Ruthenium Pyrazole Complexes: A Family of Highly Active Metallodrugs for Photoactivated Chemotherapy.

Ruthenium complexes bearing bis pyrazole (pzH) ligands, -[Ru(bpy)(R-pzH)] (bpy = 2,2'-bipyridine, R = -H, -Cl), were examined as photoactivated anticancer prodrugs. A dicationic pyrazole complex deprotonated to give monocationic pyrazole-pyrazolate complexes, [Ru(bpy)(R-pz)(R-pzH)], in an aqueous solution with p values of 9.5 and 7.

A Synthetic Route to a Ruthenium Complex via Successive Photosubstitution Reactions.

Photosubstitution reactions of -[Ru(bpy)(MeCN)] with a pyrazole ligand (pzH) were studied under various conditions toward the development of a photochemical synthetic route to polypyridyl ruthenium complexes (bpy = 2,2'-bipyridine). In the absence of a base, light irradiation of an acetonitrile solution of pyrazole and -[Ru(bpy)(MeCN)] gave a mixture of the reactant and -[Ru(bpy)(pzH)(MeCN)]. In the presence of a mild base such as ,-dimethylaminopyridine, a second photosubstitution from -[Ru(bpy)(pzH)(MeCN)] to -[Ru(bpy)(pz)(pzH)] () was greatly enhanced, as confirmed by UV-vis and H nuclear magnetic resonance spectroscopy.

A multi-stimuli responsive ruthenium complex for catalytic water oxidation.

A ruthenium complex showing multi-stimuli-responsive isomerization was synthesized. The catalytic activity of this complex toward water oxidation showed responses to visible-light irradiation and heat due to photoisomerization and thermal back-isomerization, respectively. DFT calculations suggested that a pendant moiety in the complex was key to controlling the catalytic activity.

Intramolecular Hydrogen Bonding: A Key Factor Controlling the Photosubstitution of Ruthenium Complexes.

Photosubstitution reactions of ruthenium complexes with pyrazole ligands, [Ru(bpy)(pzH)] (), [Ru(bpy)(pz)(pzH)] (), and [Ru(bpy)(pz)] () (pzH = pyrazole, bpy = 2,2'-bipyridine), were investigated. Dicationic complex was deprotonated to using moderate base (p = 15.2, MeCN), while the second deprotonation to give required more severe conditions (p = 26.

Photoisomerization and thermal isomerization of ruthenium aqua complexes with chloro-substituted asymmetric bidentate ligands.

A series of ruthenium complexes with chloro-substituted bidentate ligands, proximal-[Ru(tpy)(Cl-pyqu)L] [ = 1 for L = Cl, and = 2 for L = OH, tpy = 2,2';6',2''-terpyridine, pyqu = 2-(2'-pyridyl)quinoline] were synthesized and their reversible photoisomerizations and thermal isomerizations were investigated experimentally. The crystal structures of the complexes indicated that introduction of a chloro substituent at the 4- or 4'-position of the pyqu ligand did not change the structure around the metal center from that of the non-substituted complex, proximal-[Ru(tpy)(pyqu)L] . In contrast, the 6'-substituted complexes had sterically hindered environments around the metal center.

Mechanistic Insight into Reversible Core Structural Changes of Dinuclear μ-Hydroxoruthenium(II) Complexes with a 2,8-Di-2-pyridyl-1,9,10-anthyridine Backbone Prior to Water Oxidation Catalysis.

proximal,proximal-(p,p)-[Ru(tpy)LXY] (tpy = 2,2';6',2″-terpyridine, L = 5-phenyl-2,8-di-2-pyridyl-1,9,10-anthyridine, and X and Y = other coordination sites) yields the structurally and functionally unusual Ru(μ-OH)Ru core, which is capable of catalyzing water oxidation with key water insertion to the core (Inorg. Chem. 2015, 54, 7627).

Visible-Light-Induced Morphological Changes of Giant Vesicles by Photoisomerization of a Ruthenium Aqua Complex.

