Cu-ABNO Catalyst for the Synthesis of Quinolines and Pyrazines Aerobic Double Dehydrogenation of Alcohols.

In this report, a new imidazole- and amide-functionalized pincer-like Cu(II) complex () was synthesized and characterized. By employing and 9-azabicyclo[3.3.

Fixation of CO with Epoxides Catalyzed by Pincer-Type Azo-Aromatic Complexes of Cobalt as Catalysts.

Employing a series of azo-aromatic pincer-type cobalt(II) complexes, -, and an imine-based cobalt complex, , a highly efficient catalytic protocol for the cycloaddition of CO with epoxides at low pressure of CO is reported. The electron-withdrawing group-substituted ligands containing complexes and were most efficient. The catalytic protocol with involved a synergistic participation of an azo-aromatic catalyst (0.

Progress of Photoantibiotics in Overcoming Antibiotic Resistance.

Antibiotic resistance has emerged as a global public health crisis in the 21 century, leading to treatment failures. To address this issue, the medical and pharmaceutical sectors are confronted with two challenges: i) finding potent new antimicrobial agents that would work against resistant-pathogens, and ii) developing conceptually new or unconventional strategies by which a particular antibiotic would remain effective persistently. Photopharmacology with the aid of reversibly controllable light-active antibiotics that we call "photoantibiotics" shows great promise to meet the second challenge, which has inspired many research laboratories worldwide to align their research in inventing or developing such antibiotics.

Ligand redox controlled amine dehydrogenation and imine hemilability in singlet diradical azo-aromatic Ni(II) complexes: characterization of the electron transfer series of azo-imine complexes of Ni(II).

Herein, using azo-amine (H2L) and azo-imine (L) ligands, singlet diradical Ni(II) complexes [1] and [2] were synthesized from Ni(0)(COD) in THF. In separate reactions, homoleptic Ni complexes, [3a]2+-[3c]2+, were synthesized from [Ni(HO)](ClO) and L, respectively. All these complexes were characterized thoroughly.

A Phosphine-Oxide Cobalt(II) Complex and Its Catalytic Activity Studies toward Alcohol Dehydrogenation Triggered Direct Synthesis of Imines and Quinolines.

Herein, a new pincer-like amino phosphine donor ligand, , and its phosphine-oxide analog, , were synthesized. Subsequently, cobalt(II) complexes and were synthesized by the reaction of anhydrous Co(II)Cl with ligands and respectively. The ligands and complexes were fully characterized by various physicochemical and spectroscopic characterization techniques.

Photoisomerization and Light-Controlled Antibacterial Activity of Fluoroquinolone-Azoisoxazole Hybrids.

Photopharmacology holds a huge untapped potential to locally treat diseases involving photoswitchable drugs via the elimination of drugs' off-target effects. The growth of this field has created a pressing demand to develop such light-active drugs. We explored the potential for creating photoswitchable antibiotic hybrids by attaching pharmacophores norfloxacin/ciprofloxacin and azoisoxazole (photoswitch).

Visible-Light-Sensitive Photoliquefiable Arylazoisoxazoles for the Solar Energy Conversion, Storage and Controlled-Release of Heat at Room Temperature or Lower Temperatures.

The photoswitchable MOlecular Solar Thermal (MOST) energy storage systems that are capable of exhibiting high energy storage densities are found to suffer from the poor cyclability, the use of less abundant UV light of the solar spectrum, or reduced charging/discharging rates and poor photoconversions in solid states. Herein, we have designed and readily synthesized a novel set of para-thioalkyl substituted arylazoisoxazoles, that undergo high trans-cis and cis-trans photoconversions under visible light, and show fast charging/discharging and impressive cyclability. Remarkably, the presence of C6-or C10-thioalkyl chainin photochromes permitted reversible solid-liquid phase transition with the formation of cis-enriched charged states by 400 nm light irradiation and trans-enriched discharged states by 530 nm light at various temperatures (10-35 °C).

Direct Growth Control of Antibiotic-Resistant Bacteria Using Visible-Light-Responsive Novel Photoswitchable Antibiotics.

In addition to the discovery of new (modified) potent antibiotics to combat antibiotic resistance, there is a critical need to develop novel strategies that would restrict their off-target effects and unnecessary exposure to bacteria in our body and environment. We report a set of new photoswitchable arylazopyrazole-modified norfloxacin antibiotics that present a high degree of bidirectional photoisomerization, impressive fatigue resistance and reasonably high cis half-lives. The irradiated isomers of most compounds were found to exhibit nearly equal or higher antibacterial activity than norfloxacin against Gram-positive bacteria.

Noninnocent Azo-Aromatic Cobalt(II)-Catalyzed sp C-H Alkylation of Fluorenes with Alcohols.

