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Artificial metal enzymes that combine proteins with synthesized unnatural metal complexes as cofactors are attracting attention. The preparation of artificial metal enzymes not only clarifies the behavior of metal ions in biology, but also leads to the development of synthetic chemistry fields such as the discovery of new catalytic reactivity and substrate selectivity that are not observed in nature. In addition, a certain Schiff base zinc (II) complex is known to exhibit antioxidant and anticancer activity, too. Therefore, in this study, we investigated a rapid synthesis method of two known amino acid Schiff base zinc (II) complexes using microwave method and the complexation of zinc (II) complex with chicken egg white lysozyme, which is a relatively low molecular weight protein. Furthermore, investigation of weakly non-covalent intermolecular interaction features between the zinc (II) complexes and lysozyme was also carried out using some spectroscopic measurements.

In this paper, we report on the chiral crystallization of achiral mol­ecules., The compound, {6,6′-dimeth­oxy-2,2′-[(4-azaheptane-1,7-di­yl)bis­(nitrilo­meth­an­yl­idyne)]diphenolato}zinc(II) methanol monosolvate, [Zn(C22H27N3O4)]·CH3OH, at 298 K crystallizes in the ortho­rhom­bic space group Pna21. The Zn atom is coordinated by a penta­dentate Schiff base ligand in a distorted trigonal–bipyramidal N3O2 geometry. The equatorial plane is formed by the two phenolic O and one amine N atom. The axial positions are occupied by two amine N atoms. The distorted bipyramidal geometry is also supported by the trigonality index (τ), which is found to be 0.85 for the mol­ecule. In the crystal, methanol solvent mol­ecule is connected to the complex mol­ecule by an O—H⋯O hydrogen bond and the complex mol­ecules are connected by weak supra­molecular inter­actions, so achiral mol­ecules generate a chiral crystal. The Hirshfeld surface analysis suggests that H⋯H contacts account for the largest percentage of all inter­actions.

Herein we have originally designed chiral azo-salen Mn(II) and Zn(II) complexes for interacting silver nanoparticles (AgNPs) exhibiting localized surface plasmon resonance (LSPR). Understanding excited state and reaction intermediate during light irradiation to return to ground state may be important for such composite systems. Therefore, we investigated such optical properties for systems using time-resolved luminescence and transient absorption measurements. DMSO solutions of the four newly prepared and characterized complexes (MMn, MZn, CMn, and CZn) and ethanol solutions of the composite materials of each complex with AgNPs were served for optical measurements. The time-correlated single photon counting (TCSPC), the streak camera which is much shorter period of time than TCSPC and transient absorption measurement, was performed for the eight samples. The fluorescence lifetime of the sole complexes and the composite materials with AgNPs was derived from curve-fitting analysis of luminescence decay curves of TCSPC. Lifetime of the composite systems with AgNPs was longer than that of the corresponding sole metal complexes for three cases. It was revealed that composite systems may go through three reaction intermediates during relaxation from excited state to ground state.

The crystal structure of the amino acid Schiff base copper(II) complex with a tridentate ligand synthesized from salicyl­aldehyde, l-threonine and copper(II) acetate is reported., In the title complex mol­ecule, [Cu(C11H11NO4)(CH4O)(H2O)], the Cu atom is coordinated in a distorted square-pyramidal geometry by a tridentate ligand synthesized from l-threonine and salicyl­aldehyde, one methanol mol­ecule and one water mol­ecule. In the crystal, the mol­ecules show intra- and inter­molecular O—H⋯O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are H⋯H (49.4%) and H⋯O/O⋯H (31.3%) contacts.

Synthesis of Cu(II) complexes with condensation products of 2,4-dihydroxybenzaldehyde and four amino acids (L-alanine, L-valine, L-phenylalanine, and glycine) is reported. Their physicochemical properties are compared to each other and a previously studied Schiff base Cu(II) complex, the product of condensation of salicylaldehyde and L-aspartic acid. The complexes were characterized by means of electrochemical, spectroscopic, and X-ray diffraction techniques. (TD-) DFT calculations were used for the assignment of transitions in UV-Vis spectra. Photocatalytic activity for reduction from Cr(VI) to Cr(III) was studied under UV to visible light irradiation in methanol or water as sole complexes or hybrid systems with TiO2. For the first time among the analogous systems, in aqueous solutions, the complexes with TiO2 reduced Cr(VI) to Cr(III) efficiently. The Cr(VI) reduction ratio with the CuVDB–TiO2 system reached 91%.

