Ring, chain, and cluster compounds in the Cl-Ga-N-H system

The formation of gas-phase oligomer compounds in the Cl-Ga-N-H system is considered using hybrid Hartree-Fock/density functional theory and a polarized double-zeta quality basis set. Geometric parameters, vibrational frequencies, and thermodynamic characteristics for the Cl(3)GaNH(3) adduct, its dissociation products GaCl(n), NH(n), (n= 1-3), the amidochlorogallanes [Cl(2)GaNH(2)](n) (n = 1-3), their donor-acceptor complexes with GaCl(3) and NH(3), and the imidochlorogallanes [ClGaNH](n) (n = 1-4,6) have been obtained. Generation of amidochlorogallanes is expected to be viable during laser assisted chemical vapor deposition (CVD) at low temperatures. High-temperature association processes in the gas phase during the CVD of GaN from the Cl(3)GaNH(3) adduct are predicted to be less important, in contrast to previous findings for the aluminum analogue. This difference may be explained in terms of a much lower Ga-N bond energy compared to Al-N in the ring and cluster compounds.     

Multi-configurational quantum chemical studies of the Tc2X8(n-) (X = Cl, Br; n = 2, 3) anions. Crystallographic structure of octabromoditechnetate(3-)

The [Cs((2 + x))][H(3)O((1 - x))]Tc(2)Br(8)·4.6H(2)O (x = 0.221) salt has been synthesized and characterized by single crystal XRD. Multi-configurational quantum chemical calculations on Tc(2)X(8)(n-) (X = Cl, Br; n = 2, 3) have been performed and indicate the π component in the Tc-Tc bond to be stronger for n = 3.     

Some chemical properties of monochlorogallane: decomposition to gallium(I) trichlorogallate(III), Ga(+)[GaCl3H](-), and other reactions

Thermal decomposition of monochlorogallane, [H2GaCl]n, at ambient temperatures releases H2 and results in the formation of gallium(I) species, including the new compound Ga[GaHCl3], which has been characterized crystallographically at 100 K (monoclinic P2(1)/n, a = 5.730(1), b = 6.787(1), c = 14.508(1) A, beta = 97.902(5) degrees ) and by its Raman spectrum. The gallane suffers symmetrical cleavage of the Ga(mu-Cl)2Ga bridge in its reaction with NMe3 but unsymmetrical cleavage, giving [H2Ga(NH3)2](+)Cl(-), in its reaction with NH3. Ethene inserts into the Ga-H bonds to form first [Et(H)GaCl]2 and then [Et2GaCl]2.     

Myths and reality of hypervalent molecules. The electronic structure of FClO(x), x = 1-3, Cl3PO, Cl3PCH2, Cl3CClO, and C(ClO)4

In the present work we examine a series of hypervalent molecules, namely, FClO(x) (x = 1-3), Cl(3)PO, Cl(3)PCH(2), Cl(3)CClO, and C(ClO)(4), through single-reference [CCSD(T)] and multireference (MRCI) ab initio methods, the principal aim being the deciphering of their binding pattern. Our electronic structure calculations consistently show that the bonding occurs through an electron pair transfer from the Cl or P atoms of the molecules considered to the (1)D state of the O atom(s). We strongly believe that the term "hypervalency" when viewed from an unbiased side and with a critical eye reveals a simple chemical bonding situation that is in conformity with a scientific parsimony that dissolves the mythology of an enormous class of molecular systems that are categorized under the term hypervalent.     

Cl(3)V(mu-S(CH(3))(2))(3)VCl(3)(2)(-): a first-row,face-shared bioctahedral complex with multiple metal-metal bonding

Density functional theory calculations have been used to investigate the structure and bonding of the d(3)d(3) bioctahedral complexes X(3)V(mu-S(CH(3))(2))(3)VX(3)(2)(-) (X = F(-), Cl(-), OH(-), SH(-), NH(2)(-)). According to geometry optimizations using the broken-symmetry approach and the VWN+B-LYP combination of density functionals, the halide-terminated complexes have a V-V bond order of approximately 2, while complexes featuring OH(-), SH(-), or NH(2)(-) as terminal ligands exhibit full triple bonding between the vanadium atoms. The tendency toward triple bonding in the latter complexes is consistent with an increased covalency of the vanadium-ligand bonds, and the influence of bond covalency is apparent also in the tendency for V-V bond elongation in the complexes with OH(-) and NH(2)(-) terminal ligands. Detailed examination of the composition of molecular orbitals in all of the thioether-bridged V(II) complexes substantiates the conclusion that the strong antiferromagnetic coupling which we have determined for these complexes (-J > 250 cm(-)(1)) is due to direct bonding between metal atoms rather than superexchange through the bridging ligands. As such, these V(II) complexes comprise the first apparent examples of multiple metal-metal bonding in first-transition-row, face-shared dinuclear complexes and are therefore of considerable structural and synthetic interest.     

