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Thorium chalcogenolates Th(ER)4 react with 2,2′-bipyridine (bipy) to form complexes with the stoichiometry (bipy)2Th(ER)4 (E = S, Se; R = Ph, C6F5). All four compounds have been isolated and characterized by spectroscopic methods and low-temperature single crystal X-ray diffraction. Two of the products, (bipy)2Th(SC6F5)4 and (bipy)2Th(SeC6F5)4, crystallize with lattice solvent, (bipy)2Th(SPh)4 crystallizes with no lattice solvent, and the selenolate (bipy)2Th(SePh)4 crystallizes in two phases, with and without lattice solvent. In all four compounds the available volume for coordination bounded by the two bipy ligands is large enough to allow significant conformational flexibility of thiolate or selenolate ligands. 77Se NMR confirms that the structures of the selenolate products are the same in pyridine solution and in the solid state. Attempts to prepare analogous derivatives with 2,2′,6′,2′′-terpyridine (terpy) were successful only in the isolation of (terpy)(py)Th(SPh)4, the first terpy compound of thorium. These materials are thermochromic, with color attributed to ligand-to-ligand charge transfer excitations. [ABSTRACT FROM AUTHOR]

A series of mercury(II) complexes, [Hg(N N)(SCN) 2 ] (N N is 4,4′-dimethyl-2,2′-bipyridine in 1 , 5,5′-dimethyl-2,2′-bipyridine in 2 , 6,6′-dimethyl-2,2′-bipyridine in 3 and 6-methyl-2,2′-bipyridine in 4 ), were prepared from the reactions of Hg(SCN) 2 with mentioned ligands in methanol. Suitable crystals of these complexes were obtained for X-ray diffraction measurement by methanol diffusion into a DMSO solution. The four complexes were thoroughly characterized by spectral methods (IR, UV–Vis, 13 C{ 1 H}NMR, 1 H NMR and luminescence), elemental analysis (CHNS) and single crystal X-ray diffraction. The X-ray structural analysis indicated that in the structures of these complexes, the mercury(II) cation is four-coordinated in a distorted tetrahedral configuration by two S atoms from two thiocyanate anions and two N atoms from one chelating 2,2′-bipyridine derivative ligand. Also, in these complexes intermolecular interactions, for example C H⋯N hydrogen bonds (in 1 – 4 ), C H⋯S hydrogen bonds (in 1 , 2 and 4 ), π … π interactions (in 2 – 4 ), Hg⋯N interactions (in 2 ) and S⋯S interactions (in 4 ), are effective in the stabilization of the crystal structures and the formation of the 3D supramolecular complexes. Furthermore, the luminescence spectra of the title complexes show that the intensity of their emission bands are stronger than the emission bands for the free bipyridine derivative ligands. [ABSTRACT FROM AUTHOR]

Nowadays, the design and development of novel phosphorescent iridium(III) complexes for various optoelectronic applications is a well-recognized area of research. The fascinating photophysical properties of iridium(III) compounds are strongly influenced by the spin-orbit coupling exerted by the iridium(III) core, usually resulting in intense emissions with short excited-state lifetimes, which can be precisely controlled with the aid of molecular engineering of the chelating ligand. This review focuses on the recent developments and state of the art knowledge on phosphorescent iridium(III) compounds, especially on heteroleptic complexes derived from 2,3′-bipyridine class of cyclometalating and ancillary ligands, highlighting the excited state phenomenon behind their emission behavior. [ABSTRACT FROM AUTHOR]

