Electrostatic layer-by-layer assembly of ultrathin films containing hexacyclen and p-sulfonatocalix[n]arene macrocycles.

Formation and characteristic properties of new layer-by-layer (LbL) assembled ultrathin films based on 1,4,7,10,13,16-hexaazacyclooctadecane (aza6) and p-sulfonatocalix[n]arenes with n=6 (calix6) and n=8 (calix8) are described. In particular, multilayered films of aza6 and polystyrenesulfonate (PSS), aza6 and calix8 or calix6, aza6 and hexacyanoferrate(II) (HCFII), calix8 and lanthanum(III), and calix8, 18-crown-6 and lanthanum(III) were investigated. The films were prepared upon alternating electrostatic adsorption of the cationic and anionic compounds from aqueous solution at charged substrates. Since the protonation of aza6 proceeds over a wide pH range, the film formation is strongly pH dependent. Linear growth of aza6/PSS films is found at pH 1.7 and 6.0, and superlinear growth at pH 0.9, 2.7, 3.7, and 5.0. The high affinity of aza6 towards inorganic ions favours the formation of LbL-assemblies of aza6 and HCFII counterions. Exposure of these films to Fe(III) leads to formation of Prussian Blue at the surface. The high affinity of p-sulfonato-calix[n]arenes towards La(III) favours the formation of LbL-assemblies of calix6 or calix8 and lanthanum. If additional 18-crown-6 is present in the La(III)-containing dipping solution, multilayered films of calix8, 18-crown-6 and La(III) are obtained.