Coordinate Square Research Articles

Airborne Short-Baseline Millimeter Wave InSAR System Analysis and Experimental Results

For the challenges of high-precision mapping in complex terrain, a novel airborne Interferometric Synthetic Aperture Radar (InSAR) system is designed. This system, named ASMIS (Airborne Short-Baseline Millimeter-Wave InSAR System), adopts the coplanar antenna and a pod-type structure. This design makes the system lightweight and highly integrated. It can be compatible with small general aviation flight platforms. The baseline is millimeters in size, which greatly simplifies the unwrapping process. The coplanar antennas have two advantages: they maximize the baseline utilization and minimize the Doppler decorrelation and the motion error inconsistency. Acquisition campaigns of the system have been carried out in Boao, Bayannur, and Chengde, China. In the Chengde experimental area, we designed an antiparallel flight experiment to account for the topographic relief. High-precision Digital Orthophoto Maps (DOMs) and Digital Surface Models (DSMs) at a scale of 1:5000 were obtained. The coordinate Root Mean Square Error (RMSE) of the checkpoints within the obtained DSM is less than 0.82 m in altitude and 3 m horizontally. The RMSE of the Sparse Ground Control Points (GCPs) within the obtained DSM is less than 0.3 m in altitude. Experimental results from different areas, including plains, mountains, and coastlines, demonstrate the system’s performance.

Pathway selection in the self-assembly of Rh4L4 coordination squares under kinetic control

Pathway selection principles in reversible reaction networks such as molecular self-assembly have not been established yet, because achieving kinetic control in reversible reaction networks is more complicated than in irreversible ones. In this study, we discovered that coordination squares consisting of cis-protected dinuclear rhodium(II) corner complexes and linear ditopic ligands are assembled under kinetic control, perfectly preventing the corresponding triangles, by modulating their energy landscapes with a weak monotopic carboxylate ligand (2,6-dichlorobenzoate: dcb–) as the leaving ligand. Experimental and numerical approaches revealed the self-assembly pathway where the cyclization step to form the triangular complex is blocked by dcb–. It was also found that one of the molecular squares assembled into a dimeric structure owing to the solvophobic effect, which was characterized by nuclear magnetic resonance spectroscopy and single-crystal X-ray analysis.

Isolation of a Dodecanuclear Polyoxo Cluster {Nb12O21} Showing a Rare Case of Five‐fold Coordinated Niobium(V) Centers with a Square Pyramidal Geometry

AbstractThe reactivity of the complexing anthracene‐9‐carboxylate ligand has been investigated with a niobium(IV) tetrachloride precursor (NbCl4 ⋅ 2THF) in isopropanol solvent. This resulted in the crystallization of a molecular assembly containing two distinct {Nb12O21} cores surrounded by multiple isopropanolate and anthracenoate ligands. The compound is formulated [Nb12((μ3‐O)3(μ‐O)18(C15H9O2)8(OiPr)10] ⋅ [Nb12(μ3‐O)2(μ‐O)19(C15H9O2)8(OiPr)10] illustrating the two different dodecameric oxo‐clusters, for which the niobium(IV) precursor was oxidized in the niobium(V) state during the reactional process. The two distinct {Nb12O21} units mainly differs by the environment of the niobium centers, which exhibits unexpected five‐fold coordination (square pyramid) for some of them, together with the classical six‐fold coordination (octahedron) as usually found for niobium(V). In the crystallization process, the. IR spectroscopy was used to analyze the esterification reaction occurring between the anthracene acid an isopropanolate ligands responsible of the production of water used in the oxo‐condensation of the niobium centers. 93Nb Solid state NMR was tentatively used to assess the occurrence of the different niobium environments.

A generalized Kirkwood implicit solvent for the polarizable AMOEBA protein model.

