Journal article
Light-Induced Copper(II) Coordination by a Bicyclic Tetraaza Chelator through a Ligand-to-Metal Charge-Transfer Reaction
Risø National Laboratory for Sustainable Energy, Technical University of Denmark1
Biomedical Tracers, Radiation Research Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark2
Radiation Research Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark3
University of Copenhagen4
To enable utilization of the broad potential of copper isotopes in nuclear medicine, rapid and robust chelation of the copper is required. Bowl adamanzanes (bicyclic tetraaza ligands) can form kinetically stable copper complexes, but they are usually formed at low rates unless high pH values and high temperatures are applied.
We have investigated the effects of the variation in the pH, different anions, and UV irradiation on the chelation rate. UV spectra of mixtures of Cu2+ and [24.31]adz in water show the existence of a long-lived two-coordinated copper(II) intermediate (only counting coordinated amine groups) at pH above 6.
These findings are supported by pH titrations of mixtures of Cu2+ and [24.31]adz in water. Irradiation of this complex in the ligand-to-metal charge-transfer (LMCT) band by a diode-array spectrophotometer leads to photodeprotonation and subsequently to formation of the four-coordinated copper(II) complex at a rate up to 7800-fold higher at 25 °C than in the dark.
Anions in the solution were found to have three major effects: competitive inhibition due to CuII binding anions, inhibition of the photoinduced transchelation from UV-absorbing anions, and photoredox inhibition from acido ligands capable of acting as electron donors in LMCT reactions. Dissolved O2 was also found to result in photoredox inhibition.
Language: | English |
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Year: | 2011 |
Pages: | 12705-12713 |
ISSN: | 1520510x and 00201669 |
Types: | Journal article |
DOI: | 10.1021/ic201839w |
ORCIDs: | 0000-0002-8410-627X and Jensen, Mikael |
1,4,7,10-TETRAAZABICYCLO<5.5.3>PENTADECANE Agents Chemistry Complexes Hevesy Laboratory Hevesy laboratoriet IN-VIVO EVALUATION Mechanism Photochemistry RADIOPHARMACEUTICALS UV
Anions Azabicyclo Compounds Chelating Agents Coordination Complexes Copper Electron Spin Resonance Spectroscopy Hydrogen-Ion Concentration Kinetics Photochemical Processes Positron-Emission Tomography Radioisotopes Radiopharmaceuticals Spectrophotometry Static Electricity Ultraviolet Rays Water