Bestimmung der Stabilit?tskonstanten von mehrkernigen Komplexen mit Hilfe einer spektrophotometrischen Methode

Zusammenfassung Es wurde eine allgemeine Gleichung für die Berechnung der Stabilitätskonstante von Komplexen L _mH_iM_nZ_j (Z=OH^–, usw.) abgeleitet und für Maximumbedingungen der Jobschen Kurve die Schwarzenbachsche graphische Methode so modifiziert, daß sie die allgemeine Bestimmung der Zusammensetzung und Stabilität von Komplexen L _mH_iM_nZ_j ermöglicht.

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Summary A general equation has been derived for the calculation of stability constants of complexes L _mH_iM_nZ_j (Z=OH^–, etc.). The graphic method of Schwarzenbach has been modified for maximum conditions of Job's curve in order to make possible the general determination of the composition and stability of complexes L _mH_iM_nZ_j.

     

Electrospray Ionization Mass Spectrometry: A Powerful Platform for Noble‐Metal Nanocluster Analysis

Electrospray ionization mass spectrometry (ESI‐MS) is an analytical technique that measures the mass of a sample through “soft” ionization. Recent years have witnessed a rapid growth of its application in noble‐metal nanocluster (NC) analysis. ESI‐MS is able to provide the mass of a noble‐metal NC analyte for the analysis of their composition (n, m, q values in a general formula [M_nL_m]^q), which is crucial in understanding their properties. This review attempts to present various developed techniques for the determination of the composition of noble metal NCs by ESI‐MS. Additionally, advanced applications that use ESI‐MS to further understand the reaction mechanism, complexation behavior, and structure of noble metal NCs are introduced. From the comprehensive applications of ESI‐MS on noble‐metal NCs, more possibilities in nanochemistry can be opened up by this powerful technique.     

Thermal behaviour of new Ni(II) and Cu(II) complexes with macrocyclic ligands functionalised with 1,2,4-triazole

The investigations concerning the thermal behaviour of a series of Ni(II) and Cu(II) complexes of type [NiLCl₂]·mH₂O ((1) L:L₁, m=6; (3) L:L₂, m=4) or [CuLCl]_nCl _n ·mnH₂O ((2) L:L₁, m=6; (4) L:L₂, m=4) are presented. The ligands L(1) and L(2) have been synthesised by template condensation of 3,6-diazaoctane-1,8-diamine or 1,2-diaminoethane with formaldehyde and 2-amino-4H-1,2,4-triazole. The bonding and stereochemistry of the complexes have been characterised by IR, electronic and magnetic studies at room temperature. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against planktonic as well as biofilm embedded Gram-negative, Gram-positive and fungal strains. The thermal behaviour provided confirmation of the complexes composition as well as the number and nature of water molecules and the intervals of thermal stability.     

Spectrophotometric investigation of analytically important metal complexes

Summary A convenient way of estimation of composition, molar absorptivity, effective and overall stability constants of complexes M _m Y _i H _j L _n is described.

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Spektrophotometrische Untersuchung von analytisch bedeutenden Metallkomplexen

Zusammenfassung Methoden zur Berechnung der Zusammensetzung, des molaren Extinktionskoeffizienten sowie der effektiven und Brutto-Stabilitätskonstanten von Komplexen der Art M _m Y _i H _j L _n werden beschrieben.

     

Self-Assembly of Coordination Polyhedra with Highly Entangled Faces Induced by Metal–Acetylene Interactions

The self-assembly of nanostructures is dominated by a limited number of strong coordination elements. Herein, we show that metal–acetylene π-coordination of a tripodal ligand (L) with acetylene spacers gave an M₃L₂ double-propeller motif (M=Cu^I or Ag^I), which dimerized into an M₆L₄ interlocked cage (M=Cu^I). Higher (M₃L₂)_n oligomers were also selectively obtained: an M₁₂L₈ truncated tetrahedron (M=Cu^I) and an M₁₈L₁₂ truncated trigonal prism (M=Ag^I), both of which contain the same double-propeller motif. The higher oligomers exhibit multiply entangled facial structures that are classified as a trefoil knot and a Solomon link. The inner cavities of the structures encapsulate counteranions, revealing a potential new strategy towards the synthesis of functional hollow structures that is powered by molecular entanglements.     

