Effect of the Metal within Regioisomeric Paddle-Wheel-Type Metal–Organic Frameworks

The effect of metal on the degree of flexibility upon evacuation of metal–organic frameworks (MOFs) has been revealed with positional control of the organic functionalities. Although Co-, Cu-, and Zn-based DMOFs (DMOF = DABCO MOF, DABCO = 1,4-diazabicyclo[2.2.2]octane) with ortho-ligands (2,3-NH₂Cl) have frameworks that are inflexible upon evacuation, MOFs with para-ligands (2,5-NH₂Cl) showed different N₂ uptake amounts after evacuation by metal exchange. Considering that the structural analyses were not fully sufficiently different to explain the drastic changes in N₂ adsorption after evacuation, quantum chemical simulation was explored. A new index (η) was defined to quantify the regularity around the metal based on differences in the oxygen-metal-oxygen angles. Within 2,5-NH₂Cl, the η value becomes larger as the metal are varied from Co to Zn. A large η value means that the structures around the metal center are less ordered. These results can be used to explain flexibility changes upon evacuation by altering the metal cation in this regioisomeric system.     

Effect of the nature of the phosphido bridge on the Co labilisation in heterobimetallic η-phosphido complexes

In contrast to their μ-PPh₂ analgoues, the compounds (OC)₅M(μ-PRH)Pt(H)(PPh₃)₂ M  Cr, Mo, W; R  Ph or cyclohexyl) do not rearrange to form (OC)₄M(μ-PRH)(μ-H)Pt(PPh₃)₂.     

Sorption of Am(Ⅲ) on Na-bentonite:Effect of pH,ionic strength,temperature and humic acid

Sorption of Am(Ⅲ) on Na-bentonite as a function of contact time,pH,ionic strength,humic acid(HA) and temperature was investigated under ambient conditions.The results showed that the sorption was strongly dependent on pH and ionic strength. Am(Ⅲ) sorption can be described well by pseudo-second-order model.The presence of HA takes a positive effect at low pH;but a negative influence under high pH range.Enthalpy,entropy and Gibbs free energy(i.e.,△H~0,△S~0 and△G~0) calculated from sorption isotherms suggested that sorption process of Am(Ⅲ) was spontaneous and endothermic.     

Metal complexes as ligands—VII: The chemistry of the monothiooxalate complexes

A synthesis of potassium monothiooxalate, K₂C₂SO₃, and its reactions with metal ions are reported. The spectroscopic properties of the complexes, M(C₂SO₃)_nⁿ⁻, for M  Ni(II), Cu(II), Zn(II) (n = 2); and M  Cr(III), Co(III), Fe(III) (n = 3) are indicative of (SO) chelated ligands while the Al(III) (n = 3) complex is an (OO) bonded chelate. The copper(II) complex undergoes an irreversible oxidation at 0.43 V. This oxidation is accompanied by reduction of the copper(II) and evolution of CO₂ and SCO.The inert cations which accompany the anionic monothiooxalate complexes are readily replaced by the coordinatively unsaturated (Ph₃P)₂M⁺, M  Ag(I), Cu(I) complex cations. The bridging of the monothiooxalate ligand in the resulting polynuclear complexes is of the type MOOC₂SOM′, M  Al(III), Fe(III), M′  Ag(I), Cu(I); M  Cr(III), M′  Cu(I) and MSOC₂O₂M′, M  Cr(III), Co(III), M′  Cu(I).     

