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

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.