Chromones were reacted with dimethyl acetonedicarboxylate in the presence of DBU in THF at room temperature to furnish good yields of products, their structure depending on the substituent at 3-position. Unsubstituted chromones lead to methyl 7-hydroxy-6-oxo-6H-benzo[c]chromone-8-carboxylates 2, whereas by using 3-bromochromone, the methyl furoate 3c along with the unexpected furylcyclopropyl-chromene carboxylate 4c was isolated. Finally, from 3-formyl-chromones functionalized benzophenones 5 were isolated, in good yields. Plausible mechanisms are proposed. 相似文献
Three new linear trinuclear nickel(II) complexes, [Ni3(salpen)2(OAc)2(H2O)2]·4H2O (1) (OAc = acetate, CH3COO−), [Ni3(salpen)2(OBz)2] (2) (OBz = benzoate, PhCOO−) and [Ni3(salpen)2(OCn)2(CH3CN)2] (4) (OCn = cinnamate, PhCHCHCOO−), H2salpen = tetradentate ligand, N,N′-bis(salicylidene)-1,3-pentanediamine have been synthesized and characterized structurally and magnetically. The choice of solvent for growing single crystal was made by inspecting the morphology of the initially obtained solids with the help of SEM study. The magnetic properties of a closely related complex, [Ni3(salpen)2(OPh)2(EtOH)] (3) (OPh = phenyl acetate, PhCH2COO−) whose structure and solution properties have been reported recently, has also been studied here. The structural analyses reveal that both phenoxo and carboxylate bridging are present in all the complexes and the three Ni(II) atoms remain in linear disposition. Although the Schiff base ligand and the syn–syn bridging bidentate mode of the carboxylate group remain the same in complexes 1–4, the change of alkyl/aryl group of the carboxylates brings about systematic variations between six- and five-coordination in the geometry of the terminal Ni(II) centres of the trinuclear units. The steric demand as well as hydrophobic nature of the alkyl/aryl group of the carboxylate is found to play a crucial role in the tuning of the geometry. Variable-temperature (2–300 K) magnetic susceptibility measurements show that complexes 1–4 are antiferromagnetically coupled (J = −3.2(1), −4.6(1), −3.2(1) and −2.8(1) cm−1 in 1–4, respectively). Calculations of the zero-field splitting parameter indicate that the values of D for complexes 1–4 are in the high range (D = +9.1(2), +14.2(2), +9.8(2) and +8.6(1) cm−1 for 1–4, respectively). The highest D value of +14.2(2) and +9.8(2) cm−1 for complexes 2 and 3, respectively, are consistent with the pentacoordinated geometry of the two terminal nickel(II) ions in 2 and one terminal nickel(II) ion in 3. 相似文献
Complex [Fe(II)Gd(III){pyCO(OEt)pyCOH(OEt)py}(3)](ClO(4))(2) (1) crystallizes in the Cc space group and contains one hexacoordinate ferrous ion and one enneacoordinate Gd(III) ion. Complex [Fe(2)(II)Gd(III){pyCO(OEt)py}(4)(NO(3))(H(2)O)][Gd(NO(3))(5)](0.5)(ClO(4)) (2) crystallizes in the C2/c space group and contains two hexacoordinate ferrous ions and one octacoordinate Gd(III) ion. Both complexes have been prepared by the metal-assisted ethanolysis of ligands di-2,6-(2-pyridylcarbonyl)pyridine (pyCOpyCOpy, dpcp) and di-2-pyridyl ketone ((py)(2)CO, dpk), which exhibit similar structures. M?ssbauer spectroscopic studies of 2 revealed the presence of two quadrupole-split doublets of equal intensities, each assigned to a ferrous site. These doublets exhibit similar isomer shifts (δ(1) = 1.14 mm s(-1), δ(2) = 1.11 mm s(-1)) but quite different quadrupole splittings (ΔE(Q1) = 3.55 mm s(-1), ΔE(Q2) = 2.74 mm s(-1)). Magnetic studies revealed weak ferromagnetic Fe(II)-Gd(III) interactions for both complexes (J(FeGd) = +0.68 cm(-1), D(Fe) = 12.0 cm(-1) for 1 and J(FeGd) = +0.03 cm(-1), J(FeFe) = -1.73 cm(-1) for 2, according to the -JS(i)S(j) spin-Hamiltonian formalism). 相似文献
The accurate measurement of the maximum possible number of elements in ancient ceramic samples is the main requirement in provenance studies. For this reason neutron activation analysis (NAA) and X-ray fluorescence (XRF) have been successfully used for most of the studies. In this work the analytical performance of inductively coupled plasma-optical-emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) has been compared with that of XRF and NAA for the chemical characterization of archaeological pottery. Correlation coefficients between ICP techniques and XRF or NAA data were generally better than 0.90. The reproducibility of data calculated on a sample prepared and analysed independently ten times was approximately 5% for most of the elements. Results from the ICP techniques were finally evaluated for their capacity to identify the same compositional pottery groups as results from XRF and NAA analysis, by use of multivariate statistics. 相似文献
