Dalton Transactions

Liu, Yuxia; Yang, Xu; Liu, Lingjun; Wang, Hongliang; Bi, Siwei

doi: 10.1039/c4dt03453hpmid: 25688909

By carrying out density functional theoretical calculations, we have performed a detailed mechanistic study of the Au(i)-catalyzed cycloisomerization of 1,6-enylnyl ester in a dry and wet dichloromethane solvent corresponding to hydrogenation and hydrolysis processes, respectively. The hydrogenation and hydrolysis mechanisms proposed in the previous literature starting from an enol ketal intermediate without the involvement of an Au(i) catalyst are found to involve high barriers and thus contradict the observed experimental findings. Alternatively, based on the theoretical calculations, a novel hydrogenation mechanism (i.e., Au-induced H-shift followed by enol intermediate self-promoted H-shift) and a hydrolysis mechanism (i.e., Au-stabilized H-shift/C–O binding with subsequent H2O-assisted H-shift) from an Au–enol ketal adduct corroborate the experimental observations. The calculated results indicate that under unchanged wet conditions, the formation of a hydrolysis product is not involved in the intermediacy of the hydrogenation product. However, if the initial dry environment is provided, a hydrogenation product will be afforded. And then it will relentlessly evolve into a hydrolysis product in the subsequent wet conditions. The present theoretical results not only rationalize the experimental observations well but provide new insight into the mechanisms of the significant water-mediated cycloisomerization reaction.

Wang, Chao; Lin, Shuang-Yan; Shi, Wei; Cheng, Peng; Tang, Jinkui

doi: 10.1039/c4dt03354jpmid: 25689341

A series of one dimensional chain complexes [Ln(hfac)3]2·[Cu(hfac)2]2·4(3pyvd)·n-C7H16 (Ln = Gd(1), Tb(2), Dy(3)) containing 2p, 3d and 4f spin carriers have been successfully synthesized and magnetically characterized where the verdazyl radicals represent the bridge linking copper(ii) and lanthanide(iii) ions. Rough estimation of magnetic behaviors of complex 1 revealed that the coupling between a Gd(iii) ion and a radical is weakly ferromagnetic, while alternating-current susceptibilities of complexes 2 and 3 suggest no slow magnetic relaxations exist at low temperature.

Marotta, Gabriele; Kumar, Ch. Pavan; Lobello, Maria Grazia; Cavazzini, Francesca; Salvatori, Paolo; Ganesh, Koyyada; Nazeeruddin, Mohammad Khaja; Chandrasekharam, Malapaka; De Angelis, Filippo

doi: 10.1039/c4dt03633fpmid: 25688828

Ekmekçi, Mete Kaan; Erdem, Murat; Başak, Ali Sadi

doi: 10.1039/c4dt03001jpmid: 25689851

Pure Nd3+- or Eu3+-doped CoNb2O6 powders have been prepared by a molten salt synthesis method using a Li2SO4–Na2SO4 or NaCl–KCl salt mixture as a flux at relatively low temperatures as compared to the solid state reaction method. X-ray diffraction patterns of pure CoNb2O6 samples indicated an orthorhombic single phase. For Eu3+-doped CoNb2O6 samples, the luminescence of Eu3+ was observed at 615 nm as red emission while the Nd3+ doped sample showed a typical emission at 1064 nm varying with the Eu3+ or Nd3+ doping concentrations. These luminescence characteristics of the doped samples may be attributed to the energy transfer between rare earth ions and CoO6 octahedral groups in the columbite structure.

Hu, Jiajia; Xu, Guangqing; Wang, Jinwen; Lv, Jun; Zhang, Xinyi; Xie, Ting; Zheng, Zhixiang; Wu, Yucheng

