Shape resonance and electronic autoionization in vibrationally resolved partial photoionization cross sections of O2

Vibrationally resolved partial photoionization cross sections of O₂ leading to the b⁴Σ^?_g and B²Σ^?1_g(3σ^?1_g) tonic states have been measured at high resolution in a wide photon energy range from 0.5 eV above threshold to 24.5 eV. The σ_u shape resonance is observed around 21.5 eV, in fairly good agreement with “one-electron” theoretical predictions. The series of resonances from 19 to 20 5 eV result from an autoionization process with a strong vibrational selectivity, explained by the similar geometries of the resonance states and the b ionic state. The large resonance widths originate from a strong Rydberg-valence orbital mixing Calculations using multichannel quantum defect theory reproduce the most important features.     

Theoretical Study on Resonance Raman Spectra of Tetraoxaporphyrin Dication by TDDFT Calculation

The B state excited resonance Raman scattering of tetraoxaporphyrin dication (TOP²⁺) was theoretically studied with DFT/TDDFT calculations and the sum-over-states approach of polarizability including both the A and B terms contributions. The resonance Raman spectra calculated with PBE1PBE, B3LYP, Cam-B3LYP, and B3LYP-D3 functionals are similar to each other in general, with PBE1PBE and B3LYP being better in reproducing resonance Raman intensities in comparison with the experiment. The calculated relative intensities of the totally symmetric modes are excellently consistent with the experiment. The TDDFT calculations manifested a considerable deformation of the B state along theυ2,υ6, υ7, and υ8 modes, which is responsible for the strong resonance Raman intensities of these modes. The resonance Raman intensities of non-totally symmetric modes were calculated to be weaker than the totally symmetric modes by one or two order of magnitude, whichqualitatively agrees with the experiment. However, the resonance Raman intensity of the υ10 mode (C_βC_β stretch, B_1g symmetry) predicted by TDDFT calculations is unexpectedly small whereas that of the υ11 mode (symmetric C_αC_m stretch, B_1g symmetry) is too large, which is assumed to be caused by the Jahn-Teller instability for the B state of TOP²⁺.     

Synthesis and characterization of trinuclear square-planar Ni3 and Cu3 complexes of an extended phloroglucinol ligand: Experimental evidence for the relative contributions of benzene-like and radialene-like resonance structures

The synthesis and characterization of the extended phloroglucinol ligand H₃felddien, its trinuclear Ni^II complex [(felddien)Ni₃](BF₄)₃ and its trinuclear Cu^II complex [(felddien)Cu₃](ClO₄)₃ is presented. Detailed NMR studies provide strong evidence that the ligand H₃felddien has to be described as the N-protonated tautomer and not as the O-protonated tautomer, with strong contribution of a radialene-like keto-enamine resonance structure resulting in a C_s and a C_3h isomer. The trinucleating tris(tetradentate) ligand provides three donor sets comprised of a phenolate, an imine, and two tertiary amine donors. This donor set enables the synthesis of the diamagnetic square-planar coordinated Ni^II complex [(felddien)Ni₃](BF₄)₃ which provides the opportunity to perform detailed NMR spectroscopic characterizations for the evaluation of the electronic structure of the central phloroglucinol unit. In conjunction with a single-crystal X-ray diffraction and a UV-vis absorption spectroscopic analysis, these data indicate that in the coordinated form, the benzene-like phenolate-imine and the radialene-like keto-enamine resonance structures have contributions to the overall resonance hybrid. The weakening of the central π system as a consequence of the contribution of the keto-enamine resonance structure explains the relative small ferromagnetic interactions in the trinuclear Cu^II complex [(felddien)Cu₃](ClO₄)₃. This detailed analysis identifies the strong resonance with unsaturated groups in 2,4,6 position of phloroglucinol as the main source for the low ferromagnetic couplings by the spin-polarization mechanism in all our extended phloroglucinol ligands. A replacement of the unsaturated imine functions by saturated amine functions may be a synthetic opportunity to enhance the ferromagnetic interactions by the spin-polarization mechanism in this ligand system.     

