The compound Na{[Tc6Br12]2Br} has been obtained from the decomposition of TcBr4 under vacuum in a... more The compound Na{[Tc6Br12]2Br} has been obtained from the decomposition of TcBr4 under vacuum in a Pyrex ampule at 450 °C. The stoichiometry of the compound has been confirmed by energy-dispersive X-ray spectroscopy and its structure determined by single-crystal X-ray diffraction. The compound contains a trigonal-prismatic hexanuclear [Tc6Br12] cluster. The cluster is composed of two triangular Tc3Br6 units linked by multiple Tc-Tc bonds. In the Tc3Br6 unit, the average Tc-Tc distance [2.6845(5) Å] is characteristic of Tc-Tc single bonds, while the average Tc-Tc distance between the two triangular units [2.1735(5) Å] is characteristic of Tc≡Tc triple bonds. The electronic structure of the [Tc6Br12] cluster was studied by first-principles calculations, which confirm the presence of single and triple Tc-Tc bonds in the cluster.
The hydrothermal reactions of trivalent lanthanide and actinide chlorides with 1,2-methylenedipho... more The hydrothermal reactions of trivalent lanthanide and actinide chlorides with 1,2-methylenediphosphonic acid (C1P2) in the presence of NaOH or NaNO 3 result in the crystallization of three structure types: RE[CH 2 (PO 3 H 0.5 ) 2 ] (RE = La, Ce, Pr, Nd, Sm; Pu) (A type), NaRE(H 2 O)-[CH 2 (PO 3 ) 2 ] (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy; Am) (B type), or NaLn[CH 2 (PO 3 H 0.5 ) 2 ]·(H 2 O) (Ln = Yb and Lu) (C type). These crystals were analyzed using single crystal Xray diffraction, and the structures were used directly for detailed bonding calculations. These phases form three-dimensional frameworks. In both A and B, the metal centers are found in REO 8 polyhedra as parts of edge-sharing chains or edge-sharing dimers, respectively. Polyhedron shape calculations reveal that A favors a D 2d dodecahedron while B adopts a C 2v geometry. In C, Yb and Lu only form isolated MO 6 octahedra. Such differences in terms of structure topology and coordination geometry are discussed in detail to reveal periodic deviations between the lanthanide and actinide series. Absorption spectra for the Pu(III) and Am(III) compounds are also reported. Electronic structure calculations with multireference methods, CASSCF, and density functional theory, DFT, reveal localization of the An 5f orbitals, but natural bond orbital and natural population analyses at the DFT level illustrate unique occupancy of the An 6d orbitals, as well as larger occupancy of the Pu 5f orbitals compared to the Am 5f orbitals.
A new neutral borate species, H(2)B(4)O(7) (also known as tetraboric acid), with a one-dimensiona... more A new neutral borate species, H(2)B(4)O(7) (also known as tetraboric acid), with a one-dimensional chain structure, is found in the interlayer spacing in Rb(2)[(UO(2))(2)B(8)O(12)F(6)]·H(2)B(4)O(7) (RbUBOF-2) derived from boric acid flux reaction of uranyl(VI) nitrate with RbBF(4). This new form of tetraboric acid possesses a novel borate fundamental building block with the symbol 4Δ:<3Δ>Δ.
Langmuir : the ACS journal of surfaces and colloids, Jan 21, 2015
The cation-π interaction is proposed as an important mechanism for the adsorption of aromatic hyd... more The cation-π interaction is proposed as an important mechanism for the adsorption of aromatic hydrocarbons having non-zero quadrupole moments by mineral surfaces. Direct evidence supporting such a mechanism is, however, limited. Using the model mineral calcite, we probe the cation-π interaction with adsorbed benzene, toluene, and ethylbenzene (BTE) molecules using attenuated total reflectance Fourier transform infrared spectroscopy. We show that the presence of calcite increases the energy required to excite the synchronized bending of aromatic C-H bonds of BTE molecules. The unique conformation of this vibrational mode indicates that the planar aromatic rings of BTE molecules are constrained in a tilted face-down position by the cation-π interaction, as further confirmed by density functional theory calculations. Our results suggest that the shift of the excitation energy of the aromatic C-H bending may be used as an infrared signature for the cation-π interaction occurring on mine...
The journal of physical chemistry. A, Jan 30, 2006
The sigma- and pi-bond strengths for the molecules BH2NH2, BH2PH2, AlH2NH2, and AlH2PH2 have been... more The sigma- and pi-bond strengths for the molecules BH2NH2, BH2PH2, AlH2NH2, and AlH2PH2 have been calculated by using ab initio molecular electronic structure theory at the CCSD(T)/CBS level. The adiabatic pi-bond energy is defined as the rotation barrier between the equilibrium ground-state configuration and the C(s)symmetry transition state for torsion about the A-X bond. We also report intrinsic pi-bond energies corresponding to the adiabatic rotation barrier corrected for the inversion barrier at N or P. The adiabatic sigma-bond energy is defined as the dissociation energy of AH2XH2 to AH2 + XH2 in their ground states minus the adiabatic pi-bond energy. The adiabatic sigma-bond strengths for the molecules BH2NH2, BH2PH2, AlH2NH2, and AlH2PH2 are 109.8, 98.8, 77.6, and 68.3 kcal/mol, respectively, and the corresponding adiabatic pi-bond strengths are 29.9, 10.5, 9.2, and 2.7 kcal/mol, respectively.
