Incommensurately modulated structure of quininium (R)-mandelate

What is it about?

Quininium (R)-mandelate is an organic salt with an incommensurately modulated structure at room temperature. The large number of first- and second-order satellite reflections with relatively strong intensities indicates a significant modulation, because of which no average structure solution could be obtained. Hence the structure solution was performed in two suitable superstructure approximations.

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Why is it important?

Positional modulation functions and modulation functions for the anisotropic atomic displacement parameters were introduced. The modulation originates from a competition between intramolecular and intermolecular forces, which is reflected, in the superspace formalism, in the modification of hydrogen bonds along the internal space variable t.