Hydrated alkali-metal cations: infrared spectroscopy and ab initio calculations of M+(H2O)(x=2-5)Ar cluster ions for M = Li, Na, K, and Cs

A delicate balance between competing and cooperating noncovalent interactions determines the three-dimensional structure of hydrated alkali-metal ion clusters. With a single water molecule hydrating an ion, the electrostatic ion...water interaction dominates. With more than one water molecule, however, water...water hydrogen-bonding interactions compete with the ion...water interactions to influence the three-dimensional structure. Infrared photodissociation spectra of M(+)(H2O)(x=2-5)Ar (with effective temperatures of approximately 50-150 K, depending on size and composition) are reported for M = Li, Na, K, and Cs, and dependencies on ion size and hydration number are explored.     

Infrared spectroscopy of Li(+)(CH4)1Ar(n), n = 1-6, clusters

Infrared predissociation (IRPD) spectra of Li(+)(CH(4))(1)Ar(n), n = 1-6, clusters are reported in the C-H stretching region from 2800 to 3100 cm(-1). The Li(+) electric field perturbs CH(4) lifting its tetrahedral symmetry and gives rise to multiple IR active modes. The observed bands arise from the totally symmetric vibrational mode, v(1), and the triple degenerate vibrational mode, v(3). Each band is shifted to lower frequency relative to the unperturbed CH(4) values. As the number of argon atoms is increased, the C-H red shift becomes less pronounced until the bands are essentially unchanged from n = 5 to n = 6. For n = 6, additional vibrational features were observed which suggested the presence of an additional conformer. By monitoring different photodissociation loss channels (loss of three Ar or loss of CH(4)), one conformer was uniquely associated with the CH(4) loss channel, with two bands at 2914 and 3017 cm(-1), values nearly identical to the neutral CH(4) gas-phase v(1) and v(3) frequencies. With supporting ab initio calculations, the two conformers were identified, both with a first solvent shell size of six. The major conformer had CH(4) in the first shell, while the conformer exclusively present in the CH(4) loss channel had six argons in the first shell and CH(4) in the second shell. This conformer is +11.89 kJ/mol higher in energy than the minimum energy conformer at the MP2/aug-cc-pVDZ level. B3LYP/6-31+G* level vibrational frequencies and MP2/aug-cc-pVDZ level single-point binding energies, D(e) (kJ/mol), are reported to support the interpretation of the experimental data.     

Evaporatively cooled M+ (H2O)Ar cluster ions: infrared spectroscopy and internal energy simulations

Rotationally resolved IR spectra of M+ (H2O)Ar cluster ions for M=Na, K, and Cs in the O-H stretch region were measured in a triple-quadrupole mass spectrometer. Analysis of the spectra yields O-H stretch vibrational band origins and relative IR intensities of the symmetric and asymmetric modes. The effect of the alkali-metal ions on these modes results in frequency shifts and intensity changes from the gas phase values of water. The A-rotational constants are also obtained from the rotational structure and are discussed. Experimentally, the temperatures of these species were deduced from the relative populations of the K-rotational states. The internal energies and temperatures of the cluster ions for Na and K were simulated using RRKM calculations and the evaporative ensemble formalism. With binding energies and vibrational frequencies obtained from ab initio calculations, the average predicted temperatures are qualitatively consistent with the experimental values and demonstrate the additional cooling resulting from argon evaporation.     

Entropic effects on hydrated alkali-metal cations: infrared spectroscopy and ab initio calculations of M+(H2O)(x=2-5) cluster ions for M = Li, Na, K, and Cs

A delicate balance between competing and cooperating noncovalent interactions determines the three-dimensional structure of hydrated alkali-metal ion clusters. A critical factor influencing the balance reached is the internal energy content (or effective temperature) of the ion cluster. Cold cluster ions (approximately 50-150 K) have little internal energy, and enthalpic contributions have a greater influence on the relative population of low-lying minima. In clusters whose internal energy distributions correspond to temperatures approximately 250-500 K, entropic effects are expected to influence which structural isomers are present, favoring those where free energy has been minimized. Infrared photodissociation spectra of M(+)(H2O)(x=2-5) (approximately 250-500 K) are reported for M = Li, Na, K, and Cs to explore ion dependencies and entropic effects on the observed three-dimensional structure.     

