Cationic cobaltammines as anion receptors: Synthesis and characterization of [Co(NH3)6](4-np)3.4H2O, [Co(NH3)6](2,4-dnp)3 and [Co(NH3)6](2,4,6-tnp)3 (where npZnitrophenolate, dnpZdinitrophenolate, tnp, trinitrophenolate), single crystal X-ray structure an

In an effort to utilize [Co(NH3)6]3C cation as a new host for mono-, di- and tri-substituted nitrophenolate anions, yellow solids of composition [Co(NH3)6](4-np)3.4H2O, [Co(NH3)6](2,4-dnp)3, and [Co(NH3)6](2,4,6-tnp)3 were obtained in high yields by reacting sodium salts of 4-np, 2,4-dnp and 2,4,6-tnp (where npZnitrophenolate, dnpZdinitrophenolate and tnpZtrinitrophenolate,) with [Co(NH3)6]Cl3 respectively in 3:1 molar ratio in hot aqueous medium. These cobalt(III) complex salts have been characterized by elemental analyses and spectroscopic techniques (UV/Visible, IR and NMR). Single crystal X-ray structure determination of [Co(NH3)6](4-np)3.4H2O revealed the presence of discrete ions, [Co(NH3)6]3C and C6H4NO3 K in addition to four lattice water molecules in the solid state. A strong network of hydrogen bond interactions (N–H/O (phenolate), N–H/O (nitro), O–H/O (water) stabilize the crystal lattice. The formation of these salts and measurement of solubility products suggests that [Co(NH3)6]3C present in [Co(NH3)6]Cl3 may be used as anion receptor for the nitrophenolate ions. q 2005 Elsevier B.V. All rights reserved.