Electron affinities of Al(n) clusters and multiple-fold aromaticity of the square Al4(2-) structure

The concept of aromaticity was first invented to account for the unusual stability of planar organic molecules with 4n + 2 delocalized pi electrons. Recent photoelectron spectroscopy experiments on all-metal MAl(4)(-) systems with an approximate square planar Al(4)(2-) unit and an alkali metal led to the suggestion that Al(4)(2-) is aromatic. The square Al(4)(2-) structure was recognized as the prototype of a new family of aromatic molecules. High-level ab initio calculations based on extrapolating CCSD(T)/aug-cc-pVxZ (x = D, T, and Q) to the complete basis set limit were used to calculate the first electron affinities of Al(n)(), n = 0-4. The calculated electron affinities, 0.41 eV (n = 0), 1.51 eV (n = 1), 1.89 eV (n = 3), and 2.18 eV (n = 4), are all in excellent agreement with available experimental data. On the basis of the high-level ab initio quantum chemical calculations, we can estimate the resonance energy and show that it is quite large, large enough to stabilize Al(4)(2-) with respect to Al(4). Analysis of the calculated results shows that the aromaticity of Al(4)(2-) is unusual and different from that of C(6)H(6). Particularly, compared to the usual (1-fold) pi aromaticity in C(6)H(6), which may be represented by two Kekulé structures sharing a common sigma bond framework, the square Al(4)(2-) structure has an unusual "multiple-fold" aromaticity determined by three independent delocalized (pi and sigma) bonding systems, each of which satisfies the 4n + 2 electron counting rule, leading to a total of 4 x 4 x 4 = 64 potential resonating Kekulé-like structures without a common sigma frame. We also discuss the 2-fold aromaticity (pi plus sigma) of the Al(3)(-) anion, which can be represented by 3 x 3 = 9 potential resonating Kekulé-like structures, each with two localized chemical bonds. These results lead us to suggest a general approach (applicable to both organic and inorganic molecules) for examining delocalized chemical bonding. The possible electronic contribution to the aromaticity of a molecule should not be limited to only one particular delocalized bonding system satisfying a certain electron counting rule of aromaticity. More than one independent delocalized bonding system can simultaneously satisfy the electron counting rule of aromaticity, and therefore, a molecular structure could have multiple-fold aromaticity.     

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.     

Ab initio study of the ClO + NH2 reaction: prediction of the total rate constant and product branching ratios

The mechanism for ClO + NH2 has been investigated by ab initio molecular orbital and transition-state theory calculations. The species involved have been optimized at the B3LYP/6-311+G(3df,2p) level and their energies have been refined by single-point calculations with the modified Gaussian-2 method, G2M(CC2). Ten stable isomers have been located and a detailed potential energy diagram is provided. The rate constants and branching ratios for the low-lying energy channel products including HCl + HNO, Cl + NH2O, and HOCl + 3NH (X(3)Sigma(-)) are calculated. The result shows that formation of HCl + HNO is dominant below 1000 K; over 1000 K, Cl + NH2O products become dominant. However, the formation of HOCl + 3NH (X(3)Sigma(-)) is unimportant below 1500 K. The pressure-independent individual and total rate constants can be expressed as k1(HCl + HNO) = 4.7 x 10(-8)(T(-1.08)) exp(-129/T), k(2)(Cl + NH2O) = 1.7 x 10(-9)(T(-0.62)) exp(-24/T), k3(HOCl + NH) = 4.8 x 10(-29)(T5.11) exp(-1035/T), and k(total) = 5.0 x 10(-9)(T(-0.67)) exp(-1.2/T), respectively, with units of cm(3) molecule(-1) s(-1), in the temperature range of 200-2500 K.     

