A photoelectron spectroscopic and computational study of sodium auride clusters, NanAun- (n = 1-3)

Negatively charged sodium auride clusters, NanAun- (n = 1-3), have been investigated experimentally using photoelectron spectroscopy and ab initio calculations. Well-resolved electronic transitions were observed in the photoelectron spectra of NanAun- (n = 1-3) at several photon energies. Very large band gaps were observed in the photoelectron spectra of the anion clusters, indicating that the corresponding neutral clusters are stable closed-shell species. Calculations show that the global minimum of Na2Au2- is a quasi-linear species with Cs symmetry. A planar isomer of D2h symmetry is found to be 0.137 eV higher in energy. The two lowest energy isomers of Na3Au3- consist of three-dimensional structures of Cs symmetry. The global minimum of Na3Au3- has a bent-flake structure lying 0.077 eV below a more compact structure. The global minima of the sodium auride clusters are confirmed by the good agreement between the calculated electron detachment energies of the anions and the measured photoelectron spectra. The global minima of neutral Na2Au2 and Na3Au3 are found to possess higher symmetries with a planar four-membered ring (D2h) and a six-membered ring (D3h) structure, respectively. The chemical bonding in the sodium auride clusters is found to be highly ionic with Au acting as the electron acceptor.     

Size resolved infrared spectroscopy of Na(CH3OH)n (n = 4-7) clusters in the OH stretching region: unravelling the interaction of methanol clusters with a sodium atom and the emergence of the solvated electron

Size resolved IR action spectra of neutral sodium doped methanol clusters have been measured using IR excitation modulated photoionisation mass spectroscopy. The Na(CH(3)OH)(n) clusters were generated in a supersonic He seeded expansion of methanol by subsequent Na doping in a pick-up cell. A combined analysis of IR action spectra, IP evolutions and harmonic predictions of IR spectra (using density functional theory) of the most stable structures revealed that for n = 4, 5 structures with an exterior Na atom showing high ionisation potentials (IPs) of ~4 eV dominate, while for n = 6, 7 clusters with lower IPs (~3.2 eV) featuring fully solvated Na atoms and solvated electrons emerge and dominate the IR action spectra. For n = 4 simulations of photoionisation spectra using an ab initio MD approach confirm the dominance of exterior structures and explain the previously reported appearance IP of 3.48 eV by small fractions of clusters with partly solvated Na atoms. Only for this cluster size a shift in the isomer composition with cluster temperature has been observed, which may be related to kinetic stabilisation of less Na solvated clusters at low temperatures. Features of slow fragmentation dynamics of cationic Na(+)(CH(3)OH)(6) clusters have been observed for the photoionisation near the adiabatic limit. This finding points to the relevance of previously proposed non-vertical photoionisation dynamics of this system.     

Addition of water to Al5O4- determined by anion photoelectron spectroscopy and quantum chemical calculations

The anion photoelectron spectra of Al5O4- and Al5O5H2- are presented and interpreted within the context of quantum chemical calculations on these species. Experimentally, the electron affinities of these two molecules are determined to be 3.50(5) eV and 3.10(10) eV for the bare and hydrated cluster, respectively. The spectra show at least three electronic transitions crowded into a 1 eV energy window. Calculations on Al5O4- predict a highly symmetric near-planar structure with a singlet ground state. The neutral structure calculated to be most structurally similar to the ground state structure of the anion is predicted to lie 0.15 eV above the ground state structure of the neutral. The lowest energy neutral isomer does not have significant Franck-Condon overlap with the ground state of the anion. Dissociative addition of water to Al5O4- is energetically favored over physisorption. The ground state structure for the Al5O4- +H(2)O product forms when water adds to the central Al atom in Al5O4- with -H migration to one of the neighboring O atoms. Again, the ground state structures for the anion and neutral are very different, and the PE spectrum represents transitions to a higher-lying neutral structure from the ground state anion structure.     

