Crystal and molecular structures of potassium cobalt hydrogen phthalate K-2[Co(H2O)(6)](C8H5O4)(4)center dot 4H(2)O and mechanism of Co2+ impurity trapping in KAP crystals

The single-crystal X-ray diffraction analysis of K-2[Co(H2O)(6)](C8H5O4)(4) . 4H(2)O has been carried out. The K-2[Co(H2O)(6)](C8H5O4)(4). 4H(2)O singl e crystals are obtained in attempting to grow the KAP crystals with the max imum possible content of Co2+ impurity cations. The crystals are isostructu ral to the earlier-studied similar crystals with Ni(II). The structure is f ormed by double layers of biphthalate anions and the Co2+ and K+ cations in between. The Co2+ cations are coordinated only by water molecules, whereas the coordination of the K+ cations involves both the biphthalate anions an d water molecules. A detailed crystal chemical analysis, together with the data on the growth kinetics of KAP crystals in the presence of Co2+ and the mass-spectrometric data obtained earlier for the KAP crystals, leads to th e conclusion that the Co2+ impurity cations should be located in the form o f the [Co(H2O)(6)](2+) cationic complexes in the interblock layers of the K AP crystals. (C) 2000 MAIK "Nauka/Interperiodica".