CO(2) capture by Mn(i) and Re(i) complexes with a deprotonated triethanolamine ligand

CO(2) capture at low concentration by catalysts is potentially useful for developing photocatalytic and electrocatalytic CO(2) reduction systems. We investigated the CO(2)-capturing abilities of two complexes, fac-Mn(X(2)bpy)(CO)(3)(OCH(2)CH(2)NR(2)) and fac-Re(X(2)bpy)(CO)(3)(OCH(2)CH(2)NR(2)) (X(2)bpy = 4,4′-X(2)-2,2-bipyridine and R = –CH(2)CH(2)OH), which work as efficient catalysts for CO(2) reduction. Both complexes could efficiently capture CO(2) even from Ar gas containing only low concentration of CO(2) such as 1% to be converted into fac-M(X(2)bpy)(CO)(3)(OC(O)OCH(2)CH(2)NR(2)) (M = Mn and Re). These CO(2)-capturing reactions proceeded reversibly and their equilibrium constants were >1000. The substituents of X(2)bpy strongly affected the CO(2)-capturing abilities of both Mn and Re complexes. The density functional theory (DFT) calculation could be used to estimate the CO(2)-capturing abilities of the metal complexes in the presence of triethanolamine.