Partial disorder in organic crystals. The domain structure of C16H16O4Se crystals

Zorkiĭ, P. M.; Nesterova, Ya. M.

doi:10.1007/bf00763577

Cited by 2 publications

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“…They can, for example, depend on the volume of coherently scattering domains. In general, on the basis of X-ray analysis only it is not trivial to distinguish between a partly disordered structure and a structure consisting of completely ordered coherently conjugated domains of two types (see Herbstein, 1964;Zorky & Nesterova, 1986, 1993. In the case of the III -form of chlorpropamide, we consider a structure with a stochastic static disorder of the alkyl tails as unrealistic because the gauche conformation of the neighbouring molecules in the space group P2/c would lead to an extremely short distance between their methyl fragments.…”

Section: Comparison With Phase Transitions In Other Crystals With Flementioning

confidence: 99%

“…because of unrecognized crystal twinning (Herbstein, 1964). Structures with Z 0 > 1 can indicate that the crystal is actually a domain intergrowth of two or more different polymorphs (Bernstein et al, 2008;Bishop & Scudder, 2009;Bond, 2009;Bond et al, 2007;Zorky & Nesterova, 1986, 1993. Structures with high Z 0 values are often characterized by pseudosymmetry or modulation (Kuleshova et al, 2003;Schö nleber et al, 2003) and can be modified, distorted or modulated versions of the lower Z 0 structures (Bernstein et al, 2008).…”

Section: Comparison With Other Molecular Crystals Withmentioning

confidence: 99%

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Solid-state transformations in the β-form of chlorpropamide on cooling to 100 K

Drebushchak

Boldyreva

2011

Acta Crystallogr Sect B

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A single-crystal X-ray diffraction study of the effect of cooling down to 100 K on the β-form of chlorpropamide, 4-chloro-N-(propylaminocarbonyl)benzenesulfonamide, has revealed reversible phase transitions at ∼257 K and between 150 and 125 K: β (Pbcn, Z' = 1) ⇔ β(II) (P2/c, Z' = 2) ⇔ β(III) (P2/n, a' = 2a, Z' = 4); the sequence corresponds to cooling. Despite changes in the space group and number of symmetry-independent molecules, the volume per molecule changes continuously in the temperature range 100-300 K. The phase transition at ∼257 K is accompanied by non-merohedral twinning, which is preserved on further cooling and through the second phase transition, but the original single crystal does not crack. DSC (differential scanning calorimetry) and X-ray powder diffraction investigations confirm the phase transitions. Twinning disappears on heating as the reverse transformations take place. The second phase transition is related to a change in conformation of the alkyl tail from trans to gauche in 1/4 of the molecules, regularly distributed in the space. Possible reasons for the increase in Z' upon cooling are discussed in comparison to other reported examples of processes (crystallization, phase transitions) in which organic crystals with Z' > 1 have been formed. Implications for pharmaceutical applications are discussed.

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Section: Comparison With Phase Transitions In Other Crystals With Flementioning

confidence: 99%