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The dn number or configuration is a very useful parameter in transition metal chemistry because it conveys information about the expected properties of a d-block metal complex, including its shape, magnetism, thermodynamic stability, kinetic lability, and spectroscopic properties. The dn number can be determined from either the oxidation state (OS) or valence number (VN) of the metal centre, and since, in most cases, these are numerically equal, the derived dn value is the same. However, examples are discussed where the OS and VN are not equal, which results in unavoidable ambiguities in dn values. Following a discussion of these examples, a revised definition of dn is proposed based on the occupation of the frontier molecular orbitals of the complex.

Sigma complexes containing η²-H2 ligands, with both hydrogen atoms interacting with the metal center and with each other, are well known nowadays. The possibility of η¹-H2 coordination, with only one hydrogen atom interacting with the metal center, remains an intriguing, but unreported, possibility. In this study, we used the hidden descriptors (HD) strategy previously developed in our group to investigate the capacity of well-established metal fragments to achieve stable LnM (η¹-H2) metal complexes. Computational techniques, including low-cost density functional theory (DFT) calculations and the BDE Matrix App are used. The results confirm that the search for stable LnM(η¹-H2) complexes is challenging, as no obvious candidate can be identified. Hints are obtained about what the properties of this hypothetic metal fragment should be, such as a strong tendency to covalent association with ligands. The outcomes of this research provide a comprehensive framework for comparing and investigating atypical candidates for this type of bonding and serve as a valuable resource for future explorations in this field. [ABSTRACT FROM AUTHOR]

The dn number or configuration is a very useful parameter in transition metal chemistry because it conveys information about the expected properties of a d-block metal complex, including its shape, magnetism, thermodynamic stability, kinetic lability, and spectroscopic properties. The dn number can be determined from either the oxidation state (OS) or valence number (VN) of the metal centre, and since, in most cases, these are numerically equal, the derived dn value is the same. However, examples are discussed where the OS and VN are not equal, which results in unavoidable ambiguities in dn values. Following a discussion of these examples, a revised definition of dn is proposed based on the occupation of the frontier molecular orbitals of the complex. [ABSTRACT FROM AUTHOR]

The β− emitter, rhenium-188 (188Re), has long been recognized as an attractive candidate for targeted cancer radionuclide therapy (TRNT). This transition metal shares chemical similarities with its congener element technetium, whose nuclear isomer technetium-99m (99mTc) is the current workhorse of diagnostic nuclear medicine. The differences between these two elements have a significant impact on the radiolabelling methods and should always receive critical attention. This review aims to highlight what needs to be considered to design a successful radiopharmaceutical incorporating 118Re. Some of the most effective strategies for preparing therapeutic radiopharmaceuticals with 188Re are illustrated and rationalized using the concept of the inorganic functional group (core) and a simple ligand field theoretical model combined with a qualitative definition of frontiers orbitals. Of special interest are the Re(V) oxo and Re(V) nitrido functional groups. Suitable ligands for binding to these cores are discussed, successful clinical applications are summarized, and a prediction of viable future applications is presented. Rhenium-188 decays through the emission of a high energy beta particle (2.12 MeV max energy) and a half-life of 16.9 h. An ideal biological target would therefore be a high-capacity target site (transporters, potential gradients, tumour microenvironment) with less emphasis on saturable targets such as overexpressed receptors on smaller metastases. [ABSTRACT FROM AUTHOR]

In this Concept article we provide a brief overview of the design and preparation of N‐heterocyclic carbenes carrying weakly coordinating anions (WCA‐NHCs). The anionic charge in these ligand systems is located on an exocyclic group, for example, B(C6F5)3, tethered to the backbone of the imidazole ring, thus resembling a weakly coordinating moiety. With the general guiding principle behind the application of WCA‐NHCs being the conversion of otherwise cationic NHC complexes into their overall neutral congeners, numerous transition metal as well as main group element complexes were isolated during the last decade, which are summarized herein. [ABSTRACT FROM AUTHOR]