FT-IR、XPS和DFT研究水杨酸钠在针铁矿或赤铁矿上的吸附机理

采用傅里叶变换红外(FT-IR)光谱、X射线光电子能谱(XPS)以及基于周期平面波的密度泛函理论(DFT)分别研究了水杨酸钠在针铁矿或赤铁矿表面上的吸附结构,并将计算得到的光电子能谱移动(CLS)和电荷转移与实验得到的XPS结果进行对比。FT-IR结果表明,水杨酸钠可能以双齿双核(V)和双齿单核(IV)的形式分别吸附于针铁矿或赤铁矿表面。由DFT计算结果可知,水杨酸钠在针铁矿(101)晶面上形成双齿双核化合物(V)的吸附能为-5.46 eV。而水杨酸钠在针铁矿(101)晶面上形成双齿单核化合物(IV)的吸附能为3.80 eV,因此水杨酸钠在针铁矿上基本不以双齿单核化合物(IV)构型存在。水杨酸钠在赤铁矿(001)晶面上形成双齿单核化合物(IV)时吸附能为-4.07 eV,说明水杨酸钠在赤铁矿(001)晶面上形成了双齿单核化合物(IV)。另外,理论计算的针铁矿(101)晶面上吸附位点铁原子的Fe 2p的CLS值(-0.68 eV)与实验观察到的Fe 2p的CLS值(-0.5 eV)吻合。理论计算的赤铁矿(001)晶面上吸附位点铁原子的Fe 2p的CLS值(-0.80 eV)与实验观察到的Fe 2p的CLS值(-0.8 eV)吻合。因此,水杨酸钠吸附在针铁矿表面时能够通过羧酸基团上一个氧原子和酚羟基上的氧原子与针铁矿(101)表面上的两个铁原子形成双齿双核(V)结构,而在赤铁矿(001)表面上,水杨酸钠中羧酸基团上一个氧原子和酚羟基上的氧原子与赤铁矿(001)表面上的一个铁原子形成了双齿单核(IV)结构。     

Microscopic solvation of NaBO2 in water: anion photoelectron spectroscopy and ab initio calculations

We investigated the microscopic solvation of NaBO(2) in water by conducting photoelectron spectroscopy and ab initio studies on NaBO(2)(-)(H(2)O)(n) (n = 0-4) clusters. The vertical detachment energy (VDE) of NaBO(2)(-) is estimated to be 1.00 ± 0.08 eV. The photoelectron spectra of NaBO(2)(-)(H(2)O)(1) and NaBO(2)(-)(H(2)O)(2) are similar to that of bare NaBO(2)(-), except that their VDEs shift to higher electron binding energies (EBE). For the spectra of NaBO(2)(-)(H(2)O)(3) and NaBO(2)(-)(H(2)O)(4), a low EBE feature appears dramatically in addition to the features observed in the spectra of NaBO(2)(-)(H(2)O)(0-2). Our study shows that the water molecules mainly interact with the BO(2)(-) unit in NaBO(2)(-)(H(2)O)(1) and NaBO(2)(-)(H(2)O)(2) clusters to form Na-BO(2)(-)(H(2)O)(n) type structures, while in NaBO(2)(-)(H(2)O)(3) and NaBO(2)(-)(H(2)O)(4) clusters, the water molecules can interact strongly with the Na atom, therefore, the Na-BO(2)(-)(H(2)O)(n) and Na(H(2)O)(n)···BO(2)(-) types of structures coexist. That can be seen as an initial step of the transition from a contact ion pair (CIP) structure to a solvent-separated ion pair (SSIP) structure for the dissolution of NaBO(2).     

