Design and self-assembling behaviour of comb-like stereoregular cyclolinear methylsiloxane copolymers with chiral lactate groups

Several new comb-like stereoregular cyclolinear methylsiloxane copolymers exhibiting the self-assembling behaviour have been designed and studied. For the resulting macromolecular materials, the chiral mesogenic unit, namely (S)-(–)-4-[1-ethoxycarbonyl)ethoxycarbonyl]phenyl-4′-[11-tetramethyldisiloxyl)-undecenyloxy)-biphenyl-4′-carboxylate, has been used as a side group to assure the mesomorphic behaviour. The mesomorphic and structural properties were studied by the polarising optical microscopy, differential scanning calorimetry and small-/wide-angle X-ray diffraction techniques. The designed copolymers form the orthogonal smectic A* and the tilted smectic C* phases over relatively broad temperature range, down to room temperatures. The obtained results are discussed in order to contribute to better understanding of the molecular architecture–nano-organisation relationship for a specific type of macromolecular system based on the lactic acid derivatives used as a flexible side groups.     

Smooth exact penalty functions: a general approach

In the article, we present a new perspective on the method of smooth exact penalty functions that is becoming more and more popular tool for solving constrained optimization problems. In particular, our approach to smooth exact penalty functions allows one to apply previously unused tools (namely, parametric optimization) to the study of these functions. We give a new simple proof of local exactness of smooth penalty functions that significantly generalizes all similar results existing in the literature. We also provide new necessary and sufficient conditions for a smooth penalty function to be globally exact.     

Absolute Configuration from Different Multifragmentation Pathways in Light‐Induced Coulomb Explosion Imaging

The absolute configuration of individual small molecules in the gas phase can be determined directly by light‐induced Coulomb explosion imaging (CEI). Herein, this approach is demonstrated for ionization with a single X‐ray photon from a synchrotron light source, leading to enhanced efficiency and faster fragmentation as compared to previous experiments with a femtosecond laser. In addition, it is shown that even incomplete fragmentation pathways of individual molecules from a racemic CHBrClF sample can give access to the absolute configuration in CEI. This leads to a significant increase of the applicability of the method as compared to the previously reported complete break‐up into atomic ions and can pave the way for routine stereochemical analysis of larger chiral molecules by light‐induced CEI.     

“Bottled” spiro-doubly aromatic trinuclear [Pd2Ru]+ complexes

Following an ongoing interest in the study of transition metal complexes with exotic bonding networks, we report herein the synthesis of a family of heterobimetallic triangular clusters involving Ru and Pd atoms. These are the first examples of trinuclear complexes combining these nuclei. Structural and bonding analyses revealed both analogies and unexpected differences for these [Pd₂Ru]⁺ complexes compared to their parent [Pd₃]⁺ peers. Noticeably, participation of the Ru atom in the π-aromaticity of the coordinated benzene ring makes the synthesized compound the second reported example of ‘bottled’ double aromaticity. This can also be referred to as spiroaromaticity due to the participation of Ru in two aromatic systems at a time. Moreover, the [Pd₂Ru]⁺ kernel exhibits unprecedented orbital overlap of Ru d_z² AO and two Pd d_xy or d_x²−y² AOs. The present findings reveal the possibility of synthesizing stable clusters with delocalized metal–metal bonding from the combination of non-adjacent elements of the periodic table which has not been reported previously.

Synthesis of a triangular [Pd₂Ru]⁺ complex with delocalized metal–metal bonding between non-adjacent elements of the periodic table, double aromaticity and overlap of d-AOs with different angular momentum.     