Infrared spectroscopy of Mn+ (H2O) and Mn2+ (H2O) via argon complex predissociation

Singly and doubly charged manganese-water cations, and their mixed complexes with attached argon atoms, are produced by laser vaporization in a pulsed nozzle source. Complexes of the form Mn(+)(H(2)O)Ar(n) (n = 1-4) and Mn(2+)(H(2)O)Ar(4) are studied via mass-selected infrared photodissociation spectroscopy, detected in the mass channels corresponding to the elimination of argon. Sharp resonances are detected for all complexes in the region of the symmetric and asymmetric stretch vibrations of water. With the guidance of density functional theory computations, specific vibrational band resonances are assigned to complexes having different argon attachment configurations. In the small singly charged complexes, argon adds first to the metal ion site and later in larger clusters to the hydrogens of water. The doubly charged complex has argon only on the metal ion. Vibrations in all of these complexes are shifted to lower frequencies than those of the free water molecule. These shifts are greater when argon is attached to hydrogen and also greater for the dication compared to the singly charged species. Cation binding also causes the IR intensities for water vibrations to be much greater than those of the free water molecule, and the relative intensities are greater for the symmetric stretch than the asymmetric stretch. This latter effect is also enhanced for the dication complex.     

Infrared predissociation spectroscopy of ammonia cluster cations (NH3)n+ (n=2-4) produced by vacuum-ultraviolet photoionization

Infrared predissociation spectroscopy of vacuum ultraviolet-pumped ion (IRPDS-VUV-PI) is performed on ammonia cluster cations (NH3)n+ (n=2-4) that are produced by VUV photoionization in supersonic jets. The structures of (NH3)2+ and (NH3)4+ are determined through the observation of infrared spectra and vibrational calculations based on ab initio calculations at the MP2/6-31G** and 6-31++G** levels. (NH3)2+ is found to be of the "hydrogen-transferred" form having the (H3N+-...NH2) composition. In contrast, (NH3)4+ exhibits the "head-to-head" dimer cation (H3...NH3+ core structure, where the positive charge is shared between two ammonia molecules in the core, and two other molecules are hydrogen bonded onto the core. An unequivocal assignment of the infrared spectrum of (NH3)3+ has not been achieved, because the presence of two isomeric structures could be suggested by the observed spectrum and theoretical calculations.     

Photoelectron imaging of Ag(-)(H2O)x and AgOH(-)(H2O)y (x=1,2, y=0-4)

The photoelectron images of Ag(-)(H(2)O)(x) (x=1,2) and AgOH(-)(H(2)O)(y) (y=0-4) are reported. The Ag(-)(H(2)O)(1,2) anionic complexes have similar characteristics to the other two coinage metal-water complexes that can be characterized as metal atomic anion solvated by water molecules with the electron mainly localized on the metal. The vibrationally well-resolved photoelectron spectrum allows the adiabatic detachment energy (ADE) and vertical detachment energy (VDE) of AgOH(-) to be determined as 1.18(2) and 1.24(2) eV, respectively. The AgOH(-) anion interacts more strongly with water molecules than the Ag(-) anion. The photoelectron spectra of Ag(-)(H(2)O)(x) and AgOH(-)(H(2)O)(y) show a gradual increase in ADE and VDE with increasing x and y due to the solvent stabilization.     

Photoelectron spectroscopic study of the hydrated nucleoside anions: Uridine(-)(H(2)O)(n=0-2), cytidine(-)(H(2)O)(n=0-2), and thymidine(-)(H(2)O)(n=0,1)

The hydrated nucleoside anions, uridine(-)(H(2)O)(n=0-2), cytidine(-)(H(2)O)(n=0-2), and thymidine(-)(H(2)O)(n=0,1), have been prepared in beams and studied by anion photoelectron spectroscopy in order to investigate the effects of a microhydrated environment on parent nucleoside anions. Vertical detachment energies (VDEs) were measured for all eight anions, and from these, estimates were made for five sequential anion hydration energies. Excellent agreement was found between our measured VDE value for thymidine(-)(H(2)O)(1) and its calculated value in the companion article by S. Kim and H. F. Schaefer III.     