The β− emitter, rhenium-188 (188Re), has long been recognized as an attractive candidate for targeted cancer radionuclide therapy (TRNT). This transition metal shares chemical similarities with its congener element technetium, whose nuclear isomer technetium-99m (99mTc) is the current workhorse of diagnostic nuclear medicine. The differences between these two elements have a significant impact on the radiolabelling methods and should always receive critical attention. This review aims to highlight what needs to be considered to design a successful radiopharmaceutical incorporating 118Re. Some of the most effective strategies for preparing therapeutic radiopharmaceuticals with 188Re are illustrated and rationalized using the concept of the inorganic functional group (core) and a simple ligand field theoretical model combined with a qualitative definition of frontiers orbitals. Of special interest are the Re(V) oxo and Re(V) nitrido functional groups. Suitable ligands for binding to these cores are discussed, successful clinical applications are summarized, and a prediction of viable future applications is presented. Rhenium-188 decays through the emission of a high energy beta particle (2.12 MeV max energy) and a half-life of 16.9 h. An ideal biological target would therefore be a high-capacity target site (transporters, potential gradients, tumour microenvironment) with less emphasis on saturable targets such as overexpressed receptors on smaller metastases.

The collagen-integrin interactions are mediated by the doubly charged Mg2+ cation. In nature this cation seems to have the optimal binding strength to stabilize this complex. It is essential that the binding is not too weak so that the complex becomes unstable, however, it is also of importance that the ligand-receptor binding is still labile enough so that the ligand can separate from the receptor in a suited environment. In the case of crystal growing for experimentally useful integrin-collagen fragment complexes it turned out that Co2+ cations are ideal mediators to form stable complexes for such experiments. Although, one can argue that Co2+ is in this context an artificial cation, however, it is now of special interest to test the impact of this cation in cell-culture experiments focusing on integrin-ligand interactions. In order to examine, in particular, the role cobalt ions we have studied a Co2+ based model system using quantum chemical calculations. Thereby, we have shown that hybrid and long-range corrected functional, which are approximations provide already a sufficient level of accuracy. It is of interest to study a potential impact of cations on the binding of collagen-fragments including collagens from various species because different integrins have numerous biological functions (e.g. Integrin – NCAM (Neural cell adhesion molecule) interactions) and are triggered by intact and degraded collagen fragments. Since integrin–carbohydrate interactions play a key role when bio-medical problems such as tumor cell adhesion and virus-host cell infections have to be addressed on a sub-molecular level it is essential to understand the interactions with heavy-metal ions also at the sub-atomic level. Our findings open new routes, especially, in the fields of tissue repair and neuro-oncology for example for cell-culture experiments with different ions. Since Co2+ ions seem to bind stronger to integrin than Mg2+ ions it should be feasible to exchange these cations in suited tumor tissues although different cations are present in other metalloproteins which are active in such tissues. Various staining methods can be applied to document the interactions of integrins with carbohydrate chains and other target structures. Thereby, it is possible to study a potential impact of these interactions on biological functions. It was therefore necessary to figure out first which histological–glycobiological experimental settings of tumor cells are suited for our purpose. Since the interactions of several metalloproteins (integrin, ADAM12) with polysialic acid and the HNK-1 epitope play a crucial role in tumor tissues selected staining methods are proper tools to obtain essential information about the impact of the metal ions under study.

Transition metal porphyrazines are a widely used class of compounds with applications in catalysis, organic solar cells, photodynamic therapy, and nonlinear optics. The most prominent members of that family of compounds are metallophtalocyanines, which have been the subject of numerous spectroscopic and theoretical studies. In this work, the electronic structure and X‐ray absorption characteristics of three Cu‐porphyrazine derivatives are investigated by means of modern electronic structure theory. More precisely, the experimentally observed N K‐edge and Cu L‐edge features are presented and reproduced by time‐dependent density functional theory, restricted open‐shell configuration interaction, and a restricted active space approach. Where possible, the calculations are used to interpret the observed spectroscopic features in terms of electronic transitions and, furthermore, to connect spectral differences to chemical variations. Part of the discussion of the computational results concerns the impact of various parameters and approximations that are used for the calculations, for example, the choice of active space. [ABSTRACT FROM AUTHOR]

