Synthesis and f-element ligation properties of ^NCMPO-decorated pyridine N-oxide platforms

Abstract

Stepwise syntheses of 2-{[2-(diphenylphosphoryl)acetamido]methyl}pyridine 1-oxide, 2-[Ph2P(O)CH2C(O)N(H)CH2]C5H4NO (6), 2-{[2-(diphenylphosphoryl)acetamido]methyl}-6-[(diphenylphosphoryl)methyl]pyridine 1-oxide, 2-[Ph2P(O)CH2C(O)N(H)CH2]-6-[Ph2P(O)CH2]C5H3NO (7) and 2,6-bis{[2-(diphenylphosphoryl)acetamido]methyl}pyridine 1-oxide, 2,6-[Ph2P(O)CH2C(O)N(H)CH2]2C5H3NO (8), are reported along with spectroscopic characterization data and single crystal X-ray diffraction structure determination for 6·2H2O, 7 and 2,6-[Ph2P(O)CH2C(O)N(H)CH2]2C5H3N·MeOH 18·MeOH, the pyridine precursor of 8. Molecular mechanics computations indicate that 6, 7 and 8 should experience minimal steric hindrance to donor group reorganization that would permit tridentate, tetradentate and pentadentate docking structures for the respective ligands on lanthanide cations. However, crystal structure determination for the lanthanide complexes, {[Yb(6)(NO3)3]·(MeOH)}n, {[Lu(6)(NO3)3]·(MeOH)}n, [Er(6)2(H2O)2](NO3)3·(H2O)4}n, {[La(13)(NO3)3(MeOH)]·(MeOH)}n, {[Eu(7)(NO3)2(EtOAc)0.5(H2O)0.5](NO3)}2·MeOH and [Dy3(7)4(NO3)4(H2O)2](NO3)5·(MeOH)5·(H2O)2 reveal solid-state structures with mixed chelating/bridging ligand : Ln(III) interactions that employ lower than the maximal denticity. The binding of 6 and 7 with Eu(III) in the solid state and in MeOH solutions is also accessed by emission spectroscopy. The acid dependence for solvent extractions with 6 and 7 in 1,2-dichloroethane for Eu(III) and Am(III) in nitric acid solutions is described and compared with the behavior of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (OPhDiBCMPO, 1b) and 2-[(diphenyl)phosphinoylmethyl]pyridine N-oxide (DPhNOPO, 4a).

Synthesis and selected lanthanide coordination chemistry of new ((1H-pyrazol-1-yl)methyl)pyridine and -pyridine 1-oxide ligands

“…Subsequent formation of the complex [Eu(4) 3+ ] with a tridentate coordination mode occurs with (G) = 4.78 kcal/mole or 1.59 kcal/mol/donor group. Although the ligand reorganization energy is significantly higher for 4 compared to 2, it is still lower than the value computed for the NOPOPO ligand, I (R = Ph), 8.8 kcal/mol or 2.93 kcal/mol/donor group[45], and it is well known that ligands of type I readily form strong lanthanide complexes utilizing the tridentate binding mode[22][23][24][45][46][47][48][49]. Interestingly, addition of the N-oxide group back into the ligand framework and subsequent formation of the tridentate chelate structure [ Eu(5) 3+ ], as shown inFigure 7b, leads to a decrease in strain free energy, (G) = 3.78 kcal/mol or 1.26 kcal/mol/donor.…”

“…The resulting calculated relative strain free energies (G) per donor group were then compared with data for similar ligand types. The method has been used in the evaluation of a number of other ligand systems[43] including studies of several related NOPO and NOPOPO ligands[22][23][24][44][45][46][47][48]. The energy minimized free ligand conformers for 2, 4 and 5 are shown in Figures 5a, 6a and 7a, respectively.…”

Crystal structures of two bis-carbamoylmethylphosphine oxide (CMPO) compounds

“…Of these, seven structures have two or more CMPO groups tethered to one another via an organic scaffold. The most similar structures to compound (I) are CIWFAR (Ouizem et al, 2014) and SISLIQ (Artyushin et al, 2006). Both structures use an aromatic ring as the scaffold to present two phenyl-substituted CMPO groups.…”

Synthesis, Structural Characterisation and Solution Behaviour of High‐Symmetry Lanthanide Triflate Complexes with the Sterically Demanding Phosphine Oxides Cy3PO and tBu3PO

“…Lanthanide complexes of phosphine oxides, R 3 PO, continue to attract interest due to their various potential applications. The chemically robust nature of phosphine oxides and the availability of synthetic routes to fine‐tune the nature of the R groups has allowed development of extractants suitable for reprocessing nuclear fuels , . Judicious selection of R groups can also enhance the light‐harvesting properties of complexes and facilitate ligand‐to‐metal energy transfer in potential photoluminescent devices , .…”