A Polymorph Lost and Found: The High-Temperature Crystal Structure of Pentacene


  • We thank A. P. Ramirez for valuable discussions. Work at Bell Laboratories was in part supported by the U.S. Department of Energy, contract DE-FG02-04ER46118. We are also grateful to the Swiss National Science Foundation for financial support and to the Swiss–Norwegian Beamlines Consortium for providing access to synchrotron radiation.


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A well-defined structural phase transformation is observed in bulk single crystals of pentacene, whereas pentacene powders heated above the phase-transformation temperature do not always fully convert, and upon cooling, coexistence of the two polymorphs is observed down to room temperature. The first-order phase transformation is isostructural: the close-packed herringbone-type layers shift against each other, keeping the same symmetry.