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Abstract: The use of aluminium salts in papermaking has been linked well for over a century with causing degradation of paper. This is because the typical salts used in papermaking hydrolyse to release acid, which is a known catalyst that promotes degradation of cellulose, reducing both its degree of polymerisation and intrinsic strength. However, data reported here show that simplistic statements about the acidity of aluminium salts hide an interesting and complicated chemistry. In particular the presence of anions capable of coordinating with aluminium in solution is shown to exert an overwhelming influence on degradation reactions catalysed by the metal. Furthermore, the work highlights potential ways of pacifying aluminium cations contained in paper, effectively reducing or eliminating the degradation reactions they promote. [Copyright &y& Elsevier]

High interest in the detection and quantification of (elevated) intracellular zinc levels in tumor cells has been aroused due to the crucial physiological roles and the pathophysiological implications of zinc. Despite their diverse applications, benzo[1,2- b :4,5- b′ ]difuran (BDF) derivatives as a fluorescent Zn(II) probe in living cells have not been reported. By careful chemical design of molecular components, we prepared and fully characterized a new amphiphilic BDF-based fluorophore. A series of experiments were carried out to test the cytotoxicity and cellular uptake behavior in human cancer derived HeLa cells. The ligand fluorescence is strongly quenched upon the addition of Zn(II) ions. The high cell membrane permeability, low cytotoxicity and significant fluorescence quenching behavior render this ligand very promising for in vitro detection of Zn(II) ions in biological systems. [ABSTRACT FROM AUTHOR]

The tetranuclear Cu2+/Ca2+/Ca2+/Cu2+ complex based on Malten ligand has been investigated as a platform for anion binding. Simple organic carboxylates and non‐steroidal anti‐inflammatory drugs (NSAIDs) have been tested, revealing the ability of the platform to bind them. The receiving platform hosts at least two guests in solution although a third anion can be bound, as suggested by X‐ray diffraction analysis. The addition of the anions is accompanied by a color change of the solution, making the system a colorimetric sensor for carboxylates (LOD values comprised between 3.6 and 20.7 ppm). A fluorescent system consisting of the 2‐(3‐oxido‐6‐oxoxanthen‐9‐yl)benzoate (fluorescein anion) linked to the tetranuclear platform has been also prepared and used in a chemosensing ensemble approach to signal the presence of the selected anions (Log K between 2.6 and 5.6 for the addition of two guests). The latter also works in a paper strip test, offering the chemosensor a possible practical application. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hydrogen tunneling is a type of quantum tunneling in which a hydrogen atom passes through a potential barrier without reaching the transition state governed by classical mechanics. The participation of hydrogen tunneling in a chemical reaction (stoichiometric or catalytic) can result in the formation of products that without this phenomenon would be impossible to achieve or would be formed in a very slow way. This concept paper aims to review some of the most representative examples of transition‐metal mediated chemical reactions involving hydrogen tunneling. The experimental tools to determine the possibility of the participation of quantum tunneling in a chemical reaction are presented. In addition, the theoretical methods that have been developed to calculate the effect of quantum tunneling on chemical reactions are discussed. Finally, from a personal perspective, the steps to be taken in order to predict and implement this phenomenon are proposed. [ABSTRACT FROM AUTHOR]

The C═N bond is a critical structural piece of many N-donor ligand scaffolds and is central to the properties and reactivity of important coordination complexes. For example, C═N units play a key role in the "redox non-innocence" of α-diimine complexes and in making charge-transfer excited-state character available to complexes of N-heterocyclic ligands such as bipyridine. In N-heterocycles like pyridine, benzannulation can be used to extend the conjugated C═N-containing π-system to quinoline (2,3-benzopyridine) to acridine (2,3-benzoquinoline). This stabilizes the lowest unoccupied molecular orbital of the molecule and boosts its electron-accepting properties, but the position of the benzannulation matters. For example, phenanthridine (3,4-benzoquinoline), an asymmetric isomer of acridine, bears a similarly electronically accessible extended π-system but with a more chemically isolated "imine-like" C═N moiety. This award paper presents an overview of our work investigating the impact of such site-selective benzannulation on the chemistry and properties of phenanthridine as a molecule and ligand. [ABSTRACT FROM AUTHOR]

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of University Chemistry is the property of Peking University, College of Chemistry & Molecular Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thiosemicarbazone complexes possess structural diversity and variable bonding patterns and potential biological implications and ion sensing abilities. The ability of the transition metals to acquire different geometries like octahedral, square planar and tetrahedral in different coordination environments has encouraged researchers to explore the coordination chemistry of thiosemicarbazone complexes which can also vary upon changing aldehydes and ketones, substituents attached to the carbonyl moiety, metal and its oxidation state, geometries, counter ions, presence of a solvent or additional molecules in the structures and substituents on the S or N(4)-atoms. This review aims to summarize recent developments in the synthesis and medicinal importance of thiosemicarbazone ligands and particular emphasis on their metal complexes. The mixed ligand-metal complexes have an important role to play in biological systems because a number of ligands try to combine with the same metal ions in vivo. Different ligands have different biological activities producing synergetic results and enhancing the potency of the formed complex. They also have a role to play in the storage and transport of substances, therefore the review article also covers the mixed ligand complexes of thiosemicarbazones with hetero ligands like 1,10-phenanthroline, pyridine, triphenyl phosphine etc. and their mechanistic action and medicinal benefits in recent years. The binuclear complexes of thiosemicarbazones with two different and same metal ions have also been explored here. Dinuclear complexes have been shown to possess interesting structures and in most cases, such complexes containing metal–metal bond also affects the complex's magnetic properties as well. It has been well discussed in the course of this study that metal complexes show enhanced biological activity than the free ligand or metal ion. The studies cited in the review have been sourced from publications indexed in known databases. Some of the recently explored structural alterations have been discussed in the paper and future substituted thiosemicarbazones and their complexes may emerge as multi-target inhibitors. [ABSTRACT FROM AUTHOR]