Herein, employing well-defined redox noninnocent cobalt(II) complexes an efficient sp C-H alkylation of fluorenes using alcohols as alkylating agents to result in alkylated fluorenes is reported. The catalytic protocol was versatile with various fluorenes and benzyl alcohols. It also showed very good functional group tolerance with both alcohols and fluorenes.

Photoswitchable Antibiotic Hybrids: Spacer Length-Dependent Photochemical Control of Antibacterial Activity.

Photopharmacology holds huge potential for the permanent (long-term) eradication of antibiotic resistance by the application of photoswitchable antibiotics. To construct such antibiotics, various methods have been employed to modify known antibiotics with photoswitches, such that the irradiated state shows activity comparable to or higher than that of the parent antibiotic and that a large activity difference between irradiated and nonirradiated states is achieved. However, most of those methods are ineffective when dealing with more than one drug with dissimilar structures.

Photoisomerization of 2-Arylazoimidazoles under Visible Light: Identifying a Predictive Tool to Anticipate and Tune Likely Photoswitching Performance and Cis Half-Life.

Azopyrazoles are an emerging class of photoswitches, whereas analogous azoimidazole-based switches are unable to draw much attention because of their short cis half-lives, poor cis-trans photoreversion yields, and toxic ultraviolet (UV) light-assisted isomerization. A series of 24 various aryl-substituted -methyl-2-arylazoimidazoles were synthesized, and their photoswitching performances and cis-trans isomerization kinetics were thoroughly investigated experimentally and theoretically. -π-donor-substituted azoimidazoles with highly twisted T-shaped cis conformations showed nearly complete bidirectional photoswitching, whereas di--substituted switches exhibited very long cis half-lives (days-years) with nearly ideal T-shaped conformations.

Genetically Encoded Aminocoumarin Lysine for Optical Control of Protein-Nucleotide Interactions in Zebrafish Embryos.

The strategic placement of unnatural amino acids into the active site of kinases and phosphatases has allowed for the generation of photocaged signaling proteins that offer spatiotemporal control over activation of these pathways through precise light exposure. However, deploying this technology to study cell signaling in the context of embryo development has been limited. The promise of optical control is especially useful in the early stages of an embryo where development is driven by tightly orchestrated signaling events.

Completely -Phenylene Bridged -Cyclophane: A Missing Link in the Phenylene Bridge -Cyclophane Family.

Unprecedented types of metal-free complete -phenylene bridged -cyclophanes ( and ) have been synthesized via sequential palladium-catalyzed Buchwald-Hartwig -arylation reactions. These cyclophanes may be considered as aromatic analogues of aliphatic group-spaced -macrocycles. These have been characterized fully using physicochemical characterization techniques and finally by single crystal X-ray structure determination.

Alcohol Dehydrogenation-Triggered Selective C3-Alkylation of Indoles by Homogeneous Azo-aromatic Cobalt Catalysts.

Herein, we report azo-benzimidazole containing cobalt complexes (-) for alcohol dehydrogenation-triggered C3-alkylation of indoles. In complexes , ligands are redox noninnocent and showed facile irreversible reduction followed by Co(II)/Co(I) reduction in close-lying potentials. Taking advantage of facile redox events in -, the first aerial dehydrogenation of alcohols to their corresponding carbonyl compounds is explored.

Hemilabile Amine-Functionalized Efficient Azo-Aromatic Cu-Catalysts Inspired by Galactose Oxidase: Impact of Amine Sidearm on Catalytic Aerobic Oxidation of Alcohols.

A series of azo-aromatic copper(II) complexes, [] and a Cu(I) complex, [], with varying amine-functionalized hemilabile pincer-like [] and [], methyl-substituted azo [], and imine [] ligands, were synthesized and characterized. These complexes were investigated for aerobic oxidation of a variety of aromatic alcohols in the presence of 2.0 mol % precatalysts [], cobaltocene (2.

Near-Complete Bidirectional Photoisomerization of -Dialkylamino-Substituted Arylazopyrazoles under Violet and Green or Red Lights.

-Dimethylamine- and -pyrrolidine-substituted arylazopyrazoles display very high to near-quantitative or quantitative bidirectional isomerization under violet and green or red lights in both polar (DMSO and DMSO/aqueous buffer, pH 7.5) and nonpolar solvents. These switches confer a reasonable thermal stability to their -states ( ≈ 4-7 h in DMSO and DMSO/buffer) and also show a high level of resistance to photobleaching and an impressive stability to reduction by glutathione.

Polymerisation of styrene using pincer type amine functionalized azo aromatic complexes of Co(II) as catalysts.