Single atom catalysts (SACs) are emergent catalytic materials that have the promise of merging the scalability of heterogeneous catalysts with the high activity and atom economy of homogeneous catalysts. Computational, first-principles modeling can provide essential insight into SAC mechanism and active site configuration, where the sub-nm-scale environment can challenge even the highest-resolution experimental spectroscopic techniques. Nevertheless, the very properties that make SACs attractive in catalysis, such as localized d electrons of the isolated transition metal center, make them challenging to study with conventional computational modeling using density functional theory (DFT). For example, Fe/N-doped graphitic SACs have exhibited spin-state dependent reactivity that remains poorly understood. However, spin-state ordering in DFT is very sensitive to the nature of the functional approximation chosen. In this work, we develop accurate benchmarks from correlated wavefunction theory (WFT) for relevant octahedral complexes. We use those benchmarks to evaluate optimal DFT functional choice for predicting spin state ordering in small octahedral complexes as well as models of pyridinic and pyrrolic nitrogen environments expected in larger SACs. Using these guidelines, we determine Fe/N-doped graphene SAC model properties and reactivity as well as their sensitivities to DFT functional choice. Finally, we conclude with broad recommendations for computational modeling of open-shell transition metal single-atom catalysts.

The Evans method is routinely utilised to collect paramagnetic susceptibility data via the employment of relevant Nuclear Magnetic Resonance (NMR) methods. As the sample is normally spun, the lack of such a function on benchtop NMR instrumentation required a “static” approach to be employed. We have utilised the static Evans method approach to measure the magnetic susceptibilities, and subsequently the effective magnetic moment, of a series of synthesised transition metal acetylacetonate complexes in order to appraise the d-electron configuration. The obtained values were compared to those obtained using a Guoy balance and theoretical calculations. The collection of T1 relaxation data further exemplifies the effect of the paramagnetic centre in terms of aiding relaxation, and therefore links to Magnetic Resonance Imaging (MRI) contrast agents, thus providing students with real-world perspective of the experiment conducted. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis, spectral properties and structural futures of NHC stabilized halosilylene have been reviewed. • Reactions of NHC stabilized halosilylene with organic substrates have been presented. • Reactions of NHC stabilized halosilylene with main group substrates have been discussed. • Reactions of NHC stabilized halosilylene with transition metal substrates have been presented. Abstract The isolation of a rare and highly unstable silicon(II) dihalide using N-heterocyclic carbene (NHC) proved to be a landmark achievement in the field of silicon chemistry. The first stable NHC stabilized halosilylene was isolated and structurally characterized in 2009. Subsequently the study of NHC stabilized halosilylenes over the past nine years has opened-up a new dimension in the field of organosilicon chemistry. NHC stabilized halosilylene compounds have been extensively used as starting materials for the synthesis of rare organosilicon compounds like small ring systems with high ring-strain energy containing silicon (silaoxirane), C4-silyl substituted NHC, Si–Si multiple bond, molecule with rare Si–M bond (M = main group or transition metals), dichlorosilamines (Si N), silaisontriles, trisilaallenes (silicon analogue of allene) etc. These studies clearly demonstrated the potential applications of NHC stabilized halosilylenes in various fields of organosilicon chemistry. The present review summarizes the progress and scope of NHC-halosilylene chemistry. In particular, an overview of synthetic strategies, spectral properties, key structural features and available bonding analysis are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Two cobalt(II) oxaporphyrins (OTPPCoCl and OTPPCoSbF6) are synthesized in this work and are characterized, including by X‐ray crystallography. Both complexes are tested as catalysts in the copolymerization of propylene oxide (PO)/cyclohexene oxide (CHO) and CO2. Polycarbonate is obtained in CHO/CO2 copolymerization with OTPPCoCl as a catalyst, whereas in the case of PO, cyclic carbonate (CC) is majorly formed. An anion exchange from Cl− to SbF6− of the cobalt(II) oxaporphyrin leads to a drastic change in the product selectivity: sole polyether is afforded for both epoxides. The polyether formation by OTPPCoSbF6 is postulated to proceed via a cationic mechanism. Further, an equivalent admixture of OTPPCoCl and OTPPCoSbF6 allows the formation of poly(propylene carbonate). In this copolymerization, the latter catalyst acts as a PO activator, while OTPPCoCl functions as the initiator. In addition, density functional theory (DFT) calculations reveal a lower ring‐opening energy of PO by OTPPCoSbF6, compared with the usual propagating species, OTPPCo‐alkoxides and OTPPCo‐carbonates. [ABSTRACT FROM AUTHOR]

