Molecular and Supramolecular Structure of a New Luminescent Hybrid Compound: (C₅N₂H₁₄)₂[BiBr₆]Br·H₂O

Abstract

The reaction of homopiperazine, C5N2H12, with BiBr3 in strong hydrobromic acid affords a new organic-inorganic hybrid (C5N2H14)2[BiBr6]Br·H2O. It crystallizes in the orthorhombic space group, Pbca, with unit cell dimensions of a = 15.0775 (2), b = 15.7569 (2), and c = 20.7881 (4) Å, and eight formula units per unit cell. The crystal structure features slightly distorted octahedral BiBr63− and monoatomic Br− anions in the inorganic substructure and C5N2H142+ dications and adjacent water molecules in the organic substructure. Various weak interactions that include (N)H···Br, (N)H···O, and (O)H···Br hydrogen bonds ensure the assembling of the structural moieties into a 3D supramolecular structure. (C5N2H14)2[BiBr6]Br·H2O shows two emission bands in the photoluminescence spectrum, a rather narrow deep-blue PL at 432 nm, and a broadband red PL centered at 650 nm. Their nature and relations to the crystal structure are discussed in this paper.

Keywords

• hybrid organic-inorganic compounds
• halometallates
• bismuth
• crystal structure
• supramolecular ensemble
• photoluminescence