Theoretical calculations of the substituent effect on molecular properties of the RCN⋯HF hydrogen-bonded complexes with R = NH2, CH3O,CH3, OH,SH, H,Cl, F,CF3, CN and NO2

DFT calculations with B3LYP and PBE1PBE functionals and 6–311++G(d,p) basis set have been performed in order to obtain molecular geometries, binding energies and vibrational properties of the RCN?HF H-bonded complexes with R = NH₂, CH₃O, CH₃, OH, SH, H, Cl, F, CF₃, CN and NO₂. As expected, it has been verified as a red-shift of the HF stretching frequency (ν_HF), in conformity with the elongation of the bond after complexation. On the other hand, the CN stretching frequency (ν_CN) is blue-shifted and corresponds to a shortening of the bond. The binding energies (ΔE_c), including BSSE and ZPVE corrections, show a linear correlation with several structural, electronic and vibrational properties. In particular, an important linear dependence between the binding energy and the calculated dipole moment of the free RCN molecule (μ_RCN) has been found. This result suggests that μ_RCN can be a useful quantity in order to predict the ability of this fragment to form a hydrogen-bond. The IR intensities of stretching and bending modes of complexed HF acid fragment are adequately interpreted through the atomic polar tensor of the hydrogen atom in HF using the modified CCFO model for infrared intensities. The new vibrational modes arising from complexation show several interesting features.     

Molecular Nitrides with Titanium and Group 13–15 Elements

Several heterometallic nitrido complexes were prepared by reaction of the imido–nitrido titanium complex [{Ti(η⁵‐C₅Me₅)(μ‐NH)}₃(μ₃‐N)] ( 1 ) with amido derivatives of Group 13–15 elements. Treatment of 1 with bis(trimethylsilyl)amido [M{N(SiMe₃)₂}₃] derivatives of aluminum, gallium, or indium in toluene at 150–190 °C affords the single‐cube amidoaluminum complex [{(Me₃Si)₂N}Al{(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] ( 2 ) or the corner‐shared double‐cube compounds [M(μ₃‐N)₃(μ₃‐NH)₃{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] [M=Ga ( 3 ), In ( 4 )]. Complexes 3 and 4 were also obtained by treatment of 1 with the trialkyl derivatives [M(CH₂SiMe₃)₃] (M=Ga, In) at high temperatures. The analogous reaction of 1 with [{Ga(NMe₂)₃}₂] at 110 °C leads to [{Ga(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] ( 5 ), in which two [GaTi₃N₄] cube‐type moieties are linked through a gallium–gallium bond. Complex 1 reacts with one equivalent of germanium, tin, or lead bis(trimethylsilyl)amido derivatives [M{N(SiMe₃)₂}₂] in toluene at room temperature to give cube‐type complexes [M{(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] [M=Ge ( 6 ), Sn ( 7 ), Pb ( 8 )]. Monitoring the reaction of 1 with [Sn{N(SiMe₃)₂}₂] and [Sn(C₅H₅)₂] by NMR spectroscopy allows the identification of intermediates [RSn{(μ₃‐N)(μ₃‐NH)₂Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] [R=N(SiMe₃)₂ ( 9 ), C₅H₅ ( 10 )] in the formation of 7 . Addition of one equivalent of the metalloligand 1 to a solution of lead derivative 8 or the treatment of 1 with a half equivalent of [Pb{N(SiMe₃)₂}₂] afford the corner‐shared double‐cube compound [Pb(μ₃‐N)₂(μ₃‐NH)₄{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] ( 11 ). Analogous antimony and bismuth derivatives [M(μ₃‐N)₃(μ₃‐NH)₃{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] [M=Sb ( 12 ), Bi ( 13 )] were obtained through the reaction of 1 with the tris(dimethylamido) reagents [M(NMe₂)₃]. Treatment of 1 with [AlCl₂{N(SiMe₃)₂}(OEt₂)] affords the precipitation of the singular aluminum–titanium square‐pyramidal aggregate [{{(Me₃Si)₂N}Cl₃Al₂}(μ₃‐N)(μ₃‐NH)₂{Ti₃(η⁵‐C₅Me₅)₃(μ‐Cl)(μ₃‐N)}] ( 14 ). The X‐ray crystal structures of 5 , 11 , 13 , 14 , and [AlCl{N(SiMe₃)₂}₂] were determined.     

On Nonlinear Quantum Mechanics,Noncommutative Phase Spaces,Fractal-Scale Calculus and Vacuum Energy

A (to our knowledge) novel Generalized Nonlinear Schrödinger equation based on the modifications of Nottale-Cresson’s fractal-scale calculus and resulting from the noncommutativity of the phase space coordinates is explicitly derived. The modifications to the ground state energy of a harmonic oscillator yields the observed value of the vacuum energy density. In the concluding remarks we discuss how nonlinear and nonlocal QM wave equations arise naturally from this fractal-scale calculus formalism which may have a key role in the final formulation of Quantum Gravity.     

Orbital and magnetic structure of quasi-1D cobaltites: Ab initio calculations and experiment

The magnetic properties of the orbitally degenerate quasi-one-dimensional cobaltites Sr_xBa_1−xCoO₃ are explained on the basis of a phase separation phenomenon. Noninteracting magnetic particles embedded in a nonferromagnetic matrix develop in the system. Details are given about the electronic and magnetic structure for x=0,0.2$x=0,0.2$ and 0.5. At x=0.5$x=0.5$, the geometry of the CoO₆ trigonally distorted octahedra changes by about 1–2%, but magnetic particles get 3 times bigger, compared to the parent compound, with the corresponding changes in the magnetic properties. The electronic structure of the Co⁴⁺ ion, however, stays roughly unchanged.     

