Molecular Structures Of Complexes Research Articles

Removal of Indigo Dye by CaCO3/Ca(OH)2 Composites and Resource Recovery

Indigo dye wastewater from blue denim-manufacturing industries poses a significant threat to the environment if not adequately treated before discharge to water bodies. Indigo dye residues in the process effluent have complex molecular structures relatively stable to light and heat and resistant to biodegradation, making affordable and straightforward removal difficult. We demonstrate indigo dye removal using a low-cost, nontoxic, biodegradable, readily regenerated common adsorbent made of the CaCO3/Ca(OH)2 composite. The optimized catalyst loadings at 20 g/L for sulfur and non-sulfur indigo dye mixtures (MIX-ID) affirm 13% chemical oxygen demand (COD), 68.5% dissolved organic matter (as UVA254), and 98.4% color (indigo) removal. However, the non-sulfur indigo dye was tested with 10 g/L of the adsorbent, giving 45.4% COD, 74.6% dissolved organic matter (as UVA254), and 99% color (indigo) removal. The removal of indigo dye was compared to ozone- and peroxone-based advanced oxidation processes. Ozonation was ineffective at oxidizing the effluent, and even though the peroxone process was able to remove the color, the process increased COD. A regeneration pathway was proposed to recycle the used adsorbent and allow for resource recovery by separating pure indigo dye and reusable effluent for the textile process. The catalyst was reused three times to remove the dye from textile effluents without any loss of efficiency.

Half-Sandwich Iridium Complexes Based on β-Ketoamino Ligands: Preparation, Structure, and Catalytic Activity in Amide Synthesis.

A series of β-ketoamino-based N,O-chelate half-sandwich iridium complexes with the general formula [Cp*IrClL] have been prepared in good yields. These air-insensitive iridium complexes showed desirable catalytic activity in an amide preparation under mild conditions. A number of amides with diverse substituted groups were furnished in a one-pot reaction with good-to-excellent yields through an amidation reaction of NH2OH·HCl with aldehydes in the presence of these iridium(III) precursors. The excellent catalytic activity, mild reaction conditions, and broad substrate scope gave this type of iridium catalyst potential for use in industry. All of the obtained iridium complexes were well characterized by different spectroscopy techniques. The exact molecular structure of complex 3 has been confirmed by single-crystal X-ray analysis.

Bioinspired Durable Antibacterial and Antifouling Coatings Based on Borneol Fluorinated Polymers: Demonstrating Direct Evidence of Antiadhesion.

Substituting natural products for traditional poison-killing antifouling agents is an efficient and promising method to alleviate the increasingly serious ecological crisis and aggravate the loss due to marine biofouling. Herein, the successful synthesis of poly(methyl methacrylate-co-ethyl acrylate-co-hexafluorobutyl methacrylate-co-isobornyl methacrylate) copolymer (PBAF) with borneol monomers and fluorine by a free radical polymerization method is reported. The PBA0.09F coating exhibits outstanding antibacterial and antifouling activity, achieving 98.2% and 92.3% resistance to Escherichia coli and Staphylococcus aureus, respectively, and the number of Halamphora sp. adhesion is only 26 (0.1645 mm2) in 24 h. This remarkable antibacterial and antifouling performance is attributed to the incorporation of fluorine components into the copolymer, which induces a low surface energy and hydrophobicity and the complex molecular structure of the natural nontoxic antifouling agent borneol. In addition, the results showed that the contents of the adhesion-related proteins mfp-3, mfp-5, and mfp-6 were significantly reduced, which proved that natural substances affect the secretion of biological proteins. Importantly, the PBAF coating exhibits excellent environmental friendliness and long-term stability. The antifouling mechanism is clarified, and an effective guide for an environmentally friendly antifouling coating design is proposed.

Modeling molecular structure and behavior of microbial extracellular polymeric substances through interacting-particle reaction dynamics

Extracellular polymeric substances (EPS) are essential for bacteria to interact with external environments and play a key role in the formation of microbial aggregates. Unveiling the black box of EPS has become an urgent topic in the field of microbiology, medical science and environmental science. Here, we develop an explicit approach to describe the molecular structure and behaviors of EPS using interacting-particle reaction dynamics (iPRD). Three representative states of EPS (i.e., normal EPS layer, metal bridging EPS layer and extracted EPS layer) are qualitatively simulated at molecular scale and validated with previous research results on EPS. Furthermore, an averaged concentration representation method is proposed to quantitatively model the EPS-oriented bioprocesses. Through this method, the contents of protein and polysaccharide in EPS extracted by cation exchange resin are accurately predicted by our model (R2>0.982). This work gives new insights into EPS at the molecular scale and opens up new avenues for further exploring and modeling complex molecular structure and behaviors of EPS.

