Femtosecond vibrational dynamics of self-trapping in a quasi-one-dimensional system

We have directly time resolved the lattice motions associated with the formation of the self-trapped exciton in the quasi-one-dimensional system [Pt(en)(2)] [Pt(en)2Br2];(PF6)(4) ( en = ethylene-diamine, C2H8N2), using femtosecond impulsive excitation techniques. A strongly damped, low-frequency wave packet modulation at approximately 110 cm(-1) accompanies the formation of the self-trapped exciton on a approximately 200 fs time scale following excitation of the intervalence charge-transfer transition. Coherent oscillations at the ground state vibrational frequency and its harmonics are also detected.     

Real-time capturing of the nuclear wave-packet shape in self-trapped excitons

We measured the time evolutions of the luminescence spectra in a quasi-1D halogen-bridged platinum complex [Pt(en)(2)][Pt(en)(2)Br(2)](ClO4)(4) with a 50 fs resolution up-conversion spectroscopy and succeeded in real-time visualization of the shape of the wave packet (WP) propagating on the adiabatic potential surface of a self-trapped exciton. The behavior of the WP is in excellent agreement with a calculation based on a harmonic oscillator. We have found that the damping of the WP oscillation is highly nonexponential.     

The Electroabsorption in Quasi-One-Dimensional Halogen-Bridged Mixed-Valence Platinum Complexes

The electroa bsorp tion spectra of the halogen- bridged mixed-valence Pt complexes, [Pt(en)₂][Pt(en)₂X₂] (ClO₄)₄(X = Cl, Br, I) (HMPC's) (en=ethylenediarnine) are calculated using Maxwell equations and dipole approximation, taking into account of the ground state and odd and even charge-transfer (CT) excitons, and only one phonon is involved. The modulation mechanism is quantitatively explained by the electric-field-induced mixing between the odd and the even CT excitons. It agrees with the measured data.     

Novel optical and magnetic bistability and photoinduced transition in a one-dimensional halogen-bridged binuclear pt complex

In iodine-bridged binuclear Pt compounds, R(4)[Pt(2)(pop)(4)I]nH(2)O and R(')(2)[Pt(2)(pop)(4)I]nH(2)O (pop=P(2)O5H2-2), electronic structures on the PtPtI chains have been controlled between a diamagnetic charge-density-wave (CDW) state and a paramagnetic charge-polarization (CP) state by modification of the counterions (R, R') located between chains. In the R=(C2H5)2NH+2 compound, a pressure-induced CP to CDW transition with a drastic color change is identified. This transition is accompanied by a large hysteresis loop within which photoinduced transition between CDW and CP can be driven by selecting the excitation photon energy.     

Soliton wall superlattice in the quasi-one-dimensional conductor (Per)(2)Pt(mnt)(2)

We suggest a model to explain the appearance of a high resistance high magnetic field charge-density-wave (CDW) phase, discovered by Graf et al. [Phys. Rev. Lett. 93, 076406 (2004)10.1103/PhysRevLett.93.076406] in (Per)(2)Pt(mnt)(2), where Per is perylene and mnt is maleonitriledithiolate molecules. In particular, we show that the Pauli spin-splitting effects improve the nesting properties of a realistic quasi-one-dimensional electron spectrum and, therefore, a high resistance Peierls CDW phase is stabilized in high magnetic fields. In low and very high magnetic fields, a periodic soliton wall superlattice (SWS) phase is found to be a ground state. We suggest experimental studies of the predicted phase transitions between the Peierls and SWS CDW phases in (Per)(2)Pt(mnt)(2) to discover a unique SWS phase.     

NMR paramagnetic relaxation enhancement: test of the controlling influence of zfs rhombicity for S = 1

Prior theoretical work has predicted that the NMR paramagnetic relaxation enhancement (NMR-PRE) produced by electron spin S = 1 ions is highly sensitive to orthorhombic terms in the static zero field splitting (zfs) tensor. Zfs orthorhombicity (which implies chemical inequivalence of the three principal directions of the zfs-principal axis system and is described by the zfs E-parameter) is predicted to suppress the NMR-PRE profoundly relative to the reference cylindrical zfs-limit situation. This expectation was tested experimentally by a comparison of the zfs-limit NMR-PRE produced by [Ni(II)(en)(3)](2+) (en = ethylenediamine), a trigonal complex which lacks zfs-rhombicity, with the zfs-limit NMR-PRE produced by two orthorhombic complexes, [Ni(II)(en)(2)(H(2)O)(2)](2+) and [Ni(II)(en)(H(2)O)(4)](2+). As predicted, the zfs-limit NMR-PRE produced by the orthorhombic complexes in the proton resonance of a dioxane probe species in the solvent was strongly suppressed (by factors of approximately 5 and 7, respectively) relative to the comparable measurement on the trigonal complex. The suppression of the NMR-PRE due to the orthorhombic zfs terms is counteracted by an applied Zeeman field, leading to a predicted rise in the NMR-PRE with increasing Zeeman field strength; this rise occurs when the Zeeman energy is comparable to the orthorhombic zfs splitting, 2E. This second prediction of theory was likewise confirmed: the expected rhombicity-induced magnetic field dependence in the NMR-PRE was observed for the orthorhombic complexes but not for the trigonal complex.     

