Change of magnetic and electronic features through subtle substitution in cubic, non-centrosymmetric extended rare-earth metal cluster complexes {TR3}X3

The new compound {IrCe3}I3 was synthesized by comproportionation reactions of stoichiometric ratios of CeI3, Ce and Ir. Single crystal X-ray diffraction structure determination shows that {IrCe3}I3 crystallizes with the cubic variant of the {TR3}X3 family (I4132, Z=8, a=12.450(1) A, V=1930.0(3) A3) and is isostructural with the recently reported {RuLa3}Br3. Octahedral {IrCe6} clusters share three common edges forming interpenetrating chains that run along the 41 screw axes. Magnetic measurements on pure powder samples of {IrCe3}I3 show paramagnetic behavior and, at temperatures below 2 K, a mictomagnetic state. The isostructural {RuLa3}Br3 is a Pauli paramagnet suggesting metallic conductivity which is consistent with band structure calculations where the Fermi level is placed below a pseudogap. For {IrCe3}I3, on the contrary, the Fermi level falls in a narrow gap rather than a pseudogap suggesting activated conductivity.