We report the synthesis and properties of new ruthenium- p -cymene complexes [(η 6 - -cymene)Ru(L)Cl][Cl] prepared from tetracarboxylic acid ligands L = 3,3′,4,4′-tetracarboxylicacid-2,2′-bipyridine (3,3′,4,4′-H 4 tcbpy), their methyl and ethyl ester derivatives (R 4 tcbpy), 4,4′,5,5′-tetracarboxylicacid-2,2′-bipyridine (4,4′,5,5′-H 4 tcbpy), and 4,4′-di- n -nonyl bipyridine (4,4′-dnbpy). The complexes were fully characterized by NMR, IR, MS, elemental analysis, UV–vis spectroscopy, and cyclic voltammetry. The single-crystal structure of [(η 6 - p -cymene)Ru(4,4′,5,5′-H 4 tcbpy)Cl]Cl 2 shows a ‘piano stool’ geometry with Ru-C (2.177(2)-2.231(2) Å), Ru-N (2.0791–2.0801 Å) distances and an N-Ru-N bond angle (77.4°) similar to equivalents in the 4,4′-dicarboxylic acid sister complex. Compared to the latter and also the 4,4′-dnbpy derivative 3 , the UV–vis spectra show MLTC absorptions of the tetracarboxylates shifted to lower energy. The CVs show Ru(II/III) oxidation processes at 0.56–0.98 V ( vs Fc/Fc + ), depending on the ligand substitution. Changes in the electronic situation at the Ru centre reflected in the UV–vis and voltammetric data are correlated to HOMO levels calculated from photoelectron spectroscopy in air spectra recorded for all complexes. According to NMR experiments rapid ligand dissociation occurred when dissolving [(η 6 - p -cymene)Ru(3,3′,4,4′-Me 4 tcbpy)Cl]Cl 1b in DMF. In hot DMF decarboxylation led to the isolation of the 4′-dicarboxylic acid complex derivative. [ABSTRACT FROM AUTHOR]

Complexes of Co(iii) containing mixed chelating diimine and o-quinone ligand sets are of fundamental interest on account of their fascinating magnetic and electronic properties. Whilst complexes of this type containing one diimine and two o-quinone ligands have been studied extensively, those with the reverse stoichiometry (two diimines and one o-quinone) are much rarer. Herein, we describe a ready route to the synthesis of the complex [CoIII(o-catecholate) (2,2′-bipyridine)2]+ (1), and also report the synthesis of [CoIII(o-catecholate)(5,5′-dimethyl-2,2′-bipyridine)2]+ (2) and [CoIII(o-benezenedithiolate)(5,5′-dimethyl-2,2′-bipyridine)2]+ (3) for the first time. Spectroscopic studies show that complex 2 displays intriguing solvatochromic behaviour as a function of solvent hydrogen bond donation ability, a property of this type of complex which has hitherto not been reported. Time-dependent density function theory (TD-DFT) shows that this effect arises as a result of hydrogen bonding between the solvent and the oxygen atoms of the catecholate ligand. In contrast, the sulfur atoms in the benzenedithiolate analogue 3 are much weaker acceptors of hydrogen bonds from the solvent, meaning that complex 3 is only very weakly solvatochromic. Finally, we show that complex 2 has some potential as a molecular probe that can report on the composition of mixed solvent systems as a function of its absorbance spectrum. [ABSTRACT FROM AUTHOR]

The regioselective polymerizations of isoprene and 3-methyl-pentadiene catalyzed by a cationic iron (II) complex bearing bipyridine ligand have been computationally studied. Having achieved an agreement between calculation and experiment, it is found that the open-shell unpaired 3d-electrons localize on Fe center rather than partially distribute on the redox-active bipyridine ligand. The steric effect plays a more important role in controlling the regioselectivity in comparison with electronic factors. The deformation energy is mainly contributed by monomer and Fe-alkyl moieties rather than the bipyridine ligands themselves, although noncyclopentadienyl ancillary ligands are often deformed in most insertion transition states for selective polymerization of olefin. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

