Linear Coordination Research Articles

Artificial Protein Cages Assembled via Gold Coordination.

Artificial protein cages made from multiple copies of a single protein can be produced such that they only assemble upon addition of a metal ion. Consequently, the ability to remove the metal ion triggers protein-cage disassembly. Controlling assembly and disassembly has many potential uses including cargo loading/unloading and hence drug delivery. TRAP-cage is an example of such a protein cage which assembles due to linear coordination bond formation with Au(I) which acts to bridge constituent proteins. Here we describe the method for production and purification of TRAP-cage.

Mathematical modelling of motion control system in the MLC mode

Performing different manoeuvres in vertical and horizontal planes is one of the most important tasks that rise during the control of any object. In the paper the problem of implementing movement in the mode of moving along a linear coordinate (depth) for an unmanned underwater vehicle is considered. The algorithm for construction the control law that satisfy the specified conditions, e.g. the specified equilibrium position in vertical plane, astaticism, is presented. The control law with filter is constructed. This algorithm was implemented in MATLAB with the subsystem Simulink. MATLAB one of the most powerful systems for computer modelling and analysis of dynamic systems, so this algorithm and its realization with small changes can be easily used for any object.

Structure and Properties of Heterometallics Based on Lanthanides and Transition Metals with Methoxy-β-Diketonates

The possibility of obtaining volatile polynuclear heterometallic complexes containing lanthanides and transition metals bound by methoxy-β-diketonates was studied. New compounds were prepared by cocrystallization of monometallic complexes from organic solvents. Ln(tmhd)3 were used as initial monometallic complexes (Ln = La, Pr, Sm, Gd, Tb, Dy, Lu; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate) in combination with TML2 in various ratios (TM = Cu, Co, Ni, Mn; L: L1 = 1,1,1-trifluoro-5,5-dimethoxypentane-2,4-dionate, L2 = 1,1,1-trifluoro-5,5-dimethoxy-hexane-2,4-dionate, L3 = 1,1,1-trifluoro-5-methoxy-5-methylhexane-2,4-dionate). Heterometallic complexes of the composition [(LnL2tmhd)2TM(tmhd)2] were isolated for light lanthanides Ln= La, Pr, Sm, Gd, and L= L1 or L2. By single crystal XRD, it has been established that heterometallic compounds containing La, Pr, Cu, Co, and Ni are isostructural linear coordination polymers of alternating mononuclear transition metal complexes and binuclear heteroleptic lanthanide complexes, connected by donor-acceptor interactions between oxygen atoms of the methoxy groups and transition metal atoms. A comparison of powder XRD patterns has shown that all heterometallic complexes obtained are isostructural. Havier lanthanides Ln = Tb, Dy, Lu did not form heterometallics. Instead, homometallic complexes Ln(L3)3 were identified for Ln = Dy, Lu as well as for Ln = La. The thermal properties of the complexes were investigated by TG-DTA and vacuum sublimation tests. The heterometallic complexes were found to be not volatile and decomposed under heating to produce inorganic composites of TM oxides and Ln fluorides. In contrast, Ln(L3)3 is volatile and may be sublimed in a vacuum. Results of magnetic measurements are discussed for several heterometallic and homometallic complexes.

Gold(III) Catalyzed Overman Rearrangements: Controlling Steric Interactions using Pincer‐Type Ligands

AbstractSpatial control of reactivity is intrinsically difficult in gold catalysis due to the linear coordination mode of Au(I) and the commonly flat ligands employed for Au(III) complexes. Our recent report of a novel and sterically encumbered (NNN)diiPrAu−OH complex (Eur. J. Inorg. Chem. 2021, 3561–3564.) suggested that the (NNN) ligand framework is capable of sterically interacting with substrates through its conveniently oriented aryl groups. We have now examined these steric properties in more detail by varying the ortho‐substituent of the aryl group in (NNN)xAu−Cl complexes. With just small modifications we were able to vary the buried volume around the Cl atom and correlate this to yields obtained in a Au‐catalyzed Overman rearrangement. Computationally we further elucidate that the stark difference in yields obtained originates from a shift in binding mode of the substrate to the Au catalyst in the rate limiting step of the reaction. We thus conclude that delicate spatial control can be exercised in gold catalysis and propose the (NNN) ligand framework to be an attractive platform for the efficient design of Au(III) complexes for stereoselective catalysis.

