Synthesis, structure and optoelectronic properties of hybrid iodobismuthate & iodoantimonate semiconducting materials

Abstract

The syntheses and structures of five iodobismuthate and nine iodoantimonate hybrid materials are presented. The 1,3-dimethyl-2-oxo-2,3-dihydropyrimidinium cation has been used to template the isostructural, one-dimensional [C6H9N2O][SbI4] (I) and [C6H9N2O][BiI4] (II), while 4-methylmorpholinium templates the compounds, [C5H12NO]4[Sb6I22] (III) and [C5H12NO]4[Bi4I16] (IV), both containing isolated iodopnictogenide cluster anions. Five iodoantimonate compounds, templated by piperazinium cation derivatives, have been synthesised; [C4H12N2][SbI4]2·4H2O (V), [C5H14N2][SbI4]2·3H2O (VI), two polymorphs of [C6H16N2][SbI4]2·2H2O (VII and VIII) and [C6H16N2][Sb4I16]0.5·H2O (IX), mainly adopting structures closely related to previously published 1D iodobismuthate hybrid materials. 1-Ethyl-2-methylbenzimidazolium cations, formed in situ in the reaction medium, template the isostructural 1D structures of [C10H13N2][SbI4] (X) and [C10H13N2][BiI4] (XI). 1,4-Diazabicyclo[2.2.2]octandiium (DABCOH2)2+ di-cations are shown to template a hydrated iodoantimonate structure [C6H14N2]2[Sb4I16]·2H2O (XII) containing [Sb4I16]4- complex anions and a mixed phase of two iodobismuthate materials; one phase contains, uniquely, a mixture of the complex anions [Bi2I10]4- and [BiI6]3- in the form [C6H14N2]10[Bi2I10]2[BiI6]4·(H2O)8 (XIII), and the second, [C6H14N2]2[Bi4I16]·2H2O (XIV), contains discrete [Bi4I16]4- clusters. The stability and thermal decomposition routes of these phases have been determined using thermogravimetric analysis. UV-vis spectroscopy has been used to determine band gap energy estimates which are related, for a range of iodobismuthate and iodoantimonate materials, to their structural features and potential optoelectronic applications.