Monolayers of novel calix[4]arene derivative and its palladium(II) complexes formed at the air-water interface

5,11,17,23-Tetra-tert-butyl-25,27-di{[(2'-amino-4'-methylthio)butyryl]amino ethoxy}-26,28-dihydroxycalix[4]- arene (L) and its mono- and binuclear pall adium(II) complexes (PdLCl2 and Pd2LCl4) were synthesized. Their monolayers at the air-water interface were investigated by film balance measurements (compression/expansion experiments, area relaxation experiments, viscosity measurements) and Brewster angle microscopy. The monolayer oft is inclined to form domains and multilayers, while the monolayer of PdLCl2 demonstrates good reversibility and high collapse pressure. The monolayer formed by Pd2 LCl4 exhibits extraordinary cohesiveness, stability, and robustness. Its ex traordinary properties are likely due to the intermolecular cross-linkage o f precursor complex of Pd2LCl4 via strong chloride bridges. This provides a n example of improving mechanical, properties of film through intermolecula r metal complexing.