Magnetoactive coordination compounds exhibiting bi- or multistability between two or more magnetic stable states present an attractive example of molecular switches. Currently, the research is focused on molecular nanomagnets, especially single molecule magnets (SMMs), which are molecules, where the slow relaxation of the magnetization based on the purely molecular origin is observed. Contrary to ferromagnets, the magnetic bistability of SMMs does not require intermolecular interactions, which makes them particularly interesting in terms of application potential, especially in the high-density storage of data. This paper aims to introduce the readers into a basic understanding of SMM behaviour, and furthermore, it provides an overview of the attractive Co(II) SMMs with emphasis on the relation between structural features, magnetic anisotropy, and slow relaxation of magnetization in tetra-, penta-, and hexacoordinate complexes. [ABSTRACT FROM AUTHOR]

In this paper, the adsorption of cyanide and its combination with zinc sulfate on the surface of sphalerite (110) was studied by density functional theory (DFT), and its configurational relationship was analyzed by coordination chemistry. The calculation results show that the adsorption configuration stability of CN− is stronger than that of Zn(CN)2; the chemical bond of Zn(OH)2 is less covalent. The three adsorption modes all make the surface of sphalerite lose more electrons, thereby weakening the reactivity of S and Zn atoms on the sphalerite surface. During the CN− adsorption process, both the 3d and 4p orbital peak energy levels of Zn decrease, indicating the strong inhibitory effect of CN−. Coordination chemistry also shows that CN− matches the Zn ion orbital in sphalerite and the π electron pair on the Zn ion can easily interact with the empty π orbital on CN− to form π-backbonding. [ABSTRACT FROM AUTHOR]

The unsubstituted bis-hydrotris(1-pyrazolyl)borate) (Tp) ligand framework has been used to synthesise a range of heteroleptic Ln(III) coordination complexes [Ln(Tp)2(X)]. The precursor complexes [Ln(Tp)2(OTf)] 1-Ln (Ln = Y, Eu, Gd, Yb; OTf = triflate) were synthesised by reaction of Ln(OTf)3 with two equivalents of K(Tp). The 8-coordinate β-diketonate complexes [Ln(Tp)2(hfac)] 2-Ln (Ln = Y, Eu, Yb; hfac = hexafluoroacetylacetonate) were synthesised from Ln(OTf)3 by reacting 1-Ln generated in situ with an equivalent of K(hfac). The 7-coordinate amide complexes [Ln(Tp)2(N″)] 3-Ln (Ln = Y, Yb; N″ = bis(trimethylsilyl)amide) were synthesised from 1-Ln by reaction with K(N″). Reactivity of 3-Ln towards protonolysis was demonstrated by the isolation of the hydroxide dimer [{Y(Tp)2(μ -OH)}2] 4-Y from adventitious reaction with water and the aryloxide complex [Ln(Tp)2(OAr)] 5-Ln (Ln = Y, Yb; OAr = 2,6- t Bu2-4-Me-phenoxide) from reaction with H(OAr). Full characterisation data are presented for all complexes, including solid-state molecular structure determination by single-crystal X-ray diffraction. Scorpionate nitrogen-donor trispyrazolylborate (Tp) ligands are well-known in transition metal chemistry. However, in lanthanide chemistry the literature is dominated by substituted analogues of Tp and the chemistry of the unsubstituted Tp ligand has remained largely unexplored. We discovered as part of a different research project that the [Ln(Tp)2]+ unit is both highly reactive and capable of supporting a variety of co-ligands. This paper builds on this discovery to present rational synthetic routes to a series of heteroleptic lanthanide complexes, [Ln(Tp)2(X)]. [ABSTRACT FROM AUTHOR]

Electron donor–acceptor (EDA) complexes are characterized by charge-transfer (CT) processes between electron-rich and electron-poor counterparts, typically resulting in a new absorption band at a higher wavelength. In this paper, we report a series of novel 2,6-di(imino)pyridine ligands with different electron-rich aromatic substituents and their 1:2 (metal/ligand) complexes with zinc(II) in which the formation of a CT species is promoted by the metal ion coordination. The absorption properties of these complexes were studied, showing the presence of a CT absorption band only in the case of aromatic substituents with donor groups. The nature of EDA interaction was confirmed by crystallographic studies, which disclose the electron-poor and electron-rich moieties involved in the CT process. These moieties mutually belong to both the ligands and are forced into a favorable spatial arrangement by the coordinative preferences of the metal ion. [ABSTRACT FROM AUTHOR]

• Coordination chemistry of thiosemicarbazide and its non-Schiff base derivatives. • Summary of development in TSC ligands over the 90 years since the first complexes. • Different possibilities of thiosemicarbazide modification. • Structural properties and synthesis of complexes with non-Schiff base ligands. • Structural variety, biological and physicochemical properties of TSC complexes. Very rich coordination chemistry of thiosemicarbazide based ligands is mainly associated with the diversity of their Schiff base derivatives, known as thiosemicarbazones. The significant interest in thiosemicarbazones and their metal complexes arises from a wide range of valuable biological, chemical and physico-chemical features, as documented by numerous review papers in medicinal, structural, analytical chemistry, catalysis and other. The thiosemicarbazide based ligands other than Schiff bases did not draw the same attention. A literature survey, however, shows considerable number of non-Schiff base derivatives with interesting coordination chemistry, giving rise to metal complexes with pronounced structural diversity and useful properties. Considering the polydentate thiosemicarbazide scaffold [N–N–C(=S)–N] it is not surprising that its other derivatives can offer versatile coordination modes and stable complexes with variety of metal ions. This article attempts to bring together the thiosemicarbazide derived ligands other than Schiff bases, and to explore their coordination tendencies as well as the structural aspects of their metal complexes. The first papers in coordination chemistry of thiosemicarbazide were reported exactly 90 years ago. Therefore, it is also our aim to gain better overview of various types of thiosemicarbazide ligands that have emerged since, and to understand different possibilities of thiosemicarbazide modification. In order to present and compare the molecular and supramolecular properties the review primary relies on structurally characterized coordination compounds. It also includes some experimental charge density findings in an effort to explain behaviour of thiosemicarbazide ligands at subatomic level. [Display omitted] [ABSTRACT FROM AUTHOR]

