SUBTLE CONTROL IN SOLUTION AND CRYSTAL STRUCTURES WITH WEAK HYDROGEN BONDS: THE UNUSUAL PROFILE OF DIMETHYL 3, 12-DIOXO-7, 8 DITHIA 4, 11-DIAZABICYCLO[12.2.2]OCTADECA-1(16), 14, 17-TRIENE 5, 10-DICARBOXYLATE (TDA1)

[摘要]：The structural features of the title compound were determined or examined by three diverse procedures: single crystal X-ray diffraction analysis, solution spectroscopic procedures and quantum mechanical theoretical calculations. The conformational asymmetry of the macrocycle provides the opportunity to form one strong N-H center dot center dot center dot O-C intermolecular hydrogen bond, as well as, a number of weak C-H center dot center dot center dot O-C bonds. The interior of the macrocycle has short approaches for N-H center dot center dot center dot pi and N-H center dot center dot center dot S. The many weak hydrogen bonds cooperate to form a very hard, robust crystal. Crystal parameters: C18H22N2O6S2, P2(1)2(1)2(1), a = 5.108(1) angstrom, b = 18.948(4) angstrom, c = 21.029(3) angstrom, alpha = beta = gamma = 90 degrees. Quantum chemical calculations have provided a strong foundation for weak hydrogen bonds. Contrary to popular belief, the present work has conclusively proved that the importance of weak hydrogen bonds is perhaps underestimated.

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