The investigation of Ag decorated double‐wall hollow TiO2 spheres as photocatalyst

In this paper, a novel TiO₂ nanosheets assembled double‐wall hollow sphere (DHS)has been prepared successfully via hydrothermal treatment of SiO₂@TiO₂ with the assistant of CTAB.The prepared samples are characterized with transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron spin resonance (ESR), X‐ray diffraction (XRD) and X‐ray photoelectron spectra (XPS), etc.Results show that redeposited silica species play a key role in the formation of the double‐wall structure. The as‐synthesized DHS nanostructure exhibits a large surface area (417.6 m² g^‐1) and excellent mechanical strength. Furthermore, after decoration of Ag and calcination treatment, the double‐shelled TiO₂/Ag heterostructures show an enhanced photocatalytic performance in the degradation of RhB under UV or visible light irradiations for the following reasons: the surface plasmon resonance effect of Ag, strong interaction between Ag and TiO₂ nanosheets, large surface area, excellent adsorption capacityand unique double‐wall structure. On the basis of the experimental results, a possible mechanism for pollutantdegradation under visual light irradiation has been proposed.     

Ag@AgCl修饰的锐钛矿相TiO2纳米管的制备及其光催化性能

首先采用水热合成法和双氧水处理制备了具有锐钛矿相的TiO2纳米管,然后通过沉淀和光化学反应将Ag@AgCl纳米粒子负载于其上,从而制得TiO2纳米管负载的表面等离子体光催化剂.结果表明,经Ag@AgCl纳米粒子修饰后,锐钛矿相TiO2纳米管因表面等离子共振效应而对可见光具有明显的响应,光生电子-空穴对更容易分离,因而T...     

4-Amino-1,8-naphthalimide-based anion receptors: employing the naphthalimide N-H moiety in the cooperative binding of dihydrogenphosphate

The 4-amino-1,8-naphthalimide-based anion receptor 3 binds dihydrogenphosphate with 1:1 stoichiometry through cooperative hydrogen bonding to a naphthalimide N-H and thiourea N-H groups. This was clearly established from ¹H NMR titration experiments in DMSO-d₆ where a substantial shift in the resonance for the naphthalimide N-H was observed concomitant with the expected thiourea N-H chemical shift migration upon successive additions of H₂PO₄⁻. However, whilst ¹H NMR titration experiments indicate that 3 was capable of binding other anions such as acetate, the naphthalimide N-H does not participate and the N-H resonance was essentially invariant during the titration. The lack of cooperative binding in this instance was justifiable on steric grounds.     

Autocollimation spectroscopy for fast hydrogenic ions

We propose a new experimental method (Autocollimation Spectroscopy), which provides a strong suppression of systematic error contributions in the laser resonance spectroscopy of broad resonances. Using a bidirectional laser beam with a fixed wavelength in connection with high current pulsed ion beams an accuracy ofΔE _Exp/Γ≈5·10^?5 (Γ: resonance width) for the resonance energy seems to be achievable. Applying this technique to 2S-Lamb shift (LS) measurements on medium heavy ions would yield a precision ofΔE _Exp/E _LS≈1·10^?5, i.e. an improvement by a factor up to 100 as compared to present experiments.     

