Electronic structures of transition metal–C60 coordination polymers (η6-C60)nMn (M=Sc, Ti, V, or Cr)

The electronic structures of a series of transition metal (M)–C60 dumbbell polymers (η6-C60)nMn have been examined with the one-dimensional (1D) tight-binding crystal orbital (TBCO) method at the extended Hückel (EH) approximation level. The band structures for M=Sc, Ti, and V are metallic but that for M=Cr is semiconductive with a narrow bandgap, EG≈8.15×10−3 eV. For all the polymers, there are five specific bands near the Fermi level, four of which show the interaction between the d atomic orbitals (AO) (dxy and dx2−y2; the coordinate axes are given in the text) of M and the π orbitals on C60. The structural instability of the 1D polymer for M=Cr is discussed based on the very narrow bandgap.