Charge-Transfer Forces in the Self-Assembly of Heteromolecular Reactive Solids:  Successful Design of Unique (Single-Crystal-to-Single-Crystal) Diels−Alder Cycloadditions

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American Chemical Society

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Journal of the American Chemical Society

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Electron donor/acceptor (EDA) interactions are found to be a versatile methodology for the engineering of reactive heteromolecular crystals. In this way, a series of the charge-transfer π-complexes between bis(alkylimino)-1,4-dithiin acceptors and anthracene donors are shown to form heteromolecular (1:1) crystalline solids that spontaneously undergo stereoselective [2 + 4] Diels−Alder cycloadditions. The flexible nature of the 1,4-dithiin moiety allows this homogeneous topochemical transformation to proceed with minimal distortion of the crystal lattice. As a result, a unique (single) crystal phase of the Diels−Alder adduct can be produced anti-thermodynamically with a molecular arrangement very different from that in solvent-grown crystals. Such a topochemical reaction between bis(methylimino)-1,4-dithiin and anthracene proceeds thermally and homogeneously up to very high conversions without disintegration of the single crystal. This ideal case of the mono-phase topochemical conversion can be continuously monitored structurally (X-ray crystallography) and kinetically (NMR spectroscopy) throughout the entire range of the crystalline transformation. The resultant “artificial” crystal of the Diels−Alder adduct is surprisingly stable despite its different symmetry and packing mode compared to the naturally grown (thermodynamic) crystal.


Accepted version. Journal of the American Chemical Society, Vol. 123, No. 21 (2001): 4951-4959. DOI. © 2001 American Chemical Society. Used with permission.

Sergey V. Lindeman was affiliated with the University of Houston at the time of publication.