Electrochemical quartz crystal admittance studies of ion adsorption on nanoporous composite carbon electrodes in aprotic solutions

This paper describes the application of Electrochemical Quartz Crystal Admittance (EQCA) methodology to the tracking of ion adsorption on composite electrode coatings consisting of highly porous activated carbon particles and polyvinylidene difluoride (PVdF) binder rigidly attached to quartz crystal surfaces. Solutions of LiBF₄ and (C₂H₅)₄NBF₄ in propylene carbonate (PC) were used in this study. At small charge densities, the effect of frequency change is nearly of gravimetric nature. We propose a new method to determine the mass contribution to the resonance frequency shift due to adsorption of ions and accompanying solvent molecules, revealing different ion/solvent population ratios for Li⁺, (C₂H₅)₄?N⁺ and BF₄ ^? ions correlated to the ion solvation ability. The EQCA model applied describes the change in the frequency and in resonance peak width in terms of dimensional changes of large carbon particles (bumps) and of pseudo-uniform layers of smaller particles mixed with PVdF. The type of oscillation energy dissipation in composite carbon electrodes with PVdF binder strongly depends on non-uniform potential-induced deformations of electrode particles, and this suggests a strong effect of solvent nature on the mechanical properties of polymeric binders. EQCA may provide important information on the role of polymeric binders during cycling of composite electrodes both for supercapacitors and for Li-ion batteries electrodes.     

A surface enhanced Raman study of the adsorption of tris(2,2-bipyridine)ruthenium(II) and substituted analogues on chemically-deposited silver films

The surface enhanced resonance Raman spectroscopy (SERRS) of a series of tris(2,2′-bipyridine)ruthenium(II) complexes on chemically produced silver films is reported. The SERR spectra of [Ru(bipy)₃]²⁺, several tris complexes of Ru(II) containing substituted 2,2′-bipyridine (4,4′-dimethyl-,4,4′diphenyl-, 4,4′-diamino- and 4,4′-diethylcarboxylate-2,2′-bipyridine) ligands and the neutral cis-bis complexes [Ru(bipy)₂(NCS)₂] and [Ru(bipy)₂Cl₂] show very high band intensities. The large enhancement arises from the combination of the inherent resonance Raman effect and the surface plasmon resonance (due to the rough nature of the silver film). The molecules are not chemisorbed on the silver surface and hence the enhancement occurs solely via the electromagnetic mechanism. Ale SERR spectra are virtually free of the fluorescence which dominates the corresponding RR spectra thus illustrating the use of SERRS in the vibrational spectroscopy of strongly luminescing species. The SERRS spectra of the substituted 2,2′-bipyridine complexes are discussed.     

Conjugated Polyelectrolyte‐Induced Self‐Assembly of Alkynylplatinum(II) 2,6‐Bis(benzimidazol‐2′‐yl)pyridine Complexes

Water‐soluble cationic alkynylplatinum(II) 2,6‐bis(benzimidazol‐2′‐yl)pyridine (bzimpy) complexes have been demonstrated to undergo supramolecular assembly with anionic polyelectrolytes in aqueous buffer solution. Metal–metal‐to‐ligand charge transfer (MMLCT) absorptions and triplet MMLCT (³MMLCT) emissions have been found in UV/Vis absorption and emission spectra of the electrostatic assembly of the complexes with non‐conjugated polyelectrolytes, driven by Pt???Pt and π–π interactions among the complex molecules. Interestingly, the two‐component ensemble formed by [Pt(bzimpy‐Et){C?CC₆H₄(CH₂NMe₃‐4)}]Cl₂ ( 1 ) with para‐linked conjugated polyelectrolyte (CPE), PPE‐SO₃^?, shows significantly different photophysical properties from that of the ensemble formed by 1 with meta‐linked CPE, mPPE‐Ala. The helical conformation of mPPE‐Ala allows the formation of strong mPPE‐Ala– 1 aggregates with Pt???Pt, electrostatic, and π–π interactions, as revealed by the large Stern–Volmer constant at low concentrations of 1 . Together with the reasonably large Förster radius, large HOMO–LUMO gap and high triplet state energy of mPPE‐Ala to minimize both photo‐induced charge transfer (PCT) and Dexter triplet energy back‐transfer (TEBT) quenching of the emission of 1 , efficient Förster resonance energy transfer (FRET) from mPPE‐Ala to aggregated 1 molecules and strong ³MMLCT emission have been found, while the less strong PPE‐SO₃^?– 1 aggregates and probably more efficient PCT and Dexter TEBT quenching would account for the lack of ³MMLCT emission in the PPE‐SO₃^?– 1 ensemble.     

