C. H. Griffiths, M. Walker, P. Goldstein
Aug 29, 2007
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Journal
Molecular Crystals and Liquid Crystals
Abstract
Abstract Two polymorphic modifications, a stable orange monoclinic form (mp 231°C) and a metastable yellow orthorhomic form (mp 228.5°C) of dinaphtho(1,2-2′,3′]furan-7,12-dione have been indentified by single crystal X-ray diffraction. The transition from the metastable to the stable phase occurred rapidly at melting and slowly just below the melting temperature. Fluorescence and long wavelength absorption spectra indicate greater overlap of adjacent molecules in the monoclinic phase and this is supported by the greater calculated X-ray density. Differences in molecular packing between this furan-quinone and the isomeric dinaphtho-[2,1–2′,3′]furan-8,13-dione are probably due to a significant departure from planarity in the former caused by the proximity of the quinone oxygen and the benzene ring.