Low-temperature topochemical transformation of Bi13Pt3I7 into the new layered honeycomb metal Bi12Pt3I5.

Ordered single-crystals of the metallic subiodide Bi13 Pt3 I7 were grown and treated with n-butyllithium. At 45 °C, complete pseudomorphosis to Bi12 Pt3 I5 was achieved within two days. The new compound is air-stable and contains the same ${{{\hfill 2\atop \hfill \infty }}}$[(PtBi8/2 )3 I](n+) honeycomb nets and iodide layers as the starting material Bi13 Pt3 I7 , but does not include ${{{\hfill 1\atop \hfill \infty }}}$[BiI2 I4/2 ](-) iodidobismuthate strands. Electron microscopy and X-ray diffraction studies of solid intermediates visualize the process of the topochemical crystal-to-crystal transformation. In the electronic band structures of Bi13 Pt3 I7 and Bi12 Pt3 I5 , the vicinities of the Fermi levels are dominated by the intermetallic fragments. Upon the transformation of Bi13 Pt3 I7 into Bi12 Pt3 I5 , the intermetallic part is oxidized and the Fermi level is lowered by 0.16 eV. Whereas in Bi13 Pt3 I7 the intermetallic layers do not interact across the iodidobismuthate spacers (two-dimensional metal), they couple in Bi12 Pt3 I5 and form a three-dimensional metal.