98437-49-1Relevant academic research and scientific papers
Electronic Effects of Ligand Substitution in a Family of CoII2 PARACEST pH Probes
Thorarinsdottir, Agnes E.,Tatro, Scott M.,Harris, T. David
supporting information, p. 11252 - 11263 (2018/09/14)
We report three new Co2-based paramagnetic chemical exchange saturation transfer (PARACEST) probes with the ability to ratiometrically quantitate pH. A CoII2 complex, [LCo2(etidronate)]-, featuring tetra(carboxamide) and OH-substituted etidronate ligands with opposing pH-dependent CEST peak intensities, was previously shown to exhibit a linear correlation between log(CESTOH/CESTNH) and pH in the pH range 6.5-7.6 that provided a sensitivity of 0.99(7) pH unit-1 at 37 °C. Here, we demonstrate through a series of CF3-functionalized CoII2 complexes [(XL′)Co2(etidronate)]- (X = NO2, F, Me), that modest changes in the electronic structure of CoII centers through remote ligand substitution can significantly affect the NMR and CEST properties of Co2-based PARACEST probes. Variable-pH NMR and CEST analyses reveal that the chemical shifts of the ligand protons are highly affected by the nature of the X substituent. The ratios of OH and NH CEST peak intensities at 115 and 88, 93 and 79, and 88 and 76 ppm for X = NO2, F, and Me, respectively, afford pH calibration curves with remarkably high sensitivities of 1.49(9), 1.48(7), and 2.04(5) pH unit-1 across the series. The 1.5-2-fold enhancement in pH sensitivity for the CF3-functionalized Co2 probes stems from the complete separation of the OH and NH CEST peaks. Furthermore, incorporation of electron-withdrawing CF3 groups shifts the detection window to a more acidic range of pH 6.2-7.4. Finally, the CoII2 complexes are found to be extremely robust toward substitution and oxidation in aqueous solutions. Taken together, these results highlight the unique ability of transition metal-based PARACEST probes to provide a highly sensitive concentration-independent measure of pH and demonstrate that modest ligand modifications can be a powerful tool for optimizing the pH sensing performance of these probes.
Ratiometric pH Imaging with a CoII2 MRI Probe via CEST Effects of Opposing pH Dependences
Thorarinsdottir, Agnes E.,Du, Kang,Collins, James H. P.,Harris, T. David
supporting information, p. 15836 - 15847 (2017/11/14)
We report a Co2-based magnetic resonance (MR) probe that enables the ratiometric quantitation and imaging of pH through chemical exchange saturation transfer (CEST). This approach is illustrated in a series of air- and water-stable CoII2 complexes featuring CEST-active tetra(carboxamide) and/or hydroxyl-substituted bisphosphonate ligands. For the complex bearing both ligands, variable-pH CEST and NMR analyses reveal highly shifted carboxamide and hydroxyl peaks with intensities that increase and decrease with increasing pH, respectively. The ratios of CEST peak intensities at 104 and 64 ppm are correlated with solution pH in the physiological range 6.5-7.6 to construct a linear calibration curve of log(CEST104 ppm/CEST64 ppm) versus pH, which exhibits a remarkably high pH sensitivity of 0.99(7) pH unit-1 at 37 °C. In contrast, the analogous CoII2 complex with a CEST-inactive bisphosphonate ligand exhibits no such pH response, confirming that the pH sensitivity stems from the integration of amide and hydroxyl CEST effects that show base- and acid-catalyzed proton exchange, respectively. Importantly, the pH calibration curve is independent of the probe concentration and is identical in aqueous buffer and fetal bovine serum. Furthermore, phantom images reveal analogous linear pH behavior. The CoII2 probe is stable toward millimolar concentrations of H2PO4-/HPO42-, CO32-, SO42-, CH3COO-, and Ca2+ ions, and more than 50% of melanoma cells remain viable in the presence of millimolar concentrations of the complex. The stability of the probe in physiological environments suggests that it may be suitable for in vivo studies. Together, these results highlight the ability of dinuclear transition metal PARACEST probes to provide a concentration-independent measure of pH, and they provide a potential design strategy toward the development of MR probes for ratiometric pH imaging.
