Nano-fiim structures constructed by self-assembly of co(lll) biuretato complexes and long alkyl imidazolium cations

A Co(III) biuretato complex, [Co ^III{ph(biu) ₂)] (ph(biu) ₂ = o-phenylenebis(biuretato)) can form layer structures by its self-assembling with a multiply hydrogen bonding network. PPh ₄[Co ^III{ph(biu) ₂)]. 3CHCL ₃ (PPh ₄ ⁺ = Tetraphenylphosphonium cation) crystallizes in the triclinic, space group P1, with a = 9.740(5) A, b = 13.980(8) A, c = 16.792(9) A, a = 103.976(7)°, 13 = 95.592(8)°, 'y = 103.1 65(8)°, V = 2132 A, and Z = 2. In the crystal, counter cations, PPh, are inserted between the layer structures of [Co ^III{ph(biu) ₂}] ^- aggregates, resulting in formation of a multi-layered structure. A treatment of K[Co ^III{ph(biu) ₂}] with C ₁₈MelmCl (C ₁₈Mel m ⁺ = 1 -octadecyl-3-methyl-imidazolium cation) in an aqueous solution with a trace amount of PPh ₄Cl, gave the glaring silver solution containing self-organized nano-film structures. Optical microscopic and AFM studies clearly showed that rectangle-shaped nano-film structures were formed by self-assembly of [Co ^III{ph(biu) ₂}] ^- and C ₁₈Melm ⁺ in the solution, and their sizes were approximately ranged to 6∼13 μm in length, 3∼7 μm in width and 25.2 ± 6.2 nm in thickness. Using spectroscopic and XRD data, we concluded that these nano-films have a alternatively accumulated multilayer-structure of [Co ^III{ph(biu) ₂}] ^- layer and C ₁₈Melm ⁺ bilayer structures, the repeating distance being d ₀₀₁ = 2.22 nm.