Theoretical studies on photoelectron and IR spectral properties of Br2.-(H2O)n clusters

We report vertical detachment energy (VDE) and IR spectra of Br2.-.(H2O)n clusters (n=1-8) based on first principles electronic structure calculations. Cluster structures and IR spectra are calculated at Becke's half-and-half hybrid exchange-correlation functional (BHHLYP) with a triple split valence basis function, 6-311++G(d,p). VDE for the hydrated clusters is calculated based on second order Moller-Plesset perturbation (MP2) theory with the same set of basis function. On full geometry optimization, it is observed that conformers having interwater hydrogen bonding among solvent water molecules are more stable than the structures having double or single hydrogen bonded structures between the anionic solute, Br2.-, and solvent water molecules. Moreover, a conformer having cyclic interwater hydrogen bonded network is predicted to be more stable for each size hydrated cluster. It is also noticed that up to four solvent H2O units can reside around the solute in a cyclic interwater hydrogen bonded network. The excess electron in these hydrated clusters is localized over the solute atoms. Weighted average VDE is calculated for each size (n) cluster based on statistical population of the conformers at 150 K. A linear relationship is obtained for VDE versus (n+3)(-1/3) and bulk VDE of Br2.- aqueous solution is calculated as 10.01 eV at MP2 level of theory. BHHLYP density functional is seen to make a systematic overestimation in VDE values by approximately 0.5 eV compared to MP2 data in all the hydrated clusters. It is observed that hydration increases VDE of bromine dimer anion system by approximately 6.4 eV. Calculated IR spectra show that the formation of Br2.--water clusters induces large shifts from the normal O-H stretching bands of isolated water keeping bending modes rather insensitive. Hydrated clusters, Br2.-.(H2O)n, show characteristic sharp features of O-H stretching bands of water in the small size clusters.     

Complexes of Li,Na, Ba,and Er with 1,5-Bis[2-(diphenylphosphinyl)phenoxy]-3-oxapentane

Complexes of Li, Na, Ba, and Er with 1,5-bis[2-(diphenylphosphinyl)phenoxy]-3-oxapentane (L) were synthesized and their IR spectra were examined. Some of the complexes were studied by thermogravimetric methods. The structures of the synthesized compounds were suggested on the basis of their spectra and previous X-ray studies. In Ba and Er complexes, L was found to be coordinated to the metal atom through the phosphoryl oxygen atoms, whereas in Li and Na complexes, both the phosphoryl and anisole oxygen atoms are involved in coordination. The structures of complexes was determined to depend on the nature of a metal and acidoligand and on the ratio of reagents used in the synthesis.     

Synthesis and Crystal Structure of Novel Mixed-metal Alkoxide Clusters of Ytterbium and Sodium: Yb4O4（OiPr）16Na12

The mixed-metal cluster Yb4O4(OiPr)16Na12 has been synthesized and structurally determined by IR, elemental analysis, and single-crystal X-ray diffraction. The crystal belongs to the cubic system, space group P23 with a = b = c = 13.9788(3), V = 2731.55(10)3 , Z = 1, Dc = 1.202 g/cm 3 , Mr = 1977.42, = 3.480 mm-1 , F(000) = 972, the final R = 0.0288 and wR = 0.1511 for 1677 observed reflections with Ⅰ > 2σ(Ⅰ). X-ray analysis reveals that Yb4O4 (OiPr)16Na12 is centrosym-metric and the structure contains four ytterbium metals and twelve sodium metals, and each ytterbium atom is coordinated by six oxygen atoms. In addition, an ancillary computational analysis of the optimized molecular unit was provided. The large energy gap (3.31 eV) between HOMO and LUMO indicates that the structure framework is particularly stable.     