Effects of double substitution on the thermodynamic stabilities of nitrogen radicals

Ｓｔｕｄｉｅｓｏｎｋｉｎｅｔｉｃｓｏｆｒａｄｉｃａｌｒｅａｃｔｉｏｎｓ[1]ａｎｄｏｎＣＨｂｏｎｄｄｉｓｓｏｃｉａｔｉｏｎｅｎｅｒｇｉｅｓ(ＢＤＥ)[2]ｈａｖｅｓｈｏｗｎｔｈａｔｃａｒｂｏｎｒａｄｉｃａｌｓａｒｅｓｔａｂｉｌｉｚｅｄｂｙｅｉｔｈｅｒａｎｅｌｅｃｔｒｏｎｄｏｎａｔｉｎｇｇｒｏｕｐ(ＥＤＧ)ｏｒａｎｅｌｅｃｔｒｏｎｗｉｔｈｄｒａｗｉｎｇｇｒｏｕｐ(ＥＷＧ),ａｎｄｔｈａｔｉｆａｃａｒｂｏｎｒａｄｉｃａｌｉｓｓｕｂｓｔｉｔｕｔｅｄｗｉｔｈｂｏｔｈａｎＥＤＧａｎｄａｎＥＷＧａｔｔｈｅｓａｍｅｃｅｎ…     

Effect of Larger Pore Size on the Sorption Properties of Isoreticular Metal–Organic Frameworks with High Number of Open Metal Sites

Four isostructural CPO-54-M metal-organic frameworks based on the larger organic linker 1,5-dihydroxynaphthalene-2,6-dicarboxylic acid and divalent cations (M=Mn, Mg, Ni, Co) are shown to be isoreticular to the CPO-27 (MOF-74) materials. Desolvated CPO-54-Mn contains a very high concentration of open metal sites, which has a pronounced effect on the gas adsorption of N₂, H₂, CO₂ and CO. Initial isosteric heats of adsorption are significantly higher than for MOFs without open metal sites and are slightly higher than for CPO-27. The plateau of high heat of adsorption decreases earlier in CPO-54-Mn as a function of loading per mole than in CPO-27-Mn. Cluster and periodic density functional theory based calculations of the adsorbate structures and energetics show that the larger adsorption energy at low loadings, when only open metal sites are occupied, is mainly due to larger contribution of dispersive interactions for the materials with the larger, more electron rich bridging ligand.     

Effect of pH on the Rheology of Al-Mg Mixed Metal Hydroxide——Montmorilonite Aqueous Suspension

ＥｆｅｃｔｏｆｐＨｏｎｔｈｅＲｈｅｏｌｏｇｙｏｆＡｌ┐ＭｇＭｉｘｅｄＭｅｔａｌＨｙｄｒｏｘｉｄｅ——ＭｏｎｔｍｏｒｉｌｏｎｉｔｅＡｑｕｅｏｕｓＳｕｓｐｅｎｓｉｏｎＨＯＵＷａｎ－ｇｕｏ＊，ＳＵＮＤｅ－ｊｕｎ，ＷＵＴａｏ，ＳＯＮＧＳｈｕ－ｅａｎｄＺＨＡＮ...     

Effect of the nature of lanthanide on intramolecular C-F→Ln dative interactions in hexafluoroisopropoxide complexes

Russian Chemical Bulletin - Electronic structures of a series oflanthanide complexes with hexafluoroisopropoxide ligands [Ln(OCH(CF3)2)2(μ2-OCH(CF3)2)(DME)]2 (Ln = Ce, Sm, Tm, Yb; DME is...     

Studies on the Effect of Glass Transition on the Crystalline Transition in Syndiotactic Polystyrene – Solvent Complexes

Summary: Amorphous syndiotactic polystyrene (sPS) was crystallized at room temperature in Norbornadiene (bicyclo[2,2,1]-hepta-2,5-diene), Mesitylene (1,3,5- Trimethylbenzene), 3-Carene (3,7,7-trimethyl bicyclo[4,1,0]hept-3-ene) and DMN (1,4-Dimethylnaphthalene) to form the sPS-solvent complex (δ form) with respective solvent molecules. In situ HTFTIR studies showed that the δ form to γ form transformation temperature occurs well below the glass transition temperature of sPS, which is depressed due to the presence of solvent in the amorphous phase; higher the solvent content in the complex, lower the transition temperature. Glass transition temperatures determined by Modulated differential scanning calorimetry (MDSC) coincide with the transition temperatures, indicating that the δ form transforms into γ form at the glass transition temperature for these complexes. Such a behavior is very different from the behaviour of the sPS- solvent complexes formed by dichloromethane, chloroform, toluene, o-dichlorobenzene, decalin (cis-trans) etc. and for these complexes the transition occur well above the T_g. 1     

Effect of the Loading of Metal Salts on the Formation of Fe–Co Solid Solution Nanoparticles in the IR-Pyrolyzed Chitosan Matrix

Russian Journal of General Chemistry - In this study, metal-carbon nanocomposites have been synthesized via the method of simultaneous formation of bimetallic Fe–Co nanoparticles and carbon...     

