Size-Dependent π + π Combination Band Intensities of Polyynes CH ( = 1-9) Analyzed by the Local CCH Bending and the Linear Response Functions.

Polyynes (CH) show the unusually strong π + π combination bands in the infrared absorption spectra. We calculated them as the first overtone of the local CCH bending; the strong intensities are interpreted as a consequence of the large-amplitude bending vibration of the acidic acetylenic hydrogen combined with the size-dependent π electron conjugation. Our theoretical calculations show that the absorption intensity increases steadily and their increase rate is gradually slowed down by increasing the number of acetylene units up to = 9.

Graphical Transition Moment Decomposition and Conceptual Density Functional Theory Approaches to Study the Fundamental and Lower-Level Overtone Absorption Intensities of Some OH Stretching Vibrations.

The investigation of electron density migrations caused by molecular structure changes is of central importance in various fields of chemistry. To address this topic in general and to study absorption intensities of vibrations, we analyze sensitive dipole moment functions (DMFs) of a molecule by combining the linear response function of conceptual DFT and bond dipoles separated by the quantum theory of atoms in molecules with a graphical transition moment decomposition scheme. The fundamental intensities of OH stretching vibrations depend strongly on the substituents but only weakly on the molecular conformations.

Importance of the Parallel Component of the Transition Moments to the Π (5A') and Π (3A') Excited States of ICN in the Ã-Band Photodissociation.

ICN is one of the few simple triatomic molecules whose photodissociation mechanisms have been thoroughly investigated. Since it has a linear structure in the electronic ground state, the dissociation follows a photoexcitation at a linear or slightly bent structure. It is generally believed that the Ã-band consists of the dominant excitation to Π (4A') with the transition dipole moment (TDM) parallel to the molecular axis ( z), a slightly weaker transition to Π (5A', 4A″), and a much weaker transition to Π (3A', 2A″), both of the latter two having perpendicular TDMs.

Potential energy surfaces and nonadiabatic transitions in the asymptotic regions of ICN photodissociation to study the interference effects in the F and F spin-rotation levels of the CN products.

One of the most spectacular yet unsolved problems for the ICN -band photodissociation is the non-statistical spin-rotation F = N + 1/2 and F = N - 1/2 populations for each rotation level N of the CN fragment. The F /F population difference function f(N) exhibits strong N and λ dependences with an oscillatory behavior. Such details were found to critically depend on the number of open-channel product states, namely, whether both I ( P ) and I ( P ) are energetically available or not as the dissociation partner.

Calculation of photoionization differential cross sections using complex Gauss-type orbitals.

Accurate theoretical calculation of photoelectron angular distributions for general molecules is becoming an important tool to image various chemical reactions in real time. We show in this article that not only photoionization total cross sections but also photoelectron angular distributions can be accurately calculated using complex Gauss-type orbital (cGTO) basis functions. Our method can be easily combined with existing quantum chemistry techniques including electron correlation effects, and applied to various molecules.

Optimization of complex slater-type functions with analytic derivative methods for describing photoionization differential cross sections.

The complex basis function (CBF) method applied to various atomic and molecular photoionization problems can be interpreted as an L2 method to solve the driven-type (inhomogeneous) Schrödinger equation, whose driven term being dipole operator times the initial state wave function. However, efficient basis functions for representing the solution have not fully been studied. Moreover, the relation between their solution and that of the ordinary Schrödinger equation has been unclear.

Theoretical Study on the Photoelectron Spectra of Ln(COT): Lanthanide Dependence of the Metal-Ligand Interaction.

We have performed a theoretical analysis of the recently reported photoelectron (PE) spectra of the series of sandwich complex anions Ln(COT) (Ln = La-Lu, COT = 1,3,5,7-cyclooctatetraene), focusing on the Ln dependence of the vertical detachment energies. For most Ln, the π molecular orbitals, largely localized on the COT ligands, have the energy order of e < e < e < e as in the actinide analogues, reflecting the substantial orbital interaction with the Ln 5d and 5p orbitals. Thus, it would be expected that the lanthanide contraction would increase the orbital interaction so that the overlaps between the COT π and Ln atomic orbitals tend to increase across the series.

