Synthesis of Open‐Cage Fullerenes Containing a H‐Bond between the Encapsulated Water Molecule and the Amide Moiety on the Rim of the Orifice

Abstract

Further hydrolysis of an open‐cage fullerene derivative with an epoxy moiety on the rim of the orifice led to the formation of a new open‐cage fullerene with a 17‐membered orifice and an amide group directly above the orifice. The water encapsulation ratio in the new open‐cage compound reached 100 % as a result of heating with water at 80 °C. The amide group above the orifice completely blocks the opening and forms H‐bond with the trapped water molecule. Single crystal X‐ray structure shows that the bond length between the trapped water oxygen and the amide oxygen is 2.859 Å. The H‐bond energy is about −3.83 kcal/mol as shown by theoretical calculation.

Open-Cage Fullerene as a Macrocyclic Ligand for Na, Pt, and Rh Metal Complexes

“…Only the oxygen atom directed further away from the center of the cavity acted as the donor atom in the COO group. The other oxygen atom directed toward the center of the cavity showed weak H-bond interaction with the trapped water molecule. − The presence of the carboxylic group blocks the orifice and escape of the trapped water molecule. The O···O distance is 2.870(5) and 2.902(16) Å, and the H-bond energy was calculated as −3.99 and −4.25 kcal/mol for the heterodimer and homodimer, respectively.…”

Open‐Cage Fullerene as a Selective Molecular Trap for LiF/[BeF]+

“…Reduction of carbonyl groups on the rim of the orifice has been already reported in a few cases with the resulting hydroxy group located on the rim of the orifice pointing above the orifice. These hydroxy groups on the rim of the orifice could form H‐bonds with H 2 O 2 [22] and H 2 O [6] trapped in the cavity. In these compounds, the H 2 O 2 and H 2 O were trapped before the formation of the hydroxy group on the rim of the orifice.…”

“…For example, water could be easily trapped inside open-cage C 60 derivatives with a suitable orifice size under ambient conditions. [4][5][6][7] A trace amount of water in the solvent was observed to enter the cavity during purification of some open-cage fullerenes. A number of noble gas atoms and small molecules have been successfully inserted into the cavity of open-cage fullerenes, such as He, [8,9] Ne, [10] Ar, [11] Kr, [12] H 2 , [8,13] N 2 , [14] O 2 , [15][16][17] HF, [18,19] CO, [20,21] CO 2 , [14] H 2 O 2 , [17,22] CH 4 , [23] NH 3 , [24] HCOH, [25] HCCH, [26] and CH 3 OH.…”

“…As a result, the center of fullerenes has a positive charge (Figure 1), which can act as a Lewis acid to interact with various electron‐rich atom(s) or molecules. For example, water could be easily trapped inside open‐cage C 60 derivatives with a suitable orifice size under ambient conditions [4–7] . A trace amount of water in the solvent was observed to enter the cavity during purification of some open‐cage fullerenes.…”