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Herein we report the direct observation of C–H bond activation at an isolated mononuclear Pd(iii) center.

Catalytic transformations involving Pd(0)/Pd(II) catalytic cycles are very well known, and processes involving high-valent 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

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 Csp2-Csp3 Kumada cross-coupling reaction vs. their Pd(0) or Pd(II) analogs.

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.

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 Cu2+; however, both complexes displayed a large signal increase when the complex was reduced. DLS studies showed that the CuL1 nanoemulsion (NECuL1) had a hydrodiameter of approximately 100 nm and that it was stable for four weeks post-preparation. Hypoxic cells incubated with NECuL1 showed that 40% of the Cu2+ taken up was reduced in low oxygen environments.

We reported a set of water-soluble transition metal complexes that can serve as both 19F and PARACEST magnetic resonance imaging agents. The high number of equivalent fluorine atoms and the paramagnetic effect of metals offer these complexes high 19F sensitivity as demonstrated by in vitro19F MRI experiments. The complexes contain carboxamide groups appended onto a cyclen macrocycle, which provide 1H CEST peaks well differentiated from bulk water. The Co(ii) agent displays two CEST peaks that can be utilized for ratiometric pH determination and the concept of combining 19F MR and PARACEST as complementary imaging techniques was demonstrated with the Fe(ii) complex.

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 conjunction with UV-vis and EPR spectroscopies. Importantly, complexes with –CH2CF3 tags display good water solubility. Studies with this complex in HeLa cells demonstrate the applicability of these probes to detect cysteine in complex biological environments.

We reported a set of water-soluble transition metal complexes that can serve as both (19)F and PARACEST magnetic resonance imaging agents. The high number of equivalent fluorine atoms and the paramagnetic effect of metals offer these complexes high (19)F sensitivity as demonstrated by in vitro (19)F MRI experiments. The complexes contain carboxyamide groups appended onto a cyclen macrocycle, which provide (1)H CEST peaks well differentiated from bulk water. The Co(II) agent displays two CEST peaks that can be utilized for ratiometric pH determination and the concept of combining (19)F MR and PARACEST as complementary imaging techniques was demontrated with the Fe(II) complex.

Cysteine plays an essential role in maintaining cellular redox homeostasis and perturbations in cysteine concentration are associated with cardiovascular disease, liver disease, and cancer. (19)F 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 (19)F 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 (19)F signal following addition of cysteine in addition to UV-vis and EPR spectroscopies. Importantly, complexes with -CH(2)CF(3) 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.