Dimeric cyclopalladated azobenzenes: structural differences between 2-hydroxypyridine and 2-mercaptopyridine bridged complexes

Binuclear chloro-bridged cyclopalladated azobenzenes [Pd(A)Cl]₂ (A=ortho-metallated azobenzene or its derivatives) have been reacted with aqueous (aq.) AgNO₃ followed by the addition of 2-hydroxypyridine (2-PyOH; donor centres of deprotonated form abbreviated N,O)/2-mercaptopyridine (2-PySH; donor centres of deprotonated form abbreviated N,S) in presence of Et₃N to synthesise bridged dinuclear compound [Pd(A)(μ-N,O)]₂–[Pd(A)(μ-N,S)]₂. The compositions of the complexes have been established by elemental analyses, IR, UV–vis, ¹H and ¹³C-NMR spectral data. The structural confirmation has been carried out by X-ray crystallography. The structures show anti-symmetric metallacycle in the dimer and N,O/N,S bridging arrangement. The dimer [Pd(A₁)(μ-N,X)]₂ shows strong PdPd interaction (A₁=2-(phenylazo)benzene). The coordination mode in [Pd(A₁)(μ-N,O)]₂ shows trans pyridine-N to Pd---N(azo) bond while in [Pd(A₁)(μ-N,S)]₂ pyridine-N is trans to the Pd---C bond. The square planes are convergent towards heterocyclic bridging side.     

Lithium inserted ZnSnN2 thin films for solar absorber: n to p-type conversion

ZnSnN₂ is a non-toxic and earth-abundant photoabsorber material for flexible photovoltaic devices because of its excellent optoelectronic behavior. However, theoretical studies show that the alkaline-earth metallic (Li, Na, K, Rb, Cs, and Fr) dopants in ZnSnN₂, particularly lithium (Li), display shallow-acceptor behavior and improve the performance of ZnSnN₂ semiconductors. Orthorhombic phase structure with (002) preferred orientation was observed for Li-doped films and the lattice parameters agree well with reported standards. Secondary ion mass spectroscopy (SIMS) analysis revealed the incorporation of Li in Li:ZnSnN₂ films. XPS, the density of states, and Born effective charge analysis revealed the chemical bonding states of Li–ZnSnN₂. In contrast to the pristine n-type ZnSnN₂, Li:ZnSnN₂ thin films showed conductivity with p-type hole concentrations varying between 1.14 × 10²⁰–9.47 × 10¹⁹ cm^?3 and the highest mobility of 20.03 cm²V^?1s^?1. Therefore, we obtained p-type conductivity by substituting an organolithium reagent (C?H?Li) on the Zn site, which highlights that Li:ZnSnN₂ can be effectively used as the photoanode layer for next-generation thin-film solar cell devices.     

Crystal structure and conformational analysis of N-formyl and N-nitroso derivatives of piperidinone

Single crystal X-ray studies for N-formyl-2,6-diortho chlorophenyl-3,5-dimethyl piperidin-4-one (FOCDMPO) and N-nitroso-2,6-di(3,4,5-trimethoxyphenyl)-3,5-dimethyl piperidin-4-one (NTMPO) are reported. Crystals of FOCDMPO and NTMPO belong to the monoclinic space groups P2₁/n and C2/c, respectively. FOCDMPO: a = 9.147(2), b = 14.586(3), c = 13.665(5) Å and = 101.68(2)° NTMPO: a = 38.52(2), b = 13.727(5), c = 9.564(3) Å and = 98.60(1)°. In both the structures, the piperidine ring adopts a boat conformation with slight distortion. In FOCDMPO, one of the phenyl and methyl groups are in axial positions while the other phenyl and methyl groups are in equatorial orientations. In NTMPO, the situation is reversed. The molecules are stabilized by weak intermolecular C—H ··· O interactions in addition to van der Waals forces.     