Computational simulation of biomolecules can provide important insights into protein design, protein-ligand binding interactions, and abinitio biomolecular folding, among other applications. Accurate treatment of the solvent environment is essential in such applications, but the use of explicit solvents can add considerable cost. Implicit treatment of solvent effects using a dielectric continuum model is an attractive alternative to explicit solvation since it is able to describe solvation effects without the inclusion of solvent degrees of freedom. Previously, we described the development and parameterization of implicit solvent models for small molecules. Here, we extend the parameterization of the generalized Kirkwood (GK) implicit solvent model for use with biomolecules described by the AMOEBA force field via the addition of corrections to the calculation of effective radii that account for interstitial spaces that arise within biomolecules. These include element-specific pairwise descreening scale factors, a short-range neck contribution to describe the solvent-excluded space between pairs of nearby atoms, and finally tanh-based rescaling of the overall descreening integral. We then apply the AMOEBA/GK implicit solvent to a set of ten proteins and achieve an average coordinate root mean square deviation for the experimental structures of 2.0 Å across 500ns simulations. Overall, the continued development of implicit solvent models will help facilitate the simulation of biomolecules on mechanistically relevant timescales.

Digital Self-Interference Cancellation for Full-Duplex UAV Communication System over Time-Varying Channels

Full-duplex unmanned aerial vehicle (UAV) communication systems are characterized by mobility, so the self-interference (SI) channel characteristics change over time constantly. In full-duplex UAV communication systems, the difficulty is to eliminate SI in time-varying channels. In this paper, we propose a pilot-aid digital self-interference cancellation (SIC) method. First, the pilot is inserted into the data sequence uniformly, and the time-varying SI is modeled as a linear non-causal function. Then, the time-varying SI channel is estimated by the discrete prolate spheroidal basis expansion model (BEM). The error of block edge channel estimation is reduced by cross-block interpolation. The result of channel estimation is convolved with the transmitted data to obtain the reconstructed SI, which is subtracted from the received signal to achieve SIC. The simulation results show that the SIC performance of the proposed method outperforms the dichotomous coordinate descent recursive least square (DCD-RLS) and normalized least mean square (NLMS) algorithms. When the interference to noise ratio (INR) is 25 dB, the performance index normalized least mean square (NMSE) is reduced by 5.5 dB and 4 dB compared with DCD-RLS and NLMS algorithms, which can eliminate SI to the noise floor, and the advantage becomes more obvious as the INR increases.

Mannich metal complex: Synthesis, reaction mechanism and computational studies

Metal mediated Mannich aminomethylation reaction involving metal(II)glycinato complex, formaldehyde, and ethyl acetoacetate (EAA) was carried out under mild aqueous conditions. Under the optimized condition, the reaction yielded only a single Mannich base product in a moderate yield without any contamination with the aldol condensation by-product. The Mannich base product obtained was characterized and confirmed by elemental analysis, UV–Vis spectroscopy, IR, ESI-MS, ESR, and GCMS–. The structure of the Mannich base product was investigated by Density Functional Theory (DFT). The structure interpretation of the product from the DFT data supported the proposed structure and was found to have an N2O2 four coordination square planar geometry around the Cu ion. HOMO and LUMO energy values for the product complex were calculated and the optimized condition for the maximum yield of the product was determined.

Thermal evolution of the EuBaCo2O5.5 crystal structure

Crystal structure of the EuBaCo2O5.502(1) perovskite obtained by equilibration and slow cooling in closed ampoule is studied between 100 and 400 ​K by high-resolution synchrotron powder X-ray diffraction, and its thermally induced phase transitions by differential scanning calorimetry (DSC). The low-temperature Pmma perovskite supercell 2ap 2bp 2cp has Eu and Ba alternating along c, Co3+ coordination square pyramids and octahedra alternating along b and orbital-order alternating along a. The last order is lost upon warming through a transition topping at 365 ​K (ΔS ​≈ ​2.25R per mole EuBaCo2O5.5 by DSC) that forms an ap 2bp 2cp supercell as refined at 380 and 400 ​K. The DSC detects also the twin magnetic phase transition at 248 ​K and 269 ​K as weak endothermic effects upon heating (ΔS ​≈ ​0.41 ​J/molK and 0.19 ​J/molK, resp.). Intermittent negative thermal expansion of some cobalt coordination polyhedra is discussed in the context of possible Co3+ spin states and of the DSC entropy change at the structure transition.

