How does hybrid bridging core modification enhance the nonlinear optical properties in donor‐π‐acceptor configuration? A case study of dinitrophenol derivatives

This study spotlights the fundamental insights about the structure and static first hyperpolarizability (β) of a series of 2,4‐dinitrophenol derivatives (1–5), which are designed by novel bridging core modifications. The central bridging core modifications show noteworthy effects to modulate the optical and nonlinear optical properties in these derivatives. The derivative systems show significantly large amplitudes of first hyperpolarizability as compared to parent system 1 , which are 4, 46, 66, and 90% larger for systems 2, 3, 4 , and 5 , respectively, at Moller–Plesset (MP2)/6‐31G* level of theory. The static first hyperpolarizability and frequency dependent coupled‐perturbed Kohn–Sham first hyperpolarizability are calculated by means of MP2 and density functional theory methods and compared with respective experimental values wherever possible. Using two‐level model with full‐set of parameters dependence of transition energy (ΔΕ), transition dipole moment (μ⁰) as well as change in dipole moment from ground to excited state (Δμ), the origin of increase in β amplitudes is traced from the change in dipole moment from ground to excited state. The causes of change in dipole moments are further discovered through sum of Mulliken atomic charges and intermolecular charge transfer spotted in frontier molecular orbitals analysis. Additionally, analysis of conformational isomers and UV‐Visible spectra has been also performed for all designed derivatives. Thus, our present investigation provides novel and explanatory insights on the chemical nature and origin of intrinsic nonlinear optical (NLO) properties of 2,4‐dinitrophenol derivatives. © 2014 Wiley Periodicals, Inc.     

Enhanced diterpene lactone (andrographolide) production from elicited adventitious root cultures of Andrographis paniculata

Research on Chemical Intermediates - The influence of different chemical elicitors was evaluated for increased andrographolide production using adventitious root cultures of Andrographis...     

Synthesis,characterization, POM analysis and antifungal activity of novel heterocyclic chalcone derivatives containing acylated pyrazole

Research on Chemical Intermediates - A series of heterocyclic chalcone derivatives (4a–h) were synthesized and characterized by IR, 1H and 13C NMR as well as MS. All the synthesized compounds...     

Study of binding interaction of rivaroxaban with bovine serum albumin using multi-spectroscopic and molecular docking approach

Background

Rivaroxaban is a direct inhibitor of coagulation factor Xa and is used for venous thromboembolic disorders. The rivaroxaban interaction with BSA was studied to understand its PK and PD (pharmacokinetics and pharmacokinetics) properties. Multi-spectroscopic studies were used to study the interaction which included UV spectrophotometric, spectrofluorometric and three dimensional spectrofluorometric studies. Further elucidation of data was done by molecular simulation studies to evaluate the interaction behavior between BSA and rivaroxaban.

Results

Rivaroxaban quenched the basic fluorescence of BSA molecule by the process of static quenching since rivaroxaban and BSA form a complex that results in shift of the absorption spectra of BSA molecule. A decline in the values of binding constants was detected with the increase of temperatures (298–308 K) and the binding constants were in range from 1.32 × 10⁵ to 4.3 × 10³ L mol^?1 indicating the instability of the BSA and rivaroxaban complex at higher temperatures. The data of number of binding sites showed uniformity. The site marker experiments indicated site I (sub-domain IIA) as the principal site for rivaroxaban binding. The thermodynamic study experiments were carried at the temperatures of 298/303/308 K. The ?G⁰, ?H⁰ and ?S⁰ at these temperatures ranged between ? 24.67 and ? 21.27 kJ mol^?1 and the values for ?H⁰ and ?S⁰ were found to be ? 126 kJ mol^?1 and ?S ? 340 J mol^?1 K^?1 The negative value of ?G⁰ indicating spontaneous binding between the two molecules. The negative values in ?H⁰ and ?S⁰ indicated van der Waals interaction and hydrogen bonding were involved during the interaction between rivaroxaban and BSA.

Conclusions

The results of molecular docking were consistent with the results obtained from spectroscopic studies in establishing the principal binding site and type of bonds between rivaroxaban and BSA.

     

Electrical insulation performance of flame retardant fillers filled with polypropylene/ethylene propylene diene monomer composites

Flame retardant fillers composed of zinc hydroxy stannate (ZHS), calcium borates (CaB), and NP‐100 were embedded separately in 50% polypropylene (PP) and 50% ethylene propylene diene monomer (EPDM) blends. Several formulations containing flame retardant fillers, PP, and EPDM were prepared using an internal mixer and were molded in a compression mold to form test samples. The effects of filler loading (15, 30, 45, and 60 vol%) on the dielectric breakdown strength and contact angle were determined. It was found that PP/EPDM/NP‐100 has higher breakdown strength than PP/EPDM/ZHS and PP/EPDM/CaB. The contact angle of PP/EPDM/NP‐100 and PP/EPDM/ZHS showed an ascending order with filler loading, implying an increase in hydrophobicity. With regard to the PP/EPDM/CaB system, the contact angle showed an ascending order up to 30 vol% followed by a descending order at 45–60 vol%. Water absorption studies indicated that PP/EPDM/NP‐100 has lower water absorption compared with PP/EPDM/ZHS and PP/EPDM/CaB. PP/EPDM filled with 15 vol% NP‐100 was found to exhibit interesting insulating properties in comparison with other composite systems, thanks to high breakdown voltage, good hydrophobicity, and low water absorption. Copyright © 2014 John Wiley & Sons, Ltd.     

