Stability of Manganese(II)-Pyrazine, -Quinoxaline or -Phenazine Complexes and Their Potential as Carbonate Sequestration Agents.

Carbonate sequestration technology is a complement of CO sequestration technology, which might assure its long-term viability. In this work, in order to explore the interactions between Mn ion with several ligands and carbonate ion, we reported a spectrophotometric equilibrium study of complexes of Mn with pyrazine, quinoxaline or phenazine and its carbonate species at 298 K. For the complexes of manganese(II)-pyrazine, manganese(II)-quinoxaline and manganese(II)-phenazine, the formation constants obtained were log β = 4.6 ± 0.1, log β = 5.9 ± 0.1 and log β = 6.0 ± 0.1, respectively. The formation constants for the carbonated species manganese(II)-carbonate, manganese(II)-pyrazine-carbonate, manganese(II)-quinoxaline-carbonate and manganese(II)-phenazine-carbonate complexes were log β = 5.1 ± 0.1, log β = 9.8 ± 0.1, log β = 11.7 ± 0.1 and log β = 12.7 ± 0.1, respectively. Finally, the individual calculated electronic spectra and its distribution diagram of these species are also reported. The use of N-donor ligand with π-electron-attracting activity in a manganese(II) complex might increase its interaction with carbonate ions.