The Studies of the Resonance Raman Scattering and the Chemical Reactions Involved in the Gaseous Iodine Bromide Under Argon Ion Laser Light

The resonance Raman spectra of gaseous iodine bromide IBr have been studied with the excitation of various argon ion laser lines from 5017 to 4579Å. The fine structures of the fundamental and few overtones of IBr are also studied by various power of 4880Å laser line. The resonance Raman scattering is found to be strong as that of Br₂ and ICI. A new term “apparent spectroscopic temperature” is suggusted for the case of the resonance Raman scattering. The apparent spectroscopic temperatures measured in this cell show that the system is not in thermal equilibrium. Br₂ is the hottest and I₂ is the coldest. IBr is in the middle. Unfortunately, no chemical reaction enhanced phenomenon is found although there should be some chemical reactions occurring under the laser light. The initiating reaction is the photodissociation of the main component IBr which also has large absorptivity. Because of the non-crossing between the B³Π and the ¹Π states, the primary products of the photodissociation should be I and Br. The chemical reactions of I and Br with IBr follow. The reactions of I and IBr is endothermic but the reaction of Br with IBr is exothermic. Therefore vibrational hot Br₂ is produced and its apparent spectroscopic temperature should be higher. On the other hand, the apparent spectroscopic temperature of I₂ is lower.     

Raman,resonance Raman and infrared spectra of potassium uranyl croconate

The Raman, resonance Raman and IR spectra of potassium uranyl croconate, UO₂(H₂O)K₂(C₅O₅)₂ were obtained and interpreted. Several croconate modes are split indicating a substantial decrease in the oxocarbon symmetry, as is to be expected from a recent crystallographic investigation, revealing the coordination of the oxocarbon to be two non-equivalent UO²⁺₂ moieties in a monodentate fashion. In terms of vibrational frequency shifts it can be concluded that the UO²⁺₂ moiety behaves as an isolated oscillator.The resonance Raman results suggest that the strong band centered around 450 nm in the UV—vis spectrum should be assigned to a charge transfer transition from the oxocarbon to the uranyl ion. In fact, as resonance is approached, both uranyl and croconate modes are enhanced. It can also be inferred that the chromophore is rather delocalized into the oxocarbon ring, rather than localized in the carbonyl groups as previously observed for other croconate complexes.     

Synthesis, structure, electronic properties and thermal behavior of butadiynyl substituted phenylCr(CO)3-complexes

Butadiynyl-substituted η⁶-benzeneCr(CO)₃ complexes 3 are very efficiently prepared by a copper catalyzed coupling of the phenylacetylene complex 1 and bromo alkynes 2. The transmission of electronic effects through the butadiynyl bridge operates by resonance mechanisms as established by correlations between Hammett's σ_p, σ_R and σ_P⁺ parameters. Most interestingly, however, is an unusual thermal behavior that leads to intractable paramagnetic polymers of unknown structure. According to thermal analyses (thermal gravimetrical analysis, differential scanning calorimetry) the complexes 3 react in a thermal solid-state reaction under CO extrusion to give amorphous cross-linked polymers.     

Raman,spectra of matrix-isolated lead molecules

Raman spectra of lead molecules in low-temperature rare-gas matrices show that dimers and larger clusters are isolated. Besides 7 “normal” Raman bands, two strong resonance progressions are found with frequencies of 108.5 and 118.5 cm^?1 in Xe and 111 and 119 cm^?1 in Kr. The 110 cm^?1 peak is assigned to Pb₂, close to the frequency for the X-O⁺_g state of gaseous Pb₂.     