Three 1-[(1,3-benzodioxol-5-yl)methyl]-4-(halobenzo­yl)piperazines adopt very similar mol­ecular conformations but, while the mol­ecules of the 3-fluoro­benzoyl are linked by hydrogen bonds into a three-dimensional structure, there are no hydrogen bonds in either of the 2,6-di­fluoro­benzoyl and 2,4-di­chloro­benzoyl analogues., In each of the compounds 1-[(1,3-benzodioxol-5-yl)methyl]-4-(3-fluoro­benzo­yl)piperazine, C19H19FN2O3 (I), 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,6-di­fluoro­benzo­yl)piperazine, C19H18F2N2O3 (II), and 1-[(1,3-benzodioxol-5-yl)methyl]-4-(2,4-di­chloro­benzo­yl)piperazine, C19H19Cl2N2O3 (III), the piperazine rings adopt a chair conformation with the (1,3-benzodioxol-5-yl)methyl substituent occupying an equatorial site: the five-membered rings are all slightly folded across the O⋯O line leading to envelope conformations. The dihedral angle between the planar amidic fragment and the haloaryl ring is 62.97 (5)° in (I) but 77.72 (12)° and 75.50 (5)° in (II) and (III), respectively. Despite their similarity in constitution and conformation, the supra­molecular inter­actions in (I)–(III) differ: in (I), a combination of C—H⋯O and C—H⋯π(arene) hydrogen bonds links the mol­ecules into a three-dimensional framework structure, but there are no hydrogen bonds of any sort in either (II) or (III), although the structure of (III) contains a short Cl⋯Cl contact between inversion-related pairs of mol­ecules.

Based on the potential redox and catalytic ability of oxovanadium complexes, our goal was to characterize the physical properties of two such complexes to be used as mediators for laccase. Computational studies, TD-DFT calculations and docking simulations were performed to elucidate the interaction between laccase and the two anionic complexes (aquabis(oxalato)oxidovanadate(IV) (1) and bis(oxalato)dioxidovanadate(V)) (2), respectively. Electrochemical measurements carried out on anion complexes of 1 and 2 docked into laccase were compared to laccase alone, showing changes in oxidation-reduction potential and current value, especially with the oxovanadium anion of 2. Since both internal tiny magnetic fields of ferromagnetic catalysts and external applied magnetic fields were found in previous investigations to constitute effective ways to improve the oxygen transfer rate, the magnetic susceptibility was measured. A valence change proneness was confirmed with higher valence for the oxovanadium anion of 2, which is in accordance with the electrochemical results.

Single crystals of two achiral and planar heterocyclic compounds, C9H8H3O(CA1) and C8H5NO2 (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P212121 (# 19), whereas it was not observed for CA4 P21/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites.

Induced chirality (achiral target in chiral matrix such as proteins) sometimes play a useful role in evaluating supramolecular systems involving biomolecules. Enzymatic fuel cells, which generate electricity via enzymatic redox reactions at electrodes hold a significant potential for sustainable power. Bacterial laccase, a multi-copper oxidase, was used in the cathodic compartment of the enzymatic biofuel cells because of its low redox potential. Three new salen Cu(II) complexes were designed and investigated as mediators. The Schiff base ligands consisted of both a redox-active (anthraquinone) and a photochromic (azobenzene) moiety. The interaction between laccase and a mediator was examined with induced circular dichroism (CD) and the docking tool to observe in which of the laccase domains the mediators bind as well as study the photo-induced tuning of both the cis-trans photoisomerization and orientation by the Weigert effect. Both the electrochemical and photochromic properties are also discussed and compared using density functional theory (DFT), time-dependent (TD)-DFT, and docking simulations.

