Hydroxytetraphenylenes, a new type of self-assembling building block and chiral catalyst.

Tetraphenylenes are structurally exceptional molecules with rigid conformations so that substituents of these compounds demonstrate highly directional dispositions. As such, these molecules are potential candidates for employment as organocatalysts or ligands in asymmetric synthesis. Careful design and manipulation of the structural features of tetraphenylenes should also lead to the formation of supramolecular helical scaffolds or other supermolecules with fascinating arrangements. We would like to present here a brief summary on the chemistry of some hydroxytetraphenylenes that were synthesized in our laboratories in Shanghai and Hong Kong. This article will serve as a preview of the chemistry of the tetraphenylene family that hopefully has the potential to emerge.

Massive Stokes shift in 12-coordinate Ce(NO2)63-: crystal structure, vibrational and electronic spectra.

The Ce3+ ion in Cs2NaCe(NO2)6 (I), which comprises the unusual Th site symmetry of the Ce(NO2)63- ion, demonstrates the largest Ce-O Stokes shift of 8715 cm-1 and the low emission quenching temperature of 53 K. The activation energy for quenching changes with temperature, attributed to relative shifts of the two potential energy curves involved. The splitting of the Ce3+ 5d1 state into two levels separated by 4925 cm-1 is accounted for by a first principles calculation using the crystal structure data of I. The NO2- energy levels and spectra were investigated also in Cs2NaLa(NO2)6 and modelled by hybrid DFT. The vibrational and electronic spectral properties have been thoroughly investigated and rationalized at temperatures down to 10 K. A comparison of Stokes shifts with other Ce-O systems emphasizes the dependence upon the coordination number of Ce3+.

Oxadisilole-fused isobenzofurans. Synthesis and characterization of oxadisilole-substituted acenes.

Mono- and bis-oxadisilole-fused isobenzofurans were first synthesized and isolated. A series of mono-, bis-, and tris-oxadisilole-substituted acenes were then synthesized by benzyne Diels-Alder reactions with the isobenzofurans. The photophysical, redox, and thermal properties of these new acenes were characterized.