Tin Bromido Aluminate Networks with Bright Luminescence

The novel tin bromido aluminates [Sn(3)(AlBr(4))(6)](Al(2)Br(6)) (1), Sn(AlBr(4))(2) (2), [EMIm][Sn(AlBr(4))(3)] (3) and [BMPyr][Sn(AlBr(4))(3)] (4) ([EMIm]: 1‐ethyl‐3‐methylimidazolium, [BMPyr]: 1‐butyl‐1‐methyl‐pyrrolidinium), are obtained from a ionic‐liquid‐based reaction of AlBr(3) and SnCl(2) or SnBr(2), resulting in colorless and transparent crystals. 1 contains a neutral, inorganic (∞) (3)[Sn(3)(AlBr(4))(6)] network filled with intercalated Al(2)Br(6) molecules. 2 represents a 3D structure isotypic to Pb(AlCl(4))(2) or α‐Sr[GaCl(4)](2). 3 and 4 exhibit infinite (∞) (1)[Sn(AlBr(4))(3)](n−) chains that are separated by the voluminous [EMIm](+)/[BMPyr](+) cations. All title compounds contain Sn(2+) coordinated by AlBr(4) tetrahedra, resulting in chains or 3D networks. Moreover, all title compounds show photoluminescence due to Br(−)→Al(3+) ligand‐to‐metal charge‐transfer excitation, followed by 5s (2) p (0)←5s (1) p (1) emission on Sn(2+). Most surprisingly, the luminescence is highly efficient (quantum yield >50 %). Specifically, 3 and 4 exhibit outstanding quantum yields of 98 and 99 %, which are the highest values observed for Sn(2+)‐based luminescence so far. The title compounds have been characterized by single‐crystal structure analysis, elemental analysis, energy‐dispersive X‐ray analysis, thermogravimetry, infrared and Raman spectroscopy, UV‐Vis and photoluminescence spectroscopy.