Experimental Results of Three-Dimensional Modeling and Mapping with Airborne Ka-Band Fixed-Baseline InSAR in Typical Topographies of China

Interferometric synthetic aperture radar (InSAR) has become a key technology for producing high-precision digital surface models (DSMs) and digital orthophoto maps (DOMs) in full time and all weathers. Airborne millimeter-wave InSAR, with large-scale and high-resolution imaging, is characterized by high spatial resolution, flexibility, and immunity to loss-of-correlation. This paper introduces our modeling experiments with airborne dual-antenna, Ka-band InSAR regarding typical topographies of China. Ka-band SAR data were acquired in designated experimental areas in flat (Heyang area in Shaanxi) and mountainous areas (Shibing area in Guizhou and Qionglai area in Sichuan). The key processing of the experimental data for DSMs and DOMs is demonstrated in the paper, especially the proposed robust and efficient phase unwrapping (PU) method for the interferometric data and block adjustment method of strip calibration. The results show that the proposed unwrapping method can provide reliable unwrapped phase results in undulating areas, and the block adjustment can carry out consistent calibration for strips with sparse ground control points (GCPs). The accuracy assessment of the DSM shows that the coordinate root mean square error (RSME) of the obtained DSM is less than 2 m in height, and 2.5 m horizontally, which meets the 1:5000 requirement for topographic mapping in difficult areas.

Synthesis, Antimicrobial Evaluation of Substituted Indole and Nitrobenzenamine based Cr(III), Mn(III) and Fe(III) Metal Complexes.

Schiff base ligand (E)-5-methyl-3-(1-(4-nitrophenylimino)ethyl)-1H-indol-2-amine was synthesized by the condensation of 1-(2-amino-5-methyl-1H-indol-3-yl)ethanone and 4-nitrobenzenamine in methanol at 70 oC. The prepared Schiff base ligand doped with Cr(III), Mn(III) and Fe(III) ion, respectively and it is denoted as [M(C34H32N8O4)X]X2. The complexes have been characterized with the help of elemental analysis, conductance measurements, magnetic measurements and their structural configuration have been determined by various spectroscopic (electronic, IR, 1H NMR, 13C NMR, GCMS) techniques. Electronic and magnetic moments of the complexes indicate that the geometry of the metal center was five coordinate square pyramidal. These metal complexes were also tested for their antimicrobial activities to assess their inhibiting potential against Staphylococcus aureus, Bacillus subtilis (positive bacteria) and Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi (negative bacteria) and fungi Rizoctonia sp., Aspergillus sp., Penicillium sp. [Cr(C34H32N8O4)OAc](OAc)2 shows best antimicrobial activity against all the pathogens.

Variations of structures on changing the ratios of metal ions in rare Ca(II)–Zn(II) hetero-metallic self-assembled coordination polymers of hexamethylenetetramine and benzoate

