Conductometric study of some alkali metal halides in (dimethyl sulfoxide + acetonitrile) at T = 298.15 K

Electrolytic conductivities of some alkali metal halides, MX (M⁺ = Li⁺, Na⁺, and K⁺; X^? = Cl^?, Br^?, and I^?), NaBPh₄ and Bu₄NBr have been investigated in (20, 40, and 60) mass% {dimethyl sulfoxide (DMSO) in DMSO + acetonitrile} at T = 298.15 K. The conductance results have been analyzed by the Fuoss-conductance-concentration equation in terms of the limiting molar conductance Λ° the association constant K_A and the association diameter R. The ionic contributions to the limiting molar conductance have been estimated using Bu₄NBPh₄ as the “reference electrolyte”. The association constant K_A tends to increase in the order mass percent 20 < 40 < 60 DMSO in (DMSO + acetonitrile) which is explained by the thermodynamic parameter ΔG° and Walden product Λ°η. The results have been interpreted in terms of ion–solvent interactions and structural changes in the mixed solvents.     

Synthetic protocols towards homodithiacalix[n]arenes

Synthetic procedures towards homodithiacalix[n]arenes are developed, starting from simple and readily available bifunctional aryl building blocks, by a dynamic covalent chemistry approach. Reaction of 1,3-bis(mercaptomethyl)-5-tert-butyl-2-methoxybenzene under basic conditions leads to a mixture of trimeric, tetrameric and pentameric dimethylenedithia-bridged cyclooligomers, whereas reaction of 5-tert-butyl-2-methoxy-1,3-bis(thiocyanatomethyl) benzene under reducing conditions (and subsequent oxidation) affords the homodithiacalix[4]arene macrocycle in a very selective fashion through efficient disulphide exchange chemistry.     

Ambient temperature activation of haloporphyrinic-enediynes: electronic contributions to bergman cycloaromatization

We have synthesized the nickel(II) 2,3-bis(haloethynyl)-5,10,15,20-tetraphenylporphyrins with -Br (2a) or -I (2b) at the alkyne termini position from the corresponding 2,3-diethynyl analogue (1). The cross coupling of nickel(II) 2,3-dibromo-5,10,15,20-tetraphenylporphyrin with trimethyl(trimethylstannanylethynyl)silane in the presence of a Pd0 catalyst and subsequent deprotection with base under aqueous conditions yields the nickel(II) 2,3-diethynyl-5,10,15,20-tetraphenylporphyrin (1). Subsequent reaction of 1 with N-bromo- or N-iodosuccinimide in dry acetone in the presence of AgNO3 yields 2,3-bis(haloethynyl)-5,10,15,20-tetraphenylporphyrins in 70% (2a) and 68% (2b) yields. The X-ray crystal structures of 2a,b show that the porphyrin backbone deviates significantly from planarity due to a Ni(II)-induced mixture of the classic ruffle and saddle distortions. Thermolysis of 2a at 190 degrees C for 6 h in chlorobenzene and 30-fold 1,4-cyclohexadiene (CHD) generates the Bergman cyclized nickel(II) dibromopicenoporphyrin product (3) in 65% yield, which derives from diradical addition across the adjacent meso-phenyl substituents. Similarly, nickel(II) 2,3-bis(iodoethynyl)-5,10,15,20-tetraphenylporphyrin, 2b, cyclizes at 190 degrees C in chlorobenzene/CHD via high-temperature substitution of iodine by hydrogen (from CHD) or chlorine (from solvent) to afford a mixture of 4 (15%) and 5 (45%). Remarkably, ambient temperature incubation of 2a in MeOH/CHCl3 (1:3, 22 h) or chlorobenzene/CHD (3:1, 24 h) leads to generation of 3 in 15% and 22% isolated yields, respectively. Addition of 1.2 equiv of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) in CHCl3/MeOH dramatically accelerates the rate of reaction, producing 3 in 30% yield within 0.5 h. The origin of the ambient temperature activation of 2a derives from the ability of electron-withdrawing functionalities at the alkyne termini to decrease the activation barrier to the Bergman product.     

Bio-inspired Design of Bidirectional Oxygen Reduction and Oxygen Evolution Reaction Molecular Electrocatalysts

The proper utilization of renewable energy sources has emerged as a major challenge in our pursuit of a sustainable and carbon-neutral energy landscape. Small molecule activation is a key component for proper utilization of renewable energy resources, where O₂/H₂O redox couple is reckoned to be a potential game changer. In this regard, electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have become the prime interest of catalyst designers. Typically, these ORR and OER electrocatalysts are developed distinctly; however, very soon, the requirement of a bidirectional ORR/OER electrocatalyst becomes obvious for practical applicability and rapid energy transduction purposes. A bidirectional catalyst is defined as a catalyst capable of driving a redox reaction in opposing directions. This review has portrayed the development of enzyme structure-inspired design of molecular bidirectional ORR/OER catalysts. The strategic incorporation of secondary and outer coordination sphere features has significantly enhanced the performance of these catalysts, which can be monitored via the key catalytic parameters. These bifunctional OER/ORR catalysts are vital for metal-air battery and fuel cell applications and appropriately poised to lay the foundation for an efficient, economical, and eco-friendly pathway for sustainable energy usage with the rational assembly of energy converting and storage devices.     

Synthesis,characterization, and applications with the manifestation of antifungal activity and seed germination properties of nickel doped zinc oxide nano platform by biochemical contrivance

In the recent era, nanotechnology, a rapidly emerging field, has been explored as the most studied field worldwide. The goal of this study is to use neem leaves extract as an effective ‘reducing agent’ and ‘stabilizing agent’ in the green synthesis of bio-medically important Zn_1-XNi_XO (X = 0.00, 0.04, 0.08, 0.12) nanoparticles. The molar concentrations of nickel nitrate and zinc nitrate are varied to produce nickel-doped ZnO nanoparticles. Color change is the first indicator of nanoparticle formation during this biosynthesis. The hexagonal wurtzite structure with good crystallinity is confirmed by X-ray diffraction. FTIR analysis reveals the fact that the Zn–O stretching vibration shifts with the introduction of impurities into the ZnO matrix. UV–Vis spectra show the typical surface plasma resonance around 370 nm and the hydrodynamic diameter is larger than the size calculated from the XRD value, according to DLS. The main finding of this study is that Ni_0.12Zn_0.88O has a strong antifungal activity against and a significant growth rate after treating wheat seeds with biologically synthesized Ni_0.12Zn_0.88O nanoparticles.     

Dynamic distortion of C4N+-skeleton in (CH3)4NC1

The polarization data and concentration dependence of the Raman spectra of aqueous solutions of tetramethyl ammonium chloride in the region 2700–3100 cm^-1 are studied. Group theoretically consistent assignments reveal that the C₄N₊-skeleton acquires a dynamic distortion to C_3v symmetry due to outof-phase combinations of the four CH₃,-stretching oscillations.