Takashiro Akitsu

Triply phenoxo bridged Eu(III) and Sm(III) complexes with 2,6-diformyl-4-methylphenol-di(benzoylhydrazone): structure, spectra and biological study in human cell lines

Two dinuclear lanthanide(III) complexes, [M2(HL)3] (M = Sm(III) (1), Eu(III) (2); H3L, 2,6-diformyl-4-methylphenol-di(benzoylhydrazone)) were generated with good yield and characterised systematically. The single crystal X-ray structure determination of [Eu2(HL)3] (2) confirmed the tricapped trigonal prismatic geometry of the N3O6 coordination environment around europium. Indeed, Eu(1) and Eu(2) are bridged by phenolato-O belonging to the p-cresol ring, by deprotonated ‘enol’ groups from the benzoyl hydrazide part and by the imine-N centres. A temperature dependent magnetic study suggested that anti-ferromagnetic coupling occurs between the two Eu(III) ions and the magnetic moment was found to vary from 0.48 B.M. at 5 K to 3.03 B.M. at 300 K. Electron paramagnetic resonance spectroscopy confirmed that anti-ferromagnetic coupling occurs between the atoms of Eu(III) and Sm(III). Both the complexes show emission in the visible range. The ligand, H3L and the complexes exhibit anti-mycobacterial activity against M. tuberculosis H37Rv (ATCC 27294) and M. tuberculosis H37Ra (ATCC 25177) strains. The molecular docking of H3L with the enoyl acyl carrier protein reductase of M. tuberculosis H37Rv (PDB ID: 4U0K) was examined and the best docked pose of H3L was shown to have one hydrogen bond with Thr196 (2.03 A).

Simulation of a tetramer form of 5-chlorouracil: The vibrational spectra and molecular structure in the isolated and in the solid state by using DFT calculations

A Raman and FT-IR study of the biomolecule 5-chlorouracil in the solid state was carried out. The unit cell found in the crystal was simulated as a tetramer form by density functional calculations. They were performed to clarify the assignments of the experimentally observed bands in the spectra. Calculations in the monomer form and comparisons with the experimental data in Ar matrix were also carried out. The error in the calculated frequencies was analyzed and reduced by using scaling equations and scaling factors deduced from the uracil molecule. The calculations with the B3LYP method and with the 6-31G(d,p) and 6-311+G(2d,p) basis set, appear in general to be useful, when combining with a scaling equation procedure or with the specific scale factors, for interpretation of the general features of the IR and Raman spectra. The scaled values were used in the reassignment of the IR and Raman experimental bands. Comparison of the results with those determined in uracil and 5-halogenated derivatives were performed. The substitution at 5-position of the uracil ring by a chlorine atom has a little effect on the geometric parameters.

Polarized spectroscopy and polarized UV light-induced molecular orientation of chiral diphenyl Schiff base Ni(II) and Cu(II) complexes and azobenzene in a PMMA film

We have investigated polarized UV light-induced molecular orientation, namely increasing optical anisotropy of chiral diphenyl Schiff base Ni(II) and Cu(II) complexes (diph(SS)Ni and diph(SS)Cu) as well as azobenzene (AZ), as organic/inorganic hybrid materials in polymethylmethacrylate (PMMA) cast films. The driving force and reason for polarized UV light-induced molecular orientation of AZ are the so-called Weigert effect and accompanying molecular alignment of diph(SS)Ni or diph(SS)Cu is attributed to intermolecular interactions between two components dispersed in a flexible matrix environment of PMMA, which is confirmed with CD spectra. Gradual increase of the degree of dichroism was measured with polarized absorption electronic spectra. The anisotropic parameters were evaluated from them and were discussed based on interactions between electric transition dipole moments calculated by TD-DFT.

A Ni(II) dinuclear complex bridged by end-on azide-N and phenolate-O atoms: spectral interpretation, magnetism and biological study

A potential tetradentate monoanionic N2O2 chelator, HL, derived from the condensation of o-vanillin and N,N-dimethylethylenediammine, has been reacted with nickel perchlorate and sodium azide to yield the dinuclear Ni(II) complex [Ni(L)(μ1,1-N3)Ni(L)(OH2)2]·ClO4 (1), where L = Me2N(CH2)2NCH–C6H3(O−)(OCH3). The complex has been characterized by X-ray diffraction analysis and different spectroscopic techniques. The coordination geometry around the Ni(II) centres is a distorted octahedron, with the azide ligand and the phenolato oxygen atom bridging in μ1,1 and μ2 mode, respectively. The EPR spectra, recorded at liquid nitrogen temperature (77 K) and room temperature (298 K), show g factors of 2.080 and 2.085, in agreement with the structure determined by X-ray diffraction analysis. The VTM study confirms that there are ferromagnetic interactions between the bridging binuclear Ni(II) ions (S = 1). The evaluation of cytotoxic effects on different human cancer cell lines (A-549, MCF-7 and CaCo-2) suggests that both the ligand and complex 1 have potential anticancer properties. Furthermore, they also exhibit anti-mycobacterial activity against M. tuberculosis H37Rv (ATCC 27294) and M. tuberculosis H37Ra (ATCC 25177) strains. Molecular docking of HL with the enoyl acyl carrier protein reductase of M. tuberculosis H37Rv (PDB ID: 4U0K) has been examined, showing that HL forms two hydrogen bonds with Lys165 (1.94 and 2.53 A) in its best docked pose.