Quantum Interference Effects Theoretically Found in the Photodissociation Processes of the Second Absorption Bands of ICl and IBr Molecules.

Some quantum interference effects are exposed directly in experiments, but others are not and remain just hidden and thus require thorough theoretical analysis to be exposed. In this respect, the second absorption bands of IX (X = Cl, Br) molecules show an interesting behavior in the photofragment anisotropy of the lowest I((2)P3/2)+X((2)P3/2) product channel; it changes from strongly parallel distribution on the shorter wavelength side to strongly perpendicular distribution on the longer wavelength side. Because the responsible perpendicular third Ω = 1 (1(III)) excited state correlating adiabatically to this product channel has only a weak absorption, the parallel component flux yielding the same products must be comparatively weak, even though the responsible parallel excitations to the 0(+)(III) and/or 0(+)(IV) excited states have strong absorptions.

Near IR Emitting Red-Shifting Ratiometric Fluorophores Based on Borondipyrromethene.

Two distyryl-BODIPY-based NIR red-shifting ratiometric fluorescent probes are reported: KBHR-1 for pH and KBAHgR-1 for Ag(+) and Hg(2+). KBHR-1 showed a red-shifting ratiometric response to pH in the NIR region. The identical fluorophore core structure applied to KBAHgR-1 with a different recognition moiety resulted in a ratiometric response to Ag(+) and Hg(2+) in the NIR region.

Interpretation of semiclassical transition moments through wave function expansion of dipole moment functions with applications to the OH stretching spectra of simple acids and alcohols.

Semiclassical description of molecular vibrations has provided us with various computational approximations and enhanced our conceptual understanding of quantum mechanics. In this study, the transition moments of the OH stretching fundamental and overtone intensities (Δv = 1-6) of some alcohols and acids are calculated by three kinds of semiclassical methods, correspondence-principle (CP) approximation, quasiclassical approximation, and uniform WKB approximation, and their respective transition moments are compared to those by the quantum theory. On the basis of the local mode picture, the one-dimensional potential energy curves and the dipole moment functions (DMFs) were obtained by density functional theory calculations and then fitted to Morse functions and sixth-order polynomials, respectively.

Why does the IR spectrum of hydroxide stretching vibration weaken with increase in hydration?

The infrared absorption intensity of hydroxide stretching vibration is strong in the gas phase, however it becomes weak in the aqueous phase. To provide an understanding of this relationship, we performed theoretical studies on OH(-)(H2O)n, n = 0-5 clusters, with the water molecules bound to the oxygen edge of the hydroxide. We found that with the increase in n, the infrared intensity of hydroxide stretching vibration decreases.

Investigation of the electronic structures of organolanthanide sandwich complex anions by photoelectron spectroscopy: 4f orbital contribution in the metal-ligand interaction.

The electronic structures of lanthanide (Ln) ions sandwiched between 1,3,5,7-cyclooctatetraene (COT), Ln(COT)2(-), have been investigated by anion photoelectron spectroscopy. Complexes of 12 Ln atoms were investigated (excluding promethium (Pm), europium (Eu), and ytterbium (Yb)). The 213 nm photoelectron (PE) spectra of Ln(COT)2(-) exhibit two peaks assignable to the highest occupied molecular orbital (HOMO; e2u) and the next HOMO (HOMO-1; e2g) approximately at 2.

Formation and electronic structures of organoeuropium sandwich nanowires.

