Deviation from the Planarity - a Large Dy₃N Cluster Encapsulated in an I_h-C₈₀ Cage: An X-ray Crystallographic and Vibrational Spectroscopic Study

The high-yield synthesis of Dy₃N@C₈₀ (I) opens the possibility of characterizing its molecular and vibrational structures. We report on the structure determination of Dy₃N@C₈₀ (I) by X-ray crystallographic study of single crystal of Dy₃N@C₈₀ (I)•Ni(OEP)•2C₆H₆, revealing a nearly planar Dy₃N cluster encapsulated in an I_h-C₈₀ cage. The vibrational structure of Dy₃N@C₈₀ (I) is studied by FTIR and Raman spectroscopy in combination with force-field calculations. A correlation was found between the antisymmetric metal-nitrogen stretching vibration and the structure of the M₃N cluster of M₃N@C₈₀ (I) (M = Y, Gd, Tb, Dy, Ho, Tm). Moreover, a stronger interaction between the encaged nitride cluster and the C₈₀ carbon cage was found in the class II M₃N@C₈₀(I) (M=Y, Gd, Tb, Dy, Ho, Tm) than in Sc₃N@C₈₀ (I). This study demonstrates that the cluster size (determined by the ionic radius of the metals involved) plays the dominating role in the structure of the M₃N cluster in M₃N@C₈₀ (I).