Assembly of a new circle connecting circle chain through exerting the template role of a Keggin polyoxometalate

By using the flexible bis(triazole) ligand 1,2-bis(1,2,4-triazol-1-yl)ethane (bte), a polyoxometalate-templated compound, [Zn₂(bte)₄(SiW₁₂O₄₀)]·2H₂O (1), was synthesized under hydrothermal conditions. The compound was characterized by single-crystal X-ray diffraction, elemental analyses, IR spectroscopy, photoluminescence spectroscopy, and cyclic voltammetry. Compound 1 is constructed from two motifs: the [SiW₁₂O₄₀]^4? polyanion and a bi-nuclear metal-organic circle [Zn₂(bte)₂]⁴⁺. The polyanion exerts a template role, inducing the formation of the bi-nuclear circle. The circles build a 1-D circle connecting circle chain through sharing the same Zn ions. Adjacent circles in the chain are vertical with each other. The template polyanion is surrounded by four circles from four different 1-D chains, forming a 3-D supramolecular structure.     

Two copper(II) metal–organic networks derived from bis-pyridyl-bis-amide ligands and aromatic polycarboxylates: a 2-D layered structure and a 4-connected trinodal 3-D topology

Two metal–organic coordination polymers, [Cu₃(4-bpcb)₂(1,2,4-btc)₂(H₂O)₂] (1) and [Cu₃(3-bpcb)₃(btec)_1.5] (2), have been synthesized from hydrothermal reaction of copper chloride with mixed ligands [4-bpcb?=?N,N′-bis(4-pyridinecarboxamide)-1,4-benzene, 3-bpcb?=?N,N′-bis(3-pyridinecarboxamide)-1,4-benzene, 1,2,4-H₃btc?=?1,2,4-benzenetricarboxylic acid, and H₄btec?=?1,2,4,5-benzenetetracarboxylic acid]. X-ray diffraction analysis reveals that 1 exhibits a 2-D layer structure and 2 possesses a three-dimensional (3-D) network. In 1 and 2, Cu^II ions are connected by bridging 1,2,4-btc or btec to form 2-D polymeric layers. Cu-1,2,4-btc layer does not propagate into a 3-D coordination framework in 1 due to 4-bpcb showing monodentate coordination (via ligation of only one pyridyl nitrogen). In 2, Cu-btec 2-D layers are further extended into a 3-D network with (6⁴.8²)₃ topology by 3-bpcb ligand in μ ₂-bridging coordination (via ligation of two pyridyl nitrogens). The different structures of the two complexes illustrate the influence of different polycarboxylates and N-donor positions of organic ligands on the formation of such coordination architectures. Moreover, the thermal properties and electrochemical properties of the copper complexes bulk-modified carbon paste electrodes have been studied.     

Synthesis,Characterization and Crystal Structure of an Unsymmetric Samarium(III) Cryptate

Abstract

The complex [Sm(H₃L)(NO₃)(H₂O)](NO₃)₂ · H₂O was synthesized by the (2+3) condensation of tris(2-aminoethyl)amine with 2,6-diformyl-4-chlorophenol in the presence of Sm³⁺. Its crystal structure has been determined. In the complex the coordination number of Sm³⁺ is nine. A water molecule is encapsulated in the cryptate as a guest, confirmed by electrospray mass spectrometry, thermal analysis and the X-ray crystal structure.     

SYNTHESIS OF MONOSUBSTITUTED PENTAKIS(2,6-DIETHYLPHENYLISO CYANIDE)- COBALT(I) COMPLEXES WITH BIDENTATE TERTIARY PHOSPHINE LIGANDS. I. MONOMETALLIC COMPLEXES

Abstract

Reaction of [Co(CNC₆H₃Et₂-2,6)5]BF₄ with bidentate phosphines leads to monosubstituted Co(I) complexes, [Co(CNC₆H₃Et₂-2,6)₄(L-L)]BF4, where L-L = Ph₂P(CH₂)n PPh₂, n = 1-4,6; Ph₂PCH₂-CH₂AsPh₂, Ph₂PC₆H₄PPh₂-p, Ph₂PCH[dbnd]CHPPh₂-trans. Reaction conditions are such that disubstitution would be possible, but bidentate bridging to form bimetallic complexes is not favoured. Comparison of v([sbnd]N°C) IR, electronic spectra, and molar conductivities with values for [Co(CNC₆H₃Et₂-2,6)4L]X, where X = ClO₄, BF₄; L = monodentate triarylphosphine; indicates that these new complexes must also be five-coordinate Co(I) complexes, in which the potentially bidentate phosphine ligands are coordinated through only one P atom. Structures are approximately trigonal bipyramidal in solution and the solid state, with the phosphine ligand occupying an axial position.     

Syntheses,crystal structures,and spectroscopic properties of copper(II) complexes with 3,14-diethyl-2,6,13,17-tetraazatricyclo(16.4.0.07,12)docosane

[Cu(L)(NO₃)₂] (1) and [Cu(L)(H₂O)₂](SCN)₂ (2) [L?=?3,14-diethyl-2,6,13,17-tetraazatricyclo(16.4.0.0^7,12)docosane] have been prepared and structurally characterized by single-crystal X-ray diffraction at 100?K. For these constrained macrocycle complexes, copper(II) exists in a tetragonally distorted octahedral environment with the four nitrogen atoms of the macrocyclic ligands and two oxygen atoms from either nitrate or water in axial positions. The macrocyclic ligands in both complexes adopt the most stable trans-III conformation. The Cu–N distances are 2.021(2)–2.047(2)?Å and typical but the axial ligands are weakly coordinating, with Cu–O bond lengths, 2.506(2)?Å for 1 and 2.569(2)?Å for 2, due to the pseudo Jahn–Teller effect. The crystals are stabilized by a 3-D network by intra and intermolecular hydrogen bonds that are formed among the secondary nitrogen hydrogen atoms and nitrate in 1, and intermolecular hydrogen bonds are formed by water and thiocyanates in 2. The electronic absorption and IR spectral properties are also discussed.     