Several radiometals are of interest in the development of new α-emitting radiopharmaceuticals. This review highlights the role of coordination chemistry in the design of 225Ac, 212/213Bi, 212Pb, 149Tb, 227Th, and 223/224Ra radiopharmaceuticals to treat cancer. Several chelators have recently been developed that are addressing the specific requirements of each radiometal to provide outstanding radiolabelling and in vivo properties. These advances are supporting the momentum that is building around radiopharmaceuticals for targeted α therapy. This paper is a review of the coordination chemistry of radiometals for targeted α therapy. [ABSTRACT FROM AUTHOR]

The phosphanoxy‐substituted phosphaalkene bearing the P=C−O−P skeleton can be prepared from diphosphene Mes*P=PMes* (Mes*=2,4,6‐tBu3C6H2), and their use for catalysis is of interest. In this paper, complexation of the phosphanoxy‐substituted phosphaalkenes with gold are investigated, and the catalytic activity of the mono‐ and bis(chlorogold) complexes are subsequently evaluated. Reaction of the P=C−O−P compound with (tht)AuCl (tht=tetrahydrothiophene) showed dominant coordination on the sp3 phosphorus, and complete coordination on the sp2 phosphorus required removal of tetrahydrothiophene. Atoms In Molecules (AIM) analysis based on the X‐ray structure of the mono(chlorogold) complex indicated a pseudo coordinating interaction between the gold center and the P=C unit. The bis(chlorogold) complexes displayed conformational isomerism, and catalyzed the cycloisomerization/alkoxycyclization of 1,6‐enyne and for hydration of terminal alkyne without activation treatment. Even the mono(chlorogold) complexes catalyzed the alkoxycyclization reactions without a silver co‐catalyst, indicating that the alcohols were effective in activating the AuCl unit. [ABSTRACT FROM AUTHOR]

In view of their intensive use as ligands in many reactions catalyzed by transition-metal complexes, modulation of the bonding properties of N-heterocyclic carbenes (NHCs) on a rational basis is highly desirable, which should enable optimization of current applications or even promote new functions. In this paper, we provide a quantitative analysis of the chemical bond between a metal fragment AuCl and a series of 29 different NHCs in [(NHC)AuCl] complexes. NHCs electronic properties are modified through: i) variation of the groups attached to the NHC nitrogen atoms or backbone; ii) change of unsaturation/size of the NHC ring; iii) inclusion of paracyclophane moieties; or iv) heteroatom substitution on the NHC ring. For evaluating the donation and back-donation components of the Dewar-Chatt-Duncanson (DCD) model in the NHC−AuCl bond, we apply the charge-displacement (CD) analysis within the NOCV (natural orbitals for chemical valence) framework, a methodology that avoids the constraint of using symmetrized structures. We show that modulation of the NHC bonding properties requires substantial modification of their structure, such as, for instance, insertion of two ketone groups into the NHC backbone (which enhances the π back-donation bond component and introduces an effective electronic communication within the NHC ring) or replacement of a nitrogen atom in the ring with an sp3 or sp2 carbon atom (which increases and decreases the π back-donation bond component, respectively). We extend our investigation by quantitatively comparing the NHC electronic structures for a subset of 13 NHCs in [(NHC)PPh] adducts, the 31P NMR chemical shift values of which are experimentally available. The latter have been considered as a suitable tool for measuring the NHCs π acceptor properties [Bertrand et al., Angew. Chem. Int. Ed. 2013, 52, 2939-2943]. We show that information obtained using the metal fragment can be transferred to the PPh moiety and vice versa. However, the 31P NMR chemical shift values only qualitatively correlate with the π acceptor properties of the NHCs, with the stronger π acidic carbenes as the most outliners. [ABSTRACT FROM AUTHOR]

Cis-trans isomerization of the oxamide function, that allows preparation of heterodinuclear complexes in which two different 3d metal ions are introduced in identical coordination sites, does not work in the case of 3d-4f complexes. [Display omitted] • Isomerization of the oxamido group is governed by the basicity of the reaction medium. • Heterodinuclear transition metal complexes can be obtained with symmetrical ligands. • This cis-trans isomerization does not work with transition metal-lanthanide complexes. Synthesis of heterodinuclear 3d transition metal complexes in which two metal ions are introduced in equivalent coordination sites of a ligand is quite uncommon. We have previously shown that the application of the cis–trans isomerization of the oxamido group was able to furnish such a possibility. In the present paper we demonstrate that this synthetic pathway, relying on the possibility of changing the conformation (cis vs trans) of the oxamido group, can be extended to other ligands. Although we have not been able to characterize these complexes by structural determinations, FAB-MS, EPR and magnetic data do confirm the efficiency of this reaction pathway. We also demonstrate that the cis–trans isomerization of the oxamido group is not due to a particular property of the ion involved in the reaction. In fact, isomerization is governed by the basicity of the reaction medium. According to the reaction condition, it is possible to favor or not this phenomenon, and to increase the accessibility to a larger number of novel genuine complexes. But the oxophilic character of the lanthanide ions limits the use of this synthetic pathway because it impedes this isomerization. Eventually, the very weak magnetic interactions observed in these Cu-Gd complexes can be explained thanks to spin polarization. [ABSTRACT FROM AUTHOR]

