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. Author manuscript; available in PMC: 2021 Jan 9.
Published in final edited form as: Chem. 2019 Nov 7;6(1):41–60. doi: 10.1016/j.chempr.2019.10.013

Figure 2.

Figure 2.

a) Chelate structures of commonly employed ligand systems DFO (M=Zr(IV), Ga(III)), DOTA (M = Cu(II), Ga(III), In(III), Y(III), Lu(III)), NOTA (M = Cu(II), Ga(III)), CHX-A”-DTPA (M = In(III), Lu(III)). The typical site of functionalization is indicated by R. b) Structures of clinically evaluated MRI contrast agents. c) Structure and mechanism of action of responsive MR probes: (A) Modulation of inner-sphere hydration of a Gd(III) complex by enzymatic activity, (B) redox-responsive Mn(II)/Mn(III) pair involving inner-sphere hydration modulation and T1e, (C) redox-responsive Eu(II)/Eu(III) probe with signal change arising from variation of T1e.