Coordination Geometrical Effect on Ligand-to-Metal Charge Transfer-Dependent Energy Transfer Processes of Luminescent Eu(III) Complexes.

Photophysical properties of europium (Eu(III)) complexes are affected by ligand-to-metal charge transfer (LMCT) states. Two luminescent Eu(III) complexes with three tetramethylheptadionates (tmh) and pyridine (py), [Eu(tmh)3(py)1] (seven-coordinated monocapped-octahedral structure) and [Eu(tmh)3(py)2] (eight-coordinated square antiprismatic structure), were synthesized for geometrical-induced LMCT level control. Distances between Eu(III) and oxygen atoms of tmh ligands were estimated using single-crystal X-ray analyses. The contribution percentages of π-4f mixing in HOMO and LUMO at the optimized structure in the ground state were calculated using DFT (LC-BLYP). The Eu-O distances and their π-4f mixed orbitals affect the energy level of LMCT states in Eu(III) complexes. The LMCT energy level of an eight-coordinated Eu(III) complex was higher than that of a seven-coordinated Eu(III) complex. The energy transfer processes between LMCT and Eu(III) ion were investigated using temperature-dependent and time-resolved emission lifetime measurements of 5D0 → 7FJ transitions of Eu(III) ions. In this study, the LMCT-dependent energy transfer processes of seven- and eight-coordinated Eu(III) complexes are demonstrated for the first time.

All-electron relativistic spin-orbit multireference computation to elucidate the ground state of CeH.

The all-electron relativistic spin-orbit multiconfiguration/multireference computations with the Sapporo basis sets were carried out to elucidate the characters of the low-lying quasi-degenerate electronic states for the CeH diatomic molecule. The present computations predict the ground state of CeH to be a pure quartet state of 4f15d1(5dσ-H1s)26s1 configuration (Ω = 3.5). The first excited state (Ω = 2.5) shows a doublet dominant of 4f1(5dσ-H1s)26s2 configuration at a short bond length while it changes to a quartet dominant at a long bond length. The Ce-H stretching fundamental frequency was calculated to be 1345 cm-1 in the ground state, which is in good agreement with the experimental value, 1271 cm-1, measured by a matrix-isolation technique.

All-electron relativistic computations on the low-lying electronic states, bond length, and vibrational frequency of CeF diatomic molecule with spin-orbit coupling effects.

Ab initio all-electron computations have been carried out for Ce+ and CeF, including the electron correlation, scalar relativistic, and spin-orbit coupling effects in a quantitative manner. First, the n-electron valence state second-order multireference perturbation theory (NEVPT2) and spin-orbit configuration interaction (SOCI) based on the state-averaged restricted active space multiconfigurational self-consistent field (SA-RASSCF) and state-averaged complete active space multiconfigurational self-consistent field (SA-CASSCF) wavefunctions have been applied to evaluations of the low-lying energy levels of Ce+ with [Xe]4f1 5d1 6s1 and [Xe]4f1 5d2 configurations, to test the accuracy of several all-electron relativistic basis sets. It is shown that the mixing of quartet and doublet states is essential to reproduce the excitation energies. Then, SA-RASSCF(CASSCF)/NEVPT2 + SOCI computations with the Sapporo(-DKH3)-2012-QZP basis set were carried out to determine the energy levels of the low-lying electronic states of CeF. The calculated excitation energies, bond length, and vibrational frequency are shown to be in good agreement with the available experimental data. © 2018 Wiley Periodicals, Inc.

Development of efficient time-evolution method based on three-term recurrence relation.

The advantage of the real-time (RT) propagation method is a direct solution of the time-dependent Schrödinger equation which describes frequency properties as well as all dynamics of a molecular system composed of electrons and nuclei in quantum physics and chemistry. Its applications have been limited by computational feasibility, as the evaluation of the time-evolution operator is computationally demanding. In this article, a new efficient time-evolution method based on the three-term recurrence relation (3TRR) was proposed to reduce the time-consuming numerical procedure. The basic formula of this approach was derived by introducing a transformation of the operator using the arcsine function. Since this operator transformation causes transformation of time, we derived the relation between original and transformed time. The formula was adapted to assess the performance of the RT time-dependent Hartree-Fock (RT-TDHF) method and the time-dependent density functional theory. Compared to the commonly used fourth-order Runge-Kutta method, our new approach decreased computational time of the RT-TDHF calculation by about factor of four, showing the 3TRR formula to be an efficient time-evolution method for reducing computational cost.

