Synthesis,Structure, and Theoretical Study of Trifluoromethyl Derivatives of C84(23) Fullerene

Trifluoromethylation of a higher fullerene mixture with CF₃I was performed in ampoules at 550 °C. HPLC separation followed by crystal growth and X‐ray diffraction study resulted in the structure elucidation of nine CF₃ derivatives of D_2d‐C₈₄ (isomer 23). The molecular structures of C₈₄(23)(CF₃)₄, C₈₄(23)(CF₃)₈, C₈₄(23)(CF₃)₁₀, C₈₄(23)(CF₃)₁₂, two isomers of C₈₄(23)(CF₃)₁₄, two isomers of C₈₄(23)(CF₃)₁₆, and C₈₄(23)(CF₃)₁₈ were discussed in terms of their addition patterns and the relative formation energies. Extensive theoretical DFT calculations were performed to identify the most stable molecular structures. It was found that the addition of CF₃ groups to the C₈₄(23) fullerene is governed by two main rules: no additions in positions of triple hexagon junctions and predominantly para additions in C₆(CF₃)₂ hexagons on the fullerene cage. The only exception with an isolated CF₃ group in C₈₄(23)(CF₃)₁₂ is discussed in more detail.     

Selective Dimerization of Lewis‐Acid/Base‐Stabilized Phosphanylalanes

The reaction of [{(CO)₅W}PRH₂] (R=H, Ph) with H₃Al ? NR₃ (R=Et, Me) leads to the formation of four‐membered heterocyclic compounds [({(CO)₅W}P(H)AlH ? NEt₃)₂] and [({(CO)₅W}PhPAlH ? NMe₃)₂]. Upon dissolving the solid compounds, fast equilibria between the isomers are observed on the NMR timescale. Further insight into the stability and reactivity of the isomers was gained by applying theoretical methods. DFT calculations predict that hydrogen elimination in the case of [({(CO)₅W}PhPAlH ? NMe₃)₂] may be reversible.     

[6,6]‐Open and [6,6]‐Closed Isomers of C70(CF2): Synthesis,Electrochemical and Quantum Chemical Investigation

Novel difluoromethylenated [70]fullerene derivatives, C₇₀(CF₂)_n (n=1–3), were obtained by the reaction of C₇₀ with sodium difluorochloroacetate. Two major products, isomeric C₇₀(CF₂) mono‐adducts with [6,6]‐open and [6,6]‐closed configurations, were isolated and their homofullerene and methanofullerene structures were reliably determined by a variety of methods that included X‐ray analysis and high‐level spectroscopic techniques. The [6,6]‐open isomer of C₇₀(CF₂) constitutes the first homofullerene example of a non‐hetero [70]fullerene derivative in which functionalisation involves the most reactive bond in the polar region of the cage. Voltammetric estimation of the electron affinity of the C₇₀(CF₂) isomers showed that it is substantially higher for the [6,6]‐open isomer (the 70‐electron π‐conjugated system is retained) than the [6,6]‐closed form, the latter being similar to the electron affinity of pristine C₇₀. In situ ESR spectroelectrochemical investigation of the C₇₀(CF₂) radical anions and DFT calculations of the hyperfine coupling constants provide evidence for the first example of an inter‐conversion between the [6,6]‐closed and [6,6]‐open forms of a cage‐modified fullerene driven by an electrochemical one‐electron transfer. Thus, [6,6]‐closed C₇₀(CF₂) constitutes an interesting example of a redox‐switchable fullerene derivative.     

Synthesis of tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone

A general strategy for the assembly of previously unknown tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone is described. The strategy involves N,N-bis(siloxy)enamines as key intermediates. The latter are accessible by double silylation of alkylnitro compounds. Nickel(II) and copper(II) complexes of tris(β,β,γ-oximinoalkyl)amines are prepared and structurally characterized.     

Enumeration of non-labile oxygen atoms in dissolved organic matter by use of 16O/18O exchange and Fourier transform ion-cyclotron resonance mass spectrometry

We report a simple approach for enumeration of non-labile oxygen atoms in individual molecules of dissolved organic matter (DOM), using acid-catalyzed ¹⁶O/¹⁸O exchange and ultrahigh-resolution Fourier-transform ion-cyclotron-resonance mass spectrometry (FTICR-MS). We found that by dissolving DOM in H₂ ¹⁸O at 95 °C for 20 days it is possible to replace all oxygen atoms of DOM molecules (excluding oxygen from ether groups) with ¹⁸O. The number of exchanges in each molecule can be determined using high-resolution FTICR. Using the proposed method we identified the number of non-labile oxygen atoms in 231 molecules composing DOM. Also, using a previously developed hydrogen–deuterium (H/D)-exchange approach we identified the number of labile hydrogen atoms in 450 individual molecular formulas. In addition, we observed that several backbone hydrogen atoms can be exchanged for deuterium under acidic conditions. The method can be used for structural and chemical characterization of individual DOM molecules, comparing different DOM samples, and investigation of biological pathways of DOM in the environment.     

Enhancement of single‑photon emission from nitrogen‑vacancy centers with TiN/(Al,Sc)N hyperbolic metamaterial

The broadband enhancement of single‑photon emission from nitrogen‐vacancy centers in nanodiamonds coupled to a planar multilayer metamaterial with hyperbolic dispersion is studied experimentally. The metamaterial is fabricated as an epitaxial metal/dielectric superlattice consisting of CMOS‐compatible ceramics: titanium nitride (TiN) and aluminum scandium nitride (Al_xSc_1‐xN). It is demonstrated that employing the metamaterial results in significant enhancement of collected single‑photon emission and reduction of the excited‐state lifetime. Our results could have an impact on future CMOS‐compatible integrated quantum sources.

     

Efficient time integration in multiplicative inelasticity

In Shutov et al. (Comput Methods Appl Mech Eng 265:213–225, 2013), the numerical time integration of a famous large strain model of Maxwell fluid type has been considered. The underlying model is based on the multiplicative decomposition of the deformation gradient and includes a Neo-Hookean hyperelasticity relation as well as an incompressible viscous flow rule. Shutov et al. presented a time stepping algorithm for implicit time integration of the inelastic flow rule, which is based on Euler backward time discretisation, prevents error accumulation and is iteration free. In this contribution, the basic idea of the this approach is applied to more general models of multiplicative viscoelasticity. Here, extended hyperelastic relations including general functions of the first principal invariant of deformation tensors are regarded. An efficient time stepping algorithm is derived, where only one scalar equation for one scalar unknown has to be solved within every time step. The approach is applied to a specific viscoelastic model. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Prandtl Number in Classical Hard-Sphere and One-Component Plasma Fluids

The Prandtl number is evaluated for the three-dimensional hard-sphere and one-component plasma fluids, from the dilute weakly coupled regime up to a dense strongly coupled regime near the fluid-solid phase transition. In both cases, numerical values of order unity are obtained. The Prandtl number increases on approaching the freezing point, where it reaches a quasi-universal value for simple dielectric fluids of about ≃1.7. Relations to two-dimensional fluids are briefly discussed.