New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). III. Synthesis and characterization of poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene)

The synthesis of a new glassy-rubbery-glassy triblock copolymer poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) has been demonstrated. The key to the synthesis was the preparation by inifer method of a perfectly bifunctional polyisobutylene which carries tert-chlorine end groups Cl-PIB-Cl. In conjunction with Et₂AlCl coinitiator, the telechelic Cl-PIB-Cl molecule initiates the polymerization of α-methylstyrene at both ends of the prepolymer. Triblock composition can be controlled by the judicious selection of synthesis conditions; that is, Cl-PIB-Cl molecular weight, α-methylstyrene concentration, and solvent polarity. Theoretical triblock M _n calculated from M _n of Cl-PIB-Cl and triblock overall composition is in excellent agreement with experimental M _n which indicates negligible homopolymer contamination. Extraction with a series of hydrocarbon solvents reveals broad composition distribution. The stress-strain profile of a triblock is similar to that of a poly(styrene-b-butadiene-b-styrene) thermoplastic elastomer of similar composition.     

Porphyrin‐functionalized amphiphilic diblock copolypeptides for photodynamic therapy

A series of amphiphilic diblock copolypeptides (ADCs), 5‐(4‐aminophenyl)‐10,15,20‐triphenyl‐porphyrin (APP) conjugated poly(L ‐leucine)‐block‐polylysine (APP‐L_nK_m) with different molar ratios of L ‐leucine unit and lysine unit were designed and synthesized. The optimized composition of the polypeptide was determined to be APP‐L₁₀₉K₁₈₆, which has high fluorescence quantum yield and could self‐assemble into micelles in an aqueous medium with mean particle size <30 nm. The in vitro study indicates that APP‐L₁₀₉K₁₈₆ shows no significant dark cytotoxicity when the concentration is below 200 mg L^?1 for HepG2 and HeLa cells. In contrast, the polymer exhibits apparent phototoxicity with low IC₅₀ values toward HepG2 and HeLa cells, implying that the potential high photodynamic therapy efficacy of the polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Self‐Assembly of Coordination Polyhedra with Highly Entangled Faces Induced by Metal–Acetylene Interactions

The self‐assembly of nanostructures is dominated by a limited number of strong coordination elements. Herein, we show that metal–acetylene π‐coordination of a tripodal ligand (L) with acetylene spacers gave an M₃L₂ double‐propeller motif (M=Cu^I or Ag^I), which dimerized into an M₆L₄ interlocked cage (M=Cu^I). Higher (M₃L₂)_n oligomers were also selectively obtained: an M₁₂L₈ truncated tetrahedron (M=Cu^I) and an M₁₈L₁₂ truncated trigonal prism (M=Ag^I), both of which contain the same double‐propeller motif. The higher oligomers exhibit multiply entangled facial structures that are classified as a trefoil knot and a Solomon link. The inner cavities of the structures encapsulate counteranions, revealing a potential new strategy towards the synthesis of functional hollow structures that is powered by molecular entanglements.     

Preparation and microstructural analysis of poly(lactic‐alt‐glycolic acid)

Alternating copolymers of glycolic (G) and lactic (L) acid were prepared by the condensation of the preformed dimers: L_LG and L_racG. By size exclusion chromatography (THF, PS standards), poly(L_LG) exhibited a molecular weight (M_n) of 15.6 kg mol^?1, with a weight average molecular weight (M_w) of 26.9 kg mol^?1 and a PDI of 1.72. The M_n for poly(L_racG) was 9.2 kg mol^?1, with a M_w of 12.9 kg mol^?1 and a PDI of 1.40. The NMR spectra of poly(L_LG) were consistent with an isotactic microstructure. NMR spectra of the racemic poly(L_racG) were consistent with an atactic structure. The methylene region of the ¹H NMR spectrum showed a tetrad level of resolution of the nearby stereochemical relationships, for example, iii. Resonances for other groups in both the ¹H and ¹³C NMR spectra gave only a triad level of resolution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4704–4711, 2008     