Gas phase vibrational spectroscopy of mass-selected vanadium oxide anions

The vibrational spectra of vanadium oxide anions ranging from V(2)O(6)(-) to V(8)O(20)(-) are studied in the region from 555 to 1670 cm(-1) by infrared multiple photon photodissociation (IRMPD) spectroscopy. The cluster structures are assigned and structural trends identified by comparison of the experimental IRMPD spectra with simulated linear IR absorption spectra derived from density functional calculations, aided by energy calculations at higher levels of theory. Overall, the IR absorption of the V(m)O(n)(-) clusters can be grouped in three spectral regions. The transitions of (i) superoxo, (ii) vanadyl and (iii) V-O-V and V-O single bond modes are found at approximately 1100 cm(-1), 1020 to 870 cm(-1), and 950 to 580 cm(-1), respectively. A structural transition from open structures, including at least one vanadium atom forming two vanadyl bonds, to caged structures, with only one vanadyl bond per vanadium atom, is observed in-between tri- and tetravanadium oxide anions. Both the closed shell (V(2)O(5))(2,3)VO(3)(-) and open shell (V(2)O(5))(2-4)(-) anions prefer cage-like structures. The (V(2)O(5))(3,4)(-) anions have symmetry-broken minimum energy structures (C(s)) connected by low-energy transition structures of C(2v) symmetry. These double well potentials for V-O-V modes lead to IR transitions substantially red-shifted from their harmonic values. For the oxygen rich clusters, the IRMPD spectra prove the presence of a superoxo group in V(2)O(7)(-), but the absence of the expected peroxo group in V(4)O(11)(-). For V(4)O(11)(-), use of a genetic algorithm was necessary for finding a non-intuitive energy minimum structure with sufficient agreement between experiment and theory.     

三苯基锗杂环羧酸酯的合成与表征

合成了8种三苯基锗杂环羧酸酯Ph~3GeO~2CR(R=2-呋喃、2-呋喃乙烯基、2-噻吩基、2-吡啶基、3-吡啶基、4-吡啶基、3-吲哚甲基、3-吲哚丙基),利用元素分析、红外光谱、核磁共振氢谱和质谱表征了这些化合物的结构。体外实验表明,这些化合物对MCF-7和WiDr癌细胞具有较好的抑制活性。     

Sulfur X-ray absorption and vibrational spectroscopic study of sulfur dioxide, sulfite, and sulfonate solutions and of the substituted sulfonate ions X3CSO3- (X = H, Cl, F)

Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra have been recorded and the S(1s) electron excitations evaluated by means of density functional theory-transition potential (DFT-TP) calculations to provide insight into the coordination, bonding, and electronic structure. The XANES spectra for the various species in sulfur dioxide and aqueous sodium sulfite solutions show considerable differences at different pH values in the environmentally important sulfite(IV) system. In strongly acidic (pH < approximately 1) aqueous sulfite solution the XANES spectra confirm that the hydrated sulfur dioxide molecule, SO2(aq), dominates. The theoretical spectra are consistent with an OSO angle of approximately 119 degrees in gas phase and acetonitrile solution, while in aqueous solution hydrogen bonding reduces the angle to approximately 116 degrees . The hydration affects the XANES spectra also for the sulfite ion, SO32-. At intermediate pH ( approximately 4) the two coordination isomers, the sulfonate (HSO3-) and hydrogen sulfite (SO3H-) ions with the hydrogen atom coordinated to sulfur and oxygen, respectively, could be distinguished with the ratio HSO3-:SO3H- about 0.28:0.72 at 298 K. The relative amount of HSO3- increased with increasing temperature in the investigated range from 275 to 343 K. XANES spectra of sulfonate, methanesulfonate, trichloromethanesulfonate, and trifluoromethanesulfonate compounds, all with closely similar S-O bond distances in tetrahedral configuration around the sulfur atom, were interpreted by DFT-TP computations. The energy of their main electronic transition from the sulfur K-shell is about 2478 eV. The additional absorption features are similar when a hydrogen atom or an electron-donating methyl group is bonded to the -SO3 group. Significant changes occur for the electronegative trichloromethyl (Cl3C-) and trifluoromethyl (F3C-) groups, which strongly affect the distribution especially of the pi electrons around the sulfur atom. The S-D bond distance 1.38(2) A was obtained for the deuterated sulfonate (DSO3-) ion by Rietveld analysis of neutron powder diffraction data of CsDSO3. Raman and infrared absorption spectra of the CsHSO3, CsDSO3, H3CSO3Na, and Cl3CSO3Na.H2O compounds and Raman spectra of the sulfite solutions have been interpreted by normal coordinate calculations. The C-S stretching force constant for the trichloromethanesulfonate ion obtains an anomalously low value due to steric repulsion between the Cl3C- and -SO3 groups. The S-O stretching force constants were correlated with corresponding S-O bond distances for several oxosulfur species.     

