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The supramolecular inclusion complexes of two mandelic acid-based chiral host compounds with dimethylformamide (DMF), (1) and (2), show reversible solid–solid state phase transitions upon lowering the temperature. For both inclusion complexes, the low- [(1a) and (2a) at 170 K] and the high- [(1b) at 250 and (2b) at 270 K] temperature structures were solved. (R)-1,1-Bis(4-tert-butylphenyl)-2-phenylethan-1,2-diol–dimethylformamide (1/1), C28H34O2.C3H7NO (1a), T = 170 K, monoclinic, P21, a = 14.4530 (14), b = 6.0540 (2), c = 16.1117 (14) Å, β = 105.332 (7)°, V = 1359.6 (2) Å3, Z = 2, Dx = 1.162 g cm−3; (1b), T = 250 K, monoclinic, P21, a = 24.8110 (20), b = 6.0739 (2), c = 18.8645 (10) Å, β = 98.100 (6)°, V = 2814.5 (3) Å3, Z = 4, Dx = 1.123 g cm−3. (R)-1,1-Bis(4-tert-butylphenyl)-2-(4-methylphenyl)ethan-1,2-diol–dimethylformamide (1/1), C29H36O2.C3H7NO (2a), T = 170 K, monoclinic, P21, a = 24.4457 (38), b = 5.9519 (6), c = 20.4609 (38) Å, β = 101.95 (1)°, V = 2912.5 (8) Å3, Z = 4, Dx = 1.117 g cm−3; (2b), T = 270 K, triclinic, P1, a = 14.4172 (28), b = 6.0303 (4), c = 17.5636 (56) Å, α = 88.74 (1), β = 101.43 (2), γ = 93.13 (1)°, V = 1494.4 (6) Å3, Z = 2, Dx = 1.088 g cm−3. The low-temperature forms have the higher crystallographic symmetry. In (1b) half of the DMF guests are twisted by 45.0° with respect to those in (1a). A comparative discussion of the four crystal packings is presented.
