A Planar [15]Metallacrown‐5 That Selectively Binds the Uranyl Cation

Abstract

---COMMUNICATIONS otides I and 3 as primers, as well as 10 mM Tris-HC1 (pH 8.3), 50 mM KCI, 1.5 mM MgCI,. 0.03"/0 polyoxyethylenesorbitan monolaurate (Tween 20). 0.001 % gelatin.200 p~ of each dNTP. and 0.02 U pL-' Taq DNA Polymerase. in five cycles at 9 4 ' C for 1 min. 55 C for 1 min. and 72°C for 2 min. This PCR was followed by three cycles of PCR (20 mL) conducted under the same reaction conditions using 0.4 p~ 2 and 3 as primers. Cycles of PCR were performed at 94 'C for 4 min, 55 "C for 7 min. and 7 2 ' C for 7 min. During selection, eluted DNA was amplified first in 7 ~ 12 cycles of PCR (1 00 pL) using 0.2 p~ 1 and 3. Cycles of PCR were performed at 94 C for 1 min. 55 C for 1 min, and 72 "C for 2 min. A 1OpL sample of the reaction mixture was then subjected to 7-10 cycles of PCR (200 pL One of the enduring legacies of the Cold War is the vast quantity of radioactive isotopes generated as a result of nuclear weapons development. Predictably, considerable current interest is focused on the sequestration of actinides as a means of safe

Synthesis and Structural Characterisation of Copper(II) 15‐Metallacrown‐5 Complexes with PbII, HgII, AgI, NaI and YIII Central Metal Ions

“…Thus, the complex has a pseudo fivefold symmetry. In this way, all five copper(II) ions exhibit identical coordination environments, in contrast to previously reported copper(II) 15-metallacrown-5 complexes, [2][3][4][5][6] which exhibit a variation in the axial donor sets of the copper(II) ions. The Pb II ion is coordinated in the centre of the metallacrown by five hydroximate oxygen atoms [the Pb-O distances range from 2.491 to 2.590(3) Å] and is additionally coordinated by one axial pyridine molecule with a Pb-N py bond length of 2.493(3) Å. Interestingly, this pyridine molecule and all five pyridine molecules coordinated to the Cu II ions are positioned on the same side of the macrocycle.…”

“…In particular, the geometric requirements of the α-aminohydroximates, that form only five-membered chelate rings, result in a pentagonal arrangement of the 15-metallacrown-5 system (Figure 1), as observed in the interesting heteropolynuclear copper(II)-lanthanide(III) complexes [2][3][4][5] 3 , {where Ln is the lanthanide(III) ion, picha is the 2-picolinehydroxamic acid dianion and pheha is the (S)-phenylalaninehydroxamic acid dianion ( Figure 2)} or analogous uranyl(VI) and calcium(II) complexes. [6] These complexes, which contain five copper(II) ions and which were discovered by the Pecoraro group, are assembled in the presence of an additional central metal ion, i.e. Ln 3+ , UO 2 2+ or Ca 2+ , and they correspond to complexed forms of crown ethers.…”

“…The 15-metallacrown-5 system formed by five Cu II ions and five bridging 2-picolinehydroximate anions in this complex is less planar (the deviation of the atoms from the mean equatorial plane ranges from -1.061 Å for C43 to +0.804 Å for O41) relative to that in other copper(II) 15-metallacrown-5 complexes. [2][3][4][5][6] The buckling of the metallacrown most likely results from the relatively large size of the Pb II ion. Two of the 2-picolinehydroximate fragments are tilted with respect to the plane formed by the remaining three 2-picolinehydroximate ligands in such a way that the diameter of the ring formed by the five hydroximate oxygen atoms increases.…”

Mandelohydroxamic Acid as Ligand for Copper(II) 15‐Metallacrown‐5 Lanthanide(III) and Copper(II) 15‐Metallacrown‐5 Uranyl Complexes

“…The key property of these two ligand scaffolds is that they are able to form two fused five-membered chelate rings, which allows five metals and five ligands to form a planar 15-metallacrown-5 structure. [22,23] The planar 15-metallacrown-5 complexes formed in this way are capable to incorporate in their central cavity cations with a larger ionic radius and with a higher coordination number than 12-metallacrown-4 complexes. As a result, lanthanide() [24][25][26][27][28] and uranyl (UO 2 2+ ) [23,28,29] ions have been incorporated in the center of a 15-metallacrown-5 ring.…”

Lanthanide(III)‐Induced Conversion of 12‐Metallacrown‐4 to 5‐Metallacrown‐5 Complexes in Solution

“…The cavity size of this ring is larger than the cavity size of the 12-metallacrown-4 complexes and affords the incorporation of lanthanide(iii) [5][6][7][8][9][10][11] or uranyl ions. [11][12][13] 15-Metallacrown-5 complexes of lanthanide(iii) ions with either chiral or nonchiral α-aminohydroximate ligands have been structurally characterized. [5][6][7][8][9][10] Careri and coworkers showed that α-aminohydroximate ligands form the 12-metallacrown-4 structural motif in aqueous solution in the absence of lanthanide(iii) ions.…”