Effective Photosensitization in Excited-State Equilibrium: Brilliant Luminescence of TbIII Coordination Polymers Through Ancillary Ligand Modifications.

Molecular photosensitizers provide efficient light-absorbing abilities for photo-functional materials. Herein, effective photosensitization in excited-state equilibrium is demonstrated using five TbIII coordination polymers. The coordination polymers are composed of TbIII ions (emission center), hexafluoroacetylacetonato (photosensitizer ligands), and phosphine oxide-based bridges (ancillary ligands). The two types of ligand combinations induces a rigid coordination structure via intermolecular interactions, resulting in high thermal stability (with decomposition temperatures above 300 °C). Excited-triplet-state lifetimes of photosensitizer ligands (τ=120-1320 µs) are strongly dependent on the structure of the ancillary ligands. The photosensitizer with a long excited-triplet-state lifetime (τ≥1120 µs) controls the excited state equilibrium between the photosensitizer and TbIII , allowing the construction of TbIII coordination polymer with high TbIII emission quantum yield (≥70 %).

Effective Photosensitization in Excited-State Equilibrium: Brilliant Luminescence of TbIII Coordination Polymers Through Ancillary Ligand Modifications.

Invited for this month's cover are the collaborating groups of Yuichi Kitagawa, Yasuchika Hasegawa, Tetsuya Taketsugu, and co-workers at Hokkaido University. The cover picture shows a photosensitizer that has a long excited-state lifetime and provides strong emissions for TbIII coordination polymers. The photosensitization ability can be considerably altered by changing the ancillary ligands in the TbIII coordination polymers. The results provide new insights on the design of photosensitizers for improving the properties of photo-functional materials. More information can be found in the Research Article by Y. Kitagawa, Y. Hasegawa, and co-workers.

Reconsidering an analytical gradient expression within a divide-and-conquer self-consistent field approach: exact formula and its approximate treatment.

An analytical energy gradient formula for the density-matrix-based linear-scaling divide-and-conquer (DC) self-consistent field (SCF) method was proposed in a previous paper by Yang and Lee (YL) [J. Chem. Phys. 103, 5674 (1995)]. Since the formula by YL does not correspond to the exact gradient of the DC-SCF energy, we derive the exact formula by direct differentiation, which requires solving the coupled-perturbed equations while including the inter-subsystem coupling terms. Next, we present an alternative formula for approximately evaluating the DC-SCF energy gradient, assuming the variational condition for the subsystem density matrices. Numerical assessments confirmed that the DC-SCF energy gradient values obtained by the present formula are in reasonable agreement with the conventional SCF values when adopting a reliable buffer region. Furthermore, the performance of the present method was found to be better than that of the YL method.

Short-time Fourier transform analysis of real-time time-dependent Hartree-Fock and time-dependent density functional theory calculations with Gaussian basis functions.

We propose a novel analysis of real-time (RT) time-dependent Hartree-Fock and time-dependent density functional theory (TDHF/TDDFT) calculations using a short-time Fourier transform (STFT) technique. RT-TDHF/TDDFT calculations of model dimers were carried out and analyzed using the STFT technique, in addition to the usual Fourier transform (FT). STFT analysis revealed that the induced polarization propagated between the molecules through the intermolecular interaction; that is, it directly showed the electron dynamics of the excited system. The dependence of the propagation period on the intermolecular distance of the dimer was investigated. We also proved the possibility of describing, not just the valence, but also the core excitations by FT analysis of the RT-TDHF/TDDFT calculations of a formaldehyde monomer with Gaussian basis functions compared with conventional TDHF/TDDFT results.

Increase in secretion of glial cell line-derived neurotrophic factor from glial cell lines by inhibitors of vacuolar ATPase.