Five metal dithiocarbamate complexes [M(PTHIQDTC)2] [where PTHIQDTC is (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline dithiocarbamate anion and M is Ni(II) (1), Sn(II) (2), Hg(II) (3), Pb(II) (4) and Zn(II) (5)] were synthesized from the reaction of MX2 (X is Cl– for 1–3 and OAc– for 4–5) with ligand of triethylammonium (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline dithiocarbamate [Et3NH][PTHIQDTC] in methanolic solution at room temperature. The five complexes were characterized by IR, 1H and13C NMR, mass spectrometry, elemental analysis and TGA analysis. Recrystallization of [Zn(PTHIQDTC)2] (5) in dimethylsulfoxide (DMSO) converts 5 to [Zn(PTHIQDTC)2(DMSO)] (6). The structure of complex 6 has been determined by X-ray crystallography. The X-ray structural analysis of 6 indicated that the zinc(II) is five-coordinated in a distorted trigonal-bipyramidal by four S atoms from two (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline dithiocarbamate anion ligands (PTHIQDTC) and one O atom from DMSO. [ABSTRACT FROM AUTHOR]

The preparation and characterization of two novel europium–azobenzene complexes that demonstrate the effectiveness of this ligand for stabilizing reactive, redox-active metals are reported. With the family of rare earth metals receiving attention due to their potential as catalysts, critical components in electronic devices, and, more recently, in biomedical applications, a detailed understanding of factors contributing to their coordination chemistry is of great importance for customizing their stability and reactivity. This study introduces azobenzene as an effective nonprotic ligand system that provides novel insights into rare earth metal coordination preferences, including factors contributing to the coordinative saturation of the large, divalent europium centers. The two compounds demonstrate the impact of the solvent donors (tetrahydrofuran (THF) and dimethoxyethane (DME)) on the overall coordination chemistry of the target compounds. Apart from the side-on coordination of the doubly-reduced azobenzene and the anticipated N-N bond elongation due to decreased bond order, the two compounds demonstrate the propensity of the europium centers towards limited metal-π interactions. The target compounds are available by direct metallation in a straightforward manner with good yields and purity. The compounds demonstrate the utility of the azobenzene ligands, which may function as singly- or doubly-reduced entities in conjunction with redox-active metals. An initial exploration into the computational modeling of these and similar complexes for subsequent property prediction and optimization is performed through a methodological survey of structure reproduction using density functional theory. [ABSTRACT FROM AUTHOR]

A DFT (density functional theory) investigation using the generalized gradient approximation BP86 and the hybrid B3LYP functionals and TZP basis set is dealing with the bonding, the electronic structure and the interaction types occurred within the XCuL' and (LCuL')+ (X = Cl, CH3, CN, CF3, L = CO, NH3, PH3, and L' = C2H2, C2H4, C4H6, C6H6, and NHC) complexes. The optimized structures and energy decomposition analysis of XCuL' and (LCuL')+ complexes were employed to provide a relationship between the bond lengths, the X-Cu-L' and L-Cu-L' bond angles, the Wiberg indices, the Mayer bond orders, interaction energies, and the Cu-L' bonding character. The energy decomposition analysis indicates that the interactions occurred for various L' ligands are more electrostatically than covalently bonded to the Cu(I) center formally of + I oxidation state. The different contributions stemming from electrostatic and orbital interactions are significant, in relationship with the ionic and covalent characters, respectively. The contribution from σ-donation to the bonding energy was found more important for the NHC ligand than the alkene and alkynes ones. However, the contribution from π-back-donation was found to be comparable for all complexes. The σ-bonding contributes more than 50% into the total orbital interaction overtaking those of π type, in accordance with the population of the copper 4s orbital, particularly in the presence of C6H6 and NHC ligands. The interactions in all complexes exhibit comparable deformation densities and NOCV orbital shapes. Besides, it has been shown that the ΔEprep contributes weakly in the deformation of the interacting fragments as well as the BSSE correction which impacts weakly or negligibly the interactions between the fragments composing different XCuL' and (LCuL')+ complexes. [ABSTRACT FROM AUTHOR]

The mode of coordination of copper(II) ions with dopamine (DA, L) in the binary, as well as ternary systems with Ado, AMP, ADP, and ATP (L′) as second ligands, was studied with the use of experimental—potentiometric and spectroscopic (VIS, EPR, NMR, IR)—methods and computational—molecular modeling and DFT—studies. In the Cu(II)/DA system, depending on the pH value, the active centers of the ligand involved in the coordination with copper(II) ions changed from nitrogen and oxygen atoms (CuH(DA)3+, Cu(DA)2+), via nitrogen atoms (CuH2(DA)24+), to oxygen atoms at strongly alkaline pH (Cu(DA)22+). The introduction of L′ into this system changed the mode of interaction of dopamine from oxygen atoms to the nitrogen atom in the hydroxocomplexes formed at high pH values. In the ternary systems, the ML′-L (non-covalent interaction) and ML′HxL, ML′L, and ML′L(OH)x species were found. In the Cu(II)/DA/AMP or ATP systems, mixed forms were formed up to a pH of around 9.0; above this pH, only Cu(II)/DA complexes occurred. In contrast to systems with AMP and ATP, ternary species with Ado and ADP occurred in the whole pH range at a high concentration, and moreover, binary complexes of Cu(II) ions with dopamine did not form in the detectable concentration. [ABSTRACT FROM AUTHOR]

Metal complexes of benzotriazole-type ligands continue to attract the intense interest of many inorganic chemistry groups around the world for a variety of reasons, including their aesthetically beautiful structures, physical properties and applications. 1-methylbenzotriazole (Mebta) is the N-substituted archetype of the parent 1H-benzotriazole. The first attempt to build a "periodic table" of Mebta, which includes its complexes with several metal ions, is described in this work. This, at first glance, trivial ligand has led to interesting results in terms of the chemistry, structures and properties of its metal complexes. This work reviews the to-date published coordination chemistry of Mebta with Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(I), Cu(II), Zn(II), Pd(II), Au(I) and {UVIO2}2+, with emphasis on their preparations, reactivity, structures and properties. Unpublished results from our group comprising other Co(II), Ni(II), Cu(II) and Zn(II) complexes, as well as Cd(II), Hg(II), Ag(I), In(III) and Sn(IV) ones are briefly reported. Mebta can also provide access to 1D and 3D heterometallic thiocyanato-bridged Co(II)/Hg(II) and Ni(II)/Hg(II) compounds. In almost all cases, Mebta behaves as a monodentate ligand with the nitrogen of position 3 of the azole ring as the donor atom. However, there are two copper complexes in which this molecule adopts a bidentate bridging coordination behavior. Our efforts to complete the "periodic table" of Mebta are continued. [ABSTRACT FROM AUTHOR]