飞秒时间分辨质谱和光电子影像对分子激发态动力学的研究

分子量子态的研究,特别是分子激发态演化过程的研究不仅可以了解分子量子态的基本特性和量子态之间的相互作用,而且可以了解化学反应过程和反应通道间的相互作用.飞秒时间分辨质谱和光电子影像是将飞秒抽运-探测分别与飞行时间质谱和光电子影像相结合的超快谱学方法,为实现分子内部量子态探测,研究分子量子态相互作用及超快动力学过程提供了强有力的工具,可以在飞秒时间尺度下研究单分子反应过程中的光物理或光化学机理.本文详细介绍了飞秒时间分辨质谱和光电子影像的技术原理,并结合本课题组的工作,展示了这两种方法在量子态探测及相互作用研究领域,特别是激发态电子退相、波包演化、能量转移、分子光解动力学以及分子激发态结构动力学研究中的广泛应用.最后,对该技术的发展前景以及进一步的研究工作和方向进行了展望.     

Study of the Heterocyclic-Substituted Platinum-1,2-Enedithiolate 3ILCT Excited States by Transient Absorption Spectroscopy

The photoluminescent 1,2-enedithiolate complexes, (dppe)Pt{S₂C₂(2-quinoxaline)(H)}, [L₂Pt{S₂C₂(2-pyridinium)(H)}]⁺ where L₂ = dppm and dppe, [L₂Pt{S₂C₂(4-pyridinium)(H)}]⁺, [L₂Pt{₂C₂(N-Methyl-4-pyridinium)(H)}]⁺ and [L₂Pt{S₂C₂(CH₂CH₂-N-2-pyridinium)}]⁺ where L₂ = dppm, dppe, and dppp are room temperature dual emitters where the emissions have thiolate to heterocycle * intraligand charge transfer character (ILCT) singlet and triplet character. The pyridinium complexes have strong triplet-triplet absorption bands at approximately 400, 520 and 630 nm with a weaker band at 800 nm while (dppe)Pt{S₂C₂(2-quinoxaline)(H)} has strong triplet-triplet absorption bands at 385 and 550 nm with weaker bands at 610 and 805 nm. By fitting the decay of the transients to single exponential kinetics, the ³ILCT* lifetimes of the pyridinium complexes where determined to be 0.7 to 15.9 s (DMSO) while the ₃ILCT* lifetime of (dppe)Pt{S₂C₂(2-quinoxaline)(H)} was determined to be 2.8 s (CH₃CN). The transient absorption spectra of the complexes is affected by the appended heterocycle rather than the bulk of ancillary phosphine ligand or whether the heterocycle is protonated or alkylated.     

Modulation of third-harmonic generation conversion in the presence of a rotational wave packet

We report a modulation of third-harmonic generation (THG) owing to a rotational coherence in CO(2). The variation in conversion efficiency is mostly attributed to the dependence of chi(3)(tau) on the molecular alignment. THG via type I processes mainly depends on chi(3)(tau), while type II processes are influenced by the wave packet owing to both chi(3)(tau) and Delta k(tau). Observation of the generated third harmonic also shows significant changes of the polarization state owing to the birefringence induced by the rotational wave packet. Numerical modeling shows good qualitative agreement with the experimental data.     

Improved O2 sensing performance by modifying P–P ligand in [Cu(N–N)(P–P)] complex