Amino group-driven distinguishing homocysteine from cysteine and glutathione in photoluminesecent signal of the iridium(III) complexes

In this work, six iridium(III) complexes have been designed, synthesized and characterized. The molecular structures of complex 1 ([(pba)2Ir(bpy-2N(CH3)2)]PF6), 2 ([(pba)2Ir(bpy-2NH2)]PF6) and 3 ([(pba)2Ir(bpy-2CH3)]PF6) were determined by single crystal X-ray diffraction. Upon addition of Hcy (homocysteine) to the solution of complex 1, a luminescent variation from orange red to green was observed by the naked eye, corresponding to a large blue shift from 604 nm to 498 nm (~106 nm). While the emission intensity of complex 1 was almost no change after addition of other common amino acids including Cys (cysteine) and GSH (glutathione). The aldehyde group of complex 1 formed a new thiazinane/thiazolidine ring with Hcy/Cys confirmed by 1H NMR and high-resolution mass spectrometry. And the new product 1-Hcy had a higher quantum yield than 1-Cys. Theoretical calculations showed that the HOMO (highest occupied molecular orbital) of 1-Hcy was located on the newly formed six-membered thiazinane ring, which was different from the HOMO of 1-Cys. Compared with the other iridium(III) complexes, we can speculate that the large blue shift and enhancement of the emission intensity of the complex 1 were related to the strong electron donating ability of the modified amino groups on bipyridine ligand. This will provide an idea for the design of ratio-based luminescence probes for Hcy in future.

Coordination from Heteroscorpionate Ligand Towards Pd(II) via Pd⋅⋅⋅Hδ−C(sp3) Interaction: Structural and Catalytic Studies

AbstractThe coordination ability of the heteroscorpionate ligand 2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1‐p‐tolylethanol (1) towards palladium (II) dihalides was evaluated. The structures of the respective palladium complexes (2 and 3) were elucidated in solution by NMR spectroscopy, and their molecular structures were established by single crystal X‐ray diffraction analyses. Both studies revealed the existence of Pd⋅⋅⋅Hδ−C(sp3) anagostic interactions. The molecular structure of complexes 2 and 3 displays coordination of ligand 1 to palladium in a κ3‐NNH tridentate fashion via two nitrogen atoms and one δ‐anagostic H⋅⋅⋅Pd interaction. The metal center exhibits a square pyramidal geometry. The distances of anagostic Hδ⋅⋅⋅Pd interactions ranged from 2.566 to 2.576 Å. The δ‐anagostic H⋅⋅⋅Pd interactions in complexes 2 and 3 were also identified by Bader's quantum theory of atoms in molecules (QTAIM) and non‐covalent interaction (NCI) analysis. The catalytic efficiencies of complexes 2 and 3 in the Suzuki‐Miyaura cross‐coupling reactions were evaluated and the results showed that palladium (II) dibromide complex is the most efficient of the series. Complex 3 was also evaluated in Mizoroki‐Heck cross‐coupling reactions.

Chemical Synthesis of Cell Wall Constituents of Mycobacterium tuberculosis.

The pathogen Mycobacterium tuberculosis (Mtb), causing tuberculosis disease, features an extraordinary thick cell envelope, rich in Mtb-specific lipids, glycolipids, and glycans. These cell wall components are often directly involved in host–pathogen interaction and recognition, intracellular survival, and virulence. For decades, these mycobacterial natural products have been of great interest for immunology and synthetic chemistry alike, due to their complex molecular structure and the biological functions arising from it. The synthesis of many of these constituents has been achieved and aided the elucidation of their function by utilizing the synthetic material to study Mtb immunology. This review summarizes the synthetic efforts of a quarter century of total synthesis and highlights how the synthesis layed the foundation for immunological studies as well as drove the field of organic synthesis and catalysis to efficiently access these complex natural products.

Base-Free Catalytic Wittig-/Cross-Coupling Reaction Sequence as Short Synthetic Strategy for the Preparation of Highly Functionalized Arylbenzoxepinones

AbstractThe facile synthesis of highly functionalized building blocks with potential biological activity is of great interest to medicinal chemistry. The benzoxepinone core structures commonly exhibit biological activity. Thus, a short and efficient synthetic route towards benzoxepine containing scaffold, which enables late stage modification was developed. Namely, base-free catalytic Wittig reactions enabled the synthesis of bromobenzoxepinones from readily available starting materials. Subsequent, Suzuki–Miyaura and Stille reactions proved to be suitable methods to access a variety of benzoxepinone diaryl derivatives by late stage modification in only three steps. This three-step reaction sequence is suitable for high throughput applications and gives facile access to highly complex molecular structures, which are suitable for further functionalization. The antiproliferative properties of selected arylbenzoxepinones­ were tested in vitro on monolayer tumor cell line A549. Notably, in this initial screening, these compounds were found to be active in the micromolar range.

