| Popis: |
Crystal structures of pyridinium 1,3-dihydro-1,3-dioxo-2 H -inden-2-ylide (PI) of a zwitterionic molecule and its nitrogen substituted compounds, 4N-PI and 5N-PI, were solved with X-ray diffraction analyses. Whereas PI and 5N-PI showed centrosymmetric crystal structures, 4N-PI demonstrated a noncentrosymmetric crystal structure where all the molecules orient to almost the same direction. To elucidate the stability of such a polarized structure, we examined interatomic close contacts among the nearest neighbor molecules in the crystals and calculated intermolecular interaction energies with relation to those contacts. As a result, the noncentrosymmetric crystal structure of 4N-PI turns out to be realized by a weak hydrogen bond in the C–H···N manner formed only in the case of this compound. |
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