ABSTRACT Sterically demanding Fe- and Co-based olefin polymerization catalysts 2-Fe and 2-Co bearing 2,6-bis(biphenylmethyl)-4-methylaniline substituted bis(imino)pyridine ligands were synthesized and evaluated for ethylene polymerization. The late-transition metal complexes were characterized by X-ray diffraction, NMR spectroscopy, and HRMS, while their resultant polymers were characterized by size-exclusion chromatography and 1H NMR spectroscopy. While catalyst 2-Fe was inactive, catalyst 2-Co was found to polymerize ethylene and avoid any detectable chain-transfer to aluminum events that are known to plague other Fe- and Co-based catalyst systems and to limit molecular weight. Furthermore, 2-Co displays virtually perfect thermal stability up to 80 °C and shows greatly enhanced thermal stability at 90 °C as compared to previously reported analogues. These observations are attributed to the extreme steric demand imposed by the ligand which mitigates catalyst transfer, deactivation, and decomposition reactions. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3990-3995 [ABSTRACT FROM AUTHOR]

ABSTRACT Metal-ligand coordination has been proven to be an attractive strategy to tune a polymer network's dynamic mechanical properties, such as self-healing ability. Nonetheless, the role of counter anions is often overlooked. To address this, a series of polydimethylsiloxane (PDMS) films crosslinked through lanthanide metal cations (Eu3+, Tb3+)-bipyridine interactions have been prepared and studied. Neutral 2,2'-bipyridine ligands were embedded into the linear polydimethylsiloxane (PDMS) chain through polycondensation. With nitrate ( [ABSTRACT FROM AUTHOR]

An activated fragment which is structurally unstable when considered isolated can be stabilized through binding to a suitable molecular environment; for instance, to a transition-metal fragment. The metal fragment may be designed in a shell-wise build-up of a surrounding molecular environment. However, adding more and more atoms in a consecutive fashion soon leads to a combinatorial explosion of structures, which is unfeasible to handle without automation. Here, we present a fully automated and parallelized framework that constructs such an embedding environment atom-wise. Molecular realizations of such an environment are constructed based on simple heuristic rules intended to screen a sufficiently large portion of the possible compound space and are then subsequently optimized by electronic structure methods. (Constrained-optimized) structures are then evaluated with respect to a scoring function, for which we choose here the concept of gradient-driven molecule construction. This concept searches for structure modifications that reduce the forces on all atoms. We develop and analyze our approach at the example of CO2 activation by reproducing a known compound and mapping out possible alternative structures and their effect on the stabilization of a (bent) CO2 ligand. For all generated structures, the nuclear gradient on the activated fragment and its coordination energy are evaluated to steer the design process. © 2017 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Reaction between lithium indenyl and a chlorine substituted alpha diimine of the form [{Cl(NPh) 2 }C)] 2 unexpectedly yielded the corresponding NH rearranged derivative [PhN(H)C(C 9 H 6 )] 2 ( 1 ) rather than the predicted symmetrical α-diimine. This compound 1 was characterised by 1 H NMR, 13 C{ 1 H} NMR and mass spectrometry, and additionally by X-ray diffraction. It was found that 1 was the first indene-substituted and symmetric secondary amine which was also highly fluorescent in DMSO. The reactivity of 1 towards simple inorganic and organometallic transition metals precursors based on the MX 2 fragments, where M = Group 10 metals and X = halides or methyl groups, has been investigated. Surprisingly, the reaction with [PtMe 2 (COD)] led to the coupling reaction between the indenyl groups incorporated at the C–C ligand backbone and a new ligand ( 2 ) was discovered, in an attempt to synthesise the metal-linked diamine. Single crystal X-ray diffraction studies confirm this compound 2 to feature coupled indenyl residues and delocalised C–C bonds in the solid state. Structural authentication by X-ray crystallography showed compound 2 to be a very rare example of flat and extended aromatic organic molecule and mass spectrometry, IR and NMR spectroscopy were carried out to gain further insight into the solid state and solution phase structures. Further experiments to synthesise analogues of [PhN(H)C(Ind)] 2 aiming to shift a likely equilibrium in favour the imine tautomer, by introducing bulky ortho substituents onto the benzene ring (R = Me, iPr) showed the presence of the imine tautomer to be increasingly favoured in 1 H NMR spectra, with an increase in the steric bulk of the ortho substituents. However, the enamine tautomer is still observed to a minor extent even with isopropyl substituents and yields of these desired compounds were low on steric grounds. [ABSTRACT FROM AUTHOR]

