Elevated levels of reactive oxygen species and peroxidase expression are often associated with inflammation and inflammatory diseases. We developed two novel Co(II) complexes that can be used to detect oxidative activity associated with inflammation using F magnetic resonance imaging (MRI). These agents display a large change inF chemical shift upon oxidation from Co(II) to Co(III), facilitating selective visualization of both species using chemical shift selective pulse sequences. This large chemical shift change is attributed to a large magnetic anisotropy in the high spin Co(II) complexes. Importantly, the differing reactivity of the two agents allows for detection of either HO production and/or the activity of peroxidase enzymes, providing two useful platforms for F MR hot spot imaging of oxidative events associated with biological inflammation.

Two azobenzenesulfonamide molecules with thermally stable cis configurations resulting from fluorination of positions ortho to the azo group are reported that can differentially regulate the activity of carbonic anhydrase in the trans and cis configurations. These fluorinated probes each use two distinct visible wavelengths (520 and 410 or 460 nm) for isomerization with high photoconversion efficiency. Correspondingly, the cis isomer of these systems is highly stable and persistent (as evidenced by structural studies in solid and solution state), permitting regulation of metalloenzyme activity without continuous irradiation. Herein, we use these probes to demonstrate the visible light mediated bidirectional control over the activity of zinc-dependent carbonic anhydrase in solution as an isolated protein, in intact live cells and in vivo in zebrafish during embryo development.

Cysteine plays an essential role in maintaining cellular redox homeostasis and perturbations in cysteine concentration are associated with cardiovascular disease, liver disease, and cancer. 19F MRI is a promising modality for detecting cysteine in biology due to its high tissue penetration and negligible biological background signal. Herein we report fluorinated macrocyclic copper complexes that display a 19F NMR/MRI turn-on response following reduction of the Cu(II) complexes by cysteine. The reactivity with cysteine was studied by monitoring the appearance of a robust diamagnetic 19F signal following addition of cysteine in addition to UV-vis and EPR spectroscopies. Importantly, complexes with -CH2CF3 tags display excellent water solubility. Studies with this complex in HeLa cells demonstrate the applicability of these probes to detect cysteine in complex biological environments.

Highly fluorinated, water-soluble transition metal complexes serve as both 19F and PARACEST magnetic resonance imaging agents.

Catalytic transformations involving Pd(0)/Pd(II) catalytic cycles are very well known, and processes involving highvalent Pd(III) and Pd(IV) and low-valent Pd(I) intermediates have also gained interest in recent years. Although low-valent Pd(I) intermediates are proposed in these catalytic cycles, isolated and characterized mononuclear Pd(I) species are very rare. Herein, we report the isolation of two heteroleptic mononuclear Pd(I) complexes stabilized by dithiapyridinophane ligands that were fully characterized by single-crystal X-ray diffraction; EPR, IR, UV−vis spectroscopies; and computational studies. Excitingly, one of these Pd(I) complexes shows Kumada Csp 3 −Csp 2 crosscoupling competency, and initial studies of the other shows direct evidence for Csp 3 −H bond activation proposed to occur at the Pd(I) center.

We report two highly fluorinated Cu-based imaging agents, CuL1 and CuL2, for detecting cellular hypoxia as nanoemulsion formulations. Both complexes retained their initial quenched 19F MR signals due to paramagnetic...

Herein we report the direct observation of C-H bond activation at an isolated mononuclear Pd(III) center. The oxidation of the Pd(II) complex (MeN4)PdII(neophyl)Cl (neophyl = -CH2C(CH3)2Ph; MeN4 = N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane) using...

<p>Palladium complexes are among the most commonly used transition metal catalysts for different organic transformations with wide applications in the chemical synthesis. Currently, catalytic transformations involving Pd(0)/Pd(II) catalytic cycles are very well-known, and processes involving Pd(II)/Pd(III)/Pd(IV) intermediates are also gaining interest in recent years due to the increasing relevance of high-valent Pd species. By contrast, isolated low-valent Pd(I) complexes, especially mononuclear Pd(I) species, are very rare. Herein, we report the isolation of two heteroleptic Pd(I) complexes stabilized by dithiapyridinophane ligands that were fully characterized by single-crystal X-ray diffraction, EPR, IR, and UV-Vis spectroscopies, and computational studies. Excitingly, these Pd(I) complexes are shown to be superior catalysts for the C<i>sp²</i>-C<i>sp³ </i>Kumada cross-coupling reaction vs. their Pd(0) or Pd(II) analogs.</p>