In this paper, a diamine ligand of 2-(5-phenyl-[1,3,4]oxadiazol-2-yl)-pyridine (OP) and its corresponding Cu(I) complex of [Cu(OP)(POP)]BF₄ with bis(2-(diphenylphosphanyl)phenyl) ether (POP) as the phosphorous ligand are synthesized. Full characterization on [Cu(OP)(POP)]BF₄, including NMR, elemental analysis and single crystal analysis, confirms its molecular identity. Upon photon excitation, the emission of [Cu(OP)(POP)]BF₄ owns a long excited state lifetime of 42.92 μs and shows a maximum at 570 nm, under pure N₂ atmosphere. Theoretical calculation on [Cu(OP)(POP)]BF₄ single crystal suggests that the excited state has a triplet metal-to-ligand-charge-transfer character. By embedding [Cu(OP)(POP)]BF₄ into a optical silica supporting matrix of MCM-41, the emission signal is found to be sensitive towards various oxygen concentrations, with a maximum sensitivity of 7.31 (sensitivity=luminescence intensity in O₂ medium/luminescence intensity in N₂ medium). This improved sensitivity value compared with literature values is attributed to the introduction of POP ligand, which can suppress the intermolecular aggravation between [Cu(OP)(POP)]BF₄ molecules and favor the oxygen attack on [Cu(OP)(POP)]BF₄ excited state. Due to the same reason, a short response time is also observed with stable quenching signal.     

Ultrafast dynamics of a charge-transfer dimer as a model for the photoinduced phase transition of charge-transfer compounds

By applying ultrafast pump-probe spectroscopy with 15 fs temporal resolution to (TMTTF(+))(2) dimers we provide a full picture of the structural relaxation following photoexcitation of their CT transition. Both population and coherent phonon dynamics allow tracking wave packet motion onto the multidimensional excited state potential energy surface, as obtained by density functional theory calculations. We show that the vibrations that are strongly coupled to the charge-transfer transition of the dimer correspond to those driving the photoinduced phase transition occurring in charge-transfer crystalline solids.     

Thermally generated gauge singlet scalars as self-interacting dark matter

We show that a gauge singlet scalar S, with a coupling to the Higgs doublet of the form lambda(S)S+SH+H and with the S mass entirely generated by the Higgs expectation value, has a thermally generated relic density Omega(S)approximately equal to 0.3 if m(S)approximately equal to (2.9-10.5) (Omega(S)/0.3)(1/5)(h/0.7)(2/5) MeV. Remarkably, this is very similar to the range [m(S) = (6.6-15.4)eta(2/3) MeV] required in order for the self-interaction (eta/4) (S+S)(2) to account for self-interacting dark matter when eta is not much smaller than 1. The corresponding coupling is lambda(S)approximate(2.7 x 10(-10)-3.6 x 10(-9)) (Omega(S)/0.3)(2/5)(h/0.7)(4/5), implying that such scalars are very weakly coupled to the standard model sector.     

Theory of dynamics of electron wave packets in time-resolved two-photon photoemission via image states

Time-resolved two-photon photoemission (TR2PPE) from the Cu(100) surface is investigated by the Keldysh Green function method in order to analyze ultrafast dynamics of an electron wave packet in the image states of the surface. By numerical analysis, the quantum beats in the TR2PPE spectrum due to interference among the image states are reproduced, and the motion of the electron wave packet in front of the surface is demonstrated. It is discussed on the basis of the obtained results as to how the motion of the electron wave packet is evaluated from the TR2PPE spectrum.     

Solid state multinuclear NMR study of sigma-acetylide complexes of platinum, trans-[ClPt(PnBu3)2-C=C-p-C6H4-C=C-Pt(PnBu3)2Cl] and trans-[-Pt(PnBu3)2-C=C-p-C6H4-C=C-]n.

Solid state 13C, 31P and 195Pt NMR has been employed to study the electronic and geometric structure of the dimeric and polymeric sigma-acetylide complexes of platinum, trans-[ClPt(PnBu3)2-C identical to C-p-C6H4-C identical to C-Pt(PnBu3)2Cl] and trans-[-Pt(PnBu3)2-C identical to C-p-C6H4-C identical to C-]n. The 195Pt shielding tensor has been measured and analysed to reveal details about the electronic properties of the Pt-ligand bonds.     

Theoretical studies and antibacterial activity for Schiff base complexes

New ligand 4‐((2‐Hydroxy1‐naphthyl) methylene amino)‐1.5‐dimethyl‐2‐phenyl‐1H‐pyrazol‐3(2H)‐one (HL) was synthesized from the reaction of 2‐hydroxy‐1‐naphthaldehyde and 4‐aminophenaz one. A complexes of this ligand [VO(II)(HL)(SO₄)], [Pt(IV)(L)Cl₃], [Re(V)(L)Cl₃]Cl, and [M(II)(L)Cl] (M═Pd(II), Ni(II), Cu(II)) were synthesized. The resulted compounds were characterized by IR, NMR (¹H and ¹³C), mass spectrometry, element analysis, and UV‐Vis spectroscopy. Additionally, the spectroscopic studies revealed octahedral geometries for the Re(V), Pt(IV) complexes, and square pyramidal for VO(II), square planar for Pd(II) complex, and tetrahedral for the Ni(II) and Cu(II) complexes. Thermodynamic parameters (ΔE^*, ΔH^*, ΔS^*, ΔG^*, and K) were calculated using from the TGA curve Coats‐Red fern method. Therefore, hyper Chem‐8 program has been used to predict structural geometries of compounds in the gas phase. Finally, the synthesized Schiff base and its metal complexes were screened for their biological activity against bacterial species, 2 Gram‐positive bacteria (Bacillus subtilis and Staphylococcus aureus) and 2 Gram‐negative bacteria (Escherichia coli and Pseudomonas aeruginosa).     

