| Metal halides are a kind of promising functional materials and have attracted huge interest recently owing to their tunable structures as well as excellent photoelectric properties.In these hybrid solids,the abundant coordination modes of halides can make the halometallate products diverse with different structures and numerous types of charge transfer.With the assistance of multitudinous organic species,a large number of metal halide based compounds have been assembled and reported.The organic molecules can not only serve as structure-directing agents to direct the formation of inorganic skeletons but act as coordination linkers to bridge the low-dimensional metal halide units into a complicate framework.At present,it is still a great challenge and task to fabricate functional halometallates with high stability and excellent performance from the combination of inorganic components and organic moieties.In this thesis,by virtue of a hexamethylenetetramine(Hmta)molecule with a high symmetric geometry and multiple coordination sites,a series of silver/lead/cadmium based halometallates have been successfully prepared.The compounds have been characterized by X-ray single crystal diffraction analysis.Moreover,we have further investigated the photoluminescence,photochromism and photocatalysis of the corresponding metal halide hybrids.The main work content is as follows:(1)The assembly of silver halide with Hmta gives rise to five novel silver-based compounds featuring diverse architectures from chains to layers and even 3D intricate frameworks[Me-Hmta][Ag I2]·H2O(1),[Me-Hmta][Ag2I3](2),[Me-Hmta][Ag2Br3](3),[NH4][Ag5I6(Hmta)](4),[NH4][Me-Hmta][Ag4Br6(Hmta)](5).In compounds 1-3,the in-situ methylated[Me-Hmta]cations serving as the templates and counter ions are located in the space of the structures.For compounds 4 and 5,the Hmta molecule acts as coordination linkers to connect with the silver centers,resulting in a 2D and 3D infinite network for 4 and 5,respectively.Interestingly,compounds 1,2,and 4 display reversible photochromism behaviors due to the photolysis of inorganic silver halide components.Remarkably,compound 5 could emit two luminescent emission bands(high energy,HE and low energy,LE),and the change of intensity for IHE:ILEat different temperature results in a luminescent thermochromism phenomenon.Resultantly,a white-light-emissive compound could be prepared.In addition,the metal halides exhibit narrow band gaps and show the great photocatalytic ability to accelerate the degradation of dye molecules with good reproducibility and reusability.(2)The combination of lead/cadmium halides with Hmta affords six original lead or cadmium based halometallates with different structures[Me-Hmta][Pb I3](6),[Me-Hmta]4[Pb3I10](7),[Me-Hmta]6[Pb5Cl16](8),[Me-Hmta]4[Cd2I8](9),[Cd5I10(Hmta)3(DMF)6](10),[Cd3Cl6(Hmta)3(H2O)2](11).In these compounds,the Hmta molecules can be in-situ alkylated to balance the overall charge or adopt variable coordination modes to meet the coordination requirements of the metal centers,indicating the great potential of Hmta for the construction of novel metal halides.Compounds 6 and7 could display bright yellow emission at room temperature with both good structural and luminescence stability,which may be considered as potential candidates to prepare high-resolution white light LEDs.Additionally,the emissive behaviors for compounds9-11 could be readily modulated by temperature.With the temperature decreasing from298 to 77 K,the emission intensity gradually increased owing to the reduced non-radiative transition. |
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