Non-planar Configuration Research Articles

Catena-Poly[[dichloridozinc(II)]-μ-1,4-bis(pyridin-2-ylmethoxy)benzene-κ2N:N′

In the title compound, [ZnCl2(C18H16N2O2)]n, the ZnII ion is tetra­hedrally coordinated by two Cl atoms and by two N atoms from different 1,4-bis­(pyridin-2-ylmeth­oxy)benzene ligands. The ligand shows a non-planar configuration, in which the dihedral angles between the two terminal pyridine rings and the linking benzene ring are 7.86 (12) and 70.74 (11)°. The flexible ligand coordinates to the ZnII ions, generating an infinite chain propagating along [001].

Molecular structure elucidation and hydrogen bonding analysis of a pyrazolone derivative

The title compound crystallizes in the monoclinic crystal system with space group P21/c having unit cell parameters: a=7.6329(4), b=7.8137(4), c=28.0651(14) Å, ? =95.995o. The structure converges to a final R-value of 0.0563. The two C-N bonds in Ring B are puckered as the torsion around these bonds is 29.67(2)o and -18.49(2)o , respectively. The two methyl carbons as well as the oxygen atom of the central N-containing five-membered ring (B) are significantly deviated from their mean positions. The magnitude of dihedral angle between the phenyl ring A and B is 133.09(1)o while it is 170.43(1)o between ring B and the phenyl ring C. This indicates that the molecule adopts a non-planar configuration. The crystal structure is stabilized by few C-H…O and C-H…N inter and intramolecular hydrogen interactions.

Noncovalent Interactions in the Gas Phase: The Anisole–Phenol Complex

The present paper reports on an integrated spectroscopic study of the anisole-phenol complex in a molecular beam environment. Combining REMPI and HR-LIF spectroscopy experimental data with density functional computations (TD-M05-2X/M05-2X//N07D) and first principle spectra simulations, it was possible to locate the band origin of the S(1) ← S(0) electronic transition and determine the equilibrium structure of the complex, both in the S(0) and S(1) electronic states. Experimental and computational evidence indicates that the observed band origin is due to an electronic transition localized on the phenol frame, while it was not possible to localize experimentally another band origin due to the electronic transition localized on the anisole molecule. The observed structure of the complex is stabilized by a hydrogen bond between the phenol, acting as a proton donor, and the anisole molecule, acting as an acceptor through the lone pairs of the oxygen atom. A secondary interaction involving the hydrogen atoms of the anisole methyl group and the π electron system of the phenol molecule stabilizes the complex in a nonplanar configuration. Additional insights about the landscapes of the potential energy surfaces governing the ground and first excited electronic states of the anisole-phenol complex, with the issuing implications on the system photodynamic, can be extracted from the combined experimental and computational studies.

Internal Proton Transfer and H2 Rotations in the H5+ Cluster: A Marked Influence on Its Thermal Equilibrium State

Classical and path integral Monte Carlo (CMC, PIMC) "on the fly" calculations are carried out to investigate anharmonic quantum effects on the thermal equilibrium structure of the H5(+) cluster. The idea to follow in our computations is based on using a combination of the above-mentioned nuclear classical and quantum statistical methods, and first-principles density functional (DFT) electronic structure calculations. The interaction energies are computed within the DFT framework using the B3(H) hybrid functional, specially designed for hydrogen-only systems. The global minimum of the potential is predicted to be a nonplanar configuration of C(2v) symmetry, while the next three low-lying stationary points on the surface correspond to extremely low-energy barriers for the internal proton transfer and to the rotation of the H2 molecules, around the C2 axis of H5(+), connecting the symmetric C(2v) minima in the planar and nonplanar orientations. On the basis of full-dimensional converged PIMC calculations, results on the quantum vibrational zero-point energy (ZPE) and state of H5(+) are reported at a low temperature of 10 K, and the influence of the above-mentioned topological features of the surface on its probability distributions is clearly demonstrated.

