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Crystal structure of 2-(aza ­ niumylmeth ­ yl)pyridinium bis(hydrogen squarate)

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ABSTRACT

The asymmetric unit of the title compound, C6H10N22+·2C4HO4−, comprises two hydrogen squarate (Hsq−; systematic name: 2-hy­droxy-3,4-dioxo­cyclo­butano­late) anions and a 2-(aza­niumylmeth­yl)pyridinium dication. The squaric acid mol­ecules each donate an H atom to the N atoms of the pyridine ring and the amino­methyl units of a 2-(amino­meth­yl)pyridine mol­ecule, forming the 1:2 salt. The Hsq− anions are linked by strong O—H⋯O hydrogen bonds and an N—H⋯O hydrogen bond links the 2-(aza­niumylmeth­yl)pyridinium cation to one of the squaric acid anions. The crystal structure features additional N—H⋯O and O—H⋯O hydrogen bonds, π–π stacking and unusual weak C—O⋯π(ring) inter­actions.

No MeSH data available.


A packing diagram showing the C—O⋯π and π–π stacking inter­actions. [Symmetry codes: (ii) −x + 1, −y + 1, −z + 1; (iv) −x + , y + , −z + ; (v) −x + , y − , −z + .] H atoms not involved in the inter­actions have been omitted for clarity.
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fig3: A packing diagram showing the C—O⋯π and π–π stacking inter­actions. [Symmetry codes: (ii) −x + 1, −y + 1, −z + 1; (iv) −x + , y + , −z + ; (v) −x + , y − , −z + .] H atoms not involved in the inter­actions have been omitted for clarity.

Mentions: The two hydrogen squarate anions are linked in the asymmetric unit by a short hydrogen-bonding inter­action O5—H5A⋯O3 [2.4583 (14) Å] related to the proton-sharing inter­action discussed earlier. This pair of anions is further linked to the 2-(aza­niumylmeth­yl)pyridinium dication by an N1—H1A⋯O1 hydrogen bond, Fig. 1 ▸, Table 1 ▸. O5—H5A⋯O3, N2—H2B⋯O2i and N2—H2B⋯O5i hydrogen bonds form rings with an (7) graph-set motif while N2—H2C⋯O6i and N2—H2B⋯O5i hydrogen bonds combine to form (7) rings. In addition, heteronuclear N2—H2C⋯O6i, and N2—H2A⋯O8ii and homonuclear O4—H4A⋯O6iii and O5—H5A⋯O3 hydrogen bonds generate a larger (14) ring motif (Fig. 2 ▸, Table 1 ▸). The crystal packing also features unusual weak C7—O1⋯Cg2ii, C7—O1⋯Cg3iv and C13—O7⋯Cg2v inter­actions reinforced by π–π stacking inter­actions. These latter contacts [Cg1· · ·Cg3 = 2.5382 (9) Å, Cg2· ··Cg2ii = 3.5997 (9) Å, Cg2· · ·Cg3iv = 3.6406 (10) Å and Cg3·· ·Cg2v = 3.6406 (10) Å; symmetry codes: (ii) 1 − x, 1 − y, 1 − z; (iv)  − x,  + y,  − z; (v)  − x, − + y,  − z] also contribute to the stabilization of the crystal packing (Fig. 3 ▸).


Crystal structure of 2-(aza ­ niumylmeth ­ yl)pyridinium bis(hydrogen squarate)
A packing diagram showing the C—O⋯π and π–π stacking inter­actions. [Symmetry codes: (ii) −x + 1, −y + 1, −z + 1; (iv) −x + , y + , −z + ; (v) −x + , y − , −z + .] H atoms not involved in the inter­actions have been omitted for clarity.
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fig3: A packing diagram showing the C—O⋯π and π–π stacking inter­actions. [Symmetry codes: (ii) −x + 1, −y + 1, −z + 1; (iv) −x + , y + , −z + ; (v) −x + , y − , −z + .] H atoms not involved in the inter­actions have been omitted for clarity.
Mentions: The two hydrogen squarate anions are linked in the asymmetric unit by a short hydrogen-bonding inter­action O5—H5A⋯O3 [2.4583 (14) Å] related to the proton-sharing inter­action discussed earlier. This pair of anions is further linked to the 2-(aza­niumylmeth­yl)pyridinium dication by an N1—H1A⋯O1 hydrogen bond, Fig. 1 ▸, Table 1 ▸. O5—H5A⋯O3, N2—H2B⋯O2i and N2—H2B⋯O5i hydrogen bonds form rings with an (7) graph-set motif while N2—H2C⋯O6i and N2—H2B⋯O5i hydrogen bonds combine to form (7) rings. In addition, heteronuclear N2—H2C⋯O6i, and N2—H2A⋯O8ii and homonuclear O4—H4A⋯O6iii and O5—H5A⋯O3 hydrogen bonds generate a larger (14) ring motif (Fig. 2 ▸, Table 1 ▸). The crystal packing also features unusual weak C7—O1⋯Cg2ii, C7—O1⋯Cg3iv and C13—O7⋯Cg2v inter­actions reinforced by π–π stacking inter­actions. These latter contacts [Cg1· · ·Cg3 = 2.5382 (9) Å, Cg2· ··Cg2ii = 3.5997 (9) Å, Cg2· · ·Cg3iv = 3.6406 (10) Å and Cg3·· ·Cg2v = 3.6406 (10) Å; symmetry codes: (ii) 1 − x, 1 − y, 1 − z; (iv)  − x,  + y,  − z; (v)  − x, − + y,  − z] also contribute to the stabilization of the crystal packing (Fig. 3 ▸).

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ABSTRACT

The asymmetric unit of the title compound, C6H10N22+·2C4HO4−, comprises two hydrogen squarate (Hsq−; systematic name: 2-hy­droxy-3,4-dioxo­cyclo­butano­late) anions and a 2-(aza­niumylmeth­yl)pyridinium dication. The squaric acid mol­ecules each donate an H atom to the N atoms of the pyridine ring and the amino­methyl units of a 2-(amino­meth­yl)pyridine mol­ecule, forming the 1:2 salt. The Hsq− anions are linked by strong O—H⋯O hydrogen bonds and an N—H⋯O hydrogen bond links the 2-(aza­niumylmeth­yl)pyridinium cation to one of the squaric acid anions. The crystal structure features additional N—H⋯O and O—H⋯O hydrogen bonds, π–π stacking and unusual weak C—O⋯π(ring) inter­actions.

No MeSH data available.