Single crystal growth,structural, optical,mechanical, dielectric and thermal studies of formic acid doped potassium dihydrogen phosphate crystal for NLO applications

Optically transparent formic acid (FA) doped potassium dihydrogen phosphate (KDP) crystal of dimension 21×15×9 mm³ has been grown by slow evaporation solution technique (SEST). The X‐ray diffraction (XRD) technique was used to confirm the cell parameters and the shifts in peak positions of identified reflecting planes. The incorporation of FA in KDP has been qualitatively analyzed by fourier transform infrared analysis. The UV‐visible absorption spectrum of crystals has been recorded in the range of 200 to 900 nm and the doped KDP crystal is found to have improved optical parameters than pure KDP. The color centered photoluminescence emission spectrum of grown crystal has been illustrated in visible region. The mechanical behavior of pure and doped KDP crystal has been investigated using the Vicker's microhardness analyzer and hardness parameters have been calculated. The effect of FA on thermal stability of KDP crystal was examined by means of thermogravimetric and differential thermal analysis. The temperature dependent dielectric behavior of crystals was studied.     

GPS patch antenna performance by modification of Zn(1−x)CaxAl2O4-based microwave dielectric ceramics

This study reports the characterization, fabrication, and performance of global positioning systems (GPS) patch antennas as a function of calcium (Ca) concentration and dielectric constant (? _r ). Zn_(1?x)Ca_xAl₂O₄ (x = 0.00, 0.05, 0.10, 0.20, 0.25, and 0.30) thin films were prepared through a sol–gel method. The effects of added Ca on the nanostructures and dielectric properties of ZnAl₂O₄ ceramics were investigated. The addition of Ca increased the crystallite size, grain size, and surface morphology, thereby increasing the density and dielectric constant. As the Ca content increased, the ? _r values linearly increased. However, the Q _u values decreased (at x = 0.25 to x = 0.25) after achieving the optimum values at x = 0.20. Finally, GPS patch antennas were successfully fabricated using the Zn_(1?x)Ca_xAl₂O₄ material. The patch antenna sizes decreased as ? _r increased from 2.88  × 4.37 cm (? _r  ≈ 8.52) to 2.88  × 4.37 cm (? _r  ≈ 10.16). The performance (return loss analysis) and operating frequencies of the GPS patch antennas were measured using the PNA series network analyzer. Results show that the patch antenna resonates at frequency of 1.570 GHz and produces a return loss bandwidth between ?16.6 and ?27.5 dB. The optimal performance of GPS patch antenna with ? _r  ≈ 9.95, Q _u  ≈ 6,186, and return loss = ?27.5 dB was obtained from specimen using Zn_0.80Ca_0.20Al₂O₄ (x = 0.20) ceramics.     

以对二甲苯氧化为对苯二甲酸为例简要综述一级C–H键活化(英文)

The oxidation of para‐xylene to terephthalic acid has been commercialised as the AMOCO process(Co/Mn/Br) that uses a homogeneous catalyst of cobalt and manganese together with a corrosive bromide compound as a promoter. This process is conducted in acidic medium at a high tempera‐ture(175–225 °C). Concerns over environmental and safety issues have driven studies to find mild‐er oxidation reactions of para‐xylene. This review discussed past and current progress in the oxida‐tion of para‐xylene process. The discussion concentrates on the approach of green chemistry in‐cluding(1) using heterogeneous catalysts with promising high selectivity and mild reaction condi‐tion,(2) application of carbon dioxide as a co‐oxidant, and(3) application of alternative promoters. The optimisation of para‐xylene oxidation was also outlined.     

Preparation and Properties of Poly（vinyl alcohol）/Chitosan Blend Bio-nanocomposites Reinforced by Cellulose Nanocrystals

The aim of this paper is to report the effect of the addition of cellulose nanocrystals（CNCs） on the mechanical, thermal and barrier properties of poly（vinyl alcohol）/chitosan（PVA/Cs） bio-nanocomposites films prepared through the solvent casting process. The characterizations of PVA/Cs/CNCs films were carried out in terms of X-ray diffraction（XRD）, transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, thermogravimetric analysis（TGA and DTG）, oxygen transmission rate（OTR）, and tensile tests. TEM and SEM results showed that at low loading levels, CNCs were dispersed homogenously in the PVA/Cs matrix. The tensile strength and modulus in films increased from 55.1 MPa to 98.4 MPa and from 395 MPa to 690 MPa respectively, when CNCs content went from 0 wt% to 1.0 wt%. The thermal stability and oxygen barrier properties of PVA/Cs matrix were best enhanced at 1.0 wt% of CNCs loading. The enhanced properties attained by incorporating CNCs can be beneficial in various applications.