Binding energies of water to sodiated valine and structural isomers in the gas phase: the effect of proton affinity on zwitterion stability

The structures of valine (Val) and methylaminoisobutyric acid (Maiba) bound to a sodium ion, both with and without a water molecule, are investigated using both theory and experiment. Calculations indicate that, without water, sodiated Val forms a charge-solvated structure in which the sodium ion coordinates to the nitrogen and the carbonyl oxygen (NO-coordination), whereas Maiba forms a salt-bridge structure in which the sodium ion coordinates to both carboxylate oxygens (OO-coordination). The addition of a single water molecule does not significantly affect the relative energies or structures of the charge-solvated and salt-bridge forms of either cluster, although in Maiba the mode of sodium ion binding is changed slightly by the water molecule. The preference of Maiba to adopt a zwitterionic form in these complexes is consistent with its higher proton affinity. Experimentally, the rates of water evaporation from clusters of Val.Na(+)(H(2)O) and Maiba.Na(+)(H(2)O) are measured using blackbody infrared radiative dissociation (BIRD). The dissociation rates from the Val and Maiba complexes are compared to water evaporation rates from model complexes of known structure over a wide range of temperatures. Master equation modeling of the BIRD kinetic data yields a threshold dissociation energy for the loss of water from sodiated valine of 15.9 +/- 0.2 kcal/mol and an energy of 15.1 +/- 0.3 kcal/mol for the loss of water from sodiated Maiba. The threshold dissociation energy of water for Val.Na(+)(H(2)O) is the same as that for the charge-solvated model isomers, while the salt-bridge model complex has the same water threshold dissociation energy as Maiba.Na(+)(H(2)O). These results indicate that the threshold dissociation energy for loss of a water molecule from these salt-bridge complexes is approximately 1 kcal/mol less than that for loss of water from the charge-solvated complexes.     

Structure of the Na(x)Cl(x+1) (-) (x=1-4) clusters via ab initio genetic algorithm and photoelectron spectroscopy

The application of the ab initio genetic algorithm with an embedded gradient has been carried out for the elucidation of global minimum structures of a series of anionic sodium chloride clusters, Na(x)Cl(x+1) (-) (x=1-4), produced in the gas phase using electrospray ionization and studied by photoelectron spectroscopy. These are all superhalogen species with extremely high electron binding energies. The vertical electron detachment energies for Na(x)Cl(x+1) (-) were measured to be 5.6, 6.46, 6.3, and 7.0 eV, for x=1-4, respectively. Our ab initio gradient embedded genetic algorithm program detected the linear global minima for NaCl(2) (-) and Na(2)Cl(3) (-) and three-dimensional structures for the larger species. Na(3)Cl(4) (-) was found to have C(3v) symmetry, which can be viewed as a Na(4)Cl(4) cube missing a corner Na(+) cation, whereas Na(4)Cl(5) (-) was found to have C(4v) symmetry, close to a 3x3 planar structure. Excellent agreement between the theoretically calculated and the experimental spectra was observed, confirming the obtained structures and demonstrating the power of the developed genetic algorithm technique.     

Infrared Multiple Photon Dissociation Action Spectroscopy and Theoretical Studies of Triethyl Phosphate Complexes: Effects of Protonation and Sodium Cationization on Structure

The gas-phase structures of protonated and sodium cationized complexes of triethyl phosphate, [TEP + H]⁺ and [TEP + Na]⁺, are examined via infrared multiple photon dissociation (IRMPD) action spectroscopy using tunable IR radiation generated by a free electron laser, a Fourier transform ion cyclotron resonance mass spectrometer with an electrospray ionization source, and theoretical electronic structure calculations. Measured IRMPD action spectra are compared to linear IR spectra calculated at the B3LYP/6-31 G(d,p) level of theory to identify the structures accessed in the experimental studies. For comparison, theoretical studies of neutral TEP are also performed. Sodium cationization and protonation produce changes in the central phosphate geometry, including an increase in the alkoxy ∠OPO bond angle and shortening of the alkoxy P–O bond. Changes associated with protonation are more pronounced than those produced by sodium cationization.     