Reactivity of the inversely polarized phosphaalkenes RP=C(NMe2)2 (R = tBu, Me3Si, H) towards arylcarbene complexes [(CO)5M=C(oEt)Ar] (Ar= Ph, M = Cr, W; Ar = 2-MeC6H4, 2-MeOC6H4, M = W)

The reaction of the arylated Fischer carbene complexes [(CO)5M=C(OEt)Ar] (Ar=Ph; M = Cr, W; 2-MeC6H4; 2-MeOC6H; M = W) with the phosphaalkenes RP=C(NMe2), (R=tBu, SiMe3) afforded the novel phosphaalkene complexes [[RP=C(OEt)Ar]M(CO)5] in addition to the compounds [(RP=C(NMe2)2]M(CO)5]. Only in the case of the R = SiMe3 (E/Z) mixtures of the metathesis products were obtained. The bis(dimethylamino)methylene unit of the phosphaalkene precursor was incorporated in olefins of the type (Me2N)2C=C(OEt)(Ar). Treatment of [(CO)5W=C(OEt)(2-MeOC6H4)] with HP=C(NMe2)2 gave rise to the formation of an E/Z mixture of [[(Me2N)2CH-P=C(OEt)(2-MeOC6H4)]W(CO)5] the organophosphorus ligand of which formally results from a combination of the carbene ligand and the phosphanediyl [P-CH(NMe2)2]. The reactions reported here strongly depend on an inverse distribution of alpha-electron density in the phosphaalkene precursors (Pdelta Cdelta+), which renders these molecules powerfu] nucleophiles.     

Structures of [(CO2)n(H2O)m]- (n=1-4, m=1,2) cluster anions. I. Infrared photodissociation spectroscopy

The infrared photodissociation spectra of [(CO(2))(n)(H(2)O)(m)](-) (n=1-4, m=1, 2) are measured in the 3000-3800 cm(-1) range. The [(CO(2))(n)(H(2)O)(1)](-) spectra are characterized by a sharp band around 3570 cm(-1) except for n=1; [(CO(2))(1)(H(2)O)(1)](-) does not photodissociate in the spectral range studied. The [(CO(2))(n)(H(2)O)(2)](-) (n=1, 2) species have similar spectral features with a broadband at approximately 3340 cm(-1). A drastic change in the spectral features is observed for [(CO(2))(3)(H(2)O)(2)](-), where sharp bands appear at 3224, 3321, 3364, 3438, and 3572 cm(-1). Ab initio calculations are performed at the MP2/6-311++G(**) level to provide structural information such as optimized structures, stabilization energies, and vibrational frequencies of the [(CO(2))(n)(H(2)O)(m)](-) species. Comparison between the experimental and theoretical results reveals rather size- and composition-specific hydration manner in [(CO(2))(n)(H(2)O)(m)](-): (1) the incorporated H(2)O is bonded to either CO(2) (-) or C(2)O(4) (-) through two equivalent OH...O hydrogen bonds to form a ring structure in [(CO(2))(n)(H(2)O)(1)](-); (2) two H(2)O molecules are independently bound to the O atoms of CO(2) (-) in [(CO(2))(n)(H(2)O)(2)](-) (n=1, 2); (3) a cyclic structure composed of CO(2) (-) and two H(2)O molecules is formed in [(CO(2))(3)(H(2)O)(2)](-).     

不饱和类硅烯H2C＝SiMBr (M＝Li, Na)的DFT研究

采用密度泛函理论方法, 在B3LYP/6-311G (d,p)水平上研究了不饱和类硅烯H₂C＝SiMBr (M＝Li, Na)的结构. 结果表明, 不饱和类硅烯H₂C＝SiLiBr与H₂C＝SiNaBr各有三种平衡构型, 其中非平面的p-配合物型构型能量最低, 是这两种不饱和类硅烯存在的主要构型. 对平衡构型间异构化反应的过渡态进行了计算, 求得了转化势垒. 计算预言了最稳定构型的振动频率和红外强度.     

Al(6)(2-) - fusion of two aromatic Al(3)(-) units. A combined photoelectron spectroscopy and ab initio study of M(+)[Al(6)(2-)] (M = Li,Na, K,Cu, and Au)

Photoelectron spectroscopy is combined with ab initio calculations to elucidate the structure and chemical bonding of a series of MAl(6)(-) (M = Li, Na, K, Cu, and Au) bimetallic clusters. Well-resolved photoelectron spectra were obtained for MAl(6)(-) (M = Li, Na, Cu, and Au) at several photon energies. The ab initio calculations showed that all of the MAl(6)(-) clusters can be viewed as an M(+) cation interacting with an Al(6)(2-) dianion. Al(6)(2-) was found to possess an O(h) ground-state structure, and all of the MAl(6)(-) clusters possess a C(3v) ground-state structure derived from the O(h) Al(6)(2-). Careful comparison between the photoelectron spectral features and the ab initio one-electron detachment energies allows us to establish firmly the C(3v)ground-state structures for the MAl(6)(-) clusters. A detailed molecular orbital (MO) analysis is conducted for Al(6)(2-) and compared with Al(3)(-). It was shown that Al(6)(2-) can be considered as the fusion of two Al(3)(-) units. We further found that the preferred occupation of those MOs derived from the sums of the empty 2e' MOs of Al(3)(-), rather than those derived from the differences between the occupied 2a(1)' and 2a(2)' ' MOs of Al(3)(-), provides the key bonding interactions for the fusion of the two Al(3)(-) into Al(6)(2-). Because there are only four bonding MOs (one pi and three sigma MOs), an analysis of resonance structures was performed for the O(h)Al(6)(2-). It is shown that every face of the Al(6)(2-) octahedron still possesses both pi- and sigma-aromaticity, analogous to Al(3)(-), and that in fact Al(6)(2-) can be viewed to possess three-dimensional pi- and sigma-aromaticity with a large resonance stabilization.     

