The first "organic zeolite" with isomerizing building blocks: Single-crystal-to-single-crystal desolvation and structure of the empty matrix

The microporous beta polymorph of the title compound has been prepared as a crystalline product by slow removal of the guest from the inclusion compound with methylene chloride, [CuL2]*2/3(CH2Cl2) (L is 1,1,1-trifluoro-5,5-dimethyl-5-methoxyacetylacetonate, {CF3COCHCOC(CH3)(2)OCH3}(-)) Collapse of the crystals of the beta polymorph into the thermodynamically stable alpha form has been studied by visual observation and DSC calorimetry, the product exhibiting much higher kinetic stability than the polycrystalline samples prepared so far. The crystal structure of the beta polymorph was determined by single-crystal XRD methods both at 293 and 173 K. The beta polymorph retains the same 31) polymeric coordination framework as found previously in inclusion compounds of the complex. The structures of the beta and alpha polymorphs are compared and the variation of the beta matrix in a series of compounds was analyzed. The beta framework described in this work seems to be the most flexible of all coordination polymers known so far, preserving its microporous structure upon guest exchange or removal; the complete range of change in molar volume observed for the matrix is 8.6%.