This article demonstrates a series of cyclometalated Ir(III) complexes of the type [IrIII(CN)2(NN)](PF6), where CN is 2-phenylpyridine, and NN corresponds to the 4,4′-π-conjugated 2,2′-bipyridine ancillary ligands. All these compounds were synthesized through splitting of the binuclear dichloro-bridged complex precursor, [Ir(CN)2(μ-Cl)]2, with the appropriate bipyridine ligands followed by the anion exchange reaction. The linear and nonlinear absorption properties of the synthesized complexes were investigated. The absorption spectra of all the title complexes exhibit a broad structureless feature in the spectral region of 350-700 nm with two bands being well-resolved in most of the cases. The structures of all the compounds were modeled in dichloromethane using the density functional theory (DFT) algorithm. The nature of electronic transitions was further comprehended on the basis of time-dependent DFT analysis, which indicates that the origins of various bands are primarily due to intraligand charge transfer transitions along with mixed-metal and ligand-centered transitions. The synthesized compounds are found to be nonemissive at room temperature because of probable nonradiative deactivation pathways of the T1 state that compete with the radiative (phosphorescence) decay modes. However, the frozen solutions of compounds Ir(MS 3) and Ir(MS 5) phosphoresce at the near-IR region, the other complexes remaining nonemissive up to 800 nm wavelength window. The two-photon absorption studies on the synthesized complexes reveal that values of the absorption cross-section are quite notable and lie in the range of 300-1000 GM in the picosecond case and 45-186 GM in the femtosecond case. [ABSTRACT FROM AUTHOR]

The most relevant manifestations of ligand noninnocence of quinone and bipyridine derivatives are thoroughly scrutinized and discussed through an extensive and systematic set of octahedral ruthenium complexes, [(en)2RuL]z, in four oxidation states (z = +3, +2, +1, and 0). The characteristic structural deformation of ligands upon coordination/noninnocence is put into context with the underlying electronic structure of the complexes and its change upon reduction. In addition, by means of decomposing the corresponding reductions into electron transfer and structural relaxation subprocesses, the energetic contribution of these structural deformations to the redox energetics is revealed. The change of molecular electron density upon metal- and ligand-centered reductions is also visualized and shown to provide novel insights into the corresponding redox processes. Moreover, the charge distribution of the p-subspace is straightforwardly examined and used as indicator of ligand noninnocence in the distinct oxidation states of the complexes. The aromatization/dearomatization processes of ligand backbones are also monitored using magnetic (NICS) and electronic (PDI) indicators of aromaticity, and the consequences to noninnocent behavior are discussed. Finally, the recently developed effective oxidation state (EOS) analysis is utilized, on the one hand, to test its applicability for complexes containing noninnocent ligands, and, on the other hand, to provide new insights into the magnitude of state mixings in the investigated complexes. The effect of ligand substitution, nature of donor atom, ligand frame modification on these manifestations, and measures is discussed in an intuitive and pedagogical manner. [ABSTRACT FROM AUTHOR]

The introduction of a simple methyl substituent on the bipyridine ligand of [Ru( tBu3tpy)(bpy)(NCCH3)]2+ ( tBu3tpy=4,4′,4′′-tri- tert-butyl-2,2′:6′,2′′-terpyridine; bpy=2,2′-bipyridine) gives rise to a highly active electrocatalyst for the reduction of CO2 to CO. The methyl group enables CO2 binding already at the one-electron reduced state of the complex to enter a previously not accessible catalytic cycle that operates at the potential of the first reduction. The complex turns over with a Faradaic efficiency close to unity and at an overpotential that is amongst the lowest ever reported for homogenous CO2 reduction catalysts. [ABSTRACT FROM AUTHOR]

A new tetrapyridine ligand, 5,5′-(3-pyridyl)-2,2′-bipyridine (2) was prepared from 5,5′-dibromo-2,2′-bipyridine (1) via Pd(0)-mediated Suzuki coupling. The reaction was performed either directly upon the free ligand, or upon its Ru(II) complex. The structures of [Ru(1)3](PF6)2and [Ru(2)3](PF6)2were studied in solution by NMR, and in the solid state by single crystal X-ray diffraction. Solution NMR data suggests distorted structures, consistent with the observed slow reactivity of the ligands towards Ru(II) ions, and their reluctance to coordinate to Fe(II) ions. However, solid-state X-ray data indicated little distortion from ideal geometries, suggesting the effect may be more electronic than steric in nature. [ABSTRACT FROM AUTHOR]