Iron is an essential element for almost all organisms on Earth. It is necessary for a number of crucial processes such as hemoglobin and myoglobin transport and storage of oxygen in mammals; electron transfer support in a variety of iron-sulfur protein or cytochrome reactions; and activation and catalysis of reactions of a wide range of substrate like alkanes, olefins, and alcohols. Living organisms adopted iron as the main metal to carry out all of these functions due to the rich coordination chemistry of its two main redox states, Fe2+ and Fe3+, and because of its abundance in the Earth's crust and oceans. This paper presents an overview of the coordination chemistry of iron that makes it suitable for a large variety of functions within biological systems. Despite iron's chemical advantages, organisms were forced to manage with some drawbacks: Fe3+ insolubility and the formation of toxic radicals, especially the hydroxyl radical. Iron chemistry within biology is an example of how organisms evolved by creating molecular machinery to overcome these difficulties and perform crucial processes with extraordinary elegance and efficiency. © 2017 IUBMB Life, 69(6):382-388, 2017 [ABSTRACT FROM AUTHOR]

Sophus Mads Jørgensen (1837-1914) was one of the important chemists of the second half of the XIX century and the first decade of the XX century. He was one of the founders of the chemistry of complex compounds. He also made major contributions to the chemistry of platinum, cobalt, chromium and rhodium compounds. The purpose of this paper is to familiarize readers with the important events in the life of Jørgensen and his writing activities, in particular with his chemistry books. In addition, his research activities are briefly described. [ABSTRACT FROM AUTHOR]

The noncovalent interactions of heavy pnictogens with π‐arenes play a fundamental role in fields like crystal engineering or catalysis. The strength of such bonds is based on an interplay between dispersion and donor/acceptor interactions, and is generally attributed to the presence of π‐arenes. Computational studies of the interaction between the heavy pnictogens As, Sb and Bi and cyclohexane, in comparison with previous studies on the interaction between heavy pnictogens and benzene, show that this concept probably has to be revised. A thorough analysis of all the different energetic components that play a role in these systems, carried out with state‐of‐the‐art computational methods, sheds light on how they influence one another and the effect that their interplay has on the overall system. Furthermore, the analysis of such interactions leads us to the unexpected finding that the presence of the pnictogen compounds strongly affects the conformational equilibrium of cyclohexane, reversing the relative stability of the chair and boat‐twist conformers, and thus suggesting a possible application of tuneable dispersion energy donors to stabilise the desired conformation. [ABSTRACT FROM AUTHOR]

Transition metal complexes have historically played a pivotal role in creating vibrant pigments utilized across artistic mediums such as ceramics, paintings, and glass mosaics. Despite their extensive historical use, our understanding of the mechanisms governing transition metal complex behavior has predominantly emerged in recent times, leaving numerous aspects of this process ripe for exploration. These complexes exhibit striking color variations under diverse conditions when employed in pigment formulations. This review utilizes a bottom-up scientific approach, spanning from microscopic to macroscopic scales, to unravel the molecular origins of the colors generated by transition metal complexes in pigments and ceramic glazes. Advanced spectroscopy techniques and computational chemistry play pivotal roles in this endeavor, highlighting the significance of understanding and utilizing analytical data effectively, with careful consideration of each technique's specific application. Furthermore, this review investigates the influence of processing conditions on color variations, providing valuable insights for artists and manufacturers aiming to enhance the precision and quality of their creations while mitigating environmental impact. [ABSTRACT FROM AUTHOR]

A complex of the natural flavonoid kaempferol with zinc (Kam-Zn) was synthesized, and its physicochemical properties were investigated using spectroscopic methods such as Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible (UV-Vis) spectroscopy and theoretical chemistry. Biological studies were conducted to evaluate the cytotoxic and antiproliferative effects of these complexes on MCF-7 breast cancer cells. Treatment with Kam 100 µM (84.86 ± 7.79%; 64.37 ± 8.24%) and Kam-Zn 100 µM (91.87 ± 3.80%; 87.04 ± 13.0%) showed no significant difference in proliferation between 16 h and 32 h, with the gap width remaining stable. Both Kam-Zn 100 μM and 200 μM demonstrated effective antiproliferative and cytotoxic activity, significantly decreasing cell viability and causing cell death and morphology changes. Antioxidant assays revealed that Kam (IC50 = 5.63 ± 0.06) exhibited higher antioxidant potential compared to Kam-Zn (IC50 = 6.80 ± 0.075), suggesting that zinc coordination impacts the flavonoid's radical scavenging activity by the coordination of metal ion to hydroxyl groups. Computational studies revealed significant modifications in the electronic structure and properties of Kam upon forming 1:1 complexes with Zn2+ ions. Spectroscopy analyses confirmed structural changes, highlighting shifts in absorption peaks and alterations in functional group vibrations indicative of metal–ligand interactions. FT-IR and UV-Vis spectra analysis suggested that Zn coordinates with the 3-OH and 4C=O groups of ligand. These findings suggest that the Kam-Zn complex exhibits interesting antiproliferative, cytotoxic and modified antioxidant effects on MCF-7 cells, providing valuable insights into their structural and anticancer properties. [ABSTRACT FROM AUTHOR]

