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) 34In4S10H4 (1), (NH3) 4Ga4S6 (2), NH3CH2CH35 (NH2CH2CH3) 2Ga11S19 (3), and NH3CH2CH2OH6Ga10S18·2NH2CH2CH2OH (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-In4S10H44– clusters (for 1) and Ga10S18n6n– 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) 2n5n– 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.