Four new compounds prepared from the ligand 2,3-dipyridyl ketone oxime (L23) with varying Cu(II) salts were synthesised and structurally characterised, {[Cu(L23)(L23-H)](ClO4)}∞(1), {[Cu(L23)(L23-H)](BF4)¼(H2O)}∞(2), [Cu3(L23-H)2(L23′)(NO3)2OH]2(NO3)2(C3H8O)6(3) and [Cu(L23)Cl2]∞(4). The effects of differing counterions, as well as the rotational conformational versatility ofL23, were demonstrated by the differing polymeric structures that were observed. Complex1and2both existed as 1-D polymeric chains withL23acting as a pseudo-tetradentate ligand through an oxime–oximato bridge. Complex1formed a helical arrangement while2formed a chiral chain with both1and2exhibiting similar chiral packing. Complex3formed an unusual inverse–9–metallacrown–3 complex, with one of theL23ligands in a zwitterionic form. Complex4was present as a simple 1-D meso-helical chain. [ABSTRACT FROM AUTHOR]

A series of platinum(ii) biphenyl 2,2′-bipyridine complexes containing electron-donating and electron-withdrawing moieties on the 4 and 4′ positions of the bipyridine ligand exhibit emission from excited states in the 600 nm region of the spectrum upon excitation in the metal-to-ligand charge transfer transition located near 450 nm. These complexes are distorted from planarity based on both single crystal structure determinations and density functional theory (DFT) calculations of isolated molecules in acetonitrile. The DFT also reveals the geometry of the lowest-lying triplet state (LLTS) of each complex that is important for emission behavior. The LLTS are assigned based on the electron spin density distributions and correlated with the singlet excited states to understand the mechanism of electronic excitation and relaxation. Time-dependent DFT calculations are performed to compute the singlet excited state energies of these complexes so as to help interpret their UV-Vis absorption spectra. Computational and experimental results, including absorption and emission energy maxima, electrochemical reduction potentials, LLTS, singlet excited states, and LUMO and HOMO energies, exhibit linear correlations with the Hammett constants for para-substituents σp. These correlations are employed to screen complexes that have not yet been synthesized. The correlation analysis indicates that the electronic structure and the HOMO–LUMO energy gap in Pt(ii) complexes can be effectively controlled using electron-donating and electron-withdrawing moieties covalently bonded to the ligands. The information presented in this paper provides a better understanding of the fundamental electronic and thermodynamic behavior of these complexes and could be used to design systems with specific applications. [ABSTRACT FROM AUTHOR]

The 4-toluenesulfonyl-L-serine ligand (1), (tsserH2), was prepared from the reaction of L-serine and 4-toluenesulfonyl chloride in sodium hydroxide solution 1 M. The complexes [Pd(4,4′-dmbipy)(tsser)] (2) and [Pd(5,5′-dmbipy)(tsser)].0.5CH3CN (3) (4,4′-dmbipy is 4,4′-dimethyl-2,2′-bipyridine and 5,5′-dmbipy is 5,5′-dimethyl-2,2′-bipyridine) were also prepared from the reaction of PdCl2and 2,2′-bipyridine derivatives with 4-toluenesulfonyl-L-serine ligand in mixture of CH3CN/CH3OH (3:1) and in presence of sodium hydroxide solution 0.5 M. These compounds were characterized by elemental analysis, IR,1H NMR, and UV–Vis spectroscopy and their structures were studied by single-crystal X-ray diffraction method. The X-ray structure determinations show that in the both complexes, the PdIIatoms are four-coordinated in a distorted square-planar configuration by two N atoms from a bidentate bipyridine ligand and one N atom and one O atom from a bidentate tsser2-ligand. [ABSTRACT FROM AUTHOR]

Three coordination polymers of zinc(II) and cadmium(II) of formula {[Zn(bipy)(NIPH)]·5HO} ( 1), {[Cd(bipy)(NIPH)]·2HO } ( 2) and {[Cd(bipy)(BDAC)(NO)](NO)·6HO} ( 3) (NIPH = 5-nitro-isophthalic acid, HBDAC = 1,4-benzenediacrylic acid and bipy = 2,2′-bipyridine) have been synthesized and structurally characterized by X-ray single crystal diffraction analysis. All the complexes display 1D coordination polymers where M(bipy) units are connected by dicarboxylate anions(and also by nitrate in 3)acting as bridging ligands. While in 1 and 3 a zig-zag chain is generated, in case of 2 a double linear chain is formed by the two crystallographic distinct Cd atoms. In solid state all the complexes expand the dimensionality to 3D by means of π-π interactions among π rings and H-bonds generated by lattice water molecules. The fluorescence study indicates intraligand π-π* charge transfer is the reason for emission in all the complexes. [ABSTRACT FROM AUTHOR]

