility in alkyl-benzenes [34]... 

Figure 7. C6o fullerene solubility (mg ml1) in 1 - tret-butyl benzene 2 - isopropyl benzene 3 - ethyl benzene 4 - toluene, as a function of the amount of respective ortho-isomer (%) (= of the 7i-electron density in the orf/zo-position).

TABLE 4. C6o fullerene solubility in halogen derivatives of benzene... 

In addition, there exist other factors revealed by studies on C6o fullerene solubility. These factors conform to the requirements of a number of criteria, which were formulated on a basis of studies of charge-transfer processes, and enable identification of the charge transfer ... 

The found parallels between donor activity in a series of aromatic hydrocarbons, fullerene solubility in these hydrocarbons and their reactivity relative to electrophilic attack (series 2) will become regular if the process of C6o dissolution in aromatic hydrocarbons is considered as an intermediate stage for the reaction of electrophilic substitution in an aromatic series. 

The working solution for electrochemical studies on fullerenes must assure both good fullerene solubility and sufficient electrical conduction of the solution. Fullerenes dissolve readily in many benzene-type organic solvents including toluene in which fullerene solubility has been much studied. At room temperature the maximum solubility is as much as 2.8 mg-ml 1. 

Abstract. A comparative investigation of Cgo fullerene solubility and donor force of alkyl derivatives of benzene has been performed. Based on the found correlation, which was determined by current methods, between C60 solubility and donor force of solvents, it has been concluded that the process of C60 dissolution in aromatic hydrocarbons is a process of intermolecular interaction combined with charge-transfer and formation of complexes of the donor-acceptor type. The agreement between a series of physical and chemical phenomena (factors, properties) observed in studies of C60 solubility and a number of existing criteria which allow the phenomena to be inteipreted as a manifestation of the charge-transfer interaction substantiates our conclusion. 

Keywords fullerene, solubility, 71-complex, electrophilic substitution, atomatic hydrocarbons. 

An appreciable C60 fullerene solubility is observed in many solvents relating to different classes of organic compounds as evidenced by experimental results. The process of C6o dissolution in solvents of different chemical nature is mainly interpreted in the context of an old based on experience rule the similar dissolves in the similar . Different physical and chemical properties of substances are considered as the similarity factor. 

Based on a study of fullerene solubility [1], it has been found that C6o fullerene, being a nonpolar molecule, is insoluble in polar solvents, such as alcohol, acetone, tetrahydrofurane etc. Relying on the above, it has been concluded that the solvation mechanism of dissolving plays an insignificant part in the processes of fiillerene dissolution. 

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