Effect of the Nature of Crosslinking Agent on the Catalase‐Like Activity of Polystyrene‐Bound Glycine–Metal Complexes

Abstract

Catalase‐like activity of metal complexes of various crosslinked polystyrene‐supported glycines were carried out and correlated with the nature of crosslinking agent in the polymer support. Polystyrenes with 2 mol% divinyl benzene (DVB), ethylene glycol dimethacrylate (EGDMA), and 1,6‐hexanediol diacrylate (HDODA) crosslinking were used as polymer supports. Glycine functions were incorporated to the chloromethylpolystyrenes by polymer analogues reactions and complexed with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) ions. The metal uptake varied in the order: Cu(II) > Cr(III) > Mn(II) > Co(II) > Fe(III) > Ni(II) > Zn(II), and extent of metal uptake by various crosslinked systems varied with the nature of crosslinking agent. The polymeric ligands and the metal complexes were characterized by various analytical techniques. The catalytic activities of these metal complexes were investigated towards the decomposition of hydrogen peroxide and was found to decrease in the order: Co(II) > Cu(II) > Ni(II) > Cr(III) > Fe(III) > Mn(II) > Zn(II). With increasing rigidity of the crosslinking agent the catalytic activity also decreased.     

Effect of fluorine doping on the ionic (O2−, H+) conductivity of oxygen-deficient complex oxides

Russian Chemical Bulletin - The effect of fluorine doping on the transport properties (oxygen-ion and proton conductivity) of perovskite-related complex oxides Ba2In2O5, Ba4In2Zr2O11, and...     

Effect of N-donor sites of bis-pyridyl-bis-amide ligands on the architectures of three Anderson-type polyoxometalate-based metal–organic complexes

Three polyoxometalate-based metal–organic complexes [Co₂(H₂O)₆(TeMo₆O₂₄)](3-H₂dpyb)·2H₂O (1), [M₂(4-Hdpyb)₂(H₂O)₆(TeMo₆O₂₄)]·6H₂O [M = Co (2), Zn (3); 3-dpyb = N,N′-bis(3-pyridinecarboxamide)-1,4-butane, 4-dpyb = N,N′-bis(4-pyridinecarboxamide)-1,4-butane] have been hydrothermally synthesized and characterized by elemental analysis, IR, TG, powder diffraction and single-crystal X-ray diffraction analysis. The structure of complex 1 consists of 1D [Co₂(H₂O)₆(TeMo₆O₂₄)] inorganic chains, which are joined together by the 3-dpyb ligands through weak hydrogen bonds to generate a 2D supramolecular network. Complexes 2 and 3 are isostructural; each [TeMo₆O₂₄]^6? (TeMo₆) polyoxoanion chelates either two cobalt or two zinc atoms to generate the discrete complexes [Co₂(4-Hdpyb)₂(H₂O)₆(TeMo₆O₂₄)] and [Zn₂(4-Hdpyb)₂(H₂O)₆(TeMo₆O₂₄)], respectively. The electrochemical properties, electrocatalytic and photocatalytic activities of the complexes have been investigated.     

