Abstract
The crystal structure of di-ammonium potassium citrate, 2NH4 +·K+·C6H5O7 3-, has been solved and refined using laboratory X-ray powder diffraction data and optimized using density functional theory. The KO7 coordination polyhedra are isolated. The ammonium cations and the hydro-phobic methyl-ene sides of the citrate anions occupy the spaces between the coordination polyhedra. Each hydrogen atom of the ammonium ions acts as a donor in a charge-assisted N-H⋯O, N-H⋯(O,O) or N-H⋯(O,O,O) hydrogen bond. There is an intra-molecular O-H⋯O hydrogen bond in the citrate anion between the hydroxide group and one of the terminal carboxyl-ate groups.