ABSTRACT Pd-initiated polymerization and oligomerization of diazo compounds containing a dialkoxyphosphinyl group are described. Polymerization of 2-dialkoxyphosphinylethyl diazoacetates with π-allylPdCl-based initiating systems afforded CC main chain polymers bearing phosphonate on each main chain carbon atom. The quantitative transformation of the side chain phosphonate to phosphonic acid resulted in the formation of water soluble polymers having the acid groups accumulated around their main chains, although the carbonyl ester linkage in the side chain was cleaved via intramolecular acid-assisted hydrolysis in water at 80 °C. Pd-initiated oligomerization of diethyl diazomethylphosphonate yielded an oligomeric product bearing diethoxyphosphiny groups directly attached to its main chain carbons, with unexpected incorporation of azo group in the main chain framework. Hydrolysis of the phosphonate of the oligomer afforded a water-soluble product, which was revealed to show higher proton conductivity than poly(vinylphosphonic acid) under certain conditions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1742-1751 [ABSTRACT FROM AUTHOR]

ABSTRACT In this work, we investigate the influence of the amide solvent chemical structure on the properties of poly(3-hexylthiophene) (P3HT) prepared via direct arylation polymerization (DArP). Our findings indicate that for successful polymerization the amide must possess an acyclic aliphatic structure since cyclization of an amide results in a complete shutdown of DArP reactivity as evidenced by failed polymerization in N-methylpyrrolidone, whereas the presence of an aromatic motif renders the amide solvent susceptible to CH activation and leads to incorporation of the solvent structure into the P3HT backbone, as demonstrated on the example of N, N-diethylbenzamide. Additionally, we observed that the steric bulk of alkyl substituents on both the nitrogen atom and the carbonyl group within the amide structure has to be delicately balanced for optimal DArP reactivity. In the optimal cases, P3HT is obtained in high yield, with high molecular weight and contains a minimal amount of structural defects. The obtained polymer samples were comprehensively studied in terms of their chemical structure, optical, thermal and solid-state properties in thin films using GPC analysis, 1H NMR, MALDI, UV-vis, GIXRD spectroscopy, and DSC. We additionally note a drastic difference of the amide solvent effect between DArP and Stille polymerization. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2494-2500 [ABSTRACT FROM AUTHOR]

Three half ‐ metallocene ruthenium(III) complexes, [(Cp*RuCl2)PPh2R] (R   =   C6H4–OCH3,C6H5, and C5H5N were prepared. These Ru(III) complexes polymerized MMA successfully via ATRP in the absence of any reducing agent or free radical initiator. All of three complexes produced a linear relationship between ln[Mn]0/[Mn] versus the reaction time and the living properties through a linear increase in molecular weight versus conversion. Especially, well ‐ defined PMMA and high initiation efficiency were obtained in the presence of 10 ppm catalysts. [ABSTRACT FROM AUTHOR]