Ab initio electronic structure calculations are reported for S2, and its ions S2+ and S2-. Geomet... more Ab initio electronic structure calculations are reported for S2, and its ions S2+ and S2-. Geometric parameters are calculated using the singles and doubles coupled cluster method, including a perturbational correction for connected triple excitation, together with systematic sequences of correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. Energetic and structural properties of S2 and the S2 cation and anion are reported. The heat of formation of S2 (3Sigmag-) at 0 K in the gas phase is predicted to be 29.8 kcal/mol from the average of CBS two extrapolation procedures, less than the experimental heat of formation of S2 of 30.66+/-0.07 kcal/mol. The 0 K adiabatic ionization potential and electron affinity are predicted to be 9.37 and 1.68 eV, respectively.
High level ab initio electronic structure calculations using the coupled cluster CCSD(T) method w... more High level ab initio electronic structure calculations using the coupled cluster CCSD(T) method with augmented correlation-consistent basis sets extrapolated to the complete basis set limit have been performed on the PNO, NOP, and NPO isomers and their corresponding anions and cations. Geometries for all species were optimized up through the aug-cc-pV(Q+d)Z level and vibrational frequencies were calculated with the aug-cc-pV(T+d)Z basis set. The most stable of the three isomers is NPO and it is predicted to have a heat of formation of 23.3 kcal/mol. PNO is predicted to be only 1.7 kcal/mol higher in energy. The calculated adiabatic ionization potential of NPO is 12.07 eV and the calculated adiabatic electron affinity is 2.34 eV. The calculated adiabatic ionization potential of PNO is 10.27 eV and the calculated adiabatic electron affinity is only 0.24 eV. NOP is predicted to be much higher in energy by 29.9 kcal/mol. The calculated rotational constants for PNO and NPO should allow f...
The journal of physical chemistry. A, Jan 29, 2009
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for diammoniosila... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for diammoniosilane, H(4)Si(NH(3))(2), and its dehydrogenated derivates at the CCSD(T) and G3(MP2) levels. To achieve near chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first-order atomic spin-orbit effects. Vibrational zero-point energies were computed at the CCSD(T) or MP2 levels. The edge inversion barrier of silane is predicted to be 88.9 kcal/mol at 298 K at the CCSD(T) level and a substantial amount, -63.6 kcal/mol, is recovered upon complexation with 2 NH(3) molecules, so that the diammoniosilane complex is only 25.6 kcal/mol at 298 K above the separated reactants SiH(4) + 2NH(3). The complex is a metastable species characterized by all real frequencies at the MP2/aV(T+d)Z level. ...
The journal of physical chemistry. A, Jan 16, 2009
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for SiH(3)X, SiH(... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for SiH(3)X, SiH(2)XCH(3), and SiH(3)CH(2)X with X = F, Cl, Br, and I from coupled cluster theory (CCSD(T)) calculations with effective core potential correlation-consistent basis sets for Br and I. To achieve near chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first order atomic spin-orbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory and the C-H and Si-H stretches scaled to experiment. The C-H, Si-H, Si-C, C-X, and Si-X (X = F, Cl, Br, and I) bond dissociation energies (BDEs) in the halosilanes, halomethysilanes, and methylhalosilanes were predicted. Except for methyliodosilane, methyl substitution leads to an increase in Si-X BDE when compared to...
The journal of physical chemistry. A, Jan 28, 2009
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for (CH3)H2N-BH3,... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for (CH3)H2N-BH3, (CH3)HN=BH2, (BH3)HN=CH2, (CH3)H2B-NH3, (CH3)HB=NH2, and (NH3)HB=CH2, as well as various molecules involved in the different bond-breaking processes, from coupled cluster theory (CCSD(T)) calculations. In order to achieve near-chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core CCSD(T) energies, corrections for core-valence, scalar relativistic, and first-order atomic spin-orbit effects. Scaled vibrational zero-point energies were computed with the MP2 method. The heats of formation were predicted for the respective dimethyl- and trimethyl-substituted ammonia boranes, their dehydrogenated derivatives, and the various molecules involved in the different bond breaking processes, based on isodesmic reaction schemes calculated at the G3(MP2) level. Thermodynamics for dehydrogenation pathways in the monomethyl-substi...
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for XeF(3)(+), Xe... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for XeF(3)(+), XeF(3)(-), XeF(5)(+), XeF(7)(+), XeF(7)(-), and XeF(8) from coupled cluster theory (CCSD(T)) calculations with effective core potential correlation-consistent basis sets for Xe and including correlation of the nearest core electrons. Additional corrections are included to achieve near chemical accuracy of +/-1 kcal/mol. Vibrational zero point energies were computed at the MP2 level of theory. Unlike the other neutral xenon fluorides, XeF(8) is predicted to be thermodynamically unstable with respect to loss of F(2) with the reaction calculated to be exothermic by 22.3 kcal/mol at 0 K. XeF(7)(+) is also predicted to be thermodynamically unstable with respect to the loss of F(2) by 24.1 kcal/mol at 0 K. For XeF(3)(+), XeF(5)(+), XeF(3)(-), XeF(5)(-), and XeF(7)(-), the reactions for loss of F(2) are endothermic by 14.8, 37.8, 38.2, 59.6, and 31.9 kcal/mol at 0 K, respectively. The F(+) affini...
