We report a detailed study of the thermodynamic stability and dissociation kinetics of lanthanide complexes with two ligands containing a cyclen unit, a methyl group, a picolinate arm and two acetate pendant arms linked to two nitrogen atoms of the macrocycle either in cis (1,4-H3DO2APA) or trans (1,7-H3DO2APA) positions. The stability constants of the Gd 3+ complexes with these two ligands are very similar, with logKGdL values of 16.98 and 16.33 for the complexes of 1,4-H3DO2APA and 1,7-H3DO2APA, respectively. The stability constants of the complexes with 1,4-H3DO2APA follow the usual trend, increasing from logKLaL = 15.96 to logKLuL = 19.21. However, the stability of [Ln(1,7-DO2APA)] complexes decreases from logK = 16.33 for Gd 3+ to 14.24 for Lu 3+ . The acid-catalyzed dissociation rates of the Gd 3+ complexes differ by a factor of 15, with rate constants (k1), of 1.42 and 23.5 M -1 s -1 for [Gd(1,4-DO2APA)] and [Gd(1,7-DO2APA)]. This difference is magnified across the lanthanide series to reach a five orders of magnitude higher k1 for [Yb(1,7-DO2APA)] (1475 M -1 s -1 ) than for [Yb(1,4-DO2APA)] (5.79 10 -3 M -1 s -1 ). The acid-catalysed mechanism involves the protonation of a carboxylate group, followed by a cascade of proton-transfer events that result in the protonation of a nitrogen atom of the cyclen unit. DFT calculations suggest a correlation between the strength of the Ln-Ocarboxylate bonds and the kinetic inertness of the complex, with stronger bonds providing more inert complexes. The 1 H NMR resonance of the coordinated water molecule in the [Yb(1,7-DO2APA)] complex at 176 ppm provides a sizeable chemical exchange saturation transfer (CEST) effect thanks to a slow water exchange rate (15.9 + 1.6) 10 3 s -1 ).