Synthesis and structural analysis of the polymetallated alkali calixarenes [M4(p-tert-butylcalix[4]arene-4H)(thf)x]2.n THF (M=Li,K; n=6 or 1; x=4 or 5) and [Li2(p-tert-butylcalix[4]arene-2H)(H2O)(mu-H2O)(thf)].3 THF

To study the structures and reactivities of alkali metallated intermediates of calix[4]arenes, three compounds were isolated: [Li(4)(p-tert-butylcalix[4]arene-4H)(thf)(4)](2).6 THF (1), [Li(2)(p-tert-butylcalix[4]arene-2H)(H(2)O)(mu-H(2)O)(thf)].3 THF (2), and [K(4)(p-tert-butylcalix[4]arene-4H)(thf)(5)](2).THF (3). The structure of 1 is shown to be dependent on the coordinating solvent. Partial hydrolysis of 1 leads to the formation of 2. The potassium compound 3 features a different structure to that of 1, due to a higher coordination number as well as stronger cation-pi-bonding interactions.     

(C5M2-n)(n-) (M = Li,Na, K,and n = 0, 1, 2). A new family of molecules containing planar tetracoordinate carbons

By highly correlated ab initio methods and DFT calculations, we have shown that alkaline metals can stabilize planar tetracoordinate carbon-containing molecules with the C(C4) skeleton. This family of molecules is C5M2, where M is an alkaline metal. The stability of these compounds is rationalized in terms of the delocalization of the p-orbital perpendicular to the molecular plane, the global hardness, and the electrophilicity. The analysis of several molecular scalar fields shows that the bonding between the C52- dianion and the metals is strongly ionic. The structures reported are the first examples with a planar tetracoordinate carbon, surrounded by carbon atoms, and stabilized, only, by electronic factors.     

Vibrational spectroscopy and structures of Ni+(C2H2)(n) (n =1-4) complexes

Nickel cation-acetylene complexes of the form Ni(+)(C(2)H(2))(n), Ni(+)(C(2)H(2))Ne, and Ni(+)(C(2)H(2))(n)Ar(m) (n = 1-4) are produced in a molecular beam by pulsed laser vaporization. These ions are size-selected and studied in a time-of-flight mass spectrometer by infrared laser photodissociation spectroscopy in the C-H stretch region. The fragmentation patterns indicate that the coordination number is 4 for this system. The n = 1-4 complexes with and without rare gas atoms are also investigated with density functional theory. The combined IR spectra and theory show that pi-complexes are formed for the n = 1-4 species, causing the C-H stretches in the acetylene ligands to shift to lower frequencies. Theory reveals that there are low-lying excited states nearly degenerate with the ground state for all the Ni(+)(C(2)H(2))(n) complexes. Although isomeric structures are identified for rare gas atom binding at different sites, the attachment of rare gas atoms results in only minor perturbations on the structures and spectra for all complexes. Experiment and theory agree that multiple acetylene binding takes place to form low-symmetry structures, presumably due to Jahn-Teller distortion and/or ligand steric effects. The fully coordinated Ni(+)(C(2)H(2))(4) complex has a near-tetrahedral structure.     

