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1.
Phys Chem Chem Phys ; 22(22): 12403-12411, 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32452480

RESUMO

The anions pertechnetate, TcO4-, and perrhenate, ReO4-, exhibit very similar chemical and physical properties. Revealing and understanding disparities between them enhances fundamental understanding of both. Electrospray ionization generated the gas-phase proton bound dimer (TcO4-)(H+)(ReO4-). Collision induced dissociation of the dimer yielded predominantly HTcO4 and ReO4-, which according to Cooks' kinetic method indicates that the proton affinity (PA) of TcO4- is greater than that of ReO4-. Density functional theory computations agree with the experimental observation, providing PA[TcO4-] = 300.1 kcal mol-1 and PA[ReO4-] = 297.2 kcal mol-1. Attempts to rationalize these relative PAs based on elementary molecular parameters such as atomic charges indicate that the entirety of bond formation and concomitant bond disruption needs to be considered to understand the energies associated with such protonation processes. Although in both the gas and solution phases, TcO4- is a stronger base than ReO4-, it is noted that the significance of even such qualitative accordance is tempered by the very different natures of the underlying phenomena.

2.
J Am Chem Soc ; 2020 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-32383858

RESUMO

The reaction of atomic boron with benzene in solid neon has been investigated by matrix isolation infrared spectroscopy with isotopic substitutions as well as quantum chemical calculations. The reaction is initiated by boron atom addition to benzene in forming an η2-(1, 4) π adduct (A). A borepinyl radical (B) formed by C-C bond insertion is also observed on annealing. The η2-(1,4) π adduct photoisomerizes to an unprecedented borole substituted vinyl radical intermediate (C) via ring-opening and rearrangement reactions involving an antiaromatic borole subunit. A previously unconsidered 1-ethynyl-2-dihydro-1H-borole radical (D) is generated as the final product under UV light irradiation. The results presented herein give new insight into the benzene carbon-carbon bond cleavage and rearrangement reactions mediated by a nonmetal and provide a possible route for the construction of heterocyclic borepinyl and borole species via benzene ring opening and rearrangement reactions.

3.
Phys Chem Chem Phys ; 21(36): 19868-19878, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31475264

RESUMO

Electrospray ionization of solutions containing a tripodal hydroxylamine ligand, H3TriNOx ([((2-tBuNOH)C6H4CH2)3N]) denoted as L, and a hydrogen halide HX: HCl, HBr and/or HI, yielded gas-phase anion complexes [L(X)]- and [L(HX2)]-. Collision induced dissociation (CID) of mixed-halide complexes, [L(HXaXb)]-, indicated highest affinity for I- and lowest for Cl-. Structures and energetics computed by density functional theory are in accord with the CID results, and indicate that the gas-phase binding preference is a manifestation of differing stabilities of the HX molecules. A high halide affinity of [L(H)]+ in solution was also demonstrated, though with a highest preference for Cl- and lowest for I-, the opposite observation of, but not in conflict with, what is observed in gas phase. The results suggest a connection between gas- and condensed-phase chemistry and computational approaches, and shed light on the aggregation and anion recognition properties of hydroxylamine receptors.

4.
Inorg Chem ; 58(15): 10148-10159, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31318537

RESUMO

A gas-phase uranyl peroxide dimer supported by three 12-crown-4 ether (12C4) ligands, [(UO2)2(O2)(12C4)3)]2+ (A), was prepared by electrospray ionization. Density functional theory (DFT) indicates a structure with two terminal 12C4 and the third 12C4 bridging the uranium centers. Collision induced dissociation (CID) of A resulted in elimination of the bridging 12C4 to yield a uranyl peroxide dimer with two terminal donor ligands, [(12C4)(UO2)(O2)(UO2)(12C4)]2+ (B). Remarkably, CID of B resulted in elimination of the bridging peroxide concomitant with reduction of U(VI) to U(V) in C, [(12C4)(UO2)(UO2)(12C4)]2+. DFT studies indicate that in C there is direct interaction between the two UO2+ species, which can thus be considered as a so-called cation-cation interaction (CCI). This formal CCI, induced by tetradentate 12C4 ligands, corresponds to destruction of the linear uranyl moieties and creation of bridging U-O-U oxo-bonds. On the basis of the structural rearrangement to achieve the structurally extreme CCI interaction, it is predicted also to be accessible for PaO2+ but is less feasible for transuranic actinyls.

5.
Chem Commun (Camb) ; 55(17): 2441-2444, 2019 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-30734779

RESUMO

Selectivity for An(iii) vs. Ln(iii) binding and extraction using dipicolinamide analogs containing the C[double bond, length as m-dash]O vs. C[double bond, length as m-dash]S groups was investigated in solution and the gas-phase, and by DFT calculations. The results show higher selectivity for complex formation and extraction for Am(iii) vs. Eu(iii) for the softer dithioamide vs. the diamide ligand, while in CH3CN the diamide binds more strongly than the thioamide to several Ln(iii), forming 1 : 1 complexes.

