Zeolite-like sorption of volatile organics in beta-[CuL2] (L = {CF3COCHCOC(CH3)(2)OCH3}(-))

The beta -form of the title copper(II) acetylacetonate derivative shows zeo lite-like behavior, as exemplified by its ability to absorb volatile guests instantly and reversibly over a wide range of guest pressures. Sorption is otherms with methylene chloride, chloroform, carbon tetrachloride, n-pentan e, acetone, tetrahydrofuran, and diethyl ether were determined at 30 degree sC or over a range of temperatures. For all guests tested, sorption occurre d even at minimal guest pressure, indicating the presence of porosity of th e host sorbent even without included species present. The nature of the iso therms as well as other characteristics suggests a physical mode of sorptio n on the inner hydrophobic surface of the host pores. With increasing press ure, the isotherms quickly reached plateau values corresponding to a guest/ host ratio of 2/3 for compact molecules and to a lower value for n-pentane and diethyl ether. At elevated temperatures and low guest pressure, the por ous beta -form collapses to the dense, alpha -form of the complex, as does the guest-free beta -form. At 70 degreesC; the enthalpy of the alpha -to-be ta transformation equals 1.31(5) kJ/mol as determined from DSC experiments. In the beta-[CuL2]*2/3(chloroform) compound studied by X-ray diffraction, 1D channel segments of both larger and Smaller widths are filled stoichiome trically with guest species, thus explaining the limiting guest-host ratio observed.