In this paper, we report a facile hydrothermal route to prepare different morphologies of zinc sulfide nanostructures, using a new inorganic precursor, zinc phthalate [Zn(pht)(HO)], and different sulfur sources. This study focuses on the effect of different sulfur sources on the crystal structure and morphology of the products. The structural and morphological studies of the products were performed by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction. The high temperature (over 1020 °C) hexagonal ZnS nanostructured spheres self-assembled from ZnS nanocrystals have been synthesized at a low temperature of 160 °C by using thioglycolic acid as sulfur source. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are versatile ligands capable of forming a wide range of cluster motifs when reacted with 3d, 4for 3d/4fmetal ions. Synthetic modification at the calix[4]arene methylene bridge offers a unique opportunity to explore cluster formation with these alternative building blocks. Here, we present the synthesis of a range of bis-calix[4]arenes that are tethered by alkyl chains, as well as exploratory structural studies into cluster-forming reactions. Single crystals were formed in four cases, and from the X-ray structures elucidated it is possible to conclude that sufficiently long alkyl tethers allow for the formation of established cluster topologies without disruption to the core coordination chemistry. Synthetic modification at the calix[4]arene methylene bridge offers a unique opportunity to synthesise alternative supramolecular building blocks. This paper describes the synthesis of a range of alkyl-tethered bis-calix[4]arenes, as well as exploratory structural studies into polymetallic cluster formation. [ABSTRACT FROM AUTHOR]

Two copper(II) complexes with benzotriazole-based ligands having pyridyl and quinolinyl arms were synthesized in good yields and characterized fully via spectroscopic and crystallographic techniques. The crystal structures of the complexes revealed different coordination environments around copper(II) centers. The difference in structure was due to the steric effect of the ligands, which resulted in an octahedral and a square pyramidal geometry of the resulting complexes in the solid state. Both the air-stable complexes were utilized as precatalysts in catalytic click reactions and A3 coupling. [ABSTRACT FROM AUTHOR]

The ligand H3L (6‐[3‐oxo‐3‐(2‐hydroxyphenyl)propionyl]pyridine‐2‐carboxylic acid), which exhibits two different coordination pockets, has been exploited to engender and study energy transfer (ET) in two dinuclear [LnIIILnIII′] analogues of interest, [EuYb] and [NdYb]. Their structural and physical properties have been compared with newly synthesised analogues featuring no possible ET ([EuLu], [NdLu], and [GdYb]) and with the corresponding homometallic [EuEu] and [NdNd] analogues, which have been previously reported. Photophysical data suggest that ET between EuIII and YbIII does not occur to a significant extent, whereas emission from YbIII originates from sensitisation of the ligand. In contrast, energy migration seems to be occurring between the two NdIII centres in [NdNd], as well as in [NdYb], in which YbIII luminescence is thus, in part, sensitised by ET from Nd. This study shows the versatility of this molecular platform to further the investigation of lanthanide‐to‐lanthanide ET phenomena in defined molecular systems. [ABSTRACT FROM AUTHOR]

Six pyridylideneamine (PYE)‐containing bidentate ligands and their bis‐cyclometallated Ir(III) complexes have been synthesised and fully characterised. The PYE groups show a contribution from a neutral imine resonance form and a zwitterionic pyridinium form. NMR spectroscopy of the para‐substituted ligands and complexes show those with a C6H4 bridging group have the fastest PYE rotation. X‐ray crystallography of p‐1 and p‐3 shows the PYE N‐donor is trigonal planar whereas for the ortho‐complexes it is more pyramidalized implying an increased contribution of the zwitterionic resonance form for the ortho‐complexes. [ABSTRACT FROM AUTHOR]

Unexpected inversion‐symmetry breaking was observed in the order–disorder phase transitions of [M(acac)2(abco)2] (1; M=Co2+, 2; Ni2+, acac−=2,4‐pentanedionato, abco=1‐azabicyclo‐[2.2.2]‐octane=quinuclidine) during heating. The isostructural, transition‐free complexes [M(acac)2(cabco)2] (3; M=Co2+, 4; Ni2+, cabco=3‐chloro‐1‐azabicyclo‐[2.2.2]‐octane=3‐chloroquinuclidine) were also studied for comparison. Complexes 1 and 2 crystallized in ordered phases in the centrosymmetric I2/m space group at 100 K, whereas they crystallized in disordered phases in the non‐symmetric I2 space group at 300 K. The 60° step rotation disordering of the abco ligands was observed in the electron density maps of 1 and 2, which was consistent with the transition enthalpies estimated by differential scanning calorimetry (DSC). Gradual phase transitions were observed for 1 and 2 by DSC and powder X‐ray diffraction (PXRD) at approximately 225 K. The inversion‐symmetry disordering was likely induced by the local pseudo‐symmetry of the abco ligands, increasing from trigonal to hexagonal and the increased steric repulsion pathways among them. [ABSTRACT FROM AUTHOR]

This paper discusses the development of environmentally-friendly precursor inks suited for ink-jet printing of functional ceramic coatings. We synthesized superconducting materials, SrTiO3 thin films for coated conductor applications and transparent TiO2 photocatalytic coatings. Here, we discuss all aspects of ink formulation, including the stabilization of metal ions, nanoparticle inks or combination of both. This demands the investigation and determination of the inks rheological parameters. Ceramic nanoparticles are often incorporated in our inks to decrease thermal processing temperatures (e.g., TiO2 or YSZ coatings...) or enhance the properties of the functional ceramic coating (e.g., pinning centres in superconducting coatings). These ceramic nanoparticles (ZrO2, HfO2, TiO2...) are synthesized through methods based on microwave heating from aqueous and/or organic solutions. With that, we aim at developing smart and environmentally friendly processes that require lower energy input. [ABSTRACT FROM AUTHOR]