Metal–organic frameworks (MOFs) have been of particular interest to researchers because of their structural designability, robustness, and rich science arising from uniform porosity. Among them, Hofmann-type MOFs, which are one of the earliest examples of a MOF, have been intensively studied. For the bulk state of Hofmann-type MOFs, their spin transition behavior induced by guest molecules and external stimuli has long been discussed as a key subject. On the other hand, the use of Hofmann-type MOFs as a nanoscale architecture has recently attracted significant attention toward future practical applications, such as stimuli-responsive sensors and switching devices. In this review, we present an overview of the recent development of fabrication of crystalline architectures at the nanoscale including thin films and nanoparticles utilizing Hofmann-type MOFs.

We report the fabrication and characterization of the first example of a tetracyanonickelate-based two-dimensional-layered metal–organic framework, {Fe(py)2Ni(CN)4} (py = pyridine), thin film. To fabricate a nanometer-sized thin film, we utilized the layer-by-layer method, whereby a substrate was alternately soaked in solutions of the structural components. Surface X-ray studies revealed that the fabricated film was crystalline with well-controlled growth directions both parallel and perpendicular to the substrate. In addition, lattice parameter analysis indicated that the crystal system is found to be close to higher symmetry by being downsized to a thin film.

A salen-type Schiff base Zn(II) complex included in human serum albumin (HSA) protein was examined by UV-Vis, circular dichroism (CD), and fluorescence (PL) spectra. The formation of the composite material was also estimated by a GOLD program of ligand&ndash, protein docking simulation. A composite cast film of HSA and Zn(II) complex was prepared, and the effects of the docking of the metal complex on the degradation of protein molecules by mid-infrared free electron laser (IR-FEL) were investigated. The optimum wavelengths of IR-FEL irradiation to be used were based on experimental FT-IR spectra and vibrational analysis. Using TD-DFT results with 6-31G(d,p) and B3LYP, the IR spectrum of Zn(II) complex could be reasonably assigned. The respective wavelengths were 1652 cm&minus, 1 (HSA amide I), 1537 cm&minus, 1 (HSA amide II), and 1622 cm&minus, 1 (Zn(II) complex C=N). Degradation of HSA based on FT-IR microscope (IRM) analysis and protein secondary structure analysis program (IR-SSE) revealed that the composite material was degraded more than pure HSA or Zn(II) complex, the inclusion of Zn(II) complex enhanced destabilization of folding of HSA.

The title compound is composed of a benzene ring linked to an indazole unit by an N=N bond and has high planarity. The diazenyl group adopts a trans (E) conformation., The title azo compound, C16H16N4, was synthesized from 2,6-di­methyl­aniline. The diazenyl group adopts a trans (E) conformation, with an N=N bond length of 1.265 (4) Å. The pyrazole ring is approximately planar. In the crystal, zigzag chains along the b-axis direction with a C(3) is graph-set motif are formed by N—H⋯N hydrogen bonds involving the pyrazole moiety.

The planar achiral title compound has C 2v symmetry and crystallizes in the chiral space group P21., The title compound, C10H10O4, was synthesized from tetra­methyl-1,4-benzo­quinone. In the crystal, the almost planar mol­ecule (r.m.s. deviation = 0.024 Å) forms intra­molecular hydrogen bonds between the aldehyde and hy­droxy groups and exhibits C 2v symmetry. This achiral mol­ecule crystallizes in the chiral space group P21 with inter­molecular O—H⋯O and C—H⋯O hydrogen bonding and C—H⋯π and C=O⋯π inter­actions stabilizing the crystal packing.

Chiral crystals were discovered due to spontaneous resolution when enantiomers of 4-phenyldiazenyl-2-[(R or S)-(1-phenylethyl)-iminomethyl]phenol and its racemic mixture were prepared. Using two ligands per molecule, optically active R,R and S,S enantiomers and meso R,S diastereomer of Cu(II) complexes were prepared. Strong chiral recognition was expected for them. Laccase has attracted attention as a catalyst that reduces oxygen to water in a cathode of biofuel cells, which can be effectively mediated by metal complexes. Furthermore, azobenzene can align perpendicularly to the polarization direction of irradiating linearly polarized ultraviolet light (Weigert effect) as well as to the conventional cis-trans photoisomerization accompanying the shift of redox potential. Thus, we also studied the photo-induced control of cis-trans forms and the alignment of these Cu(II) complexes as a mediator to fit laccase appropriately. We discuss photo-induced control on not only electronically but also sterically-favored redox conditions. The meso(R,S)-form of the Cu(II) complex in cis-form was found to be the best at increasing the current of cyclic voltammetry (CV) among the three R,R and S,S enantiomers and the R,S diastereomer of the Cu(II) complexes.