Visible- and red-light responsive vesicles were prepared by incorporating a ruthenium aqua complex having two alkyl chains on tridentate and asymmetrical bidentate ligands (proximal-2: [Ru(C10 tpy)(C10 pyqu)OH2 ](2+) , C10 tpy=4'-decyloxy-2,2';6',2"-terpyridine, C10 pyqu=2-[2'-(6'-decyloxy)-pyridyl]quinoline). The ruthenium complex of proximal-2 with closed alkyl chain geometry and a cylinder-like molecular shape exhibited photoisomerization to distal-2 with an open alkyl chain geometry and a cone-like shape, both in an aqueous solution and in vesicle dispersions. We observed that light irradiation of giant vesicles containing proximal-2 induced diverse morphological changes.

Fabrication of Three-Layer-Component Organoclay Hybrid Films with Reverse Deposition Orders by a Modified Langmuir-Schaefer Technique and Their Pyroelectric Currents Measured by a Noncontact Method.

In an aqueous clay mineral (montmorillonite) dispersion at a low concentration, isolated clay nanosheets with negative charges were suspended. When a solution of amphiphilic octadecylammonium chloride (ODAH(+)Cl(-)) was spread on an air-dispersion interface, the clay nanosheets were adsorbed on the ODAH(+) cations at the interface to form a stable ultrathin floating film. The floating film was transferred onto a substrate by the Schaefer method, and then the film was immersed in a [Ru(dpp)3]Cl2 (dpp = 4,7-diphenyl-1,10-phenanthroline) solution.

Structure-distortion-induced photomagnetic effect in azobenzene/polyoxometalate Langmuir-Blodgett films.

We have prepared photomagnetic Langmuir-Blodgett films composed of an amphiphilic azobenzene and a magnetic polyoxometalate. The obtained film possesses a well-organized layered structure where polyoxometalate anions are sandwiched by azobenzene cations in a single-layered manner. Reversible photoisomerization of azobenzene was achieved even at low temperature, accompanying intensity changes in the d-d transition of polyoxometalate anions.

Surface potential studies on adsorption processes of clay nanosheets onto a floating molecular film of an amphiphilic alkylammonium cation.

A floating molecular film was formed when a chloroform solution of dimethyldioctadecylammonium bromide (DMDOA(+)Br(-)) was spread on an aqueous dispersion of a clay mineral (sodium montmorillonite). At a low concentration (<50 ppm: ppm = mg dm(-3)), a clay mineral was exfoliated into negatively charged layers (denoted by clay nanosheets). Clay nanosheets in a dispersion were adsorbed onto a floating film because of electrostatic interactions.

Surface nano-architecture of a metal-organic framework.

The rational assembly of ultrathin films of metal-organic frameworks (MOFs)--highly ordered microporous materials--with well-controlled growth direction and film thickness is a critical and as yet unrealized issue for enabling the use of MOFs in nanotechnological devices, such as sensors, catalysts and electrodes for fuel cells. Here we report the facile bottom-up fabrication at ambient temperature of such a perfect preferentially oriented MOF nanofilm on a solid surface (NAFS-1), consisting of metalloporphyrin building units. The construction of NAFS-1 was achieved by the unconventional integration in a modular fashion of a layer-by-layer growth technique coupled with the Langmuir-Blodgett method.

Preparation of Langmuir-Blodgett films of aligned sepiolite fibers and orientation of methylene blue molecules adsorbed on the film.

Sepiolite is a clay mineral with a fibrous morphology; the fibers possess rectangular channels along the fiber direction, and have cation-exchange ability. Amphiphilic octadecylammonium cations (ODAH(+)) spread at an interface between the air and a dispersion of sepiolite fibers have hybridized with the fibers to form a floating monolayer. Surface pressure-molecular area isotherms did not indicate clear collapse points of the hybrid monolayers.

Photoreduction of Prussian Blue intercalated into titania nanosheet ultrathin films.

Ultrathin films composed of titania nanosheets and Prussian Blue were prepared by using the modified Langmuir-Blodgett technique. The ultrathin films could be deposited in a layer-by-layer manner with lamellar structure. Upon band gap excitation of titania nanosheets, the generated electrons were injected into ferromagnetic Prussian Blue, resulting in reduction to paramagnetic Prussian White.

Ultrathin hybrid films of clay minerals.