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the neutral a... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the neutral and ionic N(x)F(y) and O(x)F(y) systems using coupled cluster theory with single and double excitations and including a perturbative triples correction (CCSD(T)) method with correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. To achieve near chemical accuracy (±1 kcal/mol), three corrections to the electronic energy were added to the frozen core CCSD(T)/CBS binding energies: corrections for core-valence, scalar relativistic, and first order atomic spin-orbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory where possible. The calculated heats of formation are in good agreement with the available experimental values, except for FOOF because of the neglect of higher order correlation corrections. The F(+) affinity in the N(x)F(y) series increases from N(2) to N(2)F(4) by 63 kcal/mol, while that in the O(2)F(y) series dec...
High-level electronic structure calculations have been used to map out the relevant portions of t... more High-level electronic structure calculations have been used to map out the relevant portions of the potential energy surfaces for the release of H2 from dimers of ammonia borane, BH3NH3 (AB). Using the correlation-consistent aug-cc-pVTZ basis set at the second-order perturbation MP2 level, geometries of stationary points were optimized. Relative energies were computed at these points using coupled-cluster CCSD(T) theory with the correlation-consistent basis sets at least up to the aug-cc-pVTZ level and in some cases extrapolated to the complete basis set limit. The results show that there are a number of possible dimers involving different types of hydrogen-bonded interactions. The most stable gaseous phase (AB)2 dimer results from a head-to-tail cyclic conformation and is stabilized by 14.0 kcal/mol with respect to two AB monomers. (AB)2 can generate one or two H2 molecules via several direct pathways with energy barriers ranging from 44 to 50 kcal/mol. The diammoniate of diborane ion pair isomer, [BH4-][NH3BH2NH3+] (DADB), is 10.6 kcal/mol less stable than (AB)2 and can be formed from two AB monomers by overcoming an energy barrier of approximately 26 kcal/mol. DADB can also be generated from successive additions of two NH3 molecules to B2H6 and from condensation of AB with separated BH3 and NH3 molecules. The pathway for H2 elimination from DADB is characterized by a smaller energy barrier of 20.1 kcal/mol. The alternative ion pair [NH4+][BH3NH2BH3-] is calculated to be 16.4 kcal/mol above (AB)2 and undergoes H2 release with an energy barrier of 17.7 kcal/mol. H2 elimination from both ion pair isomers yields the chain BH3NH2BH2NH3 as product. Our results suggest that the neutral dimer will play a minor role in the release of H2 from ammonia borane, with a dominant role from the ion pairs as observed experimentally in ionic liquids and the solid state.
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the borane co... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the borane compounds H(3-n)BX(n) for (X = F, Cl, Br, I, NH2, OH, and SH) and various radicals from coupled cluster theory (CCSD(T)) calculations with an effective core potential correlation-consistent basis set for I. In order to achieve near chemical accuracy (+/-1.5 kcal/mol), three corrections were added to the complete basis set binding energies calculated from frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first-order atomic spin-orbit effects. Vibrational zero point energies were computed at the MP2 level. The calculated heats of formation are in excellent agreement with the available experimental data for the closed shell molecules, but show larger differences with the reported "experimental" values for the BX2 radicals. The heats of formation of the BX2 radicals were also calculated at the G3(MP2) level of theory, and the values were in excellent agreement with the more accurate CCSD(T) values. On the basis of extensive comparisons with experiment for a wide range of compounds, our calculated values for these radicals should be good to +/-1.5 kcal/mol and thus are to be preferred over the experimental values. The accurately calculated heats of formation allow us to predict the B-X and B-H adiabatic bond dissociation energies (BDEs) to within +/-1.5 kcal/mol. The B-F BDEs in the H(3-n)BF(n) compounds and in BF (1Sigma+) are the largest BDEs in comparison to the other substituents that were investigated. The second and third largest B-X BDEs in the H(3-n)BX(n) and BX compounds are predicted for X = OH and NH2, respectively. The substituents have a minimal effect on the B-H BDEs in HBX2 and H2BX compared to the first B-H BDE of borane. The differences in adiabatic and diabatic BDEs, which are related to the reorganization energy in the product, can be estimated from singlet-triplet splittings in these molecules, and can account for the large fluctuations in adiabatic BDEs observed, specifically for the BX2 and HBX radicals, during the stepwise loss of the respective substituents.
Heats of formation at 0 and 298 K are predicted for PF3, PF5, PF3O, SF2, SF4, SF6, SF2O, SF2O2, a... more Heats of formation at 0 and 298 K are predicted for PF3, PF5, PF3O, SF2, SF4, SF6, SF2O, SF2O2, and SF4O as well as a number of radicals derived from these stable compounds on the basis of coupled cluster theory [CCSD(T)] calculations extrapolated to the complete basis set limit. In order to achieve near chemical accuracy (+/-1 kcal/mol), additional corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, a correction for first-order atomic spin-orbit effects, and vibrational zero-point energies. The calculated values substantially reduce the error limits for these species. A detailed comparison of adiabatic and diabatic bond dissociation energies (BDEs) is made and used to explain trends in the BDEs. Because the adiabatic BDEs of polyatomic molecules represent not only the energy required for breaking a specific bond but also contain any reorganization energies of the bonds in the resulting products, these BDEs can be quite different for each step in the stepwise loss of ligands in binary compounds. For example, the adiabatic BDE for the removal of one fluorine ligand from the very stable closed-shell SF6 molecule to give the unstable SF5 radical is 2.8 times the BDE needed for the removal of one fluorine ligand from the unstable SF5 radical to give the stable closed-shell SF4 molecule. Similarly, the BDE for the removal of one fluorine ligand from the stable closed-shell PF3O molecule to give the unstable PF2O radical is higher than the BDE needed to remove the oxygen atom to give the stable closed-shell PF3 molecule. The same principles govern the BDEs of the phosphorus fluorides and the sulfur oxofluorides. In polyatomic molecules, care must be exercised not to equate BDEs with the bond strengths of given bonds. The measurement of the bond strength or stiffness of a given bond represented by its force constant involves only a small displacement of the atoms near equilibrium and, therefore, does not involve any reorganization energies, i.e., it may be more appropriate to correlate with the diabatic product states.
