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 N-H⋯O H-bond from the NH3+ and the CO2−. Apart from the N-H⋯O H-bond, the O-H•••O H-bonds were also found at 5, 6, 9 and 10. 3, 9 and 10 had the additional N-H⋯N, N-H•••I and N-H•••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.