Mixed Solvothermal Synthesis of Tn Cluster-Based Indium and Gallium Sulfides Using Versatile Ammonia or Amine Structure-Directing Agents

Metal chalcogenide supertetrahedral Tn clusters are of current interest for their unique compositions and structures, which rely highly on the structure-directing agents. Herein, we report four novel Tn cluster-based indium and gallium sulfides, namely, [NH(CH3)3]4In4S10H4 (1), (NH3)4Ga4S6 (2), [NH3CH2CH3]5(NH2CH2CH3)2Ga11S19 (3), and [NH3CH2CH2OH]6Ga10S18·2NH2CH2CH2OH (4). All four compounds were solvothermally synthesized in mixed amine–ethanol solutions or deep eutectic solvent (DES), where ammonia/amine molecules play significant structure-directing roles in the speciation and crystal growth. (1) Being protonated, the trimethylamine and ethanolamine molecules surround the T2-[In4S10H4]4– clusters (for 1) and [Ga10S18]n6n– open framework (for 4), respectively, compensating for the negative charge of the inorganic moieties. (2) With the lone pair of electrons, the ammonia molecules in 2 coordinate directly to corner Ga3+ ions of the {Ga4S6} cage to give a neutral T2-(NH3)4Ga4S6 cluster. (3) For compound 3, part of the ethylamine molecules act as terminating ligands for the T1 and T3 units in the [Ga11S19(NH2CH2CH3)2]n5n– layer, while the rest act as interlamellar countercations upon protonation. Theoretical studies reveal the contributions of N, C, and H to the density of states (DOS) for 2 and 3 because of their hybrid structures that combine the ammonia/amine ligands with sulfide moieties together.