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted from high level a... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted from high level ab initio electronic structure calculations using the coupled cluster CCSD(T) method with augmented correlation-consistent basis sets extrapolated to the complete basis set (CBS) limit for the H(1,2)O(m)S(n) (m, n = 0-3) compounds, as well as various radicals involved in different bond breaking processes. To achieve near chemical accuracy (+/-1.0 kcal/mol), additional corrections were added to the CBS binding energies based on the frozen core CCSD(T) energies including corrections for core-valence, scalar relativistic, and first-order atomic spin-orbit effects. Geometries were optimized up through the CCSD(T)/aV(T+d)Z level. Vibrational zero point energies were computed at the MP2/aV(T+d)Z level. The calculated heats of formation are in excellent agreement with the available experimental data and allow the prediction of adiabatic bond dissociation energies (BDEs) to within +/-1.0 kcal/mol. The decomposition mechanisms were largely determined by a preference to maintain a strong S=O bond in the dissociated products as opposed to O=O and S=S bonds, exactly matching the ordering of the BDEs in the diatomics. For the H(2)X(2) and H(2)X(3) systems, as well as the HX(3) radicals, the energetically favorable decomposition pathway leads to the formation of XH radicals and breaking the X-X bond as opposed to breaking the X-H bond. For the HX(2) radicals, however, the more thermodynamically favorable pathway leads to a breaking of the H-X bond and forming X(2) molecules.
High level ab initio electronic structure calculations at the coupled cluster level with a correc... more High level ab initio electronic structure calculations at the coupled cluster level with a correction for triples extrapolated to the complete basis set limit have been made for the thermodynamics of the BrBrO 2 , IIO 2 , ClBrO 2 , ClIO 2 , and BrIO 2 isomers, as well as various molecules involved in the bond dissociation processes. Of the BrBrO 2 isomers, BrOOBr is predicted to be the most stable by 8.5 and 9.3 kcal/mol compared to BrBrO 2 and BrOBrO at 298 K, respectively. The weakest bond in BrOOBr is the O-Br bond with a bond dissociation energy (BDE) of 15.9 kcal/mol, and in BrBrO 2 , it is the Br-Br bond of 19.1 kcal/mol. The smallest BDE in BrOBrO is for the central O-Br bond with a BDE of 12.6 kcal/mol. Of the IIO 2 isomers, IIO 2 is predicted to be the most stable by 3.3, 9.4, and 28.9 kcal/mol compared to IOIO, IOOI, and OIIO at 298 K, respectively. The weakest bond in IIO 2 is the I-I bond with a BDE of 22.2 kcal/mol. The smallest BDEs in IOIO and IOOI are the terminal O-I bonds with values of 19.0 and 5.2 kcal/mol, respectively. Supporting Information Available: Calculated geometry parameters for the XY (X, Y ) O, Cl, Br, and I) diatomics as a function of basis set, for the OXO and XOY (X, Y ) Cl, Br, and I) triatomics as a function of basis set, for the XYO (X, Y ) Cl, Br, and I) triatomics as a function of basis set, for the XOO, XOOY, and OXYO isomers (X, Y ) Cl, Br, and I) as a function of basis set, for the XOYO (X, Y ) Cl, Br, and I) tetraatomics as a function of basis set, and for the XYO 2 (X, Y ) Cl, Br, and I) tetraatomics as a function of basis set, calculated CCSD(T)/aVTZ frequencies, CCSD(T) total energies (E h ) as a function of the basis set, and calculated T 1 diagnostics at the CCSD(T)/aVQZ level. This material is available free of charge via the Internet at http://pubs.acs.org.
The compound Na(4)[(UO(2))(S(2))(3)](CH(3)OH)(8) was synthesized at room temperature in an oxygen... more The compound Na(4)[(UO(2))(S(2))(3)](CH(3)OH)(8) was synthesized at room temperature in an oxygen-free environment. It contains a rare example of the [(UO(2))(S(2))(3)](4-) complex in which a uranyl ion is coordinated by three bidentate persulfide groups. We examined the possible linkage of these units to form nanoscale cage clusters analogous to those formed from uranyl peroxide polyhedra. Quantum chemical calculations at the density functional and multiconfigurational wave function levels show that the uranyl-persulfide-uranyl, U-(S(2))-U, dihedral angles of model clusters are bent due to partial covalent interactions. We propose that this bent interaction will favor assembly of uranyl ions through persulfide bridges into curved structures, potentially similar to the family of nanoscale cage clusters built from uranyl peroxide polyhedra. However, the U-(S(2))-U dihedral angles predicted for several model structures may be too tight for them to self-assemble into cage clusters with fullerene topologies in the absence of other uranyl-ion bridges that adopt a flatter configuration. Assembly of species such as [(UO(2))(S(2))(SH)(4)](4-) or [(UO(2))(S(2))(C(2)O(4))(4)](4-) into fullerene topologies with ~60 vertices may be favored by use of large counterions.