The enzymatic reaction-induced configuration change of the prosthetic group PQQ of methanol dehydrogenase

Methanol dehydrogenase is a heterotetrameric enzyme containing the prosthetic group pyrroloquinoline quinone (PQQ), which catalyzes the oxidation of methanol to formaldehyde. The crystal structure of methanol dehydrogenase from Methylophilus W3A1, previously determined at high resolution, exhibits a non-planar configuration of the PQQ ring system and lends support for a hydride transfer mechanism of the enzymatic reaction catalyzed by the enzyme. To investigate why PQQ is in the C5-reduced form and to better understand the catalytic mechanism of the enzyme, three structures of this enzyme in a new crystal form have been determined at higher resolution. Two of the three crystals were grown in the presence of 1 and 50 mM methanol, respectively, both structures of which show non-planar configurations of the PQQ ring system, confirming the previous conclusion; the other was crystallized in the presence of 50 mM ethanol, the structure of which displays a planar ring system for PQQ. Comparison of these structures reveals that the configuration change of PQQ is induced by the enzymatic reaction. The reaction takes place and the C5-reduced PQQ intermediate is produced when the enzyme co-crystallizes with methanol, but the enzymatic reaction does not take place and the PQQ ring retains a planar configuration of the oxidized orthoquinone form when ethanol instead of methanol is present in the crystallization solution.

Three-dimensional imaging with detector arrays on arbitrarily shaped surfaces

Conventional multiview imaging systems commonly utilize a planar lenslet array and a rigid, flat image sensor in the pickup stage to capture different views of the scene. In this Letter, we remove this constraint by proposing the concept of three-dimensional (3D) imaging with detector arrays that may conform to arbitrarily shaped surfaces or platforms. A nonplanar detector array configuration can be used in combination with a flexible lenslet array to capture different views. The orientation and optical axes of individual image sensing elements could vary. A point-by-point 3D reconstruction algorithm is described and the feasibility of the proposed approach is demonstrated through simulated imagery.

A ratiometric fluorescent pH probe based on aggregation-induced emission enhancement and its application in live-cell imaging

A ratiometric fluorescent pH probe, 4-carboxylaniline-5-chlorosalicylaldehyde Schiff base (1) was synthesized via a facile reaction and used for pH sensing in live cells. While exhibiting weak fluorescence when dispersed in solution, 1 displayed aggregation-induced emission enhancement (AIEE) characteristics in its aggregate/solid state, as a result of the restriction of free intramolecular rotation of a C–N bond and the non-planar configuration in the aggregate/solid state. The integration of hydroxyl and carboxyl groups provided 1 with a ratiometric fluorescent response to pH based on AIEE and the pH-dependent spectral characteristics of compound 1, with proton dissociation constants pKa1 and pKa2 of 4.8 ± 0.1 and 7.4 ± 0.1, respectively. The probe exhibited a significant fluorescence color change from orange to green with an intensity ratio (I516 nm/ I559 nm) enhanced when the pH increased from 5.0 to 7.0 in aqueous solution. Confocal fluorescence imaging of intracellular pH through ratiometric response was successfully achieved in live HepG2 cells. The results demonstrate that probe 1 is a good candidate for monitoring pH fluctuations in live cells with good selectivity, stability, and excellent membrane permeability.

THE LIGHT CURVE OF THE WEAKLY ACCRETING T TAURI BINARY KH 15D FROM 2005-2010: INSIGHTS INTO THE NATURE OF ITS PROTOPLANETARY DISK

Photometry of the unique pre-main sequence binary system KH 15D is presented, spanning the years 2005-2010. This system has exhibited photometric variations and eclipses over the last 50 years caused by a precessing circumbinary disk. Advancement of the occulting edge across the binary orbit has continued and the photospheres of both stars are now completely obscured at all times. The system is now visible only by scattered light, and yet it continues to show a periodic variation on the orbital cycle with an amplitude exceeding two magnitudes. This variation, which depends only on the binary phase, has likely been present in the data since at least 1995. It can, by itself, account for shoulders on the light curve prior to ingress and following egress, obviating the need for components of extant models such as a scattering halo around star A or forward scattering from a fuzzy disk edge. A plausible source for the variable scattering component is reflected light from the far side of a warped occulting disk. We have detected color changes in V-I of several tenths of a magnitude to both the blue and red that occur during times of minima. These may indicate the presence of a third source of light (faint star) within the system, or a change in the reflectance properties of the disk as the portion being illuminated varies with the orbital motion of the stars. The data support a picture of the circumbinary disk as a geometrically thin, optically thick layer of perhaps mm or cm-sized particles that has been sculpted by the binary stars and possibly other components into a decidedly nonplanar configuration. A simple (infinitely sharp) knife-edge model does a good job of accounting for all of the recent (2005-2010) occultation data.

