Host guest compound: Synthesis, characterization and single crystal X-ray structural study of [Co(NH3)6]Br·S2O3·H2O at variable temperatures

The reaction of [Co(NH3)6]Br3 with Na2S2O3 in aqueous medium (1:1 molar ratio) leads to formation of a new product of composition [Co(NH3)6]Br·S2O3·H2O in approximately 88% yield. The prepared complex salt has been characterized by elemental analyses, solubility product measurement and spectroscopic techniques (e.g. UV/Visible and IR). Single-crystal X-ray structure determination of title complex salt revealed the presence of discrete ions i.e., cation [Co(NH3)6]3+ and mixed anions, Br−, S2O32−, and one lattice water molecule in structure. Crystal lattice is stabilized by supramolecular hydrogen bonding network between ionic groups (i.e. thiosulphate and bromide) and NH group of coordinated NH3 molecules i.e. NH…O interactions apart from coulombic forces of attraction. Moreover, the water weakly interacts with the environment and does not form hydrogen bonds with the ammonia ligands so that it can be regarded as a ‘inclusion water’. In order to explore the behaviour of the solvent molecule, data collection experiments were repeated on the same crystal at three different temperatures.