Sodium or lithium ion-binding-induced structural changes in the K-ring of V-ATPase from Enterococcus hirae revealed by ATR-FTIR spectroscopy

V-ATPase from Enterococcus hirae forms a large supramolecular protein complex (total molecular weight ～700,000) and physiologically transports Na(+) and Li(+) across a hydrophobic lipid bilayer. Stabilization of these cations in the binding site has been discussed on the basis of X-ray crystal structures of a membrane-embedded domain, the K-ring (Na(+)- and Li(+)-bound forms). Here, sodium or lithium ion-binding-induced difference IR spectra of the intact V-ATPase have for the first time been measured at physiological temperature under a sufficient amount of hydration. The results suggest that sodium or lithium ion binding induces the deprotonation of Glu139, a hydrogen-bonding change in the tyrosine residue, and a small conformational change in the K-ring. These structural changes, especially the deprotonation of Glu139, are considered to be important for reducing energetic barriers to the transport of cations through the membrane.     

Influence of submonolayer sodium adsorption on the photoemission of the Cu(111)/water ice surface

Photoemission from an ice film deposited on Cu(111) as a function of thickness has been observed in the presence and absence of sodium atoms at the surface-vacuum interface. For either adsorbate alone and photon energies below 4 eV, two-photon photoemission from the Cu(111) substrate dominates. The Cu(111) photoelectron spectrum is perturbed by low coverages of Na, and its intensity is strongly attenuated by a few monolayers of ice. For a low density amorphous ice film, strong charging effects are observed. For ice films annealed to yield either the dense amorphous or crystalline phase, this effect is absent. Deposition of only 0.02 monolayer of Na leads to a dramatic decrease in the threshold for photoemission to 2.3+/-0.2 eV. Thus, photoelectrons are generated by visible radiation in a one-photon process with a cross section that exceeds 10(-18) cm(2). The initial state for the photoemission is identified as a metastable surface trapped electron, which decays thermally with an activation energy of 10+/-2 kJ mol(-1). Quantum calculations are described which support this model and show that the Na atom is accommodated in the first layer of the ice surface.     

Na2EuAs2S5, NaEuAsS4, and Na4Eu(AsS4)2: controlling the valency of arsenic in polysulfide fluxes

The reactivity of europium with As species in Lewis basic alkali-metal polysulfide fluxes was investigated along with compound formation and the As(3+)/As(5+) interplay vis-à-vis changes in the flux basicity. The compound Na(2)EuAs(2)S(5) containing trivalent As(3+) is stabilized from an arsenic-rich polysulfide flux. It crystallizes in the monoclinic centrosymmetric space group P2(1)/c. Na(2)EuAs(2)S(5) has [As(2)S(5)](4-) units, built of corner sharing AsS(3) pyramids, which are coordinated to Eu(2+) ions to give a two-dimensional (2D) layered structure. A sodium polysulfide flux with comparatively less arsenic led to the As(5+) containing compounds NaEuAsS(4) (orthorhombic, Ama2) and Na(4)Eu(AsS(4))(2) (triclinic, P1) depending on Na(2)S/S ratio. The NaEuAsS(4) and Na(4)Eu(AsS(4))(2) have a three-dimensional (3D) structure built of [AsS(4)](3-) tetrahedra coordinated to Eu(2+) ions. All compounds are semiconductors with optical energy gaps of ～2 eV.     

