Reversible hydration of tetraaquabis(4-aminobenzoato)cobalt(II)

Abstract

The octahedral red complex tetraaquabis(4-aminobenzoato) cobalt(II) (1) exhibits a water induced crystallineamorphous-crystalline transformation accompanied by chromotropism. The loss of coordinated water from [Co(4-aba)2(H2O)4] (1) (4-aba=4-aminobenzoate) on heating, leads to the formation of tetrahedral anhydrous [Co(4-aba)2] (2). The amorphous blue compound (2) can be rehydrated to original composition by equilibrating (2) over water vapour. The rehydrated crystalline compound exhibits properties identical with (1). The variation in the structure and properties of (1) due to the coordination and decoordination of water are studied by spectral, thermal, magnetic and conductivity measurements.