Synthesis, Characterization, and Handling of EuII-Containing Complexes for Molecular Imaging Applications

Abstract

Considerable research effort has focused on the in vivo use of responsive imaging probes that change imaging properties upon reacting with oxygen because hypoxia is relevant to diagnosing, treating, and monitoring diseases. One promising class of compounds for oxygen-responsive imaging is EuII-containing complexes because the EuII/III redox couple enables imaging with multiple modalities including magnetic resonance and photoacoustic imaging. The use of EuII requires care in handling to avoid unintended oxidation during synthesis and characterization. This review describes recent advances in the field of imaging agents based on discrete EuII-containing complexes with specific focus on the synthesis, characterization, and handling of aqueous EuII-containing complexes.

Europium‐Catalyzed Aerobic Oxidation of Alcohols to Aldehydes/Ketones and Photoluminescence Tracking

“…[11][12][13] Considering the oxidation state of lanthanides, the trivalent cation is the general oxidation state for all metals. Recently, a variety of europium organometallic complexes with Eu 2 + and/or Eu 3 + have been intensively studied because of their unique photochemical properties, [16,17] and the oxidation state changes of europium were successfully applied to catalytic organic transformations. [15] In particular, Eu(II) has a halffilled 4f 7 electron configuration and high stabilization from exchange energy.…”

“…The oxidation state change of europium was successfully applied to organic transformations. [17,23] Herein, we have developed a europium-catalyzed aerobic oxidation of alcohols to corresponding aldehydes or ketones with external catalytic oxidants. Dimerization of a-methyl styrene, [18] allylation of aldehydes, [19] and reductive coupling of benzyl chloride [20] were performed with europium salts and the their redox cycles under photochemical conditions.…”

Recent Advances of Bioresponsive Nano-Sized Contrast Agents for Ultra-High-Field Magnetic Resonance Imaging

“…Cutting-edge interdisciplinary subjects of chemistry, physical, biological, and engineering shall also be included to resolve the current limitations of developing nanoparticle contrast agents. After implementing the rational design and surface modification of nanoparticles, this will inevitably promote MRI capable of molecular imaging for better monitoring during biological process (Zhu and Moser, 2017;Basal and Allen, 2018). For instance, Figure 13 shows a representative example about the functionalized nanoparticle contrast agents ranging from the initial design to the final multimodal imaging applications, where doping technique has been adopted to functionalize a variety of nanoparticles with the employed various surfactants, such as poly(allylamine hydrochloride) (PAH), polyacrylic acid, and polyethylene glycol (PEG).…”

Colorimetry of Luminescent Lanthanide Complexes

“…A famous example is Eu(II), which is found in the blue luminescent BaMgAl 10 O 17 :Eu phosphor. New exciting developments have also been achieved in the field of divalent Eu(II) chemistry [ 15 , 16 , 17 ]. Furthermore, it was shown that photoinduced electron transfer from the excited photosensitiser to some Ln(III) ions, thereby forming divalent states, probably plays a role in the photophysical properties of a lot of luminescent Ln complexes [ 18 , 19 ].…”