The Studies of Conditions for Inducing Chirality to Cu(II) Complexes by Chiral Zn(II) and Ni(II) Complexes with Schiff Base

Recently, we have discovered that some chiral Schiff-base nickel(II) complexes induced d-d bands of CD spectra of some achiral copper(II) complexes. However, the novel phenomenon could be observed only a few systems of hybrid materials or limited conditions so far. In order to test conditions about copper(II) ions, we investigated model systems (1) metal-dendrimer (Cu-PAMAM; G4-NH2 terminal) containing relatively small amount of copper(II) ions (4.5 equivalent to PAMAM) for modeling separated systems of achiral copper(II) complex from chiral Schiff-base nickel(II) or zinc(II) complexes, Bis(𝑁-𝑅-1-naphtylethyl-3,5-dichlorosalicydenaminato)nickel(II) or zinc(II) by polymer matrix. (2) equilibrium of copper(II) 𝑁-ethylethylenediamine complexes to measure absorption spectra of d-d band, pH, and electron conductivity during titration of copper(II) ions. The results showed that (1) 4.5Cu-PAMAM could not be induced their d-d bands by the chiral nickel(II) or zinc(II) complexes, which suggested that separation by polymers prevented from inducing CD peaks. (2) Although 36Cu-PAMAM was known, uncoordinated copper(II) ions excess to ligands mainly attributed to increase electron conductivity by remained ions in methanol solutions, which was not associated with intermolecular interaction or dipole moments being effective for the induced CD mechanism by using molecular recognition between neutral molecules of metal complexes.

An enolato-bridged dinuclear Cu(II) complex with a coumarin-assisted precursor: a spectral, magnetic and biological study

A new, phenoxo-bridged CuII dinuclear complex Cu2[(L)2(DMF)2] (1) has been obtained by employing the coumarin-assisted tridentate precursor, H2L, [benzoic acid(7-hydroxy-4-methyl-2-oxo-2H-chromen-8-ylmethylene)-hydrazide]. Complex 1 has been systematically characterized by FTIR, UV-Vis, fluorescence and EPR spectrometry. The single crystal X-ray diffraction analysis of 1 shows that the geometry around each copper ion is square pyramidal, comprising two enolato oxygen atoms belonging to different ligands (which assemble the dimer bridging the two metal centers), one imine-N and one phenolic-O atoms of the Schiff base and one oxygen atom from the DMF molecule. The temperature dependent magnetic interpretation agrees with the existence of weak ferromagnetic interactions between the bridging dinuclear Cu(II) ions. Both the ligand and complex 1 exhibit anti-mycobacterial activity and considerable efficacy towards M. tuberculosis H37Rv ATCC 27294 and M. tuberculosis H37Ra ATCC 25177 strains. The cytotoxicity study on human adenocarcinoma cell lines (MCF7) suggests that the ligand and complex 1 have potential anticancer properties. Molecular docking of H2L with the enoyl acyl carrier protein reductase of M. tuberculosis H37Rv (PDB ID: 4U0K) is examined and the best docked pose of H2L shows one hydrogen bond with Thr196 (1.99 A).

Crystal structure of hexa­kis­(urea-κO)chromium(III) dichromate bromide monohydrate from synchrotron X-ray data

The title compound, [Cr(urea)6](Cr2O7)Br·H2O, is isotypic with the corresponding chloride salt and consists of discrete [Cr(urea)6]3+ cations, staggered Cr2O7 4− and Br− anions and water solvent molecules that are held together by an intricate three-dimensional network of hydrogen-bonding interactions.

Variety of Crystal Structures of Chiral Schiff Base Lu(III)-Ni(II)/ Cu(II)/Zn(II) and the Related Complexes

New mononuclear (Cu2(L1)2(H2O))2H2OCH3OH) (cyCu)2, multinuclear (Cu2(L1)2K2)(Ni(CN)4) (cy- CuKNi), and dinuclear Ni(L1)Lu(NO3)3 (cyLuNi), Cu(L1)Lu(NO3)3 (cyLuCu) and Zn(L1)Lu((NO3)2CH3COO)CH3OH (cyLuZn) complexes incorporating chiral Schiff base ligands were prepared and characterized by various techniques such as solid-state CD spectra, diffuse reflectance electronic spectra, IR spectra, and single crystal X-ray diffraction analysis. Crystal structures were also compared with previous ones, namely (Cu(L2))(H2O) (diCu), Cu(L1)Gd(NO3)3 (cyGdCu). Interestingly, determined crystal structures exhibited drastically different structural characteristics as regards coordination numbers, crystalline solvents, features and strain condition, nevertheless with little modification in 3d metal substitution and/or modified organic ligands. In this paper, comparison of common components of structures will be discussed sys- tematically.

Polarized light spectroscopy of azobenzene or disperse red 1 with Mn12 single-molecule magnets in PMMA film hybrid materials

A series of organic/inorganic hybrid materials containing the single-molecule magnet [Mn12(CH3COO)16(H2O)4O12]·2CH3COOH·4H2O with the photochromic compounds azobenzene or disperse red 1 cast into polymethyl methacrylate films was prepared. To understand the photomodulation of analogous mixtures’ AC susceptibility, we investigated the molecular alignment based on Weigert’s effect accompanying cycles of cis-trans photoisomerization by alternate irradiations with polarized UV and visible light. Polarized electronic spectra of the hybrid materials demonstrated gradually increasing anisotropy. These features suggest interactions between photochromic compounds and the Mn12 complex in polymethyl methacrylate.

4-Phenyl-diazenyl-2-[(R)-(1-phenyl-ethyl)imino-meth-yl]phenol.

The title chiral photochromic Schiff base compound, C21H19N3O, was synthesized from (R)-1-phenylethylamine and the salicylaldehyde of an azobenzene derivative. The molecule corresponds to the phenol–imine tautomer, the C=N and N—C bond distances being 1.279 (3) and 1.477 (3) Å, respectively. An intramolecular O—H⋯N hydrogen bond occurs. The diazenyl group adopts a trans form with an N=N distance of 1.243 (3) Å.