Is Macrocycle a Synonym for Kinetic Inertness in Gd(III) Complexes? Effect of Coordinating and Noncoordinating Substituents on Inertness and Relaxivity of Gd(III) Chelates with DO3A-like Ligands
ABSTRACT Gadolinium chelates with octadentate ligands are widely used as contrast agents for magnetic resonance imaging (MRI), with macrocyclic ligands based on DO3A being preferred for the high kinetic inertness of their Gd chelates. A major challenge in the design of new bifunctional MRI probes is the need to control the rotational motion of the chelate, which greatly affects its relaxivity. In this work we explored facile alkylation of a secondary amine in macrocyclic DO3A-like ligands to create a short, achiral linkage to limit the undesired internal motion of chelates within larger molecular constructs. The acetate moiety on the trans nitrogen was also replaced with either a bidentate (ethoxyacetate, L1 or methyl picolinate, L2) or bulky monodentate (methyl phosphonate, L3) donor arm to give octa- or heptadentate ligands, respectively. The resultant Gd(III) complexes were all monohydrated (q = 1) and exhibited water residency times that spanned 2 orders of magnitude (τM = 2190 ± 170, 3500 ± 90, and 12.7 ± 3.8 ns at 37 °C for GdL1, GdL2, and GdL3, respectively). Alkylation of the secondary amine with a noncoordinating biphenyl moiety resulted in coordinatively saturated q = 0 complexes of octadentate ligands L1 and L2. Relaxivities were limited by slow water exchange and/or lack of water coligand. All complexes showed decreased inertness compared to [Gd(DO3A)] despite higher ligand denticity, and inertness was further decreased upon N-alkylation. These results demonstrate that high kinetic inertness and in vivo safety of Gd chelates with macrocyclic ligands should not be generalized.
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- "In this study, according to the literature we synthesized a new type of soft ligand compounds 2,6-bis(5,6-dipropyl- 1,2,4-triazine-3-yl)pyridine (BDPTP), and studied the extraction of cadmium, copper, lead and nickel  . The extraction behavior of heavy metal Cd(II), Pd(II), Cu(II), Ni(II) and BDPTP/20% 1-octanol−80% sulfonated kerosene with a change in different concentrations of sodium chloride from 0.1 to 0.5M was studied at 298 K. Extraction rate increases with the increase of chloride ion concentration and can get best extraction effect of Cadmium. "
ABSTRACT: 2, 6-bis (5,6-dipropyl-1,2,4-triazine-3-yl) pyridine (BDPTP) was synthesized with 2, 6 - dimethyl pyridine and ethyl butyrate as raw materials. And characterized by IR, 1HNMR and element analysis etc. The extraction performance of this kind of complexes for four kinds of cations, Cu II ,Cd II ,Pb II ,Ni II is studied in hydrochloric acid system. The results show that the extraction rate of cadmium chloride with BDPTP in dichloromethane can reach to 97.25%. It is meaningful to cadmium chloride wastewater treatment.03/2014; DOI:10.2991/icmaee-14.2014.21
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ABSTRACT: This review describes recent advances in strategies for tuning the water-exchange rates of contrast agents for magnetic resonance imaging (MRI). Water-exchange rates play a critical role in determining the efficiency of contrast agents; consequently, optimization of water-exchange rates, among other parameters, is necessary to achieve high efficiencies. This need has resulted in extensive research efforts to modulate water-exchange rates by chemically altering the coordination environments of the metal complexes that function as contrast agents. The focus of this review is coordination-chemistry-based strategies used to tune the water-exchange rates of lanthanide(III)-based contrast agents for MRI. Emphasis will be given to results published in the 21st century, as well as implications of these strategies on the design of contrast agents.Molecules 08/2013; 18(8):9352-81. DOI:10.3390/molecules18089352 · 2.42 Impact Factor
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ABSTRACT: We report the synthesis and MR relevant properties of CyPic3A, a heptadentate chelator that forms ternary Gd(iii) complexes of hydration state q = 2. [Gd(CyPic3A)(H2O)2](-) affords an r1 value of 5.70 mM(-1) s(-1) at 1.41 T and 310 K and displays thermodynamic stability and kinetic inertness comparable to FDA approved MR imaging probes.Chemical Communications 08/2013; 49(73). DOI:10.1039/c3cc44116d · 6.83 Impact Factor