The compound Na{[Tc6Br12]2Br} has been obtained from the decomposition of TcBr4 under vacuum in a... more The compound Na{[Tc6Br12]2Br} has been obtained from the decomposition of TcBr4 under vacuum in a Pyrex ampule at 450 °C. The stoichiometry of the compound has been confirmed by energy-dispersive X-ray spectroscopy and its structure determined by single-crystal X-ray diffraction. The compound contains a trigonal-prismatic hexanuclear [Tc6Br12] cluster. The cluster is composed of two triangular Tc3Br6 units linked by multiple Tc-Tc bonds. In the Tc3Br6 unit, the average Tc-Tc distance [2.6845(5) Å] is characteristic of Tc-Tc single bonds, while the average Tc-Tc distance between the two triangular units [2.1735(5) Å] is characteristic of Tc≡Tc triple bonds. The electronic structure of the [Tc6Br12] cluster was studied by first-principles calculations, which confirm the presence of single and triple Tc-Tc bonds in the cluster.
The hydrothermal reactions of trivalent lanthanide and actinide chlorides with 1,2-methylenedipho... more The hydrothermal reactions of trivalent lanthanide and actinide chlorides with 1,2-methylenediphosphonic acid (C1P2) in the presence of NaOH or NaNO 3 result in the crystallization of three structure types: RE[CH 2 (PO 3 H 0.5 ) 2 ] (RE = La, Ce, Pr, Nd, Sm; Pu) (A type), NaRE(H 2 O)-[CH 2 (PO 3 ) 2 ] (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy; Am) (B type), or NaLn[CH 2 (PO 3 H 0.5 ) 2 ]·(H 2 O) (Ln = Yb and Lu) (C type). These crystals were analyzed using single crystal Xray diffraction, and the structures were used directly for detailed bonding calculations. These phases form three-dimensional frameworks. In both A and B, the metal centers are found in REO 8 polyhedra as parts of edge-sharing chains or edge-sharing dimers, respectively. Polyhedron shape calculations reveal that A favors a D 2d dodecahedron while B adopts a C 2v geometry. In C, Yb and Lu only form isolated MO 6 octahedra. Such differences in terms of structure topology and coordination geometry are discussed in detail to reveal periodic deviations between the lanthanide and actinide series. Absorption spectra for the Pu(III) and Am(III) compounds are also reported. Electronic structure calculations with multireference methods, CASSCF, and density functional theory, DFT, reveal localization of the An 5f orbitals, but natural bond orbital and natural population analyses at the DFT level illustrate unique occupancy of the An 6d orbitals, as well as larger occupancy of the Pu 5f orbitals compared to the Am 5f orbitals.
A new neutral borate species, H(2)B(4)O(7) (also known as tetraboric acid), with a one-dimensiona... more A new neutral borate species, H(2)B(4)O(7) (also known as tetraboric acid), with a one-dimensional chain structure, is found in the interlayer spacing in Rb(2)[(UO(2))(2)B(8)O(12)F(6)]·H(2)B(4)O(7) (RbUBOF-2) derived from boric acid flux reaction of uranyl(VI) nitrate with RbBF(4). This new form of tetraboric acid possesses a novel borate fundamental building block with the symbol 4Δ:<3Δ>Δ.
Langmuir : the ACS journal of surfaces and colloids, Jan 21, 2015
The cation-π interaction is proposed as an important mechanism for the adsorption of aromatic hyd... more The cation-π interaction is proposed as an important mechanism for the adsorption of aromatic hydrocarbons having non-zero quadrupole moments by mineral surfaces. Direct evidence supporting such a mechanism is, however, limited. Using the model mineral calcite, we probe the cation-π interaction with adsorbed benzene, toluene, and ethylbenzene (BTE) molecules using attenuated total reflectance Fourier transform infrared spectroscopy. We show that the presence of calcite increases the energy required to excite the synchronized bending of aromatic C-H bonds of BTE molecules. The unique conformation of this vibrational mode indicates that the planar aromatic rings of BTE molecules are constrained in a tilted face-down position by the cation-π interaction, as further confirmed by density functional theory calculations. Our results suggest that the shift of the excitation energy of the aromatic C-H bending may be used as an infrared signature for the cation-π interaction occurring on mine...
The journal of physical chemistry. A, Jan 30, 2006
The sigma- and pi-bond strengths for the molecules BH2NH2, BH2PH2, AlH2NH2, and AlH2PH2 have been... more The sigma- and pi-bond strengths for the molecules BH2NH2, BH2PH2, AlH2NH2, and AlH2PH2 have been calculated by using ab initio molecular electronic structure theory at the CCSD(T)/CBS level. The adiabatic pi-bond energy is defined as the rotation barrier between the equilibrium ground-state configuration and the C(s)symmetry transition state for torsion about the A-X bond. We also report intrinsic pi-bond energies corresponding to the adiabatic rotation barrier corrected for the inversion barrier at N or P. The adiabatic sigma-bond energy is defined as the dissociation energy of AH2XH2 to AH2 + XH2 in their ground states minus the adiabatic pi-bond energy. The adiabatic sigma-bond strengths for the molecules BH2NH2, BH2PH2, AlH2NH2, and AlH2PH2 are 109.8, 98.8, 77.6, and 68.3 kcal/mol, respectively, and the corresponding adiabatic pi-bond strengths are 29.9, 10.5, 9.2, and 2.7 kcal/mol, respectively.