Organoeuropium sandwich clusters, comprising europium (Eu) and 1,3,5,7-cyclooctatetraene (COT) (Eu(n)(COT)(m)), were produced in the gas phase using a laser vaporization synthesis method. Photoionization mass spectra revealed an exclusive Eu(n)(COT)(m) formation with three compositions: m = n + 1, m = n, and m = n - 1, which, we propose, correspond to full-sandwich, half-sandwich, and inverted-sandwich structures, respectively. The charge distributions, metal-ligand bonding characteristics, and electronic structures of the clusters were comprehensively investigated by photoionization measurements of Eu(n)(COT)(m) neutrals and by photoelectron spectroscopy of Eu(n)(COT)(m)(-) and isoelectronic Ba(n)(COT)(m)(-) anions.

Theoretical analysis of weak adjacent substituent effect on the overtone intensities of XH (X = C, O) stretching vibrations.

It is known that the overtone intensities of some set of OH and CH stretching vibrations show only a weak dependence on the adjacent substituent, in sharp contrast to the much stronger dependence of their fundamental intensities. To understand this characteristic, we calculated the fundamental and overtone intensities of the Δv = 1-6 transitions for the OH stretching of alcohols and acids and the CH stretching of hydrocarbons with different types of hybridization. Based on the local-mode model, from the three components of the dipole moment function (DMF) of each molecule, a one-component effective DMF that recovered about 95% of the total intensity for the Δv = 1-6 transitions was constructed and expressed as a sixth-order polynomial of the bond displacement ΔR, with the leading expansion coefficients M1, M2, and M3 for the linear, quadratic, and cubic terms, respectively.

Theoretical study on the f-f transition intensities of lanthanide trihalide systems.

The photoabsorption intensities of intra-4f(N) transitions (f-f transitions) in lanthanide systems have been extensively studied with the semiempirical Judd-Ofelt theory. The oscillator strengths of most f-f transitions are insensitive to a change of surrounding environment because 4f electrons are shielded by closed-shell 5s and 5p electrons from outside. However, there are some exceptional transitions, so-called hypersensitive transitions, whose intensities are very sensitive to a change of surrounding environment, and the reason for this hypersensitivity has not been clarified.

Photoionization cross sections of H2(+) and H2 with complex Gaussian-type basis functions optimized for the frequency-dependent polarizabilities.

Within the framework of the complex basis function method, the photoionization cross sections of H(2)(+) and H(2) were calculated based on the variational principle for the frequency-dependent polarizabilities. In these calculations, complex orbital exponents of Gaussian-type basis functions for the final state continuum wavefunctions were fully optimized for each photon energy with the numerical Newton-Raphson method. In most cases, the use of only one or two complex Gaussian-type basis functions was enough to obtain excellent agreement with previous high precision calculations and available experimental results.

Photoionization cross sections with optimized orbital exponents within the complex basis function method.

We show a new direction to expand the applicability of the complex basis function method for calculating photoionization cross sections through the imaginary part of the frequency-dependent polarizability. Based on the variational stability of the frequency-dependent polarizability, we made nonlinear optimizations of complex orbital exponents in basis functions representing continuum wave functions, and obtained fairly accurate results for H atom with only one or two complex basis functions particularly with dipole velocity gauge. Results were almost independent of whether Slater-type or Gaussian-type orbitals are used, implying the applicability to general many electron problems.

Stern-Gerlach experiments of one-dimensional metal-benzene sandwich clusters: Mn(C6H6)m (M = Al, Sc, Ti, and V).

A molecular beam of multilayer metal-benzene organometallic clusters Mn(C6H6)m (M = Al, Sc, Ti, and V) was produced by a laser vaporization synthesis method, and their magnetic deflections were measured. Multidecker sandwich clusters of transition-metal atoms and benzene Scn(C6H6)n+1 (n = 1, 2) and Vn(C6H6)n+1 (n = 1-4) possess magnetic moments that increase monotonously with n. The magnetic moments of Al(C6H6), Scn(C6H6)n+1, and Vn(C6H6)n+1 are smaller than that of their spin-only values as a result of intracluster spin relaxation, an effect that depends on the orbital angular momenta and bonding characters of the orbitals containing electron spin.