In the present report, three mononuclear azo-aromatic complexes of Co(II), 1-3, and an imine-based Co(II) complex, 4, were synthesized through a reaction of respective amine-functionalized pincer-like ligands, HL1-4, with CoCl·6HO in the ligand-to-metal ratio of 1 : 1. All the complexes, 1-4, were thoroughly characterized using various physicochemical characterization techniques, single-crystal X-ray structure determination, and density functional theory (DFT) calculations. Complexes 1-4 were explored for the catalytic styrene polymerisation reaction separately in the presence of modified methyl aluminoxane (MMAO).

Azide-Alkyne "Click" Reaction in Water Using Parts-Per-Million Amine-Functionalized Azoaromatic Cu(I) Complex as Catalyst: Effect of the Amine Side Arm.

A series of Cu(II) complexes, - and , were synthesized through a reaction of amine-functionalized pincer-like ligands, , , and a bidentate ligand with CuCl·2HO. The chemical reduction of complex using 1 equiv of sodium l-ascorbate resulted in a dimeric Cu(I) complex in excellent yield. All of the complexes, -, were thoroughly characterized using various physicochemical characterization techniques, single-crystal X-ray structure determination, and density functional theory calculations.

Irreversible Resistive State Switching in Devices with a Homoleptic Cobalt(II) Complex Active Layer.

Molecules with bi-stable electronic transport behaviour have been in upfront research topics of the molecular semiconductor devices in the past few decades due to the use of such materials in resistive data storage devices. Transition metal complexes (TMC) are expected to be potential candidates in regard to the tunable and manifold redox behaviour expecting multiple bulk transport states. Finding alternate mechanisms in such devices with TMC as the active layer materials would revoke the multifaceted approach to the functional gain.

Robust bi-directional photoswitching of thiomethyl substituted arylazopyrazoles under visible light.

Mono-ortho- and para-thiomethyl-substituted arylazopyrazoles show substantial absorbance in visible wavelengths, enabling very high to near-quantitative forward and reverse isomerization in DMSO and aqueous solution by visible light. cis isomers display excellent thermal stability (∼3 days, 27 °C). Additionally, these switches possess good photostability and are resistant to reduction by glutathione.

Dehydrogenation of amines in aryl-amine functionalized pincer-like nitrogen-donor redox non-innocent ligands via ligand reduction on a Ni(ii) template.

We have synthesized a series of new redox non-innocent azo aromatic pincer-like ligands: 2-(phenylazo)-6-(arylaminomethyl)pyridine (HLa-c: HLa = 2-(phenylazo)-6-(2,6-diisopropylphenylaminomethyl)pyridine, HLb = 2-(phenylazo)-6-(2,6-dimethylphenylaminomethyl)pyridine, and HLc = 2-(phenylazo)-6-(phenylaminomethyl)pyridine), in which one side arm is an arylaminomethyl moiety and the other arm is a 2-phenylazo moiety. Nickel(ii) complexes, 1-3, of these ligands HLa-c were synthesized in good yield (approximately 70%) by the reaction of ligands : (NiCl2·6H2O) in a 1 : 1 molar ratio in methanol. The amine donor in each of the ligands HLa-c binds to the Ni(ii) centre without deprotonation.

Reversible and Tunable Photoswitching of Protein Function through Genetic Encoding of Azobenzene Amino Acids in Mammalian Cells.

The genetic encoding of three different azobenzene phenylalanines with different photochemical properties was achieved in human cells by using an engineered pyrrolysyl tRNA/tRNA synthetase pair. In order to demonstrate reversible light control of protein function, azobenzenes were site-specifically introduced into firefly luciferase. Computational strategies were applied to guide the selection of potential photoswitchable sites that lead to a reversibly controlled luciferase enzyme.

Effects of Ancillary Ligands on Redox and Chemical Properties of Ruthenium Coordinated Azoaromatic Pincer.

In this work, the effect of the electronically different ancillary ligands on the overall properties of the RuL moiety (L = 2,6-bis(phenylazo)pyridine) in heteroleptic complexes of general formula [RuLQCl] was investigated. Four different ancillary ligands (Q) with different electronic effects were used to prepare the heteroleptic compounds from the precursor complex, [RuL(CHCN)Cl] (1); Q = pcp: 2-(4-chloro-phenylazo)pyridine (strong π-acceptor), [2]; bpy: 2,2'-bipyridyl (moderate π-acceptor), [3]; acac: acetylacetonate (strong σ-donor), 4; and DTBCat: 3,5-di- tert-butyl catecholate (strong π-donor), 5. The complexes [2], [3], 4, and 5 were fully characterized and structurally identified.

Genetic Code Expansion in Zebrafish Embryos and Its Application to Optical Control of Cell Signaling.

Site-specific incorporation of unnatural amino acids into proteins provides a powerful tool to study protein function. Here we report genetic code expansion in zebrafish embryos and its application to the optogenetic control of cell signaling. We genetically encoded four unnatural amino acids with a diverse set of functional groups, which included a photocaged lysine that was applied to the light-activation of luciferase and kinase activity.