Fist oxidovanadium complexes containing chiral derivatives of dihydrophenanthroline and diazafluorene

© 2017 Elsevier Ltd Reactions of VCl 3 with chiral derivatives of dihydrophenanthroline (2R,4R,9R,11R)-3,3,10,10-tetramethyl-1,2,3,4,6,7,9,10,11,12-decahydro-2,4:9,11-dimethanodibenzo[b,j][1,10] phenanthroline (L1) and diazafluorene (1R,3R,8R,10R)-2,2,9,9-tetramethyl-2,3,4,7,8,9,10,12-octahydro-1H-1,3:8,10-dimethanocyclopenta[1,2-b:5,4-b′]diquinoline (L2) in acetonitrile in air yield mixtures of [V III (L1/L2)(CH 3 CN)Cl 3 ] and [V IV O(L1/L2)(CH 3 CN)Cl 2 ] (I, II) which were characterized by elemental analysis, IR spectroscopy and magnetic susceptibility data. The behavior of these mixtures in different solvents was investigated by 51 V NMR and EPR spectroscopies as well as optical rotation. Recrystallization of a [V III (L1)(CH 3 CN)Cl 3 ]/[V IV O(L1)(CH 3 CN)Cl 2 ] mixture from CH 2 Cl 2 /Et 2 O affords a V(IV) complex, [V IV O(L1)(H 2 O)Cl 2 ]·nCH 2 Cl 2 (III). Recrystallization from MeOH/Et 2 O leads to complete oxidation to V(V) complex [V V O(L1)(OMe)Cl 2 ] (IV), which was characterized by X-ray crystallography, IR, 51 V and 1 H NMR spectroscopies

Coherence properties of a single dipole emitter in diamond

On-demand, high repetition rate sources of indistinguishable, polarised single photons are the key component for future photonic quantum technologies. Colour centres in diamond offer a promising solution, and the narrow line-width of the recently identified nickel-based NE8 centre makes it particularly appealing for realising the transform-limited sources necessary for quantum interference. Here we report the characterisation of dipole orientation and coherence properties of a single NE8 colour centre in a diamond nanocrystal at room-temperature. We observe a single photon coherence time of 0.21 ps and an emission lifetime of 1.5 ns. Combined with an emission wavelength that is ideally suited for applications in existing quantum optical systems, these results show that the NE8 is a far more promising source than the more commonly studied nitrogen-vacancy centre and point the way to the realisation of a practical diamond colour centre-based single photon source.Comment: 10 pages, 4 colour figure

Volatile Heterobimetallic Complexes from PdIIand CuIIβ-Diketonates: Structure, Magnetic Anisotropy, and Thermal Properties Related to the Chemical Vapor Deposition of Cu-Pd Thin Films

A novel approach for preparing volatile heterometallic complexes for use as precursors for the chemical vapor deposition of various materials is reported. New Cu¢Pd complexes based on b-diketonate units were prepared, and their structures and compositions were determined. [PdL2*CuL2] (1) and [PdL2*Cu(tmhd)2] (2) (L=2-methoxy-2,6,6-trimethylheptane-3,5-dionate; tmhd=2,2,6,6- tetramethylheptane-3,5-dionate) are 1D coordination polymers with alternating metal complexes, which are connected through weak interactions between the Cu atoms and the OCH3 groups from the ligand of the Pd complexes. The volatility and thermal stability were studied using thermogravimetric and differential thermal analyses and mass spectrometry. Compound 1 vaporizes without decomposition into monometallic complexes. It exhibits magnetic anisotropy, which was revealed from the angular variations in the EPR spectrum of a single crystal. The vapor thermolysis process for 1 was investigated using mass spectrometry, allowing the process to be framed within the temperature range of 200–3508C. The experimental data, supported by QTAIM calculations of the allowed intermolecular interactions, suggest that 1 likely exists in the gas phase as bimetallic molecules. Compound 1 proved to be suitable as a single-source precursor for the efficient preparation of Cu¢Pd alloy films with tunable Cu/Pd ratio. A possible mechanism for the film growth is proposed based on the reported data

Infrared Absorption Investigations Confirm the Extraterrestrial Origin of Carbonado-Diamonds

