Ligand-Directed Valence\nBand Engineering in Pb<sup>2+</sup> Hybrid Crystals: Achieving Dispersive\nBands and Shallow\nValence Band Maximum

While\ncrystalline hybrid solids hold great potential\nas novel semiconductors,\nmost semiconductive hybrids utilize transition metal ions, which inherently\nlimit carrier mobility due to the small band dispersion derived from\nthe d orbitals. The filled s orbitals of post-transition metal ions\noffer the potential to design dispersed valence bands, but a method\nto translate the local structure design of these metal ions to valence\nband engineering is still in development. This study focuses on Pb<sup>2+</sup>-containing hybrid crystals, developing a simple strategy\nto control the Pb<sup>2+</sup> coordination geometry through the molecular\ndesign of azole ligands. By preprogramming the coordination number\nof Pb<sup>2+</sup> with azolate ligands, we succeeded in obtaining\nan isotropic coordination environment at a higher coordination number,\nresulting in a dispersed valence band and shallow valence band maximum\nwhile having a wide band gap. Detailed analysis of the band structures\nreveals that the energy levels and symmetry of the molecular orbitals\nof the anions play important roles in realizing these antinomic properties.\nThis ligand-directed approach achieves both isotropy and covalency\nin the coordination bond by exploiting the diversity of the molecular\norbitals. Our findings provide a foundation for future design strategies\nto optimize electronic structures in hybrid materials, advancing their\napplication in semiconductive devices.