Structure and Color of Substituted Pentaphenylbismuth

The square‐pyramidal structure is one reason for the intense color of pen‐taphenylbismuth and many of its derivatives, such as 1. The easy electronic excitation is made possible, in this case, by a low‐lying LUMO, which is oriented toward the sixth coordination site of the octahedron. Noteworthy are the lack of shielding by the 4f electrons and the relativistic effects. The trigonal‐bipyramidal derivative 2 is orange instead of violet. equation image