Abstract:The development of ligands with high selectivity and affinity for uranium is critical in the extraction of uranium from human body, radioactive waste, and seawater. A scientific challenge is the improvement of the selectivity of chelators for uranium over other heavy metals, including iron and vanadium. Flat ligands with hard donor atoms that satisfy the geometric and electronic requirements of the UO exhibit high selectivity for the uranyl moiety. The bis(hydroxylamino)(triazine) ligand, 2,6-bis[hydroxy(methy… Show more
“…Interactions of UO 2 2+ with two H 2 BHT chelators lead to formation of the corresponding 1:2 complexes depicted in Supplementary Fig. 1, which is in agreement with the experimental data 32 .Fig. 2Structural and potentiometric studies of the H 2 BHT complexation with uranyl.…”
Section: Resultssupporting
confidence: 87%
“…Single crystals of UO 2 (BHT) (Fig. 2a) were readily obtained from the stoichiometric aqueous solution of uranyl nitrate and H 2 BHT on standing over the period of three weeks, however, all attempts to isolate crystals of UO 2 (BHT) 2 2− suitable for X-ray diffraction studies were unsuccessful 32 . As seen from Fig.…”
Over millennia, nature has evolved an ability to selectively recognize and sequester specific metal ions by employing a wide variety of supramolecular chelators. Iron-specific molecular carriers—siderophores—are noteworthy for their structural elegance, while exhibiting some of the strongest and most selective binding towards a specific metal ion. Development of simple uranyl (UO22+) recognition motifs possessing siderophore-like selectivity, however, presents a challenge. Herein we report a comprehensive theoretical, crystallographic and spectroscopic studies on the UO22+ binding with a non-toxic siderophore-inspired chelator, 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H2BHT). The optimal pKa values and structural preorganization endow H2BHT with one of the highest uranyl binding affinity and selectivity among molecular chelators. The results of small-molecule standards are validated by a proof-of-principle development of the H2BHT-functionalized polymeric adsorbent material that affords high uranium uptake capacity even in the presence of competing vanadium (V) ions in aqueous medium.
“…Interactions of UO 2 2+ with two H 2 BHT chelators lead to formation of the corresponding 1:2 complexes depicted in Supplementary Fig. 1, which is in agreement with the experimental data 32 .Fig. 2Structural and potentiometric studies of the H 2 BHT complexation with uranyl.…”
Section: Resultssupporting
confidence: 87%
“…Single crystals of UO 2 (BHT) (Fig. 2a) were readily obtained from the stoichiometric aqueous solution of uranyl nitrate and H 2 BHT on standing over the period of three weeks, however, all attempts to isolate crystals of UO 2 (BHT) 2 2− suitable for X-ray diffraction studies were unsuccessful 32 . As seen from Fig.…”
Over millennia, nature has evolved an ability to selectively recognize and sequester specific metal ions by employing a wide variety of supramolecular chelators. Iron-specific molecular carriers—siderophores—are noteworthy for their structural elegance, while exhibiting some of the strongest and most selective binding towards a specific metal ion. Development of simple uranyl (UO22+) recognition motifs possessing siderophore-like selectivity, however, presents a challenge. Herein we report a comprehensive theoretical, crystallographic and spectroscopic studies on the UO22+ binding with a non-toxic siderophore-inspired chelator, 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H2BHT). The optimal pKa values and structural preorganization endow H2BHT with one of the highest uranyl binding affinity and selectivity among molecular chelators. The results of small-molecule standards are validated by a proof-of-principle development of the H2BHT-functionalized polymeric adsorbent material that affords high uranium uptake capacity even in the presence of competing vanadium (V) ions in aqueous medium.
