Competing Roles of Crystallization and Degradation of a Metal Organic Chalcogenolate Assembly under Biphasic Solvothermal Conditions

Metal organic chalcogenolate assemblies have attracted recent interest as ensemble nanomaterials that contain one- or two-dimensional inorganic nanostructures in a periodic array with supramolecular isolation provided by an associated organic ligand lattice. Biphasic immiscible synthesis at liquid-liquid interfaces is a convenient way to grow crystalline d(10) metal-organic chalcogenolate assemblies. However, there has been little systematic study of the role of temperature on the nucleation, growth, and stability of hybrid chalcogenolates during biphasic synthesis. Silver benzeneselenolate, a robustly blue-luminescent, lamellar metal-organic chalcogenolate assembly, was crystallized at biphasic immiscible liquid-liquid interfaces under solvothermal conditions. A positive correlation between temperature and nucleation density was observed, and the luminescence was conserved in all examples of the crystalline phase. Applying solvothermal conditions to the biphasic synthesis generally increased the lateral dimensions of the crystals and strongly favored the crystalline phase of the compound. Although thin, well-formed crystals were observed within 1 h for interfacial reactions performed at high temperatures, degradation was observed in long duration growths resulting in aggregated silver metal. A study of the thermal stability of the material via thermogravimetric analysis revealed that the decomposition is likely a redox reaction reverting the compound to silver metal and diphenyl diselenide. In situ analysis of this degradation was performed by grazing incidence wide-angle X-ray scattering, which confirmed that the decomposition occurs in a single step with no preceding changes to the structure of the material. This work demonstrates that biphasic solvothermal methods are amenable to the synthesis of hybrid metal-organic chalcogenolate assemblies and that temperature can be used to control product morphology and lateral crystal growth at the immiscible interface.