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Crystal structures of 2-amino-pyridine citric acid salts: C 5 H 7 N 2+·C 6 H 7 O 7- and 3C 5 H 7 N 2+·C 6 H 5 O 73

Crystal structures of 2-amino-pyridine citric acid salts: C 5 H 7 N 2+·C 6 H 7 O 7- and 3C 5 H 7 N 2+·C 6 H 5 O 73

Shet M Prakash, S Naveen, N K Lokanath, P A Suchetan, Ismail Warad

Acta Crystallogr E Crystallogr Commun. 2018 Jul 17;74(Pt 8):1111-1116.

PMID: 30116573

Abstract:

2-Amino-pyridine and citric acid mixed in 1:1 and 3:1 ratios in ethanol yielded crystals of two 2-amino-pyridinium citrate salts, viz. C5H7N2+·C6H7O7- (I) (systematic name: 2-amino-pyridin-1-ium 3-carb-oxy-2-carb-oxy-methyl-2-hy-droxy-propano-ate), and 3C5H7N2+·C6H5O73- (II) [systematic name: tris-(2-amino-pyridin-1-ium) 2-hy-droxy-propane-1,2,3-tri-carboxyl-ate]. The supra-molecular synthons present are analysed and their effect upon the crystal packing is presented in the context of crystal engineering. Salt I is formed by the protonation of the pyridine N atom and deprotonation of the central carb-oxy-lic group of citric acid, while in II all three carb-oxy-lic groups of the acid are deprotonated and the charges are compensated for by three 2-amino-pyridinium cations. In both structures, a complex supra-molecular three-dimensional architecture is formed. In I, the supra-molecular aggregation results from Namino-H⋯Oacid, Oacid⋯H-Oacid, Oalcohol-H⋯Oacid, Namino-H⋯Oalcohol, Npy-H⋯Oalcohol and Car-H⋯Oacid inter-actions. The mol-ecular conformation of the citrate ion (CA3-) in II is stabilized by an intra-molecular Oalcohol-H⋯Oacid hydrogen bond that encloses an S(6) ring motif. The complex three-dimensional structure of II features Namino-H⋯Oacid, Npy-H⋯Oacid and several Car-H⋯Oacid hydrogen bonds. In the crystal of I, the common charge-assisted 2-amino-pyridinium-carboxyl-ate heterosynthon exhibited in many 2-amino-pyridinium carboxyl-ates is not observed, instead chains of N-H⋯O hydrogen bonds and hetero O-H⋯O dimers are formed. In the crystal of II, the 2-amino-pyridinium-carboxyl-ate heterosynthon is sustained, while hetero O-H⋯O dimers are not observed. The crystal structures of both salts display a variety of hydrogen bonds as almost all of the hydrogen-bond donors and acceptors present are involved in hydrogen bonding.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP84477872	H-7		84477-87-2	Price

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