Systematic Synthesis of Lead–Benzenethiolate Coordination Polymers: Influence of Halogen Substituents on Crystal Structure and Semiconducting Properties

Coordination polymers containing sulfur coordination atoms (S-CPs) represent an emerging class of organic–inorganic hybrid semiconductors. Notably, Pb(II)-based S-CPs have garnered increasing attention due to their high electron mobility and narrow band gaps, rendering them promising materials for use in a wide-range optoelectronic applications. Although the semiconducting properties of Pb(II) S-CPs are significantly influenced by the local coordination environment and the (–Pb–S–)n dimensionality, rational design strategies for precisely tuning their crystal structure remain limited. In this study, Pb(II) S-CPs are systematically synthesized using halogen-substituted benzenethiol ligands (HSPhX = 4-halobenzenethiol; X = F, Cl, Br, I), giving the general formula [Pb(SPhX)2]. Single-crystal X-ray diffraction and density functional theory calculations suggest that the electron-withdrawing ability of the halogen substituents modulates the electron density on the thiolate S atoms, thereby governing the S-coordination mode and dimensionality of the (–Pb–S–)n network. Among the synthesized series, KGF-70(I), which was obtained using the weakly electron-withdrawing HSPhI, forms a holodirected coordination geometry and a two-dimensionally-extended (–Pb–S–)n network, resulting in enhanced charge carrier mobility, narrow band gap energy, and anomalous band structure. Furthermore, the potential applicability of KGF-70(I) as a photodetector is demonstrated. Overall, this systematic investigation offers a rational design strategy for tailoring the crystal structure and semiconducting properties of Pb(II) S-CPs.