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

Abstract

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.

A Cyclic‐RGD Dinuclear TbIII Macrocyclic Complex as a Tumor Integrin‐Selective Luminescent Probe

“…Note that in the previous study, the structural analogous heterodinuclear TbEu( m ‐ODO2A‐dimer) or TbEuL complex was predicted to be in the “open‐form“ conformation in the pH range 6.7–10.6 assuming that the fluorescence energy transfer (FRET) between the Tb III ion and the Eu III ion could be characterized by the dipole–dipole mechanism . Because the number of inner‐sphere coordinated water molecules ( q ) of the Tb 2 (cRGDfK‐ODO2A‐dimer) was determined to be 1.6–2.0, it was possible that both Tb 2 L and the Tb 2 (cRGDfK‐ODO2A‐dimer) complexes were in the “closed‐form“ conformation at pH 7.4.…”

“…Disodium ethylenediaminetetraacetic acid (Na 2 H 2 EDTA) was purchased from Fisher. The ligand m ‐ODO2A‐dimer {1,3‐bis[4,10‐bis(carboxymethyl)‐1,4,10‐triaza‐7‐oxa‐cyclododec‐1‐ylmethyl]benzene} was prepared and purified according to a published method . The ligand cRGDfK‐ODO2A‐dimer was prepared and purified as described below.…”

“…Mononuclear Ln III systems that we have studied often did not offer this kind versatility for various applications , . To understand the fundamental coordination properties, the solution speciation, density functional theory (DFT) calculations, luminescence properties and promoted nitrophenyl‐phosphate hydrolysis rates of the parent dinuclear Ln III ‐ m ‐ODO2A‐dimer macrocyclic complexes (Ln 2 L, Ln = La, Eu, Tb, Yb, Y; L = m ‐ODO2A‐dimer) of the current studies have been reported …”

“…In our translational medicine research program, to develop macrocyclic dinuclear trivalent lanthanide (Ln III ) complexes as luminescent imaging probes in conjunction with the discovery of tumor targeting fusion protein drugs,, we have selected the cRGDfK peptide biomarker as a common delivery vehicle to the tumor cells. As luminescent probes, thermodynamically stable and kinetically inert Ln III macrocyclic complexes are preferred as compared to their linear structural analogues, and their long emission lifetimes are often advantageous for use in the time‐resolved mode .…”

Ag(I) Pyridine–Amidoxime Complex as the Catalysis Activity Domain for the Rapid Hydrolysis of Organothiophosphate-Based Nerve Agents: Mechanistic Evaluation and Application

“…While natural organophosphorus hydrolase (OPH) has been found to be highly effective for organothiophosphate decomposition, its poor stability and short life limit their broad applications . To overcome these shortcomings, various OPH mimics have been developed, including metal complexes, − metal organic frameworks (MOFs), , molecular imprinted polymers (MIPs), − and so on. , The formation of imprinted polymer is mainly based on the interactions between the template and functional monomer such as covalent interactions, noncovalent interactions, electrostatic interactions, and metal-ion coordination interactions. Also, MIPs exhibit great potential among these candidates, which are very typical mimicking enzymes as highly cross-linked polymers with specific shape cavity incorporating oriented functional groups at imprinting sites. , This has been demonstrated over the past few decades by the outstanding catalytic performance of imprinted polymers in a variety of reactions. − MIPs have also been demonstrated to effectively degrade organophosphate (OP); however, their catalytic activity is usually far behind phosphoresterase.…”