Living carbocationic copolymerization of isobutylene with styrene

The carbocationic copolymerization of isobutylene (IB) and styrene (St), initiated by 2‐chloro‐2,4,4‐trimethylpentane/TiCl₄ in 60/40 (v/v) methyl chloride/hexane at ?90 °C, was investigated. At a low total concentration (0.5 mol/L), slow initiation and rapid monomer conversion were observed. At a high total comonomer concentration (3 mol/L), living conditions (a linear semilogarithmic rate and M_n–conversion plots) were found, provided that the St concentration was above a critical value ([St]₀ ～ 0.6 mol/L). The breadth of the molecular weight distribution decreased with increasing IB concentration in the feed, reaching M_w/M_n ～ 1.1. St homopolymerization was also living at a high total concentration, yielding polystyrene with M_n = 82,000 g/mol, the highest molecular weight ever achieved in carbocationic St polymerization. An analysis of this system by both the traditional gravimetric–NMR copolymer composition method and FTIR demonstrated penultimate effects. IB enrichment was found in the copolymers at all feed compositions, with very little drift at a high total concentration and above the critical St concentration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1778–1787, 2007     

Atomvolumina und Ladungsverteilungen in Nitridometallaten

Atom Volumina and Charge Distributions in Nitridometalates The linear relation between the nitride volumina calculated by use of the QTAIM‐method developed by Bader and those derived from the tables of volume increments reported by Biltz does not hold for nitridometalates A_a[M_mN_n] (A = alkali or alkaline earth metal, M = transition metal). The clear deviation from linearity is caused by the different kinds of chemical bonds being present within the complex [M_mN_n] anions on the one hand and between the complex anions and the cations on the other hand. The significant covalency of the chemical bonds within the complex [M_mN_n] anions is reflected by the calculated volumina and the charge distributions between the M and N atoms using the Bader method. By comparing the oxidation numbers of the atoms forming the complex anions with their calculated charge assignments (QTAIM method) a significant charge reduction becomes evident.     

Proton mobility in complex [RhL4Cl2]HSO4 · nH2SO4 · mH2O salts (L = Py, γ-picoline)

The method of deposition from solutions was used to synthesize [RhL ₄Cl₂]HSO₄ · nH₂SO₄ · mH₂O complex salts (L = Py, γ-picoline), n ≈ 0.5−0.6, m ≈ 5−6. According to the data of X-ray phase analysis, the crystal structure of these salts is formed by layers of cations separated by layers consisting of anions molecules of sulfuric acid and water connected through a system of hydrogen bonds. Calorimetric methods were used to study phase transitions and the range of thermal stability of salts. The method of ¹H NMR spectroscopy discovered that protons within the {HSO₄⁻ · nH₂SO₄ · mH₂O} subsystem featured enhanced conductivity. Conductivity studies showed that trans-[RhL ₄Cl₂]HSO₄ · nH₂SO₄ · mH₂O samples had high proton conductivity.     

Application of the Generalized Molar‐Ratio Method to the Determination of the Stoichiometry and Apparent Binding Constant of Nanoparticle‐Organic Capping Systems

A generalization of the molar‐ratio method is applied to the determination of the stoichiometry and apparent binding constant of metal nanoparticle‐organic capping complexes (M_mL_x) using voltammetric data for the oxygen reduction reaction (ORR) in air‐saturated aqueous phosphate buffer solutions. The method is applied to the formation of binary nanohybrids consisting of gold nanoparticles (AuNPs) capped with a rigid spacer, cucurbit[7]uril (CB), termed AuNP@CB, as well as to the formation of their ternary complexes (M_mL_xB_z) with methylene blue (MB), termed AuNP@CB@MB. The obtained stoichiometries correspond to binding of four Au surface atoms for each CB unit.     

