Structure and stability of molecular and ionic complexes of AlCl3 with pyrazine and 4,4′-bipyridyl

Structural and thermodynamic characteristics of molecular and ionic complexes of aluminum trichloride with pyrazine (pyz) and 4,4′-bipyridyl (bipy) are calculated at the RI-BP86/def2-SVP level. It is found that for molecular 2AlCl₃·3L and 4AlCl₃·3L complexes an energy difference between isomers does not exceed 4 kJ/mol, and the rotation barrier of the AlCl₃ moiety relative to the N-Al-N bond does not exceed 24 kJ/mol. A comparison of the stability of molecular and ionic complexes of aluminum in the gas phase shows that the maximum energy difference is ～60 kJ/mol. For L = pyz the molecular complex is more stable whereas for L = bipy it is the ionic one.     

New complexes of heavy lanthanides with 4,4′-bipyridine and trichloroacetates

Novel mixed-ligand complexes with empirical formula Ln(4-bpy)₂(CCl₃COO)₃·nH₂O [where Ln(III)?=?Dy, Ho, Er, Tm, Yb, Lu; 4-bpy?=?4,4??-bipyridine] were prepared and characterized by chemical and elemental analysis, infrared spectroscopy, and conductivity measurements (in methanol, dimethylformamide, and dimethyl sulfoxide). X-ray powder diffraction patterns indicate that the complexes are small crystalline compounds. IR spectra of complexes show that all carboxylate groups and 4-bpy are engaged in coordination of lanthanide ions. The thermal behavior of complexes was studied by means of TG, DTG, DTA techniques in the solid state under nonisothermal conditions in air atmosphere. During heating, the complexes decompose via intermediate products to the oxide Ln₂O₃. The combined TG?CFTIR technique was employed to study the decomposition pathway of the Ho(III) and Tm(III) complexes in flowing argon atmosphere.     

Cyclopalladated 2-phenyldihydrooxazole complexes with ethylenediamine, 2,2′-bipyridine,and bridging acetate ligands

The ¹H NMR, electronic absorption, and luminescence spectra, as well as voltammograms of the reduction and oxidation of the complexes [Pd(C∧N)(N∧N)]ClO₄ and [Pd(C∧N)(μ-OOCCH₃)]₂ [where (C∧N)⁻ is deprotonated 2-phenyl-4,5-dihydro-1,3-oxazole, and N∧N is ethylenediamine or 2,2′-bipyridine (bpy)] were compared. Magnetic nonequivalence of protons in the dihydrooxazole ring and upfield shift of the corresponding signals were observed as a result of anisotropic effect of the ring current in palladated phenyl substituents in the [Pd(C∧N)(μ-OOCCH₃)]₂ complex having a C ₂ symmetry. One-electron reduction wave of [Pd(C∧N)bpy]⁺ was assigned to ligand-centered electron transfer to the π* orbital of 2,2′-bipyridine, and two oxidation waves of [Pd(C∧N)(μ-OOCCH₃)]₂ were attributed to successive one-electron oxidations of the palladium centers. Low-temperature (77 K) phosphorescence of [Pd(C∧N)En]⁺ and [Pd(C∧N)bpy]⁺ was ascribed to optical transition localized on the metal-complex fragment {Pd(C∧N)} and to interligand charge transfer between the chelating and cyclopalladated ligands. The formation of metal-metal bond in the complex [Pd(C∧N)(μ-OOCCH3₎]₂ gives rise to radiative decay of photoexcitation energy from two electronically excited states, one of which is localized on the {Pd(C∧N)} fragment, and the second corresponds to the charge transfer metal-metal-cyclopalladated ligand.     

Molecular complex of iodine with 2,3′-bipyridyl

Thermodynamic data for the formation of a 1:1 charge-transfer (CT) complex of iodine with 2,3′-bipyridyl (2,3′-Bpy) in carbon tetrachloride solution have been obtained from measurements of the blue-shifted iodine band; ΔH⁰ = −28.62±4.78kJ mol⁻¹ and ΔS⁰ = −54.7±1.6 Jmol⁻¹K⁻¹.Infrared spectra of the iodine complex of 2,3′-Bpy in solids, together with those of iodine—bromide and iodine—chloride complexes, have been measured. Comparing the spectra of three halogen complexes with that of 2,3′-Bpy, it is suggested that the nitrogen atom at the 3-position is involved in 1:1 complex formation. Far i.r. spectra of the iodine complex in cyclohexane solution and those of the three halogen complexes in solids have also been obtained. Assignments for the modified IX (X = I, Br and Cl) stretching and the intermolecular NI stretching vibrations have been proposed. The force constants were calculated under the assumption of a linear triatomic model, DIX, where D denotes the donor molecule. The results were compared with those for the pyridine (Py).IX complexes.     