[Ba(5,5´-dcbipy)(μ-H2O)2(H2O)2]n(1) complex was obtained from the reaction of one equivalent of 2,2'-bipyridine-5,5'-dicarboxylic acid (5,5´-dcbipy.H2) and one equivalent of ethylene diamine (en) with one equivalent of BaCl2.2H2O in water. This complex was characterized by elemental analysis, IR, UV-Vis, and luminescence spectroscopy and its structure was studied by the single-crystal X-ray diffraction method. The thermal stability of1was studied by thermogravimetric and differential thermal analyses. [ABSTRACT FROM AUTHOR]

Theoretical calculations (density functional theory with the scalar relativistic ZORA Hamiltonian) have been performed to obtain the energy and Gibbs free energy of formation of cationic 1 : 3 complexes of americium(iii) and europium(iii) with a tri-O-dentate diglycolamide ligand TEDGA (a model of TODGA extractant), as well as the free energy of their partition between water and an organic diluent. The distribution of electron density over the atoms, bonds, and molecular orbitals was analyzed by means of Mulliken population analysis, the localization procedure of natural bond orbitals, and the Quantum Theory of Atoms-in-Molecules. The stabilities of both [M(TEDGA)3]3+ complexes are similar to each other. On the other hand, our recent data for a similar pair of cationic Am/Eu complexes with a softer (HSAB) tetra-N-dentate ligand C2-BTBP show that the [Am(C2-BTBP)2]3+ complex is significantly more stable in aqueous solution than its Eu counterpart. The decisive factor stabilizing the Am3+ complexes over their Eu3+ analogues is the charge transfer from the ligands, somewhat greater on the 6d(AmIII) than on 5d(EuIII) orbitals. The covalency of M–N bonds in the [M(C2-BTBP)2]3+ complexes is greater than that of M–O bonds in [M(TEDGA)3]3+, but the latter is not negligible, in particular in the bonds with the oxygen atoms of the amide groups in TEDGA. The analysis of charge distribution over the whole molecules of the complexes shows that the TEDGA molecule is not hard as expected, but a relatively soft Lewis base, only slightly harder than BTBP. This conclusion has been confirmed by the calculation of the chemical hardness of the ligands. Moreover, the comparison of the results of bonding analysis with the calculated energies of complex formation in water and in the gas phase allows us to conclude that the population analysis, QTAIM topological parameters, and SOPT stabilization energy, as well as Wiberg and overlap-weighted NAO indices are the tools for analyzing the covalency rather than the total bond strength. [ABSTRACT FROM AUTHOR]

The binuclear complex {[UO(5,5′-dmbpy)(NO)](μ-O)}, where 5,5′-dmbpy is 5,5′-dimethyl-2,2′-bipyridine, was prepared by reaction of UO(NO).6HO with 5,5′-dimethylbipyridine in 1:1 methanol-acetonitrile. The complex was characterized by FT-IR and UV-visible spectroscopy, cyclic voltammetry (CV), and single-crystal X-ray diffraction analysis. The crystal data for {[UO(5,5′-dmbpy)(NO)](μ-O)} at 25 °C are: monoclinic, space group P2 /n with a = 9.8(7) Å, b = 16.0 (12) Å, c = 10.3 (8) Å, β = 111.023(9)° and Z = 2. [ABSTRACT FROM AUTHOR]