Induced-Drag Minimization of Nonplanar Geometries Based on the Euler Equations

The induced drag of several nonplanar configurations is minimized using an aerodynamic shape optimization algorithm based on the Euler equations. The algorithm is first validated using twist optimization to recover an elliptical lift distribution. Planform optimization reveals that an elliptical planform is not optimal when side-edge separation is present. Optimized winglet and box-wing geometries are found to have span efficiencies that agree well with lifting-line analysis, provided the bound constraints on the entire geometry are accounted for in the linear analyses. For the same spanwise and vertical bound constraints, a nonplanar split-tip geometry outperforms both the winglet and box-wing geometries, because it can more easily maximize the vertical extent at the tip. The performance of all the optimized geometries is verified using refined grids consisting of 88-152 million nodes.

ChemInform Abstract: Vibrational Potentials of the Low Frequency Out-of-Plane Motion in the Ground and Excited Singlet Electronic States of 9,10- Dihydrophenanthrene

The absorption and single vibronic level fluorescence spectra of jet cooled 9,10‐dihydrophenanthrene possesses long progressions of a low‐frequency vibration identified as the out‐of‐plane nontotally symmetric CH2–CH2 bridge deformation. The intensity distribution in the observed progressions indicate that the molecule is nonplanar in the ground and the first two excited singlet electronic states described as the plus and minus combinations of the Lb states of the two perturbed benzene rings. The barrier height between the two equivalent nonplanar configurations, with the planar configuration being the transition state, is 2640 cm−1 in S0 and 1430 cm−1 in S1. These values are much larger than those in 9,10‐dihydroanthracene. The observed intensity distributions are reproduced well by model calculations with double minimum potentials whose parameters are in good agreement with those obtained by geometry optimization and force field and vibrational frequency calculations by the quantum chemical force field ...

Hydrogen bonding interaction of small acetaldehyde clusters studied with core-electron excitation spectroscopy in the oxygen K-edge region

In order to examine inner-shell electron excitation spectra of molecular clusters with strong multipole interactions, excitation spectra and time-of-flight (TOF) fragment-mass spectra of small acetaldehyde (AA) clusters have been studied under the beam conditions. The TOF spectra at the oxygen K-edge region showed an intense growth of the protonated clusters, MnH+ (M=CH3CHO) in the cluster beams. "cluster-specific" excitation spectra could be generated by monitoring partial-ion-yields of the protonated clusters. The most intense band of O1s→π*CO was found to shift to a higher energy by 0.15 eV relative to the monomer band upon clusterization. X-ray absorption spectra (XAS) were also calculated for the representative dimer configurations using a computer modelling program based on the density functional theory. The XAS prediction for the most stable (non-planar) configuration was found to give a close comparison with the cluster-band shift observed. The band shift was interpreted as being due to the HOMO–LUMO interaction within the complex where a contribution of vibrationally blue-shifting hydrogen bonding could be identified.

On the properties of new benzothiazole derivatives for organic light emitting diodes (OLEDs): A comprehensive theoretical study

The present investigation explored theoretically the geometry structures, the electronic and the optical properties of new benzothiazole derivatives with incorporated triphenylamine/diphenylnaphthylamine or (4-vinylphenyl)acrylonitrile as highly efficient emitting molecular materials for organic light emitting diodes (OLEDs). This study is accomplished in order to provide an in-depth understanding of the structure–properties correlation and their effects on optoelectronic devices. In this contribution, we apply quantum-chemical methods (semiempirical Austin Model 1 (AM1), ab-initio Hartree–Fock (HF) and density functional theory (DFT)) to elucidate the photophysical properties of these molecules. First of all, the geometry structures of these compounds in the ground and the excited states were fully optimized, showing a non-planar configuration structures. Whereas, the geometrical structure of benzothiazole with cyano-PV unit is more planar. Structural parameters and vibrational properties of these compounds are then derived. Moreover, absorption and luminescence properties, lying in a bluish white or red light emission, were elucidated by ZINDO/S methods. The molecular orbital (highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)), the ionization potentials (IPs) and the electron affinities (EAs) of compounds under study were also investigated. It was found that the detailed results obtained from theoretical simulations are consistent with the available experimental data. This kind of theoretical approach has been proved to be reliable for the structure and spectroscopic properties, and predicts the favorable qualities of these benzothiazole derivatives, which make them as the materials of choice for high performance applications.