6.
Chem Commun (Camb) ; 54(76): 10698-10701, 2018 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-30187044

RESUMO

Oxo group activation with reduction of neptunyl(vi) and plutonyl(vi) to tetravalent hydroxo species by the hydroxypyridinone siderophore derivative 3,4,3-LI-(1,2-HOPO) was investigated in the gas-phase via electrospray ionization mass spectrometry, in solution via Raman spectroscopy, and computationally via density functional theory. Dissociation of the gas-phase tetravalent complexes resulted in actinide-hydroxo bond cleavage.

7.
Inorg Chem ; 57(7): 4125-4134, 2018 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-29558121

RESUMO

The following gas-phase uranyl/12-crown-4 (12C4) complexes were synthesized by electrospray ionization: [UO2(12C4)2]2+ and [UO2(12C4)2(OH)]+. Collision-induced dissociation (CID) of the dication resulted in [UO2(12C4-H)]+ (12C4-H is a 12C4 that has lost one H), which spontaneously adds water to yield [UO2(12C4-H)(H2O)]+. The latter has the same composition as complex [UO2(12C4)(OH)]+ produced by CID of [UO2(12C4)2(OH)]+ but exhibits different reactivity with water. The postulated structures as isomeric [UO2(12C4-H)(H2O)]+ and [UO2(12C4)(OH)]+ were confirmed by comparison of infrared multiphoton dissociation (IRMPD) spectra with computed spectra. The structure of [UO2(12C4-H)]+ corresponds to cleavage of a C-O bond in the 12C4 ring, with formation of a discrete U-Oeq bond and equatorial coordination by three intact ether moieties. Comparison of IRMPD and computed IR spectra furthermore enabled assignment of the structures of the other complexes. Theoretical studies of the chemical bonding features of the complexes provide an understanding of their stabilities and reactivities. The results reveal bonding and structures of the uranyl/12C4 complexes and demonstrate the synthesis and identification of two different isomers of gas-phase uranyl coordination complexes.

8.
Inorg Chem ; 56(21): 12930-12937, 2017 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-29019408

RESUMO

Recent efforts to activate the strong uranium-oxygen bonds in the dioxo uranyl cation have been limited to single oxo-group activation through either uranyl reduction and functionalization in solution, or by collision induced dissociation (CID) in the gas-phase, using mass spectrometry (MS). Here, we report and investigate the surprising double activation of uranyl by an organic ligand, 3,4,3-LI(CAM), leading to the formation of a formal U6+ chelate in the gas-phase. The cleavage of both uranyl oxo bonds was experimentally evidenced by CID, using deuterium and 18O isotopic substitutions, and by infrared multiple photon dissociation (IRMPD) spectroscopy. Density functional theory (DFT) computations predict that the overall reaction requires only 132 kJ/mol, with the first oxygen activation entailing about 107 kJ/mol. Combined with analysis of similar, but unreactive ligands, these results shed light on the chelation-driven mechanism of uranyl oxo bond cleavage, demonstrating its dependence on the presence of ligand hydroxyl protons available for direct interactions with the uranyl oxygens.

9.
J Phys Chem A ; 121(41): 7861-7868, 2017 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-28972761

RESUMO

The reactions of early lanthanide metal atoms (Ce, Pr, and Nd) with carbon monoxide and nitric oxide mixtures are studied by infrared absorption spectroscopy in solid argon. The reaction intermediates and products are identified via isotopic substitution as well as theoretical frequency calculations. The results show that the reactions proceed with the initial formation of inserted NLnO molecules, which subsequently react with CO to form the NLnO(CO) complexes on annealing. The NLnO(CO) complexes further isomerize to the more stable isocyanate OLnNCO species under UV light excitation.

10.
Chem Sci ; 8(6): 4443-4449, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28936331

RESUMO

The organo-boron species formed from the reactions of boron atoms with acetylene in solid neon are investigated using matrix isolation infrared spectroscopy with isotopic substitutions as well as quantum chemical calculations. Besides the previously reported single C-H bond activation species, a cyclic-HBC2BH diboron species is formed via double C-H bond activation of acetylene. It is characterized to have a closed-shell singlet ground state with planar D2h symmetry. Bonding analysis indicates that it is a doubly aromatic species involving two delocalized σ electrons and two delocalized π electrons. This finding reveals the very first example of double C-H bond activation of acetylene in forming new organo-boron compounds.

11.
Chem Sci ; 8(5): 4035-4043, 2017 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-28580119

RESUMO

The neutral molecule NPrO and its anion NPrO- are produced via co-condensation of laser-ablated praseodymium atoms with nitric oxide in a solid neon matrix. Combined infrared spectroscopy and state-of-the-art quantum chemical calculations confirm that both species are pentavalent praseodymium nitride-oxides with linear structures that contain Pr≡N triple bonds and Pr=O double bonds. Electronic structure studies show that the neutral NPrO molecule features a 4f0 electron configuration and a Pr(v) oxidation state similar to that of the isoelectronic PrO2+ ion, while its NPrO- anion possesses a 4f1 electron configuration and a Pr(iv) oxidation state. The neutral NPrO molecule is thus a rare lanthanide nitride-oxide species with a Pr(v) oxidation state, which follows the recent identification of the first Pr(v) oxidation state in the PrO2+ and PrO4 complexes (Angew. Chem. Int. Ed., 2016, 55, 6896). This finding indicates that lanthanide compounds with oxidation states of higher than +IV are richer in chemistry than previously recognized.

