Infrared Spectroscopy of Dioxouranium(V) Complexes with Solvent Molecules: Effect of Reduction (original) (raw)
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Sequestering ability of polycarboxylic ligands towards dioxouranium(VI)
Talanta, 2008
In this paper we report a comparison on the sequestering ability of some polycarboxylic ligands towards dioxouranium(VI) (UO(2)(2+), uranyl). Ligands taken into account are mono- (acetate), di- (oxalate, malonate, succinate and azelate), tri- (1,2,3-propanetricarboxylate) and hexa-carboxylate (1,2,3,4,5,6-benzenehexacarboxylate). The sequestering ability of polycarboxylic ligands towards UO(2)(2+) was quantified by a new approach expressed by means of a sigmoid Boltzman type equation and of a empirical parameters (pL(50)) which defines the amount of ligand necessary to sequester 50% of the total UO(2)(2+) concentration. A fairly linear correlation was obtained between pL(50) or log K(110) (log K(110) refers to the equilibrium: UO(2)(2+)+L(z-)=UO(2)L((2-z)); L=generic ligand) and the polyanion charges. In order to complete the picture, a tetra-carboxylate ligand (1,2,3,4-butanetetracarboxylate) was studied in NaCl aqueous solutions at 0<or=I (mol L(-1))<or=1.0 and t=25 degrees C, by potentiometry, ISE-[H(+)] glass electrode. The formation of ML(2-), MLH(-), MLH(2)(0) and MLOH(3-) species (M=UO(2)(2+) and L=1,2,3,4-butanetetracarboxylate) was found, with log beta(110)=7.937+/-0.028, log beta(111)=13.066+/-0.027, log beta(112)=17.401+/-0.013, log beta(11-1)=2.062+/-0.040 at I=0 mol L(-1) and t=25 degrees C [beta(pqr) refer to reaction: pUO(2)(2+)+qL(4-)+rH(+)=(UO(2)(2+))(p)L(q)H(r)((2p-4q+r))]. The dependence on ionic strength of all ligand protonation constants and of the complex formation constants of UO(2)(2+)-polycarboxylate systems was modelled by the SIT (specific ion interaction theory) approach and by the Pitzer equations.
2012
Ionic complexes havc long been studied by mass spcctrometry while leisurely spectroscopic studies of neutral complexcs can be studied using matrix isolation spectroscopy. Experimental rcsuJts aiming to elucidatc the structures o f neutral and ionic complexes are often complemented by electronic structure calculations as has been done in th is work. Comple.\:es of divalent metal ions and uracil have been investigated using FTICR mass spectrometry. Positive ion electrospray mass spectra show that [M(Ura-H)(Ura)]', where M is formally a divalent metal ion, are the most abundant ions evcn al low concentrations of uracil. MS/M S experiments show that the lowest energy dt:eomposi tion pathway for [M(Ura-H)(Ura»)' complexes is loss of HNCO for all metals studied with the exception OfST, Ba and Pb which do lose a molecule of uracil. The computed binding energies between neutral uracil and rM(Ura-H)(, M'" Zn, Cu, Ni, Fe, Cd, Pd , Mg, Ca, Sr, Ba, and Pb have also been ca1culalt:-d and aTe consistent with the experimentallyobserved differences in fragmentation pathways. The potential energy surfaces associated with the fragmentation pathways ofrCu(Ura-H)(Um)r were computed to help explain the collision induced dissociation spectra Complexes of uracil and Pbl +, as well the water-solvated complexes have been studied by infrared multi ple photon dissociation (IRMPD) spectroscopy in the N-H and 0-1-1 stretching region. The co mputed IR spectra for the lowest energy structures arc consistent with the experimental IRMPD spectrum_ The experimental spectra for !l'b(Ura-H)(H20)nr (n"' I-2) revealed that the first water molecule binds to the lead ion and indicates the presence of intramolecular hydrogen bonding to a carbonyl of uracil. The second molecule of water also attaches directly to the lead ion, but does not participate in any hydrogen bonding. The infrared absorption spectra of hydrogen-bonded complexes of propylene oxide with either ethanol or 2-nuoroethanol have been recorded in neon matrices, The results indicate that hydrogen-bonded complexes were formed with propylene oxide as the hydrogen bond acceptor and either ethanol or 2-nuoroethanol as the hydrogen bond donors. The features assigned to the O-H stretch were red-shifted by 175 em' I and 193 cm'l for ethanol and 2-ftuoroethanol containing complexes. From the peak shifts and the comparison with the calculations, a 1:1 propylene oxide/ethanol and propylene oxidel2fluorocthanol complexes arc fonnl"1l. Acknowledgement I wou ld like to offer my thanks to the people who have he lped me along the way to make this thesis possible. I would like to express my deepest gratitude 10 my supervisor, Dr. Travis Fridgen, who introduced me to fascinating field s of Matrix Isolation and FTICR mass spectrometry. His support, encouragement, and advice have been a great help during thesc years. Also, hi s kindnesses, valuable guidance, and endless hours of help and contribution have made this a remarkable learning experience. I would like to thank my supervisory commillee, Dr. Peter Pickup and Dr. Christina BOllaro, for their help and suggestions. I would to thank our research group, for their continual support, help and encouragements throughout my program Finally, and most importantly, I would like to express my deepest gratitude for the co ntinuous support and encouragement that I received from my parents. my love, and brothers and sisters. This work would never have been completed wi thout their support. Also, I cannot forget to thank my friends who have he lped throughout my program.