Luminescence of a binuclear europium complex bearing a 4-nitrophenolate chromophore: A different way of seeing pH dependence
Blackburn, Octavia A.,Tropiano, Manuel,Natrajan, Louise S.,Kenwright, Alan M.,Faulkner, Stephen
supporting information, p. 6111 - 6114 (2016/05/19)
A europium complex derived from NP-(DO3A)2 exhibits pH-dependent europium-centred luminescence following excitation of the nitrophenolate chromophore. Such behaviour is not observed with an analogous mononuclear complex, suggesting coordination of both lanthanide ions to the phenolate oxygen in the emissive species.
The role of Zn-OR and Zn-OH nucleophiles and the influence of para-substituents in the reactions of binuclear phosphatase mimetics
Daumann, Lena J.,Dalle, Kristian E.,Schenk, Gerhard,McGeary, Ross P.,Bernhardt, Paul V.,Ollis, David L.,Gahan, Lawrence R.
scheme or table, p. 1695 - 1708 (2012/03/22)
Analogues of the ligand 2,2′-(2-hydroxy-5-methyl-1,3-phenylene) bis(methylene)bis((pyridin-2-ylmethyl)azanediyl)diethanol (CH3H 3L1) are described. Complexation of these analogues, 2,6-bis(((2-methoxyethyl)(pyridin-2-ylmethyl)amino)m
Development of bis(2-picolyl)amine-zinc chelates for imidazole receptors
Routasalo, Taina,Helaja, Juho,Kavakka, Jari,Koskinen, Ari M. P.
experimental part, p. 3190 - 3199 (2009/04/07)
New phenyl and phenol bis(2-picolyl)amine (Dpa) derivatives have been synthesized in order to generate zinc chelates for imidazole anion receptors. Previously, binuclear phenolic zinc and copper chelates have shown affinity for pyrophosphate and guanidine anions, respectively. Herein we report significant imidazole affinity increasing from 2.38 × 106 to 2.90 × 107 for phenol-bridged binuclear zinc-Dpa chelates, as evidenced by dynamic and titration 1H NMR studies. Among the Dpa chelates investigated, the zinc-coordinated phenol group plays a crucial role in the mechanism of anion binding. Low-temperature 1H NMR experiments suggest a σν-symmetric geometry for the imidazole chelate. Computational DFT studies at the B3LYP level of theory imply that imidazole binding displaces the phenol bridge between the zinc ions. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Self-assembled monolayer electrode of a diiron complex with a phenoxo-based dinucleating ligand: Observation of molecular oxygen adsorption/desorption in aqueous media
Inomata, Tomohiko,Shinozaki, Kazuma,Hayashi, Yuya,Arii, Hidekazu,Funahashi, Yasuhiro,Ozawa, Tomohiro,Masuda, Hideki
, p. 392 - 394 (2008/09/19)
The phenoxo-based dinucleating ligand, 2,6-bis[bis(6-pivalamido-2- pyridylmethyl)amino-methyl]-4-aminophenol (1), and its Fe2(ii) complex, [Fe2(ii)(1)(PhCOO)2](CF3SO 3) (2), were prepared and 2 deposited on the Au surface (2/Au) is much more stable than in solution and exhibits redox behavior in aqueous media as well as reversible adsorption/desorption of oxygen at room temperature. The Royal Society of Chemistry.
A stepwise synthesis of functionalized calix [4]arenes and a calix[6]arene with alternate electron-withdrawing substituents
De Mendoza, Javier,Nieto, Pedro M.,Prados, Pilar,Sanchez, Concha
, p. 671 - 682 (2007/10/02)
Simple modifications of the TiCl4-induced cyclocondensation of phenol derivatives raise the yields of pure calix [4]arenes, even in the presence of electron-withdrawing substituents. The first example of a calix [6]arene with alternate substitu