Two rare hetero-metallic calcium(II)-zinc(II) complexes [CaZn4(OBz)10(μ2-hmt)2]n (1) and [Ca2Zn4(OBz)12(μ2-hmt)2]n (2) have been synthesized using basic zinc carbonate, benzoic acid (HOBz), hydrated calcium chloride and hexamethylenetetramine (hmt) by varying the molar ratio of the reactants. Both the complexes have been analyzed by elemental analysis, IR spectroscopy and X-ray crystallography. The complex 1 is a 1D polymer which contains one calcium ion and four zinc atoms in the asymmetric unit together with ten benzoates and two hmts. The polymer has been constructed by the alternate joining of paddle-wheel Zn2(OBz)4 units and Zn2Ca trinuclear species by μ2-hmt bridging molecules connecting Zn2+ ions. Zinc atoms have five coordinate square pyramidal geometries and four coordinate tetrahedral geometries in Zn2(OBz)4 and Zn2Ca moieties, respectively, whereas calcium atoms have six-coordinate distorted octahedral geometry. Complex 2 is also a 1D polymer but unlike complex 1, it contains four independent zinc and two independent calcium atoms in the asymmetric unit together with twelve benzoates and two hmts. By contrast, the polymeric structure of complex 2 has been formed by the connection of Zn2Ca trinuclear species via μ2 hmt bridging molecules at Zn centers. Complex 2 is also a 1D polymer but unlike complex 1, it contains four independent zinc and three independent calcium atoms in the asymmetric unit together with twelve benzoates and two hmts. All four zinc atoms are four coordinate with tetrahedral environments and the calcium atoms are six coordinated (two are located on a center of symmetry) exhibiting a distorted octahedral geometry.

Constructing p-sulfonatothiacalix[4]arene-based coordination squares as new type of efficient proton-conducting solid electrolytes

To develop high-conductivity solid-state proton-conducting materials is a hot topic in the fuel-cell technology. Herein, p-sulfonatothiacalix[4]arene was chosen as the terminal ligand to construct porous coordination compounds, {[Co4Cl(H2TC4AS)]4(BDC)8}12- (CIAC-240) and {[Co4Cl(H4TC4AS)]4(SIP)8}12- (CIAC-241) (Na4H4TC4AS = tetrasodium p-sulfonatothiacalix[4]arene; H2BDC = isophthalic acid; NaH2SIP = 5-sulfoisophthalic acid sodium salt). Both structures are featured with some window frame-like squares which are constructed by bridging the shuttlecock-like Co4-TC4AS secondary building units (SBUs) with the BDC/SIP ligands and further stacked into the supramolecular extended structures. The proton conduction and vapor adsorption of the compounds were discussed and compared. The experimental results gave the maximum values of 3.22 mS cm−1 and 11.6 mS cm−1 for the proton conductivity of CIAC-240 and CIAC-241, respectively.

Order-disorder Twinning of Malachite

Abstract Malachite has a layered structure composed of triangular CO3 groups and CuO2(OH)2 coordination squares of two types. In 2D projection, each layer can be decomposed into two OD strips: the A strip, containing CO3 groups and square co-ordinations of Cu2, with idealized symmetry pgm2, and the B strip, without CO3 groups, with symmetry p2 (the b axis of malachite is the infinite strip direction). In the 3D structure, these strips form the ‘A' OD-layers with symmetry reduced by coordination requirements to approximately p2212, which alternate with the ‘B' OD-layers with layer symmetry . The B-layer can assume two positions, which are related by a 180° rotation axis running through the C1 and O1 atoms of the CO3 group in the A-layer. This axis is oriented close to [100]*. The fit of the A-layer and of the coplanar rotated B-layer is hindered by the presence of important partial gaps and overlaps at the boundary. Inclining these two structure portions towards one another, together with small positional adjustments, appears to alleviate the misfit problems; the two layer portions so related form an angle of about 124°, i.e., they form a twin relationship. This desymmetrization of the malachite structure away from the ideal model results in occasional twinning instead of the fully developed monoclinic polytype structure which is derived in this paper. In the structure of the Cu-Zn analogue, rosasite, the above-described match problem is solved in a different way, by shifting a Zn coordination octahedron (which replaces Cu2 in malachite) into the interlayer space. Malachite polytypes 1 and 2 and rosasite illustrate three different orientations of P21/a symmetry elements with respect to the structural layers, resulting in three different structure configurations.

