| CPC C07D 213/55 (2013.01) [C07D 213/79 (2013.01); C07D 213/89 (2013.01); C07D 401/04 (2013.01); C07D 471/04 (2013.01); C09K 8/03 (2013.01); C09K 11/07 (2013.01); E21B 43/16 (2013.01); E21B 47/11 (2020.05); E21B 49/08 (2013.01); G01N 21/6408 (2013.01); G01N 21/643 (2013.01); C09K 2211/1018 (2013.01); C09K 2211/182 (2013.01); E21B 49/0875 (2020.05); G01N 2021/641 (2013.01); G01N 2021/6441 (2013.01); G01N 2201/129 (2013.01)] | 20 Claims |

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1. A complexing agent of Formula (III), or an anion or salt thereof:
![]() wherein:
each of X1 and X2 is absent;
each of R1 and R2 is -aryl that is substituted with from 1-3 Rb;
each occurrence of Rb is independently selected from the group consisting of:
(i) —C(═O)(C1-4 alkyl);
(ii) —C(═O)O(C1-4 alkyl);
(iii) —C(═O)OH; and
(iv) —C(═O)N(R′)(R″); and
each occurrence of R′ and R″ is independently selected from the group consisting of: H and C1-4 alkyl; or, if R′ and R″ are bonded to the same atom, R′ and R″ together with the atom to which each is attached forms a ring including from 3-8 ring atoms, wherein the ring includes: (a) from 1-7 ring carbon atoms; and (b) from 0-3 ring heteroatoms (in addition to the atom attached to R′ and R″), which are each independently selected from the group consisting of N, NH, O, and S.
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