Sodium borohydride-iodine mediated reduction of γ-lactam carboxylic acids followed by DDQ mediated oxidative aromatisation: a facile entry to N-aryl-formylpyrroles

A simple methodology for the conversion of substituted N-aryl-γ-lactam 2/3-carboxylic acids to substituted N-aryl-2/3-formyl-pyrroles has been developed. Several N-aryl-γ-lactam 2/3-carboxylic acids were reduced to substituted (N-aryl-pyrrolidine-2/3-yl)-methanols in good yields at room temperature using sodium borohydride-iodine. Controlled oxidation and aromatisation of these alcohols using DDQ produced N-aryl-2/3-formyl-pyrroles.     

The Nonclassicality and Decoherence of a Superposition State Generated in a Resonant Cavity

We discuss nonclassicality of a superposition of coherent states in terms of sub-Poissonian photon statistics as well as the negativity of the Wigner function. We derive an analytic expression for the Wigner function from which we find that the function has some negative region in phase space. We obtain a compact form of the Wigner function when decoherence occurs and study the effect of decoherence on the state. We demonstrate the behaviour of the nonclassicality indicator.     

Investigations of silicon-nitrogen hydrides from reaction of nitrogen atoms with silane: experiments and calculations

Using a quadrupole mass filter and vacuum-ultraviolet ionization, we measured the time-of-flight spectra of species at mass-to-charge ratios of m/ z = 45-42 from the reaction of N + SiH 4 in crossed molecular beams. Species with m/ z = 44 and 43 correspond to reaction products HSiNH/SiNH 2 and HSiN/HNSi, respectively; species with m/ z = 45 and 42 are assigned to isotopic variants and daughter ions, respectively, of those two reaction products. We measured the photoionization yields and branching ratios for dissociative ionization of reaction products as a function of photoionization energy. The ionization thresholds of products HSiNH/SiNH 2 and HSiN/HNSi were determined to be 6.7 and 9.2 eV, respectively. Furthermore, we calculated the equilibrium structures, electronic energies, and vibrational wavenumbers of various silicon-nitrogen hydrides H x SiNH y ( x + y = 0-3) using quantum-chemical methods. SiNH 2 (X (2)B 2) and HNSi (X (1)Sigma (+)) are more stable than HSiNH (X (2)A') and HSiN (X (1)Sigma (+)) by 0.82 and 2.81 eV, respectively. SiNH 2 (X (2)B 2), HSiNH (X (2)A'), HNSi (X (1)Sigma (+)), and HSiN (X (1)Sigma (+)) have adiabatic ionization energies of 6.81, 8.19, 10.21, and 10.23 eV, respectively. These experimental and calculated results indicate that SiNH 2 (X (2)B 2) and HNSi (X (1)Sigma (+)) are dominant among isomeric products in the reaction of N + SiH 4. This work presents the first observation of products from the reaction of N + SiH 4 in crossed beams and extensive calculations on pertinent silicon-nitrogen hydrides.     

Chemical Approach Towards Broadband Spintronics on Nanoscale Pyrene Films

The injection of pure spin current into the non-magnetic layer plays a crucial role in transmitting, processing, and storing data information in the realm of spintronics. To understand broadband molecular spintronics, pyrene oligomer film (≈20 nm thickness) was prepared using an electrochemical method forming indium tin oxide (ITO) electrode/pyrene covalent interfaces. Permalloy (Ni₈₀Fe₂₀) films with different nanoscale thicknesses were used as top contact over ITO/pyrene layers to estimate the spin pumping efficiency across the interfaces using broadband ferromagnetic resonance spectra. The spintronic devices are composed of permalloy/pyrene/ITO orthogonal configuration, showing remarkable spin pumping from permalloy to pyrene film. The large spin pumping is evident from the linewidth broadening of 5.4 mT at 9 GHz, which is direct proof of spin angular momentum transfer across the interface. A striking observation is made with the high spin-mixing conductance of ≈1.02×10¹⁸ m⁻², a value comparable to the conventional heavy metals. Large spin angular moment transfer was observed at the permalloy-pyrene interfaces, especially at the lower thickness of permalloy, indicating a strong spinterface effect. Pure spin current injection from ferromagnetic into electrochemically grown pyrene films ensures efficient broadband spin transport, which opens a new area in molecular broadband spintronics.     

Observation of the nd 1Delta(g) (n = 6, 7, and 8) Rydberg states of Na2 by optical-optical double resonance spectroscopy: L uncoupling and perturbations

