Crystal structure of a new molecular salt: 4-aminobenzenaminium 5-carboxypentanoate

Abstract

The asymmetric unit of the title molecular salt (systematic name: 4-aminoanilinium 5-carboxypentanoate), C 6 H 9 N 2 + ÁC 6 H 9 O 4 À , consists of half a 4-aminobenzenaminium cation (4-ABA) and half a 5-carboxypentanoate anion (5-CP); the other half of each ion is generated by inversion symmetry. Protonation of p-phenylenediamine (PPDA) leads to the formation of a 1:1 salt, but scrutiny of the crystal structure reveals that both of the amine groups of PPDA are partially protonated, with a half-occupied H atom. For the 5-CP anion, an H atom is positioned on an inversion center midway between two O atoms of inversion-related 5-CP ions. In the crystal, the 5-CP anions are linked by the O-HÁ Á ÁO hydrogen bond to form chains propagating along the [110] direction. The chains are linked via N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds involving the 4-ABA cations, forming a three-dimensional supramolecular framework. The title salt was also prepared by mechanochemical synthesis using liquid-assisted grinding (LAG). Its PXRD pattern matches that of the simulated pattern of the crystal structure of the title molecular salt.

2-Aminoanilinium 4-methylbenzenesulfonate

“…1) with all atoms located in general positions. The geometric parameters of the cation and the anion are in their normal ranges and are in agreement with previously reported data (Mishra & Pallepogu, 2018;Narvekar & Srinivasan, 2020).…”

Benzene-1,2-diaminium bis(4-methylbenzene-1-sulfonate)

“…The aromatic diamine, benzene-1,2-diamine also known as o-phenylenediamine, can function as a neutral ligand and bind to a metal via both amine N atoms (Koizumi & Fukuju, 2011;Guillé n et al, 2018) or by a single nitrogen in a monodentate fashion (Nelson et al, 1982;Dickman, 2000). In addition, benzene-1,2-diamine can function as a charge-balancing dication in which both the amine N atoms are protonated (Raghavaiah et al, 2006;Powers & Geiger, 2019) or as a monocation (Raghavaiah et al, 2005;Mishra & Pallepogu, 2018). The structural diversity of the compounds of benzene-1,2-diamine in neutral or cationic form is highlighted by the results of a survey of the Cambridge Structural Database (CSD; Groom et al, 2016), which had more than 220 hits for the above three types of compounds.…”