Structure and bonding in the aluminum radical species Al x NH(3), HAlNH(2), HAlNH(2) x NH(3), and Al(NH(2))(2) studied by means of matrix IR spectroscopy and quantum chemical calculations

Experimental matrix IR spectra in alliance with extensive quantum chemical calculations provide a framework for the detailed evaluation of the structures and electronic properties of the doublet species Al x NH(3), Al(NH(3))(2), HAlNH(2), HAlNH(2) x NH(3), and Al(NH(2))(2). These species were the products of the reaction of Al atoms with NH(3) in an Ar matrix. While the two species Al x NH(3) and HAlNH(2) were already sighted in previous experiments, the results described herein lead to the first identification and characterization of HAlNH(2) x NH(3) and Al(NH(2))(2), the products of the reaction of Al atoms with two NH(3) molecules. The results allow a detailed reaction scheme leading to all the product species to be established. The unpaired electron in each of the species Al x NH(3), Al(NH(3))(2), HAlNH(2), HAlNH(2) x NH(3), and Al(NH(2))(2) is located near the Al atom, but there is a significant degree of delocalization, especially in Al(NH(2))(2), due to pi bonding interactions. The consequences for the barrier to pyramidalization at the N-atom are discussed.     

A theoretical study on structural, spectroscopic and energetic properties of acetamide clusters [CH3CONH2] (n=1-15)

Insights into the formation of hydrogen bonded clusters are of outstanding importance and quantum chemical calculations play a pivotal role in achieving this understanding. Structure and energetic comparison of linear, circular and standard forms of (acetamide)(n) clusters (n = 1-15) at the B3LYP/D95** level of theory including empirical dispersion correction reveals significant cooperativity of hydrogen bonding and size dependent structural preference. A substantial amount of impact of BSSE is observed in these calculations as the cluster size increases irrespective of the kind of arrangement. The interaction energy per monomer increases from dimer to 15mer by 90% in the case of the circular arrangement, by 76% in the case of the linear arrangement and by 34% in the case of the standard arrangement respectively. The cooperativity in hydrogen bonding is also manifested by a regular decrease in average OH and C-N bond distances, while average C=O and N-H bond lengths increase with increasing cluster size. Atoms-In-Molecules (AIM) analysis is used to characterize the nature of hydrogen bonding between the acetamide molecules in the cluster on the basis of electron density (ρ) values obtained at the bond critical point. An analysis of N-H bond stretching frequencies as a function of the cluster size shows a marked red shift as the cluster size increases from 1 to 15.     

Bonding and isomerism in SF(n-1)Cl (n = 1-6): a quantum chemical study

Using high-level MRCI and CCSD(T) quantum chemical calculations, we report structures, energetics, and other properties of the sulfur fluoromonochloride family (SF(n-1)Cl, n = 1-6). Our group previously studied the sulfur fluoride family (SF(n), n = 1-6) and found that several of the excited states of SF and SF(2) as well as the ground states of SF(3)-SF(6) exhibited a new type of bonding, called recoupled pair bonding. Comparing the SF(n-1)Cl and SF(n) species allows us to study isomerism, apicophilicities, and substituent effects due to the Cl substitution. The primary findings of this work are twofold. First, replacing F with Cl weakens the adjacent S-F bonds by destabilizing the molecule with respect to the pure SF(n) analog. Second, an isomer with a singly occupied S-Cl antibonding orbital is more stable than the analogous isomer with a singly occupied S-F antibonding orbital, thus explaining apicophilicities. This work has also allowed us to further refine and expand our understanding of the nature of the recoupled pair bond model. Finally, we discovered the presence of bond-stretch isomers in the first excited ((3)A') state of SFCl.     

