Expanding the Spectral Range in T2‐Supertetrahedral Nonlinear Optical Chalcogenides via Incorporating Inorganic Polycations

• Published in: Angewandte Chemie International Edition Vol. 64; no. 23; pp. e202505421 - n/a
• Main Authors: Pei, Shao‐Min, Jiang, Xiao‐Ming, Liu, Bin‐Wen, Guo, Guo‐Cong
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 02.06.2025
• Edition: International ed. in English
• Subjects: Atmospheric windows; Cations; Chalcogenides; Clusters; Far infrared radiation; Harmonic generations; Ligands; Nonlinear optical crystals; Nonlinear optics; Polycations; Polyelectrolytes; Second‐harmonic‐generation; Silver gallium sulfide; T2‐supertetrahedra; Chalcogenides; Second‐harmonic‐generation; T2‐supertetrahedra; Nonlinear optical crystals
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202505421

Metal‐chalcogenide supertetrahedral clusters that exhibit significant hyperpolarizability are highly sought after as promising nonlinear optical (NLO) function modules. However, these “naked” anionic clusters are commonly coordinated with organic ligands to maintain electrical neutrality, which unfortunately limits their utility in the mid‐ and far‐infrared (MFIR) region due to strong absorption. In this study, we successfully substituted the organic ligand with the unprecedented (X4K8Ba2)8+ supertetrahedral cations, which are suitable size and high charge, and integrated them with (In4Se10)8− supertetrahedral clusters to form 3D salt‐inclusion chalcogenides (SICs), [K4BaX2][In6Se11] (X = Cl 1, Br 2). As anticipated, the parallel arrangement of the (In4Se10)8− clusters yielded splendid second‐harmonic generation intensities (2.2–2.4 × benchmark AgGaS2 @1910 nm for 1 and 2, respectively), ranking among the top within the SICs category. Most importantly, the introduction of inorganic polycations with a broad cut‐off IR edge is a key factor in enabling 1 to achieve an ultrawide transparency range (0.7 to 18.1 µm) that covers the crucial atmospheric windows (3–5 and 8–14 µm). Indeed, replacing the organic ligand with an inorganic polycation allows supertetrahedra‐based chalcogenides to fulfill the broad‐spectrum criteria of NLO materials. The incorporation of the inorganic (Cl4K8Ba2)8+ salt cation instead of an organic ligand cation endowed [K4BaCl2][In6Se11] with a wide infrared transparency range (0.7–18.1 µm), which can be considered the finishing touch in advancing [K4BaCl2][In6Se11] as a viable IR NLO candidate.