  Organic metal halide hybrids with low-dimensional structures at the molecular
level have received great attention recently for their exceptional structural
tunability and unique photophysical properties. Here we report for the first
time the synthesis and characterization of a one-dimensional (1D) organic metal
halide hybrid material, which contains metal halide nanoribbons with a width of
three octahedral units. It is found that this material with a chemical formula
C$_8$H$_{28}$N$_5$Pb$_3$Cl$_{11}$ shows a dual emission with a
photoluminescence quantum efficiency (PLQE) of around 25% under ultraviolet
(UV) light irradiation. Photophysical studies and density functional theory
(DFT) calculations suggest the coexisting of delocalized free excitons and
localized self-trapped excitons in metal halide nanoribbons leading to the dual
emission. This work shows once again the exceptional tunability of organic
metal halide hybrids that bridge between molecular systems with localized
states and crystalline ones with electronic bands.