On the gas-phase reactivity of complexed OH+ with halogenated alkanes

OH(+) is an extraordinarily strong oxidant. Complexed forms (L--OH(+)), such as H(2)OOH(+), H(3)NOH(+), or iron-porphyrin-OH(+) are the anticipated oxidants in many chemical reactions. While these molecules are typically not stable in solution, their isolation can be achieved in the gas phase. We report a systematic survey of the influence on L on the reactivity of L--OH(+) towards alkanes and halogenated alkanes, showing the tremendous influence of L on the reactivity of L--OH(+). With the help of with quantum chemical calculations, detailed mechanistic insights on these very general reactions are gained. The gas-phase pseudo-first-order reaction rates of H(2)OOH(+), H(3)NOH(+), and protonated 4-picoline-N-oxide towards isobutane and different halogenated alkanes C(n)H(2n+1)Cl (n=1-4), HCF(3), CF(4), and CF(2)Cl(2) have been determined by means of Fourier transform ion cyclotron resonance measurements. Reaction rates for H(2)OOH(+) are generally fast (7.2x10(-10)-3.0x10(-9) cm(3) mol(-1) s(-1)) and only in the cases HCF(3) and CF(4) no reactivity is observed. In contrast to this H(3)NOH(+) only reacts with tC(4)H(9)Cl (k(obs)=9.2x10(-10)), while 4-CH(3)-C(5)H(4)N-OH(+) is completely unreactive. While H(2)OOH(+) oxidizes alkanes by an initial hydride abstraction upon formation of a carbocation, it reacts with halogenated alkanes at the chlorine atom. Two mechanistic scenarios, namely oxidation at the halogen atom or proton transfer are found. Accurate proton affinities for HOOH, NH(2)OH, a series of alkanes C(n)H(2n+2) (n=1-4), and halogenated alkanes C(n)H(2n+1)Cl (n=1-4), HCF(3), CF(4), and CF(2)Cl(2), were calculated by using the G3 method and are in excellent agreement with experimental values, where available. The G3 enthalpies of reaction are also consistent with the observed products. The tendency for oxidation of alkanes by hydride abstraction is expressed in terms of G3 hydride affinities of the corresponding cationic products C(n)H(2n+1) (+) (n=1-4) and C(n)H(2n)Cl(+) (n=1-4). The hypersurface for the reaction of H(2)OOH(+) with CH(3)Cl and C(2)H(5)Cl was calculated at the B3 LYP, MP2, and G3(m*) level, underlining the three mechanistic scenarios in which the reaction is either induced by oxidation at the hydrogen or the halogen atom, or by proton transfer.     

Gallium halide induced heterocycle expansion of dihalodiphosphadiaryldiazanes [(XPNR)2] to the corresponding triphosphatriazanes [(XPNR)3

Reactions of the cyclic diphosphadiazanes (XPNR)(2) (X = Cl, Br; R = 2,6-dimethylphenyl = Dmp, 2,6-diisopropylphenyl = Dipp) with GaX(3) followed by 4-(dimethylamino)pyridine (DMAP) give the corresponding trimers (XPNR)(3). An unusual cyclophosphazanium tetrachlorogallate salt [(DippN)(3)P(3)Cl(2)][GaCl(4)] has been isolated from the reaction of (ClPNDipp)(2) with GaCl(3) and represents an intermediate in the disproportionation process. Dissociation of the gallate ion on reaction of [(DippN)(3)P(3)Cl(2)][GaCl(4)] with DMAP releases a halide ion, which associates with the dicoordinate phosphenium center to give (ClPNDipp)(3). The observations indicate that the presence of medium-sized substituents at nitrogen (R) thermodynamically destabilize the dimer with respect to the trimer, without offering sufficient stabilization of the monomer, as observed for MesNPX (Mes* = 2,4,6-tri-tert-butylphenyl) (Mes* > Dipp > Dmp). Nevertheless, lability of the N-P bond in these derivatives of (XPNR)(2) allows for transformations between dimer and trimer that may include transient existence of the corresponding monomer. Manipulation of substituent steric strain to modify the relative stability of phosphazane oligomers provides a new methodology for diversification of phosphazane chemistry.     

Synthesis of the pivalamidate-bridged pentanuclear platinum(II,III) linear complexes with Pt...Pt interactions

Pentanuclear linear chain Pt(II,III) complexes [[Pt2(NH3)2X2((CH3)3CCONH)2(CH2COCH3)]2[PtX'4]].nCH3COCH3 (X = X' = Cl, n = 2 (1a), X = Cl, X' = Br, n = 1 (1b), X = Br, X' = Cl, n = 2 (1c), X = X' = Br, n = 1 (1d)) composed of a monomeric Pt(II) complex sandwiched by two amidate-bridged Pt dimers were synthesized from the reaction of the acetonyl dinuclear Pt(III) complexes having equatorial halide ligands [Pt2(NH3)2X2((CH3)3CCONH)2(CH2COCH3)]X' ' (X = Cl (2a), Br (2b), X' ' = NO3-, CH3C6H4SO3-, BF4-, PF6-, ClO4-), with K2[PtX'4] (X' = Cl, Br). The X-ray structures of 1a-1d show that the complexes have metal-metal bonded linear Pt5 structures, and the oxidation state of the metals is approximately Pt(III)-Pt(III)...Pt(II)...Pt(III)-Pt(III). The Pt...Pt interactions between the dimer units and the monomer are due to the induced Pt(II)-Pt(IV) polarization of the Pt(III) dimeric unit caused by the electron withdrawal of the equatorial halide ligands. The density functional theory calculation clearly shows that the Pt...Pt interactions between the dimers and the monomer are made by the electron transfer from the monomer to the dimers. The pentanuclear complexes have flexible Pt backbones with the Pt chain adopting either arch or sigmoid structures depending on the crystal packing.     

