Supramolecular Band Gap Engineering and Solvatochromic Nanowires

The electronic structures of Upid/one-dimensional mixed valence complexes can be controlled based on the combination of metal ions [64], On the other hand, the lipids also exert significant effect on the electronic structures. For example, the CT absorption peaks observed for [Pt(en)2][PtX2(en)2](19)4 in chlorocyclohexane (X = Cl, 2.15 eV X = Br, 0.87 eV X = I, less than 0.56 eV). These CT peaks are significantly red shifted compared to those observed for the crystalUne perchlorates [Pt(en)2][PtX2(en)2](C104)4 (X = Cl, 2.72 eV X = Br, 1.95 eV) [82]. 

The observed red-shift is ascribed to the enhanced delocahzation of the excited Pt(Ill)-Pt(III) states in the coordination chain, which decreases the LUMO-HOMO energy gap of the one-dimensional complex. In the lipid complexes, densely packed sulfonate groups seem to direct the electrostatically bound Pt(en)2 and PtCl2(en)2 complexes to coordinate in higher density. This causes the increase in the overlap between dz2 and p orbitals, depending on the molecular packing and chemical structure of the lipid molecules. The shortened inter-platinum (Pt -Cl-Pt ) distance would pro- 

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