Efficient one-pot three-component method for the synthesis of highly fluorescent coumarin-containing 3,5-disubstituted-2,6-dicyanoaniline derivatives under microwave irradiation

A simple and concise approach to the synthesis of coumarin-containing highly fluorescent asymmetric/symmetric 3,5-diaryl/heteroaryl-2,6-dicyanoaniline derivatives are reported. The compounds were synthesized through base catalyzed three-component one-pot synthesis reaction of 2-(1-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)ethylidene)malononitrile, aliphatic, aromatic/heteroaromatic aldehydes, and malononitrile in solvent-free reaction medium, catalyzed by piperidine under microwave irradiation method. The reaction gave the novel, highly fluorescent coumarin-containing 3,5-disubstituted-2,6-dicyanoaniline derivatives in good yields at 300?W, 80?°C in 2?min. This method provides several advantages; such as shorter reaction time, environmental friendliness, simple workup procedure, lower energy consumption and, generally, good yields with high purity. In addition, the synthesized compounds are fluorescently active dyes even in day light, except for compounds including nitro substituent, and show maximum absorption wavelengths (λ_abs.max) in the visible region in DMSO at room temperature. Thermal properties of all the synthesized compounds were also evaluated with thermal gravimetric analysis for usability as optic dye. Optical and thermal screening studies of the compounds showed that the dyes have excellent photophysical and thermal stability properties.     

Three-dimensional polarization-independent visible-frequency carpet invisibility cloak

We miniaturize all features in a previously introduced polarization-independent three-dimensional carpet invisibility cloak by more than a factor of 2. This leads to operation wavelengths in the visible. The structures are characterized by electron and optical microscopy. In contrast to our previous work at IR wavelengths, we can directly measure two-dimensional images at visible frequencies, perform control experiments from the backside, and compare the images with theory. We find excellent agreement. Furthermore, we study the wavelength dependence in the range from 900 nm down to 500 nm. Cloaking action deteriorates as the woodpile stop band at around 575 nm is approached.     

Minimal Surfaces in Three-Dimensional Riemannian Manifold Associated with a Second-Order ODE

We show that a surface corresponding to a first-order ODE is minimal in three-dimensional Riemannian manifold which is determined by the first prolongation of \({\text {d}}y/\mathrm{d}x=p(x,y)\) if and only if \(p_{yy}=0\). Accordingly, any linear first-order ODE describes a minimal surface which is not necessarily totally geodesic.     

The unique minimal dual representation of a convex function

Suppose (i) X is a separable Banach space, (ii) C is a convex subset of X that is a Baire space (when endowed with the relative topology) such that aff(C) is dense in X, and (iii) f:C→R is locally Lipschitz continuous and convex. The Fenchel-Moreau duality can be stated as

     

Collective firing regularity of a scale-free Hodgkin–Huxley neuronal network in response to a subthreshold signal

We consider a scale-free network of stochastic HH neurons driven by a subthreshold periodic stimulus and investigate how the collective spiking regularity or the collective temporal coherence changes with the stimulus frequency, the intrinsic noise (or the cell size), the network average degree and the coupling strength. We show that the best temporal coherence is obtained for a certain level of the intrinsic noise when the frequencies of the external stimulus and the subthreshold oscillations of the network elements match. We also find that the collective regularity exhibits a resonance-like behavior depending on both the coupling strength and the network average degree at the optimal values of the stimulus frequency and the cell size, indicating that the best temporal coherence also requires an optimal coupling strength and an optimal average degree of the connectivity.     

The 39K(2) 2(3)Sigma(g)+ state: observation and analysis

The (39)K(2) 2 (3)Sigma(g) (+) state has been observed by perturbation-facilitated infrared-infrared double resonance spectroscopy and two-photon excitation. Resolved fluorescence spectra into the a (3)Sigma(u) (+) state have been recorded. The observed vibrational levels have been assigned as the v=23-25, 27, 28, 31-33, 38-45, 47, and 53 levels by comparing the observed and calculated spectra of the 2 (3)Sigma(g) (+)-->a (3)Sigma(u) (+) transitions. Molecular constants have been obtained using a global fitting procedure with a comprehensive set of experimental data. Fine and hyperfine splittings have been resolved in the excitation spectra. Perturbations between the 2 (3)Sigma(g) (+) and 2 (3)Pi(g) states were observed. The hyperfine patterns of the 2 (3)Sigma(g) (+) levels are strongly affected by the perturbation. The perturbation-free and weakly perturbed levels follow the case b(betaS) coupling scheme, while the perturbed levels follow case b(beta J) coupling. A Fermi contact constant, b(F)=65+/-10 MHz, has been obtained. Intensity anomalies of rotational lines appeared both in the 2 (3)Sigma(g) (+) approximately 2 (3)Pi(g)<--b (3)Pi(u) excitation spectra and in the 2 (3)Sigma(g) (+) approximately 2 (3)Pi(g)-->a (3)Sigma(u) (+) resolved fluorescence spectra. These intensity anomalies can be explained in terms of a quantum-mechanical interference effect.     

Temperature dependence of the short-range hydration (solvation) of Mg2+, Ca2+, Sr2+, and Ba2+ cations in dilute solutions in H2O and D2O

Journal of Structural Chemistry -