Article pubs.acs.org/crystal
The Third Ambient Aspirin Polymorph Alexander G. Shtukenberg,† Chunhua T. Hu,† Qiang Zhu,*,‡ Martin U. Schmidt,§ Wenqian Xu,∥ Melissa Tan,† and Bart Kahr*,†,⊥ †
Department of Chemistry and Molecular Design Institute, New York University, 100 Washington Square East, Room 1001, New York City, New York 10003, United States ‡ Department of Physics and Astronomy, High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Las Vegas, Nevada 89154, United States § Institute of Inorganic and Analytical Chemistry, Goethe University, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany ∥ X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States ⊥ Department of Advanced Science and Engineering (TWins), Waseda University, Tokyo 162-0056, Japan S Supporting Information *
ABSTRACT: Polymorphism of aspirin (acetylsalicylic acid), one of the most widely consumed medications, was equivocal until the structure of a second polymorph II, similar in structure to the original form I, was reported in 2005. Here, the third ambient polymorph of aspirin is described. It was crystallized from the melt, and its structure was determined using a combination of X-ray powder diffraction analysis and crystal structure prediction algorithms.
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banded spherulites.14 A few milligrams of aspirin (SigmaAldrich lot 081M0194V or Spectrum lot 2AI0521) was melted (Tm = 133 °C) between glass slides on a hot plate to form a ca. 5 μm film. This melt undergoes spontaneous crystallization at room temperature to give aspirin I as striking banded spherulites12,13 (Figure 1). These structures are accompanied by a small fraction (
