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  1. Two efficient lanthanide ion sensitizers 2,6-bis(oxazoline)-4-phenyl-pyridine (PyboxPh, 1 ) and 2,6-bis(oxazoline)-4-thiophen-2-yl-pyridine (Pybox2Th, 2 ) were synthesized. 1 crystallizes in the monoclinic space group P 21/ c with cell parameters a = 16.3794(4) Å, b = 7.2856(2) Å, c = 11.7073(3) Å, β = 97.229(1)° and V = 1385.97(6) Å 3 . 2 crystallizes in the monoclinic space group P 21/ n with cell parameters a = 5.9472(2), b = 16.0747(6), c = 14.3716(5) Å, β = 93.503(1)° and V = 1371.35(8) Å 3 . Photophysical characterization of 1 shows that its triplet state energy is located at 22 250 cm −1 and efficient energy transfer is observed for Eu III and Tb III . Solutions of [Ln(PyboxPh) 3 ] 3+ in dichloromethane display an emission efficiency of 37.2% for LnEu and 24.0% for LnTb. The excited state lifetimes for Eu III and Tb III are 2.227 ms and 723 μs, respectively. The triplet state energy of 2 is located at 19 280 cm −1 and is therefore too low to efficiently sensitize Tb III emission. However, the sensitization of Eu III is effective, with an emission quantum yield of 14.5% and an excited state lifetime of 714 μs. This shows that themore »derivatization of the chelator is strongly influenced by the aromatic substituents on the para -position of the pyridine ring. New isostructural 1 : 1 complexes of PyboxPh with Eu III ( 3 ) and Tb III ( 4 ) were also isolated and crystallize in the triclinic space group P 1̄ with cell parameters a = 9.1845(2) Å, b = 10.3327(2) Å, c = 11.9654(2) Å, α = 98.419(1)°, β = 108.109(1)°, γ = 91.791(1)°, V = 1064.08(4) Å 3 and a = 7.8052(1) Å, b = 11.8910(1) Å, c = 14.2668(2) Å, α = 72.557(1)°, β = 86.355(1)°, γ = 77.223(1)°, V = 1231.95(3) Å 3 , respectively.« less
  2. We report the solution structure of a europium-nicotianamine complex predicted from ab initio molecular dynamics simulations with density functional theory. Emission and excitation spectroscopy show that the Eu 3+ coordination environment changes in the presence of nicotianamine, suggesting complex formation, such as what is seen for the Eu 3+ –nicotianamine complex structure predicted from computation. We modeled Eu 3+ –ligand complexes with explicit water molecules in periodic boxes, effectively simulating the solution phase. Our simulations consider possible chemical events ( e.g. coordination bond formation, protonation state changes, charge transfers), as well as ligand flexibility and solvent rearrangements. Our computational approach correctly predicts the solution structure of a Eu 3+ –ethylenediaminetetraacetic acid complex within 0.05 Å of experimentally measured values, backing the fidelity of the predicted solution structure of the Eu 3+ –nicotianamine complex. Emission and excitation spectroscopy measurements were also performed on the well-known Eu 3+ –ethylenediaminetetraacetic acid complex to validate our experimental methods. The electronic structure of the Eu 3+ –nicotianamine complex is analyzed to describe the complexes in greater detail. Nicotianamine is a metabolic precursor of, and structurally very similar to, phytosiderophores, which are responsible for the uptake of metals in plants. Although knowledge that nicotianamine binds europiummore »does not determine how plants uptake rare earths from the environment, it strongly supports that phytosiderophores bind lanthanides.« less