A Systems Approach to a One-Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode

An unprecedented one-pot fully electrochemically driven Wittig olefination reaction system without employing a chemical reductant or sacrificial electrode material to regenerate triphenylphosphine (TPP) from triphenylphosphine oxide (TPPO) and base-free in situ formation of Wittig ylides, is reported. Starting from TPPO, the initial step of the phosphoryl P=O bond activation proceeds through alkylation with RX (R=Me, Et; X=OSO₂CF₃ (OTf)), affording the corresponding [Ph₃POR]⁺X⁻ salts which undergo efficient electroreduction to TPP in the presence of a substoichiometric amount of the Sc(OTf)₃ Lewis acid on a Ag-electrode. Subsequent alkylation of TPP affords Ph₃PR⁺ which enables a facile and efficient electrochemical in situ formation of the corresponding Wittig ylide under base-free condition and their direct use for the olefination of various carbonyl compounds. The mechanism and, in particular, the intriguing role of Sc³⁺ as mediator in the TPPO electroreduction been uncovered by density functional theory calculations.     

Copper(II) complexes of symmetrical and unsymmetrical tetradentate Schiff base ligands incorporating 1-benzoylacetone: Synthesis,crystal structures and electrochemical behavior

Three new copper(II) complexes [CuL¹]₂(ClO₄)₂ (1), [CuL²]ClO₄ (2) and [CuL³] (3) with three Schiff base ligands [HL¹ = 1-phenyl-3-{3-[(pyridin-2-ylmethylene)-amino]-propylimino}-butan-1-one, HL² = 1-phenyl-3-[3-(1-pyridin-2-yl-ethylideneamino)-propylimino]-butan-1-one and H₂L³ = 3-[3-(1-methyl-3-oxo-3-phenyl-propylideneamino)-propylimino]-1-phenyl-butan-1-one] have been synthesized and structurally characterized by X-ray crystallography. The mono-negative tetradentate asymmetric Schiff base ligands (L¹)⁻ and (L²)⁻ are chelated in complexes 1 and 2 to form square planar copper(II) complexes. In complex 1, the two units are associated weakly through ketonic oxygen of benzoylacetone fragment to form the dimeric entity. The square planar geometry of complex 3 is unusually distorted towards tetrahedral one. All three complexes exhibit reversible cyclic voltammetric responses in acetonitrile solution corresponding to the Cu^II/Cu^I redox process. The E_1/2 (−0.47 V versus SCE) of 3 shows significant anodic shift due to the tetrahedral distortion around Cu(II) compare to that of 1 and 2 (−0.82 and −0.87 V versus SCE, respectively).     

Quantum Brownian Motion on Non-Commutative Manifolds: Construction,Deformation and Exit Times

We begin with a review and analytical construction of quantum Gaussian process (and quantum Brownian motions) in the sense of Franz (The Theory of Quantum Levy Processes, [math.PR], 2009), Schürmann (White noise on bioalgebras. Volume 1544 of Lecture Notes in Mathematics. Berlin: Springer-Verlag, 1993) and others, and then formulate and study in details (with a number of interesting examples) a definition of quantum Brownian motions on those non-commutative manifolds (a la Connes) which are quantum homogeneous spaces of their quantum isometry groups in the sense of Goswami (Commun Math Phys 285(1):141–160, 2009). We prove that bi-invariant quantum Brownian motion can be ‘deformed’ in a suitable sense. Moreover, we propose a non-commutative analogue of the well-known asymptotics of the exit time of classical Brownian motion. We explicitly analyze such asymptotics for a specific example on non-commutative two-torus A_q{\mathcal{A}_\theta} , which seems to behave like a one-dimensional manifold, perhaps reminiscent of the fact that A_q{\mathcal{A}_\theta} is a non-commutative model of the (locally one-dimensional) ‘leaf-space’ of the Kronecker foliation.     

Rare example of mu-nitrito-1kappa2O,O':2kappaO coordinating mode in copper(II) nitrite complexes with monoanionic tridentate Schiff base ligands: structure, magnetic, and electrochemical properties

