Effect of ring substituent position on the structural and optoelectronic properties of novel quasi low-dimensional hybrid 2-, 3-, and 4-(bromomethyl)pyridinium lead bromides.

In this work, the synthesis, crystal structure, morphology, and optoelectronic properties of novel quasi low-dimensional hybrid (bromomethyl)pyridinium crystalline phases (2-BrCH2PyH)Pb2Br5, (3-BrCH2PyH)PbBr3, and (4-BrCH2PyH)PbBr3 are reported. The first compound formed quasi 2D crystals, while the other two species crystallized as quasi 1D structures. DFT calculations predicted that the bromides are semiconductors featuring electronic VB-to-CB transitions of ∼3.2 eV. (2-BrCH2PyH)Pb2Br5 and (3-BrCH2PyH)PbBr3 exhibited low-temperature (77 K) photoluminescence (PL). However, PL was not observed in (4-BrCH2PyH)PbBr3, which was presumably due to the small distance between the lead cations and bromine atoms of the 4-BrCH2PyH cations, resulting in a radiationless electronic transition. Furthermore, the studied species demonstrated quantum size effects.