Synthesis and characterization of positively charged pentacationic [60]fullerene monoadducts for antimicrobial photodynamic inactivation

We designed and synthesized two analogous pentacationic [60]fullerenyl monoadducts, C₆₀(>ME₁N₆⁺C₃) (1) and C₆₀(>ME₃N₆⁺C₃) (2), with variation of the methoxyethyleneglycol length. Each of these derivatives bears a well-defined number of cationic charges aimed to enhance and control their ability to target pathogenic Gram-positive and Gram-negative bacterial cells for allowing photodynamic inactivation. The synthesis was achieved by the use of a common synthon of pentacationic N,N′,N,N,N,N-hexapropylhexa(aminoethyl)amine arm (C₃N₆⁺) having six attached propyl groups, instead of methyl or ethyl groups, to provide a well-balanced hydrophobicity-hydrophilicity character to pentacationic precursor intermediates and better compatibility with the highly hydrophobic C₆₀ cage moiety. We demonstrated two plausible synthetic routes for the preparation of 1 and 2 with the product characterization via various spectroscopic methods.