Journal of the American Chemical Society, 2006
The gas-phase infrared spectra of discrete uranyl ([UO2] 2+ ) complexes ligated with acetone and/ or acetonitrile were used to evaluate systematic trends of ligation on the position of the OdUdO stretch and to enable rigorous comparison with the results of computational studies. Ionic uranyl complexes isolated in a Fourier transform ion cyclotron resonance mass spectrometer were fragmented via infrared multiphoton dissociation using a free electron laser scanned over the mid-IR wavelengths. The asymmetric OdUdO stretching frequency was measured at 1017 cm -1 for [UO2(CH3COCH3)2] 2+ and was systematically red shifted to 1000 and 988 cm -1 by the addition of a third and fourth acetone ligand, respectively, which was consistent with increased donation of electron density to the uranium center in complexes with higher coordination number. The values generated computationally using LDA, B3LYP, and ZORA-PW91 were in good agreement with experimental measurements. In contrast to the uranyl frequency shifts, the carbonyl frequencies of the acetone ligands were progressively blue shifted as the number of ligands increased from two to four and approached that of free acetone. This observation was consistent with the formation of weaker noncovalent bonds between uranium and the carbonyl oxygen as the extent of ligation increases. Similar trends were observed for [UO 2(CH3CN)n] 2+ complexes, although the uranyl asymmetric stretching frequencies were greater than those measured for acetone complexes having equivalent coordination, which is consistent with the fact that acetonitrile is a weaker nucleophile than is acetone. This conclusion was confirmed by the uranyl stretching frequencies measured for mixed acetone/acetonitrile complexes, which showed that substitution of one acetone for one acetonitrile produced a modest red shift of 3-6 cm -1 .
Infrared spectroscopy of discrete uranyl anion complexes
Journal of Physical Chemistry A, 2008
The Free-Electron Laser for Infrared Experiments (FELIX) was used to study the wavelength-resolved multiple photon photodissociation of discrete, gas-phase uranyl (UO 2 2+ ) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO 2 A(S) n ] + , where A was hydroxide, methoxide, or acetate; S was water, ammonia, acetone, or acetonitrile; and n ) 0-3. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO 2 A] + ) were as low or lower than measurements for [UO 2 ] 2+ ligated with as many as five strong neutral donor ligands and are comparable to solution-phase values. This result was surprising because initial DFT calculations predicted values that were 30-40 cm -1 higher, consistent with intuition but not with the data. Modification of the basis sets and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO 2 A] + produced [UO 2 AS] + , which produced only very modest changes to the uranyl antisymmetric stretch frequency, and did not universally shift the frequency to lower values. DFT calculations for [UO 2 AS] + were in accord with trends in the data and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO 2 AS] + species having different solvent neutrals, values decreased with increasing neutral nucleophilicity.
Polyhedron, 2017
A combined experimental and theoretical study has been put forward to investigate the complexation behaviour of tetravalent Pu 4+ and hexavalent UO 2 2+ ions with the N,N-dihexyloctanamide (DHOA) ligand in different diluents. Solvent extraction experiments were conducted with Pu 4+ and UO 2 2+ ions using DHOA in different diluents, namely dodecane, toluene, chloroform, octanol, nitrophenyl-octyl ether (NPOE) and nitrobenzene (NB). The experimentally measured distribution coefficients (D) of both the Pu 4+ and UO 2 2+ ions followed the order: nitrobenzene > NPOE > octanol > chloroform > toluene > dodecane. In order to complement the experimental distribution data, the structure, energetic and thermodynamic parameters of the Pu 4+ and UO 2 2+ complexes with DHOA have been calculated using density functional theory. The free energy of extraction, ∆G ext , for the Pu 4+ and UO 2 2+ ions with DHOA was calculated using the Born-Haber thermodynamic cycle in the different experimentally studied diluents. The value of ∆G ext for the Pu 4+ ion in dodecane was found to be higher than that of the UO 2 2+ ion, as measured in the experiments. The value of ∆G ext was shown to increase with the increase in the dielectric constant of the diluent for both Pu 4+ and UO 2 2+ ions, similar to the experimental studies. Thus, the combined experimental and theoretical studies help to understand the underlying complexation mechanism of the UO 2 2+ and Pu 4+ ions with DHOA, which explains its selectivity towards the Pu 4+ ion.