Comparison of calix[n]arenes phosphorylated in the upper and lower rims as applied to extraction of nitrosoruthenium nitrite species

Compared were dialkylcalix[4]phosphine oxides (L) having PO groups in the opposing rims as regards the extraction of [RuNO(NO₂)₄(OH)]²⁻, nonprecious metals (M²⁺), and Ru/M heterometallic complexes of their base. The extraction constants for the ion association {(Na⁺)₂(LH₂O) _r [RuNO(NO₂)₄(OH)]²⁻ and the degree of aggregation of L were calculated. The destruction of (LH₂O) _r upon metal extraction was verified IR-spectroscopically. The stoichiometry was determined and extraction constants were calculated for mono- and binuclear complexes [M _m L _n (NO₃)_2m ] and mononuclear Ru/M species [RuNO(NO₂)₄(OH)ML _n ]. Nonprecious metals form mononuclear ML complexes in the lower rim. The size of the upper rim is responsible for the addition of a second metal nitrate molecule or addition to L or the addition of a second L molecule to the metal. Ru/M complexes with all L are present in an organic phase as two mononuclear species, ML and ML₂. Rationale is given to the selection of extraction systems for recovery of ruthenium from nitrated nitric acid solutions selectively or together with actinides and lanthanides in the form of Ru/M complexes.     

Atomically Precise Alloy Nanoclusters

Metal nanoclusters (NCs) have a particle size of about one nanometer, which makes them the smallest unit that can give a function to a substance. In addition, metal NCs possess physical and chemical properties that are different from those of the corresponding bulk metals. Metal NCs with such characteristics are expected to be important for use in nanotechnology. Research on the precise synthesis of metal NCs and elucidation of their physical/chemical properties and functions is being actively conducted. When metal NCs are alloyed, it is possible to obtain further various electronic and geometrical structures and functions. Thus, research on alloy NCs has become a hot topic in the study of metal NCs and the number of publications on alloy NCs has increased explosively in recent years. Such publications have provided much insight into the effects of alloying on the electronic structure and function of metal NCs. However, the rapid increase in knowledge has made it difficult for researchers (especially those new to the field) to grasp all of it. Therefore, in this review, we summarize the reported chemical composition, geometrical structure, electronic structure, and physical and chemical properties of Au_n−xM_x(SR)_m, Ag_n−xM_x(SR)_m, Au_n−xM_x(PR₃)_l(SR)_m, and Ag_n−xM_x(PR₃)_l(SR)_m (Au=gold, Ag=silver, M=heteroatom, PR₃=phosphine, and SR=thiolate) NCs. This review is expected to help researchers understand the characteristics of alloy NCs and lead to clear design guidelines to develop new alloy NCs with intended functions.     

Properties of binary complex compounds

The current state of studies on binary complex compounds [M¹L _a ] _x ·[M²A _b ] _y (M¹ and M² are the central ions, L and A are ligands) is considered, notably: synthesis, composition, structures, magnetic properties, and thermal decomposition.     

Lewis‐Base Stabilized N‐Silver(I) Succinimide Complexes: Synthesis,Crystal Structures and Their Use as CVD‐Precursors

Four Lewis‐base stabilized N‐silver(I) succinimide complexes of type [L_n·R_m·AgNC₄H₄O₂] (L = N,N,N′,N′‐tetramethylethylenediamine (TMEDA), n = 1, m = 0, 2a ; L = P(OEt)₃, n = 2, m = 0, 2b ; L = PPh₃, m = 0, n = 2, 2c ; L = P(OMe)₃, R = TMEDA, n = 1, m = 1, 2d ) were prepared by a “one‐pot” synthesis methodology and characterized. The molecular structures of 2a and 2c have been determined by using X‐ray single crystal analysis. Complex 2a exists as ion pair {[Ag(TMEDA)₂]⁺[Ag(NC₄H₄O₂)₂]^–} in the solid state and complex 2c is a monomer with the three‐coordinate silver atom. Complex 2b was used as precursor in the deposition of silver for the first time by using MOCVD technique. The silver films obtained were characterized using scanning electron microscopy (SEM) and energy‐dispersion X‐ray analysis (EDX). SEM and EDX studies show that the dense and homogeneous silver films could be obtained.     

