Synthesis and Crystal Structures of [(Nicotinic Acid)₂H]⁺I⁻, [(2-Amino-6-methylpyridine)H]⁺(NO₃)⁻, and the 1:1 Complex Between 1-Isoquinoline Carboxylic Acid (Zwitter Ion) and L-Ascorbic Acid Assembled via Hydrogen Bonds

Summary.

Three new complexes, namely [(nicotinic acid)₂H]⁺I⁻, [(2-amino-6-methylpyridine)H]⁺ (NO₃)⁻, and the 1:1 complex between 1-isoquinoline carboxylic acid (zwitter ion form) and L-ascorbic acid were synthesized. The IR spectra revealed different types of hydrogen bonds in these compounds. The X-ray structure determination has shown the first compound to consist of a packing of [(nicotinic acid)₂H]⁺ cations and I⁻ anions. In the dimeric cation the two nicotinic acid molecules (zwitter ions) are connected through hydrogen bonds (O–H⋯O). Each dimer is further engaged in other hydrogen bonds with adjacent dimers giving 2D layers. The I⁻ ion is located at the inversion center. In the second compound the cation and anion are connected via hydrogen bonds formed between oxygen atoms of the NO₃ ⁻ anion and NH and NH₂ of the cation generating a layer structure. All atoms are coplanar on mirror planes. In the 1:1 complex the two molecules are connected through hydrogen bonds formed between the two oxygen atoms of the carboxylate group of 1-isoquinoline carboxylic acid (zwitter ion) and the oxygen atoms of the two adjacent hydrogen groups of the L-ascorbic acid molecule. These complex molecules are engaged in other hydrogen bonds with each other forming a 2D system normal to the long b-axis of the unit cell.