Mechanisms of supramolecular ordering of water-soluble derivatives of fullerenes in aqueous media

Abstract

Fullerenols C₆₀(OH)_X and C₇₀(OH)_X (X ∼ 30) have been studied in aqueous solutions at the concentrations 0.05–22wt% by X-ray and neutron scattering and using modeling hydroxyls’ arrangements on carbon cages to explain the molecular assembly defined by hydrophobic and hydrophilic interactions of molecules. In the case of C₆₀ quantum chemical calculations minimizing molecular energy for different configurations of OH-groups on the carbon cages showed their preferred localization at C₆₀ spheroids’ equatorial zone and at the opposite poles. However, less symmetric hydroxyls’ localization on C₇₀ molecules was found since hydroxyls do not create closed chains on them. As a result, the molecules C₆₀(OH)_X are associated into primary chain-like aggregates (∼20 units, few nanometers in size) more likely in water than the fullerenols C₇₀(OH)_X forming similar groups of lower aggregation degree. For C₆₀(OH)_X and C₇₀(OH)_X the peculiarities in hydroxyls’ grafting affected a coordination of primary groups integrated into secondary and tertiary structures at the distances R ∼ 5 nm and R ∼ 30 nm at the concentrations C > 5wt% and C > 10wt%, respectively. The discovered mechanism of fullerenols’ assembly in water will facilitate their use in chemistry and biomedicine.

Keywords:

• Fullerene
• solution
• structure

Acknowledgments

Authors are thankful to I. N. Ivanova, L. I. Lisovskaya, M. V. Suyasova, and D. N. Orlova for technical assistance.

Additional information

Funding

The work was supported by Russian Foundation for Basic Researches (grant no. 18-29-19008).