Self-Assembly of Ion-Pair Complexes

Solid-state structures of cobalt(II) complexes of 4-methylumbelliferone-8-methyleneiminodiacetic acid (H₃muia), also named Calcein Blue, are presented. Interestingly, ion-pair complexes with different solvation in cation, namely, [Co(H₂O)₄(CH₃CN)₂][Co(muia)(H₂O)₂]₂ (1) and [Co(H₂O)₆][Co₂(muia)₂(H₂O)₂]·2CH₃CN (2), exhibit self-assembly in one-pot crystallization. By variation of the experimental conditions, 1D coordination polymer [{Co(H₂O)₄}{Co₂(muia)₂(H₂O)₂}]·11H₂O (3), which can be considered a pseudo-supramolecular isomer, is obtained. Hydrogen bonding between the cation and anion core gives an interesting hydrogen-bonded network structure. The condensation of ion-pair complexes to a 1D coordination polymer by the influence of solvents is demonstrated.