Molecular structures of ten ionic hydrogen bond-mediated anhydrous tert-butylammonium salts from different carboxylic acids

Abstract

Cocrystallization of the simplest bulky organic amine, tert‑butylamine (L), with a series of organic acids got a whole of 10 anhydrous salts with the compositions: tert‑butylammonium 2-(4-chlorophenoxy)-2-methylpropionate [(HL)+·(cpmppa−), cpmppa−=2-(4-chlorophenoxy)-2-methylpropionate] (1), bis(tert‑butylammonium) dibenzoyl-l-tartarate [(HL+)2·(dbztat)2−, (dbztat)2- = dibenzoyl-l-tartarate] (2), tert‑butylammonium pyrazinecarboxylate [(HL+)·(pyrca)−, pyrca = pyrazinecarboxylate] (3), tert‑butylammonium 2-(4-chlorobenzoyl)benzoate [(HL+)·(cbzbz)−, cbzbz = 2-(4-chlorobenzoyl)benzoate] (4), tert‑butylammonium 3-methylsalicylate [(HL+)·(3-msal)−, 3-msal = 3-methylsalicylate] (5), tert‑butylammonium 4-methylsalicylate [(HL+)·(4-msal)−, 4-msal = 3-methylsalicylate] (6), tert‑butylammonium 2‑chloro-4-nitrobenzoate [(HL+)·(cnba)−, cnba = 2‑chloro-4-nitrobenzoate] (7), tert‑butylammonium 4‑bromo-3,5-dimethoxy benzoate [(HL+)·(bdmbza)−, bdmbza = 4‑bromo-3,5-dimethoxy benzoate] (8), tert‑butylammonium 3,5-diiodosalicylate [(HL+)·(didsal)−, didsal = 3,5-diiodosalicylate] (9) and tert‑butylammonium 3,5,6-trichlorosalicylate [(HL+)·(tcsal)−, tcsal =3,5,6-trichlorosalicylate] (10). The salts have been featured by XRD, IR and EA, the melting points were also gauged. Their structural and supramolecular aspects are analyzed in detail; all compounds are ionic with H-transferring to the tert‑butylamine.The result unveils that among the whole investigated crystals the NH2 units in L are protonated when the acids are deprotonated and the crystal packing is interpreted via the strong charge-assisted NH⋯O H-bond from the NH3+ and the CO2−. Apart from the NH⋯O H-bond, the OH···O H-bonds were also found at 5, 6, 9 and 10. 3, 9 and 10 had the additional NH⋯N, NH···I and NH···Cl H-bonds, respectively. Deep analysis of the crystal packing uncovered that a different set of additional O···O, Cl···Cl, Cl···O, Br···O, I···I, CH3···C, CH3···CH, CH3···CH3, CH···O/CH3···O, CH3···Cl and CH3···π contacts contribute to the stabilization and expansion of the total structures. For the synergism of the various nonbonding forces these structures had the homo/hetero supramolecular synthons. Some classical synthons of R22(8), R42(8), R43(10) and R44(12), commonly contained in solids of organic acids with amine, were present in these hydrogen bonding nets.