Growing crystalline selenidostannates in deep eutectic solvent

Abstract By using deep eutectic solvent mixture of ChCl (ChCl = choline chloride) and 1,8-diaminooctane as reaction medium, three new selenidostannates were synthesized, namely [Cr(en) 3 ] 2.5 [SnSe 4 ]·Cl 3.5 ·(pip) 0.5 ·1.5H 2 O ( 1 ) (en = ethylenediamine, pip = piperazine), [Ni(en) 3 ][Sn 3 Se 6.5 (Se 2 ) 0.5 ] ( 2 ), and [Ni(en) 3 ][Sn 3 Se 7 ] ( 3 ). Compound 1 features a primary unit of SnSe 4 tetrahedron, in which the [Cr(en) 3 ] 3+ complex acts as charge balance agent. In compound 2, there are two kinds of one dimensional chains, including [Sn 3 Se 7 ] n 2 n – and [Sn 3 Se 6 (Se) 2 ] n 2 n – anionic chains. The [Sn 3 Se 7 ] n 2 n – chain is constructed by connecting [Sn 3 Se 9 ] units via edge-sharing Se 2- ion, while the [Sn 3 Se 6 (Se) 2 ] n 2 n – chain is constructed by linking [Sn 3 Se 10 ] units via sharing one Se 2- ion and one Se 2 2- ion. Compound 3 features a lamellar anionic [Sn 3 Se 7 ] n 2 n – structure, where the [Ni(en) 3 ] 2+ ions are located in inter-lamellar space. The optical absorption spectra indicate band gaps of 2.23 eV for 1 , 1.95 eV for 2 , and 2.01 eV for 3 .