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 aza6and polystyrenesulfonate (PSS), aza6 and calix8 or calix6, aza6 and hexacyanoferrate(II) (HCFII), calix8 and lanthanum(III), and calix8, 18-crown-6and 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 aza6proceeds 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 super-linear 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-6is present in the La(III)-containing dipping solution, multilayered films of calix8, 18-crown-6and La(III) are obtained.