Most magnetic resonance contrast agents such as gadolinium-DTPA and technetium 99m DTPA fall into this class of molecules.  
Most magnetic resonance contrast agents such as gadolinium-DTPA and technetium 99m DTPA fall into this class of molecules.  They are often formed in solution by sequestration agents just as in alkaline soils where the blue color of hydrangeas can be retained by using iron compounds.  From the Greek for "crab claw", other examples include EDTA and chlorophyll, which has a magnesium center, though its most famous example might be hemoglobin.  FTP, identify this type of molecule that forms two or more bonds to a central metal ion.
Most magnetic resonance contrast agents such as gadolinium-DTPA and technetium 99m DTPA fall into this class of molecules.  
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