ABSTRACT In this work, we present a powerful set of synthetic strategies aimed at minimization of auxiliary reagent loading for direct arylation polymerization (DArP) of 2-bromo-3-hexylthiophene. As such, we report efficient lowering of Pd(OAc)2 catalyst loading as well as loading of other auxiliary reagents, such as neodecanoic acid and N, N-dimethylacetamide. Unprecedented low loadings of catalyst down to 0.0313% (313 ppm) were achieved, while producing polymer in high yield (91% after Soxhlet extraction), with a high molecular weight (24.2 kDa) and carefully controlled chemical structure thus making the optimized DArP protocol significantly more cost-effective, convenient, sustainable, and environmentally friendly. The resulting polymer samples were thoroughly investigated in terms of their chemical structure as well as optical, thermal, chain ordering and electronic properties using GPC analysis, 1H NMR, MALDI, UV-vis, GIXRD spectroscopy, DSC, and SCLC hole mobility measurements. The results demonstrate that the reagent lowering strategies increase the polymer regioregularity from 94.6 to 96.5% as evidenced by 1H NMR spectra and corroborated by GIXRD, DSC, and UV-vis measurements. Additionally, polymer samples obtained at low reagent loading are more uniformly proton-terminated as evidenced by 1H NMR and MALDI end-group analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1492-1499 [ABSTRACT FROM AUTHOR]

A series of 2-(1-(2,4-bis((di(4-fluorophenyl)methyl)-6-methylphenylimino)ethyl)-6-(1-(aryl­imino)ethyl)pyridines is synthesized and used to form their corresponding iron(II) and cobalt(II) chloride complexes thereof. All the organic compounds are fully characterized by elemental analysis, and IR and 1H/13C NMR spectroscopy, whereas the corresponding iron and cobalt complexes are characterized by elemental analysis and IR spectroscopy, as well as single-crystal crystallography for the Fe2, Co1, and Co2 complexes, revealing a distorted trigonal bipyramidal structure. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all the iron complexes exhibit high activities toward ethylene polymerization at 60 °C; meanwhile, all the cobalt analogs demonstrate slightly lower activities at the optimized temperatures of 60 °C (MAO as cocatalyst) or 70 °C (MMAO as cocatalyst). All the polyethylenes obtained from cobalt precatalysts possess narrow polydispersity and lower molecular weights than those from their iron analogs. [ABSTRACT FROM AUTHOR]

Water-soluble binary and ternary copper complexes of polyelectrolytes were synthesized, and the toxicity of these complexes was tested in mouse fibroblast cell line (L929) in vitro. Both the binary and ternary complexes were prepared at the ratio of 0.4 mole copper(II) ions per monomer of acrylic acid and 0.5 mole copper(II) ions per monomer of methyl vinyl ether maleic anhydride, furthermore at the ratio of 1 and 2 mole bovine serum albumin per mole of polyacrylic acid and poly(methyl vinyl ether-co-maleic anhydride), respectively. Compared to binary copper(II)–polyelectrolyte complexes, these ternary complexes have been determined to be of least toxicity. [ABSTRACT FROM PUBLISHER]

Bearing a negative charge in the backbone of the heterocycle, these carbenes can convert otherwise cationic NHC complexes into their overall neutral congeners. Catalysis, main group element chemistry, N-heterocyclic carbene, transition metal chemistry, weakly coordinating anions Keywords: catalysis; main group element chemistry; N-heterocyclic carbene; transition metal chemistry; weakly coordinating anions EN catalysis main group element chemistry N-heterocyclic carbene transition metal chemistry weakly coordinating anions 1 1 1 06/22/22 20220615 NES 220615 B Piggyback b : N-heterocyclic carbenes carrying weakly coordinating anions (WCA-NHCs) are an important and versatile ligand class used in transition-metal as well as main-group element chemistry. [Extracted from the article]