Department of Chemistry, Tokyo University of Science, Tokyo, Japan E-mail: akitsu2@rs.tus.ac.jp Chemical Sciences Division, Saha Institute of Nuclear Physics, Kolkata-700 064, India E-mail: sayan23us@gmail.com Manuscript received online 03 March 2019, revised 17 April 2019, accepted 18 April 2019 Artificial metalloenzymes (ArM) have emerged as a promising strategy to emulate the catalytic efficiency of natural metalloenzymes in new to nature reactions. ArM consisting of lysozyme derived from hen egg white lysozyme (HEWL) and several chiral salen-type Cu(II) complexes was prepared in this study. Twenty types of salen-type metal complexes were obtained from crystal database and then were virtually screened with help of molecular docking procedure. Docking results verified that the Cu(II) complexes interacts with lysozyme by hydrogen and hydrophobic bonds. Four Cu(II) complexes with best docking score were synthesized. It was confirmed by the CV curve that there is an electrochemical difference between lysozyme simple substance and complex to attempt to reduce oxygen.

The title compound, C19H12N2O3, obtained as an intermediate in the synthesis of a pyrrole derivative, is composed of a five-membered heterocycle with substituted groups via double or triple bonds as well as single bonds, without an asymmetric carbon atom. An intramolecular O—H...O link occurs. In the crystal, O—H...N hydrogen bonds link the molecules.

We report a step-by-step route to fabricate the first example of a crystalline oriented metal–organic framework thin film having an anionic inorganic pillar ligand, {Cu(4,4′-bipyridyl)2(SiF6)}. X-ray study and sorption analysis revealed its high crystallinity and porous character.

We have prepared supramolecular systems of chiral Schiff base Ni(II), Cu(II), Zn(II) complexes and colloidal gold nanoparticles (AuNP) of 10 nm diameters. They demonstrated that direct adsorption of chiral Schiff base metal complex on the surface of AuNP owing to observation of clear induced CD spectra for the first time. We observed and discussed induced CD bands on AuNP from chiral Schiff base Ni(II), Cu(II), Zn(II) complexes.

Fabrication of thin films made of metal–organic frameworks (MOFs) has been intensively pursued for practical applications that use the structural response of MOFs. However, to date, only physisorption-induced structural response has been studied in these films. Chemisorption can be expected to provide a remarkable structural response because of the formation of bonds between guest molecules and reactive metal sites in host MOFs. Here, we report that chemisorption-induced two-way structural transformation in a nanometer-sized MOF thin film. We prepared a two-dimensional layered-type MOF Fe[Pt(CN)4] thin film using a step-by-step approach. Although the as-synthesized film showed poor crystallinity, the dehydrated form of this thin film had a highly oriented crystalline nature (Film-D) as confirmed by synchrotron X-ray diffraction (XRD). Surprisingly, under water and pyridine vapors, Film-D showed chemisorption-induced dynamic structural transformations to Fe(L)2[Pt(CN)4] thin films [L = H2O (Film-H), pyridi...

As resource- and time-saving and environmentally friendly synthetic methods than conventional one in a solution, microwave, and wet mechanochemical synthesis are tested for l -amino acid derivative Schiff base copper(II) complexes. Herein, we systematically compared efficiency (low-temperature, time, and yield (if possible to detect)) for both conventional solution method and microwave or mechanochemical methods. The wet mechanochemical synthesis promoted fast reaction (typically 20 ​min by mechanochemical vs 4 ​h by conventional) by a little amount of solvent for preparations of amino acid derivative Schiff base copper(II) complexes. New crystal structure of a five-coordinated square pyramidal copper(II) complex as one of the products of microwave method was also reported.