Ab initio electronic structure calculations are reported for S2, and its ions S2+ and S2-. Geomet... more Ab initio electronic structure calculations are reported for S2, and its ions S2+ and S2-. Geometric parameters are calculated using the singles and doubles coupled cluster method, including a perturbational correction for connected triple excitation, together with systematic sequences of correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. Energetic and structural properties of S2 and the S2 cation and anion are reported. The heat of formation of S2 (3Sigmag-) at 0 K in the gas phase is predicted to be 29.8 kcal/mol from the average of CBS two extrapolation procedures, less than the experimental heat of formation of S2 of 30.66+/-0.07 kcal/mol. The 0 K adiabatic ionization potential and electron affinity are predicted to be 9.37 and 1.68 eV, respectively.
High level ab initio electronic structure calculations using the coupled cluster CCSD(T) method w... more High level ab initio electronic structure calculations using the coupled cluster CCSD(T) method with augmented correlation-consistent basis sets extrapolated to the complete basis set limit have been performed on the PNO, NOP, and NPO isomers and their corresponding anions and cations. Geometries for all species were optimized up through the aug-cc-pV(Q+d)Z level and vibrational frequencies were calculated with the aug-cc-pV(T+d)Z basis set. The most stable of the three isomers is NPO and it is predicted to have a heat of formation of 23.3 kcal/mol. PNO is predicted to be only 1.7 kcal/mol higher in energy. The calculated adiabatic ionization potential of NPO is 12.07 eV and the calculated adiabatic electron affinity is 2.34 eV. The calculated adiabatic ionization potential of PNO is 10.27 eV and the calculated adiabatic electron affinity is only 0.24 eV. NOP is predicted to be much higher in energy by 29.9 kcal/mol. The calculated rotational constants for PNO and NPO should allow f...
The journal of physical chemistry. A, Jan 29, 2009
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for diammoniosila... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for diammoniosilane, H(4)Si(NH(3))(2), and its dehydrogenated derivates at the CCSD(T) and G3(MP2) levels. To achieve near chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first-order atomic spin-orbit effects. Vibrational zero-point energies were computed at the CCSD(T) or MP2 levels. The edge inversion barrier of silane is predicted to be 88.9 kcal/mol at 298 K at the CCSD(T) level and a substantial amount, -63.6 kcal/mol, is recovered upon complexation with 2 NH(3) molecules, so that the diammoniosilane complex is only 25.6 kcal/mol at 298 K above the separated reactants SiH(4) + 2NH(3). The complex is a metastable species characterized by all real frequencies at the MP2/aV(T+d)Z level. ...
The journal of physical chemistry. A, Jan 16, 2009
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for SiH(3)X, SiH(... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for SiH(3)X, SiH(2)XCH(3), and SiH(3)CH(2)X with X = F, Cl, Br, and I from coupled cluster theory (CCSD(T)) calculations with effective core potential correlation-consistent basis sets for Br and I. To achieve near chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first order atomic spin-orbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory and the C-H and Si-H stretches scaled to experiment. The C-H, Si-H, Si-C, C-X, and Si-X (X = F, Cl, Br, and I) bond dissociation energies (BDEs) in the halosilanes, halomethysilanes, and methylhalosilanes were predicted. Except for methyliodosilane, methyl substitution leads to an increase in Si-X BDE when compared to...
The journal of physical chemistry. A, Jan 28, 2009
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for (CH3)H2N-BH3,... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for (CH3)H2N-BH3, (CH3)HN=BH2, (BH3)HN=CH2, (CH3)H2B-NH3, (CH3)HB=NH2, and (NH3)HB=CH2, as well as various molecules involved in the different bond-breaking processes, from coupled cluster theory (CCSD(T)) calculations. In order to achieve near-chemical accuracy (+/-1 kcal/mol), three corrections were added to the complete basis set binding energies based on frozen core CCSD(T) energies, corrections for core-valence, scalar relativistic, and first-order atomic spin-orbit effects. Scaled vibrational zero-point energies were computed with the MP2 method. The heats of formation were predicted for the respective dimethyl- and trimethyl-substituted ammonia boranes, their dehydrogenated derivatives, and the various molecules involved in the different bond breaking processes, based on isodesmic reaction schemes calculated at the G3(MP2) level. Thermodynamics for dehydrogenation pathways in the monomethyl-substi...
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for XeF(3)(+), Xe... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for XeF(3)(+), XeF(3)(-), XeF(5)(+), XeF(7)(+), XeF(7)(-), and XeF(8) from coupled cluster theory (CCSD(T)) calculations with effective core potential correlation-consistent basis sets for Xe and including correlation of the nearest core electrons. Additional corrections are included to achieve near chemical accuracy of +/-1 kcal/mol. Vibrational zero point energies were computed at the MP2 level of theory. Unlike the other neutral xenon fluorides, XeF(8) is predicted to be thermodynamically unstable with respect to loss of F(2) with the reaction calculated to be exothermic by 22.3 kcal/mol at 0 K. XeF(7)(+) is also predicted to be thermodynamically unstable with respect to the loss of F(2) by 24.1 kcal/mol at 0 K. For XeF(3)(+), XeF(5)(+), XeF(3)(-), XeF(5)(-), and XeF(7)(-), the reactions for loss of F(2) are endothermic by 14.8, 37.8, 38.2, 59.6, and 31.9 kcal/mol at 0 K, respectively. The F(+) affini...
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the neutral a... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the neutral and ionic N(x)F(y) and O(x)F(y) systems using coupled cluster theory with single and double excitations and including a perturbative triples correction (CCSD(T)) method with correlation consistent basis sets extrapolated to the complete basis set (CBS) limit. To achieve near chemical accuracy (±1 kcal/mol), three corrections to the electronic energy were added to the frozen core CCSD(T)/CBS binding energies: corrections for core-valence, scalar relativistic, and first order atomic spin-orbit effects. Vibrational zero point energies were computed at the CCSD(T) level of theory where possible. The calculated heats of formation are in good agreement with the available experimental values, except for FOOF because of the neglect of higher order correlation corrections. The F(+) affinity in the N(x)F(y) series increases from N(2) to N(2)F(4) by 63 kcal/mol, while that in the O(2)F(y) series dec...