Divalent Lanthanide Metallocene Complexes with a Linear Coordination Geometry and Pronounced 6s-5d Orbital Mixing.

A small but growing number of molecular compounds have been isolated featuring divalent lanthanides with 4fn5dz21 electron configurations. While the majority of these possess trigonal coordination geometries, we previously reported the first examples of linear divalent metallocenes Ln(CpiPr5)2 (Ln = Tb, Dy; CpiPr5 = pentaisopropylcyclopentadienyl). Here, we report the synthesis and characterization of the remainder of the Ln(CpiPr5)2 (1-Ln) series (including Y and excluding Pm). The compounds can be synthesized through salt metathesis of LnI3 and NaCpiPr5 followed by potassium graphite reduction for Ln = Y, La, Ce, Pr, Nd, Gd, Ho, and Er, by in situ reduction during salt metathesis of LnI3 and NaCpiPr5 for Ln = Tm and Lu, or through salt metathesis from LnI2 and NaCpiPr5 for Ln = Sm, Eu, and Yb. Single crystal X-ray diffraction analyses of 1-Ln confirm a linear coordination geometry with pseudo-D5d symmetry for the entire series. Structural and ultraviolet-visible spectroscopy data support a 4fn+1 electron configuration for Ln2+ = Sm, Eu, Tm, and Yb and a 4fn5dz21 configuration for the other lanthanides ([Kr]4dz21 for Y2+). Characterization of 1-Ln (Ln = Y, La) using electron paramagnetic resonance spectroscopy reveals significant s-d orbital mixing in the highest occupied molecular orbital and hyperfine coupling constants that are the largest reported to date for divalent compounds of yttrium and lanthanum. Evaluation of the room temperature magnetic susceptibilities of 1-Ln and comparison with values previously reported for trigonal Ln2+ compounds suggests that the more pronounced 6s-5d mixing may be associated with weaker 4f-5d spin coupling.

Variable Dimensionality of Europium(III) and Terbium(III) Coordination Compounds with a Flexible Hexacarboxylate Ligand.

A reaction between 4,4',4″-(benzene-1,3,5-triyltris(oxy))triphthalic acid (H6L) and lanthanide(III) nitrates (Ln = Eu3+, Tb3+) in water under the same conditions gave a molecular coordination compound [Tb(H4.5L)2(H2O)5]∙6H2O in the case of terbium(III) and a one-dimensional linear coordination polymer {[Eu2(H3L)2(H2O)6]∙8H2O}n in the case of europium(III). The crystal structures of both compounds were established by single-crystal X-ray diffraction, and they were further characterized by powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. The compounds demonstrated characteristic lanthanide-centered photoluminescence. The lanthanide-dependent dimensionality of the synthesized compounds, which are the first examples of the coordination compounds of hexacarboxylic acid H6L demonstrates its potential as a linker for new coordination polymers.

Дослідження взаємного впливу між каналами управління квадрокоптером за рахунок малої приводності БПЛА

The subject of study in this article is the processes of controlling an unmanned aerial vehicle (UAV) of the quadcopter type. A quadcopter is a special case of a multicopter built according to the helicopter scheme, which has four main rotors. Such aircraft are widely used for many purposes, both civilian and military: from video recording of any phenomena to performing aerial reconnaissance of inaccessible territories, adjusting artillery weapons. The quadcopter belongs to the class of mechanical systems with low driveability, as the number of its drives (four propeller motors) is less than the number of degrees of freedom (six degrees). This is significantly different from the control of an aircraft-type UAV, where each degree of freedom is controlled by its own actuator. The low driveability of the quadcopter imposes its own peculiarities during its control. For example, the horizontal movement of the quadcopter in a given direction is accomplished by tilting the quadcopter in that direction by influencing certain propeller motors. Thus, when demanding the execution of the simplest movement of the device (movement along the linear X coordinate), at least three coordinates are controlled by the executive motors of the quadcopter: the formation of a lifting force to control the hovering of the UAV at a certain height, the change of the angle of inclination of the quadcopter according to the pitch angle, and the direct control of the movement speed of the quadcopter. Simultaneously, this influence induces the emergence of movement conditions along other coordinates. The research method involves constructing a mathematical model of a quadcopter based on the known equations of UAV motion. Several methods and algorithms of quadrocopter control are known, in this work, PID coordinate controllers are used. The Matlab Simulink dynamic simulation environment was used to build the mathematical model. In the process of studying the mutual influence in the process of controlling coordinates, the influence of controlling one coordinate in the static state of others (not necessarily at rest, but also in the state of movement) was revealed. Further, the mutual influence between the degrees of freedom during simultaneous control of at least two coordinates is considered (for example, control of pitch angle and yaw angle, height change with simultaneous braking along one of the linear coordinates). Conclusions. Studies have confirmed the existence of mutual influences, although in most cases such influence is manifested by a slight deterioration in the quality of transient processes along the adjustable coordinates. Only the change of the Euler angles when changing the height significantly worsens the quality of transient processes, which must be considered when designing control systems or recording algorithms of movement by coordinates.