An infrared free electron laser (IR-FEL) can decompose aggregated proteins by excitation of vibrational bands. In this study, we prepared hybrid materials of protein (human serum albumin, HSA) including several new Schiff base Zn(II) complexes incorporating amino acid (alanine and valine) or dipeptide (gly-gly) derivative moieties, which were synthesized and characterized with UV-vis, circular dichroism (CD), and IR spectra. Density functional theory (DFT) and time dependent DFT (TD-DFT) calculations were also performed to investigate vibrational modes of the Zn(II) complexes. An IR-FEL was used to irradiate HSA as well as hybrid materials of HSA-Zn(II) complexes at wavelengths corresponding to imine C=N, amide I, and amide II bands. Analysis of secondary structures suggested that including a Zn(II) complex into HSA led to the structural change of HSA, resulting in a more fragile structure than the original HSA. The result was one of the characteristic features of vibrational excitation of IR-FEL in contrast to electronic excitation by UV or visible light.

The title indole derivative, C11H11NO2, was synthesized from 1-methyl-1H-indole-3-carboxylic acid and methanol. The molecule is planar as it is situated on a mirror plane present in the space group Pbcm. In the crystal, molecules form three kinds of intermolecular C—H...O hydrogen bonds, resulting in a sheet structure in the ab plane. Parallel sheets interact by C—H...π stacking, stabilizing the crystal packing.

Department of Chemistry, Faculty of Science, Tokyo University of Science, Tokyo 162-3601, Japan E-mail: akitsu@rs.tus.ac.jp Department of Chemistry, National Institute of Technology, Rourkela-769 008, Odisha, India Department of Applied Sciences, Haldia Institute of Technology, Haldia-721 657, West Bengal, India Center for Molecular and Biophysics Research, Mar Ivanios College, Thiruvananthapuram-695 015, Kerala, India Manuscript received online 26 September 2018, accepted 03 October 2018 As a promising renewable energy, dye sensitized solar cell (DSSC) has been developed to improve performance of every material and system. From the viewpoint of dye metal complexes/organic compounds, we have reported on chiral Schiff base (salen-type) metal complexes and induced CD from chiral Schiff base metal complexes involving azo-dye groups to Au nanoparticles, and recently we have also conducted research on their optical interactions. In this paper, we showed the results of Z-scan NLO measurements for the analogous achiral organic ligands and metal complexes.

We have investigated linearly polarized UV light-induced molecular orientation due to Weigert effect of composite materials of new six binuclear nickel(II), copper(II), and zinc(II) complexes of two rigid Schiff base ring ligands (L1 and L2) composite materials with methyl orange (MO), an azo-dye, in polyvinylalchol (PVA) cast films. To compare the degree of molecular orientation, two ligands, namely flexible aliphatic cyclohexane (ML1: NiL1, CuL1, ZnL1) and rigid aromatic (ML2: NiL2, CuL2, ZnL2), were synthesized using amine moiety. We have also characterized these complexes by means of elemental analysis, IR, and UV-vis spectra, single crystal or powder X-ray diffraction (XRD) analysis, and so on. Composite materials of ML1 or ML2+MO+PVA were also prepared to separately disperse the solutes in a polymer matrix. For any metal complexes, optical anisotropy (represented as the R parameters) of ML2+MO+PVA was larger than ML1+MO+PVA because of the rigidness of the ligands.

Department of Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan E-mail: akitsu@rs.kagu.tus.ac.jp Manuscript received 04 March 2018, accepted 11 March 2018 Laccase is mainly used as an enzyme of a cathode electrode of a biofuel cell. One problem is rate limiting of electron transfer between electrodes and enzymes. To enhance transfer of electron from the electrode to the redox center in the enzyme, using mediators instead of substrates of laccase is one the solution. A selection of the mediator is important in improving the performance of the biofuel cell. Our laboratory has succeeded in improving the electron transfer function by controlling the polarization-induced molecular orientation of a complex having an azo dye in a laccase matrix. In this study, we will synthesize a mononuclear complex including azobenzene, a binuclear complex and a tetranuclear complex containing CuII or MnII/III ions, and evaluate how much multistep electron transfer and molecular orientation by multinuclear complex will contribute to function as a mediator