Polymerisation of pentadienyl compounds in the presence of transition-metal compounds: the polymorphic compound deca-1,3,7,9-tetraenediiron hexacarbonyl

The reaction between Fe(CO)₅ and penta-1,4-dien-3-ol gives two forms of di(pentadienyliron tricarbonyl).     

Ferromagnetic interaction in an asymmetric end-to-end azido double-bridged copper(II) dinuclear complex: a combined structure, magnetic, polarized neutron diffraction and theoretical study

A new end-to-end azido double-bridged copper(II) complex [Cu(2)L(2)(N(3))2] (1) was synthesized and characterized (L=1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato). Despite the rather long Cu-Cu distance (5.105(1) A), the magnetic interaction is ferromagnetic with J= +16 cm(-1) (H=-JS(1)S(2)), a value that has been confirmed by DFT and high-level correlated ab initio calculations. The spin distribution was studied by using the results from polarized neutron diffraction. This is the first such study on an end-to-end system. The experimental spin density was found to be localized mainly on the copper(II) ions, with a small degree of delocalization on the ligand (L) and terminal azido nitrogens. There was zero delocalization on the central nitrogen, in agreement with DFT calculations. Such a picture corresponds to an important contribution of the d(x2-y2) orbital and a small population of the d(z2) orbital, in agreement with our calculations. Based on a correlated wavefunction analysis, the ferromagnetic behavior results from a dominant double spin polarization contribution and vanishingly small ionic forms.     

Crystal Structures of AlCr2 and MoSi2: Same Structure Type vs. Different Bonding Pattern

In a joint effort utilizing modified sample preparation, microscopy, X-ray diffraction and micro-fabrication, it became possible to prepare single crystals of the “hidden” phase AlCr₂. High-resolution X-ray diffraction analysis is described in detail for two crystals with the similar overall composition, but different degree of disorder, which seems to be the main cause for the differing unit cell parameters. Chemical bonding analysis of AlCr₂ in comparison to prototypical MoSi₂ shows pronounced differences reflecting the interchange of main group element vs. transition metal as majority component.     

Synthetic and Structural Studies on Methyl‐, tert‐Butyl‐ and Phenylmercury(II) Azide

The reaction of organomercury(II) halogenides (RHgHal, Hal = Cl, I) with silver azide furnished the corresponding covalent organomercury(II) azides RHgN₃ (R = Me ( 1 ), tBu ( 2 ), Ph ( 3 )). In addition to the characterization by multinuclear NMR spectroscopy, IR and Raman spectroscopy as well as mass spectrometry, the mercury content was determined. A dependance on the solventpolarity for the ¹⁴N NMR resonances was observed. Furthermore, X‐ray diffraction studies were performed and the crystal structures for mercury(II) azides 1 – 3 are reported. A comparison of the bond lengths and angles with data from theoretical calculations is given.     

Structural modification of nanocrystalline ceria by ion beams

Exceptional size-dependent electronic-ionic conductivity of nanostructured ceria can significantly alter materials properties in chemical, physical, electronic and optical applications. Using energetic ions, we have demonstrated effective modification of interface volume and grain size in nanocrystalline ceria from a few nm up to ～25 nm, which is the critical region for controlling size-dependent material property. The grain size increases and follows an exponential law as a function of ion fluence that increases with temperature, while the cubic phase is stable under the irradiation. The unique self-healing response of radiation damage at grain boundaries is utilized to control the grain size at the nanoscale. Structural modification by energetic ions is proposed to achieve desirable electronic-ionic conductivity.     

Control of dopants/modifiers in differential mobility spectrometry using a piezoelectric injector

A piezoelectric injector has been interfaced to a differential mobility spectrometer to enable fast and reversible control of dopant/transport-gas modifier levels within the reaction region of the instrument. Operating at 1 Hz with optimised bipolar waveforms for the piezoelectric injector and gas flows within the injector, steady-state 2-butanol mass fluxes of 21 to 1230 ng min(-1) and 1-bromohexane mass fluxes of 149 to 2644 ng min(-1) were delivered to the differential mobility cell. Control of split-flow and transport-gas flow rates enabled rapid and flexible control of the dopant concentrations. The system was consistently reproducible with a relative standard deviation (RSD) of 7.9% at every mass- flux level studied. Stable responses were achieved between 3 to 5 s following a change in the control levels and no significant hysteresis effects were observed. In the positive mode it was possible to control the extent of formation protonated monomer and proton bound cluster ions, tentatively assigned to{C(4)H(9)OH(H(2)O)(n)H}(+) and {(C(4)H(9)OH)(2)(H(2)O)(n)H}(+) and similar control was possible in the negative mode where the concentration relationship for the formation of bromide clusters indicated the presence of multiple ionisation mechanisms. A dopant formulation for the simultaneous control of ions in both the positive and negative modes was demonstrated by the injection of a 50%/50% v/v solution of 2-butanol/1-bromohexane with mass fluxes of 2-butanol in the mixture of between 11 and 1161 ng min(-1) and between 13 and 1325 ng min(-1) for 1-bromohexane.     

Laser-cluster-interaction in a nanoplasma-model with inclusion of lowered ionization energies

The interaction of intense laser fields with silver and argon clusters is investigated theoretically using a modified nanoplasma model. Single pulse and double pulse excitations are considered. The influence of the dense cluster environment on the inner ionization processes is studied including the lowering of the ionization energies. There are considerable changes in the dynamics of the laser-cluster interaction. Especially, for silver clusters, the lowering of the ionization energies leads to increased yields of highly charged ions.     

Excited-State Kinetics of an Air-Stable Cyclometalated Iron(II) Complex

The complex class [Fe(N^N^C)(N^N^N)]⁺ with an Earth-abundant metal ion has been repeatedly suggested as a chromophore and potential photosensitizer on the basis of quantum chemical calculations. Synthesis and photophysical properties of the parent complex [Fe(pbpy)(tpy)]⁺ (Hpbpy=6-phenyl-2,2′-bipyridine and tpy=2,2′:6′,2′′-terpyridine) of this new chromophore class are now reported. Ground-state characterization by X-ray diffraction, electrochemistry, spectroelectrochemistry, UV/Vis, and X-ray spectroscopy in combination with DFT calculations proves the high impact of the cyclometalating ligand on the electronic structure. The photophysical properties are significantly improved compared to the prototypical [Fe(tpy)₂]²⁺ complex. In particular, the metal-to-ligand absorption extends into the near-IR and the ³MLCT lifetime increases by 5.5, whereas the metal-centered excited triplet state is very short-lived.     

Ramanujan’s Master Theorem

S. Ramanujan introduced a technique, known as Ramanujan??s Master Theorem, which provides an explicit expression for the Mellin transform of a function in terms of the analytic continuation of its Taylor coefficients. The history and proof of this result are reviewed, and a variety of applications is presented. Finally, a multi-dimensional extension of Ramanujan??s Master Theorem is discussed.