Synthesis and properties of 2,2′-dipyridyl and 4,4′-dipyridyl complexes with thulium salts

Summary New complexes of 2,2-dipyridyl and 4,4-dipyridyl with thulium salts TmX ₃ (whereX=Cl^–, Br^–, NO ₃ ^– , NCS^–, and ClO ₄ ^– ) have been prepared and their solubilities in water at 21 °C were determined. The IR spectra of these compounds are discussed. The conditions of thermal decomposition of the complexes were also studied.

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Synthese und Eigenschaften von 2,2-Dipyridyl- und 4,4-Dipyridylkomplexen mit Thuliumsalzen

Zusammenfassung Es wurden neue 2,2-Dipyridyl- und 4,4-Dipyridyl-Komplexen mit Thuliumsalzen TmX ₃ (X=Cl^–, Br^– No ₃ ^– , NCS^–, ClO ₄ ^– ) dargestellt und ihre Wasserlöslihkeit bei 21 °C bestimmt. Die IR-Spektren werden diskutiert. Das thermische Verhalten der erhaltenen Komplexe wurde untersucht.

     

Belousov-Zhabotinskii oscillatory chemical reactions involving complexes of transition metals with 1,10-phenanthroline and 2,2′-bipyridyl

An analysis is given of features of the catalytic effect of complexes of manganese, iron and ruthenium with 1,10-phenanthroline and with 2,2-bipyridyl on the oscillatory Belousov-Zhabotinskii chemical reaction. On the basis of the experimental results, the redox properties of the various complexes and the composition of their coordination spheres consideration is given to the possibility (not previously taken into account) of the conversion of the catalyst during the formation and consumption of key substances [bromide ion, bromous acid HBrO₂, the bromyl and malonyl radicalsBrO₂ andCO(COOH)₂], the concentrations of which govern the oscillatory regime of the reaction. A scheme is proposed for the action of the complexes of transition metals with 1,10-phenanthroline and 2,2-bipyridyl which removes the discrepancies between the usually accepted mechanism for the Belousov-Zhabotinskii reaction and the experimental results.Sonar Scientific Research Center for the Automation of Biotechnical Systems, Cybernetics Institute of the Ukrainian SSR, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 3, pp. 346–353, June, 1991. Original article submitted March 14, 1991.     

Preparation and characterization of ruthenium complexes with the new 4,4′,4″-tri-tert-butylterpyridine ligand and with 4,4′-di-tert-butylbipyridine

An efficient procedure for the preparation of 4,4′,4″-tri-tert-butylterpyridine (trpy*) which is formed together with 4,4′-di-tert-butylbipyridine (bipy*) is described, and the preparation of the complexes (trpy*)RuCl₃, [(trpy*)L₂RuCl]PF₆ (L₂ = bipy, bipy*), and (bipy*)₂RuCl₂ and their characterization by cyclic-voltametry, UV—vis and ¹H NMR spectroscopy are reported. It is shown that introduction of tert-butyl substituents increases the solubility of the resultant complexes and enhances the electron donating influence of the trpy ligand.     

Investigation of complexes of zinc(II) and cadmium(II)DI-n-butyldithiocarbamates with 2,2′-bipyridyl

A new mixed-ligand complex, Cd(S₂CN(C₄H₉)_{2 2})₂(2,2′-Bipy), was synthesized. A polycrystal X-ray diffraction analysis was performed (DRON-3M and DRON-UM1 diffractometers, CuK_α radiation, Ni filter) and the crystal structure was determined [Enraf-Nonius CAD-4 automatic diffractometer, MoK_α radiation, 2440 nonzero independent reflections, 153 refined structural parameters, R is 0.11 for I>2σ(I)]. Crystal data for C₂₈H₄₄CdN₄S₄ : a = 28.716(4), b = 6.848(6), c = 17.188(2) Å, space group Pcca, V-3380.2(7) ų, Z = 4, M = 679.42, dcaU.= 1.335 g/cm3. The structure consists of monomeric molecules in which the cadmium atom has a distorted octahedral environment. The polycrystal diffraction analysis revealed that the complex is isostructural with the defined complex Zn(S₂CN(C₄Hg)₂)₂(2,2′-Bipy). A crystal-chemical search on metal dialkyldithiocarbamates in the Cambridge Structural Database was accomplished and isostructural pairs of Zn and Cd metal complexes were found.     

