Synthesis and crystal structures of polynuclear complexes of Cu with 1-methyl-1,3-imidazoline-2-thione

Reactions of equimolar solutions of copper(I) halides with 1-methyl-1,3-imidazoline-2-thione (SC₄H₆N₂) in acetonitrile have yielded a trinuclear complex, {Cu₃(η¹-Br)₃(μ-SC₄H₆N₂)₃} · CH₃CN 1, and 1D polymer, {Cu₂(μ-I)₂(μ-SC₄H₆N₂)₂}_n2. The thio-ligands/halogens adopt μ-S, η¹-X or μ-X modes. There is weak interaction between trinuclear units {Cu···Br, 3.025 Å} and Cu···Cu contacts lie in the range, 2.974(2)–3.650(2) Å. Polymer 2 has alternating Cu₂I₂ and Cu₂S₂ cores involving sulfur/iodine bridging in a twisted ribbon type arrangement with short Cu···Cu distances {2.6912(9) and 2.785(9) Å}, respectively. The polynuclear complexes in dimethyl sulfoxide exhibit intense fluorescent bands {λ_em = 319 (1) and 322 (2)}.     

Stereoselective synthesis and Lewis acid mediated functionalization of novel 3-methylthio-β-lactams

A proficient etiquette for the stereoselective synthesis of novel 3-methylthio-β-lactams and their Lewis acid mediated functionalization is described. Treatment of 2-methylthioethanoic acid and appropriate imines in the Staudinger reaction leads to the stereocontrolled synthesis of novel trans-3-methylthio-β-lactams in excellent yields. cis-3-Chloro-3-methylthio-β-lactams, obtained from stereoselective chlorination of trans-3-methylthio-β-lactams using N-chlorosuccinimide (NCS) and AIBN, were subjected to Lewis acid (TiCl₄ or SnCl₄) mediated functionalization using various active aromatic, heterocyclic and aliphatic compounds (nucleophiles). This reaction provides an easy access to novel, stereoselective cis-3-monosubstituted-3-methylthio-β-lactams, which further undergo smooth desulfurization with Raney-nickel to afford C-3 cis- and trans-monosubstituted-β-lactams. The cis or trans configuration of the hydrogen/chloro/nucleophile substituent at C-3 was assigned with respect to C4–H.     

3-Phenyl-4-benzoyl-5-isoxazolonate complex of Eu3+ with tri-n-octylphosphine oxide as a promising light-conversion molecular device

Three new europium complexes, [Eu(PBI)3.3H2O] (1), [Eu(PBI)3.2TOPO] (2), and [Eu(PBI)3.2TPPO.H2O] (3) (where HPBI, TOPO, and TPPO stand for 3-phenyl-4-benzoyl-5-isoxazolone, tri-n-octylphosphine oxide, and triphenylphosphine oxide, respectively), with different neutral ligands were synthesized and characterized by elemental analysis, Fourier transform infrared, (1)H NMR, thermogravimetric analysis, and photoluminescence (PL) spectroscopy. The coordination geometries of the complexes were calculated using the Sparkle/AM1 (Sparkle Model for the Calculation of Lanthanide Complexes within the Austin Model 1) model. The ligand-Eu3+ energy-transfer rates were calculated in terms of a model of the intramolecular energy-transfer process in lanthanide coordination compounds reported in the literature. The room-temperature PL spectra of the europium(III) complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5D0) and the multiplet (7F(0-4)). On the basis of emission spectra and lifetimes of the 5D0-emitting level, the emission quantum efficiency (eta) was determined. The results clearly show that the substitution of water molecules by TOPO leads to greatly enhanced quantum efficiency (i.e., 26% vs 92%) and longer 5D0 lifetimes (250 vs 1160 micros). This can be ascribed to a more efficient ligand-to-metal energy transfer and a less nonradiative 5D0 relaxation process. Judd-Ofelt intensity parameters (Omega2 and Omega4) were determined from the emission spectra for the Eu3+ ion based on the 5D0 --> 7F2 and 5D0 --> 7F4 electronic transitions, respectively, and the 5D0 --> 7F1 magnetic-dipole-allowed transition was taken as the reference. A point to be noted in these results is the relatively high value of the Omega2 intensity parameter for all of the complexes. This may be interpreted as being a consequence of the hypersensitive behavior of the 5D0 --> 7F2 transition. The dynamic coupling mechanism is, therefore, dominant, indicating that the Eu3+ ion is in a highly polarizable chemical environment.     

