Water Entrapped inside Fullerene Cages: A Potential Probe for Evaluation of Bond Polarization

• Published in: Angewandte Chemie (International ed.) Vol. 55; no. 42; pp. 13109 - 13113
• Main Authors: Hashikawa, Yoshifumi, Murata, Michihisa, Wakamiya, Atsushi, Murata, Yasujiro
• Format: Journal Article
• Language: English
• Published: Germany Blackwell Publishing Ltd 10.10.2016; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: bond polarization; Buckminsterfullerene; Cages; Chemical bonds; Chemical reactions; Covalence; Covalent bonds; Electronegativity; Evaluation; Fullerenes; NMR spectroscopy; Polarization; Potential probes; relaxation times; water; fullerenes; relaxation times; NMR spectroscopy; water; bond polarization
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201607040

The concept of the bond polarization is a useful tool to understand chemical reactions and fundamental properties of compounds. However, experimental considerations are limited owing to its difficulty of reliable description. We demonstrated that geometrically isolated H2O inside the cage of fullerene C60 is a possible probe to evaluate the polarization degree of covalent bonds C(C60)−X (X=heteroatom) on the C60 cage. The 1H NMR relaxation times of entrapped H2O have been systematically measured at variable temperatures for H2O@C60X (X=CR2, NR, O, and O2). The results followed in the order of electronegativities of C (2.55), N (3.04), and O (3.44), indicating that entrapped H2O can sensitively respond to the degree of the bond polarization. It's a trap: Bond polarization is a useful parameter for understanding and considering reaction mechanisms and products. C−X bonds on the C60 cage affect the electrostatic environment inside the cage, resulting in changes in dynamic behavior of entrapped H2O. This difference can be detected by 1H NMR relaxation times of entrapped H2O, which correlate with the degree of bond polarization.