Hybrid Inorganic–Organic Materials with an Optoelectronically Active Aromatic Cation: (C₇H₇)₂SnI₆ and C₇H₇PbI₃

Inorganic materials with organic constituentshybrid materialshave shown incredible promise as chemically tunable functional materials with interesting optical and electronic properties. Here, the preparation and structure are reported of two hybrid materials containing the optoelectronically active tropylium ion within tin- and lead-iodide inorganic frameworks with distinct topologies. The crystal structures of tropylium tin iodide, (C7H7)2SnI6, and tropylium lead iodide, C7H7PbI3, were solved using high-resolution synchrotron powder X-ray diffraction informed by X-ray pair distribution function data and high-resolution time-of-flight neutron diffraction. Tropylium tin iodide contains isolated tin­(IV)-iodide octahedra and crystallizes as a deep black solid, while tropylium lead iodide presents one-dimensional chains of face-sharing lead­(II)-iodide octahedra and crystallizes as a bright red-orange powder. Experimental diffuse reflectance spectra are in good agreement with density functional calculations of the electronic structure. Calculations of the band decomposed charge densities suggest that the deep black color of tropylium tin iodide is attributed to iodide ligand to tin metal charge transfer, while the bright red-orange color of tropylium lead iodide arises from charge transfer between iodine and tropylium states. Understanding the origins of the observed optoelectronic properties of these two compounds, with respect to their distinct topologies and organic–inorganic interactions, provides insight into the design of tropylium-containing compounds for potential optical and electronic applications.带有有机组分的无机材料——即杂化材料（hybrid materials）——作为可化学调控的功能材料，展现出了极佳的应用潜力，其具备引人关注的光学与电子性质。本文报道了两种杂化材料的制备方法与晶体结构：这两种材料将具有光电活性的 tropylium 离子（tropylium ion）引入拓扑结构各异的锡基与铅基碘化物无机骨架中。通过高分辨率同步辐射粉末X射线衍射，并结合X射线对分布函数（X-ray pair distribution function）数据与高分辨率飞行时间中子衍射（time-of-flight neutron diffraction）辅助解析，确定了碘化 tropylium 锡（(C₇H₇)₂SnI₆）与碘化 tropylium 铅（C₇H₇PbI₃）的晶体结构。碘化 tropylium 锡包含孤立的四价锡-碘八面体，结晶为深黑色固体；而碘化 tropylium 铅则呈现由共面铅(II)-碘八面体构成的一维链状结构，结晶为亮红橙色粉末。实验测得的漫反射光谱与电子结构的密度泛函计算（density functional calculations）结果吻合良好。能带分解电荷密度计算表明，碘化 tropylium 锡的深黑色源于碘配体向锡金属的电荷转移（charge transfer），而碘化 tropylium 铅的亮红橙色则源自碘与 tropylium 离子态之间的电荷转移。针对这两种化合物迥异的拓扑结构与有机-无机相互作用，阐明其观测到的光电性质的起源，可为设计含 tropylium 离子的化合物以应用于潜在的光学与电子领域提供理论指导。