The sulfonated bipyridine derivative disodium 6,6′-bis(sulfonatomethyl)-2,2′-bipyridine [Na2(smbipy)] was synthesized, and its complexation behaviour towards divalent 3d metals in aqueous solution was explored. The complexes of late 3d metals [M(smbipy)(H2O)2] ·H2O (M = Co, Ni, Zn) and [Cu(smbipy)(H2O)] are sparingly soluble in water, and their crystal structures show fourfold equatorial coordination (κ4 N, N′, O, O′) of the smbipy ligand. Ammonia-rich solutions of the NiII and CuII aqua complexes yield the decomplexation products [Ni(NH3)6](smbipy), [Ni(NH3)5(H2O)](smbipy) and [Cu(NH3)4](smbipy) ·2H2O. Buffered solutions with a reduced ammonia content lead to [Ni(smbipy)(NH3)2] and [Cu(smbipy)(NH3)3] ·2H2O, and the latter shows twofold coordination of the smbipy ligand through the nitrogen atoms only (κ2 N, N′). When nearly quantitative amounts of ammonia are applied, two closely related complexes with the core motif [(smbipy)Cu(μ-OH)2Cu] form. Crystal structures of all complexes were obtained, and their features are discussed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Synthesis and characterization of two novel 6′-phenyl-2,2′-bipyridine ligands (L1, L2) and their CdL1,2 I2 complexes are presented. [•] Single crystal study indicated that Cd(II) ion is in a distorted tetrahedral structure. [•] Linear absorption and single-photon exited fluorescence properties have been investigated. [•] The results showed that the complex 2 has the longest fluorescence lifetime. [•] Linear absorption spectral features are studied by TD-DFT methods. [Copyright &y& Elsevier]

In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′-dicarboxylic acid), which could activate the C–H bonds of cycloalkanes with high secondary (2°) C–H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C–H bonds, 1 always preferred to oxidise the 2° C–H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and ＞99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C–H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst. [ABSTRACT FROM AUTHOR]

Two 1-D CdIIcoordination polymers, {[Cd(4-abpt)(hip)(H2O)2](H2O)7/2}n(1) and {[Cd(4-Habpt)(sip)(H2O)](H2O)2}n(2) (4-abpt = 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole, H2hip = 5-hydroxyisophthalic acid, H3sip = 5-sulfoisophthalic acid), have been hydrothermally synthesized and structurally characterized. Complex1has a comb-like 1-D coordination chain, while2presents a 1-D dual-track motif. The structural modulation of the coordination polymers can be achieved by simply changing the 5-substituent of the isophthalate from a hydroxyl group to a sulfonate group. Further, supramolecular architectures with higher dimensionality are constructed via hydrogen bonding and/or aromatic π-stacking interactions. Both complexes have been characterized by IR, microanalysis, and powder X-ray diffraction techniques. In addition, the solid fluorescence properties of both complexes have also been investigated. [ABSTRACT FROM AUTHOR]

A new generation of a flexible bipyridine-based ligand, 1,4-bis(4-pyridyl)-piperazine, with two main stable states (chair and twist-boat forms) was employed in the construction of unusual dirhenium metallacycles. A new generation of a flexible bipyridine-based ligand, 1,4-bis(4-pyridyl)piperazine, with two main stable states (chair and twist-boat forms) was employed in the construction of unusual metallacycles. The successful assembly of dirhenium metallacycles proves the applicability of the concept of self-adaptation and switching of the title building unit. [ABSTRACT FROM AUTHOR]

A hexapositively charged tetrahedral geometry Co(II) complex was synthesized using a new positively charged ligand prepared quaternizing 4,4ʹ-bipyridine by 1-bromobutane. It is characterized by spectrometry (1H NMR, ESI MS, Uv-Vis, ICP OES), carbon, hydrogen and nitrogen (CHN) elemental analysis, halide estimation and conductivity measurement. The complex showed significantly high molar conductivity value in water (640.83 S mol−1 cm2). Its in vitro biological activities were tested on one gram-positive (Staphylococcus aureus) and one gram-negative (Klebsiella pneumoniae) bacteria. It was found active against both bacteria with improved and better activity against the latter. [ABSTRACT FROM AUTHOR]

A simple and efficient Morita-Baylis-Hillman (MBH) reaction of bipyridine carbaldehydes and unexplored activated alkenes affords highly functionalized bipyridyl ligands. [ABSTRACT FROM AUTHOR]