Conformational analysis of the salts of N-[(2,3-dimethylphenoxy)alkyl]aminoalkanol derivatives.

Four new crystal structures of the salts of N-[(2,3-dimethylphenoxy)alkyl]aminoalkanol derivatives with anticonvulsant activity are reported. Bis{D,L-trans-N-[(2,3-dimethylphenoxy)ethyl]-1-hydroxycyclohexan-2-aminium} succinate, 2C16H26NO2+·C4H4O42-, 1, and its polymorph 1p, crystallize in the monoclinic space group P21/n, 1 with two cations and one anion, and 1p with four cations and two anions in the asymmetric unit. The other two salts, D,L-trans-N-[(2,3-dimethylphenoxy)ethyl]-1-hydroxycyclohexan-2-aminium 6-carboxypyridine-2-carboxylate, C16H25NO2+·C7H4O4-, 2, and N-[(2,3-dimethylphenoxy)propyl]-3-hydroxypiperidinium pyridine-2-carboxylate, C16H26NO2+·C6H4O2-, 3, crystallize in the monoclinic space group P21/c, with one cation and one anion in each asymmetric unit. The geometry of the created polymorphs indicates the main differences in the conformation of the linker between the two rings. The arrangement of the ether O atom and the N atom shows an unusual antiperiplanar conformation for the cations of 1p. The crystal packing of all four salts is dominated by charge-assisted hydrogen bonding between the protonated N atom and the carboxylate group of the corresponding acid. Structural studies have been enriched by quantum chemical calculations.