A Presentation of Ionic Liquids as Lubricants: Some Critical Comments

Ionic liquids (ILs) are liquid materials at room temperature with an ionic intrinsic nature. The electrostatic interactions therefore play a pivotal role in dictating their inner structure, which is then expected to be far from the traditional pattern of classical simple liquids. Therefore, the strength of such interactions and their long-range effects are responsible for the ionic liquid high viscosity, a fact that itself suggests their possible use as lubricants. More interestingly, the possibility to establish a wide scenario of possible interactions with solid surfaces constitutes a specific added value in this use. In this framework, the ionic liquid complex molecular structure and the huge variety of possible interactions cause a complex aggregation pattern which can depend on the presence of the solid surface itself. Although there is plenty of literature focusing on the lubricant properties of ionic liquids and their applications, the aim of this contribution is, instead, to furnish to the reader a panoramic view of this exciting problematic, commenting on interesting and speculative aspects which are sometimes neglected in standard works and trying to furnish an enriched vision of the topic. The present work constitutes an easy-to-read critical point of view which tries to interact with the imagination of readers, hopefully leading to the discovery of novel aspects and interconnections and ultimately stimulating new ideas and research.

On mechanism of lignin decomposition – Investigation using microscale techniques: Py-GC-MS, Py-FT-IR and TGA

Lignin stands the most abundantly available source of renewable aromatic compounds which is generated as a useless waste by-product in numerous industrial processes, e.g., in pulp and paper manufacturing as well as during second-generation ethanol production. The present work aims to investigate the effect of reaction conditions (particularly the reaction atmosphere type) on the composition of the volatiles that evolved during the pyrolysis of lignin. The pyrolytic studies were carried out using coupled microscale techniques, i.e., Py-GC-MS, and Py-FT-IR. The pyrolysis is usually carried out under an inert atmosphere. Herein, there was additionally studied comprehensively the effect of oxidizing (CO2 and air) and reducing atmosphere (H2). There was found a profound impact of the processing temperature on the composition changes of volatiles. A minor effect was noted for the pyrolysis atmosphere on the qualitative composition of the volatiles, but certain quantitative differences between their concentration were observed. Their composition confirmed the complex molecular structure of lignin. Among the identified compounds, there were found phenol derivatives as primary products of cleavage of lignin structures as well as aliphatic oxygen compounds and aromatic hydrocarbons as the products of the secondary decomposition and deoxygenation thereof.

Simulating molecules on a cloud-based 5-qubit IBM-Q universal quantum computer

Simulating the behaviour of complex quantum systems is impossible on classical supercomputers due to the exponential scaling of the number of quantum states with the number of particles in the simulated system. Quantum computers aim to break through this limit by using one quantum system to simulate another quantum system. Although in their infancy, they are a promising tool for applied fields seeking to simulate quantum interactions in complex atomic and molecular structures. Here, we show an efficient technique for transpiling the unitary evolution of quantum systems into the language of universal quantum computation using the IBM quantum computer and show that it is a viable tool for compiling near-term quantum simulation algorithms. We develop code that decomposes arbitrary 3-qubit gates and implement it in a quantum simulation first for a linear ordered chain to highlight the generality of the approach, and second, for a complex molecule. We choose the Fenna-Matthews-Olsen (FMO) photosynthetic protein because it has a well characterised Hamiltonian and presents a complex dissipative system coupled to a noisy environment that helps to improve the efficiency of energy transport. The method can be implemented in a broad range of molecular and other simulation settings.

