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

Abstract

A metal-rich niobium oxyiodide was prepared by soft reduction of NbI₄. The structure of the new compound Nb₄OI₁₀ was determined by single-crystal X-ray diffraction and contains a rectangular Nb₄(μ₄-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 two-dimensional van der Waals material $$ Nb₄OI₈I_4/2] is a small band-gap semiconductor (<1 eV), as analysed by electrical conductivity measurements, photoresponse, experimental band gap determination, and band structure calculation.