ABSTRACT A new terpolymer ligand involving 2-amino-6-nitro- benzothiazole, melamine, and formaldehyde (BMF) has been synthesized in the presence of dimethyl formamide medium. The BMF ligand was characterized by elemental analysis and various spectral techniques like Fourier transform infrared (FTIR) spectroscopy, ultraviolet (UV)-visible spectroscopy, and 1H & 13C nuclear magnetic resonance (NMR) spectroscopy to elucidate the structure and properties of the terpolymer ligand. The BMF metal complexes were prepared using the BMF ligand with some transition metal ions, such as Cu2+, Ni2+, and Zn2+ ions, in the presence of ethanol medium. The prepared complexes have been characterized by elemental analysis and FTIR, electronic, electron spin resonance, and 1H & 13C NMR spectral studies. The molecular weight of the BMF ligand and its metal complexes was determined by gel permeation chromatography. The surface features and crystalline behavior of the ligand and its complexes were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) methods. Thermal stability of the ligand and its metal complexes was studied by thermogravimetric analysis (TGA). Kinetic parameters such as activation energyand order of reaction ( n), and thermodynamic parameters namely entropy change, free energy change, apparent entropy, and frequency factor were calculated using Freeman-Carroll, Sharp-Wentworth, and Phadnis-Deshpande (PD) methods. Thermal degradation model of the terpolymer ligand and its metal complexes was also proposed using the PD method. The antibacterial activities of the BMF ligand and its metal complexes were checked against chosen microbes such as Shigella sonnei, Escherichia coli, Klebsiella species, Staphylococcus aureus, Bacillus subtilis, and Salmonella typhimurium. © 2013 Wiley Periodicals, Inc. Adv Polym Technol 2013, 32, 21376; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21376 [ABSTRACT FROM AUTHOR]

ABSTRACT The radical polymerization of vinyl acetate (VAc) is moderated by iron(II) acetylacetonate (Fe(acac)2) by the organometallic route (OMRP), as well as by degenerative transfer polymerization (DTP) when in the presence of excess radicals, through the formation of thermally labile organometallic FeIII dormant species. The poly(vinyl acetate) (PVAc)-FeIII(acac)2 dormant species has been isolated in the form of an oligomer and characterized by 1H NMR, EPR, and IR methods, and then used as a single-component initiator for the OMRP of VAc. The degree of polymerization of this isolated oligomeric species demonstrates the limited ability of Fe(acac)2, relative to the Co(acac)2 congener, to rapidly trap the growing PVAc radical chain. Control under OMRP conditions is improved by the presence of Lewis bases, especially PMe2Ph. On the other hand, iron(II) phthalocyanine inhibits the radical polymerization of VAc completely. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3494-3504 [ABSTRACT FROM AUTHOR]

ABSTRACT The radical polymerization of vinyl acetate (VAc) is moderated by iron(II) acetylacetonate (Fe(acac)2) by the organometallic route (OMRP), as well as by degenerative transfer polymerization (DTP) when in the presence of excess radicals, through the formation of thermally labile organometallic FeIII dormant species. The poly(vinyl acetate) (PVAc)-FeIII(acac)2 dormant species has been isolated in the form of an oligomer and characterized by 1H NMR, EPR, and IR methods, and then used as a single-component initiator for the OMRP of VAc. The degree of polymerization of this isolated oligomeric species demonstrates the limited ability of Fe(acac)2, relative to the Co(acac)2 congener, to rapidly trap the growing PVAc radical chain. Control under OMRP conditions is improved by the presence of Lewis bases, especially PMe2Ph. On the other hand, iron(II) phthalocyanine inhibits the radical polymerization of VAc completely. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3494-3504 [ABSTRACT FROM AUTHOR]

Detailed ethylene oligomerizations were performed over highly active nickel complexes ligated by N-((4-butyl-6-phenylpyridin-2-yl)methylene)-2,6-diisopropylaniline derivatives. The activity trend according to the structure of the complex was attempted to understand using the concept of ion-pair formation during activation process. The active species were characterized by comparing the oligomerization results with the UV-Vis spectroscopic and the cyclic voltammetry experiments. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Chelating N-heterocyclic carbene zirconium and titanium complexes, combined with MAO, have been employed in the polymerization of ethylene and styrene. These complexes have been designed to simulate the highly successful phenoxy-imine ligated, non-metallocene complexes developed by scientists at Mitsui. Investigations into the effects of metal center, pressure, temperature, and time on the polymerization of ethylene were carried out. Extremely high molecular weight polyethylene could be produced (approaching 1 million Da), with industrially desirable, broad molecular weight distributions. In the case of styrene polymerizations utilizing the titanium catalyst, highly syndiotactic polystyrene was produced. [Copyright &y& Elsevier]

