Synthesis of a distinct water dimer inside fullerene C70

• Published in: Nature chemistry Vol. 8; no. 5; pp. 435 - 441
• Main Authors: Zhang, Rui, Murata, Michihisa, Aharen, Tomoko, Wakamiya, Atsushi, Shimoaka, Takafumi, Hasegawa, Takeshi, Murata, Yasujiro
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2016; Nature Publishing Group
• Subjects: 119/118; 140/131; 140/58; 639/638/403; 639/638/541/965; 639/925/357/73; Analytical Chemistry; Biochemistry; Carbon; Chemical speciation; Chemistry; Chemistry/Food Science; Fullerenes; Hydrogen; Hydrogen bonds; Inorganic Chemistry; Organic Chemistry; Physical Chemistry; X-ray diffraction; Japan
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/nchem.2464

The water dimer is an ideal chemical species with which to study hydrogen bonds. Owing to the equilibrium between the monomer and oligomer structure, however, selective generation and separation of a genuine water dimer has not yet been achieved. Here, we report a synthetic strategy that leads to the successful encapsulation of one or two water molecules inside fullerene C 70 . These endohedral C 70 compounds offer the opportunity to study the intrinsic properties of a single water molecule without any hydrogen bonding, as well as an isolated water dimer with a single hydrogen bond between the two molecules. The unambiguously determined off-centre position of water in (H 2 O) 2 @C 70 by X-ray diffraction provides insights into the formation of (H 2 O) 2 @C 70 . Subsequently, the 1 H NMR spectroscopic measurements for (H 2 O) 2 @C 70 confirmed the formation of a single hydrogen bond rapidly interchanging between the encapsulated water dimer. Our theoretical calculations revealed a peculiar cis -linear conformation of the dimer resulting from confinement effects inside C 70 . Endohedral C 70 fullerenes containing either one or two water molecules have now been prepared using a molecular-surgery approach. The structure of H 2 O@C 70 was determined by single-crystal X-ray analysis, revealing the encapsulated water molecule to be in an off-centre position. In (H 2 O) 2 @C 70 , the two water molecules form a discrete dimer held together with a single hydrogen bond.