Lanthanides (Ln) are critical raw materials, however, their mining and purification have a considerable negative environmental impact and sustainable recycling and separation strategies for these elements are needed. In this study, the precipitation and solubility behavior of Ln complexes with pyrroloquinoline quinone (PQQ), the cofactor of recently discovered lanthanide (Ln) dependent methanol dehydrogenase (MDH) enzymes, is presented. In this context, the molecular structure of a biorelevant europium PQQ complex was for the first time elucidated outside a protein environment. The complex crystallizes as an inversion symmetric dimer, Eu2PQQ2, with binding of Eu in the biologically relevant pocket of PQQ. LnPQQ and Ln1Ln2PQQ complexes were characterized by using inductively coupled plasma mass spectrometry (ICP‐MS), infrared (IR) spectroscopy, 151Eu‐Mössbauer spectroscopy, X‐ray total scattering, and extended X‐ray absorption fine structure (EXAFS). It is shown that a natural enzymatic cofactor is capable to achieve separation by precipitation of the notoriously similar, and thus difficult to separate, lanthanides to some extent. [ABSTRACT FROM AUTHOR]

Because of their rigidity, polycyclic aromatic hydrocarbons (PAHs) have become a significant building block in molecular materials chemistry. Fusion or doping of boron into PAHs is known to improve the optoelectronic properties by reducing the LUMO energy level. Herein, we report a comprehensive study on the syntheses, structures, and photophysical properties of a new class of fused N‐heterocyclic boranes (NHBs), pyrene‐ and benzene‐linked in a "Janus‐type" fashion (2–4, 6–9, and 11). Remarkably, these examples of fused NHBs display fluorescent properties, and collectively their emission spans the visible spectrum. The pyrene‐fused NHBs all display blue fluorescence, as the excitations are dominated by the pyrene core. In notable contrast, the emission properties of the benzene‐fused analogues are highly tunable and are dependent on the electronics of the NHB fragments (i.e. the functional group directly bound to the boron atoms). Pyrene‐fused 2–4 and 11 represent the only molecules in which the K‐region of pyrene is functionalized with NHB units, and while they exhibit distorted (twisted or stair‐stepped) pyrene cores, benzene‐fused 6–9 are planar. The electronic structure and optical properties of these materials were probed by computational studies, including an evaluation of aromaticity, electronic transitions, and molecular orbitals. [ABSTRACT FROM AUTHOR]

The rational control of the electrochemical properties of polyoxovanadate‐alkoxide clusters is dependent on understanding the influence of various synthetic modifications on the overall redox processes of these systems. In this work, the electronic consequences of ligand substitution at the heteroion in a heterometal‐functionalized cluster was examined. The redox properties of [V5O6(OCH3)12FeCl] (1‐[V5FeCl]) and [V5O6(OCH3)12Fe]X (2‐[V5Fe]X; X=ClO4, OTf) were compared in order to assess the effects of changing the coordination environment around the iron center on the electrochemical properties of the cluster. Coordination of a chloride anion to iron leads to an anodic shift in redox events. Theoretical modelling of the electronic structure of these heterometal‐functionalized clusters reveals that differences in the redox profiles of 1‐[V5FeCl] and 2‐[V5Fe]X arise from changes in the number of ligands surrounding the iron center (e.g. 6‐coordinate vs. 5‐coordinate). Specifically, binding of the chloride to the sixth coordination site appears to change the orbital interaction between the iron and the delocalized electronic structure of the mixed‐valent polyoxovanadate core. Tuning the heterometal coordination environment can therefore be used to modulate the redox properties of the whole cluster. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fluorimetric determination of formaldehyde using a nickel complex immobilized as a solid phase. • Formaldehyde analysis was able to be conducted in 05 min with a relative standard deviation estimated at 1.10 %. • Nickel waste was completely recovered implementing the principles of greener and sustainable chemistry. Formaldehyde (FA) is a highly toxic substance present in many matrices, including freshwater as well as found in natural mechanisms such as rainfall and combustion of organic matter. Consumption of water contaminated with high levels of FA can cause severe short-term or long-term health problems. Due to these health risks, procedures are necessary to determine and quantify FA in aqua sources This paper reports on a study of fluorimetric determination of FA using a nickel(2 +)-diketonate coordination compound immobilized as a solid precursor. The compound was characterized by electronic absorption, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetry (TG), optical microscopy (OM), and scanner electron microscopy (SEM). The methodology was based on the reaction of the synthesized compound with an ammoniacal buffer generating a selective reagent for formaldehyde: fluoral-P. The product of the reaction generates 3,5-diacetyl-1,4-dihydrolutidine (DDL), which is responsible for the fluorescence of the system. Several parameters such as temperature, duration of heating time, and dilution effect with the best effects were studied to carry out FA determination. Under the optimum experimental conditions, a linear response ranging from 1.0 to 10.0 mg/L FA (R = 0.997 and n = 10), and a detection (3σ criterion) and quantification (10 σ criterion) limit estimated at 0.129 and 0.389 mg/L, respectively were achieved. The FA analysis was able to be conducted in 05 min with a relative standard deviation estimated at 1.10 %. [ABSTRACT FROM AUTHOR]

The study of small synthetic models for the highly selective removal of uranyl ions from seawater with amidoxime-containing materials is a valuable means to enhance their recovery capacity, leading to better extractants. An important issue in such efforts is to design bifunctional ligands and study their reactions with trans-{UO2}2+ in order to model the reactivity of polymeric sorbents possessing both amidoximate and another adjacent donor site on the side chains of the polymers. In this work, we present our results concerning the reactions of uranyl and pyrimidine-2-amidoxime, a ligand possessing two pyridyl nitrogens near the amidoxime group. The 1:2:2 {UO2}2+/pmadH2/external base (NaOMe, Et3N) reaction system in MeOH/MeCN provided access to complex [UO2(pmadH)2(MeOH)2] (1) in moderate yields. The structure of the complex was determined by single-crystal X-ray crystallography. The UVI atom is in a distorted hexagonal bipyramidal environment, with the two oxo groups occupying the trans positions, as expected. The equatorial plane consists of two terminal MeOH molecules at opposite positions and two N,O pairs of two deprotonated η2 oximate groups from two 1.11000 (Harris notation) pmadH− ligands; the two pyridyl nitrogen atoms and the –NH2 group remain uncoordinated. One pyridyl nitrogen of each ligand is the acceptor of one strong intramolecular H bond, with the donor being the coordinated MeOH oxygen atom. Non-classical Caromatic-H⋯X (X=O, N) intermolecular H bonds and π–π stacking interactions stabilize the crystal structure. The complex was characterized by IR and Raman spectroscopies, and the data were interpreted in terms of the known structure of 1. The solid-state structure of the complex is not retained in DMSO, as proven via 1H NMR and UV/Vis spectroscopic techniques as well as molar conductivity data, with the complex releasing neutral pmadH2 molecules. The to-date known coordination chemistry of pmadH2 is critically discussed. An attempt is also made to discuss the technological implications of this work. [ABSTRACT FROM AUTHOR]

