Dinuclear Lanthanide(III)-m-ODO2A-dimer Macrocyclic Complexes: Solution Speciation, DFT Calculations, Luminescence Properties, and Promoted Nitrophenyl-Phosphate Hydrolysis Rates.

Potentiometric speciation studies, mass spectrometry, and DFT calculations helped to predict the various structural possibilities of the dinuclear trivalent lanthanide ion (Ln , Ln=La, Eu, Tb, Yb, Y) complexes of a novel macrocyclic ligand, m-ODO2A-dimer (H L), to correlate with their luminescence properties and the promoted BNPP and HPNP phosphodiester bond hydrolysis reaction rates. The stability constants of the dinuclear Ln (m-ODO2A-dimer) complexes and various hydrolytic species confirmed by mass spectrometry were determined. DFT calculations revealed that the Y LH and the Y LH species tended to form structures with the respective closed- and open-form conformations. Luminescence lifetime data for the heterodimetallic TbEuL system confirmed the fluorescence resonance energy transfer from the Tb to Eu ion. The internuclear distance R values were estimated to be in the range of 9.4-11.3 Å (pH 6.7-10.6), which were comparable to those of the DFT calculated open-form conformations. Multiple linear regression analysis of the k data was performed using the equation: k =k -k =kLn2LHM->1 [Ln LH ]+kLn2LH-2 [Ln LH ] for the observed Ln L-promoted BNPP/HPNP hydrolysis reactions in solution pH from 7 to 10.5 (Ln=Eu, Yb). The results showed that the second-order rate constants for the Eu LH and Yb LH species were about 50-400 times more reactive than the structural analogous Zn (m-12 N O-dimer) system.