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)

Abstract

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···O-C intermolecular hydrogen bond, as well as, a number of weak C-H···O-C bonds. The interior of the macrocycle has short approaches for N-H··Π and N-H···S. The many weak hydrogen bonds cooperate to form a very hard, robust crystal. Crystal parameters:C₁₈H₂₂N₂O₆S₂,P2₁2₁2₁, a = 5.108(1) Å, b = 18.948(4) Å, c = 21.029(3) Å, α = β = γ = 90°. 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.