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

Two novel one-dimensional (1D) lead halide elastic crystals, [Pb2Br4(DMA)2]n (1) (DMA = N,N-dimethylacetamide) and [Pb2Br4(DMF)2]n (2) (DMF = N,N-dimethylformamide), were reported. Both compounds 1 and 2 feature a neutral 1D bimetallic axis chain structure. The bending strain of compound 1 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 1 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 1. The large Stokes shift and broad fwhm of compound 1 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.