Anomalous magnetism of uranium(IV)-oxo and -imido complexes reveals unusual doubly degenerate electronic ground states

Anomalous magnetism of uranium(IV)-oxo and -imido complexes reveals unusual doubly degenerate electronic ground states

Multidimensional analytical protocols for the fractionation and analysis of complex polyolefins

AbstractAlthough produced from simple monomers that contain just carbon and hydrogen, polyolefin have complex molecular structures that are characterized by distributions in molar mass, chemical composition, and branching. Accordingly, a variety of advanced analytical techniques are needed for the comprehensive characterization of the molecular heterogeneity of polyolefins. These include different fractionation, spectroscopic, and thermal analysis methods. Very frequently, method couplings such as two‐dimensional liquid chromatography or the coupling of crystallization‐ and column‐based techniques are required. This review presents the current state of the art in multidimensional analysis of complex polyolefins. It discusses methods for bulk analysis as well as different analytical and preparative fractionation protocols. For different types of polyolefins it is shown that a preparative fractionation according to chemical composition/branching or molar mass helps to reduce the molecular complexity of the sample. Sample libraries can be obtained that may have narrow distributions regarding one molecular parameter. A detailed investigation of such library samples regarding other (broadly distributed) molecular parameters helps to fully explore the molecular heterogeneity of a complex sample.

Bis(diphenylphosphino)ethane nickel polychloridophenylthiolate complexes: synthesis and characterization

Reactions of (dppe)NiCl2 (dppe = 1,2-bis(diphenylphosphino)ethane) with chlorido-substituted phenyl thiolates (RClS−) produced the corresponding nickel thiolate complexes (dppe)Ni(SRCl)2 (RCl = 3,5-C6H3Cl2 (1), C6Cl5 (2)) in high isolated yields. Complexes 1 and 2 were characterized by spectroscopic techniques such as (UV–Vis, IR, 1H-, 31P{1H}-, 13C{1H}-NMR) as well as elemental analysis. The molecular structures of complexes 1 and 2, determined by X-ray diffraction measurements, have a cis square planar geometry.

Synthesis, Structure, and Catalytic Hydrogenation Activity of [NO]-Chelate Half-Sandwich Iridium Complexes with Schiff Base Ligands.

A series of N,O-coordinate iridium(III) complexes with a half-sandwich motif bearing Schiff base ligands for catalytic hydrogenation of nitro and carbonyl substrates have been synthesized. All iridium complexes showed efficient catalytic activity for the hydrogenation of ketones, aldehydes, and nitro-containing compounds using clean H2 as reducing reagent. The iridium catalyst displayed the highest TON values of 960 and 950 in the hydrogenation of carbonyl and nitro substrates, respectively. Various types of substrates with different substituted groups afforded corresponding products in excellent yields. All N,O-coordinate iridium(III) complexes 1-4 were well characterized by IR, NMR, HRMS, and elemental analysis. The molecular structure of complex 1 was further characterized by single-crystal X-ray determination.

In-depth phenolic characterization of iron gall inks by deconstructing representative Iberian recipes

Iron-gall ink is one of the most important inks in the history of western civilization. The deep black colour results from Fe3+ complexes with phenolic compounds available in gall extracts. Unfortunately, it induces the degradation of both ink and support over time. Furthermore, our knowledge of these complex molecular structures is limited. This work aims to overcome this gap, revealing essential information about the complex structures of these pigments and dyes that will create a breakthrough in the next generation of conservation treatments. It presents the first in-depth phenolic identification and quantification of extracts and inks, prepared with and without gum arabic (an essential additive in medieval recipes). Five representative Iberian recipes were selected and prepared. Their phenolic profile was analysed by HPLC–DAD and HPLC–ESI–MS, which revealed that the phenolic compounds present in higher concentration, in the gall extracts, are pentagalloylglucose and hexagalloylglucose (0.15 ± 0.01–32 ± 3 mg/mL), except for one recipe, in which gallic acid is the main phenolic. The influence of the ingredients is also discussed by deconstructing the recipes: extracts of additives as pomegranate peel and solvents used in the extraction of the galls (vinegar and white wine) were characterized.