Multiple bumps can enhance robustness to noise in continuous attractor networks.

A central function of continuous attractor networks is encoding coordinates and accurately updating their values through path integration. To do so, these networks produce localized bumps of activity that move coherently in response to velocity inputs. In the brain, continuous attractors are believed to underlie grid cells and head direction cells, which maintain periodic representations of position and orientation, respectively. These representations can be achieved with any number of activity bumps, and the consequences of having more or fewer bumps are unclear. We address this knowledge gap by constructing 1D ring attractor networks with different bump numbers and characterizing their responses to three types of noise: fluctuating inputs, spiking noise, and deviations in connectivity away from ideal attractor configurations. Across all three types, networks with more bumps experience less noise-driven deviations in bump motion. This translates to more robust encodings of linear coordinates, like position, assuming that each neuron represents a fixed length no matter the bump number. Alternatively, we consider encoding a circular coordinate, like orientation, such that the network distance between adjacent bumps always maps onto 360 degrees. Under this mapping, bump number does not significantly affect the amount of error in the coordinate readout. Our simulation results are intuitively explained and quantitatively matched by a unified theory for path integration and noise in multi-bump networks. Thus, to suppress the effects of biologically relevant noise, continuous attractor networks can employ more bumps when encoding linear coordinates; this advantage disappears when encoding circular coordinates. Our findings provide motivation for multiple bumps in the mammalian grid network.

Influence of cellulose-containing sorbent preparation method based on linen fiber on its functional properties

The creation of biosorbents based on modified flax fiber is aimed at solving the problem of water pollution from heavy metal ions. A method for obtaining a sorbent on the basis of linen fiber including sequential treatment of polysaccharide material with sodium metaperiodate and sodium bisulfite has been developed. Modification conditions for obtaining an effective sorbent have been selected. Equilibrium and kinetics of copper ions sorption with the use of native and modified linen fiber in comparison with Lewatit S100 cationic exchange resin have been studied. It is established that the time of achieving sorption equilibrium in the heterophase system 'aqueous solution of copper sulfate - a modified sorbent' is reduced by 1.5-2 times while the degree of extraction of copper ions is increased by about 1.5 times as compared to the initial fiber. The influence of solution pH on the sorption of copper ions by native flax fiber has been studied. It has been found that in the pH range of the medium 1-7, along with the sorption of Cu ions, the sorption of H ions is observed, which indicates a competitive mechanism of sorption of heavy metal cations and protons with the participation of the cellulose-containing sorbent. Experimental isotherms of copper ions sorption have been processed in linear coordinates of Langmuir's equation that made it possible to determine the values of maximum sorption capacity of sorbents under study which increase in a series: native flax fiber (0.86 mol/kg) < flax fiber, oxidized and treated with sodium bisulfite (1.69 mol/kg) < Lewatit S100 cationite (1.89 mol/kg). Data from infrared spectroscopy and elemental analysis indicate the appearance of new sorption-active groups in the sorbent structure. The sorbent has been tested for purification of aqueous solutions and beverages from heavy metal ions under laboratory conditions. Peculiarities of the sorption of copper (II) ions from juice and white wine have been revealed. It has been found that the obtained modified sorbent on the basis of flax fiber in the purification of beverages is not inferior to the industrial cationic exchange resins in its sorption properties.

