Photoluminescent Layered Crystal Consisting of Anderson-Type Polyoxometalate and Surfactant toward a Potential Inorganic-Organic Hybrid Laser

The hybridization of inorganic and organic components is a promising strategy to build functional materials. Among several functions, luminescence is an important function which should be considered for practical usage. Inorganic-organic hybrid luminescent materials have been investigated as phosphors, sensors, and lasers. Organic luminescent centers such as dye molecules have often been hybridized with inorganic matrices. Polyoxometalate anions (POMs) are effective inorganic luminescent centers due to their luminescent properties and structural designability. However, most luminescent POM components are limited to lanthanide-based POMs. In this report, a photoluminescent inorganic-organic hybrid crystal based on a non-lanthanide POM was successfully synthesized as a single crystal. Anderson-type hexamolybdochromate ([CrMo₆O₁₈(OH)₆]^3-, CrMo₆) anion exhibiting emission derived from Cr³⁺ was utilized with n-dodecylammonium ([C₁₂H₂₅NH₃]⁺, C₁₂NH₃) surfactant cation to obtain a photoluminescent hybrid crystal. The grown single crystal of C₁₂NH₃-CrMo₆ comprised a distinct layered structure consisting of inorganic CrMo₆ layers and interdigitated C₁₂NH₃ layers. In the CrMo₆ layers, the CrMo₆ anions were associated with water molecules by hydrogen bonding to form a densely packed two-dimensional network. Steady-state and time-resolved photoluminescence spectroscopy revealed that the C₁₂NH₃-CrMo₆ hybrid crystal exhibited characteristic emission from the CrMo₆ anion. Preliminary lasing properties were also observed for C₁₂NH₃-CrMo₆, which shows the possibility of using the C₁₂NH₃-CrMo₆ hybrid crystal as an inorganic-organic hybrid laser.