Copper(I) and Silver(I) 2-Methylimidazolates: Extended Isomerism, Isomerization, and Host-Guest Properties

Syntheses, structures, and properties of univalent coinage metal 2-methylimidazolate supramolecular isomers [M(mim)] (1, M = Cu; 2, M = Ag) were investigated in detail. In addition to the known isomers, namely, zigzag chains [Cu(min-)] (1a) and [Ag(mitn)] (2a), molecular octagon [Cu-8(mim)(8)]center dot C6H6 (1b), decagon [Cu-10(mim)(10)]center dot C8H10 (1c), helical chain [Ag-4(mim)(4)]center dot C6H6 (2b), and S-shaped chain [Ag-4(mim)(4)]center dot C8H10 (2c), two new structures including a polyrotaxane [Cu-10(mim)(10)]center dot[Cu(mim)] (1d, C2/m, a = 14.452(4) angstrom, b = 27.712(7) angstrom, c= 11.427(3) angstrom, beta = 125.899(4)degrees, V = 3707(2) angstrom(3)) and a new octagon [Ag-8(mim)(8)]center dot Me2CO (2d, C2/c, a = 21.852(3) angstrom, b = 12.101(2) angstrom, c = 20.907(3) angstrom, beta = 90.875(2)degrees, V= 5528(2) angstrom(3)) were discovered. The potential porous properties of guest-containing [M(rnim)] isomers were studied by thermogravimetry, X-ray powder diffraction, vacuum thermal desorption, and CO2 sorption experiments. The isomers show distinctly different guest removal behaviors depending on their pore structures. By heating, the guest-containing isomers, 1b-1c and 2b-2d, undergo irreversible, two-step, crystal-to-crystal structural transformations to form the guest-free isomers la or 2a, respectively. Except 1b, other guest-containing isomers can retain their porous structures after removal of the template molecules, which were confirmed by CO2 sorption experiments.