A series of o-aryloxide-N-heterocyclic carbene ruthenium complexes 2-4 is synthesized via sequential reactions of the o-hydroxyaryl imidazolium proligands (2-OH-3,5- tBu2C6H2)(R)(C3H3N2)+Br− (R = Me ( 1a), iPr ( 1b), Mes ( 1c)) with Ag2O and [(C6H6)RuCl2]2. All of the complexes are characterized by 1H and 13C NMR spectroscopy, high-resolution mass spectrometry (HRMS), and elemental analysis. The molecular structure of 2 is determined by single-crystal X-ray diffraction analysis. The ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with 2- 4 is studied. Among them, complex 4 exhibits the highest activity and efficiency toward ROMP of NBE at 85 °C without any cocatalyst, and the resultant polymers have very high molecular weight (>106 Da) and narrow molecular weight distributions. This complex can also efficiently catalyze the alternating copolymerization of NBE and cyclooctene. [ABSTRACT FROM AUTHOR]

Polycarbosilane (PCS) with highly crosslinked structure and high surface area was synthesized by the polycondensation reaction between trimethoxyvinylsilane and trichloromethylsilane. The reaction was conducted in the presence of sodium metal. Manganese ion was supported on PCS. The immobilization of transition metal ions to polymer support leads to a number of advantages over homogeneous catalyst, viz easy product recovery, increased selectivity, etc. The catalytic activity of PCS supported manganese ion was studied by considering three-component Mannich reaction. Reaction with diverse sets of aldehydes, amines, and ketones was examined. PCS-supported manganese ion catalyst has been prepared for the first time and used successfully in Mannich reaction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012 [ABSTRACT FROM AUTHOR]

Nitrile-ligated copper(II) and zinc(II) complexes comprising (fluoroalkoxy)aluminates as weakly coordinating anions (WCAs) have been synthesized and applied for the polymerization of isobutylene at room temperature (30°C). The polymers obtained are in the low and moderate molecular weight range and show characteristics of the highly reactive polyisobutylene. Results indicate that the fluoroalkoxy aluminate WCAs have even a higher tolerance toward water in IB polymerization than the earlier tested perfluoroborate WCAs. Studies showed that water plays an important role in the polymerization process, which indicates a polymerization mechanism similar to a proton-initiated carbocation polymerization. The role of the WCAs and their importance for the room-temperature polymerization process was re-examined, and the effect of the addition of proton and electron donors including proton traps (2,6-di- tert-butyl-4-methylpyridine or DTBP) was studied in detail. The polymerization reaction seems to be dominated by transfer reactions that lead to the high content of exo double bonds while propagation proceeds via conventional cationic polymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

The accurate description of open-shell molecules, in particular of transition metal complexes and clusters, is still an important challenge for quantum chemistry. Although density-functional theory (DFT) is widely applied in this area, the sometimes severe limitations of its currently available approximate realizations often preclude its application as a predictive theory. Here, we review the foundations of DFT applied to open-shell systems, both within the nonrelativistic and the relativistic framework. In particular, we provide an in-depth discussion of the exact theory, with a focus on the role of the spin density and possibilities for targeting specific spin states. It turns out that different options exist for setting up Kohn-Sham DFT schemes for open-shell systems, which imply different definitions of the exchange-correlation energy functional and lead to different exact conditions on this functional. Finally, we suggest possible directions for future developments. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: An electrophilic substitution–carbonylation reaction on phenylpyridine based on the concept of ‘umpolung’ was used to prepare a series of pyridine based carbonyl compounds and bispyridine derivatives. The key intermediate which enhances this reaction is a base aggregate formed by the association of BuLi with lithium 2-dimethylaminoethanolate (LiDMAE) which is stabilized in nonpolar solvents. The presence of polar chelating amides that are used as acyl donors was found to collapse the superbase aggregates liberating nucleophilic ‘free’ BuLi. These nucleophiles lead a classical nucleophilic reaction to introduce butyl tails on the pre-ligand molecules. Pyridine carbonyl compounds produced by these electrophilic substitution–carbonylation reactions, on treatment with 2,6-diisopropylaniline and (DME)NiBr2 in glacial acetic acid at reflux temperature, gave Ni(II) complexes in good yields in a one pot protocol. These complexes are active toward ethylene, producing selective dimerization and trimerization products. [Copyright &y& Elsevier]