Pyridine‐functionalized N‐heterocyclic carbene gold(I) binuclear complexes as molecular electrocatalysts for oxygen evolution reactions

N‐heterocyclic carbene (NHC) complexes of gold(I/III) attained immense interest in catalytic organic transformations and as anticancer agents against several types of human cancers; however, their potential as electrocatalysts is scarce. The electrocatalytic oxygen evolution reaction was performed for the first time using pyridine‐functionalized NHC gold(I) binuclear metallacycles (8 and 9) possessing aptly designed ligand field. Complexes were prepared by the transmetallation of corresponding silver(I) NHC complexes, which were prepared by in situ deprotonation of pyridine and aryl substituted 1,2,4‐triazolium hexafluorophosphate salts (6 and 7) with Ag2O under dark. Both triazolium salts and binuclear gold(I) metallacycles were thoroughly characterised by NMR and ATR‐IR spectral and elemental analyses. A bromide salt 4 and a binuclear gold complex 9 were elucidated for structure by single crystal X‐ray diffraction analysis. Complex 9 possesses distorted linear coordination geometry around the gold atoms by the coordination of carbene carbon and pyridine nitrogen atoms bearing close Au–Au interaction (3.251 Å). The binuclear gold complexes 8 and 9 (along with 10 wt% conductive mesoporous carbon) were investigated as molecular electrocatalysts in oxygen evolution reaction (OER), which evidenced an oxygen evolution overpotential of 2.422 and 2.370 V versus reversible hydrogen electrode (RHE), respectively, to attain a current density of 10 mA.cm−2. The Tafel slope values of 40.9 and 30.4 mV dec−1 for 8 and 9, respectively, indicate the reaction mechanism involved and the suitability of these complexes as apt electrocatalysts for OER. The stability of the prepared molecular electrocatalysts was investigated by cyclic voltammetry and chronoamperometry techniques.

The Synthesis and Photocatalytic Properties of a Cuprous Iodide-based Coordination Polymer

Abstract A staple-shaped linear coordination polymer containing a single metal node was constructed via a conformational adaptive synthesis strategy. Such well-defined coordination polymer CP 1 could aggregate into a highly-ordered two-dimensional supramolecular framework with ultrasmall pores through weak intermolecular π⋯π stacking interactions. The emissive complex CP 1 showed excellent photocatalytic activity for azide-alkyne cycloaddition reaction (CuAAC) in solution at room temperature.

Coordination of a Pyrazole Functionalized Acetylacetone to the Coinage Metal Cations: An Unexpected Packing Similarity and a Trinuclear CuII/AuI Complex

The heteroditopic molecule HacacMePz combines a Pearson hard acetylacetone donor site with a softer trimethylpyrazole and shows site selectivity towards the coinage metal cations. The coordination of the N donor function was achieved towards AgI and AuI, leading to the salt [Ag(HacacMePz)2]PF6 (1) and the neutral complex [AuCl(HacacMePz)] (2). In either case, linear coordination about the coinage metal cation is observed. Interestingly, both complexes crystallize in space group Pbca with similar cell parameters. The two solids do not qualify as isostructural, albeit being closely related in real and reciprocal space. To probe the ligand’s ability for the envisaged synthesis of bimetallic coordination polymers, the mixed-metal CuII/AuI complex [Cu(acacMePzAuCl)2] (3) was obtained. In this mixed-metal oligomer, the central CuII cation adopts a square planar coordination environment with two O,O′-coordinated acacMePz− ligands, whose softer N donor sites are saturated with a AuCl moiety.

Copper-Catalyzed Azide-Alkyne Cycloaddition (CuAAC) by Functionalized NHC-Based Polynuclear Catalysts: Scope and Mechanistic Insights.