Compatibility and mesophase separation in blends of α-helical polyglutamates

Blends composed of the α-helical polymers, poly-L-glutamates [(? NHC^αHRC′O? )_n, R = ? CH₂CH₂COO? (CH₂)_m(C₆H₅] (Lm) and the corresponding D enantiomers (Dm), have been studied by x-ray diffraction and viscoelastic measurements. Binary blends of L2, D2, L3, and D3 are compatible and form isomorphous mixed crystals at all compositions, whereas other pairs, with the exception of L1/D1, are incompatible. The demixing process is described for a ternary system consisting of L1, D3, and a diluent chloroform at 40°C. The phase diagram comprises four regions, I, IA, A, and AA, with increasing polymer concentration; I: isotropic, A: anisotropic, IA: I–A biphasic, and AA: A–A biphasic. The IA biphasic gap is greater in the ternary system than in the binary ones. The high-molecular-weight component (D3) is partitioned into the A phase in the IA region. The AA separation originates from incompatibility of the polymers. The phase behavior is discussed on the basis of the Abe-Flory theory by incorporating the polymer-polymer interaction parameter.     

Regularities of the formation of binuclear homo- and heteroleptic complexes of <Emphasis Type="Italic">d</Emphasis> metals with 3,3′-bis(dipyrrolylmethenes) in DMF

The reactions of seven symmetrically alkylated tetradentate ligands 3,3′-bis(dipyrrolylmethenes) (H₂L) with d-metal acetates (M(AcO)₂) in DMF solutions at 298.15 K were studied by spectrophotometry. Helicands H2L were found to be structurally preorganized to form stable binuclear homoleptic two-helix helicates [M₂L₂] with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) acetates. The coordination of the ligands by the metal ions included consecutive stages of formation of the heteroleptic [M₂L(AcO)₂] and homoleptic [M₂L₂] complexes. The [M₂L(AcO)₂] complexes were spectrally revealed in solutions containing a ligand excess (c _{H 2 L} / c _{M(AcO) 2} > 1). An increase in the salt concentration shifted the system of equilibria to the homoligand product [M₂L₂]. The thermodynamic constants of the reactions increased in the series of complexing agents: Cu(II) < Cd(II) < Hg(II) < Ni(II) < Co(II) < Zn(II). An analysis of the data on the thermodynamic constants of [M₂L₂] helicate formation in solutions and the earlier obtained results of the IR and ¹H NMR studies of the hydrobromic salts of the ligands (H₂L · 2HBr) showed that the key regularities of the influence of the structural factors on the coordination properties of the ligands were in an increase in the stability of the [M₂L₂] complexes with an increase in the basicity of the ligands.     

Synthesis,characterisation and thermal behaviour of some complexes with ligands having 1,3,4-thiadiazole moieties

Summary The investigations concerning the thermal behaviour of a series of Ni(II) and Cu(II) complexes of type [MLCl_n]·mH₂O ((1) M:Ni, L:L(1), n=1, m=2; (2) M:Cu, L:L(2), n=1, m=2; (3) M:Ni, L:L(3), n=2, m=0; (4) M:Cu, L:L(3), n=1, m=2) are presented in this paper. The ligands L(1)-L(3) have been synthesised by template condensation of 1,2-diaminoethane with formaldehyde and 2-amino-1,3,4-thiadiazole-5-thiole or 2-acetamino-1,3,4-thiadiazole-5-sulfonamide. The bonding and stereochemistry of the complexes have been characterised by IR, electronic and magnetic studies at room temperature. The thermal behaviour provided confirmation of the complex composition as well as the number and the nature of water molecules and the intervals of thermal stability. The different nature of the ligands and/or the metallic ions generates a different thermal behaviour for complexes. The complexes do not show biological activity against HIV virus.