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.