From KBa ₄ Ge ₃ S ₁₀ Cl to ABa ₃ EuGe ₃ S ₁₁ (A = Na, K) Synthesized by Reactive Flux Assisted Metal Oxide-Boron-Chalcogen (MOBQ) Method: Effect of Cation/Anion Cosubstitution on Cryst

Chalcogenides are promising candidates to solve the scarcity of currently applicable middle nonlinear optical (NLO) crystals. Herein, heterovalent cosubstitution strategy was applied to [KBa 4 Cl][Ge 3 S 10 ] ( 0 ), which resulted in the discovery of new ABa 3 EuGe 3 S 11 (A = Na ( 1 ), K ( 2 )). Both of them were synthesized via the reactive flux assisted metal oxide-boron-chalcogen (RFMOBQ) routine, and crystallize in the chiral P 6 3 space group. Their quasi-3D structures are constructed by EuS 7 monocapped trigonal prisms and Ge 3 S 9 rings when considering the covalence of Eu–S bonds, which are different from the isolated Ge 3 S 9 cluster in 0 . 1 and 2 show strong NLO responses (0.7 and 0.6 × AgGaS 2 @2.1 μ m) and enhanced laser-induced damage thresholds (4.01 and 4.85 × AgGaS 2 @1064 nm). This work provides a referential case for increasing the structural dimension, which can be applied to the exploration of new NLO crystals.