Three new copper(II) complexes, [CuL(1)(NO(2))](n) (1), [CuL(2)(NO(2))] (2), and [CuL(3)(NO(2))] (3), with three similar tridentate Schiff base ligands [HL(1) = 6-amino-3-methyl-1-phenyl-4-azahept-2-en-1-one, HL(2) = 6-amino-3-methyl-1-phenyl-4-azahex-2-en-1-one, and HL(3) = 6-diethylamino-3-methyl-1-phenyl-4-azahex-2-en-1-one] have been synthesized and characterized structurally and magnetically. In all three complexes, the tridentate Schiff base ligand and one oxygen atom of the nitrite ion constitute the equatorial plane around Cu(II), whereas the second oxygen atom of the nitrite ligand coordinates to one of the axial positions. In 1, this axially coordinated oxygen atom of the nitrite ligand also coordinates weakly to the other axial position of a Cu(II) ion of another unit to form a one-dimensional chain with the mu-nitrito-1kappa(2)O,O':2kappaO bridging mode. Complexes 2 and 3 are discrete monomers that are joined together by intermolecular H bonds and C-H....pi interactions in 2 and by only C-H....pi interactions in 3. A weak antiferromagnetism (J = -1.96(2) cm(-1)) is observed in complex 1 due to its asymmetric nitrite bridging. Complexes 2 and 3 show very weak antiferromagnetic interactions (J = -0.089 and -0.096 cm(-1), respectively) attributed to the presence of intermolecular H-bonding and C-H....pi interactions. The corresponding Cu(I) species produced by the electrochemical reduction of complexes 1 and 2 disproportionate to Cu(0) and Cu(2+,) whereas the reduced Cu(I) species of complex 3 seems to be stable presumably due to a higher tetrahedral distortion of the equatorial plane in 3 compared to that in 1 and 2.     

Reversal of stability on metalation of pentagonal-bipyramidal (1-MB6H7(2-) 1-M-2-CB5H7(1-) and 1-M-2,4-C2B4H7) and Icosahedral (1-MB11H12(2-) 1-M-2-CB10H12(1-) and 1-M-2,4-C2B9H12) boranes (M = Al, Ga, In, and Tl): energetics of condensation and relationship to binuclear metallocenes

The usual assumption of the extra stability of icosahedral boranes (2) over pentagonal-bipyramidal boranes (1) is reversed by substitution of a vertex by a group 13 metal. This preference is a result of the geometrical requirements for optimum overlap between the five-membered face of the ligand and the metal fragment. Isodesmic equations calculated at the B3LYP/LANL2DZ level indicate that the extra stability of 1-M-2,4-C(2)B(4)H(7) varies from 14.44 kcal/mol (M = Al) to 15.30 kcal/mol (M = Tl). Similarly, M(2,4-C(2)B(4)H(6))(2)(1-) is more stable than M(2,4-C(2)B(9)H(11))(2)(1-) by 9.26 kcal/mol (M = Al) and by 6.75 kcal/mol (M = Tl). The preference for (MC(2)B(4)H(6))(2) over (MC(2)B(9)H(11))(2) at the same level is 30.54 kcal/mol (M = Al), 33.16 kcal/ mol (M = Ga) and 37.77 kcal/mol (M = In). The metal-metal bonding here is comparable to those in CpZn-ZnCp and H(2)M-MH(2) (M= Al, Ga, and In).     

Identification of Non‐Carbonaceous Cathodes in Al Batteries: Potential Applicability of Black and Blue Phosphorene Monolayers

In the present era of growing energy demands, low‐dimensional materials are emerging as the suitable choices for energy storage due to their excellent ion transport properties, improved reversible capacity, fine rate performance and good cycling stability. In this context, we have investigated the applicability of black and blue phosphorene monolayers as potential cathodes for Al batteries. Both black and blue phosphorene monolayers show similar electrochemical behavior as that of experimentally reported graphite with a charge transfer from the surface in order to bind the tetrahedral geometry of AlCl₄ during the charging process. The adsorption of AlCl₄ drives semiconductor‐to‐metallic transformation of black/blue phosphorene, which ensures constant conductivity in Al batteries. Following the systematic adsorption of AlCl₄, the voltage for black and blue phosphorene is calculated to be ≈1.50 V and ≈1.80 V with storage capacities of 144 mAh g^?1 and 108 mAh g^?1, respectively. Besides, low diffusion barriers of 0.11 eV and 0.14 eV are predicted for AlCl₄ on the respective systems of black and blue phosphorene monolayers. Our work suggests that both black and blue phosphorene monolayers can be potential cathodes for Al batteries with delivery of high storage capacity and high voltage, respectively.     

Working group report: High energy and collider physics

This is a summary of the projects undertaken by the working group I on high energy and collider physics.     

Sequence‐Dependent Duplex Stabilization upon Formation of a Metal‐Mediated Base Pair

An artificial nucleoside surrogate with 1H‐imidazo[4,5‐f][1,10]phenanthroline ( P ) acting as an aglycone has been introduced into DNA oligonucleotide duplexes. This nucleoside surrogate can act as a bidentate ligand, and so is useful in the context of metal‐mediated base pairs. Several duplexes involving a hetero base pair with an imidazole nucleoside have been investigated. The stability of DNA duplexes incorporating the respective Ag^I‐mediated base pairs strongly depends on the sequence context. Quantum mechanical/molecular mechanical (QM/MM) calculations have been performed in order to gain insight into the factors determining this sequence dependence. The results indicated that, in addition to the stabilizing effect that results from the formation of coordinative bonds, destabilizing effects may occur when the artificial base pair does not fit optimally into the surrounding B‐DNA duplex.