High-level electronic structure calculations have been used to map out the relevant portions of t... more High-level electronic structure calculations have been used to map out the relevant portions of the potential energy surfaces for the release of H2 from dimers of ammonia borane, BH3NH3 (AB). Using the correlation-consistent aug-cc-pVTZ basis set at the second-order perturbation MP2 level, geometries of stationary points were optimized. Relative energies were computed at these points using coupled-cluster CCSD(T) theory with the correlation-consistent basis sets at least up to the aug-cc-pVTZ level and in some cases extrapolated to the complete basis set limit. The results show that there are a number of possible dimers involving different types of hydrogen-bonded interactions. The most stable gaseous phase (AB)2 dimer results from a head-to-tail cyclic conformation and is stabilized by 14.0 kcal/mol with respect to two AB monomers. (AB)2 can generate one or two H2 molecules via several direct pathways with energy barriers ranging from 44 to 50 kcal/mol. The diammoniate of diborane ion pair isomer, [BH4-][NH3BH2NH3+] (DADB), is 10.6 kcal/mol less stable than (AB)2 and can be formed from two AB monomers by overcoming an energy barrier of approximately 26 kcal/mol. DADB can also be generated from successive additions of two NH3 molecules to B2H6 and from condensation of AB with separated BH3 and NH3 molecules. The pathway for H2 elimination from DADB is characterized by a smaller energy barrier of 20.1 kcal/mol. The alternative ion pair [NH4+][BH3NH2BH3-] is calculated to be 16.4 kcal/mol above (AB)2 and undergoes H2 release with an energy barrier of 17.7 kcal/mol. H2 elimination from both ion pair isomers yields the chain BH3NH2BH2NH3 as product. Our results suggest that the neutral dimer will play a minor role in the release of H2 from ammonia borane, with a dominant role from the ion pairs as observed experimentally in ionic liquids and the solid state.
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the borane co... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted for the borane compounds H(3-n)BX(n) for (X = F, Cl, Br, I, NH2, OH, and SH) and various radicals from coupled cluster theory (CCSD(T)) calculations with an effective core potential correlation-consistent basis set for I. In order to achieve near chemical accuracy (+/-1.5 kcal/mol), three corrections were added to the complete basis set binding energies calculated from frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, and a correction for first-order atomic spin-orbit effects. Vibrational zero point energies were computed at the MP2 level. The calculated heats of formation are in excellent agreement with the available experimental data for the closed shell molecules, but show larger differences with the reported "experimental" values for the BX2 radicals. The heats of formation of the BX2 radicals were also calculated at the G3(MP2) level of theory, and the values were in excellent agreement with the more accurate CCSD(T) values. On the basis of extensive comparisons with experiment for a wide range of compounds, our calculated values for these radicals should be good to +/-1.5 kcal/mol and thus are to be preferred over the experimental values. The accurately calculated heats of formation allow us to predict the B-X and B-H adiabatic bond dissociation energies (BDEs) to within +/-1.5 kcal/mol. The B-F BDEs in the H(3-n)BF(n) compounds and in BF (1Sigma+) are the largest BDEs in comparison to the other substituents that were investigated. The second and third largest B-X BDEs in the H(3-n)BX(n) and BX compounds are predicted for X = OH and NH2, respectively. The substituents have a minimal effect on the B-H BDEs in HBX2 and H2BX compared to the first B-H BDE of borane. The differences in adiabatic and diabatic BDEs, which are related to the reorganization energy in the product, can be estimated from singlet-triplet splittings in these molecules, and can account for the large fluctuations in adiabatic BDEs observed, specifically for the BX2 and HBX radicals, during the stepwise loss of the respective substituents.
Heats of formation at 0 and 298 K are predicted for PF3, PF5, PF3O, SF2, SF4, SF6, SF2O, SF2O2, a... more Heats of formation at 0 and 298 K are predicted for PF3, PF5, PF3O, SF2, SF4, SF6, SF2O, SF2O2, and SF4O as well as a number of radicals derived from these stable compounds on the basis of coupled cluster theory [CCSD(T)] calculations extrapolated to the complete basis set limit. In order to achieve near chemical accuracy (+/-1 kcal/mol), additional corrections were added to the complete basis set binding energies based on frozen core coupled cluster theory energies: a correction for core-valence effects, a correction for scalar relativistic effects, a correction for first-order atomic spin-orbit effects, and vibrational zero-point energies. The calculated values substantially reduce the error limits for these species. A detailed comparison of adiabatic and diabatic bond dissociation energies (BDEs) is made and used to explain trends in the BDEs. Because the adiabatic BDEs of polyatomic molecules represent not only the energy required for breaking a specific bond but also contain any reorganization energies of the bonds in the resulting products, these BDEs can be quite different for each step in the stepwise loss of ligands in binary compounds. For example, the adiabatic BDE for the removal of one fluorine ligand from the very stable closed-shell SF6 molecule to give the unstable SF5 radical is 2.8 times the BDE needed for the removal of one fluorine ligand from the unstable SF5 radical to give the stable closed-shell SF4 molecule. Similarly, the BDE for the removal of one fluorine ligand from the stable closed-shell PF3O molecule to give the unstable PF2O radical is higher than the BDE needed to remove the oxygen atom to give the stable closed-shell PF3 molecule. The same principles govern the BDEs of the phosphorus fluorides and the sulfur oxofluorides. In polyatomic molecules, care must be exercised not to equate BDEs with the bond strengths of given bonds. The measurement of the bond strength or stiffness of a given bond represented by its force constant involves only a small displacement of the atoms near equilibrium and, therefore, does not involve any reorganization energies, i.e., it may be more appropriate to correlate with the diabatic product states.
Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted from high level a... more Atomization energies at 0 K and heats of formation at 0 and 298 K are predicted from high level ab initio electronic structure calculations using the coupled cluster CCSD(T) method with augmented correlation-consistent basis sets extrapolated to the complete basis set (CBS) limit for the H(1,2)O(m)S(n) (m, n = 0-3) compounds, as well as various radicals involved in different bond breaking processes. To achieve near chemical accuracy (+/-1.0 kcal/mol), additional corrections were added to the CBS binding energies based on the frozen core CCSD(T) energies including corrections for core-valence, scalar relativistic, and first-order atomic spin-orbit effects. Geometries were optimized up through the CCSD(T)/aV(T+d)Z level. Vibrational zero point energies were computed at the MP2/aV(T+d)Z level. The calculated heats of formation are in excellent agreement with the available experimental data and allow the prediction of adiabatic bond dissociation energies (BDEs) to within +/-1.0 kcal/mol. The decomposition mechanisms were largely determined by a preference to maintain a strong S=O bond in the dissociated products as opposed to O=O and S=S bonds, exactly matching the ordering of the BDEs in the diatomics. For the H(2)X(2) and H(2)X(3) systems, as well as the HX(3) radicals, the energetically favorable decomposition pathway leads to the formation of XH radicals and breaking the X-X bond as opposed to breaking the X-H bond. For the HX(2) radicals, however, the more thermodynamically favorable pathway leads to a breaking of the H-X bond and forming X(2) molecules.
High level ab initio electronic structure calculations at the coupled cluster level with a correc... more High level ab initio electronic structure calculations at the coupled cluster level with a correction for triples extrapolated to the complete basis set limit have been made for the thermodynamics of the BrBrO 2 , IIO 2 , ClBrO 2 , ClIO 2 , and BrIO 2 isomers, as well as various molecules involved in the bond dissociation processes. Of the BrBrO 2 isomers, BrOOBr is predicted to be the most stable by 8.5 and 9.3 kcal/mol compared to BrBrO 2 and BrOBrO at 298 K, respectively. The weakest bond in BrOOBr is the O-Br bond with a bond dissociation energy (BDE) of 15.9 kcal/mol, and in BrBrO 2 , it is the Br-Br bond of 19.1 kcal/mol. The smallest BDE in BrOBrO is for the central O-Br bond with a BDE of 12.6 kcal/mol. Of the IIO 2 isomers, IIO 2 is predicted to be the most stable by 3.3, 9.4, and 28.9 kcal/mol compared to IOIO, IOOI, and OIIO at 298 K, respectively. The weakest bond in IIO 2 is the I-I bond with a BDE of 22.2 kcal/mol. The smallest BDEs in IOIO and IOOI are the terminal O-I bonds with values of 19.0 and 5.2 kcal/mol, respectively. Supporting Information Available: Calculated geometry parameters for the XY (X, Y ) O, Cl, Br, and I) diatomics as a function of basis set, for the OXO and XOY (X, Y ) Cl, Br, and I) triatomics as a function of basis set, for the XYO (X, Y ) Cl, Br, and I) triatomics as a function of basis set, for the XOO, XOOY, and OXYO isomers (X, Y ) Cl, Br, and I) as a function of basis set, for the XOYO (X, Y ) Cl, Br, and I) tetraatomics as a function of basis set, and for the XYO 2 (X, Y ) Cl, Br, and I) tetraatomics as a function of basis set, calculated CCSD(T)/aVTZ frequencies, CCSD(T) total energies (E h ) as a function of the basis set, and calculated T 1 diagnostics at the CCSD(T)/aVQZ level. This material is available free of charge via the Internet at http://pubs.acs.org.
The compound Na(4)[(UO(2))(S(2))(3)](CH(3)OH)(8) was synthesized at room temperature in an oxygen... more The compound Na(4)[(UO(2))(S(2))(3)](CH(3)OH)(8) was synthesized at room temperature in an oxygen-free environment. It contains a rare example of the [(UO(2))(S(2))(3)](4-) complex in which a uranyl ion is coordinated by three bidentate persulfide groups. We examined the possible linkage of these units to form nanoscale cage clusters analogous to those formed from uranyl peroxide polyhedra. Quantum chemical calculations at the density functional and multiconfigurational wave function levels show that the uranyl-persulfide-uranyl, U-(S(2))-U, dihedral angles of model clusters are bent due to partial covalent interactions. We propose that this bent interaction will favor assembly of uranyl ions through persulfide bridges into curved structures, potentially similar to the family of nanoscale cage clusters built from uranyl peroxide polyhedra. However, the U-(S(2))-U dihedral angles predicted for several model structures may be too tight for them to self-assemble into cage clusters with fullerene topologies in the absence of other uranyl-ion bridges that adopt a flatter configuration. Assembly of species such as [(UO(2))(S(2))(SH)(4)](4-) or [(UO(2))(S(2))(C(2)O(4))(4)](4-) into fullerene topologies with ~60 vertices may be favored by use of large counterions.
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