Hybrid Charge-Transfer Semiconductors: (C7H7)SbI4, (C7H7)BiI4, and Their Halide Congeners

The family of hybrid metal-halide semiconductors (C₇H₇)MX₄ (M = Bi³⁺, Sb³⁺; X = Cl^–, Br^–, I^–) was synthesized. The optical and electronic properties of the new compounds were elucidated, revealing electronic band gaps that span the visible region. The tropylium cations stack into columns separated by chains of edge-sharing M-X octahedra to yield a low dimensional crystal structure with electron and hole charge carriers confined to the organic and inorganic components, respectively.