Six two- and three-component ammonium carboxylate salt structures with a ladder-type hydrogen-bonding motif, three incorporating neutral carboxylic acid molecules

Abstract

Six ammonium carboxylate salts are synthesized and reported, namely 2-propylammonium benzoate, C(3)H(10)N(+)·C(7)H(5)O(2)(-), (I), benzylammonium (R)-2-phenylpropionate, C(6)H(10)N(+)·C(9)H(9)O(2)(-), (II), (RS)-1-phenylethylammonium naphthalene-1-carboxylate, C(8)H(12)N(+)·C(11)H(7)O(2)(-), (III), benzylammonium-benzoate-benzoic acid (1/1/1), C(6)H(10)N(+)·C(7)H(5)O(2)(-)·C(7)H(6)O(2), (IV), cyclopropylammonium-benzoate-benzoic acid (1/1/1), C(3)H(8)N(+)·C(7)H(5)O(2)(-)·C(7)H(6)O(2), (V), and cyclopropylammonium-ea-cis-cyclohexane-1,4-dicarboxylate-ee-trans-cyclohexane-1,4-dicarboxylic acid (2/1/1), 2C(3)H(8)N(+)·C(8)H(10)O(4)(2-)·C(8)H(12)O(4), (VI). Salts (I)-(III) all have a 1:1 ratio of cation to anion and feature three N(+)-H...O(-) hydrogen bonds which form one-dimensional hydrogen-bonded ladders. Salts (I) and (II) have type II ladders, consisting of repeating R(4)(3)(10) rings, while (III) has type III ladders, in this case consisting of alternating R(4)(2)(8) and R(4)(4)(12) rings. Salts (IV) and (V) have a 1:1:1 ratio of cation to anion to benzoic acid. They have type III ladders formed by three N(+)-H...O(-) hydrogen bonds, while the benzoic acid molecules are pendant to the ladders and hydrogen bond to them via O-H...O(-) hydrogen bonds. Salt (VI) has a 2:1:1 ratio of cation to anion to acid and does not feature any hydrogen-bonded ladders; instead, the ionized and un-ionized components form a three-dimensional network of hydrogen-bonded rings. The two-component 1:1 salts are formed from a 1:1 ratio of amine to acid. To create the three-component salts (IV)-(VI), the ratio of amine to acid was reduced so as to deprotonate only half of the acid molecules, and then to observe how the un-ionized acid molecules are incorporated into the ladder motif. For (IV) and (V), the ratio of amine to acid was reduced to 1:2, while for (VI) the ratio of amine to acid required to deprotonate only half the diacid molecules was 1:1.