Dipyrrolyldiketone PtII Complexes: Ion-Pairing π-Electronic Systems with Various Anion-Binding Modes

A variety of π-electronic ion-pairing assemblies can be constructed by combining anion complexes of π-electronic systems and countercations. In this study, a series of anion-responsive π-electronic molecules, dipyrrolyldiketone Pt^II complexes containing a phenylpyridine ligand, were synthesized. The resulting Pt^II complexes exhibited phosphorescence emission, with higher emission quantum yields (0.30–0.42) and microsecond-order lifetimes, and solution-state anion binding, as revealed by our spectroscopic analyses. These Pt^II complexes displayed solid-state ion-pairing assemblies, exhibiting various anion-binding modes, which derived from pyrrole-inverted and pyrrole-non-inverted conformations, and packing structures, with the contribution of charge-by-charge assemblies, which were dependent on the substituents in the Pt^II complexes and the geometries and electronic states of their countercations.     

Arylethynyl Groups That Modulate Anion-Binding and Assembling Modes of Rod- and Fan-Shaped π-Electronic Systems

The introduction of arylethynyl moieties at the pyrrole α- and β-positions of dipyrrolyldiketone BF₂ complexes as anion-responsive π-electronic molecules was investigated. The arylethynyl-substituted derivatives formed a variety of anion complexes with planar [1+1]- and interlocked [2+1]-type structures in solution and in the solid state. The derivatives with long alkyl chains in the introduced arylethynyl groups also formed mesophases in the form of ion pairs of the anion complexes and a counter cation. The geometries of the constituent anion complexes affected the packing modes of the dimension-controlled assemblies.     

Structure and Electric Conductivity of (La,Sr)(Ga,Mg)O3-α Solid Electrolyte

Electric conductivity, Raman spectra, and thermal expansion of La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 solid solution (LSGM1218) based on lanthanum gallate were studied at various temperatures, and Xray phase analysis was performed at room temperature. Dilatometric measurements showed that secondorder phase transitions occur at 775±10$ and 880± 20 K. The transition around 880 K is confirmed by Raman spectra and by a change in the conductivity activation energy in this temperature range. This transition is associated with a symmetry change in the oxygen sublattice.     

Deciphering Internal and External π-Conjugation in C3-Symmetric Multiple Azobenzene Connected Systems in Self-Assembly

Two tripodal C₃-symmetric photoswitchable molecular systems T1 and T2 are reported that have extended conjugation at external and internal positions using an acryl group. The influence of the extended π-bonds in their absorption properties, thermal relaxation of the photoisomers and their propensities in forming supramolecular self-assemblies have been explored through spectroscopy, and microscopic studies. In particular, the investigations on the self-assembly have been carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), polarized optical microscopy (POM), X-ray diffraction studies (XRD) and atomic force microscopy (AFM). Remarkably, the position of the acryl group influences the behaviour of the two target molecules in supramolecular assembly, and also in the formation of photoresponsive organic hydrogels or microcrystals.     

Alkali-Metal Aminotroponiminates: Selectivities and Equilibria in Reversible Radical Coupling of Delocalized π-Electron Systems

Aminotroponiminates (ATIs) have recently been shown to belong to the growing class of redox-active ligands. The choice of the metal center allowed to switch between reversible electron transfer (M=Rh) and reductively induced dimerization (M=Na). Here, we investigate if the reductively induced dimerization of ATIs is a more general phenomenon for their alkali-metal complexes. Lithium ATI complexes are shown to undergo reductively induced dimerizations, which are equilibrium reactions and chemically reversible. The choice of the metal center (Li vs. Na), the substitution pattern at the nitrogen atoms of the ATI ligands, and the solvent critically influence the regioselectivity and diastereoselectivity of the radical-dimerization reactions. Potassium ATIs are shown to be susceptible to side reactions, more specifically a reduction accompanied by hydrogen-atom transfer. Products and intermediates of the reductively induced dimerizations were characterized by techniques including NMR and EPR spectroscopy, cyclic voltammetry, DFT calculations, single-crystal X-ray diffraction, and mass spectrometry.     

Preparation,Structure and Properties of 3D Supramolecular Architecture,on the Basis of Hydrogen Bonds and π-π Stacking Between 2D Layers,with Windmill Building Blocks

A novel three-dimensional（3D） supramolecular architecture, {[Nd（OH-BDC）（OH-HBDC）（H2O）2]·2HaO）n（1） （OH-H2BDC=5-hydroxyisophthalic acid）, which was formed through hydrogen bonds and π-π stacking between two-dimensional（2D） layers, was hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Windmill building blocks, which consist of two nine-coordinated metal centers and four OH-H2BDC groups are connected through two carboxyl groups, to lead to a one-dimensional infinite inorganic chain（… M--O--C--O--M…） along the [100] direction. An observed intense blue luminescence with an emission band peaked at 390 nm for compound 1 may results from ligand-to-metal charge transfer（LMCT）. Variable-temperature magnetic susceptibility of compound 1 was investigated and the value was deviated from the Curie-Weiss law.     