Synthesis and some properties of light lanthanide complexes with 4,4′-bipyridine and dibromoacetates

In this study, new complexes with formulae: Ce(4-bpy)(CHBr₂COO)₃·H₂O, Ln(4-bpy)_0.5(CHBr₂COO)₃·2H₂O (where Ln(III) = Pr, Nd, Sm; 4-bpy = 4,4′-bipyridine) and Eu(4-bpy)(CHBr₂COO)₃·2H₂O were prepared, and characterized by chemical and elemental analyses, and IR spectroscopy. The way of metal–ligand coordination was discussed. They are small crystalline. The complexes of Pr(III), Nd(III), and Sm(III) are isostructural in group. Conductivity studies (in methanol, dimethylformamide, and dimethylsulfoxide) were also performed and described. The thermal properties of complexes in the solid state were studied using TG–DTG techniques under dynamic flow of air atmosphere. TG–MS system was used to analyze principal volatile thermal decomposition and fragmentation products evolved during pyrolyses of Ce(III) and Sm(III) complexes in dynamic flow of air atmosphere.     

Spectral and electrochemical properties of mono-, bi-, and tetranuclear cyclopalladized complexes based on 2-(2-thienyl)pyridine and 2-phenylpyridine with pyridine and 4,4′-bipyridyl

Mono-, bi-, and tetranuclear cyclopalladized complexes based on 2-(2-thienyl)pyridine and 2-phenylpyridine with pyridine and 4,4′-bipyridyl were prepared and characterized by the methods of ¹H NMR, electron absorption and emission spectroscopy, and also by the voltammetry method. The values of the coordination-induced shifts of proton in the ligands of the complexes were determined; the upfield displacement of chemical shifts of protons of the cyclopalladized ligand nearest to the metal was assigned to the anisotropic action of a ring current of the pyridine rings orthogonal to the coordination plane in 4,4′-bipyridyl and pyridine. Long-wave absorption bands of the complexes were assigned to the spin-allowed optical d-π charge-transfer transitions, and the bands of the low-temperature phosphorescence, to the intraligand π-π_NyyC^* transitions. Three waves of the reduction of the complexes were assigned to the ligand-centered processes of successive electron transfer on π* orbitals preferentially localized on coordinated pyridine and cyclopalladized ligands.     

Features of condensation of 4,4′-Dihydroxybiphenyl with phenylphosphonous tetraethyldiamide

4,4′-Dihydroxybiphenyl was condensed with phenylphosphonous tetraethyldiamide. The moleccular mass, chemical composition, and structural features of the product, oligo(4,4′-biphenylene phenylphosphonite), were elucidated using the method of matrix-activated laser desorption/ionization, with a time-of-flight (TOF) mass analyzer. The oligophenylphosphites containing labile P-N bond, which are unstable under conditions of recording mass spectra, were stabilized by conversion into oligophenylphosphonates. 1H-Tetrazole catalyzes the reaction of phenylphosphonous tetraethyldiamide with 4,4′-dihydroxybiphenyl. Cross-linking in the solid state of the oligo(4,4′-biphenylene phenylphosphonite) containing terminal phosphonamidite group leads to gradual increase in the molecular weight and is accompanied by redox processes.     

Coordination behaviour and thermolysis of some rare-earth complexes with 4,4′-bipyridine and di- or trichloroacetates

A novel mixed-ligand complexes with empirical formulae: Dy(4-bpy)(CCl₂HCOO)₃ · H₂O and Ln(4-bpy)_1.5(CCl₃COO)₃ · 2H₂O (where Ln(III) = Ce, Nd) were prepared and characterized by chemical and elemental analysis and IR spectroscopy, conductivity (in methanol, dimethyloformamide and dimethylsulfoxide). Analysis of the diffractograms showed that the obtained complexes are crystalline. Way of metal-ligand coordination discussed. The thermal properties of complexes in the solid state were studied under non-isothermal conditions in air atmosphere. During heating the complexes decompose via intermediate products to the oxides: Ln₂O₃ (Nd, Dy) and CeO₂. TG-MS system was used to analyse principal volatile thermal decomposition and fragmentation products evolved during pyrolysis of Dy(4-bpy)(CCl₂HCOO)₃ · H₂O in air.     

Kinetic analysis of the mechanochemical syntheses of dialkyl 2,2′-bipyridyl-4,4′-dicarboxylate complexes of palladium

Kinetic models for the ‘molecular’ mechanochemical syntheses of α- and β-dialkyl 2,2′-bipyridyl-4,4′-dicarboxylate complexes of palladium (PdLⁿI₂, where n specifies the number of carbons in the alkyl chain of the ligand and α and β refer to the substitution of the alkyl chain) are explored. The Johnson–Mehl–Avrami–Yerofeev–Kolmogrov (JMAYK) model was determined to best fit the data obtained via ¹H NMR spectroscopic analysis of the reaction mixtures over time. A rate enhancement, and corresponding increase in the Avrami exponent, was observed when the complex formed was liquid crystalline at milling temperatures.     