The employment of pyridine-2-carbaldehyde oxime (paoH) in zinc(II) benzoate chemistry, in the absence or presence of azide ions, is described. The syntheses, crystal structures and spectroscopic characterization are reported for the complexes [Zn(O(2)CPh)(2)(paoH)(2)] (1), [Zn(12)(OH)(4)(O(2)CPh)(16)(pao)(4)] (2) and [Zn(4)(OH)(2)(pao)(4)(N(3))(2)] (3). The Zn(II) centre in octahedral 1 is coordinated by two monodentate PhCO(2)(-) groups and two N,N'-chelating paoH ligands. The metallic skeleton of 2 describes a tetrahedron encapsulated in a distorted cube. The {Zn(12)(μ-OH)(4)(μ(3)-ΟR)(4)}(16+) core of the cluster can be conveniently described as consisting of a central {Zn(4)(μ(3)-ΟR)(4)}(4+) cubane subunit (RO(-) = pao(-)) linked to four {Zn(2)(μ-OH)}(3+) subunits via the OH(-) group of each of the latter, which becomes μ(3). The molecule of 3 has an inverse 12-metallacrown-4 topology. Two triply bridging hydroxido groups are accommodated into the metallacrown ring. Each pao(-) ligand adopts the η(1)?:?η(1)?:?η(1)?:?μ coordination mode, chelating one Zn(II) atom and bridging a Zn(II)(2) pair. Complexes 1 and 2 display photoluminescence with maxima at ～355 nm and ～375 nm, upon maximum excitation at 314 nm; the origin of the photoluminescence is discussed. 相似文献
In the present study, two numerical methods, namely the orthogonal collocation on finite elements and the fixed pivot technique, are employed to calculate the MWD in an MMA free‐radical batch suspension polymerization reactor operating up to very high conversions (e.g., ≥95%). The theoretical MWD predictions are directly compared with experimentally measured MWDs, obtained from a pilot‐scale batch MMA suspension polymerization reactor. It is shown that there is a very good agreement between model predictions and experimental measurements on both monomer conversion and MWD. Subsequently, two different time‐optimal temperature trajectories are calculated to obtain a polymer having either a narrow or a bimodal MWD in minimum batch time. The calculated time optimal trajectories are then applied, as set point temperature changes, to a pilot plant batch polymerization reactor. It is shown that the measured MWDs are in very good agreement with the off‐line calculated optimal MWDs.
Temperature-sensitive crystalline phases, pertaining to discrete clusters of binary and ternary Co(II,III):iminodipropanol:(N,N'-aromatic binder) systems, were prepared. The rich structural speciation of such systems in alcoholic media and their unique structural, magnetic, and spectroscopic profiles have been demonstrated. The need to understand the chemical reactivity of such complex ternary Co(II)-(1,1'-iminodi-2-propanol) systems, in the presence of N,N'-aromatic chelators 2,2'-bipyridine and 1,10-phenanthroline and aromatic binder 4,4'-bipyridine in methanol, led to the synthetic development of well-defined hybrid metal-organic materials with discrete spectroscopic, structural, electrochemical, and magnetic properties. The surprisingly plethoric family of the prepared mononuclear-trinuclear-tetranuclear Co(II,III) clusters was characterized through elemental analysis, FT-IR, and X-ray crystallography. Enrichment of their physicochemical profile originated from electrochemical, optical (UV/Vis, luminescence), magnetic, and EPR studies, unequivocally supporting their structural formulation. Collectively, the experimentally and theoretically (Bond-Valence-Sum, Hirshfeld) perused structures project the influence of molecular stoichiometry and temperature on targeted synthetic efforts toward crystal engineering of discrete Co(II,III)-center assemblies, exemplifying structure-reactivity correlations and magneto-optical-structural attributes. 相似文献
The rise of lead halide perovskites as light harvesters has stunned the photovoltaic community because of the high efficiencies achieved. Owing to their unique optical and electronic properties, hybrid metal halide perovskites and their application in optoelectronic devices are a hot topic of academic research. Although Pb and Sn hybrids are used in most cases, they present stability and toxicity problems. Therefore, similar compounds with other metals have been investigated. Antimony-based hybrid perovskites are good alternatives to their Pb-based analogues for photovoltaic and other applications. In this paper, we report the synthesis of four organic–inorganic hybrid compounds of the general formula [CH3SC(NH2)2]2SbA5, (A = I, Br, Cl, and Cl/Br). They contain corner-sharing SbX6 octahedra, which form zigzag chains, and the amine groups are located in the free cavities between the chains. Their structural, optical, and vibronic properties were studied, and the results of DFT calculations were compared with the experimental findings to provide insights into the properties of these new compounds. 相似文献
The interaction of ZnCl(2) with 2-dipyridylketonoxime (=Hpko) and flufenamic acid (=Hfluf) in a basic methanolic solution leads to the formation of a hexanuclear 24-membered metallacoronate, [Zn(6)(OH)(2)(pko)(4)(fluf)(6)] (1), with a [Zn-O-C-O] repeat unit and a nonsteroidal antiinflammatory drug as the constructing ligand. Compound 1 retains its structure in a dimethyl sulfoxide solution, as shown by (1)H NMR spectroscopy and molar conductance. 相似文献
