Establishing Family Relations in Group 15 Halogenido Metalates with the Largest Molecular Antimony Iodide Anion

Abstract

Studying structurally related families of compounds is a valuable tool in understanding and predicting material properties and has been extensively used for metal halide perovskites. Due to the variable anion structures in group 15 halogenido metalates, similar family relations are still largely missing. Herein, we present compounds featuring the [Sb2nI6n+4]4− family of anions, including the first n=5 member in [Hpyz]4[Sb10I34] (Hpyz=pyrazinium), which contains the largest halogenido pentelate anion reported to date. The optical properties of compounds featuring n=1–5 anions show a clear trend as well as an outlier, a low band gap of 1.72 eV for [Hpyz]4[Sb10I34], that can be well understood using quantum chemical investigations. Also using SbI3 and [H2NMe2]3[SbI6], a compound featuring a single octahedral [SbI6]3− unit, as limiting cases, we show that structure‐property relationships can be established in group 15 halogenido metalates in a similar way as in metal halide perovskites, thus providing a framework for understanding new and known compounds in this emerging class of materials.

Optical Properties and Metal‐Dependent Charge Transfer in Iodido Pentelates

“…In both cases a very slow incline of the absorption with increasing energy is observed, in contrast to the generally quite sharp absorption edges found for other iodido pentelates. [21] For the bismuth compound the similarly small pyrazineÀ iodine contacts suggest that CT is also the main mechanism of absorption in this case. However, as shown by Neilson and co-workers for a series of tropylium halogenido pentelates the effect of the metalate-to-cation-CT on the optical band gap of bismuthates is weaker than for antimonates due to the energetically lower lying valence band maximum.…”

“…Additionally, we observed in previous works that pyrazine does not form di-cations under the reaction conditions employed in the synthesis of 1 and 2. [21] One of the three crystallographically independent pyrazinium ions is disordered over two positions. For both 1 and 2 the occupancies were refined freely to about 3 = 4 and 1 = 4 for the two parts.…”

“…For the antimony compound this is very close to the corresponding distance of 3.75 Å observed in (Hpyz) 4 Sb 10 I 34 where it gives rise to a charge-transfer excitation between the anions and cations. [21] Optical Properties When looking at the optical properties, specifically the optical band gap E g , of isostructural iodido pentelates, a typical observation can be made: The bismuthates will generally display smaller values of E g than the antimonates. This is shown for a number of examples in Table 1.…”

“…Pyrazinium iodide was synthesized according to our previously published method. [21] Acetonitrile was generally flashdistilled prior to use. For filtration cellulose filters with a pore size of 5-8 μm were used.…”

Trendbericht Festkörperchemie 2023

“…Hierbei haben sie das noch fehlende Glied mit n 5 hervorgehoben, das bisher größte Halogenidopentelation. 46) Wie Breu, Matjedes, Senker und Mitarbeitende mit Röntgenkleinwinkelstreuung, 23 Na-MAS-NMR-Spektroskopie und Röntgenbeugung zeigten, lässt sich synthetisches Natriumhectorit lösungsmittelgesteuert mit verschiedener oberflächlicher Ladung delaminieren. 47) Abb.…”