The N-oxide functional group has been exploited for synthetic strategies and drug design, and it has been utilized in imaging agents. Herein, we present rare examples of neutral heteroleptic cyclometallated Ir(III) compounds that contain an uncoordinated N-oxide functional group. These species, along with others described within, were verified by NMR, EA, HRMS, and single-crystal X-ray analysis. N-oxide-containing Ir(III) species were prepared selectively in high yields > 66% from chloro-bridged Ir(III) dimers with Acipimox, a picolinate-type ligand containing the N-oxide functional group. Non-N-oxide analogs were synthesized in a similar fashion (yields > 77%). Electrochemical comparison (cyclic voltammetry) indicates that the presence of an N-oxide functional group anodically shifts the reduction potential, suggesting that the N-oxide is acting as an electron-withdrawing group in these species. Crystallographic studies were pursued to examine the coordination behavior of these N-oxides compared to their non-oxidized congeners. The Ir(III) complexes with Acipimox indeed leave the N-oxide uncoordinated and exposed on the complexes. The uncoordinated N-oxide group is influential in directing the packing structures of these complexes directly through C-H···O and O···π interactions at the N-oxide. The crystallographic characterization of cationic Ir(III) compounds with uncoordinated nitrogen atoms is also presented. The C-H···N interactions between these complexes form a variety of dimers, finite chains, and continuous chains. Future work will focus on functionalizing the cationic Ir(III) species into their corresponding N-oxide derivatives and rigorously characterizing how the N-oxide functional group impacts the optical properties of transition metal compounds in both cationic and neutral complexes. [ABSTRACT FROM AUTHOR]

Cooperative effect: This cover artwork is inspired by the ancient Chinese myth of "King Yi Shooting Down Nine Suns". In the picture, bamboo represents the trans‐isomer of the ligand. After chelation of metallic ions with trans‐ligands under solvothermal condition, a cis‐LMIICl2 could be formed. Similarly, a bow, which stands for the cis‐LMIICl2, is made from pieces of bamboo and rope under hot temperatures. Just as the spectra discrepancy between cis‐LMIICl2 and trans‐isomer is sharply magnified, the bow can send arrows far away, as the legend goes, even to shoot the other nine suns down. More information can be found in the Full Paper by H.‐B. Xu, M.‐H. Zeng, et al. on page 5177. [ABSTRACT FROM AUTHOR]

In this paper we test a solvent-free microwave assisted synthesis method with a known Ni 7 complex, [Ni 7 (chp) 12 (OH) 2 (CH 3 OH) 6 ] (2), and then extended the method to a more complex ligand system. We prepare two new trinuclear Ni(II) complexes ([Ni 3 (chp) 4 (tBuSALOH) 2 (MeOH) 5 ] (4) and [Ni 3 (chp) 4 (iPrSALOH) 2 (MeOH) 6 ] (5)) and report here their characterization and magnetic properties. [ABSTRACT FROM AUTHOR]

The hydration reaction is defined as the transfer of an ion or neutral chemical species from the gaseous phase into water, Mn+(g) → Mn+(aq). In this process, water molecules bind to metal ions through ion-dipole bonds of mainly electrostatic character. The hydration reaction is always strongly exothermic with increa sing heat of hydration with increasing charge density of the ion. The structures of the hydrated metal ions in aqueous solution display a variety of configurations depending on the size and electronic properties of the metal ion. The basic configurations of hydrated metal ions in aqueous solution are tetrahedral, octahedral, square antiprismatic, and tricapped trigonal prismatic. This paper gives an overview of the structures of hydrated metal ions in aqueous solution with special emphasis on those with a non-regular coordination figure. Metal ions without d-electrons in the valance shell form regular aqua complexes with a coordination figure, allowing a maximum number of water molecules to be clustered around the metal ion. This number is dependent on the ratio of the metal ion radius to the atomic radius of oxygen in a coordinated water molecule (1.34 Å). The lighter lanthanoid(III) ions have a regular tricapped trigonal prismatic configuration with the M-O distance to the capping water molecules somewhat longer than to the prismatic ones. However, with increasing atomic number of the lanthanoid( III) ions, an increasing distortion of the capping water molecules is observed, resulting in a partial loss of water molecules in the capping positions for the heaviest lanthanoids. Metal ions with d4 and d9 valance shell electron configuration, as chromium(II) and copper( II), respectively, have Jahn—Teller distorted aqua complexes. Metal ions with low charge and ability to form strong covalent bonds, as silver(I), mercury(II), palladium(II), and platinum( II), often display distorted coordination figures due to the second-order Jahn—Teller effect. Metal ions with d10s² valence shell electron configuration may have a stereochemically active lone electron pair (hemi-directed complexes) or an inactive one (holo-directed). The hydrated tin(II), lead(II), and thallium(I) ions are hemi-directed in aqueous solution, while the hydrated bismuth(III) ion is holo-directed. The structures of the hydrated cationic oxometal ions are reported as well. [ABSTRACT FROM AUTHOR]