Solvent-mediated purification of hexa-molybdenum cluster halide, Cs-2[Mo6Cl14] for enhanced optical properties

Norio Saito (1, 2, 3) , Pierric Lemoine (4) , Stéphane Cordier (4) , Yoshiki Wada (2) , Takeo Ohsawa (2) , Noriko Saito (2) , Fabien Grasset (2, 3) , Jeffrey Scott Cross (1) , Naoki Ohashi (2, 3, 1)

1 TITECH - Tokyo Institute of Technology [Tokyo]
2 NIMS - National Institute for Materials Science
3 LINK - Laboratory for Innovative Key Materials and Structures
4 ISCR - Institut des Sciences Chimiques de Rennes

The crystallization of a high-purity hexamolybdenum cluster chloride, Cs-2[Mo6Cl14], was investigated with the aim of improving its intrinsic properties, including optical properties. In particular, we used the hydrophilicities of alcoholic solvents to purify Cs-2[Mo6Cl14] by dehydration. The precursor, trigonal Cs-2[Mo6Cl14] with water impurities, or monoclinic Cs-2[Mo6Cl14]center dot H2O, was dispersed in methanol (MeOH), ethanol (EtOH), or 1-propanol (1-PrOH) to induce recrystallization during stirring. As a result, regardless of the precursor, Cs-2[Mo6Cl14] crystallized from EtOH and 1-PrOH, while Cs-2[Mo6Cl14]center dot H2O crystallized from MeOH, which indicates that EtOH and 1-PrOH behave as dehydrating agents during recrystallization. Subsequent characterization by X-ray diffraction, thermal desorption, and infrared spectroscopic techniques confirmed that the Cs-2[Mo6Cl14] crystallized from EtOH or 1-PrOH, particularly 1-PrOH, is of high purity (fewer inserted water molecules) and high crystallinity. Improved luminescence efficiency following purification was evidenced by time-resolved photoluminescence measurements; the Cs-2[Mo6Cl14] purified by dehydration on recrystallization clearly exhibited an increased luminescence lifetime.

Domains: Chemical Sciences

Norio Saito, Pierric Lemoine, Stéphane Cordier, Yoshiki Wada, Takeo Ohsawa, et al.. Solvent-mediated purification of hexa-molybdenum cluster halide, Cs-2[Mo6Cl14] for enhanced optical properties. CrystEngComm, 2017, 19 (40), pp.6028-6038. ⟨10.1039/c7ce01440f⟩. ⟨hal-01631919⟩