Anion Binding Properties of N-Confused Porphyrins at the Peripheral Nitrogen

Ni(II), Pd(II), and Cu(II) complexes of N-confused porphyrin (NCP) exhibit anion binding properties through a hydrogen bonding interaction at the peripheral NH of confused pyrrole ring. The binding constants of the tetrakis(pentafluorophenyl)-NCP metal complexes (1-M, M= Ni, Pd, Cu) for various halide anions in CH₂C1₂ increase in the order of F^? > Cl^? > Br^? > I^?, respectively. Zwitterionic resonance form of the NCP complexes as well as interactions between halide anions and a pentafluorophenyl group are suggested to be important for efficient anion binding.     

Non-radiative decay and mode mixing in benzene

The non-radiative decay of mixed vibronic states is studied using the Fermi resonance 6²l⁰−11² states in S₁ benzene as a prototype. A strong dependence on the mixing coefficient is exhibited, and the results are compared with the experimental data of Stephenson et al. to elucidate the nature of the mixed state.     

Mesoporous Au/TiO2 Nanocomposite Microspheres for Visible‐Light Photocatalysis

Mesoporous Au/TiO₂ nanocomposite microspheres have been synthesized by using a microemulsion‐based bottom‐up self‐assembly (EBS) process starting from monodisperse gold and titania nanocrystals as building blocks. The microspheres had large surface areas (above 270 m² g^?1) and open mesopores (about 5 nm), which led to the adsorption‐driven concentration of organic molecules in the vicinity of the microspheres. Au nanoparticles, which were stably confined within the microspheres, enhanced the absorption over the broad UV/Vis/NIR spectroscopic range, owing to their strong surface plasmon resonance (SPR); as a result, the Au nanoparticles promoted the visible‐light photo‐induced degradation of organic compounds.     

Resonance raman spectra and quantum yields of MoS42−

Resonance Raman scattering of MoS₄^2? was studied in aqueous solution by irradiating its strong 4700 Å absorption band with five different lines of an Ar⁺ laser. The vibrational structure of the resonance spectra is discussed. Cross sections and quantum yields for the total scattered radiation were determined using NO₃^? as an internal standard.     

Tetrafluoro-orthoperjodsäure und Joddioxidtrifluorid

Of the new iodine(VII) compounds HOIOF₄ and IO₂F₃ the preparation and chemical and physical properties are reported. According to the ¹⁹F nuclear magnetic resonance spectra, both exist in two non-separable isomeres. HOIOF₄ is a very strong acid. IO₂F₃ forms yellow needles, which are not wetted by water. Both are very strong oxidising species. IO₂F₃ is probably the first trigonal-bipyramidal molecule with two simultaneously existing isomeres.     

Detection and Characterization of a Novel Copper-Dependent Intermediate in a Lytic Polysaccharide Monooxygenase

Lytic polysaccharide monooxygenases (LPMOs) are copper-containing enzymes capable of oxidizing crystalline cellulose which have large practical application in the process of refining biomass. The catalytic mechanism of LPMOs still remains debated despite several proposed reaction mechanisms. Here, we report a long-lived intermediate (t_1/2=6–8 minutes) observed in an LPMO from Thermoascus aurantiacus (TaLPMO9A). The intermediate with a strong absorption around 420 nm is formed when reduced LPMO-Cu^I reacts with sub-equimolar amounts of H₂O₂. UV/Vis absorption spectroscopy, electron paramagnetic resonance, resonance Raman and stopped-flow spectroscopy suggest that the observed long-lived intermediate involves the copper center and a nearby tyrosine (Tyr175). Additionally, activity assays in the presence of sub-equimolar amounts of H₂O₂ showed an increase in the LPMO oxidation of phosphoric acid swollen cellulose. Accordingly, this suggests that the long-lived copper-dependent intermediate could be part of the catalytic mechanism for LPMOs. The observed intermediate offers a new perspective into the oxidative reaction mechanism of TaLPMO9A and hence for the biomass oxidation and the reactivity of copper in biological systems.