Smectites or swelling clay minerals are naturally occurring nanomaterials that can be fully delaminated to elementary clay mineral platelets in dilute aqueous dispersion. This review article gives an overview of the recent progress on how the elementary clay mineral platelets can be reorganized in monolayered or multilayered hybrid nanofilms by layer-by-layer assembly or the Langmuir-Blodgett technique. In the latter case one hybrid layer consists of one layer of elementary clay mineral platelets with a theoretical thickness of 0.

Sensing of molecular chirality on an electrode modified with a clay-metal complex hybrid film.

A chiral sensing electrode has been prepared by coating an indium tin oxide (ITO) substrate with a hybrid film of metal complexes and a clay layer (montmorillonite). By applying the combined method of the Langmuir-Blodgett and self-assembly techniques, a monolayer of a water-soluble chiral metal complex (Lambda-[Os(phen)(3)](2+)), which acted as a mediator of oxidizing a target molecule, was fixed electrostatically onto a single-layered clay film. Chiral sensing was demonstrated by monitoring a photocurrent when the electrode was in contact with an aqueous NaClO(4) solution of 1,1'-2-binaphthol.

Photocatalytic decomposition of an alkylammonium cation in a Langmuir-Blodgett film of a titania nanosheet.

The formation of inorganic-organic hybrid films of a titania nanosheet and an amphiphilic alkylammonium cation has been investigated, and the photocatalytic decomposition of the alkylammonium cation in the film has been pursued. When a solution of the amphiphilic alkylammonium salt (octadecylammonium chloride: ODAH+ Cl-) was spread on an interface between the air and a titania nanosheet suspension, the negatively charged nanosheets were adsorbed onto the floating monolayer of ODAH+ to form a hybrid monolayer. The hybridization was confirmed by pi-A isotherm measurements, atomic force microscopy, and X-ray photoelectron spectroscopy.

Observation of the anisotropic photoinduced magnetization effect in Co-Fe Prussian blue thin films fabricated by using clay Langmuir-Blodgett films as a template.

Thin films of cobalt-iron cyanide (Co-Fe Prussian blue) have been fabricated by means of the modified Langmuir-Blodgett (LB) method using a smectite clay mineral (montmorillonite). In this combined method, clay LB films play a template role in the formation of the Co-Fe Prussian blue thin layer. The films were revealed to possess a well-organized structure not only in perpendicular directions to the film surface but also in parallel directions to the film surface.

Formation of Langmuir-Blodgett films of a clay and a water-soluble alkylammonium cation.

We have studied the formation of ultrathin hybrid films composed of a water-soluble alkylammonium cation (trimethyloctadecylammonium caiton: TMODAH+) and clay nanosheets at an air-water interface. When a chloroform solution of the ammonium salt of TMODAH+Cl- was spread onto a surface of an aqueous clay suspension in a Langmuir trough, a stable monolayer of the water-soluble ammonium cation was formed by hybridization with the clay nanosheets at the air-water interface. Surface pressure--molecular area (pi-A) isotherm curve of the hybrid monolayer shifted to the smaller molecular area side with the increase in the concentration of the ammonium salt in the solution or with the decrease in that of the clay in the suspension.

Two-dimensional molecular ordering of Os(II) complexes in organo-clay hybrid ultrathin films.

An ordered structure of [OsL(3)](2+)(L = 2, 2'-bipyridine or 1, 10-phenanthroline) layer in an ultrathin film composed of the complex cations, clay nanosheets and alkylammonium cations is reported on the basis of its in-plane X-ray diffraction and polarized electronic spectral data.

Langmuir-Blodgett films of a clay mineral and ruthenium(II) complexes with a noncentrosymmetric structure.

Mono- and multilayers of amphiphilic [Ru(phen)(2)(dcC12bpy)](2+) (phen = 1,10-phenanthroline, dcC12bpy = 4,4'-caboxyl-2,2'-bipyridyl didodecyl ester) hybridized with a clay mineral have been prepared by a modified Langmuir-Blodgett method, and their structures and properties have been investigated. Formation of a hybrid monolayer of the Ru(II) complex cations and the clay platelets at an air-clay suspension interface was confirmed by surface pressure-molecular area (pi-A) isotherm measurement and atomic force microscopic (AFM) observation. Multilayers were fabricated by depositing the hybrid monolayers onto glass substrates.