One-Dimensional Organic Lead Bromide Elastic Crystals with Strong Electron–Phonon Coupling

Two novel one-dimensional (1D) lead halide elastic crystals, [Pb₂Br₄(DMA)₂]_<i>n</i> (<b>1</b>) (DMA = <i>N</i>,<i>N</i>-dimethylacetamide) and [Pb₂Br₄(DMF)₂]_<i>n</i> (<b>2</b>) (DMF = <i>N</i>,<i>N</i>-dimethylformamide), were reported. Both compounds <b>1</b> and <b>2</b> feature a neutral 1D bimetallic axis chain structure. The bending strain of compound <b>1</b> is 1.36%, higher than those of all reported 1D single-metal axis chain coordinate polymers, indicating the superior elastic properties of the 1D bimetallic axis chain polymers. Compound <b>1</b> exhibits strong red-to-near-infrared (NIR) fluorescence emission below 200 K, with an emission peak at 700 nm and a full width at half maximum (fwhm) of 200 nm, indicating strong electron-phonon coupling in compound <b>1</b>. The large Stokes shift and broad fwhm of compound <b>1</b> may be attributed to its excellent elasticity, as this elasticity allows the molecule's self-trapped exciton state to undergo greater structural distortion. It is suggested that 1D organic lead halide elastic crystals could be promising candidates for emerging applications in efficient NIR light-emitting diodes, supercontinuum sources, and flexible NIR optical waveguides.