Copper(I) [Cu2(μ-Br)2(tBuImCH2pyCH2L)]n (L = OMe, NEt2, NHtBu) compounds supported by flexible functionalized NHC-based polydentate ligands have been prepared in a one-pot procedure by reacting the corresponding imidazolium salt with an excess of copper powder and Ag2O. An X-ray diffraction analysis has revealed that [Cu2(μ-Br)2(tBuImCH2pyCH2NEt2)]n is a linear coordination polymer formed by bimetallic [Cu(μ-Br)]2 units linked by the lutidine-based NHC-py-NEt2 ligand, which acts as a heteroditopic ligand with a 1κC-2κ2N,N′ coordination mode. We propose that the polymeric compounds break down in the solution into more compact tetranuclear [Cu2(μ-Br)2(tBuImCH2pyCH2L)]2 compounds with a coordination mode identical to the functionalized NHC ligands. These compounds have been found to exhibit high catalytic activity in the Cu-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. In particular, [Cu2(μ-Br)2(tBuImCH2pyCH2NEt2)]2 efficiently catalyzes the click reaction of a range of azides and alkynes, under an inert atmosphere at room temperature in neat conditions at a very low catalyst loading, to quantitatively afford the corresponding 1,4-disubstituted 1,2,3-triazole derivatives in a few minutes. The cycloaddition reaction of benzyl azide to phenylacetylene can be performed at 25–50 ppm catalyst loading by increasing the reaction time and/or temperature. Reactivity studies have shown that the activation of the polynuclear catalyst precursor involves the alkyne deprotonation by the NHC moiety of the polydentate ligand to afford a copper(I)-alkynyl species bearing a functionalized imidazolium ligand. DFT calculations support the participation of the dinuclear species [(CuBr)2(μ-tBuImCH2pyCH2NEt2)], resulting from the fragmentation of the tetranuclear compound, as the catalytically active species. The proposed reaction pathway proceeds through zwitterionic dinuclear intermediates and entails the active participation of both copper atoms, as well as the NHC moiety as an internal base, which activates the reacting alkyne via deprotonation.

Absorption of methylene blue from aqueous solutions on activated coal CAN-9: kinetics and equilibrium studies

The adsorption of methylene blue and kinetics of its adsorption from aqueous solutions on activated carbon CAN-9, obtained from walnut shells by chemical activation with orthophosphoric acid were studied. It has been shown that methylene blue adsorption isotherm from aqueous solutions on CAN-9 in the linear coordinates of the Langmuir model is a straight line (R = 0.99427) and is of Langmuir type. The kinetics of methylene blue adsorption on CAN-9, measured at two initial concentrations, showed an increase in Kint and C values with the increase of the initial concentrations. The process of intra-particular diffusion occurs in only one stage and takes place in the mesopores.

An Analysis of Lower Limb Coordination Variability in Unilateral Tasks in Healthy Adults: A Possible Prognostic Tool.

Interlimb coordination variability analysis can shed light into the dynamics of higher order coordination and motor control. However, it is not clear how the interlimb coordination of people with no known injuries change in similar activities with increasing difficulty. This study aimed to ascertain if the interlimb coordination variability range and patterns of healthy participants change in different unilateral functional tasks with increasing complexity and whether leg dominance affects the interlimb coordination variability. In this cross-sectional study fourteen younger participants with no known injuries completed three repeated unilateral sit-to-stands (UniSTS), step-ups (SUs), and continuous-hops (Hops). Using four inertial sensors mounted on the lower legs and thighs, angular rotation of thighs and shanks were recorded. Using Hilbert transform, the phase angle of each segment and then the continuous relative phase (CRP) of the two segments were measured. The CRP is indicative of the interlimb coordination. Finally, the linear and the nonlinear shank-thigh coordination variability of each participant in each task was calculated. The results show that the linear shank-thigh coordination variability was significantly smaller in the SUs compared to both UniSTS and Hops in both legs. There were no significant differences found between the latter two tests in their linear coordination variability. However, Hops were found to have significantly larger nonlinear shank-thigh coordination variability compared to the SUs and the UniSTS. This can be due to larger vertical and horizontal forces required for the task and can reveal inadequate motor control during the movement. The combination of nonlinear and linear interlimb coordination variability can provide more insight into human movement as they measure different aspects of coordination variability. It was also seen that leg dominance does not affect the lower limb coordination variability in participants with no known injuries. The results should be tested in participants recovering from lower limb injuries.

