Improving the hydrolase-like activity of a lanthanum(III) complex through second coordination sphere

In this study, we present a new La(III) complex (2) that demonstrates the ability to catalyze the hydrolysis of 2,4-bis(dinitrophenyl)phosphate (2,4–BDNPP), 2,4-dinitrophenylphosphate (2,4–DNPP), and plasmid DNA. By modulating the second coordination sphere in 2, we were able to independently monitor both mono- and diester hydrolysis. Kinetic studies revealed a 7-fold enhancement in the diesterase performance of 2 relatives to the bare complex (1) and ca 30,000 times the uncatalyzed reaction. Data also indicate that 2 dissociates in solution to yield a binuclear complex, which possesses superior activity compared to its mononuclear counterpart. Finally, DNA assays further confirmed a high cleavage rate promoted by the catalyst. Electrospray ionization mass spectrometry (ESI–MS), potentiometric titration, and kinetic studies were instrumental in identifying catalytically active species and proposing reaction mechanisms.