Unusual polymerization in the Li4C60 fulleride

TL;DR

This paper reports a novel 2D polymerization in Li4C60 fulleride, revealing a monoclinic structure with covalently bonded fullerene chains, resulting in insulating properties and electron localization.

Contribution

It introduces a new type of 2D polymerization in lithium fullerides, characterized by a monoclinic structure with covalent fullerene chains, confirmed through multiple spectroscopic techniques.

Findings

Li4C60 exhibits a monoclinic I2/m structure.

Fullerenes form chains via [2+2]-cycloadditions.

The material is insulating with localized electrons.

Abstract

Li4C60, one of the best representatives of lithium intercalated fullerides, features a novel type of 2D polymerization. Extensive investigations, including laboratory x-ray and synchrotron radiation diffraction, 13C NMR, MAS and Raman spectroscopy, show a monoclinic I2/m structure, characterized by chains of [2+2]-cycloaddicted fullerenes, sideways connected by single C-C bonds. This leads to the formation of polymeric layers, whose insulating nature, deduced from the NMR and Raman spectra, denotes the complete localization of the electrons involved in the covalent bonds.