98437-49-1Relevant articles and documents
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.
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.
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.