Iodobenzene diacetate on alumina: Efficient synthesis of 1,3,4‐oxadiazolyl‐1,8‐naphthyridines in solventless system using microwaves

1‐(5‐Aryl‐[1,3,4]oxadiazol‐2‐ylmethyl)‐3‐(p‐methoxyphenyl)‐1H‐[1,8]naphthyridin‐2‐ones ( 5 ) were synthesized by the oxidative cyclization of [2‐oxo‐3‐(p‐methoxyphenyl)‐2H‐[1,8]naphthyridin‐1‐yl]acetic acid arylidene‐hydrazides ( 4 ) with alumina‐supported iodobenzene diacetate (IBD) in solvent‐free conditions under microwave irradiation. The products are obtained in good yields and in a state of high purity.     

Impact of generalized dissipative coefficient on warm inflationary dynamics in the light of latest Planck data

The warm inflation scenario in view of the modified Chaplygin gas is studied. We consider the inflationary expansion to be driven by a standard scalar field whose decay ratio \(\Gamma \) has a generic power-law dependence with the scalar field \(\phi \) and the temperature of the thermal bath T. By assuming an exponential power-law dependence in the cosmic time for the scale factor a(t), corresponding to the intermediate inflation model, we solve the background and perturbative dynamics considering our model to evolve according to (1) weak dissipative regime and (2) strong dissipative regime. Specifically, we find explicit expressions for the dissipative coefficient, scalar potential, and the relevant inflationary observables like the scalar power spectrum, scalar spectral index, and tensor-to-scalar ratio. The free parameters characterizing our model are constrained by considering the essential condition for warm inflation, the conditions for the model evolves according to weak or strong dissipative regime, and the 2015 Planck results through the \(n_s\)–r plane.     

Influence of plasticizer on ionic conductivity of PVC-PBMA polymer electrolytes

Plasticized polymer electrolytes comprising of ethylene carbonate as the plasticizing agent in poly (vinyl chloride) [PVC]–poly (butyl methacrylate) [PBMA] blended polymer electrolytes were prepared by solution casting technique. Complex formation, structural elucidation, conductivity, dielectric parameters (?′, ?″, M′, and M″), thermal stability, and surface morphology are brought out from FTIR, XRD, ac impedance analysis, dielectric studies, thermogravimetry/differential thermal analysis, and scanning electron microscopic studies, respectively. Polymer electrolytes are found to exhibit higher ionic conductivity at higher concentration of plasticizer at the cost of their mechanical stability. Conductivity of 1.879 × 10^?4 S cm^?1 is exhibited by the polymer electrolyte consisting of 69% of plasticizer with appreciable thermal stability up to 523 K. Temperature and frequency dependence of conductivity is found to follow Vogel Tammann Fulcher relation and Jonscher power law, respectively. Real and imaginary parts of dielectric constants are found to decrease with increase in frequency which could be due to the electrode polarization effect.     

Anisotropic Inflationary Scenario Via Generalized Chaplygin Gas Model

We investigate generalized chaplygin gas for warm inflationary scenario in the context of locally rotationally symmetric Bianchi type I universe model.We assume two different cases of dissipative coefficient,i.e.,constant as well as function of scalar field.We construct dynamical equations as well as a relationship between scalar and radiation energy densities under slow-roll approximation.We also derive slow-roll parameters,scalar and tensor power spectra,scalar spectral index,tensor to scalar ratio for analyzing inflationary background during high dissipative regime.We also use the WMAP7 data for the discussion of our parameters.     

Pilgrim dark energy in f(T) gravity

We discuss the interacting f(T) gravity with pressureless matter in an FRW spacetime. We construct an f(T) model by following the correspondence scheme incorporating a recently developed pilgrim dark energy model and taking the Hubble horizon as the IR cutoff. We use constructed model to discuss the evolution trajectories of the equation-of-state parameter, the ω _T -ω′ _T phase plane, and state-finder parameters in the evolving universe. It is found that the equation-of-state parameter gives a phantom era of the accelerated universe for some particular range of the pilgrim parameter. The ω _T -ω′ _T plane represents freezing regions only for an interacting framework, while the ΛCDM limit is attained in the state-finder plane. We also investigate the first and second laws of thermodynamics assuming equal temperatures at and inside the horizon in this scenario. Due to the violation of the first law of thermodynamics in f(T) gravity, we explore the behavior of the entropy production term. The validity of a generalized second law of thermodynamics depends on the present-day value of the Hubble parameter.     

An Efficient Green Synthesis of a New Class of α‐Aminophosphonates under Microwave Irradiation Conditions in the Presence of PS/PTSA

The present work focuses on the study of catalytic activity of polystyrene‐supported p‐toluenesulfonic acid (PS/PTSA) and the synthesis of α‐aminophosphonates from the Kabachnik–Fields (KF) reaction under microwave irradiation in solvent‐free conditions. Recently, the catalytic activity of PS/PTSA was tested with good yields. This procedure is the simplest, most straightforward, environment friendly method for the synthesis of α‐aminophosphonates from simple to different substituted aldehyde substrates. Furthermore, this catalyst can be recovered and reused without loss of its catalytic activity.