π‐π Interactions, Architecture, and Bandwidths in “Molecular Metals”. A Synthetic and Electronic Structure Study of Monomeric and Cofacially Joined Dimeric Germanium Phthalocyanines

Small molecule spectroscopy on M(Pc)(OR) 2 and ROM(Pc)OM(Pc)OR molecular fragments (M = Si, Ge; Pc = phthalocyaninato) of the conductive polymer [M(Pc p+ )O] n provides a unique probe of the band structure‐forming π‐π interactions. We describe here the synthesis and characterization of the M = Ge monomer and dimer where R = ( t ‐Bu)Me 2 Si‐. The lowest energy He I photoelectron spectroscopic feature of the dimer is a doublet with a splitting of 0.19(3) eV. This splitting can be associated with the cofacial HOMO‐HOMO Pc‐Pc interaction and translates into a tight‐binding bandwidth in the polymer of 0.38(6) eV. This result is in good agreement with an experimental bandwidth of 0.48(5) eV obtained from a Drude analysis of the {[Ge(Pc)0]I 1.1 } n reflectance spectrum and a bandwidth of 0.50 eV derived from theoretical calculations.