Aqueous Mediated Synthesis of Mesostructured Manganese Germanium Sulfide with Hexagonal Order

Research on the self-assembly of inorganic clusters around organized sets of organic molecules is of great interest, primarily because of the valuable lessons which could be learned for materials design and due to the potential high impact materials so designed could have in technology.1 Incorporation of electrical properties into nanoand mesostructured materials presents a special challenge, because non-oxidic building blocks have to be employed and, at the same time a great opportunity, because new functionality could be expected in these systems.2 Synthesis of mesostructured silicates by the Mobil group3 showed a way to achieve tunable ordered structures in the mesoscale using surfactants as templating agents. These materials are promising for applications in catalysis,4 but lack potential as optical or electronic materials. Our effort is to incorporate electronic properties into nanoand mesostructured materials. The report of the synthesis of microstructured metal sulfides5 stimulated the preparation of a number of metal sulfides with microstructured open framework structures.6 This was followed by reports on the synthesis of mesostructured CdS,7 SnS,8 and ZnS9 with the incorporation of cationic surfactants. In addition, the hydrothermal treatment of amorphous GeS2 and cetyltrimethylammonium bromide was reported to give lamellar mesostructured GeSx phases.10 Recently, MacLachlan et al. reported the supramolecular assembly of mesostructured metal germanium sulfides from Ge4S10 clusters.11 They have emphasized the need for nonaqueous solvent formamide, playing a key role in their synthesis of hexagonal ordered phase. The reported phases claimed to have flexible and adjustable composition. Indepentendly, we focused our efforts on the self-assembly of Ge4S10 adamantane ions12 with surfactant micelles in aqueous medium and have prepared mesostructured materials [CnH2n+1N(CH3)3]2MGe4S10 (CnMGeS) with divalent metal ions with divalent metal ions Zn2+, Cd2+, Hg2+, Ni2+, and Co2+. These materials are different from those of MacLachlan et al. and contain pores resembling wormholes.13 During our investigation, we observed reactions with Mn2+ ions in aqueous medium behaved differently and did not result in an immediate precipitation as with the other divalent metal ions. Subsequently, we carried out reactions with Mn2+ ions under hydrothermal conditions and discovered a new mesostructured phase of MnGe4S10 with hexagonally ordered pores with mesityltrimethylammonium surfactant. [C14H29N(CH3)3]2MnGe4S10 (C14MnGeS) was synthesized by reacting a mixture of Na4Ge4S10, MnCl2‚4H2O, and mesityltrimethylammonium bromide in a stoichiometric ratio 1:1:2, at 120 °C under hydrothermal conditions.14 The reaction could be expressed by the following