Water deficit stress effects on reactive oxygen metabolism in Catharanthus roseus; impacts on ajmalicine accumulation

In the present work, we have analysed the changes in the reactive oxygen metabolism of Catharanthus roseus (L.) G. Don. plants in terms of H(2)O(2) content, lipid peroxidation and the free radical quenching systems (non-enzymatic and enzymatic antioxidants) under drought stress. In addition to this, the root alkaloid ajmalicine was extracted and quantified from both control and drought stressed plants. The H(2)O(2) content was analysed from both stressed and unstressed control plants. Lipid peroxidation was estimated as thiobarbituric acid reactive substances. The non-enzymatic antioxidants viz., ascorbic acid, alpha-tocopherol and reduced glutathione contents, antioxidant enzymes like superoxide dismutase, ascorbate peroxidase, and catalase were extracted and estimated from the samples. The alkaloid ajmalicine was extracted and quantified from shade dried root samples and found significantly increased over control. From the results of this investigation, it can be concluded that the water deficit areas may be well used for the cultivation of medicinal plants like C. roseus and the economically important alkaloid production can be enhanced in the plant level.     

Protection of Vigna unguiculata (L.) Walp. plants from salt stress by paclobutrazol

A pot culture experiment was conducted to estimate the stress ameliorating ability of paclobutrazol, a triazole fungicide in Vigna unguiculata (L.) Walp. plants. Treatments were given as 80 mM NaCl, 80 mM NaCl + 15 mg l⁻¹ paclobutrazol and 15 mg l⁻¹ paclobutrazol alone. The samples were collected on 60 and 80 days after sowing (DAS). NaCl stress inhibited the root and stem length, total leaf area, fresh weight (FW), dry weight (DW) and activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX). Plants treated with NaCl with paclobutrazol increased these parameters to a larger extent when compared to NaCl stressed plants. The results showed that the paclobutrazol significantly ameliorated the adverse effects of NaCl stress in V. unguiculata plants.     

Ligand influence on the formation of P/Se semiconductor materials from metal-organic complexes

The complexes [Ni{(SeP(i)Pr(2))(2)N}(2)] (), [Ni(Se(2)P(i)Pr(2))(2)] (), and [Co(Se(2)P(i)Pr(2))(2)] () were synthesised and the X-ray single crystal structures of () and () were determined. Thin films of nickel selenide, cobalt selenide and cobalt phosphide have been deposited by the chemical vapour deposition method using imidodiselenophosphinato-nickel(ii) (), -cobalt(ii) [Co{(SeP(i)Pr(2))(2)N}(2)] (), diselenophosphinato-nickel(ii) (), -cobalt(ii) () and diselenocarbamato-nickel(ii) [Ni(Se(2)CNEt(2))(2)] (), and -cobalt(iii) [Co(Se(2)CNEt(2))(3)] () precursors.     

An Improved Method to Resolve Plant Saponins and Sugars by TLC

Thin-layer chromatography (TLC) plays an important role in the initial selection of mutants having a unique seed saponin composition from the germplasm collections of the subgenus Soja. In the conventional TLC procedure, the dehydrated free sugars are retained just below the major saponins and interrupt the identification of some minor saponin constituents. To resolve this problem, we developed an efficient and reliable method to move sugars from the saponin area on TLC. A developing chamber was saturated with the lower phase of chloroform:methanol:water (65:35:10, v/v) for 2 h and the TLC plates were developed in it for 50 min. Plates were then dried at 100 °C for 10 min to evaporate the excess mobile phase and developed again with 10 % H₂SO₄ for 15 min. While sulfuric acid migrates over the surface of SiO₂, sugar molecules are dehydrated and hydrophilic interactions between free sugars and SiO₂ are strongly reduced. Thus, the positions of dehydrated sugars were shifted to above the saponin area on the TLC plate. This resulted in easy recognition of the saponin composition without any discrimination. This amended protocol would be applicable to all TLC analyses in which the target components should be separate from the interrupting sugar molecules.