Construction of functional supramolecules based on the electronic properties of heteroatoms and nonalternant conjugation

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A nonaltemant organyl ligand derived from azulene, a 1,3-dichloro-2-azulenyl group, is introduced for the first time into the bismuth and antimony center. Conversion of the azulenylbismuthanes into the pentacoordinated difluorides by xenon difluoride promotes the π-polarization of the azulene nucleus, which is detected as a color change in solution as well as changes in the chemical shifts of the ^<13>C NMR spectra. Similar tendency is observed in the antimony congeners. The X-ray crystallographic study of (1,3-dichloro-2-azulenyl)diphenylbismuth difluoride reveals that the intermolecular π-π stacking takes place between the azulenyl groups through the interaction of the five-membered ring with the seven-membered ring. This may reflect the more polarized azulenyl group of the difluorides, which strengthens the stacking interaction.(1,3-Dihalo-2-azulenyl)diphenylphosphines [halogen=Cl,Br] have been synthesized, and the effect of the nonaltemant azulenyl group on the reactivity and properties of these phosphines has been studied in comparison with that of the group 15 congeners. The electronic structure of the nonalternant conjugation is dramatically affected by the change in the valency at the phosphorus. Thus, oxidation of the azulenyldiphenylphosphines with hydrogen peroxide proceeded with a dramatic color change from green to blue, giving the corresponding phosphine oxides. The ^<13>C NMR study shows the enhanced π-polarization in the azulenyl group of the phosphine oxides compared to that of the parent phosphines, but the degree is not as marked as that observed in the bismuth and antimony systems. Azulenylphosphine oxide has head-to-tail π-π stacking in crystals, reflecting the enhanced π-polarization in the high oxidation state of the phosphorus center.