Novel hydrogen-bonded three-dimensional networks encapsulating one-dimensional covalent chains: [M(4,4'-bipy)(H2O)(4)](4-abs)(2).nH2O (4,4'-bipy = 4,4'-bipyridine; 4-abs = 4-aminobenzenesulfonate) (M = Co,n = 1; M = Mn,n = 2)

Two novel compounds, [Co(4,4'-bipy)(H(2)O)(4)](4-abs)(2).H(2)O (1) and [Mn(4,4'-bipy)(H(2)O)(4)](4-abs)(2).2H(2)O (2) (4,4'-bipy = 4,4'-bipyridine; 4-abs = 4-aminobenzenesulfonate), have been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analyses, UV-vis and IR spectra, and TG analysis. X-ray structural analysis revealed that 1 and 2 both possess unusual hydrogen-bonded three-dimensional (3-D) networks encapsulating one-dimensional (1-D) covalently bonded infinite [M(4,4'-bipy)(H(2)O)(4)](2+) (M = Co, Mn) chains. The 4-abs anions in 1 form 1-D zigzag chains through hydrogen bonds. These chains are further extended through crystallization water molecules into 3-D hydrogen-bonded networks with 1-D channels, in which the [Co(4,4'-bipy)(H(2)O)(4)](2+) linear covalently bonded chains are located. Crystal data for 1: C(22)H(30)CoN(4)O(11)S(2), monoclinic P2(1), a = 11.380(2) A, b = 8.0274(16) A, c = 15.670(3) A, alpha = gamma = 90 degrees, beta = 92.82(3) degrees, Z = 2. Compound 2 contains interesting two-dimensional (2-D) honeycomb-like networks formed by 4-abs anions and lattice water molecules via hydrogen bonding, which are extended through other crystallization water molecules into three dimensions with 1-D hexagonal channels. The [Mn(4,4'-bipy)(H(2)O)(4)](2+) linear covalent chains exist in these channels. Crystal data for 2: C(22)H(32)MnN(4)O(12)S(2), monoclinic P2(1)/c, a = 15.0833(14) A, b = 8.2887(4) A, c = 23.2228(15) A, alpha = gamma = 90 degrees, beta = 95.186(3) degrees, Z = 4.     

First principles study on the solvation and structure of C2O4(2-)(H2O)n, n = 6-12

The structures and energies of hydrated oxalate clusters, C2O4(2-)(H2O)n, n = 6-12, are obtained by density functional theory (DFT) calculations and compared to SO4(2-)(H2O)n. Although the evolution of the cluster structure with size is similar to that of SO4(2-)(H2O)n, there are a number of important and distinctive futures in C2O4(2-)(H2O)n, including the separation of the two charges due to the C-C bond in C2O4(2-), the lower symmetry around C2O4(2-), and the torsion along the C-C bond, that affect both the structure and the solvation energy. The solvation dynamics for the isomers of C2O4(2-)(H2O)12 are also examined by DFT based ab initio molecular dynamics.     

New metalloligands [M(SC[O]Ph)(4)](-): synthesis and characterization of polymeric [A(MeCN)(x)[M(SC[O]Ph)(4)]] compounds (A = Li,Na and K; M = Ga and In; x = 0-2)

Exploiting the ability of the [M(SC[O]Ph)(4)](-) anion to behave like an anionic metalloligand, we have synthesized [Li[Ga(SC[O]Ph)(4)]] (1), [Li[In(SC[O]Ph)(4)]] (2), [Na[Ga(SC[O]Ph)(4)]] (3), [Na(MeCN)[In(SC[O]Ph)(4)]] (4), [K[Ga(SC[O]Ph)(4)]] (5), and [K(MeCN)(2)[In(SC[O]Ph)(4)]] (6) by reacting MX(3) and PhC[O]S(-)A(+) (M = Ga(III) and In(III); X = Cl(-) and NO(3)(-); and A = Li(I), Na(I), and K(I)) in the molar ratio 1:4. The structures of 2, 4, and 6 determined by X-ray crystallography indicate that they have a one-dimensional coordination polymeric structure, and structural variations may be attributed to the change in the alkali metal ion from Li(I) to Na(I) to K(I). Crystal data for 2 x 0.5MeCN x 0.25H(2)O: monoclinic space group C2/c, a = 24.5766(8) A, b = 13.2758(5) A, c = 19.9983(8) A, beta = 108.426(1) degrees, Z = 8, and V = 6190.4(4) A(3). Crystal data for 4: monoclinic space group P2(1)/c, a = 10.5774(7) A, b = 21.9723(15) A, c = 14.4196(10) A, beta = 110.121(1) degrees, Z = 4, and V = 3146.7(4) A(3). Crystal data for 6: monoclinic space group P2(1)/c, a = 12.307(3) A, b = 13.672(3) A, c = 20.575(4) A, beta = 92.356(4) degrees, Z = 4, and V = 3458.8(12) A(3). The thermal decomposition of these compounds indicated the formation of the corresponding AMS(2) materials.