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.

Synthesis, Structure, and Optical Properties of a 0D Hybrid Organic–Inorganic Metal Halide (C5N2H14Cl)GeCl3

“…As shown in the gray part of Figure 3b, the emission peak ranges of them are very similar, and the narrower full-width-halfheight (fwhm) and smaller Stokes shifts are unlikely to correspond to the STE processes. 24,26,28 It is interesting that the inorganic [GeCl 3 ] − trigonal pyramid is not the PL center in (C 5 N 2 H 14 Cl)GeCl 3 since generally inorganic groups are severely distorted in low-dimensional structures which are beneficial to the exciton−phonon interactions for strong radiative recombination and relatively high PLQY. 42−44 Our first-principles geometrical optimizations of the ground and excited states show that the [GeCl 3 ] groups in (C 5 N 2 H 14 Cl)GeCl 3 undergo a very small structural deformation upon electronic excitation, as shown by the bond lengths and angles displayed in Tables S4 and S5.…”

“…In order to probe the origin of the emission centers, we conducted a comparative study of the optical properties of organic precursors C 5 N 2 H 12 and (C 5 N 2 H 14 Cl)­GeCl 3 . As shown in the gray part of Figure b, the emission peak ranges of them are very similar, and the narrower full-width-half-height (fwhm) and smaller Stokes shifts are unlikely to correspond to the STE processes. ,, …”

“…As a result, free excitons (FEs) captured by organic cations always exhibit high-energy emission. Several related reports have shown that a number of low-dimensional hybrid halides are exhibiting double emission bands, which are generated by the STEs-induced broadband emission and the FEs-assisted narrow emission. − With the synergistic effect of STEs and FEs, the adsorption of the OIMHs can realize dual-band emission, thus greatly broadening the emission range.…”

Synthesis, Crystal, and Electronic Structure of (HpipeH2)2[Sb2I10](I2), with I2 Molecules Linking Sb2X10 Dimers into a Polymeric Anion: A Strategy for Optimizing a Hybrid Compound’s Band Gap

“…Each nitrogen atom forms two such bonds; therefore, four (N)H•••I bonds are formed by each cation, which means that the cation realizes all its capacity to form hydrogen bonds. As a matter of fact, in various polyiodides and iodobismuthates, HpipeH 2 2+ always behaves in a similar fashion in forming four hydrogen bonds, thus serving as a strong structure-directing template [30,31].…”

“…As for the organic cationic part, the choice of homopiperazine (1,4-diazacycloheptane, Hpipe) is explained by the ability of its doubly protonated cation to function as a structure-directed template. We previously showed that the (HpipeH 2 ) 2+ cation forms four hydrogen bonds in various polyiodides and halobismuthates, leading to hybrid compounds with the enhanced stability [30,31].…”