Dissociation of polyether-transition metal ion dimer complexes in a quadrupole ion trap
Journal of the American Society for Mass Spectrometry, 1997
The formation and dissociation of dimer complexes consisting of a transition metal ion and two polyether ligands is examined in a quadrupole ion trap mass spectrometer. Reactions of three transition metals (Ni, Cu, Co) with three crown ethers and four acyclic ethers (glymes) are studied. Singly charged species are created from ion-molecule reactions between laserdesorbed monopositive metal ions and the neutral polyethers. Doubly charged complexes are generated from electrospray ionization of solutions containing metal salts and polyethers. For the singly charged complexes, the capability for dimer formation by the ethers is dependent on the number of available coordination sites on the ligand and its ability to fully coordinate the metal ion. For example, l&crown-6 never forms dimer complexes, but 12-crown4 readily forms dimers. For the more flexible acyclic ethers, the ligands that have four or more oxygen atoms do not form dimer complexes because the acyclic ligands have sufficient flexibility to wrap around the metal ion and prevent attachment of a second ligand. For the doubly charged complexes, dimers are observed for all of the crown ethers and glymes, thus showing no dependence on the flexibility or number of coordination sites of the polyether. The nonselectivity of dimer formation is attributed to the higher charge density of the doubly charged metal center, resulting in stronger coordination abilities. Collisionally activated dissociation is used to evaluate the structures of the metal-polyether dimer complexes. Radical fragmentation processes are observed for some of the singly charged dimer complexes because these pathways allow the monopositive metal ion to attain a more favorable 2 + oxidation state. These radical losses are observed for the dimer complexes but not for the monomer complexes because the dimer structures have two independent ligands, a feature that enhances the coordination geometry of the complex and allows more flexibility for the rearrangements necessary for loss of radical species. Dissociation of the doubly charged complexes generated by electrospray ionization does not result in losses of radical neutrals because the metal ions already exist in favorable 2+ oxidation states. (J Am Sot Mass Spectrom 1997,8,620-629) 0 1997 American Society for Mass Spectrometry T he examination of reactions of metal ions with organic ligands in the gas phase has been an ongoing field of research over the past two decades because of both the fundamental interest in metal ion chemistry [ l---8] and the interesting analogies between solution and gas-phase chemistry. Recent advances in mass spectrometry have allowed the generation of selectivity solvated metal complexes [g-lo], measurement of binding energies of metal-containing clusters 18-111, and elucidation of metal binding sites of oligonucleotides [12], to name just a few of the active areas of research involving metal complexation in the gas phase. Metal complexation has also been viewed as a versatile method of ionizing molecules, and there have been numerous reports of metal complexation in fast-atom bombardment (FAB) [13-181 or electrospray ionization (ESI) mass spectrometry Address reprint requests to Jennifer Brodbelt, resulting in the creation of stable complexes, such as those containing saccharides or peptides.
Journal of Solution Chemistry, 2009
The formation constants of dioxouranium(VI)-2,2 -oxydiacetic acid (diglycolic acid, ODA) and 3,6,9-trioxaundecanedioic acid (diethylenetrioxydiacetic acid, TODA) complexes were determined in NaCl (0.1 ≤ I ≤ 1.0 mol·L −1 ) and KNO 3 (I = 0.1 mol·L −1 ) aqueous solutions at T = 298.15 K by ISE-[H + ] glass electrode potentiometry and visible spectrophotometry. Quite different speciation models were obtained for the systems investigated, namely: ML 0 , MLOH − , ML 2− 2 , M 2 L 2 (OH) − , and M 2 L 2 (OH) 2− 2 , for the dioxouranium(VI)-ODA system, and ML 0 , MLH + , and MLOH − for the dioxouranium(VI)-TODA system (M = UO 2+ 2 and L = ODA or TODA), respectively. The dependence on ionic strength of the protonation constants of ODA and TODA and of both metal-ligand complexes was investigated using the SIT (Specific Ion Interaction Theory) approach. Formation constants at infinite dilution are [for the generic equilibrium pUO 2+ 2 + q(L 2− ) + rH + (UO 2+ 2 ) p (L) q H (2p−2q+r) r ; β pqr ]: log 10 β 110 = 6.146, log 10 β 11−1 = 0.196, log 10 β 120 = 8.360, log 10 β 22−1 = 8.966, log 10 β 22−2 = 3.529, for the dioxouranium(VI)-ODA system and log β 110 = 3.636, log 10 β 111 = 6.650, log 10 β 11−1 = −1.242 for dioxouranium(VI)-TODA system. The influence of etheric oxygen(s) on the interaction towards the metal ion was discussed, and this effect was quantified by means of a sigmoid Boltzman type equation that allows definition of a quantitative parameter (pL 50 ) that expresses the sequestering capacity of ODA and TODA towards UO 2+ 2 ; a comparison with other dicarboxylates was made. A visible absorption spectrum for each complex reaching a significant percentage of formation in solution (KNO 3 medium) has been calculated to better characterize the compounds found by pH-metric refinement.