The first crystal structure of an actinide complex of the macrocyclic ligand DOTA: a two-dimensional uranyl–organic framework

Coordination of Tetravalent Actinides (An=ThIV, UIV, NpIV, PuIV) with DOTA: From Dimers to Hexamers

“…The p K a is indeed closest to the one of the free DOTA molecule out of the six p K a values (the four of the carboxylic acids are p K a1 =1.71, p K a2 =1.88, p K a3 =4.18, and p K a4 =4.24 and the two of the opposite amine functions are p K a5 =9.23 and p K a6 =11.08) . The deprotonation of the protonated amine groups is not favored and indicates that the proton is located inside the DOTA cage (steric constrains) …”

“…These experiments reveals that the existence rangeso f uranium (0.1 < pH < 5.3), neptunium (0.2 < pH < 7.5), and plutonium (0.05 < pH < 6) partly superimpose the pH values of the natural waters (from pH 2t o9 ). [51] Finally,the solubility wasevaluated for severalpHvalues, adjusted by addition of HNO 3 and NaOH (1 or 0.1 m). Once such ah exameric complex is formed, it appearst ob es table in moderate acidic or nearly neutral media.…”

“…[45] The deprotonation of the protonated amine groups is not favored and indicates that the proton is located inside the DOTAcage (steric constrains). [51] Finally,the solubility wasevaluated for severalpHvalues, adjusted by addition of HNO 3 and NaOH (1 or 0.1 m). Concerning uranium,t he delay to reacht he equilibrium, particularly at elevated pH, was too long to prevent partial oxidation of U IV to U VI .T herefore, this experiment could be reasonably carried out only for neptunium and plutonium.…”

Time-controlled synthesis of the 3D coordination polymer U(1,2,3-Hbtc)2 followed by the formation of molecular poly-oxo cluster {U14} containing hemimellitate uranium(iv)

“…The in situ formation of the oxalate from polycarboxylate molecules are also described in detail in literature, even in terms of the formation of coordination polymers of actinides. [63][64][65][66][67][68][69] The generation of oxalate can be reasonably interpreted as a result of the oxidative benzene ring-opening followed by decarboxylation to generate the dicarboxylate moiety. 70 The low synthetic yield of the {U 14 } cluster is therefore correlated to the slow in situ degradation of the initial 1,2,3-benzene tricarboxylic acid and acetonitrile into the oxalate and acetate species, respectively.…”

The Scope of Application of Macrocyclic Polyamines Beyond Metal Chelation

“…Hudson and co‐workers also thoroughly investigated the chemistry of MPA‐peptide conjugates, developing a straightforward access via either MPA peralkylation strategies implemented with cyclen to produce DOTA‐type conjugates (but also TACN and cyclam derivatives) or click chemistry approach performed with non‐symmetrical DOTA derivatives and based on the prior incorporation of a terminal alkyne into the side‐chain of tyrosine residue(s) (i.e., propargyl ether moiety) . Finally, DOTA was also used, yet more anecdotally, as a “square assembler” in metal‐organic frameworks (MOF): in this assembly, DOTA does not chelate metal within its cavity but is surrounded by four uranyl U IV cations (UO 2 2+ ), likely due to the excess of metal (i.e., 4 mol. equiv.…”