doi: 10.1039/c4dt03953jpmid: 25689541

A Bi2O3 nanoparticle modified BiOCl composite was synthesized by a solvothermal method combined with in situ reduction and oxidation in KBH4 and H2O2 solutions respectively. The thickness of a BiOCl nanosheet and the amount of Bi2O3 nanoparticle can be adjusted by changing the KBH4 concentration. The structure, morphology, elemental composition and optical absorption performance were characterized by using an X-ray diffraction diffractometer, a scanning electron microscope, a high resolution transmission electron microscope, an X-ray photoelectron spectroscope and a UV-Vis diffuse reflection spectroscope respectively. A nanolayered hierarchical structure of BiOCl was observed, and Bi2O3 nanoparticles were found to be evenly distributed on the surface/interface of the nanosheets. The photocatalytic activity of the composite was tested by the degradation of 40 mg L−1 methyl orange solution under UV light illumination. The Bi2O3/BiOCl composite prepared in a KBH4 concentration of 0.02 M achieved the highest photocatalytic rate of 95.7% in 8 min under UV light illumination with a kinetic constant of 0.3125 l min−1. The photocatalytic mechanism of the composite has been discussed.

Vamvakidis, Kosmas; Katsikini, Maria; Vourlias, George; Angelakeris, Mavroeidis; Paloura, Eleni C.; Dendrinou-Samara, Catherine

doi: 10.1039/c5dt00212epmid: 25689845

Manganese doped ferrite (MnxFe3−xO4) nanoparticles with x = 0.29–0.77 were prepared under solvothermal conditions in the presence solely of a polyol using the trivalent manganese and iron acetylacetonates as precursors. In this facile approach, a variety of polyols such as polyethylene glycol (PEG 8000), tetraethylene glycol (TEG), propylene glycol (PG) and a mixture of TEG and PG (1 : 1) were utilized in a triple role as a solvent, a reducing agent and a surface-functionalizing agent. The composition of the fine cubic-spinel structures was found to be related to the reductive ability of each polyol, while determination of structural characteristics plus the inversion parameter (i = 0.18–0.38) were provided by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy at both the Fe and Mn K-edges. The saturation magnetization increased up to 80 emu g−1 when x = 0.35 and i = 0.22. In addition, the as-prepared nanocrystals coated with PEG, PG and PG&TEG showed excellent colloidal stability in water, while the TEG-coated particles were not water dispersible and converted to hydrophilic when were extra PEGylated. Measurements of the 1H NMR relaxation in water were carried out and the nanoprobes were evaluated as potential contrast agents.

Meng, Jiang-Ping; Gong, Yun; Lin, Qiang; Zhang, Miao-Miao; Zhang, Pan; Shi, Hui-Fang; Lin, Jian-Hua

doi: 10.1039/c4dt03702bpmid: 25689346

Two thermally stable MOFs formulated as CoL(1,4-bdc)·2DMF (L = 3,5-bis(5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)pyridine), 1,4-H2bdc = 1,4-benzenedicarboxylic acid) (1) and CdL(4,4′-bpc)·3DMF (4,4′-H2bpc = 4,4′-biphenyldicarboxylic acid) (2) have been solvothermally synthesized and exhibit a similar uninodal 6-connected 3D architecture with {412·63}-pcu topology. MOF 1 shows a non-interpenetrated network with larger channel, whereas MOF 2 exhibits a 3-fold interpenetrating framework with smaller pore size. When the two MOFs are used as separator membranes in a supercapacitor, the equivalent series resistance (Res) is larger than the Res in the blank supercapacitor, and the smaller the current density, the more the Res. After being charged and discharged at the low current density, the supercapacitor with MOF 1 as separator membrane (denoted as 1a) possesses a much larger specific capacitance (SC) than the blank supercapacitor, and the amorphous separator membrane 1a shows a more porous morphology than the original MOF membrane 1.

Maloubier, Melody; Solari, Pier Lorenzo; Moisy, Philippe; Monfort, Marguerite; Den Auwer, Christophe; Moulin, Christophe

doi: 10.1039/c4dt03547jpmid: 25689216

Seawater contains radionuclides at environmental levels; some are naturally present and others come from anthropogenic nuclear activity. In this report, the molecular speciation in seawater of uranium(vi) and neptunium(v) at a concentration of 5 × 10−5 M has been investigated for the first time using a combination of two spectroscopic techniques: Time-resolved laser-induced fluorescence (TRLIF) for U and extended X-ray absorption fine structure (EXAFS) for U and Np at the LIII edge. In parallel, the theoretical speciation of uranium and neptunium in seawater at the same concentration is also discussed and compared to spectroscopic data. The uranium complex was identified as the neutral carbonato calcic complex UO2(CO3)3Ca2, which has been previously described in other natural systems. In the case of neptunium, the complex identified is mainly a carbonato complex whose exact stoichiometry is more difficult to assess. The knowledge of the actinide molecular speciation and reactivity in seawater is of fundamental interest in the particular case of uranium recovery and more generally regarding the actinide life cycle within the biosphere in the case of accidental release. This is the first report of actinide direct speciation in seawater medium that can complement inventory data.