Preparation and Reactivity of Mixed‐Ligands Hydride Complexes [RuHCl(CO)(PPh3)2{P(OR)3}]

Mixed‐ligands hydride complexes [RuHCl(CO)(PPh₃)₂{P(OR)₃}] ( 2 ) (R = Me, Et) were prepared by allowing [RuHCl(CO)(PPh₃)₃] ( 1 ) to react with an excess of phosphites P(OR)₃ in refluxing benzene. Treatment of hydrides 2 first with triflic acid and next with an excess of hydrazine afforded hydrazine complexes [RuCl(CO)(κ¹‐NH₂NHR1)(PPh₃)₂{P(OR)₃}]BPh₄ ( 3 , 4 ) (R1 = H, CH₃). Diethylcyanamide derivatives [RuCl(CO)(N≡CNEt₂)(PPh₃)₂{P(OR)₃}]BPh₄ ( 5 ) were also prepared by reacting 2 first with HOTf and then with N≡CNEt₂. The complexes were characterized spectroscopically and by X‐ray crystal structure determination of [RuHCl(CO)(PPh₃)₂{P(OEt)₃}] ( 2b ).     

A Simple Approach to Design Proteins for the Sustainable Synthesis of Metal Nanoclusters

Metal nanoclusters (NCs) are considered ideal nanomaterials for biological applications owing to their strong photoluminescence (PL), excellent photostability, and good biocompatibility. This study presents a simple and versatile strategy to design proteins, via incorporation of a di‐histidine cluster coordination site, for the sustainable synthesis and stabilization of metal NCs with different metal composition. The resulting protein‐stabilized metal NCs (Prot‐NCs) of gold, silver, and copper are highly photoluminescent and photostable, have a long shelf life, and are stable under physiological conditions. The biocompatibility of the clusters was demonstrated in cell cultures in which Prot‐NCs showed efficient cell internalization without affecting cell viability or losing luminescence. Moreover, the approach is translatable to other proteins to obtain Prot‐NCs for various biomedical applications such as cell imaging or labeling.     

Nature's Combinatorial Biosynthesis Produces Vatiamides A–F

Hybrid type I PKS/NRPS biosynthetic pathways typically proceed in a collinear manner wherein one molecular building block is enzymatically incorporated in a sequence that corresponds to gene arrangement. In this work, genome mining combined with the use of a fluorogenic azide‐based click probe led to the discovery and characterization of vatiamides A–F, three structurally diverse alkynylated lipopeptides, and their brominated analogues, from the cyanobacterium Moorea producens ASI16Jul14‐2. These derive from a unique combinatorial non‐collinear PKS/NRPS system encoded by a 90 kb gene cluster in which an upstream PKS cassette interacts with three separate cognate NRPS partners. This is facilitated by a series of promiscuous intermodule PKS‐NRPS docking motifs possessing identical amino acid sequences. This interaction confers a new type of combinatorial capacity for creating molecular diversity in microbial systems.     

Effects of Reaction Operation Policies on Properties of Core–Shell Polymer Supports Used for Preparation of Highly Active Biocatalysts

Core–shell polymer supports with different morphological features and compositions are prepared through combined suspension and emulsion polymerizations. It is shown that proper manipulation of the divinylbenzene (DVB) feed content allows for maximization of specific areas, porosities, and mechanical resistances. Additionally, it is shown that feeding of previously prepared miniemulsions leads to core–shell particles with smaller specific areas, due to less efficient coating of the cores. Particularly, the combined manipulation of polymerization times and DVB feed compositions allows for production of particles with pronounced specific area (50 m² g^?1) and porosity (0.30 cm³ g^?1). Produced core–shell polymer particles are employed as supports for the immobilization of lipase B from Candida antarctica, and the obtained enzymatic activities for both hydrolysis (A _hyd) and esterification (A _est) reactions are very high (A _hyd = 34.7 ± 3.8 U/g; A _est = 3564.6 ± 581 U/g), even when compared to activities obtained using the reference commercial biocatalyst Novozym 435 (A _hyd = 7.6 ± 1.8 U/g, A _est = 2384.7 ± 307.2 U/g). Finally, biocatalysts prepared with the core–shell supports present higher enzymatic activities than biocatalysts prepared with supports of higher specific area obtained through conventional emulsion polymerizations, indicating that the porous structure of the shell can be beneficial for the immobilization and activity of the enzymes.     

Solutions of xanthan gum/guar gum mixtures: shear rheology,porous media flow,and solids transport in annular flow

Mixtures of xanthan and guar gum in aqueous solution were studied in two flow situations: simple shear and porous media. In addition, solids transport in vertical annular flow of sand suspensions was explored. The zero shear rate viscosity of the solutions displayed a pronounced synergy: the viscosity of the mixture is higher than that of the polymer solutions in a wide range of relative concentrations of the two polymers, in agreement with previous literature. However, at relatively high shear rates, the viscosity approaches the value of the more viscous xanthan gum solutions at mass fractions of xanthan gum between 0.1 and 0.15, and the degree of synergy substantially decreases. Stress relaxation experiments in simple shear indicate that the polymer mixtures exhibit a well-defined yield stress after relaxation that is absent in solutions of pure polymers. In porous media flow experiments, a synergistic behavior mimicking the shear flow results was obtained for the polymer mixtures at low shear rates. However, at a critical shear rate, the apparent viscosity in porous media flows exceeds the shear viscosity due to the elongational nature of flow in the pores. The solids transport capacity in annular flows is well-represented by trends in shear viscosity and stress relaxation behavior. However, the lack of viscosity synergy at high shear rates limits the applicability of the mixtures as a way to improve solids suspension capacity in annular flows.