Changes in the structural dimensionality of selenidostannates in ionic liquids: Formation, structures, stability, and photoconductivity

In situ transformations of selenidostannate frameworks in ionic liquids (ILs) were initiated by treatment of the starting phase K2[Sn 2Se5] and the consecutive reaction products by means of temperature increase and/or amine addition. Along the reaction pathway, the framework dimensionalities of the five involved selenidostannate anions develop from 3D to 1D and back, both in top-down and bottom-up style. Addition of ethane-1,2-diamine (en) led to the reversion of the 2D1D step from 2D-{[Sn24Se56]16-} to 1D-{[Sn 6Se14]4-}. As rationalized by DFT investigations, the 2D anion is thermodynamically favored. Photoconductivity measurements reveal that all samples show Schottky contact behavior with absolute thresholds below 10 V. One of the samples exhibits conductive states within the energy range of visible photons. New dimensions: Three selenidostannate phases yielded from complex transformation pathways in ionic liquids include (in part reversible) dimensionality changes o f the anionic Sn/Se substructures (see figure). As rationalized by DFT investigations, the transformations are provoked by competing influences of temperature and amine addition (DMMP=2,6-dimethylmorpholine, en=ethane-1,2-diamine).