1,2,4-Triazine -picolinamide functionalized, nonadentate chelates for the segregation of lanthanides( iii ) and actinides( iii ) in biphasic systems

A novel family of nonadentate ligands based on the (5,6-diphenyl-1,2,4-triazin-3-yl)-picolinamide donor moiety has been synthesized from simple starting materials in high yield and purity. This group of ligands is an addition to the neutral nonadentate group but the first to incorporate 1,2,4-triazine. Their ability to extract a select group of lanthanides from acidic aqueous solution has been correlated to their ability to meet the ideal trigonal tricapped prismatic geometry that is seen by lanthanides and actinides in aqueous solution. The rate of metallation was determined using UV/VIS spectroscopy with pseudo first order conditions and showed similar behaviour to literature examples. Theoretical calculations were used to probe the bonding structure with lanthanides and actinides to predict the potential Ln/An segregating ability of the new ligands.