1H,89Y HMQC and Further NMR Spectroscopic and X‐ray Diffraction Investigations on Yttrium‐Containing Complexes Exhibiting Various Nuclearities

2D ¹H,⁸⁹Y heteronuclear shift correlation through scalar coupling has been applied to the chemical‐shift determination of a set of yttrium complexes with various nuclearities. This method allowed the determination of ⁸⁹Y NMR data in a short period of time. Multinuclear NMR spectroscopy as function of temperature, PGSE NMR‐diffusion experiments, heteronuclear NOE measurements, and X‐ray crystallography were applied to determine the structures of [Y₅(OH)₅(L ‐Val)₄(Ph₂acac)₆] ( 1 ) (Ph₂acac=dibenzoylmethanide, L ‐Val=L ‐valine), [Y( 2 )(OTf)₃] ( 3 ), and [Y₂( 4 )(OTf)₅] ( 5 ) ( 2 : [(S)P{N(Me)N?C(H)Py}₃], 4 : [B{N(Me)N?C(H)Py}₄]^?) in solution and in the solid state. The structures found in the solid state are retained in solution, where averaged structures were observed. NMR diffusion measurements helped us to understand the nuclearity of compounds 3 and 5 in solution. ¹H,¹⁹F HOESY and ¹⁹F,¹⁹F EXSY data revealed that the anions are specifically located in particular regions of space, which nicely correlated with the geometries found in the X‐ray structures.     

Photomagnetism of a sym‐cis‐Dithiocyanato Iron(II) Complex with a Tetradentate N,N′‐Bis(2‐pyridylmethyl)1,2‐ethanediamine Ligand

A comprehensive study of the magnetic and photomagnetic behaviors of cis‐[Fe(picen)(NCS)₂] (picen=N,N′‐bis(2‐pyridylmethyl)1,2‐ethanediamine) was carried out. The spin‐equilibration was extremely slow in the vicinity of the thermal spin‐transition. When the cooling speed was slower than 0.1 K min^?1, this complex was characterized by an abrupt thermal spin‐transition at about 70 K. Measurement of the kinetics in the range 60–70 K was performed to approach the quasi‐static hysteresis loop. At low temperatures, the metastable HS state was quenched by a rapid freezing process and the critical T(TIESST) temperature, which was associated with the thermally induced excited spin‐state‐trapping (TIESST) effect, was measured. At 10 K, this complex also exhibited the well‐known light‐induced excited spin‐state‐trapping (LIESST) effect and the T(LIESST) temperature was determined. The kinetics of the metastable HS states, which were generated from the freezing effect and from the light‐induced excitation, was studied. Single‐crystal X‐ray diffraction as a function of speed‐cooling and light conditions at 30 K revealed the mechanism of the spin‐crossover in this complex as well as some direct relationships between its structural properties and its spin state. This spin‐crossover (SCO) material represents a fascinating example in which the metastability of the HS state is in close vicinity to the thermal spin‐transition region. Moreover, it is a beautiful example of a complex in which the metastable HS states can be generated, and then compared, either by the freezing effect or by the LIESST effect.     

A study of the removal of heavy metals from aqueous solutions by Moringa oleifera seeds and amine-based ligand 1,4-bis[N,N-bis(2-picoyl)amino]butane

Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using the Moringa oleifera seeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II) > Cu(II) > Cd(II) > Ni(II) > Mn(II) and Zn(II) > Cu(II) > Ni(II). The general trend of the heavy metal ions uptake by the amine-based ligand followed decreased in the order Mn > Cd > Cu > Ni > Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5–8.     

Spectrophotometric studies of the formation of charge transfer complex of iron(III) with N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane di-Schiff base ligand in methanol

The complex formation reaction between N,N′-bis(2-pyridylmethylidene)-1,2-diiminoethane (BPIE) di-Schiff base ligand as an electron donor and iron(III) chloride as an electron acceptor have been studied spectrophometrically in methanol at 28°C. The values of equilibrium constants, K and molar absorptivities, ε were obtained from the Benesi–Hildebrand, Scott and Foster–Hammick–Wardley equations. The results indicate the formation of 1?:?1 charge transfer complex. The absorption band energy of the complex, E _CT, the ionization potential of the BPIE Schiff base ligand, I ^D, and the Gibbs energy changes of the above reaction, ΔG ⁰, were calculated. Finally, the kinetics of the complex formation reaction were studied and was found to be second-order in each reactant. The values of the rate constants of the forward and reverse reactions k ₁ and k _?1 were determined.     

A Tandem Olefin Migration and Prins Cyclization Using Cu(OTf)(2)-Bisphosphine Complexes: An Improved Synthesis of Functionalized Tetrahydropyrans

In situ-generated (bis-DPPMB)-Cu(OTf)₂ complex has been examined to catalyze a tandem olefin migration and Prins cyclization of an alkenol with various aldehydes. The reaction proceeded with electron-rich aromatic aldehydes at room temperature and provided functionalized tetrahydropyrans in good yields. An efficient synthesis of the bis-DPPMB ligand has also been described.