Modification of Metal Complex on the StereoselectiveHydrogenation of 2,3-Butanedione

Nanoscopic metal clusters, because of their substantial difference from metal atoms and bulk metals in size and structure, have attracted great interest especially in the field of catalysis1. It is well known that additives can markedly affect the properties of metal catalysts. The effect of metal ions has been well studied in the field of heterogeneous catalysis2. However, the study of metal complex effect is scarce. We have reported that the metal complex can considerably modulate both the a…     

Effect of intraligand π-delocalization on the photophysical properties of two new Ru(II) complexes

Two new Ru(II) complexes, [Ru(bpy)₂(1-COO-iqu)]⁺ (2; bpy = 2,2′-bipyridine, 1-COO-iqu^? = isoquinoline-1-carboxylate) and [Ru(bpy)₂(3-COO-iqu)]⁺ (3; 3-COO-iqu^? = isoquinoline-3-carboxylate), were prepared and their crystal structures solved. The ground and excited state properties of 2 and 3 were characterized and compared to those of [Ru(bpy)₃]²⁺ (1). The presence of the oxygen atom in the Ru(II) coordination sphere makes 2 and 3 easier to oxidize than 1. The Ru → bpy MLCT absorption and emission of 2 and 3 are red-shifted relative to that of 1 in CH₂Cl₂, and the E₀₀ energies were estimated to be 1.89 eV and 1.95 eV from the low temperature emission of 2 and 3, resulting in excited state oxidation potentials of ?1.03 V and ?1.10 V vs SCE, respectively. In addition to the short-lived emissive ³MLCT state, a long-lived species is observed in the transient absorption of 3 in DMSO (τ = 49 μs) and pyridine (τ = 44 μs), assigned to a solvent-coordinated complex. This intermediate is not observed for 3 in non-polar solvents or for 2. The absence of the solvent coordinated intermediate in 2 is explained by the stronger Ru–O bond afforded by the lower conjugation in that extends onto the carboxylic acid in the 1-COO-iquo^?ligand, compared to that in the 3-COO-iqu^?ligand in 3. Transient absorption experiments also show that the ³MLCT excited state of 3 is able to reduce methyl viologen.     

Effect of γ-substitution on the thermoluminescence properties of terbium (III) acetylacetonate complexes with 1,10-phenanthroline

The coordination compounds [Tb(NO₃)₂ acac(phen)₂]H₂O (where acac is acetylacetone or its derivatives substituted in the γ-position) were synthesized and studied by luminescence, IR, and UV spectroscopy. Thermoluminescence of the complexes containing acetylacetonate, 3-phenylthio-2,4-pentadioñate, and 3-(p-methoxyphenylthio)-2,4-pentadionate was found. The structural and electronic aspects of the crystal thermoluminescence were discussed.     

Effect of the composition of dimethyl sulfoxide–acetonitrile solvent on the stability of silver(I) complexes with 2,2'-bipyridyl

The effect of composition of the dimethyl sulfoxide–acetonitrile solvent on the shift in complexation equilibrium of silver(I) and 2,2'-bipyridyl was studied potentiometrically at 298.15 K. The stability of mono- and bis(bipyridyl) complexes of silver(I) was found to rise with increasing acetonitrile content in the mixed solvent. The difference in changes in the solvation state of the central and complex ions (the solvation effect of ions) was found to make a major contribution to the changes in stability of silver(I) complexes with 2,2'-bipyridyl in dimethyl sulfoxide–acetonitrile binary solvent.     

Effect the conditions of the acid–thermal modification of clinoptilolite have on the catalytic properties of palladium–copper complexes anchored on it in the reaction of carbon monoxide oxidation

The dependence of the physicochemical and structural–adsorption properties of natural and acid–thermal modified clinoptilolite, and of Pd(II)–Cu(II) catalysts based on them, on the duration of acid–thermal modification is investigated. The samples under study are described via XRD and thermal gravimetric (DTG and DTA) analysis, IR, DR UV–Vis, EPR spectroscopy, and water vapor adsorption. Values of both the specific surface area (S_sp) and pH of aqueous suspensions are determined. The resulting catalysts are tested in the reaction of low-temperature carbon monoxide oxidation with air oxygen. A conclusion is drawn about the nature of surface bimetallic Pd(II)–Cu(II) complexes. The greatest catalytic activity is shown by complexes based on clinoptilolite and modified with 3 M HNO₃ for 0.5 and 1 h.