Oriented crystalline monolayers and bilayers of 2 x 2 silver(I) grid architectures at the air-solution interface: Their assembly and crystal structure elucidation

Oriented crystalline monolayers, similar to 14 Angstrom thick, of a 2 x 2 A g+ grid complex, self-assembled at the air-solution interface starting from an water-insoluble ligand 3,6-bis[2-(6-phenylpyridine)]pyridazine spread o n silver-ion-containing solutions,were examined by grazing-incidence X-ray diffraction and specular X-ray reflectivity using synchrotron radiation. Th e monolayer structure was refined, including a determination of the positio ns of the counterions, with the SHELX-97 computer program. The monolayers w ere transferred from the interface onto various solid supports and visualiz ed by scanning force microscopy, and characterized by X-ray photoelectron s pectroscopy in terms of molecular structure. On surface compression, the in itial self-assembled monolayer undergoes a transition to a crystalline bila yer in which the two layers, almost retaining the original arrangement, are in registry. Such a phase transition is of relevance to the understanding of crystal nucleation.