Characterization of a New Monoclinic Polymorph of 1,3-Diacetylpyrene

What is it about?

This article reports on a new monoclinic polymorph of 1,3-diacetylpyrene (2°AP-β) characterized in a wide temperature and pressure range. Crystallographic and spectroscopic studies revealed that the structure of 2°AP-β is based on well separated π-stacks of antiparallel molecules in the [100] direction, leading to notable piezochromism and strong luminescence in the solid state. The study also found that the new polymorph exhibits negative thermal expansion (NTE) over a 300 K temperature range and that application of external stimuli provides means to modify crystal structures in a controllable manner.

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Why is it important?

The research described in this article is significant because it reports the characterization of a new polymorph of 1,3-diacetylpyrene, denoted 2°AP-β, which features distinct π-stacks and leads to significantly red-shifted strong photoluminescence, and which also exhibits negative thermal expansion (NTE) over a 300 K temperature range. The article highlights the application of external stimuli to modify crystal structures in a controllable manner and the study of the intricacies of intermolecular interactions. The research demonstrates the use of quantum crystallography approaches, and the possibility of obtaining high-quality and over 80%-complete high-pressure X-ray diffraction data for a weakly scattering low-symmetry organic sample. Key Takeaways: 1. A new polymorph of 1,3-diacetylpyrene, denoted 2°AP-β, was characterized in a wide temperature and pressure range from structural and spectroscopic points of view. 2. The structure of 2°AP-β is based on well separated π-stacks of antiparallel molecules in the [100] direction, which leads to notable piezochromism and strong luminescence in the solid state. 3. The use of quantum crystallography approaches and high-pressure X-ray diffraction data allows for the study of the intricacies of intermolecular interactions in organic crystals.