New polymethacrylic nonlinear optical materials containing multichromophores in the side chain

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Separation of different hydrogen-bonded clusters by femtosecond UV-ionization-detected infrared spectroscopy: 1H-pyrrolo[3,2-h]quinoline.(H2O)(n=1,2) complexes

Experimental and theoretical studies are presented for complexes of water with 1H-pyrrolo[3,2-h]quinoline (PQ), a bifunctional compound acting simultaneously as a hydrogen-bond donor and acceptor. A 1:1 complex, which is not fluorescent and only very short-lived in the electronically excited state, was analyzed by isolating the complex under supersonic jet conditions and characterizing its structure by infrared-induced ion depletion spectroscopy utilizing multiphoton ionization by femtosecond UV pulses (IR/fsMPI spectroscopy). On the other hand, a long-lived 1:2 complex was identified as the smallest microhydrate of PQ contributing to the laser-induced fluorescence excitation spectrum. Its structure was assigned by fluorescence-detected IR spectra and analyzed using density functional theory. The structures of the 1:1 and 1:2 clusters are assigned to species in which the water molecule(s) form a hydrogen-bonded solvent bridge between the two functional groups. In accord with calculations, both 1:1 and 1:2 PQ/water complexes reveal weaker hydrogen bonding than the analogous clusters of PQ with methanol.     

Prospective for biodegradable microstructured optical fibers

We report fabrication of a novel microstructured optical fiber made of biodegradable and water soluble materials that features approximately 1 dB/cm transmission loss. Two cellulose butyrate tubes separated with hydroxypropyl cellulose powder were codrawn into a porous double-core fiber offering integration of optical, microfluidic, and potentially drug release functionalities.     

A photochemical synthesis of functionalized trans-cyclooctenes driven by metal complexation

Described is a scalable procedure for driving photochemical sytheses of trans-cyclooctene derivatives through metal complexation. During photoirradiation, reaction mixtures are continuously pumped through a column of a AgNO3-impregnated silica gel. The trans-cyclooctene derivative is selectively retained by the AgNO3-impregnated silica, but the cis-isomer elutes from the column back to the reaction flask, where it is photoisomerized and recirculated through the column. The method provides access to a range of usefully functionalized derivatives of trans-cyclooctene, including a derivative of 5-aza-trans-cyclooctene that underwent transannular cyclization upon treatment with bromine. The alkene stereochemistry is transferred with high fidelity to the hexahydropyrrolizine framework in the transannular cyclization.     

Oxidative C-H/C-H Coupling of Dipyrromethanes with Azines by TiO2-Based Photocatalytic System. Synthesis of New BODIPY Dyes and Their Photophysical and Electrochemical Properties

Oxidative C-H/C-H coupling reactions of dipyrromethanes with azines in the presence of a heterophase oxidative photocatalytic system (O₂/TiO₂/visible light irradiation) were carried out. As a result of cyclization of obtained compounds with boron trifluoride etherate, new hetaryl-containing derivatives of 4,4-difluoro-4-boron-3a,4a-diaza-s-indacene were synthesized. For the obtained compounds, absorption and luminescence spectra, quantum yields of luminescence as well as cyclic volt-amperograms were measured.     

Bifurcation and Entropy Analysis of a Chaotic Spike Oscillator Circuit Based on the S-Switch

This paper presents a model and experimental study of a chaotic spike oscillator based on a leaky integrate-and-fire (LIF) neuron, which has a switching element with an S-type current-voltage characteristic (S-switch). The oscillator generates spikes of the S-switch in the form of chaotic pulse position modulation driven by the feedback with rate coding instability of LIF neuron. The oscillator model with piecewise function of the S-switch has resistive feedback using a second order filter. The oscillator circuit is built on four operational amplifiers and two field-effect transistors (MOSFETs) that form an S-switch based on a Schmitt trigger, an active RC filter and a matching amplifier. We investigate the bifurcation diagrams of the model and the circuit and calculate the entropy of oscillations. For the analog circuit, the “regular oscillation-chaos” transition is analysed in a series of tests initiated by a step voltage in the matching amplifier. Entropy values are used to estimate the average time for the transition of oscillations to chaos and the degree of signal correlation of the transition mode of different tests. Study results can be applied in various reservoir computing applications, for example, in choosing and configuring the LogNNet network reservoir circuits.