Computational studies of nonstoichiometric sodium auride clusters

The molecular structures of low-lying isomers of anionic and neutral sodium auride clusters have been studied computationally at the second-order M?ller-Plesset perturbation theory level using quadruple-ζ basis sets augmented with a double set of polarization functions. The first vertical detachment energies were calculated at the M?ller-Plesset level as the energy difference between the cluster anion and the corresponding neutral cluster. The photodetachment energies of higher-lying ionization channels were calculated by adding electronic excitation energies of the neutral clusters to the first vertical detachment energy. The excitation energies were calculated at the linear response approximate coupled-cluster singles and doubles level using the anionic cluster structures. The obtained ionization energies for NaAu(-), NaAu(2)(-), NaAu(3)(-), NaAu(4)(-), Na(2)Au(2)(-), Na(2)Au(3)(-), Na(3)Au(3)(-), and Na(2)Au(4)(-) were compared to values deduced from experimental photoelectron spectra. Comparison of the calculated photoelectron spectra for a few energetically low-lying isomers shows that the energetically lowest cluster structures obtained in the calculations do not always correspond to the clusters produced experimentally. Spin-component-scaled second-order M?ller-Plesset perturbation theory calculations shift the order of the isomers such that the observed clusters more often correspond to the energetically lowest structure, whereas the spin-component-scaled approach does not improve the photodetachment energies of the sodium aurides. The potential energy surface of the sodium aurides is very soft, with several low-lying isomers requiring an accurate electron correlation treatment. The calculations show that merely the energetic criterion is not a reliable means to identify the structures of the observed sodium auride clusters; other experimental information is needed to ensure a correct assignment of the cluster structures. The cluster structures of nonstoichiometric anionic sodium aurides have been determined by comparing calculated ionization energies for low-lying structures of the anionic clusters with experimental data.     

氮混杂金属卟啉吸收光谱性质的理论研究

采用密度泛函理论在B3LYP/6-31+G(d)水平上研究了4种金属Mg, Ni, Cu, Zn配位的自由卟啉(FBP)及氮混杂卟啉(NECP)的几何结构及分子轨道能级. 采用含时密度泛函理论(TD-DFT)方法计算了金属与2种卟啉配位后在气体条件下的电子吸收光谱, 包括激发能、 吸收波长、 跃迁组成和振子强度.计算结果表明, 与金属配位的FBP(M-FBP)具有D_4h对称性, 分子轨道能级HOMO/HOMO-1和LUMO/LUMO+1因能级相近发生简并, HOMO-LUMO轨道能级差大约3.0 eV, 在Soret带出现较强吸收峰.由于C/N原子位置的改变, 非对称性结构的M-NECP前线轨道组成发生改变, 轨道能级差(HOMO-LUMO)减小至2.6 eV左右, 且能级发生分裂, Soret带出现多个电子吸收谱峰, Q带也出现吸收峰. 本文研究了水、 氯仿和苯3种不同极性溶剂对M-FBP和M-NECP的分子轨道及电子吸收光谱的影响, 结果表明, 随溶剂极性减弱金属配合物的电子吸收光谱发生红移, 并且吸收峰强度增强.     

A Gaussian-3 theoretical study of small silicon-lithium clusters: electronic structures and electron affinities of SinLi(-) (n = 2-8)

The molecular structures of neutral Si n Li ( n = 2-8) species and their anions have been studied by means of the higher level of the Gaussian-3 (G3) techniques. The lowest energy structures of these clusters have been reported. The ground-state structures of neutral clusters are "attaching structures", in which the Li atom is bound to Si n clusters. The ground-state geometries of anions, however, are "substitutional structures", which is derived from Si n+1 by replacing a Si atom with a Li (-). The electron affinities of Si n Li and Si n have been presented. The theoretical electron affinities of Si n are in good agreement with the experiment data. The reliable electron affinities of Si n Li are predicted to be 1.87 eV for Si 2Li, 2.06 eV for Si 3Li, 2.01 eV for Si 4Li, 2.61 eV for Si 5Li, 2.36 eV for Si 6Li, 2.21 eV for Si 7Li, and 3.18 eV for Si 8Li. The dissociation energies of Li atom from the lowest energy structures of Si n Li and Si atom from Si n clusters have also been estimated respectively to examine relative stabilities.