Synthesis, Structure, and Orange Emission of Sb ³⁺ ‐Doped (C ₄ H ₁₂ N ₂ ) ₂ In ₂ Br ₁₀ (H ₂ O)

Luminescent hybrid metal halides were prepared by doping with Sb 3+ the compound (C 4 H 12 N 2 ) 2 In 2 Br 10 (H 2 O) (C 4 H 12 N 2 2+ is a doubly protonated piperazine) using simple evaporative crystallization. The crystals were characterized by single crystal X‐ray diffraction, powder X‐ray diffraction, and TG‐DSC. The structure of the ionic compound (C 4 H 12 N 2 ) 2 In 2 Br 10 (H 2 O) corresponds to the formula (C 4 H 12 N 2 ) 4 [InBr 6 ][InBr 4 (H 2 O) 2 ][InBr 4 ] 2 Br 2 , and it consists of C 4 H 12 N 2 2+ cations, distorted octahedral [InBr 6 ] 3− and [InBr 4 (H 2 O) 2 ] − , tetrahedral [InBr 4 ] − anions and Br − anions. The entire structure is stabilized by O─H···Br, N─H···Br, and C─H···Br hydrogen bonds, forming a three‐dimensional network. When excited in the range of 325–405 nm, undoped and Sb 3+ ‐doped compounds exhibit broadband orange emission with a maximum at 617 ± 1 nm and a FWHM of 149–150 nm. Microsecond lifetimes of 1.31–1.47 μs and a large Stokes shift of 253–256 nm indicate that the emission in undoped and Sb 3+ ‐doped (C 4 H 12 N 2 ) 2 In 2 Br 10 (H 2 O) originates from the recombination of triplet self‐trapped excitons. Sb 3+ ‐doping of (C 4 H 12 N 2 ) 2 In 2 Br 10 (H 2 O) significantly increases the photoluminescence quantum yield from 1% to 56%.