Ultrafast solvent-induced spin-flip and nonadiabatic coupling: ClF in argon solids

Femtosecond pump-probe spectra show direct evidence for ultrafast solvent-induced spin flip in photodissociation-recombination events of ClF, a light diatomic molecule, for which the spin-orbit coupling is weak. The bound triplet states ((3)Pi) of ClF are probed and the dynamics for excitation to the singlet state ((1)Pi(1)) is compared with excitation to the triplet state B((3)Pi(0)). The population initially excited to the singlet state (1)Pi(1) is transferred to the bound triplet states (3)Pi within tau(f)=0.5 ps. Oscillations in the spectra indicate wave packet dynamics with the triplet state period of 300 to 400 fs in both cases. According to simulations of F(2)/Ar, most of the initially excited singlet state population is converted to repulsive and weakly bound triplet states within approximately 60 fs. In the first ps, 40% of the triplet population accumulates in the weakly bound (3)Pi states, in good accord with the experiment.     

醋酸铜和多氮杂环配体配合物的低热固相合成

室温下 ,醋酸铜分别与 1,2 ,4 三氮唑和苯并三氮唑充分研磨 ,能发生固相配位反应 ,研磨过程有醋酸逸出 ,杂氮配体取代了醋酸与Cu (Ⅱ )配位形成混配配合物 ,元素分析表征表明产物的组成为Cu(C2 H2 N3) (Ac)·H2 O和Cu (C6 H4 N3) (Ac)·H2 O。红外光谱图显示了杂氮配体的 CN ,醋酸的 CO 和水的O—H特征吸收。固相反应为合成新配合物提供了一条快速、温和及不需溶剂的途径。     

Exploration of magnetic field generation of H32+ by direc ionization and coherent resonant excitation

Coherent electronic dynamics are of great significance in photo-induced processes and molecular magnetism. We theoretically investigate electronic dynamics of triatomic molecule H₃²⁺ by circularly polarized pulses, including electron density distributions, induced electronic currents, and ultrafast magnetic field generation. By comparing the results of the coherent resonant excitation and direct ionization, we found that for the coherent resonant excitation, the electron is localized and the coherent electron wave packet moves periodically between three protons, which can be attributed to the coherent superposition of the ground A' state and excited E⁺ state. Whereas, for the direct single-photon ionization, the induced electronic currents mainly come from the free electron in the continuum state. It is found that there are differences in the intensity, phase, and frequency of the induced current and the generated magnetic field. The scheme allows one to control the induced electronic current and the ultrafast magnetic field generation.     

Pt纳米微粒自组装体系的电化学和原位FTIR反射光谱研究

用化学还原法制备了铂金属纳米微粒 ,透射电子显微镜 (TEM)表征纳米Pt微粒的平均直径为 2 5nm。通过二硫醇将Pt纳米微粒组装到多晶金电极表面。以Fe(CN) 4- 3-6 的氧化还原作为探针反应的电化学研究表明 ,Au表面组装二硫醇后抑制了电极 /溶液界面的电子传递过程 ,而在二硫醇上再组装铂纳米微粒后 ,电子传递又可进行。运用电化学FTIR反射光谱研究了Pt纳米微粒组装电极在酸性介质中CO的吸附 ,检测到CO的线型、桥式吸附态 ,分别在 2 0 30和 184 5cm- 1 附近给出红外吸收谱峰 ,并且有增强红外效应。此外 ,还观察到Pt纳米微粒上的CO孪生吸附态。红外吸收峰位于 2 10 0cm- 1 附近。     

Control the revisit time of the electron wave packet

Ionization of molecules by strong laser fields launches an electron wave packet. This electron wave packet, which can be driven back by the field to recollide with the parent ion, has been widely explored to probe the ultrafast nuclear dynamics. We numerically demonstrate the precise control of the temporal characteristic of the recolliding electron wave packet (REWP) by orthogonally polarized two-color fields. Through changing the relative phase of the two fields, the revisit time of REWP can be manipulated with a resolution of less than 200 attos, thus significantly improving the resolution of the well known molecular clock. This provides an efficient method for real-time observation of the ultrafast molecular dynamics with attosecond resolution.