Synthesis and Structure of Cyclopropenone π-Complexes with Pentacarbonyliron(0) and Hexacarbonyltungsten(0). Hydrophosphorylation of Cyclopropenone in the Transition Metal Coordination Sphere

New -complexes of pentacarbonyliron(0) and hexacarbonyltungsten(0) containing ²-coordinated cyclopropenone molecules were synthesized. The geometric, electronic structure, and energy parameters of the coordinated cyclic oxo diene were determined by nonempirical quantum-chemical methods. According to the theoretical and experimental (IR and NMR) data, the conjugation between the double carbon-carbon and carbon-oxygen bonds is broken as a result of coordination. The coordinated cyclopropenone reacts with dialkyl hydrogen phosphites to give the corresponding -hydroxyphosphonate via addition at the carbonyl group, whereas hydrophosphorylation of the free ligand occurs at the double carbon-carbon bond.     

Intramolecular donor-acceptor interaction in stilbene and styrene π-complexes with tricarbonylchromium. Observation in the IR spectra

The IR spectra of complexes derived from conjugated arylalkenes and tricarbonylchromium, namely (stilbene)tricarbonylchromium and (styrene)tricarbonylchromium, displayed three absorption bands instead of two expected in the region of carbonyl stretching vibrations (1800–2000 cm⁻¹). Additional absorption bands also appeared in the region corresponding to metal-π-fragment stretching vibrations (250–400 cm⁻¹). These findings indicated additional interaction involving the central metal atom, carbonyl ligands, and aromatic π-system. Such interaction increases mobility of the tricarbonylchromium fragment which may become capable of readily migrating from one π-fragment to another under certain conditions.     

Cooperativity of H-bonding and anion-π interaction in the binding of anions with neutral π-acceptors

A rare anion-π complex between bromide and a neutral receptor is reported and related receptor systems are studied with a series of anions. The interaction is observed in the solid state and in solution, and further evidence for it is obtained by a computational study.     

Ionic polymers and oligomers with expanded π-conjugation system derived from through-space interaction in piperazinium ring

Reactions of N-(2,4-dinitrophenyl)-4-arylpyridinium chlorides (aryl (Ar) = phenyl and 4-pyridyl) with piperazines caused the ring opening of the pyridinium ring and yielded polymers that consisted of 5-piperazinium-3-aryl-penta-2,4-dienylideneammonium chloride units [N(CH(R)CH₂)₂N⁺(Cl⁻)CHCHC(Ar)CHCH, RH, Me, and phenyl]. However, the same reactions occurring in the presence of piperidine yielded oligomers that consisted of 5-piperazinium-3-aryl-penta-2,4-dienylideneammonium chloride units having piperidine and/or piperazine rings at both ends. ¹H NMR spectra suggested that π-electrons of the penta-2,4-dienylideneammonium group of the polymers and the oligomers were delocalized. UV-vis measurements revealed that the π-conjugation system expanded along the polymer and oligomer chains due to the orbital interaction between electrons on the two nitrogen atoms of the piperazinium ring. Conversion of the piperazinium ring from the boat form to the chair form caused decrease in the π-conjugation length. The rate constants of the conversion of the oligomers depended on their chain lengths. The surface of pellets that were molded from the polymers and oligomers exhibited metallic luster. These polymers and oligomers underwent electrochemical oxidation in solution.     

Effect of Buffer Constituents on Retention and Separation in Achiral and Chiral HPLC Systems with β-Cyclodextrin-Based Stationary Phase

In HPLC, cyclodextrin-based stationary phases allow separation of both achiral and chiral analytes. Complexation of analytes into the cyclodextrin cavity is a very important part of the interaction mechanism. However, possible complexation of buffer constituents must be also considered. This fact should not be overlooked in method development procedures. In this study, β-cyclodextrin-based stationary phase (CYCLOBOND I 2000) was used, and two different buffers, namely aqueous solutions composed of lithium hydroxide/benzoic acid 10.0/24.5 mM, pH 4.00 and lithium hydroxide/acetic acid 9.9/60.0 mM, pH 4.01 of the same ionic strength were compared. Methanol was added as organic modifier in a methanol/buffer volume ratio 40/60. The linear free energy relationship method was used for evaluation of interactions contributing to chromatographic performance of the separation system. Strong complexation of benzoic acid with cyclodextrin was obvious from the results. This effect was clearly reflected in reduced retention and restricted (enantio) separation ability of the separation system containing benzoic acid in the buffer. On the other hand, complexing buffer constituents of mobile phases can offer a worthy alternative, to less “green”organic solvents, for reduction of the analysis time.