Novel star-shaped host materials for highly efficient solution-processed phosphorescent organic light-emitting diodes

Two novel star-shaped host materials for solution processed blue phosphorescent organic light-emitting devices, 9-(5′,5‴-diphenyl[1,1′:3′,1″:3″,1‴:3‴,1⁗-quinquephenyl]-5″-diyl)-9H-carbazole (DQC) and 9,9′-(5′-phenyl[1,1′:3′,1″-terphenyl]-3,5-diyl)bis-9H-carbazole (PTC), were synthesized by the Suzuki coupling reaction. These compounds both exhibited high glass-transition temperatures (Tg ≥ 128 °C) and excellent film-forming ability. The nonplanar star-shaped configuration of DQC and PTC limited the effective extension of their π–conjugation, leading to the same triplet energy of 2.81 eV. The solution processed single layer devices using DQC and PTC as the host for the phosphorescence emitter iridium(III) bis(4,6-difluorophenylpyridinato)-picolinate (FIrpic) showed the maximum luminance efficiencies of 9.2 and 12.8 cd A−1, respectively. By introducing a thin 1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBI) electron-transporting and exciton-confining layer, the maximum efficiencies of the solution processed devices based on DQC and PTC were further improved to 21.7 and 25.7 cd A−1 with the maximum external quantum efficiencies up to 9.2% and 11.9%, respectively. Furthermore, the DQC- and PTC-based devices showed significantly high performance compared with the corresponding devices based on 1,3-bis(9-carbazolyl)benzene (mCP).

Theoretical and Experimental Study of Valence-Shell Ionization Spectra of Guanine

The full valence-shell ionization spectra of the four most stable guanine tautomers were studied theoretically. The third-order algebraic-diagrammatic construction (ADC(3)) method for the one-particle Green's function was used to calculate the energies and relative intensities of the vertical ionization transitions. For low-lying transitions, the influence of planar and nonplanar guanine configurations on the ionization energies, as well as the convergence of the results with respect to basis set was studied at the level of the outer-valence Green's function (OVGF) approximation scheme. The results of the calculations were used to interpret recent synchrotron radiation valence-shell photoionization spectra of guanine in the gas phase under thermal equilibrium conditions. The photoelectron spectrum was modeled by summing individual tautomer spectra weighted by Boltzmann population ratios (BPR) of tautomers from our previous high-level ab initio thermochemical calculations. The theoretical spectra are in good agreement with the experimental results, providing assignments of most observed structures and offering insight into tautomerism of guanine in the gas phase. The first six molecular orbitals give rise to single-hole states with a binding energy of about 7-12 eV. At higher binding energy the spectral features are mainly due to satellite states.

Aeroelastic coupling of geometrically nonlinear structures and linear unsteady aerodynamics: Two formulations

Two different time domain formulations of integrating commonly used frequency-domain unsteady aerodynamic models based on a modal approach with full order finite element models for structures with geometric nonlinearities are presented. Both approaches are tailored to flight vehicle configurations where geometric stiffness effects are important but where deformations are moderate, flow is attached, and linear unsteady aerodynamic modeling is adequate, such as low aspect ratio wings or joined-wing and strut-braced wings at small to moderate angles of attack. Results obtained using the two approaches are compared using both planar and non-planar wing configurations. Sub-critical and post-flutter speeds are considered. It is demonstrated that the two methods lead to the same steady solution for the sub-critical case after the transients subside. It is also shown that the two methods predict the amplitude and frequency of limit cycle oscillation (when present) with the same accuracy.

Antioxidant effects of phenothiazine, phenoxazine, and iminostilbene on free‐radical‐induced oxidation of linoleic acid and DNA

AbstractAntioxidant effects of phenothiazine (PtzNH), phenoxazine (PozNH), and iminostilbene (IsbNH) on the oxidation of linoleic acid (LH) and DNA induced by 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH) were investigated in this work. LH was suspended in the liposome of dipalmitoyl phosphatidylcholine (DPPC) to mimic a biomembrane. In the course of AAPH‐induced oxidation of LH, the inhibition period (tinh) generated by PtzNH, PozNH, and IsbNH was proportional to the concentrations of PtzNH, PozNH, and IsbNH employed. The abilities of PtzNH, PozNH, and IsbNH to protect LH were similar to that of trolox (6‐hydroxyl‐2,5,7,8‐tetramethylchroman‐2‐carboxylic acid). Quantum chemical calculations elucidated that the nonplanar configurations of PtzNH, PozNH, and IsbNH transformed to planar ones when they were converted into radicals. In addition, spin‐densities (SDs) on the N atom in the radicals derived from PtzNH, PozNH, and IsbNH were calculated. The N atom in the radical of PtzNH possessed the lowest SD, indicating that the radical of PtzNH was the most stable one. Moreover, PtzNH, PozNH, and IsbNH were applied to protect the DNA against AAPH‐induced oxidation, in which PozNH and IsbNH were able to generate tinh. The tinh generated from PozNH and IsbNH was also proportional to their concentrations. The antioxidant effect of PozNH on the oxidation of DNA was higher than that of IsbNH. Copyright © 2009 John Wiley & Sons, Ltd.

