Synthesis and Characterizations of Ti(O‐i‐Pr)Cl3(THF)(PhCOR) (R = H,Me, Ph) and Ti(O‐i‐Pr)Cl3(PhCOR)2 (R = Me,Ph). The Molecular Structure of Ti(O‐i‐Pr)Cl3(PhCOPh)2

A series of titanium(IV) complexes Ti(O‐i‐Pr)Cl₃(THF)(PhCOR) (R = H ( 1 ), CH₃ ( 2 ), or Ph ( 3 )) is prepared quantitatively from reactions of [Ti(O‐i‐Pr)Cl₂(THF)(μ‐Cl)]₂ with 2 molar equiv. PhCOR. Treatment of Ti(O‐i‐Pr)Cl₃ with 2 molar equiv. of PhCOR affords the disubstituted complexes Ti(O‐i‐Pr)Cl₃(PhCOR)₂ (R = CH₃ ( 4 ) or Ph ( 5 )). The ¹³C NMR study of these complexes shows that the relative bonding abilities are in the order of PhCOCH₃ > PhCHO > PhCOPh. The molecular structure of 5 reveals that one of the benzophenone ligands is trans to the strongest 2‐propoxide ligand with a long Ti‐O(carbonyl) distance of 2.193(5) Å which is much longer than the other Ti‐O(carbonyl) distance of 2.097(4) Å by ?0.1 Å. All ligands cis to the alkoxide ligand are bending away from the alkoxide ligand with the RO‐Ti‐L angles ranging from 93.6(2) to 99.0(2)°.     

Extraction of polychlorinated biphenyl with supercritical carbon dioxide, sulfur hexafluoride and subcritical water

In the extraction of spiked PCB from soil, three extracting fluids were investigated: supercritical carbon dioxide (CO₂), supercritical sulfur hexafluoride (SF₆) and subcritical water. Among the tested fluids SF₆ appeared to be appropriate especially for the extraction of low polar PCB. CO₂ and water were found to be suitable for the quantitative extraction of all PCB. Water was judged as the best because of its low price, good availability and environmental safety.     

Dielectronic recombination of positive ions—I. A generalized cascade theory

A generalized theory of dielectronic recombination is formulated, explicitly incorporating the higher-order effect of cascade transitions to all the captured final states which are stable against Auger emission. The previously-used rate formulas contain only the two-step process of target excitation followed by a single radiative transition. The formal reaction theory is employed to precisely define the contribution of the successive open channels to energy shifts and resonance widths. Correct expressions are derived for the radiative and Auger branching ratios associated with each stage of the cascade. Various angular momentum averaging procedures and the effect of the spectator electrons in the participating subshells are discussed.     

Dielectronic recombination of positive ions—III. Rate coefficients for Mo32+

Dielectronic recombination rate coefficients for Mo³²⁺ recombining to Mo³²⁺ are given for electron temperatures of 1.4, 2.8, and 5.6 keV. Nonrelativistic results in the resonance approximation were obtained and tables of selected Auger (A_a) and radiative (A_r) rates, fluorescence yields, and dielectronic recombination rates are given. Excitation of 2p electrons to higher shells is found to be dominant over other transitions including direct capture at the temperatures considered. The effect of the cascade transitions is estimated to be of the order of 30%. Different angular momentum averaging procedures change the results very significantly.     

Auger and radiative transition probabilities of high Rydberg states

The dependence of the Auger and radiative transition probabilities of high Hydberg states on their principal and orbital quantum numbers n and l is studied. Based on explicit calculations, a simple empirical l-dependence of the gaussian type is obtained, which differs drastically from any of the previously assumed behavior.     

Numerical Radii for Tensor Products of Operators

For bounded linear operators A and B on Hilbert spaces H and K, respectively, it is known that the numerical radii of A, B and ${A\otimes B}$ are related by the inequalities ${w(A)w(B)\le w(A\otimes B)\le {\rm min}\{\|A\|w(B), w(A)\|B\|\}}$ . In this paper, we show that (1) if ${w(A\otimes B) = w(A)w(B)}$ , then w(A) = ρ(A) or w(B) = ρ(B), where ρ(·) denotes the spectral radius of an operator, and (2) if A is hyponormal, then ${w(A\otimes B) = w(A)w(B) = \|A\|w(B)}$ . Here (2) confirms a conjecture of Shiu’s and is proven via dilating the hyponormal A to a normal operator N with the spectrum of N contained in that of A. The latter is obtained from the Sz.-Nagy–Foia? dilation theory.     

Electro-optical properties of planar nematic cells impregnated with carbon nanosolids

We report electro-optical effects in planar-aligned liquid-crystal cells of pristine and doped calamitics in the presence of dc voltage. The doped cells comprise both a nematic host and a minute amount of either buckminsterfullerene or multiwalled carbon nanotubes. The voltage–transmittance and voltage–capacitance hystereses were observed from the sample cells in the range of applied dc voltage up to 8 V. Experimental evidence indicates that a nanoscale carbon dopant can affect the behavior of a nematic in terms of ion-charge effects and that doping with nanotubes can effectively reduce the driving voltage.     

Metallophilic and Inter-Ligand Interactions in Diargentous Compounds Bound by a Geometrically Flexible Macrocycle

A series of mono- and di-nuclear Ag^I complexes supported by a flexible macrocyclic ligand are reported. The geometric flexibility of the ligand was found to allow for a range of Ag−Ag interactions in the disilver complexes, depending on the identities of both the ancillary ligand and the counterion. Studies of the solution-phase dynamic exchange processes for these latter complexes found rapid interconversion through a mechanism that retained the multi-nuclearity. Quantum Theory of Atoms in Molecules (QTAIM) and Independent Gradient Model based on Hirshfeld partition (IGMH) analyses are used to evaluate the d¹⁰-d¹⁰ interactions between silver centers in the various geometries observed for the solid-state structures of these complexes, revealing nearly identical Ag−Ag interactions, regardless of the relative geometries of the Ag centers. Instead, a weak, but non-negligible, inter-ligand interaction between two isocyanide units may contribute to the folded-ligand geometry observed in the solid state.     

Interfacial properties of Pluronics and the interactions between Pluronics and cholesterol/DPPC mixed monolayers

Pluronics are triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) with wide range of hydrophilic-lipophilic balance. In order to investigate the relationship between the chemical structures of Pluronics and the interfacial properties at the air-water interface by monolayer techniques, Pluronics L61, P65, F68, P84, P123, L35, and P105 were selected. Since cholesterol influenced substantially the molecular packing stage and the characteristics of cell membranes, the interactions between Pluronics and model cell membranes in the absence and presence of cholesterol were compared. The results of pi-A isotherms and surface elasticities of Pluronic monolayers indicated that the first and second transition like stage were mainly affected by the numbers of EO and PO monomers, respectively. Pluronics with higher hydrophobicities demonstrated larger surface activities and penetration abilities to dipalmitoylphosphatidylcholine (DPPC) monolayers, which might be due to hydrophobic interactions and van der Waals forces. In the presence of cholesterol, hydrogen bonding effects was supposed to exist between the 3beta-hydroxy group of cholesterol and ether oxygen of PEO chains, which led Pluronic F68, with the longest PEO chain herein, to exhibit significantly higher penetration ability. Our findings proposed a theoretical basis for selection of optimized drug carriers and the starting point for further investigations.