Pd(II) and Pt(II) complexes with amphiphilic ligands: formation of micelles and [5]rotaxanes with alpha-cyclodextrin in aqueous solution.

[3]Pseudorotaxanes [1(alpha-CD)(2)][X] (X=Cl, NO(3)), prepared from reaction of an N-alkylbipyridinium [4,4'-bpy-N-(CH(2))(10)OC(6)H(3)-3,5-(OMe)(2)][X] ([1][X]) and alpha-CD, react with M(NO(3))(2)(en) (M=Pd, Pt; en=1,2-ethylenediamine) in a 2:1 molar ratio to afford [5]rotaxanes [M{(4,4'-bpy-N-(CH(2))(10)OC(6)H(3)-3,5-(OMe)(2))(alpha-CD)(2)}(2) (en)][NO(3)](4) ([2(alpha-CD)(4)][NO(3)](4), M=Pd; [3(alpha-CD)(4)][NO(3)](4), M=Pt). A similar reaction of [1][Cl] with [M(NO(3))(2)(en)] (M=Pd, Pt) produces amphiphilic Pd and Pt complexes, [2][NO(3)](4) and [3][NO(3)](4). Complexes [2][NO(3)](4) and [3][NO(3)](4) form micelles in the presence of small amounts of dyes (Nile red and pyrene) in water. The critical micelle concentration (CMC) was determined by the absorption peak of the dye, which is encapsulated in the micelles in solution. Micelle formation is confirmed by dynamic light scattering measurement of the solution and TEM (transmission electron microscopy) images of the micelles deposited from the solution. Addition of alpha-CD to the aqueous solution containing these amphiphilic complexes results in degradation of the micelle structure and the formation of [5]rotaxanes, [2(alpha-CD)(4)][NO(3)](4) and [3(alpha-CD)(4)][NO(3)](4).