Density functional theory studies on the molecular structures and thermodynamic properties of polychlorinated anthracenes

Geometric molecular structures of 287 polychlorinated anthracenes (PCANs) were optimized using density functional theory (DFT) at the B3LYP/6-311G(d,p) level and their thermodynamic properties in the ideal gas state (heat capacity at constant volume ( C θ v ), entropy ( S θ ), enthalpy ( H θ ), Gibbs energy ( G θ ), standard enthalpy of formation (Δ f H θ ) and standard Gibbs energy of formation (Δ f G θ )) were computed. The relations of C θ v , S θ , Δ f H θ and Δ f G θ with the number and position of chlorine atoms were also explored. According to the magnitude of the relative standard Gibbs energy of formation (Δ r,f G θ ), the relative stability of PCAN congeners was theoretically proposed. It was found that some PCAN isomers have a planar configuration while others adopt a nonplanar configuration. Both the values of C θ v and S θ increase with successive chlorination while the values of Δ f H θ and Δ f G θ of the most stable PCAN isomers decrease initially and then increase with increasing the degree of chlorination. The values of Δ f H θ and Δ f G θ of PCAN congeners with the same number of chlorine atoms show a strong dependence on the position of chlorine substitution. The relative thermodynamic stability of PCAN isomers is determined mainly by relative magnitude of intramolecular delocalized π bond and Cl–Cl nuclear repulsive interaction.

EPnP: An Accurate O(n) Solution to the PnP Problem

We propose a non-iterative solution to the PnP problem--the estimation of the pose of a calibrated camera from n 3D-to-2D point correspondences--whose computational complexity grows linearly with n. This is in contrast to state-of-the-art methods that are O(n 5) or even O(n 8), without being more accurate. Our method is applicable for all n?4 and handles properly both planar and non-planar configurations. Our central idea is to express the n 3D points as a weighted sum of four virtual control points. The problem then reduces to estimating the coordinates of these control points in the camera referential, which can be done in O(n) time by expressing these coordinates as weighted sum of the eigenvectors of a 12×12 matrix and solving a small constant number of quadratic equations to pick the right weights. Furthermore, if maximal precision is required, the output of the closed-form solution can be used to initialize a Gauss-Newton scheme, which improves accuracy with negligible amount of additional time. The advantages of our method are demonstrated by thorough testing on both synthetic and real-data.

Analytic and Experimental Investigation of Dihedral Configurations of Three-Winglet Planforms

An analytic and experimental effort was undertaken to assess the effectiveness and efficiency of three winglets mounted chordwise to the tip of a rectangular wing. The winglets, with an aspect ratio of 4.6, were mounted on a half-span wing having an effective aspect ratio of 6.29. 13 configurations of varying dihedral arrangements were analyzed with a vortex lattice method and tested in a low-speed wind tunnel at a Reynolds number of 600,000. While the analytic method provided fair agreement with the experimental results, the predicted trends in lift, drag, and (to a lesser degree) pitching moment were in good agreement. The analytic distributions of wake velocity, circulation, and downwash angle verified that highly nonplanar configurations tended to reduce and diffuse the regions of highest circulation and to create more moderate downwash angles in the wake. This was manifest as an overall drag reduction. More specifically, the results showed that the winglets could be placed in various optimum orientations to increase the lift coefficient as much as 65% at the same angle of attack, decrease the drag coefficient as much as 54% at the same lift coefficient, or improve the maximum L∕D by up to 57%. The most dramatic findings from this study show that positioning the winglet dihedral angles had the result of adjusting the magnitude and slope of the pitching moment coefficient. These observations suggest that multiple winglet dihedral variations may be feasible for use as actively controlled surfaces to improve the performance of aircraft at various flight conditions and to “tune” the longitudinal stability characteristics of the configuration.

Symmetry of planar four-body convex central configurations

We study the relationship between the masses and the geometric properties of central configurations. We prove that, in the planar four-body problem, a convex central configuration is symmetric with respect to one diagonal if and only if the masses of the two particles on the other diagonal are equal. If these two masses are unequal, then the less massive one is closer to the former diagonal. Finally, we extend these results to the case of non-planar central configurations of five particles.