Proton reduction by phosphinidene-capped triiron clusters

Bis(phosphinidene)-capped triiron carbonyl clusters, including electron rich derivatives formed by substitution with chelating diphosphines, have been prepared and examined as proton reduction catalysts. Treatment of the known cluster [Fe3(CO)9(µ3-PPh)2] (1) with various diphosphines in refluxing THF (for 5, refluxing toluene) afforded the new clusters [Fe3(CO)7(µ3-PPh)2(κ2-dppb)] (2), [Fe3(CO)7(µ3-PPh)2(κ2-dppv)] (3), [Fe3(CO)7(µ3-PPh)2(κ2-dppe)] (4) and [Fe3(CO)7(µ3-PPh)2(µ-κ2-dppf)] (5) in moderate yields, together with small amounts of the corresponding [Fe3(CO)8(µ3-PPh)2(κ1-Ph2PxPPh2)] cluster (x = -C4H6-, -C2H2-, -C2H4-, -C3H6-, -C5H4FeC5H4-). The molecular structures of complexes 3 and 5 have been established by X-ray crystallography. Complexes 1–5 have been examined as proton reduction catalysts in the presence of p-toluenesulfonic acid (p-TsOH) in CH2Cl2. Cluster 1 exhibits two one-electron quasi-reversible reduction waves at –1.39 V (ΔE = 195 mV) and at –1.66 V (ΔE = 168 mV; potentials vs. Fc+/Fc). Upon addition of p-TsOH the unsubstituted cluster 1 shows a first catalytic wave at –1.57 V and two further proton reduction processes at –1.75 and –2.29 V, each with a good current response. The diphosphine-substituted derivatives of 1 are reduced at more negative potentials than the parent cluster 1. Clusters 2–4 each exhibit an oxidation at ca. +0.1 V and a reduction at ca. –1.6 V; for 4 conversion to a redox active successor species is seen upon both oxidation and reduction. Clusters 2–4 show catalytic waves in the presence of p-TsOH, with cluster 4 exhibiting the highest relative catalytic current (icat/i0 ≈ 57) in the presence of acid, albeit at a new third reduction process not observed for 2 and 3. Addition of the dppf ligand to the parent diphosphinidene cluster 1 gave cluster 5 which exhibited a single reduction process at –1.95 V and three oxidation processes, all at positive values as compared to 2–4. Cluster 5 showed only weak catalytic activity for proton reduction with p-TsOH. The bonding in 4 was investigated by DFT calculations, and the nature of the radical anion and dianion is discussed with respect to the electrochemical data.

Thermal Field-Flow Fractionation as a Powerful Tool for the Fractionation of Complex Synthetic Polymers: A Perspective

Synthetic polymers have complex molecular structures with distributions in molar mass, chemical composition, functionality and molecular topology. For the comprehensive analysis of polymer structures, a number of advanced spectroscopic and fractionation techniques are used. For the fractionation of polymers, most frequently column-based methods are applied. These are of limited value for the separation of very high molar mass and fragile analytes. Thermal field-flow fractionation (ThFFF) as a channel-based method has developed into a powerful alternative and complementary technique to column-based fractionations. This perspective discusses novel applications of ThFFF and highlights its potential for the fractionation of polymer assemblies such as micelles, vesicles and nanogels.

Superconducting Scanning Tunneling Microscope Tip to Reveal Sub-millielectronvolt Magnetic Energy Variations on Surfaces.

Combining the complex ordering ability of molecules with their local magnetic properties is a little-explored technique to tailor spin structures on surfaces. However, revealing the molecular geometry can be demanding. Nickelocene (Nc) molecules present a large spin-flip excitation leading to clear changes of conductance at the excitation-threshold bias. Using a superconducting tip, we have the energy resolution to detect small shifts of the Nc spin-flip excitation thresholds, permitting us to reveal the different individual environments of Nc molecules in an ordered layer. This knowledge allows us to reveal the adsorption configuration of a complex molecular structure formed by Nc molecules in different orientations and positions. As a consequence, we infer that Nc layers present a strong noncollinear magnetic-moment arrangement.

ONO‐Pincer‐Type Coumarin‐Based Copper(II) Metalates: Effect on Alzheimer's Disease Pathologies in Caenorhabditis elegans

AbstractFour copper(II) complexes 1–4 of 3‐acetylchromene‐2‐one and substituted 3‐acetylchromene‐2‐one derived Schiff bases were synthesized and structurally characterized using analytical and spectral techniques. The molecular structure of complex 1 has been confirmed by single crystal X‐ray diffraction studies, which revealed that ligand 3‐acetylchromene‐2‐one‐4 N‐semicarbazone is coordinated to the metal as ONO pincer type ligand. Two nitrate molecules are coordinated to the copper ion through oxygen atoms, of which one nitrate molecule was found to coordinate via two oxygen atoms, thereby achieving six‐coordination. Preliminary biological studies like DNA and protein binding analyses indicated the binding of the ligands and complexes to CT‐DNA (Calf Thymus DNA) and BSA (Bovine Serum Albumin). We investigated the effects of complexes 1–4 against amyloid‐β (Aβ) toxicity using transgenic Caenorhabditis elegans strains expressing muscle‐ and neuronal‐specific human Aβ1‐42. The results showed that the complexes 2–4 remarkably reduced the Aβ‐induced paralysis phenotype, Aβ plaque deposition, and other Alzheimer's disease‐associated functional deficits in C. elegans by their potent antioxidant and anti‐aggregative properties. Complexes 2–4 delayed Alzheimer's disease pathologies, providing a basis for further investigating these effects on higher models.