The first complete infrared FTIR absorption spectra for carbonado-diamond confirm the interstellar origin for the most enigmatic diamonds known as carbonado. All previous attempts failed to measure the absorption of carbonado-diamond in the most important IR-range of 1000-1300 cm-1 (10.00-7.69 micro-m.) because of silica inclusions. In our investigation, KBr pellets were made from crushed silica-free carbonado-diamond and thin sections were also prepared. The 100 to 1000 times brighter synchrotron infrared radiation permits a greater spatial resolution. Inclusions and pore spaces were avoided and/or sources of chemical contamination were removed. The FTIR spectra of carbonado-diamond mostly depict the presence of single nitrogen impurities, and hydrogen. The lack of identifiable nitrogen aggregates in the infrared spectra, the presence of features related to hydrocarbon stretch bonds, and the resemblance of the spectra to CVD and presolar diamonds indicate that carbonado-diamonds formed in a hydrogen-rich interstellar environment. This is consistent with carbonado-diamond being sintered and porous, with extremely reduced metals, metal alloys, carbides and nitrides, light carbon isotopes, surfaces with glassy melt-like patinas, deformation lamellae, and a complete absence of primary, terrestrial mineral inclusions. The 2.6-3.8 billion year old fragmented body was of asteroidal proportions

23-electron octahedral molybdenum cluster complex [{Mo 6 I 8 }Cl 6 ] –

Photoactive transition metal compounds that are prone to reversible redox reactions are important for myriad applications, including catalysis, optoelectronics and sensing. This article describes chemical and electro-chemical methods to prepare cluster complex (Bu4N)[{Mo6I8}Cl6], a rear example of 23ē cluster complex within the family of octahedral clusters of Mo, W, and Re. The low temperature and room temperature crystal structures, electronic structure and the magnetic, optical and electrochemical properties of this complex are described

A novel use of hyperfine structure in the electron paramagnetic resonance of interacting pairs of paramagnetic defects in diamond

It is the hyperfine structure of N-14 and C-13 in the electron paramagnetic resonance (EPR) spectrum which indicates that the unpaired electron of a single substitutional nitrogen atom in diamond is in one of the four anti-bonding N-C orbitals. We show that, for diamonds containing a very high concentration of nitrogen, the hyperfine structure of interacting pairs of nitrogen atoms indicates that for close neighbours there are unique orientations of the constituent N-C bonds, while at larger distances the orientations are random

A novel Nb<inf>2</inf>S<inf>4</inf> complex with a dithiophosphinate ligand: Synthesis, structure and redox properties

© 2018 Elsevier Ltd A new diisobutyldithiophosphinate complex, [Nb2S4(S2PiBu2)4] (1), was obtained by a ligand substitution reaction using (Bu4N)4[Nb2S4(NCS)8] and NaS2PiBu2·3H2O. Its crystal structure has been determined. The Nb–Nb distance is 2.9034(7) Å. The cyclic voltammogram (CV) of 1 in dichloromethane exhibits two successive chemically reversible one-electron oxidation waves at +0.55 and +1.10 V (versus Ag/AgCl) attributed to the NbIV/NbV couple. This is the first {Nb2S4} cluster that shows two reversible oxidations. The paramagnetic mixed-valence Nb(IV/V) product of the one-electron oxidation, [Nb2S4(S2PiBu2)4]+ (1+), was generated in situ. The EPR spectrum of 1+ in acetonitrile reveals a 19-line signal arising from the hyperfine interaction between the unpaired electron and two equivalent 93Nb nuclei with I = 9/2, indicating complete delocalization of the unpaired electron over both metal centers. DFT calculations have been performed for the complexes [Nb2S4(S2PMe2)4], [Nb2S4(S2P(OMe)2)4], [Nb2S4(S2CNMe2)4] and [Nb2S4(S2COMe)4] and their single and double oxidized species in order to explain the peculiarities of their redox behavior. The results show that the HOMOs responsible for oxidation have a predominantly metallic character in all cases, but they are significantly more high-lying for the dithiophosphinate and dithiocarbamate complexes, which explains their ability to be oxidized