Roy, Sanjay; Mondal, Palash; Sengupta, Partha Sarathi; Dhak, Debasis; Santra, Ramesh Chandra; Das, Saurabh; Guin, Partha Sarathi

doi: 10.1039/c4dt03635bpmid: 25691434

A 1 : 2 copperII complex of 1-amino-4-hydroxy-9,10-anthraquinone (QH) having the molecular formula CuQ2 was prepared and characterized by elemental analysis, NMR, FTIR, UV-vis and mass spectroscopy. The powder diffraction of the solid complex, magnetic susceptibility and ESR spectra were also recorded. The presence of the planar anthraquinone moiety in the complex makes it extremely difficult to obtain a single crystal suitable for X-ray diffraction studies. To overcome this problem, density functional theory (DFT) was used to evaluate an optimized structure of CuQ2. In the optimized structure, it was found that there is a tilt of the two planar aromatic anthraquinone rings of the complex with respect to each other in the two planes containing the O–Cu(ii)–O plane. The present study is an important addition to the understanding of the structural aspects of metal-anthracyclines because there are only a few reports on the actual structures of metal-anthracyclines. The theoretical vibrational spectrum of the complex was assigned with the help of vibrational energy distribution analysis (VEDA) using potential energy distribution (PED) and compared with experimental results. Being important in producing the biochemical action of this class of molecules, the electrochemical behavior of the complex was studied in aqueous and non-aqueous solvents to find certain electrochemical parameters. In aqueous media, reduction involves a kinetic effect during electron transfer at an electrode surface, which was characterized very carefully using cyclic voltammetry. Electrochemical studies showed a significant modification in the electrochemical properties of 1-amino-4-hydroxy-9,10-anthraquinone (QH) when bound to CuII in the complex compared to those observed for free QH. This suggests that the copper complex might be a good choice as a biologically active molecule, which was reflected in the lack of stimulated superoxide generation by the complex.

Kauf, Thomas; Rosa, Vitor; Fliedel, Christophe; Pattacini, Roberto; Deibel, Naina; Avilés, Teresa; Sarkar, Biprajit; Braunstein, Pierre

doi: 10.1039/c4dt03956dpmid: 25689916

The reactions of TCNE- and TCNQ-functionalized (TCNE: tetracyanoethylene and TCNQ: 7,7′,8,8′-tetracyanoquinodimethane) zwitterionic benzoquinonemonoimines with a Cu(i)-BIAN complex (BIAN = bis(o,o′-bisisopropylphenyl)acenaphthenequinonediimine) have been investigated and found to follow a diversity of interesting patterns. The complexes [Cu(BIAN)(NCMe)(L2)]BF4 (2) and [Cu(BIAN)(L2)2]BF4 (4) were obtained by reacting [Cu(BIAN)(NCMe)2]BF4 (1) with one and two equivalents of L2, respectively. Following similar procedures, the complexes [Cu(BIAN)(NCMe)(L3)]BF4 (6) and [Cu(BIAN)(L3)2]BF4 (7) were obtained by reaction of 1 with L3. The reaction of 2 with 0.5 equiv. of 4,4′-bipyridine afforded [{Cu(BIAN)(L2)}2(μ-4,4′-bipyridine)](BF4)2 (3). The complexes were characterized by multinuclear NMR, IR and UV-Vis spectroscopic techniques, mass spectrometry, cyclic voltammetry and elemental analysis. The molecular structures of complexes 3·4CH2Cl2 and 4·CH2Cl2 were determined by single crystal X-ray diffraction. An unexpected coordination polymer [Cu(L2−)2]∞ (5) was also structurally characterized, which contains Cu(ii) centres chelated by two N,O-bound ligands resulting from the monodeprotonation of L2.