Luminescent mu-ethynediyl and mu-butadiynediyl binuclear gold(I) complexes: observation of (3)(pi pi*) emissions from bridging C(n)(2-) units.

The synthesis and X-ray structural and spectroscopic characterization for LAuC triple bond CAuL x 4CHCl(3) and LAuC triple bond C--C triple bond CAuL x 2CH(2)Cl(2) (1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively; L = PCy(3), tricyclohexylphosphine) are reported. The bridging C(n)(2-) units are structurally characterized as acetylene or diacetylene units, with C triple bond C distances of 1.19(1) and 1.199(8) A for 1 x 4CHCl(3) and 2 x 2CH(2)Cl(2), respectively. An important consequence of bonding to Au(I) for the C(n)(2-) moieties is that the lowest-energy electronic excited states, which are essentially acetylenic (3)(pi pi*) in nature, acquire sufficient allowedness via Au spin-orbit coupling to appear prominently in both electronic absorption and emission spectra. The origin lines for both complexes are well-defined and are observed at 331 and 413 nm for 1 and 2, respectively. Sharp vibronic progressions corresponding to v(C triple bond C) are observed in both emission and absorption spectra. The acetylenic (3)(pi pi) excited state of 2 has a long lifetime (tau(0) = 10.8 mus) in dichloromethane at room temperature and is a powerful reductant (E degrees [Au(2)(+)/Au(2)] < or = -1.85 V vs SSCE).     

Chalcogenide-halides of niobium (V). 1. Gas-phase structures of NbOBr(3), NbSBr(3), and NbSCl(3). 2. Matrix infrared spectra and vibrational force fields of NbOBr(3), NbSBr(3), NbSCl(3), and NbOCl(3)

The molecular structures of NbOBr(3), NbSCl(3), and NbSBr(3) have been determined by gas-phase electron diffraction (GED) at nozzle-tip temperatures of 250 degrees C, taking into account the possible presence of NbOCl(3) as a contaminant in the NbSCl(3) sample and NbOBr(3) in the NbSBr(3) sample. The experimental data are consistent with trigonal-pyramidal molecules having C(3)(v)() symmetry. Infrared spectra of molecules trapped in argon or nitrogen matrices were recorded and exhibit the characteristic fundamental stretching modes for C(3)(v)() species. Well resolved isotopic fine structure ((35)Cl and (37)Cl) was observed for NbSCl(3), and for NbOCl(3) which occurred as an impurity in the NbSCl(3) spectra. Quantum mechanical calculations of the structures and vibrational frequencies of the four YNbX(3) molecules (Y = O, S; X = Cl, Br) were carried out at several levels of theory, most importantly B3LYP DFT with either the Stuttgart RSC ECP or Hay-Wadt (n + 1) ECP VDZ basis set for Nb and the 6-311G basis set for the nonmetal atoms. Theoretical values for the bond lengths are 0.01-0.04 A longer than the experimental ones of type r(a), in accord with general experience, but the bond angles with theoretical minus experimental differences of only 1.0-1.5 degrees are notably accurate. Symmetrized force fields were also calculated. The experimental bond lengths (r(g)/A) and angles ( 90 degree angle (alpha)()/deg) with estimated 2sigma uncertainties from GED are as follows. NbOBr(3): r(Nb=O) = 1.694(7), r(Nb-Br) = 2.429(2), 90 degree angle (O=Nb-Br) = 107.3(5), 90 degree angle (Br-Nb-Br) = 111.5(5). NbSBr(3): r(Nb=S) = 2.134(10), r(Nb-Br) = 2.408(4), 90 degree angle (S=Nb-Br) = 106.6(7), 90 degree angle (Br-Nb-Br) = 112.2(6). NbSCl(3): r(Nb=S) = 2.120(10),r(Nb-Cl) = 2.271(6), 90 degree angle (S=Nb-Cl) = 107.8(12), 90 degree angle (Cl-Nb-Cl) = 111.1(11).     