Photodissociation of gas-phase I3-: comprehensive understanding of nonadiabatic dissociation dynamics.

Photodissociation of the gas-phase tri-iodide anion, I3-, was investigated using photofragment time of flight (TOF) mass spectrometry combined with the core extraction method. An analysis of the TOF profiles provided the kinetic energy and angular distributions of photofragment ions and photoneutrals, from which the photoproduct branching fractions were determined in the excitation energy range of 3.26-4.

Lanthanide organometallic sandwich nanowires: formation mechanism.

A molecular beam of europium-cyclooctatetraene sandwich nanowires Eu(n)()(COT)(m)() was produced by a laser vaporization synthesis method. The formation mechanism of the nanowires was quantitatively revealed by photoelectron and photoionization spectroscopies of the Eu-COT species, together with supporting theoretical calculations. From these results, it is confirmed that growth processes extending the length of Eu-COT nanowires involve a series of elementary reactions in which efficient charge transfer occurs at the terminal reaction sites.

Effective one-dimensional dipole moment function for the OH stretching overtone spectra of simple acids and alcohols.

To gain insight on the absorption intensities, as well as the direction of the transition moment for the OH stretching vibration in alcohols and acids, we performed detailed analyses for nitric acid, acetic acid, methanol, tert-butyl alcohol, water, and OH radical. We obtained both the potential energy surface and the dipole moment function (DMF) by the B3LYP method and performed quantum mechanical vibrational calculation using the grid variational method based on the local mode model. In this work, we employed the sum rule of the absorption intensities for the one-dimensional (1-D) vibrational Hamiltonian to construct an effective 1-D DMF, which is responsible for the total sum of the overtone intensities.

Geometric and electronic structures of multiple-decker one-end open sandwich clusters: Eu(n)(C8H8)n- (n = 1-4).

We have measured the photoelectron spectra of the multiple-decker 1:1 sandwich clusters of Eu(n)(COT)n- (n = 1-4; COT = 1,3,5,7-cyclooctatetraene), synthesized in the gas phase, and studied theoretically the bonding scheme, charge distribution, valence orbital energies, and photodetachment energies. We calculated the ground electronic state X- and the first excited electronic state A-, both of which have strong ionic bonding and a characteristic charge distribution. Moreover, we found that the valence orbital energies of Eu (6s) and COT (L delta) depend strongly on cluster size and their positions in the clusters.

Ferromagnetism in one-dimensional vanadium-benzene sandwich clusters.

A molecular beam of multilayer vanadium-benzene organometallic complexes Vn(C6H6)m was produced by a laser vaporization synthesis method. The magnetic moments of the complexes were measured by a molecular beam magnetic deflection technique, and were found to increase with the number of vanadium atoms in the cluster, showing that the unpaired electrons, which occupy the nonbonding dsigma orbitals localized on the metal atoms, couple ferromagnetically. These sandwich species represent a new class of one-dimensional molecular magnets in which the transition metal atoms are formally zerovalent.

Detachable immobilization of liposomes on polymer gel particles.

Immobilization of liposomes on hydrophobized Sephacryl gel and controlled detachment of the liposomes from the gel were examined. The gel was chemically modified and bore octyl, hexadecyl or cholesteryl moiety via disulfide linkage as anchors to liposomal bilayer membrane. Upon interaction with the gel, egg phosphatidylcholine liposomes were successfully immobilized onto the gel.

Theoretical study on the photochromic cycloreversion reactions of dithienylethenes; on the role of the conical intersections.

The mechanism of the photochromic cycloreversion reactions is theoretically examined in a model system of dithienylethenes by means of the CASSCF and CASPT2 methods. The structures of its conical intersections (CIs), which are the branching points of the internal conversions, were obtained. The analyses of the minimum energy paths from the Franck-Condon states and the CI points suggest that the cycloreversion reaction occurs during the intramolecular vibrational energy redistribution (IVR) toward the quasi-equilibrium on the 2A state.