Syntheses and structures of copper benzene-1,4-dioxydiacetate complexes with 4,4′-bipyridine and 1,10-phenanthroline

Two new copper complexes, [Cu₂(BDOA)(4,4′-bpy)₂] ? 2H₂O (1) and [Cu(BDOA)(phen)] (2) (H₂BDOA = benzene-1,4-dioxydiacetic acid; 4,4′-bpy = 4,4′-bipyridine; phen = 1,10-phenanthroline), were synthesized and characterized by IR, elemental analysis, and single-crystal X-ray diffraction. Complex 1 exhibits a 2-D three-connected network structure with 6³ topology. Complex 2 displays a 1-D chain structure. Furthermore, the 3-D supramolecular networks of 1 and 2 are constructed via rich hydrogen bonds. Thermal stability of 1 is discussed in this article.     

Four transition metal complexes constructed with mixed mercaptotetrazole and 4,4′-bipyridine ligands

Based on 5-mercapto-1H-tetrazole-1-methanesulfonic acid disodium salt (Na₂mtms) and 4,4′-bipyridine (bpy) as ligands, four new transition metal complexes, namely {[Cd₂(mtms)(bpy)₂(OAc)₂]·H₂O} _n (1), {[Cd(mtms)(bpy)₂(H₂O)₂]₂·bpy·4H₂O} _n (2), {[Zn₂(μ ₂-OH)(mtms)(bpy)₃(H₂O)]·ClO₄·H₂O} _n (3), and {[Co(mtms)₂(bpy)(H₂O)₂]·[Co(bpy)₂(H₂O)₄]·H₂O} _n (4), have been synthesized and characterized by single-crystal X-ray diffraction. Complex 1 features a pillared-layer coordination architecture linked by acetate, mtms, and bridging bpy ligands. Complex 2 has a 1D polymeric structure with [Cd(mtms)(bpy)₂(H₂O)₂] as the repeating unit; these infinite chains are further connected into a 3D supramolecular framework through π–π stacking of bpy ligands. In complex 3, the mtms ligand combined with μ ₂-OH bridges two Zn atoms to form a dimer structure, which is different from that of complex 2. Complex 4 shows a 3D supramolecular network containing infinite [Co(mtms)₂(bpy)(H₂O)₂]^2? anionic chains and free [Co(bpy)₂(H₂O)₄]²⁺ cationic components. The luminescence properties of 1 and 2 and the electrochemical properties of 3 are reported.     

Electronic structure and electro-optical properties of ion radicals formed during the reduction of N,N′-dialkylsubstituted salts of 4,4′-bipyridyl

Symmetric N,N′-disubstituted salts of 4,4′-bipyridyl (viologens) are synthesized and described. It is shown by cyclic voltammetry that disubstituted salts of 4,4′-bipyridyl have a tendency toward reversible two-electron reduction. Normal first and second step oxidation-reduction potentials with respect to saturated silver chloride electrodes at various potential scan rates are found. The spectra of the high-resolution electron paramagnetic resonance of viologen cation radicals formed during the reduction of N,N′-disubstituted salts of 4,4′-bipyridyl are obtained and interpreted. It is established that the nature of substitutes and counterions in a viologen molecule considerably influences the distribution of its spin density, voltammetric curves, and electro-optical properties.     

Coordination polymer with a staircase molecular architecture: Connecting binuclear Zn(II) bis-chelate platforms with bridging 4,4′-bipyridyl

A new tetraketone ligand with two separated β-diketone functions was prepared, 1,3-[CO-CH₂-COC(CH₃)₂OCH₃]₂Ph (H₂L ^iPrOMe). The title coordination polymer, [Zn₂(L ^iPrOMe)₂(DMSO)₂(bipy)]_n (DMSO = dimethylsulfoxide; bipy = 4,4′-bipyridyl), formed as the only crystalline product upon interaction of Zn(II) acetate, H₂L ^iPrOMe and bipy in 1:1:1 to 1:1:5 molar ratios in DMSO as a solvent. A single crystal XRD study of the compound revealed a staircase polymeric architecture of the complex. The architecture is based on binuclear ′Zn₂(L ^iPrOMe)_2′ platforms where each Zn(II) cation is chelated by two β-diketonate groups of two L ^iPrOMe ligands in the equatorial plane, while each L ^iPrOMe ligand chelates two Zn(II) cations. The coordination environment of each Zn(II) is completed to a distorted octahedron by an O atom of a terminal DMSO and an N atom of bridging bipy ligands. The resulting staircase polymeric ribbons are packed in a self-inclusion mode as would be expected for van der Waals interactions. Most fragments of the molecule were found to be disordered over two equally populated orientations, which was interpreted as evidence of a modulated structure. In addition, several fragments reveal additional minor disordering and high thermal motion.