The Rectangular Niobium Oxyiodide Cluster Nb₄OI₁₀ – A Narrow Band-Gap Semiconductor

A metal-rich niobium oxyiodide was prepared by soft reduction of NbI4. 4 . The structure of the new compound Nb4OI10 was determined by single-crystal X-ray diffraction and contains a rectangular Nb-4(mu(4)-O) cluster that is interconnected into layers by iodide ligands. The local structure of the Nb4OI10 cluster bears a close relationship to a defect Nb6I11 structure. The twodimensional van der Waals material (2)(infinity)[Nb4OI8I4/2]is a small band-gap semiconductor ( < 1 eV), as analysed by electrical conductivity measurements, photoresponse, experimental band gap determination, and band structure calculation.