Glial cell line-derived neurotrophic factor (GDNF) was reported to be effective for treating subjects with neurodegenerative diseases such as Parkinson's disease. In search of finding a compound which promotes GDNF secretion, we found that concanamycin A (ConA), a vacuolar ATPase (V-type ATPase) inhibitor purified from Streptomyces diastatochromogens, enhanced GDNF secretion from glioma cells. The rat glioma cell line, C6, and the human glioma cell lines, U87MG and T98G, abundantly expressed GDNF mRNA, and secreted GDNF into culture media, and this event was potently enhanced by a Ca(2+) ionophore and by phorbol ester, as noted in other cells. ConA concentration dependently and potently increased GDNF release from C6, U87MG and T98G cells into culture media. In addition, ConA enhanced GDNF secretion from astrocyte primary cultures prepared from the human fetus with the same potency seen in glioma cell lines. Likewise, another V-type ATPase inhibitor, bafilomycinA1 facilitated GDNF release from C6, U87MG and T98G glioma cells, in a concentration-dependent manner. The potencies of these V-type ATPase inhibitors in enhancing GDNF secretion were consistent with those which inhibited V-type ATPase activity. These results suggest that blockade of V-type ATPase potently stimulates the secretion of GDNF from glial cells. The V-type ATPase inhibitors may be beneficial to use for the treatment of diseases in which increase in GDNF could be effective.

Implementation of divide-and-conquer method including Hartree-Fock exchange interaction.

The divide-and-conquer (DC) method, which is one of the linear-scaling methods avoiding explicit diagonalization of the Fock matrix, has been applied mainly to pure density functional theory (DFT) or semiempirical molecular orbital calculations so far. The present study applies the DC method to such calculations including the Hartree-Fock (HF) exchange terms as the HF and hybrid HF/DFT. Reliability of the DC-HF and DC-hybrid HF/DFT is found to be strongly dependent on the cut-off radius, which defines the localization region in the DC formalism. This dependence on the cut-off radius is assessed from various points of view: that is, total energy, energy components, local energies, and density of states. Additionally, to accelerate the self-consistent field convergence in DC calculations, a new convergence technique is proposed.

Second-order Møller-Plesset perturbation energy obtained from divide-and-conquer Hartree-Fock density matrix.

The density matrix (DM) obtained from Yang's [Phys. Rev. Lett. 66, 1438 (1991)] divide-and-conquer (DC) Hartree-Fock (HF) calculation is applied to the explicit second-order Møller-Plesset perturbation (MP2) energy functional of the HF DM, which was firstly mentioned by Ayala and Scuseria [J. Chem. Phys. 110, 3660 (1999)] and was improved by Surján [Chem. Phys. Lett. 406, 318 (2005)] as DM-Laplace MP2. This procedure, termed DC-DM MP2, requires the HF DM of holes, for which we propose two evaluation schemes in DC manner. Numerical studies reveal that the DC-DM MP2 energy deviation from canonical MP2 is the same order of magnitude as DC-HF energy deviation from conventional HF whichever type of hole DM is adopted. It is also confirmed that the central processing unit time of DC-DM MP2 is less than that of DM-Laplace MP2 because the DC-HF DM is sparser than conventional DM.

Biological evaluation of sphingomyelin analogues as inhibitors of sphingomyelinase.

Seeking neutral sphingomyelinase inhibitors, we designed and synthesized hydrolytically stable analogues of sphingomyelin. These novel analogues replace the phosphodiester moiety of sphingomyelin with carbamate and urea moiety, resulting in inhibition of neutral sphingomyelinase. Compound 1 prevented ceramide generation and apoptotic neuronal cell death in a model of ischemia based on organotypic hippocampal slice cultures.

Sphingomyelin analogues as inhibitors of sphingomyelinase.

To search for neutral sphingomyelinase inhibitors we designed and synthesized hydrolytically stable analogues of sphingomyelin. The novel compounds 8 and 9 which were replaced the phosphodiester moiety of sphingomyelin with the carbamate moiety showed inhibitory activity with an IC(50) value of micro M on neutral sphingomyelinase in rat brain microsomes. Compound 8i showed a selective neutral sphingomyelinase inhibitory activity.