The route choosing methodology for networks and communications laying

In this paper a new route selecting method for laying engineering communications taking into account the urban development saturation with various infrastructural objects, designed communications type and purpose, communications rotation angles around a given axis when avoiding obstacles, and other restrictions is proposed. The communications laying routes unlike the traditional representation are considered as three-dimensional object in space which has a restriction according both plan and profile. In addition, the communications placement region is considered as a three-dimensional space and is modeled as a three-dimensional computational network. The communications optimization task in the form of minimal hypernet structure with restrictions and requirements imposed on the designed communications is proposed. A modified ray tracing method enabling to choose a path depending on the angular and linear coordinates predetermining the communications position in space is proposed.

High-Pressure Synthesis and Order-Disorder Transition of Layered Oxytelluride Ba2ZnO2Ag2Te2.

A layered oxytelluride, Ba2ZnO2Ag2Te2, which consists of alternating stacks of ZnO2 and Ag2Te2 layers with Ba ions in between, has been synthesized via high-pressure reaction. At ambient temperature, it contains discrete [ZnO2]2- linear units similar to Ba2ZnO2Ag2Se2 (Cmca), meaning that the unusual linear coordination around zinc center is stable even when a greater tensile strain is applied by the sandwiched Ag2Te2 layers in addition to barium ions. Upon heating, this compound undergoes an order-disorder phase transition from orthorhombic (Cmca) to tetragonal (I4/mmm) system at 350 K, transforming the ZnO2 lattice in linear coordination into a lattice with disordered oxide ions, suggesting the presence of cis/trans coordination coexistence as well as correlated disorder.

Linear Programming Coordination for Overcurrent Relay in Electrical Distribution Systems with Distributed Generation

Electric power distribution networks are generally radial in nature, with unidirectional power flows transmitted from the highest voltage levels to the consumption levels. The protection system in these distribution networks is relatively simple and consists mainly of fuses, reclosers (RC) and overcurrent relays (OCRs). The installation of distributed generation (DG) in a network causes coordination problems between these devices, because the power flows are no longer unidirectional and can flow upstream to the substation. For this reason, the work proposed here analyzes the most significant impacts that DG has on the protection devices and proposes an adjustment method for the OCRs based on linear programming (LP) techniques with the aim of improving their response time to the different faults that may occur in the main feeder of the network. The distribution system selected for the study is the IEEE 34 bus system using DIgSILENT 14.1 software for its modeling and Matlab for the adjustment of the overcurrent devices. Results indicate that better coordination between protection devices are achieved if LP is used.

Gold‐Catalyzed Desymmetric Lactonization of Alkynylmalonic Acids Enabled by Chiral Bifunctional P,N ligands

Due to the linear coordination nature of gold(I) catalysts, achieving high enantiocontrol in asymmetric gold catalysis is a great challenge. To improve the enantiocontrol of gold catalysis, an ion-pairing strategy was therefore proposed. A series of bifunctional P,N ligands based on chiral spirocyclic and biaryl scaffolds were synthesized and applied in the gold(I)-catalyzed desymmetric lactonization of alkynylmalonic acids. A wide range of chiral lactones containing an α-position quaternary stereocenter were synthesized with high yields, excellent regioselectivity and enantioselectivity under mild reaction conditions. The synthetic utilities of the current reaction were demonstrated by gram-scale synthesis and transformations of chiral lactones. The origin of enantioselectivity and the role of the alcohol additive were elucidated via control experiments and DFT calculations.

Gold‐Catalyzed Desymmetric Lactonization of Alkynylmalonic Acids Enabled by Chiral Bifunctional P,N ligands

AbstractDue to the linear coordination nature of gold(I) catalysts, achieving high enantiocontrol in asymmetric gold catalysis is a great challenge. To improve the enantiocontrol of gold catalysis, an ion‐pairing strategy was therefore proposed. A series of bifunctional P,N ligands based on chiral spirocyclic and biaryl scaffolds were synthesized and applied in the gold(I)‐catalyzed desymmetric lactonization of alkynylmalonic acids. A wide range of chiral lactones containing an α‐position quaternary stereocenter were synthesized with high yields, excellent regioselectivity and enantioselectivity under mild reaction conditions. The synthetic utilities of the current reaction were demonstrated by gram‐scale synthesis and transformations of chiral lactones. The origin of enantioselectivity and the role of the alcohol additive were elucidated via control experiments and DFT calculations.