12.
Phys Chem Chem Phys ; 18(45): 31125-31131, 2016 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-27812577

RESUMO

The experimentally known highest oxidation state of iron has been determined to be Fe(vi) so far. Here we report a combined matrix-isolation infrared spectroscopic and theoretical study of two interconvertible iron oxide anions: a dioxoiron peroxide complex [(η2-O2)FeO2]- with a C2v-structure and a tetroxide FeO4- with a D2d tetrahedral structure, which are formed by co-condensation of laser-ablated iron atoms and electrons with O2/Ar mixtures at 4 K. Quantum chemistry theoretical studies indicate that the Jahn-Teller distorted tetroxide FeO4- anion is a d1 species with hereto the highest iron formal oxidation state Fe(vii).

13.
Angew Chem Int Ed Engl ; 55(29): 8371-4, 2016 07 11.
Artigo em Inglês | MEDLINE | ID: mdl-27240114

RESUMO

A ground-state boron atom inserts into the C=C bond of ethylene to spontaneously form the allene-like compound H2 CBCH2 on annealing in solid neon. This compound can further isomerize to the propyne-like HCBCH3 isomer under UV light excitation. The observation of this unique spontaneous C=C bond insertion reaction is consistent with theoretical predictions that the reaction is thermodynamically exothermic and kinetically facile. This work demonstrates that the stronger C=C bond, rather than the less inert C-H bond, can be broken to form organoboron species from the reaction of a boron atom with ethylene even at cryogenic temperatures.

14.
Chemistry ; 22(7): 2376-85, 2016 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-26773594

RESUMO

A combined experimental and theoretical study on the main-group tricarbonyls [B(CO)3 ] in solid noble-gas matrices and [C(CO)3 ](+) in the gas phase is presented. The molecules are identified by comparing the experimental and theoretical IR spectra and the vibrational shifts of nuclear isotopes. Quantum chemical ab initio studies suggest that the two isoelectronic species possess a tilted η(1) (µ1 -CO)-bonded carbonyl ligand, which serves as an unprecedented one-electron donor ligand. Thus, the central atoms in both complexes still retain an 8-electron configuration. A thorough analysis of the bonding situation gives quantitative information about the donor and acceptor properties of the different carbonyl ligands. The linearly bonded CO ligands are classical two-electron donors that display classical σ-donation and π-back-donation following the Dewar-Chatt-Duncanson model. The tilted CO ligand is a formal one-electron donor that is bonded by σ-donation and π-back-donation that involves the singly occupied orbital of the radical fragments [B(CO)2 ] and [C(CO)2 ](+) .

15.
J Phys Chem A ; 119(35): 9286-93, 2015 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-26284964

RESUMO

The infrared spectra of mass-selected Ni(O2)n(+) (n = 2-4) and their argon-tagged complexes are measured by infrared photodissociation spectroscopy in the gas phase. The experimental spectra provide distinctive patterns allowing the determination of their geometric and electronic structures by comparison with the simulated vibrational spectra from density functional theory calculations. The [Ni(O2)2Ar2](+) cation complex was determined to have D2h symmetry involving a Ni(O2)2(+) core ion with two equivalent superoxide ligands side-on bound to a Ni(3+) cation center. The higher Ni(O2)3(+) and Ni(O2)4(+) cation complexes were determined to have structures with a chemically bound Ni(O2)2(+) core ion that is weakly coordinated by neutral O2 molecule(s).

16.
J Phys Chem A ; 118(25): 4519-26, 2014 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-24898322

RESUMO

Infrared spectra of mass-selected oxygen-rich iron dioxygen complexes Fe(O2)n(+) with n = 3-5 are measured via infrared photodissociation spectroscopy in the gas phase. These cation complexes are produced via a laser vaporization supersonic ion source. The structures are established by comparison of the experimental spectra with the simulated spectra derived from density functional calculations. All of the Fe(O2)n(+) complexes studied have a single IR-active band in the 1050-1100 cm(-1) region, arising from the O-O stretching vibration of the superoxo ligand(s). These complexes are determined to have structures with a chemically bound Fe(O2)2(+) core ion that is weakly coordinated by neutral O2 molecules. The Fe(O2)2(+) core ion has a planar D2h symmetry with two equivalent side-on superoxo ligands bound to an Fe(3+) cation center.


Assuntos
Cátions/química , Complexos de Coordenação/química , Compostos Férricos/química , Oxigênio/química , Espectrofotometria Infravermelho/métodos , Modelos Moleculares , Simulação de Dinâmica Molecular , Estrutura Molecular
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