The limited influence of glaciations in Tibet on global climate over the past 170000 yr

Thiacalixarenes bearing phenylazo or ethynylic groups on the lower rims were prepared and fully characterized. The functional groups were chosen for their ability to increase the electron delocalisation over the molecule and to form metal complexes. The formation of complexes between phenylazothiacalixarenes and metal salts (Zn2+, Ag+...), and the synthesis of platinum acetylides from ethynylthiacalixarenes were investigated. Preliminary studies on optical limiting properties for both ligands and complexes is reported. Clamping levels of ~4 µJ at 532 nm, were observed for both tetra(pentylphenylethynyl)tetrapropoxythiacalix[4]arene (150 mM in THF, 99% transmission) and the platinum complex (30 mM in THF, 83% transmission). A second functionalisation (upper rims) with metal alkoxide groups has also been investigated in order to prepare hybrid materials incorporating the optically active molecule. The same macrocycle core was thus bifunctionalised, and used for its optical properties on one side and as a precursor of an inorganic network for hybrid materials on the other.