Photoluminescence and semiconductive properties of a 4f–5d compound

A novel 4f–5d compound [Ho(H2O)2(μ-IA)3Hg3Br6]n (1, HIA = isonicotinic acid) was prepared. It is characterized by single-crystal X-ray diffraction. The title compound crystallizes in the space group P21/n of the monoclinic system. The holmium ion is coordinated by six oxygen atoms to yield a slightly distorted tetragonal antiprism configuration. Three crystallographically independent mercury ions exhibit two different coordination environments, i.e., tetrahedron geometry and square pyramidal configuration. In the title compound, there are two types of one-dimensional (1D) chains, namely Hg–Br chains and Ho–IA chains. Both chains are interconnected by the μ3-bridging isonicotinic acid ligands to form a three-dimensional (3D) frame structure. Photoluminescence from solid samples showed that the title compound could emit up-conversion red fluorescence, and its half-peak width was about 14 nm. The emission peak comes from its characteristic emission of 5F5 → 5I8 of Ho3+. The CIE color coordinates of the title compound are (0.693, 0.307). The title compound displays a broad semiconductor gap being of 2.47 eV, as discovered by the solid-state diffuse reflection. A novel 4f–5d compound has been prepared. It features a 3D framework structure. It displays a red up-conversion photoluminescence emission band. Diffuse reflection spectrum with solid-state sample shows that it possesses a wide optical band gap of 2.47 eV.

Angle-differential elastic-electron scattering off C60: a simple semi-empirical theory versus experiment

We prove in the present paper that simple modeling of a complicated highly polarizable C60 target by a rectangular (in a radial coordinate) square well potential in combination with the static polarization potential provides a viable approximation for a low-energy elastic-electron scattering off this target. The proof is based on the results of the comparison of the calculated angle-differential elastic-electron scattering cross section off C60 versus corresponding experimental data.

Synthesis and Structure of Heterobinuclear Complexes [AuCl(μ-Dien*)PtCl3] and [AuCl(μ-Dien*)PtCl3] · 0.5H2O

New binuclear complexes [AuCl(μ-Dien*)PtCl3] and [AuCl(μ-Dien*)PtCl3] · 0.5H2O, where Dien* is deprotonated diethylenetriamine, have been prepared and studied by elemental analysis, X-ray diffraction, and IR spectroscopy. The crystal structures are built of binuclear complexes of the composition [AuCl(μ-Dien*)PtCl3] with the average Au⋯Pt intramolecular distance equal to 3.403 A. Gold and platinum atoms have distorted square coordination; the (AuN3Cl) and (PtNCl3) coordination cores are found; the middle Dien nitrogen atom acts as a bridge bonding the Au and Pt coordination squares.

PtAu3 cluster complexes with narrow-band emissions for solution-processed organic light emitting diodes

Solution-processed OLEDs based on PtAu3 cluster complexes show high-efficiency electroluminescence with narrow emission bands through enhancing the co-planarity between their aromatic acetylides and platinum(ii) coordination square planes.

Competition between coordination bonds and hydrogen bonding interactions in solvatomorphs of copper(II), cadmium(II) and cobalt(II) complexes with 2,2′-bipyridyl and acetate

Abstract The delicate balance among conformation, coordination bonds and hydrogen bonding has been probed in solvatomorphs of known metal-organic molecules synthesised from copper(II), cadmium(II) and cobalt(II) with acetate (OAc) and 2,2′-bipyridine (bipy). The Cu(OAc)2(bipy) complex, isolated as a pentahydrate, has the acetate ligands oriented to opposite sides of the coordination square plane. DFT calculations show the energy difference between this structure and a syn form amount to approximately 16 kJ/mol. The presence of lattice water enables the formation of O–H···O hydrogen bonds with the acetate ligands. Different coordination numbers and energies are found as a function of the number of water molecules co-crystallising in the Cd(OAc)2(bipy)(OH2)·3H2O and [Co(OAc)(bipy)2](OAc)·3H2O complexes.