The nd (1)Delta(g) (n = 6, 7, and 8) Rydberg states of Na(2) correlating with the asymptotic limits of Na(3s) + Na(nd) have been observed using high-resolution cw optical-optical double resonance spectroscopy corresponding to the rovibrational transitions X (1)Sigma(g)(+)(v("),J(")) + h nu(pump) --> B (1)Pi(u)(v('),J(')) + h nu(probe) --> nd (1)Delta(g)(v,J). Totals of 104, 83, and 45 identified rovibrational e/f-parity levels in the ranges of v = 0-11, 11 < or = J < or = 83; v = 0-10, 11 < or = J < or = 83; and v = 0-10, 11 < or = J < or = 65, have been assigned to the 6d (1)Delta(g), 7d (1)Delta(g), and 8d (1)Delta(g) states, respectively. Using the observed quantum levels, molecular constants were determined from the Dunham fits of the e-parity levels and the Rydberg-Klein-Rees potential curves were constructed for the nd (1)Delta(g)(n = 6-8) states. The characteristics of the estimated Lambda-doubling splitting constants (q(0), q(v), and mu) with n(= 5-8) of the nd (1)Delta(g) series have been explored. Detailed investigations reveal that the nd (1)Delta(g)(n = 6-8) states involve L uncoupling from the internuclear axis and each of these states is affected by an asymmetric perturbation caused by the up and down adjacent states. The rotational-branch intensity and position anomalies in the observed spectra of the nd (1)Delta(g) series (n = 5-8) of Na(2) lead to the conclusion that due to the effects of the L-uncoupling perturbations, the same l complexes approaching the same ion-core limits result in the same l-mixing processes which lead to the formation of the supercomplexes due to the anisotropy of the molecular-ion [Na(2)(+)(3s)] field. This would open up opportunities to study the effects of L uncoupling and perturbations in the nd series and high Rydberg states of other alkali dimers.     

RETRACTED ARTICLE: Effect of electromagnetic field on the stability of viscoelastic fluid film flowing down an inclined plane

The stability of thin electrically conducting viscoelastic fluid film flowing down on a non-conducting inclined plane in the presence of electromagnetic field is investigated under induction-free approximation. Surface evolution equation is derived by long-wave expansion method. The stabilizing role of Hartman number M (magnetic field) and the destabilizing role of the viscoelastic property \({\varGamma}\) and the electric parameter E on such fluid film are established through the linear stability analysis of the surface evolution equation. Investigation shows that at small values of Hartman number (M), the influence of electric parameter (E) on the viscoelastic parameter \({(\varGamma)}\) is insignificant, while for large values of M, E introduces more destabilizing effect at low values of \({\varGamma}\) than that at high values of \({\varGamma }\). An interesting result also perceived from our analysis is that the stabilizing effect of Hartman number (M) is decreasing with the increase of the values of \({\varGamma}\) and E, even it gives destabilizing effect after a certain high value of the electric field depending on the high value of \({\varGamma}\). The weakly nonlinear study reveals that the increase of \({\varGamma}\) decreases the explosive and subcritical unstable zones but increases the supercritical stable zone keeping the unconditional zone almost constant.     

Double versus single helical structures of oligopyridine-dicarboxamide strands. Part 2: The role of side chains

A series of heptameric oligoamides comprising 4-alkoxy-substituted 2,6-diaminopyridine and 2,6-pyridine-dicarbonyl units have been synthesized using convergent methods. The hybridization of these compounds into double helical dimers was studied in solution by ¹H NMR spectroscopy in CDCl₃ or DMSO-d₆ at various concentrations, and in the solid state using X-ray crystallographic analysis. Both solid state and solution data suggest that these compounds follow identical hybridization schemes. In CDCl₃, the oligomers possess dimerization constants considerably (up to 2000-fold) higher than related compounds having no alkoxy substituents on their 2,6-diaminopyridine units. The origin of this effect can be in part interpreted as a result of interactions between the 4-alkoxy side chains when they are present on all pyridine rings. For example, 4-benzyloxy-substituted oligomer 2 has a higher dimerization constant than 4-decyloxy and 4-methoxy-substituted analogues 1 and 3. The crystal structure of 2 reveals multiple aromatic-aromatic interactions between the benzyl side chains, both face-to-face and edge-to-face at various angles surrounding the duplex. In the solid state, these double helices are stacked on top of each other to form long channels filled with water molecules. The 4-methoxy and 4-decyloxy-substituted analogues 1 and 3 have similar dimerization constants, showing that interactions between side chains are not significant between purely aliphatic residues. Consequently, the high stability of the double helices formed by 1 and 3 compared to related compounds having alkoxy substituents on their 2,6-pyridine-dicarbonyl units only does not find its origin in interactions between side chains but in the direct effect of the alkoxy substituents upon main chain aryl-aryl interactions.     

Dipolar relaxation within the protein matrix of the green fluorescent protein: a red edge excitation shift study

The fluorophore in green fluorescent protein (GFP) is localized in a highly constrained environment, protected from the bulk solvent by the barrel-shaped protein matrix. We have used the wavelength-selective fluorescence approach (red edge excitation shift, REES) to monitor solvent (environment) dynamics around the fluorophore in enhanced green fluorescent protein (EGFP) under various conditions. Our results show that EGFP displays REES in buffer and glycerol, i.e., the fluorescence emission maxima exhibit a progressive shift toward the red edge, as the excitation wavelength is shifted toward the red edge of the absorption spectrum. Interestingly, EGFP displays REES when incorporated in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), independent of the hydration state. We interpret the observed REES to the constrained environment experienced by the EGFP fluorophore in the rigid protein matrix, rather than to the dynamics of the bulk solvent. These results are supported by the temperature dependence of REES and characteristic wavelength-dependent changes in fluorescence anisotropy.     

A strategy for designing "multi-prong" enzyme inhibitors by incorporating selective ligands to the liposomal surface

We offer a novel strategy for designing "multi-prong" inhibitors of enzymes by incorporating selective ligands on the liposomal surface.