Coordination and solvation of copper ion: infrared photodissociation spectroscopy of Cu(+)(NH(3))(n) (n = 3-8)

Coordination and solvation structures of the Cu(+)(NH(3))(n) ions with n = 3-8 are studied by infrared photodissociation spectroscopy in the NH-stretch region with the aid of density functional theory calculations. Hydrogen bonding between NH(3) molecules is absent for n = 3, indicating that all NH(3) molecules are bonded directly to Cu(+) in a tri-coordinated form. The first sign of hydrogen bonding is detected at n = 4 through frequency reduction and intensity enhancement of the infrared transitions, implying that at least one NH(3) molecule is placed in the second solvation shell. The spectra of n = 4 and 5 suggest the coexistence of multiple isomers, which have different coordination numbers (2, 3, and 4) or different types of hydrogen-bonding configurations. With increasing n, however, the di-coordinated isomer is of growing importance until becoming predominant at n = 8. These results signify a strong tendency of Cu(+) to adopt the twofold linear coordination, as in the case of Cu(+)(H(2)O)(n).     

Bonding of the chain structure for novel boranes B_(3k+)H_(5k+p+3)~-

The molecular orbitals obtained from conventional quantum chemistry calculations, are expressed in terms of symmetrized valence bond functions of fragment, and a direct picture of chemical bonding can be drawn easily. This method is utilized, together with extended Huckel calculations, to interpret the bonding properties of a centipede-like chain structure for novel laser-producing boranes B3k+pH5k+p+3- which is constructed from the repeated unit B3H5 linked to each other by three B-H-B bonds.     

Soft x-ray photoreactions of CF3Cl adsorbed on Si(111)-7x7 studied by continuous-time photon-stimulated desorption spectroscopy near F(1s) edge

The continuous-time core-level photon-stimulated desorption (PSD) spectroscopy was employed to monitor the monochromatic soft x-ray-induced reactions of CF3Cl adsorbed on Si(111)-7x7 near the F(1s) edge (681-704 eV). Sequential F+ PSD spectra were measured as a function of photon exposure at the CF3Cl-covered surface (dose=0.3x10(15) molecules/cm2, approximately 0.75 ML). The F+ PSD and total electron yield (TEY) spectra of molecular solid CF3Cl near the F(1s) edge were also measured. Both F+ PSD and TEY spectra show two features at the energy positions of 690.2 and 692.6 eV, and are attributed to the excitations of F(1s) to 11a1[(C-Cl)*] and (8e+12a1)[(C-F)*] antibonding orbitals, respectively. Following Auger decay, two holes are created in the F(2p) lone pair and/or C-F bonding orbitals forming the 2h1e final state which leads to the F+ desorption. This PSD mechanism, which is responsible for the F+ PSD of solid CF3Cl, is employed to interpret the first F+ PSD spectrum in the sequential F+ PSD spectra. The variation of spectrum shapes in the sequential F+ PSD spectra indicates the dissipation of adsorbed CF3Cl molecules and the formation of surface SiF species as a function of photon exposure. From the sequential F+ PSD spectra the photolysis cross section of the adsorbed CF3Cl molecules by photons with varying energy (681-704 eV) is determined to be approximately 1.0x10(-17) cm2.     

G3 and density functional theory investigations of the structures and energies of SF(n)Cl (n=0-5) and their anions

Computations of structures and total energies have been carried out for neutral and anionic SF(n)Cl (n=0-5), using the composite G3 method and density functional theory (DFT) at the B3LYP6-311+G(3df) level. The total energies and zero-point energies have been used here to derive electron affinities, bond dissociation energies, and heats of formation. In addition, vibrational frequencies, polarizabilities, and dipole moments are reported. Results are compared with earlier work for SF(m) (m=1-6) and demonstrate how the relatively weak S-Cl bond and reduced symmetry influence the properties of these molecules and anions. Comparisons are also made between G3 and DFT results for SF(n)Cl. Of particular interest is the alternating pattern of agreement between calculated electron affinity values with n. These calculations also provide critical energetic data needed to understand experimental measurements of electron attachment to SF(5)Cl [Van Doren et al., J. Chem. Phys. 128, 094309 (2008)] for which numerous ion products have been reported in the literature at low electron energy.