Self-assembly of bolaamphiphiles forming alternating layer arrangements with lead and copper divalent ions

Five bifunctional alpha -amino acid-epsilon -carboxy bolaamphiphiles [(2-RS , or RS)-(HOOC)-(CH2)(m)-CONH-(CH2)(n)-CH(COOH)(NH2) m=20,22, n=3,4 labeled (l), (d,l)-C(22)Orn (l), (d), (d,l)-C(22)Lys, (d,l)-C(24)Lys respectively] were synthesized. These molecules were deposited on different aqueous subp hases, and studied by means of grazing incidence X-ray diffraction (GIXD). On deionized water, the bolaamphiphiles (dl)-C(22)Lys yield a mixture of cr ystallites: both a monolayer, in which the chains are tilted from the norma l, and a multilayer in which the molecules lie parallel to the water. On th e other hand, when deposited on mono- or bi-metal ionic subphases, they sel f-assemble into crystalline multilayer films in which the molecules lie par allel to the aqueous solution surface, linked head-to-head and tail-to-tail in the form of extended chains. The latter are juxtaposed such that the me tal ions form sheets separated by the organic molecules, aligned perpendicu lar to the plane of the aqueous solution. Deposition of either the enantiom erically pure or racemic bifunctional bolaamphiphiles on an aqueous solutio n of mixed Cu(Acetate)(2) and Pb(Acetate)(2), yields self-assembled crystal line films composed of the two different metal cations, arranged in alterna ting sheets, separated by the organic spacer. Both GIXD and X-ray-photoelec tric-spectroscopy (XPS) studies (after deposition on solid support) demonst rate that the structures of these films differ form the ones formed on eith er pure Pb(Ac)(2) or on Cu(AC)(2) solutions, thus excluding the simultaneou s formation of the two monometallic crystalline phases.