     

One New Schiff Base Complex with One in Situ Synthesized Ligand： Synthesis and Structure

1 INTRODUCTION The transition-metal Schiff base complexes have attracted much attention due to their beautiful struc- tures, multifunctions like catalysis[1～3] and materials science[4～6]. Recently, some Schiff base complexes based on guanidinate ligands have been explored[7～9], and most of them were synthesized by stepwise reactions. Due to the steric and electrical flexibility and abundant donor functionality of the guanidinate species, the ligand may adopt various coordination modes.…     

Redox-active π-conjugated polymer nanotubes with viologen for encapsulation and release of fluorescent dye in the nanospace

We report the encapsulation of negatively charged Au nanoparticles and anionic fluorescent (FL) dye in the inner cavity of redox-active cationic polymer nanotubes with viologen via electrostatic interaction and the release of the FL dye from the FL dye confined in the cavity of the polymer nanotubes by electrochemical and chemical reduction.     

Experimental Study on the Determination and Degradation of Pyoluteorin in Soil via CE with Soxhlet’s Extraction and Field-Amplified Sample Stacking

A sensitive analytical method based on capillary electrophoresis with field-amplified sample stacking, Soxhlet’s extraction and ultrasonic extraction for studying the degradation of trace amounts of pyoluteorin (Plt, a broad-spectrum fungicide produced by fluorescent Pseudomonas) in soil samples was first developed. The limits of detection and the limits of quantification for Plt of the developed method were 0.107 and 0.36 μg mL^?1, respectively. The recoveries of Plt at three spiking concentrations of 500, 200, and 50 μg kg^?1 were 94.18, 79, and 78.25%, respectively. In this communication, we successfully performed the investigation on the dynamic residue of Plt during its decomposition in agriculture soil using the method developed. The calculated t _1/2 values for Plt residue in near-surface and rhizosphere soil were 42.26 and 32.84 h, respectively. The results show that Plt has good environmental compatibility.     

Preparation, Crystal Structure and Enthalpy Change of Formation of the Reaction in Liquid Phase of a New Three- Dimensional Mixed-Ligand Holmium（Ⅲ）Coordination Polymer Based on Strong π-π Stacking Interactions

A new three-dimensional coordination polymer, [Ho（5-nip）（phen）（NO3）（DMF）] （5-nip=5-nitroisophthalic acid and phen=1,10-phenanthroline）, was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum and DTG-DSC techniques. The results show that the title complex crystallizes in space group P2/m with a= 1.0906（3） nm, b =1.2804 （3） nm, c= 1.6987（4） nm, β=91.400（5）°, Z=4, Dc= 1.931 Mg/m^3, F（000）= 1352. Each Ho（Ⅲ） ion is nine-coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate NO3 anion, one DMF molecule and one 1,10-phenanthroline molecule. The complex is constructed with one-dimensional ribbons featuring dinuclear units and the one-dimensional ribbons are further assembled into two-dimensional networks by strong π-π stacking interactions with the distance of 0.327 nm, then the networks are arranged into three-dimensional structure according to ABAB fashion. The complex exhibits high stability up to 600 ℃. Its enthalpy change of formation of the reaction in liquid-phase in solvent DMF was measured using an RD496-Ⅲ type microcalorimeter with a value of （-11.016±0.184） kJ·mol^-1.     

Synthesis and spectroscopic studies on charge-transfer molecular complexes formed in the reaction of imidazole and 1-benzylimidazole with σ- and π-acceptors

The spectrophotometric characteristics of the solid charge-transfer molecular complexes (CT) formed in the reaction of the electron donors imidazole (IML) and 1-benzylimidazole (BIML) with the σ-acceptor iodine and π-acceptors 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), tetracyanoethylene (TCNE) and 2,3,5,6-tetrachloro-1,4-benzoquinone (CHL) have been studied in chloroform at 25 °C. These were investigated through electronic and infrared spectra as well as elemental analysis. The results show that the formed solid CT-complexes have the formulas [(IML)2 I]I3, [(IML)(DDQ)], [(IML)2(TCNE)5] and [(IML)(CHL)] for imidazole and [(BIML) I]I3, [(BIML)(DDQ)2], [(BIML)(TCNE)2] and [(BIML)(CHL)2] for 1-benzylimidazole in full agreement with the known reaction stoichiometries in solution as well as the elemental measurements. The formation constant KCT, molar extinction coefficient ?CT, free energy change ΔG0, CT energy ECT and ionization potential Ip have been calculated for the CT-complexes [(IML)2 I]I3, [(IML)(DDQ)], [(IML)(CHL)], [(BIML) I]I3, [(BIML)(DDQ)2], [(BIML)(TCNE)2] and [(BIML)(CHL)2].     

Chromophores with quinoxaline core in π-bridge and aniline or carbazole donor moiety: synthesis and comparison of their linear and nonlinear optical properties

Russian Chemical Bulletin - Two new D—π—A chromophores with the tricyanofuranyl acceptor (A), an amphi-divinyl quinoxaline π-electron conjugated bridge, and the carbazole or...