“…As chelate group for V V we have chosen the siderophore hydroxylamino-triazine (Scheme 1), targeting to enhance the hydrolytic stability of the V V complexes as much as possible. This chelate group, for example in the ligand H 2 bihyat (Scheme 1) forms very strong complexes with hard acids such as Fe III , V V , Mo VI and U VI [41][42][43][44], with Fe III and U VI to exert the higher affinity for this chelate coordination. The V V complexes of this study exhibiting a chromanol hydroxy group unavailable for coordination, present no significant toxicity to cells.…”
Novel vitamin E chelate siderophore derivatives and their VV and FeIII complexes have been synthesised and the chemical and biological properties have been evaluated. In particular, the α- and δ-tocopherol derivatives with bis-methyldroxylamino triazine (α-tocTHMA) and (δ-tocDPA) as well their VV complexes, [V2VO3(α-tocTHMA)2] and [V2IVO3(δ-tocTHMA)2], have been synthesised and characterised by infrared (IR), nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and ultra violet-visible (UV-Vis) spectroscopies. The dimeric vanadium complexes in solution are in equilibrium with their respefrctive monomers, H2O + [V2VO2(μ-O)]4+ = 2 [VVO(OH)]2+. The two amphiphilic vanadium complexes exhibit enhanced hydrolytic stability. EPR shows that the complexes in lipophilic matrix are mild radical initiators. Evaluation of their biological activity shows that the compounds do not exhibit any significant cytotoxicity to cells.
“…To that end, we report that stabilization of the Mo(O) 2 dioxo functionality by the ligand 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H 2 bihyat) yields a catalyst that effectively oxidizes model sulfides. This compact pincer ligand was utilized by Kabanos and co-workers to chelate a variety of high oxidation, hard metal ions (Mo(VI), V(V), Fe(III)) including uranium(VI) . Recently, the H 2 bihyat system was grafted to a polyethylene support to selectively bind UO 2+ .…”
Section: Introductionmentioning
confidence: 99%
“…This compact pincer ligand was utilized by Kabanos and co-workers to chelate a variety of high oxidation, hard metal ions (Mo(VI), V(V), Fe(III)) 13 including uranium-(VI). 14 Recently, the H polyethylene support to selectively bind UO 2+ . 15 We report the first case of utilizing this chelator for the catalytic oxidation of model alkyl sulfides selectively to the corresponding sulfoxide.…”
Sulfide oxidation is accomplished by a new class of dioxomolybdenum(VI)
catalyst (1) that uses the tridentate 2,6-bis[hydroxyl(methyl)amino]-4-morpholino-1,3,5-triazine
ligand to form a five-coordinate molybdenum(VI) center. Resonance
Raman spectra show that the dioxo groups on the Mo(VI) oxygens readily
exchange with water in an acetonitrile media that allows 18O labeling of catalyst 1. The model oxidation reaction
was the conversion of thioanisole (2) to the corresponding
sulfoxide with 4% of 1 using an equimolar amount of H2O2 in MeCN-d
3. Oxygen-18
labeling experiments with either 18O-labeled 1 or 18O-labeled H2O2 are consistent
with a sulfide oxygenation pathway that uses a η1-Mo(OOH) hydroxoperoxyl species (3). The hypothesized
intermediate 3 is initially formed in a proton transfer
reaction between 1 and H2O2. Oxidation
is hypothesized via nucleophilic attack of the sulfide on 3 that is supported from a Hammett linear free-energy relationship
for para-derivatives of 2. A Hammett reactivity constant
(ρ) of −1.2 ± 0.2 was obtained, which is consistent
with other ρ values found in prior sulfide oxidation reactions
by group 6 complexes. An Eyring plot of the 2 oxidation
by 1 gives an E
a of 63.0
± 5.2 kJ/mol, which is slightly higher than that of a similar
oxidation of 2 by the molybdenum(VI) complex, oxodiperoxo
(pyridine-2-carboxylato)molybdate(VI) bis(pyridine-2-carboxylic acid)
monohydrate (5). Computational modeling with density
functional theory (DFT) of the complete reaction profile gave enthalpy
and entropy of activations (64 kJ/mol and −120 J/mol·K,
respectively) within 1 standard deviation of the experimental values,
further supporting the hypothesized mechanism.
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