Synthesis and Antibacterial Activity of Isatin Schiff Base Derivative with 3-Aminoacetophenone and its Ni(II), Co(II) Transition Metals Complexes

The (E)-3-(3-acetylphenylimino) indolin-2-one (Bidentate) ligand type [HL], has been prepared from Isatin and 3-aminoacetophenone in the presence of KOH. In general, the ligand contains oxygen (O) and nitrogen (N) donor atoms. The reaction of Isatin and 3-aminoacetophenon was carried out in ethanol by condensation reaction at 80°C with reflux for 4 h, to form [HL] ligand type. This ligand has been used to prepare NiII and CoII complexes in the ratio of 1:1 metal-ligand. All compounds have been characterized by spectroscopic methods (Fourier transform infrared and ultravioletvisible), C.H.N, thin-layer chromatography, mass spectrum, X-ray diffraction, magnetic moment, conductivity measurements and milting point, the synthesized ligand and its metal complexes have been tested for their antibacterial activity against Staphylococcus aureus and Bacillus subtilis using agar disc diffusion method. The ligand and its complexes showed significant activities against S. aureus and B. subtilis. Our study revealed the formation of four coordinate square planar complexes around NiII and CoII metal ions.

Magnetic Anisotropy from Trigonal Prismatic to Trigonal Antiprismatic Co(II) Complexes: Experimental Observation and Theoretical Prediction.

A family of trigonal antiprismatic Co(II) complexes was synthesized, which exhibited field-induced Raman process dominated single-molecule magnet behavior. Despite the coordination environment of Co(II) being of similar symmetry, the four complexes exhibit distinct dynamic magnetic properties owing to their packing arrangements and dipole-dipole interactions. On the basis of computational results we have demonstrated that the g z and giso values follow a cosine relation with respect to the rotated angle φ (twist angle φ defined as the rotation angle of one coordination square away from the eclipse conformation to the other).

Low-spin manganese(II) and high-spin manganese(III) complexes derived from disalicylaldehyde oxaloyldihydrazone: Synthesis, spectral characterization and electrochemical studies

Low-spin manganese(II) complexes [MnII(H2slox)].H2O (1), [MnII(H2slox)(SL)] (where SL (secondary ligand) = pyridine (py, 2), 2-picoline (2-pic, 3), 3-picoline (3-pic, 4), and 4-picoline (4-pic, 5) and high-spin manganese(III) complex Na(H2O)4[MnIII(slox)(H2O)2].2.5H2O have been synthesized from disalicyaldehyde oxaloyldihydrazone in methanolic – water medium. The composition of complexes has been established by elemental analyses and thermoanalytical data. The structures of the complexes have been discussed on the basis of data obtained from molar conductance, UV visible, 1H NMR, infrared spectra, magnetic moment and electron paramagnetic resonance spectroscopic studies. Conductivity measurements in DMF suggest that the complexes (1–5) are non-electrolyte while the complex (6) is 1:1 electrolyte. The electronic spectral studies and magnetic moment data suggest five – coordinate square pyramidal structure for the complexes (2–5) and square planar geometry for manganese(II) in complex (1). In complex (6), both sodium and manganese(III) have six coordinate octahedral geometry. IR spectral studies reveal that the dihydrazone coordinates to the manganese centre in keto form in complexes (1–5) and in enol form in complex (6). In all complexes, the ligand is present in anti-cis configuration. Magnetic moment and EPR studies indicate manganese in +2 oxidation state in complexes (1–5), with low-spin square planar complex (1) and square pyramidal stereochemistries complexes (2–5) while in +3 oxidation state in high-spin distorted octahedral stereochemistry in complex (6). The complex (1) involves significant metal – metal interaction in the solid state. All of the complexes show only one metal centred electron transfer reaction in DMF solution in cyclic voltammetric studies. The complexes (1–5) involve MnII→MnI redox reaction while the complex (6) involves MnIII→MnII redox reaction, respectively.