Investigation of DOTA-Metal Chelation Effects on the Chemical Shift of 129Xe

Recent work has shown that xenon chemical shifts in cryptophane‐cage sensors are affected when tethered chelators bind to metals. Here, we explore the xenon shifts in response to a wide range of metal ions binding to diastereomeric forms of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) linked to cryptophane‐A. The shifts induced by the binding of Ca2+, Cu2+, Ce3+, Zn2+, Cd2+, Ni2+, Co2+, Cr2+, Fe3+, and Hg2+ are distinct. In addition, the different responses of the diastereomers for the same metal ion indicate that shifts are affected by partial folding with a correlation between the expected coordination number of the metal in the DOTA complex and the chemical shift of 129Xe. These sensors may be used to detect and quantify many important metal ions, and a better understanding of the basis for the induced shifts could enhance future designs. The Xe factor: A cryptophane–DOTA (1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) metal‐ion sensor showed distinct 129Xe chemical shifts for various metal ions that were dependent on the chirality. The chemical shifts of hyperpolarized xenon detected with this sensor provide a firm basis for detecting and quantifying many important metal ions and further our understanding of xenon‐based metal‐ion detection.